GB767960A - Improvements in or relating to concrete vibrators - Google Patents

Abstract

767,960. Agitating appliances. JOHNSON (MACHINERY), Ltd., C. H. Feb. 2, 1955 [Jan. 8, 1954], No. 550/54. Class 86 [Also in Group XXIV] A vibrating unit for an internal concrete vibrator comprises a casing in which inner and outer out-of-balance elements are rotatably mounted coaxially one with the other so as to be angularly adjustable relatively to each other and having means for effecting such adjustment as the elements rotate whereby the amplitude of vibration generated can be varied in dependence upon the load on the vibrator. As shown, the vibrating unit comprises outer casing 10 connected to the outer casing 11 of a flexible driving shaft. Within the casing 10 is journalled the end 13 of an unbalanced rotor 14. Each end of the rotor has a cylindrical portion on which is journalled an outer unbalanced element 17. The element is provided at one end with a trunnion 14 journalled in a bearing 19 in the casing 10. The rotor 14 and element 17 are connected together by a torsion spring 20. Stops are provided on the unbalanced elements to limit relative angular movement between them. When the unit is at rest or running under light load the element 17 overlies the inner element 14 as shown in Fig. 5, providing the maximum amplitude of vibration. As compacting progresses the inner element will take an angular lead over the outer element and the amplitude of vibration will decrease. In an alternative arrangement the elements are arranged so that when at rest one element has a lead over the other and in addition a torsion spring is selected having two rates of loading, so that the amplitude of vibration is initially small, gradually building up to a maximum and gradually decreasing as the elements approach and pass the position where the outer one overlaps the inner one. In a further arrangement two separate torsion springs are used having different rates of loading.