Patent GB-661930-A (GB)
Title: Improvements in and relating to extrusion presses
IPC: B21C23/21
Filed: 1949-04-06
Abstract: 661,930. Extruding. LOEWY ENGINEERING CO., Ltd. April 6, 1949 [April 24, 1948], No. 9348/49. [Class 83 (iv). In a press for extruding metal tubes, having a die, an extrusion ram or stem and a removable unit comprising a mandrel and a mandrel holder, the mandrel unit is retractable to a freely accessible position remote from the operating zone of the press for effecting the exchange of one unit for another. In one form, the extrusion press comprises a die 31, billet container 36, extrusion stem 35 and mandrel 43 secured to a holder 44, Fig. 1. The extrusion stem is mounted in a holder carried by a main crosshead 33 movable by rams 32 in cylinders 20 to effect the extrusion of the billet 90. Retraction of the cross-head 33 is effected by cylinders 38 acting through pull rods 37. The rear end of the mandrel holder has an enlargement 45 adapted to fit within a bore 47 of a piercer stem 48, adapted to be moved forwardly to effect the piercing of the billet by cylinders 49A mounted in a fixed cross-head 39 and carrying rams 50 connected to a movable cross-head 42 which may be coupled to the stem 48 by a clutch or coupling 51. On the withdrawal of the stem 48, the mandrel holder is ejected by a rod 66 projecting forwardly into the stem from a stop 67. A disc 55 may be provided on the stem 48 so as to abut the cross-head 33 and so apply the force of the piercing cylinders to the extrusion stem also. In order to withdraw the mandrel into the extrusion stem immediately upon the release of pressure in the piercer cylinders 49A a retraction device may be provided comprising hydraulic cylinders 59, Fig. 4, kept under pressure and connected with a member 60 guided in the cross-head 33 and engaged by the enlarged end 45 of the mandrel holder during a piercing operation. Complete retraction of the mandrel and stem 48 takes place in three stages, firstly by the cylinders 59, then by the rearward movement of the cross-head 42 and lastly by means of doubleacting shifting cylinders 62 mounted in the cross-head 42, the coupling 51 having to be released before this latter withdrawal can be made. As the stem 48 approaches the point at which the mandrel holder 44 is ejected therefrom, a roller 74 on the disc 55 engages and rotates a pivoted member 73, Fig. 10, and so brings into position mandrel-supporting arms 69 which co-operate with transfer arms 76 actuated by a cylinder 80, Fig. 8, to transfer the heated mandrel to a rotating carrier device by which a number of mandrels are carried intermittently through a cooling station. A cooled mandrel is then carried back into alignment with the stem 48 which is moved forwardly by the cylinders 62 so that the end of the stem receives the end 45 of the mandrel, and the disc 55 operates the member 73 in the reverse direction to withdraw the supporting arms 69. After re-engaging the clutch 51 to secure the stem 48 to the cross-head 42, the press is ready for a further piercing and extruding stroke. In a modification, Fig. 16, the main extrusion-stem operating-cylinders 130 are located at the sides of the piercer stem 131, the mandrel cooling means is mounted on the top of the press and the transfer arm 140A is operated by a hydraulic cylinder 142 through a flexible chain 143. In another modification, the extrusion stem is operated by a single cylinder having a ram with a bore which is traversed by the piercing stem.