U.S. patent number RE29,527 [Application Number 05/489,395] was granted by the patent office on 1978-01-31 for safety for fastener driving tool.
This patent grant is currently assigned to Duo Fast Corporation. Invention is credited to Allen R. Obergfell, Howard B. Ramspeck.
United States Patent |
RE29,527 |
Ramspeck , et al. |
January 31, 1978 |
Safety for fastener driving tool
Abstract
A pneumatic fastener driving tool includes a safety arrangement
that requires the tool to be placed against a workpiece before a
manual trigger valve is operated in order to permit the tool to
fire. Once the tool is placed against the workpiece the safety
arrangement prevents "touch" firing by moving the tool toward and
away from the workpiece. In two embodiments, the safety arrangement
includes a piston valve which is fluid operated to close off a
control line to the main valve of the tool whenever the trigger is
operated before the tool is placed against a workpiece and when an
attempt is made to "touch" fire the tool with the trigger held
operated. In a third embodiment, metering orifices in a valve
actuated by moving the tool against a workpiece prevent repeated
"touch" operation of the tool.
Inventors: |
Ramspeck; Howard B. (Elmhurst,
IL), Obergfell; Allen R. (Park Ridge, IL) |
Assignee: |
Duo Fast Corporation (Franklin
Park, IL)
|
Family
ID: |
21996144 |
Appl.
No.: |
05/489,395 |
Filed: |
July 17, 1974 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
055178 |
Jul 15, 1970 |
03677456 |
Jul 18, 1972 |
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Current U.S.
Class: |
227/8; 227/130;
91/356; 91/461 |
Current CPC
Class: |
B25C
1/044 (20130101) |
Current International
Class: |
B25C
1/04 (20060101); B27F 007/22 () |
Field of
Search: |
;227/130,8
;91/356,461 |
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 as new and desired to be secured by Letters Patent
of the United States is:
1. In a tool for driving fasteners into a workpiece using a
pressurized fluid motor for actuating a fastener driving means,
a manually actuated trigger valve means,
a safety means actuated by placing the tool adjacent the
workpiece,
fluid actuated valve means controlled by the trigger valve means
and the safety means for controlling the application of pressurized
fluid to the fluid motor,
and a control means including a fluid pressure operated piston
means, said control means interconnecting the trigger valve means
and the safety means to prevent the operation of the fluid actuated
valve means unless the safety means is first actuated followed by
the actuation of the trigger valve means.
2. In a tool for driving fasteners into a workpiece using a fluid
motor actuated driving means,
a fluid actuated valve means for controlling the application of
pressurized fluid to the fluid motor,
a trigger valve means,
a safety valve means actuated by placing the tool adjacent the
workpiece,
passage means coupling the trigger and safety valve means to the
fluid actuated valve means to control the operation of the fluid
actuated valve means,
and control means coupled to said passage means and controlled by
the trigger and safety valve means for preventing actuation of the
fluid actuated valve means unless the safety valve means is first
operated followed by the trigger valve means.
3. In a tool for driving fasteners into a workpiece using a fluid
motor actuated driving means,
a fluid actuated valve means for controlling the application of
pressurized fluid to the fluid motor;
a trigger valve means,
a safety valve means actuated by placing the tool adjacent the
workpiece,
passage means coupling the trigger and safety valve means to the
fluid actuated valve means to control the operation of the fluid
actuated valve means,
and a fluid actuated valve in said passage means having both a
normal position and an operated position, said fluid actuated valve
being selectively coupled to pressurized fluid and the atmosphere
by one of said trigger and safety valve means and being actuated
from said normal position to said operated position to prevent
operation of said fluid actuated valve means in response to the
actuation of one of said trigger and safety valve means prior to
the operation of the other of said valve means.
4. In a tool for driving fasteners into a workpiece using a fluid
motor to actuate a fastener driver,
a trigger valve means,
a safety means actuated by placing the tool adjacent the
workpiece,
means controlled by the trigger valve means and the safety means
for controlling the application of pressurized fluid to the fluid
motor,
a movably mounted means movable between a first position permitting
the application of fluid to the fluid motor and a second position
preventing the application of fluid to the fluid motor, said
movably mounted means having a fluid pressure responsive
surface,
and passage means communicating with the fluid pressure responsive
surface and coupling said surface to the trigger valve means for
controlling the fluid pressure applied to said surface so that the
movement of the movably mounted means to its first and second
positions is controlled in dependence on the sequence in which the
trigger valve means and the safety means are operated.
5. The tool set forth in claim 4 in which
the tool includes a reservoir of pressurized fluid,
and the trigger valve means is operable to alternate positions
connecting said surface to the reservoir and the atmosphere.
6. The tool set forth in claim 5 including
biasing means biasing the movably mounted means to its second
position,
and in which the trigger valve means normally connects said surface
to the reservoir to hold the movably mounted means in its first
position against the bias of the biasing means.
7. The tool set forth in claim 6 in which
the biasing means includes pressurized fluid supplied in dependence
on the position of the safety means, which pressurized fluid is
removed by the actuation of the safety means.
8. In a tool for driving fasteners into a workpiece using a fluid
motor to actuate a fastener driver,
a trigger valve means,
a safety means actuated by placing the tool adjacent the
workpiece,
means controlled by the trigger valve means and the safety means
for controlling the application of pressurized fluid to the fluid
motor,
a movably mounted means movable between a first position permitting
the application of fluid to the fluid motor and a second position
preventing the application of fluid to the fluid motor, said
movably mounted means having a fluid pressure responsive surface
for controlling the movement of the movably mounted means,
and means including passage means supplying a biasing pressurized
fluid to the fluid responsive surface on the movably mounted means
and responsive to the position of the movably mounted means for
permitting the trigger valve means and the safety means to effect
the application of fluid to the fluid motor only when the safety
means is operated first followed by the operation of the trigger
valve means.
9. In a tool for driving fasteners into a workpiece using a fluid
motor for actuating a fastener driver,
fluid controlled main valve means for controlling the application
of fluid to the fluid motor,
a trigger valve means,
passage means coupled to the main valve means and selectively
connected to fluid pressure and the atmosphere by the trigger valve
means to control the operation of the main valve means,
a slidable valve in said passage means movable to a first position
closing the passage means and to a second position opening the
passage means, said slidable valve having two opposed fluid
responsive surfaces, one of said surfaces being selectively coupled
to fluid pressure and the atmosphere under the control of the
trigger valve means,
a safety means actuated by positioning the tool adjacent a
workpiece,
and valve means controlled by the safety means for selectively
coupling the other surface on the slidable valve to fluid pressure
and the atmosphere.
10. In a tool for driving fasteners into a workpiece using a fluid
motor to actuate a fastener driver,
trigger valve means operable between a normal and an operated
position to control the application of fluid pressure to the fluid
motor,
safety means biased to a normal position and actuated to an
operated position against the bias when the tool is placed adjacent
the workpiece, the trigger valve means and the safety means each
being independently operable between their normal and operated
positions to permit the trigger valve means and the safety means to
be actuated to their operated position in any sequence,
first control means operated when both the trigger valve means and
the safety means are in their operated positions for rendering the
fluid pressure effective to operate the fluid motor,
and second control means for rendering the first control means
ineffective unless the safety means is operated prior to the
trigger valve means.
