U.S. patent number 3,929,176 [Application Number 05/517,920] was granted by the patent office on 1975-12-30 for machine for automatically driving threaded fasteners.
This patent grant is currently assigned to Babette Dixon, Trustee. Invention is credited to Paul H. Dixon.
United States Patent |
3,929,176 |
Dixon |
December 30, 1975 |
Machine for automatically driving threaded fasteners
Abstract
A screw is blown through a flexible tube and into the jaws of a
transfer mechanism which is associated with a hand-held screw
driving gun. Thereafter, the jaws are advanced to deliver the screw
into telescoping relation with a retractible tubular finder which
surrounds the driving bit of the gun, the jaws holding the screw
during initial driving of the screw and then returning to receive
another screw from the tube. The machine includes unique means for
(a) placing the screw into and blowing the screw through the tube,
(b) advancing and returning the jaws along different paths to
enable the jaws to place the screw in the finder while holding and
maintaining control over the screw during initial driving, (c)
momentarily retracting the finder during advance of the jaws to
enable the screw to be telescoped with the finder, (d)
automatically controlling the advance and return of the jaws in
response to extension and retraction of the finder, and (e)
controlling opening and closing of the jaws to enable the jaws to
tightly grip the screw during its delivery while still holding the
screw during initial driving.
Inventors: |
Dixon; Paul H. (Belvidere,
IL) |
Assignee: |
Dixon, Trustee; Babette
(Belvidere, IL)
|
Family
ID: |
24061782 |
Appl.
No.: |
05/517,920 |
Filed: |
October 25, 1974 |
Current U.S.
Class: |
81/430; 29/813;
227/119; 227/117 |
Current CPC
Class: |
B25B
23/04 (20130101); Y10T 29/535 (20150115) |
Current International
Class: |
B25B
23/04 (20060101); B25B 23/02 (20060101); B25B
023/10 () |
Field of
Search: |
;144/32 ;29/211,240 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Smith; Al Lawrence
Assistant Examiner: Smith; Gary L.
Attorney, Agent or Firm: Wolfe, Hubbard, Leydig, Voit &
Osann, Ltd.
Claims
I claim as my invention
1. A machine for automatically driving a threaded fastener into a
workpiece and comprising a power-rotated fastener driver, a finder
telescoped over said driver and having an end portion sized to
telescope over a fastener, means for supporting said finder for
movement between extended and retracted positions along said
driver, means for urging said finder to and for normally keeping
said finder in said extended position, mechanism for delivering a
fastener to a driving position in which the fastener is in line
with said end portion of said finder, and means associated with
said mechanism for causing said finder to move from its extended
position and toward its retracted position as said fastener is
moved toward said driving position and then for causing said finder
to move back to its extended position and into telescoping relation
with said fastener after the fastener has been delivered to said
driving position.
2. A machine as defined in claim 1 in which said mechanism
comprises a pair of opposed jaws adapted to move between closed and
open positions to hold and release said fastener, a carriage
mounting said jaws for movement between said open and closed
positions and also for movement between a pick-up station where the
jaws receive a fastener and a delivery station where the jaws place
said fastener in said driving position, said last-mentioned means
comprising elements connected to said carriage and said finder and
coacting to move said finder toward said retracted position as said
carriage moves said jaws toward said delivery station.
3. A machine as defined in claim 2 in which said coacting elements
comprise a cam connected to said carrier and a linkage connected to
said finder, said cam engaging said linkage as said jaws are moved
toward said delivery station and acting through said linkage to
move said finder toward said retracted position.
4. A machine as defined in claim 3 in which said linkage comprises
a pivoted lever positioned to engage said cam, a link extending
between said lever and said finder to move said finder toward said
retracted position when said lever is rocked in one direction, and
a lost-motion connection between said finder and said link to
enable said finder to move back and forth between said extended and
retracted positions without said finder imparting movement to said
lever.
5. A machine as defined in claim 4 further including signaling
means carried by said lever and adapted to be switched back and
forth between a first state and a second state when said finder
moves back and forth between said extended and retracted positions
without imparting motion to said lever, said signaling means
remaining in an unchanged state when said finder is moved from said
extended position toward said retracted position by said lever and
said link, and said signaling means being operable to initiate
movement of said jaws back and forth between said stations when
said signaling means are switched back and forth between said
states.
6. A machine as defined in claim 5 in which said signaling means
comprise a valve carried by said lever, said valve being opened and
closed when said finder moves back and forth between its positions
without imparting motion to said lever, the state of said valve
remaining unchanged when said finder is moved toward retracted
position by said lever and said link.
7. A machine for automatically driving a threaded fastener into a
workpiece and comprising a power-rotated fastener drive, a finder
telescoped over said driver and having an end portion sized to
telescope over a fastener, means for supporting said finder for
movement between extended and retracted positions along said
driver, said finder normally being disposed in said extended
position, a holder movable between pick-up and delivery stations
and being disposed in said delivery station when said finder is in
said normal extended position, said holder receiving a fastener
when in said pick-up station and thereafter moving to said delivery
station and retaining the fastener in a driving position in
telescoping relation with said end portion of said finder, said
finder being moved toward said retracted position upon pressing the
telescoped fastener against the workpiece and then returning toward
said extended position upon being released from the driven
fastener, and means responsive to movement of said finder toward
said retracted position for causing said holder to move from said
delivery station to said pick-up station to receive a new fastener
and responsive to return movement of said finder toward said
extended position to cause said holder to move back toward said
delivery station and place the new fastener in said driving
position.
8. A machine as defined in claim 7 in which last-mentioned means
comprise signaling means adapted to be switched back and forth
between first and second states when said finder moves back and
forth between said extended and retracted positions.
9. A machine as defined in claim 8 in which said signaling means
comprise a valve, and a link between said finder and said valve and
operable to cause opening and closing of the valve as the finder is
moved back and forth between its positions.
10. A machine as defined in claim 9 further including a movable
member connected to said link and operable to cause movement of
said finder from said extended position toward said retracted
position and then back to said extended position as said holder is
moved from said pick-up station to said delivery station, said
valve being carried on said member and remaining in an unchanged
state when movement of said finder is caused by movement of said
member.
11. A machine as defined in claim 10 in which said member comprises
a pivoted lever, and means associated with said holder for causing
said lever to rock first in one direction and then in the other
direction as said holder is moved from said pick-up station to said
delivery station.
12. A machine for automatically driving a threaded fastener into a
workpiece and comprising a power-rotated fastener driver, a finder
telescoped over said driver having an end portion sized to
telescope over and seat against a fastener, first means for
supporting said finder for movement between extended and retracted
positions along said driver, second means for urging said finder to
and for normally keeping said finder in said extended position, a
holder movable between pick-up and delivery stations and being
disposed in said delivery station when said finder is in said
normal extended position, said holder receiving a fastener when in
said pick-up station and thereafter moving to said delivery station
and retaining the fastener in telescoping relation with said end
portion of said finder, said finder being moved toward said
retracted position upon pressing the telescoped fastener against
the workpiece and then being urged back to said normal extended
position upon being released from the driven fastener, third means
responsive to movement of said finder toward said retracted
position for causing said holder to move from said delivery station
to said pick-up station to receive a new fastener and responsive to
return movement of said finder toward said normal extended position
to cause said holder to move back toward said delivery station with
a new fastener, and fourth means associated with said holder and
operable as said holder is moved back toward said delivery station
to first cause said finder to retract and thereby enable the new
fastener to be placed in line with said end portion of said finder
and thereafter to cause said finder to extend and telescope over
the new fastener.
13. A machine as defined in claim 12 in which said third and fourth
means comprises a pivoted lever, a cam associated with said holder
for causing said lever to rock back and forth as said holder is
moved from said pick-up station to said delivery station, a link
extending between said lever and said finder and operable to cause
said finder to move back and forth between said extended and
retracted positions when said lever is rocked back and forth, a
lost-motion connection between said finder and said link to enable
said finder to move between said retracted and extended positions
during and after driving of the fastener without imparting motion
to said lever, a valve carried by said lever and normally held in a
closed position by said link, said link allowing said valve to open
only when said finder is moved toward said retracted position
during driving of the fastener, said link closing said valve when
said finder returns to said extended position after driving of the
fastener, and means responsive to said valve for moving said holder
from said delivery station toward said pick-up station as said
valve is opened and for returning said holder from said pick-up
station toward said delivery station as said valve is closed.
