US20080035113A1

US20080035113A1 - Rotary motor and a method for its manufacture

Info

Publication number: US20080035113A1
Application number: US11/501,160
Authority: US
Inventors: Thomas Friedrich
Original assignee: Individual
Current assignee: Kinshofer GmbH
Priority date: 2006-08-08
Filing date: 2006-08-08
Publication date: 2008-02-14

Abstract

The present invention relates to a rotary motor, preferably a pivot drive for construction machinery, trucks and the like comprising an elongate housing, preferably an approximately tubular housing, a piston displaceably received in the housing, which is axially displaceable by charging with a pressure medium in a pressure chamber, and a shaft received axially fixedly, but rotatably in the housing, with the piston being in screw engagement with the shaft and/or the housing. The invention furthermore relates to a method for the manufacture of such a rotary motor. The present invention departs from the previous approach of separating the sealing of the piston at the shaft and at the housing from the section effecting the rotary guide or the screw engagement. In accordance with the invention, a surface pair of piston and shaft and/or of piston and housing effecting the screw engagement can simultaneously form a sealing surface pair for the sealing of the pressure chamber for the charging of the piston with pressure. The same piston section simultaneously serves the transfer of torque and sealing. A considerably reduced construction length can hereby be achieved since the axial spacing between the sealing section and the rotary guide section or the screw engagement section of the piston is omitted. In addition, the respective components, in particular the housing and the shaft, can be manufactured in an endless manner and be produced as needed and in the required length.

