DE102018200951B3 - Hydraulic seat valve with defined leakage, hydraulic pressure booster and hydraulic tool - Google Patents

Abstract

The present invention relates to a hydraulic seat valve (100) having a working pressure area (110, a discharge pressure area (120), a housing (130) having a valve seat (140), a closing member (150) movable relative to the housing (130) and a biasing means The biasing means (100) biases the closure member (150) in a direction opposite the working pressure such that the closure member (150) lifts off the valve seat (140) when the working pressure at the closure member (150) is less than one in that the closing member (150) rests on the valve seat (140) when the working pressure at the closing member (150) is at least equal to the switching pressure. so that a leakage flow of fluid from the working pressure area (110) into the discharge pressure area (120) flows when the closing member (150) on the valve itz (140).

Description

The invention relates to a hydraulic seat valve. Such poppet valves are known from the prior art and regularly have a working pressure range, a Ablassdruckbereich, a housing with a valve seat, a relative to the housing movable and spring-loaded closing member and a biasing means which biases the closing member in a pressure applied in the working pressure range opposite direction ,

The DE 198 03 751 A1 shows a pressure-dependent closing valve for a hydraulic consumer.

The known from the prior art Hydrauliksitzventile with a spring-loaded closing member are commonly used to shut off a line section relative to the return as soon as in the working pressure range - in relation to Ablassdruckbereich - a certain pressure difference at which the hydraulic valve switches, is reached. As long as no corresponding pressure equalization takes place to the discharge pressure range, high pressures can be realized in the working pressure range shut off to the environment by the hydraulic seat valve without the hydraulic seat valve being opened.

For this purpose, the biasing means usually biases the closing member such that the closing member lifts off the valve seat when the working pressure is less than a switching pressure dependent on the biasing means and the closing member rests on the valve seat when the working pressure is at least equal to the switching pressure.

Practical applications for this are found in particular in mobile, hand-operated hydraulic tools such as hydraulically operated cutting or pressing tools or pressure accumulators.

In particular, in hydraulic tools of the return stroke of the driving cylinder is then initiated when the piston is in the cylinder in the end position. Such a tool is for example from the EP 1 319 475 A2 known. In these hydraulic tools, it may happen that the tool can not perform any further closing movement, although the piston is not yet in the end position and thus no return stroke can be initiated. For example, this can happen when the user operates the hydraulic tool intermittently. Thus, in such cases always raises the question of how the pressure built-up from the working pressure range can be returned to the return to get back to the starting position. Usually, this is another, specially operated pressure relief valve is provided. This inevitably requires an additional component in the hydraulic circuit and further there is a risk that the hydraulic tool remains in the pressurizing position, which is not always desirable. Furthermore, it is also conceivable to provide a hand-operated relief. This has the disadvantage that the hydraulic tool has a higher weight.

Against this background, it is an object of the present invention to show a hydraulic seat valve for a hydraulic tool, which has improved pressure relief properties without additional pressure relief devices.

The solution of the problem is achieved with a hydraulic seat valve according to claim 1. Advantageous further developments are described in the dependent claims.

The hydraulic seat valve according to the invention is distinguished in particular from the known hydraulic seat valves in that the hydraulic seat valve has a leakage means which is designed such that a leakage flow of fluid flows from the working pressure area into the discharge pressure area when the closing element rests on the valve seat.

This special embodiment makes it possible that in the closed state of the hydraulic seat valve, so when the closing member rests on the seat, there is always a minimum pressure relief from the working pressure range via the leakage means in the Ablassdruckbereich. In the broadest sense, a leakage means is understood to mean a fluid channel which is formed in the hydraulic seat valve and allows a flow of hydraulic fluid from the working pressure range into the discharge pressure range. Due to the resulting leakage current, the pressure in the working pressure range is reduced over time until the switching pressure is sufficient to completely lift the closing member from the seat.

In this case, the leakage means can advantageously be such that when the closing member rests on the valve seat, the differential pressure drop is significantly lower than the realizable in the working line differential pressure increase. Thus, at any time a desired working pressure can be produced in the working line and possibly maintained by means of low and continuously applied hydraulic fluid supply. However, interruption of the hydraulic fluid supply in the working pressure range leads to a gradual differential pressure reduction to the point where the hydraulic seat valve fully opens.

