U.S. patent number 3,905,535 [Application Number 05/396,878] was granted by the patent office on 1975-09-16 for fastener driving tool.
This patent grant is currently assigned to Duo-Fast Corporation. Invention is credited to Bernard W. Geist, Raymond F. Novak, Frank R. Potucek, Howard B. Ramspeck.
United States Patent |
3,905,535 |
Novak , et al. |
September 16, 1975 |
Fastener driving tool
Abstract
A pneumatic stapler includes a housing in which is mounted for
limited sliding movement a drive cylinder containing a piston
coupled to a driver blade. A nosepiece structure on the housing
contains a drive track slidably receiving the blade and supporting
an annular or cylindrical member aligned with the lower end of the
cylinder and carrying a valve seat. A main valve engages the top of
the cylinder and forces the cylinder downwardly to seat on the
valve seat in the normal condition of the tool. When the main valve
moves upwardly, it closes an upper cylinder exhaust valve, and the
cylinder follows through its limited travel to move out of
engagement with the valve seat and exhausts the lower end of the
drive cylinder. Further upward movement of the main valve admits
compressed air to move the drive piston downwardly through a power
stroke. A cycle valve receiving air from the cylinder at the end of
the power stroke controls the main valve to move downwardly and not
only seat the cylinder lower end on the valve seat, but also
exhaust the upper end of the cylinder interior. A return valve
senses this condition and supplies compressed air through the
nosepiece within the annular member to return the drive piston and
to supply compressed air to the cycle valve to prevent a premature
opening of the main valve. The completion of the return stroke of
the piston releases the return valve. A magazine includes a biased
staple strip pusher with a pair of rigid legs pivoting in the
planes of the staple legs to facilitate loading the staple
strips.
Inventors: |
Novak; Raymond F. (Schiller
Park, IL), Ramspeck; Howard B. (Chicago, IL), Geist;
Bernard W. (Melrose Park, IL), Potucek; Frank R. (Des
Plaines, IL) |
Assignee: |
Duo-Fast Corporation (Franklin
Park, IL)
|
Family
ID: |
23568979 |
Appl.
No.: |
05/396,878 |
Filed: |
September 13, 1973 |
Current U.S.
Class: |
227/120; D8/61;
227/130 |
Current CPC
Class: |
B25C
1/008 (20130101); B25C 1/044 (20130101); B25C
5/16 (20130101) |
Current International
Class: |
B25C
5/00 (20060101); B25C 5/16 (20060101); B25C
1/04 (20060101); B25C 005/10 (); B25C 005/16 () |
Field of
Search: |
;227/7,120,130
;91/356 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Custer, Jr.; Granville Y.
Attorney, Agent or Firm: Mason, Kolehmainen, Rathburn &
Wyss
Claims
What is claimed and desired to be secured by Letters Patent of the
United States is:
1. A tool for driving fasteners into a workpiece comprising
a powered fastener driving assembly including a driver element
actuated by a drive piston slidable within a drive cylinder,
a fluid controlled main valve means opened to supply pressurized
fluid to and closed to exhaust fluid from the cylinder to move the
piston through power and return strokes,
a cycle valve coupled to the main valve means and operable to
alternate positions to open and close the main valve means, said
cycle valve being biased to a position to close the main valve
means, said cycle valve also including valve piston means,
passage means coupling the valve piston means to the drive cylinder
to receive pressurized fluid for biasing the cycle valve to a
position to close the main valve means,
return valve means responsive to the exhaust of the drive cylinder
above the drive piston for supplying pressurized fluid into the
drive cylinder below the drive piston to move the drive piston
through a return stroke, the pressurized fluid below the drive
piston being supplied to the valve piston means to bias the cycle
valve to a position to close the main valve means,
and means responsive to the completion of the return stroke of the
drive piston for controlling the return valve means to terminate
the supply of pressurized fluid to the drive cylinder below the
piston means and thus to the valve piston means.
2. A tool as set forth in claim 1 including
a bias piston movable into engagement with the valve piston
means,
and means coupling the bias piston to the return valve means to
receive pressurized fluid from the return valve means.
3. A tool as set forth in claim 1 including
a valve seat adjacent the lower end of the drive cylinder
communicating with the atmosphere,
and means movably mounting the drive cylinder for movement into
engagement with the valve seat when the main valve means is closed
and out of engagement with the valve seat when the main valve means
is opened to exhaust the drive cylinder below the piston.
4. A tool as set forth in claim 3 including
port means in the cylinder forming a part of said passage means,
said port means being opened to pressurized fluid in the drive
cylinder above the drive piston when the cylinder is out of said
engagement with the valve seat and the drive piston is at the end
of its power stroke, said port means being closed by said drive
piston when the drive cylinder engages said valve seat and the
drive piston is at the end of its power stroke.
5. A tool for driving fasteners into a workpiece comprising
a housing,
a cylinder slidably mounted in the housing and slidably receiving a
piston movable through power and return strokes,
a fastener driving blade actuated by the piston,
a main valve means opened to supply a pressurized fluid to the top
of the cylinder and closed to exhaust fluid from the top of the
cylinder, said main valve means including means engaging the
cylinder to move the cylinder down when the main valve means is
closed and permitting upward movement of the cylinder when the main
valve means is opened,
a nosepiece structure on the housing adjacent the lower end of the
cylinder and having a drive track through which the fastener
driving blade extends,
a cylindrical valve seat engaged by the lower end of the cylinder
when the main valve means is closed and spaced below the lower end
of the cylinder when the cylinder moves upwardly as the main valve
means is opened, the space between the valve seat and the lower end
of the cylinder exhausting the lower interior of the cylinder,
a fluid actuated cycle valve means coupled to the main valve means
and automatically operable through a sequence of two spaced
positions to open and close the main valve means, said cycle valve
means including means responsive to pressurized fluid from the
lower end of the cylinder to effect closure of the main valve
means,
a fluid controlled return valve means responsive to the closure of
the main valve means for supplying pressurized fluid to the cycle
valve means to hold the main valve means closed and to the lower
end of the cylinder below the piston to move the piston through a
return stroke, said fluid controlled return valve means being
released to terminate the supply of pressurized fluid when the
piston completes its return stroke,
and control means for initiating movement of the cycle valve means
to start a power stroke of the piston.
6. A tool as set forth in claim 5 in which
the cylindrical valve seat is fixedly secured to and projects
upwardly from the nosepiece structure,
and the return valve means is carried on the housing and includes
passage means through the housing and nosepiece structure
terminating in a discharge port disposed within the cylindrical
valve seat.
7. A tool for driving fasteners into a workpiece comprising
a housing defining a chamber,
a cylinder slidably mounted within the chamber for limited
movement,
a fluid actuated main valve assembly movable into and out of
engagement with the top portion of the cylinder, said cylinder
being fluid biased toward the main valve assembly and movable over
a limited travel with the main valve assembly before separation of
the top portion of the cylinder and the main valve assembly,
a piston slidable within the cylinder,
a fastener driving blade actuated by the piston,
a nosepiece structure on the housing adjacent the lower end of the
cylinder and defining a drive track slidably receiving the fastener
driving blade,
an annular member fixedly secured to the nosepiece structure
encircling the fastener driving blade and aligned with the lower
portion of the cylinder,
a resilient sealing element carried on the annular member adapted
to be engaged by the lower portion of the cylinder when the main
valve means is moved into engagement with the top of the cylinder
to move the cylinder down into seating engagement with the sealing
element, said sealing element being spaced from the lower portion
of the cylinder when the main valve assembly is moved upwardly out
of engagement with the cylinder to permit limited upward movement
of the cylinder away from the sealing element,
a fluid passage passing through the housing and the nosepiece
structure and having a port in the nosepiece structure within the
annular member,
and fluid control means coupled to the main valve assembly and to
the fluid passage to move the main valve assembly into and out of
engagement with the top portion of the cylinder and to supply fluid
to the fluid passage.
