Patent Publication Number: US-5290027-A

Title: Article positioning apparatus and method for positioning an article

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to apparatus and method for positioning an article and more particularly to such apparatus and method for positioning an article in an predetermined X position, Y position and predetermined angular orientation. 
     Automated manufacturing processes frequently require that the article being processed be precisely positioned before a certain operation on the article is performed. For instance, if a seam on a piece of fabric is to be sewn, it is necessary that the fabric piece be properly aligned before being fed into a sewing machine. The need for precise alignment has necessitated in the apparel industry that aligning just prior to sewing be carried out be hand, significantly adding to the cost of the process. In the past, automatic or machine accomplished alignment of fabric in one direction has been used. However, proper alignment of an piece of fabric in a plane requires orientation in two linear directions and angular orientation. In some instances, it is desirable to center the fabric before further processing. Moreover, the alignment must be accomplished quickly so that a bottleneck in the manufacturing process is not created at the alignment station. 
     SUMMARY OF THE INVENTION 
     Among the several objects of the present invention may be noted the provision of article positioning apparatus and method for positioning an article which positions the article in an X direction, Y direction perpendicular to the X direction, and in an angular orientation; the provision of such apparatus and method which carries out alignment in the X direction, Y direction and angular orientation simultaneously; and the provision of such apparatus and method which centers the article. 
     Article positioning apparatus constructed according to the principles of the present invention includes a positioning surface and means for sensing the location of an article on the positioning surface with reference to an X direction, with reference to a Y direction perpendicular thereto, and with reference to an angular orientation in the plane of the positioning surface about an axis generally perpendicular to the X direction and the Y direction. Means are provided for moving the article in the X direction, the Y direction and for rotating the article generally about the axis. Control means is responsive to said sensing means for selectively activating said X moving means, said Y moving means, and said rotating means. 
     A method of positioning an article on a positioning surface according to the present invention includes the steps of sensing the location of the article on the positioning surface in reference to an X direction, in reference to a Y direction perpendicular to the X direction, and in reference to an angular orientation in the plane of the positioning surface about an axis generally perpendicular to the X direction and the Y direction. The article is moved in the X direction in response to X direction sensing, in the Y direction in response to Y direction sensing and rotated generally about the axis in response to angular sensing. 
     Other objects and features of the present invention will be in part apparent and in part pointed out hereinafter. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic diagram of the apparatus; 
     FIG. 2 is a fragmentary top plan showing a manipulator arm; 
     FIG. 3 is a fragmentary top plan showing a sensor array; and 
     FIG. 4 is an elevation of the manipulator arm and supporting structure therefor. 
     Corresponding reference characters indicate corresponding parts throughout the several views of the drawings. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, an article positioning apparatus generally indicated at 10 for positioning an article such as a flat, limp work piece of fabric P is capable of orienting the fabric on the positioning surface with reference to an X direction, with reference to a Y direction and with reference to an angular or theta orientation 8 in the plane of the positioning surface about an axis generally perpendicular to the X direction and Y direction, as indicated by the coordinate system 12 in FIG. 3. The apparatus includes a table 14 having a positioning surface 16 thereon made of a relatively slick material, such as a sheet of anodized aluminum or stainless steel, on which fabric may freely slide, and a manipulator, indicated generally at 18, for sliding the fabric work piece P over the positioning surface. The manipulator 18 is controlled by a microprocessor (controller 20), such as Shark model XL programmable controller manufactured by Reliance Electric Company of Cleveland, Ohio. 