This has several implications for practical application. On the one hand, the deflection of a connected working cylinder is reduced by the continuous fluid drain with interrupted fluid supply. On the other hand, this also generates a certain damping of the movement of the working cylinder in the actuating direction. This also means that the achievable in comparison to conventional applications maximum pressure difference in the work area is slightly lower. However, this extreme value is not of particular importance for the actual handling of the tool, since the nominal operation of most technical applications, such as hydraulic shears, is anyway well below the said maximum value.

As mentioned, the absence of separate pressure relief devices simplifies handling and also the weight of the hydraulic tool. After reaching the desired deflection of the hydraulic tool, the user can interrupt the hydraulic supply depending on the application, thus initiating a gradual decrease in the deflection of the tool or maintaining a small, continuous hydraulic flow to keep the tool in the desired deflection.

An accidental incorrect operation of the hydraulic tool is largely excluded. This also avoids that a hydraulic tool unintentionally remains in the deflected position, which may be relevant in terms of safety in hydraulic cutters or pressing tools. As a result, the use of the inventive hydraulic seat valve makes handling of the hydraulic tool easier and safer for the user.

Advantageously, the closing member is arranged on a control piston. The control piston may be in operative engagement with a biasing means and transmit forces from the biasing means to the closure member. The control piston serves as a bearing of the closing member and directs forces from the biasing device in the closing member. The control piston and the closing member can also be designed as a one-piece component, which fulfills the function of closing at its first end and the function of the force absorption from the biasing device at its second end.

Advantageously, the closing member is a cone. A cone has the advantage that a large attack surface for the fluid pressure is formed on the working pressure-side end of the cone. Furthermore, a large sealing surface can be achieved on the side of the closing member oriented towards the valve seat. The leakage means may be mounted either on the closing member and / or the valve seat.

It is advantageous if the control piston has a working area facing the circular area, wherein the working pressure is applied to the circular area. With the aid of the circular area, the impacting flow can be converted into fluid pressure particularly effectively.

Alternatively, the shape of the closure member is at least partially spherical. For example, the closing member to the working pressure side facing a circular area and the valve seat towards a spherical shape.

The biasing means may comprise a compression spring, wherein the compression spring may be made adjustable. The spring force counteracts the pressure applied in the working pressure fluid pressure. The force equilibrium determining the differential pressure between the working pressure range and the discharge pressure range can be influenced correspondingly by a corresponding adjustment of the spring force. As a result, depending on the setting of the spring force, the switching pressure of the hydraulic seat valve can be set.

Preferably, the leakage means is formed on the closing member and / or the valve seat surface structure. The term "surface structure" in this context is to be understood as a general, somewhat geometric structure which is at least partially formed in the surface of the respective body (closure member and / or valve seat). It is advantageous that the surface structure can be relatively easily introduced into a conventional closing member and / or a conventional valve seat.

The surface structure may have a notch. Such a notch may, for example, be a structure introduced by a machining process, such as one or more grooves. The advantage here is the simple realization of such a surface structure that can be implemented quickly and inexpensively workshop. Also, the notch can be realized with a defined flow cross-section. Thus, it can be precisely determined at which pressure difference across the leakage agent which leakage flow of fluid sets.

According to a further advantageous embodiment, the notch on at least one thread. Threads can be easily and inexpensively introduced into the closing member and / or the valve seat when turning. Accordingly, an external thread and / or an internal thread on the valve seat would be introduced on the closing member become. The thread itself can be a catchy or multi-start thread. Relevant tests have shown that if the leakage means has at least one thread, contaminants present in the hydraulic fluid are particularly easily entrained by the flow of hydraulic fluid, thereby enabling a noticeable self-cleaning of the leakage agent. When opening the closing member therefore results in a self-cleaning of the hydraulic seat valve, so that the accumulation of contamination is effectively prevented. Another advantage of the thread is the particularly easy switchability of the closing member, which is due to a favorable flow characteristics in the boundary region between closing member and valve seat. More specifically, the hydraulic fluid is displaced by the thread geometry particularly low interference.