8. A tool for driving fasteners comprising
a tool housing with a nosepiece structure including a drive
track,
power actuated fastener driving means on the tool housing including
a driver element movable in said drive track,
a magazine housing with an open top coupled to the nosepiece
structure and having a fastener supporting structure disposed below
said open top for supporting and feeding a series of fasteners into
the drive track,
a pusher carriage mounted on said housing for movement toward and
away from the drive track along an elongated path,
a rigid fastener engaging pusher element for engaging fasteners on
said fastener supporting structure,
pivot structure coupling the pusher carriage and the pusher element
to mount the rigid pusher element for pivotal movement into and out
of the open top of the magazine about an axis extending transverse
to the direction of the elongated path of movement of the pusher
carriage,
and resilient means coupled to the pusher carriage to resiliently
bias the pusher carriage for movement toward the drive track.
9. The tool set forth in claim 8 in which
the resilient means includes an extensible elongated flat spring
means coupled between the tool housing and the pusher carriage and
disposed at the open end of the magazine housing overlying the
fasteners on the fastener supporting structure.
10. The tool set forth in claim 9 for use with U-shaped fasteners
with spaced legs in which
a pair of rigid pusher elements are pivotally mounted on the pusher
carriage and spaced from each other in the direction of said axis
to engage the spaced legs of the U-shaped fasteners,
and the flat spring means includes a portion disposed between the
spaced pair of pusher legs.
11. In a fastener driving tool having a reciprocable driver for
driving generally U-shaped fasteners successively supplied to a
drive track,
a magazine housing communicating at one end with the drive track
and having an open top,
a support disposed within the housing for supporting a strip of
U-shaped fasteners,
a carriage slidably mounted on the housing adjacent its open end
for movement toward and away from the drive track,
flat spring means connected between the tool and the carriage and
overlying the portion of the strip and the support that is disposed
between the carriage and the drive track, said flat spring means
biasing the carriage toward the drive track,
pusher means with at least one rigid pusher arm pivotally mounted
on the carriage for movement into and out of the open top of the
housing and adapted to engage the U-shaped fasteners when disposed
within the magazine housing, the flat spring means being provided
with a clearance to permit the pusher arm to move past the flat
spring in moving into and out of the open end of the magazine
housing,
and biasing means normally biasing the pusher arm into the open top
of the magazine housing to a position for engaging a U-shaped
fastener.
12. The tool set forth in claim 11 in which
the pusher means includes a pair of rigid pusher arms connected for
joint movement and normally disposed within the magazine housing on
opposite sides of the support,
said pair of pusher arms being spaced a given distance apart, and
the flat spring means having a width less than said given distance
in the portion of the length of the flat spring means adjacent the
pusher arm so as to permit the pair of pusher arms to move into and
out of the open top of the magazine housing.
13. A tool for driving fasteners comprising
a housing having a cylinder means closed at its lower end by a
lower wall structure,
a power actuated drive means in the housing including a coupled
piston and driver blade movable within the cylinder means,
valve means for selectively connecting the cylinder means to
pressurized fluid to move the piston and driver blade through a
power stroke,
a bumper on said lower wall structure and cooperating with the
cylinder means and the lower wall structure to provide a peripheral
passage around the bumper adjacent the lower wall structure
communicating with a plurality of upwardly extending passages
spaced circumferentially around the outer surface of the
bumper,
and means for supplying pressurized fluid to the peripheral passage
to be conveyed over said peripheral and upwardly extending passages
to the interior of the cylinder means to move said piston and
driver blade through a return stroke,
said means including a source of pressurized fluid and control
means responsive to said drive stroke for interconnecting said
source with said peripheral and upwardly extending passages.
14. A tool for driving fasteners into a workpiece comprising
a housing,
a powered fastener driving assembly in said housing including a
driver element actuated by a drive piston slidable within a movable
drive cylinder,
fluid controlled main valve means opened to supply pressurized
fluid to and closed to exhaust fluid from the cylinder to move the
piston through power and return strokes,
said main valve means including passageways exhausting said main
valve means, and valve means movable to open and close said
passageways,
said drive cylinder being movable with said passageway valve means,
and
control means for controlling the main valve assembly, said control
means actuating said valve means to close said passageways prior to
supplying pressurized fluid to said cylinder to drive said piston
and opening said passageways prior to the return stroke of said
piston.
15. The tool set forth in claim 14 further comprising
a lower wall structure closing said cylinder at its lower end,
means for exhausting the portion of said housing beneath said drive
piston, and said control means controlling the movement of said
cylinder from its closed position with said lower wall structure to
an open position communicating said cylinder with said exhaust
means.
16. The tool set forth in claim 14 further comprising
a bumper on said lower wall structure cooperating with said
cylinder and said lower wall structure to provide a peripheral
passage around the bumper adjacent the lower wall structure
communicating with a plurality of upwardly extending passages
spaced circumferentially around the outer surface of the
bumper,
means for supplying pressurized fluid to the peripheral passage to
be conveyed over said peripheral and upwardly extending passages to
the interior of the cylinder means to move said piston and drive
blade through a return stroke, and
said means including a source of pressurized fluid and control
means responsive to said drive stroke for interconnecting said
source with said peripheral and upwardly extending passages.
Description
This invention relates to a fastener driving tool and, more
particularly, to a fastener driving tool including new and improved
fastener driving and feeding means.
There is a growing tendency to extend the applications in which
power driven fasteners, such as staples and nails, are used. This
extension frequently involves driving fasteners of larger sizes
with the result that the power required of the driving tools must
be increased. However, this increase in driving power must be
obtained within the limits imposed by the pressures and quantities
of compressed air available in most manufacturing and fabricating
locations and by weight that can be conveniently manipulated by an
operator. In general, this requires the design of more efficient
tools, tools that are more efficient in the utilization of power
available from existing compressed air sources, and tools that are
more efficient in the quantity of air consumed. Included in any
consideration of the efficiency of use by the operator are the ease
of replenishing the supply of fasteners and, in the case of
multifire tools, the assurance by the operator that a fastener will
be driven in each successive power stroke of the tool.
Accordingly, one object of the present invention is to provide a
new and improved fastener driving tool.
A further object is to provide a fastener driving tool including a
new and improved drive system.
A further object is to provide a fastener driving tool including a
new and improved piston drive and return system.
A further object is to provide a fastener driving tool including a
shiftable cylinder for venting the lower end of the cylinder prior
to the power stroke of a drive piston and new and improved means
for effecting the return of the drive piston.
A further object is to provide a fastener driving tool using a
cycle valve for effecting an automatic sequence of power and return
strokes and a controlled source of pressurized fluid for insuring
that each return stroke is completed before the initiation of the
following power stroke.
A further object is to provide a fastener driving tool including a
new and improved magazine for feeding fasteners to a drive
track.
In accordance with these and many other objects, an embodiment of
the present invention includes a pneumatic fastener or staple
driving or applying tool having a housing containing a drive
cylinder mounted for limited vertical reciprocation. A main valve
movable into and out of engagement with the upper end of the
cylinder normally holds the lower end of the cylinder seated on a
cylindrical member upstanding from the housing at its lower end to
close off communication between the cylinder and the atmosphere.
When the main valve is elevated, the cylinder moves with the main
valve through its limited travel so that the upper cylinder exhaust
valve is first closed and the lower end of the cylinder moves out
of engagement with the valve seat defined by the cylindrical
member, thereby connecting the lower interior of the cylinder to
the atmosphere. The main valve then moves out of engagement with
the top of the cylinder to admit compressed air for driving a
piston slidably mounted in the cylinder and a connected driver
blade through a power stroke.
A cycle valve assembly senses the arrival of the piston at the end
of its power stroke and controls a cycle valve in the control valve
assembly to effect reclosure of the main valve. Closure of the main
valve moves the cylinder downwardly so that its lower end seats on
the cylindrical valve seat and closes off communication between the
atmosphere and the lower interior of the cylinder. This movement of
the main valve also vents the upper interior of the cylinder which
is detected by a return valve assembly. The return valve assembly
supplies compressed air to the lower interior of the cylinder
beneath the piston through a system of passageways extending to a
point inside of the cylindrical lower valve. This compressed air
elevates the piston to its normal position and also provides a
supplemental signal or bias for retaining the cycle valve in its
prior position. When the drive piston returns to its normal
position, this condition is sensed by the return valve, and the
supply of pressurized fluid below the piston is terminated to
terminate one cycle of operation of the tool. When the pressurized
fluid beneath the drive piston and the cycle valve leaks to the
atmosphere, the cycle valve returns to its alternate state, and an
additional cycle of operation of the tool is initiated.
