Patent GB-799244-A (GB)
Title: Improvements in powder compacting presses
IPC: B29C43/00
Filed: 1955-11-14
Abstract: 799,244. Powder-compacting presses. BLISS CO., E. W. Nov. 14, 1955 [Nov. 17, 1954], No. 32507/55. Class 87(2). A moulding die and opposed pressing dies of a powder compacting press define a mould chamber in which material is compacted by relative movement of the pressing dies and means associated with one of the pressing dies cause the moulding die to move therewith and further compact the material and the other pressing die moves relatively to the moulding die to eject the compressed material. At the start of a cycle the parts are in the relative positions shown in Figs. 3, 18 and 19a. A slide 12 which carries an upper die 13 and is reciprocable by a crank shaft is in its upper position. A table 15 which carries a mould 16 and is also reciprocable is held in its upper position by rods 19 which carry pistons 20, 21 reciprocable in cylinders 22, 23. The rods 19 pass through the table 15 and have bumpers 19a at their top ends. Hydraulic pressure beneath the pistons 20, 21 holds up the table 15 at the start of the cycle. A cylinder 32, to which a lower die 30 is adjustably attached by a screwed connection rests freely on a fixed casing 33. Rods 34 depend from the bottom of the cylinder 32 (passing through the casing 33) and carry a piston 36 reciprocable in a cylinder 37 forming the top part of a casing 38. A pit 6 accommodates the lower members. Inside the casing 38 is another cylinder 40, accommodating a piston 41 on a piston rod 42 extending from the piston 36. The casing 38 is supported from the slide 12 by rods 39 ; thus at the start of the cycle the pistons 36, 41 are at the bottoms of their cylinders. The slide 12 first moves down and the die 13 moves into the mould 16 until the slide has made contact with the table 15 and upper die adjusting blocks 13a seat on the top of the table 15, the powder charge A thus being initially compressed around a core 55 and against the lower die 30, Fig. 19b. At this point the slide 12 causes e.g., by a solenoid, a valve 26a to open and release pressure from the cylinders 22, 23 so allowing the table 15 and mould 16 to move with the slide for the remainder of the downstroke, whereby the powder is finally compressed from the bottom by the lower die 30 into the article B, Fig. 19c. The casing 38 also moves downwards and the piston 41 compresses the air above it in the cylinder 40 and a space 43 above oil 44 contained in the annular chamber between the walls of the casing 38 and cylinder 40. A tubular passage 45, Fig. 5, in one side of the casing 38 provides communication between the lower part of the space 43 and the bottom of the cylinder 37 when a valve 46 is open. This valve 46, closed by fluid pressure on a piston 47 through a valve 48b, is opened by operating the valve 48b to allow the oil behind the piston to bleed off. The valve 48b is solenoid operated by movement of the slide 12. At the start of the cycle the valve 48b is open and so is the valve 46 and the air pressure in the space 43 therefore forces oil into the bottom of the cylinder 37 beneath the piston 36, oil under pressure also passing through a port 50 to hold the valve 46 open. When the slide 12 commences its upstroke it causes the valve 48b to operate to close the valve 46 and stop oil from flowing back from the cylinder 37, resulting in the die 3. being hydraulically locked to the upward movement of the die 13. During this upward movement fluid pressure is admitted to the lower ends of cylinders 22, 23 and the table 15 is raised to its upper position, Fig. 11. The core 55 remains stationary, and there the die 30 forces the article B upwards, starting to strip its inner surface from the outer surface of the core without at the same time stripping the outer surface of the article from the mould, Fig. 19d. The core 55 is connected by a stem 57 to a piston 58 reciprocable in a cylinder 59 in the casing 33, Fig. 18. A chamber 60 surrounds the cylinder 59 with which it can communicate through a passage 61, Fig. 4, as controlled by a valve 62 similar to the valve 46 and operated from the slide 12 by a valve 63b similar to the valve 48b. The valve 62 remains closed as the slide 12 descends until the table 15 begins its downward movement at which time the valve 63b is solenoid operated to release the plunger 63 and the valve 62 thereupon opens to permit downward movement of the core 55 with the table 15 to the position shown in Fig. 19c. The valve 63b is then operated to close the valve 62, compressed air thus being imprisoned in the chamber 60 above the oil. So the core remains stationary for the Fig. 19c and Fig. 19d parts of the cycle, as already mentioned, and also till the top of the die 30, in its upward movement, comes level with the top of the core 55, Fig. 19e, completing the stripping of the article B from the core. At about this time the valve 63b is operated to cause the valve 62 to re-open and allow the oil under pressure to act on the piston 58 to raise the core 55 to its highest position, so stripping the outer surface of the article from the inner surface of the mould until it is entirely ejected, Fig. 19f. Stripping in stages, as described, eases the removal of the compressed article. The full ejection position is reached shortly before the end of the cycle, at which time also the valve 46 re-opens and allows the lower die 30 to drop to its starting position, Fig. 19a. At the end of the cycle the crank shaft is stopped, the articles B are removed and the mould is recharged with powder to be compressed.