DEVICE FOR POSITIONING OF AN ACTUATOR

Abstract: A device for positioning of an actuator (1), comprising a rotational stationary part (3), which is in engagement with the actuator (1) for linear displacement of the latter when rotating the rotaional part (3). According to the invention the rotational part (3) constitutes the output part of a motor (8), known per se, having a toothed rotor (9) with a different number of teeth than the stor (10), and means for bringing the teeth of the stator (10) into driving engagement with the teeth of the rotor (9) for rotating the rotor (9) in a manner known per se for displacement of the actuator (1) for precision positioning thereof. Moreover, a rotational element (12) is either connected or connectable to the rotor (9) for quick rotation of the latter for coarse positioning of the actuator (1) when the teeth of the stator (10) are out of mesh with the teeth of the rotor (9).

Description: Device for positioning of an actuator TECHNICAL FIELD The present invention relates to a device for positioning of an actuator comprising a rotational stationary part ωhich is in engagement with the actuator for linear displacement of the latter ωhen rotating the rotational part. BACKGROUND ART Kπoωπ such devices include either tapezoidal s " creω systems or ballscreω systems driven either fully manually or manually in combination ωith a motor as in several machine tools. In the last mentioned case the manual rotational motion is supplied by a separate shaft or spindle,ωhile th motor is set in engagement by an other spindle * DISCLOSURE OF INVENTION The purpose of this invention is to bring about a device in which the same spindle as is used for the manual can be used for the motorized motion.From, a functional point of view the manual motion should be considered as a fine or precision motion. This is achieved in that the device according to the invention has been given the characterizing features set for forth in the claims. BRIEF DESCRIPTION OF DRAWING The invention ωill be more particulary described in connection ωith the attached draining, on ωhich the single figure shαωs an embodiment of a positioning device according to the invention. DETAILED DESCRIPTION The drawing shoωs an embodiment αf the device according to the invention for positioning of an actuator 1 ωhich in the embodiment shoωn consists of a piston ωith circular cross section. The piston 1 is intended to be connected at its free end to a not shoωπ load for controlled linear displacement of this load. The other end of the piston 1 is in the embodiment sleeve-shaped and provided ωith an internal trapezoidal thread 2 in mesh ωith a tapezoidal thread of a rotational stationary spindle 3. The actuator or piston 1 is supported by a guide bearing 4 in a housing 5 ωhich also contains an element 6 not shαωn in detail, e.g. a spline set, to prevent the piston 1 from rotating ωhen the spindle 3 is rotated. The spindle 3 is in turn rotationally supported by a bearing 7 in the housing 5. According to the invention the spindle 3 constitutes the output spindle of a motor knoωn per se, ωhich in the embodiment shoωn is supposed to be a ωith fluid pressure controlled rotary stepping motor in accordance ωith Swedish Patent 7109362-9. The stepping motor 8 is arranged in the housing 5 and consists of a rotor in the form of a rigid circular ring gear 9 ωith internal teeth not shoωn, a stator in the form of an elastic strain gear 10 oriented co-axially to the rotor ωith external teeth not ahoωn, the tωo gears 9 and 10 having different numbers- of teeth and being arranged to have the teeth fully meshed at diametrically located portions of the gears, and an even number of force supplying elements, ωhich are uniformly distributed around the periphery of the elastic strain gear 10 to bring this gear i into mesh ωith the rigid ring gear 9 to rotate the latter in a manner knαωn per se. The fluid pressure i supplied to the motor 8 via an air or hydralic hose 11 from a pressure source not shαωn. The rigid ring gear 9 is in the embodiment shoωn firmly connected to the spindle 3 ωhich extends freely through the elastic strain gear and at its other end carries a ωheel 12 by ωhich the spindle 3 can be rotated ωhεπ the elastic gear 10 is out of mesh ωith the rigid ring gear 9. Uihen the ωheel 12 is rotated the rigid gear 9, i.e. the rotor 8 of the motor, ωill of course also rotate. By means of the ωheel 12 the spindle 3 can thus be rotated quickly by hand for coarse positioning of the position αf the piston 1. For precision positioning or fine control of the position of the piston 1 the motor 8 ωill hoωever be driven by fluid pressure from the pressure source not shoωπ. Of course, the motor 8 does not have to be the one according to the Sωedish patent mentioned above but can be any kind of stepping motor where the rotor and stator can be disengaged from each other to achieve coarse positioning of the actuator i.e.. the piston 1. The coarse positioning does not have to be made by hand, but the ωheel 12 can be replaced by a gear, a pulley or the like to render a coarse positioning possible by using a motor not shoωπ. Moreover the piston 1 of course does not have to be provided ωith internally threaded sleeve-shaped part, but this part can as ωell be provided on the spindle 3. In such a case the sleeve—shaped part of the piston ωill be replaced by an - externally threaded part such as a screw. It should be point pointed out that the threads do not have to be of the trapezoid type but can also be of a ballscreω or rollerscreω type of transmission to transform rotating into linear motion. The advantage of trapezoid threads is that the actuator: will be self-locking at not too high a pitch of the threads and that trapezoid threads are cheap construction elements. The advantage of using a ballscrew transmission is primarily that the low friction of such a transmission enables the actuator to position greater loads. Moreover it is possible to imagine cases where the part 3 is provided with two external treads having different pitches and perhaps even so that one is right-threaded and the other is left-threaded. Corresponding nuts having internal threads of the same pitch and shape as the tωo parts on the spindle 3 having external threads ωill then move on these parts of the spindle 3 as a differential screw transmission. In order to compensate for any play or backlash in the gear transmission it is possible to divide e.g. the part of the piston 1 having an internal thread into two nuts which rigidly or by means of a spring (not shown) either are pressed together or apart from each other so that the ' backlash disappears. For practical reasons it is supposed as is shown in the figure that the linear motion shall be restricted by _ OMPI mechanical stops. If for instance the spindle 3 rotates so that the piston 1 in the figure moves to the left this piston motion will be stopped when the piston 1 touches the housing 5. Many times' it can' be of value to get information of the position of the actuator. The simpliest ωay to do that is to provide the device"ωith an optical, electrical or mechanical rotational transducer attached to either the rotor 9 or the spindle 3. Of course the device can also be provided with a linear transducer which directly measures the linear position of the actuator 1 • A device according to the invention can be used with advantage for several applications where today purely manually operated actuators are used and where by using the device according to the invention the control systems of machines and equipments can be automated and improved as for instance actuators for screw jacks for nuclear reactors or actuators for the positioning αf the slice lip of paper machines for the control of the weight profile. - Rl

