DOUBLE ACTING TWO STAGE PISTON TYPE PUMP

Abstract

A double acting two stage piston type pump includes a pump housing having a piston arrangement connected to a driving shaft which, when driven, sets the piston arrangement into movement. The piston arrangement has at least two primary stage pistons, the primary stage pistons being slidably seated in respective primary stage cylinders formed in the pump housing. The piston arrangement also includes at least two secondary stage pistons slidably seated in respective secondary stage cylinders formed in the primary stage pistons. The primary stage pistons and the secondary stage pistons are mounted on, and directly driven by, eccentrics mounted on the driving shaft.

Claims

1. A piston type pump comprising: a pump housing having a piston arrangement connected to a driving shaft which, when driven, sets said piston arrangement into movement; said piston arrangement including a first primary stage piston, a first secondary stage piston, a second primary stage piston, and a second secondary stage piston; said first primary stage piston being slidably seated in a first primary stage cylinder formed in said pump housing; said first secondary stage piston being slidably seated in a first secondary stage cylinder formed in said first primary stage piston; said second primary stage piston being slidably seated in a second primary stage cylinder formed in said pump housing; said second secondary stage piston being slidably seated in a second secondary stage cylinder formed in said second primary stage piston; said driving shaft including a first eccentric and a second eccentric which are phase shifted by 180; said first secondary stage piston including a first secondary stage piston rod and said second secondary stage piston including a second secondary stage piston rod; said first primary stage piston and said second secondary stage piston rod being configured to be mounted on and directly driven by said second eccentric; and, said first secondary stage piston rod and said second primary stage piston being mounted on, and directly driven by, said first eccentric.

2. The piston type pump of claim 1, wherein said driving shaft includes a stud, said first eccentric and said second eccentric being mounted on said stud.

3. The piston type pump of claim 2, wherein at least one of said first eccentric and said second eccentric is fixedly mounted on said stud.

4. The piston type pump of claim 2, wherein at least one of said first eccentric and said second eccentric is in threaded engagement with said stud.

5. The piston type pump of claim 2, wherein said first eccentric is provided with a first torque-transmitting and aligning arrangement configured to engage in a predetermined angular way with a second torque-transmitting and aligning arrangement provided on said second eccentric.

6. The piston type pump of claim 5, wherein said first torque-transmitting and aligning arrangement provided on said first eccentric has a first protrusion and a second protrusion; and, said second torque-transmitting and aligning arrangement provided on said second eccentric has at least a third protrusion configured to fit with said first protrusion and said second protrusion provided on said first eccentric.

7. The piston type pump of claim 5, wherein said first torque-transmitting and aligning arrangement provided on said first eccentric and said second torque-transmitting and aligning arrangement provided on said second eccentric are located in proximity to said stud.

8. The piston type pump of claim 2 further comprising a nut disposed on said stud; and, said nut being in threaded engagement with said stud and in contact force transmitting engagement with said second eccentric.

9. The piston type pump of claim 1, wherein said driving shaft includes a cap screw; and, said first eccentric and said second eccentric are mounted on said cap screw.

10. The piston type pump of claim 9, wherein at least one of said first eccentric and said second eccentric is fixedly mounted on said cap screw.

11. The piston type pump of claim 9, wherein at least one of said first eccentric and said second eccentric is in threaded engagement with said cap screw.

12. The piston type pump of claim 9, wherein said second eccentric is provided with a flange configured to fit with a recess provided on said first eccentric.

13. The piston type pump of claim 12 further comprising a pin configured to fixedly secure said flange provided on said second eccentric with said recess provided on said first eccentric.

