NL1025806C2 - Hydraulic cylinder, for example, for use with a hydraulic tool. - Google Patents

Abstract

The invention relates to a hydraulic cylinder, for use in a hydraulic tool, comprising a hollow cylinder body (8) accommodating a first piston, which first piston is composed of a hollow first piston rod (14), which extends from the cylinder body, and a first piston body (20) connected thereto, said cylinder body and said first piston body defining a first cylinder chamber (21) and said cylinder body, said first piston body and said first piston rod defining a second cylinder chamber (22), as well as a second piston accommodated in the hollow first piston rod, which second piston is composed of a second piston rod (26), which extends through the first piston body and which is connected to the cylinder body, and a second piston body (25) connected thereto, said first piston rod and said second piston body defining a third cylinder chamber (23) and said first piston rod, said second piston rod and said second piston body defining a fourth cylinder chamber (24), wherein the second piston rod is at least provided with a bore that terminates in the third cylinder chamber, and wherein the cylinder chambers can be connected to a first (P1) and a second supply line (P2), respectively, for extending and retracting the first piston rod.

Description

Short indication: Hydraulic cylinder for example for use with a hydraulic tool.

DESCRIPTION

The invention relates to a hydraulic cylinder, for example for use with a hydraulic tool comprising a hollow cylinder body with a first piston received therein, which first piston is composed of a hollow first piston rod extending from the cylinder body and a first piston-connected thereto. Body, wherein the cylinder body and the first piston body define a first cylinder chamber and the cylinder body, the first piston body and the first piston rod define a second cylinder chamber, as well as, and a second piston accommodated in the hollow first piston rod, which second piston is composed of a piston first piston body extending and connected to the cylinder body and a second piston body connected thereto, wherein the first piston rod and the second piston body a third cylinder chamber and the first piston rod, the first piston body, the second piston rod and the second piston body a fourth cylinder bounding the chamber, wherein the second piston rod 20 is at least provided with a bore terminating in the third cylinder chamber and wherein the cylinder chambers can be connected to a first and / or a second supply indication for a pressurized fluid for the purpose of extending or resp. shorten the first piston rod.

A hydraulic tool which is operated with the aid of a hydraulic cylinder as described above is known from, for example, European patent no. 0641618 B1. In this patent specification a frame which can be coupled to a boom of a soil tillage machine or the like is disclosed, to which an assembly of two jaws can be coupled. One of the jaws can be pivoted relative to the other jaw with the aid of a hydraulic adjusting cylinder.

With the outgoing stroke of the cylinder rod of the adjusting cylinder, the pivotable jaw is moved to the other, fixed jaw, while with the incoming stroke of the cylinder rod the pivotable jaw is moved away from the fixed jaw.

An adjusting cylinder of such a tool is controlled or energized by the hydraulics of the relevant machine, the construction of which more or less determines the available operating pressure of the fluid as well as the fluid flow to be supplied. A large bore diameter of the cylinder body allows high cylinder forces, but this requires high fluid flows through the hydraulic circuit, so that the cycle times become unnecessarily long.

On the other hand, it is desirable to operate the hydraulic tool with the lowest possible return fluid flow rate, because the unnecessary continuous pumping of high fluid flows through the hydraulic circuit to and from the adjusting cylinder on the one hand promotes unnecessary pump losses (pressure loss) due to pipe resistances, while furthermore, heat development and the additional fuel consumption of the relevant machine further adversely affect the efficiency.

A hydraulic cylinder according to the aforementioned preamble is known, for example, from German patent publication No. 10121612. The current adjusting cylinders are for the time being characterized only during the outgoing stroke of the cylinder rod by low cycle times, low return fluid flows and high ciunder forces, but the known cylinders lack in particular high cylinder forces during the input stroke.

This latter characteristic is particularly desirable with hydraulic demolition tools, such as scrap shears and the like, because it sometimes happens that iron gets stuck between the jaws, which does not come loose from the cylinder rod when the cylinder stroke enters into force without high cylinder forces.

It is therefore an object of the invention to provide an improved cylinder of the aforementioned preamble which, on the one hand, has fast cycle times and low return fluid flows in both the outgoing and the incoming stroke, but can also generate high cylinder forces for both the outgoing and incoming stroke.