11. In a tool for driving fasteners into a workpiece using a fluid
motor to actuate a fastener driver,
trigger valve means operable between normal and operated positions
to control the application of fluid pressure to the fluid
motor,
safety means biased to a normal position and actuated to an
operated position against the bias when the tool is placed adjacent
the workpiece, the trigger valve means and the safety means each
being independently operable between their normal and operated
positions to permit the trigger valve means and the safety means to
be actuated to their operated position in any sequence,
first control means operated when both the trigger valve means and
the safety means are in their operated positions for rendering the
fluid pressure effective to operate the fluid motor,
and second control means operative following the actuation of the
trigger valve means and the safety means to their operated
positions for rendering the first control means ineffective to
cause repeated operation of the fluid motor when the safety means
is returned to its normal position and again actuated to its
operated position.
12. In a tool for driving fasteners into a workpiece using a fluid
motor to actuate a fastener driver,
fluid controlled main valve means for controlling the application
of fluid pressure to the fluid motor,
trigger valve means,
safety means operable when the tool is disposed adjacent the
workpiece, said safety means including a safety valve means,
passage means connected to and controlled by the trigger valve
means and the safety valve means for selectively coupling fluid
pressure and the atmosphere to the main valve means to control the
operation of said main valve, the main valve means causing
operation of the fluid motor only when both of the trigger valve
means and the safety means are operated,
and control means coupled to the passage means and effective only
after the fluid motor has been operated by the operation of the
trigger valve means and the safety means for rendering the passage
means ineffective to control additional operations of the fluid
motor under the control of subsequent releases and reoperations of
the safety means so long as the trigger valve means is maintained
operated.
13. The tool set forth in claim 12 in which
the safety valve means has a first position supply fluid pressure
to the passage means and a second position coupling the passage
means to the trigger valve means.
14. The tool set forth in claim 12 in which
the safety valve means has a first position in which a limited
quantity of pressurized fluid is supplied to the passage means and
a second position in which the passage means is placed in open
communication with the trigger valve means.
15. In a tool for driving fasteners into a workpiece using a fluid
motor to actuate a fastener driver,
a reservoir of pressurized fluid in the tool,
main valve means for controlling the application of fluid from the
reservoir to the fluid motor and including a fluid control for
controlling operation of the main valve means,
a passage extending to the fluid control for selectively coupling
the fluid control to the reservoir and the atmosphere,
trigger valve means with an outlet coupled to the reservoir and the
atmosphere in alternate positions of the trigger valve means,
safety valve means having a normal position coupling the passage to
the reservoir and an operated position coupling the passage to the
outlet of the trigger valve means, the safety valve means being
actuated to its operated position when the tool is disposed
adjacent the workpiece,
and a fluid operated valve movable between a first position placing
the safety valve means in communication with the outlet of the
trigger valve and second position closing off communication between
the safety valve means and the outlet of the trigger valve means,
said fluid operated valve having a pair of opposed fluid responsive
surfaces for moving the fluid operated valve between said first and
second position, a first one of said surfaces being supplied with
fluid from the reservoir under the control of the trigger valve
means and a second one of the fluid responsive surfaces being
supplied with fluid under the control of the safety valve
means.
16. The tool set forth in claim 15 in which
the first fluid responsive surface is coupled to the outlet of the
trigger valve means.
17. The tool set forth in claim 16 in which
the safety valve means includes an additional valve which couples
the second fluid responsive surface to the reservoir when the
safety valve means is in its normal position and which couples the
second fluid responsive surface to the atmosphere when the safety
valve means is in its operated position.
18. The tool set forth in claim 15 in which
the first and second fluid responsive surfaces are of equal
area.
19. The tool set forth in claim 15 in which
the first and second fluid responsive surfaces have differential
areas. .Iadd. 20. A fastener driving device including a portable
housing, fluid pressure operated fastener driving means carried by
said housing for movement through successive cycles of operation
each of which includes a fastener driving stroke and a return
stroke, fastener magazine means carried by said housing for
receiving a supply of fasteners and feeding successive fasteners
into a position to be driven into a workpiece during successive
fastener driving strokes of said fastener driving means, fluid
pressure control means including an actuating member carried by
said housing for movement from a normal inoperative position into
an operative position for initiating the movement of said fastener
driving means through a fastener driving stroke, a work contact
responsive member carried by said housing for movement from a
normal inoperative position into an operative position in response
to the movement of said device into cooperating engagement with a
workpiece, and a trigger member carried by said housing for manual
movement from a normal inoperative position into an operative
position, the improvement in combination therewith which comprises
enabling means operatively associated with said members for (1)
enabling movement of said trigger member into its operative
position when said work contact responsive member is in its
inoperative position without movement of said actuating member into
its operative position, (2) enabling movement of said trigger
member into its operative position when said work contact
responsive member is in its operative position to effect movement
of said actuating member into its operative position, and (3)
enabling movement of said work contact responsive member into its
operative position when said trigger member is in its operative
position without movement of said actuating member into its
operative position. .Iaddend. .Iadd. 21. A fastener driving device
including a portable housing having a handle adapted to be manually
gripped by an operator, fluid pressure operated fastener driving
means carried by said housing for movement through successive
cycles of operation each of which includes a fastener driving
stroke and a return stroke, fastener magazine means carried by said
housing for receiving a supply of fasteners and feeding successive
fasteners into a position to be driven into a workpiece during
successive fastener driving strokes of said fastener driving means,
fluid pressure control means including an actuating member carried
by said housing for reciprocating movement from a normal
inoperative position into an operative position for initiating the
movement of said fastener driving means through a single fastener
driving stroke and from said operative position into said
inoperative position for initiating the movement of said fastener
driving means through a single return stroke, a work contact
responsive member carried by said housing for reciprocating
movement adjacent said actuating member from a normal inoperative
position into an operative position in response to the movement of
said device into cooperating engagement with a workpiece and from
said operative position into said inoperative position in response
to the movement of said device out of cooperative engagement with
the workpiece and a trigger member carried by said housing adjacent
said actuating member in a position to be engaged by a finger of an
operator grasping said handle for pivotal movement from a normal
inoperative position into an operative position in response to
digital pressure and from said operative position into said
inoperative position in response to the release of said digital
pressure, the improvement in combination therewith which comprises
enabling means operatively associated with said members for (1)
enabling movement of said trigger member into its operative
position when said work contact responsive member is in its
inoperative position without movement of said actuating member into
its operative position, (2) enabling movement of said trigger
member into its operative position when said work contact
responsive member is in its operative position to effect movement
of said actuating member into its operative position, and (3)
enabling movement of said work contact responsive member into its
operative position when said trigger member is in its operative
position without movement of said actuating member into its
operative position. .Iaddend. .Iadd. 22. In a tool for driving
fasteners into a workpiece using a pressurized fluid motor for
actuating a fluid driving means, a manually actuated trigger means,
a safety means actuated by placing the tool adjacent the workpiece,
actuating means controlled by the trigger means and the safety
means for controlling the application of pressurized fluid to the
fluid motor, and a control means operatively associated with said
trigger means and said safety means to prevent operation of the
actuating means unless the safety means is first actuated followed
by the actuation of the trigger means and to prevent operation of
said actuation means upon said safety means being actuated
subsequent to actuation of said trigger means. .Iaddend.
