Title of Invention : Radial piston rotary machine

Technical Field

[0001 ] The invention relates to a radial piston rotary machine, which can be used as a pump, a compressor, a vacuum pump or a motor.

Background Art

[0002] Reciprocating rotary machines are known, especially pumps or compressors, which comprise a rotor of circular cross-section, in which chambers for pistons are provided, where the pistons are mounted on circular cams to perform reciprocating movement, and these cams are arranged on a shaft, which is mounted eccentrically to the rotor. The eccentricity of the axis of the shaft from the axis of the rotor axis s equal to the eccentricity of the cam from the axis of the shaft.

[0003] US 6206661 Bl discloses a hermetic compressor including a compressor mechanism section, which includes first and second rotary cylinders, and first and second pistons eccentrically rotated in first and second grooves in the first and second rotary cylinders. The compressor mechanism is in a casing and is between, upper and lower bearings which clamp the first and second rotary cylinders and the casing. The pistons have circular shape, where sides of the piston open and close alternately inlet and outlet openings created in bodies of the upper and lower bearing. Disadvantage of this solution is that the circular piston and the cylinder are in contact at a single point, in fact a single line, which can present critical point regarding for example the wear and tear and subsequent leaks. Also, use of this machine for applications other than those described in the mentioned document is limited, which is considered as disadvantage.

[0004] Object of the invention is a piston rotary machine that can be used as a pump, a compressor, a vacuum pump or a motor, which is characterized in manufacturing simplicity, while practically eliminating all disadvantages and limitations resulting from designs of the state of the art. Such piston rotary machine would also allow production of pumps, compressors and vacuum pumps for a wide range of applications and pressure ranges while maintaining the same design arrangement. At the same time, it is also desirable that such design in particular a compressor or a vacuum pump would be able to work without a lubricant, or in the so-called oil-free operation.

Summary of Invention

[0005] Said object is achieved by a radial piston rotary machine according to the invention comprising a housing, at least one opening for inlet of a medium to the machine and at least one opening for outlet of the medium from the machine, where the housing comprises end caps between which a rotor is rotatably mounted, this rotor is composed of at least two plates, where a chamber for a reciprocating piston is provided in the rotor plate, and the rotor plates are separated by a partition plate with an opening for a shaft of the machine, the shaft being mounted in rotary bearings in the end caps of the housing, circular cams are arranged on the shaft, the shaft is mounted eccentrically to the rotor, where the eccentricity of the axis of rotation of the shaft from the axis of the rotor is equal to the eccentricity of the axis of the circular cam from the axis of rotation of the shaft, each piston is placed movably in reciprocation motion in the chamber for the piston in the rotor plate and rotatably on the circular cam on the shaft, where the inlet and outlet of the medium to and from the piston chamber are opened and closed by valve means. The machine according to this invention is characterized in that the chamber for the piston is formed as a hole in the rotor plate, where at least two opposite walls of the hole are parallel for sliding arrangement of the piston. This piston has at least two parallel opposing sides corresponding to two parallel opposing walls of the hole in the rotor plate, where the piston is closed axially in the chamber at one side by the partition plate of the rotor plates and at the other side by an end plate of the rotor. The end plate comprises an opening for the shaft and apertures for the inlet and outlet of the medium to and from the piston chamber located by the walls of the hole in the plate forming the piston chamber that are against free ends of the piston. The apertures lead in the axial direction to the end cap of the housing, and are opened and closed by valve means in the form of separate arcuate slots.

Brief Description of Drawings

[0006] The invention is for better understanding illustrated in attached drawings, in which:

[0007] Fig. 1 shows axonometric section view of the radial piston rotary machine, namely a compressor;

[0008] Fig. 2 shows axonometric exploded view of the machine of Fig. 1 with electric motor;

[0009] Fig. 3 shows axonometric sectional view of the assembled machine of Fig. 2;

[0010] Fig. 4 shows axonometric view of the rotor of the machine with the shaft;

[0011 ] Fig. 5 shows axonometric view of the valve means;

[0012] Fig. 6 shows front view of the valve means from the inside of the machine;

[0013] Fig. 7 shows front view in direction towards the end cap of the housing, with exposed part of the rotor within the machine, in the phase of the operation of the machine with the piston in one extremity;

[0014] Fig. 8 shows front view in direction towards the end cap of the housing, with exposed part of the rotor within the machine, in the phase of the operation of the machine with the piston in middle position;

[0015] Fig. 9 shows overall axonometric external view of the radial piston rotary machine with electric motor.

