GB1250468A - - Google Patents

Abstract

1,250,468. Casting machines. GEB. BUHLER A.G. 1 Nov., 1968 [8 Nov., 1967], No. 51833/68. Heading B3F. [Also in Division B5] In a die-casting machine having a mould cavity 13 connected to a gas suction device 50 via a shut-off valve 52 and having an injection monitoring element 60 positioned near the connection between the cavity and the suction device, control of the shut-off valve 52 is effected by an adjustable time switch 72 which is started in dependence on the commencement of injection. A time measuring device which may be constructed as part of the time switch, is provided for ascertaining the time interval from injection commencement and/or the closing the shut-off valve 52 to the response of the injection monitoring element 60, the value ascertained by the time measuring element being used for adjustment of the time switch. The time measuring element and the time switch may be constructed as one unit 72 or they may be separate units connected by a time delay element (93), Fig. 2 (not shown). Molten material is fed into the injection sleeve 9 through an aperture 10 and is then forced into the mould cavity 13 by a piston 19. At the commencement of injection the cam 15 on the piston-rod 14 moves away from the contact 76 which then closes and switches on the time switch 72. As soon as the piston 19 has closed the aperture 10, the cam follower of the vacuum control switch 69 runs off the cam 15, switches on the solenoid 63 and opens valve 53 thus allowing the mould cavity to be evacuated by the suction fan 50. When an arm in the time switch 72 reaches a pre-set control cam 721, the change over contact 74 is operated and thus causes the shut-off valve 52 to close. The time switch 72 continues to run as a time measuring device until molten material impinges on the injection monitoring element 60. The time interval between commencement of injection and the response of the injection monitoring element 60 is thus known and the position of the control cam 721 can be adjusted accordingly in preparation for subsequent injections. In an embodiment, the position of the control cam 721 is adjusted automatically between each operational cycle in dependence on the time interval measured by the time measuring element during the previous cycle. The actual time interval used for this adjustment is the time measured by the time measuring element minus the time delay associated with the time delay element (93). This time delay is so chosen as to be approximately equal to the time elapsing between excitation of the solenoid 62 and complete closure of the vacuum line 51 by the shut-off valve 52. The shortest time interval measured by the time measuring element during several previous cycles of the machine may be used as the basis for the adjustment.