A RADIAL PISTON MOTOR OR PUMP

Abstract: A motor or pump assembly (1) comprises a cylinder block (4) with a plurality of radially positioned cylinders (3), a piston (2) arranged slidably reciprocable in each of the cylinders, a cam ring (7) cooperating with the pistons and being rotatably journalled on the cylinder block, and a distributor valve (9) arranged centrally in the cylinder block to control a flow of fluid to and from the cylinders in operation. To obtain a relatively large diameter on the rollers and thereby less wear on both the cam ring and the rollers while reducing the outside diameter of the assembly, the rollers are journalled without axial lateral guide at the top end of the pistons, the pistons (2) being guided by the sides (32a, 32b) in a groove provided in the cam ring (7). The material of the pistons is moreover removed from both sides as far as the roller so that the piston with a central portion (33) can follow the roller into the groove, whose depth thereby partly overlaps the travel of the piston.

Description: A radial piston motor or pump The invention concerns a motor or pump assembly comprising a cylinder block with a plurality of radially positioned cylinders, a piston arranged slidably reciprocable in each of the cylinders, a cam ring cooperating with the pistons and being rotatably journalled on the cylinder block, and a distributor valve arranged centrally in the cylinder block to control a flow of fluid to and from the cylinders in operation, said cam ring cooperating with the pistons via rollers, each of which being rotatably journalled at the top of the associated piston. Assemblies of this type operate in the manner that during mutual rotation between the cam ring and the cylinder block the pistons travel to and fro in their cylinders in step with a boss or roller on the piston top running up and down a plurality of wave-shaped cams on the inner side of the cam ring. This special pattern of motion entails that the assembly cannot or has difficulty in operating at greater relative speeds of rotation, and that it must be constructed with corresponding large dimensions to be able to provide the desired power. It therefore frequently pre- sents considerable difficulties to incorporate conventio¬ nal assemblies of this type in machinery with restricted space, as is e.g. the case in the apparatus described in the applicant's International Patent Application PCT/DK89/00213 for drilling underground bore holes. Owing to the large output moment of the assembly at low speeds of rotation it would otherwise, i.e. apart from its great space requirement, be extremely suitable for direct incor¬ poration as a drive motor in the wheels of the drilling apparatus, as well as in other cases where the special properties of the assembly can be utilized to advantage. The object of the invention is to provide an assembly of the type stated in the opening paragraph, which, with a reduced outside diameter with respect to the capacity, operates with less wear on both the cam ring and the rollers than known before, and which is simultaneously of a simple and inexpensive structure that is easy to dis¬ mantle and assemble again in connection with service and repair. The rollers, which run on the cam ring in operation, serve to reduce friction between the cam ring and the piston as much as possible. To obtain a relatively large diameter on the roller and thereby less wear on both the cam ring and the rollers, the invention is novel and unique in that each of the rollers is journalled in a slide bearing pro¬ vided directly at the top end of the piston without the roller being axially guided. In an advantageous embodiment, such guide takes place in that the rollers run in a ring-shaped groove whose sides have a mutual distance just slightly greater than the roller width, and whose bottom contains the cams of the cam ring. To facilitate production and possible exchange of worn parts, the groove can advantageously be formed by three rings positioned side by side, the central one of which forming the bottom of the groove and the two outermost ones the sides of the groove. When the width of the rollers is smaller than the diameter of the piston, which will usually be the case for practi¬ cal reasons, the material of the piston is removed in an area at the piston top at both sides of the roller, so as to leave a central portion on the piston of the same width as the roller. The travel of the piston and the radial ex- tent of the groove can hereby partly overlap each other, and the piston, with its central portion, can follow the roller into the actual groove. This arrangement additio¬ nally contributes to limiting the outside diameter of the assembly without reducing the support of the roller, since the bearing for this is fully maintained in the central portion. Also, to ensure that the rollers are never dis¬ engaged from the groove, the groove is constructed such that its sides at the mouth have a smaller diameter than the cylinder face enveloping