Patent GB-974678-A (GB)
Title: Improvements in or relating to composite articles and method of fabricating them
IPC: H01B17/64
Filed: 1962-09-24
Abstract: 974,678. Assembling resilient insulating mounts. CAMBRIDGE THERMIONIC CORPORATION. Sept. 24, 1962 [June 20, 1962], No. 36211/62. Heading F2S. [Also in Division H2] A method of manufacturing a composite article composed of a dielectric body having an axial recess and performed of a material having the physical characteristics of polyfluoroethylene in solid state and of a rigid insert having on a stem a non-circular portion and an anchor portion with a sharply-edged taper portion to prevent relative axial movement between the body and the insert, comprises the steps of compressing the body in solid state to an outside diameter slightly smaller than the preformed outside diameter of the body and pressing the insert into the recess in the body while the body is compressed in the solid state whereby the body material flows into the spaces at and between the non-circular and anchor portions and the outside of the body remains essentially undistorted. As shown a cylindrical dielectric insulation body 21 of fluorocarbon resin has a flange 23 and a blind bore 24 for receiving a rigid electricallyconductive pin 31 which is made of metal or other suitable rigid material and has a stem 32 with a knurled collar portion 33, sharplyedged tapered anchor portion 35, and preferably a seating flange 36 and a soldering lug 37, which can be split or forked. The rotation-preventing collar 33 can be replaced by non-circular deformations such as fluted portions, the diameter of the stem 32 being slightly smaller than, and the knurled and anchor portions 33, 35 being considerably larger than, the recess 24 in the body 21 and the stem lengths between the portions 33, 35 and between the portion 33 and the flange 36 being of sufficient size to ensure that the body 31 will not tend to shear. The taper on the anchor part 35 is preferably 30 degrees the edge E, and the edge K on the knurled part 3, being made sharp and preferably undercut. The pin may extend out from both sides of the insulator body 21, and the portions 33, 35 of the pin can be increased in length as long as the neck dimensions remain sufficient. The cross-section of the insert and body can be polygonal, e.g. square of hexagonal. In carrying out the method the dielectric body 23 is squeezed in a segmented-die 56, 57 to reduce it by from one half to two per cent of its preformed outer diameter and then the insert pin 31 is forced into the recess 24 in the body 21, the segments of the die being separated when the insert pin has been fully driven home. Upon being released the body 21 has no expansion, the whole of the process taking place at normal ambient temperature in which the body acts as a solid. In a machine for carrying out the method three die-sectors 119.1-119.3 are secured by screws 120 to three resilient jaws 118.1-118.3 formed by slits 118.5-118.7 in a shank 111 which is screwed at 115 to a base 121 of a hydraulic actuating device having a piston 124 which is movable upwards against spring 128 to contract the jaws 118.1-118.3 by means of a supply of compressed air fed through a pipe 131. The die sectors are interchangeable for different sizes and shapes of composite article. The bottom of the die 116 is formed by an interchangeable rod 141 which is secured to a block 143 fastened to the shank 111 by a set screw 144 and which has an axial bore 147 to accommodate an insert with an extension such as 32.5, Fig. 7. For an insert, e.g. with a flange on its lower face, three die-forming jaws are movable along axes forming 120 degrees angles. A device for forcing the insert into the body 21 comprises a pneumatic piston and cylinder unit 172, 173 having a vacuum holding device 192.