EP1387972B1

EP1387972B1 - Sequence controlled hydraulic cylinders

Info

Publication number: EP1387972B1
Application number: EP02726540A
Authority: EP
Inventors: Martin Marklund
Original assignee: HYDRAUTO AB
Current assignee: Wipro Infrastructure Engineering AB
Priority date: 2001-05-17
Filing date: 2002-05-15
Publication date: 2009-03-04
Anticipated expiration: 2022-05-15
Also published as: ES2323945T3; ATE424366T1; SE0101739D0; EP1387972A1; SE0101739L; SE522200C2; DE60231391D1; WO2002093055A1

Abstract

Means of sequential operation of controlled units, comprising a piston unit (13) for operating a first controlled unit that is slip-mounted in a cylinder barrel (1) and valve bodies (9, 15, 16, 20, 33) intended for controlling the flow of fluid from the first controlled unit to a second controlled unit for its operation. The first unit's piston unit (13) contains a passage that in order to convey fluid to the second controlled unit passes over part of the piston unit's (13) outer edge, and that the valve bodies (9, 15, 16, 20) contain an axially displaceable moving ring-shaped valve body (9) surrounding the piston unit (13) that opens and closes the said passage depending on the relative position of the piston unit (13) in the cylinder.

Description

The present invention concerns sequence controlled hydraulic cylinders according to the preamble to claim 1, which is generally known.
When operating for example telescopic crane arms using a piston-cylinder means such as hydraulic cylinders it is desirable that the telescope elements are extended or contracted in a specific order so that it is possible to reliably determine the strength and thereby the dimensions of the telescope elements used in the crane arm. However, on known telescopic crane arms arranged with two or more hydraulic cylinders, the plus sides of the cylinders are in many cases under pressure at the same time. This means that the part of the crane arm that is extended is the one with the least friction or resistance due to load. In most cases during a minus stroke, the minus sides of all the cylinders are under pressure at the same time and all the cylinders can move inwards until a valve is closed. Furthermore, the cylinders can contract even more through the compression of the oil due to the load or similar. This means that the crane arm must be dimensioned for its weakest part and that the actual length extension of the crane arm can deviate from the desired length. The order in which the telescopic elements move and the position to which they are to move can be determined by electronic means or by hydraulic valves with pilot lines but this can entail high cost.
One object of the present invention is to achieve a means of alleviating or remedying these shortcomings.
This object of the invention is achieved by pressurising only the innermost cylinder during a plus stroke and only the outermost cylinder during a minus stroke and that each cylinder must reach its end position before the next cylinder is allowed to start its movement. This invention in comparison to other conventional solutions also means that even if the cylinder movement stops immediately the passage of oil via a valve to the next cylinder is opened, the valve's opening area will be large and the oil can pass. This involves considerably smaller pressure losses and thereby less heating of the oil than in conventional solutions where the valve's opening area is wholly dependent on how much the cylinder has moved after the valve has started to open. Furthermore, the invention entails the flow of oil taking place through pipes inside and between the cylinders without the use of hoses.
The following is a more detailed description of this invention with references to attached drawings, where

fig. 1 shows a longitudinal section of a hydraulic cylinder according to the invention plus a partial enlargement of a plunger and seat seal, and
fig. 2 shows an assembly of three interconnected cylinders.