the rollers in the bottom position of the pistons. The invention will be explained more fully by the follow¬ ing description of embodiments, which just serve as ex- amples, with reference to the drawing, in which fig. 1 is a radial section through an assembly according to the invention, fig- 2 shows a first embodiment of an assembly according to the invention, seen along the line II-II in fig. 1, fig. 3 shows a second embodiment of an assembly according to the invention, seen along the line III-III in fig. 1, fig. 4 is a perspective view of a fragment of a tripartite cam ring associated with the assembly and a piston with a roller running in a groove in the cam ring, and fig- 5 is an enlarged end view of a carrier pin with two mutually angularly displaced slots for reversing the rela¬ tive direction of rotation. In principle, the assembly of the invention can work with any fluid and serve as either a motor or a pump in re¬ sponse to the circuit of the fluid. The invention is des- cribed below on the assumption that the assembly is a mo¬ tor working with hydraulic oil fed from a source of pres¬ sure, e.g. a hydraulic pump. In fig. 1, the hydraulic motor, which is generally indi¬ cated by 1, is shown in radial section. In this case the motor has eight pistons 2 capable of travelling to and fro in cylinders 3, which are provided in a cylinder block 4 and extend radially outwardly in it at equidistant angu- lar distances. Each piston rotatably mounts a roller 5 in a slide bearing 6 provided at the top of the piston 2. A cam ring 7 having six wave-shaped cams 8 on the inner side is arranged around this arrangement, and, as shown, the rollers 5 rest against these cams in any of the positions of the pistons. As shown in fig. 2, a drum-shaped distributor valve 9 is arranged centrally in the cylinder block 4, said distri¬ butor valve being firmly connected with the cam ring 7 by means of a carrier plate 10, which is screwed firmly on to the cam ring 7 by screws 11 and engages, by means of a carrier pin 12 with a slot 13, a tongue 14 on a coupling member 15 secured to the distributor valve 9. The carrier plate 10 extends at a small distance past the cylinder block 4, which can therefore rotate freely with respect to the cam ring 7. The carrier plate 10 has a feed channel 16 for the hydraulic oil which is fed under pressure from a pump having an oil reservoir, which receives the return oil from an outlet channel 17 in the carrier plate. These channels 16, 17 are connected in the carrier pin 12 with a first set of distributor channels 18a which, via a second set of distributor channels 18b in the bottom of the cy¬ linders 3, control the flow of oil out of and into these. Three 0-rings provide a safeguard against overflow between the individual channels and out to the other parts of the motor. The arrangement and mode of operation of the dis- tributor valve per se are of a conventional type and will therefore not be described more fully here. The carrier plate 10 continues into a flange 20 with fix- ing holes 21 for attaching the motor on the site of use. In this case, the cam ring 7 is thus stationary, while the cylinder block rotates when the motor works. The torque is made available via a shaft 22 which with a shaft plate 23 is screwed firmly onto the cylinder block 4 by means of screws 24. Of course, the arrangement might be the re¬ verse, so that it was the cylinder block that was statio¬ nary, while the cam ring rotated, the output shaft being provided on the carrier plate. As shown in figs. 2 and 3, the cylinder block 4 is con¬ structed as a disc which is only so much wider than the pistons 2 as is necessary for reasons of strength. The cam ring 7 is provided with approximately the same width as the cylinder block 4 and is journalled on it with balls 25 running in grooves, which are provided in an area close to the sides and periphery of the disc-shaped cylinder block on the cam ring and the cylinder block, respectively, which will thereby form the inner and outer race in a bearing. By means of the above-mentioned arrangement the bearing, which is constructed as an angular contact bearing in the shown embodiment, will be capable of absorbing much greater loads laterally as well as radially because of its large diameter than corresponding conventional structures. In addition to this advantage, the motor is given a very compact structure in the form of a relatively narrow disc having a relatively small diameter and axial extent. Fig. 3 shows a second embodiment of a motor which is arranged as a wheel for the self-propelling drilling appa- ratus described in the applicant's previously mentioned patent application PCT/DK89/00213, which is incorporated in the present application as a reference. In this case, the cylinder block 4, which is swingably suspended from the drilling apparatus (not shown) with a wheel plate 26, is stationary, while the cam ring 7 is rotatable and serves to transfer the traction forces of the drilling apparatus to the wall of the