A magazine assembly is provided for feeding successive staples into
the drive track in the nosepiece structure beneath the driver
blade. This magazine assembly includes a resiliently biased pusher
having a pair of rigid arms pivotally mounted in the planes of the
staple legs. When staple strips are inserted into the magazine
behind the pusher, rearward movement of the pusher pivots the legs
upwardly to a position clearing their crowns from which they are
returned to a position engaging the legs of the last staple in the
strip by a resilient bias.
Many other objects and advantages of the present invention will
become apparent from considering the following detailed description
in conjunction with the drawings in which:
FIG. 1 is a side elevational view of a pneumatically operated
fastener driving tool embodying the present invention;
FIG. 2 is an end elevational view of the tool shown in FIG. 1;
FIG. 3 is an enlarged fragmentary sectional view taken along line
3--3 in FIG. 2;
FIG. 4 is a sectional view taken along line 4--4 in FIG. 3;
FIG. 5 is a fragmentary sectional view similar to FIG. 3
illustrating the tool after the opening of a main valve assembly
but prior to the initiation of a power stroke of the tool;
FIG. 6 is an exploded perspective view of a structure for closing
the lower end of a drive cylinder in the tool;
FIG. 7 is a fragmentary sectional view illustrating the tool at the
end of a power stroke and portions of the magazine assembly;
FIG. 8 is a sectional view taken along line 8--8 in FIG. 7;
FIG. 9 is a sectional view taken along line 9--9 in FIG. 7;
FIG. 10 is an enlarged fragmentary sectional view taken in the
direction of line 10--10 in FIG. 8;
FIG. 11 is a sectional view of a control valve assembly for the
tool shown in a normal state;
FIG. 12 is a sectional view similar to FIG. 11 illustrating the
control valve assembly at the conclusion of a power stroke of the
tool; and
FIG. 13 is a schematic diagram illustrating the control functions
performed by the control valve assembly shown in FIGS. 11 and
12.
Referring now more specifically to FIGS. 1-3 of the drawings,
therein is illustrated a fastener driving tool which is indicated
generally as 20 and which embodies the present invention. The tool
20 includes a housing shown generally as 22 including a vertically
extending forward head portion 22A and a rearwardly extending
hollow handle portion 22B. The cavity defined by the head portion
22A and the hollow handle portion 22B provide a reservoir 24 of
pressurized fluid or compressed air for operating the tool 20.
Slidably mounted within the head portion 22A for limited movement
is a drive cylinder 26 normally engaged at its upper end by a main
valve assembly indicated generally as 28 for selectively connecting
the upper interior of the cylinder 26 to the atmosphere or to the
pressurized fluid in the reservoir 24. A lower cylinder exhaust
valve assembly indicated generally as 30 selectively connects the
lower interior of the cylinder 26 to the atmosphere prior to and
during the power stroke to improve the efficiency of drive of the
tool 20. A piston 32 slidably mounted within the cylinder 26 is
secured to the upper end of a fastener driving blade or element 34,
the lower end of which is slidably received within a drive track 36
formed in a nosepiece assembly indicated generally as 38. On each
power stroke of the piston 32, the driver blade 34 engages and
drives a staple 40 supplied to the drive track 36 by a magazine
assembly indicated generally as 42. The power and return strokes of
the piston 32 are controlled by a control valve assembly indicated
generally as 44.
Nosepiece Assembly 38 and Magazine 42
The magazine assembly 42 is secured at its forward end to and
supported by the nosepiece assembly 38 and feeds successive staples
40 from a strip thereof into the drive track 36 defined by the
nosepiece assembly 38. This assembly also includes a quick release
assembly indicated generally as 46 (FIG. 1) for obtaining access to
the drive track 36.
The nosepiece assembly 38 is carried out on a laminated plate
assembly indicated generally as 48 which closes the lower open end
of the head portion 22A of the housing and which is secured thereto
by a plurality of nuts 50 threaded on inserts 52, the upper ends of
which are threaded within tapped openings 54 (FIG. 6) at the lower
end of the head portion 22A. A nose insert 56 (FIGS. 1-3 and 10) is
disposed within aligned openings 58 (FIG. 6) in the plate assembly
48 and welded thereto. The rear wall of the nose insert 56 provides
the front wall of the upper portion of the drive track 36.
The nosepiece assembly 38 further includes a multiplate or welded,
laminated, and generally T-shaped structure 60 including depending
side walls 60A and spaced transverse cross members 60B which are
secured to and are on opposite sides of the nose insert 56 by
suitable fasteners 62, such as a bolt carrying a nut. A shear block
64 (FIG. 3) is secured between depending leg portions 60A of the
structure 60 and defines a substantial portion of the back wall of
the drive track 36 as well as defining a generally U-shaped opening
through which the staples 40 pass into the drive track 36.
A substantial portion of the front wall of the drive track 36 is
defined by the assembly 46. This assembly includes a removable
front plate 66 fitting within the recess defined between the spaced
depending legs 60A of the structure 60 with longitudinally
extending flanged edges overlying the front walls of the legs 60A.
The rear wall surface of the plate 66 is recessed in accordance
with the desired configuration of the drive track 36.
To provide means for detachably mounting the front plate 66 on the
nosepiece assembly 38, there is provided a generally U-shaped bail
68 (FIGS. 1 and 2), a bight portion 68A of which passes around the
front wall of the nosepiece structure 38 to be received within an
indentation 66A in the front wall of the plate 66. The free ends of
the rearwardly extending legs 68B of the bail 68 are slidably
received within two angled and elongated slots 70 formed in a lever
72. The lever 72 is pivotally mounted on a rearwardly extending
portion of the shear block 64 by a pivot pin 74 which passes
through an elongated opening 76 in the lower rearwardly disposed
portion of the shear block 64 adjacent a resilient body 77 (FIGS. 3
and 5). The bail 68 and the lever 72 provide an over-center linkage
for clamping the front plate 66 in its desired position. When the
plate 66 is to be removed, the lever 72 is pivoted about the pivot
pin 74 in a clockwise direction (FIG. 1) to displace the bail 68
sufficiently to permit the plate 66 to be removed. When the plate
66 has been reassembled following, for example, the removal of a
jammed staple from the drive track 36, the bight portion 68A of the
bail 68 is placed in the recess 66A, and the lever 72 is pivoted in
a counterclockwise direction to the position shown in FIG. 1.
The magazine assembly 42 comprises a generally U-shaped magazine
housing indicated generally as 80 which is open at its top and
closed at its bottom by a bottom wall 80A (FIG. 4) to define a
narrow recess approximately the size of a strip of staples 40. At
its forward end, the lower wall 80A of the housing 80 is secured,
as by a plurality of machine screws 82, to a rearwardly extending
portion of the shear block 64 (FIGS. 3 and 4). At its upper end,
the magazine is secured to and within the outer lamina of the cross
pieces 60B of the nosepiece structure 60 by a plurality of machine
screws 84 (FIG. 4).
To provide means for slidably supporting a strip of staples 40
within the cavity in the housing 80, there is provided a staple
rail 86 which is generally U-shaped in configuration and mounted
within the housing 80 so that a wall 86A defining the bight portion
of the rail 86 faces upwardly to provide a support for the crown
portions 40A of the staples 40 (FIGS. 3 and 4). At its forward end
indicated as 86B (FIG. 3), the rail 86 is closed to encircle a
rearwardly extending portion 64A of the shear block 64. A
compression spring 88 biases the lower wall of the closed portion
86B of the rail 86 against the adjacent structure 64A to retain the
rail 86 in position. This interfitting resiliently biased
connection of the front end of the rail 86 to the shear block 64
aids in controlling manufacturing tolerances and prevents wear
which might result in eccentric or misaligned positioning of the
rail 86 relative to the shear block 64 and the structures defining
the drive track 36. The rear end of the rail 86 is secured to the
housing 80 in any suitable manner such as by a member 90 which is
secured to the housing 88 by machine screws 92 (FIG. 1) and which
interfits with the rear end of the rail 86.
