Abstract:
This patent pertains to a work piece clamping system with manual or powered clamping. Work piece locations of all three axis can be determined from the device. Various clamping devices can be included in the system. Single or multiple work pieces of various sizes and shapes can be clamped.

Description:
RELATED APPLICATIONS  
       [0001]     This patent relates to a Provisional Patent Application filed Nov. 10, 2004. (Application # 60/626,431)  
         [0002]     This application varies from the preference application in the following ways:  
         [0003]     The grooves located along the T-shots in the pallet are spaced a greater distance apart. Hardened keys are permanently fixed to these grooves and project above the surface to engage one of many grooves located in a clamping and/or locating device.  
         [0004]     The grooves located in the locators are larger and spaced a greater distance apart than described in the first referenced application.  
         [0005]     Since the slots in the bases and locators are further apart, the incremental positioning of the locators along the T-slot is much greater.  
         [0006]     Since this incremental distance exceeds the practical maximum travel of the wedge clamp, means are provided to pre-adjust the clamping wedge to provide the optimum wedge clamping travel. The optimum clamping travel must provide enough displacement to account for the width tolerance of the work piece to be clamped plus any deflection encountered by the clamping force plus a small clearance to allow placement and removal of the work piece in the unclamp position.  
         [0007]     Since the wedge clamp depends on vertical force and displacement to provide horizontal force and displacement to clamp the work piece, the vertical height of the wedge in the clamped condition can be controlled by the pre-adjustment of the wedge. This is particularly important when the work piece to be clamped is very thin.  
         [0008]     The base grooves are marked with their location from a zero reference point. Location grooves are marked with their distance from the work piece location surface. Adding or subtracting the locations of the base locator as marked at the key engagement, provides the work piece location from zero reference.  
         [0000]     A second provisional application was filed May 15, 2006 (application #60/800,321). The present non provisional patent application includes additional features not found in either provisional application.  
     
    
     BACKGROUND OF THE INVENTION  
       [0009]     1. Field of the Invention  
         [0010]     This patent relates to work piece holding devices used to hold work pieces for machining or other purposes. Work pieces that are machined must be held or clamped to prevent their movement caused by forces acting against them.  
         [0011]     It is generally desirable to have a high degree of rigidity and accurate work piece location so that the surfaces which are treated (usually by cutting) on the work piece is well within acceptable tolerance.  
         [0012]     2. Description of Prior Art  
         [0013]     Existing work piece holding devices range from a simple vice designed to hold one work piece, wedge lock side clamping of single or multiple work pieces located on a single base and dedicated fixtures constructed for a specific work piece.  
         [0014]     Vertical hold down clamps (called swing down clamps) are available for clamping work pieces against their top surface. They swing out of the way when unclamped to permit removal of the work piece.  
         [0015]     Exiting wedge clamps are generally fixed to a base with serrations or keys that are difficult to clean and difficult to determine the exact work piece location.  
         [0016]     They generally require manual clamping.  
         [0017]     Swing down clamps are generally located on dedicated fixtures. They are usually powered by hydraulic systems. Their hydraulic lines tend to collect chips and are difficult to clean.  
         [0018]     Power clamping is usually accomplished using hydraulic systems. This complicates the systems need for decoupling the hydraulic lines when the clamping system is removed from a machine tool for off machine work piece handling.  
       SUMMARY OF INVENTION  
       [0019]     This patent relates to a work piece holding system that provides rigid, powerful and accurate clamping of various sizes and shapes of work pieces. Work piece location in all three axes is easily read from the system. Power lines are located in channels below the clamping surface. Cleanliness is maintained by protective covers. Various clamps, (wedge and slide down) are used in a single system.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]      FIG. 1  is a view showing a single station base showing a device for locating a work piece in 3 axes and a device for clamping the work piece against the locator.  
         [0021]      FIG. 2  is a view showing the basic parts of a single station base.  
         [0022]      FIG. 3  is a top view of the work part locator.  
         [0023]      FIG. 4  is a side view of the locator.  
         [0024]      FIG. 5  is a side view of a work piece locator reduced in length.  
         [0025]      FIG. 6  is the same as  FIG. 1  with the addition of a combined locator and clamp. It is used when two or more work pieces are clamped on the same station.  
         [0026]      FIG. 7  is a side view of the locator/clamp.  
