Patent GB-1387751-A (GB)
Title: Method and apparatus for inductively heating valve seats
IPC: H05B6/02
Filed: 1972-02-14
Abstract: 1387751 Induction heating PARK OHIO INDUSTRIES Inc 14 Feb 1972 [9 June 1971] 6789/72 Heading H5H A conical surface of a body, e.g. the valve seat D of an engine head B, is heat treated by a single turn inductor 30 whose shape matches the surface, the inductor 30 being reciprocably mounted on a support frame 20 which is movable towards and away from said surface and being biased towards the surface, e.g. by spring 190. In operation, the frame 20 is moved towards the surface with the inductor 30 generally aligned with the surface, the movement of the inductor 30 is stopped at a predetermined distance from the surface, e.g. by the engagement of the inductor 30 with its valve seat D, the frame 20 continues its movement towards the surface and is then stopped, the inductor 30 is locked to the frame 20 by locking device 12, the frame 20 and inductor 30 are moved away from the surface a predetermined distance and the inductor 30 is energized. In a practical embodiment a plurality of inductors are reciprocably mounted on a common frame 20 so that they can all be simultaneously accurately spaced from their appropriate conical surface. The inductor 30 is also mounted for transverse movement to enable it to align with the conical surface D. At tone end of the inductor 30 is an insulating insert 50 which holds the inductor 30 in place and is provided with a tapered tip 52 which in operation registers with a bore F in engine head B and tends to shift the inductor 30 transversely into concentric relation with valve seat D. The inductor 30 is connected by hollow leads 32, 34 to concentric insulated tubes 36, 38. An insulating carrier 60 mounted on tube 38 supports the inductor 30. The carrier 60 is mounted for transverse movement in a support frame 70 by means of ball cages 94, 96 between bearing rings 90, 64 and 66, 92. The support frame 70 is mounted on a rearwardly extending sleeve 72 which may only move towards and away from engine head B. The carrier 60 and inductor 30 are centred by means of a pair of spring-pressed balls 134 mounted in the carrier 60 which co-operate with a pair of conical cam surfaces 120 provided in the support frame 70. A pin 140 carried by frame 70 co-operates with a bore 150 in carrier 60 to prevent rotational movement of the carrier 60. The locking device 12, Fig. 12, comprises a frame 170 supporting a housing 172. Within housing 172 are two aligned bearings 174, 176 which reciprocably support the sleeve 72. Rotation of the sleeve 72 is prevented and axial movement thereof limited by a key 182 cooperating with a keyway 184 in the sleeve 72. Spring 190 acting between bearing 176 and support frame 70 bias the inductor 30 towards the valve seat D. The sleeve 70 is locked in a predetermined longitudinal position relative to housing 172 by a clamp ring 202 which surrounds the sleeve and which can be locked on to the sleeve 70 and released therefrom by a cylinder 210 and rod 212. Switches 230, 232 are used to indicate whether the locking device is locked or unlocked. The inductor 30 is supplied by a 1 : 1 transformer 14. Transformer 14 has a single sheet primary 272 (Figs. 6 and 7) connected to insulated bus-bars 250, 252 by input strips 260, 262. Hollow conductors 274, 276 are provided on the single sheet primary and a series of flux concentrators 280 are provided within the primary 272. A single sheet secondary 290 with hollow conductors 392, 396 surrounds the primary and is spaced therefrom by a gap 299. Secondary 290 is cantilever supported on the coaxial insulated tubes 36, 38 and by virtue of gap 299 can follow the transverse movement of inductor 30. One end 29 of secondary 290 is coupled to tube 36 by a block 302 welded to the end 298 and a clamping plate (not shown) for clamping tube 36 against the block 302. The other end 296 of secondary 290 is connected to tube 38 by a block 322 welded to end 296 and a co-operating clamp plate (not shown). The construction of the transformer permits axial and transverse movement of the secondary winding. An arm 340 carried by block 302 actuates a switch to indicate forward movement. The primary 272 is cooled by coolant flowing from inlet 380, to hollow strip 262, a pair of passages 382 extending through conductors 274, 276, passage 384 in hollow strip 260, and outlet 386. The secondary coolant circuit comprises an inlet 390, circumferential tube 392, a cross-over conductor 394, tube 396 and outlet 398. The inductor cooling circuit comprises (Fig. 8) an inlet 400, a cavity 402 in block 302, ports 404 in tube 36, tube 36, lead 32, inductor 30, lead 34, a port in tube 38, annular passage 412, ports 414, cavity 416 in block 322 and outlet 418. Reference is made to Specifications 1,387,761, 1,387,762, 1,387,763 and 1,387,805.