GB2197692A - Hydraulic actuator - Google Patents
Hydraulic actuator Download PDFInfo
- Publication number
- GB2197692A GB2197692A GB08626736A GB8626736A GB2197692A GB 2197692 A GB2197692 A GB 2197692A GB 08626736 A GB08626736 A GB 08626736A GB 8626736 A GB8626736 A GB 8626736A GB 2197692 A GB2197692 A GB 2197692A
- Authority
- GB
- United Kingdom
- Prior art keywords
- cylinder
- inlet
- drive piston
- actuator
- ports
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B9/00—Piston machines or pumps characterised by the driving or driven means to or from their working members
- F04B9/08—Piston machines or pumps characterised by the driving or driven means to or from their working members the means being fluid
- F04B9/10—Piston machines or pumps characterised by the driving or driven means to or from their working members the means being fluid the fluid being liquid
- F04B9/103—Piston machines or pumps characterised by the driving or driven means to or from their working members the means being fluid the fluid being liquid having only one pumping chamber
- F04B9/105—Piston machines or pumps characterised by the driving or driven means to or from their working members the means being fluid the fluid being liquid having only one pumping chamber reciprocating movement of the pumping member being obtained by a double-acting liquid motor
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
- F01L25/00—Drive, or adjustment during the operation, or distribution or expansion valves by non-mechanical means
- F01L25/02—Drive, or adjustment during the operation, or distribution or expansion valves by non-mechanical means by fluid means
- F01L25/04—Drive, or adjustment during the operation, or distribution or expansion valves by non-mechanical means by fluid means by working-fluid of machine or engine, e.g. free-piston machine
- F01L25/06—Arrangements with main and auxiliary valves, at least one of them being fluid-driven
- F01L25/066—Arrangements with main and auxiliary valves, at least one of them being fluid-driven piston or piston-rod being used as auxiliary valve
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Reciprocating Pumps (AREA)
Abstract
A double-acting hydraulic piston and cylinder motor wherein the cylinder (4) has an inlet (39) and a pair of outlets (35, 37) and the drive piston (3) is constructed to connect the inlet (39) to a respective one of the outlets (35, 37) at the completion of each working stroke of the drive piston (3) whereby hydraulic fluid supplied to the inlet (39) is alternately delivered to the outlets for operating a changeover valve (6) controlling the supply and removal of hydraulic fluid to and from the ends of the cylinder (4) &cirf&
Description
HYDRAULIC ACTUATOR
This invention relates to hydraulic actuators of the type in which a drive piston is reciprocated in a cylinder by hydraulic fluid alternately supplied to and removed from each end of the cylinder under the control of valve means operable to changeover the supply and removal of hydraulic fluid at the completion of each working stroke of the drive piston. Hydraulic actuators of the type above-described will hereinafter be referred to as of the type specified.
It is already known to use a link mechanism connected to the drive piston and arranged to actuate respective valve actuating cams positioned externally of the cylinder at the completion of each working stroke for operating the valve means mechanically. The known link mechanisms are often of complex construction requiring special linkages and seals to accommodate movement of the linkage with the drive piston and to prevent loss of hydraulic fluid from the cylinder.
It is also known to use a pair of valves positioned internally of the -cylinder on opposite sides of the drive piston which are alternately actuated by the drive piston at the completion of each working stroke to supply hydraulic fluid for operating the valve means hydraulically. The provision of separate valves complicates assembly and adds to the manufacturing.costs by increasing the number of components required for the actuator.
It is an object of the present invention to provide a hydraulic actuator of the type specified in which operation of the valve means does not rely on a mechanical link mechanism or the provision of-separate valves as above-described.
According to the present invention there is provided a hydraulic actuator of the type specified wherein the cylinder has an inlet and a pair of outlets and the drive piston is constructed to connect the inlet to a respective one of the outlets at the completion of each working stroke of the drive piston whereby hydraulic fluid supplied to the inlet is alternately delivered to the outlets for operating the valve means to changeover the supply and removal of hydraulic fluid to and from the cylinder.
By the instant invention, the use of separate valves operated by the drive piston for operating the valve means is avoided by the use of the drive piston and cylinder as a valve for the same purpose. As a result the construction of the invented actuator is considerably simplified.
Preferably, the inlet and outlets comprise respective ports opening into the cylinder and the drive piston has an inlet land for connecting the inlet port to a respective one of the outlet ports at the completion of each working stroke.
Conveniently the outlet ports are arranged on opposite sides of the inlet port and are axially spaced therefrom.
