1295116 Vibrators; connecting-rods VIBRATECHNIQUES SA 19 Nov 1970 [21 Nov 1969] 55085/70 Headings F2T and F2X A vibrator comprises a support 12 for a mass, e.g. of concrete, to be vibrated and means for vibrating the support, the latter including a reciprocable connecting-rod 15 having an elastic portion 23 between two rigid portions 21, 22 for increasing the acceleration of the support when it is near its extreme positions of vibration. The elastic portion 23 (Fig. 2) comprises a piston 24 connected to the connecting-rod big end by the rigid portion 22, and adapted to slide in a cylinder 25. This cylinder is closed at both ends by screw stoppers 26a, 26b. The stopper 26a is fixed to the rigid portion 21 and hence the cylinder 25 is connected to the connecting-rod little end. Each of the faces of the piston 24 is provided with a groove 27 receiving the end of a coil spring 28a, 28b bearing respectively against the stoppers 26a, 26b. The springs apply opposite forces to the piston 24 and when the elastic portion 23 is not subjected to any longitudinal stress, these opposite forces tend to hold the piston 24 and cylinder 25 in an intermediate relative position. The big end 16 of the connecting-rod 15 is connected to a pulley 17 driven by a motor 18, and its little end is connected to a piston 14 adapted to reciprocate in a cylinder 13 communicating with a container 1. The container 1 surrounds a coaxial cylinder 3 and the annular chamber resulting is filled with oil and closed at the top by a flexible diaphragm 6. A guide piston 9 fastened at the top to a ring 10 is adapted to slide in the cylinder 3, the ring 10 being integral with a suport table 12. The bottom surface of the ring 10 rests on the diaphragm 6, the vibrations of which are thus transmitted to the table 12. The elastic portion 23 stores energy in the course of its forward and rearward strokes and releases this energy at the ends of the strokes, with the result that for a constant speed of rotation of the pulley 17 the acceleration of the piston 14 is reduced towards the middle of each of its strokes and increased at the end of the stroke, the overall acceleration of the piston 14 (and therefore of the support 12) tending to be practically constant.