         [0027]      FIG. 8  is the same as  FIG. 7  but showing a pre-clamp hand knob.  
         [0028]      FIG. 9  is an end view of the locator/clamp showing a nut used for manual clamping.  
         [0029]      FIG. 10  is a section taken through  FIG. 9  showing detail of the locator/clamp.  
         [0030]      FIG. 11  is a top view of a wedge clamp.  
         [0031]      FIG. 12  is a side view of the wedge clamp.  
         [0032]      FIG. 13  is a section taken through  FIG. 11 .  
         [0033]      FIG. 14  is a view and partial section taken through view  15 . It shows a log with locator/clamps and locator and a power actuator supplied with compressed air conveyed through a tale stock piston and stored in the log.  
         [0034]      FIG. 15  is an end view of the log mounted to rotary table on one end and supported by a tale stock on the other end.  
         [0035]      FIG. 16  is a side view of  FIG. 15 .  
         [0036]      FIG. 17  is an end view of a power actuator used to clamp work pieces.  
         [0037]      FIG. 18  is a section taken through  FIG. 17  showing means for increasing the clamping force imposed by a pneumatic piston.  
         [0038]      FIG. 19  is a view of a multiple station clamping system.  
         [0039]      FIG. 20  is a view of another multiple station clamping system showing a single work piece.  
         [0040]      FIG. 21  is a view of a four sided clamping systems mounted on a tombstone.  
         [0041]      FIG. 22  is a section through the center of an alternate power actuator using hydraulic pressure.  
         [0042]      FIG. 23  is a top view of a combination of a locator and wedge clamps used to clamp a sheet metal work piece when the work piece size varies.  
         [0043]      FIG. 24  is a side view of  FIG. 23   FIG. 25  is a side view of a system for clamping round work pieces.  
         [0044]      FIG. 26  is a view of a single station base showing a wedge clamp and a locator/slide down clamp used to clamp a work piece with both horizontal and vertical force.  
         [0045]      FIG. 27  shows varying work pieces clamped with vertical force.  
         [0046]      FIG. 28  shows varying work pieces clamped with vertical force.  
         [0047]      FIG. 29  shows varying work pieces clamped with vertical force.  
         [0048]      FIG. 30  shows a section taken through  FIG. 26  showing details of a power clamp that retracts to allow a work piece to be placed and then extends over the work piece and moves down to clamp the work piece with vertical force.  
         [0049]      FIG. 31  is a section of locator/slide down clamp taken from  FIG. 26   
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0050]     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.  
         [0051]     The clamping system consists of three basic parts. These parts are identified by  FIG. 1 . A base  1 , a locator  2 , and a clamp  3 . The base is used to support and locate the locator, and support the clamp, and contain a power actuator  55   FIG. 14  or manual clamping nut  25  see  FIG. 9 .  
         [0052]     The base  FIG. 2  consists of a supporting structure  4 , rails  5 , used to partially enclose a large channel  6  in the structure and support wear resistant rails,  7 , provided with precisely located keys  8  used to locate the locators.  
         [0053]      FIG. 2  slot covers  9  may be sprung into recesses located in wear resistant rails  7 , cover the T-SLOTS  11 ,  FIG. 2  to prevent foreign matter from entering the channel  6 . Two overlapping covers  9  may be used to cover the distance needed between the clamps and locators. Multiple sets of various length covers  9  are needed to cover the full range of possible lengths.  
         [0054]      FIG. 2  shows a single T-slot  11 , identified as a station. Any number of stations on a single plane or multiple planes can be provided. See  FIG. 19, 20 , and  21 . The bases, locators, and clamps are configured in various ways to provide clamping for a wide variety of parts. Furthermore, the clamps and locators are configured to enable one part or multiple parts to be clamped on a single station. The bases are configured with a single side,  FIG. 1  or multiple sides  FIGS. 15, 16 , and  21 .  
         [0055]     The locators are configured with a single locating surface  FIG. 5 , and double ended  FIG. 3  and  FIG. 4  enabling round, hex, or flat parts to be located. The locators are also combined with clamps  18   FIG. 6  and  FIG. 7  to enable more parts to be located on a single station by reducing the clamp and locator length.  
         [0056]     The locators  FIG. 4 ,  FIG. 5  are provided with slots  19  that are accurately located from the work piece locating surface  12 . The slot locations are clearly marked on both sides of the locator.  
