Patent GB-572973-A (GB)
Title: Improvements in or relating to pressing machines
IPC: B28B3/02
Filed: 1943-10-12
Abstract: 572,973. Moulding, concrete &c. blocks. RICE, C. J. Oct. 12, 1943, No. 15418. [Class 87 (ii)] Relates to pressing - machines suitable for pressing concrete or the like in moulds, for example in making building units of the kind described in Specifications 561,881 and 566,801, [both in Group X]. According to the invention, a ram is vertically reciprocable towards and away from a bed supporting the base of a mould, spring mechanism normally urging the ram upwardly and being so arranged that the upward pressure is greatest when the ram is in the upper part of its stroke, and pedal-operated means are provided for varying the pressure exerted by the spring mechanism. Depression of the pedal decreases the spring pressure exerted upwardly on the ram, while release of the pedal allows the spring pressure to increase. Actuation of the ram by means of hand levers is thus facilitated. The machine shown comprises a ram 4 carried by a cross-head 5 which is slidably mounted on columns 2 for reciprocation relatively to a mould 10, the ram being adapted to enter the mould at the bottom of its stroke. The mould is mounted on a platform 11, which may be adjustable in height, and which has an opening to accommodate a tray 12 at the bottom of the mould, as described below. The bed 13<1>, on which the tray 12 is slidable, may be adjusted vertically by a hand wheel 16. A plunger 7 extending from the ram is guided in a cross member 8, and carries a collar 9 to which weights may be fitted. The ram is cushioned at the top of its stroke by means of a spring 20 adapted to engage a collar (not shown) on the plunger, and at the bottom of the stroke by means of adjustable and resiliently mounted plates 22 co-operating with the plate 5. Swing- ing catches 25, adapted to engage automatically with projections on the plunger when the ram is at the top of its stroke, are provided to lock the ram in its uppermost position when desired ; the catches may be moved by hand so as to be inoperative, if required. A pin which may pass through a hole 33 in the plunger may be provided as an additional locking device. Plunger-operating mechanism.-The ram and plunger are operated by means of a pair of bellcrank levers 34; 36 (only one of which is shown), the arms 34 of which are slotted to engage, with pins 40 on brackets mounted on the plate 5. Each of the arms 36 is anchored to the base of the press by means of springs 42, 45 connected together by a chain 43 and turnbuckle 44. When the ram is lowered by depressing the handles 35 of the levers 34, the springs 42, 45 at first exert their maximum opposition to downward movement of the ram, but as the line of action of the springs approaches the pivotal axis of the bell-crank levers, the turning moment exerted by the springs decreases until little or no opposition is offered during the lower portion of the stroke. Adjustable rollers 46 are preferably so mounted as to engage the chains 43 at a selected point of their movement, so that the point in the stroke of the ram at which it is allowed to fall under its own weight may be predetermined. A treadle-operated lever 47 is arranged to act on the springs 45, so that the pull of these springs is counteracted by depressing the treadle before the handles 35 are pulled down to lower the ram. When the ram is to be raised, before lifting the bell-crank levers the treadle is released, so as to allow the springs 45 to become effective in assisting to raise the ram. Hand control of the levers may be dispensed with, the machine being modified to be operated by foot control only. Moulds, strickles, and delivery devices.- The mould 10 is preferably of the kind which can be opened to allow lateral removal of the moulded article. The tray 12, Fig. 4, having a pallet 14 thereon which normally lies below the mould to support the moulded article, is drawn forward to remove the article when the mould is opened. Outward movement of the tray is limited by a buffer on an adjustable screw 17. Associated with the mould is a hopper 50 and a screeding member or strickle 51, slidably mounted thereon. Before the mould is filled, the screed 51 is drawn forward over the front of the mould, and the moulding aggregate is then raked from the hopper into the mould. The charge is levelled and excess is removed by pushing back the screeding member. A modified form of screed consists of an apertured flat plate forming a false bottom to the hopper.