Abstract:
The present invention relates to a hydropneumatic shock absorber. This new telescopic system comprises an outer sliding tube, an inner sliding tube and structure for adjusting the braking level of the shock absorber in expansion. Fastened on the base of the outer sliding tube is the bottom of a barrel on which rests an elastic structure, such as a counter-acting spring, which pushes on the inner sliding tube in the expansion stroke. The inner sliding tube carries at its internal end a bell which cooperates with a stop spring when in the expansion stroke. The liquid filled barrel contains an axially movable piston connected to the closure plug assembly with the piston contains a first valve, which opens only in the compression phase, and a second valve, which acts as variable throttle and is controlled by the padded end of a screw axially placed within the support tube. By acting on a screw, the expansion braking level of the shock absorber can be adjusted.

Description:
This Appln is a continuation of Ser. No. 08/992,752 filed Dec. 17, 1997 now U.S. Pat. No. 6,042,091. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a hydropneumatic shock absorber, adjustable in the braking level in expansion, particularly intended to form, in combination with an equal shock absorber, the telescopic legs of a fork for mountain-bikes, trail-bikes or other bikes or motorbikes. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The characteristics of the invention, and the advantages deriving from it, will appear evident from the following description of a preferred embodiment of the same, illustrated by way of example in the Figures of the attached drawings, in which: 
     FIGS. 1 and 2 illustrate the shock absorber sectioned lengthwise, respectively in the expanded position and in the compressed position; 
     FIGS. 3 and 4 illustrate enlarged and longitudinally sectioned as in the preceding figures, the portion of the shock absorber equipped with adjustable valve means, respectively in the compression phase and in the expansion phase; 
     FIG. 5 illustrates some details according to section line V—V of FIG. 4; 
     FIG. 6 illustrates, longitudinally sectioned and enlarged, the upper part of the inner sliding tube of the shock absorber shown in FIGS.  1  and  2 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In FIGS. 1 and 2,  1  outer sliding tube of the shock absorber is equipped for the formation of a stem of a fork for mountain-bike, in the lower part with a fork appendix  101 , for the fastening to the axis of the front wheel of the bike and is possibly equipped with additional appendices  201  for the support a disc brake caliper. The outer sliding tube  1  in the upper part ends with an extended portion  301  with a seat  2  having a diameter greater than that of the internal cavity of the outer sliding tube itself and on the bottom of such seat rests the annular neck  103  of a thin bushing  3  made of “Teflon” (registered trademark) or of other suitable material with a low friction coefficient which is highly wearproof, which covers the cavity of the outer sliding tube for an adequate length (see further on). On the neck  103  of said bushing  3  is positioned a washer  4  of suitable material, surmounted by a sealing ring  5  which is blocked in seat  2  by means of a snap ring  6 . Seat  2  is then pre-set to restrain a closing ring  7  with internal parts having the function of dust scraper. 
     In the cavity of the outer sliding tube  1  there is mounted axially sliding and with lateral seal, through the above mentioned bushing  3 , the round section inner sliding tube  8 , which by its upper end is fastened to the non illustrated cross-bar, integral with the inner sliding tube of a telescopic system equal and parallel to the one in question and which carries the steering axis. A damping cartridge comprising at least a piston  38 , barrel  13 , and a support tube  35  is utilized. The lower end of the inner sliding tube  8  is internally equipped with an annular recess  9  (see also FIGS. 3 and 4) in which stays and is axially blocked by the snap ring  10  and the annular neck  111  of a bell  11 , and which is open in the upper part and traversed, with the clearance  12 , by a round section small cylindrical tube. or barrel  13  is made with a suitable light alloy and provided in one piece, on the bottom, with a threaded axial shank  113  screwed in a cap nut  14  which in turn is equipped with a truing threaded axial shank  114  which engages with precision and with lateral seal, through the gasket  15 , a hole obtained at the centre of the raised base  401  of the outer sliding tube  1 . The outer sliding tube  1  is open at the lower end to allow access to the base  401  to the nut  14 . The barrel  13  is closed in the upper part by a plug  16  laterally equipped with an annular recess  17  in which a corresponding lateral portion of the barrel  13  is headed. In such annular recess  17  is set an open snap ring  18 , on which a cap  19  is rested in the upper part and rimmed in the lower part. Against the lower end of such cap rests the end of a helical spring  20  which with the other end rests against the top of the lower bell  11  of the inner sliding tube  8  when this is in the position of maximum expansion as from FIG.  1 . The spring  20  is preferably made with a square or rectangular section. On the upper end of the cap  19  rests at least one helical counter-acting spring  21  which concerns the inner sliding tube  8  for its entire length and which is held in this by a plug  22  equipped with means for preloading this spring  21  whose function is to urge the inner sliding tube  8  in expansion and to absorb the compression stress to which the telescopic system in question is subjected by the roughness of the ground. 