bore hole via a bandage 27 of an elastic material, e.g. rubber. In the shown embodiment the cam ring 7 is divided into three rings which are clamped together with screws 28. The three rings consist of a central ring 29 and two lateral rings 30a, 30b. These three rings together define a groove whose bottom contains the cams 8 of the cam ring 7, and whose sides 32a, 32b serve to guide the rollers 5 in their axial direction in a manner which will be explained more fully below. A corresponding groove is provided in the embodiment shown in fig. 2, where, however, the cam ring is not correspondingly divided into three rings. This di¬ vision provides the advantage that it is cheaper to manu¬ facture the cam ring with the groove, and that the motor can be disassembled and assembled again more easily for service and replacement of worn parts. Otherwise, the general arrangement of the wheel essentially corresponds to that of the previously described embodiment, to which reference is therefore made in this connection. As shown in fig. 4, the roller 5 is constructed with a smaller axial length than the width of the piston 2 for practical reasons; the piston 2 is moreover so machined in an area at the roller as to leave a central member 33 which has the same width as the roller, and in which a slide bearing 34 is provided to support the roller. During mounting, the roller is pushed inwardly from the end of the bearing, the roller being supported radially, but not axially. However, axial support is provided in the as¬ sembled state of the motor by the sides 32a, 32b of the previously mentioned groove, which have the same or a slightly different mutual distance than the axial length of the roller, the sides 32a, 32b also having a diameter at the mouth of the groove which is smaller than the cy¬ linder face enveloping the rollers in the bottom position of the pistons, so that the rollers cannot leave the groove at any point of it. The cams 8 are positioned in the bottom 31 of the groove, which limits outward travel of the pistons at the deepest point between the cams, while the bottom of the cylinders limits the travel inwardly. Since the central member 33 has the same width as the axial extent of the roller, this part of the piston can follow the roller into the groove. The piston travel and the depth of the groove will hereby partially overlap each other and reduce the outside dia¬ meter of the motor by a size corresponding to twice this overlap. This arrangement and the previously described bearing structure provide the advantage that the motor of the invention can be constructed with a much smaller dia¬ meter than conventional motors of this type with the same performance. Fig. 4 also shows a piston ring 35 to seal the pistons 2 with respect to the cylinders 3 during ope¬ ration. Fig. 5 is an end view of an embodiment of a piston pin 12 with two slots 13a, 13b forming such an angle a with each other that, when engaged with the tongue 14 of the coup¬ ling part 15 (fig. 2), they position the distributor valve 9 in positions which correspond to their respective oppo¬ sitely directed relative directions of rotation, which can be reversed simply and easily, if desired. The angle a is a function of the cam number n and can be expressed by a = 1/2 x 360 ' + m x 360 ' n n m being a whole multiple of the angle between two cams. In the shown example with six cams: σ = 30° + m x 60°. The assembly of the invention is described above in its function as a hydraulic motor and with exemplary ways of attaching the stationary part, i.e. either the cylinder block or the cam ring, and making the torque available from the rotating part. However, the said connections of the two parts can take place in many other ways within the scope of the invention, which might be expedient for the purposes for which the motor is to be used in each indivi¬ dual case. As mentioned before, with the same fundamental structure as "the motor the assembly can conversely serve as a hy¬ draulic pump, either the cylinder block or the cam ring being then caused to rotate by means of an outer source of power, e.g. a motor. In this case too, the compact struc¬ ture of the assembly is beneficial when the assembly is to be used in restricted space. The working range of the pump is substantially at relative low numbers of revolutions, and the pump is therefore extremely suitable for purposes where the pump is to be incorporated in machinery, e.g. agricultural machinery with slow-speed shafts for driving the pump, since the pump can then be used directly without any costly intermediate gear having to be inserted. It should moreover be mentioned that both in its function as a motor and as a pump the assembly can work with any suitable fluid. Thus, hydraulic oil is mentioned by way of example in the foregoing, but also air may advantageously be chosen as working fluid for many purposes, so that the motor is driven by compressed air and the pump will be in the nature of a compressor that generates compressed air.

