US 3835747 A
A fabric lay-up is held against the upper side of a porous carrier adjacent to a cutting tool by suction applied by vacuum chambers at the opposite carrier side. A series of vacuum chambers are located adjacent to the cutting tool, each being partially evacuated to a different subatmospheric pressure than adjacent chambers, the most reduced pressure being in the chamber directly opposite the cutting tool. The subatmospheric pressures in the other chambers are always higher fore and aft of the lowest pressure chamber. The carrier may be reciprocated, and the vacuum chamber series may be fixed relative to the cutting tool in the direction of carrier reciprocation. Alternatively, the cutting tool may be reciprocable relative to a stationary vacuum chamber series, and chamber-evacuating means may be operable to change the absolute subatmospheric pressures, though not their relative pressure differentials, in synchronism with such reciprocation.
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Description (OCR text may contain errors)
United States Patent [191 Bystron [111 3,835,747 Sept. 17,1974
FABRIC WEB HOLD-DOWN APPARATUS FOR TAILORING MACHINES Inventor: Bruno Bystron, lngolstadt, Germany Assignee: Schubert & Salzer Maschineniabrik Aktiengesellschaft, lngolstadt, Germany Filed: Aug. 1, 1973 Appl. No.: 384,562
Foreign Application Priority Data Aug. 5, 1972 Germany 2238746 US. Cl. 83/422, 83/451, 83/925 CC Int. Cl D06h 7/24 Field of Search 83/374, 422, 451, 925 CC;
References Cited UNITED STATES PATENTS Gerber et al 83/451 X Primary ExaminerJ. M. Meister I Attorney, Agent. or Firm-Robert W. Beach; Ms. R. M. Van Winkle  ABSTRACT A fabric lay-up is held against the upper side of a porous carrier adjacent to a cutting tool by suction applied by vacuum chambers at the opposite carrier side. A series of vacuum chambers are located adjacent to the cutting tool, each being partially evacuated to a different subatmospheric pressure than adjacent chambers, the most reduced pressure being in the chamber directly opposite the cutting tool. The subatmospheric pressures in the other chambers are always higher fore and aft of the lowest pressure chamber. The carrier may be reciprocated, and the vacuum chamber series may be fixed relative to-the cutting tool in the direction of carrier reciprocation. Alternatively, the cutting tool may be reciprocable relative to a stationary vacuum chamber series, and chamberevacuating means may be operable to change the absolute subatmospheric pressures, though not their relative pressure differentials, in synchronism with such reciprocation.
3 Claims, 3 Drawing Figures The present invention relates to apparatus for holding fabric webs on an air-pervious carrier by means of suction during tailoring of the fabric by a cutting tool.
It is conventional to arrange suction devices below an air-pervious fabric carrier so that the fabric webs are pressed against the carrier and held thereon. For economic reasons, the suction created by subatmospheric pressure is applied on the fabric within the limited region in which the cutting tool moves. The amount of suction applied is calculated to assure that the fabric lay-up is neither lifted nor displaced during the motion of the cutting tool; Experience has shown, however, particularly in devices with reciprocable fabric carriers, that the fabric webs carried thereon are subjected to sudden displacement in the transition zone between the suction-free area and the suction area as a result of the sudden application of pressure substantially below atmospheric, producing a thrashing effect on the carrier and causing folds or wrinkles in the fabric which lead to cutting distortions during fabric tailoring. The thrashing effect persists even when a foil or paper layer is laid on top of the fabric stack for the purposes of improving fabric hold-down and preventing imperfect fabric travel by penetration of the cutting tool.
It is the principal object of the present invention to eliminate fabric displacement in the transition from the suction-free area to the suction area in such tailoring machines.
The foregoing object can be accomplished in accordance with the present invention by providing a series of vacuum chambers on the side of the fabric carrier opposite the fabric webs, which chambers are gradationally evacuated so that the chamber located directly in the cutting area has a pressure farther below atmospheric than the chamber adjacent to it. It is advantageous to provide vacuum chambers which are stationary to avoid the problems of air leakage associated with movable chambers. A modification of the present invention is to provide in conjunction with a cutting area movable lengthwise relative to the fabric carrier, a series of vacuum chambers arranged along the carrier having a gradational pressure system which is variable in synchronism with travel of the cutting area, so that the subatmospheric pressure in particular chambers is variable to create stronger or weaker suction on the fabric lay-up as required.
FIG. 1 is a schematic longitudinal section through tailoring mechanism showing one form of a gradational suction system according to the present invention, for use with a reciprocable fabric carrier; and FIG. 2 is a similar view of a modified suction system.
FIG. 3 is a schematic longitudinal section through tailoring mechanism showing another form of gradational suction system, for use with a cutting tool reciprocable lengthwise of a series of vacuum chambers.