         [0057]     The keys  8  located in the wear resistant rails  7   FIG. 2  are clearly marked with their location from a zero reference location near the end of the base.  
         [0058]     When the locator is mounted to the base, one set of aligned keys  8  in the base will engage one set of aligned slots  19  in the locator. To determine the part location from zero reference, add the indicated location of the engaged key on the base to the indicated location of this key as marked on the locator.  
         [0059]     The arrows marked on the base and locator must be pointed in the same direction when addition is used. Otherwise subtraction must be used.  
         [0060]     Either or both ends of the base may be assigned as zero reference and marked with two rows of dimensions, each value ascending from its zero reference point. This allows the locator to be rotated to locate work pieces from their opposite side. Since the arrow directions of the base and locator will coincide on one side of the locator, addition may be used to calculate the distance from reference zero regardless of the locator orientation.  
         [0061]     The locator  FIG. 4  can be used to locate round or hex work pieces. The top set of numbers on both sides of the locator  FIG. 4  identifies the intersection point of the angled locating surfaces  21  from the locator slots. To find the distance from the center of a round or hex work pieces from zero reference; add the location of the key as marked on the base to the location of the slot engaged by the key as marked by the top numbers on the locator. Add this addition to the product of the round work piece diameter or the hex cross flats dimension times 0.57735. As before, the arrow directions must coincide and zero reference may be assigned to either or both ends of the base. The locator is clamped against the wear rails by a bolt and T-nut  10 .  
         [0062]     A wedge clamp  3  is shown mounted to a base  FIG. 6  and is further described by  FIG. 12 . This clamp consists of a taper wedge  26  that is forced against a tapered surface contained by a clamp housing  23 . This causes the wedge to move parallel to the base to clamp a work piece  15  against a locator and move down to force the work piece against a clamp spacer  16 ,  FIG. 6  used to locate the work piece above the base. The wedge is manually forced against the tapered surface by rotating a threaded rod  24   FIG. 10  into a threaded nut  25 . Alternatively, the wedge may be vertically displaced by a powered actuator  FIG. 14  located in the channel  6  contained in the base  FIG. 2 .  
         [0063]     The clamp housing  23   FIG. 13  is accurately guided along the wear resistant rails by T-slots  11  located between the rails. One or more bolts  29  are used to prevent the clamp housing movement caused by the clamping forces. The clamp housing  23  is relieved on the bottom to allow its location to be adjusted along the rails with out interference from the keys located on the wear resistant rails.  
         [0064]     A combination clamp/locator  18  is shown by  FIG. 6 , and further described by  FIG. 10 . In this case, a locating surface is provided on one end and a wedge clamp is provided on the other end. The locator housing  20  is fixed and its location dimension is measured as described for a locator.  
         [0065]     The wedge location is adjusted with respect to the locator housing to compensate for relative large incremental positioning of the locator and relatively small travel of the wedge clamp. The wedge  26  is forced against a tapered surface of wedge housing  27  contained by the locator housing  20 . The wedge housing is located and retained by an adjusting screw  28 . The wedge housing and locator housing are bolted to each other and the base by one or more bolts  29 . The wedge is forced against the wedge housing taper by a threaded rod  24  either by manual rotation or vertical displacement by a power actuator. Thrust bearing  31  and  32  may be used with the wedge clamp or locator/clamp to reduce the manual torque required to achieve the desired wedge clamping force.  
         [0066]     Spring plungers  33  are located in the wedge to retain work pieces before and after clamping  
         [0067]     A hand tightening nut  34   FIG. 8  may be used to increase the part retention force to prevent heavier work pieces from falling from the clamping device before and after clamping. This is most needed when multiple work pieces are simultaneously clamped and unclamped.  
         [0068]      FIG. 6  spacers are used to locate work pieces above the wear rails. The clamp spacers  16  are bolted  35  to a clamp housing  12  or a wedge housing  23   FIG. 12  as applicable. The clamp spacers are configured with extensions that project into slots provided in the wedge  26 . This is necessary to assure that work pieces are fully supported at the line of contact with the wedge so the down ward wedge force does not tip the work piece. The clamp spacers  16  are relieved at the center to prevent interference with the keys  8 . The locater spacers  17  are bolted to the locator as shown. All spacers are marked to indicate their height above the wear rails.  