Description
The present invention relates to a fastener driving tool and more
particularly to a safety arrangement for a fastener driving tool
which prevents accidental or inadvertent firing of the tool.
Pneumatic fastener driving tools, particularly those adapted to
drive large fasteners in certain industrial working conditions,
have long included safety devices effective to prevent the tool
from being fired or operated by trigger actuation unless or until
the tool is adjacent the workpiece. These safety devices have
included both pneumatic and mechanical interlocks. Some of these
safety devices are such that the safety and trigger can be operated
in any sequence, and others require the operation of the safety
prior to the operation of the trigger. Some of these safety
devices, generally those that are indifferent to the sequence of
the trigger and safety operation, are capable of "touch" firing,
i.e., the tool can be operated by moving the tool toward and away
from the workpiece while holding the trigger operated. This "touch"
firing is quite desirable in a number of applications because it
increases the speed at which the fasteners can be driven.
As an example, the mechanical safety arrangements shown and
described in U.S. Pat. No. 3,198,412 and shown in FIGS. 1-5 of U.S.
Pat. No. 3,056,965 are ones in which the usual trigger control is
mechanically locked in a released state until a mechanical latch is
released by placing the tool against a workpiece. This mechanical
latch is, however, incapable of "touch" firing. In the mechanical
arrangement shown, for example, in FIGS. 6-11 of U.S. Pat. No.
3,056,965 and in U.S. Pat. No. 3,194,324, the safety arrangements
include differential levers or shifting lever fulcrums to achieve
"touch" firing of the tool using the safety. However, these tools
are not disabled when the trigger is actuated prior to the safety.
The natures of these mechanical interlocks used to achieve either
control over the sequence of safety-trigger operation or "touch"
firing using the safety are not such that a single basic tool
design can be used in the factory to construct either of the two
types of controls. Further, the mechanical linkages are often
capable of being "teased" with the result that undesired multiple
firing may occur due to tool recoil.
Pneumatic safety arrangements are known which require the tool to
be adjacent the workpiece before the tool can be fired. Examples of
this type of safety are shown and described in U.S. Pat. Nos.
2,979,725; 3,112,489; and 3,252,641. In this type of safety, the
tool is operated by the last to be operated of the trigger and
safety, and there is no control requiring the safety to be operated
first in order to fire the tool. These tools are, however, capable
of "touch" firing.
There is a growing tendency to establish more demanding safety
standards for pneumatic fastener driving tools, particularly those
tools using larger fasteners and particularly in those industrial
applications in which working conditions are such that accidental
operation of a tool may cause injury. These standards can require
two separate and distinct operations to cause the operation of the
tool, or that the tool cannot be operated unless the tool is placed
against a workpiece before the trigger is operated, or that the
tool is disabled if the tool is lifted from the workpiece, thus
preventing "touch" firing. Some standards may permit an initial
"touch" firing but none after the initial tool operation. It would
be desirable to satisfy all of these standards with a pneumatic
safety because of the advantage in this type of control. Further,
because the safety standards are not universally applicable, it
would be desirable to provide a basic tool that could be factory
constructed to either meet these standards or provide the old
safety arrangement providing "touch" firing.
Accordingly, one object of the present invention is to provide a
new and improved pneumatic or fluid actuated fastener driving
tool.
Another object is to provide a fastener driving tool including a
new and improved safety arrangement.
A further object is to provide a new and improved pneumatic safety
arrangement for fastener driving tools which requires the operation
of the safety prior to the manual or trigger operation of the tool
in order to achieve tool operation.
A further object is to provide a new and improved pneumatic safety
for a fastener driving tool which prevents "touch" firing of the
tool.
A further object is to provide a pneumatic safety arrangement for a
fastener driving tool which is easily constructed to provide an
inhibited actuating sequence or "touch" firing of the tool.
A further object is to provide a pneumatic safety arrangement using
a pneumatically biased control valve whose pressure responsive
surfaces are selectively vented and pressurized by the safety and
trigger valves to control the firing of the tool.
In accordance with these and many other objects, an embodiment of
the present invention comprises a pneumatically actuated tool for
driving fasteners such as staples and nails which includes a
housing defining a pressurized fluid reservoir and including a
cylinder in which is slidably mounted a piston actuated fastener
driving means. A main valve assembly and an exhaust valve assembly
for the top of the cylinder are provided by which the upper end of
the interior of the cylinder is selectively connected to the
reservoir or to the atmosphere to drive the fastener driving means
through power and return strokes. The main and exhaust valve means
are selectively controlled by a trigger actuated valve means and a
safety valve means actuated by engagement between the tool and the
workpiece in which the fastener is to be driven. A control
arrangement is provided relating the safety valve means and the
trigger valve means to insure that the tool cannot be operated when
the trigger is actuated before the tool is placed against a
workpiece and to further insure that once the tool has been removed
from the workpiece the tool cannot be again actuated without
releasing and reoperating this trigger after the tool has again
been placed against the workpiece.
In two embodiments the control arrangement includes a piston valve
pneumatically biased in opposite directions and normally held in a
position permitting operation of the tool by a bias supplied under
the control of the trigger valve. If the trigger valve is operated
prior to the actuation of the safety means, one of the pneumatic
biases is removed and the piston valve is shifted to a blocking
position to insure that the tool cannot thereafter be operated
without restoring the tool to its normal condition. In these two
embodiments the removal of the tool from the workpiece to release
the safety means while the trigger is held operated is also
effective to shift the piston valve to an obstructing position to
prevent any further operation of the tool by "touch" firing, i.e.,
by reciprocating the tool relative to the workpiece.
In a third embodiment, the safety valve stem is provided with a
pair of metering orifices interconnecting the controls for the main
valve with the reservoir and the trigger valve. In this
arrangement, the tool can be "touch" fired for its first operation
but thereafter the tool is rendered incapable of being operated
unless the trigger valve is released and reoperated.
