Vacuum supply system for movable cutter
BACKGROUND OF THE INVENTION 
     This invention relates to sheet material cutters, such as cloth cutters, having a table for supporting the material to be cut and wherein vacuum is applied to at least a portion of the support surface to compress the material as it is cut, and/or to aid in holding the material to the support surface, and deals more particularly with a system for supplying vacuum to such a cutting table in the case where the table is movable over a horizontal floor between a number of different cutting stations. 
     It is known, for example from U.S. Pat. No. 3,790,154, to provide the cutting table of a sheet material cutter with a vacuum which is applied to the material supporting surface at least in the vicinity of the cutting tool to compact and hold in place the material being cut, the vacuum generally working in cooperation with a sheet of thin plastic or similar air impermeable material spread over the material to be cut. It is also known, for example from U.S. Pat. Nos. 4,345,496, 4,646,911 and 4,476,756 to make the table of such a cutter in such a way that the support surface for the material to be cut is provided by an endless conveyor so that the material to be cut may be first spread on a separate spreading or lay-up table to form a lay-up consisting of a number of layers of material and may then be moved from the spreading table to the cutter through the conveying action of the cutting table&#39;s endless conveyor. It is also known, in a sheet material cutting plant, to provide a number of spreading tables serviced by a single cutter movable relative to the spreading tables to bring it into a position of cooperation with any selected one of the spreading tables. Thus, in the latter situation, while the cutter cooperates with one spreading table to receive and cut the layout made available at that table spreading may take place at one or more of the remaining tables to form one or more new lay-ups for later cutting by the cutter. 
     In known cutters of the type intended for movement between a number of spreading tables, the vacuum needed for application to the material support surface has been provided by a vacuum pump and drive motor carried by the frame of the cutter table so as to be part of the table and movable with it between its various cutting stations. Such movable cutting tables with built-in vacuum sources have a number of disadvantages including the fact that a relatively large amount of electrical power has to be supplied to the drive motor through some sort of connection permitting movement of the table, the fact that a relatively high degree of noise is produced in the vicinity of the cutting table by the running of the motor and the pump and the exhaust of air from the pump, and the fact that the flow of air through the vacuum system may have an adverse effect on the heating or air conditioning of the room containing the cutter, which effect is difficult to control because of the moving nature of the vacuum pump. Another disadvantage is that different cutting applications using the same general cutting table may require quite different amounts of vacuum power, yet it is difficult for the manufacturer of cutters with built-in vacuum sources to make such tables available with a wide selection of different built-in vacuum sources to precisely match the needs of different applications. In other words, it may be practical for the manufacturer to make available cutters with only one standard vacuum source, or with a very limited selection of standard vacuum sources, which may provide a much higher maximum vacuum power than needed for the application in question. 
     The general object of this invention is therefore to provide a system for supplying vacuum to a movable sheet material cutter which overcomes the above described disadvantages of movable cutters with built-in vacuum sources. 
     Other objects and advantages of the invention will be apparent from the following detailed description of a preferred embodiment. 
     SUMMARY OF THE INVENTION 
     The invention resides in the combination, in a sheet material cutting plant, of a cutter movable over the floor of the plant between a number of different cutting stations, a stationary vacuum generator, a plurality of vacuum junction boxes or outlets located one at each of the cutting stations, a duct arrangement connecting each junction box or outlet to the vacuum generator, and cooperable means on the various junction boxes or outlets and on the cutter for making a releasable connection between the junction box or outlet associated with the station at which the cutter is positioned and the cutter to allow the cutter to be provided with vacuum from the vacuum generator while positioned at any one of the cutting stations. 
     The invention also more particularly resides in the construction of the cooperable means on the individual junction boxes and on the vacuum inlet means of the cutter whereby a releasable connection may be made between the inlet means and any selected one of the junction boxes, such construction being such that during the making of a connection an airtight seal is first made between the inlet means and the junction box before a valve in the junction box is opened to admit vacuum to the inlet means, and so that during the breaking of a connection between the valve in the junction box is closed before the airtight seal between the junction box and the inlet means is released. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a somewhat schematic perspective view of a cutting plant using a movable cutter and vacuum supply system embodying the present invention. 
