Information
-
Patent Grant
-
6212978
-
Patent Number
6,212,978
-
Date Filed
Tuesday, June 15, 199925 years ago
-
Date Issued
Tuesday, April 10, 200123 years ago
-
Inventors
-
-
Examiners
- Smith; James G.
- Shakeri; Hadi
-
CPC
-
US Classifications
Field of Search
US
- 081 357
- 081 355
- 081 358
- 081 359
- 081 360
- 081 361
- 081 364
- 081 342
- 081 367
- 081 368
- 081 370
- 081 372
-
International Classifications
-
Abstract
A self-adjusting pliers has an upper arm with an upper jaw at a first end and an upper handle at a second end. A support extends downwardly from an intermediate location of the upper arm. The support has a first downwardly extending slot and a second downwardly extending slot that is parallel to the first downwardly extending slot and closer to the upper handle than the first downwardly extending slot. The second downwardly extending slot has a plurality of second-slot teeth on a side thereof adjacent to the first downwardly extending slot. A lower arm includes a first end, and a lower handle at a second end. A control arm is pivotably connected at a first end to the upper handle and at a second end to the lower arm at an intermediate location between the first end and the lower handle. A spring is affixed at a first end to the upper arm at a location adjacent to the first end thereof, and affixed at a second end to the control arm so as to resist rotation of the control arm. A lower jaw member includes a lower jaw at a first end and in a facing relationship to the upper jaw. A slider extends from a side of the lower jaw member and is slidably engaged to the first downwardly extending slot. A pawl is disposed within the second downwardly extending slot and has a set of pawl teeth in facing relationship to the second slot teeth. A shifter has three pivot points arranged in a triangular pattern, the three pivot points being respectively connected to the lower jaw member, to the pawl, and to the first end of the lower arm.
Description
BACKGROUND OF THE INVENTION
This invention relates to pliers, and, more particularly, to a self-adjusting pliers that grips workpieces of various sizes without manual adjustment.
The traditional version of a pliers includes two elongated members joined at a pivot pin. One end of each elongated member forms a jaw, and the other forms a handle. Workpieces of different sizes are grasped in different manners, due to the constant geometry of the elongated members and the jaws. Some adjustability may be achieved by providing a slotted receiver in one of the handles, so that the handle with the pivot pin may be moved between different positions in the slot to provide adjustability for gripping objects of different sizes.
U.S. Pat. No. 4,651,598 provides an improved pliers whose jaws are self adjusting according to the size of the workpiece. Commercial versions of this pliers are useful, but have important drawbacks. Perhaps the most significant problem with the pliers made according to the '598 patent is that the jaws move relative to each other in an end-to-end manner as they are clamped down onto a workpiece. Soft workpieces such as brass or copper may be marred as a result. The clamping force applied by these pliers depends upon the size of the workpiece being grasped. Additionally, these pliers cannot be locked closed for convenient carrying and storage.
Another problem with the pliers of the '598 patent is that they do not lock to the workpiece, an important convenience in some uses of pliers. Overcenter locking pliers are described in a series of patents such as U.S. Pat. No. 4,541,312. Conventional overcenter locking pliers provide adjustability in the size of the workpiece that may be gripped through a screw adjustment to the pivoting position of the control arm, but this adjustability is not automatic in the sense of the pliers of the '598 patent.
Other types of locking pliers such as the AutoLock™ pliers combine the self-adjusting feature with an overcenter locking mechanism. This pliers can be inconvenient to use for some sizes of workpieces, suffers from some of the problems of the pliers of the '598 patent, does not achieve a large gripping force, and may unexpectedly unlock when large objects are being gripped.
There is a need for a self-adjusting pliers which does not experience shifting of the jaw position as the object is grasped, and which may be provided in a locking version. The present invention fulfills this need.