Description

The present invention relates to a rotary motor, preferably a pivot drive for construction machinery, trucks and the like comprising an elongate housing, preferably an approximately tubular housing, a piston displaceably received in the housing, which is axially displaceable by charging with a pressure medium in a pressure chamber, and a shaft received axially fixedly, but rotatably in the housing, with the piston being in screw engagement with the shaft and/or the housing. The invention furthermore relates to a method for the manufacture of such a rotary motor.
Such a rotary motor is known, for example, from DE 201 07 206 in which the piston is guided rotationally fixedly at the inner jacket surface of the circularly cylindrical housing, on the one hand, and is in screw engagement on a threaded section of the shaft, on the other hand. If the piston is axially displaced in the housing by hydraulic charging, its axial movement is translated into a rotary movement of the shaft via the screw engagement. To be able to seal the piston with respect to the housing and to the shaft and thus to be able to charge the pressure chamber correspondingly with hydraulic pressure, the piston has a sealing section which is spaced apart from the screw engagement section and which slides on a shaft sealing section, on the one hand, and on the housing inner jacket surface, on the other hand, and is sealed. Piston constructions of this type are, however, disadvantageous with respect to the construction size and are associated with a high production effort. In addition, different force relationships result for the operation in different direction of rotation.
The present invention attempts to provide a remedy here. It has the underlying object of providing an improved rotary motor of the said kind which avoids disadvantages of the prior art and further develops the latter in an advantageous manner. A rotary motor should in particular be provided which has a compact construction and is characterized by favorable torque generation and transfer at the piston.
This object is solved in accordance with the invention by a rotary motor in accordance with claim 1. The named object is solved in a technical method aspect by a method in accordance with claim 21. Preferred aspects of the invention are the subject of the dependent claims.
The present invention therefore departs from the previous approach of separating the sealing of the piston at the shaft and at the housing from the section effecting the rotary guide or the screw engagement. In accordance with the invention, a surface pair of piston and shaft and/or of piston and housing effecting the screw engagement can simultaneously form a sealing surface pair for the sealing of the pressure chamber for the charging of the piston with pressure. The same piston section simultaneously serves the transfer of torque and sealing. A considerably reduced construction length can hereby be achieved since the axial spacing between the sealing section and the rotary guide section or the screw engagement section of the piston is omitted. In addition, the respective components, in particular the housing and the shaft, can be manufactured in an endless manner and be produced as needed and in the required length.
The piston advantageously has equally large effective piston surfaces at its two oppositely disposed sides so that no oil store is required as such. The complete piston surface can effectively be used with equal forces in both directions. The total inner diameter surface of the housing is practically available on both piston sides as the piston pressing surface, only reduced by the shaft cross-section. The same torques can hereby be generated in both drive directions with the same hydraulic pressures. In addition, a maximum torque yield results for a given pressure.
In a further development of the invention, the screw engagement between the shaft and the piston is not achieved by a conventional threaded mesh section of the shaft and of the piston. The shaft is advantageously twisted in itself so that its outer contour forms a spiral polygonal section twisted around the longitudinal axis of the shaft. This not only simplifies the production, but also improves the sealing capability between the shaft and the piston. The inner jacket surface in screw engagement with the twisted polygonal section can be made free of thread meshing and have a continuous, constant surface extent without impressions or projections so that the piston and the twisted polygonal section of the shaft are seated on one another in the manner of a plain bearing surface pair.
To achieve a sealing of the pressure chamber which is as free of leakage as possible, a seal can be inserted into the inner peripheral piston surface in screw engagement with the shaft, said seal sealing the piston on the outer contour of the shaft. The inner peripheral piston surface is advantageously likewise made as a polygonal sectional surface which can be approximately cylindrical with an axially very short design of the piston and in another respect can be slightly twisted in itself around the longitudinal axis of the piston, as is the shaft.
Generally, a screw engagement could also be provided between the housing and the piston, in particular in that the housing also forms a polygonal section spirally twisted around its longitudinal axis. Advantageously, however, the housing has a cylindrical inner jacket surface which advantageously has a cross-sectional geometry deviating from the circular shape at which the piston is longitudinally displaceable guided and rotationally fixedly supported with its outer jacket surface. The housing can in particular have a pressed flat, preferably approximately elliptical or oval cross-section. A design of the rotary motor of shallow construction can hereby be achieved. However, other pressed flat cross-sections can be used which are adapted to the respective installation situation. In particular when extruded or extrusion molded sections are used, the outer contour and the inner contour of the housing can differ from one another in order, on the one hand, to adapt the outer contour to the installation situation and, on the other hand, to achieve a piston surface which is as large as possible. In accordance with an embodiment of the invention, the housing can have a substantially rectangular contour at the outer side. Above all, a favorable torque yield can be achieved with a pressed flat cross-section since a large lever arm is achieved. The housing can advantageously be made pressed flat such that a longitudinal axis of the cross-section is longer than the transverse axis of the cross-section by at least 30%, preferably by more than 50%.
Generally, different cross-sectional geometries are possible at the housing. The housing advantageously has a cross-section free of kinks and edges, whereby the sealing capability is improved. In particular an elliptical or oval cross-section combines a good sealing capability with a favorable torque yield. An annularly peripheral seal can be inserted into the piston outer jacket surface in rotationally fixed engagement with the inner jacket surface of the housing to achieve a largely leak-free sealing of the pressure chamber.
The spirally twisted polygonal section of the shaft can likewise advantageously have a cross-section pressed flat, e.g. be rectangular or in particular elliptical or oval. To achieve a favorable torque yield, the cross-section can advantageously have a longitudinal axis which is at least 30% and preferably more than 50% longer than the transverse axis of the cross-section. A square cross-section or a hexagonal section would admittedly also generally be usable in which the ratio of longitudinal axis to transverse axis of the cross-section substantially amounts to 1:1. However, less favorable lever ratios result for the torque yield there than with a cross-section pressed flat. The cross-section is advantageously also free of sharp kinks or edges on the shaft to improve the sealing capability.
The favorable torque yield achieved by the pressed flat cross-sectional profiles of the housing and/or of the shaft due to lower radial forces reduces the axial frictional forces acting against the axial displacement of the piston, whereby a higher efficiency can be achieved.
In particular with very compact construction dimensions, an optimum torque yield can take place with a low friction in that the shaft is made as a winged shaft which has at its periphery at least one rail-shaped projection which is screwed around the shaft axle and via which the torques can be borne off ideally. The wing shape can in particular be made with two wings, i.e. the shaft has two mutually opposite radial projections which are each made in rail shape and screw around the shaft axle. These projections so-to-say form the yield noses for the bearing off of torques. In accordance with an advantageous embodiment of the invention, the shaft can have circularly cylindrical segments between the said projections.
The respective piston seated on the shaft has an inner peripheral surface which is adapted to the said shaft contour and in which groove-shaped recesses are provided which are adapted to the aforesaid wings of the shaft and which engage around the wings and effect the torque yield between the shaft and the piston.
In order also to achieve an optimum torque yield between the piston and the housing with very small construction dimensions and with very low friction, the piston can also have a wing shape. A winged piston of this type advantageously likewise has at least one radial rail-shaped projection which engages into a corresponding groove-shaped recess in the inner peripheral surface of the housing engaging around it. In accordance with a preferred embodiment of the invention, the piston also has two mutually opposed wing-like radial projections which engage into corresponding recesses in the inner peripheral surface of the housing.
With the help of wing shapes of this type at the shaft and/or at the piston, large load yield levers can be achieved, whereby small frictional forces and thus high degrees of efficiency can be achieved.
In accordance with a preferred embodiment of the invention, the housing is made in a compound construction. Such a compound housing can have a plurality of shells which are placed into one another and connected to one another. In this connection, at least one inner shell is expediently provided which is in engagement with the piston and can be adapted to its outer contour and an outer shell is provided which forms the outer skin of the housing. These two shells can be directly connected, in particular adhesively bonded, to one another with a corresponding design of the outer shell. Alternatively, a support body made of a suitable integral material, preferably hard foam, aluminum foam or another suitable cast mass and/or foam mass, can be provided between the inner shell and the outer shell and can connect the inner shell to the outer shell. It can not only be achieved in a simple manner by such a compound construction that the outer contour of the outer shell is adapted to the connecting contours and deviates in cross-section from the inner shell adapted to the piston contour. At the same time, a high stiffness which brings along a small gap enlargement at the piston can be achieved by such a compound housing with a low weight. With a suitable choice of material, a high corrosion stability can additionally be achieved, for example when the outer shell is made of aluminum or of a galvanized steel sheet. In addition, the possibility is provided of integrating connection options, for example to a loading board wall or to a vehicle frame, into the outer shell. On the other hand, the inner running surface of the inner shell can be made in a low wear and low friction manner. The outer shell and the inner shell can be adapted to different demands independently of one another.
The said compound construction of the housing is in particular suitable for mass production. For a small series production, the housing can alternatively be manufactured in a shaping technology; for example, hydraulic cylindrical tubes can be brought into the desired pressed flat shape by being pressed flat and/or spread while maintaining their surface quality.
In accordance with an advantageous embodiment of the invention, the piston is supported by plain bearings at the housing and/or at the shaft. The plain bearing surfaces at the outer jacket surface and/or at the inner jacket surface of the piston can simultaneously form the sealing surfaces into which, optionally, separate seals can be inserted. Depending on the design of the rotary motor, a slight leak via the plain bearing surfaces of the piston can be accepted. If this should be avoided, it must be determined in each case that seals can be inserted in a simple manner into the plain bearing surfaces at the outer jacket surface and/or at the inner jacket surface of the piston. The piston can, for example, have hardened jacket surfaces which form the plain bearings. Alternatively or additionally, separate plain bearing inserts can also be provided at the jacket surfaces of the piston. In accordance with an embodiment of the invention, the piston, in particular its jacket surface, can also be made of a soft, plasticizing material, with the housing then being made of a corresponding material to achieve a suitable plain bearing surface pairing.
In accordance with a further preferred embodiment of the invention, the piston can be supported by roller bearings at the housing and/or at the shaft. A friction further reduced over plain bearings can hereby be achieved. The roller bodies are in this connection arranged at the piston and roll off at roller body roll-off surfaces at the housing and/or at the shaft. Optionally, roller bearing guide tracks, which are preferably hardened, can be provided at the housing and/or at the shaft. Advantageously, contour roller bodies are matched whose running surface is matched to the contour of the housing or of the running surface formed thereon. With an ovally or elliptically curved housing, roller bodies can thus be used having a running surface correspondingly made in spherical shape in order to achieve a line contact where possible between the roller bodies and the housing.
The twisted polygonal section of the shaft can generally have a pitch remaining constant over the length of the shaft. A translation of the oil feed into a corresponding rotary movement which remains constant is hereby achieved over the total adjustment path of the rotary motor.
In accordance with an alternative embodiment of the invention, the twisted polygonal section of the shaft can, however, also have a pitch changing over the length of the shaft. A torque adaptation and a rotational speed adaptation of the rotary motor can hereby be achieved with a constant oil flow, for example a reduction of the rotary speed at the end of the travel path.
To achieve an increase in the torque with a limited housing diameter, a plurality of pistons can be arranged on the shaft.
In particular, in a further development of the invention, at least two pistons which are to be moved in opposite senses can be arranged on the shaft, with the shaft and/or the housing advantageously having counter-revolving screw engagement sections so that the one piston interacts with the shaft in a left-handed manner and the other piston in a right-handed manner. An axial force compensation can hereby be achieved in addition to the achieved doubling of the torque. The bearings of the shaft only have to take up radial forces; the axial forces put onto the shaft by the piston cancel one another.
Alternatively or additionally, a freedom of clearance of the powertrain can also be achieved by two pistons seated on the shaft of the motor. For this purpose, the two pistons are advantageously seated on the same twisted polygonal section of the shaft and are axially biased with respect to one another. The axial bias between the two pistons can be effected mechanically, for example, by a spring and/or hydraulically by pressure charging of the intermediate space between the two pistons.
The shaft can advantageously be supported by means of two bearing covers which are seated axially at the end face on the oppositely disposed ends of the housing. Seals can in each case be provided between the bearing covers and the shaft for the sealing of the pressure chamber. The seals are advantageously integrated into the respective bearing surface at which the shaft is supported at the bearing cover.
The support of the shaft at the bearing cover can advantageously be a plain bearing. Alternatively or additionally, a roller bearing with roller bodies can also be provided here between the respective bearing cover and the shaft.
The shaft advantageously passes through the bearing cover at both sides. The shaft stubs projecting at the respective housing head can form the output elements via which the torque is output.
The polygonal section of the shaft deviating from the circular shape in cross-section can advantageously be used directly to achieve the torque yield. Alternatively, a connector piece can, however, be rotationally fixedly fastened to the shaft ends, for example welded on or pressed on.
The polygonal section twisted in itself can be put on the shift in different manners. Optionally, one could think of working the polygonal section in a cutting process. In accordance with an advantageous aspect of the present invention, the polygonal section twisted in itself is, however, manufactured by non-cutting shaping. The shaft can be shaped from a substantially cylindrical shaft blank which has a polygonal sectional cross-section differing from the circular shape. This shaft blank can be cut to the desired length from an endless bar section. The shaft blank is twisted itself around its longitudinal axis by non-cutting shaping so that its outer contour forms the polygonal section twisted in itself effecting the screw engagement with the piston. The shaping can take place by cold twisting or hot twisting. It will be appreciated that the manufacture of the shaft does not have to take place in a completely non-cutting manner. Optionally, the surface of the shaft can be worked in a cutting manner, in particular polished, before or after the twisting. Optionally, the shaft blank can also be given its polygonal section by cutting processing. The twisting of the polygonal section, however, advantageously takes place in a non-cutting manner.
If the shaft should cooperate in the previously described manner with two pistons working in opposite senses, the shaft blank is advantageously twisted starting from a direction change section toward oppositely disposed sides in a counter-revolving manner. The shaft manufactured in this manner is shaped from an integrally one-piece shaft blank.
Alternatively, two shaft blanks twisted in opposite senses can be rigidly connected to one another, in particular welded and/or screwed to one another, so that the shaft hereby created has two shaft sections twisted in opposite senses.