Description of Embodiments

[0016] A radial piston rotary machine according to the present invention is explained more in detail by examples of embodiments shown in the figures.

[0017] The machine shown in Fig. 1 to 9 is namely a compressor.

[0018] The machine according to the examples shown is provided with two pistons 4, each slidingly reciprocating in one chamber 22 of a rotor 2, where chambers 22 are arranged at an angle of 90° to each other. [0019] The machine, the compressor, according to Fig. 1 to 9, comprises a housing, in the example shown in the form of a case 1 closed by end caps 11. The rotor 2 is rotatably mounted in the housing. The rotor 2 is composed of plates 23, between which a partition plate 24 is arranged and a free side of each plate 23 is then provided by an end plate 7 of the rotor 2. An opening 21 for a shaft 5 of the machine is provided in the partition plate 24 and the end plates 7. Further, apertures 71 are provided in the end plates 7 for the inlet and outlet of a medium to and from the chamber 22 formed in the plate 23 for a piston 4, where the apertures 71 lead in the axial direction to the end cap 11 of the housing.

[0020] Thus, the chamber 22 for the piston 4 is provided in each plate 23 of the rotor 2. The chamber 22 is formed in the plate 23 as a hole, where two opposite walls of the hole are parallel for sliding arrangement of the piston 4. In the embodiment shown in the figures, the chambers 22 and their respective pistons 4 have the shape of a rectangle in their cross-section. The term hole means an opening, void, and so, created in the plate 23 for example by cutting, punching, milling, and so, the material of the plate 23, or also by excluding the material of the plate 23 for example during casting, moulding, 3D printing and so.

[0021 ] In particular, the chambers 22 are rectangular and the pistons 4 are square in their cross-sections. The piston 4 is arranged in the chamber 22 in reciprocating manner, slidably with its two parallel opposite surfaces along two respective parallel opposite surfaces of the chamber 22. The piston 4 is axially closed in the chamber 22 at one side by a partition plate 24 between the plates 23 of the rotor 2 and at the other side by the end plate 7 of the rotor 2. The partition plate 24 of the rotor 2 separates the chambers 22 and prevents passage of the working medium from one chamber 22 to the other.

[0022] Thus, the piston 4 moves in the chamber 22, where walls of the chamber 22 are formed by the walls of the hole in the rotor plate 23, adjacent surface of the partition plate 24 between the plates 23, and adjacent surface of the end plate 7 of the rotor 2. The end plate 7 of the rotor 2 is connected to the plate 23 of the rotor 2 in a position, in which the apertures 71 for the inlet and outlet of the medium to and from the chamber 22 are located by the walls of the hole forming the chamber 22, which are facing free end faces of the piston 4. A thickness of the piston 4 is substantially the same as the thickness of the plate 23, taking into account appropriate tolerances of the piston 4 to ensure its sliding reciprocating movement in the chamber 22.

[0023] Particular embodiment of the rotor 2 according to the example of embodiment shown, is in Fig. 4. The rotor 2 is composed of two plates 23 separated by the partition plate 24 and covered by the end plates 7. In this example, said individual parts of the rotor 2 are connected to each other by screws through boreholes created in these individual parts for the screws. Connecting the individual parts of the rotor 2 can be carried out, in general, by any known suitable type of detachable or non-detachable connection. The plates 23 preferably have a disc shape and are mounted in bearings 12, preferably rolling bearings, for mounting the rotor 2 within the case 1 of the machine housing. The embodiment of the rotor 2, shown and described, represents particular preferable arrangement of the rotor 2 regarding the stability and strength of the rotor 2 mounting in the machine housing. Other embodiments are also possible, where parts of the rotor 2 are made such that the rotor 2 can be arranged in sliding manner in the case 1 without rolling bearings. Also, it is not excluded that the rotor 2 bearings are provided for example in the end caps 11 of the housing, where in such a case it is also not necessary for parts of the rotor 2, such as the plates 23, the partition plate 24, and the end plate 7, to have particularly a disc shape, as specifically shown in the figures.

