Abstract:
An adjustable locking pliers-type tool has a first handle provided with a fixed jaw, a movable jaw pivotally connected to the first handle, a second handle pivotally connected to the movable jaw, and a toggle linkage system cooperatively connected between the two handles. The linkage system includes a toggle link connected to one of a pair of wedges disposed in the first handle and coacts through a shoulder thereon with the second wedge. The two wedges are magnetically attracted into close contact with a floater plate separating the wedges with a force sufficient to prevent formation of oil films between their mating surfaces.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to plier-type tools and, more particularly, to a tool of this type which includes a pair of coacting wedges for automatically adjusting the tool proportionally to the size of a work piece engaged by its jaws whereby a thick or thin work piece can be consecutively engaged by the tool without the necessity of adjusting it for the size of the work piece. 
     2. Description of the Prior Art 
     This invention is an improvement of the self-adjusting locking tool described in U.S. Pat. No. 3,600,986, titled Self-Adjusting Locking Wrench, issued to Earl M. Baldwin, Jr., on Aug. 24, 1971, which, in turn, describes an improvement of the wrench described in U.S. Pat. No. Re 26,280, titled Self-Adjusting Plier-Type Toggle Locking Wrench, reissued to John L. Hostetter on Oct. 17, 1967. The Hostetter and Baldwin wrenches both utilize an elongated handle having a stationary jaw secured to the forward end, and a movable handle having a triangularly-shaped jaw pivotally connected to its forward end and partially received in a recess defined by the body portion of the first handle. A toggle link is pivotally connected at one end to the movable handle, with the other end extending rearwardly and into the recess in the stationary handle and pivotally connected to the forward end of a first of a pair of coacting wedges slidably disposed within the stationary handle. The forward end of the second wedge is connected by a spring to the rearward side of the movable jaw which exerts a constant forward pull on the second wedge. The inclined surfaces of the wedges are separated by a plate which is prevented from forward or rearward movement by integral laterally extending lugs which engage apertures formed in the side walls of the handle. 
     In operation, when the movable handle is moved toward the stationary handle, the toggle link moves the first wedge rearwardly to an extent proportional to the size of a work piece engaged between the jaws until the wedges jam against the separation or floater plate and against the surfaces of the recess in the stationary handle and are stopped from further movement. 
     While the Baldwin tool enjoyed acclaim by the trade and briefly found an important niche in the market, it disappeared and has been missing for many years, reportedly because of manufacturing difficulties. A complaint voiced by auto mechanics while the tool was available was that if accidentally dropped in oil the wedge system would sometimes fail, resulting in unwanted release of the tool from the work piece clamped between the jaws. The failure is believed to have been due to formation of a slippery film of oil between the wedge surfaces and the surfaces of the floater plate which reduced the friction between these relatively slidable elements to a degree that even if the wedges are jammed against the floater plate and the surfaces of the recess in the stationary handle, the clamping force on the work piece transferred through the toggle link to the locking unit would cause one or both of the wedges to move enough to release them. 
     Accordingly, there exists a need for, and it is a primary object of this invention to provide, a self-adjusting plier-type locking tool having an interconnectable self-adjusting and locking wedge system which is not prone to failure if accidently immersed in oil. 
     Another object is to provide a self-adjusting tool having a pressure adjustment screw disposed to be easily accessible and which can be provided at minimal expense. 
     SUMMARY OF THE INVENTION 
     The self-adjusting locking tool of this invention has a pair of plier-like handles, the first of which has a stationary jaw, and the second of which has a movable jaw pivotally connected thereto and also to the first handle, and a toggle link pivotally connected at one end to the movable handle and pivotally connected at the other end to a first of a pair of coacting wedges slidably disposed within an enclosure in the stationary handle. The forward end of the second wedge is urged forwardly by a compression spring which surrounds a shaft which threadably engages the wedge and is disposed between the rear end of the wedge and the rear wall of the enclosure. The forward end of this shaft projects from the forward end of the wedge into engagement with a rearwardly facing shoulder formed on the toggle link. 
