WO1981001447A1

WO1981001447A1 - Apparatus generating a reciprocating motion

Info

Publication number: WO1981001447A1
Application number: PCT/SE1979/000239
Authority: WO
Inventors: P Toernqvist
Original assignee: P Toernqvist
Priority date: 1979-11-19
Filing date: 1979-11-19
Publication date: 1981-05-28
Also published as: JPS56501534A; EP0041062A1; DE2953895A1; GB2076477A

Abstract

The apparatus can be used in several applications, for instance for a pump, an engraving pen. Most apparatuses of this type call for precision-manufactured parts and consequently are expensive to manufacture. Other disadvantages of certain prior art apparatuses of this type is that they are difficult to start. The present invention is based on the insight that the surface of the part (1) performing the stroke motion must be small during the compression stage of the work stroke and large after the compression stage.

Description

Apparatus generating a reciprocating motion

This invention relates to an apparatus generating a reciprocating motion, the movable part of which is arranged to be driven, for instance in a casing or the like, in the forward direction by a pressurized fluid during simultaneous compression of a power accumulator, for example a spring, which after compression is arranged to impart to the moving part its return motion, the moving part with a small portion of its surface then being arranged sealed via a seal close to an inlet for the said pressurized fluid, whereby the said fluid during an initial stage of the work stroke works against the said small portion of the surface of the moving part, the duration in time of the initial stage being determined by the resistance of the said power accumulator to compression and by the pressure in said fluid.

Pumps, engraving pens and similar apparatuses with pulsating stroke motions are previously known in innumerable embodiments. Examples of apparatus of this kind are shown through the Swedish patent 316 985, the Swedish patent application 7503970-1, the Swedish published patent applications 319 085, 370 265 and 372 797, and the U.S. patents 2 919 650 and 3 402 667. Virtually all prior art apparatuses of this kind are expensive, complicated to manufacture, require high precision in manufacture and assembly and have a relatively short service life, one reason being because they have frictionating surfaces. An exception with regard to this characteristic is nevertheless made for the apparatus shown through the Swedish patent appliction 7503970-1, since this apparatus is of simple design and, because it is closest to certain embodiments of the present invention, it will be dealt with more closely hereinafter.

According to this latter patent application and more specifically according to Fig. 10 thereof, use is made of a sealing ring 6, guided and held by a circular flange 4a, said sealing ring being sited in the proximity of the outer parts of the piston 4 and far from the inlet aperture of the pressure medium. The disadvantage of this prior art embodiment is primarily that the surface of the piston 4 subjected to the pressure of the medium during the compression part of the stroke motion is large, whereby a relatively stout spring 13 is required, which in turn offers great resistance during the forward motion of the piston.

A further disadvantage of this prior art apparatus is the difficulty in getting the stroke motion to start.

The present invention endeavours to disclose a simple, inexpensive and uncomplicated apparatus without mutually frictionating surfaces and without starting difficulties, by means of which apparatus the driving pressure medium is appropriately separated from the medium the apparatus is able to influence. A further object -of the invention is to also utilize the expansion work generated by the pressure medium pump to drive the apparatus, since most prior art apparatuses of this type allow the pump work to take place under constant pressure from the drive medium.

The invention is based on the realization that the surface of that portion which performs the stroke motion must be small during the compression stage of the work stroke and large after the compression stage . The present invention is characterized - in order to solve the above problems - in the case of the type of apparatus mentioned in the preamble of the specification in that the pressure of the said fluid after the said initial stage, owing to the moving part in consequence of the development of pressure of the fluid being arranged to be removed from sealing close to the inlet, is moved to instead work against a surface of the moving part, which surface is significantly larger than the said small portion thereof, and in that the moving part after the initial stage is essentially sealed off against an outer member, for example against the casing, during at least an essential portion of the forward motion of the moving part. In order to elaborate the apparatus according to the present invention as a pump with separation between the drive fluid and the fluid which is to be pumped, it is appropriate if the said drive fluid exerts the pressure on only a portion of the moving part and in that a different, preferably separated portion of the moving part, is utilized to perform work and in that the said separated portion of the moving part is connected to an inlet and an outlet for a second fluid which is to be pumped with the aid of the apparatus, the said inlet and outlet being provided with valves openable by a pressure difference, the said pressure difference being generated by the motion of the moving part.

A closer description of the invention now follows, wherein reference is made to the accompanying drawings, of which Fig. 1-10 show different principal embodiments of the object according to the invention, Fig. 11 shows a special embodiment for viscous liquids, Fig. 12 shows a second practical, appropriate embodiment of the pump according to the invention, Fig. I3a-c illustrate the work stroke of the pump according to Fig. 12, Fig. 14 shows a modified -embodiment of the pump according to Fig. 12 with a low construction height, Fig. 15 shows an engraving pen which exploits the present invention but which may also serve as a model for other tools working with strokes, Fig. 16 shows a further embodiment of the pump according to the invention, Fig. 17a-b illustrate the work strokes of the pump according to Fig. 16, Fig. 18 shows a modified pump which also exploits the expansion work of the air, Fig. 19 and 20 illustrate the invention applied to a tenon saw and a pair of scissors, respectively, Fig. 21 shows the invention applied to a reciprocating toothbrush with rinsing, Fig. 22 shows the invention applied to a simple pressure booster, Fig. 23 and 24 illustrate different embodiments which also exploit the expansion of for exemple air, the said embodiments being applied to moving pistons, Fig. 25 shows an embodiment working with two balls which also exploit the expansion work and Fig. 26 and 27 illustrate two work positions for an embodiment of the inventive concept for operation with a long stroke length.

In the description, the same reference numerals are used in essential parts for equivalent or similar details. In fig. 1, reference numeral 1 designates a circular, rigid plate, which is placed opposite an inlet 2 fitted with a regulatable valve for a drive fluid, for example air or water, which has been put under pressure. The orifice of the inlet 2 is in this case fitted with a sealing ring 3 for instance of rubber, which in an appropriate manner is fixed in the position at the orifice illustrated in Fig. 1. The plate 1 is kept in contact against the sealing ring 2 by means of a spring 4 which works against the surface of the moving plate 1 which faces away from the sealing ring 3. The size of the plate 1 is so selected that it largely agrees with the inner space in a casing 10, which in turn is provided with an inlet 6 fitted with a pretensioned valve 8 for the fluid which is to be pumped and with an outlet 7 fitted with a pretensioned valve 9 for the fluid which is to be pumped and with an outlet 23 for the drive fluid. The embodiment illustrated in Fig. 1 functions in the following manner. The pressurized drive fluid is supplied through the inlet 2 and is compressed slightly in consequence of the opposing force of the spring 4. When this opposing force has been overcome, the contact between the sealing ring 3 and the plate 1 releases, whereby the pressure is permitted to act over an essentially larger area of the plate 1, whereby the latter forces the fluid which is to be pumped in the direction which is determined by the valves 8 and 9 in course of the forward - downward according to Fig. 1 - stroke. After the forward stroke when the pressure has fallen, the plate returns thanks to the compression force of the spring 4 to rest against the sealing ring 3, whereupon the cycle is repeated.

In the embodiment according to Fig. 2, the smaller surface against which the initial pressure from the drive medium works is elaborated as an outer, circular surface on a plate 1. Shown in Fig. 3 is an embodiment which is modified in comparison with Fig. 1 and 2, with a seal 3 sited centrally on a plate 1 with a post 18 to raise a valve ball 5. In addition, an expansion chamber 17 consisting of for example a rubber bladder may also be disposed with its inlet and outlet, respectively, sited between the seat of the valve ball 5 and the seal 3, which in this case is conical and seals against the orifice of the inlet 2. Shown in Fig. 4 is a further embodiment of the same inventive context with a plate 1 deviced as a piston in order to obtain a bigger second surface than in the embodiment according to Fig. 1-3. In this latter embodiment, there are two outlets 23 and 23'. The plate or piston 1 is, in this embodiment, provided with a centrally sited seal 3.

Utilized in the embodiment according to Fig. 5 is an elastic seal 3 of bowl shape, which interacts with an inclined surface in order to give a different development of pressure in that the seal 3 seals with its lips against the side wall during a part of the forward stroke. An outlet 23 runs in this case through the plate 1 and the chamber 17 thus acts as an expansion chamber.

In the embodiment according to Fig. 6, the seal 3 consists of an elastic plate and the piston I is here provided with an upper annular flange, which together with the elastic plate forms a seal. An outlet 23 may be sited some distance downwards in the wall of the casing 10 or in the bottom of the casing 10 as indicated by reference numeral 23'. In the latter case, the piston 1 must be provided with a through-going duct, as indicated by broken lines in Fig. 6. In the embodiment according to Fig. 7 , the spring 4 according to Fig. 1-6 has been replaced by a ring magnet 21 and the plate 1 must then be attracted by the said magnet, i.e. must be magnetically conductive. By this means, the advantage is obtained that the force of attraction will be greatest during the compression part of the work stroke. The plate 1 is also connected to a rod 22 from which a reciprocating motion can be extracted. The same condition naturally also applies for the embodiments according to Fig. 2, 4, 5, 5 and 8.

Fig. 8 illustrates an embodiment in which use is made of a ball 1 with essential weight and a rubber sleeve 3 as a seal. A rod 22 with for example a tip of cemented carbide which is controlled by the casing 10 is imparted by the ball 1 a stroke motion which can be utilized for percussive machining, for example as in an engraving pen, percussion hammer, slag chipper, etc. An outlet 23 may for instance be placed around the rod 22 to blow the workpiece clean. A more detailed description of the engraving pen is presented below in connection with Fig. 15. The ball 1 according to Fig. 8 can be arrested with the aid of for example a screw, not shown in the drawing, screwed through the casing 10 and located roughly in between the turning positions of the ball 1 and screwed in so that its outer tip is in the vicinity of the periphery of the ball 1 when this is moved. The stroke frequency can, thus, be changed.

Instead of using a cone 1 in the form of a ball according to Fig. 8, obviously some other shape can be utilized, for example a cylindrical, extended body. An extended body of this kind may advantageously be provided with a hole running through it which during the compression stage and the forward work stroke is covered in consequence of the positive pressure by a cover plate pretensioned by means of a weak spring. When the stroke has been completed, the said positive pressure disappears, whereby the weak spring is able to open the said hole so that the latter is opened during the return stroke. This outlined embodiment is, however, not shown in the drawings.

In the embodiment according to Fig. 9, the moving piston 1 is fitted with a flap valve 29 which is normally open during the return, whereby the return of the piston 1 is retarded considerably less.

In the embodiment according to Fig. 10, the plate 1 consists of an elastic and movable diaphragm 1, which is centrally fitted with a seal 3 or itself forms a seal against an inlet 2. In the periphery of the diaphragm are a plurality of equally spaced clamps 30, 30', which retain the diaphragm 1 but allow air or other drive medium to be permitted to flow out, i.e. an outlet for drive medium is formed as indicated by reference numeral 23. Via lever arm 11, the diaphragm 1 can be made to actuate a gearwheel 12, whereby the reciprocating motion is converted into a rotational motion. If it is desired to pump a viscous medium, such as syrup, a special embodiment of the invention will be required, the said embodiment being indicatively sketched in Fig. 11. The function, in principle, is as in the embodiment shown in Fig. 1 with the exception that the plate 1 is deviced as an elastic diaphragm. In addition, an arrestment spring 24 has been placed between the diaphragm 1 and the sealing cone 5 and a sealing plate 13 is placed between the latter. The embodiment functions in the following manner. When the spring 4 with associated diaphragm 1 moves slowly upwards according to the Figure in consequence of a viscous medium, for example syrup, being pumped into the inlet 6 and outlet 7, the spring 24 is tensioned in consequence of the entering, driving air pressure stands against the upper part of the sealing cone 5. The function is such that even if the diaphragm 4 moves upwards only negligibly or not at all, the valve cone 5 will nevertheless never be in equilibrium but will tip over in one direction or the other. This makes it possible to pump highly viscous media without the pump ceasing to work, which is often the case when other types of pumps are used.

Shown in Fig. 12 is another, practical embodiment of a pump according to the invention for pumping of a relatively volatile medium, for example petrol. An inlet 2 for a pressurized drive medium, for example compressed air, is sited centrally and the springs 4 and 4' are made for instance of rubber in one piece with the diaphragm 1 and 1' respectively and with flaps 6 and 6'. The flaps 7 and 7' are, in contrast, made as separate rubber items. The other parts of the pump are appropiately made of some plastic material. This embodiment is particularly appropriate in cases when an inexpensive pump is wanted, which is simple and cheap to manufacture and which requires few components. Illustrated in Fig. 13 are the various stages of the pump of which a) shows the compression of the spring 4', b) shows the subsequent compression of the spring 4 and the return of the spring 4' and finally c) shows the return of the spring 4. The arrows in these Figures a-c show the flow directions for the drive fluid and pumped medium respectively.

Shown in Fig. 14 is a further embodiment of the pump, wherein the springs 4, 4' which are required face each other and run overlapping and work against the wall 14. In this embodiment there are common inlets 6 and outlets 7 respectively for pumped medium to both chambers of the pump and the valves in the inlet and outlet respectively are made as flap valves 8, 8', 9, 9', which are mounted on the wall. Pressurized drive fluid, for example compressed air, is admitted via inlet 2, which is equipped with a ball valve 5 influencable by the diaphragm 1. The inlet 2 also communicates via an external line 51 with a second inlet 2' to the other side of the pump. The work cycle for this embodiment corresponds largely to that described in connection with the embodiment according to Fig. 12 and therefore will not be described in more detail. The advantage of the embodiment according to Fig. 14 is that the pump will have a low installation height and that the springs 4, 4' are exactly controlled, and that the pump is simple and thus inexpensive to manufacture. Instead of pressurized fluid, the various embodiments of the inventive object can obviously also be manually actuatable for instance via a lever arm. This possibility has not, however, been illustrated in the drawings.

The engraving pen, indicated in principle in Fig. 8, is shown in its practical embodiment in Fig. 15. The body 10 may for example consist of a suitable plastic material with incorporated lugs and duct for supplied fluid pressure and for the ball 1, the spring 4 and for the machining part 22, which appropriately is elaborated with a tip of cemented carbide. The ball 1 with the spring 4 and the processing part 22 are retained in position by a body 24 provided with external threads, which centrally may also be provided with suitable surfaces to keep the friction against the processing part 22 as low as possible and which is also provided peripherally with outlets for air. The dimensions of the apparatus shown in Fig. 15 may naturally vary as may individual parts in order to adapt the apparatus for other applications, for example a hewing hammer or slag chipper. This embodiment of engraving pen has i.a. the advantage that the percussive effect can easily be stopped by screwing in of the body 24 without the drive pressure at the inlet 2 having to be removed. The seal 3 is in this case elaborated in the form of a rubber sleeve, on the top of which an appropriate throttling plate 15 is placed.

There is also an interesting possibility of generating both a pumping action and a reciprocating motion on the part of a machining tool. For example, on the basis of the embodiment according to Fig. 8, it is possible to exploit a pressurized cleaning liquid as drive fluid but to allow the consumed liquid to flow out around the machining part 22 in order thereby to obtain a clean flushing - pulsating jet of liquid together with a mechanical machining action. The machining part 22 obviously does not have to be percussive but may also consist of a reciprocating and/or rotating brush or of a grinding device. An embodiment of this kind is described below in connection with Fig. 21.

The embodiment of the inventive concept which has been illustrated in Fig. 16 consists of an outer tube 25 in which a flexible hose 4 for instance of rubber is clamped so that it acts as a draw spring and presses the piston - the check valve - 1 towards the seat 16. On the inside, the piston 1 is elaborated as a seat for a check valve 19 and a check valve 20 is also provided in the other end of the hose 4. The mode of function is illustrated more closely in Fig. 17 where a) shows the compression of the hose 4 and b) shows the expansion of the hose 4. The drive pressure fluid enters through the inlet 2 and squeezes the hose 4 whereupon the pump medium leaves the hose 4 through the check valve 19. When the hose 4 is completely squeezed together, the pressure on the "annular area" between the piston 1 and the seat 16 increases until the thus achieved pulling force exceeds the pulling force attained in the hose 4. When the piston 1 ceases to seal against the seat 16, the pressure fluid penetrates behind the piston 1 and is then able - thanks to its several times bigger surface - to keep the piston 1 away from the seat 16 until the pressure in the hose 4 has fallen considerably. The hose 4 is then expanded and fresh pump medium enters into it via the valve 20 which has been raised in consequence of the pressure difference. In order also to exploit the expansion work of the pressure fluid, the latter can be conducted to a pump which is connected in parallel, as indicated by broken lines to the right in Fig. 16. The embodiment shown in Fig. 16 is appropriate for small pumps and if it is desired to exploit the embodiment for larger pumps, it is appropriate for the piston 1 and the check valve 19 to be separated and for a spring for instance of rubber to replace the pulling force of the hose 4.

Fig. 18 shows the invention applied as a hydraulic pump and the embodiment also exploits expansion of the drive air and works with two work surfaces of different sizes. Pressurized drive air or similar medium is admitted through an inlet 2 and the pressure extends over a flexible diaphragm 26 which thereby bends downwards and moves a piston 27 against the influence of a spring 28. When the piston 27 has reached its lower position according to Fig. 18, build-up of pressure occurs against the surface 32 of the inner cone 31, the pressure then becoming so great above the said surface 32 that it is able to overcome the counterforce of a further spring 33, whereupon the inner cone with its rod 34 makes a stroke, whereby a pump stroke occurs so that liquid is transported from an inlet 6 to an outlet 7. Discharge of drive fluid takes place at 23.

In Fig. 19 and 20, the invention is shown applied to a tenon saw and to a scissors respectively with the inlet for pressurized drive fluid marked with an arrow. For the rest, these embodiments should be fairly obviously and are therefore not explained in greater detail hereinafter.

Fig. 21 shows the invention applied to a toothbrush, in which the brush is driven to and fro and/or possibly also rotated at the same time as the drive fluid, for instance pressurized tap water, after driving the brush pulsating cleans the brushed place. The flow of drive water is marked with arrows in the Figure and the reciprocating motion of the brush is achieved in a corresponding manner as indicated in Fig. 5. A piston 35 seals against the wall of the casing 10. In the elongation of the piston 35 is a tube 36, which is connected at its other end with a housing 35 , in which the regulating mechanism according to Fig. 5 is placed with a holding spring 4. In the opposite end, the tube 36 emanates in the processing part, a tothbrush or similar device. When pressurized water, for instance from the water mains, is admitted in an inlet 2, a pressure is built up above a seal 3. This pressure is counteracted by a spring 4. The pressure above the piston 35 thereby rises and the piston moves downward until the pressure reaches equalibrium with the opposing force of a spring 38, whereupon the pressure over the seal 3 increases so that the force becomes bigger than the spring 4 is able to resist. The plate 1 with seal 3 are then moved downward so far that the pressure is exercised on a bigger surface and the water can flow in the direction indicated by the arrows, whereupon the spring 38 is subsequently able to press the piston 35 back to the starting position. This process is subsequently repeated.

The stroke motion is out of time with the spraying and the function is uninfluencable if an external force is applied against the brush - only the stroke frequency may possibly be influenced. Fig. 22 shows a simpler type of hydraulic pump which acts as a pressure booster and may be used for example as a paint sprayer. The pressure medium enters from the right in the Figure in the direction indicated by the arrow and the small surface on a conical upper part 3 against which a leaf spring 39 exerts pressure exists. The drive pressure works against an elastic diaphragm 1 with associated rod 22 and the said rod thus performs a downward stroke. When the diaphragm 1 has completed its stroke against the opposing force of a spring 4, the pressure increases and becomes so large over the small surface of the seal 3 that it overcomes the opposing force of the leaf spring 39 and opens, whereupon the pressure runs out over the large surface, whereby the drive pressure is evacuated around the edges. The diaphragm 1 thus first completes a stroke and the opens the outlet. In this case, the expansion work of the drive air is not utilized and instead discharge takes place after completion of the stroke. Fig. 23 illustrates how the expansion work of the air is utilized according to the present invention in a percussive tool. There are two moving parts, the outer 42 and the inner 43. Air or some other pressurized medium enters as indicated by the arrow and first so that the sleeve 42, which on account of the counter-pressure of the spring 41 is disposed towards its end position and which then thus closes off the inlet to the centre, is worked down against the action of the spring 41 and the sleeve 42 strikes in the neck of the impact part 44. When this has occurred, the drive air passes through the central duct whereupon the customary takes place, namely that the pressure first works against the small surface - i.e. upwards in the Figure and when the pressure has become sufficiently high, the inner piston 42 moves down. Evacuation takes place either at 23 or at 23'.

Within each work cycle, two strokes are thus obtained if the expansion work of the air or some other drive gas is exploited in this manner.

Shown in Fig. 24 is largely the same process as in Fig. 23 but with the difference that the embodiment is envisaged as a slag or rust chipper, both moving parts then striking directly against the material which is to be worked. Initially one part moves down in consequence of the fact that the air pressure is being exercised on an outer sleeve 45. When this has moved down and against the workpiece to be treated, the pressure increases further on an outer smaller annular surface on an inner sleeve 46 and when the pressure has become sufficiently high, it opens. Hereupon the pressure strikes down on a large surface of the inner sleeve 46, so that the inner sleeve 46 strikes down. At the same time, the outer sleeve 45 strikes back. The sleeves 45 and 46 thus strike alternately. This mode of function thus gives double stock removal at the same time as the expansion work of the air is also exploited.

The embodiment according to Fig. 25 corresponds largely to the embodiments according to Fig. 23 and 24, but here use is made in stead of two balls 47 and 48. This embodiment also works in a similar manner to the double-acting pumps according to Fig. 12 and 13. The right-hand ball strikes down first, since a spring 49 imparts different spring forces to the two bolls 47 and 48. The lever arm of the ball 47 for the spring 49 is shorter than the lever arm of the ball 48 for the spring 49. As a result of this fact, the right-hand ball according to Fig. 25 has greater spring resistance than that of the left-hand ball. On the other hand, the left-hand ball 48 has a small surface which resists the pressure and it then occurs that the right-hand ball 47 first goes down and when it has done this, the pressure on the left-hand ball increases still further and the latter therefore strikes down.

The mode of function is such that exerted in principle on the right-hand ball 47 is a force corresponding to the area of the entire ball 47. It is thus the diaphragm 50 which moves over the entire cross sectional surface of the ball 47 and over the left-hand ball 48 it is in principle only the area of. the ball 47 covered by the hole that resists the pressure. The latter ball 48 thus requires less spring force to resist than that required by the right-hand ball 47. The embodiment according to Fig. 26 and 27 may be used for instance to drive pressure boosters hydraulic pumps tooth sprayers, brushes, grinders, vibrators and percussive tools with long strokes.

Parts 51 and 56 according to Fig. 26 move leftwards in consequence of the compressed opposing force of the spring 64 and/or in consequence of the power developed by the pressure medium on the surace A (a certain amount of leakage is permitted).

Parts 51 and 56 cannot approach one another until the position for the outlet 68 is attained and permits evacuation of the medium in between them.

When the outlet 68 is reached, parts 51 and 56 rapidly approach one another, whereupon sealing occurs at the surface A and the ball 53 opens whereupon liquid or gas enters behind the piston 51 and presses this and part 56 towards the right according to Fig. 26. When the piston 51 reaches the stop 69, the piston 51 is retained, whereupon the sealing at the surface A ceases and the medium fills the cavity between the two parts 51 and 56, whereupon the part 56 is able to fill the part 51 in front of it and the cycle is repeated.

With the ball valves 71, 72 according to Fig. 27, a higher pressure is obtained. This higher pressure may either be extracted or else a mechanical motion may be extracted or both of these extracted. In the embodiment shown in Fig. 26, this is elaborated as a reciprocating toothbrush with a high pulsation frequency for both brushing and flushing. By providing the seal 58 with an extra lip 58a (see Fig. 27), it also becomes possible to separate the drive fluid and the fluid passing through 71, 72, and by this means an air-driven liquid pump, for example, may be obtained.

In the above description, the present invention has been indicated as applicable to various designs and it may also be used for example as a lifting jack which is driven by for example the exhaust gases from a vehicle. Other suitable examples are bilge pumps, drum pumps, laboratory pumps, spray pumps, cleaning sprayers, air humidifiers, chemical pumps, transfer pumps, hydraulic pumps, etc.

Claims

C L A I M S

1. Apparatus generating a reciprocating motion, the moving part (1) is arranged to be driven in the forward direction for example in a casing (10) or the like, by a pressurized fluid during simultaneous compression by a power accumulator (4), for example a spring, which after compression is arranged to impart to the moving part (1) its return motion, whereupon the moving part (1) by a small portion of its surface is arranged sealed via a seal (3) in the vicinity of an inlet (2) for the said pressurized fluid, whereby the said fluid during an initial stage of the work stroke works against the said small portion of the surface of the moving part (1), the duration of which initial stage is determined by the resistance of the said power accumulator (4) against compression and by the pressure in the said fluid, c h a r a c t e r i z e d in that the pressure of the said fluid after the said initial stage in consequence of the moving part (1) being arranged to be removed through build-up of pressure in the fluid from sealing near the inlet (2) will move so that it instead works against a surface of the moving part (i) which surface is significantly larger than the aforesaid small portion thereof and in that the moving part (1) after the initial stage is essentially sealed off against an outer member, for example against the casing (10), during at least a significant portion of the forward motion of the moving part (l).

2. The apparatus according to Claim 1, c h a r a c t e r i z e d in that the moving part is elaborated as a ball (1 in Fig. 8 and 15), a diaphragm (1 in Fig. 10-12, 14, 25 in Fig. 18 and in Fig. 19, 20, 22), a disc (1 in Fig. 1-3, 5 and 7), one or more pistons (1 in Fig. 4, 6, 9 and 16 and 51, 56 in Fig. 26 and 27) or a cone (i in Fig. 16).

3. The apparatus according to Claim 1 or Claim 2, c h a r a c t e r i z e d in that the said seal (3) consists of an elastic material, preferably rubber, and is sited between the said inlet (2) and the moving part (1) either close to the inlet (2) or on the moving part (1).

4. The apparatus according to any of the preceding Claims, c h a r a c t e r i z e d in that the moving part (1) is arranged to actuate a machining part (22) during at least a part of its motion.

5. The apparatus according to any of the preceding Claims, c h a r a c t e r i z e d in that the moving part (1) is arranged to actuate and preferably open a valve (5) during at least its return movement.

6. The apparatus according to Claim 4, c h a r a c t e r i z e d in that the said machining part (22) is connected to an inlet (6) and an outlet (7) for a second fluid which is to be pumped with the aid of the apparatus, said inlet and outlet (6 and 7) being provided with valves (8, 9) openable by a pressure difference, the said pressure difference being generated by the motion of the machining part (22).

7. The apparatus according to any of Claims 1, 2 or 4, c h a r a c t e r i z e d in that the reciprocating motion of the moving part is arranged to actuate a rod (22) with machining tip, for instance of cemented carbide, and in that the moving part preferably comprises a ball or the said ball (1 in Fig. 15).

8. The apparatus according to any of Claims 1, 2, 3, 4 or 6, c h a r a c t e r i z e d in that it is provided with a duct (51) running from the inlet (2) to a second inlet (2;), which interacts with a further moving part (1') which is arranged to be actuated by a further power accumulating member (4') for example a second spring, and which in turn also interacts with two further valves (8', 9'), openable by a pressure difference and in that the said power accumulating members (4, 4') are sited relatively overlapping and work against either side of a common wall (14),

9. The apparatus according to Claim 1 or 2, c h a r a c t e r i z e d in that the power accumulator is deviced as a tube (4 in Fig. 16) composed of elastic material which is connected with the movable part (1 in Fig. 16) which is elaborated as a hollow cone, in the interior of which a valve (19) is provided, the said cone (1) working against a seat (16) which is si.ted on the inside of an outer pipe (25) and in that the pressure of the said fluid is exerted on the inside of a pipe (4) consisting of elastical material, the end of which facing away from the cone (1) is also fitted with a valve (20), the said valves (19, 20) being arranged to be opened by a pressure difference.