U.S. patent number 3,563,438 [Application Number 04/781,433] was granted by the patent office on 1971-02-16 for fastener driving tool.
This patent grant is currently assigned to Fastener Corporation. Invention is credited to Richard H. Doyle, Edward J. Novak.
United States Patent |
3,563,438 |
Doyle , et al. |
February 16, 1971 |
FASTENER DRIVING TOOL
Abstract
A fastener driving tool comprising a drive track for guiding
fasteners as they are driven, a driver slidable in said track and
movable on a power stroke to drive fasteners and return stroke in
the opposite direction, pusher means for feeding fasteners into the
lower end of said drive track and movable between a forward
position projecting into said drive track and a rearward position
rearwardly retracted therefrom, initiating a power stroke of the
driver, and means for retracting said pusher means from said drive
track operable to prevent a power stroke of said driver until said
pusher means is clear of said drive track.
Inventors: |
Doyle; Richard H. (Mount
Prospect, IL), Novak; Edward J. (Franklin Park, IL) |
Assignee: |
Fastener Corporation (Franklin
Park, IL)
|
Family
ID: |
25122721 |
Appl.
No.: |
04/781,433 |
Filed: |
December 5, 1968 |
Current U.S.
Class: |
227/8; 227/130;
227/136 |
Current CPC
Class: |
B25C
5/1627 (20130101); B25C 1/041 (20130101); B25C
1/003 (20130101); B25C 1/008 (20130101) |
Current International
Class: |
B25C
5/00 (20060101); B25C 5/16 (20060101); B25C
1/04 (20060101); B25C 1/00 (20060101); B25c
001/04 () |
Field of
Search: |
;227/8,112,130,136 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Custer, Jr.; Granville Y.
Claims
We claim:
1. A fastener driving tool comprising a drive track for guiding
fasteners as they are driven, a pneumatically powered driver in
said drive track movable on a power stroke to drive fasteners and a
return stroke, pusher means for feeding fasteners into said drive
track and movable between a forward position extending into said
drive track and a rearward position rearwardly retracted therefrom,
and fluid control means including a piston slidable in a cylinder,
said piston interconnected with said pusher means for moving the
same and providing valving action for preventing the initiation of
a power stroke of said driver until said pusher means is retracted
from said drive track.
2. The driving tool of claim 1 wherein said control means includes
first motor means for moving said driver on a power and return
stroke and second motor means for moving said pusher means, and
passage means operably interconnecting said first and second motor
means whereby said second motor means normally closes said passage
means preventing a power stroke of said driver until said pusher
means is clear of said drive track.
3. The driving tool of claim 2 including safety valve means
responsive to the position of said drive track relative to a
workpiece movable between a safe and a fire position and operable
upon movement from said safe to said fire position to retract said
pusher means from said drive track, said safety valve means
operable to activate said second motor means to feed a fastener
into said drive track with said pusher means when returned from
said fire position to said safe position.
4. The driving tool of claim 2 wherein said control means comprises
a manual trigger valve operable to open and close said passage
means between said first and second motor means.
5. The driving tool of claim 3 wherein said second motor means
includes valve means operable to open communication between one end
of said passage means and the atmosphere when said safety valve
means is moved from the safe to the fire position.
6. The driving tool of claim 5 wherein said valve means on said
second motor means is operable to close communication between said
one end of said passage means and the atmosphere when said safety
valve means is returned from the fire to the safe position.
7. A fastener driving tool comprising a drive track, a driver
slidable in said drive track, pneumatic motor means operable to
move said driver on a power and return stroke in said drive track,
pusher means operable to move into and out of said drive track to
position fasteners therein to be driven, control valve means for
activating said motor means to initiate a power stroke of said
driver, means for retracting said pusher including a piston
slidably mounted in a cylinder and a valve, said piston operable to
actuate said valve for preventing a power stroke of said driver
until said pusher means is retracted from said drive track.
8. The driving tool of claim 7 wherein said control valve means
includes exhaust passage means in communication between said motor
means and the atmosphere for initiating a power stroke, said
retracting means normally closing said passage means and operable
to open said passage means after retraction of said pusher means
from said drive track.
9. The driving tool of claim 8 wherein said retracting means is
operable to advance said pusher means into said drive track after
said motor means has initiated a return stroke of said driver.
10. A fastener driving tool comprising a drive track for receiving
fasteners, a driver slidable in said drive track and movable on a
power stroke to drive fasteners and a return stroke in an opposite
direction, pusher means movable on a feed stroke from a retracted
position clear of said drive track forwardly to a forward position
extending into said drive track and movable rearwardly on a return
stroke in the opposite direction to said retracted position, first
valve means for initiating a power stroke of said driver and second
valve means associated therewith preventing the initiation of a
power stroke until said pusher means moves on a return stroke to
said retracted position.
11. The driving tool of claim 10 wherein said second valve means
comprises piston means slidable in a bore, and said first valve
means includes passage means intersecting said bore and blocked by
said piston means when said pusher means is in said forward
position.
12. The driving tool of claim 11 wherein said piston means moves to
open communication between said passage means and said bore when
said pusher means is moved to said retracted position.
13. The tool of claim 12 including safety valve means movable
between a safe and a fire position, and means controlled by said
safety valve means to supply pressurized fluid to move said piston
means to retract said pusher means when said safety valve means is
moved from said safe to said fire position.
14. The driving tool of claim 10 wherein said first valve means
includes passage means and a pair of valve members in series
communication in said passage means, each valve member movable
between a first and second position and operable to initiate a
power stroke of said driver only when both valve members are moved
to said second position.
15. The driving tool of claim 10 wherein said second valve means
includes a piston member interconnected with said pusher means and
a second valve member, said first valve means including a valve
member operable between a first and second position to move said
piston member to retract and advance respectively said pusher
means.
16. The driving tool of claim 15 wherein said piston member is
operable to open and close said second valve member upon retraction
and advancement of said pusher means, said second valve member
opening to initiate a power stroke of said driver and said one
valve member operable to initiate a return stroke thereof.
17. The driving tool of claim 16 wherein said piston member is
movable to a third position in response to the absence of fasteners
in said tool to close said second valve member and prevent the
initiation of a power stroke of said driver.
18. The driving tool of claim 17 wherein said first valve means
includes a first valve passage between said piston member and a
pair of valves in series movable between open and closed positions
to connect and disconnect an end of said first valve passage to the
atmosphere.
19. A fastener driving tool comprising a drive track and a driver
slidably disposed therein, motor means for reciprocating said
driver to drive successive fasteners positioned in said drive
track, safety valve means movable on an operating cycle between a
safe and a fire position and operably connected with said motor
means to prevent initiation of a drive stroke of said driver until
said safety valve means has been cycled between said safe and fire
positions, said safety valve means including a workpiece engaging
structure movably mounted adjacent the lower end of said drive
track for movement between a safe position projecting below said
lower end of said drive track and a fire position spaced upwardly
thereof, and reciprocating feeder means for advancing successive
fasteners into said drive track and means operatively
interconnecting said feeder means and said safety valve means for
initiating a feeding stroke of said feeder means in response to
cycling of said safety valve means between said safe and fire
positions.
