Workpiece Holding Device for Automatic Sewing

This invention relates to the holding of workpieces that are to be sewn by an automatic sewing machine. In particular, this invention relates to the registering of a workpiece within a workpiece holder so that it may be sewn by the automatic stitching machine.

U.S. Pat. No. 3,988,993 to Robert V. Brophy discloses a workpiece holding arrangement for use with automatic sewing machines. The workpiece holding arrangement consists of a book pallet having hinged leaves that are used to orient and locate several pieces of work which are to be sewn together. In this regard, each leaf of the book pallet contains one or more cavities that orient and accurately register the pieces of work that are to be sewn with respect to each other. The book pallet is connected to a high resolution positioning system which accurately positions the pieces of work relative to a reciprocating sewing needle.

Various other approaches have been used in orienting pieces of work that are to be registered with respect to each other and thereafter sewn by an automatic sewing machine. These approaches have included using a few pins strategically located within the pallet. Workpieces having the same pattern of holes therein are positioned over the pins. Still another approach has been to clamp the workpiece parts relative to each other after having aligned an edge of at least one piece with respect to an edge guide. Examples of these workpiece registration clamps are illustrated in U.S. Pat. No. 4,171,672 and U.S. Pat. No. 4,455,952.

The above arrangements for workpiece registration work well with material such as leather that is stiff enough to be manipulated relative to an edge, or positioned over pins or located within a cavity. A workpiece of a less stiff nature often requires a different approach. One such approach is disclosed in U.S. Pat. No. 4,449,463. The workpiece in this patented arrangement is placed between clamps which subject the workpiece to tension. This is a rather sophisticated arrangement for stretching the workpiece while registering it for sewing.

It is an object of the present invention to provide a workpiece registration and clamping device that allows at least one piece of flexible fabric to be accurately registered and held for automatic sewing.

It is another object of the present invention to provide a workpiece registration and clamping device that does not require an elaborate mechanism to stretch and position the one or more pieces that are to be accurately registered and held for automatic sewing.

The above and other objects are achieved according to the present invention by a workpiece holding arrangement having a base plate with a plurality of sharp pins extending upwardly therefrom. A base piece of a workpiece, which may be elastic, is positioned over all of the sharp pins. The number and spacing of the pins is such as to maintain the base piece in a stretched and flat position. A subset of these pins is located around the periphery of at least one opening in the base plate which is covered when the base piece of the work has been positioned. A second piece of work, which may also be elastic, is now positioned over the subset of pins located around the periphery of the opening. A second plate, preferably hinged to the base plate, is now pivoted downwardly over the positioned pieces of work. The second plate has a plurality of holes therein which allow the sharp locating pins extending upwardly from the base plate to project therethrough. The second plate moreover has separate shields associated with each projecting pin so as to guard against any undesirable contact therewith during the subsequent handling of the workpiece holding arrangement. In this regard, the operator takes the workpiece holder and attaches it to a positioning apparatus of an automatic sewing machine. The accurately registered pieces of work within the workpiece holder are successively positioned under the reciprocating sewing needle which sews the pieces of work together. The shields mounted to the cover plate do not interfere with the needle as the workpiece holder is being moved by the positioning apparatus during automatic sewing. The workpiece holder may be subsequently removed from the sewing machine and opened so as to remove the joined pieces. It is to be appreciated that all such handling of the workpiece holder can be accomplished without concern for the sharp points of the locating pins which remain shielded.

FIG. 1 is a perspective view of a workpiece holder in an open position with a workpiece located therein;

FIG. 2 is a view of the workpiece holder of FIG. 1 connected to positioning apparatus of an automatic sewing machine;

FIG. 3 is an exploded view of the workpiece holder and workpiece; and

FIG. 4 is a detailed showing of a shield element appearing on the top cover plate of the workpiece holder.

Referring to FIG. 1, a workpiece holder 10 is illustrated in an open position with a workpiece 12 located therein. The workpiece 12 is held in place by a number of sharp pointed pins which extend upwardly from a base plate 14. A cover plate 16 is pivotally attached via a set of hinges 18 and 20 to the base plate 14. The cover plate 16 pivots downwardly over the base plate and is latched thereto by a pair of slideable latches (such as latch 22) which engage posts (such as post 24). The series of sharp pointed pins extend upwardly through holes in the cover plate 16 at this time. These pins are shielded by individual shield devices mounted to the top of the cover plate. The workpiece 12, located within the closed workpiece holder 10, is now ready for further processing. In this regard, a person picks up the workpiece holder 10 and connects it to the positioning apparatus of an automatic sewing machine.

Referring to FIG. 2, the workpiece holder 10 is generally illustrated relative to a positioning apparatus 26 of an automatic sewing machine. The positioning apparatus includes a moveable carriage 28 having a shelf 30 which receives the workpiece holder 10. Referring to FIG. 1, the workpiece holder 10 has a registration slot 32 and a registration hole 34. These are located over registration posts 36 and 38 extending upwardly from the shelf 30 of the movable carriage 28. The thus registered workpiece holder may be secured by any convenient means such as clamps or threadable devices. The workpiece holder 10 is now in a plane defined by the shelf 30 and the bed (not shown) of a stationary automatic sewing machine. The workpiece holder 10 is movable in the indicated X and Y directions of movement by the positioning apparatus so as to present the workpiece 12 under a reciprocating sewing needle 38 associated with the stationary head of the automatic sewing machine. It is to be appreciated that the degree of accuracy in presenting the workpiece for sewing is premised in part upon the accurate registration of the workpiece within the workpiece holder 10.

