Abstract:
The invention concerns a hydraulic decelerator with a fluid tank ( 28 ), in which a main piston ( 14 ) operates, and a compensation chamber ( 25 ), in which a compensation piston ( 15 ) operates. The fluid tank and the compensation chamber communicate by passing the fluid from one to the other in answer to the movements of the main piston in said tank, in a work direction under the control of a flow stop-adjustment member ( 12 ). The latter has a conical shank ( 22 ) that interacts with a cylindrical bore ( 31 ) provided in the main piston in an opposite direction through return conduits ( 32 ) also provided in the main piston associated with a one-way valve.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention concerns a hydraulic decelerator according to the preamble of claim  1 , to be used in the deceleration of devices, bodies or objects in movement such as slides, guided linear axes, rotating actuators and the like, susceptible to stopping at the end of a movement and/or to invert the direction of the movement. 
       PRIOR ART 
       [0002]    In many devices for various working processes, systems provided with alternative, repetitive movements following pre-established linear or rotary actions are used. Consequently, every stop or change of direction at the end of each stroke requires a dissipation of kinetic energy which otherwise could turn into impact forces that could be transmitted harmfully to the equipment. 
         [0003]    A function of a hydraulic decelerator is to absorb the energy of an object in movement at the end of its controlled travel avoiding impact effects. 
         [0004]    A hydraulic decelerator usually has a movable part compared to a fixed part and contains a hydraulic fluid, such as oil or like, between the two parts. This fluid is susceptible to passing, as a result of an axial thrust on the moving part, from a collection tank, or a high pressure chamber, to a second low pressure compensation chamber by means of one or more throttling conduits for a progressive damping action of the thrust taking place until it is nullified, and then from the compensation chamber to the collection tank for the return of the decelerator in the rest position once the thrust on the movable part has stopped. 
         [0005]    The movable part of the hydraulic decelerator is usually designed to move into contact with the body or object to decelerate, whereas the fixed part acts as a support and guide of the movable part. 
         [0006]    Usually, the fixed part is formed by a substantially tubular body and carries at least a regulator flow means; the movable part comprises a main piston operating in the hydraulic fluid collection tank and has a relative guide rod in the fixed part, and a compensation piston stressed by a spring and moveable in the second compensation chamber in an opposite direction to the main piston; the throttling conduits for the flow of the hydraulic fluid from the tank to the compensation chamber are provided in the main piston/or in its rod so as to interact with the flow adjuster means. 
         [0007]    With the decelerator in an inactive position, that is resting, its fixed and moveable parts are in an extended position in which the moveable part protrudes axially from the fixed part and the hydraulic fluid is confined in the storage tank by the main piston, which is in a retracted position, and with the help of the compensation piston placed in the compensation chamber and which is in an advanced position towards the main piston. 
         [0008]    The hydraulic decelerator activates adopting a so-called compressed position, when its moveable part is subject to an axial thrust. So, the moveable part re-enters into the fixed one, exercising a pressure on the hydraulic fluid in the tank by an advance of the main piston, causing by it, with the help of the flow adjuster, a progressive flow of the fluid towards the compensation chamber through the throttling conduits for the damping of the thrust and making the compensation piston retract. 
         [0009]    The hydraulic decelerator disclosed in the documents U.S. Pat. No. 5,102,109, US 2009/001636, WO 2008/139780 and JP10246266 are indicative of the state of art. However these known hydraulic decelerators are not without drawbacks. 
         [0010]    For example, the main piston has a guide rod that extends in the compensation chamber and which is guided only for a brief portion of its length in a ring at an end of the fixed body. This disposition however does not always appear to be ideal to ensure the coaxiality between the two moveable and fixed parts and to prevent flections or deviations of the rod in particular when undergoing a thrust at the time of the activation of the decelerator. Furthermore, the throttling conduits for the flow of hydraulic fluid between the collection tank and the compensation chamber have varying states, axial and radial, so much so as to complicate the realization of the piston and the relative guide rod. In addition, the adjustment of the flow of hydraulic fluid between the tank collection and the compensation chamber is carried out by difficult to produce valve means and to insert them in the decelerator. And also where, as in the document U.S. Pat. No. 5,102,109, there is a flow stop-adjustment device made up of a rod, the latter is cylindrical and designed to interact with a conical bore provided in the main piston to reach a progressive throttling effect of the flow of fluid from the tank to the compensation chamber. However, and evidently, this disposition implies the formation of a conical conduit in the main piston which has the disadvantage of compromising the possibility of being able to vary and finely adjust the degree of throttling of the conduit if not opening the device and replacing the main piston with another having a conical conduit with a different size. 
       OBJECTIVE AND ADVANTAGE 
       [0011]    The objective of this invention is to avoid the drawbacks and disadvantages of the well known technique and to correspondently propose a hydraulic decelerator simple to produce and with precise and reliable functioning. 
         [0012]    The objective and the implicit advantages that derive from it are reached, in accordance with the invention, by a hydraulic decelerator as claimed in claim  1 . 