14. A method for mounting a piston type pump, the piston type pump having a pump housing, said pump housing having a piston arrangement connected to a driving shaft which, when driven, sets the piston arrangement into movement, the piston arrangement including a first primary stage piston, a first secondary stage piston, a second primary stage piston, and a second secondary stage piston, the first primary stage piston being slidably seated in a first primary stage cylinder formed in the pump housing, the first secondary stage piston being slidably seated in a first secondary stage cylinder formed in said first primary stage piston, the second primary stage piston being slidably seated in a second primary stage cylinder formed in the pump housing, the second secondary stage piston being slidably seated in a second secondary stage cylinder formed in the second primary stage piston, the driving shaft including a first eccentric and a second eccentric which are phase shifted by 180, the first secondary stage piston including a first secondary stage piston rod and the second secondary stage piston including a second secondary stage piston rod, the first primary stage piston and the second secondary stage piston rod being configured to be mounted on and directly driven by the second eccentric, and the first secondary stage piston rod and the second primary stage piston being mounted on, and directly driven by, the first eccentric, the method comprising: mounting the first secondary stage piston rod and the second primary stage piston on the first eccentric; interference mounting the driving shaft into the first eccentric; inserting the first secondary stage piston rod, the second primary stage piston, the first eccentric and the driving shaft into the pump housing; mounting the second eccentric on the driving shaft and aligning it with the first eccentric; and, mounting the first primary stage piston and the second secondary stage piston rod on the second eccentric.

15. A vehicle comprising: a piston type pump including a pump housing having a piston arrangement connected to a driving shaft which, when driven, sets said piston arrangement into movement; said piston arrangement including a first primary stage piston, a first secondary stage piston, a second primary stage piston, and a second secondary stage piston; said first primary stage piston being slidably seated in a first primary stage cylinder formed in said pump housing; said first secondary stage piston being slidably seated in a first secondary stage cylinder formed in said first primary stage piston; said second primary stage piston being slidably seated in a second primary stage cylinder formed in said pump housing; said second secondary stage piston being slidably seated in a second secondary stage cylinder formed in said second primary stage piston; said driving shaft including a first eccentric and a second eccentric which are phase shifted by 180; said first secondary stage piston including a first secondary stage piston rod and said second secondary stage piston including a second secondary stage piston rod; said first primary stage piston and said second secondary stage piston rod being configured to be mounted on and directly driven by said second eccentric; and, said first secondary stage piston rod and said second primary stage piston being mounted on, and directly driven by, said first eccentric.

16. The vehicle of claim 15, wherein the vehicle is a passenger car or a commercial vehicle.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0041] The invention will now be described with reference to the drawings wherein:

[0042] FIG. 1 shows a perspective view of a prior art piston type pump including a Scotch yoke mechanism;

[0043] FIG. 2 shows a cut view of the piston type pump of the disclosure;

[0044] FIG. 3 shows a simplified cut view of the crank mechanism of a first embodiment of the piston type pump of the disclosure;

[0045] FIG. 4 shows a perspective view of the crank mechanism of FIG. 3;

[0046] FIG. 5 shows a perspective view of a first eccentric and of second eccentric making part of the crank mechanism of FIGS. 3 and 4;

[0047] FIG. 6 shows a simplified cut view of the crank mechanism of a second embodiment of the piston type pump of the disclosure;

[0048] FIG. 7 shows a perspective view of the crank mechanism of FIG. 6;

[0049] FIG. 8 shows a perspective view of a first eccentric and of second eccentric making part of the crank mechanism of FIGS. 6 and 7; and,

[0050] FIG. 9 shows a schematic view of a vehicle.

DETAILED DESCRIPTION

[0051] A piston type pump 1 according to the present disclosure is suitable to be mounted within a vehicle 100 (see FIG. 9) and used as a vacuum pump to provide vacuum for a braking system or any other consumer in this vehicle. The piston type pump 1 in particular is suitable to be driven by an electric motor which for simplicity is not shown in the drawings.

[0052] The following embodiments show the piston type pump 1 prepared to be used as a vacuum pump and to induce a vacuum at a pump inlet (not shown). However, the same construction may also be used as a compressor.