According to the invention, the cylinder is characterized for this purpose in that at least one pressure-limiting valve is provided, which controls the supply of fluid under pressure to the different cylinder chambers in dependence on the pressure difference between the first and second supply line. With the cylinder according to the invention a highly functional cylinder chamber is realized with which, depending on the operating conditions, the different cylinder chambers can be connected to the supply lines for fluid under pressure.

More in particular, the pressure-limiting valve controls a pressure-controlled valve on the basis of the pressure difference between the first and second supply lines, such that if, for the outgoing or respectively. starting stroke of the first piston rod, the pressure caused by the load resistor is lower than the predetermined pressure level, the pressure-controlled valve is a first resp. second extreme position and if the pressure caused by the load resistor is higher than the predetermined pressure level, the pressure-controlled valve assumes a middle position.

If the load resistance decreases again, the pressure-controlled valve will again be a first resp. take the second extreme position.

In a special embodiment the pressure-controlled valve in the central position connects the first and the third cylinder chamber with the first supply line and the second and the fourth cylinder chamber with the second supply line, while in the first or second extreme position the cylinder chambers first, second, third and fourth cylinder chambers can be connected to the first and / or second supply line.

More specifically, if at both the outgoing and the inward stroke of the first piston rod, the pressure caused by the load resistor 30 is lower than a predetermined pressure level, the speed of movement, respectively. the force of the first piston rod rapidly resp.

1025806 4 is low and that if the pressure caused by the load resistor is higher than the predetermined pressure level, the moving speed resp. the force of the first piston rod slowly resp. is high.

High cylinder speeds (and therefore low cycle times) can hereby be realized and, on the other hand, high cylinder forces can also be generated with the outgoing and in particular with the incoming stroke.

The pressure-controlled valve can herein connect the second, third and fourth cylinder chamber to the second supply line in the first extreme position, while the pressure-controlled valve in the second extreme position connects the third cylinder chamber and at least the second cylinder chamber to the second supply line .

On the other hand, in a special embodiment, the pressure-controlled valve in the second extreme position connects the fourth cylinder chamber 15 with the second supply line.

According to a special aspect of the invention, the second cylinder chamber and fourth cylinder chamber are in communication with each other, where in a first embodiment the second cylinder chamber and fourth cylinder chamber are connected to each other by means of at least one opening arranged in the first piston rod. In another embodiment, the second piston rod is provided with a further bore ending in the fourth cylinder chamber, which further bore connects the fourth cylinder chamber with a fourth supply line for the pressurized fluid.

A fourth cylinder chamber is hereby realized, which can be energized independently of the other cylinder chambers. This results in a still versatile hydraulic cylinder.

In a special embodiment, the second and third cylinder chamber are each connected via a non-return valve to a storage vessel for the fluid. In this case, the non-return valve for the third cylinder chamber can be a pressure-controlled non-return valve and in particular a non-return valve controlled by the pressure-limiting valve. As a result, the return fluid flow through the pipes is further reduced by, during the input stroke, a portion of the return flow from the second resp. temporarily capture the third cylinder chamber in a storage vessel depending on the prevailing return pressure of the fluid.

With the outgoing stroke of the cylinder rod, the stored fluid is again delivered to the hydraulic circuit. This further reduces pump losses, resistance losses, etc.

The invention will now be explained in more detail with reference to a drawing, which drawing successively shows in: Figures 1a and 1b are views of an embodiment of a hydraulic tool according to the prior art coupled to the boom of an excavator;

Figures 2a-2d show four operating states of a basic embodiment of a hydraulic cylinder according to the invention;

Figure 3 shows other configurations of operating states of a hydraulic cylinder according to the invention;

Figures 4a-4d show four operating states of a special embodiment of a hydraulic cylinder according to the invention;

Figure 5 shows another embodiment of a hydraulic cylinder according to the invention;

Figure 6 is yet another embodiment of a hydraulic cylinder according to the invention.

For a better understanding of the invention, the corresponding parts will be indicated in the following description of the figures with the same reference numeral.

Figures 1a and 1b show two views of a hydraulic tool that is driven or energized by a hydraulic adjusting cylinder. The illustrated tool according to the prior art comprises a frame 1, which comprises a first frame part 2, which is coupled to a second frame part 3 by means of a turntable 2 '. With the aid of the turntable 2 ', the two frames and 2 and 3 can be rotated relative to each other with the aid of (not shown) means, for example hydraulically operable iristelling means, which are known per se.