14. A machine for automatically driving a threaded fastener and
comprising a power-rotated fastener driver, a tubular finder
telescoped over said driver and having an end portion sized to
receive a fastener, and mechanism for transferring a fastener from
a pick-up station to a delivery station where the fastener is in
axial alinement with said finder, said mechanism comprising a pair
of opposed jaws adapted to hold a fastener, and means supporting
said jaws for final movement into said delivery station along a
path extending generally radially of said finder and for initial
movement out of said delivery station along a different path
extending generally axially of said finder.
15. A machine as defined in claim 14 in which said means comprise a
shiftable carriage which supports said jaws for movement between
said stations and also for movement between open and closed
positions, a main support having a cam track with a first portion
extending generally radially of said first and a second portion
extending generally axially of said finder, a follower on said
carriage, and means for keeping said follower in engagement with
said first portion of said cam track when said carriage is shifted
to effect final movement of said jaws into said delivery station
and for keeping said follower in engagement with said second
portion of said cam track when said carriage is shifted to effect
initial movement of said jaws out of said delivery station.
16. A machine as defined in claim 15 further including a spring
associated with said jaws and operable to apply spring pressure to
the jaws to hold the jaws in their closed position during their
initial movement from said pick-up station toward said delivery
station, means for releasing the spring pressure from said jaws
during the final movement of the jaws into said delivery station,
means on said support for engaging said jaws and clamping the jaws
in their closed position during said final movement and while the
jaws are in said delivery station, and said jaws being shifted out
of clamping engagement with said clamping means upon initial
movement of said jaws out of said delivery station whereby the jaws
are free to open and move axially along said finder.
17. A machine for automatically driving a screw into a workpiece
and comprising a power-rotated screw driver, a finder telescoped
over said driver and having an end portion adapted to telescope
over and seat againt the head of a screw, means for supporting said
finder for movement between extended and retracted positions along
said driver, means for urging said finder to and for normally
keeping said finder in said extended position, a pair of opposed
jaws movable between a closed position to hold the shank of a screw
and an open position to release the shank, means mounted said jaws
for movement between pick-up and delivery stations, said jaws
receiving a screw at said pick-up station and holding the screw
shank while moving said screw to said delivery station for
telescoping of the screw head into the end portion of the extended
finder, means for keeping said jaws in said closed position on the
screw shank as said screw first engages said workpiece whereby the
jaws continue to hold the screw shank during initial threading of
said screw into said workpiece, means for enabling said jaws to
move to said open position during continued threading of said screw
and as said finder moves to said retracted position, and means for
moving the opened jaws to said pick-up station.
18. A machine as defined in claim 17 further including means
associated with said jaws for causing said finder to move from said
extended position toward said retracted position and then back to
said extended position as said jaws move from said pick-up station
to said delivery station.
19. A machine as defined in claim 18 in which said last-mentioned
means are responsive to movement of said finder toward said
retracted position during driving of the screw and cause said jaws
to shift toward said pick-up station as an incident to such
movement, said last-mentioned means also being responsive to
movement of said finder toward said extended position after driving
of the screw and causing said jaws to shift toward said delivery
station as an incident to such movement.
20. A machine as defined in claim 17 further including means
supporting said jaws for final movement into said delivery station
along a path extending generally radially of said finder and for
initial movement out of said delivery station along a path
extending generally axially of said finder.
21. A machine as defined in claim 17 further including a spring for
holding said jaws in said closed position as said jaws are moved
from said pick-up station toward said delivery station, means for
disabling said spring and releasing pressure from the jaws during
final movement of the jaws into said delivery station, means for
engaging said jaws and clamping the jaws in their closed position
during said final movement and while the jaws are in said delivery
station, said jaws being shifted out of clamping engagement with
said clamping means upon initial movement of said jaws out of said
delivery station, and means for enabling said spring and
re-applying the spring pressure to said jaws as the jaws move into
said pick-up station.
22. A machine for automatically driving a threaded screw into a
workpiece and comprising a main support, a power-rotated screw
driver mounted on said support, a tubular finder telescoped over
said driver and having an end portion adapted to telescope over and
seat against the head of a screw, means for supporting said finder
for movement between extended and retracted positions along said
driver, means for urging said finder to and for normally keeping
said finder in said extended position, a pair of opposed jaws
movable between a closed position to hold the shank of a screw and
an open position to release the shank, a carriage pivotally
mounting said jaws for movement between said positions and also
mounting said jaws on said main support for movement between
pick-up and delivery stations, said jaws receiving a screw at said
pick-up station and holding the screw shank while moving said screw
to said delivery station, means for applying spring pressure to
said jaws during initial movement of said jaws toward said delivery
station thereby to keep the jaws closed on the screw shank, means
coacting between said carriage and said support for causing said
jaws to move along a path extending generally radially of said
finder during final movement of said jaws into said delivery
station, means operable during said final movement for shifting
said finder from said extended position toward said retracted
position and then back to said extended position whereby the screw
is moved into axial alinement with said finder by said jaws and
then is telescoped into and seated within said finder as the latter
returns to said extended position, means operable during said final
movement of said jaws into said delivery station for releasing said
spring pressure and for engaging said jaws to clamp the latter
closed while the jaws are in said delivery station, means
responsive to movement of said finder toward said retracted
position during initial driving of said screw for causing said jaws
to move out of said delivery station and return to said pick-up
station, said coating means between said carriage and said support
causing initial movement of said jaws out of said delivery station
along a path extending generally axially of said finder, said
clamping means freeing said jaws for movement to said open position
as the jaws are moved along said axial path whereby the jaws
release the screw shank and move axially alongside said finder,
means for re-applying said spring pressure to said jaws as the jaws
move into said pick-up station thereby to close the jaws, and means
responsive to movement of said finder to said extended position
after driving of the screw and operable to cause said jaws to move
from said pick-up station to said delivery station.
Description
BACKGROUND OF THE INVENTION
This invention relates generally to a machine for automatically
driving threaded fasteners such as screws into a workpiece. More
particularly, the invention relates to a machine of the type which
includes a driving gun with a power-rotated screwdriver, a finder
associated with the driver, and mechanism for transferring screws
one at a time from a pick-up station to a delivery station where
the screw is placed in the finder preparatory to being driven. The
finder of such a machine keeps the screw in alinement with the
driver and enables the driver to move into driving engagement with
the head of the screw.
Automatic machines of the foregoing type are disclosed in my U.S.
Pat. Nos. 3,279,045 and 3,675,302. In these machines, the driving
gun is mounted on a supporting bracket and is automatically
reciprocated toward and away from the workpiece to effect driving
of the screws. In another type of automatic machine, the driving
gun is held in the hand of the operator and is manually moved
toward and away from the workpiece in order to drive the screw. A
very widely used hand-held gun is of the semi-automatic type in
which the screws are not fed automatically to the finder but
instead are manually started into the workpiece and then are driven
home by the power-rotated driver. Such a gun includes a
comparatively simple tubular finder which is telescoped over the
driver and which is urged to and normally disposed in an extended
position so as to telescope over the head of the screw. During
driving of the screw, the screw head presses against the finder and
moves the latter to a retracted position along the driver. When the
driver is released from the driven screw, the finder automatically
returns to its extended position preparatory to telescoping over
the next screw.
SUMMARY OF THE INVENTION
One of the aims of the present invention is to provide a new and
improved automatic fastener driving machine which is particularly
adapted for hand-held operation and which is simpler in
construction and more trouble-free in operation than prior
automatic hand-held machines.
Another object is to provide an automatic machine having a
hand-held gun which is adapted to drive relatively short screws at
comparatively high speeds.
An important object is to provide an automatic fastener driving
machine which may utilize the relatively inexpensive semiautomatic
driving gun that is presently available, the machine being capable
of delivering each screw rapidly to and holding the screw precisely
in the comparatively simple tubular finder of such a gun and being
capable of driving the screw after the finder has been retracted
through only a very short stroke.
A more detailed object of the invention is to provide an automatic
fastener driving machine in which a normal retract-extend motion of
the finder is used to control the movement of the mechanism for
transferring the screws from the pick-up station to the finder.
Another object is to utilize the motion of the transfer mechanism
to first retract the finder and enable the screw being delivered to
be placed in line with the finder, and then to re-extend the finder
into telescoping relation with the newly delivered screw.
The invention further resides in the novel construction, mounting
and movement of the transfer mechanism to enable the mechanism to
place the screw in line with the finder, to hold the screw in a
stable position in the finder during initial driving of the screw,
and then to retract clear of the finder and the screw before
obstructing further driving of the screw.
