SYSTEM FOR ALIGNMENT AND FEEDING COOPERATING FABRIC PARTS IN SEWING OPERATIONS

Abstract: An apparatus to align a plurality of objects (14;16) comprises: transport means (24;26) for moving the objects over a predetermined path; positional detection means (32;34;36;38;40;42;44;46) located along the path for determining the actual positions of the objects and for providing an alignment correction signal; and repositioning means (52;54) for altering the movement of at least one object along said path in response to the alignment correction signal.

Description: The invention relates to an apparatus comprising the features as indicated in the precharacterizing part of claim 1. Such an apparatus for aligning end portions of two fabric pieces as known from US-A-3 867 898 comprises sensing means for detecting the end portions of fabric pieces. A controlling means is connected to said sensing means and in the case a different position of both pieces one-to-another is detected a control signal is derived based on said difference. In response to said control signal the relative speed of two feed means transporting said two fabric pieces is varied for obtaining an alignment of said pieces. It is the object of the invention to provide an apparatus for aligning end portions of two fabric pieces which works very accurately. In accordance with the invention, this object is solved by the features as claimed in the characterizing part of claim 1. The inventive apparatus controls an alignment means in response to the feeding speed of a transport means. Therefore, an accurate alignment of the fabric pieces is also possible when the feeding speed of said transport means varies. Further developments of the invention are claimed in the subclaims. Preferred embodiments of the invention will be explained in accordance with the drawings. BRIEF DESCRIPTION OF THE DRAWINGS The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself however, as well as a peferred mode of use, further objects and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein: Figure 1 is an isometric view of one embodiment of the present invention. Figure 2 is a block diagram of this invention. Figure 3 is a schematic diagram of the positioned detector pairs. Figure 4 is a schematic diagram of the positioned detection circuitry. Figure 5 is a schematic diagram of the offset circuitry. Figure 6 is a schematic diagram of an operator display. Figure 7 is a side view of the alignment mechanical arm mechanism. Figure 8A is a plan view of a fabric jig. Figure 8B is a side view of the fabric jig. Figure 8C is a isometric view of the fabric jig. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS This invention relates to an apparatus that transports objects along a path and aligns the objects in accordance with the predetermined configuration. Figure 1 is an illustration of one embodiment of the present invention. In Figure 1, two pieces of fabric 14 and 16 are placed upon a table 10 and are transported across the table in a direction 12 by a transport mechanism that includes a motor 28 connected by a pulley 29 to a shaft 30 that rotates two grooved cylinders 24 and 26 that contact fabrics 14 and 16 respectively. The rotation of shaft 30 and cylinders 24 and 26 result in the movement of fabrics 14 and 16 across table 10. A light source 20 is positioned to provide light through an encoder disk 18 attached to shaft 30. A light receiver 22 is positioned opposite the light 20 to receive this light through the encoder disk 18 holes. The light pulses received by light receiver 22 indicate the motion of shaft 30 and the linear speed of the fabrics 14 and 16 as they travel along the table. Each fabric path includes a mechanical arm 52 and 54 including a drag finger 50 and 48 located above the respective fabrics 14 and 16. The mechanical arms 52 and 54 are identical except for the arrangement over the respective sides of table 10 as shown. Only mechanical arm 54 will be discussed in more detail. The arm 54 is pivoted about axis 56 by linkage 58 that is connected to a transducer 60 positioned adjacent to table 10. Transducer 60 includes a signal line 62. When the signal is present on signal line 62, transducer 60 extends the linkage 58 outwardly causing the mechanical arm 54 to pivot about axis 56 causing the drag finger 48 to make contact with the fabric 16. The contact of the drag finger 48 against fabric 16 restrains the travel of fabric 16. The positions of the end portions of fabrics 14 and 16 are determined by photo sensitive diodes 32, 34, 36, 38, 40, 42, 44 and 46 embedded in table 10 which, when uncovered, would be exposed to a light source above table 10 (not shown). When fabrics 14 and 16 are located above these photo sensitive devices, they do not receive light. As the fabric portions 14 and 16 travel along table 10, they will sequentially uncover the light receiving devices starting with devices 44 and 46 sequentially followed by 40 and 42, etc. As each light receiving device is uncovered, the light receiving device emits a signal indicating that it has received light and therefore the end portion of the fabric has passed. The position information is provided to a circuit (not shown) which determines when misalignment has occurred. This circuit accordingly provides a signal to either of the transducers of mechanical arms 52 and 54 to restrict the travel of the fabric pieces to restore alignment. In the embodiment of Figure 1, since cylinders 24 and 26 are both connected to shaft 30, the rotation of 30 will