20. The fastener driving tool of claim 1 wherein said cylinder is
formed with a port therein for cooperation with said piston to
provide said valving action upon movement of said piston to open
and close said port.
21. The fastener driving tool of claim 1 wherein said piston
includes a pair of piston portions having different diameters, at
least one of said piston portions serving as a component for said
valving action.
22. The fastener driving tool of claim 20 wherein said piston
includes an axial stem of reduced diameter between said piston
portions forming a piston chamber movable into and out of
communication with said port.
23. The fastener driving tool of claim 7 wherein said valve
includes a port formed in said cylinder and opened and closed by
said piston.
24. The fastener driving tool of claim 23 wherein said piston
includes portions of different diameters, at least one portion
functioning as a component of said valve for controlling the
operation of said motor means for initiating a power stroke of said
driver.
Description
The present invention relates to a new and improved power operated
fastener driving tool and, more especially, to a tool of the type
capable of driving relatively large fasteners, such as common nails
and the like.
With the increased demand for power driven fastener driving tools
which are capable of handling the larger fasteners, such as 8d
common nails and the like, it is desirable to provide feeding means
for positively feeding or positioning successive nails into the
drive track for driving by the reciprocating driver on a single
power stroke. One of the problems with these types of tools is that
if the pusher means is not fully retracted from the drive track
when a power stroke is commenced, the driver may engage the forward
end portion of the pusher means while in the drive track and cause
severe damage to the tool.
Therefore, it is an object of the invention to provide a new and
improved power driven fastener driving tool.
It is also an object of the invention to provide a new and improved
power driven fastener driving tool which eliminates the foregoing
difficulties of prior tools of this type.
Another object of the present invention is to provide a new and
improved fastener driving tool employing pusher means for feeding
fasteners into the drive track movable between a forward position
projecting into the drive track and a rearward position retracted
therefrom, including means operable to positively retract the
pusher means from the drive track before initiation of a power
stroke of the driver is permitted.
Another object of the present invention is to provide a new and
improved fastener driving tool of the character described employing
means for disabling the tool from firing until the pusher has been
fully retracted from and is clear of the drive track.
Yet another object of the present invention is the provision of a
new and improved fastener driving tool having means for
automatically returning the driver after the completion of a power
stroke and positively advancing another fastener into the drive
track.
Yet another object of the present invention is the provision of a
new and improved fastener driving tool of the character described
having a safety valve means operable to prevent a drive stroke of
the driver until the nosepiece of the tool is pressed against a
workpiece and the pusher means has been fully retracted from the
drive track.
Another object of the present invention is the provision of a new
and improved fastener driving tool employing new and improved
safety valve means operable to initiate the feeding of a new
fastener into the drive track after each power stroke has been
completed.
Yet another object of the present invention is the provision of a
new and improved fastener driving tool employing means for
automatically initiating a power stroke of the driver followed by a
return stroke but preventing the power stroke from commencing until
the pusher means has been positively retracted clear of the drive
track.
Another object of the invention is to provide a new and improved
fastener driving tool of the character described including means
for positively retracting the pusher from the drive track before a
driving stroke is commenced and including plural means for
operating or cycling the tool on successive power strokes.
Another object of the invention is to provide a new and improved
fastener driving tool of the character described in the preceding
object wherein the plural means includes a manually depressible
trigger and presser foot means mounted adjacent the lower end of
the drive track for direct engagement with the workpiece.
Still another object of the invention is the provision of a new and
improved fastener driving tool having means operable to prevent the
initiation of driving strokes when the supply of fasteners in the
tool is exhausted.
These and other objects of the present invention are accomplished
in one illustrative embodiment thereof comprising a power actuated
fastener driving tool having a drive track and a driver slidably
disposed therein for movement on a power stroke and a return stroke
in an opposite direction. Pusher means are provided for feeding
fasteners supplied on a carrier strip one at a time directly into
the drive track. The pusher means is movable between a forward
position, wherein the forward end portion projects into the drive
track, and a rearward or retracted position, wherein the pusher is
completely clear of the drive track. Means are provided for
initiating successive power and return strokes of the driver and
control means are provided for positively retracting the pusher
means from the drive track before a power stroke can commence.
After each power stroke has been completed, the pusher means is
operable to feed another fastener into position in the drive track
and the tool is then ready for its next cycle of operation.
For a better understanding of the present invention, reference
should be had to the following detailed description and the
appended claims, taken in conjunction with the drawings, in
which:
FIG. 1 is a cross-sectional view taken on a longitudinal plane of a
new and improved fastener driving tool constructed in accordance
with the features of the present invention;
FIG. 1a is a transverse cross-sectional view of the magazine
feeding assembly of the tool taken substantially along line 1a of
FIG. 1;
FIG. 2 is a cross-sectional view similar to FIG. 1 illustrating
operative components of the tool in different operative positions
wherein the driver is moving downwardly on a power stroke to drive
a fastener positioned in the drive track;
FIG. 2a is a cross-sectional view similar to FIG. 1a and taken
substantially along lines 2a of FIG. 2;
FIG. 3 is a cross-sectional view similar to FIG. 1 illustrating the
operative components of the tool in another operative position,
wherein the driver is in an upper or rest position after a return
stroke has been completed;
FIG. 3a is a cross-sectional view similar to FIG. 1a taken
substantially along the lines 3a of FIG. 3;
FIG. 4 is a cross-sectional view taken along a longitudinal center
plane of another embodiment of a fastener driving tool constructed
in accordance with the features of the invention;
FIG. 5 is a fragmentary cross-sectional view of the tool similar to
FIG. 4 illustrating the operating components thereof as a drive
stroke is proceeding; and
FIG. 6 is a fragmentary cross-sectional view of the tool similar to
FIG. 5 illustrating the operative components thereof when the
supply of fasteners is exhausted.
Referring now, more particularly, to the drawings and FIGS. 1, 1a,
2, 2a 3, and 3a, therein is illustrated one embodiment of a new and
improved pneumatically operated fastener driving tool constructed
in accordance with the features of the present invention and
referred to generally by the reference numeral 10. The tool 10
includes a main body 12 formed with a hollow, rearwardly extending
handle portion 14 which serves as a reservoir for holding a volume
of compressed air for operation of the tool, the compressed air
being supplied to the rear end of the handle portion through a
suitable air line and disconnect fitting (not shown). The forward
end of the handle portion 14 is integrally joined and in
communication with a cylindrical head portion 16 extending
generally transverse to the handle and projecting upwardly and
downwardly thereof.
