Field of the invention.

The present invention relates to a hydraulic torsional motor, comprising a cylindrical housing, a cylindrical annular piston which can be moved axially inside the housing, but which is prevented from being rotated relatively thereto, and a cylindrical rotor situated inside the piston, coaxially therewith, and which can be rotated about its longitudinal axis relatively to the housing by axial movement of the piston, but which is prevented from moving axially, whereby an annular chamber in which the piston is situated is closed by end closures and has a greater length than the piston and is coupled to a supply of a drive fluid for axial movement of the piston in both directions, and whereby meshing members causing rotation of the rotor protrude into inclined recesses.

Prior art Such torsional motors are used for converting axial movement into rotational movement.

Axial movement of the piston, which is prevented from rotating, is transferred through the meshing members as rotational movement of the rotor, which is prevented from moving axially. Such a torsional motor is in the principle known from German patent application No. 3918400. The print shows a piston in the form of a sleeve; i. e. that the piston is an annular piston, having radially inwardly protruding studs meshing with inclined, for instance helical grooves in the rotor, which is situated coaxially with the piston, in the inside thereof. Rotation of the piston is prevented by balls, which protrude into axial grooves in the piston and the housing, respectively. Axial movement of the rotor is prevented by ball bearings. The piston is shorter than the chamber in which it is situated, whereby the piston can be forced axially in said chamber, by a fluid, for instance hydraulic oil or compressed air, which is supplie to the chamber near the end from which the piston is to be forced.

The axial force acting on the piston, and which is converted into torque for the rotor, is determined by the pressure of the fluid and the area of the end surfaces of the piston, while the torque at a given axial force among else is determined by the radius on which the meshing members are situated, because this radius is the"arm"which together with the rotational force determines the torque (rotational force x arm), and the rotational force is a component of the axial force, determined by the inclined direction of the grooves.

When the dimensions of the main components of the torsional motor, the location of the meshing members and the pressure of the fluid are given, the ratio between axial force against the piston and the torque transferred to the rotor mainly is determined by the inclined direction or pitch of the helical grooves, and such that a large pitch gives a relatively large torque but a relatively small angle of rotation of the rotor (per unit length of the axial movement of the piston), while a small pitch gives a relatively small torque but a relatively large angle of rotation. Thus, the choice of pitch may, when other parameters are given, be used for determining the ratio between axial force and torque.

However, the choice of pitch cannot be made unlimited, because in practice limitations will be present regarding the overall dimensions of the torsional motor and the forces which can be transferred by the meshing members. Such torsional motors are among else used in places where the space is limite, and it may be of great importance that the overall dimensions of the torsional motor are relatively small. The overall dimensions are, however, partially determined by the inner dimensions, and in particular the length and the diameter of the piston and the rotor.

In the torsional motor according to the German application 3918400 the meshing members are, as mentioned, studs fastened to the piston, and protrude radially inwardly, into grooves in the piston. Provided a given pitch for the grooves and a given axial force from the piston, the torque supplie to the rotor will be proportional with the"effective" radius at which the forces are transferred, and which in this case will be somewhat smaller than the external radius of the rotor. (The studs protruding somewhat into the rotor are not necessarily in engagement in the external surface of the rotor). Similarly, a given torque will be transferred with a force being inversely proportional with the "effective"radius.

Description of the invention.

The torsional motor according to the invention is characterized in that the inclined recesses are situated in the piston and that the meshing members protrude radially from the rotor.

Thereby is achieved that the"effective"radius has been increased, provided that the remaining dimensions are the same. The surfaces which transfer torque, i. e. the surfaces on the studs and the side surfaces in the grooves, are thus situated in the piston on the outside, i. e. on a larger radius than when they are situated in the rotor on the inside (provided that the dimensions of the components are given).

Thus, for a torsional motor of given dimensions and other features a given torque can be transferred by a smaller force, compared with a torsional motor having the studs protruding into grooves in the rotor. With a given force an increased torque can be transferred.

Therefore, the invention entails the possibility of achieving reduced wear on the studs and in the grooves, due to decreased surface pressure in the contacting surfaces, or transferring an increased torque with a corresponding wear as in the prior art motor, i. e. with the same surface pressure.

Explanation of the drawings.

The invention will in the following be explained more detailed, with reference to the accompanying drawings, showing an exemplary embodiment of a torsional motor according to the invention.

Fig. 1 shows a longitudinal section through a torsional motor according to the invention.

Fig. 2 shows a cross section through the torsional motor, along the line A-A in Fig. 1.

Fig. 3 shows in perspective a piston included in the torsional motor.

Description of an embodiment The Figs. show a torsional motor comprising a housing, formed by a cylindrical wall 1 and end flanges 12,13. At one end of the housing are shown two flanges 12 which abut each other, and having chamfers which together define an annular space for balls 17 which provide rotary journalling of a rotor 3, in that the balls 17 protrude into an annular groove in the rotor 3, which thereby is prevented from moving axially relatively to the housing 1.

