Abstract:
A clamping device is configured to ensure that a workpiece fixed between the jaws of the clamp is self centered by coupling the jaws to a pair of linkages that rotate through the same angle as the application of a first causes the jaws to translate in linear fashion across the surface of the device. In particular, the clamping device utilizes coupled linkage (e.g., a 180° bell crank), in combination with slots for retaining opposing jaws and maintaining only linear movement of the jaws, thus providing a fast and accurate self-centering arrangement. The clamping device may also be located within a hollow workpiece and controlled to move the jaws outward and engage the inner surface of the hollow workpiece in a self-aligned configuration.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/817,915, filed May 1, 2013. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a self-centering clamp and, more particularly to a clamp that utilizes coupled linkage in combination with slots for retaining opposing jaws, thus providing a self-centering clamp arrangement. 
     BACKGROUND OF THE INVENTION 
     Stationary clamping devices for milling machines, drill presses and other machines are often required, Rotary clamping configurations for other types of machines (such as a lathe, for example) are another need. In environments such as a machine shop it is often necessary to clamp a workpiece in a manner that is fast, accurate and repeatable—without needing constant adjustments. Indeed, it is often useful to have a clamp that will maintain a workpiece in a “centered” configuration without needing to adjust one clamp and then the other to adjust the position of the workpiece. 
     However, self-centering clamping devices of the prior art are often inaccurate, lack repeatability, cannot be automated and/or are expensive devices that depend on complicated arrangements, such as gear-based systems or rack-and-pinion types of mechanism, to provide the desired self-centering functionality. 
     Thus, a need remains in the art for a self-centering clamp that is relatively simple in design, yet can repeatedly and accurately provide properly centered clamping of a workpiece. 
     SUMMARY OF THE INVENTION 
     The needs remaining in the prior art are addressed by the present invention, which relates to a self-centering clamp and, more particularly to a clamp that utilizes coupled linkage in combination with slots for retaining opposing jaws, thus providing a self-centering clamp arrangement. 
     In particular, the present invention comprises a clamp that utilizes coupled linkage (e.g., a 180° bell crank), in combination with slots for retaining opposing jaws and maintaining only linear movement of the jaws, thus providing a fast and accurate self-centering arrangement. It is possible, as will be discussed below, to use arrangements other than slots to confine the jaws to the desired lateral movement in a constrained manner that provides self-centering. 
     One exemplary embodiment of the present invention comprises a pair of jaws disposed on a support substrate, each jaw positioned within a separate lateral slot formed along a portion of a top surface of the support substrate and disposed such that clamping surfaces face each other and are aligned, an aperture formed through the support substrate in a region between the clamping surfaces of the pair of jaws, an upper linkage coupled between the pair of jaws at a first, upper area of each jaw and a lower linkage coupled between the pair of jaws at a second; lower area of each jaw. The application of a lateral force to either one or both of the jaws causes the upper and lower linkages to rotate through a same angle and provide a like movement of each jaw, providing a self-centering clamping action to a workpiece disposed in the aperture between the clamping surfaces of the jaws. 
     In another embodiment, a configuration of the clamping device can be arranged with the jaws facing outward, with a hollow workpiece disposed over the clamping device such that the outward-facing jaws engage the interior of the workpiece is a self-aligned arrangement. 