The head portion 16 is formed with a cylindrical bore 18 at the
lower end, in which is slidably disposed the lower piston head 20
of a spoollike, reciprocably movable piston assembly 22. The piston
assembly 22 includes an upper piston head 24 having a diameter
slightly greater than the lower head 20, and a stem 26 of reduced
diameter integrally interconnecting the upper and lower piston
heads. An open, annular air space or piston chamber 28 is formed
around the stem between the piston heads and is continuously
supplied with compressed air from the handle 14 through a port 58
adjacent the upper end of the bore 18. The upper piston head 24 is
slidable within a cylindrical insert 30 which is threaded
externally at its lower end and seated within a threaded portion
formed in the head portion 16 of the tool above the upper end of
the lower cylindrical bore 18.
The internal diameter of the cylinder insert 30 is slightly larger
than the diameter of the lower bore 18, and when pressurized fluid
is present in the annular space or piston chamber 28 around the
stem 26, a net resultant, upward force acts on the piston assembly
22 urging the assembly upwardly on a return stroke towards an upper
or rest position, as shown in FIGS. 1 and 3, wherein the piston is
at the top end of the head portion of the tool body.
The piston assembly 22 is connected at its lower end to a
downwardly depending driver or drive rod 32, which is disposed for
sliding movement within a cylindrical drive track 34 formed in a
nosepiece 36 secured to the lower end of the head portion 16. The
nosepiece 36 includes an integral, radially extending wall or
flange 38 at the upper end which closes the lower end of the
cylindrical bore 18 in the head portion 16, and the flange or wall
is formed with a plurality of radially spaced holes 38a therein for
venting the lower end of the bore 18 to the atmosphere, thereby
maintaining atmospheric pressure on the underside of the lower
piston head 20.
The upper end of the head portion 16 of the tool body is larger in
internal diameter than the outer diameter of the cylinder insert
30, thereby forming an annular space or chamber 40 below the upper
end of the cylinder insert. The chamber 40 is in open communication
with the forward end of the hollow or handle portion 14 of the tool
and is continuously supplied with compressed air therefrom. The
upper end of the head is closed by a removable cap member 42 having
an integrally formed, centrally disposed, upwardly extending
projection 44 thereon.
In order to selectively open and close communication between the
interior bore of the upper end of the cylinder insert 30 and the
annular chamber or space 40, a slidable poppet valve member 46 is
mounted for sliding movement in the large diameter, upper end
portion of the head 16 for movement between the upper end of the
cylinder insert and the lower surface of the cap member 42. The
poppet valve 46 includes a circular, piston-type valve disc portion
48 with a resilient gasket 50 on the underside thereof adapted to
seal the upper end of the cylinder insert 30 when the valve is
closed (FIGS. 1 and 3), and includes a hollow stem 52 projecting
upwardly from the disc portion and slidable within a cylindrical
bore 44a formed in the upper projection 44 on the cap member 42.
The bore 44a is normally vented to the atmosphere through a
laterally extending exhaust port 44b when the poppet valve 46 is
closed, and when the valve is opened (FIG. 2) the stem 52 moves
upwardly in the bore and closes the port, thereby sealing the upper
end of the tool from the atmosphere.
The large diameter, upper end portion of the head 16 of the tool
body forms an annular valve chamber 54 in which the flange or disc
portion 48 of the poppet valve is slidable between an upper or open
position adjacent the lower surface of the cap member 42 and a
closed position, spaced downwardly thereof, closing off the upper
end of the cylinder insert 30. When the valve chamber is supplied
with pressurized fluid from the handle 14, the fluid pressure
acting on the upper surface of the valve disc portion 48 causes the
poppet valve 46 to move downwardly to the closed position against
the upper end of the cylinder insert 30.
In order to fire the tool and thereby cause the piston assembly 22
and driver 32 to move rapidly downward on a power stroke, the fluid
in the poppet valve chamber 54 is exhausted to the atmosphere by
means to be described hereinafter and, when this occurs, air
pressure within the annular chamber 40 beneath the outer peripheral
portion of the valve disc portion 48 acts upwardly on the valve,
forcing it upwardly to the open position. The upper end of the
cylinder insert 30 is thus opened and in direct communication with
the pressurized fluid in the annular space 40, and this fluid
rapidly flows into the upper end of the cylinder insert above the
piston head 24, causing the piston assembly 22 to be driven rapidly
downwardly on a power stroke. When a power stroke is thus initiated
by evacuation of the poppet valve chamber 54 above the valve disc
portion 48, the stem portion 52 seals off the lateral vent port 44a
in the cap projection 44 so that pressurized fluid in the upper end
of the tool cannot escape to the atmosphere, and thus maximum fluid
pressure is available for driving the piston assembly 22 rapidly
downward on a power stroke.
In order to cushion or dampen the shock of the piston assembly 22
and driver 32 at the end of the power stroke, a resilient, annular
cushion member 56 is mounted on the upper surface of the flange or
wall portion 38 of the nosepiece 6. The resilient cushion 56
includes a plurality of vent holes 56a in alignment with the ports
38a in the flange 38 to continuously vent the lower end of the bore
18 beneath the lower piston head to the atmosphere.
After a power stroke of the piston assembly 22 and driver 32 has
been completed, the poppet valve chamber 54 is again pressurized
and the poppet valve 46 returns downwardly to the closed position,
sealing off the upper end of the cylinder insert 30. When this
occurs, the valve stem 52 moves downwardly and opens the exhaust
port 44b in the cap projection 44 and the fluid in the upper end
portion of the cylinder insert 30 above the upper piston head 24 is
vented to the atmosphere through the hollow bore in the stem
portion 52 and the exhaust port 44b.
The annular piston chamber 28 around the stem 26 between the upper
and lower piston heads, is continuously supplied with pressurized
fluid from the handle reservoir portion 14 through the port 58
formed in the wall portion of the head 16 immediately below the
cylinder insert 30 and, because the upper piston head 24 is
slightly larger in diameter than the lower piston head 20, the
pressurized fluid in the piston chamber 28 acts on the piston
assembly 22 with a net resultant upward force which causes the
piston assembly to move upward on a return stroke. When the piston
assembly 22 is returned to the upper end of the cylinder, the upper
surface of the piston head 24 engages the lower surface of the
gasket 50 on the poppet valve flange 48, limiting further upward
travel of the piston assembly, and the tool is now ready for
another cycle of operation as described.
In accordance with the present invention, the tool 10 is adapted to
drive relatively large roundhead nails or fasteners 60 which are
supplied from a continuous flexible carrier strip 62 and fed into
the drive track 34 beneath the lower end of the driver 32 when the
piston assembly 22 is in its upper or rest position. A carrier
strip of the type disclosed in U.S. Pat. application Ser. No.
637,510, filed May 10, 1967, now U.S. Pat. No. 3,438,487, issued
Apr. 15, 1969 is suitable for holding the nails.