result in equal travel of both fabric pieces 14 and 16. However, in another embodiment of the present inventions (not shown) transport means may be provided to move the pieces of cloth independently of each other. In this embodiment, the misalignment indication signaled (that in the first embodiment is provided to the mechanical arm transducer) will be provided to adjust the speed of a fabric piece relative to the other fabric piece to obtain alignment. Figure 2 illustrates a block diagram of one embodiment of the present invention. In this embodiment, the light receiving diodes provide an array input 80 to a sequencer circuit 82. The sequencer circuit 82 further receives a series of reference pulses from the reference pulse circuit 84 indicating the travel of the fabric pieces along the path. The reference pulse circuit 84 which provides the clock input from the shaft encoder illustrated in Figure 1, indicates the travel of the fabric. By gating the input from the reference pulse circuit 84 by the array input circuit 80, the number of pulses gated will indicate the distance traveled between the uncovering of the first light emitter light detector combination and the time of the uncovering of the second light emitter light detector combination. This distance as measured by the reference pulse circuit 84 results in the actual offset distance specified in a series of pulses. In the preferred embodiment, the array input 80 only provides a signal to the sequencer circuit 82 when one of the photo sensitive diodes receives light before the other. The sequencer circuit 82 then measures the distance traveled between the time that light is received by one photo sensitive diode to the time when light is received by the second as clocked by the pulses from circuit 84. The magnitude of this distance provides an offset magnitude signal on line 84 which is the series of pulses and is input to the resolution selector circuit 90. The resolution selector circuit 90 provides for operator adjustment of the resolution from the resolution input circuit 91 to adjust the overall correction signal provided to an alignment correction device. The resolution of these pulses may be adjusted by the resolution selector circuit 90 by dividing by N, where N is a resolution input. For example, if a misalignment of one tenth of an inch would produce 200 pulses, the resolution selector 90 may be used to reduce the number of pulses provided for adjustment of restraint to enable the operator to adjust the apparatus for different types of fabric requiring different levels of restraint for alignment. The output of the resolution selector 90 is provided to the offset selector circuit 92 which receives an operator input from the input circuit 93. The offset selector circuit 92 allows the operator to predetermine the alignment offset desired. The offset selector input 93 provides the number M which designates a offset distance, measured in pulses from the speed indicator circuit 84, from matched alignment. Therefore, the offset selectors circuit 92 will not output any pulses to the counter 94 until this input offset distance has been achieved. The output of the offset selector circuit 92 is provided to counter 94 which accumulates the offset magnitude counts. When the second photo sensitive diode of the pair is turned on the sequencer 82 receives this indication and provides a RESET signal on line 86 accordingly. The RESET signal on line 86 outputs the contents of the counter 94 is provided to an operator display 98 and into a converter 96 which converts this digital signal into an analog signal through an output selector 100. The output selector 100 also receives an OFFSET DIRECTION signal 88 from the sequencer and provides a signal to the contact arm mechanism 106 which may result in either one of the contact arms 52 or 54 (Figure 1) restraining travel of its respective fabric piece. In the preferred embodiment, an initialization circuit 102 is provided to specify the minimum and maximum force of the contact arms 106 on the fabric. Also, in this embodiment, an OUTPUT TYPE switch 104 is provided to select either a restraining force proportional to the magnitude of the offset signal or a full force applied for a specific time. In this embodiment, the time is a specific interval but it should be apparent to those skilled in the art that the time of restraint may be varied in accordance with the magnitude of these offset alignment signals. Figure 3 is a schematic diagram of the position detector circuit components which consists of four light emitting diodes 104-107, in the preferred embodiment (Part No. SEP8506-1) that emit light to four optical detectors 100-103, in the preferred embodiment (Part No. SDP8600). The light detectors in the preferred embodiment are configured with schmidt triggered circuits such that the output is either on or off. The pair assembly is located such that fabric which passes along the path will block the light transmission from the emitters to the detectors. Therefore, light will only travel after the end portion of the fabric has passed. In the preferred embodiment, a path is provided for each fabric travel. Each path includes an individual set of light emitters and detectors having a corresponding locational relationship with emitters and detectors of the other path. Each path detector inputs the light indication signal into a logic circuit illustrated in Figure 4. For example, referring back to Figure 1, detectors 46 and 44, which are in a positional relation to