The accurate registration and holding of the workpiece 12 within the workpiece holder 10 will now be explained relative to FIG. 3. FIG. 3 is an exploded view of both the workpiece holder 10 and the workpiece 12. The various portions of the workpiece 12 are situated between the base plate 14 and the cover plate 16. The workpiece 12 is seen to comprise: a bottom piece 40, an intermediate set of pieces 42 and 44 plus a top piece 46. It is to be understood that the workpiece 12 will eventually become an elastic support for a human knee. In this regard, the bottom piece 40 and the top piece 46 are made from conventional elastic materials normally found in elastic knee supports. The intermediate pieces 42 and 44 are foam rubber parts having a thickness of approximately four tenths (0.4) of an inch . The piece 44 approximates the size of a knee cap and fits within the hole in the piece 42. The pieces 40, 42, 44 and 46 are positioned within the pallet 10 by structure which will now be described.

Referring to the base plate 14, it is seen that a plurality of sharp pointed registration pins such as pin 48 are located around the periphery of a relatively large opening 50. The size and shape of the opening 50 is such as to allow the sewing needle 38 to pass therethrough when stitching the various pieces of the workpiece. The registration pins such as 48 are preferably spaced around the periphery of the opening at a spacing between successive pins of seventh-eighths (7/8) of an inch. In addition to the spaced registration pins such as 48, the base plate 14 has at least two further sharp pointed pins 52 and 54 that are located away from the periphery of the opening 50. The location of the pins 52 and 54 is such as to allow for the registration of two corners of the bottom piece 40. The base plate 14 also has an edge gauge 56 which conforms to a mid-portion 58 of one edge of the bottom piece 40. This allows the mid-portion 58 of the bottom piece to be aligned with respect to a fixed location on the base plate before engagement with any of the sharp pointed pins. The thus aligned bottom piece is smoothed and slightly stretched so as to allow the two corners of the bottompiece 40 to be registered on pins 52 and 54. Following engagement of the pins 52 and 54, the remainder of the piece 40 is smoothed and stretched over the registration pins located around the opening 50. The intermediate pieces are next temporarily affixed to the bottom piece 40. In this regard the intermediate pieces are preferably backed with adhesive so as to allow for a temporary adherence to a specific location on the bottom piece. Finally, the top piece 46 is aligned with respect to the pattern of registration pins 48 located around the cut-out hole 50. The top piece is thereafter fitted down over this pattern of registration pins.

The cover plate 16 is now ready to be rotated downwardly over the thus located pieces on the base plate. The cover plate has a hole 60 of the same size and shape as the hole 50 in the bottom plate. This allows the appropriate portion of the workpiece 12 to be exposed for sewing.

In accordance with the invention, when the cover plate is pivoted downwardly over the base plate, the sharp pointed registration pins 48 will extend through holes such as 62 in the cover plate. In this regard, there is a hole in the cover plate 16 for each and every registration pin extending upwardly from the base plate 14. Each hole must be precisely aligned with a respective registration pin so as to avoid any interference with the cover plate when it closes over the base plate. This requires an accurate hinged connection to the base plate. Referring to the base plate 14, it is to be noted that an alignment block 64 is located between the location holes for the hinges 18 and 20. A notch 66 in the cover plate assures that the cover plate will always be accurately registered with respect to the alignment block. This prevents any lateral looseness of the hinges 18 and 20 from affecting the positioning of the cover plate 16 with respect to the base plate.

It is to be noted that each hole receiving a registration pin has a shield 68 assoclated therewith. The shield 68 is illustrated in detail in FIG. 4. The shield 68 is seen to comprise a rivoted element that extends upwardlv and thereafter outwardly over the registration pin 48 extending through the hole 62. The sharp point of the registration pin 48 is completely covered by the cantilevered, outwardly extending portion of the shield 68. It is to be furthermore noted that the outwardly extending portion is spaced above the point of the registration pin. This spacing must be sufficient to allow the cover plate 16 to cover over the base plate without a workpiece 12 being present. This spacing requirement must however be balanced against a need to minimize the total elevation of the shield 68 above the surface of the cover plate in order to avoid contact with the sewing needle 38 as the workpiece holder 10 is being positioned by the positioning apparatus either prior to, during, or after sewing. In this regard, the total height of each shield 68 above the cover plate surface is preferably one quarter (0.250) of an inch.

Referring again to FIG. 4, it is seen that a peripheral edge 70 of the opening 60 in the cover plate is illustrated relative to the shield 68 and pin 48. This peripheral edge 70 is only a short distance from the pin 48 as can be appreciated by referring to FIG. 3. It is to be noted that a thickness of rubber 72 is affixed to the underside of the cover plate 16 near the peripheral edge 70. This thickness of rubber extends around the entire periphery of the opening 60. This produces a local clamping pressure immediate to the sewing path of the needle 38.

It is to be appreciated that when the cover plate 10 is closed, the pieces 40, 42, 44 and 46 of FIG. 2 will all be accurately registered and held with respect to each other. The pattern of registration pins maintains the elastic materials in place whereas the precisely associated shields allow the workpiece holder to be easily handled for automated sewing without concern for the sharp nature of the registration pins.

From the foregoing, it is to be understood that a preferred embodiment of a workpiece holder for holding a workpiece during automatic sewing has been disclosed. Various structural aspects of this workpiece holder may be changed without departing from the scope of the invention. For instance, a different workpiece might require a different pattern of registration pins than that disclosed in the preferred embodiment.