Claims: P a t e n t C l a i m s : 1. A motor or pump assembly comprising a cylinder block with a plurality of radially positioned cylinders, a pis¬ ton arranged slidably reciprocable in each of the cylin¬ ders, a cam ring cooperating with the pistons and being rotatably journalled on the cylinder block, and a distri¬ butor valve arranged centrally in the cylinder block to control the flow of fluid to and from the cylinders in operation, said cam ring cooperating with the pistons via rollers, each of which being rotatably journalled at the top end of the associated piston, c h a r a c t e r ¬ i z e d in that the bearing for the roller is a slide bearing provided directly at the top end of the piston without an axial guide for the roller. 2. An assembly according to claim 1, c h a r a c t e r ¬ i z e in that the width of the roller is smaller than the diameter of the piston, and that the material is re¬ moved in an area at the roller bearing of the piston as far as a central portion which is defined by two prefer¬ ably parallel planes, which are perpendicular to the axis of the bearing and substantially have a mutual distance corresponding to the width of the roller. 3. An assembly according to claim 1 or 2, c h a r a c ¬ t e r i z e d in that the cams of the cam ring are posi¬ tioned in the bottom of a ring-shaped groove with sides, which have a mutual distance corresponding to the width of the rollers and, at the mouth of the groove, a smaller diameter than the cylinder face enveloping the rollers in the bottom position of the pistons. 4. An assembly according to claim 1, 2 or 3, c h a ¬ r a c t e r i z e d in that the cam ring is divided into three juxtaposed rings, the central one of which forming the bottom of the groove and the two outermost ones the sides of the groove. AMENDED CLAIMS [received by the International Bureau on 27 April 1992 (27.04.92) original claims 1-4 replaced by amended claims 1-3 (1 page)] 1. A motor or pump assembly comprising a cylinder block with a plurality of radially positioned cylinders, a pis¬ ton arranged slidably reciprocable in each of the cylin¬ ders, a cam ring cooperating with the pistons and being rotatably journalled on the cylinder block, and a distri¬ butor valve arranged centrally in the cylinder block to control the flow of fluid to and from the cylinders in operation, said cam ring cooperating with the pistons via rollers, each of which being rotatably journalled at the top end of the associated piston, wherein the bearing for the roller is a slide bearing provided directly at the top end of the piston without an axial guide for the roller, c h a r a c t e r i z e d in that the width of the roller is smaller than the diameter of the piston, and that the material is removed in an area at the roller bearing of the piston as far as a central portion which is defined by two preferably parallel planes, which are perpendicular to the axis of the bearing and substantially have a mutual distance corresponding to the width of the roller. 2. An assembly according to claim 1 , c h a r a c t e r - i z e d in that the cams of the cam ring are positioned in the bottom of a ring-shaped groove with sides, which have a mutual distance corresponding to the width of the rollers and, at the mouth of the groove, a smaller dia¬ meter than the cylinder face enveloping the rollers in the bottom position of the pistons. 3. An assembly according to claim 1 or 2, c h a r a c ¬ t e r i z e d in that the cam ring is divided into three juxtaposed rings, the central one of which forming the bottom of the groove and the two outermost ones the sides of the groove.

Inventors: HALLUNDBAEK JORGEN, HALLUNDBAEK, JOERGEN
Applicants: HTC AS, HTC A/S
Application year: 1991
Main classification: F04B1
IPC codes: F01B1, F01B13, F03C1, F04B1