each other, would input their signals to an EXCLUSIVE OR gate 110 which in turn provides an output to NAND gate 112 to OR gate 114 and finally to the bank NAND gate 116. Therefore, the EXCLUSIVE OR function of gate 110 will only provide an output when one or the other detector first receives light while the opposing detector is still covered. The output of gate 116 is the OFFSET COUNT signal. When both detectors at a location are uncovered the output of their EXCLUSIVE OR gate again becomes 0 resulting in the NOR gate 118 providing a RESET signal. The logic of Figure 4 corresponds to the Input Array circuit 80 of Figure 2. The output of this circuit, the GATE signal and RESET signal, are provided to the sequencer circuit 82 which is illustrated in Figure 5. The sequencer circuit 82 receives not only the RESET and GATE inputs from the Array circuit 80 but also reference pulses from circuit 84 which it uses as a clock. The clock signal is the output of the shaft encoder illustrated in Figure 1 and is input through a debounce circuit 124. In figure 5, the clock input is provided on terminal 122, the GATING signal on line 120 and the RESET signal on line 123. The clock and GATING signals are provided to counters 126 and 128, a 4522 circuit in the preferred embodiment, that are configured as a divide by N circuits where N is a resolution that is input by two switches 130 and 132. The output of this divide by N circuit or resolution selector circuit is provided to an offset selector circuit that includes counter 134, also a 4522. The offset selector circuit receives an operator input specifying an alignment offset represented by a number M. The counter 134 functions as a subtract by M circuit. The output of the offset selector counter 134 is provided to the counter 138 which is a frequency divider, Part No. 4017, that provides a parallel output to latches 140 and 142. This parallel output is provided to a digital to analog converter illustrated schematically as 144. Delay circuit 144 is provided to delay the RESET signal until the latched data has been output. This D/A converter includes a resistor ladder as shown that provides an output, when selected by switch 148, to amplifier 146 providing an output signal to a transducer. The D/A converter circuit 144 further includes a minimum force adjust switch 150 and a maximum force adjust switch 152. In the preferred embodiment, switch 148 is provided to vary the signal output to the transducer proportionally to the value stored in the latches 140 and 142 or to provide a maximum output as long as any alignment mismatch is detected. Figure 6 illustrates a display 160 that is provided to the operator displaying the amount of restraint being applied. In Figure 6, switches 162 and 164 are also provided which allow the operator to input the offset value M to the substract by M circuit 134 in Figure 5. Figure 7 illustrates the mechanical arm that is used to apply pressure to one of the fabrics to restrain the travel of the fabric. The arm 180 is pivoted about point 181 and connected by a pin 184 to a pneumatic cylinder 182. This cylinder is initially pneumatically charged to position the mechanical arm 180 over the fabric. The pneumatic cylinder 182 is connected by pin 192 to a lever arm 188 that is connected on one end to the table with pin 190 and on the other end to the transducer 186 by pin 189. The transducer 186 receives the signal from the output of the D/A converter 144 (Figure 5) to move the mechanical arm 180 to restrain travel of the fabric. At the end of the mechanical arm 180 is located a drag finger 183. The drag finger 183 is a cylindrical shaft extending horizontally across the fabric path. When the mechanical arm 180 is engaged, the drag finger 183 presses against the top surface of the fabric to restrain the fabric travel. In the preferred embodiment, the drag finger restrains the fabric movement provided by a sewing machine feed dog. In this embodiment, the reference pulse circuit 84 (Figure 2) producing the shaft encoded pulses previously discussed is connected to the sewing machine drive shaft that powers the feed dog and produces 480 pulses per feed dog cycle. When the feed dog engages the fabric from below then the drag will restrain the fabric travel from above when activated. Figure 8A, 8B, and 8C illustrate a fabric jig 200 that is used to position one fabric piece 204 above another fabric piece 202 as the fabric pieces are being sewn. In the preferred embodiment, this jig includes the position detection circuit devices. Figure 8A is a top view that illustrates the location of eight of the position detection devices. As previously explained, initially the fabric covers the space between the light emitter and the light detector devices inhibiting light transfer. The light transfer remains inhibited until the end portion of the fabric passes. In Figure 8A, the position detection devices will each indicate the passage of the fabric end portion at eight separate locations. Figure 8B illustrates the side view of the jig and further illustrates the vertical location of the light emitters and light detectors. In an embodiment, the light emitter 220 is positioned above the light detector 221 in the groove 203 of jig 200 which receives fabric piece 204. Fabric piece 202 is located underneath fabric piece 204 in groove 201 inhibiting the light transfer between the light emitter 220 and the light receiver 223. Figure 8C is an isometric view of jig 200 illustrating the location of fabric pieces 202 and 204.