Still another object is to provide a novel transfer mechanism
having a pair of opposed jaws which are uniquely controlled to
tightly grip, loosely hold and then completely release the screw at
appropriate times during the machine cycle.
Another object of the invention is to provide a unique unit for
receiving the screws from a remote supply and for delivering the
screws rapidly to the pick-up station adjacent the driving gun,
such delivery being effected by blowing the screws through a
flexible tube which extends between the unit and the gun.
A related object is to blow the screws through the delivery tube
while keeping the screws properly oriented even though the screws
may be of such small size as to tumble within the tube.
The invention also resides in the provision of a novel shuttling
cartridge which is adapted to carry a small screw through the tube
to keep the screw properly oriented, the cartridge discharging the
screw at the pick-up station and then traveling reversely through
the tube to receive the next screw from the main supply.
These and other objects and advantages of the invention will become
more apparent from the following detailed description when taken in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a new and improved automatic
fastener driving machine incorporating the unique features of the
present invention.
FIG. 2 is a fragmentary side elevation of the driving gun and parts
of the transfer mechanism and showing the gun and the transfer
mechanism as positioned preparatory to the start of the cycle.
FIG. 3 is a side elevation of parts of the transfer mechanism.
FIG. 4 is a fragmentary cross-section taken substantially along the
line 4--4 of FIG. 2.
FIG. 5 is an enlarged fragmentary cross-section taken substantially
along the line 5--5 of FIG. 2.
FIG. 6 is a fragmentary cross-section taken substantially along the
line 6--6 of FIG. 5 but showing parts as positioned during initial
contact of the screw with the workpiece.
FIG. 7 is a fragmentary cross-section taken substantially along the
line 7--7 of FIG. 6.
FIG. 8 is a fragmentary cross-section taken substantially along the
line 8--8 of FIG. 6.
FIG. 9 is a fragmentary cross-section taken along the line 9--9 of
FIG. 5 but showing parts in still further moved positions just
after initial driving of the screw.
FIG. 10 is a rear elevation of parts shown in FIG. 9.
FIG. 11 is a view somewhat similar to FIG. 2 but on an enlarged
scale and showing the parts as the transfer mechanism returns to
the pick-up station to receive a new screw.
FIG. 12 is an enlarged rear elevation of parts shown in FIG.
11.
FIG. 13 is an enlarged side elevation of parts shown in FIG. 11 but
showing the parts located in the pick-up station and receiving a
new screw.
FIG. 14 is a rear elevation of parts shown in FIG. 13.
FIG. 15 is an enlarged side elevation of parts which appear in FIG.
2, the parts being shown in a moved position.
FIG. 16 is a view similar to FIG. 11 but showing the parts during
initial advance of the new screw from the pick-up station.
FIG. 17 is an enlarged rear elevation of parts shown in FIG.
16.
FIGS. 18 and 19 are views generally similar to FIG. 6 but showing
successive positions of the parts during the final advance of the
new screw from the pick-up station.
FIG. 20 is an enlarged elevational view of parts of the screw
feeding and delivery unit shown in FIG. 1.
FIG. 21 is a view similar to FIG. 20 but shows certain parts in
moved positions.
FIG. 22 is an enlarged fragmentary cross-section taken
substantially along the line 22--22 of FIG. 20.
FIG. 23 is an enlarged fragmentary cross-section taken
substantially along the line 23--23 of FIG. 21.
FIG. 24 is a view generally similar to FIG. 23 but illustrates a
modified feeding and delivery unit in which the screw is carried
through the tube by a cartridge.
FIG. 25 is a perspective view of the cartridge.
FIG. 26 is a view which shows the cartridge and the screw arriving
at the pick-up station for delivery of the screw into the jaws of
the transfer mechanism.
GENERAL ORGANIZATION OF THE MACHINE
As shown in the drawings for purposes of illustration, the
invention is embodied in a machine 30 for automatically driving
threaded fasteners such as screws 31 into holes in a workpiece 33
which herein is held in a horizontal plane by a suitable fixture
34. The machine includes a driving gun 35 which, in this instance,
may be held in the hand of the machine operator and maneuvered to
any selected position over the workpiece, the gun being manually
moved downwardly to drive the screw and then returned upwardly out
of engagement with the screw. If the workpiece is disposed in other
than a horizontal plane, the operator may turn the gun at right
angles to the workpiece and then drive the screws by moving the gun
toward and away from the workpiece. It should be recognized,
however, that certain principles of the invention are applicable to
a machine having a driving gun mounted on a supporting bracket and
adapted to be reciprocated automatically by a power actuator.
Machines of this type are disclosed in my aforementioned
patents.
The driving gun 35 of the machine 30 is one of those popular guns
which are presently made available to the market in different
models by several manufacturers and which conventionally have been
used extensively to drive screws in a semi-automatic operation.
That is, guns similar to the gun 35 have been widely used to drive
the screws home after the operator has first started the screws
into the workpiece with his fingers. In general, the gun 35 is of
the so-called push-to-start type and includes an elongated barrel
36 which houses a rotary air motor (not shown) adapted to rotate a
driver such as a screwdriver bit 38 (FIGS. 6 and 7) having a flat
blade 39 sized to fit into the slotted heads of the screws 31. The
bit is telescoped into and projects downwardly out of the barrel 36
and its lower end portion is telescoped into a tubular sleeve or
finder 40 which holds the head of the screw in alinement with the
blade while the blade seeks and moves into driving engagement with
the screw head.
Except for the provision of a ring 41 (FIG. 7) whose purpose will
be explained subsequently, the finder 40 is identical to the
finders presently being used on conventional semi-automatic guns.
As shown in FIG. 7, the finder is telescoped slidably into the
lower end portion of the barrel 36 and over the lower end portion
of the driver bit 38 and is keyed against rotation by a set screw
43 threaded into the barrel and extending into a slot 44 in the
upper end portion of the finder. A coil spring 45 is telescoped
into the barrel and is compressed against the upper end of the
finder so as to urge the finder downwardly to a normal extended
position (see FIG. 2) relative to the blade 39 of the bit 38. When
the finder is in its extended position, its lower end portion
projects downwardly beyond the blade and is adapted to telescope
over the head of the screw 31 to hold the screw in a driving
position in line with the bit. The lower end of the finder is
formed with a counterbore 46 (FIG. 7) whose side wall closely
encircles the screw head and whose top wall or "roof" defines a
downwardly facing shoulder adapted to seat against the upper side
of the screw head. Accordingly, the counterbore captivates the
screw head against radial and upward movement relative to the
finder and helps keep the head in axial alinement with the bit 38
so that the blade 39 may telescope into the slot in the head.
Driving of the screw 31 is effected by moving the gun 35 downwardly
while the screw head is telescoped into the counterbore 46 of the
finder 40. When the screw is first pressed against and stopped by
the workpiece 33, the screw head bears against the roof of the
counterbore and momentarily stops downward movement of the finder.
With continued downward movement of the gun, the barrel 36 and the
driver bit 38 move downwardly relative to the stopped finder and
thus the latter assumes an upwardly retracted position (FIG. 6)
with respect to the bit and exposes the end of the blade 39. As the
finder approaches its retracted position, the blade contacts the
screw head and results in the application of upward pressure on the
bit 38. Such pressure causes opening of an air valve (not shown) to
effect the delivery of pressurized air to the rotary motor of the
gun 35 through a line 47 (FIG. 1) leading to the motor. The bit
thus begins rotating and moves into driving engagement with the
screw so as to thread the latter into the workpiece. During driving
of the screw, the barrel 36, the bit 38 and the finder 40 all move
downwardly in unison with the screw until the screw is driven to
its final home position in the workpiece. The gun 35 then is lifted
upwardly away from the screw and, as an incident thereto, the
rotary motor is stopped automatically and the finder 40 is returned
to its normal position (FIG. 2) by the spring 45.
THE INVENTION IN GENERAL
In one of the important aspects, the present invention contemplates
the utilization of a conventional driving gun 35 of the above
character in a machine 30 having a relatively simple and compact
transfer mechanism 50 (FIG. 3) which not only delivers the screws
31 automatically into the tubular finder 40 but which also holds
each screw telescoped within the finder and in alinement with the
bit 38 during initial threading of the screw into the workpiece 33.