The invention will be explained in more detail in the following with reference to preferred embodiments and to associated drawings. There are shown in the drawings:

FIG. 1: a longitudinal section through a rotary motor in accordance with an advantageous embodiment of the invention in which two pistons working in opposite senses to one another are arranged on the shaft twisted in opposite senses;

FIG. 2: a cross-section through the rotary motor of FIG. 1 which shows a piston supported by plain bearings on the oval housing and on the shaft;

FIG. 3: an end-face plan view of the housing motor of FIG. 1 which shows a bearing cover screwed to the housing and a fastening lever integrated in the bearing cover as well as the shaft of the motor going beyond the bearing position with a bearing ring;

FIG. 4: a cross-section through the rotary motor of FIG. 1 which shows the floating support of the shaft at its direction change section located at the center;

FIG. 5: a cross-section through the rotary motor of FIG. 1 in the region of an end-face bearing cover with a throughgoing shaft and a shaft stub turned on;

FIG. 6: a sectional cross-section in the region of a bearing cover in accordance with a further embodiment of the invention with a bearing stub welded to the shaft;

FIG. 7: a sectional cross-section in the region of a bearing cover in accordance with a further embodiment of the invention in which the twisted shaft goes through the bearing cover;

FIG. 8: a cross-section through the rotary motor of FIG. 1 which shows a piston outer support at the oval housing with inserted plain bearings;

FIG. 9: the plain bearing support of the piston at the housing of FIG. 8 in a longitudinal section;

FIG. 10: a cross-section through the rotary motor which shows a support of the piston at the oval housing by means of roller bearings;

FIG. 11: the roller bearing support of the piston at the housing of FIG. 10 in a longitudinal section;

FIG. 12: a roller bearing support of the piston at the housing in a longitudinal section similar to FIG. 11, with, in accordance with an alternative embodiment of the invention, a plurality of roller bodies being provided spaced apart from one another axially;

FIG. 13: a longitudinal section through a piston of the rotary motor with pressure-charged, valve-controlled inner lubrication;

FIG. 14: a longitudinal section through a rotary motor in accordance with a further embodiment of the invention in which two mutually biased pistons effect a freedom of clearance of the powertrain, with the bias taking place by a spring and by a pressure fluid charging;

FIG. 15: a longitudinal section through a rotary motor with two biased pistons similar to FIG. 14, with the two pistons only being biased mechanically by springs in this embodiment;

FIG. 16: a cross-section through the rotary motor which shows the support of the piston at the shaft by means of roller bearings;

FIG. 17: the roller bearing support of the piston at the shaft of FIG. 16 in a longitudinal section which permits pitch changes at the shaft;

FIG. 18: a roller bearing support of the piston at the shaft in a longitudinal section similar to FIG. 17, with roller bodies being provided spaced apart axially from one another in the embodiment of FIG. 18;

FIG. 19: a cross-section through the rotary motor in accordance with an alternative embodiment of the invention which shows a spherical guidance of the piston at the shaft which permits changes of pitch of the shaft;

FIG. 20: a side view of the spherical support of the piston at the shaft of FIG. 19 in a longitudinal section;

FIG. 21: a cross-section through the rotary motor in accordance with a further embodiment of the invention which shows an alternative roller bearing support of the piston at the flat sides of the shaft;

FIG. 22: a cross-section through the rotary motor in accordance with a further embodiment of the invention which shows an alternative roller bearing support of the piston at the flat side of the shaft;

FIG. 23: a cross-section through the rotary motor in accordance with a further embodiment of the invention which shows a plain bearing support of the piston at the shaft with inserted guide pieces;

FIG. 24: a cross-section through the rotary motor in accordance with a further embodiment of the invention which shows an alternative plain bearing support of the piston at the flat sides of the shaft, with hardened round wire sections inserted into the shaft being provided;

FIG. 25: a cross-section through the rotary motor in accordance with a further embodiment of the invention which shows a four-point roller bearing support of the piston at the shaft with a peripheral roller body track;

FIG. 26: a cross-section through the rotary motor in accordance with a further embodiment of the invention which shows a two-point roller bearing support of the piston at the flat sides of the shaft with a ball return;

FIG. 27: the roller bearing support of the piston at the shaft with a ball return from the preceding Figures in a longitudinal section;

FIG. 28: a sectional cross-section in the region of a bearing cover which shows the screw connection of the bearing cover to the tubular housing;

FIG. 29: a sectional cross-section in the region of the bearing cover in accordance with a further embodiment of the invention which shows a weld connection of the bearing cover to the tubular housing;

FIG. 30: a sectional cross-section in the region of a bearing cover in accordance with a further embodiment of the invention which is secured to the tubular housing by securing rings inserted radially into the housing cover;

FIG. 31: a longitudinal section through a continuously produced shaft with direction change;

FIG. 32: a sectional longitudinal section through a shaft which has a direction change and is composed of two shaft pieces which are elastically coupled to one another;

FIG. 33: a sectional longitudinal section through a shaft in accordance with a further embodiment of the invention which consists of two shaft sections of opposite senses which are friction welded to one another;

