Patent Publication Number: US-8534168-B2

Title: Compact adjustable locking pliers

Description:
FIELD OF THE INVENTION 
     The present invention relates to an adjustable locking pliers. More precisely the present invention relates to a simplified compact structure for such locking pliers. 
     BACKGROUND 
     Locking pliers are well known in the art. One such conventional device is known as a Vise Grip pliers. These devices have two jaws that may be locked on an object. The over-center locking mechanism is achieved through a fixed jaw attached to a body, a movable jaw pivoted to the body, a handle pivoted to the movable jaw, and a pivoting over-center link between the body and movable jaw that together cooperate to lock the jaws on a work piece when the handle is forced toward the body. The over-center mechanism includes a fine adjustment screw that controls the opening of the jaws over a limited range to accommodate articles of different sizes within the range and permits the over-center mechanism to lock. 
     Another common variation is known as adjustable and water pump pliers. These allow for a movable pivot location to adjust the jaw size range for a given handle position. Further locking pliers have been combined with an adjusting mechanism to provide an adjustable locking pliers. In this manner a locking pliers can maintain a relatively parallel jaw and fit a wider size range of objects to be gripped. Some designs, for example “auto adjusting” types require careful and unintuitive manipulation of handles of the pliers to adjust or maintain a jaw size. 
     However the prior attempts to combine locking and size range adjusting features have a required a bulky, inconvenient, or inefficient mechanism. One example is a pliers according to U.S. Pat. No. 3,981,209; a corresponding product is sold by Facom of France as model #509. Another related Facom product is model #500 which includes features of the &#39;209 patent along with features from French patent 1,100,105. These models are not easily adjusted and have a limp handle wherein there is no opening bias upon the lower jaw or the handle to stabilize the tool in a hand. Further without an opening bias there is no feedback for the position of the handle. All of the prior such designs have been awkward in appearance or use. According to the present invention a locking adjustable pliers includes a familiar appearance in a simple and compact design. 
     SUMMARY OF THE INVENTION 
     In the present invention a locking pliers includes a lower jaw that pivots about an upper body. The upper body preferably includes a fixed upper jaw at a front end. The pivot location between the lower jaw and upper body is movable between at least two distinct positions to enable at least two jaw opening ranges. For example in a small size range the pliers may be operated to lock the lower jaw in a minimum size to clamp directly against the upper jaw with a zero gap. The large size range has the lower jaw usually or always spaced away from the upper jaw. 
     According to the above description the jaw spacing may be changed in two ways. A continuous respective motion of the lower jaw occurs as the pliers are normally operated by moving a lever or handle pivotally attached to the lower jaw. This motion normally changes the respective angle of the jaws. A second type of motion is moving the jaws between the distinct small and large size ranges. Optionally more than two distinct pivot positions may be provided. 
     According a preferred embodiment of the invention a slot through the body extends generally vertically in the body or substantially perpendicular to the upper jaw face. A pin, protrusion, or equivalent structure of the lower jaw moves within this slot to allow the lower jaw to move toward and away from the upper jaw. The pin is fixed or located on the lower jaw. The pin preferably extends beyond the body to be exposed and operable directly by a user. A preferably enlarged head end provides a large gripping surface for such operation. A preferred embodiment further includes a recess or locally wide portion in the slot into which the pin is selectively held. A recess corresponds to each pivot position of the jaws. In the above example therefore with two jaw pivot positions there would be two recesses or sets of recesses. Optionally the pin may be located on the upper jaw while the lower jaw is moved in relation to the upper jaw. In this case the slot may be within or upon the lower jaw. 
     One feature of the invention is a compact spring assembly to provide both a reliable detent bias and a firm rotational bias to a lower jaw. The pin is spring biased in the detent action into the recess but not normally mechanically locked in position. A user operates directly on the pin to move it out of the recess and along the slot. As discussed in detail below normal gripping or clamping with the pliers adds further biasing force to retain the pin in the recess. In this manner no further locking elements are needed to securely position the pin although such features may optionally be added if desired. Therefore the pivot position may be adjusted without secondary releasing steps. Further the adjustment process is immediate and intuitive since moving the pin directly moves the lower jaw in the preferred embodiment. This contrasts with some known designs where a handle or other indirectly related element must be manipulated before the jaw size can be adjusted. With the lower jaw also biased by the spring assembly to rotate away from the upper jaw the handle is biased away from the body as a user holds the tool in its pre-locking condition about a work piece. The pliers thereby gives feedback for the handle position as the handle moves within the hand grip before it is locked. 
     In the illustrated embodiment the features of the invention are provided in a familiar locking pliers configuration. It is an object of the invention that the design be familiar whereby the additional features and functions of the invention are readily understood and usable while adding no or minimal additional bulk to the device. In contrast many prior pliers are complex in appearance and in fact without even offering the new advantages of the present invention. It is a feature of the invention that the new function is provided with the addition of only a simple wire formed part and optionally a washer to the known locking pliers device. A novel way to attach and link simple components provides an unexpected result of the invention. Other novel but visually simple features are included in the structure of the invention. The pliers of the invention can therefore be manufactured inexpensively and without great investment in tooling. 