The hydraulic cylinder illustrated in the drawings comprises a cylinder barrel 1 with a cylinder bottom 2 arranged at one end and a sealed cylinder head 3 arranged at the other end with a reduced diameter to form a ring gap 4 between the said cylinder head 3 and a piston 5, and one shoulder 6 intended for a spring 7 and one shoulder 8 intended for a valve body 9. In the cylinder bottom 2 and on the outer barrel 1 are arranged couplings 10 and 11 for the flow of a pressure medium such as hydraulic oil. Inside the cylinder barrel 1 between the cylinder bottom 2 and the cylinder head 3 there is a first chamber 12:1 and a second chamber 12:2 bounded by an axial sliding piston 13 of the same size as the inside diameter of the cylinder barrel 1. The piston unit 13 has an axial drilling 17 along its length and an axially displaceable valve body 9 designed as a ring-shaped sleeve surrounding the piston unit. A spring 14 is arranged between the valve body 9 and the piston unit 13 and a spring 7 intended to act between the valve body 9 and the shoulder 6 in the cylinder head 3. The valve body 9 has a groove 15, which together with a bevelled edge 16 on the piston unit 13 forms a seat seal 18, a plunger seal 19 and a ring chamber 20. Flush with the right-hand edge of the valve body 9 in figure 1, there is a drilled passage 21 arranged in the piston unit 13, which communicates with the chamber 12:1 and in the left-hand edge of the valve body is a chamber 36 formed between the piston unit 13 and the valve body 9 communicating with the coupling 10.
The piston rod 5, which exhibits a passage 22 extending along its length containing two pipes 23 and 24, one surrounding the other, extends from the piston unit 13 through the chamber 12:2. With the seals 18, 19 in open position, the chamber 12:2 communicates via the ring chamber 20 that is formed by the seals 18, 19 with the radial passages 25 and 26 in the piston unit 13. On the piston unit 13 coupling to the piston rod 5 is arranged a seal 27 intended to seal the ring gap 4 with the piston unit 13 in its extended position. The tubular piston 5 passes through the sealed cylinder head 3 and forms together with the pipes 23, 24 located in the passage 22 inside the piston 5 two ring chambers 28 and 29. One end of the smaller pipe 23 is connected to the coupling 10 of the next cylinder via a coupling 37 and a pipe and the other end to a chamber 12:2 via a drilling 17 extending through the piston unit 13 in the longitudinal direction of the piston rod 5. In the piston 5 is arranged a radial drilled passage 30 that communicates with a cavity 31 in the outlet 11 with the piston rod 5 in its extended position. In the piston rod head 32 is arranged a non-return valve 33 that is mechanically acted on by an arm 34 on an adjacent cylinder. The non-return valve 33 is intended to communicate with both ring chambers 28, 29 and an outlet 35.
The three cylinders in the example embodiment according to figures 1 and 2, whereof the outer cylinder comprises a conventional dual-action hydraulic cylinder, are mechanically inter-connected between the piston rod head 32 on cylinder I and the cylinder barrel 1 on cylinder II and so on, each piston rod head 32 exhibits and arm 34 to control the non-return valve 33 on the following cylinder and works as follows:
For plus movement, oil is led into cylinder I, whereby it will always start first. During the plus stroke of cylinder I, hydraulic oil is led under pressure from the oil tank (not shown) by means of a pump (not shown) via a pressure retaining valve (not shown) through the coupling 10 inside the chamber 12:2 between the piston unit 13 and the cylinder bottom 2. Thereupon the piston unit 13 with piston rod 5 and via the piston rod head 32 including the other cylinders is forced to the right as shown in figure 1, whereby the return oil from the other cylinders II and III linked with pipes is pressed out of the chamber 12:1 via the ring gap 4 and through the coupling 11 back to the tank. During this movement the plunger and seat seals 18, 19 and the chamber 20 are completely closed by the valve body 9 under the influence of the spring 14 and by the pressure difference P1-P2 between the chambers 36 and 20, where the pressure P1 in chamber 36 is higher than the pressure P2 in chamber 20. When the piston unit 13 approaches its farthest position, the seal 27 is pushed into the ring gap 4 while the spring 7 meets the cylinder head 3 shoulder 6 and is put under tension. At this time the return oil passes from the piston rod side through the ring chamber 29 and on through the non-return valve 33, after which it passes out through the ring chamber 28 into the passage 30 communicating with the cavity 31 to the coupling 11 and to the tank.
As movement continues to the right as shown in figure 1, the valve body 9 meets the cylinder head 3 shoulder 8. The seal 18 opens when the pressure is sufficient for the oil to pass via the drilling 17 and be forced into the chamber 20, thereby the closing pressure difference P1-P2 ceases. Thereupon, the spring 7 overcomes the force of the spring 14 and the valve body 9 moves in the opposite direction to the piston unit 13, whereby the plunger and seat seals 18 and 19 open fully. Seals 18 and 19 open fully even if the cylinder travel ceases immediately the valve body 9 makes contact with the cylinder 3 shoulder 8 due to the pressure difference P 1-P2 ceasing when the seat seal 18 opens plus the spring force of spring 7. When the piston unit 13 reaches its maximum extended position, the oil will be redirected through the passage 25 in the piston unit 13, via the open seals 18, 19 and the chamber 20, and on through the inner pipe 23 of the piston rod 5 and coupling 37 to the next cylinder II. During the outward movement of the next cylinder II, its return oil is pressed in through the coupling 11 on cylinder II and into cylinder I via coupling 35 into the ring chamber 28 and by the passage 30, which is now connected to the cavity 31 and the coupling 11 on cylinder I, is prevented from passing to the chamber's 12:1 piston rod side of the seal 27 and back to the tank.
For a minus movement, the outermost cylinder III, which is a conventional dual-action cylinder, will always start even though the pressurised oil has first passed through the inner cylinders I and II. During the minus movement, the pressure oil is passed via coupling 11 in cylinder I, through passage 30 into the ring chamber 28 since the ring gap 4 is sealed by seal 27 and on through coupling 35 to cylinder II and in the same way to cylinder III. The return oil is passed out through coupling 10 on cylinder III to coupling 37 on cylinder II, through the inner pipe 23 in piston rod 5 and via the open plunger and seat valves 18 and 19 to passage 25, into the chamber 12:2 and out through coupling 10 on cylinder II and in the same way through cylinder I back to the tank.
When cylinder III is almost completely retracted, the arm 34 on piston rod head 32 on cylinder III will press down the non-return valve 33 on cylinder II, whereby the non-return valve 33 on cylinder II opens. Since the non-return valve 33 is closed as long as it is not acted on by the arm 34 on the piston rod head 32, the cylinder III must be fully contracted before the next cylinder II starts its minus stroke. During the cylinder II minus stroke, oil is pressed into coupling 11 through the cavity 31 and the passage 30 to the ring chamber 28, via the open non-return valve 33 to the ring chamber 29 and on through the passage 21 to the chamber 12:1. After a short movement of the piston unit 13 to the left according figure 1, seal 27 is pressed out from the ring gap 4 and the oil is given a shorter path to the chamber 12:1 and thereby a smaller pressure drop.
The present invention is not limited to the above description and as illustrated in the drawings but can be changed and modified in a number of different ways within the framework of the idea of invention specified in the following claims.

