Abstract:
A piston-chamber combination comprising an elongate chamber which is bounded by an inner chamber wall and comprising an elastically deformable piston comprising a container in said chamber to be sealingly movable relative to said chamber at least between first and second longitudinal positions of said chamber, said chamber having cross-sections of different cross-sectional areas at the first and second longitudinal positions of said chamber and at least substantially continuously different cross-sectional areas at intermediate longitudinal positions between the first and second longitudinal positions thereof, the cross-sectional area at the first longitudinal position being larger than the cross-sections area at the second longitudinal position, said piston including a piston body and sealing means supported by the piston body being designed to adapt itself and said sealing means to said different cross-sectional areas of said chamber during the relative movements of said pistion from the second longitudinal position through said intermediate longitudinal positions to the first longitudinal position of said chamber.

Description:
TECHNICAL FIELD 
   A piston-chamber combination comprising an elongate chamber which is bounded by an inner chamber wall, and comprising a piston in said chamber to be sealingly movable relative to said chamber wall at least between a first longitudinal position and a second longitudinal positions of the chamber, said chamber having cross-sections of different cross-sectional areas and different circumferential lengths at the first and second longitudinal positions and at least substantially continuously different cross-sectional areas and different circumferential length at intermediate longitudinal positions between the first and second longitudinal positions, the cross-sectional area and circumferential length at said second longitudinal position being smaller than the cross-sectional area and circumferential length at said first longitudinal position, said piston comprising a container which is elastically deformable thereby providing for different cross-sectional areas and circumferential lengths of the piston adaptating the same to said different cross-sectional areas and different circumferential lengths of the chamber during the relative movements of the piston between the first and second longitudinal positions through said intermediate longitudinal positions of the chamber. 
   Inflation valves are the Dunlop-Woods valve, the Sclaverand valve and the Schrader valve. These are in use for inflation of closed chambers, e.g. tyres of vehicles. The last two mentioned valve types have a spring-force operated valve core pin, and may be opened by depressing this pin for inflation and deflation of the chamber. Depressing the valve core pin may be done by manual activation, by a pressure of a fluid or by a valve actuator. The first two mentioned valve types may be opened by the pressure of a fluid alone, while the last mentioned one best may be opened by a valve actuator, as otherwise a high pressure may be needed to depress the pin. 
   BACKGROUND OF THE INVENTION 
   This invention deals with solutions for the problem of obtaining a friction force low enough to at least avoid jamming between a piston, specifically a piston comprising a container having an elastically deformable container wall, and the wall of an elongate chamber during the stroke, the chamber having different sizes of cross-sectional area&#39;s in its longitudinal direction, specifically those having different circumferential length&#39;s, when the piston is sealingly movable relative to said chamber. 
   A problem with embodiments of FIGS. 6, 8 and 9-12 (incl.) of WO 00/70227 may be that the piston may jam in the smaller cross-sections of the chamber having cross-sections with different circumferential sizes. Jamming may occur due to high frictional forces of the material of the wall of the pistons. These forces may mainly be created by the compression of the material(s) of the wall of the piston when the piston is moving from a first longitudinal position in the chamber having the biggest cross-sectional area to a second longitudinal position where the cross-sectional area and the circumferential size is smaller. FIGS. 1-3 (incl.) of the current patent application show examples of high frictional forces for non-moving pistons comprising a container in a non-moving chamber with or without internal pressure in the chamber. This results in high contact pressures between the piston and the wall of the chamber: jamming may occur. 
   A further problem may be that embodiments of pistons comprising a container of WO 00/70227 may leak their fluid, and thus may change their sealing capability. As in the solutions of the earlier mentioned problem for pistons comprising a container with an elastically deformable wall the sealing force is created by internal pressure, leakage may be an important problem. 
   OBJECT OF THE INVENTION 
   The object is to provide combinations of a piston and a chamber which may sealingly move when the chambers have different cross-sectional areas when the circumferences of these cross-sections are different. 
   SUMMARY OF THE INVENTION 
   In the first aspect, the invention relates to a combination of a piston and a chamber, wherein:
         the the piston is produced to have a production size of the container in the stress-free and undeformed state thereof in which the circumferential length of the piston is approximately equivalent to the circumferential length of said chamber at said second longitudinal position, the container being expandable from its production size in a direction transversally with respect to the longitudinal direction of the chamber thereby providing for an expansion of the piston from the production size thereof during the relative movements of the piston from said second longitudinal position to said first longitudinal position.       

   In the present context, the cross-sections are preferably taken perpendicularly to the longitudinal axis (=transversal direction). 
   Preferably, the second cross-sectional area is 95-15%, such as 95-70% of the first cross-sectional area. In certain situations, the second cross-sectional area is approximately 50% of the first cross-sectional area. 
   A number of different technologies may be used in order to realise this combination. These technologies are described further in relation to the subsequent aspects of the invention. 
   One such technology is one wherein the piston comprises an elastically deformable container comprising a deformable material. 
   In that situation, the deformable material may be a fluid or a mixture of fluids, such as water, steam, and/or gas, or a foam. This material, or a part thereof, may be compressible, such as gas or a mixture of water and gas, or it may be at least substantially incompressible. 
   This may be achieved by choosing the production size (stress free, undeformed) of the piston approximately equivalent to the circumferential length of the smallest cross-sectional area of a cross-section of the chamber, and to expand it when moving to a longitudinal position with a bigger 
   And this may be achieved by providing means to keep a certain sealing force from the piston on the wall of the chamber: by keeping the internal pressure of the piston on (a) certain predetermined level(s), which may be kept constant during the stroke. A pressure level of a certain size depends on the difference in circumferential length of the cross sections, and on the possibility to get a suitable sealing at the cross section with the smallest circumferential length. If the difference is big, and the appropriate pressure level too high to obtain a suitable sealing force at the smallest circumferential length, than change of the pressure may be arranged during the stroke. This calls for a pressure management of the piston. As commercially used materials are normally not tight, specifically when quite high pressures may be used, there must be a possibility to keep this pressure, e.g. by using a valve for inflation purposes. 
   When the cross-sectional area of the chamber changes, the volume of the container may change. Thus, in a cross-section through the longitudinal direction of the chamber the container may have a first shape at the first longitudinal direction and a second shape at the second longitudinal direction, the first shape may be different from the second shape. In one situation, at least part when the deformable material is compressible and the first shape has an area being larger than an area of the second shape. In that situation, the overall volume of the container changes, whereby the fluid should be compressible. Alternatively or optionally, the piston may comprise an enclosed space communicating with the deformable container, said enclosed space having a variable volume. In that manner, that the enclosed space may take up or release fluid when the deformable container changes volume. The change of the volume of the container is by that automatically adjustable. It may result in that the pressure in the container remains constant during the stroke. 
   Also, the enclosed space may comprise a spring-biased piston. This spring may define the pressure in the piston when changing its volume. 
   The volume of the enclosed space may be varied. In that manner, the overall pressure or maximum/minimum pressure of the container may be altered. 