The drive track 34 is provided with a lateral, rearwardly facing
feed opening 34a (FIG. 3) to accommodate the nails 60 and the
carrier strip 62 which are fed forwardly into the drive track from
a rearwardly extending magazine 64, and a forwardly facing exit
opening 34b is provided on the forward wall of the drive track
opposite the feed opening 34a to accommodate the carrier strip
moving out of the drive track after each nail has been driven. The
magazine 64 includes a pair of spaced apart, parallel sidewalls 66
and 68 for guiding the nails toward the drive track, and
longitudinal grooves are formed on the facing inside surfaces
thereof as at 66a for supporting the round heads of the nails. Top
and bottom walls 67 and 69 are provided for completing the magazine
enclosure, and the nails on the carrier strip are thus held and
guided by the magazine during forward movement into the drive
track.
In accordance with the present invention, the driving tool 10
includes a fastener feeding assembly 70 which is adapted to feed
the nails 60, one at a time, from the magazine 64 into the drive
track 34 in synchronism with the operation of the driver 32. The
feeding assembly 70 is operatively interconnected with a manual
trigger valve assembly 72 which controls the firing of the tool and
a safety valve assembly 74 associated therewith for preventing a
firing stroke of the tool unless the lower end of the nosepiece 36
is positioned against a workpiece.
The magazine feeding assembly 70 includes a piston member 76 which
is disposed for sliding movement within a cylinder or bore 78
formed in the tool body 12 and extending axially parallel with the
longitudinal axis of the magazine 64. The bore 78 is closed at its
forward end and is open to the atmosphere at the rearward end, and
the feeder piston member 76 includes an elongated stem 80 coaxial
with the bore having an enlarged handle portion or knob 82 at the
outer end to facilitate manual movement of the piston. The piston
76 is movable between a rearward position, as shown in FIG. 2, a
forward position, as shown in FIG. 1 and a full forward or shutoff
position as shown in FIG. 3, in synchronism with the operating
cycle of the piston assembly 22 and driver 32. The outer end
portion of the stem 80 externally of the bore 78 is connected to a
downwardly and forwardly extending reciprocal feeder member 84
having a pivot pin 86 adjacent the forward end thereof and
laterally offset from the longitudinal axis of the magazine 64. A
nail engaging pawl or finger 88 is pivotally mounted on the pin 86
and is biased inwardly towards the central, longitudinal axis of
the magazine 64 between the opposite sidewalls 66 and 68 by means
of a spring 90, mounted on the pin 86, as best shown in FIGS. 1a,
2a, and 3a. The forward end or tip of the pawl or finger 88 is
movable inwardly into the interior of the magazine 64 between the
sidewalls and directly into the drive track 34 through a slot or
opening 66b formed in the sidewall 66 and an adjacent opening 34c
formed in the drive track adjacent the rearward lateral feed
opening 34a thereof. The forward end of the finger is adapted to
directly engage the shanks of the nails 60, as shown in FIG. 2a,
and advance the nails forwardly into a centered position in the
drive track (FIG. 1a) upon forward movement of a feeding stroke of
the feeder member 84 from the position of FIG. 2 to the position of
FIG. 1. The spring 90 urges the finger 88 in a counterclockwise
direction about the pin 86 so that the forward end or tip of the
finger is biased against the inside surface of the opposite
sidewall 68 of the magazine and this insures that a fastener or
nail 60 is positively engaged by the forward end surface of the
finger upon movement in a forward direction. As the finger 88 is
moved rearwardly of the drive track on a rearward or return stroke
of the member 84, engagement between the nail 60 in the magazine
next adjacent the drive track cams the finger outwardly or in a
clockwise direction, until the tip of the finger moves to the rear
of the nail, and at this time the spring 90 is then free to urge
the finger inwardly toward the opposite sidewall 68 so that on the
next forward or feed stroke of the finger 88 the nail is positively
engaged by the finger and is fed into a centered position in the
drive track for driving, as shown in FIG. 1a. In the forward
position (FIG. 1), the pawl finger 88 projects directly into the
drive track beneath the head of the nail, and further forward
travel is limited by the nail itself.
In order to prevent rearward movement of the nails 60 and carrier
strip 62, when the pawl or finger 88 is moved on a rearward or
return stroke, the sidewall 68 is provided with a slot 68a therein
for accommodating a spring latching member 92 which projects into
the guideway and resiliently engages longitudinally spaced slots or
openings in the web portion of the carrier strip at a position
spaced rearwardly of the drive track. The spring member 92 normally
prevents rearward movement of the nails in the magazine unless
sufficient force is used to overcome the spring latch 92 when it is
desired to rearwardly retract the nails from the magazine. On each
forward or feed stroke of the feed member 84, the nail 60, engaged
by the forward tip of the finger 88, is fed into centered position
in the drive track ready to be driven. Before the driver 32 is
activated on a downward power stroke, the feed finger 88 is
retracted rearwardly until the forward tip is clear of the drive
track and, after completion of the power stroke and during or after
return of the driver to the rest position, another feed stroke of
the feed member 84 is initiated, carrying the next nail into a
centered position in the drive track. This cycle is repeated until
all of the nails contained in the magazine 64 have been driven.
After the last remaining nail has been driven, the feed finger 88
is no longer restrained by the nail in the drive track and moves to
a full forward position shown in FIG. 3. When the feeder member 84
is in full forward position, a power stroke cannot be initiated, as
will be described hereinafter, until a new supply of nails 60 has
been loaded into the magazine and the leading nail has been
advanced into position for driving centered in the drive track, as
shown in FIG. 1. By grasping the knob 82, manual rearward
retraction of feed member 84 clears the finger 88 from the drive
track and permits the insertion of a new supply of nails into the
magazine and, after insertion of the nails, the knob 82 is released
and the spring 98 moves the member 84 forwardly carrying the first
or leading nail in the strip into the drive track.
The feeder piston 76 is formed with a pair of axially spaced piston
heads 94 and 96 mounted on or integrally formed with the small
diameter, elongated stem 80 and is biased forwardly in the bore or
cylinder 78 by means of a spring 98 having a forward end bearing on
the rearward face of the piston portion 96. The outer end of the
spring is seated against an inwardly extending, annular flange 78a
adjacent the open rearward end of the bore 78.