SUMMARY OF THE INVENTION
The present invention provides a self-adjusting pliers wherein the jaws automatically adjust to various sizes of workpieces. There is no end-to-end relative movement of the jaws as they grasp the workpiece, so that there can be no marring of the type observed with the pliers of the '598 patent. The clamping force is substantially constant regardless of the size of the workpiece, but is adjustable in some versions of the pliers. The pliers may be provided with no locking or releasable overcenter locking, or the ability to switch between the two.
In accordance with the invention, a self-adjusting pliers comprises an upper arm including an upper jaw at a first end thereof, an upper handle at a second end thereof, a support extending downwardly from an intermediate location thereof, a first downwardly extending slot in the support, and a second downwardly extending slot in the support. The second downwardly extending slot is parallel to the first downwardly extending slot and closer to the upper handle than the first downwardly extending slot. The second downwardly extending slot has a plurality of second-slot teeth on a side thereof adjacent to the first downwardly extending slot. A lower arm includes a first end thereof, and a lower handle at a second end thereof. A control arm is pivotably connected at a first end to the upper arm and at a second end to the lower arm at an intermediate location between the first end and the lower handle. A spring is affixed at a first end to the upper arm at a location adjacent to the first end thereof, and affixed at a second end to the control arm so as to resist rotation of the control arm. A lower jaw member includes a lower jaw at a first end thereof, the lower jaw being in a facing relationship to the upper jaw, and a slider extending from a side of the lower jaw member. The slider is slidably engaged to the first downwardly extending slot. A pawl is disposed within the second downwardly extending slot and has a set of pawl teeth in facing relationship to the second-slot teeth. A shifter has three pivot points arranged in a triangular pattern, the three pivot points being respectively connected to the lower jaw member, to the pawl, and to the first end of the lower arm.
The lower jaw member is not part of or rigidly fixed to the lower arm. Instead, it slides in the first slot, so that it necessarily produces a controlled, perpendicular clamping force on the workpiece being grasped. The lower jaw member cannot move in a sideways or end-to-end fashion, thereby overcoming a significant fault in some prior self-adjusting pliers. The locking and clamping force is applied by the user's hand force through the two handles and thence through the pawl mechanism acting against the teeth in the second slot and through the rigid-body pivoting shifter. The two functions of the guiding of the movement of the lower jaw member and the application of force are thus separated to ensure that the movement of the lower jaw member is true.
The two slots may be straight or curved. When the two slots are straight, the force applied to the workpiece being grasped is approximately constant, but varies slightly for different sizes of workpieces. When the slots are curved, it is preferred that they have a curvature substantially parallel to a locus of movement of the second end of the control arm as it pivots about its first end. In this case, the force applied to a workpiece is substantially constant for all sizes of workpieces, an important advantage for some applications.
The pliers may be provided with control over the force applied to the workpiece through the jaws. A manual force adjuster acting on the control arm is provided at a location adjacent to the first end of the control arm. The manual force adjuster is operable to move the control arm in a direction along the length of the upper arm. This movement of the first end of the control arm changes its angle and position relative to the lower arm and to the jaw member, with the result that the clamping force applied through the jaws is controllably variable.
The pliers may also be provided with a releasable overcenter lock for the jaws. In this version, there is a downwardly extending lobe on the control arm. A release arm is pivotably connected to the lower arm and has a release pad disposed to contact the lobe of the control arm when the release arm is pivoted. In operation, the control arm moves to an overcenter position when the clamping force is fully applied. This overcenter position may be released to unlock the jaws from the workpiece either by pulling the handles apart, or by manually pivoting the release arm. The overcenter locking is readily released by pulling the handles apart when the clamping force is small, but is more conveniently released by operating the release arm when the clamping force is large.
In another version, the pliers is controllably switchable between a non-locking function and a locking function. A locking function switch is movable between a first position whereat it does not block pivoting movement of the release arm, and a second position whereat it does block pivoting movement of the release arm. The blocking of the movement of the release arm when the locking function switch is in the second position prevents the functioning of the release arm and the movement of the control arm to the overcenter position, and thereby prevents the locking function.
