Abstract:
An hydraulic shock absorber with progressive braking effect comprising a cylinder ( 1,2 ) full of fluid and a piston ( 3 ) sliding axially into said cylinder. The piston ( 3 ) divides into two sequential chambers ( 8 ) and ( 9 ) the cylinder compartment ( 1 ). In the extension and/or compression operation, the piston ( 3 ) slides in the cylinder causing the fluid to move from the lower chamber ( 9 ) to the upper chamber ( 8 ) and viceversa, through ports ( 10 ) and compression ( 16 ) and extension ( 12 ) valves, with regulated and progressive opening/closing, with passages with calibrated and/or variable geometry.

Description:
FIELD OF THE INVENTION 
     The present invention refers to a hydraulic shock absorber with progressive braking effect. 
     More particularly, the present invention relates to a hydraulic shock absorber with progressive braking effect comprising a cylinder fixed to the body filled with a fluid and a piston sliding in the cylinder and dividing it into two sequential chambers. 
     The piston slides in the cylinder causing the fluid to move from the lower chamber to the upper chamber, and vice versa, through ports and compression and extension valves with and progressive opening/closing, with passages with calibrated and/or variable geometry. 
     The hydraulic shock absorber of the present invention is particularly suitable for transportation and competition vehicles. 
     BACKGROUND OF THE INVENTION 
     It s known that, in the suspension systems of the conventional transportation and competition vehicles, the oscillations derived from the reactions occurring on the suspension elastic components, in relation to the conditions of contact and adherence with the ground, are controlled be means of hydraulic shock absorbers with braking effect. 
     It is also known that, according to a generic evaluation and taking into account the fact that the magnitude of the braking effect affects the behaviour of the vehicles while they are running, the adoption of shock absorbers with relatively more braked action makes it possible to obtain better vehicle stability, but affects negatively their comfort. On the other hand the adoption of shock absorbers with less braked action produces opposite conditions, i.e. it makes it possible to obtain better comfort to the detriment of stability. In practice, the braking effect of the shock absorbers, in their extension and compression movements, is regulated according to compromise standards, depending on the specific intended uses of the vehicles and/or the particular tastes and requirements of the users. 
     A significant aspect to be evaluated when regulating the braking effect of shock absorbers is the load which can or must be borne by the vehicles. Depending on the load applied, the elastic suspension components react and are compressed, by reducing in length, for corresponding valves. 
     An erroneous evaluation of the braking effect, which may be more or less powerful depending on the load, may jeopardise the correct stability of the vehicles in motion. 
     Oscillation and/or instability phenomena related to the load can also be detected in vehicles in special situation of operation, such as, for example, sustained run on courses with turns, sudden accelerations and/or application of the brakes. For example, it is known that, in the case of curvilinear motion, a sudden change occurs in the distribution of weights, due to the effect of the centrifugal force. A considerable part of the load borne by the inside wheels, in turn, is transferred to the outside wheels and this effect produces greater compression of the elastic components of the corresponding suspensions, with proportional increase of the magnitude of their reactions and consequent requirements to correct said situation by increasing the braking effect of the shock absorbers, in order to prevent the wheel from bouncing. On the other hand, the inverse phenomenon occurs on the suspensions of the inside wheel, on which the load is lightened. Since the magnitude of the reaction of the elastic components, due to the lower load, is reduced, the shock absorbers undergo distension which requires a proportionally reduced braking effect, so that the wheel may correctly follow the condition of the course. Similar phenomena occur in the case of sudden acceleration and/or application of the brakes, in which the more loaded axle benefits from a greater braking effect of the shock absorbers and the less loaded axle benefits from the opposite, reduced braking effect. Basically, an elastic component, such as, for example, a spiral spring which, as it is compressed, reduces its length and, progressively increases the magnitude of its reaction, should operate in parallel with a shock absorber which would progressively increase its braking effect during compression. Vice-versa, as the two components distend, the braking effect should similarly be progressively reduced. 
     The progressive increase or decrease of the braking effect of the shock absorber can be obtained by applying, between the movable arms of the suspension and the body of the vehicles, some components, as second connectors of the shock absorbers. These components, as the geometry of the turning fulcra varies, increase or decrease the speed of the movement of the shock absorbers themselves. 
     However, taking into account that, in general, the elastic components use the same connectors, also the magnitude of their reactions is substantially proportionally heightened. Nevertheless, in any case, there is still a discrepancy between the magnitude of the reactions of the elastic components and the magnitude of the braking effect of the shock absorbers. This system presents also the drawback of being rather expensive and of not being very reliable because of the numerous components of the suspensions. 
     SUMMARY OF THE INVENTION 
     The object of this invention is to eliminate the above drawbacks. 
     In its general aspect, the present invention allows to achieve this and other objects by providing the variable volume sequential chambers of the cylinder, wherein the piston slides, with compression and extension valves with regulated and progressive opening/closing, combined with ports having variable geometry passages. Subject matter of the present invention is, therefore, a hydraulic shock absorber with progressive braking effect comprising: 
     a cylinder anchored to the body of the vehicle and filled with a driving fluid; 
     a piston anchored to a mobile component of a suspension and sliding axially into said cylinder; said piston dividing the sliding seat into two sequential coaxial chambers; and 
     means for connecting said chambers between them and through which the driving fluid is thrusted into one or the other chamber depending on the compression and/or extension action of the piston, 
     wherein, the connection means consist of (i) at least one stationary component, having optionally a variable section, which is engaged by introduction into a stationary opening of the piston and (ii) calibrates section passages with an adjustable and progressive closing/opening, depending on the pressure of the driving fluid. 
     The advantages achieved by the hydraulic shock absorber with progressive braking effect of the present invention consist essentially in that, to each change of distension and/or compression travel of the suspensions, deriving from variations of load or of speed, corresponds a proportional travel of the pistons of the shock absorbers, whose braking effect is automatically regulated by the proportional opening/closing of the passage ports. Said adjustments are obtained by means of opening/closing variable geometry ports with through sections proportional to the compression and/or extension travel of the shock absorbers, as well as by means of progressive opening/closing of compression and extension valves associated with the sequential chambers of the shock absorbers. The progressively opening ports and the valves may also be provided with external means of adjustment, on which it is possible to intervene simply and rapidly, so as to modify the intervening behaviour of the braking effect of the shock absorbers, as a function of the load, speed and/or the users&#39; particular tastes or guide requirements. 
     Another advantage consists in that the hydraulic shock absorbers with progressive braking effect are applicable to recreational or competition automobiles and motorcycles, with possible equal conditions of possible intervention on external means of adjusting the opening/closing of the variable geometry ports and of the compression and extension valves. 
     The present invention and its aspect will be more readily understood from the following description of the accompanying drawings showing some embodiments of the hydraulic shock absorber of the present invention and in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1 a  and  1   b  represent the schematic views of the circuit diagram of a first example of embodiment of the hydraulic shock absorber with progressive braking effect of the present invention with a detailed view of the variable section ports of the compression and extension valves, 
     FIG. 2 represents the schematic view of the section of the second example of embodiment of the hydraulic shock absorber with progressive braking effects of the present invention, with extension and compression valves executed directly on the piston, 
     FIG. 3 represents the schematic view of the cross section of a compression or extension valve with differentiated contrast elastic components, 
     FIGS. 4 a  and  4   b  represent the diagram of FIGS. 1 a  and  1   b  in maximum extension position and in initial compression at low speed conditions, 
     FIGS. 5 a ,  5   b  and  6   a ,  6   b  represent the diagram of FIGS. 4 a  and  4   b  in mid and end of run, at low speed conditions, 
     FIGS. 7 a  and  7   b  represent the diagram, in initial extension at, low speed conditions, starting from maximum compression, 
     FIGS. 8 a ,  8   b  and  9   a ,  9   b  represent the diagram of FIGS. 7 a  and  7   b  in mid and end of run, at low speed conditions, 
     FIGS. 10 a ,  10   b  and  10   c  illustrate the opening position of the compression valve in the conditions of the shock absorber at initial, mid run and maximum compression, at high speed, 
     FIGS. 11 a ,  11   b  and  11   c  illustrate the opening position of the extension valve in the conditions of the shock absorber at initial, half run and maximum extension, at high speed, 
     FIG. 12 illustrates the opening position of the compression valve, in the conditions of the shock absorber under compression, at very high speed, 
     FIG. 13 illustrate the opening position of the extension valve in extension condition of the shock absorber, at very high speed, 
     FIG. 14 a  represents the schematic view of the circuit diagram of the same hydraulic shock absorber with progressive braking effect of FIG. 1 a  and  1   b , equipped with bypass valve, for applications on special vehicles, such as competition vehicles, in resting conditions, and 
     FIG. 14 b  represents the schematic view of the same diagram of FIG. 14 a , with the bypass valve in operation. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The attached drawings concern the operation of the invention in the various phases of operation and not their actual construction configuration. The shock absorber of the present invention comprises an external cylinder  1 , coaxial with an internal cylinder  2 , in which a piston  3  slides. In the example, the upper connector  6  fixed to the external cylinder  1  represents the anchoring to the body of a vehicle, and the lower connector  7 , fixed to the piston  3 , represents the anchoring to the mobile components of the suspension of a wheel of a vehicle which, as such, is forced to oscillate upward and downward, following the corresponding movements of the wheel itself in following the ground configuration, during all driving conditions. 
     For the sake of simplicity of description of the device, the necessary hydraulic sealing means of the various components and the actual possible construction configurations are not shown in the drawings. 
     As is known, the braking effect of a hydraulic shock absorber is obtained by means of piston  3  which divides cylinder  2  into two coaxial communicating chambers: an upper  8  and a lower  9  chambers. 
     In the cylinder  2  said piston  3  is inserted and can slide. The upper  8  and  9  chambers are full of fluid and the fluid can move from one to the other through calibrated ducts, according to the compression or extension movements made by piston  3  along the cylinder, due to the displacements produced by its stem  4  connected to lower connector  7 . 
     With the shock absorber fully extended and at the beginning of the compression movement at low speed (FIGS. 4 a  and  4   b ), part of the fluid present in upper chamber  8  moves (in the direction of arrows  100 ) into lower chamber  9  through a hole  10  of the piston  3 , partially occluded by a coaxial pin  5 , which has, preferably, a variable section, with continuous progressive increase or increase step-by-step. 
     In the illustrated embodiment, the pin  5  is basically cone-shaped and overturned and, as the position of the piston in compression phase changes, its section gradually reduces the through ports of hole  10 . From hole  10 , the fluid moves into lower chamber  9  through a communication opening  10   a , made at the top of hollow stem  4 . The other part of the fluid is instead forced to exit from chamber  8  through line  27  (according to the direction of arrows  101 ) and to reach compression valve  16  provided with a piston  18  and a spring  17 . In order to continue its course, the fluid is forced to press on piston  18  and the displacement of the piston  18  opens a port  19  provided in the valve  16  until section A of said calibrated port  19  (FIGS. 4 a  and  4   b ) is sufficient to allow it to pass through, at that speed. From said passage, the fluid reaches chamber  9  through a fact  25 , the interspace between the two coaxial cylinders  1  and  2  and through a hole  11 . Essentially, in order to pass through valve  16 , the fluid must exercise pressure on piston  18 , proportionally to the magnitude of the reaction which the counter spring  17  exercises on the piston  18  in order to keep it closed, against the entry of line  27 . Thus, a braking effect is generated in the piston  3 —stem  4  assembly of the shock absorber, proportional to the resistance of spring  17 , multiplied by the ratio between the surface area to piston  18  of valve  16  and that of piston  3  of cylinder  2 . As the shock absorber is compressed (FIGS. 5 a ,  5   b ), the area of through hole  10  of the fluid decreases according to the increase of the section of pin  5 , integral with cylinder  1 - 2 . At equal sliding speed of the piston  3 —stem  4  assembly, the choke of passage  10  by pin  5  forces a greater amount of fluid to follow the path of line  27 , to pass through compression valve  16 . The higher flow rate requires a larger passage area A of port  19 , with consequent greater pressure on piston  18  and greater compression of counter spring  17 . Due to the fact that the magnitude of the reaction of the spring is proportional to its compression, the resistance to the passage of the liquid increases, with corresponding proportional increase also of the braking effect. If the piston  3 —stem  4  assembly proceeds in its compression run inside cylinder  1 - 2  (FIGS. 6 a  and  6   b ), until it is near maximum compression, the amount of fluid which can pass through port  10  becomes minimal or even zero, since its through section is occupied by pin  5 , the section thereof, at that point, can be equal or almost or almost equal to that of the port  10 . In such a case, the fluid can only be forced to move from upper chamber  8  to lower chamber  9  through duct  27  and compression valve  16 , farther displacing piston  18  and compressing even more spring  17  (with respect to the previously described positions), until section A of calibrated port  19  is sufficient to allow a greater volume of fluid to circulate, at the same speed, with consequent greater braking effect of the system. 
     When the direction of the movement of piston  3  in the cylinder is inverted, during extension action, the previously described phases perform in a completely opposite way (FIGS. 7 a ,  7   b    8   a ,  8   b    9   a ,  9   b  and direction of arrows  102  and  103 ), involving extension valve  12 . 
     Starting from minimum extension of the piston  3 , the pin  5  occupies a larger section of the hole  10 , creating a strong braking effect which, however, gradually decreases, as piston  3  extends and the free section of hole  10  increases, allowing the fluid to pass from upper chamber  8  to lower chamber  9 . The other portion of the fluid discharges through port  11  and line  26 , to return to upper chamber  8  through extension valve  12 . This discharge of the fluid originates movements and reactions on piston  14  and on spring  13  and changes in through area B of calibrated port  15  which, at equal speed, correspond to those previously described for compression valve  16 , although with progressively decreasing braking effect, depending on the extension of the shock absorber. 
     When the compression and/or extension speed of the piston  3 —stem  4  assembly (see FIGS. 10 a, b  and  c  and  11   a, b  and  c ) is increased, the volume of fluid circulating in a unit of time greater, but, since the passage area available between pin  5  and port  10  is variable only according to the position of the piston  3 —stem  4  assembly in the cylinder, the greater amount of fluid is forced to displace pistons  18  or  14  of valves  16  or  12 , to a greater extent, until passage areas A of B of calibrated ports  19  or  15  are sufficient to allow said volume to pass through, with consequent greater reactions of springs  17  or  13  and corresponding greater braking effects. 
     In order to allow proper functionally of the shock absorbers, even in the case of operations with excessive speed increments, the compression and/or extension intervention can be adequately corrected by performing calibrated ports  19  and  15 , of compression  16  and extension  12  valves, with through areas of lower end  20  suddenly increased. These additional through section allow greater fluid passage clearance and circulation, preventing too violent or too weak braking effects. 
     For more specific applications, such as, for example, those pertaining to competition automobiles which, while racing at high speed, may travel with the wheels on special profiles of the lanes, such as the notched profiles of the curbstones delimiting and similar changes, the braking effect of the shock absorbers is reduced so that the tires may always maintain contact with the ground. For these applications, the shock absorbers are provided with an additional bypass valve  30  (see FIGS. 14 a ,  14   b ) comprising a piston  31 , a spring  34  acting on said piston  31 , and a ratchet  32  maintaining the valve in a closed position by a rear spring  33 . In this bypass valve  30 , the piston  31  can instantaneously move backward under the effect of an impact produced by the fluids moved by sudden displacement of piston  3 , and return to its closing positions, equally fast, at the end of such occurrences. In these conditions and particularly during the compression phases, the sudden backward movement of piston  31  causes ducts  26  and  27  to connect, leaving the driving fluids to pass directly from upper chamber  8  to lower chamber  9 , or vice-versa (according to the indications of arrows  104 ), temporarily excluding the braking intervention of compression  16  and/or  12  extension valves. In order the movement of piston  31  occur suddenly, the piston  31  is normally held in closed valve position by the ratchet  32 , pushed by the calibrated rear spring  33 . By adjusting the pressure exerted by the spring  33  on ratchet  32 , for example using regulator  60  and knob  61  depicted in FIG. 14 b , it is possible to calibrate the full opening of valve  30 , or to calibrate the release of ratchet  32  and the backward movement of piston  31 , at a well-determined pressure of the driving fluid acting on the piston itself, to which an equally well-determined suspension speed corresponds. The valve  30  closes again, with piston  31  returning to the initial position under the action of the push produced on its rear part by a counter spring  34 , as soon as the intervention speed of the shock absorber falls again within the normal values and the piston  3 /stem  4  assembly exceeds one of the upper and lower dead points. 
     By varying the characteristics and ratios of the components of the hydraulic shock absorber of the present invention, or by modifying the form and/or the configuration of the variable section of pin  5 , varying the width and/or length of calibrated ports  19  and  15 , varying the dimensions and/or the form of through sections  20 , varying the diameter of pistons  18  and  14  as a function of the diameter of piston  3 , varying the characteristics of single or multiple springs  17  and  13 , whether or not adopting the calibrated bypass valves  30 , and so forth, it is possible to size and adjust, basically at the millimeter level, the shock absorbers and the corresponding desired braking effect, which the shock absorbers can produce, depending on the type of associated suspensions and on the applications of the vehicles. 
     The function of cylinder  21  and respective floating piston  22  is to absorb the changes in volume due to the dimensions of hollow stem  4  sliding in cylinder  2 . They keep the driving fluid pressure constant, thanks to the contracting action of a compressed gas in chamber  23 ; in this manner, the formation of air/oil emulsions is prevented and the boiling point of said fluid can be raised. 
     The magnitude of the braking effect at different speeds can be obtained by applying single elastic elements  17  and  13  on the compression valve  16  and extension valve  12 , as described. Alternatively, variable load elements, or even more associated contrast elements  17 , 17 ′ and  13 , 13 ′, with different characteristics and reactions, which work in series on respective pistons  18  and  14 , can be applied. 
     From the accompanying drawings it is possible to see that the connections between the shock absorber and the compression valve  16  and extension valve  12  have been represented according to an embodiment providing for an interspace  40 , coaxial between the outer  1  and the inner  2  cylinders for circulation of the control fluid with upper in/out connector. It is evident that, in the case of connection of duct  26  in lower position, this interspace is not necessary and the shock absorber consists only of the single cylinder  2  for sliding the piston  3 . 
     From the same drawings it is evident that the compression valve  16  and extension valve  12  and compensation cylinder  21  can be produced separately from the shock absorber and distinct from each other or combined as a group. In the second case, the solution may be advantageous for special applications on sport and/or competition automobiles, for a better distribution of weights and in order to facilitate the simple and quick adjustment and/or replacement of the various components of said valves, depending on the requirements at the time. The various connections can be made with rigid or flexible ducts, according to the requirements concerning position and/or maintenance operation. In this solution, the valves may be provided also with external load regulators ( 50 ,  50 ′) of springs  17  and  13  or  17 - 17 ′ and  13 - 13 ′ or with variable load elements, with manual operation by means of knobs ( 51 ,  51 ′), which can be operated directly by the vehicle drivers. For less sophisticated applications, or those requiring traditional operation or less demanding ones, the above mentioned components can be comprised in the shock absorber assembly itself, as shown in FIG.  2 . 
     Although the invention has been described in conjunction with specific embodiments, it is evident that many alternatives and variations will be apparent to those skilled in the art in the light of the foregoing description. Accordingly, the invention is intended to embrace all of the above alternatives and variations that fall within the spirit and scope of the appended claims.