HYDRAULIC ACTUATOR WITH PRESSURE AMPLIFIER

Abstract

A hydraulic actuator (1) is disclosed comprising a cylinder housing (2), a piston (5) with a piston rod (6) being displaceably arranged inside the cylinder housing (2) and a pressure amplifier (10) comprising an inlet section (18) with a pressure inlet port (20), an active section (19) with a high pressure outlet port (22), a low pressure chamber (32) and a high pressure chamber (38a). It is an objective of the invention to provide a hydraulic actuator (1) with a modular pressure amplifier (10). To this end, the inlet section (18) is arranged inside the piston rod (6), and wherein the low pressure chamber (32) is stationarily arranged relative to the inlet section (18).

Claims

1. A hydraulic actuator comprising a cylinder housing, a piston with a piston rod being displaceably arranged inside the cylinder housing and a pressure amplifier comprising an inlet section with a pressure inlet port, an active section with a high pressure outlet port, a low pressure chamber and a high pressure chamber, characterized wherein the inlet section is arranged inside the piston rod, and wherein the low pressure chamber is stationarily arranged relative to the inlet section.

2. The hydraulic actuator according to claim 1, wherein the active section is arranged inside the piston rod, and wherein the high pressure chamber is stationarily arranged relative to the active section.

3. The hydraulic actuator according to claim 1, wherein the high pressure chamber is arranged inside the active section, and wherein the piston rod comprises a piston head fixing the active section inside the piston rod.

4. The hydraulic actuator according to claim 1, wherein the low pressure chamber is arranged inside the inlet section, and wherein the piston rod fixes the inlet section inside the piston rod.

5. The hydraulic actuator according to claim 1, wherein the piston rod comprises a piston rod side port arranged in a radial direction of the piston rod establishing a fluid communication between the pressure amplifier and the cylinder housing.

6. The hydraulic actuator according to claim 1, wherein the pressure inlet port and the high pressure outlet port are coaxially arranged at opposite axial ends of the pressure amplifier.

7. The hydraulic actuator according to claim 1, wherein the inlet section comprises a pilot sequence valve being in fluid communication with the pressure inlet port and being arranged in an axial direction of the inlet section.

8. The hydraulic actuator according to claim 7, wherein the pilot sequence valve is pressure-activated when the pressure at the pressure inlet port exceeds a preset value, thereby opening a first pilot channel from the pressure inlet port to the low pressure chamber.

9. The hydraulic actuator according to claim 1, wherein the active section comprises an over-center valve establishing a fluid communication between the pressure inlet port and the high pressure outlet port and being arranged in an axial direction of the active section.

10. The hydraulic actuator according to claim 9, wherein the over-center valve is mounted on a first axial end face of the inlet section, wherein the first axial end face of the inlet section abuts a first axial end face of the active section.

11. The hydraulic actuator according to claim 1, wherein the low pressure chamber comprises a low pressure piston and a low pressure piston bushing, wherein the low pressure piston is displaceably arranged relative to the low pressure piston bushing.

12. The hydraulic actuator according to claim 1, wherein the high pressure chamber comprises a high pressure piston and a high pressure piston bushing, wherein the high pressure piston is displaceably arranged relative to the high pressure piston bushing.

13. The hydraulic actuator according to claim 12, wherein the high pressure piston bushing comprises an aperture opening a second pilot channel establishing a fluid communication between the high pressure chamber and a control valve.

14. The hydraulic actuator according claim 1, wherein the hydraulic actuator comprises an internal adapter establishing a fluid communication between the pressure inlet port and a piston inlet port.

15. The hydraulic actuator according to claim 14, wherein the internal adapter comprises a radial sealing concentrically fixing the internal adapter relative to the piston rod.

16. The hydraulic actuator according to claim 2, the high pressure chamber is arranged inside the active section, and wherein the piston rod comprises a piston head fixing the active section inside the piston rod.

17. The hydraulic actuator according to claim 2, wherein the low pressure chamber is arranged inside the inlet section, and wherein the piston rod fixes the inlet section inside the piston rod.

18. The hydraulic actuator according to claim 3, wherein the low pressure chamber is arranged inside the inlet section, and wherein the piston rod fixes the inlet section inside the piston rod.

19. The hydraulic actuator according to claim 2, wherein the piston rod comprises a piston rod side port arranged in a radial direction of the piston rod establishing a fluid communication between the pressure amplifier and the cylinder housing.