It is preferred to combine the features of the manual force adjuster and the releasable overcenter lock in a single pliers, when either feature is provided.
The clamping mechanism of the invention is operable to move the lower jaw member upwardly along the first downwardly extending slot until the lower jaw contacts the workpiece, thereafter to lock the lower jaw member to the second downwardly extending slot, and to transfer a clamping force to the lower jaw. The clamping mechanism is thus self-adjusting to accommodate any size workpiece that will fit between the jaws. The lower jaw member and the lower jaw are constrained to move along the first slot, independent of the functioning of the locking feature that operates in conjunction with the second slot, ensuring a true movement. Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. The scope of the invention is not, however, limited to this preferred embodiment.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a schematic elevational view of a pliers, with the jaws in the fully open position;
FIG. 2
is a schematic end view of the pliers, from the jaw end;
FIG. 3
is a schematic elevational view like that of
FIG. 1
, after initial activation of the pliers handles;
FIG. 4
is a schematic elevational view like that of
FIG. 1
, at the position where the lower jaw contacts the workpiece;
FIG. 5
is a schematic elevational view like that of
FIG. 1
, as force is applied to the workpiece;
FIG. 6
is a schematic elevational view like that of
FIG. 1
, as the lower handle is pivoted toward an overcenter position; and
FIG. 7
is a schematic elevational view of a second embodiment of the pliers, with force adjustment and a locking release.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1
illustrates a pliers
20
according to one embodiment of the invention. The figures are all schematic drawings illustrating external features and internal mechanisms in a single plane, for clarity in describing the interrelationships of the elements. “Up” and “down” reference directions are indicated on FIG.
1
. The pliers
20
comprises an upper arm
22
with an upper jaw
24
at a first end
26
of the upper arm
22
. The upper arm
22
has a cross-sectional shape preferably in the form of an inverted “U”, with the opening of the “U” pointing downwardly, as seen in FIG.
2
. (In
FIG. 2
, some elements are omitted for clarity.) The upper jaw
24
preferably has a pattern of gripping ridges
28
on its lower side
30
for engaging a workpiece
32
. An upper handle
34
is at an oppositely disposed second end
36
of the upper arm
22
. The upper handle
34
is configured for comfortable gripping by a user operating the pliers
20
, and may be contoured and/or provided with a resilient plastic covering.
A support
38
is affixed to and extends downwardly from the upper arm
22
at an intermediate location between the first end
26
and the second end
36
. The support
38
desirably includes two parallel and spaced-apart support bodies
38
a
and
38
b
, as seen in FIG.
2
.
Two slots are provided in the support
38
, extending through the support bodies
38
a
and
38
b
. A first slot
40
extends downwardly and has smooth side walls. A second slot
42
extends downwardly parallel to the first slot
40
, at a location rearward of the first slot and thence closer to the upper handle
34
than the first slot
40
. The two slots
40
and
42
are illustrated in
FIG. 1
as curved, and the curvature will be discussed subsequently. They are locally parallel to each other, even though curved. The slots
40
and
42
may instead be straight. A first side
44
of the second slot
42
, closest to the first slot
40
, has second-slot teeth
46
thereon. An oppositely disposed second side
48
of the second slot
42
, closest to the upper handle
34
, is smooth.
A lower arm
50
has a first end
52
and an oppositely disposed second end
54
. The lower arm
50
preferably has a cross section in the form of an upwardly opening “U” shape. A lower handle
56
is present toward the second end
54
. As with the upper handle
34
, the lower handle
56
is configured for comfortable gripping by a user operating the pliers
20
, and may be contoured and/or provided with a resilient plastic covering. Force is applied to the workpiece
32
by the hand of the user of the pliers
20
acting through the two handles
34
and
56
.