[0024] The shaft 5 passes through axial opening through the rotor 2, i.e. through the opening 21 in the partition plate 24 and the end plates 7, and is rotatably mounted in bearings 15 in the end caps 11 of the machine housing. In the example shown, rotary bearings 15 are preferably rolling bearings. The shaft 5 protrudes at one side through the end cap 11 of the housing, where it is sealed for example by a common shaft seal. Circular cams 51 are arranged on the shaft 5. The shaft 5 is placed relative to the rotor 2 eccentrically, where the eccentricity of the axis of rotation of the shaft 5 from the axis of rotation of the rotor 2 is equal to the eccentricity of the axis of the circular cam 51 from the axis of rotation of the shaft 5.

[0025] The circular cams 51 are mounted on the shaft 5 by detachable keyed joint. This is preferable in regard of manufacturing and also during assembling of the machine. The circular cams 51 then must also be secured against axial movement along the shaft 5, which can be achieved by known means, such as a shaft shoulder, or various locking, retaining rings. However, it is also equally possible to produce the shaft 5 integrally with the cams 51, as is known in the state of the art.

[0026] The piston 4 is rotatably mounted on the circular cam 51. An opening 41 is provided in the piston 4 for mounting the piston 4 on the circular cam 51. This opening 41 extends transversely through the centre of the piston 4. Thus, the piston 4 has two ends. In the embodiment shown, the piston 4 is equipped with a separate bearing 42 for the circular cam 51. The bearing 42 for the circular cam 51 is not necessary, and the opening 41 of the piston 4 can directly provide a plain bearing for the cam 51.

[0027] As described above, the chamber 22 is formed by the walls of the hole in the plate 23 of the rotor 2, the adjacent surface of the partition wall 24 between the plates 23, and the adjacent surface of the end plate 7 of the rotor 2. The end plate 7 comprises apertures 71 for the inlet and outlet of the medium to and from the chamber 22 located by the walls of the hole forming chamber 22, which are facing free ends of the piston 4.

[0028] Inlet and outlet of the medium to and from the chamber 22 for the piston 4 is controlled by valve means for opening and closing the inlet and outlet of the medium to and from the chamber 22. These valve means are provided in the form of separate arcuate slots 61 opening the aperture 71 for the inlet and outlet of the medium to and from the chamber 22. These arcuate slots 61 are on the circular trajectory of the aperture 71 during rotation of the rotor 2. Closing of the aperture 71 is provided by a solid part, between the arcuate slots 61, of the material of the body in which the separate arcuate slots 61 are formed. In the embodiment shown, the arcuate slots 61 are formed in the end cap 11 closing the case 1 of the machine housing. In another embodiment, not shown, the arcuate openings 61 can be formed in a valve plate, inserted between the end plate 7 of the rotor 2 and the end cap 11 of the case 1. Then, such valve plate must be secured against own rotation to function properly.

[0029] The above description regarding the valve means applies to the other end of the rotor 2 as well.

[0030] The apertures 71 in the end plate 7 for the inlet and outlet of the medium to or from the chamber 22 are opened or closed relative to the arcuate slots 61 of the valve means. Then, the arcuate slots 61 communicate respectively with an opening 13 for the input of the medium into the machine and an opening 14 for the output of the medium from the machine. In the embodiment shown, the opening 13 for the inlet of the medium to the machine is provided in the case 1 of the housing, preferably in the arrangement shown, such that it exits between the bearings 12 of the rotor 2, which can advantageously facilitate lubrication of the machine, for example with oil drawn in with air. The opening 13 connects inner space of the case 1 with a source of the medium, in this case the ambient air. Then, the openings 14 for the outlet of the medium from the machine are provided respectively in the end caps 11 of the case 1 and respectively lead out of one of the arcuate slots 61 in the end cap 11. In the example shown, the openings 14 preferably extend radially from the end cap 11 in the same direction as the opening 13 for the inlet of the medium.

[0031 ] Such arrangement, for example, facilitates connecting the inlet and outlet lines for the medium at one side of the machine, and also allows direct connection of a machine drive to the end cap 11 of the case 1 as will be described further.

