Hydraulic rotary actuator

Expansible chamber devices – Rectilinearly moving working member and coaxial or parallel... – Element extends through working member portion

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Details

92 31, F01B 300

Patent

active

059185309

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention relates to a hydraulic torque motor comprising a housing with a central boring, an annular piston, which can be moved axially in the housing's boring, but which is prevented from rotating about its longitudinal axis in this boring and a substantially cylindrical rotor which extends axially through the piston, and which can rotate about its longitudinal axis in the housing, but cannot be moved axially in relation thereto, there being provided in the rotor's outer surface at least one spiral groove and the piston has at least one engagement element which extends radially into the groove, the housing's boring together with one end section of the piston partially defines a first cylinder space and together with the piston's second end section partially defines a second cylinder space, the cylinder spaces are arranged for alternate connection with a source and a reservoir for a pressure fluid for movement of the piston axially between two end positions in the housing and thereby rotation of the rotor between two associated angle positions via the engagement element, at each end of the piston there is a radially outwardly projecting end flange which is arranged for sealing and sliding abutment against the housing's boring, and the housing has a centre flange which at the central area of the housing's boring, considered in the axial direction, projects radially inwards, and which works in conjunction with a section of the piston between the end flanges.


DESCRIPTION OF THE PRIOR ART

In torque motors of this kind the housing can be connected to a stationary part such as a valve body and the rotor is connected to the valve element, the valve element being rotatable for opening or closing of the valve.
A torque motor of the above-mentioned type is known, e.g. from DE 39 18 400. In this torque motor the cylinder spaces are defined by the rotor, which causes the hydraulic fluid to come into direct contact with the spiral groove and the engagement element inserted therein, i.e. those sections or components of the torque motor which are particularly prone to wear, with the result that the hydraulic fluid can easily become polluted by particles which have been worn off these parts, and which can contribute to a reduction in the working life of the motor and increase the need for its maintenance.
Since the rotor is instrumental in defining the cylinder spaces, i.e. it comes into contact with the hydraulic fluid, and the groove is not open at the ends of the rotor, the rotor cannot simply be replaced with a rotor with a differently shaped groove, e.g. with a different pitch in order to obtain a rotary distance of a different length. Thus this torque motor cannot easily be adapted to, e.g., valves with different strokes.
Furthermore from EP application no. 34069 there is known a torque motor with a housing which has a centre part with coarse, internal screw threads. The cylinders are screwed fast to each side of the centre part. In the cylinders' heads there are mounted bearings for a spindle. A piston with coarse, external threads is screwed into the centre part and has internal, axially extending splines which engage with corresponding, external splines of the spindle. The piston can rotate about its own longitudinal axis. The pitch of the threads together with the pistons' axial movement in the cylinder determine the spindle's rotation.
With this torque motor none of the components can be replaced for alteration of the torque motor's characteristics such as the required torque, rotary strokes and the like, without the hydraulic system being opened. Even though no alteration can be obtained of the motor's characteristics by replacing a spindle, even a replacement of this kind cannot be carried out without the hydraulic system being opened. The only alternative is replacement of the entire torque motor. Nor can the spindle be secured to the torque motor's housing in order to prevent rotation of the spindle and the bodies which are operated thereby when the pistons have been move

REFERENCES:
patent: 2705592 (1955-04-01), Reiser
patent: 2932206 (1960-04-01), Tootle
patent: 4196654 (1980-04-01), Sterns
patent: 4882979 (1989-11-01), Weyer
patent: 5046402 (1991-09-01), Lagace
patent: 5241895 (1993-09-01), Weyer

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