20. The hydraulic actuator according to claim 3, wherein the piston rod comprises a piston rod side port arranged in a radial direction of the piston rod establishing a fluid communication between the pressure amplifier and the cylinder housing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The invention shall be described with reference to different embodiments in connection with the figures in the forthcoming paragraphs. Therein,

[0025] FIG. 1 depicts a hydraulic actuator with a pressure amplifier according to a first embodiment of the invention;

[0026] FIG. 2 depicts a first embodiment of the pressure amplifier;

[0027] FIG. 3 depicts a second embodiment of the pressure amplifier;

[0028] FIG. 4 depicts a third embodiment of the pressure amplifier;

[0029] FIG. 5 depicts a fourth embodiment of the pressure amplifier.

DETAILED DESCRIPTION

[0030] A hydraulic actuator 1 comprises a cylinder housing 2. The cylinder housing 2 comprises at its first axial end a cylinder eye 3. It further comprises a cylinder head 4 sealing an inner volume of the cylinder housing 2 in a fluid-tight manner. The hydraulic actuator 1 also comprises a piston 5 with a piston rod 6 being displaceably arranged inside the cylinder housing 2. The piston rod 6 engages with the cylinder head 4. The piston rod 6 comprises a piston head 7 at its first axial end and a piston eye 7a at its second axial end. A working chamber 8 of the hydraulic actuator 1 is arranged at the side of the piston head 7 opposite the piston eye 7a.

[0031] The piston head 7 comprises a piston side port 9. The piston side port 9 is arranged coaxially with the piston rod 6. It establishes a first fluid communication between the working chamber 8 of the hydraulic actuator 1 and a pressure amplifier 10. The pressure amplifier 10 is arranged inside the piston rod 6. The piston rod 6 further comprises a piston rod side port 11 establishing a second fluid communication between the pressure amplifier 10 and the inner volume of the cylinder housing 2.

[0032] At an axial end of the pressure amplifier 10 in the vicinity of the piston eye 7a, an internal adapter 12 is arranged. The internal adapter 12 is fixed to its position inside the piston rod 6 by means of a radial sealing 13. The radial sealing 13 fixes the internal adapter 12 coaxially with the piston rod 6. The internal adapter 12 establishes a fluid communication between the pressure amplifier 10 and a piston inlet port 14. The piston inlet port 14 is arranged inside the piston eye 7a. A piston outlet port 15 corresponding to the piston inlet port 14 is also arranged inside the piston eye 7a.

[0033] In the embodiment of FIG. 1, the pressure amplifier 10 is concentrically mounted inside the drilled piston rod 6. The pressure amplifier 10 is arranged closer to the piston head 7 than to the piston eye 7a. The piston inlet port 14 and the piston outlet port 15 are arranged inside the piston eye 7a as drilled holes. They provide hydraulic fluid with a certain, preset pressure. The pressurized hydraulic fluid is provided by an external pump (not shown), for example. The piston inlet port 14 is arranged coaxially with the piston rod 6. It is connected to the internal adapter 12. The internal adapter 12 is connected to the pressure amplifier 10. The internal adapter 12 may be a tube. It is located coaxially with the piston rod inside the drilled piston rod 6. The internal adapter 12 may change according to the stroke of the piston rod 6. The internal adapter 12 may be fixed in its position by means of the radial sealing 13. The radial sealing 13 may be a sealing ring. This radial sealing 13 keeps the internal adapter 12 in its position coaxial with the piston rod 6. Assembly becomes more easy and effective. The piston rod 6 has a diameter larger than the diameter of the internal adapter 12. Thus, an annular piston channel opens a fluid communication between the pressure amplifier 10 and the piston outlet port 15. This annular piston channel is used for backflow of hydraulic fluid from the pressure amplifier 10 to the piston outlet port 15.

[0034] Now, the pressurized hydraulic fluid is provided via the piston inlet port 14 and the internal adapter 12 to the pressure amplifier 10. The pressure of the hydraulic fluid thus provided to the pressure amplifier 10 is enhanced by means of the pressure amplifier 10. The high pressure hydraulic fluid exits the pressure amplifier 10 via the piston side port 9 into the working chamber 8 of the hydraulic actuator 1. Thus, enhanced pressure can be supplied for the hydraulic fluid inside the hydraulic actuator 1.