Advantageously, the cylinder has a pair of axially spaced drain ports positioned on opposite sides of the inlet port and the drive piston has a pair of axially spaced outlet lands positioned on opposite sides of the inlet land, the drain ports and outlet lands being arranged so that, at the completion of-each working stroke, the respective other of the outlet ports is connected to a respective one of the drain ports by a respective one of the outlet lands. In this way the hydraulic fluid is alternately supplied to and removed from each outlet port at the completion of each working stroke of the drive piston.
Other arrangements of ports and lands may be provided to achieve the same results. For example the ports may be axially and/or circumferentially spaced apart.
Preferably the valve means comprises a spool valve and each outlet port is connected to a respective one end of a bore in which a valve spool is slidably mounted whereby the valve spool is reciprocated in the bore between first and second operating positions by the hydraulic fluid alternately supplied to and removed from each end of the bore.
The invention will now be described in more detail, by way of example only with reference to the accompanying drawings, wherein:
Figure 1 is a section through a single acting reciprocating pump incorporating a hydraulic actuator according to the present invention, showing the drive piston of the hydraulic actuator at the completion of the delivery stroke, and
Figure 2 is a section similar to Figure 1 showing the drive piston of the hydraulic actuator at the completion of the suction stroke.
Referring to the accompanying drawings, a single acting reciprocating pump 1 for intensifying the pressure of a fluid, for example for use in hydraulically operated nuts and jacks for tensioning bolts and studs, is shown incorporating a hydraulic actuator 2 according to the present invention.
The actuator 2 comprises drive piston 3 slidably mounted in a cylinder 4 formed in a cylinder block 5, and valve means 6 for controlling the supply and removal of hydraulic fluid to and from respective ducts 7,8 formed in the block 5 and connected to the opposed ends of the cylinder 4 to reciprocate the drive piston 3 within the cylinder 4 between the extreme positions shown in Figures 1 and 2.
One end of the cylinder 4 is closed by an end cap 9 releasably secured to the block 5 by screws (not shown) and sealed by any suitable means (not shown).
The other end of the cylinder 4 opens into a bore 10 of increased diameter formed in the block 5 and is closed by an end cap 11 releasably secured to the block 5 by screws (not shown) and sealed in the bore 10 by any suitable means (not shown).
The valve means 6 comprises a spool valve having a valve body 12 detachably mounted on the block 5 by means of screws (not shown) to align each of the ducts 7,8 in the block 5 with a respective duct 13,14 formed in the valve body 12.
The valve body 12 has a through bore 15 the opposed ends of which are closed by respective end caps 16,17 releasably secured to the body 12 and sealed by any suitable means (not shown). The bore 15 is formed with five axially spaced apart annular recesses 18,19,20,21,22 of which the centre recess 20 is connected to a duct 23 for the supply of hydraulic fluid, the outer recesses 18,22 are each connected to a respective duct 24,25 for the return of hydraulic fluid to a tank (not shown), and the intermediate recesses 19,21 are each connected to a respective one of the ducts 13,14.
A valve spool 26 is mounted in the bore 15 for axial sliding movement between two extreme positions shown in Figures 1 and 2. The opposed of the spool 26 are received in respective chambers 27,28 formed in the end caps 16,17 and the spool 26 is frictionally retained in each of the extreme positions by the engagement of a respective detent 29,30 with the associated end of the spool 26.
The valve spool 26 is formed with three axially spaced apart annular lands 31,32,33 for co-operating with the recesses 18,19,20,21,22 in each of the two extreme positions of the spool 26 for controlling the supply and removal of hydraulic fluid to and from the opposed ends of the cylinder 4.
More specifically, in the extreme position of the valve spool 26 shown in Figure 1, the centre or inlet land 32 connects the duct 23 to the ducts 13,7 for the supply of hydraulic fluid to the left hand end of the cylinder 4 as viewed in the drawing and the end or outlet land 33 connects the duct 25 to the ducts 14,8 for the simultaneous removal of hydraulic fluid from the right hand end of the cylinder 4 to the tank for moving the drive piston 3 from left to right as indicated by the arrow A.
In the other extreme postion of the valve spool 26 shown in Figure 2, the centre land 32 connects the duct 23 to the ducts 14,8 for the supply of hydraulic fluid to the right hand end of the cylinder 4 as viewed in the drawing and the end or outlet land 31 connects the duct 24 to the ducts 13,7 for the simultaneous removal of hydraulic fluid from the left hand end of the cylinder 4 to the tank for moving the drive piston 3 from right to left as indicated by the arrow B.