[0032] In the example of embodiment of the machine shown, all rotary bearings are provided by rolling bearings. Slide bearings, or combinations of rolling and slide bearings where necessary, can also be used as well.

[0033] The radial piston rotary machine, compressor, in the described example of embodiment shown in Fig. 1 to 9 is working as follows. [0034] The shaft 5 is connected to a drive, in the embodiment shown, to the electric motor 8, which can preferably be attached to the end cap 11 of the machine housing.

[0035] Characteristics of the machine according to this invention allow to use the electric motor 8 with dimensions not exceeding an outline of the machine, and thus it is possible to provide the machine with the drive preferably as a single compact assembly.

[0036] The shaft 5 rotates the circular cams 51, which reciprocate the pistons 4 in their respective chambers 22. The pistons 4 also rotate the rotor 2. Even with typical tolerances of bearings and alignment of relevant rotating parts, operation of the machine, in this case the compressor, is thoroughly smooth and balanced.

[0037] Positions of rotating parts after turning the shaft 5 by 180° are shown in Fig. 7 and 8, where for the sake of plainer presentation, one extremity of one of the pistons 4 is determined as the initial position, i.e. the position at the end of the travel of the piston 4 in the chamber 22. This initial position is shown in Fig. 7.

[0038] In the initial position given, the cam 51 is in one extremity of its highest eccentricity, the piston 4 is thus in the extremity at the end of its travel. One end of the piston 4 is therefore in the position closest to the adjacent wall of the hole forming the chamber 22 in the plate 23 of the rotor 2. The other end of the piston 4 is then in the position farthest from the wall of the hole on the opposite side. Body of the end cap 11 between the arcuate slots 61 of the valve means is closing in this position the apertures 71 for the inlet and outlet of the medium to or from the chamber 22.

[0039] In the mentioned phase, at one side the air is completely forced from the chamber 22 and at the other side, drawn in into the maximum working volume of the chamber 22.

[0040] By rotating the shaft 5, at one side the aperture 71 is passing by the edge of the arcuate slot 61, while connecting the chamber 22 with the air inlet, which in the example shown is provided by the opening 13 in the case 1, which allows air into the inner space of the case 1. The air is led from the inner space of the case 1 through inlet grooves 62 to the arcuate slots 61 of the valve means.

[0041 ] At the same time, at the other side the aperture 71 is passing by the edge of the second arcuate slot 61 while connecting the chamber 22 with the air outlet, which in the example shown is provided by the opening 14 in the end cap 11 of the case 1.

[0042] The arcuate slots 61 of the valve means can be continuous as well as segmented. The segmented arcuate slots 61 can preferably be applied when the separate valve plate is used, as described above, in order to provide for sufficient strength of such valve plate, while the material of the valve plate between the segments of the arcuate slot 61 does not prevent flow of the medium to and from the chamber 22 in any way. In the example of embodiment shown, due to sufficient strength of the end cap 11 itself, the slots 61 are provided as continuous. Separation of the arcuate slots 61 with respect to the separation of the input and output parts of the medium must indeed be maintained.

[0043] In the case of a pump, when pumping liquids, opening of the chamber 22 to the apertures 71 in the end plate 7 of the rotor 2 must take place at the same time due to incompressibility of liquids. In the case of compressors, depending on the output pressure, the edge of the outlet arcuate slot 61 can be shifted so that the aperture 71 is longer closed by the body of the end cap 11, in the case of the separate valve plate by the body of the valve plate, thus compression of the air is occurring while the working volume of the chamber 22 is being reduced.

[0044] By rotating the shaft 5 further, at one end of the piston 4 a decrease in the volume of the chamber 22 above the piston 4 is occurring, and at the other end of the piston 4 an increase in the volume of the chamber 22 above the piston 4 is occurring, whereby the air is forced out at one side and drawn in at the other side.

[0045] In the position, shown in Fig. 8, when the piston 4 is in the middle position, the apertures 71 are fully open. [0046] By rotating the shaft 5 further, the volume of the chamber 22 at one end of the piston 4 is decreasing, thereby forcing the air from the chamber 22 continues, and the volume of the chamber 22 at the other end of the piston 4 is increasing, thereby drawing in the air into the chamber 22 continues. The air is forced through the aperture 71 in the end plate 7 to the arcuate slot 61 and from the arcuate slot 61 to the opening 14 for the outlet of the medium from the machine.

