Patent GB-1501112-A (GB)
Title: Gripper assemblies for use in shoe upper conforming machines and shoe upper conforming machines incorporating such gripper assemblies
IPC: A43D23/02
Filed: 1974-04-11
Abstract: 1501112 Lasting shoes, &c BRITISH UNITED SHOE MACHINERY CO Ltd 10 April 1975 [11 April 1974 22 Feb 1975] 16387/74 and 7529/75 Addition to 1225023 Heading A3B A shoe upper conforming machine for pulling over and lasting the forepart and joint regions of an upper, e.g. as in Specification 1010149, and having a number of grippers to lock onto the margin of the upper, each gripper including detecting means which allows the lasting margin to slip between its jaws until a pre-determined amount of lasting margin remains between the jaws, at which time the jaws exert increased gripping pressure and pull the upper over the last, has the detecting means provided by a beam of light extending from one gripper jaw to the other with a detector sensitive to the interruption of or passage of the beam of light between the jaws. As shown, grippes jaws 2, 4, Fig. 1, have light transmitting pipes 14, 16; 20 consisting of optical fibres. Light transmitted through the pipe 14 is returned by the pipe 20 to the pipe 16, unless an excess width of the lasted margin between the jaws 2, 4 acts as a shutter and obstructs the beam. If this occurs, the lasted margin is slidden out from between the lightly engaged jaws 2, 4 until the light beam is uninterrupted, and the jaws are then engaged more firmly with the lasted margin. Instead of the light transmitting reversing pipe 20 in the jaw 4, another arrangement of optical fibres or a prism may be employed. Control is effected by a circuit, Fig. 5, having a light source S adjacent the ends of light pipes 14. Energization of a pneumatic servo 36 associated with each gripper 2, 4 against the biass of its spring is effected by opening a solenoid controlled valve SV 17, compressed air passing through pipes 13, 15; 17, 19; pressure reducing valves 21, 23; and valves W, Z to the servos. The jaws 2, 4 thus grip the lasting margin with a pressure determined by the pressure reducing valves 21, 23, it being assumed that the lasted margin interrupts the beam through the optical pipes 14, 16. As the lasted margin is withdrawn from between the jaws 2, 4, the beam is no longer interrupted. According, light is transmitted to a photoresistor 66 associated with each gripper, which is connected to an amplifier 62 in turn connected to a relay R operating a solenoidactuated valve SV 18, SV 19, respectively. Pilot air supplied through the valve SV 18 or SV 19 then shifts the valve W or Z, which connects full pressure air to the servo 36 of the associated gripper, for full power engagement of the jaws 2, 4 with the desired width of the lasting margin. In a modified construction of gripper having light transmitting pipes 214, 216; 220, Fig. 6, a spring biassed detent 225 coacts with a cam stop 223 on the servo piston rod effecting the closure of the gripper jaws 201, 203, so that under light pressure the jaws are closed only so far as to engage lightly with the upper margin. Under full pressure, the detent 225 is overcome for firm engagement with the upper margin. The position of the detent 225 relative to the servo housing is adjusted in dependence upon the thickness of the upper by turning a nut 235 meshed with a screw 233 carrying the detent.