Furthermore, it is advantageous if the at least one thread is formed over its entire area on the relevant component, ie on the closing member and / or the valve seat. As a result, the previously described self-cleaning and switching properties of the hydraulic seat valve are further enhanced.

Alternatively, it may be advantageous if the leakage means has a plurality of concave indentations. The term "concave" refers to the cross section of the relevant component. For example, the concave recesses may be dimples, such as are known in golf balls. In this case, the concave indentations must be matched to the complementary contact surface of the valve seat or the closing member so that in each case a leakage flow cross-section is always free to ensure the function of the leakage agent.

The object is also achieved with a pressure booster with a hydraulic seat valve according to one of the preceding claims, a loading piston with a first piston diameter, a delivery piston with a second piston diameter, wherein the first piston diameter is greater than the second piston diameter, and a tank, wherein the hydraulic seat valve is arranged between the delivery piston and the tank.

Such pressure intensifiers are also known as boosters and are used, in particular in hand-operated hydraulic tools for locally increasing the hydraulic pressure in the tool by a plurality of, namely two, strokes of the delivery piston are necessary for a complete stroke of the charge piston. The resulting by the translation force generated on the smaller piston surface a ratio corresponding to the ratio ratio, which is higher than the pressure in the loading piston. In this case, when the pressure booster starts up, the hydraulic circuit of the pressure booster is closed when the switching pressure of the hydraulic seat valve is exceeded, and the hydraulic tool can be operated. When the deflection of the urging piston is stopped, the hydraulic fluid supply stagnates and hydraulic fluid flows out of the working pressure range via the leakage means, whereby the displacement of the output piston slowly decreases. This process continues until the differential pressure in the leakage agent is zero, d. H. until the switching pressure of the hydraulic valve is reached in the working pressure range. The fact that no further components are required for the pressure relief, the handling of the pressure intensifier can be significantly improved without further components are necessary.

The solution of the problem also succeeds with a hydraulic tool with a hydraulic pressure booster. With the self-relieving pressure booster, an unwanted locking of the hydraulic working device can be excluded in the actuated position, since the pressure in the hydraulic circuit via the leakage means always degrades over time until the switching pressure of the hydraulic valve is reached and the line is fully released. There is no need for further influence from outside. In particular, the hydraulic tool may be a hydraulically operated pressing device.

• 1 ein Schaltbild eines Hydrauliksitzventils mit einem Leckagemittel;
• 2 eine seitliche Schnittansicht eines Hydrauliksitzventils entsprechend einer ersten Ausführungsform; und
• 3 eine seitliche Schnittansicht eines Hydrauliksitzventils entsprechend einer zweiten Ausführungsform;

Exemplary embodiments of the invention are described below with reference to figures. Here are shown schematically:

• 1 a circuit diagram of a hydraulic seat valve with a leakage means;
• 2 a side sectional view of a hydraulic seat valve according to a first embodiment; and
• 3 a side sectional view of a hydraulic seat valve according to a second embodiment;

1 shows the hydraulic seat valve 100 , which is designed as a 2/2-way valve. The hydraulic seat valve 100 is spring loaded and can either in a first switching position 100a be operated, in which the flow through the hydraulic seat valve 100 is fully released, or in a second position 100b in which the seat valve 100 closed is. In the second switching position 100b can the hydraulic fluid through the fixed aperture of the leakage agent 170 through the seat valve 100 stream.

2 shows the hydraulic seat valve 100 according to a first embodiment in a side sectional view. The hydraulic seat valve 100 open or locked -bzw. limited- the flow of hydraulic fluid from a working pressure range 110 at nominal pressure p _N in a discharge pressure range 120 at ambient pressure p _∞ , On a housing 130 this is a valve seat 140 arranged on which the closing member 150 can be placed. In this embodiment, the closing member 150 one on a control piston 180 arranged cone. The closing element 150 has a circular surface on the working pressure area side end 155 on to provide the inflowing hydraulic fluid as large as possible attack surface. In the illustration shown is the closing member 150 in the open position, ie in the first switching position 100a , By the pretensioner 160 it is held in this open position as long as the closing member 150 attacking total pressure is less than that on the circular area 155 acting biasing force, via the biasing device 160 is charged. The pretensioner 160 directs the resulting from a compression spring biasing force on the control piston 180 to the closing member 150 further. The bias of the compression spring of the biasing device 160 is opposite the case 130 via a longitudinally adjustable adjusting device 165 adjustable in a conventional manner.

