Patent GB-822803-A (GB)
Title: Apparatus for winding or unwinding a length of flexible material
Inventor: CHITTENDEN GEORGE EDWARD
IPC: B65H23/195
Filed: 1954-12-10
Abstract: 822,803. Unwinding thread &c. KEELAVITE CO. Ltd. Nov. 30, 1955 [Dec. 10, 1954], No. 35891/54. Class 120(2) [Also in Groups XVI and XXIX] An apparatus for winding or unwinding a length of flexible material, e.g. a wire, thread, cord or the like, comprises a winding drum driven by a hydraulic motor, a pump connected to the motor, metering pumps driven by the winding drum and a second drum, a variable relief valve to control the pressure of hydraulic fluid to the inlet of the motor, a control pressure passage connecting the outlet of one metering pump with the inlet of the other, the pressure in this passage being maintained constant so as to control through the relief valve the pressure of fluid supplied to the motor, thereby maintaining constant tension in material extending between the second drum and the winding drum. As shown, a web 1 is wound on a drum 2 driven by a hydraulic motor 4 through a shaft 3 which drives a variable capacity pump 9. A constant speed motor 7 drives the shaft 8 of a feed roller or drum 5 co-operating with a roller 6, the shaft 8 driving a fixed capacity pump 10. The outlet of the pump 10 is connected by a pipe 13 to the inlet of the pump 9, while the outlet of the pump 9 is connected by a pipe 15 to the right hand end of a cylinder 16 and the inlet of the pump 10. The left hand end of the cylinder 16 is connected by a pipe 18 to the pipe 13. A piston 19 within the cylinder 16 is urged to the left by a spring 20. A rod 22 attached to the piston 19 actuates a lever 21 to vary the capacity of the pump 9 and is extended by a rack 23 engaging a pinion 24 on a shaft 25 carrying a cam 26. The cam 26 actuates a valve 27 which controls the supply pressure from a pump 28 to the motor 4. In operation, at the commencement of a winding operation, the pumps 9 and 10 have approximately the same capacities, such that the pressure in pipe 13 is small. As the diameter of the roll being wound on the drum 3 increases the speed of the drum 3 and therefore the pump 9 will decrease with respect to the drum 5, thereby increasing the pressure in the pipe 13 to move the piston 19 to the right and consequently rock lever 21 to increase the capacity of pump 9, thus reducing the pressure in the pipe 13. Movement of the piston 19 causes rotation of the cam 26 to close valve 27 to increase the torque transmitted by the motor 4. Thus, by choosing a suitable profile for the cam 26 the torque applied to the shaft 3 may be varied to maintain constant tension in the web 1. During unwinding, the motor 4 acts as a pump absorbing power at a pressure determined by the setting of the valve 27, thus exerting the appropriate braking torque on the shaft 3 in dependence of the speed ratio between the drum 2 and roller 5 to maintain constant web tension. In a modification, the motor 7 has a variable speed to permit variations in winding speed and the pump 10 may have a variable capacity controlled independently of the pressure sensitive device. Reference has been directed by the Comptroller to Specification 711,486 [Group XXIX].