As a result of the unique delivery and holding action of the
transfer mechanism, the screws may be automatically placed in the
conventional but difficult-to-load finder 40 and are maintained
under extremely stable control during the critical period of
initial threading.
THE TRANSFER MECHANISM
More specifically, the transfer mechanism 50 is mounted within a
main support or housing 51 which herein is defined in part by a
pair of vertically extending and horizontally spaced side plates 53
and 54 located at the rear side of the gun 35. Cradles 55 and 56
(FIG. 2) on the front of the housing 51 serve to support the upper
portion and mid-portion, respectively, of the gun barrel 36 while
the lower portion of the barrel is secured to the housing by means
to be described subsequently. An elastic band 57 is stretched
around the upper portion of the barrel and is anchored to the upper
cradle 55 to press the barrel tightly into the cradle. Axial
movement of the barrel is restricted by a washer 59 which is fitted
into a circumferentially extending groove 60 in the barrel and
which is anchored to a vertically extending screw 61. The latter is
threaded into the upper cradle and may be adjusted vertically to
bring the washer into alinement with the grooves of different
models of semi-automatic guns.
The transfer mechanism 50 includes a holder which herein is formed
by a pair of opposed jaws 63 adapted to receive a screw 31 at a
pick-up station 64 (FIG. 13) and then move downwardly and forwardly
to a delivery station 65 (FIGS. 2 and 18) to place the screw in its
driving position in telescoping relation with the finder 40. In
addition to moving between the pick-up and delivery stations, the
jaws are mounted to swing between closed and open positions (FIGS.
14 and 10), in which the jaws hold and release the screw shank. The
screw is delivered to the jaws while the jaws are disposed in the
pick-up station 64 and are in their closed positions (see FIGS. 13
and 14). For this purpose, a flexible plastic tube 66 extends into
the housing 51 and has its lower or delivery end 67 located in the
pick-up station 64. Just after the jaws have been returned upwardly
and rearwardly to the pick-up station, a screw is blown shank-first
through the tube by pressurized air and moves between and is held
by the jaws for subsequent transfer to the delivery station 65.
Insertion of the screws into and blowing of the screws through the
tube is effected by a feeding and delivery unit 70 (FIG. 1 and
FIGS. 20 to 23) which will be described subsequently.
In this instance, each jaw 63 includes a generally upright arm 71
(FIGS. 9 and 10) whose lower end is formed with an upper
quarter-tubular boss 73 and a lower semi-tubular finger 74 of
reduced diameter, the boss and the finger being joined by a
downwardly tapering half-cone 75. When the jaws are closed and are
positioned in the delivery station 65 as shown in FIG. 5, the
bosses 73 loosely embrace the rear side of the finder 40, the screw
head rests against the inner surfaces of the half-cones 75, and the
fingers 74 encircle and hold the screw shank.
To mount the jaws 63 to move between the pick-up and delivery
stations 64 and 65 and also between their open and closed
positions, the transfer mechanism 50 includes a movable carriage
which is located between the side plates 53 and 54 of the housing
51. Herein, the carriage is of one-piece construction and is formed
by two horizontally spaced and vertically extending carrier members
76 (FIGS. 3, a and 10) whose rear sides are joined by an integral
strap 77. Each carrier member is formed with a downwardly
projecting lower leg 79 (FIG. 9) and with an upwardly and outwardly
curved upper leg 80. Formed on the upper end portion of the lower
leg of each carrier member is a tubular knuckle 81 which is
sandwiched between similar knuckles 83 on the upper end of the
adjacent jaw 63. A pin 84 is telescoped through each set of alined
knuckles and mounts the jaw to swing laterally between its open and
closed positions on the associated carrier member.
As shown in FIGS. 3, 9 and 17, a roller follower 85 is journaled
intermediate the ends of the upper leg 80 of each carrier member 76
while a similar follower 86 is journaled at the lower end of each
lower leg 79. The upper and lower followers 85 and 86 are adapted
to ride within upper and lower cam tracks 87 and 88 (FIGS. 16 and
17), respectively, which are defined by slots formed in the inner
sides of the side plates 53 and 54 of the housing 51, the lower set
of cam tracks being offset downwardly and forwardly from the upper
set. The followers and the tracks coact the one another to guide
the carrier members 76 and the jaws 63 as the latter are moved back
and forth between the pick-up and delivery stations 64 and 65.
Each of the upper cam tracks 87 extends downwardly, then downwardly
and forwardly, and then again downwardly upon progressing from top
to bottom. The sides of each upper track parallel one another
throughout the length of the track and are spaced apart by a
distance corresponding substantially to the diameter of the
adjacent upper follower 85. Thus, the upper followers 85 are
captivated to travel along the same path as the jaws 63 advance
downwardly and forwardly from the pick-up station 64 to the
delivery station 65 and as the jaws return upwardly and rearwardly
from the delivery station to the pick-up station. The lower cam
tracks 88, however, are shaped to cause the lower followers 86 to
travel along different paths during the advance and return of the
jaws, such different paths being followed for an important purpose
to be explained subsequently.
As shown in FIG. 9, each lower cam track 88 includes an upper,
downwardly extending portion whose width corresponds generally to
the diameter of the associated follower 86 so that the follower
will travel along the same path both when moving downwardly and
upwardly in the upper portion. Below the upper portion, each lower
cam track 88 widens out to a dimension significantly greater than
the diameter of the follower 86 and includes a lower edge which
extends first downwardly and forwardly at a rather steep slope and
then progresses forwardly in a direction extending substantially
radially of the finder 40. The radially extending portion of the
lower edge of the lower cam track 88 is indicated by the reference
numeral 90 in FIGS. 9 and 13 and is located adjacent the lower end
of the track. When the jaws 63 are advanced downwardly and
forwardly to the delivery station 65, each lower follower 86 rides
along the lower edge of the associated lower track 88. During the
return of the jaws to the pick-up station 64, each lower follower
86 travels along the upper edge of its lower track 88. Herein, the
upper edge includes a vertical portion 91 (FIGS. 9 and 13) which is
located adjacent the lower end of the track 88 and which extends
axially of the finder 40. The vertical portion 91 merges with a
generally upwardly and rearwardly extending portion which, in turn,
leads to the upper portion of the track.
In order to move the jaws 63 back and forth between the pick-up and
delivery stations 64 and 65, an air cylinder 93 (FIGS. 1, 2 and 4)
is secured to the upper end of the housing 51 and includes an
elongated rod 94 which is adapted to be reciprocated downwardly and
upwardly when pressurized air is admitted into the upper and lower
ends of the cylinder through lines 95 (FIG. 2). The lower end of
the rod is connected to a block 96 which is guided for up and down
movement by slots 97 (FIG. 4) formed in the inner sides of the side
plates 53 and 54 of the housing 51. Downwardly and forwardly curved
links 99 are pivotally connected at their upper ends to the block
as indicated at 100 and are pivotally connected at their lower ends
at 101 to the upper ends of the upper legs 80 of the carrier
members 76. Thus, downward advance of the rod 94 causes the carrier
members 76 and the jaws 63 to move downwardly and forwardly to the
delivery station 65 while upward retraction of the rod returns the
jaws upwardly and rearwardly to the pick-up station 64. During the
advance of the jaws, the rod 94 acts through the curved links 99
and the curved legs 80 of the carrier members 76 to apply to the
carrier members a counterclockwise force which tends to rock the
carrier members counterclockwise about the upper followers 85 so as
to keep the lower followers 86 pressed against the lower edges of
the lower cam tracks 88. Conversely, the rod 94 applies a clockwise
force to the carrier members as the jaws are returned and thus the
jaws are rocked clockwise about their upper followers to cause the
lower followers 86 to travel along the upper edges of the lower cam
tracks 88.
RETRACTING THE FINDER TO PLACE THE SCREW
The jaws 63 begin moving downwardly and forwardly from the pick-up
station 64 with the new screw 31 immediately after the previous
screw has been driven and the gun 35 has been lifted upwardly to
enable the finder 40 to return to its normal extended position
relative to the blade 39. One of the important features of the
invention is that movement of the jaws 63 from the pick-up station
64 to the delivery station 65 causes the extended finder 40 to
momentarily move upwardly to its retracted position to enable the
screw 31 to be moved past the finder and placed in its driving
position beneath and in line with the finder. Thereafter, the
finder is moved downwardly to its extended position and
automatically telescopes downwardly over the head of the newly
delivered screw.