[0035] The embodiment of FIG. 1 shows the pressure amplifier 10 comprising an inlet section 18 as well as an active section 19. The division of the pressure amplifier 10 is due to the assembly of its internal parts. The inlet section 18 and the active section 19 are held together by external force in order to assure proper function of the pressure amplifier 10. This external force is provided by the piston head 7 onto the piston rod 6 containing both the inlet section 18 as well as the active section 19.

[0036] Otherwise, the working principle of the hydraulic actuator 1 according to the embodiment of FIG. 1 is known in the state of the art.

[0037] As can be inferred from FIG. 2, the inlet section 18 comprises a pressure inlet port 20. The pressure inlet port 20 is connected to the internal adapter 12 of the embodiment of FIG. 1. Thereby, pressurized hydraulic fluid is provided to the pressure amplifier 10. The pressurized hydraulic fluid flows inside a main inlet channel 21. The main inlet channel 21 connects the pressure inlet port 20 to a high pressure outlet port 22. The high pressure outlet port 22 is connected to the piston side port 9 of the hydraulic actuator 1. Thereby, hydraulic fluid with an amplified pressure can be provided to the hydraulic actuator 1. The high pressure outlet port 22 is arranged inside the active section 19 of the pressure amplifier 10.

[0038] The active section 19 also comprises a backflow inlet port 23. The backflow inlet port 23 is connected to a main backflow channel 24 leading to a backflow outlet port 25. The backflow inlet port 23 is connected to the piston rod side port 11 of the hydraulic actuator 1. The backflow outlet port 24 is connected to the piston outlet port 14.

[0039] The working principle of the pressure amplifier 10 is as follows.

[0040] When there is no demand for hydraulic fluid with an amplified pressure, the hydraulic fluid enters through the pressure inlet port 20 and passes through the main inlet channel 21. An over-center valve 26 is arranged in the main inlet channel 21 inside the active section 19. When there is no demand for hydraulic fluid with amplified pressure, a check valve inside the over-center valve 26 allows full flow of the hydraulic fluid through the main inlet channel 21 to the high pressure outlet port 22. An amplification of pressure does not occur. At the same time, the backflow of hydraulic fluid is going directly from the backflow inlet port 23 to the backflow outlet port 25 via the main backflow channel 24.

[0041] Once an increased external load is applied to the hydraulic actuator 1, the pressure of the hydraulic fluid is also increasing at the pressure inlet port 20. When the pressure of the hydraulic fluid exceeds a certain preset value, a pilot sequence valve 27 opens a first pilot channel 28. Thus, the pilot sequence valve 27 is closed, as long as the pressure of the hydraulic fluid does not exceed the preset value. Once the pilot sequence valve 27 opens, however, hydraulic fluid passes through the first pilot channel 28 and exerts pressure on a first control valve pin 29 of a control valve 30. The pressure applied to the first control valve pin 29 moves the control valve 30 to a position in which hydraulic fluid may pass through it and into a low pressure piston channel 31.

[0042] The low pressure piston channel 31 leads to a low pressure chamber 32. In said low pressure chamber 32 a low pressure piston 33 is slidably arranged. The low pressure piston 33 comprises a low pressure piston surface 34. The hydraulic fluid acts on said low pressure piston surface 34 and the low pressure piston 33 starts moving in a direction opposite the low pressure piston channel 31 and toward a low pressure working chamber 35. The low pressure piston 33 is connected via a low pressure-high pressure piston rod 36 to a high pressure piston 37 inside a high pressure chamber 38a.

[0043] The high pressure piston 37 comprises a high pressure piston surface 38. Said high pressure piston surface 38 has a smaller area than the low pressure piston surface 34. Hence, the pressure acting on the low pressure piston surface 34 is amplified by the ratio of the two surfaces, when the high pressure piston 37 acts on hydraulic fluid inside a high pressure working chamber 39. The pressure-amplified hydraulic fluid exiting the high pressure working chamber 39 passes through a first check valve 40 opening in a direction toward the high pressure outlet port 22 by means of a first high pressure channel 41. The first high pressure channel 41 leads to a second high pressure channel 42 of the main inlet channel 21.