The frame part 2 is equipped with coupling means 4, 4 'known per se, whereby the device 1 can be coupled to, for example, the end of an excavator arm of an excavator or a similar ground implement.

A first jaw 12 is attached to the frame part 3 of the frame 1 by means of a hinge pin 10 and a pin 11. Both pins 10 and 11 are thereby accommodated in corresponding openings (but not shown) provided in the frame part 3 or drilling. Furthermore, a second movable jaw 13 is pivotally arranged around the hinge pin 10. The second movable jaw 13 is pivotable relative to the first jaw 12 by means of the adjusting cylinder 8, for which purpose the end 14a of a piston rod 14 is coupled to an end of the pivoting jaw 13 with the aid of a pin 15. The adjusting cylinder 8 is rotatably received around point 9 in the frame part 3 in order to enable the expansion of the cylinder rod 14.

Figure 1a shows the hydraulic tool in the operating condition with the cylinder rod 14 fully retracted (input stroke), while Figure 1b shows the output stroke of the cylinder rod 14, with the jaw 13 displaced against the jaw 12.

With such a hydraulic tool it is possible to carry out demolition, breaking or shearing work, wherein large cylinder forces can be transferred to the jaws 12 and 13. With hydraulic demolition tools, such as scrap shears and the like, it sometimes happens that iron gets stuck between the jaws 12 and 13 (in particular 30 between the cutting edges 16, 16 'or 17), which is not without high cylinder forces at the Input stroke of the cylinder rod 14 1025806 7 is released.

It is therefore desirable to use a hydraulic adjusting cylinder 14 which is characterized not only during the outgoing stroke of the cylinder rod 14 by high piston rod speeds and therefore low cycle times, low return fluid flows and high cylinder forces, but also during the input stroke ( from the situation in Figure 1b to the situation in Figure 1a) can generate high cylinder forces.

Figures 2a-2d show different operating states of a basic embodiment of such a hydraulic adjusting cylinder according to the invention.

The hydraulic adjusting cylinder comprises a hollow cylinder body 8 with a first piston included therein, which is composed of a first piston rod 14 extending from the cylinder body 8 and a first piston body 20 connected thereto. The outer dimensions of the first piston body 20 correspond to the inner dimension of the hollow cylinder body 8.

The hollow cylinder body 8 and the first piston body 20 define a first cylinder chamber 21, while the hollow cylinder body 8, the first piston rod 14 and the first piston body 20 define a second cylinder chamber 22 surrounding the first piston rod 14.

With reference to Figures 1a and 1b, the end 14a of the first piston rod 14 must be connected by means of a pin 15 to, for example, the pivotable jaw 13 of the cutting and / or breaking tool shown in Figures 1a and 1b.

In the hollow first piston rod 14 is incorporated a second piston composed of a second piston rod extending through the first piston body 20 and connected to the hollow cylinder body 8, as well as a second piston body connected thereto. The outer dimension of the second piston body 25 corresponds to the inner dimension of the hollow first piston rod 14.

According to the invention, the hydraulic circuit 1025806 8 is also composed of a pressure-controlled valve 31, which is provided with a first supply line P1, which can be brought into connection with the first cylinder chamber 21. If a fluid under pressure (e.g. oil) passes through the first supply line P1 is led to the first cylinder chamber 21, the piston rod 14 will extend through the pressure increase in the cylinder chamber 21 (the outgoing stroke). For this purpose, a flange B1 is provided in the cylinder body 8, to which the first supply line P1 can be connected.

The second cylinder chamber 22 is furthermore provided with a flange connection S1, which flange connection can be inter alia connected to the second supply line P2 via a supply line via the pressure-controlled valve 31. The second supply line P2 serves in particular for supplying fluid under pressure for shortening the first piston rod 14 (input stroke).

The second piston rod 26 is provided with a first through-going bore 27, which connects the third cylinder chamber 23 to a flange connection B2, which then connects with a line to the pressure-controlled valve 31. Furthermore, in this embodiment the second piston rod 26 is optionally provided with a second through bore 40, which connects the fourth cylinder chamber 23 to a flange connection S2, 20 which subsequently connects to the pressure-controlled valve 31 with a line.

According to the invention, the pressure-controlled valve 31 can take three positions, namely a first extreme position X (as shown in Figure 2a), a middle position (as shown in Figures 2b and 2d) and also a second extreme position Y (as shown in Figure 25). Figure 2c).

