EP0897480B1 - Device for saving energy - Google Patents

Abstract

A device to save energy for hydraulically-operated tool shanks uses a piston-type accumulator having a housing in which at least two longitudinally displaceable pistons are arranged and are connected to by a coupling part. The coupling part is guided to be longitudinally displaceable in a partition wall of the housing which bounds two fluid chambers with the two pistons. At least one of the pistons bounds at least partially, a fluid chamber and a pre-loaded chamber with presettable internal gas pressure on the opposite sides. A wider range of possible applications is achieved for hydraulically-operated tool shanks using this energy saving device.

Description

The invention relates to a device for saving energy in hydraulic actuatable tools with a piston accumulator.

Related energy saving and recovery devices are under Use of commercially available hydropneumatic accumulators as an energy reservoir already from PCT / WO 93/11363 and from DE 44 38 899 C1 known. In the known energy recovery device according to the PCT document is the piston chamber of a hydraulically actuated working cylinder connected to the hydraulic accumulator via a so-called cartridge valve, which is connected to a Control manifold cooperates as part of a fluid control system Pressure relay is connected. This fluid control device is again with its control input connected to a low pressure branch of the hydraulic circuit, with the moving parts of the machine in the form of Work equipment interacts. When lowering the implement, the piston-side fluid quantity of the working cylinder, taking into account the respective emitted position energy, i.e. under pressure, emitted to the hydraulic accumulator and from there it can be quantified precisely for the subsequent lifting process the work tool can be retrieved, resulting in recovery of energy introduced into the hydraulic accumulator. With this known Device results in a good energy recovery behavior if one uses three or more working cylinders as hydraulic work equipment, which, however, particularly in the case of hydraulically actuated work machines, such as Excavators or the like, is often eliminated for reasons of practicability. Also tend the cartridge valves when holding the work equipment after a lowering process under load to flutter, which leads to an unwanted rocking of the work equipment mostly in the form of an excavator or crane boom.

According to the teaching of DE 44 38 899 C1, it has already been proposed that to dispense with such cartridge valves by hydraulic arranges unlockable check valves in a connecting line that between the hydraulic accumulator and the hydraulic to be actuated Working equipment runs, which is also inexpensive and reliable. is; However, it has been shown in practice that hydraulically actuated Working cylinders this with the assigned energy when delivering the recovered energy The amount of fluid applied to different degrees, leading to inhibitions can result in the movement.

US-A-2,721,446 is an actuator for a hydraulic actuated working cylinder known, which otherwise has the features of the preamble of claim 1. Via a secured by a check valve Hydraulic pump becomes a constant supply for the hydraulic working cylinder manufactured in the event of their malfunction and interruption in the sense of an emergency supply the piston accumulator with two longitudinally movable pistons over the preloaded Gas pressure in the prestressing chamber is the further hydraulic supply for the Ensures working cylinder and causes it to extend. The one on the opposite Provided end of the biasing space of the known Piston accumulator leads to the outside via a ventilation opening. One in Secondary branch led between the piston accumulator and the working cylinder Supply line via the check valve opposite the hydraulic pump secured, enables the emergency supply for the working cylinder, however, does not allow a hydraulic connection as that with it known device a continuous energy saving in the operation of the working cylinder it is possible. In addition, there are undesirable compression-related Warming in the air-filled surrounding area and the ones to be controlled Fluid quantities for emergency operation are correspondingly large, which is energetically is unfavorable.

Starting from this prior art, the invention is based on the object a device for saving energy in hydraulically actuated work equipment to create, with advanced uses that the does not have the disadvantages described above. A related task solves one Device with the features of claim 1.

Characterized in that according to the characterizing part of claim 1, the surrounding space also connected to the hydraulic work equipment is like the fluid space provided with the filling medium, and that the other fluid space via a switchable fluid control to the hydraulic pump connected, allow the pistons of the piston accumulator to be positively coupled with a direction of travel with a decreasing preload space an increase in the internal gas pressure, which decreases in the sense of relaxation, as soon as the pistons move in the other direction with an enlargement of the Move the volume of the prestressing space. The one enclosed in the leader room The amount of gas thus forms a kind of energy storage comparable to a mechanical spring and the kinetic energy introduced into the memory by the movement can be called up again by pressing the switchable fluid control. Because the surrounding space of the piston accumulator in addition fluid-carrying are unwanted, due to compression processes Avoiding heating and the respective amounts of fluid to be controlled Carrying out a working stroke can be reduced, which is energetically favorable.