Strips of staples 40 can be inserted into the magazine 42 to be
supported on the rail 86 through the open top of the housing 80. A
plate-like extension 90A on the member 90 (FIGS. 1 and 8) extends
forwardly between the housing side walls and includes two
downwardly inclined legs 90B (FIGS. 1, 8, and 10) straddling the
U-shaped rail 86 and disposed immediately adjacent depending
opposite side walls 86C of the rail. The pointed ends at the lower
end of the legs 40B of the staples 40 in a strip can be placed in
engagement with the downwardly inclined legs 90B to guide a strip
into the magazine 42 to a position in which the legs 40B of the
staples in the strip are disposed immediately adjacent and
extending generally parallel to the rail side walls 86C with the
crown portions 40A of the staples resting on the upper wall 86A of
the rail 86.
To provide means for resiliently biasing or feeding a strip of
staples 40 toward the drive track 36 in the nosepiece assembly 38,
there is provided a pusher assembly indicated generally as 96. The
pusher assembly 96 is movably mounted on the housing 80 within a
pair of aligned and opposed grooves 99 (FIG. 9) formed in enlarged
upper end portions 80B of the side walls of the housing 80. The
grooves or slots 99 slidably receive the side edges of a supporting
plate 100 to mount this plate in a position spaced above the wall
86A of the staple supporting rail 86. A generally U-shaped bracket
102 having a pair of spaced upstanding side walls 102A is mounted
on the upper surface of the plate 100 with the lower end portion of
a handle 104 for the pusher assembly 96 disposed between the walls
102A. The handle 104 and the bracket 102 are secured to the plate
100 by a suitable fastener 106. To provide means for engaging the
staples 40, the pusher assembly 96 includes a generally U-shaped
pusher member 108 pivoted at one end to the side walls 102A of the
bracket 102 by a pivot pin 110. The opposite end of the member 108
is provided with two downwardly inclined legs 108A having staple
leg engaging portions 108B generally disposed parallel to and in
immediate proximity to the side walls 86C of the staple rail 86. To
provide means for resiliently biasing the staple legs 108A to the
position shown in FIG. 10, a torsion spring 112 is provided having
a cylindrical center portion which is mounted on the pivot pin 110
between the side walls 102A with the outer free ends bearing
against the plate 100. An end portion 112A of the torsion spring
112 bears against a bight portion 108C to pivot the pusher element
108 in a counterclockwise direction about the pivot pin 110 to the
normal position shown in FIG. 10. This position is determined by
engagement of the pusher 108 with the top surface of the plate
100.
To provide means for biasing the pusher assembly 96 toward the
nosepiece assembly 38, there is provided a constant force spring
114, one end portion 114A of which is hooked or clamped between the
bight of the bracket 102 and the lower wall of the handle 104 to
secure the constant force spring 114 to the pusher assembly 96. The
other end of the constant force spring 114 (FIG. 3) is coiled about
a spool 116 (FIG. 3) rotatably mounted within an enclosure
indicated generally as 118 by a shaft or a pin 120. The constant
force spring 114 tends to return to the coiled position whenever it
is extended by moving the pusher assembly 96 to the right. This
tendency to return to a coiled position provides a resilient bias
forcing the pusher assembly 96 to the left as shown in the
drawings, and thus forcing the staple leg engaging portions 108B on
the pusher legs 108A into engagement with the leg 40B of the last
staple 40 in the strip. The withdrawn portion of the constant force
spring 114 extending between the spool 116 and the pusher assembly
96 is narrower than the upper opening in the magazine housing 80
and is spaced above to overlie the crowns 40A of the staples 40 in
a strip disposed within the magazine assembly 42. The spring 114
passes between the pusher legs 108A.
Assuming that a partially consumed strip of staples 40 is disposed
within the magazine assembly 42 and an additional strip of staples
40 is placed on the rail 86 disposed to the right of the pusher
assembly 96 (FIG. 10), the handle 104 is grasped by the operator,
and the pusher assembly 46 is moved to the right. As the pusher
assembly 96 moves to the right, the inclined right-hand edges 108B
of the two pusher legs 108A engage the first staple 40 in the strip
to be added, and the pusher element 108 may either be pivoted in a
clockwise direction about the pivot pin 110 to the position shown
in dot and dash outline in FIG. 10 or engage the first staple 40 in
the strip and move the strip rearwardly until the last staple
engages legs 90B whereupon the pusher element 108 is pivoted in the
manner described. When the lower ends of the pusher legs 108A clear
the last staple 40 in the strip to be added, the torsion spring 112
pivots the pusher element 108 in a counterclockwise direction about
the pivot pin 110 so that the staple leg engaging portions 108B of
the pusher legs 108A and slide down legs 90B and engage the legs
40B of the last staple 40 in the strip to be added. If the handle
104 is released, the extended constant force spring 114 biases the
pusher assembly 96 to the left (FIG. 10) to move the first staple
40 in the strip to be added into engagement with the last staple 40
in the strip previously disposed in the magazine assembly 42, and
the pusher assembly 96 thereafter advances successive staples 40
into the drive track 36 as they are driven.
To provide means for limiting movement of the pusher assembly 96 to
the left so that the pusher legs 108A cannot enter the drive track
36, a drive or roll pin 122 extends through the side walls 102A and
the lower portion of the handle 104 (FIG. 8) so that the ends of
the pin 122 extend substantially beyond the side walls 102A. When
the pusher assembly 96 reaches the position at which the staple
engaging portions 108B on the pusher legs 108A are disposed
immediately adjacent the entrance to the drive track 36, the
projecting ends of the pin 122 engage the end surfaces of a pair of
plates 124 which are mounted within relieved portions along the
inner surface of the side walls of the housing 80 and secured
therein by the machine screws 84. The engagement of the ends of the
pin 122 with the plates 124 provides a positive stop for limiting
movement of the pusher assembly 96 to the left, as shown in the
drawings.
If the pusher 96 is pulled to an extreme right-hand position (FIGS.
8 and 10), the inclined right-hand edges of the pusher legs 108A
come into contact with the downwardly inclined legs 90B. This cams
the pusher element 108 in a clockwise direction against the bias of
the torsion spring 112 to permit the pusher 108 to be manually
grasped. The pusher assembly 96 can then be permitted to move to
the left with the pusher element 108 elevated. In this way, by
tipping the magazine 46, strips of staples 40 can be removed from
the rail 86 within the magazine housing 80.
Drive System
The drive system for controlling the reciprocation of the piston 32
within the slidably mounted cylinder 26 includes the main valve
assembly 28 which selectively connects the upper interior of the
cylinder 26 to the atmosphere or to the compressed air in the
reservoir 24 as well as controlling the shifting movement of the
cylinder 26 to open and close the exhaust valve assembly 30. The
exhaust valve assembly 30 opens the lower interior of the cylinder
26 prior to and during a power stroke of the piston 32 and seals
the lower interior of the cylinder 26 during a return stroke to
permit the piston 32 to be pneumatically returned to its normal
position.
To provide for slidably mounting the cylinder 26 within the head
portion 22A, this head portion 22A includes an annular or
cylindrical portion 22C (FIGS. 3-5) formed integral with the
housing 22 within which is mounted a sleeve 130 sealed by the
illustrated O-rings. The cylinder 26 is slidably mounted within the
cylindrical sleeve 130, and a similar cylindrical portion 22D
formed in the housing 22. To provide means for limiting the
movement of the cylinder 26, the cylinder carries an annular ring
132 sealed by the illustrated O-rings and bearing against a
shoulder on the cylinder 26. A space 134 between the ring 132 and
the sleeve 130 is continuously vented to the atmosphere. Upward
movement of the cylinder 26 relative to the housing 22 is limited
by engagement of the ring 132 with the lower surface of the sleeve
130 (FIG. 5). The exposed lower surface of the ring 132 provides a
continuous upwardly directed pneumatic bias tending to shift the
cylinder 26 to the elevated position shown in FIG. 5. The selective
movement of the cylinder between the upper position shown in FIG. 5
and the lower position shown in FIG. 3 is controlled by the main
valve assembly 28.
More specifically, the main valve assembly 28 includes an annular
main valve member 136, an upper annular piston portion 136A of
which is slidably mounted within an annular chamber 138 formed in a
closure cap 140 and surrounding a central hollow post 140A on the
closure cap 140. A plurality of depending lugs 140B on the cap bear
against the upper end of the sleeve 130 to mechanically hold the
sleeve 130 in position. A circular exhaust valve member 142 secured
to the cap by a fastener 144 is disposed within a central opening
in the annular valve 136. A plurality of compression springs 148
interposed between the cap 140 and the upper surface of the main
valve element 136 together with the pressurized fluid normally
supplied to the chamber 138 above the piston portion 136A normally
hold the main valve element 136 in the position shown in FIG. 3 in
which a resilient valve element 150 engages the upper end of the
cylinder 26 to hold this cylinder in the position shown in FIG. 3.
