The present invention relates to a damper assembly of the kind that may be used, for example, in automotive suspension systems.
Conventional damper assemblies for automotive suspension utilise a coil spring connected in parallel with a cylinder and piston. When the damper assembly is disturbed by the application of a load, the spring is deformed and the piston moves within the cylinder. The deformed spring provides a restorative force, urging the damper back to its default position, and movement of the piston displaces fluid within the cylinder, dissipating energy and bringing about a damping effect. In such damper assemblies, failure of the coil spring can lead to the damper assembly failing catastrophically under load. This, in turn, can cause damage to other components, for instance in the case of a vehicle suspension system the vehicle chassis or bodywork may impact the ground.
It is one object of the present invention to provide an improved or alternative damper assembly.
According to a first aspect of the present invention there is provided a damper assembly comprising: a chain having a longitudinal axis and comprising a plurality of links pivotally interconnected by transverse articulation elements, the chain having a straight configuration in which the links are substantially aligned in a linear direction and at least one resilient member configured to force adjacent links of the chain to articulate out of the straight configuration, and a first mounting element and a second mounting element each attached to the chain, the mounting elements being movable relative to one another between a first position and a second position and being arranged to urge the chain towards the straight configuration when they are moved towards the second position.
One advantage of the present invention is that it can allow the portion of the damper assembly which provides the restorative force, and the portion which brings about the damping effect, to be at least partially independent of one another. This can be advantageous in providing a degree of redundancy. For instance, if the resilient member were weaker than the chain, then any failure of the former would not be catastrophic since load applied to the damper assembly could still be carried by the chain. A second advantage arises in that the components of the damper assembly moving over each other (and/or being deformed) can provide inherent damping capabilities as outlined below. In contrast, a conventional coil spring offers very little inherent damping. Further, the extent of inherent damping may be selectively varied by virtue of the configuration and geometry of the chain and resilient member, and/or the use of lubricant and/or damping fluid (or lack thereof).
The chain may be a roller-bush chain. Where the chain is a roller bush chain, the resilient member may bear against one or more of the rollers. One or more rollers may be attached to or integral with the resilient member.
The resilient member may be connected to one of the mounting elements. For example, it may be attached to the first or second mounting element at one end. Alternatively, the resilient member may be attached to the chain. For instance, it may be attached at one end of the chain and/or resilient member, at both ends of the chain and/or resilient member, or at an intermediate location along the length of the chain and/or resilient member.
When the chain is subjected to a tensile load (i.e. is urged towards the straight configuration) by the mounting elements, the links tend towards the straight configuration but are resisted by the resilient member, which may deflect as a consequence. The resilient member is arranged such that when the tensile load is removed it returns to its original shape.
The resilient member applies a reactive force to the chain when the chain is subjected to a tensile load, by virtue of it being deflected and its resilience. The tensile load forces the chain links to move towards the straight configuration but the reactive force of the resilient member acts on the chain (and preferably on individual chain links) so as to resist such movement.
The resilient member thus acts in a manner analogous to a spring. The reactive force may act in the manner of a spring constant in that it may change in proportion to the tensile load applied. It may change in a linear or non-linear relationship. The magnitude of the reactive force may be dependent on a combination of the configuration and geometry of the resilient member and the mechanism of the chain elements. In one embodiment the resilient member acts like a constant-force spring such that the force it exerts over its range of motion is a constant.
The resilient member may provide a degree of damping by virtue of movement of the links relative to the resilient member, the friction between the two providing sufficient energy losses to achieve effective damping. Alternatively or in addition, damping may be designed into the chain by virtue of the resilient member comprising a suitable elastomeric material that absorbs some of the energy (such as an elastomeric polymer). The member may wholly comprise such a material or may be made in part from such material. For example, the resilient member may comprise a core material and an elastomeric polymer coating, such as, for example, nitrile rubber or other synthetic rubber copolymer. The core material may be any suitable material that has sufficient stiffness such as a metal. One example is steel and preferably a spring steel. Instead or in addition, the chain may have rollers made from a suitable elastomeric damping material such as a polymeric damping material. The material may be injection mouldable. The size and/or thickness of the rollers may vary along the length of the chain in order to provide different damping characteristics along the chain. Alternatively or in addition, the material of the rollers may vary along the length of the chain.
The chain may be disposed between guide members for guiding movement of the chain.
The chain may be substantially enclosed within the damper assembly. For example, it may be contained in a space provided in one of the mounting elements or in a space co-operatively provided by more than one of the mounting elements. Alternatively, the chain may be only partially enclosed or may be in an exposed position.
The resilient member may be a resilient elongate flexible member threaded along at least part of the length of the chain. One advantage of such an arrangement is that if the resilient member breaks, in some embodiments it can be retained in position by the chain, at least for a period of time, allowing any intact portions of the resilient member to continue to offer a restorative force (albeit at a reduced effectiveness). Instead, the resilient member may take the form of a resilient elongate flexible loop held within the chain, or may take the form of an elastomeric block held within the chain. Alternatively, it may take any other suitable form and be in any other suitable position, for instance it may be a resilient elongate flexible which is not threaded along at least part of the length of the chain.
Alternatively, the resilient member may take the form of a resilient elongate flexible member, but not be threaded between the chain links. In either case, it may be deflected into an undulating form as the chain links articulate towards the straight configuration, and tend towards the straight, linear configuration (but may be prevented from being perfectly straight by virtue of the chain links).
The damper assembly may have a plurality of resilient members disposed in a side-by-side relationship. This may be advantageous in that the resilient members moving against one another may increase energy dissipation, thereby improving the damping capability of the assembly.
The chain may be located within a reservoir that is arranged to contain damping fluid. The reservoir may contain damping fluid. Damping fluid is any fluid (liquid or gas) which exhibits sufficient viscosity to be useful in dissipating kinetic energy applied to it, such as natural or synthetic oil or grease, or water. The damping fluid may be manufactured from viscous synthetic oil, and/or have a viscosity in the region of 30,000-70,000 cSt and preferably around 50,000 cSt. The reservoir may be partially of completely filled with damping fluid. Alternatively, the damper assembly may have no such reservoir. In this case no damping fluid may be present in contact with the chain, or one or more moving parts of the chain may be coated with damping fluid. The moving parts may be one or more selected from the group comprising the links, rollers, pins, bushes or the resilient member. The presence of damping fluid in contact with the chain, whether it is in a reservoir or as a coating on parts of the chain itself, may increase the damper constant of the assembly. The damping fluid may also function as a lubricant, and/or have the effect of reducing the noise of the chain in use.
In one embodiment of the invention, the first mounting element comprises a mounting element cavity and the second mounting element comprises a piston, the piston being slidably received within the cavity. The mounting element cavity and the piston may be of complementary shape. Each may be cylindrical (of circular or ovoid cross-section), prismatic, or of any other suitable shape. One or more sealing members may be interposed between the piston and the mounting element cavity. The mounting element cavity and the piston may define a common longitudinal axis along which they are movable relative to one another. The longitudinal axis of the chain (when it is in the straight configuration) may or may not be in line with or parallel to the common longitudinal axis of the mounting element cavity and piston.
In the above embodiment, the piston may define a piston cavity therein. The piston cavity may be fully enclosed, substantially fully enclosed or only partially enclosed, by the piston or by the piston and other components. It may be cylindrical (of circular or ovoid cross-section), prismatic, or of any other suitable shape. Alternatively, the piston may be solid.
In an embodiment where the piston defines a piston cavity, the chain is at least partially received within the piston cavity. Where the chain is only partially received within the piston cavity it may be partially exposed, or may be partially received within another component (for example the mounting element cavity). Alternatively, the chain may be in a fully exposed position, and/or may be fully or partially received in a different component of the damper assembly (such as the mounting element cavity).
In the above embodiment one portion of the chain may be attached to the piston, and another portion of the chain attached to the first mounting element via a protrusion projecting through an aperture in the piston. Where the mounting element cavity and the piston define a common longitudinal axis along which they are movable relative to one another, the protrusion may project substantially radially through the aperture in the piston, and/or the aperture may be in the form of an elongate slot substantially parallel with the common longitudinal axis of the mounting element cavity and piston. The protrusion may be a pin extending through an aperture in a chain link.
Alternatively, in the above embodiment the damper assembly may further comprise a plug slidably received within the piston cavity, one portion of the chain being attached to the piston and another portion of the chain being attached to the plug. The plug may be of complementary shape to the piston cavity. It may be cylindrical, prismatic, or of any other suitable shape. There may be one or more sealing members interposed between the plug and the piston cavity.
Where the first mounting element comprises a mounting element cavity and the second mounting element comprises a piston slidably received within the mounting element cavity, the mounting element cavity and the piston may co-operatively form a piston pump mechanism arranged to displace a damping fluid. The damper assembly may contain damping fluid arranged to be displaced by the piston pump mechanism. In embodiments where the chain is located within a reservoir of damping fluid, the damping fluid in the reservoir and damping fluid displaced by the piston pump may or may not be of the same composition. Where the fluid is of the same composition, the fluid in the reservoir may or may not be displaced by the piston pump.
Where the damper assembly includes a piston cavity, the piston pump mechanism may be arranged to displace damping fluid into the piston cavity.
The damper assembly may further comprise a housing unit with a housing unit cavity, the first mounting element being slidably received within the housing unit cavity.
Where a damper assembly has a housing unit and a piston pump mechanism, the piston pump mechanism may be arranged to displace damping fluid into the housing unit cavity.
In one embodiment, the damper assembly comprises two counterposed second mounting elements. The two counterposed second mounting elements may or may not be substantially identical to one another and/or substantially mirror images of each other.
Where the first mounting element comprises a mounting element cavity and the second mounting element comprises a piston, in the above embodiment each of the second mounting elements may comprise a piston, both pistons being received within the mounting element cavity. Alternatively, the damper assembly may comprise more than one mounting element cavity and the pistons may be received within different mounting element cavities.
In the above embodiment, the chain may be attached to the first mounting element at a first location along its longitudinal axis, and attached to each of the second mounting elements at locations along its longitudinal axis that are on opposite sides of the first location. The first location may or may not be substantially equidistant from the points at which the second mounting elements are attached. Alternatively, the damper assembly may have separate chains attached to each of the second mounting elements.
In the above embodiment, the two counterposed second mounting elements may be connected such that their relative movement is restricted. The second mounting elements may be substantially prevented from moving relative to one another. Alternatively, each of the second mounting elements may be free to move independently of the other.
In a damper assembly according to the first aspect of the invention the chain may comprise one or more extensions configured to increase the resistance to motion of the chain due to drag. The extensions may induce drag in air, or in a damping fluid surrounding the chain. The extensions may be in the form of plates, which may each be attached to a link of the chain and be positioned substantially orthogonally to it. Alternatively, they may take any other suitable shape (for instance they may take the form of elongate members or arrays thereof), may be attached in any other suitable way and/or may be in any other suitable orientation.
The extensions may be configured to co-operatively define one or more voids between neighbouring extensions, the shape of each of said voids being variable according to the configuration of the chain.
At least some of the extensions may be shaped to maintain a predetermined clearance with neighbouring extensions when the chain articulates out of the straight configuration. For instance, some extensions may be provided with a convex shape configured to maintain a particular clearance with neighbouring extensions of a flat shape. As another example, all the extensions may have convex surfaces which are shaped to maintain a predetermined clearance with the convex surfaces of adjacent extensions. By utilising this latter arrangement, the volume of each void can be maintained at a substantially constant level when the chain articulates out of the straight configuration.
The damper assembly may comprise a plurality of said chains comprised within a chain assembly, wherein:
The first and second mounting elements of the damper assembly may be attached to the second and first connection brackets respectively, or vice versa.
Each chain may be attached to the first and second connection brackets. First and second ends of each chain may be attached to the first and second connection brackets respectively.
Each of the plurality of chains may be different, or one or more of the plurality may be substantially identical to one another. For instance, if one of the chains comprises one or more of the features described above, each of the other chains may or may not also comprise those features. Two or more of the chains may be positioned substantially parallel to one another when the first and second connection brackets are in the second position. Each of said plurality of chains may define an articulation plane within which the links can pivot, and the plurality of chains may be positioned whereby their respective articulation planes are substantially parallel.
All of the plurality of the chains may be so positioned. For the avoidance of doubt, reference to planes being parallel is intended to include their being coplanar.
Alternatively, and at least two of said chains may be positioned whereby their respective articulation planes are non-parallel.
All of the plurality of chains may be positioned such that none are parallel to each other.
The chain assembly may further comprise a damper sub-assembly configured to damp movement of the first and second connection brackets relative to one another.
The damper sub-assembly may be configured to damp movement of the connection brackets towards the first position and/or towards the second position. The damper sub-assembly may take any suitable form. For instance, it may be a dashpot, a piston pump, an electromagnetic damper, an elastomeric component which dissipates energy through hysteresis.
The damper sub-assembly may comprise an elongate piston extending between the first and second connection brackets, and at least one of the first and second connection brackets defines a fluid cavity within which the piston is slidably received, relative movement of the first and second connection brackets causing the piston to slide within the fluid cavity.
Both the first and second connection brackets may define fluid cavities within which the piston is slidably received.
The damper sub-assembly may comprise a deformable bladder which defines a fluid cavity therein, relative movement of the first and second connection brackets causing the bladder to change shape, thereby changing the shape of the fluid cavity.
The change of shape of the fluid cavity in the bladder may be a change in geometric shape (for instance a change in aspect ratio) and/or a change in volume.
The chain assembly may comprise a duct in fluid communication with the fluid cavity or cavities.
The duct may run through one or both of the connection brackets, or may be positioned in any other suitable location. For instance, where the chain assembly comprises a piston the duct may run through the piston.
The chain assembly may further comprise a resiliently deformable element configured to be deformed by relative movement of the first and second connection brackets.
The resiliently deformable element may be an elastomeric component such as a tube, sheet or block, or it may be a spring such as a coil spring, leaf spring or Belleville washer. Alternatively, it may take any other suitable form.
The resiliently deformable element is configured to be deformed by movement of the first and second connection brackets towards the first position.
Alternatively or in addition, the resiliently deformable element may be configured to be deformed by movement of the first and second connection brackets towards the second position.
The chain assembly may further comprise an alignment structure positioned to prevent at least two of the chains from contacting each other.
The alignment structure may be positioned to prevent all the plurality of chains from contacting each other.
Specific embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:
a-2c are cross-sectional side views of the chain of
a-3c are cross-sectional side views of a damper assembly according to a first embodiment of the invention, in different configurations;
a and 9b are side and perspective views respectively of a damper assembly according to a fourth embodiment of the invention, shown in partial cross-section;
a-11c are side views of the chain of
Referring now to
Each inner link assembly 2 comprises a pair of opposed spaced inner link plates 6 connected together by a pair of bushes 8 (most of which are hidden in
The outer link plates 4 are of similar configuration to the inner link plates 6 but with smaller apertures 14 and are arranged to connect together adjacent inner link assemblies 2. A given outer link plate 4 overlaps with adjacent inner link assemblies 2 such that each of its apertures 14 is aligned with a corresponding aperture 10 in the inner link assembly 2 and is connected to the inner link assemblies 2 by pins 16 that pass through the aligned apertures 10, 14 and are received in the bushes 8. The apertures 10 in the inner link assemblies 2 are sized such that the assemblies are free to rotate on the pins 16 but the outer link plates 4 are fixed to the pins 16. More specifically, the apertures 14 in the outer link plates 4 are sized such that the edge of the plate around them is an interference or friction fit with the pins 16.
The chain 1 further comprises a resilient member which in this embodiment is in the form of an elongate flexible member 20 that is threaded through the inner link assemblies 2, along the length of the chain, in a sinuous formation. The elongate flexible member 20 is made of any suitable resilient material that is elastically deformable in a direction substantially perpendicular to its longitudinal axis in the manner shown in
In this arrangement the elongate flexible member 20 is threaded through the chain 1 such that it alternately passes over and under successive rollers 12 of the chain (in other embodiments however, it may be arranged to miss one or more rollers, for instance it may pass over and under successive pairs of rollers). This can be seen most clearly in
The arrangement allows the chain 1 to behave in the manner of a spring in that a load applied to the chain in a direction that tends to straighten the chain, such that the link plates 4, 6 are moved towards a straight configuration, is resisted by the elongate flexible member 20. As the load increases the chain 1 is forced towards the straight configuration and the undulating form of the flexible member 20 increases, thereby offering greater resistance to the load. This is shown in
The resilient elongate flexible member 20 may be made from any suitable flexible material such as for example, a polymer, steel, a synthetic or natural fibrous material, or a composite material. It is resilient such that it springs back to its original linear form once the load is removed. The chain 1 is thus designed such that elongate flexible member 20 has sufficient stiffness to force the chain links 2, 4 to articulate and to resist straightening of the chain links. The member may be rectangular or any other shape that would conveniently pass along the length of the chain in the manner described above. The member may be a unitary, continuous piece or it may be discontinuous i.e. it may comprise a plurality of pieces placed at different locations along the length of the chain. In the latter instance the pieces may be disposed at selected strategic locations so as to provide a variable stiffness characteristic along the chain length.
This chain 1 may have inherent damping capabilities owing to losses in energy that occur as a result of the elongate flexible element 20 sliding over the rollers 12 as the chain flexes. The damping characteristics could be improved if the resilient elongate flexible member 20 is manufactured wholly or partly from a suitable polymeric damping material. In one example the entire member 20 is made from a polymeric damping material having suitable characteristics to provide the required damping whilst also having the capacity to carry the load applied to the chain. One example is an injection mouldable polymer such as, for example, a thermoplastic polyester elastomer. A commercially available product of this kind is available from Dupont under the trade mark Hytel®. As an alternative, the resilient elongate flexible member 20 may comprise a core of suitable material such as spring steel (for example) to which a suitable elastomeric polymer coating is applied (e.g. a nitrile rubber or other synthetic rubber copolymer).
A damper assembly according to a first embodiment of the invention is shown in
In this embodiment the first mounting element takes is in the shape of an elongate cylindrical cup of substantially uniform wall thickness, in other words it is in the shape of a substantially uniform cylindrical tube with one closed end and one open end. The internal space within the first mounting element 22 forms a mounting element cavity 28. The second mounting element 24 takes the form of a piston 26, which is slidably received within the mounting element cavity 28. The piston of this embodiment is in the shape of a closed-ended cylindrical tube of substantially constant cross section. The internal space within the piston 26 defines a piston cavity 30. The chain 1 is received fully within the piston cavity 30, which forms a reservoir which contains damping fluid and holds it in contact with the chain.
The chain 1 is connected at one end to the piston 26 by a protrusion 32 in the form of a cylindrical peg which is received within a bush 8 of the chain (which allows the adjacent link to pivot about the protrusion). The chain 1 is connected at the other end to the first mounting element 22 via another protrusion 34, also in the form of a cylindrical peg received within a bush 8. The peg 34 projects from the surface of the mounting element cavity 28, through an aperture 36 in the piston. In this embodiment the aperture is in the form of a slot which is parallel to the common axis of the piston 26 and cavity 28 (that is to say the axis about which the piston and cavity are movable relative to one another).
The damper assembly of the first embodiment is arranged to damp compressive forces (in the vertical direction from the perspective of
When a compressive force is applied, the first and second mounting elements 22, 24 are forced towards the second position (shown in
As outlined above as the extension of the chain increases, the resistive force generated by the resilient elongate flexible member 20 also increases. If the compressive force is relatively low, therefore, the mounting elements 22, 24 will only move part way to the second position and the chain will reach a configuration nearer to the straight configuration but not fully straight, as shown in
If the compressive force is relatively large, however, the biasing force from the chain 1 will be insufficient to counteract it. The mounting elements 22, 24 will therefore move to the second position and (in this embodiment) the chain will reach the straight configuration. The chain reaching the straight configuration will provide the ‘hard stop’ discussed above.
Movement of the mounting elements 22, 24 between the first and second positions undergoes a damping action by virtue of energy being dissipated by friction between the rollers 12 and the resilient elongate flexible member 20 (as well as hysteresis in embodiments where the resilient elongate flexible member and/or the rollers are elastomeric). Further damping is provided by the energy dissipated by displacement of the damping fluid as the chain 1 articulates towards/away from the straight configuration. When such a damping fluid is present between surfaces that would otherwise come into contact with one another, it requires a significant amount of energy to move those surfaces relative to each other. Further, in embodiments such as the first embodiment where the chain is in a reservoir of damping fluid, movement of the chain links acts to ‘stir’ the damping fluid, dissipating further energy. The amount of force required and therefore the amount of the damping effect can be controlled by suitable selection of the components of the damping fluid, e.g. the oil components of a grease. The higher the molecular weight of the oil the greater the internal shear resistance of the grease. The damping fluid may also have the effect of reducing the noise of the chain in use, e.g. by acting as a lubricant. A grease which may be suitable for use as a damping fluid is commercially available from Nye Lubricants Inc. of Fairhaven, Mass., USA. It is thought that a such a damping grease having a base kinematic viscosity (at 25° C.) of around 50,000 cSt (0.05 m2/s) would be appropriate for most applications.
The piston 26 being made from multiple sections may simplify the manufacturing and/or assembly processes of the damper assembly, and as outlined above the sealing members 44 assist in the prevention of leaks. Further, the provision of the gas pocket 45 provides the damper assembly with additional resistance to compression, as movement of the piston 26 further into the mounting element cavity 28 compresses the gas in the gas pocket 45, which in turn provides a restorative force acting to push the piston outwards again. The extent of this restorative force can be controlled by suitable selection of the volume of the gas pocket 45, and the pressure of the gas contained therein for a given displacement of the piston 26 (for example the gas pocket could be filled with pressurised gas during construction of the assembly). Though the gas pocket of this damper assembly is located in the mounting element cavity, other embodiments may have one or more gas pockets for the same purpose in the same or in any other suitable locations.
A further modification of the first embodiment is shown in
As in the first embodiment, the second mounting element 24 takes the form of a piston 26, which is slidably received within a mounting element cavity 28 defined by the first mounting element 22. Unlike the first embodiment, the piston of the second embodiment is solid (i.e. does not define a cavity). It also has a projection 58 which protrudes from the mounting element cavity 28. In this embodiment the chain is fully enclosed within the damper assembly by virtue of it being positioned within the mounting element cavity 28. The mounting element cavity 28 in this embodiment acts as the reservoir for damping fluid.
The damper assembly of the second embodiment has a housing unit 54 with a housing unit cavity 55. The first mounting element 22 is slidably received within the housing unit cavity 55. It will be noted that the housing unit 54 is similar in appearance to the first mounting element of the first embodiment, and the first mounting element 22 of the second embodiment is similar in appearance to the piston of the first embodiment. The first mounting 22 element has an aperture 53, which provides fluid communication between the mounting element cavity 28 and the piston cavity housing unit cavity 55.
As with the first embodiment, the chain 1 is connected at one end to the piston 26 by a protrusion 32, and the other end of the chain is connected to the first mounting element 22 by a protrusion 34. Again, both protrusions take the form of cylindrical pegs received within a bush 8 of the chain.
In the second embodiment, moving the mounting elements 22, 24 to the first position requires the piston 26 to be moved outwards within the mounting element cavity 28, away from the first mounting element 22. This can be achieved e.g. by applying a tensile force between the piston 26 and the housing unit 54, or by applying a compressive force between the first mounting element 22 and the housing unit. If a tensile force is applied between the piston 26 and the housing unit 54 (e.g. if the piston is pulled downwards from the perspective of
The second embodiment provides damping as described above, with energy being dissipated by friction between the rollers 12 and the resilient elongate flexible member 20 (and potentially by hysteresis as outlined previously), and by displacement of the damping fluid by the chain 1 as it articulates towards/away from the straight configuration. Further energy is dissipated by the piston 26 and mounting element cavity 28 functioning as a piston pump, in this case displacing damping fluid between the mounting element cavity 28 and the housing unit cavity 55.
In the second embodiment both the first mounting element 22 and the piston 26 (via the projection 58) both protrude from the housing unit cavity 55. They are therefore both accessible for the application of force, allowing the damper to work either in tension (e.g. by moving the piston 26 relative to the housing unit 54) or in compression (e.g. by moving the first mounting element 22 relative to the first housing unit). In other embodiments however, the piston 26 or the first mounting element 22 may be flush with or recessed within the mouth of the housing unit cavity 55 so that the damper functions only in tension or compression. For instance, the piston may not be provided with a projection.
It is to be understood that the relationship between movement of the piston 26 and movement of the first mounting element 22 is linked by the sizes of the mounting element cavity 28 and the housing unit cavity 55. For instance, the stroke length of the assembly (i.e. the total displacement which can be accommodated before reaching the ‘hard stop’) when compressive load is applied between the first mounting element 22 and the housing unit 54 could be decreased by narrowing the mounting element cavity 28. By doing so, the amount of damping fluid displaced from the housing unit cavity 55 by moving the first mounting element 22 a particular amount would constitute a larger proportion of the total volume of the mounting element cavity 28. The piston 26 would therefore have to move further within the mounting element cavity to accommodate this fluid, which would stretch the chain to a greater extent and mean that it reached the straight configuration sooner.
The damper assembly of the third embodiment has two identical counterposed second mounting elements 24a, 24b, either one of which can be moved to a second position with respect to the first mounting element 22. Each second mounting element 24a, 24b comprises a piston 26a, 26b. Both pistons 26a, 26b are slidably received within the mounting element cavity 28. The chain 1 is attached at one end to piston 26a by protrusion 60a, and at the other end to piston 26b by protrusion 60b. The chain is also attached to the first mounting element 22 via a protrusion 62 that projects from the surface of the mounting element cavity 28. The point along the longitudinal axis of the chain 1 at which the first mounting element 22 is attached is between the points at which the second mounting elements 24a, 24b are attached. In other words, the points along the longitudinal axis of the chain at which the second mounting elements 24 are attached are on opposite sides of the point at which the first mounting element 22 is attached.
The damper assembly of the third embodiment can function in tension or compression, with force being applied between the first mounting element 22 and one of the second mounting elements 24a, 24b. For example, if compressive force was applied between the first mounting element 22 and the second mounting element 24b, the piston 26b would move upwards (from the perspective of
If, on the other hand, a tensile force was applied between the first mounting element 22 and the second mounting element 24b, the piston 26b would move downwards (from the perspective of
In any event, when a force is applied to the damper assembly one of the second mounting elements 24a, 24b is moved to the first position relative to the first mounting element 22, which leads to one portion of the chain being stretched (i.e. moved towards the straight configuration) and another being contracted (i.e. moved away from the straight configuration). The stretched portion of chain provides a biasing force which urges the first mounting element 22 and second mounting element (the one which was moved towards the second position relative to the first mounting element by the applied force) towards the first position again. As the entire chain articulates (be it towards or away from the straight configuration), dissipating energy through friction and displacement of damping fluid, the whole chain contributes to the damping effect of the assembly.
In the third embodiment the movement of the counterposed second mounting elements 24a, 24b is restricted by the damping fluid, which (due to its incompressible nature) prevents any change in volume of the space in the mounting element cavity 28 between the two pistons 26a, 26b.
As outlined above, part of the damping capabilities of the above embodiments result from motion of the chain dissipating energy by displacing damping fluid.
A development of the above chain is shown in
It will be appreciated that in embodiments with a resilient elongate flexible member threaded along at least part of the length of the chain, in use the resilient elongate flexible member may move along the longitudinal axis of the chain under the influence of repeated contact with the moving rollers (or other components of the chain). It may therefore be preferable to include retaining means for restricting movement of the resilient member along the chain.
It will be appreciated that in embodiments where the resilient member protrudes from one or both ends of the chain, the extent to which it protrudes will be dependent on the configuration of the chain. In some situations it may be preferable to include one or more retainer lugs.
As the chain articulates, the ends 77a, 77b of the resilient member 20 move within the apertures 86a, 86b (but the retainer lugs 84a, 84b are of sufficient length that the ends of the resilient member are not completely withdrawn from the apertures at any point). The retainer lugs 84a, 84b therefore restrain the lateral movement of the ends 77a, 77b of the resilient member 20. Further, the bases 88a, 88b are positioned to restrain the axial movement of the resilient member 20, preventing it from working free of the chain and/or being damaged or damaging other components.
While in this arrangement the retainer lugs 84a, 84b are both fixed to the piston 26, in other arrangements they may be arranged differently. For instance, the lower (from the perspective of
Though the above embodiments all describe damper assemblies which can work in compression, as these are particularly suitable for use as shock absorbers in vehicle suspension systems, in other applications a damper assembly according to the invention may be designed to work solely in tension. A schematic diagram of one such arrangement, a fifth embodiment of the invention, is shown in
When a tensile force is applied to the damper assembly between the first and second mounting elements 22, 24 (e.g. if the second mounting element 24 is moved downwards from the perspective of
In damper assemblies for some applications, the required resistance to extension may be beyond what can practically be achieved with a single chain. In such circumstances a chain assembly may be utilised.
The chain assembly 112 has six chains 114 each of which is attached at one end to a first connection bracket 116 and at the other end to a second connection bracket 118. In the chain assembly 112 shown in
The chains 114 are arranged in two rows of three, with an alignment structure 128 positioned between the rows. The alignment structure 128 is loosely received within recesses 130 in the connection brackets 116, 118, so that it is able to move to a certain extent within them (see
Each chain 114 of the chain assembly 112 is a roller bush chain, as described previously. As such, each chain 114 defines an articulation plane within which its links can articulate about their respective pins 122. The articulation plane of each chain 114 is substantially perpendicular to its pins 122. In this arrangement, the chains 114 are positioned so that their articulation planes are parallel. As such, the entire chain assembly 112 can articulate within a plane that is parallel to the articulation planes of the chains 114, in a manner akin to a single chain. The articulation of the chain assembly 112 is limited, however, by the alignment structure 128. The loose fit of the alignment structure 128 in the recesses 130 permits movement to a certain extent, beyond which the alignment structure will brace against the walls of the recesses 30 and prevent any further articulation.
The chains 114 are connected to the connection brackets 116, 118 by rivets 126, about which the adjacent link plates (i.e. the distal link plates of the chains 114) can rotate. Each connection bracket 116, 118 also has a rivet 127 which may provide a mounting point for attaching that connection bracket to a first or second mounting element (not shown) of a damper assembly.
In this arrangement the first and second connection brackets 116, 118 are substantially identical. One of the connection brackets 116, 118 is attached to the first mounting element of the damper assembly and the other connection bracket 116, 118 is attached to the second mounting element, such that movement of the mounting elements towards the second position moves the connection brackets 116, 118 towards a second position (described in more detail below), which urges each chain 114 towards the straight configuration. Since the mounting elements are attached to the connection brackets 116, 118 and the connection brackets 116, 118 are attached to the first and second ends of the chains 114, the mounting elements are attached to the first and second ends of chains 114 via the connection brackets 116, 118.
For example, where the chain assembly is part of the damper assembly according to the first embodiment (see
The chain assembly 112 may comprise a plurality of the chains described in relation to the damper assemblies of the above embodiments. The chains may be identical, or may differ (for instance one of the chains may be of the form described in relation to one of the embodiments, and another may be of the form described in relation to a different embodiment).
The chain assembly 112 may be used as part of any of the damper assemblies of the above described embodiments.
The chain assembly 112 of this arrangement also comprises a damper sub-assembly 134 which provides additional damping to that supplied by the chains (as described previously). The damper sub-assembly 134 comprises a piston 136 comprised within the first connection bracket 116, which is slidably received in a fluid cavity 138 provided in the second connection bracket 118. Sealing elements may be provided between the piston 136 and fluid cavity 138, though these are not shown in
In this arrangement the fluid cavity 138 is connected to a duct 140a in the first connection bracket 116 (the duct in this case running through the piston 136) and connected to a duct 140b in the second connection bracket 118. In this arrangement the fluid cavity 138 is filled with damping fluid in the form of grease, and the ducts 140a, 140b are each connected to a bulk source of this grease (such as a reservoir provided by a damper assembly, in which case the entire chain assembly may be positioned within the reservoir and the ducts may simply be left open). The piston 136 and fluid cavity 138 cooperatively form a piston pump mechanism. Movement of the piston 136 deeper into the fluid cavity 138 (i.e. when the connection brackets 116, 118 move towards the first position) forces grease out of the cavity 138 and into the bulk source through one or both of the ducts 140a, 140b. Similarly, the piston being moved outwards from within the fluid cavity 138 (i.e. when the connection brackets 116, 118 move towards the second position) sucks grease into the cavity 138 through one or both of the ducts 140a, 140b. In other arrangements, the fluid cavity 138 may enclose a sealed volume of gas, allowing the piston 136 and fluid cavity 140 to function as an air damper.
The arrangement of
The piston 136 and each of the fluid cavities 138a, 138b co-operatively form piston pump mechanisms as described above. Moving the connection brackets 116, 118 towards the second position pulls the piston 136 outwards from within one or both of the fluid cavities 138a, 138b, sucking grease into the or each cavity through its associated duct 140a, 140b (and potentially from one fluid cavity to the other through the duct 140c in the piston 136). Similarly, moving the connection brackets 116, 118 towards the first position pushes the piston 136 deeper into one or both of the fluid cavities 138a, 138b, forcing grease out of the or each cavity through its associated duct 140a, 140b (and potentially from one fluid cavity to the other through the duct 140c in the piston 136).
The arrangement of
In other arrangements, the spring 144 may only act in tension to supplement the restorative force from the chains 114, or may only act in compression so as to allow the assembly 112 to react to compressive loads (in which case the spring may simply be held between the connection brackets 116, 188, rather than being attached thereto). Further, though in this arrangement no alignment structure is needed, in other arrangements this may be included as well. For instance, the spring 140 may be of diameter sufficient to allow it to function as an alignment structure as described in relation to
In this case, the bladder 146 is shaped so that deforming it not only changes the shape of the fluid cavity 138, but also changes the volume of the fluid cavity. The bladder can therefore function as a pump for damping fluid such as grease, as outlined in relation to
The chain assembly 112 of
As an additional point, it is to be noted that if the bladder 146 is made of a resiliently deformable material, and/or if the fluid cavity comprises a sealed volume of compressible fluid (i.e. gas), the bladder may also constitute a resiliently deformable element as described in relation to
It will be appreciated that numerous modifications to the above described designs may be made without departing from the scope of the invention as defined in the appended claims. For example, in embodiments with a resilient elongate flexible member that is threaded along at least part of the length of the chain, the particular manner in which it is threaded may vary depending on the application. Moreover, for any of the embodiments covered by the claims the rollers (where present) may be made from a polymeric damping material to improve the damping performance of the chain. The material may be injection mouldable for ease of manufacture. In one embodiment the material may be Nylon 6 but many other options would be readily appreciated by the skilled person. The size and/or thickness of the rollers may vary along the length of the chain in order to provide different damping characteristics along the chain. Alternatively, the material of the rollers may vary along the length of the chain to achieve the same effect.
It is to be appreciated that the invention may utilise different forms of chain such as a chain without rollers or bushes, or a chain comprising link plate and pins only such as a leaf chain (e.g. a fork lift truck chain) or a Galle chain. In some instances where there are multiple strands of link plates arranged in parallel along the width of the chain, selected link plates may be removed from the chain to accommodate a resilient elongate flexible member. Moreover, the inner link assembly may take any suitable form including moulded from a plastics material.
While in the described embodiments the first mounting element, second mounting element(s), mounting element cavity, housing unit, housing unit cavity, piston(s) and piston cavity are all cylindrical in shape, in other embodiments one or more of them may be any other suitable shape. For instance one or more of them may be oval, triangular, square, hexagonal or octagonal in cross-section.
In some embodiments of the invention it may be advantageous to provide one or more abutment surfaces to restrict relative motion between two components. Such abutment surfaces may restrict the relative motion between any two of a/the first mounting element, second mounting element, piston, housing unit, or two or more portions of one of said components. It may be particularly advantageous to provide the damper assembly of the second embodiment of the invention with abutment surfaces so as to prevent the piston from being entirely withdrawn from the mounting element cavity.
For the avoidance of doubt, reference above to the ‘ends’ of the chain being attached to components of the damper assembly should not be construed as limiting. Arrangements in which the chain is a continuous loop that is attached to the mounting elements at two points, and arrangements in which a length of chain is attached to the mounting elements at locations other than its ends, are intended to fall within the scope of the invention. Similarly, though the chain is defined as having a ‘straight’ configuration, it is to be appreciated that in practice the links of a chain may be incapable of reaching substantial alignment (such as if the force from the resilient member is sufficient that the chain would deform or snap under load before reaching the straight configuration).
Although in the above damper assemblies with two counterposed second mounting elements the relative motion of the second mounting elements is substantially prevented, in some applications it may be preferable for them to be partially or entirely free to move independently. For instance, it may be preferable in some situations to change the damping fluid between the pistons of the third embodiment from a grease to a gas. This would provide a degree of autonomy of the second mounting elements but still restrict their motion up to a point. Alternatively, the damping fluid may be replaced by a (vented) space. The two second mounting elements would then be entirely independent and the damper assembly would function as a pair simple tension dampers. Furthermore, though
For the avoidance of doubt, although in the described embodiments of chain assemblies the connection brackets are moved towards the second position by moving them directly apart, in other embodiments they may be movable towards the second position in any other suitable fashion. For instance, they may be moved towards the second position by rotation, pivoting, and/or movement towards and/or tangentially relative to one another, instead or in addition to movement away from one another.
The described and illustrated embodiments are to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the scope of the inventions as defined in the claims are desired to be protected. Optional and/or preferred features as set out herein may be used either individually or in combination with each other where appropriate and particularly in the combinations as set out in the accompanying claims. It should be understood that while the use of words such as “preferable”, “preferably”, “preferred” or “more preferred” in the description suggest that a feature so described may be desirable, it may nevertheless not be necessary and embodiments lacking such a feature may be contemplated as within the scope of the invention as defined in the appended claims. In relation to the claims, it is intended that when words such as “a,” “an,” “at least one,” or “at least one portion” are used to preface a feature there is no intention to limit the claim to only one such feature unless specifically stated to the contrary in the claim. When the language “at least a portion” and/or “a portion” is used the item can include a portion and/or the entire item unless specifically stated to the contrary.
Number | Date | Country | Kind |
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1218800.9 | Oct 2012 | GB | national |
1219281.1 | Oct 2012 | GB | national |
1223073.6 | Dec 2012 | GB | national |
1300689.5 | Jan 2013 | GB | national |
1304231.2 | Mar 2013 | GB | national |
1305756.7 | Mar 2013 | GB | national |
Filing Document | Filing Date | Country | Kind |
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PCT/GB2013/052731 | 10/18/2013 | WO | 00 |