The piston accumulator used in the energy saving device belong to the family of hydraulic accumulators, including bladder accumulators and membrane memory belong. One of the main tasks of this hydraulic accumulator is certain volume of a pressurized fluid in a hydraulic system record and return them to the system if necessary. The Known piston accumulators consist of a liquid and a Gas part with a piston as a gas-tight separating element, the gas side with Nitrogen is filled. The liquid side of the piston accumulator stands with the Hydraulic circuit in connection, so that when the pressure rises, the piston accumulator increasingly absorbs liquid and the gas on its gas side is compressed. When the pressure drops, the compressed gas expands and thereby displaces the stored hydraulic fluid in the hydraulic Circulation. Piston accumulators can basically work in any position, a vertical arrangement with the gas side up is preferred, so that contamination from the liquid settles on the piston seals is avoided. In contrast to the membrane and bladder accumulators the piston accumulator does not have a flexible separating element in the form of a rubber membrane or rubber bladder, but rather a rigid piston that is hardly subject to wear and as in the device according to the invention can also work without fail over very long periods of time.

By using the above-described piston accumulator in the energy saving device it has been shown that it is energetically in the sense of a Saving is particularly favorable, a middle piston or boom position the hydraulically operated work equipment with a high internal gas pressure in the Allocate the prestressing space, which results from this central position with the release of energy relaxed, if the boom may need to be lifted under load. there the energy saving device does not need to be limited to working machines to be, but can also be used in hydraulic braking systems, in elevators and hydraulic motors or the like. Find use. In these cases it is beneficial to achieve a low spring rate large volume for the prestressing space. To achieve this, it can be provided that the prestressing space is connected to a further gas supply device, especially in the form of a nitrogen storage as a buffer.

Fig.1

in einer prinzipiellen Schaltdarstellung den Einsatz eines Kolbenspeichers bei einer Energieeinsparungsvorrichtung für hydraulisch betätigbare Arbeitsgerätschaften in Form von Arbeitszylindern;

Fig.2

einen Längsschnitt durch eine erste Ausführungsform des in der Fig.1 gezeigten Kolbenspeichers;

Fig.3

einen Längsschnitt durch eine zweite Ausführungsform eines nach der Fig.1 anwendbaren Kolbenspeichers.

In the following, an embodiment of the device for saving energy is explained in more detail with reference to the drawing. They show the principle and not to scale

Fig.1

in a basic circuit diagram the use of a piston accumulator in an energy saving device for hydraulically actuated work equipment in the form of working cylinders;

Fig.2

a longitudinal section through a first embodiment of the piston accumulator shown in Figure 1;

Figure 3

a longitudinal section through a second embodiment of a piston accumulator applicable according to Fig.1.

The piston accumulator according to FIG. 2 has a reference number 10 as a whole Housing on. The housing 10 is designed in the form of a cylinder tube, can also form other cross-sectional shapes (square, elliptical). Two longitudinally displaceable pistons 12, 14 are arranged in the housing 10 via a coupling part in the form of a solid coupling rod 16 are interconnected. The coupling rod 16 is longitudinally movable in one Partition 18 of the housing 10 out, which is in the manner of a cylindrical Intermediate section of the housing 10 is formed and with the two adjacent fluid pistons 12, 14 delimit two fluid spaces 20, 22. To seal the two fluid spaces 20, 22 from one another, the circumferential one Partition 18 corresponding round seals 24. The housing 10 is delimited at the end by two end walls 26, 28 which cover the closure cover of the piston accumulator. Between the view towards Fig.2 seen left end wall 26 and the adjacent opposite Piston 12 is limited by these parts, a biasing chamber 30, the a predeterminable gas internal pressure is assigned.

