Patent GB-670074-A (GB)
Title: Improvements in molding machine for molding plastic articles
IPC: B29C43/08
Filed: 1948-05-21
Abstract: 670,074. Moulding electrical insulators &c. in rotary-mould-table machines &c. GILBERT, C. E. May 21, 1948, No. 13842/48. Class 87(ii) . A mould comprises an upper die 43, Fig. 15, having a cavity for shaping the exterior of the article, and a force member 53 having a head 55 for shaping the interior of the article. Force 53 is slidably positioned within a sleeve 54 which itself is slidably disposed in a vertically stationary member 31. Force 53 is shown retracted within sleeve 54 to provide a loading cavity. Into this loading cavity is fed moulding material such as "Bakelite" (Registered Trade Mark), then the force and sleeve rise together until the sleeve abuts die 43, as shown at 63, Fig. 5. Then the force rises to the Fig. 14 position to compress the (heated) material, descends to allow gases to escape, and rises again to mould the article. Finally the force and sleeve descend to the Fig. 15 position, the moulded article being left standing on the sleeve, whence it is removed by discharge mechanism to a place where a hole may be punched in it. The invention is described in connection with the making of plugs forming parts of electrical connectors of the type described in U.S.A. Specifications 2,012,627, 2,060,617, 2,183,016, 2,229,286 and 2,283,889, by means of a continuously-rotary-table machine. Fig. 1 is a plan view of the machine, Fig. 2 an elevation and Fig. 5 a developed view of the circular rotary moulding cylinder. Each upper die 43 is fixed on a rod 45 and slidably mounted in a part 43<SP>1</SP> of the cylinder, and is backed by a spring 47. Each force assembly comprises a force 53, sleeve 54, and another sleeve 56 which is held frictionally on force 53 by a spring 60 on a pin 58 disposed in a slot 57 in the sleeve to allow relative motion between 53 and 56. Each force carries a roller 49 which runs on a camtrack 51. The mechanism for feeding moulding powder to the mould units comprises a bar 5, Figs. 6 and 7, having;a chamber 16<SP>1</SP> at one end. The bar is reciprocated by a cam in the direction of its length, presenting the chamber alternately to a hopper 4, where it is filled, and a sleeve 54, which it fills. The bottom of the chamber is formed by a pivoted plate 18, which is pushed aside by the top of sleeve 54, as the latter rotates, to allow powder to drop into the sleeve. When the chamber is retracted, a stationary block 24 returns plate 18 to the closed position. In operation, with a moulding unit at position Bl, Figs. 5 and 15, moulding material is fed by the chamber 16<SP>1</SP> into sleeve 54, then the force 53 and sleeve rise to the position shown at 63, Fig. 5, and finally the force rises along cam-incline 62 to position B2, Figs. 5 and 14. The unit then runs along a level cam part 64, then the plunger assembly descends to the position B3, Figs. 5 and 13, being pulled down by a rocking lever Q which engages the axle 50 of the wheel 49. The gases are thereby released from the mould. The plunger assembly then continues up a short cam-incline 66 to a level portion 67 to re-close the mould, pressure being thus maintained until a gap 61 in the cam track is reached. Here the plunger assembly is pulled down by a member P having a head 69 which engages axle 50, until it reaches position B1, the sleeve 54 being prevented from descending all the way by the engagement of a collar 54a thereon with fixed stops 54b. The moulded plug is left standing on the sleeve 54, whence it is removed by mechanism comprising (Fig. 6, plan, and Fig. 9, elevation) two cam-operated bars 83, 84, secured together by a pivot 85 and sliding in guides 81, 82. Bar 83 has a pivoted spring-controlled extension 87 having a square opening 90 at its end. The bar 83 is held down by a spring-pressed roller 103. As the two bars 83, 84 move from left to right a pin 86 on bar 83 rides up cam 94. The opening 90 is thereby raised over a moulded article. The pin drops off the cam, and the extension 87 drops, the opening fitting over the plug. The plug is initially slightly oversize, having expanded on leaving the mould, but the opening 90 re-forms it to the required shape and size. The bars then retract to the left, and the extension 87 drags the plug up a gangway 106 to a position where a punch 114 descends to punch a hole in the plug and another punch 124<SP>1</SP> rises to remove flash from the inside of the plug. The punch 114 is surrounded by a cup member 123, which fits over the top of the plug, and is carried on a rod 122 secured to a crosshead 119 fast on a rod 117' which is moved up and down by a cam-operated lever 115. The punch 124<SP>1</SP> is reciprocated by a cam-operated lever 125. The flash falls down one shoot and the finished plug down another. Periodically a cam-operated lever 75 opens a valve 77 to allow a blast of air to blow through pipe 79 to remove powder spilt during filling of sleeves 54. Electric current for heating the cylinder and moulding mechanism is supplied to a radiant heater 37 from conductors 41; 42, through brushes which bear against a rotary shaft 28<SP>1</SP> and sleeve 28 to which .are connected leads 38, 39.