U.S. patent number 3,762,620 [Application Number 05/253,449] was granted by the patent office on 1973-10-02 for safety assembly for fastener driving tool.
Invention is credited to Bernard W. Geist.
United States Patent |
3,762,620 |
Geist |
October 2, 1973 |
SAFETY ASSEMBLY FOR FASTENER DRIVING TOOL
Abstract
A safety mechanism for a pneumatic fastener driving tool
prevents operation of the tool when a nosepiece structure
containing a fastener discharging opening is not disposed flush
against and covered by a workpiece. This avoids "free flight" of
power driven fasteners resulting from a tool being disposed at an
angle adjacent an edge of a workpiece so that the fastener passes
through only a portion of the workpiece. To accomplish this, the
safety assembly includes two workpiece engaging members disposed on
opposite sides of the nosepiece structure and coupled to opposite
ends of a lever centrally fulcrumed on an operator for the tool
firing control. Unless both members are elevated by engagement with
the workpiece, the lever does not operate the control. To reduce
the chances of tool operation when the tool is tipped in the plane
of the workpiece engaging members, these members are so formed as
to provide only point or small area contact with the workpiece.
Inventors: |
Geist; Bernard W. (Melrose
Park, IL) |
Family
ID: |
22960309 |
Appl.
No.: |
05/253,449 |
Filed: |
May 15, 1972 |
Current U.S.
Class: |
227/8 |
Current CPC
Class: |
B25C
1/008 (20130101) |
Current International
Class: |
B25C
1/00 (20060101); B27f 007/22 () |
Field of
Search: |
;227/7,8 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Custer, Jr.; Granville Y.
Claims
What is claimed and desired to be secured by Letters Patent of the
United States is:
1. In a fastener driving tool having a power unit for driving
fasteners into a workpiece,
nosepiece structure through which the fasteners are driven and
having a workpiece engaging portion,
a control unit for controlling the power unit and having an
operator means movable between an inoperative position and an
operated position in which the control unit can effect operation of
the power unit,
a pair of workpiece engaging means independently movable relative
to the nosepiece structure and disposed adjacent opposite sides of
the workpiece engaging portion thereof,
and coupling means coupling the pair of workpiece engaging means to
the operator means and operable to shift the operator means from it
inoperative position to its operated position only when both of the
workpiece engaging means are moved by engagement with the
workpiece.
2. The fastener driving tool set forth in claim 1 in which
at least one of the workpiece engaging means is formed with a
pointed or narrow workpiece engaging surface that provides a point
or small area of contact with the workpiece aligned with the path
of movement of the fasteners through the nosepiece structure.
3. The fastener driving tool set forth in claim 2 in which
the nosepiece structure includes a workpiece engaging surface that
is wider than the workpiece engaging surface on the workpiece
engaging means.
4. The fastener driving tool set forth in claim 1 in which
the coupling means includes a lever means engaged by the operator
means at a first point and engaged by the workpiece engaging means
at spaced second and third points.
5. The fastener driving tool set forth in claim 4 in which
the second and third points are spaced on opposite sides of the
first point.
6. The fastener driving tool set forth in claim 4 in which
the second and third points are at the ends of the lever means,
and the coupling means includes means providing a fixed pivotal
connection between the lever means and the workpiece engaging means
at the ends of the lever means.
7. In a fastener driving tool using a power unit for actuating a
driver element,
a nosepiece structure through which fasteners are driven by the
driver element, said structure including a workpiece engaging
structure adapted to be disposed adjacent a workpiece,
a control unit for controlling the operation of the power unit,
said control unit including a manually operable trigger means and a
safety operator,
a pair of workpiece engaging means mounted adjacent opposite sides
of the workpiece engaging structure for independent movement,
and linkage coupling both of the workpiece engaging means to the
safety operator and operable to actuate the safety operator only
when both of the workpiece engaging means are moved by engagement
with the workpiece.