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 fragmentary sectional view of a pneumatic fastener
driving tool including a safety control arrangement forming a first
embodiment of the invention;
FIG. 2 is a sectional view taken along line 2--2 in FIG. 1;
FIG. 3 is a sectional view taken along line 3--3 in FIG. 1;
FIG. 4 is a fragmentary sectional view in partially schematic form
of a part of the safety control arrangement rotated 90.degree. to
facilitate illustration of the control safety arrangement in a
normal condition;
FIG. 5 is a schematic sectional view similar to FIG. 4 illustrating
the control arrangement with the safety valve means actuated;
FIG. 6 is a schematic elevational view similar to FIGS. 4 and 5
showing the control arrangement with both the trigger valve and the
safety valve operated to produce tool operation;
FIG. 7 is a schematic sectional view similar to FIGS. 4-6 showing
the control arrangement in a position preventing tool operation
resulting from operation of the trigger valve prior to the
operation of the safety valve;
FIG. 8 is a schematic fragmentary sectional view of a second safety
control arrangement for the tool shown in FIG. 1, the control
arrangement being shown in its normal position;
FIG. 9 is a fragmentary sectional view similar to FIG. 8 showing a
safety valve means in an operated state;
FIG. 10 is a fragmentary sectional view similar to FIGS. 8 and 9
showing the safety control arrangement with the trigger and safety
valves operated to control the operation of the tool;
FIG. 11 is a fragmentary sectional view similar to FIGS. 8-10
showing the safety control arrangement in a setting preventing
operation of the tool arising from premature operation of the
trigger valve means;
FIG. 12 is a fragmentary sectional view of a third embodiment of a
safety control arrangement for the tool shown in FIG. 1, the
arrangement being shown in a normal position;
FIG. 13 is a fragmentary sectional view similar to FIG. 12
illustrating the setting of the arrangement used to effect
operation of the tool;
FIG. 14 is a fragmentary sectional view similar to FIGS. 12 and 13
illustrating the safety valve means in a released position and a
trigger valve means in an operated position; and
FIG. 15 is a fragmentary sectional view similar to FIGS. 12-14
illustrating the safety valve means in an operated position and the
trigger valve means in a normal position.
Referring now more specifically to FIG. 1 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 22 with a hollow handle portion 22A forming a
reservoir 24 continuously supplied with a pressurized fluid such as
compressed air. Disposed within the housing is a cylinder 26
containing a slidably mounted piston 28 to which the upper end of a
fastener driving blade or element 30 is secured. The lower end of
the blade 30 is slidably received within a drive track 32 formed
within a nosepiece structure 34 to which fasteners such as
individual staples 36 are successively supplied by a magazine
assembly indicated generally as 38. The open upper end of the
cylinder 26 is normally closed by a main valve assembly indicated
generally as 40 which is connected to an exhaust valve assembly
indicated generally as 42. The exhaust valve assembly 42 is
slidably mounted on a closure cap 44 which closes and forms part of
the housing 22.
The operation of the tool 20 or more specifically of the fluid
motor provided by the cylinder 26 and the piston 28 is controlled
by a safety valve assembly indicated generally as 46 and a trigger
valve means or assembly indicated generally as 48. A safety control
assembly indicated generally as 50 including the valve means 46 and
48 permits the main valve 40 to open and the exhaust valve 42 to
close, thereby admitting pressurized air from the reservoir 24 into
the cylinder 26 to drive the piston 28 through a fastener driving
stroke only when the safety valve assembly 46 is actuated by
placing the nosepiece 34 adjacent a workpiece and thereafter
actuating the trigger valve assembly 48. If the tool 20 is lifted
away from the workpiece so as to release the safety valve assembly
46 following an initial operation of the tool and during a period
in which the trigger valve means 48 is maintained operated, as in
an effort to achieve "touch" firing, the assembly 50 disables the
tool 20 from further operation until the trigger 48 has been
released and again operated following movement of the nosepiece 34
against the workpiece.
The construction and operation of the tool 20 except for the
provision of the safety control arrangement or assembly 50 and a
slight modification in the exhaust valve assembly 42 is identical
to that shown and described in U.S. Pat. No. 2,979,725.
Accordingly, only a brief summary of the construction and operation
of this tool is set forth herein. It should be understood that many
other arrangements using fluid actuated piston or diaphragm main
valve and exhaust assemblies that are well known in the art can be
used with the safety control assembly 50 of the present
invention.
The cylinder 26 includes a piston portion 26A slidably mounted
within a cylindrical insert 52 in the housing 22 with the upper
surface of the piston portion 26A continuously exposed to the
pressurized fluid or compressed air in the reservoir 24. In the
normal condition of the tool 20 shown in FIG. 1, the area beneath
the piston 26A and a similar shouldered portion on the lower end of
the cylinder 26 are disposed within a chamber 54 supplied with
pressurized fluid through an inlet passage 56 so that the upper
edge of the cylinder 26 is pneumatically biased upwardly by a net
upwardly directed force against a resilient gasket in the main
valve assembly 40, this assembly being biased downwardly against
the cylinder 26 by the pressurized fluid acting on its exposed
upper surface. The exhaust valve 42 provides a stop limiting
downward movement of the main valve 40.
When the tool 20 is to be operated, the passage 56 is connected to
the atmosphere under the control of the assemblies 46, 48, and 50,
and the pressurized fluid acting on the upper surface of the piston
portion 26A moves the cylinder 26 downwardly to separate its upper
edge from the main valve 40. This supplies compressed fluid to the
bottom surface of the main valve 50 so that it moves upwardly until
the upper end of a stem 58 having an axially extending passage 60
abuts against a resilient member 62, the space beneath which is
vented to the atmosphere. This closes off the exhaust connection to
the atmosphere normally provided through the passage 60 and
provides a large area separation between the main valve 40 and the
cylinder 26 so that the piston 28 is driven downwardly by the
pressurized fluid admitted to the cylinder 26 from the reservoir
24. As the cylinder 26 moves downwardly, an opening 64 therein
moves into alignment with an opening 66 in the housing 22 to
provide a vent or exhaust connection for the air trapped beneath
the piston 28. During this downward movement, the lower end of the
blade 30 strikes a staple 36 and drives it through the drive track
32 into the workpiece.
When the tool 20 is to be released, the assemblies 46, 48, and 50
again supply compressed air to the passage 56 in the chamber 54 so
that the cylinder 26 is moved upwardly. The cylinder 26 moves
upwardly until it again engages the main valve 40 which is now
disposed in an abutting relation with the closure cap 44. This
moves the opening 64 out of alignment with the opening 66 and seals
off the lower end of the interior of the cylinder 26. The cylinder
26 is now sealed by the main valve 40 with compressed air trapped
between the top of the piston 28 and main valve. This trapped air
leaks off to the atmosphere through a group of metering orifices 67
to produce a net downwardly directed force acting on the top of the
main valve 40 which moves this valve, the exhaust valve 42, and the
cylinder downwardly to the position shown in FIG. 1.
This moves another opening or passage 68 in the lower end of the
cylinder 26 into alignment with a discharge opening from a passage
70 in the housing 22. Whenever the piston 28 is displaced from its
normal position, a valve assembly indicated generally as 72 is
opened to interconnect the passage 70 with a passage 74 that is
continuously supplied with pressurized fluid from the reservoir 24.
Accordingly, pressurized piston return air from the reservoir 24 is
now supplied beneath the piston 28 which is at the lower end of its
stroke. The part of the cylinder 26 above the piston 28 is now
connected to atmosphere through the passage 60, and the air
supplied through the opening 68 beneath the piston 28 is effective
to restore the piston 28 to its normal position. When the piston 28
reaches this position, a depression in the lower end of the driver
blade 30 releases the valve 72 so that compressed air is no longer
supplied to the interior of the cylinder 26 beneath the piston 28.