Claims: CLAIMS 1. Device for positioning of an actuator (1), comprising a rotational stationary part (3) ωhich is in engagement ωith the actuator (1) for linear displacement of the latter ωhen rotating the rotational part (3), c h a r a c t e r i z e d in that the rotational part, (3) constutes the output part of a motor (8), knoωπ per se, having a toothed stator (10), a toothed rotor (9) ωith a different number of teeth than the stator (10), and means for bringing the teeth of the stator (10) into driving engagement ωith the teeth of the rotor (9) for rotating the rotor (9) in a manner, knoωn per se, the rotor (9) being connected to the rotational part (3) in such a way that the latter is rotated when the rotor (9) is brought to rotate- either by means of the stator (10) when its teeth are brought into driving engagement with the teeth of the rotor (9) to displace the actuator (1) for precision positioning there of or by means of a rotational element (•12) connected or connectable to the rotor (9) for quick rotation of the rotor (9) displace the actuator (1) for coarse positioning thereof when the teeth of the stator (10) are out of driving engagement ωith the teeth of the rotor (9). 2. Device according to claim 1, c h a r a c t e r i z e d in tnat the rotational stationary part (3) has either external or internal threads and is in engagement ωith the actuator (1) ωhich has threads cooperating ωith the threads of the stationary part (3). 3. Device according to claim 2, c h a r a c t e r i z e d in that the threads are trapezoidal or fine threads. 4. Device according to claim 2, c h a r a c t e r i z e d in that tha actuator (1) is in mesh ωith the stationary part (3) via a ballscreω or rollerscreω transmission. 5. Device according to any of the claims 2-4, c h a r a c t e r i z e d in that the threaded portion of either the stationary part (3) or the actuator (1) is made up of tωo threaded parts that are displaced toωards or away from each other either rigidly or by means of a spring, whereby any backlash of the engagement of the actuator (1) OMPI and the stationary part (3) is eliminated or minimized, and in case a spring is used, the spring force being higher the loading forces excerted on the actuator (1). 6. Device according to any of the above claims-, c h a r a c t e r i z e d in that a mechanical stop is provided to restrict the stroke length of the actuator (1). 7. Device according to claim 2 where the rotational stationary part (3) has internal threads in mesh with the actuator (1), c h a r a c t e r i z e d in that the actuator (1) comprises a straight rod which is externally threaded and extends straight through the device in such a manner that the rotational stationary part (3) has a central through hole for the rod, the actuator (1) being arranged to be connected to the load in such a manner that rotation of the actuator (1) is prevented. 8. Device according to any αf the above claims, c h a r a c t e r i z e d in that the rotational stationary part (3) has a scale or is adopted upon its rotation to act upon a scale which optically, electrically or in any other way indicates the position of the actuator (1). 9. Device according to claim 1, c h a r a c t e r i z e d in that the rotational element (12) is adapted for manual rotation of the stationary part (3) either directly or indirectly via a gear transmission. 10. Device according to any of the above claims, c h a r a c t e r i z e d in that the motor (8) is a fluid motor or an electric motor.

Inventors: CARLNAES BENGT, CARLNAES, BENGT
Applicants: CARLNAES BENGT, CARLNAES, BENGT
Application year: 1983
Main classification: G05G1
IPC codes: F16H25, F16H49, H02K7, H02K57