1,208,839. Reciprocating motors. FMC CORP. 1 Nov., 1968 [2 Nov., 1967], No. 51917/68. Heading H2A. An electromagnetic impact vibrator comprises a housing 2 having a tubular portion 4 and an end cover 5, an electromagnet 43 mounted inside the tubular portion and secured to the end cover, and an axially movable body 14 connected to the tubular portion through an elastomeric spring 11, 12 and carrying an armature 21 adapted to be attracted by the electromagnet, the latter being energizable at a predetermined frequency so that on energization, the body 14 moves towards the electromagnet against the bias of the spring, and on deenergization, the spring forces the body 14 back in the opposite direction so that a striker 30 on the body strikes an anvil 32 on a base part 3 of the housing 2. An object to be vibrated is secured to the base 3. As shown in Fig. 1 there are two springs 11 and 12; in a modification, Fig. 4 (not shown) either or both of springs 11 and 12 is (are) replaced by a plurality of circumferentially spaced elastomeric blocks (60). The springs may be pre-loaded. Elastomer buffers 28 on the cover 5 limit upward movement of the body 14. The tubular portion 4 and cover 5 may be made of aluminium or synthetic resin and the anvil 32 may be made of steel, rubber or plasticized glass fibre. The electromagnet is energized from an A.C. supply through a diode 70, Fig. 10 (not shown). Coolant gas, e.g. air, passes through ducts 47, 48 in the tubular portion 4 and ducts 52, 53 in the cylindrical body 14. Cooling fins 62, Figs. 5, 6 (not shown) may be arranged on the tubular portion 4 and cover 5. In a modification, Fig. 11, the housing comprising two intermeshing parts 75, 73, the first carrying a core 85 and coil 91 and the second being connected through a single annular spring 80 to an armature 81, the latter carrying a striker 83 adapted to strike an anvil 78. The core 85 is axially movable to adjust the length of air gap 86.
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