This completes the power and return strokes of the fastener driving
blade 30 under the control of the fluid motor provided by the
piston 28 and the cylinder 26.
The safety control assembly 50 including the safey valve assembly
or safety means 46 and the trigger valve means 48 selectively
control the alternate connection of the passage 56 to the
atmosphere and to the pressurized fluid in the reservoir 24 in
accordance with the conditions under which the tool 20 can be
operated. The safety valve assembly 46 is substantially identical
to that shown and described in the above-identified U.S. Pat. No.
2,979,725 and includes a valve stem 80 slidably mounted within a
sleeve 82 in the housing 22. A somewhat U-shaped element 84
connected to an intermediate portion of the valve stem 80 carries a
wire frame or actuating element 86 which protrudes slightly below
the lower end of the nosepiece structure 34 and is adapted to be
moved upwardly and to produce a corresponding upward movement of
the valve stem 80 when the tool 20 is placed against a workpiece,
this movement taking place against the resilient bias of a
compression spring 88 coupled to the lower end of the valve stem
80.
In the normal position of the safety valve 46 shown in FIG. 1,
compressed air is supplied directly from the reservoir 24 to the
passage 56 through a bore 90 and an opening 92 from the bore 90
through the wall of the stem 80. When the operator 86 engages the
workpiece to move the valve stem 80 upwardly against the resilient
bias provided by the spring 88 (FIG. 5), the passage 92 is sealed
off by the sleeve 82 and a reduced diameter portion 80A on the
valve stem 80 places the passage 56 in communication with passage
94. Whenever the tool 20 is moved away from the workpiece, the bias
provided by the spring 88 coupled with pneumatic bias applied to
the exposed upper surfaces of the stem 80 move the stem from the
actuated position shown in FIG. 5 to the normal position shown in
FIG. 1.
The trigger valve assembly 48 is substantially identical to that
shown and described in detail in the above-identified U.S. Pat. No.
2,979,725. In general, the assembly 48 includes a ball valve 96
resting on an O-ring 98 within a valve chamber 100 in the housing
22. The upper end of the chamber 100 is placed in direct
communication with the reservoir 24 through a passage or opening
102. In the normal position of the valve assembly 48, compressed
air is supplied through the passage 102 and the chamber 100 to an
outlet passage 104 (FIGS. 1 and 2). When a trigger element 106
pivotally mounted on the housing 22 is actuated or pivoted in a
counterclockwise direction, a fluted or ribbed valve stem 108 is
moved upwardly to engage the ball valve 96 and move it upwardly to
the position shown, for example, in FIG. 6 in which the passage 102
is closed. In this position, the ball valve 96 no longer rests on
the resilient O-ring 98, and the chamber 100 as well as the outlet
passage 104 are connected to the atmosphere through the recesses in
the fluted valve stem 108. When the trigger 106 is released, the
pneumatic bias applied to the ball 96 by the pressurized fluid in
the reservoir 24 restores the trigger valve assembly 48 to the
condition shown in FIG. 1.
A valve piston 110 (FIG. 2) in the assembly 50 effects the control
of the main valve 40 in dependence on the sequence of operation of
the safety valve assembly 46 and the trigger valve assembly 48. The
valve piston 110 includes a smaller diameter portion 110A and a
larger diameter portion 110B slidably mounted in corresponding
diameter portions 112A and 112B of a cylindrical recess 112 in the
housing 22. The cylinder 112 extends generally transverse to the
housing 22, is closed at its small diameter end 112A, and is closed
by a threaded fitting 114 at its large diameter end. The fitting
114 is provided with a passage 116 which places the outlet passage
104 from the trigger valve means 48 in communication with the large
diameter portion 112B of the cylinder 112. This large diameter
portion 112B of the cylinder 112 also communicates with the
passageway 94 extending to the safety valve assembly 46. The small
diameter portion 112A of the cylinder 112 is placed in
communication with an opening 118 (FIG. 3) in the sleeve 82 over a
pair of passageways 120 and 122. The opening 118 is so disposed in
the sleeve 82 to be positioned above a sealing O-ring 124 on the
valve stem 80 when this valve stem is in its normal position (FIGS.
1 and 3) and to be disposed beneath the O-ring 124 when the valve
stem is in its operated position.
The proper and improper operation of the tool 20 under the control
of the assembly 50 is illustrated in schematic diagrams of FIGS.
4-7. In these figures, the piston valve 110 and the connecting
passageways have been rotated to lie within a common plane to
facilitate the illustration of the operation of the assembly 50. In
the normal condition of the tool 20 and the safety control assembly
50, compressed air from the reservoir 24 passes through the bore
90, the opening 92, and the passageway 56 to the chamber 54. This
acts on the lower piston surfaces of the cylinder 26 including the
lower surface of the piston portion 26A to hold the tool 20 in a
normal inoperated state. In addition, compressed air from the
reservoir 24 passes through the passageways 102, 104, and 116 to be
supplied to the large diameter cylinder 112B. This forces the valve
piston 110 to the position illustrated in FIG. 4. In addition, the
compressed air supplied to the cylinder 112B passes through the
passageway 94 and together with air from the reservoir 24 passes
around and through the interface between the valve stem 80 and the
sleeve 82 in the area disposed above the O-ring 124 to be supplied
to the passageways 120 and 122. This air acts on the lower end of
the small diameter piston 110 and tends to bias the valve piston
110 upwardly. However, since compressed air is supplied to the
large diameter cylinder 112 to act on the greater exposed surface
of the large diameter piston 110B, the valve piston 110 is
maintained in the position shown in FIG. 4.
Assuming that the tool 20 is to be operated in the proper sequence
by first placing the nosepiece 34 against the workpiece, this
movement actuates the operator 86 (FIG. 1) and moves this operator
and the connected safety valve stem 80 upwardly from the position
shown in dot-and-dash outline in FIG. 5 to the position shown in
solid outline therein. When the safety valve stem 80 moves to the
position shown in FIG. 5, the opening 92 is sealed by the sleeve 82
to cut off the flow of air into the passage 56 from the reservoir
24 through the bore 90. However, the reduced diameter portion 80A
on the valve stem 80 moves into alignment with the illustrated
openings in the sleeve 80, and the passageway 56 is now supplied
with compressed air from the reservoir 24 over the passageways 102,
104, 116, and 94. In addition, when the safety valve stem 80 moves
to the operated position shown in FIG. 5, the O-ring 124 thereon
moves above the opening 118 in the sleeve 82. Thus, the compressed
air previously supplied to the lower end of the cylinder 112A is
vented to the atmosphere over the passageways 120 and 122 and along
that portion of the interface between the sleeve 82 and the stem 80
disposed beneath the O-ring 124. Thus, the pneumatic bias acting on
the small diameter piston 110A of the piston valve 110 is removed.