8. The fastener driving tool set forth in claim 7 in which
the linkage includes a lever means coupled to the safety operator
and having a pivotal engagement with each of the workpiece engaging
means.
9. The fastener driving tool set forth in claim 8 in which
the linkage includes means providing a pivotal connection between
opposite end portions of the lever means and separate ones of the
pair of workpiece engaging means.
10. In a fastener driving tool with a power unit for driving
fasteners into a workpiece,
a housing for the fastener driving tool,
a control unit on the housing for controlling the operation of the
power unit to drive a fastener, said control unit including an
operator means depending from the control unit, said operator means
being normally in an inoperative position and being movable
upwardly to an operative position to permit operation of the
tool,
a movably mounted coupling member beneath the control unit and
adapted to engage and move the depending operator means from its
inoperative position to its operative position, said coupling
member and operator means being engageable at a first point on the
coupling member spaced from its opposite ends,
a first member slidably mounted on the housing beneath the coupling
member for movement between a lower inoperative position and an
upper operative position in which the first member elevates one end
of the coupling member,
and a second member slidably mounted on the housing beneath the
coupling member for movement between a lower inoperative position
and an upper operative position in which the second member elevates
the other end of the coupling member, the elevation of both ends of
the coupling member by the first and second members elevating the
coupling member to engage and move upwardly the operating means
thereby to render the control unit effective to operate the power
unit.
Description
This invention relates to a fastener driving tool and, more
particularly, to such a tool having a new and improved safety means
for insuring that the fastener discharging opening of the tool is
disposed flush against a workpiece into which the fastener is to be
driven.
Pneumatic and other types of power driven fastener driving tools
have long been provided with mechanical and/or pneumatic safety or
touch-trip assemblies designed to prevent manually controlled
operation of the tool unless and until the nosepiece structure of
the tool through which the driven fastener is discharged is
disposed against the workpiece. These arrangements commonly include
a workpiece engaging element, either U-shaped or concentric with
the nosepiece structure, which projects downwardly beyond the
nosepiece to be elevated when the nosepiece is pressed against the
workpiece. These elements operate a pneumatic valve or a machanical
linkage associated with the trigger actuated firing control to
permit the tool to be operated.
These workpiece engaging elements generally are rigid and either
substantially completely embrace the nosepiece (U.S. Pat. Nos.
3,572,572 and 3,580,455) or extend almost completely across the
width of the nosepiece (U.S. Pat. Nos. 3,172,124 and 3,194,324).
These constructions are such that when the tool is inclined either
in the plane of the tool or in a plane transverse to the plane of
the tool the rigid workpiece engaging element is elevated
sufficiently to release the tool for operation even though the
lower wall of the nosepiece through which the staple or nail is
ejected is inclined or tipped relative to the workpiece surface.
This tipped position causes the fasteners to be driven at an angle
with respect to the workpiece.
When fasteners are driven under these conditions and if the
fastening operation is being performed adjacent the edge of a
workpiece, the fastener such as a nail passes through only an edge
portion of the workpiece and then enters "free flight." This
occasions the possibility of injury to an operator or equipment and
has, in some areas, led to work regulations forbidding the presence
of more than a single tool operator in an assembly area. The use of
single point contact safety actuators in some prior tools (U.S.
Pat. Nos. 3,056,964 and 3,252,641) prevents tipping of the tool in
a first plane, generally a plane transverse to the plane of the
tool, but not in the direction of elongation of the tool.
Accordingly, an object of the present invention is to provide a new
and improved fastener driving tool and, more specifically, a new
and improved safety assembly for such a tool.
A further object is to provide a safety assembly for a power
actuated fastener driving tool that requires the tool to be
properly located with respect to a workpiece before the tool can be
operated.
Another object is to provide a safety assembly including
independently movable workpiece engaging elements disposed on
opposite sides of the fastener discharge opening to insure that the
opening is placed against the workpiece before the tool can be
operated.