According to the invention, the pressure-controlled valve 31 is controlled by a pressure-limiting valve 30, which in turn is controlled by a ball valve 32.

Figure 2a shows an operating condition of a basic embodiment of the hydraulic cylinder according to the invention, wherein the piston rod 14 becomes an outgoing stroke

1025806 '

9 forced by the hydraulic circuit and wherein the piston rod 14 experiences a load resistance (via the first and second jaws 12 and 13, not shown), which load resistance generates a pressure in the hydraulic circuit that is lower than a predetermined pressure level.

In order to realize a low cycle time, the pressure-limiting valve 30 and the pressure-controlled valve 31 are connected such that the first piston rod 14 traverses its outgoing stroke at a high speed of movement.

During the outgoing stroke, fluid under pressure is supplied via the first supply line P1, which fluid sets the pressure-controlled valve 31 in its first extreme position X via the pressure-limiting valve 30 as shown in Figure 2a. The pressurized fluid is led via the supply line P1 and depending on the configuration of the tipping position X to the different flange connections B1-B2-S1-S2 and therefore the cylinder chambers 21-22-23-24. The configuration of the first extreme tilt position X results in a certain cylinder behavior during the outgoing stroke.

If during operation the piston rod 14 encounters an increasing load resistance, as a result of which the pressure realized in the hydraulic circuit by this load resistance 20 becomes higher than a predetermined pressure level, the ball valve 32 comes under the influence of this pressure caused by the load resistance and the pressure difference between the pipes. P1 and P2 in operation as shown in Figure 2b.

In this operating situation, the fluid pressure in the supply line P1 can actuate the pressure limiting valve 30 in its other position. As a result, the pressure-controlled valve 31 takes its center position In, as shown in Figure 2b. The valve configuration of the pressure-controlled valve 31 in its central position is such that the first and third chamber chambers 21-23 are jointly connected to the first supply line P1 via the flange connections B1 and B2. Both the third and the first cylinder chamber 23 resp. 21 are therefore fed with the fluid 1025806 10 under pressure which is supplied from the main supply line P1. The second and fourth cylinder chambers 22 respectively. 24 are in communication with the second supply line P2 via the flange connections S1 and S2.

In this operating condition, the second and fourth 5 cylinder chambers are 22 resp. 24 is pressureless and the fluid present in these chambers is pressed out of the cylinder body 8 during the outward stroke of the piston rod 14 in the direction of the supply line P2. Furthermore, in this operating condition, the first and third cylinder chambers 21-23 are pressurized via the fluid supplied through the main supply line PI. In this condition, the adjusting cylinder 8 is able to exert large forces with the piston rod 14 on a hydraulic tool, for example the breaking and cutting tool from Figures 1a and 1b.

Figures 2c and 2d show two operating situations of the basic embodiment of the hydraulic cylinder according to the invention during the input stroke of the piston rod 14. In these second operating situations, the second supply line P2 is in principle used for supplying fluid under pressure.

In the operating situation as shown in Figure 2c, the pressure created in the hydraulic circuit due to the load resistance experienced by the piston rod 14 is lower than a predetermined pressure. The pressure-limiting valve 30 and the ball valve 32 are connected in such a way that the fluid supplied via the second supply line P2 pressurizes the pressure-controlled valve 31 in a second extreme position Y (Figure 2c). The supply of fluid under pressure via the supply line P2 to the cylinder chambers 21-22-23-24 is determined by the valve configuration in the extreme position Y.

Because during operation, iron may become trapped between the cutting surfaces of a hydraulic cutting and / or breaking tool, as shown in Figures 1a and 30 lb, it is desirable that large forces can also be released by the piston rod 14 during the input stroke. 6 06 11, in order to separate the two jaws 12 and 13 from each other.

This operating situation is shown in Figure 2d wherein the piston rod 14 experiences such a high load resistance that the pressure generated thereby in the hydraulic circuit becomes greater than a predetermined pressure as set by the pressure limiting valve 30. The increased fluid pressure in the second supply line P2 as As a result of the increased load resistance, the ball valve 32 switches over and consequently also the pressure limiting valve 30.

As a result, the pressure-controlled valve 31 assumes its central position 10 (Figure 2d), so that the second and fourth cylinder chambers 22, 24 are connected via the flange connections S1 and S2 to the second supply line P2. The first and third cylinder chamber 21, resp. 23 operate without pressure and the fluid present in these chambers is pressed out of the cylinder body 8 during the input stroke of the piston rod 14 in the direction of the first supply line P1.