         [0069]     Gauges  13  and  14  are used to locate work pieces from the T-slot  11  center  FIG. 2 .  FIG. 6  gauges are numbered on both sides with their distance from their work piece locating surface to the center of the T-slot. The gauges are incrementally fixed to the locator or locator housing by pins and bolts as shown. Other means such as keys, serrations, etc. may be used for this purpose.  
         [0070]     The gauge may be placed to locate work pieces from either side of the T-slot. This is the purpose of numbering both sides of the gauge to determine the work piece location from zero reference on either side of the T-slot. Add or subtract the gauge stop location to the T-slot location depending on which side of the T-slot that the gauge is extended.  
         [0071]     The T-slot zero reference may be located from the center of rotation of a rotary base where applicable to facilitate machine programming with respect to the center of rotation of the work piece.  
         [0072]     The stop gauge  14  distance from the T-slot centerline is indicated by the number aligned with the arrow located on the locator housing.  
         [0073]     An alignment gauge  13  may be used as above with the exception that a work piece surface is visually aligned with a gauge surface for providing location. This enables machining a work piece surface that would otherwise be obstructed by the stop gauge.  
         [0074]     Multi face bases are called tombstones  FIG. 21  when fixed at one end and logs  36 ,  FIG. 14  when fixed at both ends. The work pieces require independent clamping for each log or tombstone face to prevent the work pieces from falling from one face when rotated to load/unload work pieces on another face.  
         [0075]      FIG. 19  and  FIG. 20  shows multiple station clamping systems. These Figs. show manual clamping capability. Power clamping and palletized clamping systems may also be provided with means for removing from the machine for parts loading/unloading or storage, they are called tombstone pallets  FIG. 21  or log pallets.  FIG. 16  shows a log pallet  36  supported and rotated by a rotary table  37 , and supported at the opposite end by a tale stock  38 . In this case a single passage for compressed air is completed  FIG. 14  when a piston  39  advances and engages a receiver  40  to support the other end of the log pallet. The compressed air flows through the piston  39  and a check valve  41  to fill and trap the air in a storage chamber  42 .  
         [0076]     Small, flexible air lines  44  are used to convey the compressed air to the actuators from the three way valve  43 . These lines are long enough to enable the actuators to be positioned at any location along the station without the need to modify the air line length. Excess air line length can be stored in the chamber or located at the end of the chamber.  
         [0077]     The power actuator  55  can be connected to a clamp  3 or locator/clamp  18   FIG. 14 .  FIG. 18  seals  46 , and covers  45  and  47  are bolted  48  to the housing  56  to prevent air from escaping from the piston and prevent foreign matter from entering the actuator  55 .  FIG. 18  shows the piston  50  acting against the long end of a lever  49  that pivots around a pin  51  and contacts threaded nut  53  on the lever short end. This multiplies the piston  50  force by the ratio between the long and short end lengths of the lever  49 . The threaded nut  53  forces the threaded rod  24  down to cause the wedge  26  to slide along a taper surface causing it to clamp a work piece against a locator.  
         [0078]     The lever  49  is provided with an oval hole to permit a bolt  29  to pass through and engage threads located in the actuator housing  56 . This bolt  29  is used to clamp the actuator to the wedge clamp and clamp/locator.  
         [0079]     Power clamping reduces operator fatigue and the time for clamping and unclamping work pieces. Power clamping is often used when pallets are transferred to and from the machine for work piece clamping/unclamping. In this case compressed air is the preferred power source for the following reasons:  
         [0080]     1: It is easily transferred from its source to the base. See  FIG. 14 .  
         [0081]     2: When a piston  39  is coupled to a receiver  40 , compressed air cleans the mating surfaces  
         [0082]     3: If the coupling is not completed, air leakage occurs. This is easily detected by measuring the resulting pressure drop after the normal air transfer duration. This can provide a signal to halt continuance until the condition is corrected.  
         [0083]     4: Also, compressed air can be stored in the base and used for off machine clamping/unclamping of work pieces when the air supply is decoupled.  
         [0084]     When a three way valve  43  is opened, air flows to all the power actuators located on a single face. This causes the actuator pistons  50  to act against the levers  49  causing the threaded rods  24  to displace the wedges  26  to clamp the work pieces. When the three way valve is rotated to the exhaust position, air flows from the pistons to the atmosphere, relieving the force on the piston and allowing the springs  52  to retract the levers, pistons, threaded rods and wedges to unclamp the work pieces.  