The resilient valve element 150 closes off communication between
the upper interior of the cylinder 26 and the compressed air
contained in the surrounding reservoir 24. In this position, the
interior surfaces of the annular valve 136 are spaced from the
exhaust valve member 142 so that the upper interior of the cylinder
26 is connected to the atmosphere through a plurality of
passageways 152 in the closure cap 140.
To provide means for controlling the shifting movement of the
annular main valve element 136, there is provided a dump valve
assembly indicated generally as 154. The dump valve assembly 154
includes a plural diameter valve element 156 carrying the
illustrated sealing O-rings and slidably disposed within a cylinder
158 formed in the cap 140. A compression spring 160 continuously
biases the valve element to the left-hand position shown in FIG. 3.
The bias provided by the spring 160 is supplemented by pressurized
fluid supplied to the right-hand end of the cylinder 158 over a
passageway 162 in the closure cap 140 which is placed in
communication with the control valve assembly 44 by a conduit 164
(FIGS. 3-5). In the normal condition of the tool, pressurized fluid
is supplied to the conduit or duct 164 by the control valve
assembly 44. This pressurized fluid in the right-hand end of the
cylinder 158 coupled with the resilient bias of the spring 160
forces the valve piston 156 to the position shown in FIG. 3. In
this position, the pressurized fluid from the reservoir 24 passes
from a passageway 166 in the closure cap into the chamber 138
through a passageway 168.
When the main valve assembly 28 is to be operated, the conduit 164
is connected to the atmosphere by the control valve assembly 44,
and the pressurized fluid supplied through the passageway 166 acts
on the enlarged right-hand portion of the valve piston 156 to shift
this valve piston against the bias of the compression spring 160 to
the position shown in FIG. 5. In this position, the passageway 168
is cut off from communication with the passage 166, and pressurized
fluid from the reservoir 24 can no longer be supplied to the
chamber 138. Further, the passageway 168 and an additional
passageway 170 are connected to the atmosphere through the
passageways 152 by means of a port 172 that is now opened by the
displacement of the valve piston 156.
When the dump valve assembly moves to the position shown in FIG. 5,
pressurized fluid in the chamber 138 above the piston portion 136A
on the annular main valve 136 is exhausted to the atmosphere
through the passageways 168 and 170, the port 172, and the
passageways 152. The pressurized fluid in the reservoir acts on the
lower effective surfaces of the main valve 136 to move this valve
upwardly toward the position shown in FIG. 5 against the resilient
bias of the compression springs 148. During the first portion of
this movement, the cylinder 26, because of the continuous upwardly
directed bias applied to the ring 132, moves with the main valve
136, and the resilient element 150 remains seated on the upper end
of the cylinder 26. When the upper surface of the ring 132 bears
against the lower surface of the sleeve 130, the cylinder 26 can no
longer move upwardly. During further movement of the main valve
element 136, an O-ring 174 carried on the inner surface of the
annular main valve element 136 seats on the outer periphery of the
exhaust valve member 142 to close off communication between the
upper interior of the cylinder 26 and the exhaust passageways 152
in the cap. Further upward movement of the main valve 136 moves the
resilient element 150 completely out of engagement with the now
stationary cylinder 26 so as to connect the upper interior of the
cylinder 26 to the reservoir 24 of pressurized fluid. This
initiates a power stroke of the piston 32 and the connected driver
blade 34.
When the main valve assembly 28 is to be closed, the control valve
assembly 44 again supplies pressurized fluid over the conduit 164
and the passageway 162 to the right-hand end of the cylinder 158.
This pneumatic bias coupled with the bias of the compression spring
160 shifts the valve piston 156 from the position shown in FIG. 5
to the position shown in FIG. 3. In this position, the port 172 is
closed, and the passageways 166 and 168 are placed in communication
so that pressurized fluid again flows into the chamber 138 above
the piston portion 136A of the main valve element 136. This
pneumatic bias coupled with the resilient bias provided by the
compression springs 148 initiates downward movement of the main
valve element 136 from the position shown in FIG. 5 to the position
shown in FIG. 3. During the initial movement, the resilient O-ring
150 seats on the upper end of the cylinder 26 so that the upper
interior of the cylinder 26 is cut off from communication with the
pressurized fluid in the reservoir 24. During subsequent movement,
the O-ring 174 is moved downwardly enough to place the cylinder 26
in communication with the exhaust passageways 152 to exhaust the
upper end of the cylinder. Continuing downward movement of the
annular main valve 136 moves the cylinder 26 downwardly from the
position shown in FIG. 5 to the position shown in FIG. 3. In this
position, the piston 32 and the driver blade 34 can be moved
through a return stroke to restore the drive system to its normal
condition.
Associated with the sliding cylinder 26 and the main valve assembly
28 is an assembly for providing the control valve assembly 44 with
signals representing the position of the piston 32. More
specifically, the cylindrical portion 22C of the housing is
provided with a hollow projection 176 (FIGS. 3-5) communicating
with the control valve assembly 44 over a duct or conduit 178. A
plug 180 (FIG. 4) with a restricted orifice therethrough places a
chamber 182 in communication with the pressurized fluid in the
reservoir 24. The chamber 182 is placed in communication with the
exterior of the sleeve 130 (FIGS. 3 and 5) through an opening or
port 184 (FIG. 4). The outer surface of the sleeve 130 (FIGS. 3 and
5) is, in turn, placed in communication with a port or passageway
186 through the upper end of the cylinder 26 by means of a
passageway 187 through the sleeve 130. These passageways are sealed
by the illustrated O-rings.
When the piston 32 occupies the normal position shown in FIG. 3,
the two illustrated O-rings on the piston 32 seal the passageways
186 and 187 so that the chamber 182 (FIG. 4) and thus the conduit
178 extending to the control valve assembly 44 becomes pressurized
to the pressure of the compressed air in the reservoir 24. This
signal indicates that the piston 32 is in its normal home position.
Alternatively, when the piston 32 is displaced from its normal
position through a power stroke and the main valve assembly 28 has
again been closed at the termination of this power stroke, the
upper interior of the cylinder 26 is placed at atmospheric pressure
in the manner described above. At this time, the passageways 186
and 187 and the port 184 vent the chamber 182 and the duct 178 to
the atmosphere because these passageways exhaust pressurized air
faster than it can be supplied through the restricted orifice in
the plug 180. Thus, when the main valve assembly 28 is closed and
the piston 32 is not in a normal home position, the conduit 178
provides an exhaust signal to the control valve assembly 44. When
the piston 32 is returned to its normal position, the port 186 is
again sealed, and the restricted orifice in the plug 180 (FIG. 4)
again pressurizes the chamber 182 and the conduit 178 to advise the
control valve assembly 44 that the piston 32 has been returned to
its normal home position.
To provide the exhaust valve assembly 30 for selectively sealing or
opening to the atmosphere the lower interior of the cylinder 26,
there is provided an annular or cylindrical member 188 (FIGS. 3, 5,
and 6) whose lower end is welded or otherwise permanently secured
to an uppermost plate 48A in the four laminated plates 48A-48D in
the plate assembly 48. The annular member 188 includes an enlarged
upper end portion 188A having a recess in which is disposed a
resilient O-ring 190 providing an exhaust valve seal. The element
190 is aligned with the lower end of the cylinder 26.
In the normal condition of the tool 20 (FIG. 3), the engagement of
the upper end of the cylinder 26 by the main valve 136 or the
resilient element 150 thereon seats the lower end of the cylinder
26 on the resilient element 190 to close off communication between
the lower interior of the cylinder 26 and the atmosphere through,
for example, a plurality of spaced ports or openings 192 (FIGS. 3,
5, and 6). When, however, the main valve assembly 28 is opened
(FIG. 5), the cylinder 26 is moved upwardly in the manner described
above, and the lower end of the cylinder 26 is spaced from the
resilient element 190. This places the lower interior of the
cylinder 26 beneath the piston 32 in communication with the
atmosphere through the openings 192. The entire lower end of the
cylinder 26 is vented through the large area openings 192, and thus
no back pressure is encountered by the piston 32 during its driving
stroke. This substantially improves the efficiency of the drive
system for the tool 20.