     Alternately it may be desired to incorporate the features of the invention into a pliers or clamping device that is of other familiar or less familiar forms. The jaws may be of various forms. In the illustrated embodiment the jaws are a straight serrated style for demonstrative purposes. Other known jaw configurations for example are smooth, needle nose, concave, or c-clamp style. Other jaw configurations are anticipated as usable with the pliers of the invention. In one example if the jaw adjusting motion is sufficiently large the device may take more the form of a bar clamp rather than a pliers. In this example a slot or recess may extend along a bar to selectively fit the pivot pin described herein. Or for example the invention may be used in a pliers that more resembles a water pump pliers type configuration. Preferably but not exclusively the pliers of the invention is a locking type, although a non-locking type will also benefit from the present invention. For example a pliers without the over-center action would be a non-locking type. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a left, top perspective view of a preferred embodiment pliers, according to the present invention, in a minimum size jaw angle. 
         FIG. 2  is a side elevation view the pliers of  FIG. 1  with a body in section to expose internal components. 
         FIG. 3  is a sectional view of the pliers of  FIG. 2 . 
         FIG. 3A  is an isometric section view of the pliers of  FIG. 2 . 
         FIG. 4  is the pliers of  FIG. 2  with internal components in hidden view. 
         FIG. 5  is the pliers of  FIG. 1  with the body not shown to expose internal components. 
         FIG. 6  is a perspective view of a pivot pin. 
         FIG. 7  is perspective view of a wire link. 
         FIG. 8  is the pliers of  FIG. 4  with the lower jaw pivoted to a larger jaw angle size. 
         FIG. 9  is the pliers of  FIG. 4  with the lower jaw translated to the large jaw size range and rotated to a minimum size jaw angle. 
         FIG. 10  is the pliers of  FIG. 9  with the lower jaw rotated to a larger jaw angle to grip a work piece. 
         FIG. 11  is a side elevation of a lower jaw. 
         FIG. 12  is the pliers of  FIG. 4  with the lever and lower jaw pivoted to an open position. 
         FIG. 13  is the pliers of  FIG. 9  with the lever and lower jaw pivoted to an open position. 
         FIG. 14  is a lower jaw with an alternate embodiment biasing spring. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows an external view of a preferred embodiment of the invention. In the views most of the pivoting links are shown as simple through holes. Normally there are rivets or pins to create respective linkages at these holes. These rivets or pins are not shown for simplicity with the exception of pin  70 . The pliers are preferably but not necessarily of a locking type including an over center mechanism of known type. In this mechanism handle  20  cooperates with linkage  30  to lock lower jaw  40  upon an object or work piece against upper jaw  50 . Upper jaw  50  is normally attached to or part of body  10 . Lower jaw includes grip surface  43  while upper jaw  50  includes grip surface  51 . Handle  20  and linkage  30  are arranged to provide a leveraged action wherein, near the closed position of handle  20 , a relatively large motion of the handle causes a small motion of jaw  40 . The advantages of the invention will benefit a leveraged type pliers with or without a locking function. End  32  of linkage  30  presses tip  92  of screw  91 . In this manner high gripping forces are possible. In the illustrated embodiment the grip surfaces are straight serrated style. Other shapes or types of grip surfaces are anticipated including concave, smooth, c-clamp style, wire cutter and other types that may be useful as clamping or gripping surfaces. 
     Knob  90  enables rotation of screw  91 , threads not shown, within a threaded opening of body  10 . Lower jaw  40  rotates about pin  70  where pin  70  is held in recess  15   a  of slot  15 . When handle  20  is moved toward body  10  linkage  30  moves past a center position. If screw  91  is properly adjusted the over center action occurs as jaws  40  and  50  fit about a work piece. Optionally the features of the invention may be used to improve an automatic adjusting locking or non locking pliers. In this case screw  91  or other appropriate feature is replaced or supplemented with an auto sizing mechanism of known type. Body  10  is preferably elongated from upper jaw  50  toward a rear end of the body to provide a hand grip surface on the body. 
     When handle  20  is moved away from body  10  the jaws move apart to an open position as or similar to that shown in  FIGS. 12 and 13 . The open position may be used to prepare the pliers to close about a work piece. Release lever  95  is optionally used to pry handle  20  away from linkage  30  to assist unlocking handle  20  from its over center locked engagement to link  30 . 
     According to the invention the pliers include at least two distinct size ranges. This feature is readily apparent by comparing  FIGS. 4 and 9 . The jaws and handle  20  are in equivalent angular positions with pin  70  being moved. Spring  60  and wire link  65  follow lower jaw  40  to extend to a different angle. In  FIG. 4  pin  70  is held on or in recess  15   a  of slot  15  and passes through hole  46 ,  FIG. 11 . In  FIG. 9  pin  70  is moved down along slot  15  to recess  15   b . Lower jaw  40  moves along with pin  70  to this lower position while normally maintaining substantially the same angular position to body  10  or jaw  50 . 