   When the enclosed space is updivided into a first and a second enclosed space, the spaces further comprising means for defining the volume of the first enclosed space so that the pressure of fluid in the first enclosed space may relate to the pressure in the second enclosed space. The last mentioned space may be inflatable e.g. by means of a valve, preferably an inflation valve, such as a Schrader valve. 
   The defining means may be adapted to define the pressure in the first enclosed space at least substantially constant during the stroke. 
   However, any kind of pressure level may be defined by the defining means: e.g. a pressure raise may be necessary when the container expands to such a big cross-sectional area at the first longitudinal position that the contact area at the present pressure value may become too little, in order to maintain a suitable sealing. The defining means may be a pair of pistons, one in each enclosed space. The second enclosed space may be inflated to a certain pressure level, so that a pressure raise may be communicated to the first enclosed space, despite the fact that the volume of the second enclosed space may become bigger as well. This may be achieved by e.g. a combination of a piston and a chamber with different cross-sectional area&#39;s in the piston rod, which is comprised in the second enclosed space. A pressure drop may also be designable. 
   Pressure management of the piston may also be achieved by relating the pressure of fluid in the enclosed space with the pressure of fluid in the chamber. By providing means for defining the volume of the enclosed space communicating with the chamber. In this manner, the pressure of the deformable container may be varied in order to obtain a suitable sealing. For example, a simple manner would be to have the defining means adapted to define the pressure in the enclosed space to raise when the container is moving from the second longitudinal position to the first longitudinal position. In this situation, a simple piston between the two enclosed spaces may be provided (in order to not loose any of the fluid in the deformable container). 
   In fact, the use of this piston may define any relation between the pressures in that the chamber in which the piston translates may taper in the same manner as the main chamber of the combination. 
   The container may be inflated by a pressure source inside the piston, or an external pressure source, like one outside the combination and/or when the chamber is the source itself. All solutions demand a valve communicating with the piston. This valve may preferably an inflation valve, best a Schrader valve. This valve type has a spring biased valve core pin and closes independant of the pressure in the piston, and all kinds of fluids may flow through it. It may however also be another valve type, e.g. a check valve. 
   The container may be inflated through an enclosed space where the spring-biased tuning piston operates as a check valve. The fluid may flow through longitudinal ducts in the bearing of the piston rod of the spring biased piston, from a pressure source. 
   When the enclosed space is divided up into a first and second enclosed space, the inflation may be done with the chamber as the pressure source, as the second enclosed space may prohibit inflation through it to the first enclosed space. The chamber may have an inlet valve in the foot of the chamber. For inflation of the container an inflation valve, e.g. a Schrader valve may be used, together with an actuator. This may be an activating pin according to WO 96/10903 or WO 97/43570, or a valve actuator according to WO99/26002. The core pin of the valve is moving towards the chamber when closing. 
   When the working pressure in the chamber is higher than the pressure in the piston, the piston may be inflated automatically. 
   When the working pressure in the chamber is lower than the pressure in the piston than it is necessary to obtain a higher pressure by e.g. temporary closing the outlet valve in the foot of the chamber. When the valve is a Schrader valve which may be opened by means of a valve actuator according to WO 99/26002, this may be achieved by creating a bypass in the form of a channel by connecting the chamber and the space between the valve actuator and the core pin of the valve. This bypass may be openened (the Schrader valve may remain closed) and closed (the Schrader valve may open) and may be accomplished by e.g. a movable piston. The movement of this piston may be arranged manually e.g. by a pedal, which is turning around an axle from an inactive position to an active position and vice versa by an operator. It may also be achieved by other means like an actuator, initiated by the result of a pressure measurement in the chamber and/or the container. 
   Obtaining the predetermined pressure in the container may be achieved manually—the operator being informed by a manometer which is measuring the pressure in the container. It may also be achieved automatically, e.g. by a release valve in the container. It may also be achieved by a spring-force operated cap which closes the channel above the valve actuator when the pressure exceeds a certain predetermined pressure value. Another solution is that of a comparable solution of the closable bypass of the outlet valve of the chamber—a pressure measurement may be necessary in the container, which may steer an actuator which is opening and closing the bypass of the valve actuator according to WO 99/26002 of a Schrader valve of the container at a predetermined pressure value. 
   The above mentioned solutions are applicable too to any pistons comprising a container, incl. those shown in WO 00/65235 and WO 00/70227. 
   In order to reduce the longitudinal stretching of the piston comprising a container when subjected to the pressure of the chamber, and to allow the expansion in the transversal direction, the container may comprise an elastically deformable material comprising reinforcement means, such as a textile, fibre or other reinforcement means, preferably positioned in the wall of the container. The piston comprising a container may also comprise reinforcement means which are not positioned in the wall, e.g. a plurality of elastic arms, which may or may not be inflatable, connected to the wall of the container. When inflatable, the reinforcement functions also to limit the deformation of the wall of the container due to the pressure in the chamber. 
   Another aspect of the invention is one relating to a combination of a piston and a chamber, wherein: the chamber defines an elongate chamber having a longitudinal axis,
         the piston being movable in the chamber from a second longitudinal position to a first longitudinal position,   the chamber having an elastically deformable inner wall along at least part of the inner chamber wall between the first and second longitudinal positions,   the chamber having, at a first longitudinal position thereof when the piston is positioned at that position, a first cross-sectional area thereof and, at a second longitudinal position thereof when the piston is positioned at that position, a second cross-sectional area, the first cross-sectional area being larger than the second cross-sectional area, the change in cross-section of the chamber being at least substantially continuous between the first and second longitudinal positions when the piston is moved between the first and second longitudinal positions.       

   Thus, alternatively to the combinations where the piston adapts to the cross-sectional changes of the chamber, this aspect relates to a chamber having adapting capabilities. 
   Naturally, the piston may be made of an at least substantially incompressible material—or a combination may be made of the adapting chamber and an adapting piston—such as a piston according to the above aspects. 
   Preferably, the piston has, in a cross section along the longitudinal axis, a shape tapering in a direction from the first longitudinal position to the second longitudinal position. 
   A preferred manner of providing an adapting chamber is to have the chamber comprise:
         an outer supporting structure enclosing the inner wall and   a fluid held by a space defined by the outer supporting structure and the inner wall.
 
In that manner, the choice of fluid or a combination of fluids may help defining the properties of the chamber, such as the sealing between the wall and the piston as well as the force required etc.
       

   It is clear that depending on from where the combination is seen, one of the piston and the chamber may be stationary and the other moving—or both may be moving. This has no impact on the functioning of the combination. 
   The piston may also slide over an internal and an external wall. The internal wall may have a taper form, while the external wall is cylindrical. 
   Naturally, the present combination may be used for a number of purposes in that it primarily focuses on a novel manner of providing an additional manner of tailoring translation of a piston to the force required/taken up. In fact, the area/shape of the cross-section may be varied along the length of the chamber in order to adapt the combination for specific purposes and/or forces. One purpose is to provide a pump for use by women or teenagers—a pump that nevertheless should be able to provide a certain pressure. In that situation, an ergonomically improved pump may be required by determining the force which the person may provide at which position of the piston—and thereby provide a chamber with a suitable cross-sectional area/shape. 