     The floating wedge is separated from the hinged wedge by a floater plate having parallel planar upper and lower surfaces, and means are provided for magnetically attracting the wedges into such close adjacency with the floater plate as to wipe away any oil that may be present and thus prevent slippery film formation therebetween, while still allowing the wedges and floater plate to slide relative to one another. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects, features and advantages of the invention will become apparent, and its construction and operation better understood, from the following detailed description when read in conjunction with the accompanying drawings, in which: 
     FIG. 1 is a side elevation view, partly in section, of a first embodiment of the tool of this invention; 
     FIG. 2 is a plan view of the upper handle of the tool as viewed from below in FIG. 1; 
     FIG. 3 is a sectional view taken along the line  3 — 3  in FIG. 2; 
     FIG. 4 is a sectional view taken along the line  4 — 4  in FIG. 3; 
     FIG. 5 is a sectional view taken along the line  5 — 5  in FIG. 3; 
     FIG. 6 is a plan view of the movable handle of the tool as viewed from above in FIG. 1; 
     FIG. 7 is a sectional view taken along the line  7 — 7  in FIG. 6; 
     FIG. 8 is a sectional view taken along the line  8 — 8  in FIG. 7; 
     FIG. 9 is a sectional view taken along the line  9 — 9  in FIG. 1; 
     FIG. 10 is a plan view of the floater plate separating the wedges; 
     FIG. 11 is a sectional view taken along the line  11 — 11  in FIG. 10; 
     FIG. 12 is a side elevation view,partly in section, of a second embodiment of the tool of this invention; 
     FIG. 13 is a top view of the tool; 
     FIG. 14 is a left end view of the tool; 
     FIG. 15 is a view taken along the line  15 — 15  of FIG. 12; and 
     FIG. 16 is a side elevation view, partly broken away, of the tool in an open position. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIGS. 1-11 of the drawings, a first embodiment of the self-adjusting tool  10  of this invention comprises a first handle unit  12 , a second handle unit  14 , and a self-adjusting locking unit  16  interconnected between the handle units  12  and  14 . 
     The first handle unit  12  includes an elongated handle  18  having a U-shaped body portion which forms an elongated enclosure, and a stationary jaw  20  secured to the forward end of handle  18 . Stationary jaw  20  in this embodiment has a curved outer edge. If desired, the outer edge of jaw  20  can be otherwise configured (e.g. squared) to provide additional strength, manufacturing economy or other functional advantages. The rear portion of handle  18  has an inverted U-shaped upper wall  22 , a U-shaped lower wall  24 , and parallel side walls, which together form a housing  28  that is closed at the rearward end thereof by an integral end wall  26 . A portion of end wall  26  is disposed forwardly of the rearward end of handle  12  and forms a recess for accommodating means (to be described) for adjusting the locking pressure of the self-adjusting locking unit  16 . The upper and lower U-shaped surfaces  22  and  24  of housing  28  are parallel to each other and to the longitudinal axis of the handle, and the opposing side walls have aligned apertures  30  and  32  formed therein, the purpose of which is described hereinbelow. 
     Operatively associated with the first handle unit  12  is a triangularly-shaped movable jaw  34  pivotally connected by a pin  36  to the forward end of handle  18  to be operable for coaction with the stationary jaw. As previously noted with respect to stationary jaw  20 , if desired movable jaw  34  can also be otherwise shaped (e.g., squared at its forward end) to provide additional strength, manufacturing economies or other functional advantages. The second handle unit  14 , a channel-shaped arm  38  substantially equal in length to handle  12 , is pivotally secured at its forward end to movable jaw  34  by a pivot pin  40 . 
     The interconnecting, self-adjusting locking unit  16  comprises a toggle link  42  pivotally secured at one end thereof to arm  38  by a pivot pin  44 , with the other end thereof extending rearwardly and into the forward end of the enclosure formed by the side walls of U-shaped handle  18 . The rearward end of toggle link  42  is pivotally connected by a pivot pin  46  to the thick end of a first or hinged wedge  48 , typically made of hardened tool steel, that has an upper surface conforming in shape to the upper inverted U-shaped surface of housing  28  and is slidably disposed therein. A second or floating wedge  50 , also made of hardened tool steel and corresponding in cross-section to and slidably disposed in housing  28 , is separated from the hinged wedge by a floater plate  52  having parallel planar and smooth upper and lower surfaces. Projecting laterally from each side of plate  52  are holding tabs  54  which, as will be seen in FIG. 91 are wider than the distance between the inner surfaces of the side walls of housing  28 ; in assembly, the floater plate is inserted into the housing  28  at an angle and then turned into position with tabs  54  projecting into the apertures  30  and  32  to prevent forward or rearward movement of the plate in housing  28  while permitting it to move vertically. 
     Without a floater plate separating the wedges, the friction therebetween would normally become too great to overcome when in a locked position, making opening of the jaws difficult, if not impossible, and is therefore required. However, should the wrench be accidentally immersed in oil and a lubricating film formed on the mating surfaces, the friction between the floater plate and the wedges may be reduced to a degree that the locked wrench may open inadvertently, or by application of little force to the second handle, and cause unwanted release from the work piece clamped between the jaws. 