A control arm
58
is pivotably connected at a first end
60
thereof to an upper control arm pivot pin
62
on the upper arm
22
at a location within or adjacent to the upper handle
34
. A second end
64
of the control arm
58
is pivotably connected to a lower control arm pivot pin
66
at an intermediate location between the ends
52
and
54
of the lower arm
50
.
A spring
68
is affixed at a first end
70
thereof to the upper arm
22
at a location adjacent to the first end
26
of the upper arm
22
. A second end
72
of the spring
68
is affixed to a spring extension
74
of the control arm
58
. The spring extension
74
extends beyond the portion of the control arm
58
that is affixed to the upper control arm pivot pin
62
, preferably at an angle to the control arm
58
. The preferred angle between the spring extension
74
and the control arm
58
is about
45
degrees, although other angles are operable. The spring force of the spring
68
applied through the spring extension
74
serves to resist rotation of the control arm
58
, in the clockwise direction in the view of FIG.
1
.
The mechanism associated with the upper arm
22
, including the first end
60
of the control arm
58
, the upper control arm pivot pin
62
, the spring
68
, and the spring extension
74
, are hidden from external view within the interior of the U-shaped upper arm
22
. Similarly, the second end
64
of the control arm
58
and the lower control arm pivot pin
66
are hidden from external view within the interior of the U-shaped lower arm
50
.
A lower jaw member
76
includes a lower jaw
78
at a first end
80
thereof. The lower jaw
78
preferably has a pattern of upwardly facing gripping ridges
82
thereon. The gripping ridges
28
and
82
are in facing relationship to each other, and serve to grasp the workpiece
32
firmly therebetween.
A slider
84
extends from each side of the lower jaw member
76
, as seen in
FIGS. 1 and 2
. The slider
84
is shaped to be received within, and to slide within, the first slot
40
. The slider
84
is straight where the first slot
40
is straight, and is curved to match the curvature of the first slot
40
, when the first slot
40
is curved. The slider
84
is dimensioned so that its fit into the first slot
40
is sufficiently loose to prevent binding of the slider
84
to the sides of the first slot
40
during operation. The slider
84
constrains the movement of the lower jaw
78
so that it has a perpendicular or near-perpendicular incidence to the upper jaw
24
when the workpiece is grasped between the jaws. This constraint prevents any end-to-end or side-to-side relative movement of the jaws
78
and
24
, which would tend to gouge the workpiece. This constraint is an important advantage of the present invention, achieved with the use of two slots
40
and
42
, rather than a single slot.
A pawl
86
is captured within and disposed within the second slot
42
of each of the support bodies
38
a
and
38
b
. (That is, there are preferably two pawls
86
, but one pawl would be sufficient for the pliers to operate.) Each pawl
86
has a set of pawl teeth
88
thereon, in facing relationship to the second slot teeth
46
. A second side
90
of the pawl
88
, oppositely disposed from the pawl teeth
88
, is smooth and in facing relationship to the smooth second side
48
of the second slot
42
. The functioning of the pawl
86
will be subsequently discussed in relationship to
FIGS. 3-6
.
A shifter
92
is a plate that transfers force applied to the handles into the lower jaw
78
. There may be two plate shifters
92
, one outside of each of the support bodies
38
a
and
38
b
. Equivalently, there may be a single shifter
92
disposed between the two support bodies
38
a
and
38
b
. Each shifter
92
has three pivot points thereon arranged in a triangular pattern. The three pivot points on the shifter
92
are respectively connected to a lower jaw member pivot pin
94
on the lower jaw member
76
, a pawl pivot pin
96
on the pawl
86
, and a lower arm pivot pin
98
at the first end
52
of the lower arm
50
. The shifter
92
provides the interconnection between the lower arm
50
, the pawl
86
, and the lower jaw member
76
. That is, the lower jaw member
76
is not integral with the lower arm
50
.
A torsion spring
99
is wound around the lower arm pivot pin
98
and anchored on the lower arm
50
. The torsion spring
99
resists rotational movement of the lower arm
50
relative to the lower arm pivot pin
98
.