In the embodiment of the present invention shown in FIG. 1, the stack 2 of fabric webs is covered by a foil or paper overlayer l and lies on a perforated backing sheet 20. The composite layup is carried on an airpervious fabric carrier 3 supported by rollers 30 for lengthwise reciprocation in the direction of arrows P1 and P2 relative to a cutting tool 4. Such cutting tool is vertically movable toward and away from carrier 3, and
is reciprocable transversely of the carrier. A backing roller 31 supports the fabric lay-up directly beneath cutting tool 4 to maintain the lay-up height in opposition to the downward force exerted by the cutting tool. Below the fabric carrier 3 are three vacuum chambers 5, 6 and 7, which are connected by conduits 50, 60 and 70, respectively, to an evacuating system (not shown). The subatmospheric pressure of each chamber can be adjusted by regulating means, such as regulating valves 51, 61 and 71, for example, or cam shutoffs or other conventional pressure-regulating means.
Vacuum chamber 6, which lies directly in the cutting region is evacuated to a pressure substantially below atmospheric to create a strong suction force required for precisely holding the fabric stack 2 during cutting. The subatmospheric pressure in chambers 5 and 7 is higher than the pressure in chamber 6, and such chambers 5 and 7 are located adjacent to chamber 6, fore and aft thereof, relative to the length of carrier 3.
Assuming that a fabric lay-up is to be fed to the cutting tool 4 by carrier 3 moving in the direction of arrow P1, the leading edge of the paper or foil overlayer l which extends beyond the leading edge of fabric stack 2 and backing sheet 20 is first subject to a relatively weak suction force from chamber 5 upon transition from the suction-free area to the suction area. Such suction force is sufficient to hold the composite lay-up l, 2, 20 firmly on fabric carrier 3 during the forward travel of the lay-up toward the cutting region. The strong suction force necessary to hold the fabric web stack 2 in fixed position on the carrier 3 against the cutting force is not applied to the overlayer 1 or fabric 2 until the lay-up is moved to a position over chamber 6 located beneath the cutting tool 4. As the leading edge of the lay-up moves to a position overlying chamber 7, the suction is reduced.
The procedure just described also occurs when the fabric stack 2 is transported to the cutting area in the direction of arrow P2 or when the carrier 3 is reciprocated to control cutting movement along one coordinate of the cutting pattern. In the latter case, cutting tool 4 describes cutting movement along the other cutting coordinate by moving transversely of the direction of movement of carrier 3. As can now be seen, the fabric stack 2 is subjected to progressively increased or decreased suction forces, and is compressed or relieved gradually thereby so that the transitional change in suction force is far less abrupt than in conventional tailoring machines.
By increasing the number of vacuum chambers in the series, variation in compression of the fabric web stack 2 can be achieved even more gradually to an optimal value in the cutting region. A series of five chambers 52, 62, 72, 82 and 92 is shown in FIG. 2 located below the perforate carrier 3, which chambers are connected to a vacuum system (not shown) by conduits 53, 63, 73, 83 and 93, respectively. The conduits can be regulated as described in connection with FIG. 1 to achieve selectively the desired relative pressures and the desired degree of evacuation necessary for different types of fabric in the cutting region. All of the chambers will be evacuated to subatmospheric pressures, but chamber 72, which is located in the cutting region, will have the lowest pressure. The adjacent chambers 62 and 82 immediately fore and aft of chamber 72, respectively, will have a pressure higher than chamber 72 but lower than the pressure in outwardly-adjacent chambers 52 and 92. The air pressure therefore increases in the individual chambers with increased distance from cutting tool 4, or, stated conversely, the suction forces on the lay-up decrease with increased distance from the cutting tool. It has been found that the combined effect of the gradational suction system holds the lay-up so securely that the relatively low suction from the outer chambers 52 and 92 is sufficient to hold the portions of fabric stack 2 in their effective regions on the carrier 3 sufficiently securely so that the fabric webs wont slip relative to each other or relative to the carrier.
It is, of course, possible to provide a separate evacuating system for each of the chambers 5, 6 and 7, or 52, 62, 72, 82 and 92, whereby each such system can have an optimal capacity correlated to the particular evacuating requirements of the vacuum chamber to which it is connected. In such case, it would be possible to eliminate the regulating means 51, 61 and 71. However, it is preferred that such regulating mechanism be supplied so that the pressure in each chamber can be varied to obtain an overall gradational suction system best adapted to the type and quantity of fabric webs which make up the stack 2.
The present invention is advantageously applicable to a tailoring machine having a stationary fabric carrier 32, as shown in FIG. 3. The cutting tool is mounted for horizontal travel in the directions of both the X and Y coordinates of the cutting line, as well as such tool being movable in a vertical direction to be withdrawn from and inserted into the fabric stack 2. The cutting tool 40 is mounted on a conventional carriage 41. By way of example, four vacuum chambers 54, 64, 74 and 84 are shown as being arranged in series to maintain the fabric webs of the stack 2 in their positions on the carrier 3, the lay-up including a backing sheet and an overlayer 1 of paper or foil. In this instance, each of the vacuum chambers has two evacuating conduits, of which only the conduits 55 and 56 for chamber 54 are shown. Each conduit is closed by a valve or other closure member 57,58, 67,68, 77,78, 87,88, each of which members includes an actuation lever.
