GB2473452A

GB2473452A - Vibration isolator

Info

Publication number: GB2473452A
Application number: GB0915807A
Authority: GB
Inventors: William Alexander Courtney
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-09-10
Filing date: 2009-09-10
Publication date: 2011-03-16
Anticipated expiration: 2029-09-10
Also published as: GB0915807D0; GB2473452B

Abstract

According to the present invention, there is provided a two stroke, two chamber, vibration energy absorbing device having a fixed volume chamber and a variable volume chamber, partitioned in the rest state by a plate 1. At least one chamber is filled with a composite, compressible, elastic fluid. The plate is displaced into the fixed volume chamber on the first or compression stroke, creating a gap around the perimeter of the plate via which liquid can flow into the fixed volume chamber. The partition is restored on the second, or extension stroke, either forcing liquid to pass through holes in the plate or diverting the flow of liquid through an external device where it is forced to do external work before returning to the variable volume chamber. The compressible elastic fluid may be a mixture of elastomeric capsules and a chemically compatible incompressible liquid, with the capsules having a skin that increases in thickness and including a plurality of gas filled cells having walls that increase in thickness during the compression stroke.

Description

Improved Vibration Isolator

Technical Field

This invention relates to improvements in devices used to minimise the transmission of mechanical energy from vibrating bodies to their environment.

According to the present invention, there is provided a two stroke, two chamber, vibration energy absorbing device having a fixed volume chamber and a variable volume chamber, partitioned in the rest state by a plate, with at least one chamber being filled with a composite, compressible, elastic fluid, characterised by the plate being displaced into the fixed volume chamber on the first or compression stroke, creating a gap around the perimeter of the plate via which liquid can flow into the fixed volume chamber, with the partition being restored on the second, or extension stroke, either forcing liquid to pass through holes in the plate or diverting the flow of liquid through an external device where it is forced to do external work before returning to the variable volume chamber.

Background Art

The present inventor has described elastic fluid filled impact absorbers in a number of prior art documents. Two of these are particularly relevant to the present application. Application PCT1GB9603243 describes impact absorbers consisting of stout, flexible packages filled with large numbers of resilient capsules and a matrix liquid. These packages combine the elastomeric properties of closed cell foam with the lubrication, viscous damping and hydraulic pressure equalisation properties of a liquid. Patent application PCTIGB98/03594 describes impact or vibration absorbing devices consisting of a flexible or moveable walled package, filled with a mixture of matrix fluid and a plurality of resilient capsules, with the device including one or more permeable barriers, characterised by the provision of viscous damping when some of the fluid is forced through small holes in the barrier(s) during violent impacts. In particular, patent application PCT/GB98/03 594 revealed a variable damping shock isolator that offered high levels of viscous damping on the first stroke, when the isolator suffers length compression and reduced damping on the extension stroke. This earlier invention is suitable for intermittent impact buffering applications because the viscous damping increases with the violence of the impact, but is not appropriate for suspension systems which require minimal damping on the compression stroke, to provide a soft ride over bumps with higher levels of damping on the extension stroke. This prior design limitation will be overcome by the present invention.

Brief description of the drawings

Figure 1 depicts the basic components of the prior version of the invention, as designed to offer increased viscous damping on the compression stroke.

Figure 2 depicts the simplest version of the new invention.

Figures 3, 4 and 5 are further illustrations of this version of the invention with depictions of the elastic fluid added.

Figure 6 shows a low weight version of the basic form of the new invention.

Figure 7 depicts a version of the invention that offers variable stifThess on the compressive stroke.

Figure 8 depicts a version of the invention which provides the option of increased viscous damping on the extension stroke by reducing the effective size of the holes in the damping plate.

Figure 9a is a plan view of the annular plate lying on top of the damping plate in the minimum damping position.

Figure 9b is a plan view of the two plates after the viscous damping properties have been increased by nudging the annular plate so that only a small fraction of the area of the holes in the damping plate is exposed.