As previously described, the poppet valve 46 initiates a driving
stroke of the piston assembly 22 and driver 32 and the poppet valve
is moved from the closed to the open position by exhausting of air
pressure from the valve chamber 54 above the valve disc or flange
48. In order to provide a path for exhausting this valve fluid to
the atmosphere, the cap member 42 is formed with a passage 42a
therein which is in communication at its outer end with a vertical,
drilled passage 100 formed in the upper end portion of the head of
the tool body. The lower end of the passage 100 is connected to a
tubular conduit 102 extending transversely across the hollow handle
portion 14 and connected at its lower end to a short, vertical
passage 104 formed in the tool body 12 beneath the handle. The
passage 104 is connected with a rearwardly extending passage 106
which is in communication at its rearward end with a trigger valve
chamber 108 of the trigger valve assembly 72. Intermediate the ends
of the passage 106 of the tool body is provided a vertical bore or
passage 110 of the safety valve assembly 74, and mounted in the
passage for vertical sliding movement therein is a safety valve
member 112 having a lower end extended downwardly from the lower
open end of the bore 110. The trigger valve chamber 108 is in
communication with the source of compressed air in the tool handle
14 through a small passage or port 114 in communication with the
upper end thereof, and a ball valve 116 is loosely mounted in the
chamber for movement between the upper and lower ends of the
chamber. O-ring type valve seats 118 and 120 are mounted in the
valve chamber 108 at the upper and lower ends, respectively, for
cooperating seating engagement with the ball valve 116 in either
its upper or lower position. The lower end of the trigger valve
chamber 108 is in communication with a downwardly extending,
drilled passage 122 open to the atmosphere at its lower end and a
manual operator 124 is slidably disposed within the passage to
activate the ball 116 and to prevent the escape of fluid from the
valve chamber to the atmosphere through the lower end of the
passage. The operator 124 includes a reduced diameter, upper pin
portion 126 adapted to directly engage the ball 116 and move it off
the lower O-ring 120, thereby opening communication between the
passage 106 and the passage 122 through the valve chamber 108. When
the valve operator 124 is moved from the position of FIG. 1 to the
position of FIG. 2, the ball 116 is moved upwardly to seat against
the upper O-ring 118, thereby closing off the supply of pressurized
fluid in the hollow handle 14 from the valve chamber 108 through
the upper port or passage 114. At the same time, communication is
established between the passages 106 and 122 through the valve
chamber 108. The valve operator 124 is moved from the lower to the
upper position described by a manual actuation of trigger 128,
which is pivotally mounted at its rearward end on a downwardly
projecting lug 130 formed on the underside of the handle 14 of the
tool body. The forward end of the trigger 128 is connected to the
lower end portion of the operator 124 below the body of the tool,
and when the trigger is released air pressure from the passage 114
moves the ball valve 116 to seat on the lower O-ring 120.
The passage 122 below the valve chamber 108 is in communication
with the feeder piston bore 78 by a passage 132 having its lower
end in communication with the bore intermediate its ends. When the
feeder piston 76 is in the position shown in FIG. 1 and the forward
tip of the feed finger 88 is projecting into the drive track 34,
the piston head 96 blocks the lower end of the passage 132 so that
fluid cannot flow from the passage 122 into the feeder piston bore
78. However, when the feeder piston 76 is moved rearwardly to the
position shown in FIG. 2, the lower end of the passage 132 is
uncovered and fluid in the passage can flow into the bore 78
between the piston heads 94 and 96 of the piston member. An exhaust
port 134 is provided in the lower wall of the feeder piston bore 78
at a position offset longitudinally of the lower end of the passage
132, and when the feeder piston 76 is moved to the rearward
position, as shown in FIG. 2, the passage 132 and port 134 are in
communication through the bore between the piston heads 94 and
96.
Digressing momentarily to the safety valve feature of the tool, the
safety valve member 112 is slidable vertically in the bore 110
between a lower or safe position (FIG. 1) and an upper or fire
position, as shown in FIG. 2. In order to actuate the safety valve
in response to the movement of the tool into a firing position with
the lower end of the nosepiece 36 pressed against a workpiece, a
slidable foot or collar 136 is mounted for sliding movement on the
lower end portion of the nosepiece around the lower end of the
drive track 34. When the lower end of the nosepiece is out of
engagement with a workpiece, as shown in FIGS. 1 and 3, the collar
136 is biased downwardly and extends below the lower end of the
drive track 34, as shown in FIG. 1, and the biasing force is
transmitted through a bracket member 138 connected between the
collar and the lower end of the safety valve member 112. The safety
valve member is formed with an annular ring or shoulder 140
adjacent its lower end, and a spring 142 engaging the ring urges
the valve member and collar downwardly. The upper end of the spring
142 is seated against a shoulder formed by an enlarged, annular
recess 144 in the tool body around the lower end of the safety
valve passage 110. When the tool is ready for firing and the lower
end of the nosepiece is pressed against a workpiece, as shown in
FIG. 2, the collar 136 is moved upwardly on the lower end portion
of the nosepiece, and the safety valve stem 112 is moved upwardly
against the force of the spring 142 to the fire position of FIG. 2.
The safety valve member 112 includes an upper end portion 112a
having a sloping upper end face and an intermediate piston portion
112b spaced downwardly of the upper end portion and integrally
connected thereto by a reduced diameter stem 112c. The valve member
also includes a lower end or terminal portion 112d spaced
downwardly of the intermediate and integrally connected thereto by
a reduced diameter stem 112e. When the safety valve is in the lower
or safe position, as shown in FIG. 1, the sloped upper surface of
the upper end portion 112a permits communication directly between
the reservoir 14 and the left-hand segment of the passage 106
extending between the valve bore 110 and the passage 104, and
pressurized fluid is supplied to the valve chamber 54 above the
valve flange 48, causing the poppet valve member 46 to close.
Accordingly, when the safety valve stem 112 is in the safe
position, firing of the tool cannot be initiated by movement of the
trigger 128 because the upper end portion 112a of the safety valve
member blocks the passage 106 intermediate its ends and thus
prevents the fluid in the chamber 54 from being exhausted to the
atmosphere. When the valve member 112 is moved to the upper or fire
position, the upper end portion 112a is moved upwardly above the
passage 106 and communication between opposite end portions of this
passage is established through the safety valve bore 110 around the
narrow stem portion 112c. When the trigger 128 is squeezed,
unseating the ball valve 116 from its lower seat 120 in the valve
chamber 108, communication is established between the poppet valve
chamber 54 and the lower end of the passage 132 which terminates in
the feeder piston bore 78. However, the tool still cannot be fired
in this condition until the feeder piston 76 is moved rearwardly to
the position of FIG. 2, thereby withdrawing the pawl or finger 88
from the drive track so that the driver 32 on its downward power
stroke will not engage the finger, thereby damaging the tool.