Figure 3 shows various possible valve configurations of the pressure-controlled valve 31, the four cylinder chambers 21-22-23-24 (B1-B2-S1-S2) both at the outward stroke of the piston rod 14 (position X) as the input stroke (position Y) in 20 different ways with the first and second supply line P1 and P2 can be connected. The valve 31 is in position X when the piston rod 14 goes out quickly and then comes to the middle position when the cylinder has to deliver the maximum force. At the input stroke, the valve 31 is in position Y when the piston rod 14 goes in quickly and then returns to the center position when the maximum force is to be supplied.

There are a number of switch options with regard to the switch symbols X and Y. These valve configurations are shown in Figure 3. For the first extreme position X, the possibilities X1 to X10 and for the second extreme position Y the possibilities Y1 are 30 to Y5. In these valve configurations, the four cylinder chambers 21-24 are connected such that the piston rod 14, when applying pressure to the first feed line P1, has a resulting outgoing stroke. When applying pressure to the second feed line P2, the piston rod 14 has a resulting input stroke. With every other option that is not the case.

The possibilities X1 and Y1 are the same as the configuration of the valve 31 in the middle position, so in fact the valve does not switch.

The valve configuration XI to X10 are arranged such that with XI the cylinder 8 is the slowest and the return fluid flow from 10 the cylinder chambers is the largest. From configuration XI to X10, the cylinder becomes faster and faster during the outgoing stroke and the return fluid flow continues to decrease. In valve configuration X6 (first extorted position), the return fluid flow is even equal to zero and in configurations X7 to X10, the return fluid flow even becomes negative, that is, fluid (water, oil, etc.) must be sucked in.

For this purpose, a special provision in the hydraulic system is then required, for example in the form of a fluid conduit, which is connected directly to the fluid storage or buffer tank or a storage vessel closer to the cylinder 8 which it collected at that time. releasing fluid to the cylinder chambers. If the suction volumes are too large, however, there is a risk that excessive pressure will occur in the cylinder pipes and chambers, which in turn can result in cavitation.

For the second extreme position Y, the configurations are Y1 to Y5. From Y1 to Y5, the incoming cylinder stroke becomes faster and faster and the return fluid flow rate becomes lower.

In theory, therefore, 10x5 different configurations of the pressure-controlled valve 31 are possible. However, a number of variants are special: 1) Variant X10-Y5: with this valve 31 the cylinder 8 is very

1025806 '

13 fast and has the shortest cycle times. However, a great deal of post-extraction of oil occurs as a disadvantage, so it is less practical in practice.

2) Variant X6-Y5: with this valve 31, the cylinder 8 has the fastest cycle times and the lowest return fluid flow rate, while furthermore no suction of oil takes place.

3) Variant X6-Y3: with this valve 31 an alternative cylinder 8 is obtained, wherein the cylinder construction can be simplified. Here, the second and fourth cylinder spaces 22 (S1) and 24 (S2) in the cylinder can be connected to each other, so that a line in the piston rod 14 and a connecting flange (S4) can be saved.

However, other configurations of the pressure-controlled valve 31 are also suitable for use, depending on the desired cylinder behavior.

Figures 4a-4d show operating states of an embodiment of a hydraulic cylinder according to the invention, wherein the pressure-controlled valve 31 has the valve configuration in its first extreme position X, as indicated in Figure 3 with configuration X6 and in its second extreme position Y has the valve configuration, as indicated in Figure 3 by configuration Y3.

Figure 4a shows the operating condition of the hydraulic cylinder according to the invention, wherein the piston rod 14 is forced outwardly by the hydraulic circuit and wherein the piston rod 14 encounters a load resistance (via the first and second jaws 12 and 13, not shown) which load resistance generates a pressure in the hydraulic circuit that is lower than a predetermined pressure level. In order to achieve a low cycle time, the pressure-limiting valve 30 and the pressure-controlled valve 31 are connected in such a way that the first piston rod 14 traverses its outgoing stroke at a high speed of movement.

In the outgoing stroke, fluid under pressure is supplied via the first supply line P1 30, which fluid is tapped via the pressure-limiting valve 30 and as a result sets the pressure-controlled valve 31 in its first% 1025806 14 extreme position as shown in Figure 4a. In this embodiment the fluid under pressure is introduced (in contrast to the more or less similar Figure 2a) via the first supply line P1 directly via the flange connection B1 to the first cylinder chamber 21.