     This potential problem is avoided by providing a floater plate that includes a magnet which exhibits sufficient magnetic pole strength to attract the wedges and maintain the mating surfaces in sufficiently close adjacency as to prevent the entry of any foreign substances, such as oil, therebetween while, at the same time, permitting the wedges to slide relative to the floater plate. The necessary magnetic attraction may be achieved by a spaced pair of circular magnetic disks  56  and  58  fabricated, for example, by a known powder metallurgy process, from any of the several metallic elements of atomic number  57  through  71  (“rare earth” elements or “lathanides”) that exhibit a strong magnetic pole strength, such as neodymium, of the same thickness as floater plate  52 , typically {fraction (1/16)}-inch thick tool steel. The disks, typically ¼-inch in diameter, being quite frangible are secured in slightly larger diameter openings formed in plate  52  with a bead  53  of epoxy resin or other suitable adhesive. 
     A stop or shoulder  60  formed in the upper wall of handle  18  forward of hinged wedge  48  prevents forward movement of the hinged wedge beyond a predetermined position when the wrench is in its open position. A tension spring  62  or other suitable resilient means connected at one end to the movable jaw  34 , at a location intermediate the pivot pin  36  and  40  connections, and at the other end to a pin  64  located forwardly of pivot pin  46  so as to lie above and not interfere with the operation of toggle link  42 , pulls the jaws open when the handles are released. 
     The thick end of hinged wedge  48  faces the jaw end of the wrench and the thick end of floating wedge  50  faces away from the jaw end. Floating wedge  50  has a smooth cylindrical bore  50   a  of first diameter extending forwardly from its thick end for approximately half the length of the wedge to a shoulder  50   b  at which the bore diameter is reduced and internally threaded for the rest of the length of the wedge. A shaft  66  extending forwardly through an opening  68  in the rear wall of housing  28 , through bore  50   a  and threadably engaging the internally threaded bore, is surrounded by a compression spring  70  disposed between rear wall  26  and shoulder  50   b  which urges the floating wedge forwardly toward the jaw end of the wrench. The forward end of shaft  66  projects forwardly of the thin end of the floating wedge into contact with a rearwardly facing shoulder  42   a  formed on toggle link  42 . If desired, the forward end of shaft  66  may terminate rearwardly of the forward end of floating wedge  50 , in which case this forward end of floating wedge  50  will be in contact with shoulder  42   a . Shoulder  42   a  has an arcuate shape and coacts with a cam-like action with the forward end of shaft  66 . 
     The clamping pressure of the jaws may be adjusted by turning the threaded shaft  66  with a knob  72  secured to its rearward end and disposed within the recess  74  formed by the re-entrant end wall  26 . The knob  72  may be circular cylindrical in shape, or preferably it has a square cross-section of a size generally corresponding to the thickness of the handle body  28  so as to fit within the recess and give the rearward end of the handle a smooth profile and to be prevented against rotation by the rearward overhang defining the upper edge of the recess. If adjustment of the clamping pressure is desired, knob  72  is pulled rearwardly against the bias of spring  70  a distance corresponding to the axial length of the knob, at which point it may be rotated to adjust the distance the forward end of shaft  66  projects from the thin end of floating wedge  50 . Positioning of the floating wedge forwardly by turning knob  72  counterclockwise provides greater clamping pressure as the wedges set sooner in the housing. A lesser clamping pressure is accomplished by turning knob  72  in the opposite direction to move the wedge rearwardly. The thread on shaft  66  is sufficiently coarse that only a quarter turn of the knob is needed to change the clamping pressure from “low” to “medium”, for example, and another quarter turn to change from “medium” to “high”, whereby the pressure may be visually displayed by marking successive adjacent faces of the knob with the legends LOW, MED and HIGH. 
     Having described the construction of the tool, its method of operation will now be described. At the start of the closing cycle the forward wall of hinged wedge  48  lies against shoulder  60 , the tension spring  62  holds the jaws open to facilitate insertion of a workpiece, and compression spring  70  pushes the floating wedge  50  fully forward against the shoulder  42   a  of toggle link  42  and also holds the hinged wedge against shoulder  60 . The wedges are now free for repositioning, the knob  72  having previously been positioned to the desired clamping pressure of the jaws. Upon movement of the second handle  14  from its open position toward the first handle  12 , that is, toward a closed position, hinged wedge  48  will be moved rearwardly by toggle link  42  to an extent proportional to the size of a workpiece (not shown) engaged between the jaws, and the shoulder  42   a  on the toggle link will push the floating wedge rearwardly. The floater plate  52  adjusts upwardly automatically as the wedges are moved rearwardly. Rearward movement of the wedges continues until the shoulder  42   a  leaves the end of shaft  66  projecting from the floating wedge because of rotation of the toggle link about pin  46 . At this point the spring  70  cannot overcome the friction between the wedges and the floater plate  52  and the floating wedge cannot move forwardly. The floating wedge  50  and plate  52  are in a locked condition and continued closing action of the second handle causes hinged wedge  48  to move rearwardly for a short distance, jamming the wedges in the housing and locking the jaws of the tool. 