Another object is to provide such a safety assembly in which the
workpiece engaging elements have point or small area contact with
the workpiece in a position immediately adjacent the fastener
discharging opening to insure that the safety cannot be released
when the tool is tipped relative to the workpiece.
In accordance with these and many other objects, an embodiment of
the invention comprises a pneumatic fastener driving tool formed by
a housing containing a power unit whose actuation is controlled by
a control unit including a trigger operator and a safety operator,
both of which must be actuated to permit operation of the power
unit. When the power unit is operated, a fastener driving element
or blade is reciprocated through a drive track in a nosepiece
structure to drive a staple or nail supplied from a magazine
assembly into a workpiece.
In accordance with the present invention, a safety assembly is
provided which prevents operation of the tool or actuation of the
control unit unless and until the surface of the nosepiece
containing the fastener discharging opening is disposed against and
in a flush relation with the workpiece into which the fastener is
to be driven. If the tool is disposed in a tipped or canted
relation to the workpiece in virtually any plane, the control unit
cannot be actuated to effect operation of the power unit. To
accomplish this, a safety assembly is provided including a pair of
independently movable workpiece engaging elements disposed on
opposite sides of the drive track or fastener discharging opening.
These workpiece engaging elements are coupled to a lever which in
turn is coupled to the safety operator so that the safety operator
cannot be actuated unless both of the workpiece engaging elements
have been elevated by engagement with the workpiece. This insures
that the nosepiece of the tool is flush against the workpiece in
the plane of the tool. By providing the workpiece engaging elements
with point or small area contact surfaces for engagement with the
workpiece, it becomes difficult to effect full actuation of these
elements when the tool is tipped in a plane transverse to the plane
of the tool. Thus, the safety operator cannot be fully actuated in
most circumstances when the tool is tipped in any direction
relative to the workpiece, and the possibility that a fastener will
be driven through only a portion of the workpiece and enter "free
flight" is materially and substantially reduced.
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 side elevational view illustrating a
pneumatic fastener driving tool embodying the present
invention;
FIG. 2 is an end elevational view of the tool shown in FIG. 1
illustrating a dual element safety actuator assembly in a normal
condition;
FIG. 3 is an enlarged fragmentary sectional view taken along line
3--3 in FIG. 1;
FIG. 4 is an end elevational view similar to FIG. 2 illustrating
the safety assembly with one workpiece engaging element
actuated;
FIG. 5 is an end elevational view similar to FIG. 4 and
illustrating the safety assembly with the other workpiece engaging
element actuated;
FIG. 6 is an end elevational view similar to FIGS. 2, 4, and 5
illustrating the safety assembly with both workpiece engaging
elements actuated; and
FIG. 7 is an exploded perspective view of the safety actuating
assembly.
Referring now more specifically to FIGS. 1 and 2 of the drawings,
therein is illustrated a fastener driving tool which is indicated
generally as 10 and which embodies the present invention. The tool
10 includes a power unit (not shown) of a suitable type, such as a
pneumatic piston and cylinder, to which is attached a fastener
driving element or driver for driving or setting fasteners, such as
staples or nails, successively supplied to a drive track in a
nosepiece structure indicated generally as 12 by a magazine
assembly of conventional construction indicated generally as 14. To
provide means for manually controlling operation of the tool or the
power unit in the tool 10, there is provided a control unit
indicated generally as 16. When a manually actuated trigger 18
forming a part of the assembly or unit 16 is actuated, the power
unit in the tool 10 is rendered effective to drive a fastener only
when and if a safety assembly indicated generally as 20 has been
fully actuated to indicate that the fastener discharging opening in
the lower end of the nosepiece structure 12 is against the
workpiece into which the fastener is to be driven. In accordance
with the present invention, the safety assembly 20 is so designed
that the control unit 16 is inhibited to prevent actuation in
response to operation of the trigger 18 if the tool 10 is tipped or
canted with respect to the workpiece.