[0053] In more detail the piston type pump 1 includes a pump housing 2 which is substantially cylindrical. The pump housing 2 has a pump inlet (not shown) which can be connected to a consumer. Moreover, the pump housing includes a pump outlet (not shown) which opens into the environment. The pump outlet may be formed as a simple opening in the pump housing 2. Fluid, in particular air, which is drawn away from the pump inlet, is not used and only discharged to the environment instead of being provided to any consumer, when the piston type pump 1 is used as a vacuum pump.

[0054] Within the pump housing 2 a piston arrangement 8 is provided, which will be described in more detail below. The piston arrangement 8 is connected to a drive shaft 10 which, when driven, sets the piston arrangement 8 into movement for inducing a vacuum at the pump inlet. The drive shaft 10 is rotatable about a rotational axis A and may be connected to an electric motor.

[0055] The piston arrangement 8 according to the embodiment shown in FIG. 2 includes a first primary stage piston 12 which is slidably seated in a first primary stage cylinder 14 formed in the pump housing 2.

[0056] The piston type pump 1 according to the shown embodiment is formed as a twin type two-stage piston pump and therefore also includes a first secondary stage piston 16, which is provided within a first secondary stage cylinder 18, which is formed within the first primary stage piston 12. The first primary stage piston 12, therefore, is formed in a hollow manner, to form the first secondary stage cylinder 18. The first primary stage piston 12 includes a first primary stage piston wall 13 which defines the first secondary stage cylinder 18. The first secondary stage cylinder 18 in particular is formed by an inner circumferential surface of the first primary stage piston wall 13 within the first primary stage piston 12.

[0057] For movement of the first primary stage piston 12 and the first secondary stage piston 16, the first primary stage piston 12 is driven by a second eccentric 22 of the drive shaft 10 and the first secondary stage piston 16 is driven by a first eccentric 20 of the drive shaft 10. Both the first and the second eccentric 20, 22 are mounted on a stud 21. The first and second eccentrics 20, 22 are phase-shifted by 180.

[0058] In a similar fashion the piston arrangement 8 according to this embodiment also includes a second primary stage piston 40, which is slidably seated in a second primary stage cylinder 42, which again is formed inside the pump housing 2. The complete interior 3 of the pump housing 2 can be formed as a cylindrical hollow portion to form both, the first primary stage cylinder 14 and the second primary stage cylinder 42.

[0059] Also a second secondary stage piston 44 is provided which is slidably seated in a second secondary stage cylinder 46 formed within the second primary stage piston 40. Again the second primary stage piston 40 includes a second primary stage piston wall 41 which defines the second secondary stage cylinder 46 by its inner circumferential surface restricting a second hollow space 47.

[0060] For driving the second primary stage piston 40 and the second secondary stage piston 44, the second primary stage piston 40 is connected to the first eccentric 20 and the second secondary stage piston 44 is connected to the second eccentric 22. Thus, the first eccentric 20 drives the second primary stage piston 40 as well as the first secondary stage piston 16 and in turn the second eccentric 22 drives the first primary stage piston 12 and the second secondary stage piston 44. Therefore, the movement of the pistons is identical, however, phase-shifted by 180.

[0061] Moreover, in FIG. 2 it can be seen that the first primary stage cylinder 14 includes a first central axis B1 and the second primary stage cylinder 42 includes a second central axis B2, which are coaxial. Thus, the first and the second central axes B1, B2 form a single axis on which the first primary stage piston 12 and the second primary stage piston 40 move. When the first secondary stage cylinder 18 and the second secondary stage cylinder 46 are formed concentrically within the respective first primary stage piston 12 and the second primary stage piston 40, also the first secondary stage piston 16 and the second secondary stage piston 44 move coaxially with the first and second central axes B1, B2. Thus, the overall configuration of the piston type pump 1 is a boxer type piston type pump in which the single pistons move in opposing directions. This may lead to a well-balanced configuration.

[0062] The first secondary stage piston 16 includes a first piston rod 54 which extends through a first assembly opening 60 in the first primary stage piston wall 13. The portion of the first hollow space 19 which is on the opposite side of the piston rod 54 with respect to the first secondary piston face 30 can be named the first secondary stage working chamber. In the same manner the second secondary stage piston 44 includes a second piston rod 56 which extends through a second assembly opening 58 formed in the second primary stage piston wall 41 of the second primary stage piston 40.