Associated with the exhaust valve assembly 30 is a unique fluid
conveying means controlled by the control valve assembly for
supplying pressurized fluid to the lower interior of the cylinder
26 to move the piston 32 through a return stroke. More
specifically, this pressurized fluid is supplied by the control
valve assembly 44 to a passageway 194 (FIGS. 4, 6, and 8), which
passageway extends through a depending portion of the head portion
22A of the housing 22 immediately adjacent one of the tapped
openings 54 used to secure the plate assembly 48 to the head
portion 22A. This passageway 194 is aligned with an opening 196 in
the uppermost plate 48A, and the port or passageway 196 is, in
turn, aligned with a pair of elongated passageways 198 in the
plates 48B and 48C at the right-hand end thereof. The elongated
slots 198 extend through the plates 48B and 48C to a point
underlying an opening 200 (FIGS. 6 and 8) in the uppermost plate
48A. The opening 200 extends through the plate 48A to discharge air
within the annular member 188.
A resilient or elastomeric bumper or cushion 202 is disposed within
and held in position by the annular member 188 in a position to
cushion or terminate the power stroke of the piston 32. The bumper
202 includes a plurality of radially extending, tapered ribs 202A
terminating above the plate 48A so that pressurized fluid supplied
through the opening 200 can be dispersed around the periphery of
the bumper 202 through a passage 203 and then pass downwardly
through the passageways defined by the ribs 202A to be applied to
the lower surface of the piston 32 when this piston is in its lower
position (FIG. 7). The pressurized return air supplied through the
opening 200, in passing through the passageways defined by the ribs
202A, cools the bumper 202 to prevent deterioration and overheating
thereof. By thus supplying piston return air over the system of
passageways 194 and 196 and 198 and 200, and then dispersing this
air around the exterior surface of the bumper 202, the piston
return air not only is supplied directly beneath the piston 32
without passing through the side walls of the cylinder 26, but is
also used to effect cooling of the bumper 202. Further, the use of
the laminated plate assembly 48 facilitates the formation of the
passageways in a construction of welded or brazed individual plates
which are capable of absorbing the impact shocks arising from
terminating the power stroke of the piston 32.
Associated with the exhaust valve assembly 30 is an improved
arrangement for supplying a signal to the control valve assembly 44
indicating that the piston 32 has completed its power stroke. This
arrangement is best illustrated in FIG. 7 of the drawings. More
specifically, when the piston 32 reaches the end of its power
stroke, as determined by engagement with the bumper 202,
pressurized fluid from above the piston 32 flows out of the
cylinder through a plurality of spaced ports 204 to an area in the
interface between the cylinder 26 and the portion 22D of the head
22A of the housing. A passageway through the portion 22D of the
head 22A supplies this pressurized signal to the control valve
assembly 44. In the past, there has been a tendency for this end of
power stroke signal of pressurized fluid to become dissipated when
the interior of the cylinder 26 above the piston 32 is exhausted by
closing the main valve to start the return stroke of the piston
32.
However, in the present arrangement, as soon as the signal supplied
through the ports 204 controls the control valve assembly 44 to
effect the closing of the main valve, the cylinder 26 is moved
downwardly from the position shown in FIG. 7 to the position shown
in FIG. 3 in which the lower end of the cylinder 26 seats on the
exhaust valve seat 190. When this happens, the ports 204 are moved
to a position bounded on opposite sides by the two O-rings carried
on the piston 32. The pressurized signal supplied through the ports
204 is thus sealed off from communication with either the upper or
lower interior of the cylinder 26. Further, when compressed air is
supplied through the opening 200 beneath the piston 32 to start the
return stroke of the piston 32, this pressurized fluid also passes
through the ports 204 to supplement the cycle valve bias previously
supplied from the pressurized fluid above the piston 32 which may
now have been exhausted to the atmosphere by the closure of the
main valve assembly 28.
Control Valve Assembly 44
The control valve assembly 44 is controlled by a manually actuated
trigger 206 and a conventional workpiece engaging assembly
indicated generally as 208 to operate the fastener driving tool 20
through one or a number of automatically effected cycles of power
and return strokes of the piston 32. The mechanical construction of
the control valve assembly 44 can be of any suitable type and can,
for example, be of the general nature disclosed and described in
U.S. Pat. No. 3,685,396. In general, the control valve assembly is
carried in a housing 210 as an integral subassembly which can be
secured to a wall of the head portion 22A of the housing 22 by
suitable fasteners, such as machine bolts or screws 212 (FIG. 4).
The passages in the valve housing 210 communicating with the
various control components of the assembly 44 are coupled to ports
terminating related passageways formed in the housing 22. The valve
housing 210 is provided with a pair of spaced supporting lugs 210A
between which the trigger 206 is pivotally mounted on a pivot pin
214 (FIGS. 1 and 4).
The workpiece engaging assembly or means 208 which is actuated when
the tool 20 is placed adjacent a workpiece can be of any suitable
well known construction, such as that shown in U.S. Pat. No.
3,615,049. In general, the assembly 208 includes a linkage 216
mounted on the housing 22 and the nosepiece assembly 38 and
resiliently biased to a position in which a workpiece engaging
portion 216A of the mechanism projects downwardly below the lower
end of the nosepiece assembly 38. An upper portion 216B is coupled
by a lost motion arrangement to the lower end of a safety valve
stem 218 (FIG. 3) forming a part of the control valve assembly 44.
When the tool 20 is placed adjacent a workpiece, the lower end
portion 216A engages the workpiece and moves the mechanism 216
upwardly. After the lost motion has been taken up, the portion 216B
of the linkage 216 moves the safety valve stem 218 upwardly from a
normal position shown in FIG. 11 to an actuated position shown in
FIG. 12. When the tool 20 is moved away from the workpiece,
resilient biasing means 220 (FIG. 1) moves the linkage 216
downwardly so that after the lost motion is taken up, a portion
216B moves the valve stem 218 downwardly from the actuated position
shown in FIG. 12 to the normal position shown in FIG. 11.
Referring now more specifically to the valving arrangement included
in the control valve assembly 44, the assembly 44 is shown in
normal position in FIG. 11 and in an operated position in FIG. 12.
The control valve assembly includes a return air valve assembly
indicated generally as 222, a combined manual-safety valve assembly
indicated generally as 224, and a cycle valve assembly indicated
generally as 226. To provide a master source of pressurized fluid
or compressed air for use by the control valve assembly 44, there
is provided a port or passageway 228 extending from the reservoir
24 through a wall of the housing 22 and the back wall of the
housing 210 to the control valve assembly 44 to open into a valve
cylinder 230 forming a part of the return valve assembly 222. A
passageway 232 forwards this pressurized fluid to a valve cylinder
234 forming a part of the manual valve assembly 224. A further
passageway 236 forwards this pressurized air to a valve cylinder
238 forming a part of the cycle valve assembly 226.
The manual-trigger valve assembly 224 is actuated by the trigger
206 and the workpiece engaging assembly 208 to selectively connect
a passageway 240 coupled to the cycle valve assembly 226 to a
source of pressurized fluid when the control valve assembly 44 is
in its normal position and to connect the passageway 240 to the
atmosphere when the assembly 224 has been properly actuated by the
trigger 206 and the workpiece engaging assembly 208. The manual
valve assembly 224 includes the safety valve stem 218 having
therein a valve chamber 242 open at its upper end to the
atmosphere. Slidably disposed within the valve chamber or cylinder
242 is a valve element or stem 244 with an enlarged upper end
portion 244A. A compression spring 245 interposed between the lower
end of the valve stem 244 and the lower wall of the valve chamber
242 normally biases the valve stem 244 to the position shown in
FIG. 11. The pressurized fluid admitted to the interior of the
chamber 242 through a plurality of passageways 246 from the valve
cylinder 234 and the passageway 232 also acts on the enlarged
portion 244A to aid the bias of the spring 245 and normally seat
this enlarged portion 244A on an exhaust valve O-ring 248. The
spring bias insures that the tool 20 will not fire when first
coupled to pressurized air. This pressurized fluid also passes
outwardly from the chamber 242 through a plurality of ports or
passageways 250 and the portion of the valve chamber 234 bounded by
the illustrated O-rings to be conveyed over the passageway 240 to
the cycle valve assembly 226.
