GB764634A - Improvements in or relating to presses suitable for use in performing cutting operations on sheet materials - Google Patents

Abstract

764,634. Cutting-out presses. BRITISH UNITED SHOE MACHINERY CO., Ltd. Jan. 31, 1955 [Feb. 11, 1954], No. 2768/53. Class 31 (1). [Also in Group XXIX] In a press comprising a bed 10 and a presser member, e.g. a beam 16, between which sheet material 12 and a cutting die 14 are positioned, and power-operated means for bringing about relative movement of approach between the bed and presser member, to cause penetration of the sheet material by a cutting edge of the cutting die, and, subsequently, relative movement of separation between the bed and presser member, control means for the power-operated means is provided which is so constructed and arranged as automatically to arrest the relative movement of approach between the bed and presser member in the urging of the cutting edge of the cutting die through the sheet material, as a consequence of the engagement of the cutting edge of the cutting die with the bed. In the form shown, the power-operated means comprises a piston and cylinder device 20, 22 connected with a spindle 18 carrying the beam 16, and a valve 38 for controlling the admission of pressure fluid to the cylinder 22, the valve rod 40 being movable between two positions corresponding to the admission of pressure fluid to opposite ends of the cylinder. The valve rod is connected to a solenoid 50 which is included in an electric circuit containing a switch 56. The bed and beam comprise oppositely-disposed portions of electricallyconducting material which are included in an electric circuit containing a thyratron 100 in the anode circuit of which is a relay 76 adapted, when opened, to de-energize the solenoid 50, the relay 76 having in parallel therewith a time-delay means comprising a number of capacitors 152 with which coact a switch arm 158. The bed 10 comprises a plate 92 of aluminium or other electrically-conductive metal to which is bonded a layer 94 of electrically conductive rubber or plastic constituting a cutting block. The bed 10 rests upon a sheet of insulating material 96, e.g. fibreboard. In operation, when a spring-influenced handle 82 on the beam is depressed, the switch 56 is closed to energize the solenoid 50. This causes the valve rod to be moved downwardly to admit pressure fluid to the upper end of the cylinder 22 with consequent downward movement of the beam. When the cutting edge of the die 14, which is also of electrically-conducting material, completely penetrates the sheet material 12, it bridges the gap between the electrically-conducting portions of the bed and beam to close the electric circuit including these portions. The closing of this circuit renders the thyratron 100 conducting. After a very short time interval determined by the position of the switch arm 158 relatively to the capacitors 152, the relay 76 is opened to deenergize the solenoid 50. The valve rod is then moved upwardly under the action of a spring 54 to admit pressure fluid to the lower end of the cylinder 22 with consequent upward movement of the beam. The fluid-pressure operated means may be replaced by mechanical means. The sheet material may be electrically conducting, e.g. metal foil.