     FIG. 2 is a perspective view showing the cutter of FIG. 1 slightly displaced from one of its cutting stations and therefore showing the vacuum inlet means of the cutter slightly displaced from and out of connection with the vacuum junction box of the station in question. 
     FIG. 3 is a vertical sectional view taken through the vacuum inlet means of the cutter of FIGS. 1 and 2 and through an associated one of the vacuum junction boxes when the cutter is positioned at one of its cutting stations, the inlet means of the table being shown in its disconnected condition with respect to the illustrated junction box. 
     FIG. 4 is a view similar to FIG. 3 but with the inlet means of the cutter being shown in a condition intermediate its connected and disconnected conditions relative to the illustrated junction box. 
     FIG. 5 is a view similar to FIG. 3 but with the inlet means of the cutter being shown in its connected condition relative to the illustrated junction box. 
     FIG. 6 is a horizontal sectional view taken on the line 6--6 of FIG. 3. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows a portion of a cloth cutting plant embodying the present invention. As there shown, the plant includes three spreading tables 10A, 10B and 10C located at different fixed positions on the generally horizontal floor 12. Each of the three tables is elongated and has first and second ends 14 and 16, the tables being arranged so that all of their first ends 14, 14 are located along a common straight line. Each table further has an upwardly facing horizontal support surface 18 on which a lay-up 20 of a cloth may be spread using a conventional spreading machine 22 movable back and forth longitudinally of the table. 
     Associated with the three spreading tables 10A, 10B and 10C is a cutter indicated generally at 24. The cutter includes a table 26 and a cutter head 28. The table 26 has a frame 30 and a means providing a generally horizontal upwardly facing material support surface 32. The cutter head 28 has a cutting element, such as a reciprocating knife, for cutting sheet material supported on the surface 32 and is movable in two coordinate directions in the plane of the surface 32 so as to be capable of following any desired path to cut, for example, pattern pieces from sheet material for subsequent use in making garments, upholstery assemblies or the like. To achieve this motion, the cutter head 28 is supported by a tool carriage 34 movable in the illustrated Y-coordinate direction relative to another carriage 36 extending across the table and supported by the frame 30 for movement in the illustrated X-coordinate direction. Suitable motors, drive systems and controllers are provided to achieve the desired motions of the cutting head. Power and command signals for these motors, as well as for other motors which may be included in the cutter 24, are supplied to the cutter through a vertically extending mast 38 fixed to one corner of the table frame 30 and receiving flexible cables from an overhead rail system from which excess cabling is hung in festooned fashion from trolleys to accommodate movement of the cutter 24 in the manner hereinafter described. 
     A feature of the cutter 24 is that it is supported for movement relative to the floor 12 between a number of different work stations at each of which stations it is aligned with a different one of the spreading tables 10A, 10B and 10C to receive and cut sheet material spread on that spreading table. For example, in FIG. 1 the solid lines show the cutter 24 positioned at the cutting station A at which it is aligned with the spreading table 10A. The broken lines illustrate two other cutting stations B and C to which the cutter 24 may be moved to align respectively with the cutting tables 10B and 10C. Various different means may be used for supporting the cutter for movement between its different cutting stations, and in FIG. 1 such means are shown to consist of a number of wheels 42, 42 carried by the table frame 30 and supporting the frame 30 for movement along three rails 44, 44 fixed to the floor 12 and extending perpendicularly to the spreading tables 10. Preferably, the cutter includes a motor for powering one or more of the wheels 42 to drive the table between its cutting stations and a suitable control panel (not shown is provided to allow an operator to effect and control movement of the cutter between the cutting stations. 