   Another use of the combination would be for a shock absorber where the area/shape would determine what translation a certain shock (force) would require. Also, an actuator may be provided where the amount of fluid introduced into the chamber will provide differing translation of the piston depending on the actual position of the piston prior to the introducing of the fluid. 
   In fact, the nature of the piston, the relative positions of the first and the second longitudinal positions and the arrangement of any valves connected to the chamber may provide pumps, motors, actuators, shock absorbers etc. with different pressure characteristics and different force characteristics. 
   The preferred embodiments of the combination of a chamber and a piston have been described as examples to be used in piston pumps. This however should not limit the coverage of this invention to the said application, as it may be mainly the valve arrangement of the chamber besides the fact which item or medium may initiate the movement, which may be descisive for the type of application: pump, actuator, shock absorber or motor. In a piston pump a medium may be sucted into a chamber which may thereafter be closed by a valve arrangement. The medium may be compressed by the movement of the chamber and/or the piston and thereafter a valve may release this compressed medium from the chamber. In an actuator a medium may be pressed into a chamber by a valve arrangement and the piston and/or the chamber may be moving, initiating the movement of an attached device. In shock absorbers the chamber may be completely closed, wherein a compressable medium may be compressed by the movement of the chamber and/or the piston. In the case a non-compressable medium may be positioned inside the chamber, e.g. the piston may be equipeed by several small channels which may give a dynamic friction, so that the movement may be slowed down. 
   Further the invention may also be used in propulsion applications where a medium may be used to move a piston and/or a chamber, which may turn around an axis as e.g. in a motor. The principles according this invention may be applicable on all above mentioned applications. The principles of the invention may also be used in other pneumatic and/or hydraulic applications than the above mentioned piston pumps. 
   The various embodiments described above are provided by way of illustration only and should not be construed to limit the invention. Those skilled in the art will readily recognize various modifications, changes, and combinations of elements which may be made to the present invention without strictly following the exemplary embodiments and applications illustrated and described herein, and without departing from the true spirit and scope of the present invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the following, preferred embodiments of the invention will be described with reference to the drawings wherein: 
       FIG. 1A  shows a longitudinal cross-section of a non-moving piston in a non-pressurized cylinder at the first longitudinal position—the piston is shown in its production size, and when pressurized. 
       FIG. 1B  shows the contact pressure of the pressurized piston of  FIG. 1A  on the wall of the cylinder. 
       FIG. 2A  shows a longitudinal cross-section of the piston of  FIG. 1A  in a cylinder at the first (right) and second (left) longitudinal position, the piston is non-pressurized. 
       FIG. 2B  shows the contact pressure of the piston of  FIG. 2A  on the wall of the cylinder at the second longitudinal position. 
       FIG. 2C  shows a longitudinal cross-section of the piston of  FIG. 1A  in a cylinder at the second longitudinal position, the piston is pressurized on the same pressure level as the one of FIG.  1 A—also is shown the piston at the first longitudinal position (production) size. 
       FIG. 2D  shows the contact pressure of the piston of  FIG. 2C  on the wall of the cylinder at the second longitudinal position. 
       FIG. 3A  shows a longitudinal cross-section of a piston of  FIG. 1A  in a cylinder at the first longitudinal position shown in its production size, and pressurized while the piston is subjected to a pressure in the chamber. 
       FIG. 3B  shows the contact pressure of the piston of  FIG. 3A  on the wall of the cylinder. 
       FIG. 4A  shows a longitudinal cross-section of a non-moving piston according to the invention in a non-pressurized cylinder at the second longitudinal position, shown in its production size, and when pressurized to a certain level. 
       FIG. 4B  shows the contact pressure of the piston of  FIG. 4A  on the wall of the cylinder. 
       FIG. 4C  shows a longitudinal cross-section of a non-moving piston according to the invention in a cylinder at the second longitudinal position, shown in its production size, and at the first longitudinal position when pressurized to the same level as that of  FIG. 4A . 
       FIG. 4D  shows the contact pressure of the piston of  FIG. 4C  on the wall of the cylinder. 
       FIG. 5A  shows a longitudinal cross-section of the piston of  FIG. 4A  in a non-pressurized cylinder at the second longitudinal position, the piston with its production size, and when pressurized. 
       FIG. 5B  shows the contact pressure of the pressurized piston of  FIG. 5A  on the wall of the cylinder. 
       FIG. 5C  shows a longitudinal cross-section of the piston of  FIG. 4A  in a cylinder at the second longitudinal position, the piston with its production size, and when pressurized, subjected to a pressure from the cylinder. 
       FIG. 5D  shows the contact pressure of the piston of  FIG. 5C  on the wall of the cylinder. 
       FIG. 6A  shows a longitudinal cross-section of a chamber with fixed different areas of the transversal cross-sections and a first embodiment of the piston comprising a textile reinforcement with radially-axially changing dimensions during the stroke—the piston arrangement is shown at the beginning, and at the end of a stroke—pressurized—where it has unpressurized its production size. 
       FIG. 6B  shows an enlargement of the piston of  FIG. 6A  at the beginning of a stroke. 
       FIG. 6C  shows an enlargement of the piston of  FIG. 6A  at the end of a stroke. 
       FIG. 7A  shows a longitudinal cross-section of a chamber with fixed different areas of the transversal cross-sections and a second embodiment of the piston comprising a fiber reinforcement (‘Trellis Effect’) with radially-axially changing dimensions of the elastic material of the wall during the stroke—the piston arrangement is shown at the beginning, and at the end of a stroke—pressurized—where it has unpressurized its production size. 
       FIG. 7B  shows an enlargement of the piston of  FIG. 7A  at the beginning of a stroke. 
       FIG. 7C  shows an enlargement of the piston of  FIG. 7A  at the end of a stroke. 
       FIG. 8A  shows a longitudinal cross-section of a chamber with fixed different areas of the transversal cross-sections and a third embodiment of the piston comprising a fiber reinforcement (no ‘Trellis Effect’) with radially-axially changing dimensions during the stroke—the piston arrangement is shown at the beginning, and at the end of a stroke where it has its production size. 
       FIG. 8B  shows an enlargement of the piston of  FIG. 8A  at the beginning of a stroke. 
       FIG. 8C  shows an enlargement of the piston of  FIG. 8A  at the end of a stroke. 
       FIG. 8D  shows a top view of the piston of  FIG. 8A  with a reinforcement in the wall in planes through the central axis of the piston—left: at the first longitudinal position, right: at the second longitudinal position. 
       FIG. 8E  shows a top view of the piston of  FIG. 8A  having reinforcements in the skin in planes partly through the central axis and partly outside the central axis—left: at the first longitudinal position, right: at the second longitudinal position. 
