Hydraulic system

Abstract

A hydraulic system (1) is provided comprising a pressure source (2), an output (3), and a pressure booster (6) arranged between the pressure source (2) and the output (3). The operational possibilities of such a system should be extended. To this end inactivating means are provided inactivating or activating said pressure booster.

Claims

1. A hydraulic system comprising a pressure source, an output, and a pressure booster arranged between the pressure source and the output, wherein an inactivating valve is provided for inactivating or activating said pressure booster, wherein said inactivating valve is arranged in parallel to said pressure booster, said inactivating valve opening to connect a booster input and a booster output thereby inactivating said booster and closing to disconnect the booster input and the booster output when activating said booster, wherein when said booster is inactivated by said inactivating valve, the pressure at the output corresponds to a pressure supplied by the pressure source.

2. The hydraulic system according to claim 1, wherein said pressure booster is a hydraulic pressure booster.

3. The hydraulic system according to claim 2, wherein said inactivating valve is hydraulic means.

4. The hydraulic system according to claim 1, wherein said inactivating valve is hydraulic means.

5. The hydraulic system according to claim 1, wherein said inactivating valve is hydraulically operated.

6. The hydraulic system according to claim 5, wherein said inactivating valve is operated by means of a hydraulic signal line.

7. The hydraulic system according to claim 6, wherein said signal line is connected to a load dependent position within said system.

8. The hydraulic system according to claim 1, wherein said inactivating valve is electrically operated.

9. The hydraulic system according to claim 1, wherein pressure booster and/or said inactivating valve are integrated in said pressure source.

10. The hydraulic system according to claim 1, wherein said inactivating valve is positioned near said output or are part of said output.

11. The hydraulic system according to claim 1, wherein said system comprises at least two outputs, each output being connected to a branch, at least one branch being provided with the booster and inactivating valve.

12. The hydraulic system according to claim 1, wherein said booster comprises at least two amplification means, said amplification means being separately activatable.

13. The hydraulic system according to claim 1, wherein said booster is provided with means producing a variable booster pressure.

14. The hydraulic system according to claim 1, wherein said booster has a maximum amplification factor of 20 or less, in particular in a range of 1.2 to 20, preferably 1.5 to 4.

15. The hydraulic system according to claim 1, wherein said pressure booster is provided with an auxiliary pump connected to said booster input, said auxiliary pump being connected to a driving motor which can be activated on demand.

16. A hydraulic system comprising: a pressure source, an output, a pressure booster arranged between the pressure source and the output, and an inactivating valve for inactivating or activating said pressure booster, wherein said inactivating valve opens to connect a booster input and a booster output thereby inactivating said booster and closes to disconnect the booster input and the booster output when activating said booster, wherein when said booster is inactivated by said inactivating valve, the pressure at the output corresponds to a pressure supplied by the pressure source.

17. The hydraulic system according to claim 16, wherein said inactivating valve is hydraulically operated.

18. The hydraulic system according to claim 16, wherein said inactivating valve is electrically operated.

19. The hydraulic system according to claim 16, wherein pressure booster and/or said inactivating valve are integrated in said pressure source.

20. The hydraulic system according to claim 16, wherein said system comprises at least two outputs, each output being connected to a branch, at least one branch being provided with the booster and inactivating valve.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Preferred embodiments of the invention will now be described in more detail with reference to the drawing, wherein:

(2) FIG. 1 shows a schematic illustration of a hydraulic system,

(3) FIG. 2 shows the hydraulic system of FIG. 1 with more details,

(4) FIG. 3 shows an alternative embodiment to FIG. 1,

(5) FIG. 4 shows a third embodiment of a hydraulic system,

(6) FIG. 5 shows a fourth embodiment of a hydraulic system,

(7) FIG. 6 shows a pressure source having an integrated booster and inactivating means,

(8) FIG. 7 shows a schematic illustration of a booster having a variable amplification factor,

(9) FIG. 8 schematically shows possible positions for a booster being provided with inactivating means,

(10) FIG. 9 shows a more detailed view of said inactivating means,

(11) FIG. 10 shows another embodiment of said inactivating means, and

(12) FIG. 11 shows a modification of the embodiment shown in FIG. 10.

DETAILED DESCRIPTION

(13) FIG. 1 schematically shows a hydraulic system 1 having a pressures source 2, for example a pump, and an output 3 which is connected or can be connected to a hydraulic consumer 4. The pressure source 2 takes hydraulic fluid out of a tank 5 (or any other reservoir) and pumps it with elevated pressure to the output 3 to supply the consumer 4. Hydraulic fluid returning from the consumer 4 returns to said tank 5.

(14) In all Figs., the same numerals are used for the same or similar elements.

(15) A pressure booster 6, i.e. a pressure intensifier, is arranged between said pressure source 2 and said output 3. The pressure booster 6 is a hydraulic pressure booster, e.g. a pressure booster comprising a differential piston as it is known in the art. A schematic illustration of such a booster 6 can be found in U.S. Pat. No. 7,686,596 B2. The differential piston has a first front face which is loaded by a pressure of said pressure source 2, and a second front face supplying hydraulic fluid to said output 3. The second front face is smaller than the first front face. The ratio between the two front faces determines the amplification factor of the pressure booster 6. However, the booster can of course have a different design.

(16) In the present hydraulic system, the amplification factor of the pressure booster 6 is in the range from 1.2 to 20, e.g. the booster 6 adds 20% to 1900% to the output pressure of said pressure source 2.

(17) The pressure booster 6 is not permanently active. In order to inactivate the pressure booster 6, inactivating means 7 are provided. Said inactivating means 7 are able to activate or inactivate said pressure booster 6. When said inactivating means 7 activate said pressure booster 6, the pressure at said output is higher than the pressure supplied by said pressure source alone. When said pressure booster 6 is not activated, the pressure at said output 3 corresponds to the pressure supplied by the said pressure source 2. The inactivating means 7 can be operated to activate said pressure booster 6 only when a higher pressure is needed at said output 3, in other words, a pressure on demand is provided.

(18) FIG. 2 shows a first embodiment of said inactivating means 7. Said inactivating means 7 comprise hydraulic means, i.e. a valve 8, in particular a 2/2-way-valve, which is arranged in a line 9 connecting a booster input 10 and a booster output 11.

(19) Said valve 8 is provided with a spring 12 shifting the valve 8 in the position shown in FIG. 2 establishing a short circuit between the booster input 10 and the booster output 11. In other words, said booster 6 is short-circuited and therefore inactive. The pressure from the pressure source 2 is supplied via line 9 to said output 3 and said consumer 4.

(20) If said valve 8 is switched into the other position, the line 9 is interrupted so that the pressure booster 6 is active amplifying the pressure from said pressure source 2 so that the pressure at said output 3 is increased to 120% to 2000% of the pressure of said pressure source.

(21) FIG. 2 shows a possibility for operating said valve 8. An actuating valve 13 is arranged in a signal line 14. Said signal line 14 is connected to the pressure source 2 and to a signal input 15 of said valve 8. The actuating valve 13 can be actuated by means of a button 16 which can be positioned, for example, at a joystick with which an operator operates the hydraulic system 1.

(22) When the operator pushes the button 16 (or any other switch), the signal line 14 connects the pressure source 2 to the signal input 15 of said valve 8 shifting said valve 8 in a position in which the line 9 is interrupted so that the pressure booster 6 is active. As soon as the operator releases button 16, spring 12 pushes back valve 8 into a position in which line 9 short-circuits said pressure booster 6.

(23) When for example the hydraulic consumer 4 is a hydraulic cylinder provided for lifting a load and the load is a bit too heavy for the working pressure supplied by the pressure source 2, the operator presses the button 16 for a few seconds to activate an 20% to 1900% higher force on the cylinder which enables him to continue operating effectively without time consuming breaks in the working cycle. Since the amplification factor of the pressure booster 6 is limited, such a short increase in pressure does not exceed the machines-design-specifications.

(24) FIG. 3 shows another embodiment in which the same elements are designated with the same numerals.

(25) In this embodiment, the signal line 14 for the valve 8 is connected to a point 17 positioned at or near said output 3, i.e. the signal line 14 signals a pressure at a load dependent position to said valve 8.

(26) If the pressure at point 17 increases, for example due to a heavy load the signal line 14 transmit this elevated pressure to the signal input 15 of said valve 8 shifting it to a position in which said pressure booster 6 is activated to increase the pressure at the output 3. This activation of booster 6 is made automatically without requiring an action of the operator.

(27) FIG. 4 shows a third embodiment in which said valve 8 is actuated by means of a solenoid 18. The solenoid 18 is activated by switching a switch 19. Said switch 19 can be actuated by the operator. Said switch 19 can be, for example, be positioned at the above mentioned joystick with which the operator operates the hydraulic system 1.

(28) FIG. 5 shows an fourth embodiment in which said valve 8 again is actuated by said solenoid 18. Said solenoid 18 is activated via a signal line 20 which is connected to sensor means 21 sensing a pressure at or near the output 3.

(29) When the pressure at the output 3 increases due to a heavy load, this pressure demand is transmitted to said valve 8 activating said booster 6 which in turn supplies an increased pressure to said output 3.

(30) FIG. 6 shows the possibility to integrate said pressure source 2 and said pressure booster 6 together with said inactivating means 7 in a common unit 22.

(31) FIG. 7 illustrates a further embodiment showing the possibility to provide said pressure booster 6 with means 23 producing a variable booster pressure.

(32) In all hydraulic systems shown in FIGS. 1 to 7, the pressure booster 6 can be provided with an auxiliary pump connected to said booster input 10. Said auxiliary pump is connected to a driving motor which can be activated on demand. A unit showing a pressure booster, a pump and a driving motor which can be activated is shown, for example, in U.S. Pat. No. 7,726,950 B2, the disclosure of said document being incorporated by reference. Such an embodiment is useful when the pressure of the pump 2 falls below a level which is necessary for operating the consumers of the hydraulic system. If the pressure of the pump 2 falls below this level, the driving motor can be activated driving said auxiliary pump. The auxiliary pump delivers pressurised hydraulic fluid to the pressure booster 6 allowing for a sufficient operation of the consumers connected to the hydraulic system 1. Such an embodiment provides pressure on demand on the lower side of the pressure range.

(33) FIG. 8 shows a hydraulic system 1 having the above mentioned pressure source 2 and a plurality of consumers, i.e. a first cylinder 24, a second cylinder 25 and a third cylinder 26.

(34) Another branch of the hydraulic system 1 comprises a steering unit 28 having a steering cylinder 29. Furthermore, a secondary system 30 is shown having a separate pressure source 31 and a consumer 32, e.g. a motor.

(35) The hydraulic system 1 comprises a priority valve 33a, a pressure valve 33b and a distribution valve 34.

(36) The hydraulic system 1 shown in FIG. 8 is used to illustrate a number of positions for the pressure booster 6 including said inactivating means 7. To illustrate this briefly boxes are shown marked with 6+7 so that is clear that each pressure booster 6 is provided with inactivating means 7.

(37) Obviously, not all positions shown in FIG. 8 will be provided with a combination of pressure booster 6 and inactivating means 7. The illustration in FIG. 8 is merely used to show different possibilities.

(38) As can be seen in FIG. 8, the unit of pressure booster 6 and inactivating means 7 (in the following briefly unit) can be arranged directly downstream the pressure source 2 or it can be integrated into the pressure source 2.

(39) Another possibility is to arrange the unit in a line downstream the pressure source 2, i.e. in a line between the pressure source 2 and said priority valve 33a.