     The bushing  3  placed between the outer sliding tube  1  and the inner sliding tube  8 , is of such length is to guide the inner sliding tube  1  itself, but not such as to protrude in the lower part from it when the inner sliding tube itself is in the position of maximum expansion as from FIG.  1 . This solution enables to considerably limit the thickness of the bushing  3  with economical and functional advantages and ensures that such bushing is always correctly held between the parts whose sliding and lateral seal it controls. 
     Before mounting the plug  22 , which with its own externally threaded shank  122  is screwed in a corresponding internally threaded portion of the upper end of the outer sliding tube  1 , in the outer sliding  1  tube itself there is introduced a correct amount of a suitable liquid which preferably goes over the cap  19 , crossing the clearance existing between the cap itself and the internal lateral surface of the inner sliding tube  8 , for example up to the line of the level indicated with  23  in FIG.  1  and such fluid completely fills the free chamber C of the outer sliding tube  1  and completely fills the barrel  13  in which it can flow through at least one lower hole  24  of suitable section. The plug  22  is equipped with a gasket  25  for the seal connection on the inner sliding tube (FIG. 6) and is axially drilled for the passage of the upper tapered section  126 , with lateral seal  27 , of a screw  26  which is axially held in place by a snap ring  28  and which can be actuated through an external knob  29 . On screw  26  is screwed a nut screw  30  externally equipped with teeth  130  which bind some corresponding longitudinal recesses  31  of the lateral surface of the axial cavity of the plug in which lodges the said screw—nut screw group. On the lower end of the nut screw  30  rests with the interpositioning of a truing cap  32 , the upper end of the counter-acting spring  21 . By acting on the knob  29 , it will be possible to rotate the screw  26  and determine the ensuing axial shifting of the nut screw  30  towards the bottom, preloading the spring  21  to the desired point. It is understood that on top of the plug  22  and on the knob  29  could be included some reference marks (not shown), to enable the user to modify at will the level of compression of the counter-acting springs of the fork, even without the use of special fixtures. 
     It can be seen from reviewing FIG. 6 that the adjustment screw  26  is equipped with an axial cavity subdivided in three sections with the diameter decreasing towards the top. The lower section  33  is threaded and in it there is screwed and axially blocked by means of the lock nut  34 , the end of a tube  35 . The tube  35  extends towards the bottom and passes through a hole  36  in the plug  16 , entering the barrel  13  where it terminates with an externally threaded end  37  on which is screwed the bottom of the body of a small goblet-shaped piston  38 . Piston  38  includes an external annular counterbore with at least one gasket  39  which operates as a lateral seal against the barrel  13 . The base  138  of the piston  38  has a diameter suitably lesser than the internal diameter of the barrel  13 , so that between the two parts there is a permanent annular passage  40  of the right width. On the same base  138  is included a ring of suitable plastic material, which operates as a lateral seal against the barrel  13  and whose internal diameter is greater than the external diameter of the stem  238  of the piston  38 , so that between the two parts there is a permanent annular passage  42 . The height of the ring  41  is opportunely lesser than that of the stem of the piston  38 , so that when the telescopic assembly in question is stressed by compression, as from FIG. 3, said ring  41  is lifted, it moves away from the base  138  and rests on the bottom of the body of the same piston where, as illustrated in the detail of FIG. 5, are opened some radial holes  43  which communicate with the toric cavity  44  existing between the same body of the piston  38  and the rod  35  which carries it. The ring  41  and the seal gasket  39  are made with a wearproof material, for instance with an appropriate relatively rigid and non elastic plastic material, which allows them to be lodged in their respective seats thus making the piston  38  in several pieces. Alternatively, they can be provided with an oblique cut  45 , which forms flute spout ends, respectively inclined and which reciprocally overlap with good seal condition with respect to the barrel  13  (FIGS.  1  and  5 ). 