     Other and further embodiments and arrangements of the present invention will become apparent during the course of the following discussion and by reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring now to the drawings, where like numerals represent like parts in several views: 
         FIG. 1  is a front view of a self-centering clamping device formed in accordance with the present invention; 
         FIG. 2  is a top view of the embodiment as shown in  FIG. 2 ; 
         FIG. 3  is another front view of the inventive clamping device, in this case illustrating the application of a force F in  that provides for an inward movement of each jaw along the same lateral direction, allowing for any workpiece disposed between the clamping jaws to be held is a self-centered orientation with respect to the outer periphery of the clamping device; 
         FIG. 4  is yet another front view of the self-centering clamping device of the present invention, in this case illustrating the application of a force F out  that provides for a like outward movement of each jaw; 
         FIG. 5  is a front view of an alternative embodiment of the present invention, in this case using a different type of linkage to couple the jaws together and provide the uniform movement thereof; 
         FIG. 6  is a front view of yet another embodiment of the present invention, in this case using the self-centering clamping device to hold the inner surface of a pipe in a self-centered configuration; and 
         FIG. 7  shows the same embodiment as that of  FIG. 6 , in this case with the jaws of the clamping device engaging the inner surface of a pipe. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a front view of an exemplary self-centering clamp  10  formed in accordance with the present invention. As shown, self-centering clamp  10  comprises a pair of jaws  12 - 1 ,  12 - 2  that are disposed to ride back and forth within slots  14 - 1  and  14 - 2 , respectively. In the orientation of  FIG. 1 , jaws  12  are constrained to translate only in the x-axis direction (i.e., only linear movement), moving back and forth within slots  14 . The use of slots should only be considered as exemplary only. Any other arrangement that provides confinement of the jaws to maintain one-dimensional, lateral motion may be used. For example, a pair of enclosures (such as C-channels) for enclosing jaws  12  may be used. Moreover, the jaws themselves may have any suitable geometry, the V-shaped end faces shown in the drawings is considered to be exemplary only. 
     Further, and as best shown in the top view of  FIG. 2 , movement of jaws  12  out of the plane of device  10  (i.e., into the z-direction) is constrained by disposing jaws  12  (as well as the linkage that is attached to jaws  12  and controls their movement) between a pair of coverplates  13 - 1  and  13 - 2 . In  FIG. 1 , coverplate  13 - 1  has been removed to allow for the working components of the clamping device to be clearly visible. In the top view of  FIG. 2 , both coverplate  13 - 1  and coverplate  13 - 2  are clearly shown, and in particular illustrate their use in constraining movement of jaws  12  in the z-direction. It is to be noted that for the sake of clarity, the view of  FIG. 2  illustrates the details of the connections between the various components on the left-hand side only. 
     Also shown in both  FIGS. 1 and 2  is a pair of separator bars  15 - 1  and  15 - 2  that are used to define the fixed space of confinement between coverplates  13 - 1  and  13 - 2  where the device components are located. An adjustable stop  19 , as will be described below, is also shown in  FIGS. 1 and 2 . 
     A central through-hole aperture  16  is shown in  FIG. 1  as being formed through the thickness of coverplate  13 - 2  (as well as through coverplate  13 - 1  when in place), with an exemplary pipe  18  shown in phantom as positioned within aperture  16 . In accordance with the present invention, clamping device  10  functions to hold pipe  18  in a self-centered configuration (with respect to the boundaries of device  10 ), allowing for various machining operations (e.g., cutting, turning, etc.) to be performed on a “centered” pipe without worrying about the need to perform any additional adjustments (such as movement of one clamp, and then the other, to center the pipe within the fixture). While a rounded pipe is shown in  FIG. 1 , other cross-sections are possible (e.g., square, hexagonal, etc.). 
     An upper linkage  20  is shown in  FIG. 1  as coupled between jaw  12 - 1  and jaw  12 - 2 . Similarly, a lower linkage  30  is shown as coupled between jaw  12 - 1  and jaw  12 - 2 . A first upright member  22  is shown as attached to jaw  12 - 1  (at location  23 , for example) and disposed between the left-hand terminations of linkages  20  and  30 . A second upright member  32  is similarly attached to jaw  12 - 2  (at location  33 , for example) and disposed between the right-hand terminations of linkages  20  and  30 . 
     As will be described in detail below, by virtue of joining the movement of the jaws together, and constraining their movement to be one-dimensional, it is possible to create an arrangement where each jaw moves the same distance upon the application of force (to either jaw, or both jaws), forming a self-centered system. That is, the application of a force along the x-axis of self-centering clamping device  10  causes linkages  20  and  30  to rotate in a manner where jaws  12 - 1  and  12 - 2  will simultaneously move either toward each other (inward) or away from each other (outward). In either case, jaws  12 - 1  and  12 - 2  will translate the same distance d along their respective slots  14 - 1  and  14 - 2  so as to maintain the centrality of the opening therebetween. 