Momentary retraction of the finder 40 is effected through the
provision of a linkage 103 (FIG. 6) which is connected to the
finder 40 and which herein is adapted to be actuated by one of the
lower followers 86 as the carrier members 76 shift downwardly and
outwardly to move the jaws 63 to the delivery station 65. Part of
the linkage 103 is formed by the aforementioned ring 41 on the
finder 40, the ring being telescoped over and anchored rigidly to
the finder. Underlying the ring is an inwardly projecting
horizontal finger 104 (FIGS. 6 and 7) which is formed on the lower
end of a vertically extending link or lift bar 105. The latter is
guided for free up and down sliding in a hole 106 in a bracket 107
which is anchored to the side plates 53 and 54 of the housing 51
and which includes a semicircular cradle or strap 109 for anchoring
the lower end portion of the gun barrel 36 to the housing.
The upper end of the lift bar 105 is formed with an outwardly
projecting horizontal finger 110 (FIGS. 6 and 7) which coacts with
a member such as a bellcrank lever 111 having a generally
horizontal arm 113 disposed in underlying relation with the finger
110 and normally resting against a stop 114 on the upper end of the
bracket 107. A connection between the finger 110 and the bellcrank
111 is established by a screw 115 threaded into the finger and
bearing against a ball 116 carried by the bellcrank arm 113.
As shown in FIG. 6, the bellcrank 113 is located on the outer side
of the side plate 53 and is mounted to a pivot about a horizontal
pin 117 connected to the side plate. The bellcrank includes a
generally vertical arm 119 whose inner side rigidly supports a lug
120 (FIGS. 18 and 19) which extends into the housing 51 through an
opening 121 formed through the side plate 53. The lug is disposed
in the path traveled by the adjacent lower follower 86 when the
jaws 63 are advanced downwardly and forwardly from the pick-up
station 64 to the delivery station 65.
During the final portion of such advance, the lower followers 86
ride along the generally radially extending portions 90 of the
lower cam tracks 88 and cause the jaws 63 to move the screw 31
generally radially toward the finder 40. Upon entering the radial
portion 90, the follower 86 adjacent the side plate 53 engages the
rear side of the lug 120 and then passes under the lug so as to
rock the bellcrank 111 clockwise (see FIG. 18), the follower thus
acting as a cam. As an incident to such rocking, the ball 116 acts
through the screw 115 to raise the lift bar 105 upwardly in the
hole 106 and cause the lower finger 104 to bear against and lift
the ring 41. As a result, the finder 40 is raised to its retracted
position against the bias of the spring 45 and is shifted clear of
the advancing screw 31 so that the latter can make its final radial
approach to its driving position beneath the finder. As the screw
reaches such position, the lower follower 86 moves into the end of
the lower cam track 88 and passes from beneath the lug 120 to free
the bellcrank 111 for counterclockwise rocking. Accordingly, the
spring 45 is able to expand and thus snaps the finder 40 back
downwardly to its extended position (see FIG. 19) to cause the end
portion of the finder to telescope downwardly over and seat against
the screw head while the jaws 63 continue to hold the screw shank.
Thus, the momentary retraction of the finder during delivery of the
screw enables the screw to be placed beneath the finder while the
subsequent extension of the finder enables the finder to telescope
over the screw head.
CONTROLLING THE RETURN AND ADVANCE OF THE TRANSFER MECHANISM
Further in accordance with the invention, the normal retract-extend
motion undertaken by the finder 40 just before and after driving of
the screw 31 is used to advantage to initiate back and forth
movement of the jaws 63 between the pick-up and delivery stations
64 and 65. Herein, this is achieved by using the ball 116 as a
valve which switches between open and closed states or positions to
cause the creation of pneumatic signals for controlling the flow of
air through the lines 95 and to the ends of the cylinder 93.
As shown in FIG. 6, the ball 116 is located within a hole 121
formed within and opening out of the upper side of the upper arm
113 of the bellcrank 111. The hole 121 is adapted to communicate
with a horizontal passage 123 which is formed in the arm 113 and
which communicates with a flexible line 124 by way of a fitting
125. A flow of pressurized air is directed continuously into the
line 124.
When the finder 40 is in its normal extended position preparatory
to a screw 31 being driven, the ring 41 bears downwardly against
the lower flange 104 of the lift bar 105 as shown in FIG. 2 and in
phantom in FIG. 6. Thus, the screw 115 on the upper finger 110
presses downwardly against the valve ball 116 to seat the ball
against the bottom of the hole 121. The ball thus closes off the
passage 123 to prevent any air from escaping out of the line
124.
As the screw 31 is initially pressed against the workpiece 33, the
finder 40 retracts with its normal motion and pulls the ring 41
upwardly from the lower finger 104 of the lift bar 105 (see FIG.
6). Accordingly, the lift bar no longer is captivated against
upward movement and no longer presses against the valve ball 116.
Thus, the pressure within the passage 123 forces the ball and the
lift bar upwardly and unseats the ball to allow air to escape out
of the line 124 through the hole 121. The flow of air through the
line results in actuation of a control valve (not shown) which
dumps pressure from the upper end of the cylinder 93 and admits
pressurized air into the lower end of the cylinder. Accordingly,
the rod 94 is retracted and begins shifting the jaws 63 upwardly
and rearwardly toward the pick-up station 64 immediately upon
retraction of the finder. The lower end of the cylinder remains
pressurized as long as the finder is in its retracted position and
thus the jaws are moved to and held in the pickup station during
driving of the screw. As the jaws reach the pick-up station, a
probe 126 (see FIGS. 11 and 15) on the block 96 telescopes into and
closes off a line 127 which extends into the housing 51 and which
also receives a flow of pressurized air. Closure of the end of the
line 127 by the probe 126 produces a pneumatic signal which is
routed to the feeding and delivery unit 70 to cause another screw
31 to be blown through the tube 66 and into the fingers 74 of the
jaws 63 (see FIG. 13).
When the screw 31 being driven has been completely tightened, the
gun 35 is lifted away from the screw to enable the finder 40 to
spring downwardly to its normal extended position. During the final
part of such movement, the ring 41 once again bears against the
lower finger 104 (FIGS. 6 and 7) of the lift bar 105 to cause the
screw 115 on the upper finger 110 to press the ball 116 downwardly
to its closed position in the hole 121. The flow of air through the
line 124 thus is interrupted so as to produce a signal causing the
cylinder control valve to de-pressurize the lower end of the
cylinder 93 and to admit pressurized air into the upper end of the
cylinder. Accordingly, the rod 94 is extended to advance the jaws
63 downwardly and forwardly toward the delivery station 65 in order
to place a new screw 31 in the finder 40. The upper end of the
cylinder remains pressurized to keep the jaws in the delivery
station and in holding relation with the screw shank until the
screw is pressed against the workpiece 33 to once again effect
retraction of the finder and opening of the valve ball 116.
It will be apparent from the foregoing that the normal retraction
undertaken by the finder 40 as the screw 31 is first pressed
against the workpiece 33 is utilized to initiate return of the jaws
63 to the pick-up station 64 while the subsequent extension of the
finder after completion of the driving operation is used to
initiate advance of the jaws to the delivery station 65.
Importantly, however, the momentary retraction and subsequent
extension undertaken by the finder during delivery of the screw
does not change the position of the valve ball 116 and thus the
advance of the jaws 63 toward the delivery station is not
interrupted by such extension and retraction. As the follower 86
engages the lug 120 to rock the bellcrank 111 clockwise and
momentarily retract the finder 40, the valve ball 116 presses
upwardly against the screw 115 in the upper finger 110 of the lift
bar 105 (see FIG. 18). Thus, the ball 116, the screw 115 and the
lift bar 105 all move upwardly in unison with the finder 40 and,
since the ball and screw are in pressing engagement, the ball
remains in a closed position in the hole 121 to prevent the escape
of air from the line 124. Similarly, the ball 116, the screw 115
and the lift bar 105 all move downwardly in unison when the
follower 86 moves from beneath the lug 120 to enable the spring 45
to extend the finder 40. The ball thus remains seated in the hole
121 as the finder is returned to its extended position. When the
finder is subsequently retracted, however, by pressing against the
screw 31, the ring 41 simply moves upwardly away from the lower
finger 104 of the lift bar 105. This enables the air pressure in
the line 124 to act through the ball 116 and move the lift bar 105
upwardly a short distance relative to the stationary bellcrank 111
so that the ball may open the hole 121 and permit air to bleed from
the line. Accordingly, the ring 41 and the lower finger 104 of the
lift bar 105 constitute a lost-motion connection which enables the
valve ball 116 to remain closed whenever the finder is retracted by
the bellcrank 111 and the lift bar but which enables the bellcrank
to remain stationary and the ball to open whenever the finder is
retracted as a result of the screw 31 being pressed against the
workpiece.