[0063] The first primary stage piston 12 and the second secondary stage piston rod 56 are mounted on, and directly driven by, the second eccentric 22. In turn, the first secondary stage piston rod 54 and the second primary stage piston 40 are mounted on, and directly driven by, the first eccentric 20.

[0064] The mounting of the first primary stage piston 12 and of the second secondary stage piston rod 56 on the second eccentric 22 may include a needle bearing 229. In turn, the mounting of the first secondary stage piston rod 54 and of the second primary stage piston 40 on the first eccentric 20 may also include a needle bearing 209.

[0065] The flow of fluid within the piston type pump of the disclosure is well known in the art and will not be described in detail. However, reference is made to previously mentioned prior art document WO 2019/114923 A1.

[0066] The crank mechanism of FIG. 2, which is shown in detail in FIG. 3, FIG. 4 and FIG. 5, relates to a first embodiment of the present disclosure and includes a stud 21 fixedly mounted on the driving shaft 10. The first eccentric 20 is fixedly mounted on the driving shaft 10 and/or on the stud 21, for instance by screws or other form-locking mechanisms. Preferably, the first eccentric 20 is fixedly mounted on the driving shaft 10 and/or on the stud 21, through interference mounting. The first eccentric 10 includes a bore 213 to allow the insertion and the mounting on the stud 21 and/or on the driving shaft 10.

[0067] In proximity to the bore 213, a first protrusion 211 and a second protrusion 212 are provided, each having at least a flat coupling surface. The second eccentric 22 also includes a bore 223 to allow the insertion and the mounting on the stud 21. In correspondence to, preferably coaxial to, the bore 223, a third protrusion 222 is also provided, the third protrusion 222 having at least two flat coupling surfaces configured to engage, in a predetermined angular way, with the respective flat coupling surfaces of the first and second protrusions 211, 212 provided on the first eccentric 20. This way, it is possible to align the first and the second eccentrics in a predetermined angular fashion. The protrusions 211, 212, 222 are configured to transmit torque between the first and the second eccentrics 20, 22 so that they can jointly rotate around rotational axis A of the driving shaft 10 and of the stud 21. It shall be understood, that in other embodiments, the first and second protrusions 211, 212 are provided on the second eccentric 22, while the third protrusion is provided on the first eccentric 20. Also any other means for at least a partial form-locking torque transmission are envisaged. It also shall be understood that in exchange of the first and second protrusions 211, 212 a groove may be provided on one of the eccentrics 20, 22 in which the third protrusion 222 may engage.

[0068] A nut 23 is threadedly fixed on the stud 21 and further secures the second eccentric 22 in both its axial position along the rotational axis A of the stud 21 and in its rotational position in respect of the first eccentric 20.

[0069] The assembly of the piston type pump 1 according to the first embodiment of the disclosure may conveniently envisage that at least part of the pistons are assembled together before being slid down the pump housing 2. As a first assembly step, the first secondary stage piston rod 54, together with the first secondary stage piston 16, and the second primary stage piston 40 are mounted on the first eccentric 20. Subsequently, the first eccentric 20 is fixedly mounted on the driving shaft 10 and/or the stud 21, for instance by interference mounting. This way, an intermediate ,,piston pack including the driving shaft 10 and/or the stud 21, the first eccentric 20, the secondary stage piston 16 and its first secondary stage piston rod 54, as well as the second primary stage piston 40, is created. Such an intermediate ,,piston pack is then inserted into the pump housing 2. Thereafter, the second eccentric 22 is mounted on the driving shaft 10 and aligned with the first eccentric 20 thanks to the torque-transmitting and aligning arrangement, namely the protrusions, which are provided on both the first and second eccentrics. Finally, the first primary stage piston 12 and the second secondary stage piston rod 56 together with its respective second secondary stage piston 44, are mounted on the second eccentric 22.