     As shown in FIG. 1, the table 26 of the cutter 24 has a first end 46 positioned closely adjacent to the end 14 of the associated spreading table 10 when the cutter is positioned at one of its cutting stations. Therefore, when the cutter is positioned at a cutting station, the lay-up 20 previously spread on the associated cutting table may be moved from that table to the support surface 32 of the cutter for cutting by the cutter head 28. Depending on the length of the lay-up 20 relative to the length of the cutting table 26, either the entire length of the lay-up may be moved at one time onto the cutting table before any cutting occurs or the lay-up may be moved onto the cutting table in increments with each increment being cut before a new increment is moved into cutting position. The actual movement of the lay-up from the spreading table to the cutting table may take place in various different ways, but preferably and as shown the support surface 32 is formed by an endless conveyor 48 movable in the illustrated X-coordinate direction; and which is moved in such direction or from left to right in FIG. 1 to aid in pulling the lay-up from the spreading table to the cutting table. For example, the cutting table may be generally similar to those shown by U.S. Pat. Nos. 4,345,496, 4,646,911 and 4,476,756 to which reference may be made for further details of construction. As shown by these patents, the conveyor belt 48 preferably is comprised of a plurality of bristle blocks having bristles the free ends of which form the material supporting surface 32 which is penetrable by the knife of the cutter head 28. 
     In the operation of the system as shown in FIG. 1, it will be understood that a lay-up 20 is first spread on one of the spreading tables 10 until it is complete and ready for cutting. The cutter 24 is then moved to the cutting station at which it aligns with this table, the lay-up is pulled onto the support surface 32 of the cutting table, either all at one time or incrementally, and the lay-up is then cut by the cutter head 28 to produce the desired pattern pieces. During this cutting, spreading may occur on one or both of the other spreading tables so as to have a new lay-up ready for cutting as soon as the cutter 24 again becomes available. During or after the cutting of a lay-up the pattern pieces and waste material produced by the cutting are removed from the cutter before the cutter is moved to a new cutting station or while the cutter is in transit to the new cutting station. This may be done either by picking the pattern pieces and waste material up from the material supporting surface 32 of the cutter table or, after cutting, the conveyor belt 48 may be operated to move the cut material to the right, as seen in FIG. 1, onto a conveyor or other take-off device (not shown) aligned with the right hand end of the cutting table 26. 
     Although as described above the system of FIG. 1 is used for the spreading and cutting of lay-ups, it may also be used in cases where only a single layer is spread onto a spreading table before it is moved onto the cutter for cutting. Also, the system can be used for so called &#34;cutting on the fold&#34; in which case a single length of cloth is spread on a spreading table but is folded upon itself along a fold line extending longitudinally of the table to form a double layered unit presented to the cutter for cutting. 
     In accordance with the invention, the cutter 24 is one in which, during a cutting operation, vacuum is applied to the material support surface 32 at least in the vicinity of the cutting head 28 to compact the material and to aid in holding it in place on the material support surface 32 against in-plane forces exerted on it by the cutting knife. To gain full effect of this vacuum, the lay-up to be cut is, before cutting, preferably covered with a sheet of plastic or other substantially air impervious sheet material so that due to the vacuum appearing at the support surface and the atmospheric pressure applied to the top of the plastic sheet the material is compressed between the plastic sheet and the support surface in accordance with the principle of, and as explained in more detail by, U.S. Pat. No. 3,790,154. 
     To provide for the vacuum applied to the material support surface 32, the frame 30 of the cutting table carries a vacuum inlet means indicated generally at 50, and the table also includes transmission means for transmitting vacuum appearing at the inlet means 50 to the desired portion of the material support surface 32. This transmission means may take various different forms without departing from the invention and may, for example, be similar to that shown by either U.S. Pat. Nos. 4,345,496, 4,646,911 or 4,476,756 with the vacuum inlet means 50 taking the place of the vacuum pump shown in each of said patents. 
     The vacuum inlet means 50 of the cutter 24 is cooperable with a number of vacuum junction boxes or outlets 52 located one at each of the three cutting stations A, B and C. The junction boxes 52 are further so located at each cutting station that when the cutter 24 is properly positioned at a cutting station, the inlet means 50 registers or aligns with the junction box 52 of tat station. Further, the inlet means 50 and each junction box 52 include cooperable means allowing the inlet means 50 to make a releasable connection with any of the junction boxes 52 with which it may become aligned. 