When the valve stem 218 is moved upwardly to its actuated position
determined by engagement of the upper stem 218 with a shoulder
formed in the valve cylinder 234 (FIG. 12) and when the trigger 206
is pivoted in a counterclockwise direction about the pivot pin 214
to the position shown in FIG. 5, the indicated portion of the
trigger 206 moves downwardly into engagement with the upper end of
the valve stem 244 and shifts this valve stem to the position shown
in FIG. 12. In this position, an O-ring 252 seats on the inner wall
of the valve chamber 242 to close off communication between the
ports or passageways 246 and 250 to terminate the supply of
pressurized fluid to the passageway 240. At the same time, the
enlarged upper end portion 244A of the valve element 244 moves out
of engagement with the O-ring 248 to connect the passageway 240 to
the atmosphere. The valve means 244 cannot be moved to the position
shown in FIG. 12 unless both the safety valve stem 218 is elevated
to the position shown and the trigger 206 is depressed to the
position shown. Thus, the manual-safety valve assembly 224 cannot
be operated to connect the passageway 240 to the atmosphere unless
both the trigger 206 and the workpiece engaging assembly 208 are
actuated. The release of these elements restores the manual valve
assembly 224 to its normal position shown in FIG. 11 so that
pressurized fluid is reapplied to the passageway 240 and its
communication with the atmosphere is interrupted.
The return air valve assembly 222 is controlled by the pressure in
the upper interior of the drive cylinder 26 to selectively supply
return air to the lower end of the cylinder 26 at the end of a
power stroke and to terminate this supply of return air when the
piston 32 is restored to its normal position. In addition, the
return air valve assembly 222 supplies a supplemental source of
pressurized air for preventing premature operation of the cycle
valve assembly 226. The return air valve assembly 222 includes a
valve piston 254 slidably mounted in the valve chamber 230 and
having an upper greater area piston portion 254A and a lower
smaller area piston portion 254B providing a bias oppositely
directed to that provided by the piston portion 254A. The
pressurized fluid normally supplied through the conveying means 178
in the manner described above acts on the piston portion 254A to
provide a greater magnitude downwardly directed bias acting on the
valve piston 254 than is provided by the pressurized fluid supplied
by the passageway 228 to the valve chamber 230 which provides an
upwardly directed bias acting on the piston portion 254B. Thus, the
valve piston 254 normally occupies the position shown in FIG. 11 in
which its lower end seats on a resilient O-ring 256.
When the drive piston 32 reaches the end of its power stroke and
the main valve assembly 28 is closed to exhaust the upper interior
of the cylinder 26, the conduit 178 is placed at atmospheric
pressure, and the bias is removed from the large piston portion
254A on the valve piston 254. At this time the pressurized fluid
supplied to the lower end of the valve cylinder 230 by the
passageway 228 acts on the small area piston portion 254B to move
the valve piston 254 upwardly to the position shown in FIG. 12. At
this time, the lower end of the valve piston 254 moves out of
engagement with the valve seat 256, and pressurized fluid from the
passageway 228 and the valve cylinder 230 enters a passageway 258
to be forwarded through a port 260 to the passageway 194 (FIGS. 4
and 8) to be supplied in turn through the opening 200 to the lower
end of the cylinder 26. In addition, pressurized fluid from the
passageway 258 is forwarded over another passageway 262 to be
supplied to the lower end of the valve chamber 238 for the cycle
valve assembly 226. The pressurized fluid supplied by the
passageway 262 is used to avoid a premature change in the state of
the cycle valve 226.
When the drive piston 32 has been restored to its normal position
in the manner described above, the conduit 178 is again
pressurized, and the greater bias applied by the large piston
portion 254A returns the valve piston 254 to the normal position
shown in FIG. 11 so that the supply of pressurized fluid to the
passageway 258 is terminated. The pressurized fluid trapped in the
passageways 258, 260, and 262 is discharged to the atmosphere over
the connection through the opening 200 to the lower end of the
interior of the cylinder 26. From the closed cylinder, trapped
fluid can leak to the atmosphere through clearances along the
driver blade 34.
The cycle valve assembly 226 illustrated in FIGS. 11 and 12 is one
that automatically and successively cycles the main valve assembly
28 between open and closed conditions after the manual valve
assembly 224 has been operated to produce a sequence of power and
return strokes of the piston 32 and the driver blade 34. To
accomplish this, the control valve assembly 226 includes a valve
piston 264 movable to a position causing opening of the main valve
28 by a continuous bias and movable to an alternate position
closing the main valve assembly 28 in accordance with the high
pressure signal received through the ports 204 (FIG. 7) and 280
(FIG. 11) when the piston 32 has reached the end of its power
stroke. A control piston 266 slidably mounted within the valve
cylinder 238 for the cycle valve assembly 226 also forms a part of
this assembly and is controlled by the return air valve assembly
222 to prevent premature return of the valve piston 264 to its
setting effecting opening of the main valve 28.
More specifically, the cycle valve piston 264 which is slidably
mounted within the valve cylinder 238 includes a small area piston
portion 264A slidably mounted within a reduced diameter cylinder
268 formed in a plug 270 that is carried within an opening 272 in
the housing 22B immediately above and in alignment with the valve
chamber 238 in the valve housing 210. The chamber 268 is
continuously supplied with pressurized fluid from the reservoir 24
through a restricted orifice 274 formed in the plug 270. This
pressurized fluid acts on the small diameter portion 264A to
continuously bias the cycle valve piston 264 to the normal position
shown in FIG. 11.
In this position, pressurized fluid normally supplied by the manual
valve assembly 224 over the passageway 240 passes around an O-ring
276 in an enlarged portion 238A of the valve chamber to be
forwarded over a passageway 278 to one end of the conduit 164. As
described above, the conduit 164 extends to the dump valve assembly
154 (FIG. 3) in the closure cap 140 for the tool 20 and holds the
main valve assembly 28 in a position closing the open upper end of
the cylinder 26. When the manual-safety valve assembly 224 is
operated in the manner described above to connect the passageway
240 to the atmosphere, the conduit 164 and the passageway 278 are
also connected to the atmosphere to effect opening of the main
valve assembly 28 in the manner described above. In this operation,
the lower exhaust valve assembly 30 opens first, the exhaust
passageways 152 are then closed, and finally compressed air is
admitted to the top of the cylinder 26.
When the piston 32 reaches the end of its power stroke (FIG. 7),
pressurized fluid is supplied through the ports 204. This
pressurized fluid is conveyed through a passageway 280 extending
through the portion 22D of the head portion 22A and the back wall
of the housing 210 for the valve assembly 44 to supply this fluid
below a large area piston portion 264B on the cycle valve piston
264. This fluid is supplied above the upper surface of the control
piston 266. The pressurized fluid supplied through the passageway
280 provides a greater upwardly directed bias than the pressurized
fluid acting on the small area piston portion 264A. Thus, the cycle
valve piston 264 is moved upwardly from the position shown in FIG.
11 to the position shown in FIG. 12. When the piston 264 moves to
the position shown in FIG. 12, the O-ring 276 closes off
communication between the passageways 240 and 278 so that the
conduit 164 is no longer connected to the atmosphere. In addition,
an O-ring 282 moves into the enlarged portion 232A of the valve
cylinder 238 and places the passageway 278 in communication with
the pressurized fluid supplied to the valve chamber 238 by the
passageway 236. When the conduit 164 is again pressurized, the main
valve assembly 28 is closed to terminate the supply of pressurized
fluid above the piston 32 and then to connect the upper interior of
the cylinder 26 to the atmosphere. Further, when the main valve
assembly 28 is closed, the cylinder 26 is then moved downwardly to
close the lower end exhaust valve assembly 30 (FIG. 3). In this
position, the O-rings on the piston 32 seal the ports 204 so that
the pressurized fluid applied to the piston portion 264B cannot be
dissipated. This aids in holding the cycle valve piston 264 in the
elevated position shown in FIG. 12.
