EP1633987B1

EP1633987B1 - Support leg valve

Info

Publication number: EP1633987B1
Application number: EP04749000A
Authority: EP
Inventors: Martin Marklund
Original assignee: Nordhydraulic I Skelleftea AB
Current assignee: Nordhydraulic I Skelleftea AB
Priority date: 2003-06-19
Filing date: 2004-06-16
Publication date: 2012-03-07
Anticipated expiration: 2024-06-16
Also published as: WO2004111467A1; ATE548569T1; SE0301777L; SE0301777D0; SE525355C2; EP1633987A1; CN100480517C; CN1809698A

Abstract

Means designed as a valve housing (1) for distributing the flow of hydraulic oil generated from a unit (P) to a first (5:1) and a second (5:2a-5:2d) consumer with different priorities, comprising inlet (2) to the first consumer (5:1) and the second consumer (5:2a-5:2d) control valves (6a-d) and an outlet (3) in connection with a hydraulic tank (T). It comprises a housing (1) containing a means of priority (7) arranged between the first consumer (5:1) and the second consumer (5:2a-5:2d) control valve (6a-d), a means (18) in the second consumer (5:2a-5:2d) control valve (6a-d) for delivering a signal flow to the means of priority (7) via a passage (11) arranged in the housing, regulator (8) for regulating the flow to the first consumer (5:1) and the second consumer (5:2a-5:2d) control valve (6a-d) on the basis of the signal flow and a means (14, 16) of attaining a drop in pressure of the signal flow when operating the second consumer (5:2a-5:2d) control valve (6a-d).

Description

The present invention concerns a hydraulic valve with integrated priority valve, especially a support leg valve on a truck-mounted timber crane, according to the preamble to claim 1.
When loading timber using a timber crane mounted on a truck, loading is prepared by lowering a pair of support legs located on one side of the cargo space to the ground which can be extended or contracted telescopically in order to obtain a horizontal position of the cargo space. The support legs are used to stabilise the part of the chassis that contains the cargo space, e.g. a truck or its trailer. Without stabilisation, the chassis part may lean in the direction of the load in the crane and impair control of the loading process resulting in a longer working time. The valve that controls the movement of the support leg is used for a brief period before operating the crane. Subsequently, the support leg must be stable in its lowered position. Today's hydraulic systems involve either unreasonably costly valves with complicated hose arrangements or unwanted movements of the support legs. Described below are some of the most common types of systems used on truck mounted timber cranes for operating support legs.
Included in today's hydraulic systems are often one or two hydraulic pumps with fixed displacement or one larger pump with variable displacement. In the case of pumps with fixed displacement, the support leg valve is often coupled in series with the cock and comprises one open centre valve and is first in the series. This means the flow of hydraulic oil to the crane's functions flows first through the support leg valve, which is consequently always pressurised.
The support leg valve can also be connected in parallel with the cock via a separate priority valve. In this case, the support leg valve is a valve with closed centre arranged with an outer pilot line through which a pilot pressure flows to the priority valve regulating the flow. Another variant is to connect the support leg valve in parallel with a cock via an external pilot line with a load sensing pressure. The pilot line is arranged with a non-return valve to lead the load sensing pressure from the support leg valve to a shunt valve arranged in the cock. Also in this case, the support leg valve is a valve with closed centre. Both of these couplings involve a relatively costly arrangement and require relatively complicated hose arrangements in relation to the intended purpose.
A further method of solving problems that arise in conjunction with support leg functions is to use a pump with variable displacement and parallel couple the valves via a switch valve regulated by the driver. The support leg valve is then often a load sensing valve with closed centre. One disadvantage is that the valve controlling the support leg is constantly under pressure when operating the crane, which may give unwanted movements of the support leg due to the natural leakage inside the slide valves. This problem can be solved by fitting a separate priority valve in the system with an output port to the support leg valve and a port to the cock. The priority valve is controlled by a signal from the support leg valve, which is often achieved through a pilot line giving a pilot flow from the support leg valve to the priority valve. This solution also gives a relatively complicated and costly valve in relation to the simple functions of a support leg valve. The advantage with parallel connected valves via a separate priority valve is that the support leg around is not under pressure while the cock is being operated. The pressure drop across the valves is also reduced. However, the disadvantage in the form of the expensive and complicated valves with extra hose arrangements remains. Furthermore, special coupling procedures are needed depending on the type of pump to be used.
One object of the present invention is to achieve a valve for operating principally the support legs of a timber crane mounted on a truck and also the control of, for example, moving the driver's cab or log carriages in a simple and cheap way without complicated hose arrangements or additional valves. Another object is to be able to use the arrangement together with a hydraulic pump with either variable or fixed displacement.
These objects are achieved with the support leg valve comprising a one-piece unit with integrated priority valve and control valves with closed centres, the control valves regulating the flow via a signal pressure through a passage in the housing to the priority valve.
The present invention will be described more fully in the following with reference being made to the attached drawings, which illustrate one example of a selected embodiment, of which:

fig. 1 shows a cross- section through a valve according to the invention coupled to a pump with fixed displacement and
fig. 2 shows a cross-section through a valve according to the invention coupled to a pump with variable displacement.

With reference to the figures, a valve according to the invention comprises a one-piece valve housing 1 with an inlet port 2 connected to a hydraulic pump (P) with fixed or variable displacement, an outlet port 3 connected to a hydraulic tank (T), an outlet port 4 connected to the valve 5:1 controlling the functions of a consumer, such as a crane, and, in this embodiment, outlets to four consumers 5:2a - 5:2d with four identical control valves 6 a-d for controlling support legs, carriages and similar functions. The valve can be adapted to the demands placed on its functions in addition to, for example, support legs and carriages, through several control valves being able to be coupled together with the valve housing 1. The inlet port 2 is coupled to a priority valve 7 integrated in the valve housing 1 in which a spring-loaded slide 8, called the priority slide, is located. To one end of the slide 8 is arranged a first chamber 9 for building up hydraulic pressure from the inlet port 2. To the other end of the slide is arranged a second chamber 10. The second chamber 10 is connected to load sensing pressure via a passage 11 from the control valve slides 6 a-d. In the second chamber 10 is arranged a spring 12, a coil spring for instance, with one end resting against the inside of the chamber 12 and the other end against the valve housing. Through the force of the spring 12, the slide 8 is pressed towards the first chamber 9, i.e. in the direction of arrow A, to a first end position.
The inlet port 2 is in connection via the priority valve 7 with the control valves 6 a-d via a passage 13 with a first restriction 14. The load sensing pressure passage 11 is arranged with a connection to the tank T via a passage 15 with a second restriction 16. The slides in the control valves 6 a-d arranged with a first flow groove 17 of increasing size to successively open the flow path to one of the consumers 5-2a - 5:2d, for instance a support leg. The slides of the control valves 6 a-d are also equipped with a second flow groove 18, which is in connection with the second chamber 10 in the priority valve 7.
When the system is pressurised, inlet 2 will be in connection with the passage 13. When the pump P is started and the control valves 6a-6d are not operated, the flow of hydraulic oil is led in from the pump P via the inlet 2 to the first chamber 9 in the priority valve 7, whereby the pressure in chamber 9 will rise. The pressure existing in the second chamber 10 from the load sensing pressure passage 11 is simultaneously drained to the tank via the second restriction 16. When the pressure in the first chamber 9 becomes higher than the spring force from the spring in the second chamber 10, the priority slide 8 will be displaced to a second end position and the inlet 2 connection with passage 13 will be closed. This will connect the inlet 2 to the port 4 connected to the valve 5:1, which controls the crane functions, whereby the entire pump flow will go to the crane valve 5:1.
When a control valve 6a-6d is operated, i.e. the valve controlling the functions of consumer 5:2a-5:2d, for instance the support leg, a valve will be activated, i.e. control valve slide 6a will be displaced in the direction of the arrow A in figure 1. The flow groove 17 arranged in the slide will open successively, whereby the flow of hydraulic oil to the support leg will gradually increase. Meanwhile, the second flow groove 18 will open successively to gradually increase the flow to the passage 11 for the load sensing pressure. This will mean the pressure in the second chamber 10 will rise, whereby the priority slide 8 will be displaced to centre position where the pressure in passage 13 corresponds to the total pressure of the spring 12 and the pressure in the second chamber 10. With the priority slide 8 in this position, the consumer 5:2a-5:2d, in this example the support leg, can be operated in the desired manner with the requisite flow irrespective of the pressure that is needed, while the residual flow passes to the cock 5 via the outlet port 4.
To prevent the pressure rising directly to maximum level in passage 11 for the load sensing pressure during small valve actuations, a drain 19 has been arranged to the tank T at the second restriction 16. The drain 19 delivers a certain flow from the second flow groove 18 in the control valve slide 6a-6d to the tank T and thereby the desired drop in pressure before it reaches the second chamber 10.
The control valves slides 6a-6d are designed so that the drain 19 will close at the second restriction 16 for large valve actuations, whereby the first restriction 14 has the greatest effect as the main flow passes through the passage 13. The size of this first restriction 14 can be adapted to provide a limited maximum flow for large valve actuations. This can be used to provide a smooth control of the consumers 5:2a -5:2d without any sudden movements. The priority slide 8 regulates the drop in pressure across the restriction 14 to a constant value, whereby this maximum flow becomes independent from the load, i.e. the support leg in this example will maintain a constant speed irrespective of the load.
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