In the first extreme position, pressurized fluid is passed through the first valve supply line 33a and the pressure-controlled valve 31 to the first and second valve discharge lines 34a, respectively. 34b, which connect to the flange connections B2 of the bore 27 and the third cylinder chamber 23 resp. the flange connection S of the second cylinder chamber 10 22.

In this embodiment, the piston rod 14 is provided with one or more openings 28 through which the second cylinder chamber 22 is in fluid communication with the fourth cylinder chamber 24. In other words, the fluid supplied under pressure via the second valve discharge line 34b is supplied via the flange connection S second and fourth cylinder chamber 22 resp. 24 entered.

By bringing the pressure-controlled valve 31 to the first extreme position, as shown in Fig. 4a, the fluid under pressure is guided via the supply line P1 to all four cylinder chambers 21, 22, 23 and 24. Due to the mutual dimensioning of the cylinder chambers and the first and second piston bodies 20 respectively. 25, the first piston rod 14 is hereby extended with a relatively high speed of movement.

If during operation the piston rod 14 encounters an increasing load resistance, as a result of which the pressure realized by this load resistance 25 in the hydraulic circuit becomes higher than a predetermined pressure level, the ball valve 32 comes under the influence of this pressure caused by the load resistance and the pressure difference between the pipes. P1 and P2 in operation as shown in Figure 4b.

In this operating situation, the fluid pressure in the supply line P1 can actuate the pressure limiting valve 30 in its other position. As a result, the pressure-controlled valve 31 takes its central position 1n, 1025806, whereby the third end chamber 23 is connected via its bore 27, the flange connection B2 and the first valve discharge line 34a to the first valve supply line 33a and the first supply line P1. Both the third and the first cylinder chamber 23 resp. 21 are therefore fed with the fluid under pressure that is supplied from the main supply line P1. The second and fourth cylinder chambers 22 respectively. 24 are connected via the flange connection S and the second valve discharge line 34b to the second valve supply line 33b and the second supply line P2.

In this operating condition, the second and fourth 10 cylinder chambers are 22 and 22, respectively. 24 is pressureless and the fluid present in these chambers as indicated by the arrow direction is pressed during the outward stroke of the piston rod 14 from the cylinder body 8 in the direction of the supply line P2. Furthermore, in this operating condition, the first and third cylinder chambers are pressurized via the fluid supplied through the main supply line P1. In this condition, the adjusting cylinder 8 is able to exert large forces with the piston rod 14 on a hydraulic tool, for example the breaking and cutting tool from Figures 1a and 1b.

Figures 4c and 4d show two operating situations during the input stroke of the piston rod 14. In these second operating situations, in principle the second supply line P2 is used for supplying fluid under pressure.

In the operating situation as shown in Figure 4c, the pressure created in the hydraulic circuit due to the load resistance experienced by the piston rod 14 is lower than a predetermined pressure. The pressure-limiting valve 30 and the ball valve 32 are connected in such a way that the fluid supplied via the second supply line P2 sets the pressure-controlled valve 31 to a second extreme position under pressure. The fluid 30 which is supplied under pressure through the pressure controlled valve 31 via the second valve supply line 33b is led via the first and second valve discharge lines 34a, respectively. 34b to the flange connections B2, 1025806 16 resp. S of the third resp. second (and fourth) cylinder chambers 23-22 and 24.

In this operating situation, the first cylinder chamber 21 operates without pressure and the fluid present in the first cylinder chamber 21 is returned to the hydraulic circuit via the first supply line P1.

Because during operation iron can get stuck between the cutting surfaces of a hydraulic cutting and / or breaking tool, as shown in Figures 1a and 1b, it is desirable that large forces can also be exerted by the piston rod 14 during the input stroke in order to releasing the two jaws 12 and 13 from each other.

This operating situation is shown in Figure 4d where the piston rod 14 experiences such a high load resistance that the pressure generated thereby in the hydraulic circuit becomes greater than a predetermined pressure as set by the pressure limiting valve 30. The increased fluid pressure in the second supply line P2 as a result of the increased load resistance, the ball valve 32 switches over and consequently also the pressure limiting valve 30. As a result, the pressure-controlled valve 31 assumes its central position, as a result of which the second and fourth cylinder chambers 22 respectively. 24 are connected via the second valve supply line 33b and the second valve discharge line 34b and the flange connection S to the second supply line P2.