       FIG. 9A  shows a longitudinal cross-section of a chamber with fixed different areas of the transversal cross-sections and a fourth embodiment of the piston comprising an “octopus” device, limiting stretching of the container wall by tentacles, which may be inflatable—the piston arrangement is shown at the beginning, and at the end of a stroke where it has its production size. 
       FIG. 9B  shows an enlargement of the piston of  FIG. 9A  at the beginning of a stroke. 
       FIG. 9C  shows an enlargement of the piston of  FIG. 9A  at the end of a stroke. 
       FIG. 10A  shows the embodiment of  FIG. 6  where the pressure inside the piston may be changend by inflation through e.g. a Schrader valve which is positioned in the handle and/or e.g. a check valve in the piston rod, and where an enclosed space is balancing the change in volume of the piston during the stroke. 
       FIG. 10B  shows instead of an inflation valve, a bushing enabling connection to an external pressure source. 
       FIG. 10C  shows details of the guidance of the rod of the check valve. 
       FIG. 10D  shows the flexable piston of the check valve in the piston rod. 
       FIG. 11A  shows the embodiment of  FIG. 6  where the pressure inside the piston may be maintained constant during the stroke and where a second enclosed space may be inflated through a Schrader valve which is positioned in the handle, communicating with the first enclosed space through a piston arrangement—the piston may be inflated by a Schrader valve+ valve actuator arrangement with the pressure of the chamber as pressure source, while the outlet valve of the chamber may be manually controlled by a turnable pedal. 
       FIG. 11B  shows a piston arrangement and its bearing where the piston arrangement is communicating between the second and the first enclosed space. 
       FIG. 11C  shows a alternative piston arrangement adapting itself to the changing cross-sectional area&#39;s in its longitudinal direction inside the piston rod. 
       FIG. 11D  shows an enlargement of the inflation arrangement of the piston of  FIG. 11A  at the end of the stroke. 
       FIG. 11E  shows an enlargment of the bypass arrangement for the valve actuator for closing and opening of the outlet valve. 
       FIG. 11F  shows an enlargement of an automatic closing and opening arrangement of the outlet valve—a comparable system is shown for optaining a predetermined pressure value in the piston (dashed). 
       FIG. 11G  shows an enlargement of an inflation arrangement of the piston of  FIG. 11A , comprising a combination of a valve actuator and a spring force operated cap, which makes it possible to automatically inflate the piston from the chamber to a certain predetermined pressure. 
       FIG. 12  shows an arrangement where the pressure in the container may depend of the pressure in the chamber. 
       FIG. 13A  shows a longitudinal cross-section of a chamber with a flexible wall having different areas of the transversal cross-sections and a piston with fixed geometrical sizes—the arrangement of the combination is shown at the beginning and at the end of the pump stroke. 
       FIG. 13B  shows an enlargement of the arrangement of the combination at the beginning of a pump stroke. 
       FIG. 13C  shows an enlargement of the arrangement of the combination during a pump stroke. 
       FIG. 13D  shows an enlargement of the arrangement of the combination at the end of a pump stroke. 
       FIG. 14  shows a longitudinal cross-section of a chamber having a flexible wall with different areas of the transversal cross-sections and a piston with variable geometrical sizes—the arrangement of the combination is shown at the beginning, during a pump stroke and at the end of the stroke. 
   

   DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1A  shows the longitudinal cross-section of a non-moving non-pressurized piston  5  at the first longitudinal position of a non-pressurized chamber  1 , having at that position a circular cross-sections with a constant radius. The piston  5  may have a production size approximately the diameter of the chamber  1  at this first longitudinal position. The piston  5 * when pressurized to a certain pressure level is shown. The pressure inside the piston  5 * results in a certain contact length. 
     FIG. 1B  shows the contact pressure of the piston  5 * of  FIG. 1A . The piston  5 * may jam at this longitudinal position. 
     FIG. 2A  shows the longitudinal cross-section of a non-moving non-pressurized piston  5  at the first longitudinal position and the piston  5 ′ at the second longitudinal position of a non-pressurized chamber  1 , the chamber having circular cross-sections with a constant radius at both the first and second longitudinal positions. The piston  5  may have a production size approximately the diameter of the chamber  1  at this first longitudinal position. The piston  5 ′ shows the piston  5 , non-pressurized positioned into the smaller cross-section of the second longitudinal position. 
     FIG. 2B  shows the contact pressure of the piston  5 ′ on the wall of the chamber at the second longitudinal position. The piston  5 ′ may jam at this longitudinal position. 
     FIG. 2C  shows the longitudinal cross-section of a non-moving non-pressurized piston  5  at the first longitudinal position and the piston  5 ′ at the second position of a non-pressurized chamber  1 , the chamber having circular cross-sections with a constant radius at both the first and second longitudinal positions. The piston  5  may have a production size approximately the diameter of the chamber  1  at this first longitudinal position. The piston  5 ′* shows the piston  5 , pressurized to the same level as the one of  FIG. 1A , positioned into the smaller cross-section of the second longitudinal position. 
     FIG. 2D  shows the contact pressure of the piston  5 ′* on the wall of the chamber at the second longitudinal position. The piston  5 ′* may jam at this longitudinal position: the friction force may be 72 kg. 
     FIG. 3A  shows the piston  5  of  FIG. 1A , and the deformed piston  5 ″* when pressurized to the same pressure level of that of piston  5 * of  FIG. 1A . The deformation is caused by the pressure in the chamber  1 *, when the piston may not have means to limit the stretching, which is mainly in the meridian (longitudinal direction of the chamber) direction. 
     FIG. 3B  shows the contact pressure. The piston  5 ″* may jam at this longitudinal position. 
     FIG. 4A  shows the longitudinal cross-section of a piston  15  at the second longitudinal position of a non-pressurized chamber  10 , having a circular cross-section. The piston  15  may have a production size approximately the diameter of the chamber  10  at this second longitudinal position. Piston  15 ′* shows the deformed piston  15  pressurized to a certain level. The deformation is due to the fact that the Young&#39;s modulus in the hoop direction (in a cross-sectional plane of the chamber) is choosen lower than that in the meridian direction (in the longitudinal direction of the chamber). 
     FIG. 4B  shows the contact pressure on the wall of piston  15 ′*. This results in an appropriate friction force (4.2 kg), and suitable sealing. 
     FIG. 4C  shows the longitudinal cross-section of piston  15  at the second longitudinal position (production size) of the non-pressurized chamber  10 , and when pressurized  15 ″* at the first longitudinal position—the piston  15 ″* may have the same pressure as when the piston  15 ′* is positioned at the second longitudinal position of the chamber  10  ( FIG. 4A ). Also here is the deformation in the hoop—and meridian direction different. 
     FIG. 4D  shows the contact pressure on the wall of piston  15 ″*. This results in an appropriate friction force (0.7 kg) and a suitable sealing. 
   Therefore, it is possible to sealingly move a piston comprising an elastically deformable container from a smaller to a bigger cross-sectional area while having the same internal pressure—within the limitations for the diameters of the cross-sections which were chosen in this experiment. 