         [0013]    Consequently and advantageously, the flow stop-adjustment member is on board the external body and has a conical shank facing towards the main piston that is simply provided with a substantially constant axial conduit. This arrangement appears to be particularly advantageous, not only for the function of the decelerator, but also due to the fact that the flow stop-adjustment member remains accessible from the outside because of its simple removal and replacement with another different shutter-adjuster having a different conical shank depending on the required throttling progress level of the hydraulic fluid flow between the collection tank and the compensation chamber during the functioning of the decelerator. In other words, the action of the decelerator may be varied and registered without having to access its interior, but rather through an easy substitution of single component. 
         [0014]    Furthermore, both the hydraulic fluid flow conduit from the collection tank to the compensation chamber and the return bores of the fluid from the compensation chamber to said tank are all formed in the piston, each one in parallel with the others. 
         [0015]    According to a preferred way of realization, the axial conduit of the main piston is delimited by a sleeve, having a flexible lip acting as an opening/closing valve of the return conduits of the hydraulic fluid depending on the direction of the movement of the main piston of the system. 
         [0016]    Also advantageously, the guide stem is centered and guided in the external body for almost all of its length, ensuring in this way that the coaxiality between said stem and the body, both in the extended rest position, and in the compressed operating position. 
         [0017]    The collection tank of the hydraulic fluid is delimited directly by the external body, whereas the compensation chamber is in the guide stem, with the advantage that the collection tank can be compatibly ample with the dimensions of said body and that the compensation chamber, even with a reduced diameter, can develop in the direction of the length of said guide stem. This arrangement furthermore enables a continual lubrication of the coinciding surfaces, respectively internal and external, of said body and said stem from the moment that the latter during its axial movements plunges into the hydraulic fluid tank. 
         [0018]    Also worthy of note is that when the decelerator is in the rest position, the guide stem of the main piston is stopped and held axially in the external body by means of a simple fold towards the inside of an end of said body, therefore without the need of additional components. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    Further details of the invention will however be evident from the description that follows made in reference to the enclosed indicative and not limiting drawings, in which: 
           [0020]      FIG. 1  is an exploded view of the components of the hydraulic decelerator according to the invention; 
           [0021]      FIG. 2  is an external view of the assembled hydraulic decelerator; 
           [0022]      FIGS. 3 and 4  are, magnified, a section plane and a longitudinal cross section of the assembled hydraulic decelerator, in an extended, rest position, respectively; and 
           [0023]      FIGS. 5 and 6  show, magnified, a section plane and a longitudinal section of the assembled hydraulic decelerator, but in the compressed work condition, respectively. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]    As shown, the decelerator proposed herein comprises essentially—FIG.  1 —an external body  11 , a flow stop-adjustment member  12 , a guide stem  13 , a main piston  14 , a compensation piston  15  and a return spring  16 . 
         [0025]    The external body  11  can have a cylindrical shape or any other form. With its lateral wall it delimits internally a housing  17 , basically cylindrical, having a proximal end  18  and a distal end  19  and designed to receive the guide stem  13 . Externally, the body  11  is provided with means, such as a screw thread  20 , so as to allow the fixing in use of the decelerator to a fixed support with respect to a mobile part to decelerate or on a mobile part to decelerate as it nears a fixed element. The proximal end  18  of said body has a taper, resulting from a bend towards the center and delimiting a stop shoulder  21 . 
         [0026]    The stop-adjustment member  12  has a conical shank  22 . It is mounted on the distal end  19  of the external body  11  so that its conical shank  22  extends in the housing  17 . Preferably, the flow stop-adjustment member  12  is fixed to the body  11  by threading and in an interchangeable form with others having from time to time a shank, always conical, but with different sizes. 
         [0027]    The guide stem  13  includes a first portion  23 , which extends axially in the housing  17  defined by the external body  11 , and a second portion  24  that protrudes from the proximal end  18  of the body itself. Internally the guide stem  13  delimits a compensation chamber  25 , with a variable volume, open towards the distal end of the external body and closed by the opposite part. 
         [0028]    Altogether the guide stem  13  has a length about equal to the depth of the housing  17  in said body  11 , with the length of its first portion  23  which is preferably about double the length of its second portion  24 . The external surface of the first portion  23  of the guide stem  13  coincides with the internal surface of the housing  17  defined by the external body  11  and has a seal  26  which interposes between the two coinciding surfaces. 
         [0029]    The guide stem  13  is centered and guided positively in the external body for all the length of its first portion  23  and moveable between an extended rest position—FIGS.  2 - 4 —, in which the second portion  24  emerges axially from the proximal end  18  of the external body  11 , and advanced work position— FIGS. 5 ,  6 —, in which the stem  13  is moved towards the distal end  19  of the body  11  and correspondingly towards the stop-adjustment member  12 . 