     It is desirable to maintain a similar jaw angle between selected size ranges for a given position of screw  91 . This helps the usage of the pliers to be more predictable and intuitive. As seen between  FIGS. 4 and 9  the relative jaw angle is similar. To hold this angle there should be no motion that equates to adjusting the position of screw  91 . Specifically the position of handle  20  should minimally translate horizontally relative to pin  70  as pin  70  moves vertically. As defined here vertical is about in the direction which the lower jaw moves between size ranges, or alternately about perpendicular to the upper jaw face. The relevant motion of handle  20  is controlled by the pivot location at screw tip  92  against linkage end  32  as pin  70  moves; as seen handle  20  moves slightly rearward about this arc center (tip  92 ) in  FIG. 9 . Therefore pin  70  should move about the same arc center so that the pin moves a similar distance rearward. The angle of slot  15  is oriented to provide this motion. In particular slot  15  is an approximate portion of an arc that has a center at tip  92 . 
     Recesses  15  and  15   b  preferably extend forward from slot  15  as shown. Preferably body  10  is of sheet metal form and slot  15  comprises two corresponding slots in opposed sides of the body. Pin  70  is biased into these recesses in a similar force direction both for loaded and unloaded conditions. Therefore pin  70  normally maintains a same position in a recess or equivalent structure as the pliers transition between loaded and unloaded conditions, for example as gripping force begins to bear upon a work piece. This constant pivot position helps to keep the jaw action simple and predictable. The loaded condition includes the jaws being pressed against each other either directly as in  FIG. 1  or spaced and pressing a work piece  200 ,  201 ,  FIGS. 8 and 10 . The unloaded condition is normally when the jaws are spaced and no work piece is present although the jaws may be proximate as  FIG. 1  and not pressing if screw  91  or equivalent structure is backed off slightly. 
     In the loaded condition linkage  30  provides a forward force upon handle  20  at front link pivot  22 . This force is relative to body  10  as screw  91  presses the link forward. At connection  41  handle  20  pivotally connects to lower jaw  40 . Handle  20  transmits its forward force to lower jaw  40  at the connection. Therefore there is a net forward force upon lower jaw  40  relative to body  10 . This forward or lateral detent force urges pin  70  into recess  15   a  or  15   b . Pin  70  is attached to jaw  40  at hole  46 ,  FIG. 11 . At the same time in the loaded condition there is a downward force upon lower jaw  40  as it is pressed by upper jaw  50  or work piece  200 ,  201 . This force urges pin  70  to press the bottom of recess  15   a  or  15   b . These two forces combine to create a net force F, forward left and downward in the figures, on lower jaw  40 ,  FIGS. 2 ,  8 , and  10 . This direction for force F causes pin  70  to press the lower left segment of recess  15   a  or  15   b . The recess therefore need be only deep enough to provide an edge along its lower left portion to react to the direction of force F. The note  15   a  in  FIG. 9  is pointing to this general location for recess  15   a . For example there is no need in the preferred embodiment for a recess extending rearward from slot  15  since there is no force to counteract in that direction. 
     As just described for the jaw loaded condition the pliers assembly is inherently stable with respect to any selected position of pin  70 . Force F is proportionate to the gripping force so the pliers are more stable as the gripping force of the jaws increases. As further described below the assembly is also stable when it is manipulated without a load. For example pin  70  remains in its selected position as handle  20  and screw  91  are moved and adjusted to position the jaws about a work piece. However pin  70  can readily be moved between selected positions when desired. 
     For the jaw unloaded condition the force from spring  60  is used to maintain a stable selected position for pin  70 . Both a small size range and a large size range have a stable position for pin  70  in an unloaded condition. Spring  60  pulls rearward upon lower jaw  40  at spring hook  68  at a front end of the spring in opening  47 . This force creates a firm bias to open lower jaw  40  and handle  20  as handle  20  is moved away from body  10 . According to a preferred embodiment of the invention the rear end of spring  60 , at hook  69 , does not directly link to body  10  as is typical in prior locking pliers. Rather the immediate connection of hook  69  is to wire link  65 ,  FIG. 7 . Specifically the connection is to coil  67  or equivalent structure. See also  FIGS. 2 and 5 . Spring  60  and wire link  65  form at least in part a spring assembly. Opening  42  of lower jaw  40  pivotally fits hooks  66  or equivalent structure of wire link  65 . Spring  60  thus creates a compressive force on the wire link to pull wire link  65  forward. This force causes a forward bias upon lower jaw  40  at opening  42 . Opening  42  is preferably near to pin  70  relative to opening  47  so that a force at opening  42  may effectively act upon pin  70 . Pin  70  is thus biased forward toward or upon the front side of slot  15  including within recesses  15   a  or  15   b . Wire link  65  includes portions that are or may be in tension, for example the front portion of coil  67 . However the overall force between ends of wire link  65  is compressive. 