     FIG. 5A  shows the longitudinal cross-section of the piston  15  (production size) and the piston  15 ′* at the second longitudinal position of the non-pressurized chamber  10 . The piston  15 ′* is showing the deformed structure of piston  15  when the piston  15  is pressurized. The piston  15 ,  15 ′* have been attached at the lower end to an imaginary piston rod in order to prevent piston movement during application of the chamber pressure. 
     FIG. 5B  shows the contact pressure of the piston  15 ′* of  FIG. 5A . This is low enough to allow movement (friction force 4.2 kg) and suitable for sealing. 
     FIG. 5C  shows the longitudinal cross-section of the piston  15  (production size) and  15 ″* pressurized and deformed by the chamber pressure at the second longitudinal position of the pressurized chamber  10 *. The piston  15 ,  15 ′* have been attached at the lower end to an imaginary piston rod in order to prevent piston movement during the application of the chamber pressure. The deformed piston  15 ″* is approximately twice as long as the undeformed piston  15 . 
     FIG. 5D  shows the contact pressure of the piston  15 ″* of  FIG. 5C . This is low enough to allow movement (friction force 3.2 kg) and suitable for sealing. 
   Therefore, when applying a chamber pressure on a piston comprising a pressurized elastically deformable container, it is possible to sealingly move as well, at least at the longitudinal position with the smallest cross-sectional area. The stretching due to the applied chamber force is big and it may be necessary to limit this. 
     FIGS. 6-8  deal with the limitation of the stretching of the wall of the piston. This comprises a limitation of the stretching in the longitudinal direction when the piston is subjected to a pressure in the chamber, and to allow expansion in the transversal direction, when moving from the second to the first longitudinal position. 
   The stretching in the longitudinal direction of the wall of the container-type piston may be limited by several methods. It may be done by a reinforcement of the wall of the container by using e.g. textile and/or fiber reinforcement. It may also be done by an inside the chamber of the container positioned expanding body with a limitation for its expansion, while it is connected to the wall of the container. Other methods may be used, e.g. pressure management of a chamber in-between two walls of the container, pressure management of the space above the container etc. 
   The expansion behaviour of the wall of the container may be depending on the type of the stretching limitation used. Moreover, the keeping of the piston which is moving over the piston rod, while expanding, may be guided by a mechanical stop. The positioning of such a stop may be depending on the use of the piston-chamber combination. This may also be the case for the guidance of the container over the piston rod, while expanding and/or sujected to external forces. 
   All kinds of fluids may be used—a combination of a compressable and a non-compressable medium, a compressable medium only or a non-compressable medium only. 
   As the change of the size of the container may be substantial from the smallest cross-sectional area, where it has its production size, and expanded at the biggest cross-sectional area, a communication of the chamber in the container with a first enclosed space, e.g. in the piston rod may be necessary. In order to keep the pressure in the chamber, the first enclosed space may be pressurized as well, also during the change of the volume of the chamber of the container. Pressure management for at least the first enclosed space may be needed. 
     FIG. 6A  shows a longitudinal cross-section of the chamber  186  with a concave wall  185  and an inflatable piston comprising a container  208  at the beginning (=first longitudinal position in the chamber  186 ) and the same  208 ′ at the end of a stroke (=second longitudinal position in the chamber  186 ). Central axis of the chamber  186  is  184 . The container  208 ′ shows its production size, having a textile reinforced  189  in the skin  188  of the wall  187 . During the stroke, the wall  187  of the container expands until a stop arrangement, which may be the textile reinforcement  189  and/or a mechanical stop  196  outside the container  208  and/or another stop arrangement stops the movement during the stroke. And thus the expansion of the container  208 . Depending on the pressure in the chamber  186 , there still may occur a longitudinal stretching of the wall of the container, due to pressure in the chamber  186 . The main function however of the reinforcement is to limit this longitudinal stretching of the wall  187  of the container  208 . During the stroke the pressure inside the container  208 , 208 ′ may remain constant. This pressure depends on the change in the volume of the container  208 , 208 ′, thus on the change in the circumferential length of the cross-sections of the chamber  186  during the stroke. It may also be possible that the pressure changes during the stroke. It may also be possible that the pressure changes during the stroke, depending or not of the pressure in the chamber  186 . 
     FIG. 6B  shows a first embodiment of the expanded piston  208  at the beginning of a stroke. The wall  187  of the container is build up by a skin  188  of a flexable material, which may be e.g. a rubber type or the like, with a textile reinforcement  189 , which allows expansion. The direction of the textile reinforcement in relation to the central axis  184  (=braid angle) is different from 54°44′. The change of the size of the piston during the stroke results not necessarily in an identical shape, as drawn. Due to the expansion the thickness of the wall of the container may be smaller than that of the container as produced when positioned attend of the stroke (=second longitudinal position). An impervious layer  190  inside the wall  187  may be present. It is tightly squeezed ( 193 ) in the cap  191  in the top and the cap  192  in the bottom of the container  208 , 208 ′. Details of said caps are not shown and all kinds of assembling methods may be used—these may be capable to adapt themselves to the changing thickness of the wall of the container. Both caps  191 , 192  can translate and/or rotate over the piston rod  195 . These movements may be done by various methods as e.g. different types of bearings which are not shown. The cap  191  in the top of the container may move upwards and downwards. The stop  196  on the piston rod  195  outside the container  208  limits the upwards movement of the container  208 . The cap  192  in the bottom may only move downwards because the stop  197  prevent a movement upwards—this embodiment may be thought to be used in a piston chamber device which has pressure in chamber  186  beneath the piston. Other arrangements of stops may be possible in other pump types, such as double working pumps, vacuum pumps etc. and depends solely of the design specifications. Other arrangements for enabling and/or limiting the relative movement of the piston to the piston rod may occur. The tuning of the sealing force may comprise a combination of an incompressable fluid  205  and a compressable fluid  206  (both alone are also a possibility) inside the container, while the chamber  209  of the container may communicate with a second enclosed space  210  comprising a spring-force operated piston  126  inside the piston rod  195 . The fluid(s) may freely flow through the wall  207  of the piston rod through the hole  201 . It may be possible that the second enclosed space is communicating with a third chamber (see  FIG. 11A , while the pressure inside the container also may be depending on the pressure in the chamber  186 . The container may be inflatable through the piston rod  195  and/or by communicating with the chamber  186 . O-rings or the like  202 ,  203  in said cap in the top and in said cap in the bottom, respectively seal the caps  191 , 192  to the piston rod. The cap  204 , shown as a screwed assembly at the end of the piston rod  195  thighthens said piston rod. Comparable stops may be positioned elsewhere on the piston rod, depending on the demanded movement of the wall of the container. The contact area between the wall of the container and the wall of the chamber is  198 . 
