Patent GB-1455156-A (GB)
Title: Hydraulic vibrators
IPC: B06B1/18
Filed: 1974-03-02
Abstract: 1455156 Vibrators KUIBYSHEV ZAVOD KOORDINAT STANKOV 2 March 1974 9577/74 Heading F2X A hydraulic vibrator comprises a casing 2 housing a stepped piston 7 having two portions 8, 9 of different diamters, a spring-loaded twoplunger slide valve 13 disposed coaxially in the piston 7, three chambers formed by the casing 2 and the piston 7, viz. a chamber 10 between the lateral surfaces of the casing 2 and the piston portion 9 of smaller diameter communicating at 6 with a source of hydraulic fluid under pressure, a chamber 11 between the casing 2 and one end of the piston 7 communicating at 5 with a drain line, and a chamber 12 between the casing 2 and the other end of the piston 7 communicating by means of the slide valve 13 first with chamber 11 and then with chamber 10 as the valve 13 slides relative to the piston 7. Additional chambers 16, 17 are formed in the piston 7 adjacent the valve plungers 14, 15. These chambers 16, 17 communicate with the chamber 10 through throttles 23 of constant section and with the chambers 11, 12 through throttles 25, 27 of variable section. The throttle 25 comprises two sharp-edged annular grooves 30, 31, groove 30 being in the casing 2 and adjoining groove 31 which is in the piston portion 9 of smaller diameter. The throttle 27 is fashioned as a "nozzle-choke" in which a nozzle 32 is provided on the end of the piston portion 8 of larger diameter and a choke 33 is secured on a bolt 34 provided in an end cover 3 of the casing 2. Initially the slide valve 13 is in the position shown with a channel 19 between the chamber 10 and a chamber 18 between plungers 14, 15 being blocked by the plunger 15 and the chamber 10 not communicating with the chamber 12. The chamber 12 communicates with the chamber 11 via a channel 21, the chamber 18 and a channel 20. Hydraulic fluid forced under pressure into the chamber 10 goes to the additional chambers 16, 17 via the throttles 23 and channel 22. As throttles 23 create a big drop in the fluid pressure between the chamber 10, chambers 16, 17 and the chamber 12, the piston 7 moves to the right. This travel of the piston 7 continues until the nozzle 32 approaches the choke 33 closely, thus creating in the additional chamber 17 a pressure sufficient to move the slide valve 13 to the left compressing the spring 29 and opening the channel 19 by its plunger 15 but closing the channel 20 by its other plunger 14. Hydraulic fluid from the chamber 10 will then flow to the chamber 12 via channel 19, chamber 18 and channel 21. The difference in the areas of the differential piston 7 on which the equal pressure in the chambers 10, 12 acts causes the piston 7 together with the slide valve 13 to move to the left until the circular groove 31 is overlapped to close the channel 24 intended for draining the hydraulic fluid from the chamber 16. Simultaneously, the pressure in chamber 16 will rise to equal that in chamber 17, while spring 29 will return the slide valve 13 to its initial position, after which the piston 7 will start moving to the right again repeating the reciprocation cycle. The frequency of the vibrations can be varied by increasing or decreasing the pressure of the fluid supplied to the chamber 10, while the amplitude is easily controlled by means of the choke 33.