[0047] After the entire cycle is completed, i.e. during two revolutions of the shaft 5, the piston 4 is again at one end in the highest extremity, and at the other end in the lowest extremity. In this position, the body of the end cap 11 closes the apertures 71 so that no backflow of air can occur between the chambers 22 above the respective ends of the piston 4.

[0048] The mentioned working principle is indeed the same also for embodiments of the machine with the separate valve plate.

[0049] The machine according to the invention as shown in Fig. 9 in one unit with the drive, the electric motor 8, has compact closed housing formed by the case 1 closed by the end caps 11, which protects rotating parts of the machine and also contributes to the reduction of noise of the machine. Moreover, in the case of a compressor, the rotor 2 is able to be cooled by its own rotation in the surrounding medium drawn in, the air, so that no additional cooling device, such as a fan, is necessary. Unlike known piston compressor, such a compressor is capable of continuous operation. Cooling efficiency can also be further increased by injecting a small amount of oil into the air drawn in.

[0050] In order to illustrate the efficiency of the machine, the compressor, according to the example of embodiment shown, specific dimensions and parameters of produced prototype of the compressor are presented below.

[0051 ] External dimensions of the compressor housing, shown in Fig. 9, are 90 x 90 x 50 mm. Displacement of the compressor is 9 cm ³ per 1 revolution of the shaft 5. The compressor was connected to 350 W electric motor 8. Operation of the compressor was tested at operating revolutions from 200 to 4500 rpm. So far, maximum pressure measured was 24 bar. Noise of the compressor measured at 1400 rpm was 50 dBA without acoustic shielding.

[0052] It is possible to use larger tolerances between the parts when designing the machine being a pump, even of larger dimensions, as these are balanced by the working fluid.

[0053] The radial rotary machine according to this invention can be a compressor, a pump, a vacuum pump, or possibly also a motor.

[0054] Reverse operation of the machine is also possible without any additional modifications thanks to the valve means described, when practically only the function of the opening 13 for the inlet of medium into the machine is changed to the function of the opening 14 for the outlet of medium and vice versa.

[0055] Design of the radial piston rotary machine according to the invention also allows a compressor to be produced as a multi-stage one, for example to achieve higher pressures. In the example of the compressor described and shown, the chambers 22 and the pistons 4 have the same size, i.e. the working volume of each chamber 22 is equally large.

[0056] In the case of a multi-stage compressor, it is possible to create one chamber 22 with a larger volume, i.e. also with a larger piston 4, and other chamber 22 with a smaller volume, i.e. also with a smaller piston 4. Then, the inlet of the medium would be realized into the chamber 22 with the larger volume, and the output from this larger chamber 22 would be supplied to the input of the medium into the chamber 22 with the smaller volume. Then, outlet of the high-pressure medium would be the outlet of the medium from chamber 22 with the smaller volume.

[0057] Also, embodiments of the machine comprising more rotors 2 are not excluded.

[0058] Mutual angle of the chambers 22 with the pistons 4, different than in described examples of embodiment is also possible. However, in such a case, this concerns design of the chambers 22 for the pistons 4 and their arrangement in the rotor 2 only, while the principle of the solution will be retained with all its advantages.

[0059] The radial rotary piston machine according to the present invention can be produced by commonly available and used technologies and with common materials. Individual parts of the machine can also be easily produced using 3D printing technology. Use of special materials is presumed only for special applications such as oil-free compressors, extreme load pumps or compressors, and so.

Industrial Applicability

[0060] The radial piston rotary machine according to this invention can be used as a compressor, a pump, a vacuum pump, or even a motor.

[0061 ] The radial piston rotary machine as a compressor can be used for a wide variety of applications in a wide range of pressures and flow rates, for example as blowers, low pressure, medium pressure or high-pressure compressors.

[0062] The radial piston rotary machine as a vacuum pump can be used as efficient vacuum pump to create vacuum, as well as multi-stage vacuum pump to achieve high vacuum. A vacuum pump is provided simply, just by connecting the inlet to an environment where the vacuum is required, without the need for any other design modifications^