     FIG. 6C  shows the piston of  FIG. 6B  at the end of a pump stroke, where it has its production size. The cap  191  in the top is moved over a distance a′°from the stop  196 . The spring-force operated valve piston  126  has been moved over a distance b′. The bottom cap  192  is shown adjacent to the stop  197 —when there is pressure in the chamber  186 , then the bottom cap  192  is pressed against the stop  197 . The compressable fluid  206 ′°and the non-compressable fluid  205 ′. The contact area  198 ′°between the container  208 ′°and the wall of the chamber at the second longitudinal position. 
     FIG. 7A  shows a longitudinal cross-section of the chamber  186  with a concave wall  185  and an inflatable piston comprising a container  217  at the first longitudinal position of the chamber and the same  217 ′°at the second longitudinal position. The container  217 ′°shows its production size, having a fiber reinforced  219  in the skin  216  of the wall  218  according to the ‘Trellis Effect’. During the stroke, the wail  218  of the container expands until a stop arrangement, which may be the fiber reinforcement  219  and/or a mechanical stop  214  inside the container and/or another stop arrangement stops the movement during the stroke. And thus stops the expansion of the wall  218  of the container  217 . The main function of the fiber reinforcement is to limit the longitudinal stretching of the wall  218  of the container  217 . During the stroke the pressure inside the container  217 , 217 ′°may remain constant. This pressure depends on the change in the volume of the container  217 , 217 ′, thus on the change in the circumferential length of the cross-sections of the chamber  186  during the stroke. It may also be possible that the pressure changes during the stroke, depending or not of the pressure in the chamber  186 . The contact area  211  between the container  217  and the wall of the chamber at the first longitudinal position. The Trellis Effect is where a decrease of the transverse sectional area of the chamber causes a decrease in the size of the inflatable body(—chamber) in that direction and a three dimensional reduction is possible due to the fiber architecture, where fibres are shearing layer wise independently from each other. See U.S. Pat. No. 6,978,711. 
     FIG. 7B  shows a second embodiment of the expanded piston  217  at the beginning of a stroke. The wall  218  of the container is build up by a skin  216  of a flexible material, which may be e.g. a rubber type or the like, with a fiber reinforcement  219 , which allows expansion of the container wall  218 , and thus the direction of the fibers in relation to the central axis  184  (=braid angle) may be different from 54°44′. Due to the expansion the thickness of the wall of the container may be smaller, but not necessarily very different than that of the container as produced when positioned at the end of the stroke (=second longitudinal position). An impervious layer  190  inside the wall  218  may be present. It is tightly squeezed in the cap  191  in the top and the cap  192  in the bottom of the container  217 , 217 ′. Details of said caps are not shown and all kinds of assembling methods may be used—these may be capable to adapt themselves to the changing thickness of the wall of the container. Both caps  191 , 192  can translate and/or rotate over the piston rod  195 . These movements may be done by various methods as e.g. different types of bearings which are not shown. The cap  191  in the top can move upwards and downwards until stop  214  limits this movement. The cap  192  in the bottom can only move downwards because the stop  197  prevent a movement upwards—this embodiment is thought to be used in a piston chamber device which has pressure in chamber  186 . Other arrangements of stops may be possible in other pump types, such as double working pumps, vacuum pumps etc. and depends solely of the design specifications. Other arrangements for enabling and/or limiting the relative movement of the piston to the piston rod may occur. The tuning of the sealing force may comprise a combination of an incompressable fluid  205  and a compressable fluid  206  (both alone are also a possibility) inside the container, while the chamber  215  of the container  217 , 217 ′may communicate with a second enclosed space  210  comprising a spring-force operated piston  126  inside the piston rod  195 . The fluid(s) may freely flow through the wall  207  of the piston rod through the hole  201 . It may be possible that the second enclosed space  210  is communicating with a third chamber (see  FIG. 10 ), while the pressure inside the container also may be depending on the pressure in the chamber  186 . The container may be inflatable through the piston rod  195  and/or by communicating with the chamber  186 . O-rings or the like  202 ,  203  in said cap in the top and in said cap in the bottom, respectively seal the caps  191 , 192  to the piston rod. The cap  204 , shown as a screwed assembly at the end of the piston rod  195  thighthens said piston rod. 
     FIG. 7C  shows the piston of  FIG. 7B  at the end of a pump stroke, where it has its production size. The cap  191  is moved over a distance c′ from the stop  216 . The spring-force operated valve piston  126  has been moved over a distance d′. The bottom cap  192  is shown adjacent to the stop  197 —if there is pressure in the chamber  186 , than the  192  is pressed against the stop  197 . The compressable fluid  206 ′ and the non-compressable fluid  205 ′. 
   FIGS.  8 A,B,C show an inflatable piston comprising a container  228  at the beginning and  228 ′ at the end of a stroke. The production size is that of piston  228 ′ at the second longitudinal position in the chamber  186 . The construction of the piston may be identical with that of FIGS.  7 A,B,C with the exception that the reinforcement comprises of any kind of reinforcement means which may be bendable, and which may ly in a pattern of reinforcement ‘colums’ which do not cross each other. This pattern may be one of parallel to the central axis  184  of the chamber  186  or one of where a part of the reinforcement means may be in a plane through the central axis  184 . 
     FIG. 8B  shows the wall  221  with the skin  222  and  224 . The reinforcement means  227 . The contact area  225  between the container  228  and the wall of the chamber at the first longitudinal position. 
     FIG. 8C  shows the contact area  225 ′between the container  228 ′°and the wall of the chamber at the second longitudinal position. 
     FIG. 8D  shows a top view of the piston  228  and  228 ′, respectively with the reinforcement means  227 , and  227 ′°respectively. 
     FIG. 8E  shows a top view of the piston  228  and  228 ′, respectively with the reinforcement means  229 , and  229 ′ respectively. 
     FIG. 9A  shows a longitudinal cross-section of the chamber with a convex/concave wall  185  and an inflatable piston comprising a container  258  at the beginning and the same  258 ′°at the end of a stroke. The container  258 ′ shows its production size. 
     FIG. 9B  shows the longitudinal cross-section of the piston  258  having a reinforced skin by a plurality of at least elastically deformable support members  254  rotatably fastened to a common member  255 , connected to the an skin  252  of said piston  258 , 258 ′. These members are in tension, and depending on the hardness of the material, they have a certain maximum stretching length. This limited length limits the stretching of the skin  252  of said piston. The common member  255  may slide with sliding means  256  over the piston rod  195 . For the rest is the construction comparable with that of the piston  208 , 208 ′. The contact area is  253 . 
     FIG. 9C  shows the longitudinal cross-section of the piston  258 ′. The contact area is  253 ′. 
     FIGS. 10-12  deal with the management of the pressure within the container. Pressure management for the piston comprising an inflatable container with an elastically deformable wall is an important part of the piston-chamber construction. Pressure management has to do with maintaining the pressure in the container, in order to keep the sealing on the appropriate level. This means during each stroke where the volume of the container changes. And in the long term, when leakage from the container may reduce the pressure in the container, which may effect the sealing capability. A flow of fluid may be the solution. To and from the container when it changes volume during a stroke, and/or to the container as such (inflation). 