FIG. 34: a sectional longitudinal section through a shaft with direction change which is composed of two shaft pieces which are screwed to one another;

FIG. 35: a cross-section through the rotary motor in accordance with a further embodiment of the invention in which the housing consists of an extruded or extrusion molded section whose outer contour differs from its inner contour in order, on the one hand, to adapt the outer contour to the installation situation and to achieve a piston surface which is as large as possible in the inner space;

FIG. 36: a cross-section through the rotary motor of FIG. 34 which shows the support of the shaft at its direction change section located at the center; and

FIG. 37: a cross-section through the rotary motor in accordance with a further embodiment of the invention which is made as a wing motor in which the shaft and the piston each have a wing shape in order to achieve an optimum torque yield with low friction with very compact constructional dimensions;

FIG. 38: a cross-section through the rotary motor in accordance with a further embodiment of the invention, according to which the shaft, the piston and the housing each have pressed-flat, oval or elliptical cross-sections and the housing can consist of a pressed-flat or spread cylindrical tube, with an excellent torque yield being able to be achieved with low friction by the pressed-flat cross-section and likewise with a very compact constructional dimension;

FIG. 39: a representation of the winged shaft of the torque embodiment of FIG. 37, the shaft being made as a hollow shaft and being shown in cross-section in accordance with a) and in a side view in accordance with b);

FIG. 40: a cross-sectional representation of the housing of the rotary motor made as a wing motor of FIG. 37, with the house being made in compound construction and having an elliptical outer shell as well as an inner shell adapted to the wing contour of the piston which are connected to one another to form a support body of integral material;

FIG. 41: a cross-sectional representation of the housing of the wing motor of FIG. 37 in compound construction in accordance with an alternative embodiment of the invention in which the outer shell is adapted to the connection geometry of the component to be connected and has integrated securing means; and

FIG. 42: a cross-sectional representation of the housing of the wing motor of FIG. 37 in compound construction in accordance with a further alternative embodiment of the invention in which the outer shell of the housing is made as an extruded section or as an extrusion molded section and is seated on the inner shell with a gap-filling material.