       FIG. 3  is a front view of self-centering clamping device  10  that illustrates the rotation of linkages  20  and  30  when an “inward” force F in  is applied to a pair of side uprights  22  and  32  joining linkages  20  and  30 . Upright  22  is connected to jaw  12 - 1  and upright  32  is connected to jaw  12 - 2 . The application of this force is translated through rocker arms  24 ,  26  (of linkage  20 ) and rocker arms  34 ,  36  (of linkage  30 ), providing a rotating motion to shafts  28  and  38  (e.g., 180° bell cranks). In this configuration, shafts  28  and  38  are rotating counterclockwise. By virtue of the connection between linkages  20  and  30  (via uprights  22  and  32 ), jaws  12 - 1  and  12 - 2  will translate the same distance inward d along each of their respective slots  14 - 1  and  14 - 2  (where this movement is constrained to remain one-dimensional, translating only in the x-direction). Therefore, centering is maintained and, in this view, pipe  18  is clamped between jaws  12 - 1  and  12 - 2  in a self-centered arrangement with respect to clamping device  10 . 
     The force itself may be provided in numerous ways including, but not limited to, air cylinders, levers, hydraulic cylinders, ball screws, electric solenoids or, as an alternative, providing a force directly to the linkage itself. Indeed, arrangements for applying a force to one or both of the jaws may use a combination of elements, such as a turning shaft (such as a crank or other rotational element) connected to a separate element for converting rotational motion into the translational motion used for jaws  12 . 
     While the embodiment as shown in  FIG. 3  provides a force F in  at each side upright  22  and  32 , it is to be understood that only a single force is required to initiate the self-centering motion. The use of only a single force (such as, for example, applied to side upright  22  only) may be advantageous in situations where the ability to access both uprights is limited. 
       FIG. 4  is another front view of self-centering clamping device  10 , in this case illustrating the movement of jaws  12  in the opposite direction (i.e., outward along the x-axis direction). That is, a force F out  is applied to side uprights  22  and  32 , moving jaws  12 - 1  and  12 - 2  outward along their respective slots  14 - 1  and  14 - 2 , revealing a larger opening in the area of aperture  16  so as to allow for a larger workpiece to be retained within the inventive clamping device. Obviously, once the larger workpiece is inserted in place, a force F in  is applied to hold the larger workpiece in a self-centered configuration. It is to be noted that the end walls  14 -E of slots  14 - 1  and  14 - 2  function as “stops”, preventing any further movement of jaws  12 - 1  and  12 - 2 . 
     The specific length of slots  14  is considered to be a design choice, defining the greatest opening that can be created between jaws  12 - 1  and  12 - 2 . Indeed, as particularly illustrated in  FIGS. 1 and 2 , it is possible to include an adjustable stop member  19  (in this case an adjustable screw) that controls the range of motion of uprights  22  and  32 , thus controlling the dimensions of the opening created between jaws  12 - 1  and  12 - 2 . 
     While one specific embodiment has been described thus far, it is to be understood that the self-centering clamp of the present invention may utilize various arrangements and dimensions of the slots, jaws and linkages. Indeed,  FIG. 5  illustrates an alternative embodiment of the present invention, in this case showing a self-centering clamping device  50  with a different type of linkage formed in accordance with the present invention. 
     As with clamping device  10 , clamping device  50  comprises a pair of jaws  52 - 1  and  52 - 2 , where each jaw is constrained to travel only in the x direction within its associated slots  54 - 1  and  54 - 2 , respectively, formed in substrate block  53 . A first side upright  56  is attached across jaw  52 - 1  (in the y-axis direction), with a second side upright  58  attached in a similar across jaw  52 - 2 , such that uprights  56  and  58  are parallel. 