     Preferably wire link  65  includes a free position with the hook of one end in the open position  66   a ,  FIG. 7 . This will help in assembling the wire into opening  42  of the lower jaw. Once assembled the wire is held securely by the opening of the jaw with a light bias to remain in the closed condition of the solid lines in  FIG. 7 . The short legs of hook end  66  hold the hooks in position against lower jaw  40 . No further components are needed to make the connection here, although such components may be used. With hook end  66  held in opening  42  wire link  65  is able to effectively push and pivot against the lower jaw to provide the forward bias on lower jaw  40  at opening  42 . While wire link is preferably rigid with respect to its linking function it is flexible as illustrated with respect to its two arms. According to a further option described herein wire link  65  may comprise a spring or other second resilient member with respect to its linking function for example to supplement the action of spring  60 . 
     The rear of wire link  65 , along with spring hook  69 , is slidably held in body  10  by tabs  11 ,  FIGS. 3 ,  4  and  9 . As illustrated the sliding is by the wire link, although it could be by or near hook  69 . Tabs  11  or equivalent rib or other structure prevents the downward angle of spring  60  from pulling wire link  65  downward out of body  10 . Hook  69  is thereby not connected to a fixed location of body  10 , but rather is slidably or movably fitted to the body to provide a primarily longitudinal force to opening  42  through wire link  65 . In this manner spring  60  pulls upon lower jaw  40  at opening  47  substantially indirectly, through wire link  65 , rather than directly from a fixed location of body  10 . The spring assembly of spring  60  and wire link  65  thus provides two distinct functions: a detent bias of pin  70  into a selected recess, and a firm rotational bias upon lower jaw  40  away from upper jaw  50 . This rotational bias in turn biases handle  20  toward its open position. Preferably wire link is substantially horizontal or longitudinal within body  10  to provide an efficient rearward bias in a compact shape to its linked location on lower jaw  40 . 
     Optionally further arms, springs, or other members may hold wire link  65  in position relative to body  10 . For example if components beyond tabs  11  are configured or added to cause an upward bias upon the rear of wire link  65  then tabs  11  will not be required. In another alternate embodiment, not shown, a second spring may push upon lower jaw  40  at or near opening  42  or equivalent location. This second spring may replace or supplement wire link  65  to form the spring assembly with spring  60 . Then one or both springs may attach to a fixed location of body  10 , for example near to tab  11 . The function will normally be equivalent to the use of rigid wire link  65  with a possible trade off in complexity. A further option below includes a torsion spring. 
     As just described for the unloaded condition lower jaw  40  is pulled rearward at its bottom and pushed forward at its top to create a torque on the lower jaw. The pulling is at opening  47  and the pushing at opening  42 . These respective locations are substantially spaced apart from each other to create a firm rotational torque on lower jaw  40  relative to handle  20 . Specifically lower jaw  40  is biased to rotate counter clockwise away from upper jaw  50  about connection  41  in the views. Pin  70  is held in hole  46  of the jaw. Therefore pin  70  is pressed forward in slot  15 ; see  FIG. 9  for a clear view of this condition. Further lower jaw  40  is firmly biased toward its pivoted open position for any pivoted position of the lower jaw and for both positions of pin  70  in recess  15   a  or  15   b . The rotational bias may be considered in relation to handle  20  but need not be exclusively about this reference. 
     A firm rotational bias according to the invention is sufficient to cause handle  20  to reliably move against a predetermined force for a substantial majority of the possible motion of the handle in an unloaded condition. A further way to consider a firm torque is that which is sufficient to hold the handle in an open position against a predetermined force. Such a predetermined force may be the weight of handle  20  and its linked elements. For example if the views of  FIGS. 12 and 13  are reversed to be upside down, not shown, then handle  20  will be biased by its own weight to close against body  10 . The firm force from the spring assembly maintains handle  20  opened or moves handle  20  upward away from body  10  toward the open position in the upside down position of the pliers. With this firm force the pliers gently expands within a user&#39;s grip so that the user can keep the pliers steady in a hand. In contrast empirical experience shows that a limp or weakly biased handle will tend to fall out of an operator&#39;s hand as the handle collapses inward thereby requiring two hands to operate. 
     Alternately the firm rotation bias may be indirectly applied to the lower jaw. For example the bias may be directly upon the handle by a further spring connecting the handle to the jaw, the body or other element of the pliers, not shown. For example a torsion spring may be fitted at the pivot of opening  41  to bias lower jaw  40  and handle  20  toward the respective open positions. In this example the lower jaw is biased to rotate by way of the handle at opening  41 . 
     Through the rotational bias or equivalent force pin  70  is pressed into the recess by a force in relation to handle  20 . As discussed above handle  20  may be pressed forward in relation to body  10  through link  30 , so pin  70  is pressed into the recess by a force also in relation to body  10 . The unloaded force upon pin  70  from spring  60  is in a similar direction to loaded force F discussed above and in fact is normally additive to the force F, although of lesser magnitude. Therefore the applied force upon pin  70  holds the pin without shifting or otherwise substantially moving the pin in a selected recess through a transition between loaded and unloaded conditions. 