In accordance with the present invention, positive means are
provided for insuring that the finger 88 is retracted from the
drive track before a downward power stroke of the driver 32 can
commence. In order to move the feeder piston assembly 76 on a
rearward stroke, thereby withdrawing the tip of the finger 88 from
the drive track and enabling the tool to be fired, a passage 146 is
provided in communication at its upper end with the passage 58 and
in communication at its lower end with the safety valve bore 110 at
a point spaced below the passage 106. When the safety valve member
112 is in the lower safe position, as shown in FIG. 1, the
intermediate body portion 112b blocks off the lower end of the
passage 146, and when the valve member is then moved to the upper
or fire position, the intermediate portion 112b moves upwardly
above the lower end of the passage 146 and permits a flow of
compressed air into the safety valve bore 110 around the stem
portion 112e. This compressed fluid flows around the stem portion
112e and into the forward end of the feeder piston bore 78 through
a feeder passage 148, having its upper end in communication with
the safety valve bore 110 at a point beneath the lower end of the
passage 146, and the lower end of the passage 148 is in axial
communication with the forward or closed end of the feeder piston
bore 78. As the valve stem 112 is moved upwardly from the safe to
the fire position, compressed fluid from the reservoir 14 flows
into the forward end of the feeder piston chamber 78 via the
passages 58 and 146, around the stem portion 112e of the safety
valve 112, through the passage 148 communicating between the safety
valve bore 110 and into the forward end of the feeder piston bore
78. This fluid drives the feeder piston 76 rearwardly to the
position of FIG. 2 against the biasing spring 98 and, as described,
retracts the finger 88 clear of the drive track 34. As this occurs,
the piston head 96 uncovers the exhaust port 134 and the lower end
of the passage 132 which communicates with the bore, thereby
establishing an exhaust path between the passage and the atmosphere
between the piston heads 94 and 96. When the trigger 128 is now
squeezed, a power stroke is initiated by the exhausting of
pressurized fluid from the valve chamber 54 through passages 42a,
100, conduit 102, passages 104, 110 and 106, valve chamber 108,
passages 122 and 132, feeder piston bore 78 between the piston
heads 94 and 96, and finally the exhaust port 134. After the firing
stroke has been completed and the lower piston head 20 strikes the
cushion member 56 at the lower end of the cylinder bore 18, when
either the safety valve 112 or the trigger 128 is released,
compressed air is again supplied to the upper poppet valve chamber
54, causing the poppet valve 46 to close, sealing the upper end of
the cylinder insert 30. When this occurs, the piston member 22
commences an upward return stroke, as previously described.
After a power stroke, when the safety valve 112 is moved from the
fire position to the safe position, the intermediate portion 112b
moves downwardly, closing the lower end of the passage 146, and the
lower end portion 122d uncovers the upper end of an exhaust passage
150 which has a lower end in communication with the atmosphere. The
compressed fluid in the forward end of the feeder piston bore 78 is
then free to escape to the atmosphere through the passage 148,
around the stem portion 112e in the valve bore 110, and out the
exhaust passage 150. When this occurs, the biasing spring 98 at the
rearward end of the feeder piston bore 78 moves the piston assembly
76 forwardly on a feeding stroke, thereby advancing another nail 60
into a centered position in the drive track ready to be driven. The
cycle of operation is then repeated as described, until all of the
nails in the magazine have been driven.
As previously mentioned, forward movement of the feeder piston 76
is restricted by engagement of the forward tip of the pawl or
finger 88 with the shank of the nail centered in the drive track
34. However, if a nail is not present in the drive track, the
feeder piston 76 is free to move farther forward to the full
forward position, as shown in FIG. 3, until the piston is stopped
by engagement of a resilient O-ring 152 on the forward end of the
piston against the frustoconical surface of an annular recess 154.
The annular recess 154 is formed at the lower end of the passage
148 at the forward end of the feeder piston bore 78 and is mounted
on a short projection ahead of the piston head 94 for seating in
the recess 154 to close communication between the forward end of
the bore 78 and the passage 148. If the safety valve member 112 is
now moved from the safe to the fire position, thereby supplying
pressurized fluid to the passage 148, none of this fluid can reach
the forward end of the feeder piston bore 78 to move the feeder
piston 76 rearwardly and, hence, the exhaust port 134 mains covered
by the piston head 96 and the tool cannot be fired, regardless of
the position of safety valve member 112 or movement of the trigger
128 because the recess 154 has a reduced diameter which is not
great enough to permit air pressure force on the piston to overcome
the spring 98. Thus, after the last nail has been driven the tool
cannot be fired, and this feature prevents damage to the tool and
advises the operator to reload if he is not already aware that the
nail supply has been exhausted.
From the foregoing, it will be seen that the tool 10 of the present
invention automatically prevents firing of the tool when there are
no more nails in the magazine 64. In addition, the tool includes
means for positively feeding the nails into the drive track in
synchronism with the movements of the driver and the nails are
guided into the drive track by the forward tip of the finger 88.
The tool cannot be fired until the feed pawl 88 is positively
retracted from the drive track regardless of the position of the
safety valve or trigger.
After the last nail in the tool has been fired and the feeder
piston 76 is in the inoperative or full forward position, as shown
in FIG. 3, the feeder piston is retracted rearwardly by manually
grasping the knob 82 and moving it rearwardly until the forward
finger 88 is clear of the guideway between the magazine sidewalls
66 and 68. A new strip of nails is then inserted into the magazine
and advanced forwardly until the leading nail on the carrier strip
is centered in the drive track for driving. The knob 82 is then
released and the spring 98 moves the feeder piston 76 forwardly to
the position of FIG. 1 and the tool is again ready for operation by
movement of the safety valve 112 from the safe to the fire position
and manual squeezing of the trigger 128. It is also possible to
operate the tool on continuously repeating cycles by maintaining
the trigger in a depressed position and moving the lower end of the
nosepiece into and out of contact with the workpiece to thereby
initiate power strokes of the driver.
In accordance with the present invention, in FIGS. 4 through 6 is
illustrated another embodiment of the fastener driving tool
referred to generally by the reference numeral 200, and differing
generally from the previous embodiment of FIGS. 1 through 3a in
that it is not necessary to recycle the safety valve in order to
initiate each cycle of operation of the tool including a power and
return stroke of the driver 32. Components of the tool 200, which
are identical to or substantially similar to the components of the
tool 10 of the previously described embodiment are given identical
reference numerals and will not be described in detail hereinafter
except to the extent necessary in order to relate to the features
of the second illustrated embodiment of the invention.
In the tool 200, the tubular conduit 102 leading to the poppet
valve chamber 54 above the flange portion 48 of the poppet valve
assembly 46 is connected to a valve chamber 202 having a spherical
ball valve member 204 mounted therein for movement between an upper
and lower position. The tubular conduit 102 is connected into a
sidewall portion of the valve chamber 202 through a short drilled
passageway 206, and the upper end of the valve chamber is in
communication with the reservoir 14 in the tool handle via a short
passage or port 208. An O-ring 210 is provided around the port
opening 208 so that when the ball valve member 204 is forced
upwardly to the position of FIG. 5, the passage 208 is closed and
communication between the valve chamber 202 and the pressurized
fluid in the handle portion 14 is cut off. The lower end of the
valve chamber 202 is in communication with a drilled passage 212
and an O-ring 214 is provided at the lower end of the chamber 202
so that when the ball valve member 204 is in a downward position,
as shown in FIGS. 4 and 6, air pressure from the handle reservoir
14 forces the valve member 204 tightly against the O-ring 214
closing off communication between the valve chamber 202 and the
upper end of the passage 212. Immediately below the valve chamber
202, the passage 212 is in communication with an exhaust passage
216 opening to the atmosphere so that when the valve member 204 is
seated against the upper O-ring 210, the conduit 102 leading to the
poppet valve chamber can exhaust to the atmosphere through the
valve chamber 202, passage 206, upper end of the bore 212 and
passage 216 to initiate a firing stroke of the tool. The lower end
of the passage 212 is in communication with a larger diameter
cylinder or bore 218 formed in the body of the tool. Within the
coaxially aligned passage 212 and cylinder 218 is mounted for
sliding movement a movable piston member 220 including an elongated
piston rod 222 having an upper portion slidable in the passage 212.