Thus, when the safety valve assembly 46 is first operated, the tool
20 is not operated, but control over the supply of pressurized
fluid to the chamber 54 is transferred to the trigger valve
assembly 48 and the pneumatic bias is removed from one end of the
piston valve 110.
Since the nosepiece 34 of the tool 20 is now pressed against the
workpiece, as signified by the actuation of the safety valve
assembly 46, the tool 20 can be operated by manually actuating the
trigger valve assembly 48 from the normal position shown in
dot-and-dash outline in FIG. 6 to the position shown in solid
outline therein. When the trigger 106 is moved to this position,
the valve stem 108 is raised to elevate the ball valve 96 to a
position closing the passage 102. When the ball valve 96 is lifted
out of engagement with the O-ring 98, the passageway 104 is
connected to the atmosphere through the recesses along the stem
108. This connects the chamber 54 to the atmosphere over the
passageway 56, the recesses portion 80A of the valve stem 80, the
passageway 94, the upper end of the large diameter cylinder 112B,
and the passageway 116. This causes the cylinder 26 to move
downwardly as described above and initiate a power stroke or
fastener driving stroke of the tool 20. The position of the piston
valve 110 is not shifted even though the upper end of the large
diameter cylinder 112B is connected to the atmosphere inasmuch as
the small diameter cylinder 112A is also connected to the
atmosphere over the path described above. The tool 20 remains in
this condition until either the safety valve assembly 46 or the
trigger valve assembly 48 is released.
Assuming that the operator of the tool 20 now attempts to "touch"
fire the tool by moving the nosepiece 34 away from the workpiece so
that the safety assembly 46 is restored to its normal position and
the trigger valve assembly 48 is held in its operated position as
illustrated in FIG. 7 of the drawings. When the safety valve
assembly 46 moves to its normal position, the valve stem 80 moves
downwardly, and compressed air from the reservoir 24 is again
forwarded through the bore 90 and the opening 92 to the passageway
56. This causes the cylinder 26 to move upwardly and the piston 28
to be returned to its normal position in the manner described
above. At the same time the O-ring 124 moves to a position
interposed between the opening 118 and the atmosphere, and
compressed air from the reservoir 24 passes along the interface
between the stem 80 and the sleeve 82 through the opening 118 and
the passageways 120 and 122 to be collected in the small diameter
cylinder 112A. Since the trigger valve assembly 48 is held operated
to close the passageway 102 with the ball valve 96, the large
diameter cylinder 112B is held at atmosphere, and the pressurized
fluid collected in the small diameter cylinder 112A acts on the
exposed surface of the small diameter piston 110A to move the valve
piston 110 to the piston shown in FIG. 7. In this position, the
upper two O-rings on the large diameter piston 110B seal off
communication between the passageways 116 and 104 and the
passageway 94.
When an attempt is now made to cause operation of the tool 20 by
again placing the nosepiece 34 against the workpiece, the safety
valve assembly 46 is operated and the valve stem 80 moves upwardly
to the position shown in FIG. 6. This cuts off the supply of
pressurized fluid from the reservoir 24 through the opening 92, and
moves the O-ring 124 above the opening 118 so that the pressurized
fluid collected in the small diameter cylinder 112A may be
discharged to the atmosphere in the manner described above.
However, even though the reduced diameter portion 80A on the valve
stem 80 again couples the passages 56 and 94, the passageway 94 is
cut off from connection to the atmosphere through the passageways
104 and 116 since the valve piston 110 is in the position shown in
FIG. 7. Thus, the compressed air previously supplied to the chamber
54 cannot be vented to the atmosphere, and the tool 20 cannot
operate. The tool 20 can be operated only by releasing the trigger
valve assembly 48 by removing manual pressure from the trigger 106.
This permits the compressed air acting on the ball valve 96 to move
the stem 108 and thus the trigger 106 downwardly to the position
shown in dot-and-dash outline in FIG. 7. The ball valve 96 seats
against the O-ring 98 to close off the exhaust connection, and
compressed air from the passageway 102 enters the passageway 104 to
act on the greater area of the exposed surface of the large
diameter piston 110B. This moves the valve piston 110 downwardly to
the position shown in FIG. 6. When the valve piston 110 moves
downwardly, compressed air from the passgeways 104 and 116 flows
into the passageway 94. Since the safety valve assembly 46 is
operated, this air also flows through the reduced diameter portion
80A and the passageway 56 to hold the cylinder 26 in its up
position. When the trigger valve assembly 48 is reoperated, the
control assembly 50 is restored to the condition shown in FIG. 6
and the tool 20 is operated in the manner described above.
To illustrate the control over the proper sequence of operation of
the safety valve means 46 and the trigger valve means 48, it is
assumed that the control assembly 50 is restored to the normal
condition shown in FIG. 5. If the trigger valve means 48 is now
operated to the position shown in solid line in FIG. 7 without
actuating the safety valve assembly 46 so that this assembly
remains in the position shown in FIG. 7, the movement of the ball
valve 96 to close the passageway 102 and to open the exhaust
passage along the ribs on the valve stem 108 places the passageways
104 and 116 at atmosphere pressure. Since the safety valve assembly
46 has not been operated, the O-ring 124 on the valve stem 80 is
disposed beneath the opening 118, and pressurized fluid is supplied
to the small diameter cylinder 112A. This moves the piston valve
110 upwardly to the position shown in FIG. 7 and closes off
communication between the passageways 94 and 104. Thus, the
passageway 94 cannot be connected to the atmosphere, and subsequent
actuation of the safety valve assembly 46 to the position shown in
FIGS. 5 and 6 cannot cause operation of the tool 20. This can only
be achieved in the manner described above by placing the nosepiece
34 of the tool against the workpiece and thereafter releasing and
reoperating the trigger valve assembly 48.
Referring now more specifically to FIGS. 8-11 of the drawings,
therein is illustrated a control assembly 130 forming a second
embodiment of the invention for selectively preventing operation of
the tool 20 when a safety valve assembly or safety means indicated
generally as 132 is not operated prior to the actuation of the
manual trigger valve assembly 48. The assembly 130 also prevents
"touch" firing of the tool 20. The safety control assembly 130 is
shown in conjunction with a portion of the tool 20 shown in detail
in FIG. 1 of the drawings. The manual valve assembly 48 is
identical to the like numbered assembly in the tool 20.
The safety valve means 132 includes a value stem 134 slidably
mounted within a cylinder 136 in the housing 22 and coupled to the
same connecting means 84 as provided in the tool 20. The valve stem
134 carries four longitudinally spaced O-rings 138, 140, 142, and
144. A passageway 146 in the housing 22 communicated with the
atmosphere at one end and opens into the cylinder 136 at its other
end.
The safety control assembly 130 also includes a valve piston 148
slidably mounted within a cylinder 150 and carrying a pair of
O-rings 152 and 154 adjacent its opposite ends. The valve piston
148 is responsive to the operation of the safety means 132 and the
trigger valve assembly 48 to insure that the tool 20 cannot be
either "touch" fired or actuated without first operating the safety
means 132 followed by the actuation of the trigger means 48.