     When the second handle  14  is fully moved into the closed position shown in FIG. 1, the pivot pin  44  is disposed above an imaginary line connecting the pivot pins  40  and  46 . To snap over this imaginary line, toggle link  42  is compressed, subjecting pins  40 ,  44  and  46  to a deflecting force and, in effect, causing the link and the pins to store energy, the amount of which determining the force necessary to open the wrench. The stored energy is limited to an amount that will permit relatively easy opening, yet maintain the jaws in locked position, by limiting the compression of toggle link  42  which, in turn, is accomplished by limiting the distance the link moves beyond the point at which it initially snaps over the imaginary line. This is done by a screw  74  threaded into a threaded opening  76  which extends transversely through toggle link  42  at a location inwardly from pivot pin  44  opposite the highest point  38   a  of the channel  38  of handle unit  14 . As the handles are being squeezed together, the protruding end of the screw  74  engaging the bottom of channel  38  determines how closely it can be moved toward the first handle. The extent of protrusion of the screw is adjustable to a length at which the locked tool can be opened with only finger pressure. 
     The tool is opened by pivotal movement of handle  14  away from handle  12  about pivot pin  40  with sufficient force to cause pivot pin  44  to pass over the imaginary line and allow the other end of toggle link  42  to pivot about pin  46 . The shoulder  42   a  on the link contacts floating wedge  50  and pushes it rearwardly against the bias of spring  70 , while the toggle link pulls hinged wedge  48  forwardly to break the jam between the wedges, the floating plate  52  and the U-shaped upper and lower surfaces of the housing. The moment the imaginary line is passed, the energy stored in the link and pins snap the link to an open position without additional pressure on the second handle. 
     The body portion of handle  18  preferably is encased in a sleeve  80 , which may be formed of a suitable plastic, to enhance the appearance of the wrench and make it more comfortable to use. 
     FIGS. 12-16 show another presently preferred embodiment of the tool of the invention which, like the first embodiment, comprises a first handle unit  112 , a second handle unit  114 , and a self-adjusting locking unit  116  interconnected between the handle units  112  and  114 . 
     The handle unit  112  includes an elongated handle  118  made from sheet steel shaped and bent to form a rectangularly-shaped body portion  120  which defines an elongate enclosure and to form the outer laminae  122  and  124  of a laminated stationary jaw  126  at the forward end of the handle. Two generally L-shaped inner laminae  128  and  130  made of sheet steel are assembled between and pinned to laminae  122  and  124  by rivets or bolts  132  to form a sturdy stationary jaw. The outer edges of the inner laminae, of which lamina  128  is visible in FIG. 12, are coincident with the outer edges of the outer laminae and their interior edges are shaped to define together with the outer laminae a recess for receiving a portion of a movable jaw  146 , to be described presently. The outer edge of jaw  126  has a squared configuration defined by interconnected straight lines to provide added strength, economies in manufacture and other advantages. Alternatively, the inner laminae may be made of one or more layers of any suitable durable high strength plastic material having the shape shown in FIG.  12 . 
     The rear portion of handle  118  has parallel opposed upper and lower walls  134  and  136 , respectively, and parallel side walls, which together form a housing  138  that is closed at its rearward end by an inverted L-shaped end wall  140 . This end wall may be formed from any suitable rigid high strength plastic material and secured within the housing by a transverse rivet or bolt extending through aligned openings provided in the side walls and through the end wall. The inverted L-shape of the end wall forms a recess for accommodating a knob  142  for adjusting the locking pressure of the self-adjusting locking unit  116 . The upper and lower walls of housing  138  are parallel to each other and to the longitudinal axis of the handle, and the opposing side walls have aligned apertures, one of which is visible at  144  in FIG. 12, the purpose of which is described below. The body portion of the handle preferably is encased in a suitable pliant plastic material to enhance the appearance of the tool and make it comfortable to use. 