The respective fluid space 20, 22 widens in diameter from the partition 18 to the associated piston 12, 14 by one step, the Coupling between the pistons 12, 14 is designed such that in a fluid space 20 with a small volume the respective other fluid space 22 by the amount of the reduced volume is increased accordingly. The coupling rod 16 is of solid construction and is fixed at the end by means of screws 32 System with the respectively assigned pistons 12, 14. The pistons 12, 14 point in known training corresponding outer seals on the outer circumference on. The partition 18 is part of a tubular center connector 34 to which the housing tubes 36 of the housing 10 join on both sides, which the Serve longitudinal guidance of the pistons 12, 14. In the radial transverse direction to the longitudinal axis 38 and diametrically opposite each other and from the partition 18, two connection points 40 and 42 extend in the central connection piece 34, which open into the respectively assigned fluid space 20 or 22. The cross section and viewed in the direction of Fig.1 in the direction of the longitudinal axis 38 H-shaped center connector 34 is at both ends via one Sealing ring 44 in the two housing tubes 36 and the fluid spaces 20, 22 from sealing the environment. The two end walls also point 26, 28 each have a sealing ring 46 on the outer circumference.

To define the end walls 26 and 28, end sleeves 50 are used each screwed into the free ends of the two housing tubes 36 Hold the mentioned end walls 26, 28 in their position shown in FIG. The respective connection point 40, 42 opens into a cylindrical one Cross channel 52 of the coupling rod 16 in each position of the Piston 12,14 is penetrated and parallel to the longitudinal axis 38 of the piston accumulator runs. To accommodate the screws 32 and to enlarge the Bias chamber 30 and an opposite surrounding space 54 the two pistons 12 and 14 have a hollow cylindrical center recess 56 on.

The fixed end wall 26 of the housing 10, which is the biasing space 30 limited to the outside, has a connection point 58, which via a Sealing plug (not shown) can be sealed. After removal the relevant sealing plug can be connected via the connection point 58 Biasing room 30 to a gas supply device (see Fig. 1) in particular be connected in the form of a nitrogen reservoir 62. The one already mentioned Ambient space 54, the other end wall 28 and is limited by the piston 14, via a passage point 64 to a supply line 66 connectable. Furthermore, the housing 10 limits its two housing tubes 36 the fluid spaces 20, 22 on the outer circumference.

The biasing chamber 30 is filled with a working gas, for example in the form of Nitrogen, filled and assigned an internal gas pressure. For filling of the prestressing space 30 can the sealing plug, not shown be provided with a valve device 68 (see Fig. 1) which blocks the gas passage allowed in the direction of the bias chamber 30, in the sense of a check valve but blocked the exit. The gas located in the prestressing space 30 with predeterminable Gas pressure therefore forms a kind of gas or pressure cushion with, if one uses a mechanical comparison model, more predetermined Spring constant. The pressure pad addressed thus forms in the sense of mechanical Comparative model a kind of compression spring. Take the two Piston 12, 14 seen in the direction of FIG. 2 is its extreme right Driving position, the piston 12 abuts the facing end of the Center connector 34 and the piston 14 comes into contact with the end wall 28. Since the surrounding space 54 is connected to the supply line 66 is, the amount of fluid stored in the surrounding space 54 is in the Supply line 66 pushed out. In the relevant final position takes then the prestressing space 30 has its largest volume and the fluid space 22, which can be filled with a fluid via the connection point 42. The fluid space 20, then takes its lowest volume and the gas pressure inside in the prestressing space 30 is due to the volume increase of the prestressing space 30 then reduced, which is the relaxation in the mechanical model equal to the compression spring.

The volume of the prestressing space then decreases in the opposite direction of movement 30 and the fluid space 22 and the fluid space 20, takes its maximum possible volume. The gas in the prestressing chamber 30 is then accordingly compressed and pre-stressed, which is the tensioning of a mechanical Feather equals. The gas or spring energy stored in this way can then be called up to a hydraulic, which will be explained in more detail Work equipment or the like to operate in a supportive manner. In addition to the The two-piston arrangement shown can optionally be used for other control processes even more pistons (not shown) are used, which if necessary the number of fluid spaces as well as the prestressing spaces and others Gas rooms increased. Several piston accumulators could also be connected in series or interconnected in parallel.