The rotary motor 1 shown in FIG. 1 includes a cylindrical tubular housing 2 which is made of an endless bar material and was cut to the desired length. A shaft 3 is arranged in the housing 2 coaxially to its longitudinal axis and is supported rotatably, but axially fixedly, to two bearing covers 4 closing the housing 2 at the end face. In the embodiment drawn, the shaft 3 is additionally supported centrally at the housing 2 by a floating shaft bearing support 5 to prevent any sagging of the shaft 3.
The shaft 3 advantageously has a pressed-flat cross-section as is shown, for example, by FIG. 2. The longitudinal axis 6 of the cross-section is more than twice as long as the transverse axis 7 of the cross-section in the embodiment drawn in accordance with FIG. 2. Overall, the cross-section of the shaft 3 forms a pressed-flat polygonal section deviating from the circular shape and having two flat sides 8 which are parallel to one another and are chamfered in each case towards the narrow side 9 so that the cross-sectional profile is free of kinks and edges overall (cf. FIG. 2).
As FIG. 1 shows, the polygonal section of the shaft 3 is spirally twisted in itself, with the shaft 3 having a direction change at its center. From the central direction change section, the shaft 3 is twisted in itself in different direction towards its two ends so that one shaft half is made in a left handed manner and the other shaft half is made in a right handed manner.
Two pistons 10 are seated on the shaft 3 which act in opposite senses and which are each seated in a precise fit on the polygonal section of the shaft 3 so that they are in screw engagement with it. On the other hand, the pistons 10 are guided axially displaceably, but rotationally fixedly in the housing 2 so that an axial movement of the pistons 10 is translated into a rotary movement of the shaft 3 relative to the housing 2.
As FIG. 2 shows, the rotationally fixed guidance of the pistons 10 in the housing 2 is effected in that the housing 2 has a cross-section differing from the circular shape. As FIG. 2 shows, it can in particular have a pressed-flat, substantially oval or elliptical cross-section which substantially corresponds to the outer cross-section of the piston 10.
The pistons 10 can be axially driven by being charged with a pressure medium, which can generally be air or another gas, but advantageously a liquid, in particular hydraulic oil, so that the shaft 3 carries out the desired rotary movement. For this purpose, the pistons 10 can be sealed both with respect to the shaft 3 and to the housing 2. As FIG. 1 shows, a shaft seal 12, which seals the respective piston 10 with respect to the shaft 3, is seated in the inner jacket surface 11 of the pistons 10. A housing seal 14, which seals the respective piston 10 with respect to the housing 2, is in each case seated on the outer jacket surface 13 of the pistons 10. Accordingly, a pressure chamber 15, 16, 17 and 18 is provided on each side of the pistons 10 and is bounded, in addition to the respective piston surface, by the housing 2 and, in the case of the pressure chambers 15 and 18, by the housing cover 4. The pressure chambers 15, 16, 17 and 18 can be filled with pressure fluid in a manner known per se to move the pistons 10 to and fro. The pressure feed system 19 advantageously includes pressure fluid feed passages 20 which extend on the interior of the shaft 3. They can be in communication with pressure fluid feed passages 21 which extend on the interior of the pivot levers 29 which are seated rotationally fixedly on the shaft stubs 23 which exit the housing 2 through the bearing covers 4.
In the embodiment shown in FIG. 2, the pistons 10 are each supported by a plain bearing with respect to the housing 2 and the shaft 3, i.e. the outer jacket surface and the inner jacket surface 10 each form plain bearing surfaces.
As FIG. 3 shows, the bearing covers 4 closing the housing 2 at the end face are screwed to the housing 2. Fastening levers 24 or abutments can advantageously be integrated into the bearing covers 4 to intercept torques introduced from the housing 2. As FIGS. 1 and 3 show, the shaft 3 is in each case supported in the bearing covers 4 by a bearing ring 25 which is fixedly connected to the shaft 3 and is rotatably supported in the bearing cover 4. Both axial forces and radial forces can be intercepted via the bearing rings 25, although axial forces are compensated per se by the dual-piston arrangement and thus substantially only radial forces act on the shaft.
FIG. 4 shows the floating shaft support 5 supporting the shaft 3 centrally in greater detail. An intermediate support ring 26 is fixedly seated on the direction change section of the shaft 3 and is supported in a floating manner in a guide plate 27 which has a cylindrical or slightly spherically arched inner recess in which the intermediate support ring 26 is received. The guide plate 27 is adapted at its outer periphery to the oval or elliptical housing section and is supported at the housing 2.
The take-up of the torque from the shaft 3 can generally take place in different manners. As FIG. 5 shows, the shaft 3 can have, at its two end face ends, two shaft stubs 13 which are turned on and which pass through the respective bearing covers 4 and advantageously respectively have a flattened section 28 onto which the respective pivot levers 29 can be placed. In this embodiment, the shaft stub 13 is therefore made integrally from material of the shaft 3. The polygonal profile section for the screw engagement with the respective piston 10, however, only extends inside the housing up to the bearing covers 4 (cf. FIG. 5).
Alternatively, the shaft stub 13 can also, as FIG. 6 shows, first be made as a separate component and be set onto the shaft 3 and be rigidly and rotationally fixedly connected thereto. This has the advantage that the diameter of the shaft stub 13 is not restricted by the geometry of the polygonal section of the shaft 3. The shaft stub in accordance with FIG. 6 can in particular be welded to the shaft 3, with a flattened section 28 also being provided here.
Alternatively, the twisted polygonal section of the shaft 3 can itself be guided through the bearing cover 4 and be supported on it. For this purpose, a support ring 30 is seated on the polygonal section of the shaft 3 and is rotatably supported, but axially fixedly supported, in the respective bearing cover 4, as FIG. 7 shows. The support ring 20 can, for example, be welded to the shaft 3. In any case, the shaft 3 is supported axially fixedly, but rotatably.
The outer support of the pistons 10 at the inner periphery of the housing 2 can generally take place in different manners. Instead of the plain bearing support shown in FIG. 2 in which the plain bearing surface of the piston is formed from its actual material, provision can also be made in accordance with FIG. 8 that corresponding plain bearing stones 31 of special plain bearing material are inserted into the outer peripheral surface of the respective piston 10. These plain bearing stones 31 are advantageously offset away from the center towards the flat sides of the piston to achieve a lever arm which is as large as possible on the torque support at the housing 2, as FIG. 8 shows. In the embodiment drawn in FIG. 8, the plain bearing stones 31 lie in the outer third of the piston 10 with respect to the cross-sectional longitudinal axis of the piston 10. The support stones 31 can be aligned in the ball cup-like recesses in the piston 10 by the circular contour and accordingly adapt to the contour of the housing or to the load yield.
As FIG. 9 shows, the plain bearing stones 31 are advantageously offset in the axial direction of the piston 10 towards its pressure charging sides and are arranged pair-wise on oppositely disposed sides of the housing seal 14. The arrangement of the housing seal 14 centrally between the plain bearing stones 31 ensures their lubrication since pressure medium can moved from the respective pressure chamber between the piston outer jacket surface 13 and the housing inner jacket surface until it impacts the seal 14.
Alternatively to the described plain bearing support, the respective piston 10 can also be supported by a roller bearing support 32 at the housing 2. As FIGS. 10 and 11 show, the roller bodies 33 can be arranged centrally with respect to the longitudinal direction of the piston 10 and, viewed in cross-section in accordance with FIG. 10, can be moved outwardly towards the narrow side of the piston 10 in the direction of the cross-sectional longitudinal axis to achieve a good lever arm for the torque interception. Generally, at least two roller bodies 33, advantageously, however, at least four roller bodies 33, are provided, with the roller bodies optionally also being able to be made elastically. As FIG. 11 shows, housing seals can be provided at the piston 10 at the outer jacket surface 13 of the respective piston 10 to the right and to the left of the roller bearing support 32.
As FIG. 12 shows, the roller bearing support 32 can advantageously also comprise a plurality of roller boy pairs 33 which, viewed in the axial direction of the piston 10, are arranged sequentially and moved towards the two pressure charging surfaces of the respective piston 10. Tilt movements of the piston 10 can thereby be better intercepted to a certain degree. In addition, a central seal 14 can be used at the outer jacket surface 13 of the piston 10 for its sealing with respect to the housing 2 and, as FIG. 12 shows, is arranged between the roller bodies 33 viewed in the axial direction. Pressure medium can hereby penetrate between the piston outer jacket surface 13 and the inner jacket surface of the housing 2 and thereby lubricate the roller bodies 13.