Claims

Means of sequential operation of controlled, with each other mecanically connected, adjust- and operating units comprising a piston unit (13) for operating a first controlled unit that is slip-mounted in a cylinder barrel (1) and valve bodies (9, 15, 16, 20, 33) intended for controlling the flow of fluid from the first controlled unit to a second controlled unit for its operation, characterised in that the first unit's piston unit (13) contains a tubular piston (5) that forms part of a flow path that in order to convey fluid to the second controlled unit passes over part of the piston unit's (13) outer edge, and that the valve bodies (9, 15, 16, 20) contain an axially displaceable moving ring-shaped valve body (9) surrounding the piston unit (13) that opens and closes the said flow path depending on the relative position of the piston unit (13) in the cylinder.
Means according to claim 1, characterised in that that the valves contain a groove (15) and a seat (16) located between the valve body (9) and the piston unit (13).
Means according to any one of the previous claims, characterised in that the valve body (9) is balanced to seal against the seat (16) through the action of a first spring means (14) and of a difference in pressure (P1-P2) acting on each side of the valve body (9) relative seat (16), whereby one pressure (P1) is higher than the other pressure (P2).
Means according to any one of the previous claims, characterised in that the valve body (9) is driven from a sealing position against the seat (16) to open position when the valve body (9) makes contact with a first shoulder (8) arranged in the cylinder barrel (1).
Means according to any one of the previous claims 3-4, characterised in that it contains a second spring means (7) and that the movement of the valve body (9) away from the sealing position takes place in interaction with a second shoulder (6) with which the spring means (7) makes contact.
Means according to any one of the previous claims, characterised in that the flow path through the piston unit (13) includes radial drillings (25, 26) that open into the outer edge of the piston unit (13) on each side of the groove (15) and seat (16) respectively.
Means according to any one of the previous claims, characterised in that at least one of the said valves is a non-return valve (33) located in such a way that it alternately opens and closes the flow path depending on the direction of flow.
Means according to claim 7, characterised in that in the series of cylinders a device (34) for a preceding cylinder during its travel towards its inner end position opens the flow path through the non-return valve (33) to the following cylinder.
Means according to any one of the previous claims, characterised by a ring gap (4) formed between a diameter reduction arranged in the cylinder (1) and the piston rod (5), and a ring seal (27) arranged on the piston unit (13), which alternately opens and closes the flow path through the ring gap (4) depending on the position of the piston unit (13) relative to the cylinder barrel (1).