Valve housing (1) for distributing the flow of hydraulic oil generated from a unit (P) to a first (5:1) and a second (5:2a-5:2d) consumer with different priorities, comprising inlet (2) to the first consumer (5:1) and the second consumer (5:2a-5:2d) control valves (6a-d) and an outlet (3) in connection with a hydraulic tank (T), charac terised in that it comprises a housing (1) containing a means of priority (7) arranged between the first consumer (5:1) and the second consumer (5:2a - 5:2d) control valve (6a-d), a means (18) in the second consumer (5:2a - 5:2d) control valve (6a-d) for delivering a signal flow to the means of priority (7) via a passage (11) arranged in the housing, regulator (8) for regulating the flow to the first consumer (5:1) and the second consumer (5:2a - 5:2d) control valve (6a-d) on the basis of the signal flow and a means (14,16) of attaining a drop in pressure of the signal flow when operating the second consumer (5:2a - 5:2d) control valve (6a-d).
Valve housing according to claim 1, whereby the regulator (8) comprises a moving priority slide arranged in the means of priority (7) with a first chamber (9) for receiving a flow of hydraulic oil and a second chamber (10) for receiving a signal flow.
Valve housing according to claim 2, whereby the second chamber (10) comprises a spring (12) that keeps the priority slide in its first end position.
Valve housing according to claims 2-3, whereby the priority slide is displaced to a second end position by the pressure from the flow of hydraulic oil in the first chamber (9).
Valve housing according to any one of the previous claims, whereby the means (18) in the second consumer control valve for delivering a signal flow to the means of priority (7) comprises a flow groove for delivering a signal flow.
Valve housing according to claim 5, whereby the flow groove opens successively to open a flow path via a passage (11) to the second chamber (10), whereby the priority slide is displaced to a central position.
Valve housing according to any one of the previous claims, whereby the means (14,16) of attaining a drop in pressure comprises a first area reduction arranged in the passage (19) connecting the flow groove (18) to the tank (T).
Valve housing according to claim 7, whereby the means (14, 16) of attaining a drop in pressure of the signal flow comprises a second area reduction in a passage (13) between the priority valve (7) and the control valve (6a-d).