     The junction boxes 52 are each connected with a vacuum generator 54 by ducts 56, 56 so that the vacuum produced by the generator 54 is made available at each junction box. When a connection is made between the inlet means 50 and one junction box 52, as shown for example at station A in FIG. 1, the vacuum appearing inside the involved junction box is, as hereinafter described in more detail, admitted to the interior of the inlet means for transmission to the material support surface 32. 
     The vacuum generator 54 may be of generally conventional construction and consists basically of a motor driving a vacuum pump. Because of the connection of the vacuum generator 54 to the junction boxes 52, 52 by the ducts 56, 56 the generator may be located, if desired, quite remote from the spreading tables 10, 10 and cutter 24, and may even be placed in a separate room to remove its noise from the spreading table and cutter operators. Also, since the generator is not carried by the cutter 24, the cutter 24 may be made of smaller size and lighter in weight than heretofore. The stationary disposition of the vacuum generator 54 separate from the cutter 24 also has the advantage that it can readily be sized and otherwise designed to particularly suit the application to which the associated cutter 24 is put. Also, with this disposition of the generator 54 heat exchangers and other devices can, if desired, be readily associated with it to integrate it into the heating and/or air conditioning system of the cutting plant to diminish any adverse effect the generator might otherwise have on such heating and/or air conditioning system. 
     In FIG. 1, the arrangement of the ducts 56, 56 is such that a large portion of them is located high above the floor 12 so as to be out of the way of operators and equipment needed in the vicinity of the spreading tables and cutter during spreading and cutting operations. The illustrated arrangement of ducts, however, is not essential, and many other arrangements may be used without departing from the invention. For example, with junction boxes located on or in the floor 12, the ducts 56 connecting those boxes to the generator 54 may be located below the floor surface. Also, the junction boxes themselves need not necessarily be located on or in the floor, and can be located above the cutting table 24 with the inlet means 50 of the cutter being directed upwardly for cooperation with such upwardly located junction boxes rather than being downwardly directed as in FIG. 1. 
     Reference is now made to FIGS. 2 to 6 for a discussion of the details of the junction boxes 52, 52 and of the inlet means 50 of the table 24. In FIG. 2, the table 24 is shown slightly displaced from the cutting station served by the illustrated junction box 52. Therefore, the inlet means 50 of the cutter is both disconnected from and slightly laterally displaced from the illustrated junction box. In FIGS. 3, 4 and 5, the cutter is fully positioned at the cutting station associated with the illustrated junction box, the inlet means 50 therefore being vertically aligned or registered with such junction box. FIG. 3 shows the inlet means in it disconnected position relative to the junction box, whereas FIG. 5 shows it in its connected position. FIG. 4 shows the inlet means in an intermediate position at which it is sealingly associated with the junction box but the valve of the junction box is closed so that vacuum appearing in junction box is not admitted to the inlet means. 
     As shown in FIGS. 3, 4 and 5, each junction box 52 is a hollow generally rectangular box having horizontal top and bottom walls 58 and 60, vertical end walls 62 and 64 and two vertical side walls only one of which is shown at 66. The associated vacuum supply duct 56 is attached to the box by a collar 68 surrounding and defining an inlet opening 70 for the box in the end wall 62. The top wall 58 of the box has a generally circular access port 72 normally closed by a disk shaped valve member 74 as in FIGS. 3 and 4. The valve member 74 is fixed to a hub 76 fixed to a rod 78 slidably received for vertical movement by a bearing 80 fixed to and carried by the bottom wall 70. A helical compression spring 82 surrounds the bearing 80 and, rod 78 and urges the valve member 74 to its closed position. The spring 82 is further sized so that the valve member 74 will remain in its closed position against the force exerted on it by the expected maximum pressure difference which may occur across it due to the vacuum inside of the box acting on the lower surface of the valve member and atmospheric pressure acting on the upper surface of the valve member. 
     The inlet means 50 as shown by FIGS. 3, 4 and 5 includes a first generally cylindrical duct 84 fixed relative to the frame 30 of the cutter table and which through a suitable vacuum transmission means included in the table is communicable with a desired portion of the material support surface 32. Another duct 86 is telescopically received by the first duct 84 for vertical sliding movement relative thereto. An airtight flexible tubular boot 88 has one end sealingly connected to the first duct 84 and its other end sealingly connected to the second duct 86 in the manner shown to prevent the loss of vacuum through the telescopic joint. 
