Rotary actuator

Abstract: A rotary actuator (1) comprising a housing (2), which defines a working chamber (3) for actuation with a pressure fluid and having at least partially circular section, a pivoting piston (5) which is arranged sealingly against the inner wall (4) of and rotatable between two end positions in the working chamber, is featured in that the pivoting piston (5) itself is pivotally supported in bearings (16) which are arranged in the housing (2) axially at each side of the working chamber (3), and wherein it comprises means for cooperation with an external rotary shaft, whereby the housing (2) on at least one of its end walls is adapted so as to be contacted against and be fixedly fastened to a corresponding end wall portions of a second rotary actuator housing (2), and whereby these housings are fixable to one another in such a way that the axes (X) of the pivoting pistons of the respective housings are coaxial and that the pivoting pistons thereby are capable of affecting one common outgoing shaft.

Description: The present invention concerns a rotary actuator according to the preamble of claim 1. Such a rotary actuator is previously known from GB-A-2 239 053. This known rotary actuator comprises a housing having a working chamber which is divided perpendicular to the pivot axis and a pivoting piston arranged therein. The bearing arrangement of the pivoting piston is the bearing arrangement of the outgoing rotary shaft and is positioned axially outermost on each side of the housing. This construction presupposes accuracy of manufacture on several surfaces, such as the cooperating surfaces between the rotary piston and the shaft as well as the surfaces cooperating between the shaft and the housing. Furthermore, the solution presupposes complicated assembly wherein the parts in question must be adapted with precision to each other. It rotary actuators with different performances are required, the described rotary actuator must be dimensioned in accordance therewith. SE-C-224 276 describes a ring piston motor wherein the piston unit comprises bearing connection with the housing. The document however, does not discuss problems which are related to adjusting the rotary actuator to different performance demands and there are no practical possibilities of connecting one rotary actuator housing with an other. US-A-3446120 concerns an oscillating actuator having no particular means of connecting one actuator housing with another similar housing. It is a purpose of the present invention to eliminate the problems of the known art and to provide a rotary actuator which may be manufactured at low cost and with great precision. This and other purposes are achieved in a rotary actuator as mentioned initially by the features of the characterizing portion of claim 1. By the pivoting piston itself being supported by bearings in the housing the adding of tolerances is minimized so that the necessary accuracy may be easily achieved. It is further achieved that the assembly process is simplified and that the resulting product thereby may be produced at a very competitive price. By the pivoting piston comprising means for cooperation with an external rotary shaft, simple exchange further may be achieved, for example to a longer or a shorter shaft, because of the shaft only having rotary connection with the pivoting piston and no bearing connection as is the case with rotary actuators as mentioned initially. The features concerning the adaption of the end wall of the housing result in that series coupling with respect to power of two or more rotary actuator housings is possible for actuating a common outgoing shaft. This way a kind of modular construction is obtained which allows rotary actuators according to the invention to be combined such that a series of rotary actuators having different capacity is obtained simply by connecting and combining a limited number of base units. The adaption, which comes into question, is an adjusted shape of meeting surfaces, and means for fixing the connection. The feature concerning the division of the housing and assembly through tubular rivets results in reliable and labour saving assembly. Through the feature concerning the arrangement for coupling together rotary actuator housings using the holes in the tubular rivets no particular recesses, holes or the like need to be provided for. The coupling will be obtained without the respective rotary actuators in any way having to be opened or their working chamber seal being affected. By the feature according to claim 2 a useful means for cooperation with said rotary shaft is obtained, which is accentuated by the feature according to claim 3. The feature according to claim 4 defines a useful as well as cost effective way of manufacturing important components of the rotary actuator, since such rational manufacturing methods are made possible by the invention. The feature according to claim 5 further accentuates the manufacturing friendliness of the rotary actuator according to the invention, since the divider element does not comprise a separate but an integral unit which besides a seal receiving function also has a stop function. The invention will no be described in greater detail on hand of a example and the annexed drawings, wherein: Fig. 1 illustrates