     The microprocessor 20 is responsive to signals generated by a sensor array on the positioning surface which includes two laterally spaced X-theta sensors (indicated 26 and 28, respectively), two laterally spaced Y sensors (indicated 30 and 32, respectively), and a rear X sensor 34. The sensors each include two photoelectric eyes which are offset one from the other. The photoelectric eyes of the X-theta sensor 26 are designated 26A and 26B, respectively, and the photoelectric eyes of the X-theta sensor 28 are designated 28A and 28B, respectively. The photoelectric eyes of the Y sensor 30 are designated 30A and 30B, respectively, and the photoelectric eyes of the Y sensor 32 are designated 32A and 32B, respectively. The rear X sensor has two photoelectric eyes, designated 34A and 34B, respectively. The photoelectric eyes are preferably Keyence Fiber Optic Photoelectric Sensors, model FS2-60 manufactured by Keyence Corporation of Osaka, Japan and distributed by Keyence Corporation of America, Fairlawn, N.J. The photoelectric eyes operate by emitting light which is reflected by reflective tape 38 applied to the positioning surface 16 under the eyes. Referring to FIG. 3, the photoelectric eyes of the X-theta sensors 26, 28 and rear X sensor 34 are offset in the X direction, with the eyes 26A, 28A rearward of the eyes 26B, 28B. The photoelectric eyes 30A, 32A of the Y sensors are offset in the Y direction laterally inwardly of the eyes 30B, 32B. The function of the offset of the photoelectric eyes in the operation of the apparatus will be explained below. 
     The manipulator 18 includes a positioning arm 40 having a pad 42 of high friction material, such as foam rubber, mounted on its lower end for engaging the fabric work piece P. The upper end of the arm 18 is formed as a gear 44 adapted to intermesh with a worm gear 46 driven by an electric theta motor 48 for rotating the positioning arm about its long axis in the theta direction. The manipulator 18 and theta motor 48 are supported on a bracket 50 (broadly, &#34;first frame member&#34;) mounted on a ball screw mechanism, generally indicated at 52, driven by a Y motor 54 for selective motion in a Y direction along a second frame member 56 to which the ball screw mechanism is fixedly mounted. As shown in FIG. 2, the Y motor is mounted by a bracket 57 to the second frame member 56 and attached by a belt 52A to a screw 52B of the ball screw mechanism for rotating the screw and driving a ball nut 52C in the Y direction. The bracket 50 is connected to the ball nut 52C for motion therewith. The second frame member 56 is slidably mounted by a pair of rods 60 to a third frame member 58, which permits sliding motion between the second frame member and the third frame member in a vertical direction. An air cylinder 64 mounted on the third frame member 58 is attached to the second frame member 56 and connected to a source of air under pressure (not shown). Activation of the air cylinder 64 to raise and lower the second frame member 56, Y motor 54, ball screw mechanism 52 and manipulator 18 to move the pad 42 into and out of engagement with the fabric work piece P is controlled by the microprocessor 20. 
     The third frame member 58 includes slider blocks 66 for mounting the third frame member on a pair of vertically spaced rods 68 extending in the X direction along the side of the positioning surface 16 and mounted on the table 14 by support plates 69. An X motor 70 is mounted by a bracket 72 on the same side of the table 14 for driving a belt 74, riding on a pair of pulleys 76, to which the third frame member 58 is connected by a connecting portion 78. The X motor 70 is controlled by the microprocessor 20 for moving the third frame member 58 in the X direction. Limit sensors 80 are located at either end of the rods 68 to detect the third frame member 58 at the extreme forward or rearward X locations. Signals from these sensors 80 cause the microprocessor 20 to stop movement in the X direction, regardless of the indications from other sensors (26-32), thereby preventing an overrun. 
     In the embodiment of the invention disclosed herein, a mechanism is provided for centering the fabric work piece P in the Y direction. The mechanism, which includes the two movable Y sensors 30, 32 is used when the next operational step on the work piece requires, for instance, folding it in half and sewing together overlying portions of the folded fabric work piece. An example of a commercially available machine requiring a folded work piece is AMF model 84-35 semi-automatic pocket bag sewing machine manufactured and sold by AMF Apparel Machinery Company of Richmond, Va. However, it is to be understood that for many applications, centering of the fabric work piece is not necessary and a only a single, fixed Y sensor is required to locate an edge of the fabric work piece. 