   The change in the volume of the container may be balanced with a change in the volume of a first enclosed space, communicating with the container through e.g. a hole in the piston rod. The pressure may also be balanced, and this may be done by a spring force operated piston which may be positioned in the first enclosed space. The spring force may be originated by a spring or a pressurized enclosed space, e.g. a second enclosed space, which communicates with the first enclosed space by a pair of pistons. Any kind of force transfer may be arranged by each of the pistons, e.g. by a combination of the second enclosed space and a piston herein, so that the force on the piston in the first enclosed space remains equal, while the force on the piston in the second enclosed space reduces, when the pair of pistons moves more into the first enclosed space e.g. when fluid is moving from the first enclosed space into the container. This complies well with p.V=constant in the second enclosed space. The tuning of the pressure in the chamber of the container during the entire or a part of the stroke may also be done by a communication of the chamber and the chamber of the container. This has already been described in WO00/65235 and WO00/70227. 
   The container may be inflated through a valve in the piston and/or the handle. This valve may be a check valve or an inflation valve, e.g. a Schrader valve. The container may be inflated through a valve which communicates with the chamber. If an inflation valve is used, a Schrader valve is preferable because of its security to avoid leakages and its ability to allow to control all kinds of fluids. In order to enable inflation, a valve actuator may be necessary, e.g. the one disclosed in WO99/26002. This valve actuator has the advantage that inflation may be enabled by a very low force—thus very practical in case of manual inflation. 
   Having a valve communicating with the chamber, it may enable automatic inflation of the container, when the pressure in the container is lower than the pressure in the chamber. When this may not be the case, such higher pressure in the chamber may be created temporarily by closing the outlet valve of the chamber near the second longitudinal position of the container in the chamber. This closing and opening may be done manually, e.g. by a pedal, which opens a channel which communicates with a space between the valve actuator (WO99/26002) and e.g. a Schrader valve. When open, the valve actuator may move, but lacks the force to depress the core pin of the valve and hence the Schrader valve may not open—thus the chamber may be closed, and any high pressure may be build up for enabling inflation of the container. When the channel is closed, the actuator functions as disclosed in WO99/26002. The operator may check the pressure in the container by a manometer. Opening and closing of this outlet valve may also be done automatically. This may be done by all kinds of means, which initiate the closing of the outlet by a signal of any kind as a result of a measurement of pressure being lower than a predetermined value. 
   The automatic inflation of the container to a certain pre-determined value may be done by a combination of a valve communicating with the chamber and e.g. a release valve in the container. It releases at a certain predetermined value of the pressure, e.g. to the space above the container or to the chamber. Another option may be that the valve actuator of WO99/26002 may be open firstly after a pre-determined value of the pressure has been reached, e.g. by combining it with a spring. Another option may be that the opening to the valve actuator is closed when the pressure reaches a value over the pre-determined one, by e.g. a spring force operated piston. 
     FIG. 10A  shows a piston-chamber system with a piston comprising a container  208 , 208 ′ and a chamber  188  having a central axis  184  according to  FIG. 6A-C . The inflation and pressure management described here may also be used for other pistons comprising a container. The container  208 , 208 ′ may be inflated through a valve  241  in the handle  240  and/or a valve  242  in the piston rod  195 . If no handle is used, but e.g. a rotating axle, it could be hollow, communicating with e.g. a Schrader valve. The valve  241  may be an inflation valve, e.g. a Schrader valve, comprising a bushing  244  and a valve core  245 . The valve in the piston rod  195  may be a check valve, having a flexible piston  126 . The chamber between the check valve  242  and the chamber  209  of the container  208 , 208 ′°was earlier described as the ‘second’ enclosed space  210 . The manometer  250  enables control of the pressure inside the container—no further details are shown. It may also be possible to use this manometer to control the pressure in the chamber  186 . It may also be possible that the chamber  209  of the container  208 , 208 ′ has a release-valve (not drawn) which may be adjusted to a certain pre-determined value of the pressure. The released fluid may be released to the chamber  209  and/or to the space  251 . 
     FIG. 10B  shows an alternative option for the inflation valve  241 . Instead of the inflation valve  241  in the handle  240 , only a bushing  244  without a valve core  245  may be present, which enables connection to a pressure source. 
     FIG. 10C  shows details of the bearing  246  of the rod  247  of the piston  126  which may act as a check valve. The bearing  246  comprises longitudinal ducts  249  enabling passage of fluid around the rod  247 . The spring  380  enables a pressure on the fluid in the second enclosed space  210 . The stop  239 . 
     FIG. 10D  shows details of the flexible piston  126 , which may function as check valve  242 . The spring  380  keeps the pressure on the piston  126 . 
     FIG. 11A  shows a piston-chamber system with a piston comprising a container  208 , 208 ′ and a chamber  186  having a central axis  184  according to  FIG. 6A-C . The inflation and pressure management described here may also be used for other pistons comprising a container. The container  248 , 248 ′ may be inflated through a valve communicating with the chamber  186 . This valve  242  may be a piston  126  according to FIG.  10 A,D or it may be an inflation valve, preferably a Schrader valve  260 . The second closed space  210  is communicating with the chamber  209  in the container by a hole  201 , while the second enclosed space  210  is communicating through a piston arrangement with a second enclosed space  243 , which may be inflated through e.g. an inflation valve like a Schrader valve  241  which may positioned in the handle  240 . The valve has a core pin  245 . If no handle is used, but e.g. a rotating axle, it may be hollow and a Schrader valve may communicate with this channel (not drawn). The Schrader valve  260  has a valve actuator  261  according to WO99/26002. The foot  262  of the chamber  186  may have an outlet valve  263 , e.g. a Schrader valve, which may be equipped with another valve actuator  261  according to WO99/26002. In order to manually control the outlet valve  263 , the foot  262  may be equipped with a pedal  265  which can turn an angle a around an axle  264  on the foot  262 . The pedal  265  is connected to a piston rod  267  by an axle  266  in a non-circular hole  275  in the top of the pedal  265 . The foot  262  has an inlet valve  269  (not drawn) for the chamber  186 . The (schematically drawn) spring  276  keeps the pedal  265  in its initial position  277 , where the outlet valve is kept open. The activated position  277 ′ of the pedal  265  when the outlet valve is kept dosed. The outlet channel  268 . 
     FIG. 11B  shows a detail of the communication by a pair of pistons  126  (from  FIG. 10D) and 270  between the second endosed space  210  and the third enclosed space  243 . The piston rod  271  of the pair of pistons is guided by a bearing  246 . The longitudinal ducts  249  in the bearing  246  enable the transport of fluid from the spaces between the bearing  246  and the pistons  126  and  270 . The spring  380  may be present. The piston rod of the piston type container  248 , 248 ′ is  195 , with the wall  194 . 