Figure lOa depicts a version of the invention that includes a nudging rod.

Figure lOb shows the nudging rod in isolation.

Figures ha, lib and lic are close up side views in the region where the nudging rod passes through the plates.

Figures 12a and 12b reveal how the annular plate is reset during the extension stroke.

Figure 13 depicts a version of the invention that can be pre-stressed under rest conditions in order to cater for heavier than normal static loads.

Figure 14 depicts the first version of the invention that can automatically compensate for an increase in static loading.

Figure 15 depicts the second version of the invention that can automatically compensate for an increase in static loading.

Figure 16 depicts a piston and cylinder version of the invention.

Figure 17 is a reproduction of an electron micrograph of a slice through an outer segment of an elastomeric foam capsule.

Figures 18a and lSb depict the skin and wall thickening effects as a foam capsule suffers bulk compression.

Figure 19 depicts a cross section of the outer layers of a composite elastomeric foam capsule that offers non-linear characteristics under bulk compression conditions.

Figures 20a, b and c depict another type of composite capsule that offers non-linear characteristics under bulk compression conditions.

Figure 21 depicts a version of the invention in which the fixed volume chamber has been partitioned into two sub-chambers.

Figure 22 depicts an energy saving version of the invention that includes a turbine.

Figure 23 depicts a variation on the energy saving version of the invention, with the turbine being replaced by an array of piezoelectric baffles.

Figure 24 depicts a piezoelectric elastomeric capsule according to the invention.

Figure 25 depicts a cross section through the capsule as the piezoelectric cantilevers are deflected.

Figure 26 depicts a version of the invention that includes piezoelectric elastomeric capsules in the fixed volume chamber.

Figure 27 depicts a cross section through the fixed volume chamber including four piezoelectric efastomeric capsules.

Disclosure of the invention

This invention is a novel addition to a family of shock, impact and vibration energy isolating devices, all invented by the present inventor. The common characteristic which links the family together is that all the devices are variable volume containers filled with a composite elastic fluid consisting of a plurality of compressible elastomeric capsules with the void space between the capsules being filled by an effectively incompressible matrix fluid.

Figure 1 depicts the basic components of a prior version of the invention, as designed to offer increased viscous damping on the compression stroke. In Figure 1, a flexible rubber bellows 1 is mounted on top of a fixed volume lower chamber 2. The fixed volume chamber is preferably made from a low density metal having good thermal conduction properties. To prevent excessive bulging of the bellows during compression a series of concentric rings, or alternatively, an energy absorbing helix coil spring 3 is added. The spring option increases the energy absorbing capacity of the device, but unlike the elastomeric capsules to be discussed below, it does not offer a non-linear stifthess characteristic. The two chambers are killed with compressible fluid comprising compressible elastomeric capsules such as 4 and a chemically compatible matrix fluid, for example hydraulic fluid. A low mass permeable viscous damping plate 5 separates the two chambers. When the system is at rest, this sits on a step 6 in the rim of the lower chamber. Matrix fluid can pass through holes in the damping plate on the compression and extension strokes but an additional low resistance flow path is offered on the extension stroke, around a large clearance gap 7. The gap is created as a consequence of the slight fluid pressure difference on the extension stroke encouraging the damping plate to move upwards. This gap is closed on the compression stroke, forcing all of the fluid travelling between the chambers to pass through the holes in the damping plate. This version of the device was invented with intermittent shock rather than vibration isolation applications in mind.