In the normal condition of the tool (FIG. 8), compressed air from
the reservoir 24 passes through a passageway 156 and through the
cylinder 150 around the valve piston 148 in the area disposed
between the O-rings 152 and 154 to a passage 158. One branch of the
passage 158 supplies air through the cylinder 136 between the
O-rings 140 and 142 to the passage 56 so that the chamber 54 is
pressurized to hold the cylinder 26 in its upper position. The
other branch of the passage 158 supplies pressurized air which
flows through the cylinder 136 between the O-rings 138 and 140 and
over a passage 159 to apply a pneumatic bias to one end of the
valve piston 148. The other end of the cylinder 150 is connected
through a passage 160 to the reservoir 24 through the passage 102
and the trigger valve assembly 48. Thus, the equal areas on the
opposite ends of the valve piston 148 are both subjected to
pressurized fluid of equal pressure.
Assuming that the tool 20 is operated in its proper sequence, the
operator 86 (FIG. 1) is first moved upwardly by placing the
nosepiece 34 of the tool 20 against the workpiece. This shifts the
safety valve stem 134 upwardly from the position shown in
dot-and-dash outline in FIG. 9 to the position shown in solid line
therein. In this position, compressed air supplied by the passage
160 to the lower end of the cylinder 150 is now forwarded over a
passage 162 and through the cylinder 136 in the area bounded by the
O-rings 142 and 144 to the passage 56. This supplies a continuing
source of pressurized fluid for maintaining the cylinder 26 in its
upper position. When the valve stem 134 moves to the position shown
in FIG. 9, the O-ring 142 moves between the ports terminating the
passage 56 in the lower branch of the passage 158 to close off the
previous supply of pressurized fluid for the passage 56. Further,
the O-ring 140 moves to a point between the ports terminating the
upper branch of the passage 158 and the passage 159 to close off
the source of biasing pressure to the upper end of the valve piston
148. The passage 159 is now placed in communication with the
exhaust passage 146 through the portion of the cylinder 136 bounded
by the O-rings 138 and 140. Thus, the pressurized fluid is
discharged from the upper end of the cylinder 150 and the valve
piston 148 is now subjected to only an upwardly directed biasing
force.
With the nosepiece 34 (FIG. 1) of the tool 20 now disposed on the
workpiece and the safety valve means 132 actuated, the tool can now
be operated by actuating the trigger valve means 48 by moving the
trigger 106 from the normal position shown in dot-and-dash outline
in FIG. 10 to the position shown in solid outline therein. This
moves the valve stem 108 upwardly to elevate the ball valve 96 from
the position resting on the resilient O-ring 98 to a position in
which it closes off the lower end of the passage 102. The ball
valve 96 now prevents the flow of pressurized fluid from the
passage 102 to the passage 160 and connects the passage 160 to the
atmosphere along the flutes or ribs on the valve stem 108. Thus,
the chamber 54 is discharged to atmosphere over the path including
the passage 56, the portion of the cylinder 136 bounded by the
O-rings 142 and 144, the passageway 162, and the lower end of the
cylinder 150. The valve piston 148 does not move from the
illustrated position inasmuch as no pneumatic bias is applied
thereto, and this valve piston is held in position by frictional
engagement of the O-rings 152 and 154 with the adjacent walls of
the cylinder 150. The tool 20 can be restored to its normal
position in which the main valve assembly 40 is again closed either
by releasing the trigger valve assembly 48 so that compressed air
is again supplied from the passage 102 to the passage 56 through
the passages 160 and 162 or by releasing the safety means 132 so
that pressurized fluid is supplied to the passage 56 through the
lower branch of the passage 158 and the passage 156.
Assuming that an attempt is made to "touch" fire the tool 20 by
retaining the trigger valve assembly 48 in the operated position
shown in FIG. 10 and by removing the nosepiece structure 34 from
the workpiece, the valve stem 134 moves from the operated position
shown in FIG. 10 to the normal position shown in FIG. 8. In so
moving, compressed air from the lower branch of the passage 158 is
again supplied to the passage 56 to close the main valve 40 and to
open the exhaust valve 42. Further, compressed air is supplied from
the upper branch of the passage 158 to the top surface of the valve
piston 148, the connection to atmosphere being closed off by the
O-ring 138. When this happens, the valve piston 148 moves
downwardly because no bias is applied to the lower end of this
valve piston. This setting of the control assembly 130 is
illustrated in FIG. 11. In this position of the valve piston 148,
the lower O-ring 154 is disposed between the passageways 160 and
162 to close off the connection to the atmosphere. In addition, the
O-ring 142 of the valve stem 134 moves between the ports
terminating the passageways 56 and 162 to further interrupt the
connection of the chamber 54 to the atmosphere. In addition, in the
lower position of the valve piston 148 pressurized fluid from the
passage 156 passes through the cylinder 150 between the O-rings 152
and 154 to be supplied to the passage 162 as well as the passage
158.
If an attempt is now made to reactuate the tool by again pressing
the tool 20 adjacent the workpiece, the valve stem 134 moves
upwardly, and the O-ring 142 is interposed between the ports
terminating the lower branch of the passageway 158 and the
passageway 56. This interrupts the flow of pressurized fluid
supplied to the chamber 54 from the passage 158. However, the ports
terminating the passages 162 and 56 are now placed in communication
by a portion of the cylinder 136 disposed between the O-rings 142
and 144, and the passageway 162 is supplied with pressurized fluid
from the passageway 156. Thus, compressed air is supplied to the
chamber 54, and the tool is not operated.
The only way in which the tool can be operated is to release and
reactuate the trigger valve assembly 48. When this assembly is
released, the ball valve 96 seats on the O-ring 98 to close off the
connection to atmosphere for the passage 160, and this passage is
connected to reservoir air pressure through the passage 102. Since
the valve stem 134 is actuated, the top surface of the valve piston
148 is vented. Thus, the compressed air supplied to the passage 160
shifts the valve piston 148 upwardly to the position shown in FIGS.
8-10. This closes off communication between the passageways 156 and
162 and places the passageway 162 in communication with the passage
160 which is now pressurized. Thus, the tool 20 remains in its
normal state. The reactuation of the trigger valve assembly 148
connects the passageway 160 to atmosphere in the manner described
above, and the tool is then operated.
When the tool 20 is in its normal state, the safety control means
130 prevents operation of the tool if the trigger valve means 48 is
operated prior to the actuation of the safety means 132. Thus, if
the trigger valve means 48 is operated to its actuated position
(FIG. 11) with the safety valve 132 in its normal state, the ball
valve 96 closes off the passageway 102 and connects the passageway
160 to the atmosphere. Since the safety means 132 is in its normal
state, pressurized fluid is supplied from the upper branch of the
passageway 158 and the passageway 159 to the top surface of the
valve piston 148. Accordingly, when the passage 160 places the
lower end of the cylinder 150 at atmospheric pressure, the valve
piston 148 moves downwardly to the position shown in FIG. 11. This
closes off communication between the passageways 160 and 162 and
couples the passage 162 to the pressurized passageway 156. Thus,
these two passages maintain the supply of pressurized fluid to the
chamber 54, and the tool 20 cannot be operated. The tool 20 can be
operated from this position only by actuating the safety means 132
and by releasing and reactuating the trigger valve assembly 48.