     It is desirable that lower jaw  40  be firmly biased to move toward its pivoted open position for any condition of the pliers other than locked as discussed above. This pivoting bias is preferably relatively constant for all rotational jaw positions, although the resulting bias on handle  20  will be non-linear because of the varying force inherent in the over-center connection to the handle. Specifically the force moving handle  20  away from body  10  will be less as link end  32 , link pivot  22 , and opening  42  are near aligned in the on-center or locked condition of these elements. In the respective aligned positions of  FIG. 2  or  8  the force to move handle  20  will be near zero since link  30  is at or near its locked condition. In  FIGS. 12 and 13  link  30  is well into its unlocked position and handle  20  will have the firm opening bias whereby a torque on lower jaw  40  can readily cause handle  20  to pivot open. The locked condition may occur both with the jaws loaded to grip a work piece or unloaded; the locked or unlocked condition refers to the relative alignment of link  30  discussed here. 
     Comparing  FIGS. 9 and 13  is it seen that spring  60  pulls on jaw  40  at a vertically spaced distance in  FIG. 9 . This distance is preserved in  FIG. 13 . Therefore a firm pivoting bias is maintained on lower jaw  40  through its full normal pivoting range. Such opening bias transmits to handle  20  to bias or spread the handle away from body  10 . In normal use a user holds the pliers against this opening bias as the jaws are positioned about a work piece. If there is no or minimal opening bias upon the jaw then it is difficult to operate the pliers by one hand. For example a work piece may be half inch in size. Then a user would select a suitable size range for pin  70  and setting for screw  91 . In a large pliers of 10″ length for example recess  15   a  would be appropriate. The user would then hold the body  10  and handle  20  so that the jaws are open to a pre-position just greater than ½″. Then the jaws are squeezed to clamp the work piece. As long as there is enough spreading force from the spring action the pliers will be easy to grip and control. A user will have feedback for the position of the handle as the handle presses the gripping hand. The jaws can be opened as required with one hand while the pliers will not fall out of the hand. Also there is no need for a second hand to guide the handle to pull it to the suitable pre-position. 
     As discussed above the respective pushing and pulling forces are spaced apart. Opening  42  is biased forward near to pin  70  in all size range positions, compare  FIGS. 4 and 9 . At the same time opening  41  is pulled rearward in all positions. So the first force application location, opening  47 , is substantially further from pin  70  than the second force application location, opening  42 . By placing opening  42  nearly aligned vertically with pin  70  the pliers remains compact; see  FIG. 8  wherein a more distant spacing of opening  42  would force body  10  to bulge upward near opening  42 . In particular if force at opening  42  were substantially or exclusively used to bias lower jaw  4  to pivot open then opening  42  would need to be much higher in position. To illustrate this issue see  FIG. 4 . Wire link  65  is right behind pin  70  and cannot provide an opening pivot bias to the lower jaw. But in order to maintain a compact body that allows the jaw position of  FIG. 8  opening  42  should not be located higher where it could provide a light albeit still inadequate rotating bias. Wire link  65 , or equivalent spring biased element, cannot by itself bias the jaw to rotate firmly through its various possible positions According to the invention there is a distant second spring bias location below, at opening  41 , to create the firm jaw opening bias discussed earlier wherein opening  42  is substantially distant from pin  70  relative to the distance of opening  42  from pin  70 . 
     In the preferred illustrated embodiment wire link  65  or equivalent structure is an elongated narrow element that is co-extensive with the interior of body  10 . An alternate embodiment biasing spring is shown in  FIG. 14 . A first coil  162  of torsion spring  160  fits about to pin  42 A of lower jaw  40 . Proximal end  161  of the torsion spring presses against lower jaw  40  to cause the jaw to rotate counterclockwise from the torque of first coil  162  in  FIG. 14 . End  161  is or includes an extension of coil  162  to rotationally fix arm  167  or a segment of coil  162  to lower jaw  40  whereby coil  162  can transmit torque to the jaw. In the case that end  161  is fixed to the jaw there will be some deflection along arm  167  so that coil  162  is not rigidly fixed to the jaw, however it will be functionally fixed to the jaw. In  FIG. 14  this extension is preferably a bent segment of arm  167 , not shown, that extends into the page through opening  47 . This is toward the jaw open direction in the assembly of the pliers. The distal end of the spring extends to or comprises a resilient element, such as second coil  163 . The bias from the second coil or resilient element biases lower jaw  40  forward at pin  42 A to engage the recesses as discussed elsewhere herein. According to this function hook  164  is pivotally attached to body  10 , not shown, whereby lower jaw  40  is biased away from hook  164  and its mount in the body. Torsion spring  160  thereby operates upon two spaced locations of lower jaw  40 , pin  42 A for the detent bias, and end  161  for the rotation bias. It is not required that end  161  be specifically below coil  162  as shown. Optionally the end may press closer to coil  162 , including above the coil. But this pressing location will still be spaced from the center of force from the detent bias, which is the center of pin  42 A in the illustrated view. Such spacing is required to create a usefully firm torque or rotational bias on the lower jaw. To remain compact the torque biasing coil  162  shall be proximate to or concentric with pin  70  whereby it can act directly to rotate the jaw. Preferably coil  162  is relatively fixed to lower jaw  40  such that a center of the coil does not substantially move in relation to the jaw as the jaw moves through its possible positions. In this way the coil can most directly apply rotational torque to the jaw while remote coil  163  or other spring element biases coil  162  laterally. 