     In the cavity  44  of the piston  38  is opened at least one hole  46  obtained laterally in the tube  35 . The base  138  of the same piston is axially provided with a hole  47 . In the tube  35  there is located a rod  48  which ends in the lower part with a cylindrical head  148  fit to be located with an adjustable level of interference in front of said hole  46 , so as to modify its passage port. For this purpose, the rod  48  is equipped in the upper part with the following means (see FIG.  6 ): 
     a padded and threaded portion  248  which co-operates with a corresponding internally threaded section  49  of the upper extremity of the tube  35 ; 
     an upper annular portion  348  which acts as counterboring for the screwing and unscrewing of said rod  48 , in the co-operation respectively with the upper end of the tube  35  and with the top of the intermediate section  50  of the axial cavity of the screw  26 ; 
     a terminal portion  448  which goes through the upper and lower diameter section of the axial cavity of the screw  26 , which is equipped with a lateral seal gasket  52  and which protrudes from the top of the same screw with a section of the right length, equipped with an axial holding snap ring  28  and equipped at the end with a diametrical cut  53  to be activated with a screwdriver or other mean. By screwing and unscrewing the rod  48  within the limits allowed by the counterboring  348 , it is possible to modify the passage port of the hole  46 , up to the complete opening or complete closing of such hole. 
     In the compression phase of the shock absorber, as illustrated in FIGS. 1 and 3, the ring  41  is lifted against the bottom of the body of the piston  38  and the liquid contained in the lower chamber A of the barrel  13 , flows in the upper chamber of the same barrel through the openings  40 ;  42 ,  43 ,  44 , and also through the shunt represented by the hole  47 , by the cavity of the rod  35  and by the passage of the hole  46 . However, possible variations in the rate of flow of this last shunt do not appreciably modify the behaviour of the shock absorber. Since chamber A has a volume greater than that of chamber B, the exceeding liquid of the same chamber A flows in chamber C external to the barrel  13 , through the lower hole  24  of the barrel  13 . Given that in the compression phase, chamber C also decreases in volume, the liquid of this chamber flows through the opening  12  of the bell  11 , goes through clearance present between the cap  19  and the internal lateral surface of the inner sliding tube  8  and raises the level  23  of the liquid in the chamber D partially occupied by air, which decreases in volume and is compressed with an elasticity which is added to that of the counter-acting spring  21  (see FIG.  2 ). 
     The compression phase of the shock absorber can be progressively stopped, by a gradual decrease in the clearance between the cap  19  and the inner sliding tube  8 , determined by a correct internal taper of the same inner sliding tube, whereby the internal diameter of this component progressively decreases upwards, as illustrated in FIGS. 1 and 2. 
     In the expansion phase of the shock absorber, the liquid follows an inverse route to that previously considered. In this phase the ring  41  shifts downwards as from FIGS. 2 and 4 and by resting on the foot  138  of the plunger  38 , closes the passage  40  so that the liquid can flow from the upper chamber B to lower one A of the barrel  13 , exclusively through the shunt  44 ,  46 ,  47 . By modifying the passage of the hole  46 , by screwing or unscrewing the rod  48 , it will be possible to change at will the level of braking in expansion of the shock absorber. To facilitate the adjustment carried out by means of the rod  48 , on the upper part  448  of the same rod can be included some reference marks  54  which can be read when they protrude from the top of the screw  26 , as illustrated in FIG.  6 . In this same figure, reference numeral  55  and the broken lines indicate a possible protection cap which can be pressure mounted on the top equipped with lateral friction means  56  of the upper plug  22  of the inner sliding tube  8 . 
     It is clear that, by unscrewing the screw nut  14  and the plug  22 , it is possible to disassemble the shock absorber in all its components. By removing the snap ring  6  it will be possible to remove and replace the sliding bushing  3  when it is worn out. 
     While the present invention has been described with reference to one or more preferred embodiments, such embodiments are merely exemplary and are not intended to be limiting or represent an exhaustive enumeration of all aspects of the invention. The scope of the invention, therefore, shall be defined solely by the following claims. Further, it will be apparent to those of skill in the art that numerous changes may be made in such details without departing from the spirit and the principles of the invention.