a rotary actuator according to the invention in a section perpendicular its axis, Fig. 2 illustrates a rotary actuator according to Fig. 1 in an axial section, and Fig. 3 illustrates a series coupling of two rotary actuators in an axial section. The rotary actuator according to Fig. 1 comprises a housing 2, which defines a working chamber 3, the inner surface 4 of which having a circular section and cooperating with a pivoting piston 5. This pivoting piston 5 comprises as commonly a wing 6, which via piston seals 7 seals against the inner surface 4 of the working chamber. Centrally the pivoting piston 5 is provided with a cylindrical central portion 8 and centrally therein a hole 9 for cooperation with a rotary shaft (not shown) having an axis 6, said hole 9 inwardly being provided with rotation transmitting means, in this case so called splines. Lowermost in the working chamber 3 Fig. 1 shows a divider element 10 which is comprised of plate shaped parts extending from the surface 4 of the working chamber against its central area, said plate shaped parts on the one hand comprising stop for the wing 6 in the end positions of the pivoting piston 5 and on the other hand to receive a sealing element 11 for cooperation with the cylindrical central portion 8 of the pivoting piston 5, and arranged to divide the working chamber 3 into a positive and negative chamber. Coaxially with the rotary shaft of the pivoting piston 5 the housing 2 in the dividing plane is provided with a circular guide groove (recess) 12 at a small distance outside the surface 4 for receiving a guide ring (15 in Fig. 2). 13 depicts tubular rivets for fixation of the parts of the housing 2 in the axial direction. In Fig. 2 the rotary actuator is thus illustrated in an axial section whereby the dividing plane A-A is shown which thus comprises the plane shown in Fig. 1. Fig. 2 illustrates the guide groove 12 which receives the guide ring 15, whereby the cooperation of said means, when the rotary actuator housing is assembled, guide and align the housing portions in a reliable manner. Further a T-shaped sealing element 11 is illustrated which is provided with a longitudinal axial sealing portion 11" for cooperation with the cylindrical central portion of the pivoting piston, and further has a vertical portion 11'. These arrangements are however not subject of this patent application. In the example shown the pivoting piston is provided with a bearing arrangement axially outside the working chamber, whereby pivoting piston bearings 16 having roller elements are arranged on the one hand to be received in seats for this purposes in the respective portion of the housing 2, and on the other hand pivotally support the pivoting piston. The pivoting piston, as previously has been mentioned, comprises a piston seal 7 which seals against the working chamber surface and also a circular seal 7' which seals against the working chamber radially outside and surrounding said bearings 16. Fig. 2 further illustrates a tuber rivet 13 for axial fastening together of the housing and a cover 14 on each end side of the housing. In use of a rotary actuator according to Fig. 1 and 2 a working shaft is inserted, said shaft having rotary transmitting means complementary to the hole 9, in the case of for example so called splines, which means axially extending cog shaped protrusions, into the hole 9. This working shaft (which is not shown) is by this invention easily adjusted to the application in question with respect to its length, to the shape with respect to the situation outside the rotary actuator etc. This may be achieved by the pivoting piston it self comprising the means for bearing cooperation with the housing 2, said means in Fig. 2 being integral, sidewardly axially extending hub portions 8'. In the shown example the hub portions 8' have circular cylindric configuration which normally is preferred in order to receive the inner ring of each bearing 16. Easy adjustment of the rotary actuator to different applications means that only the working shaft needs to be subject of possible modification for different working situations. Hereby adjustment of the rotary actuator may be limited to modifying the length of the working shaft and/or the external configuration outside the rotary actuator. The subject of this invention is to provide a rotary actuator which, if greater power is needed on said working shaft, is adapted on at least one of its end sides such that it may be coupled to one or several other rotary actuators such that the axis X of the respective rotary actuators coincide. This is shown in Fig. 3, whereby two rotary actuators are working in series on one common shaft 9. The connection in the shown example is provided by tension bolts B or similar means extending through the holes which are formed inside the tubular rivets 13. Further, aligning sockets 20 are inserted into the recesses which are present axially outside the tubular rivets 13 in order to align the (here) two rotary actuators. This way further means inside or outside the rotary actuator housing for allowing connection of rotary actuators are avoided which could possibly weaken the housing or result in adding of dirt collecting irregularities. By the connection also the angular stroke of the resulting connected rotary