         [0030]    Around the guide stem  13 , between the first portion and the second portion  23 ,  24 , a striking surface  27  is provided which faces towards and is designed to interact with the stop shoulder  21  at the proximal end of the external body with the dual function of preventing the extraction of the guide stem from said end of said body and to delimit the retracted rest position of the guide stem. Said guide stem will also be provided with radial bores  35  for an access and an exit of air from the guide stem, so as to allow the movements of the compensation pistons  15  without unnecessary resistances. 
         [0031]    The main piston  14  is associated with the guide stem  13  to follow the movements thereof. It is attached to the open end of the compensation chamber  25  delimited by the guide stem, consequently, facing towards the stop-adjustment member  12 . Frontally, the main piston  14  delimits a collection tank  28  with the distal end  19  and with the lateral wall of the external body  11 , variable in volume and designed to contain an amortizing fluid, in particular hydraulic oil. 
         [0032]    The compensation piston  15  on the other hand is housed in the compensation chamber  25  in the guide stem  13  with the interposition of a radial seal  29 . It is moveable axially in said chamber  25  towards and away from the main piston  14  with the help of the return spring  16 . This spring  16  is positioned, held and compressible between the bottom of said compensation chamber  25  and a spring guide rod  30  attached to the compensation piston  15  and acts so as to maintain the compensation piston normally moved towards the main piston. 
         [0033]    The main piston  14  is provided with an axial conduit  31  in line with the conical shank  22  of the stop-adjustment member  12  placed at the distal end  19  of the external body  11 , and two or more peripheral conduits  32  parallel to the axial conduit  31 . This axial conduit is provided to place the fluid collection tank  28  in communication with the front main piston  13  together with compensation chamber  25 , whereas the peripheral conduits  32  are provided for placing in communication the compensation chamber  25  with said fluid collection tank. Preferably, the axial conduit  31  is delimited by a sleeve  33  inserted in axis with the main piston  14 , and this sleeve is provided with a flexible lip  34  associated at the end of the peripheral bores  32  in front of the main piston  14 , that is to say facing towards the fluid collection tank  28 . Said flexible lip  34  basically acts as a control valve of the opening/closing of the peripheral conduits  32  to allow a one way flow of fluid from the compensation chamber  25  to the collection tank  28  depending on the direction of the movement of the guide stem  13  together with that of the main piston  14 . 
         [0034]    In the example shown, the external body  11  forms a fixed part of the decelerator, whereas the guide stem  13  forms the moveable part, susceptible to axial movements in answer to a thrust F—FIG.  6 —which is applied by any object or device in movement that needs to be decelerated at the free end of the guide stem protruding from the fixed body. 
         [0035]    When the decelerator is in the rest position, the guide stem  13  is retracted against the stop shoulder  21  at the proximal end of the external body  11 . So, on the one hand, the second portion  24  of the guide stem  13  emerges from the proximal end of the external body to meet the body or object to decelerate and, on the other hand, the main piston  14  is at a distance from the stop-adjustment member  12 . Furthermore, the hydraulic fluid is contained in the collection tank; the compensation chamber  25  is basically empty; the compensation piston  15 , pushed by the spring  16 , is in an advanced position towards the main piston  14 ; the axial conduit  31  of the main piston  14  is open; the peripheral conduits  32  of the piston itself are obstructed by the flexible lip  34  acting as a valve, as shown in  FIGS. 3 and 4 . 
         [0036]    When the free end of the guide stem  13  meets a body or object in movement, the axial thrust F that originates from it activates the decelerator. In fact, the guide stem  13  moves towards the distal end  19  of the external body  11 , causing the main piston  14  to advance in the collection tank  28  and against the conical shank  22 . So, the hydraulic fluid is compelled to pass from the collection tank  28  to the compensation chamber  25  in the guide stem  13  through the axial conduit  31  of the main piston  14 , while the peripheral conduits  32  remain closed by the lip  34  of the sleeve  33  acting as a valve. So, the main piston  14  gradually advances in the collection tank  28  whereas the compensation piston  15  retracts in the compensation chamber  25  in opposition to the action of the relative spring  16 . However, the hydraulic fluid flow from the collection tank to the compensation chamber becomes gradually dwindled by the consequent penetration of the conical shank  22  of the stop-adjustment member  12  in the axial conduit  31 , that gradually reduces the span of the passage of the fluid— FIGS. 5 ,  6 —resulting in the progressive reduction of the thrust F operating on the rod and consequently the deceleration of the body or object in movement until it stops. 
         [0037]    The thrust on the guide stem ceasing, the spring  16  moves the compensation piston  15  forward causing the return of the hydraulic fluid from the compensation chamber to the collection tank  28  through the peripheral conduits  32 , (where the flexible lip  34  acting as a valve opens) as well as through the axial conduit  31  of the main piston as it gradually moves away from the conical shank  22  of the stop-adjustment device  12 . Therefore the main piston and the guide stem move back into the rest position, preparing the condition of the decelerator for a successive deceleration action— FIGS. 3 and 4 .