Irrespective of whether the piston is supported by plain bearing or roller bearing, an inner lubrication of the bearing positions can also be provided, as FIG. 13 shows. For this purpose, a pressure passage system 34 can be formed in the respective piston 10 and can advantageously have a pressure storing property or an actual pressure store 53, with the pressure passage system 34 being connected via a feed bore 35 to the bearing position of the piston 10 at the housing 2 and/or via a feed bore 36 to the bearing position of the piston 10 at the shaft 3 to provide lubricant thereto.
The pressure passage system 34 can advantageously be fed by the pressure chambers for the actuation of the piston 10, as FIG. 13 shows. The pressure passage system 34 in the interior of the piston 10 can communicate via feed bores 37 and check valves 38 with the end faces of the piston 10 in order to be supplied with pressure fluid on pressure charging of the respective chamber. As FIG. 13 shows, seals 12 and 14 can be provided at both sides of the support positions on the internal lubrication of the support positions of the piston 10.
In a similar manner as the internal lubrication, a bias of the pistons 10 or of the guide elements 41 or 42 on the shaft 3 and thus a freedom of clearance can also be achieved, as FIG. 14 shows. For this purpose, each piston 10 comprises two piston parts 10 a and 10 b which are axially displaceable with respect to one another, but are guided rotationally fixedly at the housing 2 and are in screw engagement with the shaft 3. The two piston parts are axially biased with respect to one another via a spring device 39 which can be a compression spring in the embodiment drawn in FIG. 14. Alternatively or additionally to the spring device 39, a bias of the two piston parts 10 a and 10 b can advantageously also take place by the pressure medium.
As FIG. 14 shows, the intermediate space 40 between the two piston parts 10a and 10 b communicates via check valves 38 with the respectively pressure charged side of the piston 10 which is the right hand side in FIG. 14. The pressure fluid enters into the intermediate space 40 via the check valves 38 at the pressure P so that the pressure P is also present therein. It is thereby ensured that the pressure P is borne off via the piston part at the front in the direction of movement, that is the piston part 10 a in accordance with FIG. 14. The rear piston part 10 b follows without pressure, since the same pressure P is applied at both sides. It is ensured via the compression spring 39 that the piston part at the front in the direction of movement, which bears off the pressure, or the piston guide provided thereat, contacts the respectively forwardly disposed screw thread flank so that clearance is precluded.
FIG. 15 shows a similar piston design 10 with bias and thus freedom of clearance. In contrast to FIG. 14, the pressure P is, however, borne off via the respective rear piston part, with the spring device 39 consisting of tension springs in this connection attempting to pull the two piston parts 10 a and 10 b or the guide elements toward one another so that they are in screw engagement with the shaft 3 without clearance. It is understood that both piston parts 10 a and 10 b are also rotationally fixedly guided at the housing 2 and are in screw engagement with the shaft 3 in the embodiment in accordance with FIG. 15.
To reduce the friction of the piston, it can be supported not only at its outer side by a roller bearing support at the housing 2; the piston 10 can instead also have a roller bearing support 41 instead of a plain bearing support at the shaft 3. In the embodiment drawn in the FIGS. 16 and 17, the shaft 3 can have a substantially rectangular cross-section, with the inner roller bearing support 41 of the piston 10 having roller bodies 42 which are seated at the edge of the flat sides of the shaft section, as FIG. 16 shows. The roller bodies 42 can optionally have marginal webs via which they are guided at the narrow sides of the polygonal section of the shaft 3. As FIG. 17 shows, the roller bodies 42 can be arranged centrally at the inner jacket surface 11 of the piston 10 viewed in the longitudinal direction. Shaft seals 12 can be arranged at both sides of the inner roller bearing support 41 at the inner jacket surface 11 of the piston 10.
Alternatively, a plurality of roller body pairs 42 can also be arranged spaced apart from one another at the inner periphery of the piston 10 in the axial direction with the roller bearing support 41, as FIG. 18 shows. Tilting torques acting on the piston 10 can be intercepted better to a certain degree by the arrangement of the roller bodies with respect to the pressure charged end faces of the piston 10. In addition, a sealing 12 arranged between the roller bodies 42 is sufficient so that an external lubrication of the bearing positions is simultaneously possible since, on pressure charging from one side, pressure medium can move between the shaft 3 and the inner jacket surface 11 of the piston 10.
The previously described arrangement of the inner roller bearing support 41 with only centrally arranged roller bodies 42 in accordance with FIG. 17, in contrast, has the advantage that pitch changes or pitch defects of the twisted polygonal section of the shaft 3 are possible.
To permit, on the one hand, a compensation of pitch changes or pitch defects in the twisted polygonal section of the shaft 3, but, on the other hand, nevertheless to ensure a load removal over a larger area, the pistons 10 can also be supported in each case by spherical guide elements 43 at the flanks of the shaft 3. The spherical guide elements 43 are inserted in ball cups in the inner peripheral surface 11 of the pistons 10 so that they twist in a multiaxially manner and can thus adapt to pitch changes. In the embodiment drawn in FIG. 19, the spherical guide elements 43 can form gliding stones which slidingly support the piston 10 at the shaft 3. It is, however, generally conceivable that roller bodies are fastened to the spherical guide elements 43 to achieve a roller bearing support.
A roller bearing support of the pistons 10 at the shaft 3 does not have to be restricted to an arrangement of the roller bodies at the flat sides 2 of the shaft 3. As FIG. 21 shows, the inner roller bearing support 41 of the pistons 10 can also comprise roller bodies 42 which run on the narrow sides 9 of the polygonal section of the shaft 3. In the embodiment drawn in FIG. 21, concave running tracks for the spherical roller bodies 42 are introduced into the narrow side 9 of the shaft 3 so that they also guide transversely to their running direction.
FIG. 22 shows an alternative to this. The narrow sides 9 of the shaft 3 can naturally also form spherical guide running tracks for the roller bodies 42 which have a convexly arched running surface in this embodiment (cf. FIG. 22). A transverse guidance of the roller bodies 42 with respect to the shaft 3 can also thereby be achieved.
With a plain bearing support of the pistons 10 on the shaft 3, the corresponding plain bearing surfaces can generally be formed by the material of the pistons 10. Optionally, for this purpose, the inner jacket surface of the pistons 10 can be hardened and/or worked in a suitable manner. Sliding stones 44 of a suitable plain bearing material can, however, advantageously be inserted into the inner jacket surface 11 of the pistons 10, as FIG. 23 shows. In this embodiment, the shaft 3 has a substantially rectangular cross-section with side flanks 45 chamfered toward the rim. The sliding stones 44 which are inserted into the inner jacket surface 11 of the piston 10 and whose rear side can be circular to achieve a self-adjustment run on these inclined side flanks 45.
As FIG. 24 shows, the sliding stones 44 can also be provided on the narrow sides 9 of the polygonal section of the shaft 3. The sliding stones 44 can advantageously have a spherical sliding surface which is set into a concave sliding surface in the narrow side 9 of the shaft 3, as FIG. 24 shows. A transverse guidance is hereby achieved. The sliding stones 44 can in particular be made of hardened round wire sections which are inserted into the shaft 9 and on which the narrow sides of the piston 3 run in the manner drawn in FIG. 24.
With a roller bearing support of the pistons 10 on the shaft 3, the roller bodies 42 can generally be guided in a roller body cage formed in accordance with the shaft body extent. Alternatively, however, an inner roller arrangement 41 can also be provided with peripheral roller bodies 42 and a return of the roller body 42, as FIG. 25 shows. In this connection, a roller body return passage 46 can be provided in the respective pistons 10 and the roller bodies 42 can be returned by it from the end of the roller body track between the piston and the shaft 3 to the start of the said roller body track. A constant circulation of the roller bodies 42 results, as indicated by the arrow 47 in FIG. 25.
Such a roller body return is naturally possible both with four-point roller bearing supports, as FIG. 25 shows, and with two-point roller bearing supports, as FIG. 26 shows, and also irrespective of whether the roller bodies 42 run on the flat sides 8 of the shaft 3 or on the narrow sides 9 of the shaft 3, as FIG. 26 shows. FIG. 27 illustrates the return of the roller bodies 42 via the roller body return passage 46. The return is in particular also advantageously made in the embodiment shown in FIG. 25 such that a raising of the balls is ensured and such that they can be returned with clearance, so-to-say free of force.
There are different possibilities with respect to the fastening of the bearing covers 4 to the housing 2. In addition to the screw connection of the bearing covers 4 to the end faces of the housing 2 shown in FIG. 28, the bearing covers 4 can also be welded to the housing 2, as FIG. 29 shows. Alternatively to this, the bearing covers 4 can also be inserted into the cylindrical housing 2 and can be secured to its inner jacket surface by securing rings 48 (cf. FIG. 30).