     The X-theta sensors 26, 28 and Y sensors 30, 32 are mounted on a frame including laterally spaced stanchions 86 which are attached in a suitable manner, such as by bolting, to the table 24 The stanchions 86 support a rod 88 and a screw 90 which extend between the stanchions. The X-theta sensors 26, 28 are mounted by brackets 192 on the rod 88 in a fixed position. However, by loosening a set screw 94 on the brackets 92, the X-theta sensors 26, 28 can be adjusted in the Y direction as needed for the particular shape and size of the fabric work piece P to be positioned. The Y sensors 30, 32 are each mounted by a sleeve 96 on a laterally extending bar 98. The location of the Y sensors 30, 32 may be adjusted in the Y direction by loosening the set screws 96A and sliding the sleeve 96 along the bar 98. The bar 98 is attached by a similar sleeve 100 with a set screw 100A for adjustable positioning in the X direction on an arm 102. The arm 102 has a tubular bearing member 104 at its forward end slidingly supported on the rod 88 for motion lengthwise of the rod 88 in the Y direction. The bearing member 104 is attached to a ball nut 105 on the screw 90 which is selectively turned by an electric ball screw motor 106 controlled by the microprocessor 20. The screw 90 has two components 90A, 90B, connected together by a coupling 110, which are threaded in opposite directions so that rotation of the screw in a first direction moves the Y sensors 30, 32 toward one another, and rotation in the reverse direction results in the Y sensors moving away from one another. 
     A fabric feed mechanism also supported by the frame has a pair of feed belts 112 operable by an air cylinder 114 connected to the source of pressurized air (not shown) and operable, upon receiving a signal from the microprocessor 20 that the fabric work piece P has been properly aligned, to move the feed belts 112 into engagement with the fabric work piece. Thus, the fabric work piece, once aligned, is withdrawn from the positioning surface 16 to the workstation where the next operation can be performed on the work piece. 
     OPERATION 
     The fabric positioning apparatus of the present invention operates to simultaneously monitor and position the fabric work piece P in the X, Y and theta directions. The apparatus is controlled by the microprocessor 20 programmed with the commands listed in the attached Appendix. The commands for X-Y-theta orientation of the work piece begin at line 77 and continue through line 238. The remaining commands deal with other operations of the apparatus. 
     The operation begins with the delivery of a fabric work piece P onto the table 14 which continues delivering the fabric forward in the X direction to the positioning surface 16 by means of feed conveyors 120 in the table (FIG. 2). The work piece P initially blocks the rear X sensor 34, and in response the microprocessor 20 causes the feed conveyors 120 to drop below the positioning surface 16 so that forward movement of the work piece in the X direction is stopped. At the same time, the air cylinder 64 is activated by the microprocessor 20 to drop the second frame member 56 and bring the manipulator pad 42 into engagement with the fabric work piece. 
     After a one-half second delay, the X motor 70 is activated and the manipulator 18 is moved forward, sliding the fabric work piece with it over the slick positioning surface 16. The forward motion in the X direction continues until the fabric work piece blocks photoelectric eye 26A of the X-theta sensor 26 or photoelectric eye 28A of the other X-theta sensor 28. Upon receiving the appropriate signal from one of the eyes 26A, 28A of the X-theta sensors the microprocessor 20 deactivates the X motor 70 and forward motion in the X direction stops. Orientation of the fabric work piece in the theta direction commences according to the readings of the X-theta sensors 26, 28. The goal of theta orientation is to achieve an X-theta sensor reading wherein the eyes 26A, 28A are blocked by the work piece P, but eyes 26B, 28B are unblocked, as is shown in FIG. 3. If, however, the eye 26A is blocked, but the eye 28A is unblocked, the microprocessor 20 will activate the theta motor 48 to turn the manipulator pad 42 in a counterclockwise direction. The theta motor 42 is controlled to turn the fabric in a clockwise direction if, on the other hand, the eye 28A is blocked, but the eye 26A is unblocked. 