OPENING AND CLOSING THE JAWS
In keeping with another feature of the invention, the jaws 63 of
the transfer mechanism 50 are biased to and are held in their
closed positions in a unique manner which enables the jaws to
tightly grip and maintain precise control over the screws 31 during
the advance of the screw toward the delivery station 65, to
continue to confine and control the screw during initial driving
while permitting turning of the screw, and to easily release the
screw and move axially along the finder 40 upon being initially
returned from the delivery station. Such action is produced by
using spring pressure to keep the jaws closed as they are advanced
toward the delivery station and by releasing the spring pressure
and mechanically clamping the jaws during their final approach into
the delivery station.
More specifically, the spring pressure is applied to the jaws 63 by
a so-called horseshoe spring 129 (FIGS. 9, 10 and 12) which
comprises a substantially U-shaped strip of spring metal adapted to
move into and out of straddling relation with the jaws to apply and
release the pressure. The spring 129 is positioned with its legs
130 located generally on the outboard sides of the jaws and with
its bridge 131 backed by a tang 133 formed integrally with and
depending from the connecting strap 77 of the carrier members
76.
As shown in FIGS. 9 and 14, two links 134 are pivotally connected
by pins 135 to the lower legs 79 of the carrier members 76 and are
pivotally connected by pins 136 to the ends of the legs 130 of the
spring 129, the links being located between the side plates 53 and
54 and the outboard sides of the spring legs. The spring legs 130
receive the pins 136 with a slip-fit and thus are capable of
sliding laterally on the pins and toward and away from the links
134.
The links 134 mount the spring 129 pivotally on the carrier members
76 to swing downwardly between an apply position (FIG. 13) in which
the spring is operably connected to the jaws 63 and a release
position (FIG. 9) in which the spring is disconnected from the
jaws. To effect swinging of the spring between such positions,
supplementary plates 137 (FIGS. 5 and 6) are bolted to the outer
sides of the side plates 53 and 54 adjacent the lower end portions
thereof and each includes a bottom lip 139 which underlies the
lower edge of the adjacent side plate. For the most part, the
inboard edge of each lip 137 is coplanar with the inner side of the
adjacent side plate. The upper end of each lip, however, is formed
with a lug 140 (see FIGS. 5, 6 and 9) which extends inwardly from
the side plate and whose beveled lower edge defines a stop surface
141. In addition, an inwardly extending abutment 143 is formed on
the lower end of each lip and includes a beveled upper edge which
defines a stop surface 144.
When the jaws 63 are in the pick-up station 64, the spring 129 is
located in its apply position shown in FIG. 13 and its legs 130 are
in tight engagement with raised flats 145 on the outboard sides of
the jaws 63 (see FIG. 14). The raised flats 145 are wedged rather
tightly between the spring legs 130 and thus the legs are pressed
against the links 134 which, in turn, are pressed against the
inboard sides of the side plates 53 and 54. Accordingly, the spring
129 is loaded and exerts inward pressure on the jaws 63 to bias the
fingers 74 thereof into the closed position in which the fingers
contact one another and define a tubular chuck for receiving the
shank of the screw 31. As the screw is blown through the tube 66
and into the jaws (see FIGS. 13 and 14), its shank moves between
the fingers and separates the fingers just slightly, the shank thus
being tightly gripped by the spring-loaded fingers.
As the jaws 63 are advanced from the pick-up station 64 to the
delivery station 65, the spring pressure is maintained on the jaws
except during the final approach of the jaws into the delivery
station. Thus, the fingers 74 tightly grip the shank of the screw
31 and provide good control of the screw during its rapid advance
toward the delivery station. Because of the tight grip, such good
control is maintained even if the gun 35 is in an inclined or
horizontal position.
During the final approach of the screw 31 into the delivery station
65, the lower ends of the links 134 engage and are stopped by the
stop surfaces 144 of the abutments 143 on the lips 139 (see FIG.
19). Such stopping causes the links and the spring 129 to pivot
counterclockwise about the pins 135 as the jaws 63 continue their
advance, the spring thus being moved to its release position with
respect to the jaws. With the spring 129 stopped and with continued
advance of the jaws, the raised flats 145 on the jaws move out from
between the spring legs 130 and thus the spring is disconnected
from the jaws and is no longer effective to urge the jaws to their
closed position. Just before the raised flats 145 move out from
between the spring, however, they move between and are mechanically
clamped by the inboard sides 146 of the abutments 143 on the lower
ends of the lips 139 (see FIG. 5). Hence, the abutments keep the
jaws in their closed position while the screw 31 makes its final
approach to the delivery station 65 and is placed in the finder 40.
The fingers 74 thus confine the screw shank and hold the screw in
the finder until such time as the operator starts to drive the
screw.
When the operator presses the screw 31 against the workpiece 33 and
the finder 40 retracts to initiate return of the jaws 63 out of the
delivery station 65, the lower followers 86 move upwardly along the
axial portions 91 of the lower cam tracks 88 and cause the jaw
fingers 74 to move upwardly or axially along the screw shank. The
fingers do not grip the screw shank quite so tightly when the jaws
63 are clamped by the abutments 143 as when the jaws are held
closed by the spring 129. Accordingly, the fingers may slide
upwardly along the shank and the screw may rotate within the
fingers as the fingers initially retract and as the blade 39 begins
driving the screw. The upwardly retracting fingers 74 continue to
confine the shank as the first one or two threads of the screw are
driven into the workpiece and thus the fingers maintain control
over the screw until it is started and is capable of being
controlled solely by the finder 40.
As the fingers 74 begin moving upwardly along the shank of the
screw 31, the raised flats 145 on the jaws 63 begin moving upwardly
from between the abutments 143 (see FIG. 9). As soon as the flats
clear the abutments, the jaws are no longer clamped and, since the
spring 129 is still in its release position, the jaws are free to
swing to their open position and release the fingers 74 from the
screw (see FIG. 10). Such swinging occurs as the half cones 75
first cam against the end of the finder 40. Once open, the jaws 63
remain in their open position as the fingers 74 first retract
upwardly along the finder and then are pulled rearwardly away from
the finder along a path substantially as indicated by the line 147
in FIG. 11.
The jaws 63 stay open until they make their final approach back
into the pick-up station 64. As this time, the ends of the links
134 engage the stop surfaces 141 on the lugs 140 to cause the
spring 129 to pivot downwardly to and stop in its apply position as
the jaws complete their final movement (see FIG. 13). During such
movement, cam surfaces 149 (FIGS. 9 and 13) on the ends of the
raised flats 145 engage the spring legs 130 and close the jaws 63
while simultaneously spreading the legs so that the flats may move
between the legs and place the jaws under spring pressure.
Accordingly, the spring is operably re-connected to the jaws as the
jaws complete their final movement into the pick-up station 64.
A SUMMARY OF OPERATION OF THE GUN AND THE TRANSFER MECHANISM
With the exception of the feeding and delivery unit 70, all of the
basic elements of the machine 30 have now been described. The
following summary of operation has been presented in order to
explain an overall cycle of the machine. At the beginning of each
cycle, the jaws 63 are clamped closed in the delivery station 65 by
the inboard sides 146 of the abutments 143 and hold a screw 31 in
telescoping relation with the finder 40 (see FIGS. 2 and 5). As the
first step in the cycle, the operator manipulates the gun 35 to
press the screw against the workpiece 33. As the gun then is moved
downwardly, the finder begins retracting as shown in FIGS. 6 and 7.
Just as the finder reaches its retracted position, the blade 39
presses against the screw head and starts rotating so as to
initiate driving of the screw.
Movement of the finder 40 toward its retracted position shifts the
rings 41 upwardly away from the lower finger 104 of the lift bar
105 (see FIGS. 6 and 7) and frees the lift bar and the valve ball
116 for upward movement. Accordingly, the air pressure in the
passage 123 unseats the ball from the hole 121 and allows air to
escape from the line 124. This causes the rod 94 to retract and
begin returning the jaws 63 upwardly and rearwardly to the pick-up
station 64.
