Patent GB-840437-A (GB)
Title: Improvements in or relating to impact tools
Inventor: PATEMAN REGINALD GEORGE FREDER
IPC: H01R43/26
Filed: 1957-07-02
Abstract: 840,437. Assembling force fits; spring hammers. HELLERMANN Ltd. July 30, 1958 [July 2, 1957], No. 20851/57. Class 83 (4). [Also in Group XXIII] An impact tool for inserting and extracting electrical terminal pins comprises a shaft slidable within and protruding from a housing and means within the housing for applying an impact to the shaft as a result of a predetermined relative movement between the shaft and the housing under a force applied to the protruding part of the shaft putting the shaft into either compression or tension according to the direction of the applied force, the impact being in the direction opposite to that of the applied force. The tool comprises a cylindrical housing 1 through which extends a shaft 2 and in which are located a drive spring 3, a hammer block 4, a spring-loaded cross-plunger 5 and a reset spring 6. The cross-plunger which is slidable in the hammer block has a bore 9 for receiving the larger part 2b of the shaft 2. An impact head is attachable to the end 8 of the housing and an extractor head to the end 1a. The housing is provided with a handpiece (not shown) which can be attached to either end of the tool. In operation, when used as an impact tool, the head is applied to the workpiece and the housing is urged towards the workpiece so that relative movement occurs between the housing and the shaft. When the cross plunger reaches the extremity of the enlarged portion of the interior of the housing it is moved inwardly until its bore is coaxial with the part 2b of the shaft whereupon the compressed drive spring 3 forces the hammer block against a shoulder 17 on the shaft to produce an impact on the workpiece. The shaft is returned to its initial position by the spring 6. When used as an extractor, the handpiece is attached to the end 8 of the housing and the extractor head to the shaft protruding from the opposite end of the housing. In operation, the extractor head is attached to the workpiece and the housing is withdrawn to load and release the spring 3 as hitherto. In a modification, so that both insertion and withdrawal of a terminal can be effected without making any change to the tool, two hammer blocks 42 and 43 with associated cross plungers 44 and compression springs 50 and 51 are provided (Fig. 3). A central sleeve 37 secured to the shaft 34 by a cross-pin slidably receives an upper shaft 36 fixed to the top of the tool housing. The sleeve is centralized by light springs 40 and the hammer blocks are separated by a centralizing ring 48. In operation, for insertion of a terminal into a socket, the terminal is placed in the head 54 and the housing is moved towards the head. The centralizing ring 48 causes the hammer block 43 to move with the housing and the hammer block 42 to move relatively to the housing to compress the spring 50 until the cross plunger releases the hammer block which imparts an impact to the sleeve and thence to the shaft 34. For extraction the head is engaged with the terminal and the housing is drawn away from the terminal to compress the spring 51.