     At the same time the theta orientation is being achieved, the X location of the work piece is monitored. For instance, should the rotation of the work piece cause all of the eyes of the X-theta sensors 26, 28 to become unblocked, the microprocessor 20 will activate the X-motor 70 to move the work piece further forward in the X direction. Similarly, if all of the eyes of the X-theta sensors 26, 28 become blocked, the X motor 70 will be activated to move the work piece rearwardly. The monitoring of the X and theta positions is carried on concurrently, with the X motor 70 and theta motor 48 operated independently of each other by the microprocessor 20. Once both X and theta alignment is achieved, the movement of the manipulator 18 is stopped for one-half second before the X-theta sensors 26, 28 are reactivated, to allow the work piece to stop between movements and to give the microprocessor 20 time to get an accurate reading from the X-theta sensors. 
     After completion of the initial X and theta alignment, orientation of the work piece P in the Y direction is begun. In this embodiment, Y orientation involves centering the work piece between the laterally spaced Y sensors 30, 32. At the beginning, the Y sensors 30, 32 are located at positions laterally outwardly from the lateral edges of the work piece an equal distance from a line about which the work piece is to be centered. Satisfaction of the X and theta orientation requirements causes, after the described delay, the activation of the ball screw motor 106 for turning the screw 90 in a direction which brings the Y sensors 30, 32 toward one another. Eventually, the laterally inner eye of one of the Y sensors, for instance eye 30A, will be blocked by the fabric work piece. In response to such a signal, the microprocessor 20 activates the Y motor 54 to move the work piece in a Y direction away from the Y sensor 30 which has detected the work piece. The Y motor 54 moves the work piece faster than the movement of the Y sensors 30, 32 toward one another. Movement away from the sensor 30 continues until the lateral edge of the fabric work piece is detected by the laterally inner eye 32A of the other Y sensor 32. If the inner eye 30A of the Y sensor 30 is unblocked, the Y motor 54 is activated to move the work piece back in the Y direction toward the sensor 30. Back and forth motion in the Y direction occurs until both of the laterally inner eyes 30A, 32A of the Y sensors are blocked and the laterally outer eyes 30B, 32B are unblocked. Motion away from a particular Y sensor is also triggered when the laterally outer eye (30B or 32B) of that sensor is blocked. As shown in FIG. 1, Y limit sensors 124 are provided which are disposed to detect the Y motion of the manipulator 18 to prevent an overrun in the Y direction. 
     At the same time Y orientation is occurring, the X-theta sensors 26, 28 continue to monitor the leading edge of the fabric work piece. Should the Y motion cause, for instance, eye 28A to become unblocked while eye 26A remains blocked, the theta motor 48 will be activated at the same time Y orientation is being carried out to rotate the work piece counterclockwise. Similarly, if a situation occurs where both eyes 26A, 28A are unblocked or both of the forwardmost eyes 26B, 28B are blocked, the X motor 70 will be activated to move the work piece in an appropriate X direction (forward in the first situation, and rearward in the second). Thus, it may be seen that X, theta and Y orientation are simultaneously carried out by the apparatus of the present invention. 
     As previously mentioned, it is frequently not necessary to center the fabric work piece. In that event, only one Y sensor, located for detecting one lateral edge of the work piece, is necessary. The operation of the apparatus is substantially as before, but the Y sensor remains stationary and the work piece is brought to the Y sensor by the manipulator. Again, monitoring and repositioning in the X and theta positions occurs simultaneously with the Y orientation. When all of the sensors read one eye blocked (i.e., eyes 26A, 28A, 30A and 32A) and the other eye unblocked (i.e., eyes 26B, 28B, 30B and 32B) the microprocessor 20 determines that orientation is complete. Operation of the air cylinder 114 brings the feed belts 112 into engagement with the work piece and the feed belts are activated to draw the work piece off of the positioning surface 16 and into the workstation, and the manipulator 18 is moved back to its start position rearwardly of the sensor array for positioning the next work piece. 
     In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained. 
     As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. ##SPC1##