There are also generally different possibilities with respect to the production of the shaft 3. In accordance with an advantageous embodiment of the invention, the shaft 3 can be made of one piece, and indeed also when it has a direction change and has at least one right hand section and at least one left hand section, as FIG. 31 shows. For this purpose, starting from a direction change section 49, the initially cylindrical shaft blank which differs from the circular shape in cross-section can be twisted in opposite senses toward its ends, for example by cold shaping or hot shaping, so that the right hand and left hand screw engagement sections 50 a and 50 b shown in accordance with FIG. 31 are created. Toward the end, the twisting-in-itself of the shaft section can be stopped to obtain non-twisted shaft stubs 23 which facilitate the connection of corresponding pivot levers for the torque pick-up. The previously described bearing rings 20 can be welded onto the integrally produced shaft 3 to be able to support the shaft 3 in the bearing covers 4.
Alternatively, the double-threaded shaft 3 can be made from two pieces, as FIGS. 32 to 34 illustrate. Two shaft pieces twisted in themselves can be screwed together at the end face, preferably via two coupling pieces 51, which are fixedly seated on the shaft pieces and are made elastic or can effect an elastic coupling (cf. FIG. 32).
Alternatively, the two shaft pieces of the shaft 3 can also be connected to one another in a firmly bonded manner, in particular by friction welding 52 (cf. FIG. 33).
As FIG. 34 shows, a screw connection or a butt joint of the right hand and left hand shaft pieces is also possible. For this purpose, the two shaft pieces can be inserted into a screw connection sleeve in which they are fixed by a transverse screw connection.
In the embodiment shown in FIGS. 35 and 36, the housing 2 is extruded or made as an extrusion molded section. A housing can thereby in particular be manufactured whose outer contour differs from its inner contour. The outer contour, which is made substantially rectangular in accordance with FIGS. 35 and 36, can be adapted to the respective installation situation. At the same time, with the outer contour preset by the installation situation, the inner contour of the housing 2 can be made such that a useful piston surface is achieved which is as large as possible. As FIG. 35 shows, the housing section has a plurality of axial bores in which tie bars or screw bolts are received in order, for example, to fasten the end-face covers. The inner contour of the housing 2 fits snugly around these axial bores and, in another respect, follows the outer contour—predetermined by the required wall thickness—to achieve a piston cross-sectional surface which is as large as possible.
The central shaft bearing support 5, which supports the shaft 3 centrally at its direction change section, can advantageously also be fastened to the threaded bars. The central shaft bearing support 5 can advantageously also be made as an axial bearing in order, for example, to be able to take up residual axial forces resulting from pitch defects of the shaft. Advantages can be achieved with respect to the kink length of the housing 2 and/or of the shaft 3 by a central axial bearing support of the shaft 3.
In another respect, FIG. 36 shows two passage bores 50 in the guide plate 27 and the pressure chambers 16 and 17 can be connected with one another through them.
In the embodiment shown in FIG. 37, the shaft 3 and the piston 10 each have a wing shape. As in particular FIG. 39 shows, the shaft 3 comprises a cylindrical, in particular a circularly cylindrical, base body 63 on whose outer jacket surface yield noses 60 are provided in the form of rail-like wing projections 64 which are arranged disposed oppositely one another and are wound around the axis of rotation of the shaft 3. The winged shaft formed in this manner can advantageously be manufactured by milling. The said rail-like wing projections 64 extend spirally and can advantageously be shaped integrally in one piece at the base body 63. The maximum shaft diameter measured in the region of the oppositely disposed wing projections 64 is, in the embodiment drawn, approximately 30 to 40% larger than the minimum shaft diameter measured in the region of the base body 63, cf. FIG. 37. The base body 63 advantageously has a fairly large diameter with a circularly cylindrical design to achieve a good torque yield, with the radial overhang of the wing projections 64 being dimensioned only so large that the permitted surface pressing is observed with the torque yield. The volume to be displaced can also thereby be kept small. The shaft 3 can in particular be designed as a torsion shaft with a large pitch.
As FIGS. 37 and 39 show, the shaft 3 is made as a hollow shaft. This does not only effect a reduction in weight. At the same time, the axial cut-out 61 at the interior of the shaft 3 can be used as a bore for the oil feed.
The piston 10 is adapted at its inner peripheral surface to the outer contour of the shaft 3. The piston 10 in particular has a circularly cylindrical inner cut-out in the embodiment drawn in accordance with FIG. 37 which has groove-shaped recesses at oppositely disposed sides which engage around the said wing projections 64 in a shape-matched manner, cf. FIG. 37.
At its outer contour, the piston 10 likewise has two yield noses 62 in the form of rail-shaped radial wing projections 65 on oppositely disposed sides, cf. FIG. 37. The outer contour of the piston 10 is bounded by a segmentally circularly cylindrical and/or elliptical peripheral surface between the said wing projections 65.
The inner peripheral surface of the housing 2 is adapted in a corresponding manner to the wing shape of the piston 10.
Alternatively, the rotary motor can also have the pressed-flat cross-sections, in particular elliptical or oval cross-sections, shown in FIG. 38. As FIG. 38 shows, the shaft 3 can also be made as a hollow shaft in this embodiment, whereby the inner axial cut-out 61 can be used as a bore for the oil guide. The shaft 3 is twisted in itself in this connection in its oval or elliptical cross-section, i.e. around its axis of rotation, so that it forms an oval or elliptical spiral shaft overall. The shaft 3 can in particular be cast and ground. The shaft 3 can optionally also be swirled; however, a better surface quality is immediately achieved by grinding.
The housing 2 can consist in the embodiment drawn in FIG. 38 of a cylindrical tube which can be pressed or spread into the desired flat shape while maintaining its surface property.
A smaller load yield lever is created by the oval or elliptical shape shown in FIG. 38 than in the embodiment drawn in FIG. 37; however, this smaller load yield lever is easy to compensate due to the specific form drawn.
The housings 2 are each shown with one shell in FIGS. 37 and 38. In both embodiments, in particular, however, in the embodiment of FIG. 37, the housing 2 can be made in compound construction. An embodiment of such a compound construction of the housing is shown in FIG. 40, according to which the inner shell 66 adapted to the wing shape of the piston 1 is surrounded by a support body 67 which is in turn enveloped by an outer shell 68. The different shells advantageously consist of different materials and are adapted to their respective function. The inner shell 66 can, for example, consist of a suitable metal and preferably have a hardened, for example a nitrated, inner surface to form a low-wear and low-friction running track for the piston 10. The support body 67 advantageously consists of a suitable integral material and can in particular be made from hard foam, aluminum foam or a suitable casting mass. The elliptical outer shell 68 in the drawn embodiment in accordance with FIG. 40 can consist of different materials. An advantageous embodiment can consist of the fact that the outer shell 68 consists of fiber-reinforced plastic, for example a GRP reinforced wrapping material.
A sandwich-like structure of the housing 2 with an inner shell and an outer shell of hard-surface, high-strength material and a support body connecting them of a lighter, less impact-resistant material can achieve very high strengths and shape stabilities with a low weight and can moreover effect the advantages first mentioned.
As FIG. 41 shows, the outer shell 68 can also be adapted to the connection geometry of a component to be connected to the housing 2. The outer shell 68 can in particular have at least one plane contact surface 69. It is advantageously possible to give the outer shell 68 a substantially cubic shape overall. Alternatively or additionally, fastening options can be integrated into the housing 2 in a simple manner by the compound construction. As FIG. 41 shows, threaded nuts 70 can, for example, be set onto the outer shell 68 from the inner side and be foamed into the housing 2.
Alternatively to a three-shell structure of the housing 2 with a support foam body, the inner shell 66 can also be directly embedded into the outer shell 68, as FIG. 42 shows. The outer shell 68 is in this connection advantageously made as an extrusion section or as an extrusion molded section. The outer shell 68 can, for example, be extruded from GRP or pressed from an aluminum extrusion. The outer shell 68 advantageously comprises a plurality of axial hollow spaces 72, with a uniform cross-section being provided overall in the axial direction. Securing options, for example in the form of threaded nut receivers 71, can also be integrated into the shell in the embodiment in accordance with FIG. 42.

