Patent GB-1440254-A (GB)
Title: Electro-magnetic element movement control means
IPC: B29C45/82
Filed: 1973-09-17
Abstract: 1440254 Injection moulding machines DEMAG KUNSTSTOFFTECHNIK ZWEIGNIEDERLASSUNG DER DEMAG AG 17 Sept 1973 [16 Sept 1972] 43566/73 Heading B5A [Also in Division H1] A control device (Fig. 1) comprises electromagnets 2, 3, 4, 5, each having an annular core of soft iron surrounded by a coil, serially operating at predetermined spacings; magnet 2 being screwed to base 13 of housing 1. The further magnets 3, 4, 5 are spacedly linked to corresponding displaceable sleeve elements 6, 7, 8 concentrically surrounding an innermost displaceable plunger 9, slidable in base 13 against spring 18 in recess 17 which bears against washer 16 and adjusting nut 15 of the plunger. Abutments 11 are provided at corresponding ends of the sleeves, one overlying another in an inoperative position, which bear as a unit against nut 15. Sleeve 8 is displaceable in response to magnet 5, sleeve 7 in response to magnet 4, and sleeve 6 in response to magnet 3. Plunger 9 is threaded to yoke 10 under cover 12 which is spaced from magnet 5 in turn spaced from magnet 4, which is spaced from magnet 3 spaced in turn from magnet 2. Individual magnets are energized over a multiple cable 20 and connecting strip 22 under cover 21. On energization of magnets 2, 4 (Fig. 2, not shown) plunger 9 moves outwardly by a total displacement equal to the sum of two individual displacements, e.g. to set the ram pressure valve of an injection moulding machine; the magnet signals being effective to cause magnets 3, 5 to abut magnets 2, 4 so that the displacement of magnet 5 displaces sleeve 8 and that of magnet 3 displaces sleeve 6; also displacing sleeve 7 of magnet 4 through abutments 11. The added movements of magnets 3, 5 are thus translated to plunger 9 which is displaced outwards through the total movement against spring 18. Yoke 10 and magnet 4 also move but preserve their mutual displacement, and may be subsequently energized to produce a further displacement of plunger 9, and the magnets 2, 3, 4, 5 may be selectively energized to produce (2<SP>n</SP>-1)=15 positions of displacement where n is the number of magnets. Further magnets may be used with the predetermined displacement of each being 2Î that of the preceding magnet. On deenergization of magnets 2, 4 spring 18 restores plunger 9 to its original position. The device controls the pressure valve 44 of an injection moulding machine (Fig. 3) to regulate ram pressure; the moulding machine comprising a plasticizer worm 34 rotatable in a cylinder 35 and axially displaced by pressure on a piston 38. During homogenization actual resistance pressures peculiar to the operation and the substance are applied to the plasticizer worm by application of an hydraulic medium from pump 41 and triple valve 43 to the head of piston 38; valve 43 opening communication to ram pressure set valve 44 controlled magnetically from control programme store 1 to regulate flow from cylinder 39 to tank 51, and thus estalish a required pressure resisting the axial movement of the worm 34. Pressure valves are controlled from the programme to magnetically adjust the position of plunger 9 and valve 44. On completion of a plasticizing operation, worm 34 and piston 38 are in a fully rearward position and are restored to their initial position by cessation of control signals to plunger 9, and valve 43 is changed over so that pump 41 pressurizes cylinder 40 directly to inject plastic into mould 32. The pressure values for a cycle of operations may be computed and fed into the programme store.