The first and third cylinder chamber 21 resp. 23 operate without pressure and the fluid present in these chambers is pressed out of the cylinder body 8 during the input stroke of the piston rod 14 in the direction of the first supply line P1.

As a result, as shown in Figs. 2a-2d and 4a-4d, a double cylinder action is realized, with which during operation the adjusting cylinder 8 can realize both rapid displacements of the piston rod 14 (both with the incoming and outgoing stroke), but also with both the incoming and outgoing stroke can generate large cylinder forces if the pressure generated by the load resistor meeting the adjusting cylinder 8 is greater than a predetermined pressure level in the hydraulic circuit.

According to the invention, the adjusting cylinder as described herein is in principle characterized by low cycle times and high speeds of movement of the piston rod 14 at both the input and output stroke.

Because in certain cylinder actions and associated valve configurations of the pressure-controlled valve 31, high return fluid flows adversely affect the efficiency of the basic machine driving the adjusting cylinder 8, in a specific embodiment as shown in Figure 5 in the hydraulic circuit a storage vessel 35 in which the return fluid flow rate can be stored. Unnecessary fluid flows that have to be pumped around by the hydraulic circuit give rise to additional frictional resistance in the pipes and therefore promote pump losses.

Therefore, the return fluid that is pressed out of the adjuster and inder 8 remains stored temporarily both at the input and output stroke close to the adjustment cylinder 8 and can therefore be directly re-introduced into the hydraulic circuit if additional fluid is supplied during the output stroke of the piston rod 14. is asked.

The storage vessel 35 is used in this embodiment in Fig. 5 for collecting return fluid flows from the third and third stages respectively. second and fourth cylinder chambers 23, 22 and 24, wherein the connection B2 of the third cylinder chamber 23 to the storage vessel 35 as well as the connection of the second and fourth cylinder chamber (connection S) to the storage vessel 35 through a ball valve 37 and 40 respectively. 36 have been closed. The ball valve 37 in the line between the storage vessel 35 and the third cylinder chamber 23 is designed as a pressure-controlled one-way valve (non-return valve), which non-return valve 37 is controlled by the pressure of the fluid in the second supply signal P2.

Particularly in the operating condition as shown in Figure 4d, with the input stroke of the piston rod 14, a large return fluid flow is realized from the first and third cylinder chamber 21, respectively. 23. Because in this operating condition the pressure-controlled non-return valve 37 is opened by the pressure in the second supply line P2, a portion of the fluid from the third cylinder chamber 23 can be stored in the storage vessel 35 and the volume of this return fluid is thus reduced. valve 31 and the first supply line P1 are discharged from the hydraulic circuit via the pressure-controlled valve.

On the other hand, in the outgoing stroke of piston rod 14, the stored fluid in storage vessel 35 is again delivered to the circuit via the non-return valves 36 and 37, such that this released fluid gives an extra pulse to the outgoing cylinder speed and that the storage vessel 35 is complete again emptied for the next cycle.

In the embodiment in Figure 6, the check valve 37 is controlled by the pressure limiting valve 30.

On the other hand, another embodiment (not shown) in which an adjusting cylinder 8 according to the invention as shown in Figures 2a-2d is used may be the first cylinder chamber 21 (B1) (instead of the third cylinder chamber 23) and the second cylinder chamber 22 (S1 ) are connected to the storage vessel 35 via the check valves 36-37. The third cylinder chamber 23 (B2) and the fourth cylinder chamber 24 (S2) are then connected to the pressure-controlled valve 31 via their separate lines B2 and S2.

Here too, the ball valve 37 in the line between the storage tank 35 and the first cylinder chamber 21 is designed as a pressure-controlled one-way valve (non-return valve). Analogously to the embodiments of Figs. 5 and 6, the non-return valve 37 can be controlled by the pressure of the fluid in the second supply line P2, resp. through the pressure relief valve 30.

Optionally, the pressure-controlled valve 31 may have other configurations, so that depending on the load resistance experienced by the piston rod 14 during both the input and output stroke 1025806 19, different switch valve configurations between the different cylinder chambers 21-24 can be realized and the adjusting cylinder 8 can be operated under different operating conditions, among other things.