Claims

1. A rotary motor, preferably a pivot drive for construction machinery, trucks and the like, comprising an elongate housing (2), preferably an approximately tubular housing, at least one piston (10) displaceably received in the housing (2), which is axially displaceable by charging with a pressure medium in a pressure chamber (15, 16, 17, 18), and a shaft (3) received axially fixedly, but rotatably in the housing (2), with the piston (10) being in screw engagement with the shaft (3) and/or the housing (2), wherein a surface pair (8, 9; 11) of piston (10) and shaft (3) and/or of piston (10) and housing (2) effecting the screw engagement simultaneously forms a sealing surface pair for the sealing of the pressure chamber (15, 16, 17, 18) for the pressure charging of the piston (10).

2. A rotary motor in accordance with claim 1, wherein the piston (10) has equally large effective piston surfaces on its two oppositely disposed sides for the pressure charging by the pressure chambers (15, 16, 17, 18).

3. A rotary motor in accordance with claim 1, wherein the shaft (3) has a polygonal sectional cross-section differing from the circular shape in at least one screw engagement section (50) and is twisted spirally around its longitudinal axis.

4. A rotary motor in accordance with claim 1, wherein the shaft (3) is made as winged shaft whose cross-section has at least one radially projecting wing-like yield nose (60), preferably two mutually oppositely disposed such yield noses (60), for the torque yield.

5. A rotary motor in accordance with claim 1, wherein the shaft (3) has a circular cross-section, apart from the at least one yield nose (60), viewed in cross-section.

6. A rotary motor in accordance with claim 1, wherein the outer diameter of the shaft (3) is larger in the region of the at least one yield nose (60) by at least 15%, preferably by approximately 25 to 50%, than the outer diameter of the shaft (3) in sections without a yield nose.

7. A rotary motor in accordance with claim 1, wherein the shaft (3) has a substantially oval cross-section.

8. A rotary motor in accordance with claim 1, wherein the shaft (3) is made as a hollow shaft and/or has an axial cut-out (61) in its interior for the supply and/or draining of the pressure medium.

9. A rotary motor in accordance with claim 1, wherein a seal (12) is inserted into the inner jacket surface (11) of the piston (10) being in screw engagement with the shaft (3).

10. A rotary motor in accordance with claim 1, wherein the piston (10) has an inner cut-out which forms a profile section substantially corresponding to the cross-section of the shaft (3).

11. A rotary motor in accordance with claim 1, wherein the piston (10) is made as a wing piston whose cross-section at the outer periphery has at least one radially projecting yield nose (62), preferably two mutually oppositely disposed such yield noses (62), for the torque yield with respect to the housing (2).

12. A rotary motor in accordance with claim 11, wherein the piston (10) has a contour corresponding to the flat side of an ellipse in a cross-sectional section without a yield nose (62).

13. A rotary motor in accordance with claim 1, wherein the housing (2) has a cylindrical inner jacket surface differing from the circularly cylindrical shape, at which the outer jacket surface (13) of the piston (10) is guided and rotationally fixedly supported.

14. A rotary motor in accordance with claim 1, wherein the housing (2) has a pressed-flat cross-section, preferably an approximately elliptical or oval cross-section.

15. A rotary motor in accordance with claim 1, wherein the housing (2) has a cross-section whose outer contour differs from its inner contour.

16. A rotary motor in accordance with claim 1, wherein the housing (2) is made as an extruded section and/or as an extrusion molded section.

17. A rotary motor in accordance with claim 1, wherein the housing (2) is made as a compound housing which has a plurality of mutually connected shells set into one another.

18. A rotary motor in accordance with claim 17, wherein the shells are made of different materials.

19. A rotary motor in accordance with claim 1, wherein the compound housing comprises an inner shell in engagement with the piston (10) and an outer shell forming the outer envelope of the housing.

20. A rotary motor in accordance with claim 19, wherein a support body, preferably of a foam material and/or of a cast material, which connects the outer shell to the inner shell, is provided between the inner shell and the outer shell.

21. A rotary motor in accordance with claim 1, wherein a seal (14) is inserted into the outer jacket surface (13) of the piston (10) being in rotationally fixed engagement with the inner jacket surface of the housing (2).

22. A rotary motor in accordance with claim 1, wherein the piston (10) is supported at the housing (2) and/or at the shaft (3) by plain bearings.

23. A rotary motor in accordance with claim 1, wherein the piston (10) is supported at the housing (2) and/or at the shaft (3) by roller bearings (32; 41).

24. A rotary motor in accordance with claim 1, wherein the twisted polygonal section of the shaft (3) has a uniform pitch over its length.

25. A rotary motor in accordance with claim 1, wherein the twisted polygonal section of the shaft (3) has a pitch changing over the length of the shaft (3).

26. A rotary motor in accordance with claim 1, wherein a plurality of pistons (10) are seated on the shaft (3) in screw engagement.

27. A rotary motor in accordance with claim 1, wherein two pistons (10) to be moved in opposite senses are arranged on the shaft (3) and the shaft (3) and/or the housing (2) have screw engagement sections in opposite senses.

28. A rotary motor in accordance with claim 1, wherein the shaft (3) is radially supported at a direction change section (49).

29. A rotary motor in accordance with claim 1, wherein the shaft (3) is supported at a direction change section (49) and/or axially approximately centrally.

30. A rotary motor in accordance with claim 1, wherein two pistons (10) or piston parts (10 a, 10 b) biased axially with respect to one another are seated on the shaft (3).

31. A rotary motor in accordance with claim 1, wherein a bias apparatus for the biasing of the two pistons (10) or piston parts (10 a, 10 b) comprises a hydraulic pressure store between the two pistons (10) or piston parts (10 a, 10 b) and/or can be fed by pressure medium from the pressure chambers (15, 16, 17, 18) for the actuation of the piston (10).

32. A rotary motor in accordance with claim 1, wherein the two pistons (10) or piston parts (10 a, 10 b) can be biased toward one another or apart from one another by a mechanical spring device (39).

33. A rotary motor in accordance with claim 1, wherein the shaft (3) is supported by means of bearing covers (4) which are seated axially at end faces at the ends of the housing (2) and close the latter.

34. A rotary motor in accordance with claim 1, wherein seals are provided between the bearing covers (4) and the shaft (3) for the sealing of the pressure chambers (15, 18), with the seal preferably being integrated in the bearing surface in each case at which the shaft (3) is rotatably supported at the bearing cover (4).

35. A rotary motor in accordance with claim 1, wherein the shaft (3) is shaped from a substantially cylindrical shaft blank which has a polygonal sectional cross-section differing from the circular shape, the shaft blank is twisted in itself around its longitudinal axis by non-cutting shaping so that its outer contour forms a polygonal section twisted in itself.

36. A method in accordance with 35, wherein the shaft blank is twisted in opposite senses starting from a direction change section (49) toward oppositely disposed sides.

37. A method in accordance with claim 36, wherein two shaft blanks twisted in opposite senses are rotationally fixedly connected to one another, preferably screwed to one another and/or welded to one another.

38. Use of the rotary motor in accordance with claim 1 for the pivoting of a loading board wall of a truck.