The movement of the valve spool 26 between the extreme positions is hydraulically controlled by the position of the drive piston 3 in the cylinder 4 as will now be described.
The cylinder 4 has five axially spaced apart ports 34,35,36,37,38 of which the centre port 36 is connected to a duct 39 for the supply of hydraulic fluid, the outer ports 34,38 are each connected to a respective duct 40,41 for the return of hydraulic fluid to the tank and the intermediate ports 35,37 are each connected by a respective duct 42,43 to a respective one of the chambers 27,28.
The drive piston 3 has three axially spaced apart annular lands 44,45,46 for co-operating with the cylinder ports 34,35,36,37,38 in each of the two extreme positions of the drive piston 3 shown in
Figures 1 and 2 for controlling the supply and removal of hydraulic fluid to and from the chambers 27,28.
More specifically, in the extreme position of the drive piston 3 shown in Figure 1, the centre or inlet land 45 connects the port 36 to the port 35 for the supply of hydraulic fluid to the chamber 27 and the end or outlet land 46 connects the port 38 to the port 37 for the simultaneous return of hydraulic fluid from the chamber 28 to the tank for moving the valve spool 26 from right to left.
In the other extreme position of the drive piston 3 shown in Figure 2, the centre land 45 connects the port 36 to the port 37 for the supply of hydraulic fluid to the chamber 28 and the end or outlet land 44 connects the port 34 to the port 35 for the simultaneous return of hydraulic fluid from the chamber 27 to the tank for moving the valve spool 26 from left to right.
In this way, hydraulic fluid is alternately supplied to and removed from the chambers 27,28 at the completion of each working stroke of the drive piston 3 to move the valve spool 26 to changeover the supply and removal of hydraulic fluid to and from the opposed ends of the cylinder 4 to reciprocate the drive piston 3 in the cylinder 4.
As will be understood from the foregoing description, the drive piston 3 and cylinder 4 constitute a valve controlling the operation of the spool valve at the completion of each working stroke.
The provision of the various ports in the cylinder 4 and the lands on the drive piston 3 does not require the use of separate additional components such as the mechanical link mechanism or valves of the prior art above-discussed for controlling the changeover valve.
The construction of the invented actuator is therefore considerably simplified as compared with the prior art constructions.
In the application of the hydraulic actuator 2 above-described'to the single acting reciprocating pump 1 illustrated, an output piston 47 of reduced diameter is mounted at one end of the drive piston 3 and is slidably received in a bore 48 in the end cap 11.
The output piston 47 is sealed in the bore 48 by a seal arrangement--generally-indicated by--the reference numeral 49 located at the inner end of the bore and retained by a ring 50 releasably secured to the end cap 11.
The outer end of the bore 48 opens into a further bore 51 formed in the end cap 11 and extending transversely relative to the bore 48.
One end of the transverse bore 51 is provided with an inlet 52 for supply of fluid the pressure of which is to be increased and the other end is provided with an outlet 53 for delivery of the pressurised fluid.
The inlet 52 and outlet 53 are each provided with a respective one-way valve 54,55 to prevent back-flow of the fluid. Each valve 54,55 is similar and comprises a ball 56 lightly biassed by a return spring 57 in a direction opposed to the permitted fluid flow to engage a spherical valve seat 58 and a duct 59 to drain any fluid leaking past the valve seat 58.
The operation of the pump 1 is as follows, starting from the position shown in Figure 1, the pump 1 is shown at the commencement of the suction stroke in which the drive piston 3 is moved from left to right by the delivery of hydraulic fluid to the left end of the cylinder 4 thereby retracting the output piston 47 in the bore 48. As a result, the fluid pressure in the bores 48,51 is reduced causing the outlet valve 55 to be closed by the back pressure of the fluid acting on the ball 56 and the inlet valve 54 to be opened by the pressure of the fluid supply thereby drawing fluid into the bore 51 as indicated by the arrow C.
At the completion of the suction stroke shown in
Figure 2, the supply and removal of hydraulic fluid to and from the cylinder 4 is automatically reversed as previously described thereby starting the delivery stroke in which the drive piston 3 is moved from right to left by the introduction of hydraulic fluid to the right hand end of the cylinder 4 thereby--advancing the output piston 47 in the bore 48. As a result, the fluid pressure in the bores 48,51 is increased causing the inlet valve 54 to be closed by the increased fluid pressure and the outlet valve 55 to be opened thereby delivering the fluid at an increased pressure as indicated by the arrow D.