(40) Furthermore, it is possible to arrange the unit downstream a priority valve 33a, i.e. between the priority valve 33a and a consumer like said steering unit 28.

(41) It is also possible to arrange said unit between said steering unit 28 and said steering cylinder 29. For the sake of clarity only one unit is shown. However, it is clear that said unit can supply the steering cylinder 29 for both directions.

(42) Furthermore, it is possible to arrange said unit between said priority valve 33a and said distribution valve 34. The advantage of placing the pressure booster 6 before the distribution valve 34 (can be e.g. a proportional valve group) is that all valves (or consumers) connected to this distribution valve 34, i.e. belonging to the same group, can utilize the additional pressure generated by the pressure booster 6. The distribution valve 34 could be, e.g. PVG32 valves of the applicant, which have an LS output (LSa, LSb) measuring the pressure in both the A and the B connection, and this LS output could thus be used to activate/inactivate the booster, as later explained in connection with FIG. 11.

(43) It is also possible to assign said unit to a hydraulic cylinder. An example is shown for the second cylinder 25. Here, the unit is positioned between the distribution valve 34 and the second cylinder 25.

(44) Furthermore, it is possible, to integrate said unit and said third cylinder 26.

(45) When said secondary system 30 is used, said unit can be used to increase the pressure of the secondary system 30 to the level of the pressure of the hydraulic system 1, if required. The general idea here is that, for example, a low pressure system 30 can be used that drives, for example, a fan. If a demand for a higher pressure occurs in a different hydraulic system 1, help can be given by means of an amplified pressure from the low-pressure system by means of a pressure booster 6. This connection could also be placed at another position, e.g. before the distribution valve 34.

(46) In the embodiments shown in FIGS. 2 to 5 the valve 8 is shown to short-circuit said pressure booster 6, i.e. to close line 9. Said line 9 is already present in most pressure boosters 6, so that no additional line 9 is necessary.

(47) However, in some cases it may be necessary not only to establish a through going line in parallel to said pressure booster 6, but to interrupt a connection between said line 9 and said booster input 10.

(48) FIG. 9 shows a more detailed view of said inactivating means 7. The numerals used in FIGS. 1 to 8 designate the same elements.

(49) In this embodiment line 9 comprises just a check valve 35 allowing a flow from an input connection 36 to be connected to the pressure source 2 and said output 3.

(50) The booster output 11 is connected to said output 3 by means of another check valve 37.

(51) The booster input 10 is connected to the connection 36 via a 2/2-way solenoid valve 38 which is shown in a position in which said pressure booster 6 is inactive since no fluid can flow from the connection 36 to the booster input 10. However, said solenoid valve 38 can be switched into another position in which fluid can flow from said connection 36 to said booster input 10.

(52) Furthermore, FIG. 9 shows a tank connection 39 which is connected to a return connection R of said pressure booster 6.

(53) Furthermore, a relief valve 40 is arranged between said two connections 36, 39.

(54) FIG. 10 shows another embodiment of said inactivating means 7. In this embodiment said solenoid valve 38 is replaced by a sequence valve 41. Said sequence valve 41 again is a 2/2-way valve blocking a path between said input connection 36 and said booster input 10 in the position shown. This position is set by means of a spring 42.

(55) The sequence valve 41 is loaded in the opposite direction by a pressure at the input connection 36. If this pressure increases to overcome the force of said spring 42, the sequence valve 41 is shifted into a position in which a part between said input connection 36 and said booster input 10 is established.

(56) FIG. 11 shows a modification of the embodiment shown in FIG. 10. However, in this embodiment the sequence valve 41 is actuated by a pressure at a load sensing connection LS.

(57) Overall, this idea could be used to obtain a much better energy consideration for a vehicle or another working machine, as the pump of this vehicle or machine could have a smaller output, because the pressure booster can be included in the extreme loads.

(58) While the present invention 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 invention may be made without departing from the spirit and scope of the present.