Figure 2 depicts the simplest version of the new invention. It offers minimal damping on the compression stroke, to provide a soft ride over bumps with higher levels of damping on the extension stroke to absorb energy stored in the springs. This prevents rough jolting movements or "jounce". For clarity, the compressible elastic fluid has been omitted from Figure 2. The most important innovation compared with the prior art is to place the low mass permeable viscous damping plate 1 inside the fixed volume chaniberand restrain its movement to the confines of the fixed volume chamber by adding a chamber lip 2. Preferably, but not essentially, the movement of the damping plate is restrained by a central guide post 3. Also, a skirt 4 prevents the plate from tilting and biting into the post. On the compression stroke the hydraulic pressure inside the variable volume chamber increases driving the damping plate down, creating a gap between the plate and the chamber lip, through which hydraulic fluid can pass with minimal viscous damping. On the extension stroke, the direction of the pressure gradient is reversed, causing the plate to spring back to close the gap such that all of the fluid flowing between the chambers is forced to travel through the holes in the viscous damping plate. Figures 3, 4 and 5 are further illustrations of this version of the invention with depictions of the elastic fluid added. The term "elastic fluid" is intended to cover all versions of the fluid revealed in the present inventors earlier applications. In principle any liquid can be used as the incompressible matrix fluid, but hydraulic fluid is particularly advantageous because it is chemically compatible with rubber, In what follows the matrix fluid will be referred to as "hydraulic fluid" but this is not intended to exclude the use of alternative matrix fluids. In this and all following examples of the new vibration isolator, it is assumed that guiding devices 5 are added to prevent transverse movement of the bellows piston shaft. These could take the form of a set of three roller bearings aligned with the sides of an equilateral triangle, with the piston shaft passing through the centre of the triangle.

Figure 3 shows the basic form of the new invention at rest with elastic fluid according to the invention filling both chambers. In order to minimize weight, the compressible elastomeric capsules, for example 1 are close packed. The damping plate 2 is at rest in contact with the lip of the fixed volume chamber 3.

Figure 4 shows the compression stroke of the basic form of the new invention. The elastomeric capsules have shrunk in volume as a result of the increase in hydraulic pressure. The damping plate has been displaced towards the interior of the fixed volume chamber, creating a gap through which the hydraulic fluid 1 can travel with minimal viscous damping.

Figure 5 shows the extension stroke of the basic form of the new invention. The damping plate has shifted in the direction of the variable volume chamber, closing the gap and forcing the hydraulic fluid 1 to pass through the small holes in the damping plate.

Figureó shows a low weight version of the basic form of the new invention. In this version the spherical elastonieric capsules are replaced with a segmented cylinder shaped block of elastomeric foam 1 that occupies the whole of the volume of the fixed volume chamber in the rest position. Prior to assembly the individual segments of the cylinder are preferably constructed individually by heating granules of the solid elastomer impregnated with foaming agent, such that the individual segments all have a skin and the interior foam cells have increasingly thick walls towards the exterior walls of the segments. The benefits of this feature will be revealed later with reference to Figures iSa and 18b. To ensure that hydraulic fluid can penetrate the gaps between the segments, they are preferably molded with small ridges or channels in their surfaces.

Figure 7 depicts a version of the invention that offers variable stiffhess on the compressive stroke. This is achieved by varying the maximum gap between the damping plate and the lower chamber lip during the compression stroke.

An illustrative method of achieving this, which in no way limits the scope of the invention is to provide a central guide post 1 having a threaded lower section 2 passing through a complimentary threaded section in the base of the lower chamber. The post can be rotated to raise the step 3 on which the damping plate rests, and hence reduce the maximum size of the gap. In this, and other tunable versions of the invention revealed below, the means for adjusting the energy absorbing characteristics of the invention does not limit its scope. For examples, in the version depicted in Figure 7, the central shaft may be rotated directly or instigated remotely using mechanical, hydraulic or electrical means.

In another version of the invention, a soft ride is provided by retaining minimal damping on the compression stroke but the viscous damping on the extension stroke can be increased by reducing the effective size of the holes in the damping plate. Figure 8 depicts this version of the invention. In Figure 8 the lip on the tim of the fixed volume chamber 1 takes the form of a flat annular plate have holes corresponding in size and distribution to those on a modified form of damping plate. The annular plate is retained in a groove 2 and is free to change its angular position slightly so that it can partially mask or completely expose the holes in the underlying damping plate. Figures 8a and Sb depict plan views of the flat annular plate and modified form of damping plate in that order. The central hole 3 in the damping plate is slightly angular, with the correspond section of the post that it runs along having a complementaiy geometry. This prevents the damping plate from rotating about its shaft axis. A slit 4 is cut into the annular plate and a wider slit 5 is cut into the damping plate. A tapered rod can be inserted in the slit 4 so that the annular plate can be nudged to rotate slightly, to alter its angular position with respect to the underlying damping plate.

Figure 9a is a plan view of the annular plate lying on top of the damping plate in the minimum damping position, when the holes in the damping plate are completely exposed. Figure 9b is a plan view of the two plates after the viscous damping properties have been increased by nudging the annular plate so that only a small fraction of the area of the holes in the damping plate is exposed.

An illustrative method for nudging the annular plate will now be revealed. This version of the invention automatically reduces the effective size of the of the damping holes for large compressive displacements, then resets the annular plate to the minimum damping position as the piston passes through the rest position. Figure lOa depicts the essential components for this version. These are the piston 1 that caps the end of the variable volume chamber and an annular plate nudging rod 2. This rod is shown passing through the nudging hole 3 in the annular plate 4 which is lying on top of the damping plate 5. Figure lOb shows the nudging rod in isolation. It has a downward tapering section 6 and an upward tapering section 7. These offer nudges in opposite directions at different stages during the stroke.

Figures 1 la, 1 lb and 1 ic are close up side views in the region where the nudging rod passes through the plates.

They show successive stages of the nudging process during the compression stroke. Figure 1 la shows the system at rest with the annular plate 1 in contact with the damping plate 2. Figurelib shows that for a small degree of compression the damping plate has moved down due to the slight hydraulic pressure difference between the two chambers, but the annular plate has not been displaced. Figure 1 ic shows a higher level of compression with the annular plate being displaced to the left so that the holes in the two plates are moved out of vertical alignment.

Figures 12a and 12b reveal how the annular plate is reset during the extension stroke. Figure 12a shows an early stage in the extension stage of a large stroke. The nudging rod is moving upwards, but the holes in the two plates are out of alignment, so the effective size of the damping hole is small and the damping effect is correspondingly large.

Figure 12b shows that part of the extension stroke when the piston is just about to pass through the rest position, with the annular plate having moved to the right, so that the sets of holes in the two plates are nearing vertical alignment.

The scope of the invention is extended to include vibration isolators that can be pre-stressed under rest conditions in order to cater for heavier than normal static loads. Figure 13 depicts an example of this version of the invention. In Figure 13 an antechamber 1 is fitted with a piston 2 that can used to pre-stress the elastic fluid under rest conditions by reducing the active antechamber volume. The skirt of the piston and adjacent antechamber walls are preferably crew threaded and the piston screwed in or out. This provides friction and ensures that the volume of the antechamber remains constant as the hydraulic pressure varies during duty cycles.

Two versions of the invention that can automatically pre-stress the elastic fluid to compensate for an increase in static loading will now be revealed.

Figure 14 depicts the first version of the invention that can compensate for an increase in static loading. The body being isolated is separated from the vibration isolator by a bladder 1 filled with hydraulic fluid. The bladder is flexible but has high tensile strength, so it does not stretch significantly under heavy loading. It is connected to the fixed volume chamber via a flexible high pressure tube 2, fitted with a plug of damping material, such as wire wool 3. If the static load increases under rest conditions some hydraulic fluid is forced out of the bladder and into the main body of the vibration isolator where it pie-stresses the elastomeric capsules. The damping plug offers a high level of viscous damping; at least an order of magnitude higher than that contributed by the viscous damping plate. This allows hydraulic fluid to ooze through under quasi-static conditions but prevents significant back flow into the bladder when the isolator is active. The bladder has a large horizontal cross section area compared with a typical cross section of the isolator. Consequently the reduction in the height of the upper surface of the bladder is minimal even for significant increases in loading. In order to function as described, the height of the top of the stationary isolator must remain constant. If the isolator was allowed to compress while stationary, this would produce a counter hydraulic pressure increase, preventing the flow of fluid out of the bladder. In the present version of the invention, this rigidity is provided by a sealed column of incompressible hydraulic fluid 4. The column walls comprise a rubber bellows sleeve and an external helical spring 5, to prevent the sleeve bulging at high pressure. This column is connected to a fixed volume reservoir 6 which is filled with a mixture of hydraulic fluid and compressed air. A tap 7 is closed under static conditions but opens when the main isolator is in operation.

Figure 15 depicts an alternative version of the invention that can also compensate for an increase in static loading.

The central column of fluid that is held rigid under static conditions 1 is positioned inside the main body of the isolator and is mounted on top of the central guide post. This reduces the mass of incompressible fluid required and also reduces the resultant stresses on the sleeve walls. Two tap valves acting in anti-phase are required for this version to work. One locks off the central column under static conditions. The other locks off the bladder during vibration isolating activity.

Figure 15* depicts an exploded view of an illustrative, but not exclusive example of how a single tube rotating action can operate both valves. A rigid tube 2 passes between the central column and the flexible tube from the bladder. The rigid tube is blanked off at 3 but has aligned apertures 4 and 5 which can allow hydraulic fluid to travel into the main body of the isolator from the central column and the bladder respectively. A close fitting outer tube 6 has apertures 7 and 8 which are Out of alignment with apertures 4 and 5, such that when the outer tube is rotated to line up one outer aperture and a corresponding inner aperture, fluid can flow from either the central column or the bladder, but never simultaneously both. 0 rings, for example 9, are used to provide leak proof seals between the inner and outer tubes and between the outer tube and the seal with the isolator casing 10. The scope of the invention is extended to include any mechanical, hydraulic or electrical means for rotating the outer tube, to operate the invention as specified.

Figure 16 depicts a piston and cylinder version of the present invention. The fixed volume chamber 1 lies under the damping plate 2. The variable volume chamber has a volume defined by the space between the damping plate and the piston face 3.

The range of types of elastomeric capsules includes all of those revealed in his earlier patent applications PCT/GB9603243 and PCT/0B98/03594. Since these applications were filed a deeper understanding of the structure of elastomeric foam capsules has been gained. Figure 17 is a reproduction of an electron nucrograph of a slice through an outer segment of an elastomenc foam capsule. The photograph reveals the existence of a gradation of structures that can be placed in three categories: (i) An outer skin 1 of effectively solid material.

(ii) A near boundary layer of cells such as 2 having high tangential to radial ratios. That is, they are flattened.

(iii) Deeper cells such as 3 having similar tangential to radial dimensions.

The hydraulic pressure exerted on each capsule during the compressive stage of operation of isolators according to the invention results in the capsules being subjected to bulk compression. The gas inside the cells can be compressed, but for practical purposes, the solid elastomeric material is incompressible. This results in the skin of each capsule thickening and the wall thickness of all cells increasing.

Figures 18a and 1$b summarize these skin and wall thickening effects in idealized form. In Figure 18a a typical section of the skin has a thickness AY1, a typical thickness of the tangential walls between two cells is Ày1 and the typical thickness of the radial wall between two adjacent near boundary cells is x1. After suffering bulk compression, this segment shrinks to that depicted in Figure 18b. The skin thickness has increased to ÀY2, the tangential wall thickness toÀy2, and the radial wall thickness has increased to b.x2.

All these thickening effects are beneficial compared with the use of elastomeric block or elastorneric foam vibration isolators, because the new invention offers the desirable characteristic of increasing stiffness with increasing compression of the isolator. In particular, the difference in buckling behavior should be noted. At moderate levels of compression and low strain rates, buckling of the gas filled cell walls is known to be the dominant energy absorbing mechanism for elastomeric foams. For elastomeric capsules, resistance to buckling increases with bulk compressive stress as the mean length of the cell walls decreases and wall thickness increases.

Figure 19 depicts a cross section of the outer layers of a composite elastomeric foam capsule that has been manufactured in two stages, using two different stifThess grades of elastomeric base material. For example, the inner layers 1 are stiffer than the outer layers 2, and the composite capsule has two skins, 3 and 4, one for each layer.

The invention is extended to include compressible fluids that have any number of layers of different stiffiess foams nested in this manner.

Figures 20a, b and c depict another type of composite capsule that offers non-linear characteristics under bulk compression conditions. A gas filled elastomeric sphere 1 resides inside a larger gas filled elastomeric sphere 2.

Figures 20a shows the composite capsule under rest conditions under the influence of gravity. Figure 20b shows the composite capsule suffering moderate bulk compression, with the outer sphere and its gas experiencing significant changes in volume, but with the shell of the inner sphere only suffering slight compression because its stiffness is greater that the gas compressing it. Figure 20c shows the composite capsule suffering a high degree of bulk compression, with the inner sphere experiencing a significant reduction in volume. The dashed lines linking these three diagrams have been added to help highlight the reductions in volume and consequent increases in thickness of the elastomeric layers. For some versions of the invention, the hysteresis loss suffered as thick walled elastomeric capsules go through successive compressive and expansion cycles is beneficial because it contributes to viscous damping. But for the energy saving version revealed with reference to Figure 22 it is preferable to maximize the irreversible energy fraction converted into electricity. Nested spherical capsules having thin walled outer spheres and thick walled inner spheres are appropriate here because they offer low hysteresis loss for moderate compressions, while retaining non linear characteristics for high levels of compression. The thin walled outer cells could be manufactured in the manner of bubble packing, with the stiffer spheres being inserted before the two sheets that form the bubbles are welded together. Individual bubbles could then be cut from the sheet of bubbles.

The invention is extended to include nested hollow bodies that are not spherical in shape and do not include gas in the void space between the nested bodies.

Figure 21 depicts a version of the invention in which the fixed volume chamber has been partitioned into two sub-chambers by the addition of a second damping plate 1. The variable volume chamber and the two sub chambers each retain elastomeric capsules offering different degrees of bulk compressive stiffliess.

Figure 22 depicts an energy saving version of the invention. This includes a blank plate 1 that is displaced into the fixed volume chamber on the compression stroke, as for the versions disclosed above. But, on the extension stroke, the liquid flows back into the variable volume chamber via a turbine 2. This is coupled to a generator (not illustrated) which generates electricity as the turbine shaft rotates. A valve 3 prevents the liquid passing through the turbine on the compression stroke. As an alternative to the composite elastomeric capsules discussed above, this version of the invention could include single air sacks in both chambers to provide a soft ride, with a number of thick walled elastomeric spheres being added, to provide stiff cushioning at high levels of compression.

Engineers skilled in the arts of turbo-generator design will be aware of a number of methods for varying the loading on the generator. Such methods can be incorporated into the present invention to provide a device that offers tunable damping.

Figure 23 depicts a variation on the energy saving version of the invention, with the turbine being replaced by an array of piezoelectric bafiles 1 that are deflected by the flow of the hydraulic fluid on its return to the variable volume chamber.

Figure 24 depicts a piezoelectnc elastomeric capsule according to the invention. It consists of a stiff trough with rigid side walls 1 with two cantilevers of piezoelectric material, 2 and 3 forming the upper surface in the rest condition. The cantilevers are deflected into the interior of the capsule when the surrounding hydraulic fluid increases its pressure. A gas bubble is trapped inside the capsule by adding a highly elastic membrane, shown in exploded view as item 4.

Figure 25 depicts a cross section through the capsule as the piezoelectric cantilevers 2 and 3 are deflected.

Connecting wires (not shown) draw off the current generated and feed it into the vehicle battery.

Figure 26 depicts a version of the invention that includes piezoelectric elastomeric capsule such as 1 in the fixed volume chamber. Such capsules have rigid sidewalls so they are not suitable for inclusion in the variable volume chamber. In the version depicted, the variable volume chamber is completely filled with incompressible hydraulic fluid.

To optimize usage of space and minimize the mass of liquid required, the curved rigid side walls of the capsules can be shaped and placed so that they fit snuggly against the interior walls of the fixed volume chamber, with the elastic membranes facing the interior of the chamber. Figure 27 depicts a cross section through the fixed volume chamber 1 including four piezoelectric elastomeric capsules 2, 3, 4 and 5.

The invention is extended to include movable chamber partitioning plates that also generate electricity when they are displaced.

Claims

Claims A two stroke, two chamber, vibration energy absorbing device having a fixed volume chamber and a variable volume chamber, partitioned in the rest state by a plate, with at least one chamber being filled with a composite, compressible, elastic fluid, characterised by the plate being displaced into the fixed volume chamber on the first or compression stroke, creating a gap around the perimeter of the plate via which liquid can flow into the fixed volume chamber, with the partition being restored on the second, or extension stroke, either forcing liquid to pass through holes in the plate or diverting the flow of liquid through an external device where it is forced to do external work before returning to the variable volume chamber.
2. A vibration energy absorbing device according to the first claim with the compressible elastic fluid being a mixture of elastomeric capsules and a chemically compatible incompressible liquid, with the capsules having a skin that increases in thickness and including a plurality of gas filled cells having walls that increase in thickness during the compression stroke.
3. A vibration energy absorbing device according to the first claim with the compressible elastic fluid being a mixture of elastomeric capsules and an incompressible liquid, with the capsules being constructed from nested layers elastomeric foam, each layer having a skin that increases in thickness and including a plurality of cells having walls that increase in thickness during the compression stroke.
4. A vibration energy absorbing device according to the first claim with the compressible elastic fluid being a mixture of elastomenc capsules and an incompressible liquid, with the capsules being constructed from nested layers of sealed, hollow elastomeric bodies.
5. A vibration energy absorbing device according to the first claim with the compressible elastic fluid being a mixture of elastomeric capsules and an incompressible liquid, with the capsules including piezoelectric materials that generate electricity when the capsules are deformed.
6. A vibration energy absorbing device according to the first claim with the plate including holes to provide viscous damping on the extension stroke and also including a second perforated plate which can overlap the first plate, such that the degree of overlap can be varied in order to alter the effective size of the holes through which the liquid flows, in order to vary the degree of viscous damping during the extension stroke.
7. A vibration energy absorbing device according to the sixth claim with the second plate being displaced relative to the first plate in steps, in order to vary the degree of overlap of the two plates during different stages of a stroke by means of a moving multiple tapered rod, which passes through holes in both plates and nudges the second plate into different positions as the effective thickness of the rod varies as it moves through the holes.
8. A vibration energy absorbing device according to the first claim with the device including the means to pm-stress the elastic fluid, when the device is in a rest state, in order to allow it to cope with an increased static load.
9. A vibration energy absorbing device according to the eighth claim with the device having a bladder of liquid interposed between the load being supported and a load bearing end of the device, with the bladder connected to the main body of the device such that if the static load increases, liquid is pumped into the main body, with the bladder and main body being isolated during periods of vibration and with the device being locked into a fixed compressible length when it is at rest.
10. A vibration energy absorbing device according to the ninth claim with the means of isolation being a permeable viscous damping plug that allows liquid to leak between the bladder and the main body of the device under rest conditions, but offers a high level of opposition to liquid flow during periods of vibration, such that the net flow of liquid through the plug is negligible.
11. A vibration energy absorbing device according to the first claim with an end stop controlling the depth of penetration of the plate into the fixed volume chamber, in order to control the viscous damping on the compression stroke, with an external means of varying the position of the end stop being provided.
12. A vibration energy absorbing device according to the first claim with the fixed volume chamber being partitioned into two sub-chambers by a plate that is displaced into one of the sub-chambers during the compression stroke, with the two sub-chambers including capsules having different bulk compressive stiffness or hysteresis damping characteristics.
13. A vibration energy absorbing device according to the first claim with the liquid flowing back into the variable volume chamber doing so via a turbine coupled to an electricity generator.
14. A vibration energy absorbing device according to the first claim with the liquid flowing back into the variable volume chamber doing so via an array of piezoelectric baffles which are deflected by the liquid flow, generating electrical energy.Amendments to the claims have been filed as follows Improved Vibration Isolator 1 A two stroke, two chamber, vibration energy absorbing device having a fixed volume chamber and a variable volume chamber, partitioned in the rest state by a plate, with at least one chamber being filled with a composite, compressible, elastic fluid, with the plate being displaced into the fixed volume chamber on the first or compression stroke, creating a gap around the perimeter of the plate via which liquid can flow into the fixed volume chamber, characterised by the partition being restored on the second, or extension stroke, either forcing liquid to pass through holes in the plate or diverting the flow of liquid through an external device where it is forced to do external work before returning to the variable volume chamber and the elastomeric capsules having solid outer walls and optionally solid inner partition walls such that the thickness of the walls increases during the compression stroke, such that the compressive stiffness of the device increases with the fractional degree of compression..2. A vibration energy absorbing device according to the first claim with the capsules being constructed from nested layers elastomeric foam, each layer having a skin that increases in thickness and including a plurality of cells having walls that increase in thickness during the compression stroke.3. A vibration energy absorbing device according to the first claim with the capsules being constructed from nested layers of sealed, hollow etastomeric bodies.4. A vibration energy absorbing device according to the first claim with the capsules including piezoelectric materials that generate electricity when the capsules are deformed.5. A vibration energy absorbing device according to the first claim with the plate including holes to provide viscous damping on the extension stroke and also including a second perforated plate which can overlap the .IS * first plate, such that the degree of overlap can be varied in order to alter the effective size of the holes *....: through which the liquid flows, in order to vary the degree of viscous damping during the extension stroke. * .* . 6. A vibration energy absorbing device according to the fifth claim with the second plate being displaced relative to the first plate in steps, in order to vary the degree of overlap of' the two plates during different us * stages of a stroke by means of a moving multiple tapered rod, which passes through holes in both plates and * ** nudges the second plate into different positions as the effective thickness of the rod varies as it moves * S a...through the holes. S. S * ** a *7. A vibration energy absorbing device according to the first claim with the device including the means to pre-stress the elastic fluid, when the device is in a rest state, in order to allow it to cope with an increased static load.8. A vibration energy absorbing device according to the seventh claim with the device having a bladder of liquid interposed between the load being supported and a load bearing end of the device, with the bladder connected to the main body of the device such that if the static load increases, liquid is pumped into the main body, with the bladder and main body being isolated during periods of vibration and with the device being locked into a fixed compressible length when it is at rest.9. A vibration energy absorbing device according to the eighth claim with the means of isolation being a permeable viscous damping plug that allows liquid to leak between the bladder and the main body of the device under rest conditions, but offers a high level of opposition to liquid flow during periods of vibration, such that the net flow of liquid through the plug is negligible.10. A vibration energy absorbing device according to the first claim with an end stop controlling the depth of penetration of the plate into the fixed volume chamber, in order to control the viscous damping on the compression stroke, with an external means of varying the position of the end stop being provided.11. A vibration energy absorbing device according to the first claim with the fixed volume chamber being partitioned into two sub-chambers by a plate that is displaced into one of the sub-chambers during the compression stroke, with the two sub-chambers including capsules having different bulk compressive stifihess or hysteresis damping characteristics.12. A vibration energy absorbing device according to the first claim with the liquid flowing back into the variable volume chamber doing so via a turbine coupled to an electricity generator.13. A vibration energy absorbing device according to the first claim with the liquid flowing back into the variable volume chamber doing so via an array of piezoelectric bafiles which are deflected by the liquid * flow, generating electrical energy. *S..* ***.* * I * *S S. I * S.SI * S. * S ) SSS S * S. S.