Patent GB-291389-A (GB)
Title: Tube-expander for water tubes, smoke tubes and other tubes
IPC: B21D39/10
Filed: 1927-12-29
Abstract: 291,389. Gradenwitz, H., and Neumann, H. J., (trading as Elektromotoren-werke H. Gradenwitz). June 1, 1927, [Convention date]. Tube expanders.-In a tube expander of the kind in which rollers are radially adjusted in a cage by a driven conical mandrel screwed in a . spring-pressed nut, the spindle which during operation and during withdrawal, is driven in the same direction, is controlled by a movement of the nub relative thereto so as to give a slow feed to prevent straining or deformation of the tube. A mandrel 3 with a squared rear end 4 so that it may be rotated clockwise by hand or by a motor, has a left hand square thread 2 engaging a nut 12, which is pressed against a casing 7 by a spring 13 through a ball bearing 11. The mandrel is grooved at 8 to engage a key on a flanged slidable sleeve 10 provided with recesses engaging claws 25 on a gear wheel 24 lcosely mounted thereon. This wheel 24 is connected by gears 23, 22 to a wheel 21 having pins 27 passing through longitudinal slots 26 in the nut. On rotating the mandrel the nut is rotated in the same direction at a higher speed and the mandrel is thus fed forward. When the resistance increases at the end of the operation the nut feeds back against the pressure of the spring and pushes back the sleeve 10 to release the clutch 25 and stop rotation of the nut. The mandrel rotating in the stationary nut is thus withdrawn and the nut is pushed forward by the spring into its initial position. The pressure of the spring is adjusted by an angularly adjustable abutment ring 16 having serrated rear edges 17 engaging similar edges on the end of the part 18. The mandrel may be rotated anti-clockwise in which case the screw threads are right handed. The Specification as open to inspection under Sect. 91 (3) (a) comprises also other forms of tool. In one form the nut may be driven by friction gear. In a form, Fig. 3, Cancelled, in which a reversely tapered mandrel is used, a right hand thread is used with a clockwise rotation of the mandrel. The mandrel is first fed inwards and when the pressure increases the nut feeds outwards and, being connected by levers 31 to the sleeve 10, forces the sleeve inwards to release the clutch and then stop the nut, whereupon the mandrel is fed outwards. In a further form, Fig. 2 (Cancelled), the composite gear 22, 23 is replaced by two gears loosely mounted on a pin 30 and having oblique engaging surfaces. When in operation the wheel 23 drives the wheel 22. After the clutch 25 is released to stop the nut and thus withdraw the mandrel the tendency of the mandrel to rotate the nut is avoided by the rotation of the wheel 22 which engages the wheel 23 so as to force their outer ends into contact with the sides of the casing which act as a brake to ensure stopping of the nut. The time of disengagement of the clutch is varied by the use of sleeves 10 of different sizes. The roller cage may be rotatably mounted on ball bearings on a fixed casing provided with a handle. A flange on the cage may engage between ball bearings fixed to casing by a box nut, or a flange on the casing may engage between ball bearings on a screwed ring and an extension from a disc on which the rollers are lever mounted. In some cases the nut may rotate more slowly than the mandrel. This subject-matter does not appear in the Specification as accepted.