The vacuum system to which the conduits carrying valves 58, 68, 78 and 88 are connected for respective chambers 54, 64, 74 and 84, has a greater vacuumcreating capacity than the vacuum system in which the conduits carrying valves 57, 67, 77 and 87 are connected. Consequently, the pressure in the chamber 54, for example, can be reduced to create a relatively weak suction force by opening valve 57 while valve 58 is closed. A relatively higher suction force is created in chamber 54 when valve 58 is opened, while valve 57 is closed. If both valves are opened, the cumulative effect would be to reduce the pressure in the chamber below the pressure which can be achieved by opening valve 58 alone. In the particular construction shown in FIG. 3, both valves will be closed or the lower capacity valve of a particular chamber will be opened, or both valves will be opened, as explained below. The actuation of the valve is effected synchronously with translation of the cutting tool along the X coordinate in this example.
Cutting tool carriage 41 carries two arms 42 and 43 extending lengthwise relative to carrier 32. Arm 42 is located to engage selectively the levers of the valves 57, 67, 77 and 87 connected in the lower capacity vacuum system for opening them, and projects substantially further fore and aft of carriage 41 than does arm 43. Arm
43 is located to engage selectively the levers of valves 58, 68, 78 and 88 of the higher capacity vacuum system for opening them. All of such valve members are normally closed, such as by spring force means (not shown), operable on the valve levers. In the example shown, arm 42 engageable with the low capacity valve members can open the corresponding valves of three chambers simultaneously, namely, the chamber in the cutting region, defined by the location of carriage 41 and its cutting tool, and the chambers on either side of the cutting region chamber. Arm 43 engageable with the high capacity valve levers can open only one such valve at a time, namely, the high capacity valve of the cutting region vacuum chamber.
With carriage 41 in the position shown in FIG. 3, chamber 74 is located in the cutting region defined by the area around cutting tool 40. Closure member 77 is opened by arm 42, and closure member 78 is opened by arm 43, so that chamber 74 is evacuated to create a strong suction force sufficient to hold the fabric web securely during cutting. Simultaneously, arm 42 opens closure members 67 and 87 of vacuum chamber 64 and 84, which chambers are contiguous with cutting region chamber 74, so that the adjacent chambers are evacuated to a lesser degree than chamber 74 to create a gradationally weaker suction force than is effective in chamber 74.
If the carriage 41 and cutting tool 40 are moved to the left, from the position shown in FIG. 3, to translate the cutting region toward chamber 64, high evacuating capacity closure member 68 is opened by arm 43 so that a strong suction force is produced in the newlylocated cutting region, while closure member 78 is released to reduce the suction force in chamber 74. Simultaneously, low capacity closure member 67 is maintained in its open condition as arm 42 projects progressively further beyond it toward the corresponding member 47 in chamber 57 immediately ahead of the cutting region chamber 64. Closure member 87 is correspondingly released by arm 42 so that chamber 84 which is now remote from the cutting area is no longer subjected to evacuation. Consequently, it can be seen that, regardless of which vacuum chamber is located directly beneath the cutting tool, the lowest pressure will be in the chamber corresponding to the cutting region and the chambers immediately adjacent to opposite sides thereof will be partially evacuated to create a weaker suction force. Regardless of which chamber has the lowest pressure, and therefore exerts the strongest suction, the gradational suction system is maintained relative to the cutting region.
As indicated above, the number of vacuum chambers could be increased, and additional vacuum systems could be supplied, together with corresponding closure members and carriage-mounted valve-opening arms, so that the difference in pressure between adjacent chambers can be reduced. In the case of a movable carrier, such as shown in FIG. 1, for example, the vacuum chambers and their corresponding closure members could be mounted for movement with the carrier and the valve-opening arm could be stationary.
1. In apparatus for a tailoring machine for cutting fabric webs having a cutting tool, a cutting region surrounding the cutting tool, an air-pervious fabric carrier for supporting a stack of fabric webs in the cutting region through which suction force can be applied to 2. The apparatus defined in claim 1, in which the vacuum chamber series is stationary.
3. The apparatus defined in claim 1, in which the cutting region is movable relative to the vacuum chamber series, and the evacuating means includes regulating means operable to vary the degree of evacuation in each vacuum chamber for effecting selectively stronger and weaker suction forces, and selecting means for operating said regulating means in response to movement of the cutting region for effecting stronger suction forces in the one chamber of the series located in the cutting region, and weaker suction forces in the chambers adjacent to such cutting region chamber.