[0070] FIG. 6, FIG. 7 and FIG. 8 show a crank mechanism according to a second, alternative embodiment of the present disclosure. According to such alternative embodiment, the driving shaft 10, the first eccentric 20 and the second eccentric 22 are held together with a cap screw 300. The first eccentric 20 includes a recess 302 and a bore 213 to allow the insertion and the mounting on the cap screw 300. The first eccentric 20 also includes a second bore 304, to allow the insertion and the mounting of a pin 303.

[0071] The second eccentric 22 includes a bore 223 to allow the insertion and the mounting on the cap screw 300, and a flange 301. The flange 301 is configured to fit into the recess 302 of the first eccentric 20 and includes a second bore 305 to allow the insertion and the mounting of the pin 303. In other words, the pin 303 secures the fixed coupling of the flange 301 of the second eccentric 22 with the recess 302 of the first eccentric 20 and as a result, the first and second eccentrics 20, 22 are aligned at a predetermined rotational angle, and they are capable of jointly rotate. Preferably, the pin 303 is inserted into the second bore 304 on the first eccentric 20 and into the second bore 305 on the flange 301 through interference mounting.

[0072] FIG. 9 now depicts a schematic drawing of a vehicle 100. Vehicle 100 preferably is formed as a passenger car, or a light truck and includes a pneumatic braking system 102. The braking system 102 is shown by lines 104 leading to wheels 106a, 106b, 106c, 106d for providing the wheels 106a, 106b, 106c, 106d with the respective braking pressure. Lines 104 are connected to a central module 108. The vehicle 100 moreover includes an engine 110 and a piston type pump 1 according to the disclosure, which is herein used as a vacuum pump 1. The piston type pump 1 provides the braking system 102 with vacuum, which, for example, could be used by a brake booster of the braking system 102, which could be implemented in the central module 108.

[0073] It is understood that the foregoing description is that of the preferred embodiments of the invention and that various changes and modifications may be made thereto without departing from the spirit and scope of the invention as defined in the appended claims.

LIST OF REFERENCE SIGNS (PART OF THE DESCRIPTION)

[0074] 1 piston type pump [0075] 2 pump housing 2 [0076] 3 interior of the pump housing [0077] 8 piston arrangement [0078] 10 driving shaft [0079] 12 first primary stage piston [0080] 13 first primary stage piston wall [0081] 14 first primary stage cylinder [0082] 16 first secondary stage piston [0083] 18 first secondary stage cylinder [0084] 19 first hollow space [0085] 20 first eccentric [0086] 21 stud [0087] 22 second eccentric [0088] 23 nut [0089] 30 first secondary piston face [0090] 40 second primary stage piston [0091] 41 second primary stage piston wall [0092] 42 second primary stage cylinder [0093] 44 second secondary stage piston [0094] 46 second secondary stage cylinder [0095] 47 second hollow space [0096] 54 first secondary stage piston rod [0097] 56 second secondary stage piston rod [0098] 58 second assembly opening [0099] 60 first assembly opening [0100] 100 vehicle [0101] 102 pneumatic braking system [0102] 104 lines leading to wheels [0103] 106a wheel (front right) [0104] 106b wheel (rear right) [0105] 106c wheel (front left) [0106] 106d wheel (rear left) [0107] 108 central module [0108] 110 engine [0109] 201 first torque-transmitting and aligning arrangement [0110] 209 needle bearing (first eccentric) [0111] 211 (first) protrusion on the first eccentric [0112] 212 (second) protrusion on the first eccentric [0113] 213 bore on the first eccentric [0114] 221 second torque-transmitting and aligning arrangement [0115] 222 (third) protrusion on the second eccentric [0116] 223 bore on the second eccentric [0117] 229 needle bearing (second eccentric) [0118] 300 cap screw [0119] 301 flange [0120] 302 recess [0121] 303 pin [0122] 304 second bore on first eccentric [0123] 305 second bore on second eccentric [0124] A rotational axis of drive shaft [0125] B1 first central axis [0126] B2 second central axis