1 shows the use of the piston accumulator according to FIG Device for saving energy in hydraulically actuated work equipment in the form of two hydraulic working cylinders 70. The two hydraulic cylinders 70 are equivalent to one via their respective piston rods 72 Boom 74 connected, for example in the form of a crane or excavator arm. The boom 74 can, however, also represent a lifting platform such as this is used for goods and passenger lifts as well as lifting platforms, provided that these can be moved with hydraulic cylinders. Instead of the two hydraulic cylinders 70, however, a suitably trained hydraulic motor can also be used, to operate a work tool. Furthermore, instead of the two Hydraulic working cylinder 70 also only one working cylinder for moving the Cantilever 74 can be provided, but this is associated with lower savings.

The two hydraulic cylinders 70 are on the rod side via a connecting line 76 jointly connected to a fluid control 78 in a fluid-carrying manner, for example a controllable valve unit in the form of directional valves or the like. can have. A fluid-operated control is also connected to the fluid control 78 Hydraulic pump 80 connected and a tank line 82 for the tank 84. On the output side, the fluid control 78 has a further fluid-carrying connecting line 86, which opens into the second connection point 42. The first Connection point 40 of the fluid space 20 is in the embodiment shown in FIG connected to the supply line 66 and therefore via this Supply line 66 in connection with the surrounding space 54. In one in this case, the fluid space 20 is included Hydraulic fluid is filled and, like the supply line 66, is above a Secondary branch 66a with the hydraulic work tool in the form of the two Hydraulic cylinder 70 in fluid communication. When the pistons 12, 14 move in the direction of the fluid-filled surrounding space 54 there can be no compression of air and therefore no undesirable Warmings are coming. In the latter case, the ones to be controlled can also be controlled Reduce fluid quantities to perform a working stroke. The supply line 66 and the secondary branch 66a open out as shown 1 in a further fluid-carrying connecting line 88, which is located in Direction of the hydraulic cylinder 70 and the on the piston sides 90 to the Hydraulic cylinder 70 is connected.

The energy saving device is now set such that at a middle load or boom position of the boom 74 in the biasing space 30 increased, maximum possible internal gas pressure prevails, that of a biased mechanical compression spring corresponds. If the boom 74 is now to be lifted, So moving in the direction of view of Fig.1, the Hydraulic pump 80 switched on and fluid arrives via the fluid control 78 under pressure via the connecting line 86 and the second connection point 42 into the fluid chamber 22, the pistons being viewed in the direction of view of FIG Move 12 and 14 to the right. That in the fluid space 20 of the piston accumulator stocked fluid is then together with the fluid from the surrounding space 44 via the secondary branch 66a or the connecting line 66 and the further connecting line 88 to the piston side 90 of the hydraulic cylinder 70 delivered, the pressure cushion in the biasing chamber 30 this Movement process supported and the energy stored in the leader space 30 is delivered to the boom 74 via the fluid guide. On the pole side 72 of the working cylinder 70 become the fluid quantities thus displaced via the connecting line 76 and the fluid control 78 to the tank 84 the connecting line 82 is depressurized.

Hydraulic energy is stored in the pretensioning space 30 then when the boom 74 is lowered, this being stored on the piston side 90 Fluid is returned to the fluid space 20 and the surrounding space 54 with the result that seen in the direction of Fig.1 Move pistons 12 and 14 to the left and the preload in the preload chamber 30 increases. When the boom 74 is moved about a central position support an upcoming lifting process in such a particularly energetically favorable manner. If the boom 74 can be moved on working machines, the gas supply device can 62 in the form of the nitrogen storage shown. Should however, for example because the boom 74 is a lifting platform acts, the spring constant to be reduced over longer travels The chamber volume becomes a uniform energy output of the biasing space 30 increased by the connection of the memory 62. Further becomes by switching the fluid control 78 on the rod side of the hydraulic cylinder 70 filled via the hydraulic pump 80 under pressure, which is the lowering process facilitates as well as the increase in gas pressure in the prestressing space 30.