FIGS.
1
and
3
-
6
provide a sequential depiction of the movement of the mechanism of the pliers
20
from an initial position in
FIG. 1
to a near-final position in FIG.
6
. Not all elements are shown and labeled in
FIGS. 3-6
, so that the operation of the mechanism is not obscured. In
FIG. 1
, the mechanism is in a relaxed, filly open position, with no force applied through the handles
34
and
56
. The workpiece
32
is not yet grasped between the jaws
24
and
78
, the slider
84
is free to slide within the first slot
40
to move the lower jaw member
76
upwardly, and the pawl
86
is free to slide within the second slot
42
with the second side
90
of the pawl
86
sliding along the second side
48
of the second slot
42
.
This configuration is retained, see
FIG. 3
, as a force is applied through the arms
22
and
50
, the lower handle
56
is moved upwardly, thereby acting through the shifter
92
to move the lower jaw member
76
upwardly to approach contact to the workpiece
32
. Simultaneously, the control arm
58
pivots about the upper control arm pivot pin
62
, clockwise in the view of
FIG. 3
, so that the spring
68
extends. The spring extension creates a relatively small force that resists the upward movement of the lower handle
56
, giving the user of the pliers
20
a feel for the positioning and movement of the lower handle
56
. This spring extension force also serves as a restoring force that moves the arms
22
and
50
apart to the jaw-open or relaxed position of the pliers
20
shown in
FIG. 1
, if no force is applied to the handles
34
and
56
.
With continued upward movement of the lower handle
56
, the lower jaw
78
contacts the workpiece so that it can no longer move upwardly, as seen in FIG.
4
. At this point, the continued movement of the lower handle
56
causes the shifter
92
to rotate in rigid-body motion in the clockwise direction in FIG.
4
. The rigid-body rotation of the shifter
92
draws the pawl
86
forwardly, engaging the pawl teeth
88
to the second-slot teeth
46
, as seen in FIG.
5
. This engagement between the sets of teeth
88
and
46
effectively produces a new clamping pivot point, whose location along the second slot
42
varies according to the size of the workpiece
32
. The smaller the workpiece
32
, the further upwardly along the second slot
42
is the point where the sets of teeth
88
and
46
engage. With continued upwardly movement of the lower handle
56
, as in
FIG. 6
, the shifter
92
rotates about this effective clamping pivot point, causing the lower jaw member
76
to rotate about the clamping pivot point and, in cooperation with the upper jaw
24
, to apply clamping force to the workpiece
32
.
In all of this movement depicted in FIGS.
1
and
3
-
6
, the movement of the lower jaw member
76
is constrained by the slider
84
to travel along the first slot
40
. Also during the movement of FIGS.
1
and
3
-
6
, the second end
64
of the control arm
58
follows a locus of points as it pivots about the upper control arm pivot pin
62
. Desirably, the first slot
40
and the second slot
42
are shaped with the same curvature as this locus of points or, alternatively stated, the first slot
40
and the second slot
42
are parallel to the locus of points defined by the second end
64
. With this preferred configuration for the slots
40
and
42
, the clamping force applied to the workpiece
32
is the same, regardless of the size of the workpiece
32
. The closer the curvature of the slots
40
and
42
to that of the locus of points of the second end
64
, the closer is the clamping force to a constant value for all workpiece sizes that fit between the jaws
24
and
78
. Even if the slots
40
and
42
are straight, the variation in the clamping force is relatively small, so that straight slots
40
and
42
may be used if it is not important to maintain the clamping force exactly constant.
FIG. 7
depicts an embodiment of the pliers
20
that provides for both adjustability of the clamping force applied through the jaws
24
and
78
, and also for overcenter locking and release of the clamping force. These two features of force adjustability and overcenter locking and release are desirably provided together, but they may be provided separately. The basic closing and opening mode of this pliers
20
of
FIG. 7
is the same as that shown in
FIGS. 1-6
. Features common to the embodiment of
FIGS. 1-6
are identified by the same numerals, and the prior discussion of
FIGS. 1-6
is incorporated herein.