     According to this alternate embodiment lower jaw  40  may be provided both an opening and a forward bias by a single spring element. No further link is required. This contrasts with a biasing spring known in the art wherein a torsion spring includes only a single coil remote from the lower jaw and can provide only a forward bias on a single location of the lower jaw. As a result the prior jaw and handle are limp with no opening bias upon the handle. In a further option a compression or extension spring, not shown, may be fitted to or extend along arm  165  to provide the forward bias. As illustrated the first coil  162  is mounted near a separate pin or equivalent structure spaced from pivot pin  70 . This allows the torsion coil to be fitted at a narrow extension of lower jaw  40  whereby the pliers can remain slim at the area of pivot pin  70 . Optionally coil  162  may be fitted at or around pin  70 . 
     In the preferred or alternate embodiment biasing spring designs a spring, combination of springs, or operative rigid links to the springs may be described as a spring assembly. The spring assembly provides a dual force action to the lower jaw. This force comprises both a forward bias at the pivot pin and a torque to the lower jaw. To benefit from the advantage of the invention the torque must be high enough to create the firm opening bias to the handle of predetermined force discussed above. 
     As illustrated the front side of slot  15  includes recess  15   a  and  15   b . The spring bias upon pin  70  described here is a primary positioning force for any unloaded condition of the pliers. For example it operates in  FIG. 9 ,  12  or  13 . The bias also operates in loaded conditions such as  FIG. 1 ,  8  or  10 . The bias from the loaded condition of gripping the work piece will normally be substantially greater than that from spring  60 ; the force F discussed earlier will be proportionate to the gripping force and will be a primary force in pin  70  when loaded. In either loaded or unloaded case pin  70  is held to be stable in recess  15   a  or  15   b  and pin  70  does not normally translate relative to the slot or body  10  as the condition transitions between loaded and unloaded. 
     To select a position for pin  70  in slot  15 , and a resulting size range for the pliers, the pin may be moved directly by a user&#39;s fingers. Enlarged head  71 ,  FIGS. 3A and 6 , is preferably textured or otherwise suitable for gripping by a user to slide the pin along slot  15 . The diameter of head  71  is preferably substantially larger than the diameter of a central portion of pin  70 ; a central portion for example being the area  70  shown in  FIG. 2  or  11 . A typical position from which to select an opening size range is shown in  FIGS. 12 and 13 . The jaws are unloaded with handle  20  optionally moved at least partly away from body  10 . To move to the larger size range pin  70  is urged rearward, against the bias from spring  60  or equivalent spring, from its position in recess  15   a  of  FIG. 12 . As illustrated the spring bias is the primary or only force to be overcome to move pin  70  out from the recess. The pin is then slid downward in slot  15  until it snaps or moves into recess  15   b  of  FIG. 13 . As discussed above the pin is normally biased to move fully or substantially into recess  15   b . This process is reversed to select the smaller size range. According to the invention pin  70  is normally translated between selected positions of slot  15 . The pin is readily accessed directly but need not be rotated, pressed or manipulated in any additional manner. If for any reason the pin is nearly but not fully seated into a selected recess when unloaded the pin will become fully seated when loaded as force F,  FIG. 2  for example, increases. 
     When moved rearward out of a recess pin  70  will normally be biased to slide along a front side of slot  15  to move toward the upper recess, recess  15   a  in the instant example. This is a result of the angle of spring  60  relative to slot  15  or body  10  wherein the spring pulls upward on lower jaw  40 . This creates a default position of the small or “normal” size range of  FIG. 12 . This may be convenient since the familiar size range is a good starting condition for a use session. However as discussed earlier the larger size range of  FIG. 13 , wherein pin  70  is in recess  15   b , is a stable condition that will remain so unless the pin is intentionally moved out of recess  15   b  and allowed to move to the upper position. Therefore upon operating pin  70  the pin will normally move upward toward the small jaw size range but can easily be urged downward to the lower position to engage recess  15   b . In all cases the position of pin  70  is stable in either of recess  15   a  or recess  15   b.    