FIGS. 12-15 of the drawings illustrate a third embodiment of the
invention includes a safety control assembly indicated generally as
170 which coordinates and interrelates the control of the tool 20,
the trigger valve assembly 48, and a safety means indicated
generally as 172 to prevent "touch" operation of the tool 20. The
safety control assembly 170 does not require the trigger valve
means 48 and the safety means 172 to be operated in any particular
sequence to achieve the initial operation of the tool 20, but does
insure that the trigger valve assembly 48 is operated and released
incident to each additional operation of the tool 20.
The safety valve assembly or safety means 172 includes a sleeve 174
in which is slidably mounted a safety valve stem 176. The valve 176
includes a lower sealing O-ring 178 and an upper sealing O-ring 179
between which is disposed a recessed area 176A movable into and out
of communication with a pair of aligned openings in the sleeve 174.
The upper end of the valve stem 176 is provided with a somewhat
T-shaped passage 180, one end of which is in continuous
communication with the reservoir 24 through the open end of the
sleeve 174. The passageway 180 terminates in two oppositely
extending ports or passageways 180A and 180B of equal area.
In the normal condition of the tool 20, compressed air flows
through the passageways 180 and 180A to be supplied to the
passageway 56 in the chamber 54 so as to hold the cylinder 26 in
its upper position in which the main valve 40 (FIG. 1) is closed.
The compressed air supplied by the passageway 180 is supplemented
by pressurized fluid supplied from the reservoir 24 through the
passageway 102 and a passageway 182 which communicates with the
passageway or port 180B.
Assuming that the tool is to be operated, either the safety means
172 or the trigger means 48 can be operated first. Assuming that
the trigger valve assembly 48 is first operated by moving the
trigger 106 from the position shown in dot-and-dash outline in FIG.
13 to the position shown in solid outline therein, the passageway
182 is connected to the atmosphere along the valve stem 108 when
the ball valve 96 moves off the O-ring 98, the ball valve 96
closing the passageway 102. The tool 20, however, will not operate
at this time inasmuch as the equal area ports 180A and 180B
maintain sufficient pressure in the chamber 54 to hold the cylinder
26 in its upper position. Assuming, however, that the safety means
172 is now operated to move the valve stem 176 from the position
shown in dot-and-dash outline in FIG. 13 to the position shown in
solid outline therein, the passageways 180A and 180B are sealed by
the sleeve 174 and the recessed area 176A and places the
passageways 56 and 182 in direct communication. This permits the
air in the chamber 54 to be exhausted to the atmosphere and the
tool is operated. The tool can be operated equally well by first
actuating the safety means 172 to the position shown in FIG. 13 in
which the recessed area 176 places the passageways 56 and 182 in
direct communication and thereafter operating the trigger valve
means 48 to connect the passageway 182 to the atmosphere. Thus, the
tool 20 can be actuated by operating the assemblies 48 and 172 in
any sequence.
Assuming, however, that an attempt is made to "touch" fire the tool
20 by releasing the safety means 172 while maintaining the trigger
valve assembly 48 in its actuated condition, the control assembly
170 is placed in the position shown in FIG. 14. In this position
the passageways 180, 180A and 180B again provide communication
between the passageways 56 and 182 and connect these passageways to
the reservoir 24. Since, however, the passageways or ports 180A and
180B are of equal area, the passageway 180 cannot supply adequate
air to the chamber 54 to move the cylinder 26 upwardly to its
normal position, and the tool 20 cannot be restored to its normal
condition to permit a subsequent operation. This is true even
though the safety stem 176 is reciprocated between its operated and
normal positions shown in FIGS. 13 and 14, respectively, because
the passageway 182 is held at atmosphere by the actuated trigger
valve means 48.
In connection with the inability of the tool to operate with the
safety means 170 released and the trigger valve assembly 48
operated and the inability of the tool to restore to normal after
operation with the safety means 170 released and the trigger valve
assembly 48 operated, it should be noted that the upper edge
surfaces of the cylinder 26 are sealed from exposure to the
pressurized fluid in the reservoir 24 when the tool is in its
normal position, and these same edge surfaces are exposed to the
fluid pressure when the tool is operated. This means that a greater
force is required to close the main valve 40 than to maintain it
closed. With the chamber 54 fully pressurized at the time of
opening the trigger valve assembly 48, the drop across the
passageways 180A, 180B holds the main valve assembly 40 closed.
However, when the tool has been operated, the chamber 54 starts at
atmospheric pressure, and the drop across the passageways 180A,
180B prevents enough elevation in the pressure in the chamber 54 to
provide the added upward bias to overcome the added downward bias
due to the now exposed upper edge surfaces of the cylinder 26.
In order to achieve a second operation of the tool 20 following its
initial operation, it is necessary to release and reoperate the
trigger valve assembly 48. Thus, the nosepiece structure 34 of the
tool 20 is placed against the workpiece to move the safety valve
stem 176 to the position shown in solid line in FIG. 15. This
places the passageways 56 and 182 in direct communication through
the recessed area 176A on the valve stem 176. When the trigger
valve 48 is released and moves to the position shown in FIG. 15,
compressed air from the passageway 102 passes through the
passageway 182 and around the recessed area 176A to be supplied to
the passageway 56 and the chamber 54. This restores the cylinder 26
to its normal position so that when the trigger valve 48 is
reactuated to close the passageway 102 and to open the passageway
along the valve stem 108, by moving out of engagement with the
O-ring 98, pressurized fluid in the chamber 54 is dumped to the
atmosphere, and the tool can be operated. Thus, following the
initial operation of the tool 20, the safety stem 176 must be
maintained in an operated state, and the tool can be operated only
by actuating and releasing the trigger valve means 48.
Although the safety control assemblies 51, 30, and 170 have been
illustrated in conjunction with the tool 20 in which tool actuation
is produced by venting the controls for the main valve to the
atmosphere, these control assemblies with alternations in their
normal states can be used with tools in which main valve operation
is effected by supplying pressurized fluid. Further, the tools 20
using the control arrangements 50 and 130 can be factory
constructed to provide touch-trip merely by using a plug in the
cylinders 112 and 150 to afford continuous communication between
the passageways 104 and 94 and 160 and 162, respectively, in place
of the valve pistons 110 and 148. The tool using the safety control
assembly 170 requires only the use of the usual safety valve stem
such as the valve stem 80 in place of the valve stem 176 in order
to be factory constructed to provide touch-tripping. Thus, the
safety control arrangements illustrated are such as to permit the
basic construction of the tool 20 to be factory constructed to
provide the known control permitting touch-tripping for the
controlled operation of the present invention.
Although the present invention has been described with reference to
three illustrative embodiments thereof, it should be understood
that many other objects and advantages may be devised by those
skilled in the art that will fall within the true spirit and scope
of the principles of this invention.
* * * * *