The tool 10 can be of any of the types well known in the art and
can include, for example, a cylinder in which a piston coupled to
the upper end of a driver blade is reciprocated by the selective
admission of pressurized fluid or compressed air by a main valve,
the opening and closing of which is controlled by the control unit
16. As an example, the tool can be constructed as shown and
described in detail in U.S. Pat. No. 3,638,532. The control unit 16
can also be constructed as shown and described in detail in this
patent. In general, the control unit 16 includes a housing 22
containing one or a number of valves for selectively controlling
the admission of pressurized fluid to the cylinder of the power
unit. When the trigger 18 which is pivotally mounted on the housing
22 is actuated and when the safety assembly 20 is actuated, the
power unit is rendered effective to operate through one or a
plurality of cycles during which one or a plurality of fasteners
are driven.
To provide a means for controlling the effectiveness of the control
unit 16 in dependence on the condition of the safety assembly 20,
the control unit 16 includes a safety operator or an operator means
24 which, in the control unit shown in the safety assembly shown in
the above-identified patent, comprises a valve stem. This stem 24
projects from the lower wall of the housing 22 (FIG. 3). When the
safety operator 24 is in the lower position shown in FIGS. 1 and 3,
the control unit 16 is disabled. When the operator 24 is moved
upwardly into the housing 22 to the position shown in dashed
outline in FIG. 6, the control unit 16 is placed in a condition in
which it can be operated by depression of the trigger 18.
The nosepiece structure 12 is secured to the lower end of a housing
26 for the tool 10, as by a plurality of machine screws 28. The
nosepiece structure 12 contains a drive track for reciprocably
receiving the driver element actuated by the power unit for driving
nails or staples supplied to the drive track from the magazine 14.
The magazine 14 includes a body portion 14A, the forward end of
which is secured to and between rearwardly extending projecting
portions or tabs 12A (FIGS. 1 and 7) formed integral with the
nosepiece structure 12. The lower end of the nosepiece structure 12
is provided with a downwardly and inwardly tapered portion
indicated generally as 12B which terminates in a generally planar
workpiece engaging surface or portion 12C in which is disposed a
fastener discharging opening through which fasteners driven out of
the drive track enter the workpiece.
The actuating or operating means for the safety assembly 20 is
slidably mounted on the nosepiece structure 12. This actuating
assembly includes a pair of workpiece engaging elements or members
30 and 32 preferably formed of bent wire stock and having a
generally U-shaped configuration at their lower ends. Each of the
elements 30 and 32 is formed with a somewhat V-shaped or pointed
portion 30A, 32A at its lower end to provide a point or small area
contact with the workpiece. To provide means for slidably
supporting the elements 30 and 32 for independent movement, the
nosepiece structure 12 is provided with two pairs of generally
aligned slots or recesses 34 and 36 on its opposite side walls. The
pairs of slots or recesses 34 and 36 are generally aligned with the
back and front walls, respectively, of the nosepiece structure
12.
To slidably mount the workpiece engaging elements 30 and 32 on the
nosepiece structure 12, vertically extending leg portions 30B, 32B
of the members 30, 32 are disposed within the aligned slots or
recesses 36, 34, respectively. A generally U-shaped closure element
or retaining means 38 is secured to the nosepiece structure 12, as
by a machine screw 40, with the bight portion of the member 38
overlying the front wall of the nosepiece structure 12 and with the
two legs of the member 38 overlying the pairs of slots and recesses
34, 36 to slidably retain the members 30 and 32 within the slots
and recesses. When the elements 30, 32 are mounted on the nosepiece
structure 12, the workpiece engaging ends 30A, 32A of the elements
30, 32 are generally aligned with each other, considered in the
plane of the tool, and are also aligned with the drive track and
the fastener discharge opening in the nosepiece structure 12. As
illustrated particularly in FIGS. 4 and 6 of the drawings, the
workpiece engaging portions 30A, 32A are narrower than the adjacent
wall of the workpiece engaging surface 12C of the nosepiece
structure 12.