The clamping force adjustability is provided by moving the upper control arm pivot pin
62
in a track
100
in the upper arm
22
, along the length of the upper arm
22
in the direction between the first end
26
and the second end
36
. The maximum travel required to achieve a substantial variation in the clamping force is relatively small, and typically is about ¼ inch. The movement of the upper control arm pivot pin
62
along the track
100
is accomplished with a screw drive
102
and a manual screw movement knob
104
that extends from the second end
36
of the upper arm
22
.
The overcenter locking and release is conveniently provided by placement of an unlocking lobe
106
on the lower side of the control arm
58
. A release arm
108
is pivotably connected to the lower arm
50
, at a location between the first end
52
and the second end
54
and accessible to the hand of the user of the pliers
20
at the second end
54
. A release pad
110
on the upper side of the release arm
108
is disposed to contact the unlocking lobe
106
. In operation, the lower control arm pivot pin
66
moves to an overcenter position relative to the upper control arm pivot pin
62
and the lower arm pivot pin
98
, when the lower handle
56
is moved upwardly to the limit of its travel. Stated alternatively, when the lower handle
56
is fully open (moved to its downward limit of travel) as in
FIG. 1
, the lower control arm pivot pin
66
lies below a straight line drawn between the upper control arm pivot pin
62
and the lower arm pivot pin
98
. As the lower handle
56
is moved upwardly, the lower control arm pivot pin
66
moves closer to a straight-line relationship between the pins
62
and
98
, and eventually crosses over that straight line to lie above the straight line drawn between the pins
62
and
98
. This is the overcenter lock position. To release the pliers
20
from this overcenter lock position, the release arm
108
is operated to rotate the release pad
110
upwardly against the unlocking lobe
106
, and thereby force the lower arm
50
downwardly and out of the overcenter relationship.
The embodiment of
FIG. 7
allows the pliers
20
to be selectively shifted between the non-locking version and the locking/release version. A lock switch
112
is provided to selectively prevent the pivoting movement of the release arm
108
. That is, when the movement of the pliers
20
passes into the overcenter relationship, the release arm
108
is forced to pivot in the direction (counter-clockwise in the embodiment of
FIG. 7
) opposite to the pivoting movement of the release arm
108
during unlocking (clockwise in FIG.
7
). The locking function may be prevented by preventing this movement of the release arm
108
as the movement reaches the overcenter position as the jaws are closed, so that the stationary release arm
108
prevents the movement of the control arm
58
from passing to the overcenter position. The lock switch
112
prevents the movement of the release arm
108
and the control arm
58
by physically contacting and interfering with the movement of the release arm
108
. Thus, in the embodiment of
FIG. 7
, the lock switch
112
slides into an interfering position relative to the release arm
108
when slid to the right, so that the overcenter locking is not permitted. The pliers then serves as an ordinary non-locking pliers. When the lock switch
112
is slid to the left in the view of
FIG. 7
, it does not interfere with the rotation of the release arm
108
, and the release arm
108
does not prevent the movement of the lobe
106
and thence the control arm
58
as it passes to the overcenter position. The pliers is a locking pliers in this configuration.
Although a particular embodiment of the invention has been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.