     FIG. 11C  shows an alternative wall  273  of the piston rod  272  of the piston type container  248 , 248 ′ which has a angle β°with the central axis  184  of the chamber  186 . The piston  274  is schematically drawn, and can adapt itself to the changing cross-sectional area&#39;s of the inside the piston rod  272 . 
     FIG. 11D  shows piston  248 ′ on which a housing  280  is build. The housing comprises a Schrader valve  260 , with a core pin  245 . The valve actuator  261  shown as depressing the core pin  245 , while fluid may enter the valve  260  through channels  286 ,  287 , 288  and  289 . When the core pin  245  is not depressed, the piston ring  279  may seal the wall  285  of the inner cylinder  283 . The inner cylinder  283  may be sealingly enclosed by sealings  281  and  284  between the housing  280  and the cylinder  282 . The chamber is  186 . 
     FIG. 11E  shows the construction of the outlet valve  263  with a core pin  245 , which is shown depressed by the valve actuator  261 . Fluid may flow through channels  304 ,  305 ,  306  and  307  to the openened valve. The inner cylinder  302  is sealingly enclosed between the housing  301  and the cylinder  303  by sealings  281  and  284 . A channel  297  having a central axis  296  is positioned through the wall of the inner cylinder  302 , the wall of the cylinder  303  and the wall of the housing  301 . At the outside of the housing  301  has the opening  308  of channel  297  a widening  309  which enables a piston  292  to seal in a closing position  292 ′ by a top  294 . The piston  292  may be moving in another channel  295  which may have the same central axis  296  as channel  297 . The bearing  293  for the piston rod  267  of the piston  292 . The piston rod  267  may be connected to the pedal  265  ( FIG. 11A ) or to other actuators (schematically shown in  FIG. 11E ). 
     FIG. 11F  shows the piston  248 ′ and the inflation arrangement  368  of  FIG. 11D , besides the arrangement  369  to control the outlet valve of  FIG. 11E . The inflation arrangement  368  comprises now also the arrangement  370  to control the valve of  FIG. 11E . This may be done to enabling the closing of the valve, when the predetermined pressure has been reached, and opening it when the pressure is lower than the predetermined value. A signal  360  is handled in a converter  361  which gives a signal  362  to an actuator  363 , which is actuating through actuating means  364  the piston  292 . 
   When the chamber has a lower working pressure than the pre-determined value of the pressure in the piston, the arrangement  369  to control the closing and opening of the outlet valve  263  may be controlled by another actuator  363  through means  367  initiated by a signal  365  from the converter  361 . A measurement in the chamber, giving a signal  371  to the converter  361  and/or  366  may automatically detect whether or not the actual pressure of the chamber is lower than the working pressure of the piston. This may be specifically practical when the pressure of the piston is lower than the pre-determined pressure. 
     FIG. 11G  shows schematically a cab  312 ,  312 ′ with a spring  310  connected to the housing  311  of the valve actuator  261 . The spring  310  may determine the maximum value of the pressure to depress the valve core pin  245 , of a Schrader valve  260 . 
     FIG. 12  shows en enlonged piston rod  320  in which a pair of pistons  321 , 322  are positioned at the end of a piston rod  323 , which may move in a beating  324 . The enclosed space  325 . 
   FIGS.  13 A,B,C show the combination of a pump with a pressurizing chamber with elastically deformable wall with different areas of the transversal cross sections and a piston with a fixed geometrical shape. Within a housing as e.g. cylinder with fixed geometrical sizes an inflatabel chamber is positioned which is inflatable by a fluid (a non-compressable and/or a compressable fluid). It is also possible that said housing may be avoided. The inflatable wall comprising e.g. a liner-fiber-cover composite or also added an impervious skin. The angle of the sealing surface of the piston is a bit bigger than the comparative angle of the wall of the chamber in relation to an axis parallel to the movement. This difference between said angles and the fact that the momentaneous deformations of the wall by the piston takes place a bit delayed (by having e.g. a viscose non-compressable fluid in the wall of the chamber and/or the right tuning of load regulating means, which may be similar to those which have been shown for the pistons) provides a sealing edge, of which its distance to the central axis of the chamber during the movement between two piston and/or chamber positions may vary. This provides a cross-sectional area change during a stroke, and by that, a designable operation force. The cross-section of the piston in the direction of the movement however may also be equal, or with a negative angle in relation to the angle of the wall of the chamber—in these cases the ‘nose’ of the piston may be rounded of. In the last mentioned cases it may be more difficult to provide a changing cross-sectional area, and by that, a designable operation force. The wall of the chamber may be equiped with all the already shown loading regulating means the one showed on  FIG. 12B , and if necessary with the shape regulating means. The velocity of the piston in the chamber may have an effect on the sealing. 
     FIG. 13A  shows piston  230 , 230 ′°at four positions of the piston in a chamber  231  with a central axis  236 . Around an inflatable wall  238  a housing  234  with fixed geometrical sizes. Within said housing  234  a compressable fluid  232  and a non-compressable fluid  233 . There may be a valve arrangement for inflation of the wall (not shown). The shape of the piston at the non-pressurized side is only an example to show the principle of the sealing edge. The difference in distance between the sealing edge and the central axis  236  at the end and that at the beginning of the stroke in the shown transversal cross-section is approximately 39%. The shape of the longitudinal cross-section may be different from the one shown. 
     FIG. 13B  shows the piston after the beginning of a stroke. The distance from the sealing edge  235  and the central axis  236  is z,. The angle a between the piston sealing edge  235  and the central axis  236  of the chamber. The angle v between the wall of the chamber and the central axis  236 . The angle v is shown smaller than the angle ξ. The sealing edge  235  arranges that the angle v becomes as big as the angle ξ. 
     FIG. 13B  shows the piston after the beginning of a stroke. The distance from the sealing edge  235  and the central axis  236  is z 1 . The angle ξ between the piston sealing edge  235  and the central axis  236  of the chamber. The angle v between the wall of the chamber and the central axis  236 . The angle v is shown smaller than the angle ξ. The sealing edge  235  arranges that the angle v becomes as big as the angle ξ. Other embodiments of the piston are not shown. 
     FIG. 13C  shows the piston during a stroke. The distance from the sealing edge  235  and the central axis  236  is z 2 —this distance is smaller than z 1 . 
     FIG. 13D  shows the piston almost at the end of stroke. The distance from the sealing edge  235  and the central axis  236  is z 3 —this distance is smaller than z 2 . 
     FIG. 14  shows a combination of a wall of the chamber and the piston which have changeable geometrical shapes, which adapt to each other during the pump stroke, enabling a continuous sealing. It has its production size at the second longitudinal position of the chamber. Shown is the chamber of  FIG. 13A  now with only a non-compressable medium  237  and piston  450  at the beginning of a stroke, while the piston  450 ′ is shown just before the end of a stroke. Also all other embodiments of the piston which may change dimensions may be used here too. The right choice of velocity of the piston and the viscosity of the medium  237  may have a positive effect on operations. The longitudinal cross-sectional shape of the chamber shown in  FIG. 14  may also be different.