     The second duct 86 is moved vertically relative to the first duct 84 both by gravity and by an actuator 90 located within the two ducts 84 and 86. The actual actuator used may take various different forms, but in the illustrated case it is a pneumatic piston unit served by lines 92 for the supply and exhaust of pressurized air. The body 94 of the actuator at its upper end is fixed to and carried by a part 96 located within the duct 84 and fixed relative to the frame 30 of the cutter table. A piston rod 98 extends out of the lower end of the body and has fixed it to it two vertically spaced stop collars 100 and 102. Slidably received on the rod 98 between the two stop collars is a spider 104, best shown in FIG. 6, fixed to the lower end of the duct 86. 
     Also fixed to the lower end of the duct 86 is an annular ring 106 having an annular radially extending flange 108 carrying an annular sealing ring 100 of rubber or other resilient material. 
     When the piston rod 98 is in its retracted position, as shown in FIG. 3, the stop 102 engages the spider 104 and holds it and the duct 86 in upwardly spaced relation to the top wall 58 of the junction box 52. Therefore, in this retracted condition of the piston rod 98 the inlet means 50 is in its disconnected condition relative to the junction box, and the valve 74 of the junction box is closed, allowing the inlet means to be moved horizontally to or from the junction box and thereby allowing movement of the cutter between cutting stations. To shift the inlet means 50 from a condition of disconnection with the junction box to a condition of connection, the piston rod 98 is extended. During the initial portion of this extending movement, as the stop 102 moves downwardly, the sliding duct 86 moves downwardly with the stop 102 under the influence of gravity until the duct reaches the position shown in FIG. 4 at which the sealing ring 110 sealingly engages the top wall 58 of the box in the area surrounding the access port 72. It will be noted from FIG. 4 that at the point in the extending movement of the piston 98 at which this seal is made, the valve member 74 of the junction box 58 is still in its closed condition so that when the valve member 74 is later opened no leakage of vacuum occurs. 
     Further extending movement of the piston rod 98, beyond the position shown in FIG. 4, thereafter causes the stop 102 to engage the top of the valve member 94 and shift it downwardly. At this time, further downward movement of the duct 86 is arrested by its engagement with the junction box so that the piston rod 98 slides relative to the spider 104 until reaching the fully extended position of the piston rod 98, shown in FIG. 5, at which the stop 100 engages the spider 104. Preferably, the location of the stop 100 on the piston rod 98 is so selected that when the piston rod is in its fully extended position the stop 100 urges the spider 104 slightly downwardly from its FIG. 4 position to further compress the sealing ring 110 and form a still tighter seal between the duct 86 and junction box 52. The downward movement of the valve member by the piston rod from the FIG. 4 to the FIG. 5 position, against the force of the spring 82, shifts the valve member 74 to its fully open position as illustrated in FIG. 5, and thereby admitting vacuum from the box 52 to the interior of the ducts 86 and 84 through the access port 72. 
     The operation of the parts of the junction box 52 and of the inlet means 50 in shifting the inlet means from the connected condition of FIG. 5 to the disconnected condition of FIG. 3 follows in reverse fashion to that described above for the process of making a connection. In particular, it will be noted that in shifting from the connected condition of FIG. 5 to the disconnected condition of FIG. 3, which is achieved by a retracting motion of the piston rod 98, the parts will move through the condition shown in FIG. 4, which means that the valve member 74 is closed before the sealing connection between the duct 86 and junction box 52 is broken. 
     It will also be appreciated that, if desired, a spring may be included in the inlet means and arranged to work between the first duct 84 and second duct 86 to assist gravity in urging the duct 86 downwardly for cooperation with a junction box located below the inlet means. In the case where the ducts of the inlet means are directed upwardly for cooperation with a junction box located above the cutter, such a spring means is necessary and must be of sufficient strength to urge the slidable duct upwardly to engagement with a junction box against the force of gravity.