At the upper end of the piston rod 222 is provided a short, ball
valve actuator or projection 224 of reduced diameter and adapted to
move upwardly to unseat the ball valve member 204 from the O-ring
214 and force it upwardly to seat against the upper O-ring 210 and
seal off the port 208.
The piston member 220 includes an upper piston 226 spaced below the
projection 224 and slidable in the large diameter bore or cylinder
218 from an intermediate position shown in FIG. 4 to an upper
position shown in FIG. 5, where it bears against an annular surface
at the upper end of the cylinder 218. When the piston member 220 is
in the upper position, the actuator projection 224 engages the ball
valve 204, lifting it off the lower O-ring 214 and moving it
upwardly to seat against the upper O-ring 210, thus permitting the
pressurized fluid in the poppet valve chamber 54 to exhaust into
the atmosphere and thereby initiate a power stroke of the piston
assembly 22 and driver 32 to drive a fastener 60 downwardly in the
drive track 34. The piston member 220 also includes a smaller
diameter lower piston 228 spaced below the piston 226 and slidable
within a tubular sleeve 230 inserted into the lower portion of the
cylinder 218 adjacent the exhaust end. When the piston member 220
is in the intermediate or upper position, the lower piston 228
seals off the lower end of the cylinder 218 by tightly sealed
engagement around the internal surface or bore of the insert 230
and normally prevents the exhaust of fluid in the cylinder 218
contained between the upper and lower piston members 226 and 228,
respectively.
The lower end of the piston rod 222 is pivotally connected to a
triangularly-shaped magazine actuating member 232 by means of a
cross-pin 234 which is slidably disposed in a slot 232a at the
rearward, upper corner of the actuator. The forward, upper corner
of the magazine actuator is mounted for pivotal movement relative
to the magazine 64 on a mounting pin 236, extending laterally
transversely of the longitudinal axis of the magazine. The lower
corner of the triangularly-shaped magazine actuator is pivotally
interconnected with the magazine feeder member 84 by a pin 238
which projects through an elongated slot 240a formed in a magazine
cocking member 240 which is also pivotally mounted on the pin 236.
The cocking member 240 includes a knob or handle 241 at the lower
end manually movable by a tool operator to cock the magazine member
and retract the feed pawl or finger 88 from the drive track after
the last nail has been driven and a new supply or strip of nails 60
is being inserted into the magazine. When the piston member 220 is
in the intermediate position shown in FIG. 4, the forward end or
tip 88 of the feeding finger or pawl is in contact with the leading
fastener 60 in the magazine which is in centered position in the
drive track 34 ready to be driven by a power stroke of the driver
32. When a power stroke is initiated by movement of the piston 220
from the position of FIG. 4 to the upper position of FIG. 5, the
feeder pawl or finger 88 is retracted rearwardly out of the drive
track, as in the prior embodiment, so that no interference between
the driver 32 and the feed pawl can occur.
Similar to the tool 10 of the previous embodiment, the tool 200
includes a safety valve mechanism which is operatively
interconnected with presser foot 136 and connecting bracket 138
forming a touch trip mechanism for the tool. The upper end of the
bracket 138 is connected to the lower end of a safety valve rod 242
which is slidable in an elongated bore 244, having its upper end in
communication with the interior of the handle reservoir 14 and a
lower end open to the atmosphere. The safety valve rod 242 is
biased downward by the compression spring 142 which is seated in an
enlargement 244a at the lower end of the safety valve bore 244, and
the lower end of the spring 142 bears downwardly against an annular
collar 140 provided on the lower end portion of the valve rod. The
presser foot 136 is thus biased downwardly to the safe position
below the lower end of the drive track 34 by the spring 142. When
the tool is to be fired and the lower end of the drive track 34 is
pressed against the workpiece, the presser foot 136 is moved
upwardly to the fire position and the valve rod 242 is moved
upwardly from the safe position of FIGS. 4 and 6 to the fire
position of FIG. 5. The safety valve rod includes a sloped upper
end surface 242a and an annular recess 242b in the body of the rod
spaced downwardly from the upper end surface. The safety valve
passage 244 is in communication with the upper end surface of the
cylinder 218 above the piston 226 by a cross passage 246.
When the safety valve rod 242 is in the lower or safe position,
shown in FIG. 4, the sloped upper end surface 242a permits fluid to
flow from the reservoir 14 into the upper end of the bore 244 and
through the passage 246 into the upper end of the cylinder 218
above the piston portion 226, moving the piston 220 downwardly from
the position of FIG. 5 to the position of FIG. 4. Movement of the
piston 220 in the above manner, causes a new fastener 60 to be fed
into the drive track 34 and further downward movement of the piston
member 220 is limited because of engagement of the forward end of
the feed pawl or finger 88 with the shank of the fastener when it
is centered in the drive track 34. When the safety valve member 242
is in the downward or safe position, pressurized air from the
handle reservoir 14 is continuously supplied to the upper end of
the cylinder 218 above the piston member 226 and prevents upward
movement of the piston member 220 from the position of FIG. 4 to
that of FIG. 5 and, accordingly, the valve member 204 is seated on
the lower O-ring 214 and a drive stroke of the piston assembly 22
and driver 32 cannot be initiated. When the tool 200 is moved into
working position and the presser foot 136 is depressed upwardly by
engagement against a workpiece, the safety valve rod 242 is moved
upwardly to the fire position, and the annular recess 242b is
aligned with the passage 246 and a short intermediate passageway
248 which extends into the sidewall of a trigger valve chamber 108
similar to the trigger valve chamber in the preceding
embodiment.
Within the trigger valve chamber 108 is mounted a ball valve member
116 and the upper end of the valve chamber is connected to the
interior of the handle reservoir 14 through a port 114 which is
surrounded by an upper O-ring 118 having an upper valve seat. The
lower end of the trigger valve chamber 108 is in communication with
the atmosphere through a downwardly extending port or passage 122
and a lower O-ring seat 120 is provided in the valve chamber to
seal off the passage 122 when the ball valve is seated thereon, as
in FIGS. 4 and 6. The ball valve 116 is mounted for movement within
the chamber 108 between a lower position seated against the lower
O-ring 120 and closing off the passage 122, and is movable upwardly
to a seated position against the O-ring 118 sealing off the port
114 by means of an actuator pin 126, having a diameter smaller than
the passage 122 and pivotally connected to the forward end of a
trigger 128. On upward depression of the trigger 128, the stem 126
forces the ball valve member 116 upwardly, closing off the port 114
to the reservoir 14 and the short transverse passage 248 then
permits air in the upper end portion of the cylinder 218 above the
piston 226 to exhaust to the atmosphere through the passage 246,
recess 242b on the safety valve rod 242, passage 248, valve
chambers 108, and passage 122 around the stem 126. When this
occurs, the piston member 220 moves upwardly because of the
pressurized fluid in the cylinder 218 between the pistons 226 and
228, and this movement retracts the magazine feeder pawl 88 from
the drive track 34 and unseats the ball valve 204 from the lower
O-ring seat 214, thereby permitting a drive stroke of the piston
assembly 22 and driver 32 to be initiated as the fluid from the
poppet valve 54 exhausts to the atmosphere through the passage 216.