     In accordance with this embodiment of the present invention, an upper linkage  60  is coupled between top end terminations of first side upright  56  and second side upright  58 . A lower linkage  70  is similarly coupled between lower end terminations of first side upright  56  and second side upright  58 . As with the embodiment described above, the application of a force F to one or both of side uprights  56  and  58  functions to cause linkages  60  and  70  to rotate in a manner such that jaws  52 - 1  and  52 - 2  will open (or close) by a prescribed distance d, providing a self-centering clamping to any workpiece disposed within aperture  80  between jaws  52 - 1  and  52 - 2 . 
     In this embodiment, upper linkage  60  comprises a pair of scissor-like arms  62  and  64 , coupled together at a pin location  66 . Arms  62  and  64  remain free to rotate with respect to one another when a force is applied to one of the side uprights, where pin  66  travels (in the y-direction) within an associated slot  67 . The opposite termination of first arm  62  is attached via a pin  65  to an upper portion of first side upright  56 . The opposite termination of second arm  64  is attached via a pin  67  to an upper portion of second side upright  56 . 
     Lower linkage  70  includes a like pair of coupled arms  72  and  74  (coupled together at pin  76  which travels within slot  77 ). The opposing ends of arms  72  and  74  are also connected to side uprights  56  and  58  (via pins  75  and  77 , respectively). 
     As with the embodiment described above, the application of a force F to one or both of the uprights causes the arms forming linkages  60  and  70  to rotate with respect to each other, resulting in the simultaneous movement of jaws  52 - 1  and  52 - 2  to provide self-centered clamping. 
     As mentioned above, it is also possible to use the self-centering clamping device of the present invention as an arrangement that is disposed within a hollow tube (pipe), clamping the inner surface of the pipe and holding the pipe in a self-centered position with respect to the clamping device.  FIGS. 6 and 7  are front views of an embodiment of the present invention that is suitable for this inner clamping configuration. 
       FIG. 6 , in particular, is a front view of an exemplary self-centering clamping device  100 . In order to understanding the operation of the clamping device, a cover plate has been removed (similar to the embodiment as shown in  FIG. 1 ). In comparing the particular elements of clamping device  100  to those forming clamping device  10  of  FIG. 1 , it is shown that linkages  20  and  30  may be the same, with the same pair of uprights  22  and  32  connecting together upper linkage  20  with lower linkage  30 . In contrast to device  10 , the inner clamping arrangement of device  100  includes a pair of jaws  120 - 1  and  120 - 2 , with jaw  120 - 1  shown as attached to an outer edge of upright  22  at location  230 . Jaw  120 - 2  is shown as attached to an outer edge of upright  32  at location  330 . 
     In the view of  FIG. 6 , a hollow pipe  180  is shown as disposed to surround clamping device  100 , with an inward-directed force F in  bringing jaws  120 - 1  and  120 - 2  close to the center of device  100 . In operation, an outward force F out  is applied to jaws  120 - 1  and  120 - 2 , which will then move simultaneously (and only along the x-axis direction, as noted above) and engage inner wall  181  of pipe  180 . 
       FIG. 7  shows clamping device  100  in the configuration of holding pipe  180  in a self-centered displacement with respect to device  100 . In particular, it is shown that linkages  20  and  30  have rotated (via the application of the force F out  to uprights  22  and  32 , moving jaws  120 - 1  and  120 - 2  outward until they (simultaneously) engage inner wall  181  of pipe  180 . Portions of slots  14 - 1  and  14 - 2  are evident in this view. 
     It is to be understood that the various embodiments of the self-centering clamp of the present invention may be formed of any material suitable for its intended use. For example, a self-centering clamp of the present invention may be used in many non-industrial applications (e.g., centering a flagpole (or similar banner) in a stand, a Christmas tree, or the like). In non-industrial environments a plastic or polymer-based device may be used. In industrial applications, a metal device is preferred (e.g., machine-hardened steel, aluminum, or the like). All of these variations are considered to fall within the spirit and scope of the present invention.