During the first part of the return, the lower followers 86 ride
along the vertically extending portions 91 of the lower cam tracks
88 (see FIG. 9) and cause the fingers 74 of the jaws 63 to slide
upwardly or axially along the shank of the screw 31. The fingers
thus continue to hold the screw in the finder 40 and maintain
control over the screw until the screw has been started into the
workpiece 33.
As the jaws 63 continue their upward travel, the raised flats 145
move upwardly from between the abutments 143 and free the jaws to
swing to their open position as the half-cones 75 of the jaws cam
against the screw head and the lower end of the finder 40 (see
FIGS. 9 and 10). Thus, the fingers 74 open to release the screw and
to move clear of the finder 40.
Upon opening of the fingers 74, the jaws 63 begin moving rearwardly
away from the finder 40 along the path 147 (FIG. 11) while
continuing their upward movement as the lower followers 86 ride
along the upwardly and rearwardly inclined portions of the lower
cam tracks 88. The jaws then move upwardly into the pick-up station
64. As the jaws approach the pick-up station, the links 134 engage
and stop against the lugs 140 (see FIG. 11) to prevent further
upward movement of the spring 129. During the final return movement
of the jaws, the raised flats 145 move between the legs 130 of the
spring 129 as shown in FIGS. 13 and 14 to operably connect the
spring to the jaws 63. The jaws thus are baised to their closed
position.
Final movement of the jaws 63 into the pick-up station 64 causes
the probe 126 (FIG. 15) to move into and close off the line 127 and
produce a signal for the feeding and delivery unit 70 to blow
another screw 31 through the tube 66. The screw thus shoots through
the tube and lodges between the fingers 74 of the closed jaws (see
FIGS. 13 and 14).
The entire return movement of the jaws 63 from the delivery station
65 to the pick-up station 64 occurs at great speed and takes place
during the time the first screw 31 is being driven into the
workpiece 33 (see FIG. 11). Accordingly, a new screw most usually
will be placed between the jaws 63 in the pick-up station 64 before
the first screw has been completely driven. A certain amount of
time, however, is required for the new screw to be blown through
the tube 66 and into the jaws 63 and the instant the probe 126
first closes off the line 127. To insure that the jaws will not
re-advance toward the delivery station 65 before the required
"blow" time has elapsed, a pneumatic timer (not shown) is set by
the signal which is created when the probe 126 closes off the line
127. The timer automatically times out after the elapse of a
predetermined time interval greater than the maximum required
"blow" time and, until the timer times out, the cylinder 93 is
disabled and cannot advance the jaws toward the delivery station 65
even if an "advance" signal is being produced in the line 124.
Thus, the jaws are prevented from advancing back to the delivery
station until sufficient time has elapsed for the new screw to blow
through the tube and into the jaws.
After the first screw 31 has been driven home, the operator lifts
the gun 35 from the screw and, as an incident thereto, the spring
45 forces the finder 40 to its extended position (see FIG. 16). The
ring 41 engages the lower finger 104 of the lift bar 105 (FIGS. 16
and 17) and shifts the lift bar downwardly to cause the screw 115
on the upper finger 110 to press the valve ball 116 downwardly into
seating engagement with the bottom of the hole 121. With air no
longer escaping from the line 124, the advance signal is produced
and, assuming that the pneumatic timer has timed out, the rod 94 of
the cylinder 93 is extended to start advancing the jaws 63 and the
new screw from the pick-up station 64 to the delivery station 65.
During the major portion of such advance, the spring 129 keeps the
jaw fingers 74 tightly biased around the screw shank so as to
maintain good control over the screw and to prevent the screw from
bouncing. Also, the lower followers 86 ride along the lower edges
of the lower cam tacks 88 during the advance so that the screw will
make a generally radial final approach into the delivery station
65.
Just as the lower followers 86 begin to enter the radial portions
90 of the lower cam tracks 88, one of the followers engages the lug
120 (see FIG. 18) and pivots the bellcrank 111 clockwise. The lift
bar 105 thus is raised upwardly and momentarily lifts the finder 40
to its retracted position to enable the screw 40 to be placed
beneath and in line with the finder. While the finder is lifted,
the links 134 engage and stop against the stop surfaces 144 of the
abutments 143 (see FIG. 19) and prevent further movement of the
spring 129. As the jaws 63 continue their advance, the raised flats
145 move out from between the spring legs 130 and move between the
inboard surfaces 146 of the abutments 143. The spring force thus is
removed from the jaws 63 so that the jaws may open freely when
subsequently returned toward the pick-up station 64. The abutments,
however, continue to hold the jaws in their closed position during
their final advance into the delivery station 65.
As the jaws 63 make their final advance, the lower follower 86
moves past the lug 120 (see FIG. 19) to free the bellcrank 111 for
counterclockwise pivoting and to free the lift bar 105 for downward
movement. At this time, the spring 45 expands and forces the finder
40 downwardly to its extended position and into telescoping
relation with the head of the newly delivered screw 31 (see FIGS. 2
and 19). This completes one operating cycle, and the finder 40 and
the jaws 63 continue to hold the newly delivered screw until such
time as the operator initiates the next cycle by pressing the screw
against the workpiece 33.
A typical operating cycle requires only about 11/2 seconds to
complete. The cycle time will, of course, vary depending upon the
length of the screw 31, the pitch of the screw threads, the
rotational speed of the bit 38, and the reaction time required for
the operator to lift the gun 35 upwardly after driving the screw
home. Once the gun has been lifted, a new screw is delivered to the
finder 40 almost immediately and usually is in place in the finder
before the operator can position the gun over the next hole in the
workpiece 33. Accordingly, screws can be driven at a rapid rate.
The high speed operation of the machine 30 is further enhanced by
the fact that the screw is placed into the lower end of the finder
40 rather than through an opening in the side of the finder as is
the case with many machines. With the screw being placed into the
end of the finder, the vertical spacing between the screw head and
the blade 39 may be reduced so as to enable the blade to press
against the head and begin rotating after the finder 40 has been
retracted through only a very short stroke. The short stroke of the
finder also enables better control of the screw by the finder and
the blade during the critical period of initial threading. Thus,
even relatively short screws may be driven and the gun may be
disposed at any orientation without losing control over any
significant number of screws.
THE FEEDING AND DELIVERY UNIT
The unit 70 for feeding the screws 31 into and blowing the screws
through the tube 66 is shown in FIG. 1 and in FIGS. 20 to 23 and
comprises a housing 160 which supports a power-rotated hopper 161
adapted to store a large supply of screws. Upon leaving the hopper,
the screw proceed one-by-one to the end of a downwardly inclined
track 163 where a positioning mechanism 164 picks up the leading
screw and transfers the screw away from the track for subsequent
placement into the tube 66. The tube is supported by the housing
and leads to the gun 35 through an opening 162 in the housing.
Between the unit 70 and the gun 35, a suspension device (not shown)
supports the tube 66 and the various lines 47, 95, 124 and 127, the
lines leading to a pneumatic control unit (not shown) adjacent the
housing 160.
The positioning mechanism 164 is generally similar to that
disclosed in my copending application Ser. No. 464,627, filed Apr.
26, 1974, and includes a pair of fingers 165 (FIGS. 21 and 22)
which close upon and grip the leading screw in the track when the
fingers are positioned adjacent the end of the track as shown in
FIG. 21. The fingers and the gripped screw thereafter are moved
first outwardly along a path in line with the track and then
upwardly along a right angled path to a position (see FIGS. 20 and
22) in line with and above the inlet end of the tube. After being
opened to release the screw, the fingers are returned reversely to
the track 163 to pick up the next screw.
The mechanism for moving the fingers 165 back and forth and for
effecting the opening and closing movement of the fingers is
explained fully in the aforementioned application and need not be
here described in detail. Briefly, such movements are produced in
response to back and forth rocking of a linkage 166 (FIGS. 20 and
21) which is operably connected to the fingers 165 and which is
secured to a rockshaft 167. The latter is rotatably supported by
the housing 160 and is turned back and forth as the rod 169 of a
pneumatic cylinder 170 is extended and retracted, the cylinder
being fastened to the housing.
In accordance with another feature of the invention, the fingers
deliver the screw 31 to a head 171 (FIGS. 20 to 23) which
subsequently places the screw in the tube 66 and closes off the end
of the tube to enable the screw to be blown through the tube by
pressurized air introduced into the tube through the head. The head
is mounted to move from a first position (FIGS. 20 and 22) in which
the head receives the screw from the fingers 165 and a second
position (FIGS. 21 and 23) in which the head places the screw in
the tube. In moving between its positions, the head travels along a
path whose upper portion coincides with the path followed by the
fingers 165 as the fingers move through the end of their advance
stroke and then move reversely through the first part of their
return stroke.