It is thus seen that a power or driving stroke cannot be commenced
until the forward end of the magazine feed pawl or finger 88 has
been positively retracted from the drive track 34 to be clear of
the driver 32. After a power stroke has been completed and either
the safety valve 242 is released to return to the downward or safe
position or the trigger 128 is released allowing the trigger valve
116 to reseat on the lower O-ring 120, pressurized fluid is again
introduced into the upper end of the cylinder 218 above the piston
226 via the safety valve passage 244 and passage 246 or via the
port 114, valve chamber 108, passage 248, annular recess 242b and
passage 246. When this occurs, the piston 220 moves downwardly to
the position of FIG. 4, and thereby advances another fastener or
nail 60 into a centered position in the drive track ready to be
driven. As previously stated, engagement between the forward end of
the pawl or finger 88 and the shank of the leading nail 60 in the
drive track prevents further downward movement of the piston member
220 beyond the intermediate position of FIG. 4. The tool can again
be fired if the safety valve rod 242 is still in the upper or fire
position and the trigger 128 is in the upper or fire position
unseating the trigger valve ball 116, as previously described.
Successive operative cycles may be initiated by continuously
maintaining either the trigger 128 or the safety valve rod 242 in
the upper or fire position and cycling the other one of the two
between the fire and safe positions.
When the last nail or fastener 60 in the magazine 64 has been
driven, the forward end of the feed pawl or finger 88 is moved by
the piston member 220 to a full forward position, as shown in FIG.
6 wherein the forward end of the pawl bears against the forward
wall of the drive track 34. This occurs because the fluid pressure
in the upper end of the cylinder 218 bearing downwardly on the
piston 226, forces the piston rod assembly 220 downwardly from the
position of FIG. 5 to the position of FIG. 6, wherein the lower
piston 228 is moved below a tapered lower bore portion of the
sleeve insert 230 and exhausts the fluid from the cylinder 218
between the pistons 226 and 228. When the pressure between the
piston portions 226 and 228 is relieved and exhausted to the
atmosphere, there is no upward force acting on the piston member
220 to unseat the valve 204 from its lower seat 214, and subsequent
depression of the trigger 128 and safety valve member 242 is
ineffective to initiate a firing stroke of the tool. The tool 200
cannot be fired after the last nail 60 has been driven, and this
feature prevents an inadvertent power stroke of the driver when
there are no fasteners present in the tool magazine and eliminates
damage to the tool, resulting from initiating a power stroke when
the tool is empty.
In order to reload the tool, a new supply of fasteners 60 is
inserted into the magazine 64 and is advanced forwardly until the
leading nail 60 is adjacent the entrance to the drive track. The
knob 241 on the cocking lever 240 is manually retracted rearwardly,
causing the lever to pivot counterclockwise. This movement forces
the piston rod member 220 upwardly, and the lower piston 228 again
is sealed in the insert sleeve 230. When the piston 228 is moved
into sealing engagement with the sleeve insert 230, the upper
piston 226 is spaced above the sleeve insert and compressed fluid
from the handle reservoir 14 flows into the cylinder 218 between
the pistons 226 and 228 through a passage 250. With pressurized
fluid present in the cylinder 218 between the pistons 226 and 228,
a power stroke can again be initiated by exhausting the fluid from
the upper end of the cylinder 218 above the piston 226, as
previously described.
In order to prevent an inadvertent firing stroke of the piston
assembly 22 and driver 32 when the tool is cocked by manual
movement of the cocking lever 240, as described, a stop lug 252 is
provided on an adjacent sidewall of the magazine for limiting the
pivotal movement of the lever during a cocking operation so that
the piston member 220 does not move upwardly beyond the
intermediate position of FIG. 4 to the firing position of FIG. 5.
After the tool is loaded with a new supply of fasteners and is
cocked as described, firing strokes can again be initiated by
depression of the safety valve rod 242 and trigger 128, as
previously described.
From the foregoing, it will be seen that an embodiment of the
invention illustrated in FIGS. 4 through 6 provides positive means
for retracting the feeder pawl 88 from the drive track 34 before a
power stroke of the driver 32 can be initiated. Furthermore, the
tool 200 can again be recycled for successive firing strokes while
holding the nosepiece in constant contact against the workpiece and
cycling the trigger 122. Or in the alternative, the trigger 128 can
be maintained in a depressed condition and the tool can be cycled
by moving the presser foot 136 against and away from the workpiece.
The tool 200 also includes a last nail feature which prevents
firing of the tool after the last nail magazine has been exhausted
and, once exhausted, the new fasteners can be loaded into the
magazine and the tool is manually cocked with the cocking lever
240, putting it in a ready condition for commencement of subsequent
firing operations.
In the tool 10, illustrated in FIGS. 1--3, it is necessary to cycle
the safety valve stem 112 in order to feed each new nail into the
drive track. In the tool 200 of FIGS. 4--6, it is not necessary to
cycle the safety valve 242 to feed the nails into the drive track.
It has been found in some instances that tool operators using tools
of the latter type have taped or otherwise permanently secured the
valve rod 242 in the fire position, thus enabling the tool to be
manipulated and fired somewhat easier and at a slightly higher rate
than possible otherwise. This, of course, eliminates the safety
feature afforded by the valve 242 and results in a dangerous
situation in that the tool can be fired in any position by
squeezing the trigger regardless of whether or not the lower end of
the nosepiece is pressed against a workpiece. In the tool 10,
however, the safety valve feature cannot be disabled by taping or
otherwise securing the valve stem 112 in the fire position because
it is necessary to cycle the safety valve to feed each new nail
into the drive track. The tool 10 cannot remain operative if the
safety valve is taped or restrained in the fire position and, as a
result, the tool is operative only in the safe manner as intended.
When restraining of the safety valve is not a serious problem, the
tool 200 offers the advantage of not requiring the cycling of the
safety valve each time a nail is to be driven.
Although the present invention has been described with reference to
two illustrative embodiments thereof, it should be understood that
numerous other modifications and embodiments can be devised by
those skilled in the art that will fall within the spirit and scope
of the principles of this invention.
* * * * *