To provide means for coupling the workpiece engaging elements 30
and 32 to the safety operator 24, the upper free ends of these
elements are provided with rearwardly, outwardly, and upwardly
extending segments indicated generally as 30C and 32C which
terminate in two laterally and rearwardly extending portions 30D
and 32D. The portions 30D and 32D provide pivot pins received
within two cylindrical sleeves 42A formed integral with the ends of
a lever or coupling member 42. Thus, each of the workpiece engaging
members 30, 32 is pivotally connected to an opposite end of the
lever 42. The lever 42 is provided with a centrally disposed
opening 42B in which is received a reduced diameter or shouldered
portion 24A (FIG. 3) on the safety operator 24. A compression
spring 44 interposed between the lower wall of the housing 22 for
the control unit 16 and the upper surface of the lever 42 biases
the workpiece engaging elements 30, 32 to their lower or
inoperative position shown in FIGS. 1 and 2 of the drawings in
which the workpiece engaging ends 30A, 32A project below the lower
surface 12C of the nosepiece structure 12 to be disposed on
opposite sides of or to the front and back of the drive track
extending through the nosepiece structure 12.
When the tool 10 is to be operated, this tool is moved downwardly
toward the workpiece at the point at which the fastener is to be
driven until such time as the workpiece engaging surface 12C of the
nosepiece engages the adjacent surface of the workpiece. If the
tool 10 is disposed in a generally perpendicular relation with
respect to the workpiece, both of the workpiece engaging elements
30, 32 are moved from the normal position shown in FIGS. 1 and 2 to
the position shown in FIG. 6. In this position, the lower ends of
the workpiece engaging portions 30A, 32A are substantially flush
with the surface 12C of the nosepiece structure 12, and all of
these elements are against the adjacent surface of the workpiece.
As the elements 30, 32 move to the position shown in FIG. 6, both
ends of the lever 42 are moved upwardly, and this lever compresses
the bias spring 44 during the initial portion of its movement from
the position shown in FIG. 3 to the position shown in dashed
outline in FIG. 6. This movement is permitted without causing
movement of the safety operator 24 because of the lost motion
connection afforded by the reduced diameter portion 24A of the stem
or operator 24. Toward the end of the upward movement of the lever
44, the edges defining the opening 42B in the lever 42 engage the
upper shoulder of the safety operator 24 so that further upward
movement of the lever 42 elevates the operator 24 to the position
shown in FIG. 6. In this upper or operative position, the control
unit 16 is in a condition in which actuation of the trigger 18
effects the application of power to the power unit so that the
fastener supplied by the magazine assembly 14 is driven downwardly
through the nosepiece structure 12 and into the workpiece.
The construction of the control unit 16 can be such that
"touch-trip" operation can be provided. This means that the trigger
18 can be operated, and the surface 12C is then placed against the
workpiece to actuate the safety assembly 20 so that the tool 10
operates only after the safety is actuated. Alternatively, the
safety assembly 20 can be first actuated followed by the actuation
of the trigger 18. Again alternatively, both the trigger 18 and the
safety assembly 20 can be substantially concurrently operated to
effect operation of the tool 10. On the other hand, the control
unit 16 can be a sequential fire arrangement in which the safety
assembly 20 must be actuated prior to the actuation of the trigger
18.
When the tool 10 is lifted from the workpiece, the compression
spring 44 acts on the lever 42 to move this lever and the connected
workpiece engaging elements 30, 32 downwardly to the normal
position shown in FIGS. 1 and 2. During the initial portion of this
movement, the lost motion connection afforded by the reduced
diameter portion 24A permits the safety operator 24 to remain in
its actuated position. Toward the end of the downward movement of
the lever 42 and connected elements 30, 32, the lever 42 engages
the lower shouldered portion of the operator 24 and moves this
operator downwardly to its inoperative position. The provision of
the lost motion connection afforded by the reduced diameter portion
24A tends to reduce multiple firing of the tool 10 arising from
recoil when the fastener is driven. In other words, a certain
return movement of the workpiece engaging elements 30, 32 is
permitted before the safety 24 is actuated to its inoperative
position so that continuous pressure forcing the tool 10 against
the workpiece does not result in operation induced by momentary
release and reactuation of the safety operator 24.