At the completion of the delivery stroke shown in
Figure 1, the supply and removal of hydraulic fluid to and from the cylinder 4 is automatically reversed as previously described thereby starting the suction stroke again and the above cycle is repeated continuously whilst the actuator 2 is operational.
It will be understood that the invented hydraulic actuator is not limited to the single acting reciprocating pump above-described but has application to a double acting reciprocating pump in which an output piston is attached to the other end of the drive piston as well as to other apparatus in which a reciprocating motion as provided by the drive piston is required.
It will also be understood that the invented actuator is not limited to the construction abovedescribed. For example, the valve means for changing over the supply and removal of hydraulic fluid to and from the cylinder may be of any suitable type in which a valve member is operated hydraulically in response to the position:of the drive piston in the cylinder.
Additionally, the valve means may be a separate unit detachably mounted on the cylinder block as above-described or the valve means may be incorporated in the cylinder block.
Finally, the construction and arrangement of the ports in the cylinder and the lands on-the drive piston may be changed whilst still providing the required actuation of the valve means.
Claims (7)
1. A hydraulic actuator of the type specified wherein the cylinder has an inlet and a pair of outlets and the drive piston is constructed to connect the inlet to a respective one of the outlets at the completion of each working stroke of the drive piston whereby hydraulic fluid supplied to the inlet is alternately delivered to the outlets for operating the valve means to changeover the supply and removal of hydraulic fluid to and from the cylinder.
2. An actuator as claimed in Claim 1, wherein the inlet and outlets comprise respective ports opening into the cylinder and the drive piston has an inlet land for connecting the inlet port to a respective one of the outlet ports at the completion of each working stroke.
3. An actuator as claimed in Claim 2, wherein the outlet ports are arranged on opposite sides of the inlet port and are axially spaced therefrom.
4. An actuator as claimed in Claim 2 or Claim 3, wherein the cylinder has a pair of axially spaced drain ports positioned on opposite sides of the inlet port and the drive piston has a pair of axially spaced outlet lands positioned on opposite sides of the inlet land, the drain ports and outlet lands being arranged so that, at the completion of each working stroke, the respective other of the outlet ports is connected to a respective one of the drain ports by a respective one of the outlet lands.
5. An actuator as claimed in Claim 2, wherein the ports are axially and/or circumferentially spaced apart.
6. An actuator as claimed in any one of Claims 2 to 5, wherein the valve means comprises a spool valve and each outlet port is connected to a respective one end of a bore in which a valve spool is slidably mounted whereby the valve spool is reciprocated in the bore between first and second operating positions by the hydraulic fluid alternately supplied to and removed from each end of the bore.
7. An hydraulic actuator substantially as hereinbefore described with reference to the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08626736A GB2197692A (en) | 1986-11-08 | 1986-11-08 | Hydraulic actuator |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08626736A GB2197692A (en) | 1986-11-08 | 1986-11-08 | Hydraulic actuator |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB8626736D0 GB8626736D0 (en) | 1986-12-10 |
| GB2197692A true GB2197692A (en) | 1988-05-25 |
Family
ID=10607029
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08626736A Withdrawn GB2197692A (en) | 1986-11-08 | 1986-11-08 | Hydraulic actuator |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2197692A (en) |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB873114A (en) * | 1956-10-31 | 1961-07-19 | Ibm | Improvements in hydraulic oscillators |
| GB1307963A (en) * | 1971-11-17 | 1973-02-21 | Sliver Manufacturing Co Inc | High pressure piston pump |
| GB1463257A (en) * | 1975-07-12 | 1977-02-02 | Madan Co Ltd C | Reciprocating pumps |
| GB1532020A (en) * | 1976-05-21 | 1978-11-15 | Hausherr & Soehne Maschf | High pressure pumping apparatus |
-
1986
- 1986-11-08 GB GB08626736A patent/GB2197692A/en not_active Withdrawn
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB873114A (en) * | 1956-10-31 | 1961-07-19 | Ibm | Improvements in hydraulic oscillators |
| GB1307963A (en) * | 1971-11-17 | 1973-02-21 | Sliver Manufacturing Co Inc | High pressure piston pump |
| GB1463257A (en) * | 1975-07-12 | 1977-02-02 | Madan Co Ltd C | Reciprocating pumps |
| GB1532020A (en) * | 1976-05-21 | 1978-11-15 | Hausherr & Soehne Maschf | High pressure pumping apparatus |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8626736D0 (en) | 1986-12-10 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |