WO2010070624A1

WO2010070624A1 - Linear shock absorber with rotary shaft

Info

Publication number: WO2010070624A1
Application number: PCT/IB2009/055858
Authority: WO
Inventors: Carlo Migli
Original assignee: Titus International Plc
Priority date: 2008-12-19
Filing date: 2009-12-18
Publication date: 2010-06-24

Abstract

A fluid shock absorber comprises an outer guide casing (11) inside which the piston (12) slides, the inner shape of the casing and the outer perimeter of the piston being such made that only an axial displacement of the piston without any possibility of relative rotation is allowed. The central portion of the piston has a generally helically shaped hole matching, with a minimum play, with the shaft (15) housed inside the casing (11) at a central position thereof. The shaft (15) is kept in place by the closing element (23) hermetically closing the casing (11). The shaped element (27) is fastened to the projecting part of the shaft (15) being integral therewith for rotation, so that rotation of the shaft (15) can be operated from the outside. Through rotation of the element (27), the piston (12) is constrained to slide inside the casing (11) causing compression of the fluid that fills the inner cavity thereof; thus a damping effect is generated on the force that has generated the rotation torque applied to the shaft.

Description

LINEAR SHOCK ABSORBER WITH ROTARY SHAFT

D e s c r i p t i o n

The present invention relates to a fluid shock absorber of the innovative type. In particular, the present invention concerns a linear shock absorber with rotary shaft. In addition the present invention concerns a linear shock absorber with double piston.

The linear shock absorbers of the known art essentially consist of a glass-shaped cylindrical casing inside which a piston slides, which piston is rigidly- connected to a rod. The cylindrical casing is such closed that only the free end of the rod projects externally of said casing. The end of the cylinder from which the rod comes out is protected by suitable seals so that the inner chamber within which the piston slides is perfectly insulated from the external environment. The inner chamber is filled with an incompressible fluid of suitable viscosity; in this manner, by exerting an axial force from the outside on the free end of the rod, the piston movement causes the fluid to be forced and to escape through the free space towards the inside of the casing. By suitably combining the fluid viscosity, cylinder section and clear-span section between the cylinder and piston, a braking force is obtained which is proportional to the displacement speed of the rod and ultimately the desired cushioning effect is achieved.

This production technology is used with minimum variants in a great number of application fields; recently the furniture sector too is to be added and included in the numerous applications, since important amounts of shock absorbers of small sizes and reduced costs are used for controlling the movement of doors, sliding wings and drawers.

The main use concerns braking of linear movements such as in case of end-of-stroke stops for closing drawers. There are also cases in which a linear fluid shock absorber is used for braking substantially rotary- movements, such as when door closures and hinges for furniture are concerned.

In all cases the known shock absorbers of the prior art described above have two fundamental drawbacks by which the designers are heavily constrained when studying the different applications.

1) Sliding of the piston takes place within the cylinder which is hermetically closed, so that it is necessary for the rod to emerge to the outside in the direction of the cylinder axis over a length at least equal to the piston stroke.

Due to the above consideration, for use of a shock absorber a space more than twice that actually necessary is required to be available.

2) During the power stroke, the rod penetrates into the hermetically sealed chamber containing the fluid and the piston, thus giving rise to a reduction in the inner volume of said chamber. Since the fluid filling the cylinder is incompressible, a suitable mechanism must be provided for compensating for this volume variation; to this aim, normally either air-containing closed-cell sponges or floating-seal systems are used, like the system described in patent EP1703060.

In both cases room is required for these mechanisms, the cylinder being further extended, and the ratio between the useful stroke and the overall bulkiness of the shock absorber is still more reduced.

In addition, when use of a shock absorber is provided for damping rotary motions, complex transmission systems are to be used to convert the rotary motion into a linear motion; examples of these systems are disclosed in patents EP1851406 and WO2007038815.

It is a general aim of the present invention to obviate the above mentioned drawbacks by providing a linear shock absorber that does not use a rod integral with the piston, thus enabling a more favourable ratio between the useful stroke and the overall bulkiness to be obtained and therefore advantageously allowing use of the linear fluid shock absorber also in those cases in which the available room is minimum, such as at the inside of furniture hinges.

A further object consists in reducing the number of components and, as a result, the all-in cost of the shock absorber.

In view of this aim, in accordance with the invention a shock absorber has been devised which comprises a casing of constant section inside which a piston slides with a minimum play, which piston is adapted to move along the axis of the casing itself, the movement of which is controlled by the rotation of a central shaft that in turn is constrained to have a minimum axial movement .

In view of the above aim, in accordance with the invention a shock absorber has been further devised which comprises a casing of constant section inside - A -

which two pistons slide with a minimum play, which pistons are adapted to move along the axis of the casing itself, the movement of said pistons being controlled by the rotation of a central shaft that in turn is constrained to have a zero or minimum axial movement .

In particular, this aim is achieved by a shock absorbing device in accordance with claim 1 or 19.

The dependent claims concern possible embodiments of the shock absorbing device in accordance with the present invention.

For better clarifying the explanation of the innovative principles of the present invention and the advantages it offers over the known art, some possible preferred embodiments applying these principles will be described hereinafter by way of examples, with the aid of the accompanying drawings. In the drawings:

- Fig. 1 is a perspective view of a shock absorber made following the principles of the invention;

- Fig. 2 shows a sectional view of the shock absorber seen in Fig. 1; - Fig. 3 is an exploded perspective view of the shock absorber seen in Fig. 1;

- Fig. 4 is a diagram showing the positioning of the shock absorber of Fig. 1 in a suitable seat;

- Fig. 5 is a perspective view of a diaphragm valve to be applied to the piston of a shock absorber made following the principles of the invention;

- Fig. 6 is a perspective view of a piston of a shock absorber made following the principles of the invention; - Fig. 7 is a perspective view of the inner components of a shock absorber made following the principles of the invention;

- Fig. 8 shows the same view as seen in Fig. 7 but in a situation of opposite motion; - Fig. 9 is a perspective view of a second shock absorber made following the principles of the invention;

- Fig. 10 is a sectional view of the shock absorber seen in Fig. 9; - Fig. 11 is an exploded perspective view of the shock absorber seen in Fig. 9;

Fig. Ia shows a perspective view of a shock absorber made following the principles of the invention;

- Fig. 2a is a sectional view of the shock absorber seen in Fig. Ia;

- Fig. 3a shows an exploded perspective view of the shock absorber seen in Fig. Ia;

- Fig. 4a shows a perspective view of a diaphragm valve to be applied to the piston of a shock absorber made following the principles of the invention;

- Fig. 5a is a perspective view of a piston of a shock absorber made following the principles of the invention;

- Fig. 6a is a perspective view of the inner components of a shock absorber manufactured following the principles of the invention;

- Fig. 7a shows the same view as seen in Fig. 6a, but in a situation of opposite motion;

- Fig. 8a is a perspective view of a second shock absorber made following the principles of the invention;

- Fig. 9a is a sectional view of the shock absorber seen in Fig. 8a;

- Fig. 10a shows an exploded perspective view of the shock absorber seen in Fig. 8a. With reference to Figs. 1, 2 and 3, the shock absorber or shock absorbing device made in accordance with the invention and generally denoted at 10, comprises a glass-shaped casing or container 11 inside which a piston 12 slides with a minimum play. The section of casing 11 is generally made in such a manner that it does not enable rotation of piston 12 (a square section in the figures) . In the example shown the piston and casing 11 both have a section adapted to inhibit rotation of the piston around a longitudinal axis of the shock absorber. For instance, both the piston and casing 11 have a square section so that the obtained thus shaped coupling is only suitable to enable sliding of the piston along the longitudinal axis of the shock absorber. Piston 12 has a central hollow 13 of circular section with two or more helical female grooves 14. Housed inside the hollow 13 is a shaft 15. In the example shown in the figures shaft 15 substantially consists of four coaxial portions: the first portion 16 or inner end portion has a circular section and is fitted with a minimum play in a hollow 17 formed in the inner end portion of the container 11. The second portion 18 or sliding portion has a cylindrical section with helical male ridges 19 matching with the similar female grooves 14 of the hollow 13 of piston 12. The third portion 20 or sealing portion has a cylindrical section of a smaller diameter than that of ridges 19 of the second portion 18 and is provided with a circular groove 21 in the central part thereof. The last portion 22 or outer end portion has a generally non-circular shape (an axially symmetric hexagonal shape in the figures) the maximum outer diameter of which is the same as or smaller than that of the third portion 20. Container 11 is closed by a plug 23 or closing element having a hole 24 coaxial with the cylindrical hollow 17. The diameter of hole 24 is slightly bigger relative to the third portion 20 but smaller than the ridges 19 of the second portion 18. Housed in groove 21 is a seal 25.

The components identified with 11, 12, 15 and 23 (i.e. casing 11, piston 12, shaft 15 and plug 23) are such sized that, when the plug 23 is secured to the end of casing 11, by welding for example, the second portion 18 of the shaft 15 is fully housed in the cavity thus formed, the seal 25 is in the centre of hole 24 of the plug, thus ensuring insulation of the inner chamber of the container 11, and the last portion 22 projects to the outside of the outer surface 26 of the plug 23. Fastened to this free end of shaft 15, in a manner integral therewith for rotation, is an element 27 carrying suitable means (tooth series 28 in the figures) adapted to drive the rotation of the shaft itself. For instance, the element 27 is provided with a hole the section of which has a shape matching that of the section of the last portion of shaft 15 (a hexagonal shape, for example) , adapted to receive said portion of the shaft and to be integral therewith for rotation about the longitudinal axis of the shock absorber.

Rotation of shaft 15 relative to container 11, obtained by means of a rack or other element acting on the projecting end of the shaft, due to the presence of the helical guides 14 and 19, causes axial displacement of piston 12. The shaft 15 can therefore rotate within the limits allowed by the stroke of piston 12 inside the cavity of container 11, with a minimum axial displacement limited by the inner abutment of plug 23. The variation in the inner volume of the cavity determined by the axial oscillations of shaft 15 is compensated for by small axial displacements that the seal 25 can carry out. The spaces in the cavity closed by seal 25 and left free by piston 12 and shaft 15 are filled with an incompressible fluid of suitable viscosity. In this way, by rigidly fastening the container 11, a tangential force applied to the means 28 of the element 27, causes the axial displacement of piston 12. Fluid escape through the free spaces of the piston-container and piston-shaft couplings gives rise to a damping effect proportional to the rotation speed.

A second damping effect can be obtained by acting on an end surface 29 of shaft 15: in the exemplary embodiment shown in Figs. 1, 2 and 3, through a clockwise rotation of element 27, piston 12 is axially pushed towards the end portion of container 11 opposite to plug 26 (to the left with reference to Fig. 2 or 3) ; by reaction, the shaft 15 is submitted to a thrust in the opposite direction, i.e. an axial direction towards the outside of container 11, towards plug 23; likewise, by rotating element 27 counterclockwise, piston 12 is pushed towards the outside (to the right with reference to Fig. 2 or 3) and therefore, by reaction, shaft 15 is pushed towards the inside of container 11. The movement to the outside of shaft 15 is limited by the ends of ridges 19 abutting against the edge of hole 24 while the movement in the opposite direction is limited by the first portion 16 abutting against the inside of hollow 17. Generally, the couplings of shaft 15 with container 11 and plug 23 can be such obtained that the overall length 1 of the shock absorber oscillates between two predetermined values L¹ and L² with L¹ £ 1 £ L², depending on whether forces giving rise to clockwise or counterclockwise rotations of shaft 15 are applied to the means 28. At all events, the axial oscillations of shaft 15 are restricted to such an extent that the resulting volume variations of the inner chamber of container 11 can be always compensated for by slight displacements of seal 25.

If the shock absorber 10 is contained between two parallel stiff walls 30 and 30' at a distance L forming a stiff cavity (Fig. 4) with L¹ < L < L², in such a manner that the closed portion of container 11 is rigidly fastened to wall 30 by suitable means (not shown in the figure) adapted to prevent rotation thereof, when rotation of shaft 15 takes place clockwise, its end or end surface 29 scrapes against wall 30', whereas if the rotation direction is inverted, no contact between the two surfaces exists any longer.

With reference to Figs. 1, 2, 3 and 4, through clockwise rotation of element 27, piston 12 moves to the left and finds an axial resistance F directed to the right due to the escape of fluid, in proportion to its speed. This force F is discharged on the helical coupling means (grooves and ridges) between piston 12 and shaft 15 and is essentially divided into two components, an axial and a tangential component, relative to shaft 15. Both components are still proportional to the translation speed of piston 12 and therefore the rotation speed of element 27. The tangential component directly opposes the torque applied to shaft 15 creating the desired damping effect. The axial component is discharged against the holding wall through contact between surfaces 29 and 30'. Since shaft 15 rotates relative to the holding wall, if walls 29 and 30' are made according to a shape and using materials adapted to obtain a high friction coefficient, a further braking torque is added which too is proportional to the rotation speed of element 27.

Through counterclockwise rotation of element 27, piston 12 moves to the right generating an axial resistance by effect of the fluid escape, which is analogous with, but opposite to that previously seen.

Likewise, the end surface of portion 16 of shaft 15 scrapes against the bottom of hollow 17 thus generating a further resistant torque by effect of friction. Still acting on the shape, material, and lubrication of the walls in contact, however the last-mentioned braking torque can be reduced as compared with the same torque generated by the motion in the opposite direction between walls 29 and 30'.

A further reduction in the braking torque when piston 12 moves to the outside of container 11 can be obtained by adding a one-way valve to the piston, so that the clearance between piston and container greatly increases when piston 12 moves towards the outside of container 11.

Valves of this type can be made in different ways and one of them, which is particularly simple, is shown in Figs. 5, 6, 7 and 8. Piston 120 has two opposite longitudinal grooves 121 and 121'. In a piston of square section the two longitudinal grooves 121 and 121' are for example formed at the opposite corners. Generally, at least one groove could be provided. A flexible diaphragm valve 122 is fastened to the piston face turned towards the inside of container 11 by means of opposite protrusions 123 and 123' penetrating into corresponding piston hollows (not shown in Fig. 6) . The valve 122 has flaps 124 and 124' adapted to deflect relative to the piston surface. Close to the two flaps 124 and 124' four hollows 125, 126, 125' and 126' are formed which are such obtained that when the valve is disposed close to the piston, they are at the sides of grooves 121 and 121', while the remaining portions of flaps 124 and 124' fully close the grooves themselves. When there is at least one groove, at least one flap can be provided with preferably two hollows in the vicinity of said flap.

According to the above described configuration, when the shaft 15 rotates clockwise (Fig. 7) piston 121 moves to the left and the fluid pressure causes the diaphragm 122 to completely adhere to piston 120, so that the flaps 124 and 124' close grooves 121 and 121'; when the shaft 15 rotates counterclockwise (Fig. 8), piston 121 moves to the right and the fluid pressure moves flaps 124 and 124' apart: in this manner, the fluid can run through the additional channels consisting of the cavities formed by grooves and hollows 121, 125, 126, and 121', 125', 126', respectively.

A second possible embodiment is described in Figs. 9, 10 and 11: the shock absorber or shock absorbing device, made in accordance with the invention and generally denoted at 210, comprises a casing or container 211 of a glass-shaped configuration inside which piston 212 slides with a minimum play. Piston 212 has two through hollows 213 and 213' of circular section, each having two or more helical female grooves 214 and 214'. Shafts 215 and 215' are housed in said hollows 213 and 213'. The container 211 is closed by a plug 223 having holes 224 and 224' coaxial with the hollows 217 and 217 ' formed in the inner end portion of container 211. Seals 225 and 225' acting within the holes 224 and 224' ensure insulation of the inner chamber of the shock absorber filled with the incompressible fluid. The shape of shafts 215 and 215', as well as the sizes of same as compared with the other components of the shock absorber, are the same as those previously described for the embodiment shown in Figs. 1, 2 and 3. Elements 227 and 228' are fastened to the portions 222 and 222' of shafts 215 and 215' projecting externally of the outer surface 226 of plug 223 in such a manner that they are integral therewith for rotation, said elements 227 and 227' carrying suitable means (tooth series 228 and 228' in the figures) adapted to drive rotation of said shafts. It is apparent that in this embodiment the shape in section of container 211 has no particular constraint (it is circular in the figures) , as the condition of non-rotation of piston 212 relative to container 211 is ensured by the presence of the two shafts 215 and 215' that, being axially fastened to hollows and holes 217, 222 and 217', 224' respectively, do not allow rotation of piston 212. In the configuration described in the figures it may be advantageous for the helical female grooves 214 and 214' and the corresponding helical male ridges 219 and 219' to be made with spirals of opposite winding directions: in this embodiment, a single element 231, in the form of a rack for example, by simultaneously engaging elements 227 and 227 ', causes reverse rotation of same and therefore axial displacement of piston 212 within container 211. In this manner, by rigidly fastening container 211, a force applied to the end 232 of element 231 causes axial displacement of piston 212 towards the end portion of the container 211 opposite to plug 223. Escape of fluid through the free spaces of the piston- container and piston-shaft couplings gives rise to a damping effect proportional to the translation speed of element 231.

The shock absorber described in the present invention achieves the intended purposed enabling a very favourable ratio to be obtained between the stroke of the force to be damped and the overall length of the shock absorber. Further advantages are represented by a reduction in the number of components (the system for compensation of the inner volume is not required) and by the greater simplicity of said components (scraping of the shaft relative to the seal is mainly parallel to the seal plane, while in traditional shock absorbers said scraping is perpendicular, which makes manufacture of the seal more complicated and expensive) .

Obviously, the above description of an embodiment applying the innovative principles of the present invention is given by way of example only of these principles and therefore must not be considered as a limitation of the inventive scope as claimed.

For instance, as it can be easily understood by a person skilled in the art, the means 28 of element 27 can be shaped in a quite different manner, in the form of a tooth for example, and in addition, if the force to be damped comes from a single direction, a spring mechanism can be easily added for automatic reloading of the shock absorber in the opposite direction as soon as the action of the force itself stops. For instance, the container can have other shapes, in particular coupling with the piston may be provided for defining a constraint to rotation of the piston itself around the longitudinal axis of the shock absorber.

Coupling between the shaft and the element so that they are integral with each other for rotation can be obtained by adopting any matching of shape or other types of couplings suitable for reaching this purpose, such as pegs or the like.

Generally the invention concerns a shock absorbing device comprising a glass-shaped casing internally defining a chamber filled with an incompressible fluid; a piston housed in the inner chamber of the casing and free to axially slide; at least one shaft housed in the inner chamber of the casing, structurally distinct from the piston and coupled thereto, and emerging to the outside of the casing by an end thereof through a closing element provided with seals which delimits and insulates said inner chamber, wherein the shaft-piston coupling is obtained in such a manner as to cause axial displacement of the piston by the relative rotation of said shaft with respect to said piston.

Advantageously, the piston-shaft coupling defines a coupling with lead nut and worm screw, wherein each element can perform both functions. The grooves and ridges can therefore have a shape different from that described and illustrated above.

Generally the shock absorber according to the present invention further comprises means for modifying the braking torque as a function of the direction of the external force applied. With reference to Figs. Ia, 2a and 3a, the shock absorber or shock absorbing device made in accordance with the invention and generally denoted at 10 comprises a glass-shaped casing or container 11 inside which pistons 12 and 12' slide with a minimum play. The section of casing 11 (a square section in the figures) is generally such made that rotation of pistons 12 and 12' is not allowed. In the embodiment shown the pistons and casing 11 both have a section adapted to inhibit rotation of the pistons around a longitudinal axis of the shock absorber. For instance, the pistons and casing 11 both have a square section adapted to create a coupling of a form suitable to only allow sliding of the pistons along the longitudinal axis of the shock absorber. Piston 12 has a central hollow 13 of circular section with two or more helical female grooves 14. Likewise, piston 12' has the central hollow 13' of circular section with two or more helical female grooves 14' with a winding direction opposite to that of grooves 14. The shaft 15 is housed at the inside of hollows 13 and 13'. In the embodiment shown in the figures the shaft 15 substantially consists of five coaxial portions: a first portion 16 or inner end portion has a circular section and is fitted with a minimum play into the hollow 17 formed in the inner end portion of the casing 11. The second portion 18 or sliding portion has a cylindrical section with helical male ridges 19 matching with a minimum play with the similar female grooves 14 of the hollow 13 of piston 12. The third portion 18' or further sliding portion has a cylindrical section with helical male ridges 19' matching with a minimum play with the similar female grooves 14' of the hollow 13' of piston 12'. The fourth portion 20a or sealing portion has a cylindrical section of smaller diameter than that of ridges 19' of the third portion 18' and has a circular groove 21 in the central part thereof. The last portion 22 or outer end portion or projecting portion has a generally non- circular shape (an axially symmetric hexagonal shape in the figures) the maximum outer diameter of which is the same as or smaller than that of the fourth portion 20a. The casing 11 is closed by a plug 23 having a hole 24 coaxial with the cylindrical hollow 17. The hole 24 has a diameter slightly bigger as compared with that of the fourth portion 20a but smaller with respect to ridges 19' of the third portion 18'. Housed in groove 21 is a seal 25.

The components identified with 11, 12, 12', 15 and 23 (i.e. container 11, piston 12, other piston 12', shaft 15 and plug 23) are such sized that, by securing plug 23 to the end of casing 11, by welding for example, the three first portions 16, 18 and 18' of shaft 15 are fully housed within the cavity thus formed, seal 25 is inside the hole 24 of the plug thus ensuring insulation of the inner chamber of casing 11 and the last portion 22 projects externally of the outer surface 26 of plug 23.

The abutment of the end portion of the helical ridges 19' against the plug 23 and the overall length of the three first portions 16, 18 and 18' of shaft 15 have such sizes that an axial displacement of the shaft itself equal to zero or of negligible amount is allowed.

Fastened to the projecting portion 22 is the element 27 carrying suitable means (tooth series in the figures) adapted to drive rotation of the shaft itself. The element 27 is fastened to the projecting portion 22 so that it is integral therewith for rotation. For instance, the element 27 has a hole of a section the shape of which matches the section of the last portion of shaft 15 (an hexagonal section, for example) and is adapted to receive this shaft portion and to be integral therewith for rotation about the longitudinal axis of the shock absorber.

In the described configuration, the inner cavity of casing 11, passed through by shaft 15, is essentially divided into three parts: a first cavity or cavity portion 29a is delimited by the closed end of container 11 and by piston 12, a second cavity or cavity portion 30a is delimited by the two pistons 12 and 12', and a third cavity or cavity portion 31a is delimited by piston 12' and plug 23. The three cavities 29a, 30a and 31a have a constant overall volume irrespective of the position of pistons 12 and 12 ' and are in communication with each other either through the coupling clearances of the different components or through possible gauged cavities formed in pistons 12 and 12' (not shown in the figures) . Rotation of shaft 15 relative to container 11, due to the pairs of helical guides 14, 19 and 14', 19', causes axial displacement of pistons 12 and 12' in the opposite direction. Shaft 15 can therefore rotate within the limits allowed by the stroke of pistons 12 and 12' inside the cavity of container 11. These limits are externally constituted by the abutments on the bottom of the container 11 and on the inner surface of plug 23 and internally constituted by the contact between said pistons or by the stop at the end of the respective helical ridges 19 and 19' in the junction section between the portions 18 and 18' of shaft 15.

Cavities 29a, 30a and 31a are filled with an incompressible fluid of suitable viscosity. In this manner, by rigidly fastening the container 11, a tangential force F applied to the means 28 of element 27, by a rack or other element acting on the projecting end of the shaft for example, causes axial displacement of pistons 12 and 12'. In particular, with reference to Figs. Ia, 2a and 3a, by rotating element 27 clockwise, piston 12 moves to the right and piston 12 ' moves to the left reducing the volume of the cavity 30a confined by the two pistons within the cavity of container 11. Escape of fluid through the free spaces of the piston- container and piston-shaft couplings from cavity 30a to the outer cavities 29a and 31a, exerts an axial resistant force on the pistons, which force is proportional to the piston translation speed and therefore to the rotation speed of shaft 15. This resistant force is discharged on shaft 15 through the helical couplings. Advantageously, pistons 12 and 12' and the respective helical female grooves 14 and 14 ' are mirror images: in this manner the axial components of the force exerted by pistons 12 and 12 ' on the helical ridges 19 and 19' of shaft 15 are equal and opposite and therefore the axial force acting on shaft 15 during rotation of same is altogether zero. On the contrary, since the winding directions of spirals 19 and 19' are opposite, the tangential components are added up thus creating a resistant torque proportional to the applied force F and therefore, ultimately, achieving the desired damping effect.

In many practical applications the force to be damped has a unidirectional character: this is for instance the case in which the inertia of the thrust given to a door in the direction of the door closure is wished to be damped; the undesirable effect to be eliminated is the impact of the door against the door frame; on the contrary the shock absorber must not act or must only have a minimum action on the force required for opening. In these cases the shock absorber is required to react in a different manner depending on the application direction of the force itself. A manner for obtaining this effect is that of varying the clearance between the pistons and the container by adding a oneway valve to the pistons. There are many ways for making valves of this type and a particularly simple way is shown in Figs. 4a, 5a, 6a and 7a in relation to one of the two pistons (for the other piston an identical valve can be applied and mounted in a mirror image) . Piston 112 has two opposite longitudinal grooves 132 and 132'. In a piston with a square section the two longitudinal grooves 132 and 132' are formed for example at the opposite corners. Generally, at least one groove could be provided. A flexible diaphragm valve 133 is fastened to the piston face turned towards the central cavity 30a by means of the opposite protrusions 134 and 134' to be fitted by friction into the corresponding hollows 135 and 135' of the piston. Valve 133 has the flaps 136 and 136' that are able to deflect relative to the piston surface. In the vicinity of the two flaps 136 and 136' the four hollows 137, 138, 137' and 138' are formed in such a manner that when the valve is moved close to the piston, they are at the sides of grooves 132 and 132 ' , while the remaining portions of flaps 136 and 136' fully close the grooves themselves. In case of at least one groove, at least one flap and preferably two hollows close to the flap can be provided.

According to the above described configuration, when the shaft 115 rotates clockwise (Fig. 6a in a perspective view with the drawing of the outer casing omitted) , piston 112 moves to the right and the fluid pressure causes the diaphragm 133 to completely adhere to piston 112 so that the flaps 136 and 136' close the grooves 132 and 132'; when the shaft 115 rotates counterclockwise (Fig. 7a) , piston 112 moves to the left and the fluid pressure moves the flaps 136 and 136' apart; in this manner the fluid can slide through the additional channels consisting of the cavities formed by grooves and hollows 132, 137, 138, and 132', 137', 138', respectively. Piston 112' to which the diaphragm is applied in mirror image relationship behaves in the same manner.

In the applications in which the force to be damped is of a unidirectional character, it may be useful that also the system transmitting the outer force to be damped to the shaft be configured in a more appropriate manner. In Figs. 8a, 9a and 10a a possible configuration of a shock absorber made in accordance with the invention is described, which shock absorber is particularly suitable for damping unidirectional forces. The shock absorber 210a comprises a glass- shaped holding casing 211a filled with an incompressible fluid of appropriate viscosity, inside which pistons 212a and 212a' provided with the respective one-way valves 233 and 233' slide. The axial movement of the two pistons is controlled by the rotation of the shaft 215a according to the previously described operating system. Fastened to the projecting portion 222a of shaft 215a is the element 227a having the projecting portion in the form of a tooth 239 adapted to receive the force to be damped F, causing rotation of the shaft itself. Inside element 227a, on the side of plug 223, an annular seat 240 is formed which is coaxial with shaft 215a and inside which a spring 241 is housed. The spring has the two projections 242 and 243 that are fastened into two cavities formed in plug 223 and in the seat 240 of element 227a, respectively. The spring 241 is sized in such a manner that it exerts a counterclockwise torque on the element 227a relative to the plug 223 and consequently to the shock absorber body, being the scalar value of this torque negligible relative to that of the torque of opposite orientation generated by the force to be damped F. By applying the force F to the tooth 239 of element 227a, the shaft 215a rotates clockwise and pistons 212a and 212a¹ are axially pushed in opposite directions so as to reduce the volume of the inner cavity 230. By effect of the fluid pressure, valves 233 and 233' close and the fluid is forced to escape through the minimum clearances of the piston- casing and piston-shaft couplings thus generating the desired resistant torque. When the force F is no longer applied (a situation which occurs during opening of the door for example, in the previously described application) , the torque exerted by the spring 241 causes the counterclockwise rotation of element 227a and therefore of shaft 215a; pistons 212a and 212a' are pushed to the outside so as to reduce the volume of cavities 229 and 231; by effect of the fluid pressure, valves 233 and 233' open and the available overall clearance for fluid passage greatly increases, enabling quick reloading of the shock absorber even with the only minimum torque exerted by the spring 241.

The shock absorber described in the present invention reaches the intended purposed and allows a very favourable ratio to be obtained between the stroke of the force to be damped and the overall length of the shock absorber. Further advantages are represented by a reduction in the number of components (the system for compensation of the inner volume is not required) and by the greater simplicity of said components (scraping of the shaft relative to the seal is mainly parallel to the seal plane, while in traditional shock absorbers said scraping is perpendicular, which makes manufacture of the seal more complicated and expensive) .

For instance, as can be easily understood by a person skilled in the art, the means 28 of element 27 can be shaped in a quite different manner, in the form of tooth series for example, and in addition, the winding direction of the spirals can be reversed, without the occurrence of any variation relative to the described operation. For instance, with reference to Figs. Ia, 2a and 3a, the winding directions of the helical ridges 19 and 19' and helical grooves 14 and 14' can be reversed: in this case, by mounting the shaft 15 on the opposite side relative to element 27, a mirror configuration is obtained with exactly the same operation as the described one.

Claims

C L A I M S

1. A shock absorbing device (10; 210; 210a), comprising: - a glass-shaped casing (11; 211; 211a) internally having a chamber filled with an incompressible fluid;

- a piston (12; 112; 120; 212; 212a) housed in the inner chamber of the casing and free to axially slide, which piston has at least one through hollow (13; 213); - at least one shaft (15; 115; 215; 215a) housed in the inner chamber of the casing (11; 211; 211a), passing through the through hollow (13; 213) of the piston (12; 120; 212) and emerging to the outside of the casing with an end (22; 222) thereof through a closing element (23; 223) provided with seals (25; 225) delimiting and insulating said inner chamber; wherein coupling between the shaft (15; 115; 215; 215a) and the through hollow of the piston (12; 112; 120; 212; 212a) is obtained in such a manner that axial displacement of the piston (12; 112; 120; 212; 212a) is caused through the relative rotation of said shaft (15; 115; 215; 215a) with respect to said piston.

2. A shock absorbing device (10; 210a) as claimed in claim 1, comprising:

- a glass-shaped casing (11; 211a) internally having a chamber filled with an incompressible fluid which is closed and insulated at the open end thereof by means of a plug or closing element (23; 223) ; - a pair of pistons (12, 12'; 112, 112'; 212a, 212a¹) housed in the inner chamber of the casing (11; 211a) and free to axially slide between two end positions having at least one through hollow (13, 13');

- at least one shaft (15; 115; 215a) housed in the inner chamber of the casing (11; 211a), passing through the hollows (13, 13') of the pistons (12, 12'; 112, 112'; 212a, 212a¹) and emerging with an end (22; 222a) thereof to the outside of the casing (11; 211a) through the closing element (23; 223) provided with seals (25; 225) delimiting and insulating said inner chamber; wherein coupling between the shaft (15; 115; 215a) and the hollow (13, 13') of each piston (12, 12'; 112, 112'; 212a, 212a') is obtained in such a manner that axial displacement in opposite directions of the two pistons (12, 12'; 112, 112'; 212a, 212a') is determined towards two end positions through the relative rotation of said shaft (15; 115; 215a) with respect to said pistons (12, 12'; 112, 112'; 212a, 212a') .

3. A shock absorbing device as claimed in claim 1 or 2, obtained in such a manner that mutual rotation between the casing and piston or pistons is inhibited.

4. A shock absorbing device as claimed in one or more of the preceding claims, comprising means (27) external to the casing, integral with the shaft (15) for rotation, and adapted to convert a force applied in a plane perpendicular to the casing (11) axis into a torque applied to the shaft (15) itself.