     It is possible that the pliers may be accidentally dropped. If this occurs in the unloaded condition of  FIG. 13  the impact may cause pin  70  to move upward into recess  15   a ,  FIG. 12  as a result of the upward bias discussed above. A user would then restore the pliers to the larger size range if that is still desired. However pin  70  remains stable in a selected recess for any normal adjusting or operating action in the unloaded condition. For example in the loaded condition handle  20  is not normally moved; in a locking pliers embodiment it is not freely movable with respect to body  10  since it is held in the over-center position. However in the unloaded condition handle  20  is normally freely movable for example between the positions of  FIG. 9  and  FIG. 13 . Such handle motion is a normal adjusting or operating action when unloaded. Pin  70  remains stable in either of selected recess  15   a  or  15   b , or further optional recesses or equivalent structures, as handle  20  is so moved or left open and not held at all. For example pin  70  will remain stable in any selected recess through a full motion, or a substantial portion of a full motion, of handle  20  from fully open to fully closed and locked as shown for example from  FIG. 13  to  FIG. 9  or  FIG. 12  to  FIG. 4 . The selected size range is thereby predictable and reproducible whether a user is using the pliers or not. 
     Optionally as described later herein a secondary action may be added to pin  70  or equivalent structure to positively lock it in position, although such secondary feature is not required. When loaded as described earlier pin  70  is held very securely wherein force F is a primary feature. In the loaded case the pliers will be more resistant from moving out of any recess of slot  15  when dropped or impacted. 
     Optionally spring  60  may be configured to minimize or remove the default position bias, or to make the larger size range a default position. For example spring  60  may be mounted at a different angle or further arms or springs may be linked to lower jaw  40  or other components, not shown. Then, for example, pin  70  will have no bias to move vertically along slot  15 . Or the pin may be biased to move toward lower recess  15   b.    
     In  FIG. 6  pin  70  is shown with an enlarged head  71  at each end. The inside face of these heads is normally spaced slightly away from an outer surface of body  10  to allow free motion of the pin relative to body  10 . However this inside face is preferably immediately adjacent to the outer surface to provide a most compact width to the pliers at the pin. The heads may slide against an outer surface of body  10  around slot  15  to help position lower jaw  40  within body  10  in this area. In  FIG. 6  pin  70  includes splines  72 . These splines or equivalent structures may optionally hold pin  70  securely in hole  46  so that the pin cannot rotate or slide axially in hole  46 . This may help in gripping head end  71  as the user operates pin  70  since the pin will not spin and will hold a more predicable position. It also may have an advantage to communicate the proper function of the pin; in particular that the pin operates by simple sliding and not by rotating, spinning or depressing. According to the invention the pin extends past a surface of body  10  to be readily accessed. This extension is in the apparent in  FIGS. 3A and 6  where the head end is a thick structure; out of the page in the elevation views. A smaller diameter but still thick head end may be used. As a result of this structure the pin is in the form of a slid-able button or slide switch. Preferably the button is pressed from two sides of body  10  as is apparent in  FIG. 3A , where sides are the faces into or out of the page in the elevation views. Lower jaw  40  is normally moved along slot  15  by gripping the body and squeezing the pin head areas rather than gripping the jaw or any other element of the pliers. Pin  70 , at head ends  71  moves in relation to body  10  on both sides of the body; the button on  FIG. 3A  slides along both sides of body  10 . In this manner the position of the button of pin  70  can be accurately controlled in relation to the body and to slot  15 . 
     Pin  70  may be initially formed with a single head. The opposing head may be in the form of a washer that is riveted or swaged against a shoulder, not shown, of the opposed small pin end after assembly to the pliers. Or the opposed head may be entirely formed from the small end by a riveting operation. An advantage of the washer structure is that the shoulder defines a relatively precise position for the second head. Then the pin can be fitted about body  10  with the slight spacing of the head inside faces while ensuring that the pin will not bind upon body  10 . Optionally pin  70  is a direct extension of lower jaw  40  wherein there may be no explicit separate pin  70  nor hole  46  into which the pin is fitted. Optionally pin  70  may have a minimal head. 
     A further method of selecting a size range provides that a user moves lower jaw  40  directly rather than by pin  70  to cause pin  70  to translate in slot  15  or equivalent structure. However this may be less intuitive since it is more common to operate a button type structure, i.e. the head of pin  70 , and further when lower jaw  40  is near to upper jaw  50  it will be difficult to grasp the lower jaw to manipulate it. The spring assembly is resilient such that the rotational bias is firm while the detent bias may be light. The dual action spring assembly efficiently separates the two functions so that for example a very high detent force is not required to generate a firm rotation bias. In the preferred embodiment the pushing and pulling force application locations are spaced well apart so that a firm pulling at opening  47  to create the rotating bias does not affect the pushing bias at opening  42 . Alternately a torsion spring proximate to pin  70  creates an independent rotational bias, whereby the torsion spring is biased forward by a further element of the spring assembly. With a preferably light detent bias the slide switch created at head  71  is operable by a single finger on a single side of the body  10 . Thus the size range may be readily selected by a same single hand that holds the pliers. Optionally both head ends of pin  70  may be operated. 