A characteristic feature of the adjusting cylinder 8 described in this application, which is provided with four operative cylinder chambers 21-24, is that with both the input and output stroke, the piston rod 14 has high moving speeds and therefore low cycle times and, depending on the load resistance experienced at both the incoming as outgoing stroke can generate very large cylinder forces. In addition, the adjusting cylinder 8 has a relatively low return fluid flows, thereby preventing pump losses due to frictional resistances, heat generation and the like, and thus improving the efficiency of the basic machine driving the hydraulic tool.

Furthermore, the construction of the adjusting cylinder 8 becomes simple, with small dimensions and weight, whereby use can be made of standard components and seals.

20 1025806

Claims (14)

A hydraulic cylinder, for example for use with a hydraulic tool, comprising a hollow cylinder body with a first piston accommodated therein, which first piston is composed of a hollow first piston rod extending from the cylinder body and a first piston body connected thereto, the cylinder body and the first piston body a first cylinder chamber and the cylinder body, the first piston body and the first piston rod define a second cylinder chamber, and a second piston received in the hollow first piston rod, which second piston is composed of a piston extending through the first piston body and second piston rod and a second piston body connected thereto, wherein the first piston rod and the second piston body define a third cylinder chamber and the first piston rod, the first piston body, the second piston rod and the second piston body define a fourth cylinder chamber, the second piston rod is at least provided with a bore terminating in the third cylinder chamber and wherein the cylinder chambers can be connected to a first or second supply line for a pressurized fluid for extending or extending shortening the first piston rod, characterized in that at least one pressure-limiting valve is provided, which controls the supply of fluid under pressure to the different cylinder chambers in dependence on the pressure difference between the first and second supply line. 2. Hydraulic cylinder as claimed in claim 1, characterized in that the pressure-limiting valve controls a pressure-controlled valve on the basis of the pressure difference between the first and second supply line, such that, in the case of the outgoing resp. input stroke of the first piston rod the pressure caused by the load resistor is lower than the predetermined pressure level, the pressure-controlled valve a first resp. second extreme position and if the pressure caused by the load resistor is higher than the predetermined pressure level, the pressure-controlled valve assumes a middle position. 3. Hydraulic cylinder as claimed in claim 2, characterized in that the pressure-controlled valve in the central position connects the first and the third cylinder chamber with the first supply line and the second and fourth cylinder chamber with the second supply line. 4. Hydraulic cylinder according to claim 2 or 3, characterized in that in the first or second extreme position the cylinder chambers first, second, third and fourth cylinder chambers can be connected to the first and / or second supply line. 5. Hydraulic cylinder as claimed in one or more of the claims 2 to 4, characterized in that if with both the outgoing and the inward stroke of the first piston rod the pressure caused by the load resistor is lower than a predetermined pressure level, movement speed resp. the force of the first piston rod rapidly resp. is low and that if the pressure caused by the load resistor is higher than the predetermined pressure level, the moving speed resp. the force of the first piston rod slowly resp. is high. A hydraulic cylinder according to claim 5, characterized in that in the first extreme position the pressure-controlled valve connects the second, third and fourth cylinder chamber to the second supply line. 7. Hydraulic cylinder as claimed in claim 5, characterized in that in the second extreme position the pressure-controlled valve connects the third cylinder chamber and at least the second cylinder chamber to the second supply line. 8. Hydraulic cylinder as claimed in claim 7, characterized in that in the second extreme position the pressure-controlled valve connects the fourth cylinder chamber to the second supply line. 9. Hydraulic cylinder according to one or more of the preceding 1025806 claims, characterized in that the second cylinder chamber and fourth cylinder chamber are directly connected to each other. 10. Hydraulic cylinder according to claim 9, characterized in that the second cylinder chamber and fourth cylinder chamber are connected to each other by means of at least one opening arranged in the first piston rod. 11. Hydraulic cylinder as claimed in claim 9, characterized in that the second piston rod is provided with a further bore ending in the fourth cylinder chamber. 12. Hydraulic cylinder as claimed in one or more of the foregoing claims, characterized in that the second and third cylinder chamber are each connected via a non-return valve to a storage vessel for the fluid. 13. Hydraulic cylinder according to claim 12, characterized in that the non-return valve for the third cylinder chamber is a pressure-controlled non-return valve. A hydraulic cylinder according to claim 12, characterized in that the non-return valve for the third supply line is a non-return valve controlled by the pressure-limiting valve. 20 1025806