5. A shock absorbing device as claimed in claim 1, having the shaft (15) free to axially oscillate in such a manner that the maximum length of the shock absorber between the end of the casing (11) and the emerging end (22) of the shaft is equal to 1, with L¹ < 1 < L², adapted to be fastened inside a stiff cavity of length L, with L¹ < L < L².

6. A shock absorbing device as claimed in one or more of the preceding claims, comprising a piston (120; 112) provided with a valve (122; 133) of varying configuration, such made that the free clearance in the coupling of said piston with the casing and with the shaft is different, depending on the movement direction of said piston inside the casing.

7. A shock absorbing device as claimed in one or more of the preceding claims, comprising a spring device disposed inside the casing for automatic return of the piston as soon as the effect of the force applied in a plane perpendicular to the casing axis has stopped.

8. A shock absorbing device as claimed in one or more of the preceding claims, comprising a spring device external to the casing for automatic return of the piston as soon as the effect of the force applied in a plane perpendicular to the casing axis has stopped.

9. A shock absorbing device (10) as claimed in one or more of the preceding claims, comprising a pair of pistons (12, 12') each provided with a valve (133) of varying configuration such made that the free clearance in the coupling of said pistons (12, 12') with the casing (11) and with the shaft (15) is different, depending on the movement direction of said pistons

(12, 12') inside the casing (11) .

10. A shock absorbing device (10) as claimed in anyone of the preceding claims, comprising a spring device (241) disposed inside the casing (11) for automatic return of each piston (12, 12') as soon as the effect of the force to be damped has stopped.

11. A shock absorbing device (10) as claimed in anyone of the preceding claims, comprising a spring device external to the casing (11) for automatic return of each piston (12, 12') as soon as the effect of the force to be damped has stopped.

12. A shock absorbing device as claimed in claim 5, wherein the emerging end (22) of the shaft is adapted to scrape against a wall (30') defining said stiff cavity and wherein, due to the shape and the materials used for the emerging end (22) and the wall (30'), a high friction coefficient is obtained.

13. A shock absorbing device as claimed in claim 12, wherein an end surface of a first portion (16) of the shaft (15) is adapted to scrape against the bottom of a hollow (17) housing the shaft (15) and wherein said end surface and said hollow have shapes, materials and lubrication adapted to reduce the braking torque generated by said scraping relative to the same torque generated by the movement in the opposite direction between the emerging end (22) of the shaft and the wall (30') of the stiff cavity.

14. A shock absorbing device as claimed in claim 6 or 9, wherein said valve of varying configuration comprises opposite protuberances (123, 123'; 134, 134') that are frictionally fitted into corresponding hollows of the piston.

15. A shock absorbing device as claimed in claim 6 or 9, wherein said valve of varying configuration comprises at least one flap (124, 124'; 136, 136') adapted to close at least one groove (121, 121'; 132, 132') of the piston and wherein, in the vicinity of the flap, hollows (125, 126, 125', 126'; 137, 138, 137', 138') are formed that are such disposed that when the valve is moved close to the piston they are at the sides of the groove (121, 121'; 132, 132') .

16. A shock absorbing device as claimed in one or more of the preceding claims, wherein the piston (212) has two through hollows (213, 213') each of them housing a shaft (215, 215'), and wherein portions (222, 222') of the shafts project to the outside of an outer surface (226) of a plug (223) .

17. A shock absorbing device as claimed in claim 16, wherein a single element (231) , in the form of a rack for example, simultaneously engages elements (227 , 227') associated with the projecting portions (222, 222') of the shafts (215, 215') causing inverse rotation of same and therefore axial displacement of the piston (212) inside the casing (211) .

18. A shock absorbing device as claimed in one or more of the preceding claims, further comprising means for modifying the braking torque as a function of the direction of the external force applied.

19. A shock absorbing device, comprising: - a glass-shaped casing internally having a chamber filled with an incompressible fluid;

- at least one piston housed in the inner chamber of the casing and free to axially slide;

- at least one shaft housed in the inner chamber of the casing, structurally distinct and coupled to the piston and emerging by an end thereof to the outside of the casing through a closing element provided with a seal delimiting and isolating said inner chamber; wherein coupling between the shaft and the piston is made in such a manner that axial displacement of the piston by relative rotation of said shaft with respect to said piston is caused.

20. A shock absorbing device as claimed in claim 19, wherein a pair of pistons are housed in the inner chamber of the casing and are free to axially slide between two end positions; wherein said at least one shaft is housed in the inner chamber of the casing, structurally distinct and coupled to the pistons and emerging by an end thereof to the outside of the casing through a closing element provided with a seal delimiting and insulating said inner chamber; and wherein coupling between the shaft and each piston is such obtained that the axial displacement in opposite directions of the two pistons towards two end positions is obtained through relative rotation of said shaft with respect to said pistons.

21. A furniture component comprising a shock absorbing device (10) made in accordance with anyone of the preceding claims.