     The simple structure of pin  70  requires no secondary elements to move pin  70  to, or hold the pin in, a selected recess or equivalent stable location of body  10 . Therefore no such elements need be actuated to enable moving lower jaw  40 . With no need for such additional elements or motions pin  70  normally remains in a constant position and orientation relative to lower jaw  40  as the pin moves along with the jaw as the size range is adjusted. However if desired secondary motions of pin  70  or associated elements relative to lower jaw  40  may be enabled, for example, as a supplemental locking structure or other reasons. Further lower jaw  40  need not be rotated for the purpose of size selection. 
     As illustrated there are two recesses in slot  15 . Optionally more than two may be included. The recesses are preferably rounded or smooth as shown. Optionally they may include flats with a pointed inside corner for example in the form of a notch in the front of slot  15 . Further there may be a recess or notch in a rear of slot  15  to correspond or supplement the front recesses shown. In a further embodiment pin  70  may be oblong, D shaped in section, or other non-round shape and be rotatable. Then the pin may include a further operating mode, not shown, that rotates the pin between a secure mode in a recess and a movable mode that allows the pin to slide between recesses. Or the pin may be or include an element that is movable axially. These secondarily movable pins may engage only a front recess or both a front and rear recess. Such structures may be desired for example to make changes in size range less convenient or to more positively hold a selected size range. However as discussed earlier the pliers in the illustrated embodiment is normally stable in both unloaded and loaded conditions. 
     It is a feature of the invention that the headed version of pin  70  illustrated is of a familiar appearance being minimally or no larger than a rivet in a similar location of a conventional one-sized device. Pin  70  may be compact because it does not require any secondary function. For example pin  70  does not need to be depressed, moved axially, or rotated to release jaw  40  to move to another size range. Rather pin  70  is stable in a selected position through the further structures described herein. 
     In the present invention a pliers is improved at minimal cost. In the preferred embodiment only a simple wire form, wire link  65 , need be added. A second optional component is the washer head discussed for pin  70 . Prior size range adjusting locking or similar pliers required complex or bulky assemblies to provide the adjusting function or were difficult to operate. The simplicity of the inventive structure includes a novel linkage between a spring and a lower jaw. The components of the pliers may be manufactured in a same manner as known pliers so that there is no additional cost to such components. For example lower jaw  40  and body  10  have no added complexity over conventional respective parts. This simple structure provides a novel function in a familiar, compact and intuitive pliers device. 
     According to the invention a selected size range is held as a stable condition for both loaded and unloaded states. In particular, in the preferred embodiment unloaded state, a pivot pin such as pin  70  includes a button type feature and moves to or from a selected size range with no secondary actions upon or by the pin. For example the pin may be rigidly attached to lower jaw  40  where the pin moves directly with the jaw and is directly operated upon by a user in an action similar to moving a slide switch. Optionally the pin may rotate within an opening of the jaw but need not require such rotation to allow jaw  40  to move to a different size range. To maintain a stable selected size range a spring, spring element or resilient element biases pin  70  and/or jaw  40  into a detent or equivalent engagement to slot  15  or equivalent structure. For example as pin  70  slides along slot  15  the pin will snap forward into a selected recess from the bias force of spring  60  when the pin becomes aligned with the recess. In a preferred embodiment the spring forces are spaced apart on the lower jaw to maintain a firm opening bias upon the lower jaw for all freely movable positions of the pliers. For example the spring as able to firmly pivot the lower jaw from its closed, unloaded, position to its most open position for any selected size range. 
     In contrast to the present invention prior auto adjusting pliers have required the pin, an attached handle, or a further lever, to be rotated or translated to enable moving between size ranges. Or a pin required an axial pressing motion for such movement. In certain prior auto-adjusting pliers an unloaded condition is unstable in at least one direction. For example a lower jaw maybe biased to remain in a maximum position of a size range but still be immediately and unpredictably movable toward a smaller position with only the spring bias and incidental friction resisting this upward motion. In other prior locking pliers a detent biasing spring can provide only that single function, where the lower jaw and handle are limp in all unloaded positions. According to the present invention a single spring can hold the jaws to a selected size range in a predictable and repeatable manner including for example either a small or a large size range. The same spring may provide the further functions required to facilitate operating as a locking or similar pliers once the size range is selected, including the function of providing a firm opening bias to the handle through most possible handle positions. The opening bias may be through the lower jaw as illustrated or directly upon the handle by a further spring connecting the handle to the jaw or the body, not shown. To adjust the jaw the jaw or an attached pin is moved directly by a user to the selected position without secondary rotation or other actions. The lower jaw may maintain a constant angle relative to the upper jaw as the position of pin  70  is moved to a selected size range. 
     While particular forms of the invention have been described and illustrated, it will be apparent to those skilled in the art that various modifications can be made without departing form the spirit and scope of the invention. Accordingly, it is not intended that the invention be limited except by the appended claims.