WO1994022409A1

WO1994022409A1 - Bidirectional piston pump and its use

Info

Publication number: WO1994022409A1
Application number: PCT/FI1993/000140
Authority: WO
Inventors: Aliisa Orvokki KARHUMÄKI; Matti Taavi Kalevi KARHUMÄKI
Original assignee: Karhumaeki Aliisa Orvokki; Karhumaeki Matti Taavi Kalevi
Priority date: 1991-10-02
Filing date: 1993-04-01
Publication date: 1994-10-13

Abstract

The invention relates to a bidirectional piston pump (2) controlling a working cylinder (1) or the like. Each end of the pump has two pipe fittings (7a, 7b; 8a, 8b) for the medium, and each pipe fitting has a unidirectional valve (10, 11, 12, 13). Along the length of the cylinder (3) there are further provided a first and a second pair of fittings (17a, b; 18a, b), and these are coupled individually to unidirectional valves at the respective ends. The pump piston (4) has such a length that with its whole stroke length it closes either the first pair of fittings or the second pair of fittings in order to produce the first or the second operating state (k1; k2). Thus, in the first operating state the bidirectional piston pump pumps medium in one direction and in the second operating state in the opposite direction.

Description

Bidirectional piston pump and its use

The invention relates to a bidirectional piston pump control¬ ling a working cylinder or the like, the pump being made up of a pump cylinder having ends closing it; in this cylinder there is a piston the arm of which passes in a sealed manner through at least one of the ends to a power source; and at each end or in its vicinity there are two pipe fittings for a medium, and each of these pipe fittings has a unidirectional valve for preventing backflow. The invention also relates to the use of such a bidirectional piston pump for manual raising and lower¬ ing of a seat or the like.

For example, physically handicapped persons and others with limited strength have considerable problems in shops and at workplaces, where they can indeed move using wheelchairs, but getting objects especially from upper shelves and taking them to the cashier and out of the shop or, respectively, to the point of work is difficult. To date, they have had to use, while sitting in a wheelchair, shopping carts or other similar separate transfer equipment; this is extremely inconvenient and does not solve the problem of reach. It is, of course, conceiv¬ able to design a wheelchair so that it has space for carrying objects, or it can be equipped with corresponding additional means, but even this does not solve the said problem of reach. It is conceivable that this problem of reach could be solved by adapting the seat in a wheelchair or the like so that it can be raised in some manner. In this case, however, the specific problem is from where the actuating power for the raising and lowering can be obtained. If an external power source such as a battery is resorted to, the structure will be complicated and expensive, although easy to use. If, on the other hand, an attempt is made to use the person's own strength, the problems to be solved are how to use that strength and how to avoid com¬ plicated, heavy and/or energy-wasting structures. The problems are thus considerable, and indeed there has not been on the market a single system for improving the performance of the physically handicapped in this area.

The object of the invention is therefore to provide a system by which the dimensions of operating reach of a physically handi¬ capped person can be increased substantially while the person is sitting in a seat. It is a particular object of the inven¬ tion to provide components required for such an arrangement, by means of which components a physically handicapped person can, while sitting in a seat, with reasonably low strength raise and lower himself without constraint. It is also an object to pro¬ vide components of this type, the operation of which does not waste energy and which are relatively simple in structure and can be assembled compactly in the apparatus in which the seat for a physically handicapped person is located. Furthermore, it is an object of the invention to provide such components and their combination, which are safe to use even in the event that they are used in a faulty manner or some part is damaged. It is a further object of the invention to provide such components and their combination, which can be manufactured relatively economically by using conventional tools, and will thus result in a moderately priced product.

By means of components according to the invention and their use the objects defined above can be achieved and the problems described above can be solved. In order to accomplish this, the device according to the invention is characterized in what is stated in the characterizing clause of Claim 1, and its use is characterized in what is stated in the characterizing clause of Claim 7.

The most important advantage of the invention is that, by the use of the components according to it, there is provided for a physically handicapped person a seat which can be easily raised and lowered by the person concerned, whereby the person's reach is substantially improved. Furthermore, the components accord¬ ing to the invention have the advantage that their efficiency is excellent and that they can be manufactured relatively eco¬ nomically and be placed in a small space in connection with the seat. It is a further advantage of the invention that its use is without constraint for the person sitting in the seat and that the system is safe, not causing situations of danger for the person sitting in the seat, even in cases of faulty use.

The invention is described below in detail, with reference to the accompanying drawings.

Figures 1A-1D depict the different operating states of a bidi¬ rectional piston pump according to the invention.

Figures 2A-2B depict one combination according to the invention of a bidirectional piston pump and a working cylinder, in two different operating states.

Figures 3 and 4 depict a second and a third combination accord¬ ing to the invention of a bidirectional piston pump and a work¬ ing cylinder.

Figures 5A-5B depict a fourth combination according to the invention of a bidirectional piston pump and a working cylin¬ der, in two different operating states.

Figures 6 and 7 depict a fifth and a sixth combination accord¬ ing to the invention of a bidirectional piston pump and a work¬ ing cylinder.

Figures 8A-8B depict a seventh combination according to the invention of a bidirectional piston pump and a working cylin¬ der, in two different operating states.

Figure 9 depicts schematically, in cross section, a preferred working cylinder structure according to the invention.

Figure 10 depicts in general the use of a bidirectional piston pump and a working cylinder according to the invention, in a handicapped person's carriage for doing errands.

Figure 10 depicts, in a side view, the principle of a physical¬ ly handicapped person's carriage for doing errands. The struc¬ ture is made up of a frame 40 which moves on the floor or else¬ where on turning caster wheels 47 in the front and large wheels 44 approximately at the seat. In the frame 40 there is shaped a pushing handle 46, for example, for an assisting person, a seat 30, and in the front part of the carriage a basket structure 45, which is within the reach of the person sitting in the seat. At the seat there is attached to the carriage frame 40 a working cylinder 1, and on the lower surface of the seat or in its vicinity a bidirectional piston pump 2, the conduits of which are connected, in a manner not shown in the figure, to the pressure sides of the working cylinder. In addition, the carriage has, mounted on a shaft 48 close to the backrest of the seat, armrests 43 and lever arms 42 in such a manner that the armrests and the lever arms are rigidly interconnected, in which case the moving of an armrest 43 upwards or downwards will move the lower end of the lever 42 respectively backwards or forwards. At the lower end of the lever 42 there is further articulated the piston arm 9 of a bidirectional piston pump 2. In a manner to be described later, the operation of the arm¬ rests 43 has been arranged to be as follows: when the armrests are not being manipulated, they remain in their middle position K0, at which time the seat 30 is not raised or lowered in any height position. When the person seated pushes the armrests 43 downwards as if to raise himself and, in this downwards pressed position Kl, moves the armrests reciprocally, pressure is pumped by the bidirectional piston pump 2 into the working cylinder 1 so that the seat 30 is raised. When the user pulls the armrests upwards and thus as if pulls himself downwards. and moves the armrests reciprocally in this upwards raised position K2, the bidirectional piston pump 2 pumps medium into the working cylinder 1 so that the seat 30 is lowered. The length of the working cylinder 1 has been arranged to be such that the lower position of the seat 30 corresponds approximate¬ ly to the ordinary chair height, in which case a person can work normally and pick up objects from a relatively low level. The raised position of the working cylinder corresponds to approximately double the length of the cylinder, in which case the seat 30 is raised to the height of approximately one meter, which in most shops is a sufficient height for picking objects from the shelves.

In addition, it is possible to combine with the arrangement made up of a bidirectional piston pump 2 and a working cylinder 1, as explained later, a medium container 31 and/or a pressure accumulator 51 in which there can be arranged, for example, such a preliminary pressure that under its effect the seat 30 is approximately halfway up the raising distance for a normal person. Thus the action is modified as follows: when a person wishes to raise the seat 30 from the lower position to the upper position, he presses the armrests 43 into the operating state Kl, whereupon the seat, under the effect of the prelimi¬ nary pressure, first rises halfway up, whereafter the person seated can, in the manner described above, raise himself all the way up, if necessary. When the person in the seat wishes again to lower himself, he pulls the armrests 43 into the oper¬ ating state K2, whereby the seat is lowered to the middle posi¬ tion, from which he can lower himself in the manner described above. Thus the user needs in fact to work for only half the distance in order to effect either a raising or a lowering. By lever transmissions, as well as by the dimensioning of the bidirectional piston pump and the working cylinder, the trans¬ mission from the distance of travel of the armrests to the distance of the raising or lowering movement of the seat is made suitable, not too slow and, on the other hand, not too fast or too heavy.

The bidirectional piston pump 2 which constitutes the core of the invention is discussed in detail below. In the description, the same reference numerals are used for the same or corre¬ sponding parts with respect to the different embodiments. Fig¬ ures 1 illustrate, in cross section, the principle of the bidi¬ rectional piston pump according to the invention. The device is made up of a pump cylinder 3 and ends 5, 6 closing it, as well as of a piston 4 in this cylinder, the piston arm 9 passing in a sealed manner through at least one end to the power source. Figures IB-ID depict this embodiment, and Figure 1A, in which there is also a piston arm 39 passing through the other end 6, shows another embodiment. The advantage of the structure ac¬ cording to Figure 1A is that, by means of it, the stroke vol¬ umes of both pressure chambers 32 and 33 of the pump can easily be made precisely equal. Otherwise these two embodiments func¬ tionally correspond to each other, and the same description applies to both.

In each end 5, 6, or in the vicinity of the ends, at each end of the cylinder there are two pipe fittings, i.e. at the first end 5 of the cylinder there are fittings 7a, 7b and at the second cylinder end 6 there are fittings 8a, 8b. All of these fittings have unidirectional valves, also called back-pressure valves or check valves, so that the unidirectional valves 10, 11 of the first end will permit a flow of medium through the pressure chamber 32 in the end section, and the unidirectional valves 12, 13 of the second end are coupled respectively so that they will permit a flow through the pressure chamber 33 in this end section. Thus, one 10 of the unidirectional valves in the vicinity of the first end 5 is in the reverse direction relative to the flow coming towards the cylinder 32 and the other unidirectional valve 11 is in the forward direction rela¬ tive to the flow coming towards the cylinder 32, and one 12 of the valves in the vicinity of the second cylinder end 6 is in the reverse direction relative to the flow coming towards the cylinder 33 and the other valve 13 is in the forward direction relative to the flow coming towards the cylinder 33. In the figures, these unidirectional valves are therefore drawn as triangles, the tip of each indicating the permitted flow direc¬ tion. These unidirectional valves or check valves thus, in a manner known per se, prevent the backflow of the medium during pumping.

In addition, the cylinder 2 has two pairs of pipe fittings 17a, 17b and 18a, 18b, which pairs of fittings are at a distance E from each end 5 and 6 and at a distance V from each other. The fittings of both the first pair 17a and 17b and the second pair 18a and 18b are preferably at least approximately in alignment as seen in the longitudinal direction of the cylinder. As seen in the peripheral direction, the locations of the fittings of a pair of fittings, as well as the end fittings 7a, 7b and 8a, 8b mentioned above, may be on the opposite sides of the cylinder, or alternatively relatively close to each other, according to the requirements of the intended location of the cylinder. The distance E and the distance V are preferably at least approxi¬ mately equal, i.e. approx. 1/3 of the inner length of the cyl¬ inder, but the invention is not limited to this dimensioning; the distance V may be greater or smaller than the distance E. In general it is also advantageous to make the pump 2 symmetri¬ cal in its longitudinal direction, but it may also be made asymmetrical.

In addition, the pipe fittings of the first pair 17a, 17b are coupled individually to those sides of the unidirectional valves 10, 11 which face away from the cylinder, whereby con¬ necting conduits 14a and 14b are formed. The fittings of the second pair 18a and 18b are likewise coupled individually to those sides of the unidirectional valves 12, 13 at the second end which face away from the cylinder, whereby connecting con¬ duits 15a and 15b are formed. The communication of medium to targets, including the pressure-balancing and medium containers and the pressure spaces of the working cylinder, starts from these four connecting conduits 14a, 14b, 15a, 15b, or from some of them. The piston 4 has such a length L that, when it is in the neutral position K0 (Figure 1A) , which is preferably the middle point of the cylinder, it closes both pairs of fittings 17a, 17b and 18a, 18b simultaneously. The length L of the pis¬ ton must thus be by the thickness of the fittings longer than the distance V between the pairs of fittings. Furthermore, the length L of the piston must be such that, in the first operat¬ ing state Kl (Figures IB, 1C) of the bidirectional piston pump 2, which state is the operating state on the side of the first end 5 of the cylinder, it continuously closes with its stroke length the first pair of fittings 17a, 17b but does not prevent flow through the second pair of fittings 18a, 18b. As can be seen in Figure ID, the stroke length I of the piston 4 in the first operating state Kl consists of the distance of travel of the end 24b which faces away from the piston arm 9, in which case the piston in its extreme position, pushed as close to the second end 6 as possible, just barely does not close the second pair of fittings 18a, 18b and, when pushed as far as possible towards the first end 5, barely closes the first pair of fit¬ tings 17a, 17b. The piston length L is also such that, in the second operating state K2 (Figure ID), it with its entire stroke length closes the second pair of fittings 18a, 18b but keeps the first pair of fittings 17a, 17b unobstructed. As can be seen in Figure ID, the piston 4 surface 24a facing the pis¬ ton arm 9 defines the stroke length I so that the piston, when pushed as far as possible towards the second end 6, barely closes the second pair of fittings 18a, 18b and, when pushed as far as possible towards the first end, barely leaves the first pair of fittings 17a, 17b unobstructed. The basic structure of the bidirectional piston pump according to the invention is described above. The connecting conduits 14a, 14b, 15a, 15b are coupled to different targets, according to the desired mode of operation. The operation of the bidirectional piston pump is described below in a typical embodiment corresponding to the connecting conduit coupling according to Figures 1A-1D, the embodiment being also consistent with the embodiment of Figures 4, 5A, 5B and 7.

In this embodiment, the connecting conduits 14a and 15a are coupled to pumping targets and the connecting conduits 14b and 15b are coupled to each other by a connecting conduit 16. When the piston 4 is in the middle position K0, the piston, as well as the unidirectional valves 10 and 12, prevents all flow from the targets of use towards the pump, as can be easily under¬ stood from Figure 1A. There is thus no flow of medium in the direction of the arrows in the conduits. At this time the bidi¬ rectional piston pump locks the target of use, such as the working cylinder, in the prevailing position. When the piston 4 is moved to a point close to the first end 5, to the operating state Kl, which corresponds to the operating state Kl shown in connection with Figure 10, the first pair of fittings 17a, 17b remains closed, but the movement of the piston towards the second end 6 will cause medium to flow from the chamber 33 at the second end to the chamber 32 at the first end, as shown by arrows in Figure IB. When the piston thereafter moves towards the first end (Figure 1C), the piston moves fluid from the chamber 32 via the fitting 7a to the target of use. When move¬ ment of this type is repeated, it can be seen that the end 24a of the piston 4, together with the chamber 32, serves as a single-action pump, pumping fluid via the connecting conduit 14a to the target of use and sucking it at the same time via the connecting conduit 15a from the container or from another target of use. When the piston 4 is moved to the second operat¬ ing state K2, which corresponds to the state K2 (Figure ID) shown in connection with Figure 10, the piston, while moving towards the first end, conveys fluid from the chamber 32 to the chamber 33 and, when moving towards the second end, the piston conveys fluid from the chamber 33 further via the connecting conduit 15a to the target of use. Thus the end 24b of the pis¬ ton, together with the chamber 33, serves as a single-action pump, sucking fluid from the connecting conduit 14a and pumping it into the connecting conduit 15a. It can thus be seen that, when the piston is in one operating state, the pump pumps fluid from the connecting conduit 14a to the connecting conduit 15a and, when the piston is in the other operating state, it pumps fluid in the reverse direction, from conduit 15a to conduit 14a. The pump of the invention is thus capable of pumping in the same conduits in two opposite directions, depending on the point in cylinder length at which the piston is performing the working movement, i.e. its stroke length I.

Figures 2A, 2B, 3 and 4 depict various single-type operational embodiments of the working cylinder 1 and bidirectional piston pump 2 of Figure 6, schematically, using a bidirectional piston pump of the type described above. In the embodiment of Figures 2a and 2b, the connecting conduit 15a starting from the pump chamber 33 is coupled to pressure space 23 above the piston of the double-action working cylinder 1, and the connecting con¬ duit 14a starting from the pump chamber 32 is coupled to the lower pressure space 22 of the double-action working cylinder 1. In principle the working cylinder 1 may thus be a conven¬ tional double-action cylinder which has a piston 34 and a pis¬ ton arm 25 passing through one end, the seat 30 being attached to its upper end. In addition, the connecting conduit 14b com¬ municating with the lower pressure space is coupled to a pres¬ sure accumulator 51, and the connecting conduit 15b communicat¬ ing with the upper pressure space is coupled to a medium con¬ tainer 31, and in this case in particular to their fluid spaces 20, 50. In this case the medium is thus a fluid, such as oil, and the system made up of a bidirectional piston pump and a working cylinder is a hydraulic system. The pressure accumu¬ lator and the medium container serve each as a pressure- balancing container, in which there is air or some other gas above the fluid, and the purpose is at least to serve for bal¬ ancing the pressure in the system in a case in which the fluid volumes passing from the different pressure spaces 22, 23 via the chambers 32, 33 have not with considerable precision been dimensioned to correspond to each other, in which case at least in some operating states there is flow either towards such a pressure-balancing container or from the pressure-balancing container to the system. There is no need to analyze this in greater detail in the present application.

Figure 2A shows the first operating state Kl, the person seated wishing to move the seat upwards. It is assumed that the seat has been in the lower position and that the pressure P prevail¬ ing in the system, i.e. in the pressure accumulator 51, is such that it is alone capable of raising the seat half way up the raising distance. Thus, in this case the armrest 43 is pressed downwards, whereupon the piston 4 moves to the side of the first end 5 in the cylinder. At this time, from the space 23 above the piston in the working cylinder there opens, via the pipe fitting 18a, free access to the second chamber 33, where¬ upon the pressure space 23 acquires atmospheric pressure via the fitting 18b and the connecting conduit 15b and via the con¬ tainer 31. Under the effect of this, the pressure P prevailing in the pressure accumulator 51 can act, via the connecting conduit 14b, the chamber 32, and the connecting conduit 14a, on the lower pressure space 22, whereby the seat is raised from the lower position to the middle position. When the piston 4 is now moved reciprocally in direction Gl and direction G2, a suction flow is produced from the connecting conduit 14b to the pump chamber 32 and further via the unidirectional valve 10 as a flow to the lower pressure space 22 in the working cylinder, whereby the seat 30 is raised further. The seat-raising move¬ ment can be stopped and locked at any point by bringing the piston 4 to the middle position K0.

When the person wishes to move from the upper position down- wards, he moves the armrest 43 upwards, whereupon the piston moves to the second operating state K2, shown in Figure 2B. Thereupon a connection opens from the lower pressure space 22 of the working cylinder 1 to the chamber 32 on the side of the first end of the pump via the fitting 17a and further via a pipe 37 to the pressure accumulator 51, into its fluid space 50. In this situation the seat 30 descends to the height deter¬ mined by the pressure in the pressure accumulator 51, i.e. ap¬ proximately halfway up the raising height. When the user now, by means of the armrest 43, moves the piston 4 reciprocally in direction G3 and direction G4, a suction flow is produced from the container 31 via the pipe 38 to the chamber 33, the medium passing further via the unidirectional valve 12 to the upper pressure space 23 in the working cylinder, causing the seat 30 to descend further. Thus, by pumping in the operating state Kl, the seat 30 can be raised and, by pumping in the operating state K2, the seat can be lowered by half the travel distance, and the second half of the travel distance is effected by the preliminary pressure P of the pressure accumulator 51. The system is completely hydraulic, since both pressure sides com¬ municate by mediation of their pipes 37, 38 with the medium container and respectively with the fluid spaces 20 and 50 of the pressure accumulator.

The embodiment in Figure 3 resembles the embodiment in Figures 2a and 2b except that the connecting conduit 15b is not coupled to the medium container; it opens directly into the open air 35. The second connecting conduit 14b is connected by means of a tube 37 to the fluid space 50 of the pressure accumulator. The operation is otherwise completely the same as in the case of Figures 2a and 2b, except that in the chamber 33 on the side of the second end of the bidirectional piston pump, as well as in the upper pressure space 23 of the working cylinder, there is gas, i.e. air, and in the chamber 32 on the side of the first end 5 of the bidirectional piston pump, as well as in the lower pressure space 22 of the working cylinder, there is fluid. In other words, one side of the system is hydraulic and the other side is pneumatic.

The embodiment of Figure 4 deviates somewhat from the above. In it, the connecting conduit 14b is connected by a conduit 16 to the connecting conduit 15b, and this conduit is closed in rela¬ tion to its environment. The connecting conduit 14a is con¬ nected directly to the lower pressure space 22 of the working cylinder 1, whereas the connecting conduit 15a is connected to the fluid space 50 of the pressure accumulator. In this ar¬ rangement the upper pressure space 23 of the working cylinder 1 is connected directly to the open air 35. Figure 4 shows the middle position K0 of the piston 4, in which, as in the pre¬ vious cases, the seat 30 is locked at any position. When the piston is moved to the first operating state Kl on the side of the first end 5, the seat is raised possibly first under the action of the preliminary pressure coming from the pressure accumulator via the conduit 15a, the chamber 33, the conduit 16, forward valves 11, 10, and the chamber 32 to halfway up the raising distance. Thereafter, by moving the piston reciprocally in that operating state, fluid can be pumped from the pressure accumulator 51 via the pump 2 in the manner described above to the pressure side 22 of the working cylinder, whereby the seat 30 is raised further. From the upper side 23 of the working cylinder, air flows into the open air 35. When the piston 4 is moved to its second operating state K2 close to the second end 6, the seat is lowered, since fluid returns from the pressure space 22 via the fittings 17a, 17b, the conduit 16, and the forward valves 13, 12 to the fluid space 50 of the pressure accumulator. When the piston is then moved reciprocally in that operating state, fluid is pumped from the lower pressure space

22 of the working cylinder via the pump 2 back to the fluid space 50 of the pressure accumulator, against its preliminary pressure, whereupon the seat 30 is lowered. At the same time air flows from the outer air 35 into the upper pressure space

23 of the working cylinder. Additional features necessary for the structure include the throttle valves of the fittings 17a and 18a, shown in the fig¬ ures, the valves slowing down the flow of medium through the pairs of fittings and thus the lowering of the seat from the upper position to the height determined by the preliminary pressure P and its rising from the lower position to the height determined by the preliminary pressure, when the piston 4 is being moved from the neutral position K0. Another additional feature is a mechanism by which the piston is centered to the neutral position K0. This can, for example, be done with the help of a notch 49a in the piston arm 9 and a spring-actuated counter-projection 49b, so that in the neutral position the counter-projection 49b engages the notch 49a, thereby locking the piston arm and the piston at this point, from which the user can move them for the operating states Kl and K2. The centering can also be effected by means of springs not shown in the figures, for example between the piston ends 24a, 24b and the corresponding cylinder ends 5 and 6. The springs may be conical helical springs which allow the piston to come close to the cylinder ends.

Figures 5A and 5B depict an embodiment of the bidirectional piston pump, deviating operationally from those described above. In it, the connecting conduits 14a and 15a are coupled to the pressure spaces 22 and 23 as in the embodiments of Fig¬ ures 2 and 3. In a manner deviating from these, however, in this one the connecting conduits 14b and 15b are interconnected by a conduit 16, which in turn is connected to a medium con¬ tainer 31, which serves as a pressure-balancing container. When the piston is moved to the first operating state K2 (Figure 5B) , the seat is lowered all the way down from any position, since from the lower pressure space 22 there opens a flow con¬ nection via fittings 17a, 17b and 16, first via the unidirec¬ tional valves 13 and 12 and the connecting conduit 15a to the upper pressure space 23 of the working cylinder, and secondly via a pipe 19 to the fluid space 20 of the container 31. The seat is thus lowered mainly under the action of the figure- eight-shaped flow plotted in the figure. When the piston is moved to the second operating state Kl (Figure 5A) , the seat can in any height position be pumped upwards, the bidirectional piston pump acting in the manner described above, sucking fluid from the container 31 and forcing it through the connecting conduit 14a to the lower pressure space 22 of the working cyl¬ inder. In this there is thus no halfway raising or lowering of the seat, and thus the pressure prevailing in the container 31 is approximately the ambient pressure.

The embodiment of Figure 6 otherwise corresponds to the embodi¬ ment of Figure 5 except that it has no connecting conduit 16; the pressures of the connecting conduits 14b and 15b are com¬ bined in the container 31, to which the connecting conduits are led by pipes 37 and 38. Since one 38 of the pipes opens into the gas space 21 of the container and the other one into its fluid space 20, one side of the system is pneumatic and the other side hydraulic. In other respects the operation is as described in connection with Figure 5.

The embodiment of Figure 7 corresponds to the embodiment of Figure 4, with the exception that the upper pressure space 23 of the working cylinder is connected by a pipe 36 to the gas space 21 of the medium container 31. The operation corresponds to that of the previous ones. When the piston 4 is in the oper¬ ating state close to the first end 5, the seat 30 can be pumped upwards in any position, and when the piston is in the operat¬ ing state close to the second end 6, the seat is lowered owing to the opening flow passage of the conduits 14a, 16 and the unidirectional valves 13 and 12.

In the embodiments of the invention described above, and in particular in the description of their operation, the piston structures have been conceived as being ideal, i.e. the piston arms have been considered to be extremely thin, in which case the proportion of the piston arm diameter to the cylinder dia¬ meter has no effect; the operation is completely symmetrical with respect to it. Figures 8A and 8B depict an embodiment in which both the thickness of the piston arm of the working cyl¬ inder 1 and the thickness of the piston arm of the bidirection¬ al piston pump 2 have been taken advantage of; in this case the pump has a piston arm specifically only on one side. In other respects the coupling resembles the coupling in Figures 5A, B except that the unidirectional valves have been coupled in the reverse direction and the connecting conduit 16 has been con¬ nected by means of a pipe 19 to the fluid space 50 of the pres¬ sure accumulator 51. The unidirectional valves 10' and 12' coupled to the pipe fittings 7a and 8a at the two ends facing the working cylinder are thus in the forward direction relative to the flow towards the pump cylinder 3, and the other two unidirectional valves 11' and 13' coupled to the fittings 7b and 8b at the two ends are in the reverse direction relative to the flow towards the pump 2 cylinder. Furthermore, the piston arm 25' of the working cylinder is substantially thick, and preferably its cross-sectional area is in the order of magni¬ tude of one-half of the cross-sectional area of the working cylinder. This provides the advantage that, even though both of the sides of the working cylinder communicate via the bidirec¬ tional piston pump with the common pressure accumulator 51, there is produced as a resultant from the cross-sectional dif¬ ference a force vector FR, which acts on the piston of the working cylinder and thereby raises the seat 30. In the bidi¬ rectional piston pump the piston arm 9' has also been made so as to have a substantially thick cross-sectional area, and preferably its cross-sectional area is in the order of one-half the inner cross-sectional area of the pump cylinder 3. For example, by pressing the piston 4 in one direction, the person in the seat can move himself up over some distance. By return¬ ing the arm 43 in the reverse direction he will necessarily force fluid back from the pump cylinder 33 into the rest of the system, against the pressure provided by the pressure accumu¬ lator. This energy is stored in the pressure accumulator 51 by forcing into it a fluid amount which is the product of the cross-sectional area of the piston arm 9' and the distance of the movement. During the subsequent movement of the arm, one- half of the raising movement comes from pressing energy of the arm 43 and the other half comes as a flow from the pressure accumulator. Thus, in fact, both directions of movement of the arm 43 can be exploited, and the bidirectional piston pump is made to act as if in a double-action manner. In other respects the operation corresponds approximately to what has been de¬ scribed in connection with Figures 2-4.

Figure 9 further depicts one especially advantageous embodiment of the working cylinder 1. In it, the flow to the pressure space 23 on the side facing the piston arm 25 has been arranged to pass through a central cavity 26 in the piston arm, as indi¬ cated by arrows in the figure. The flow to the lower pressure space 22 on the opposite side of the piston 34 is directed through a connecting pipe 27 located inside the piston arm and extending through the piston. By this arrangement a flow of medium can be introduced into both pressure spaces 22 and 23 from one end of the cylinder, and specifically along its piston arm. As was already noted regarding Figure 9, the seat is at¬ tached to the piston arm 25 and the bidirectional piston pump 2 below the seat 30. Thus the upper end of the piston arm 25 can be attached directly to the bidirectional piston pump, and par¬ ticularly to its two connecting conduits 14a and 15a, when the embodiments of Figures 2, 3, 5 and 6 are implemented. Thus connecting pipes which are vulnerable to damage and cumbersome are entirely avoided in the structure.

Thus a number of different manners of operating the system can be achieved by using a bidirectional piston pump according to the invention and, for example, a double-action working cylin¬ der. The invention is not limited to the examples presented.

Claims

1. A bidirectional piston pump (2) controlling a working cylinder (1) or the like, the pump comprising a pump cylinder (3) which has ends (5, 6) closing it; this cylinder has a pis¬ ton (4) the piston arm (9) of which passes in a sealed manner through at least one of the ends to a power source; and in each end or its vicinity there are two pipe fittings (7a, 7b; 8a, 8b) for the medium, and each of these pipe fittings has a uni¬ directional valve (10, 11, 12, 13) for preventing backflow of the medium, characterized in that the cylinder (3) has, at a distance (E) from each end (5 and 6) and at a distance (V) from each other, a first pair of fittings (17a and 17b) and a second pair of fittings (18a and 18b), that the fittings of the first pair (17a and 17b) are coupled individually to the unidirec¬ tional valves (10 and resp. 11) of the first end (5) on the same side and the fittings of the second pair (18a and 18b) are coupled individually to the unidirectional valves (12 and resp. 13) of the second end (6) on the same side, the communications for the medium to the target points starting at maximum from these four connecting conduits (14a, 14b, 15a, 15b), and that the piston (4) has such a length (L) that with the entire ex¬ tent of its stroke length (I), at two different points (Kl, K2) of the cylinder length, it closes either in the first operating state (Kl) the first pair of fittings (17a, 17b) or, alterna¬ tively, in the second operating state (K2) the second pair of fittings (18a, 18b).

2. A bidirectional piston pump according to Claim 1, char¬ acterized in that in the two fittings (7a and 7b; 8a and 8b) at each end of the bidirectional piston pump, or close to the end, the unidirectional valves are coupled in the forward direction relative to the flow passing through the end section of the cylinder, in which case one unidirectional valve (10 and 12) in one cylinder end is in the reverse direction relative to the flow coming towards the cylinder and the other (11 and 13) is in the forward direction relative to the flow coming towards the cylinder.

3. A bidirectional piston pump according to Claim 1, char¬ acterized in that the distance (V) between the pairs of fit¬ tings (17a,b and 18a,b) is smaller than the piston length (L), in which case the piston (4) in the neutral position (K0) closes each pair of fittings, and that the connecting conduits (14a and 15a) of the unidirectional valves (10, 12) in the re¬ verse direction relative to the flow coming towards the bidi¬ rectional piston pump, or alternatively at least one of the conduits, have/has been coupled to a working cylinder (1) or the like.

4. A bidirectional piston pump according to Claim 2, char¬ acterized in that the connecting conduits (14b, 15b) coupled to the said unidirectional valves (11, 13) in the forward direc¬ tion are either interconnected (16) or connected further to a medium container (31) or led separate from each other (37, 38) each to a medium container (31; 51) or the like, or only one of the connecting conduits (37) is led to a medium container (51) or the like and the other one opens into the open air (35).

5. A bidirectional piston pump according to Claim 2, char¬ acterized in that the connecting conduits (14b and 15b) coupled to the said unidirectional valves (11, 13) in the forward di¬ rection are interconnected (16), and that one of the connecting conduits (14a or 15a) coupled to the said unidirectional valves (10, 12) in the reverse direction is connected to a medium container (51) .

6. A bidirectional piston pump according to any of the above claims, characterized in that the centering of the piston in the cylinder to the neutral position (K0) is carried out entirely or in part by means of a counter notch (49a) in the piston arm (9) or some other part of the operating mechanism and a counter-projection (49b) pressing into the notch by spring power.

7. The use of a bidirectional piston pump according to Claim 1 for raising and lowering a seat or the like by manual force, characterized in that the seat (30) is raised and lowered by a double-action working cylinder (1) and of those connecting conduits of the bidirectional piston pump which are connected to unidirectional valves (10, 12) in the reverse direction relative to the medium flow towards the cylinder, at least one (14a or 15a) is connected to one pressure side (22 or 23) of the working cylinder.

8. The use according to Claim 7, characterized in that the connecting conduit (14a) on the side of the first end (5) of the bidirectional piston pump is coupled to one pressure side (22) of the working cylinder and one connecting conduit (15a) on the side of the second end (6) is coupled to the other pres¬ sure side (23) of the working cylinder, and that the other two connecting conduits (14b, 15b) on the sides of the different ends are connected to the fluid spaces (50 and 20) of the pres¬ sure accumulator (51) and respectively the medium container (31).

9. The use according to Claim 7, characterized in that the connecting conduit (14a) on the side of the first end (5) of the bidirectional piston pump is coupled to one pressure side (22) of the working cylinder and one connecting conduit (15a) on the side of the second end (6) is coupled to the other pres¬ sure side (23) of the working cylinder, and that the second connecting conduit (14b) on the side of the first end is con¬ nected to the fluid space (50) of the pressure accumulator (51) and the connecting conduit (15b) on the side of the second end is connected to the outer air (35), in which case in the system made up of the pump (2) and the working cylinder (1) the medium overall on one side of the pistons (4 and 34) is gas and over¬ all on the other side of the pistons it is fluid.

10. The use according to Claim 7, characterized in that one connecting conduit (14a) on the side of the first end (5) of the bidirectional piston pump is coupled to one pressure side

(22) of the working cylinder and the connecting conduit (15a) on the side of the second end (6) is coupled to the fluid space (50) of the pressure accumulator (51), and that the other two connecting conduits (14b and 15b) on the sides of different ends are interconnected (16) and that the second pressure side

(23) of the working cylinder opens into the open air (35).

11. The use according to Claim 7, characterized in that those connecting conduits (14a, 15a) of the bidirectional pis¬ ton pump which are coupled to those unidirectional valves (10", 12') which are in the forward direction relative to the flow towards the cylinder are coupled to different pressure sides (22, 23) of the working cylinder, and that those connecting conduits (14b, 15b) which are coupled to those unidirectional valves (11', 13') which are in the reverse direction relative to the flow towards the cylinder are interconnected by a con¬ duit (16), and this conduit is coupled further to the fluid space (50) of the pressure accumulator (51), and that both the piston arm (25') of the working cylinder and the piston arm

(9' ) of the pump are substantially thick as compared with the cross-sectional areas of the respective cylinders, and prefer¬ ably the cross-sectional areas of the piston arms are each ap¬ proximately one-half the cross-sectional area of the respective cylinder.

12. The use according to any of Claims 8-11, characterized in that in the pressure accumulator (51) there has been ar¬ ranged such preliminary pressure (P) that under its action the pressure effective via the pairs of pipe fittings (14a and 14b; 15a and 15b) of the bidirectional piston pump keeps the person in the seat at a height of approximately halfway up the raising distance when the pump is being shifted from one operating state to another (Kl -> K2 or K2 -> Kl).

13. The use according to Claim 7, characterized in that the connecting conduit (14a) on the side of the first end (5) of the bidirectional piston pump is coupled to one pressure side (22) of the working cylinder and one connecting conduit on the side of the second end (6) is coupled either to the other pres¬ sure side (23) of the working cylinder or to a medium container (31), and that the other two connecting conduits (14b, 15b) on the sides of the different ends are connected either individu¬ ally to the medium container (31) or first to each other by means of a conduit (16) and then to the medium container and, when necessary, one pressure side (23) of the working cylinder is additionally connected to the medium container (31) by means of a pipe (36) .

14. The use according to any of Claims 7-13, characterized in that the flow from the bidirectional piston pump (2) to the second pressure space (23)^{^} on the side of the piston arm (25) is introduced via a hollow (26) piston arm, and to the first pressure space (22) on the opposite side of the piston (34) it is introduced by means of a connecting pipe (27) located inside the hollow piston arm and extending through the piston, and that the cavity (26) in the piston arm and the connecting pipe (27) are directly coupled to a bidirectional piston pump (2) attached to the seat-side end (28) of the working cylinder, while the other end of the working cylinder is connected to the supporting structures (40).

15. The use according to any of Claims 7-14, characterized in that the bidirectional piston pump (2) is located under the seat (30), that the piston arm (9) of the pump is connected to the hinged armrests (41) of the seat by transmission of a lever mechanism (42) so that the resting position of the armrest corresponds to the middle position (K0) of the piston (4) of the bidirectional piston pump, and reciprocal movement on its one side corresponds to the piston's second operating state (K2) by means of which the seat is lowered, and reciprocal movement on its other side corresponds to the piston's first operating state (Kl) by means of which the seat is raised.