When the pressure within the upper interior of the cylinder 26
becomes sufficiently dissipated, the return air valve assembly 222
is opened, as shown in FIG. 12, and pressurized fluid is applied
over the passageways 258 and 262 to the extreme lower end of the
cycle valve cylinder 238. This pressurized fluid, in being supplied
directly from the reservoir 24 without appreciable throttling, is
of greater pressure than that trapped above this control piston and
supplied through the signal passageway 280. Accordingly, the
control piston 266 moves upwardly to the position shown in FIG. 12.
The piston 266 may not physically engage the large piston portion
264B of the cycle valve piston 264 under certain conditions where
the pressure supplied by the port 280 is great enough. In any
event, the control piston 266 provides an additional bias urging
the piston 264 upwardly to the position shown in FIG. 12 against
the bias applied to the small area piston portion 264A with the
result that the cycle valve piston 264 cannot be prematurely
restored to its alternate setting shown in FIG. 11.
The opening of the return air valve assembly 222 also supplies
pressurized fluid in the manner described above to the lower
interior of the cylinder 26 so that the piston 32 is elevated
toward its normal position. As the piston 32 clears the ports 204
(FIG. 7), the signal air supplied to the large piston portion 264B
begins to dissipate over the passageway 280 due to expansion of air
within the lower interior of the cylinder 26. However, the pressure
of this air is supplemented by that supplied by the return valve
assembly 222 so that a substantial bias remains applied to the
large piston portion 264B. In addition, the control piston 266
provides a continuing bias acting on the large piston portion 264B
to prevent any movement of the cycle valve piston 264 at this
time.
When the piston 32 is returned to its normal home position, the
conduit 178 is pressurized, and the return valve assembly 222 is
moved to the closed position shown in FIG. 11. This terminates the
supply of return air beneath the piston 32 and beneath the control
piston 266. The air acting on the piston 266 becomes dissipated
primarily by leakage around the driver blade 34, and the bias
resulting from the pressurized fluid within the chamber 268 acting
on the small piston portion 264A is now effective to move the cycle
valve piston 264 to the normal position shown in FIG. 11 along with
the control piston 266. When the cycle valve piston 264 reaches the
position shown in FIG. 11, the O-ring 282 closes off communication
between the passageway 278 and the fluid pressure supplying
passageway 236. The O-ring 276 in moving into the enlarged portion
238A connects the passageway 278 to the exhaust passageway 240 so
that the main valve 28 is again opened. This initiates another
cycle of operation of the drive system for the tool 20. This
operation continues, providing successive cycles of alternate power
and return strokes until such time as the manualsafety valve
assembly 224 is released.
The cycle valve assembly 226 can also easily be modified to provide
single cycle rather than autofire operation. The only change that
is required is to replace the plug 270 with another plug of
identical configuration except that the passageway 274 instead of
extending axially within the opening 272 to place the chamber 268
in communication with the reservoir 24 extends laterally through
the plug 270 to communicate with a passageway 290 leading to the
atmosphere. This, in effect, removes the autofire bias applied to
the small area piston portion 264A. With this modification, a small
area piston portion 264C is effective when the passageway 240 is
pressurized to hold the piston 264 for the cycle valve assembly 226
in the normal position shown in FIG. 11. However, when the valve
piston 264 is shifted to its elevated position shown in FIG. 12 in
precisely the manner described above, the piston portion 264C is
connected to the atmosphere over the passageway 240, and no bias
exists for returning the piston 264 to the normal position shown in
FIG. 11 until such time as the manual-safety trigger assembly 224
is released to repressurize the passageway 240. With this
modification, the cycle valve assembly 226 operates the tool 20
through a single power and return stroke, and further power strokes
cannot be initiated until the manual-safety valve assembly 224 is
released.
Referring now more specifically to FIG. 13 of the drawings, therein
is illustrated a schematic diagram of the control valve assembly 44
for effecting autofire operation of the tool 20. The main valve
assembly 28, in its schematic form shown in FIG.. 13, includes the
dump valve assembly 154. A small effective area piston portion 28A
shown in FIG. 13 represents the lower area of the main valve
element 136 tending to open this valve. A large effective area
piston portion shown as 28B in FIG. 13 represents the upper
effective area of the piston portion 136A as well as the bias
applied by the compression springs 148. Since the bias provided by
the large area piston portion 28B overcomes the bias provided by
the piston portion 28A, the main valve 28 in its normal position
connects the upper interior of the cylinder 26 to the atmosphere.
The large area piston portion 28B is normally connected to
pressurized fluid over the passageways 164, 240, the cycle valve
226, and the manual-safety valve assembly 224.
When the tool 20 is to be operated, and both the trigger 206 and
the workpiece engaging assembly 208 are operated, the manual-safety
valve assembly 224 is operated to its alternate setting, and the
lines 164 and 240 connect the large piston portion 28B on the main
valve assembly 28 to the atmosphere. The continuous bias applied to
the small area piston portion 28A shifts the main valve assembly 28
to its open position so that the lower exhaust valve assembly 30 is
first opened, the exhaust passages 152 are next closed, and finally
pressurized fluid is applied to the upper interior of the cylinder
26. This moves the piston 32 and the driver blade 34 through a
power stroke to drive a staple 40 supplied to the drive track 36.
At the end of the power stroke of the piston 32, pressurized fluid
collected through the ports 204 is supplied over the passageway 280
to pressurize the large piston portion 264B of the cycle valve
assembly 226.
The force applied by the large area piston portion 264B overcomes
the continuous bias applied to the small area piston portion 264A,
and the cycle valve 226 shifts to its alternate setting so that
even though the line 240 remains at atmospheric pressure, the
passageway 164 is again pressurized, and the large area piston
portion 28B shifts the main valve assembly to its normal setting
shown in FIG. 13. Incident to this, the exhaust valve assembly 30
for the lower interior of the cylinder 26 is closed.
When the upper interior of the cylinder 26 approaches atmospheric
pressure, the port 186 exhausts the passageway or conduit 178
faster than pressurized fluid can be supplied through the
restricted orifice in the plug 180, and the large area piston
portion 254A of the return air valve assembly 222 becomes
substantially depressurized. At this time, the continuous pneumatic
bias applied to the small area piston portion 254B is effective to
operate the return air valve assembly 222 to its alternate setting.
When this happens, the line 258 is pressurized to supply fluid
pressure over the passageway 262 to the control piston 266. The
control piston mechanically biases the cycle valve assembly 226
toward its alternate setting to supplement the pneumatic bias
applied by the large piston portion 264B.
The pressurized fluid supplied to the passageway 258 is also
supplied to the opening 200 below the piston 32 in the cylinder 26
over a system of passageways and ports including the components
194, 196, 198, and 200. This pressurized fluid moves the piston 32
upwardly through a return stroke toward its normal position. As the
piston 32 clears the ports 204, pressurized fluid from the opening
200 also passes out of the cylinder 26 through the ports 204 to be
applied over the passageway 280 to supplement the bias applied to
the large area piston portion 264B on the cycle valve 226. When the
piston 32 reaches its normal home position, the ports 186 are
sealed from communication with the atmosphere by the O-rings
carried on the piston.
The orifice in the plug 180 then begins to pressurize the
passageway 178. When this becomes sufficiently pressurized, the
bias applied to the large piston portion 254A on the air return
valve 222 shifts this valve to the normal position shown in FIG. 13
against the continuous bias applied to the small area piston
portion 254B. When this happens, the passageway 258 and the
passageways connected thereto tend toward atmospheric pressure
along with the passageway 280, by, for example, leakage of air from
the bottom of the cylinder 26 along the sides of the driver blade
34. When this pressure drop becomes great enough, the continuous
bias applied to the small area piston portion 264A of the cycle
valve assembly 226 shifts this cycle valve back to its normal
position shown in FIG. 13 and restores the control piston 266 to
its normal position.
With the cycle valve 226 in its normal position, the passageway or
conduit 164 is again connected to atmosphere over the passageway
240 and the operated valve assembly 224. This opens the main valve
assembly 28 in the manner described above. This cyclic operation
continues until such time as the manual-safety valve assembly 224
is released. At this time, the control components of the control
valve assembly 44 are restored to the normal position shown in FIG.
13.
Although the present invention has been described with reference to
a number of 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.
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