If the tool 10 is placed against the workpiece tipped forwardly
within the plane of the tool, the engaging portion 30A of the
element 30 engages the workpiece, and the element 30 is moved
upwardly to the position shown in FIG. 4. However, the element 32A
either does not engage the workpiece or is only partially actuated
thereby with the result that the lever 42 is tipped to the position
shown in FIG. 4. This movement of the lever 42 takes up the lost
motion provided by the reduced diameter portion 24A on the safety
operator 24 and does not cause upwardly directed movement of the
operator 24 to its operative position in which the control unit 16
is released for operation. Similarly, if the tool is tipped
rearwardly within the plane of the tool, the portion 32A of the
work engaging member 32 engages the workpiece, and the member 32 is
moved upwardly to its operative position, while the front workpiece
engaging element 30 remains in its lower position, as shown in FIG.
5. This results in pivoting or tipping the lever 42 in the opposite
direction from FIG. 4. This tipping movement of the lever 42 is
again accommodated by the reduced diameter portion 24A, and even if
some upward movement of the safety operator 24 takes place, this
movement is not sufficient to move the operator 24 to its operative
position, and the control unit remains disabled so that the tool 10
cannot be operated. Accordingly, when the tool 10 is tipped either
in a forward or a reverse direction about the workpiece engaging
surface 12C generally within the plane of the tool 10, only one or
the other but not both of the workpiece engaging elements 30, 32 is
fully actuated, and the lever or coupling member 42 is tipped
different directions but is not elevated sufficiently to shift the
operator stem 24 to its operative position. Accordingly, the
control unit 16 is not released or rendered effective to operate
the tool 10.
By providing the point or small area contact portions 30A, 32A for
engaging the surface of the workpiece, the tool 10 or, more
specifically, the safety assembly 20 is also able to provide a
degree of control over tipping of the tool 10 in a plane transverse
to the plane of this tool. More specifically, if the tool 10 is
moved toward the workpiece in a position inclined to the right or
to the left when viewed as shown, for example, in FIG. 6, the
tapered or inclined sides rather than the point of the workpiece
engaging portions 30A, 32A tend to first engage the workpiece to
cause initial upward movement of the elements 30, 32. However, on
continuing movement of the tool 10 toward the workpiece, one of the
side edges of the lower surface 12C of the nosepiece structure
tends to engage the workpiece prior to the time at which elements
30, 32 are fully elevated to a position in which the lever 42
shifts the operator 24 to its operative position. Only by pivoting
the tool 24 to a position in which the surface 12C is flush with
the workpiece surface can the elements 30, 32 be sufficiently
elevated. If the elements 30, 32 had been provided with the
conventional flat or wide area workpiece engaging surface
substantially coextensive with the width of the lower surface of
the nosepiece structure, the elements 30, 32 would be fully
actuated by moving the tool 10 toward the workpiece with this tool
tipped to either side, as viewed for example in FIG. 6.
In summary, the improved safety assembly of the present invention
insures that the tool 10 is flush against a workpiece before the
tool can be operated. Further, by providing the elements 30 and 32
on opposite sides of the drive track, the tool 10 cannot be
operated if the fastener discharging opening is not covered by a
workpiece because one of the elements 30 and 32 would not be
actuated. In addition, the provision of two workpiece engaging
elements 30 and 32, both of which must be actuated for operation of
the tool 10, reduces the possibility of a failure of the safety due
to the workpiece engaging element being locked in an operated state
by, for example, an accumulation of foreign matter in a
guideway.
Although the present invention has been described with respect to a
single illustrative embodiment thereof, it should be understood
that numerous other modifications and embodiments can be devised by
those skilled in the art which fall within the spirit and scope of
the principles of this invention.
* * * * *