3 shows a further piston accumulator, which, like the piston accumulator design according to Figure 2 is suitable for an energy saving device to be used according to the circuit diagram of Fig.1. In doing so the same components of the piston accumulator according to Figure 3 with the same reference numerals but increased by 100 as described above according to the Representation according to Fig.2 are described. That for the embodiment after the figure 2 applies accordingly to the embodiment of the piston accumulator according to Figure 3, which is described in the following only insofar as it differs significantly from the above-described embodiment according to FIG different.

In the embodiment according to FIG. 3, the end walls 126, 128 are in one piece formed and screwed to the inside of the housing tubes 136 each. The connection points 140, 142 open in one direction, i.e. 3 looking down from the inside of the housing 110 out. The two-part partition 118 again has the character a hollow cylindrical intermediate piece 134 and interlocks with each other a, the fixed connection realized via a screw connection 192 is the flange-like widenings of the two-part partition intermediate piece be upheld. Furthermore, they are in the pistons 112, 114 made cylindrical center recesses 156 coaxial to the longitudinal axis 138 arranged and facing each other. There is therefore an increase in volume of fluid spaces 120 and 122 take place.

Both embodiments of a piston accumulator both according to Fig.2 and as 3 also essentially show a central axis and its axis Longitudinal axis 38, 138 a symmetrical arrangement of parts, which allows it to be inexpensive in a large number the piston accumulator as an inexpensive standard component to manufacture and offer.

Claims (8)

1. A device to save energy for hydraulically operated tool shanks (70) using a hydraulic pump (80) and a piston-type accumulator having a housing (10; 110) in which at least two longitudinally displaceable pistons (12, 14; 112, 114) are each connected to each other by an adjacently opposite piston by way of a coupling part (16; 116) guided to be longitudinally displaceable in a partition wall (18; 118) of the housing (10; 110) which, together with the two adjacently opposite pistons, bounds two fluid chambers (20, 22; 120, 122), whereby at least one of the pistons (12; 112) bounds at least partially a pre-load chamber (30; 130) with pre-setable internal gas pressure and, at least partially on its opposite side, one of the two fluid chambers (20; 120) which is filled with a medium and connected to the tool shank (70), and whereby one of the other pistons (14; 114) bounds at least partially an ambient space (54; 154) of the piston-type accumulator, characterised in that the ambient space (54; 154) is connected to the tool shank (70) by fluid just as it is connected to the space (20; 120) filled with fluid, and that the other space (22; 122) filled with fluid is connected to the hydraulic pump (80) via a switchable fluid control unit (78).
2. A device according to Claim 1, characterised in that the preload chamber (30; 130) of the piston-type accumulator is bounded, in addition to the movable piston (12; 112), by a fixed wall (26; 126) of the housing (10; 110) which preferably has a connection port (58; 158) for a gas supply device in particular in the form of a nitrogen accumulator (62).
3. A device according to Claim 1 or 2, characterised in that the two connection ports (40, 42; 140, 142) in the housing (10; 110), each arranged on either side of the partition wall (18; 118) of the piston-type accumulator, terminate in the associated fluid-filled spaces (20, 22; 120, 122).
4. A device according to one of the Claims 1 to 3, characterised in that the tool shank (70) has at least one hydraulically operated cylinder connected at the piston rod end (72) to the fluid control unit (78) and at the piston end (90) to the ambient space (54; 154).
5. A device according to Claim 4, characterised in that the respective operating cylinder (70) is connected at the piston end to the other fluid-filled space (20; 120).
6. A device according to one of the Claims 1 to 5, characterised in that the coupling part (16; 116) is formed by a solid coupling rod, the ends of which are each firmly connected to the associated piston (12, 14; 112, 114).
7. A device according to one of the Claims 1 to 6, characterised in that the coupling part (16; 116) is in sealing contact with the partition wall (18; 118) which, as part of a centre sleeve (34; 134) forms a connecting point for the housing tubes (36; 136) of the housing (10; 110) adjoining at both ends, which guide the piston (12,14; 112,114) longitudinally.
8. A device according to one of the Claims 1 to 7, characterised in that the piston-type accumulators used are essentially mounted symmetrically to a centre axis passing across its longitudinal axis (38; 138) as well to the longitudinal axis (38; 138).

Images