As shown in FIG. 22, the head 171 comprises a cylindrical member
which is mounted for limited up and down sliding within a hole 173
in a bracket 174, the head being retained in the hole by upper and
lower snap rings 175. A coil spring 176 is telescoped over the head
and is compressed between the underside of the bracket and the
lower snap ring to urge the head downwardly while permitting the
head to slide upwardly within the hole 173.
Formed through the head 171 is an axially extending bore 177 (FIG.
22) within which a tubular fitting 179 is rigidly secured. A
part-holding device in the form of a resiliently yieldable sleeve
180 made of rubber, plastic or the like is telescoped into the bore
and is telescoped over the lower end portion of the fitting, the
lower end portion of the sleeve extending downwardly beyond the end
of the fitting. When the head 171 is in its upper position shown in
FIG. 22, the fingers 165 place the head of the screw 31 into the
lower end portion of the sleeve 180 as the fingers move away from
the track 163 and reach the end of their advance stroke. The sleeve
180 is sized to resiliently grip the screw head and thus holds the
screw after the fingers 165 are opened and are retracted from
beneath the head.
As the fingers 165 retract, the bracket 174 is moved downwardly to
shift the head 171 and the gripped screw 31 toward the
screw-receiving end of the tube 66. A rigid tubular extension 181
(FIG. 22) is telescoped into the tube and is anchored to the
housing 160 by a bracket 183. As the head 171 moves downwardly, its
lower end engages and seals against an O-ring 184 located on the
upper end of the extension 181, the head thus sealing off the upper
end of the tube as shown in FIG. 23. At the same time, the sleeve
180 places the screw 31 into the extension 181. Thereafter,
pressurized air is delivered through a line 185 (FIG. 20) and into
a passage 186 (FIG. 23) which extends through the fitting 179. The
air forces the screw out of the resilient sleeve 180 and shoots the
screw through the tube 66 (see the phantom illustration in FIG. 23)
with high velocity and into the waiting jaws 63 at the pick-up
station 64. The inside diameter of the tube corresponds closely to
the diameter of the screw head and thus the pressurized air can
easily blow the screw through the tube. Because the tube is made of
flexible plastic, the screw is not likely the become jammed in the
tube. If the screw head is slightly oversize or is formed with a
protruding burr, the plastic will yield to allow the screw to pass
through the tube. If the screw should happen to jam, the spring 176
on the head 171 will yield as air pressure builds up in the tube
and will allow the head to move upwardly within the hole 173 and
away from the tube extension 181 to relieve the pressure. Thus, the
spring 176 prevents the air pressure from building up to such a
high value as to blow the screw violently through the tube and
cause possible injury to the operator.
After the screw 31 has been blown through the tube 66, the bracket
174 is shifted upwardly to retract the head 171 away from the
extension 181 to the position shown in FIGS. 20 and 22. Thereafter,
the fingers 165 place a new screw in the sleeve 180 preparatory to
the next cycle.
To support the head 171 for up and down shifting, the bracket 174
is connected to a block 187 (FIG. 22) which, in turn, is mounted
for up and down sliding on a pair of guide rods 189 secured to the
housing 160. Shifting of the head is effected in response to
actuation of the cylinder 170 and, for this purpose, a link 190
(FIG. 20) is secured rigidly to the rockshaft 167 and is pivotally
connected to a second link 191 which extends toward the guide rods
189. The link 191 is pivotally connected to an arm 193 projecting
radially from a hub 194 (FIG. 22) which is mounted to oscillate
back and forth on a pin 195 extending from the housing 160. A
second radially projecting arm 196 also is rigid with the hub and
is pivotally connected to one end of a link 197 whose other end is
pivotally connected to the bracket 174. When the rod 169 is
extended to turn the rockshaft 167 counterclockwise and retract the
fingers 165 away from the head 171, the links 190 and 191 and the
arm 193 rock the hub 194 in a clockwise direction. The arm 196 and
the link 197 thus shift the head 171 downwardly. The head and the
fingers 165 move downwardly in unison for a short distance and then
the fingers move at right angles to the head and toward the track
163 so as to move clear of the head.
When the rod 169 is retracted, the head 171 starts moving upwardly
and the fingers 165 start moving outwardly away from the track 163.
As soon as the head has cleared the fingers, the latter start
moving upwardly and place the screw 31 in the sleeve 180. The
linkage 166 is such that the fingers 165 accelerate with respect to
the head 171 during the time both the fingers and the head are
moving upwardly. Thus, the fingers "catch up" with the head so as
to enable the screw to be placed in the sleeve 180 by the time the
head and the fingers reach the ends of their strokes.
The following described the operation of the feeding and delivery
unit 70 with respect to the operation of the gun 35. At the start
of a cycle, the head 171 is disposed in its upwardly retracted
position and the fingers 165 are holding a screw 31 in the sleeve
180 (see FIGS. 20 and 22). When the finder 40 retracts upon
pressing its screw against the workpiece 33, the signal which is
produced in the line 124 to effect return of the jaws 63 is also
used to initiate extension of the rod 169 of the cylinder 170.
Accordingly, the fingers 165 retract while the head 171 moves
downwardly and seals off the extension 181 of the tube 66 (see
FIGS. 21 and 23).
When the jaws 63 return to the pick-up station 64 and the probe 126
closes off the line 127, the resulting signal in the line sets the
pneumatic timer and simultaneously causes pressurized air to be
delivered into the line 185. Thus, the screw 31 in the sleeve 180
is blown out of the sleeve and through the tube for delivery into
the waiting jaws 63. After sufficient blow time has elapsed, the
pneumatic timer times out to shut off the flow of air through the
line 185. Then, when the signal is produced in the line 124 to
effect advance of the jaws 63, the rod 169 of the cylinder 170 is
caused to retract. This results in upward retraction of the head
171 and simultaneous advancement of the fingers 165 so as to place
a new screw in the sleeve 180.
AN ALTERNATE FEEDING AND DELIVERY UNIT
Parts of a modified machine are shown in FIGS. 24 to 26 wherein
elements corresponding to the elements of the machine 30 are
indicated by the same but primed reference numerals. The modified
machine includes a feeding and delivery unit 70' which is
characterized by the ability to deliver screws 31' of such a size
that the screws might tumble end-for-end within the tube 66' and be
blown head-first into the jaws 63'. Such tumbling is prevented by
blowing the screw through the tube while the screw is captivated in
a holding device or cartridge 210. After releasing the screw at the
pick-up station 64', the cartridge is returned reversely through
the tube by vacuum.
More specifically, the cartridge 210 comprises an elongated tubular
element made of resiliently yieldable material and having an
enlarged upper end 211 whose outside diameter corresponds closely
to the inside diameter of the tube 66'. When the head 171' is in
its upper retracted position, the cartridge 210 is disposed within
a bore 213 (FIG. 24) in the fitting 179' and is held releasably in
the bore by a resiliently yieldable element such as an O-ring 214.
While the cartridge is so positioned, the fingers of the transfer
mechanism place the screw into the open lower end of the cartridge,
the screw head being gripped by the resilient material.
When the head 171' is lowered, the cartridge 210 and the gripped
screw 31' are positioned as shown in FIG. 26 so that the cartridge
is located just above the extension 181' of the tube 66'. As
pressurized air is delivered into the passage 186', the cartridge
is blown out of the bore 213 and shoots into the tube 66' so as to
carry the screw through the tube to the pick-up station 64'. The
length of the cartridge relative to the inside diameter of the tube
is such that the cartridge cannot tumble within the tube and thus
the screw is delivered shank-first to the pick-up station.
When the cartridge 210 arrives at the pick-up station 64' (see FIG.
26), its lower end strikes the upper sides of the jaw fingers 74'
and is abruptly stopped. The screw 31', however, continues to move
by virtue of its momentum. Accordingly, the screw flys out of the
grip of the cartridge and lodges between the jaw fingers 74'. As
the pneumatic timer times out, vacuum is drawn through the line
185', the passage 186' and the tube 66' to suck the cartridge 210
reversely through the tube and to return the cartridge to the bore
213 before the head 171' is retracted upwardly to enable another
screw to be placed in the cartridge.
* * * * *