Abstract: A piston-rack rotary actuator having four pistons each with an integral rack and each displaceable along a cylinder unique thereto, the racks meshing with a center gear at equiangularly spaced points and causing angular movements of a shaft about its rotational axis when said pistons are displaced along their respective cylinders, said gear being secured to said shaft. The racks are formed in respective webs which are supported by the actuator body in such a manner as to prevent piston-slewing which would otherwise occur due to the separating force generated by the meshing gear and racks when said racks are moved relatively to the gear.

Abstract: A piston rack rotary actuator, devoid of guiding tubes or rods along which the pistons reciprocate, is provided with guide bearings which eliminate or at least reduce the incidence of the separating forces which otherwise act on the racks (particularly when the pistons are moved towards one another) to displace them towards the cylinder wall and which thereby otherwise cock the pistons in the cylinder and cause scoring of the cylinder wall.

Abstract: A device for interconverting linear and rotatory motions, and particularly a pressure fluid operated actuator for rotary plug valves and the like. A piston axially slideable and rotatable in a cylinder is supported by first and second sets of connecting elements which are spaced from and inclined to the axis of the cylinder. Each element of one set is pivotally connected at one end with a fixed member and at the other with the piston. Each element of the other set is pivotally connected at one end with the piston and at the other with a rotary output element, for example, a shaft. Axial movement of the piston is translated into rotatory movement of the output element by pivotal action of the connecting elements. The connecting elements of the first and second sets extend from the fixed member to the piston and from the piston to the output element in opposite circumferential directions.