     Operatively associated with stationary jaw  126  is a triangularly shaped movable jaw  146  partially received in the aforementioned recess at the forward end of handle  118  and pivotally connected thereto by a pin  148  to be operable for coaction with the stationary jaw. The movable jaw is also constructed from laminated flat parts, which include planar inner laminae  150  and  152  preferably made of sheet steel having a combined thickness which allows them to be received in the aforementioned recess between the outer laminae  122  and  124  of the stationary jaw, and two outer triangularly-shaped steel laminae  154  and  156  of smaller area suitably pinned to the inner laminae to form a sturdy movable jaw having the same thickness as the stationary jaw. The movable jaw is also squared at the forward end to provide additional strength and manufacturing economies. 
     The second handle unit  114  is a laminate composed of elongated rigid planar sheet steel members  158  and  160  and a spacer  162  therebetween which extends from the distal end of the member to a point short of the forward end to provide a channel between the forward ends of members  158  and  160 . The spacer  162  preferably is made from a suitable rigid plastic material, but may be made of steel, if desired. The outer laminae and the spacer are suitably pinned to form the rigid handle member  114 , the forward end of which is pivotally secured to movable jaw  146  by a pivot pin  164 . The handle member is encased in a flexible plastic sleeve to provide a comfortable hand hold for the user. 
     The construction and operation of the self-adjusting locking unit  116  being substantially the same as that of the locking unit  16  of the first embodiment, in the interest of avoiding unnecessary redundancy it will be only briefly described. The locking unit includes a toggle link  166  pivotally secured at one end to and between the forward ends of planar members  158  and  160  by a pivot pin  168  with the other end thereof extending rearwardly and being pivotally connected by a pivot pin  170  to the forwardly-facing thick end of a first steel wedge  172  having a flat upper surface in sliding contact with the upper wall  134  of housing  138 . A floating steel wedge  174  having a thick edge facing away from the jaw end and a flat under surface in sliding contact with the lower wall  136  of the housing is separated from the hinged wedge by a floater plate  176 , which may be of the same shape and construction as the floater plate of the first embodiment, including the laterally extending tabs which project into the side wall apertures (e.g., aperture  144 ) to prevent rearward or forward movement of the plate in housing  138 , while permitting the plate to move vertically. Magnetic attraction between the wedges and the floater plate  15  provided by a pair of magnets embedded in the floater plate as described above in connection with FIGS. 10 and 11. 
     A shoulder formed in the upper wall  134  of the first handle forward of wedge  172  prevents forward movement of the hinged wedge beyond a predetermined position when the tool is open. A tension spring  178  connected between a location on the movable jaw  144  intermediate the pivot pin  148  and  164  connections and a transverse pin  180  extending through handle  118  at a point forward of pivot pin  170  pulls the jaws open when the handles are released. 
     Floating wedge  174  has smooth bore  174   a  of a first diameter extending forwardly from its thick end for a portion of its length to a shoulder  174   b  at which the bore diameter is reduced and internally threaded for the rest of the length of the wedge. A shaft  182  secured to knob  142  and extending forwardly through an opening in end wall  140  and threadably engaging the internally threaded bore in wedge  174 , is surrounded by a compression spring  184  disposed between the end wall and shoulder  174   b  which urges the wedge forwardly. The forward end of shaft  184  projects forwardly from the thin end of the wedge into contact with a rearwardly facing shoulder  166   a  formed on toggle link  166 . As in the first embodiment, if desired, the forward end of shaft  182  may terminate short of the forward end of wedge  174 , with the forward end of the floating wedge instead contacting shoulder  166   a . Shoulder  166   a  has an arcuate shape and coacts with a cam-like action with the forward end of shaft  184  or floating wedge  174 , as the case may be. 
     The operation of this second embodiment being the same as that of the first embodiment detailed above, it is deemed unnecessary to repeat the description. 
     Although preferred embodiments of the invention have been described, it will now be evident to ones skilled in the art that certain modifications and changes may be made in the described locking tool without departing from the true spirit and scope of the invention. For example, the magnets secured in floater plate may have a shape other than circular, such as rectangular. Correspondingly, they may be replaced with a single rectangular centrally located magnetic element or eliminated by utilizing a floater plate composed of a ferromagnetic material which floater plate is magnetized. Also, the wedges may be dimensioned to accommodate a floater plate thicker than {fraction (1/16)}-inch, say, twice as thick, so as to increase the volume, and thus the pole strength of the magnets sufficiently to allow the use of less expensive alnico or ceramic magnets. Furthermore, the desired attraction of the wedges to the floater plate may be achieved by replacing the magnets in the floater plate with a magnet embedded in one or both of the wedges, preferably near the thick ends thereof. Accordingly, the scope of the invention should be determined with reference to the appended claims and not by the examples which have been disclosed herein.