On the closing member 150 is a leaking agent for the function according to the invention 170 arranged, which is a surface structure in this embodiment. In detail, the surface structure is in the form of a in the closing member 150 introduced external thread executed. The external thread extends over the entire surface over the entire conical surface of the closing member 150 except the circular area 155 , The to the closing member 150 complementary sealing surface of the valve seat 140 is this conventional design. When the hydraulic seat valve 100 in the second switching position 100b is, ie in a state in which the closing member 150 on the valve seat 140 rests, remains for the hydraulic fluid in the working pressure range 110 always a fluid channel open with a flow cross-section corresponding to the cross-sectional area of the thread.

Hydraulic fluid coming from the working pressure side 110 either via the leakage agent 170 (in the switch position 100b) or over the gap between the valve seat 140 and closing member 150 (in the switch position 100a) in the discharge pressure range 120 flows, flows in the 2 illustrated embodiments always in a spring dome 190 , The spring dome 190 is through the housing 130 and the adjuster 165 Are defined. Since the hydraulic fluid in this case only over the gap between the housing 130 and control piston 180 in the spring dome 190 can flow in and out, the switching movement of the hydraulic seat valve 150 steamed accordingly.

In 3 is a second embodiment of the hydraulic seat valve 100 shown. According to this embodiment, the spring dome 190 over a sealing ring 200 sealed against entry of hydraulic fluid. The spring dome 190 is over a vent 210 in the adjustment 165 open to the environment, to volume changes in the spring dome 190 to compensate. This allows a quick and low-friction switching of the hydraulic seat valve 100 be guaranteed.

LIST OF REFERENCE NUMBERS

p _N

nominal pressure

p _∞

ambient pressure

100

Hydraulic seat valve

100a

first switching position of the hydraulic seat valve

100b

second switching position of the hydraulic seat valve

110

Working pressure range

120

Discharge pressure area

130

casing

140

valve seat

150

closing member

155

Circular surface of the closing member

160

biasing means

165

adjustment

170

escape means

180

control piston

190

spring dome

200

seal

210

vent

Claims (10)

A hydraulic seat valve (100) for a hydraulic tool having a working pressure range (110), a discharge pressure range (120), a housing (130) having a valve seat (140), a closing member (150) movable and spring loaded relative to the housing (130), and biasing means (16). 160) biasing the closure member (150) in a direction opposite to a working pressure in the working pressure range (110) such that the closure member (150) lifts off the valve seat (140) when the working pressure is less than one of the biasing means (160). dependent switching pressure, and the closing member (150) rests on the valve seat (140) when the working pressure corresponds to at least the switching pressure, characterized in that the hydraulic seat valve (100) has a leakage means (170), so a leakage flow of fluid from the working pressure area (110) into the discharge pressure area (120) flows when the closing member (150) rests against the valve seat (140). Hydraulic seat valve (100) after Claim 1 , characterized in that the closing member (150) on a control piston (180) is arranged. Hydraulic seat valve (100) after Claim 2 characterized in that the closure member (150) is a cone. Hydraulic seat valve (100) according to one of the preceding claims, characterized in that the control piston (180) has a working pressure region (110) facing the circular surface, wherein the working pressure is applied to the circular surface. Hydraulic seat valve (100) according to one of the preceding claims, characterized in that the leakage means (170) on the closing member (150) and / or on the valve seat (140) formed surface structure. Hydraulic seat valve (100) after Claim 5 , characterized in that the surface structure has a notch. Hydraulic seat valve (100) after Claim 6 , characterized in that the notch has at least one thread. Hydraulic seat valve (100) after Claim 5 , characterized in that the surface structure has a plurality of concave indentations. Hydraulic pressure booster with a hydraulic seat valve (100) according to one of the preceding claims, a loading piston having a first piston diameter, a delivery piston having a second piston diameter, wherein the first piston diameter is greater than the second piston diameter, and a tank, wherein the hydraulic seat valve (100) between the dispensing piston and the tank is arranged. Hydraulic tool with a hydraulic pressure booster after Claim 9 ,

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