actuator unit may be limited by the pivoting pistons 5 and/or the dividing elements 10 of the different connected units initially having different angular position with respect to each other. The resulting rotary angle will thereby become the smallest common free pivot angle of all connected rotary actuators. By the possibility of connecting two or more rotary actuators to one unit in the described way it is obtained that a reduced number of basic sizes of rotary actuators has to be manufactured, which by coupling together will represent a large number of rotary actuator units with different performance. Using tubular rivets 13 allows connecting in a simple and clean way of rotary actuators according to the invention to a holder or another base. The rotary actuators according to the invention may be manufactured otherwise than what is shown in the Figures. Therefore housing as well as pivoting piston may be shaped otherwise with respect to for example radial to axial dimension of the rotary actuator. The rotary actuator may hereby be made flatter (Fig. 3) or more longitudinal if this is called for with respect to space reasons. Also the bearing arrangement between the pivoting piston and the housing may be arranged otherwise, for example with a different kind of bearings, another arrangement of the hub 8' etc. As an example it could be mentioned that the pivoting piston may comprise an inner socket portion comprising or being placed inside its central portion 8, said socket portion comprising the hole 9, the rotary transmitting means and possibly the hub portions 8', and said socket portion possibly being manufactured in another, for example a more resistant, material that the rest of the rotary piston and possibly comprising particular precision manufactured surfaces inside the hole 9 and/or at the hub portions 8'. It is preferred that the rotary actuator housing according to the invention is injection moulded in a form stable plastic material which is reinforced with a suitable reinforcing material, for example glass. As an example Kevlar may also be used as reinforcing material. Manufacture in a suitable metal may also come into question for many embodiments. The pivoting piston 5 is preferably also manufactured in an injection moulding process in the same or similar material and possibly with a particular socket portion according to the above in its central portion 8.

Claims: Rotary actuator (1) comprising a housing (2), which defines a working chamber (3) for actuation with a pressure fluid and having at least partially circular section, a pivoting piston (5) which is arranged sealingly against the inner wall (4) of and is pivotable between two end positions in the working chamber and which comprises means for co-operation with an external rotary shaft, whereby the housing (2) on at least one of its end walls is adapted so as to be contacted against and be fixedly fastened to a corresponding end wall portion of a second rotary actuator housing (2), and whereby these housings are fixable to one another in such a way that the axes (X) of the pivoting pistons of the respective housings are coaxial and that the pivoting pistons thereby are capable of affecting a common outgoing shaft, characterized in that the pivoting piston (5) itself is pivotally supported in bearings (16) which are arranged in the housing (2) axially at each side of the working chamber (3), wherein the housing (2) is divided (along A-A) through the working chamber (3) perpendicular to its axis (X) and the housing parts are fixed together by means of tubular rivets (13), having axes being parallel with said axis (X), said tubular rivets (13) being distributed around and outside the working chamber, whereby the housing is adapted to allow it to be fastened together with at least one second rotary actuator housing by through holes inside the tubular rivets (13) being used for receiving fastening means for mutual fastening of these housings. Rotary actuator according to claim 1, characterized in that said means are constituted of an axially extending hole (9) which extends through at least a part of the axial length of the pivoting piston (5). Rotary actuator according to claim 1 or 2, characterized in that said hole (9) comprises inward rotary transmitting means such as axially extending protrusion or so called splines over at least a part of its axial length. Rotary actuator according to any of the previous claims, characterized in that the housing parts (2) and/or the pivoting piston (5) is/are manufactured in an injection moulding process from a form stable reinforced plastic. Rotary actuator according to claim 4, characterized in that each housing part (2) comprises an integrally manufactured divider element (10) comprising stop for piston movement and holder for a sealing element (11) against a radially inner surface (8') of the pivoting piston. Rotary actuator according to any of the previous claims, characterized in that the rotary piston (5) comprises an inner socket portion which comprises said means for co-operation with an external rotary shaft and possibly hub portions (8') for said bearing arrangement (16).

Inventors: GRANBERG RUNE, GRANBERG, RUNE
Applicants: BOSCH REXROTH TEKNIK AB
Application year: 1996
Main classification: F15B15
IPC codes: F01C9, F15B15