         [0085]      FIG. 22  shows an alternate hydraulic power actuator. The lever used for the air actuator is not required because of the sufficient clamping force is generated by increased hydraulic pressure. Since the hydraulic fluid can not be vented to the atmosphere, two fluid paths are needed, one for flow to the clamp and one to return the flow from the clamp. The higher pressure fluid lines  57  are necessarily larger and less flexible than the air lines. Coupling the fluid lines  57  to and from pallets, and storing the fluid in the bases using spring or pneumatic force is considerably more complicated than required for air clamping.  
         [0086]     The hydraulic fluid acts on a piston  58  that retracts a threaded rod  59  to force the wedge against a taper surface to cause clamping. Hydraulic clamping may be a good alternative where pallets are not used and fluid coupling is not needed.  
         [0087]      FIG. 24  shows a locator and two clamps used to clamp the sides of a sheet metal work piece  60 . The wedge clamp  3  on the right hand side of  FIG. 24  is bolted to the base  1  and used to clamp the work piece against the locator  2 . The wedge clamp  3  on the left hand side is allowed to slide along the base  1  so the wedge  26  will position it against the work piece  60  and clamp it against a clamp extension  62 . The force on the threaded rod  24 ,  FIG. 13  is used to clamp the work piece and secures the clamp  3  to the base  1 . This enables a work piece  60 , with great size variation, to be clamped on both ends and secured to the base  1 . When the work piece  60  is configured as shown near the locator  2 , a spacer  61  may be employed to enable clamping against the locator  2 . The spacer  61  may contain a spring plunger  63  that prevents the spacer  61  miss locating before clamping.  FIG. 23  an alignment gauge  13  may be used to locate the work piece  60  in the other axis.  
         [0088]      FIG. 25  shows a means of clamping a round work piece  67  without causing it to rotate as a result of the downward force of the wedge. A flexible band  64  is fastened to the clamp housing  23  or wedge housing  27   FIG. 6  using a spacer  65 . The flexible band  64  prevents the downward force of the wedge  26  from acting against the round work piece  67 . A spacer  66  is fastened to the base I to support the round work piece  67 .  
         [0089]      FIG. 26  shows a locator/side down clamp  68 . This clamp is used to clamp work pieces by forcing them down against spacers.  FIG. 27 ,  FIG. 28 , and  FIG. 29  show examples of how this clamp is used.  FIG. 30  and  FIG. 31  show how this clamp works. A piston  77  is contained by a slide down housing  79 . The slide down housing  79  is fastened to a slide down cover  80 . The slide down cover  80  contains slots that engage keys  8  that are located in the base  1 . These keys and the slide down cover  80  slots position the slide down location surface  95  and location markings indicate location as earlier described for locators,  FIG. 4 .  
         [0090]     The piston  77  is fastened to a rectangular bar  81  by fasteners  75 . The bar  81  extends into the channel  6  and is guided by a bearing  82 . The bolts  87  and  94  clamp the slide down housing  79 , slide down cover  80 , and bearing  82  to the base  1  when located by a key  8 . Seals  76 ,  88  and  73  prevent air from escaping from the top side  90  of the piston. A guide rail  96  is fastened to the piston  77 . A slide bar  84  is keyed to the guide rail  96  and is able to slide left and right as viewed by  FIG. 31 . Two cam rollers  71  are attached to the slide bar  84 and ride in a slot provided in each side block  72 . The slot in each side block  72  is shaped such that when the piston  77  is forced down, the slide bar  84  is forced to the left, as viewed by  FIG. 31 , and then down. This enables a work piece to be positioned against the slide down locating surface  95  and a spacer  93  when the slide bar  84  is in the unclamped position. A clamp jaw  83  can be fastened to the slide bar  84  and adjusted to clamp the work piece. Various clamp jaw  83  sizes can be selected to adjust to the work piece height.  
         [0091]     A bearing  74  is used to guide the top half of the piston  77 . Springs  78  are used to retract the piston  77 . Air lines  44  are used to transport compressed air to the slide down clamp as described for the actuator  55 . See  FIG. 14 . The air flows through a hose fitting  92 , through the rectangular bar  81 , into the piston  77  and out a radial hole  89  to the top of the piston  90 ,  FIG. 31 . Air may enter the slide down clamp from either side. The un-used port is plugged  91  to prevent escaping air.  
         [0092]     While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.