[0044] Once the low pressure piston 33 (and therefore the high pressure piston 37) has thus reached its end position, an aperture 43 opens a fluid communication with a second pilot channel 44. The second pilot channel 44 is connected to a second control valve pin 45 of the control valve 30. As the surface area of the second control valve pin 45 is larger than the one of the first control valve pin 29, the control valve 30 moves to its previous position. After this, the first check valve 40 closes down. As now both the pilot sequence valve 27 as well as the first check valve 40 is closed, pressure is applied to a second check valve 46. The second check valve 46 opens a fluid communication from the main inlet channel 21 to the high pressure working chamber 39. The pressure applied to the high pressure working chamber 39 begins to force the high pressure piston 37 toward the low pressure chamber 32. An annular channel 47 connects the low pressure working chamber 35 to the control valve 30. Thereby, the pilot sequence valve 27 eventually returns to its original position and the cycle is repeated.

[0045] The embodiment of FIG. 3 shows how the pilot sequence valve 27 can be thread mounted in an axial direction of the inlet section 18. The bottom of the pilot sequence valve 27 is then connected to the pressure inlet port 20 through the main inlet channel 21. A side port of the pilot sequence valve 27 is connected via the first pilot channel 28 to the first control valve pin 29. Setting of the pilot sequence valve 27 can be adjustable or fixed to a certain preset value.

[0046] As can also be inferred from FIG. 3, the pressure amplifier 10 consists of two separate sections: the inlet section 18 and the active section 19. The inlet section 18 comprises a first axial end face 48 and a second axial end face 49. The active section 19 comprises a first axial end face 50 and a second axial end face 51. Therein, the first axial end face 48 of the inlet section 18 and the first axial end face 50 of the active section 19 abut. Hence, in order to achieve proper function of the pressure amplifier 10, the inlet section 18 and the active section 19 are held together by external force exerted by the piston head 7 as well as the piston rod 6.

[0047] In the embodiment of FIG. 4 the position of the over-center valve 26 inside the active section 19 is exemplified. The over-center valve 26 consists of multiple parts which are arranged in an axial direction of the active section 19. All such parts are mounted from the first axial end face 48 of the inlet section 18. The correct position of all the parts is achieved by covering of the inlet section 18. Hence, there is no need for a thread inside the active section 19. Once the inlet section 18 and the active section 19 are mounted together, it is not possible to set the pressure level on the over-center valve 26. Therefore, such setting is done by several types of springs.

[0048] The over-center valve 26 can provide a full flow from the pressure inlet port 20 to the high pressure outlet port 22. It can provide a load holding function at the high pressure outlet port 22. It can furthermore provide a controlled lowering function from the high pressure outlet port 22 to pressure inlet port 20. The over-center valve 26 has three connection ports: an over-center valve inlet port associated with the main inlet channel 21; an over-center valve outlet port associated with the second high pressure channel 42; and an over-center pilot port associated with a pilot line 52. The pilot line 52 connects the over-center valve 26 with the main backflow channel 24. In a direction from the pressure inlet port 20 to the high pressure outlet port 22, the over-center valve 26 provides a full flow function by means of an integrated check valve. In the opposite direction, the over-center valve 26 is kept blocked until sufficient pressure is applied to the pilot line 52. The over-center valve 26 is also connected to a bypass-channel 53.

[0049] In the embodiment of FIG. 5, the pressure amplifier 10 is shown with a low pressure piston bushing 54 and a high pressure piston bushing 55. Such integrated bushings are a proper way to increase the lifetime of both the low pressure piston 33 as well as the high pressure piston 37. The low pressure piston bushing 54 decreases the friction between the low pressure piston 33 and the walls of the low pressure chamber 32. The high pressure piston bushing 55 decreases the friction between the high pressure piston 37 and the walls of the high pressure chamber 38a.

[0050] The low pressure piston bushing 54 is molded into the inlet section 18. The proper position is controlled by a jig during molding process. There is a need for molding of the low pressure piston bushing 54 to a certain diameter after molding.

[0051] The high pressure piston bushing 55 comprises a first high pressure piston bushing element 56 and a second high pressure piston bushing element 57. The assembly process is the same as for the low pressure piston bushing 54. However, the first high pressure piston bushing element 56 and the second high pressure piston bushing element 57 are arranged such that the aperture 43 is arranged between them. The first high pressure piston bushing element 56 may be shorter than the second high pressure piston bushing element 57.

[0052] While the present disclosure has been illustrated and described with respect to a particular embodiment thereof, it should be appreciated by those of ordinary skill in the art that various modifications to this disclosure may be made without departing from the spirit and scope of the present disclosure.