Patent Publication Number: US-6212978-B1

Title: Self-adjusting pliers

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 &#39;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 &#39;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 &#39;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 &#39;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 &#39;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&#39;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.