Claims: An apparatus for aligning the end portions of two pieces of fabric as the fabrics are being sewn together, said apparatus comprising: A transport means (28, 24, 26, 30) for feeding the pieces of fabric (14, 16; 202, 204) along a path; a positional detecting means (32, 34, 36, 38, 40, 42, 44, 46; 100, 101, 102, 103, 104, 105, 106, 107; 210, 221, 222, 223) for providing a plurality of position signals, indicating the position of the end portion of the fabric (14, 16) as the end portion of the fabric (14, 16) travel across specific locations along the path; a reference pulse means (84) for generating reference pulses; a control means (110, 112, 114, 116, 118, 82, 90, 92, 94, 96, 100, 102, 104) connected with the reference pulse means (84) and said position detecting means (32, 34, 36, 38, 40, 42, 44, 46; 100, 101, 102, 103, 104, 105, 106, 107; 210, 221, 222, 223) for generating a positional difference signal in response to the position signals and the frequencies of the reference pulses, and for generating an alignment correction signal when the value of the positional difference signal is greater than a positional difference value whereby the magnitude of the alignment correction signal relates to the difference between the value of the positional difference signal and the positional difference value; and an alignment means (48, 58, 60; 50, 180, 182, 186, 188) for restraining the travel of at least one of the pieces of fabric (14, 16) along the path in response to the alignment correction signal, Characterized in said reference pulse means(84) generates the pulses in response to the feeding speed of said transport means (28, 24, 26, 30), and that the positional difference value has a predetermined value, and i n that the alignment means (48, 58, 60, 50, 180, 182, 186, 188) receives the alignment correctional signal, where the alignment correction signal is proportional to the number of pulses generated by the reference pulse means (84) in relation to the determined differential of the fabric piece positions. An apparatus as claimed in Claim 1, characteri sed in that said positional detecting means (32, 34, 36, 38, 40, 42, 44, 46; 100, 101, 102, 103, 104, 105, 106, 107; 210, 221, 222, 223) includes first groups (34, 38, 42, 46; 222, 223) and second groups (32, 36, 40, 44; 210, 221) of position detectors in that each position detector group (34, 38, 42, 46, 222, 223; 32, 36, 40, 44, 210, 221) includes a plurality of detector pairs (32; 36; 40, 44; 34; 38; 42; 46; 210, 221; 222, 223) whereby each pair (32; 36; 40, 44; 34; 38; 42; 46; 210, 221; 222, 223) includes a light emitter device (210; 222) and a l ight receiver circuit means, (221; 223; 32; 36; 40; 44; 34; 38; 42; 46) which provides an indication when light is received, and in that the pairs of each group (34, 38, 42, 46, 222, 223; 32, 36, 40, 44; 210, 221) are located along the path whereby each pair of the first group (34, 38, 42, 46; 222, 223) provides an indication when the end portion of the first fabric (14, 202) has passed the respective pair and each pair of the second group (32, 36, 40, 44; 210, 221) provides an indication when the end portion of the second fabric (16; 204) has passed the respective pair. An apparatus as claimed in Claim 1 or 2, characterised in that the first fabric (202) is located underneath the second fabric (204) and the alignment means (48, 54, 58, 60; 180, 182, 186, 188) only restrains the travel of the first fabric (202). An apparatus as claimed in any of the preceding Claims 1 to 3, characterised in that a travel path jig (200) is provided to locate the first fabric (202), below is the second fabric (204), and having a first fabric travel path (201) separate from a second fabric travel path (203). An apparatus as claimed in Claim 4, characterised in that the pairs of the first group (222, 223) are located along the first fabric travel path (201) and the pairs of the second group (210, 221) are located along the second fabric travel path (203). An apparatus as claimed in any of the preceding claims 1 to 5, characterised in that the alignment means (48, 58, 60, 50, 180, 182, 186, 188) includes at least one mechanical arm (48;50;180) positioned adjacent to the path and connected to a transducer (60;186) that activates in response to the alignment correctional signal causing the mechanical arm (48;50;186) to apply pressure against the fabric (14, 16) restraining said fabric travel. An apparatus as claimed in any of the preceding Claims 1 to 6, characterised in that the transducer (60; 186) is attached to a pneumatic means (182) for initially positioning the arm (48; 50; 180) adjacent to the path. An apparatus as claimed in any of the preceding Claims 1 to 7, characterised in that the magnitude of pressure applied is proportional to the magnitude of the alignment correction signal. An apparatus as claimed in any of the preceding Claims 1 to 8, characterised in that the pressure is applied for a time that is proportional to the magnitude of the alignment correction signal.

Inventors: CROYLE, GENE F.
Applicants: LEVI STRAUSS & CO.
Application year: 1986
Main classification: B65H7
IPC codes: D05B33, B65H43, D05B35, A41H43