The two flanges 12 and the flange 13 are kept together by axial bolts 18, in the example shown four bolts 18 (see Fig. 2), which in the example shown have been screwed into threaded holes in the flange 13.

Between the cylindrical wall 1 and the rotor 3 is a cylindrical piston 2, which can be shifted axially within a chamber 29 between the wall 1 and the rotor 3. The shifting of the piston 2 takes place in that a fluid, such as for instance hydraulic oil or compressed air, is supplie to the chamber 29 in which the piston 2 is situated. The wall 1 has two apertures for supply of fluid, in pipe stubs 10 which are fastened to the wall 1 and which

form coupling sites for not shown hoses or pipelines from a pump. Thus, the piston 2 can be forced towards that end of the chamber 2 to which fluid is not supplied. Sealing rings 11, of which two are mounted below one of the flanges 12 and below the flange 13, respectively, while two are mounted on a respective one of ends of the piston 2, provide sealing for the fluid.

A carrier bolt 4 extends radially through the rotor 3, and the ends of the bolt 4 extend through a respective one of inclined slits 5 (Fig. 3) in the piston 2. The piston 2 is locked against rotation in the housing, by pins 7 (Fig. 2) which are fastened in the wall 1 and protrude into axial grooves or slits 6 (Fig. 3) in the piston 2. As it appears from Fig. 2, the pins 7 are inserted in a respective sleeve 8 mounted in a boss 19 which is fastened to the wall 1, for instance by welding, as shown. Rings 25 provide sealing against intrusion of dirt along the sleeves 8. As shown in Fig. 2 the pins 7 are situated somewhat eccentrically in the sleeves 8. Provided that the pins 7 have a diameter which is somewhat smaller than the width of the axial grooves 6 in the piston 2, abutment between the pins 7 and the sides of the grooves 6 can be achieved, by adjustment prior to the use of the torsional motor, by rotation of the sleeves 8 in the corresponding bosses 19, for instance by use of s screwdriver in screwdriver grooves 28 in the sleeves 8. Fig. 2 shows that both of the pins 7 have been rotated in such a manner that they abut one side of a respective axial groove 6, in the portions 26 to the right in the Fig..

Thereby, any rotational movement of the piston 2 due to clearance is prevented, and the entire axial movement of the piston 2 can be utilized for transfer of rotational movement to the rotor 3. Unintentional rotation of the sleeves 8 can be prevented by locking screws 9. An alternative, consisting of machining the pins 7 and the grooves 6 so precisely that mainly no clearance exists, is a substantially more expensive solution. In such a case also a corresponding preciseness with respect to the position of the bosses 19 would be necessary.

The rotor is shown equipped with a seal 14,16 against dirt at each end, against one of the flanges 12 and against the flange 13, respectively. Inside the ring 16 is shown a bearing ring 15.

The carrier bolt 4 extends, as shown in Fig. 1, diametrically through the rotor and into the slits 5 in the rotor 3 (see Fig. 3). In order to reduce friction the bolt 4 may be equipped with a roller 27 on each end, extending through the slits 5.

The rotor 3 can be geometrically adapted to a member which it is to regulate or control.

In the embodiment shown the rotor 3 has an internal, centered bore 20, into which a shaft from the member to be regulated or controlled can be inserted, and the bore 20 is shown having a keyway 21 for non-rotational attachment of such a shaft. Innermost in the bore 20 is shown an enlargement 22. The rotor 3 is also shown formed with a square hole 23 in one end, which can be used for rotating the rotor 3 by use of a suitable tool, as an emergency procedure.

The torsional motor may for instance be utilized for rotating a shaft on a member having an end flange. In such a case this end flange can be fastened to the flange 13 on the torsional motor, in that the flange 13 has threaded holes 24 for fastening. The member may for instance be a valve, whereby the torsional motor constitutes a servo motor or an actuator for the valve.

As it appears from Fig. 3 the slits 5 are inclined relatively to the axial direction of the piston 2. The slits 5 may for instance be in the shape of a helical line. The pitch is chosen so that the desired ratio between the axial force from the piston 2 and the torque supplie to the rotor 3 is achieved. The slits 5 may possibly have an axial portion at one or both ends. In such a case the carrier bolt 4 will, during the last part of the axial movement of the piston 2 in one or the other direction, be moved into such an axial portion of the slits 5, whereby the rotor 3 is locked against any rotation. This may be utilized as a safety precaution against unintentional rotation of the shaft of the member which the torsional motor regulates or controls. In such a case the piston 2 must be moved a certain axial distance from this locking position before the rotational movement of the rotor 3 starts.