Claims
- 1. A self-adjusting pliers, comprising:an upper arm including an upper jaw at a first end thereof, an upper handle at a second end thereof, a support extending downwardly from an intermediate location thereof, a first downwardly extending slot in the support, and a second downwardly extending slot in the support, the second downwardly extending slot being parallel to the first downwardly extending slot and closer to the upper handle than the first downwardly extending slot, the second downwardly extending slot having a plurality of second-slot teeth on a side thereof adjacent to the first downwardly extending slot; a lower arm including a first end thereof, and a lower handle at a second end thereof; a control arm pivotably connected at a first end to the upper arm and at a second end to the lower arm at an intermediate location between said first end of said lower arm and said lower handle; a spring affixed at a first end to the upper arm at a location adjacent to said first end of said upper arm, and affixed at a second end to the control arm so as to resist rotation of the control arm; a lower jaw member including a lower jaw at a first end thereof, the lower jaw being in a facing relationship to the upper jaw, and a slider extending from a side of the lower jaw member, the slider being slidably engaged to the first downwardly extending slot; a pawl disposed within the second downwardly extending slot, the pawl having a set of pawl teeth in facing relationship to the second slot teeth; and a shifter having three pivot points arranged in a triangular pattern, the three pivot points being respectively connected to the lower jaw member, to the pawl, and to the first end of the lower arm.
- 2. The pliers of claim 1, wherein the first slot and the second slot are straight.
- 3. The pliers of claim 1, wherein the first slot and the second slot are curved.
- 4. The pliers of claim 1, wherein the first slot and the second slot are curved with a curvature substantially parallel to a locus of movement of the second end of the control arm as it pivots about its first end.
- 5. The pliers of claim 1, further includinga manual adjuster means acting on the control arm at a location adjacent to said first end of said control arm, and operable to move the control arm in a direction along the length of the upper arm between the first end and the second end of the upper arm.
- 6. The pliers of claim 1, further includinga downwardly extending lobe on the control arm, and a release arm pivotably connected to the lower arm and having a release pad disposed to contact the lobe of the control arm when the release arm is pivoted.
- 7. The pliers of claim 6, further includinga lock switch slidable movable between a first position whereat it does not block pivoting movement of the release arm, and a second position whereat it does block pivoting movement of the release arm.
- 8. The pliers of claim 1, further includinga manual adjuster means acting on the control arm at a location adjacent to said first end of said control arm, and operable to move the control arm in a direction along the length of the upper arm between the first end and the second end of the upper arm, a downwardly extending lobe on the control arm, and a release arm pivotably connected to the lower arm and having a release pad disposed to contact the lobe of the control arm when the release arm is pivoted.
- 9. The pliers of claim 8, further includinga locking function switch slidably movable between a first position whereat it does not block pivoting movement of the release arm, and a second position whereat it does block pivoting movement of the release arm.
- 10. The pliers of claim 9, wherein the locking function switch is slidably movable.
- 11. A self-adjusting pliers operable to grasp a workpiece between an upper jaw and a lower jaw, comprising:an upper arm including the upper jaw; a lower arm; a support extending downwardly from the upper arm toward the lower arm; a first downwardly extending slot in the support; a second downwardly extending slot in the support; a control arm pivotably connected at a fist end to the upper arm and at a second end to the lower arm at an intermediate location of said lower arm; a spring biasing the control arm so as to resist rotation of the control arm; a lower jaw constrained to slide along the first downwardly extending slot, the lower jaw not being integral with the lower arm; and a clamping mechanism operable to move the lower jaw along the first downwardly extending slot until it contacts the workpiece, thereafter to lock the lower jaw to the second downwardly extending slot, and to transfer a clamping force to the lower jaw.
- 12. The pliers of claim 11, wherein the first downwardly extending slot is parallel to the second downwardly extending slot.
- 13. The pliers of claim 11, wherein the first downwardly extending slot and the second downwardly extending slot are parallel.
- 14. The pliers of claim 11, further includinga manual adjuster means acting on the control arm and operable to move a pivot point at the first end of the control arm in a direction along the length of the upper arm.
- 15. The pliers of claim 11, further includinga downwardly extending lobe on the control arm, and a release arm pivotably connected to the lower arm and having a release pad disposed to contact the lobe of the control arm when the release arm is pivoted.
- 16. The pliers of claim 15, further includinga lock switch slidable movable between a first position whereat it does not block pivoting movement of the release arm, and a second position whereat it does block pivoting movement of the release arm.
US Referenced Citations (8)