Patent GB-546875-A (GB)
Title: Improvements in hydraulic cutting machines
IPC: B23D15/14
Filed: 1941-10-22
Abstract: 546,875. Hydraulic machines; valves. RIDDLE, W. J. Oct. 22, 1941, No. 13577. Convention date, March 28. [Classes 69 (ii) and 135] A hydraulic system which is particularly applicable for operating a machine for cutting sheet metal, paper, &c. in which a cutter bar is operated by piston rods 3 and the work is clamped by a series of piston rods 9, is so constructed that the cutter bar cannot be operated until the rods 9 have been operated to clamp the work in position. Upon the retracting stroke however the plungers which operate the cutter and the clamp are operated substantially simultaneously. The hydraulic system is indicated diagrammatically in Fig. 4, and comprises a pressure pump 43 the pressure pipe of which leads to a four way valve 31 which is actuated electromagnetically to start the operation by a push button 69 which energizes an electromagnet 67 to close the circuit of another magnet 54 adapted to move the valve 31 so as to connect the pressure pipe 47 to a pipe 13a connected to an admission valve 15, constructed as shown in Fig. 3. The valve 15 has a permanent connection between the pipe 13a and a pipe 13 leading to the cylinders 7 of the pistons 8 which are in the first place depressed against the action of springs so as to clamp the work. When the pressure in the valve 15 increases to a given value a valve 81a is opened against the action of an adjustable spring 82a to admit the liquid to a pipe 16 leading by a pipe 17 to the cylinders 1 so as to depress the pistons 2 and rods 3 and the cutter bar. The pistons 2 cannot descend until a spring-closed valve 27 is opened by pressure admitted by a pilot-line 28 connected to pipe 13a. At the commencement of the descent of the bar the liquid leaves via pipes 18, 26 and returns to pipe 13a via a valve 27, non-return valve 30, pipe 29, and so returns to the top of the cylinders 1. Before the pistons 2 move so as to complete the cut the outlet 19 is cut off and greater resistance to the pistons is met, as the outlet is now via pipe 22, choke valve 21 and pipes 18, 20. By adjusting the valves 21 the final movement may be slowed down as desired, and finally an adjustable screw on the cutting bar operates a limit switch 64 which de-energizes the solenoid 67 and permits a spring 74 to move the valve 31 owing to the de-energization of the magnet 54. The flow is now reversed and pressure passes from pipe 47 to pipe 32, and the pipes 13, 13a are connected to pipe 35 and tank 36. The pressure fluid passes through a valve 33, check valve 34 and pipes 26, 18, 20, and check valves 23 to the bottoms of cylinders 1. The pipe 13 is connected direct to tank 36 so that the springs 10 return the clamping bar quickly. The liquid leaves the pistons via pipes 17, 16, 24 and check valve 25 thus byepassing valve 15. Due to drop in pressure in pipe 13a the valve 27 cuts off connection between pipes 26, 29. At the end of the rise of the cutter bar a projection 77 operates the valve 31 mechanically to cut off the power by connecting the pipe 47 to tank. The bar may be given an "inching" movement by closing a shut-off valve 33 and opening a needle valve 39 to allow the weights of the pistons 2 to expel a small quantity of liquid through the valve 39. At the same time liquid is admitted to the tops of the pistons via a small check valve 41.