Abstract:
A hydraulic pump including a containment body ( 2 ) having inside a cylindrical cavity ( 3 ) provided with a conduit ( 4 ) communicating with a hydraulic actuator and capable of holding a fluid. A piston ( 5 ) is movable in the cylindrical cavity ( 3 ) and a reservoir ( 12 ) of the fluid is in fluid communication with the cylindrical cavity ( 3 ). An actuation device ( 6 ) connected to the piston ( 5 ) move the piston ( 5 ) within the cylindrical cavity ( 3 ) to operate the hydraulic actuator. The pump also comprises structure ( 13 ) for closing or opening the connection between the reservoir ( 12 ) and the cylindrical cavity ( 3 ). The reservoir ( 12 ) is substantially lined up with the cylindrical cavity ( 3 ) along an axis of longitudinal development (X) of same cylindrical cavity ( 3 ), so as to reduce the overall dimensions and the weight of the pump.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional under 37 CFR 1.53(b) of pending prior application Ser. No. 12/515,625 filed May 20, 2009 and claims the benefit (35 U.S.C. §120 and 365(c)) of International Application PCT/IB2008/000227 filed Jan. 24, 2008, which designated inter alia the United States and which claims the priority of Italian Patent Application FI2007A000018 of Jan. 31, 2007, the entire contents of each application are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a hydraulic pump for operating a hydraulic servo actuator, in particular a caliper of disc brakes for bicycles and motorcycles. 
     BACKGROUND OF THE INVENTION 
     As it is known, the disc brake comprises a disc solid to the wheel and a caliper mounted on a bracket engaged to the yoke of the motorcycle or directly on the frame and/or on the fork. 
     The caliper is provided with small pistons which exert a braking action on the disc by operating, for example, a pedal pump mounted in proximity of one of the motorcycle footboards. 
     The pump comprises a piston sliding and/or rotating within a cylinder intended to hold fluid and moved, via suitable linkages, by the driver-operated pedal. 
     The cylinder has an opening at a longitudinal end thereof, opposite to the piston and connected, by means of a suitable hydraulic connection, to the caliper, or servo actuator, of the rear brake. In the known calipers, the pump is further provided with a compensating reservoir exhibiting a conduit which leads on a side wall of the cylinder into two holes being in side-by-side relationship, a feeding hole and a compensating hole. The piston has two gaskets tight-seal sliding on the inner wall of the cylinder, and a central portion interposed between said gaskets and delimiting an annular compensating chamber or space. The feeding hole—when the fluid is under pressure during the motion of the piston—leads always into the compensating space, while the compensating hole opens always onto and between the ends delimiting the gaskets. The feeding hole has the function—besides allowing the expansion of the fluid in case the latter is heated up—also of recirculating a greater amount of brake fluid, as required by the wear of the pads. In fact, in the absence of the feeding hole, the pump&#39;s piston would advance upon every braking action by a minimum additional extent owing both to the wear of the pads and the exceeding stroke length that the pistons of the calipers have to perform. Instead, with the compensating mechanism, upon releasing the pressurizing control, the caliper&#39;s pistons move back by approximately the same extent (“roll back” effect of the caliper piston&#39;s gaskets) and the piston of the pump moves back to a position which does not coincide with the previous one. However, the increase in volume between the piston&#39;s main gasket and the pistons of the calipers is compensated through the feeding hole. 
     The volume of fluid necessary for the compensation is therefore taken usually from the reservoir through the feeding hole and, only in case of anomalous wear or knock off, from the intermediate compensating chamber between the two gaskets of the pump&#39;s piston with a lowering of the lip of the main gasket and the withdrawal of fluid from the compensating reservoir through the compensating holes disposed on the pump&#39;s float. 
     The Applicant has however found out that the structure of the current compensating systems is bulky and weighs heavily on the overall dimensions and weight of the pumps of known type. 
     Since in the field, for example, of motorcycles and bicycles—and in general in all cases where highest performance levels are sought—the current trend is to reduce weights and dimensions in order to increase the handling and performance of the means in question, the weight and dimensions of a component like the brake pump are also of great consideration. 
     In particular, the presence of the two holes lined up along the cylinder of the pump, and the presence of the compensating chamber located between said gaskets, is cause for a sizeable axial development of the brake pumps of known type. 
     A further drawback of the known systems is the limited duration of the main gasket, due to the fact that the feeding hole may have small rugs left by the manufacturing process, which require costly machining operations to remove them and, if not removed, may be cause of an early wear out the gasket, especially under operating conditions. Moreover, in the first phase of compression of the fluid held in the main chamber, the main gasket must close the feeding hole quickly, so as to prevent a portion of the fluid from returning into the reservoir and thereby nullifying the effect of part of the working stroke. Such closing is, in the known pumps, committed to the axial sliding of the piston which is solid to said main gasket, and takes place with some delay after the actuation of the pump, also according to the idle stroke. 
     SUMMARY OF THE INVENTION 
     In this context, the specific technical task of the present invention is to provided a pump, for example for disc brakes of bicycles and motorcycles, able to overcome the above cited drawbacks. 
     In particular, the object of the present invention is to provide a pump, for example for disc brakes of bicycles and motorcycles, which is compact and light-weight. 
     It is also an object of the present invention to provide a pump able to improve a steady operation and, thus, the duration of the pump, and in particular of the sealing means. 
     The above technical task and the specified objects are substantially achieved by a hydraulic pump comprising the technical characteristics of the invention. 
     The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a longitudinal section view of a first embodiment of hydraulic pump, according to the invention, in a first rest position; 
         FIG. 1 a    is a sectional view of an enlarged portion of the pump in  FIG. 1 ; 
         FIG. 2  is a longitudinal sectional view of the pump in  FIG. 1 , in a second position in which the pump is partially actuated; 
         FIG. 2 a    is a sectional view of the enlarged portion of  FIG. 1  when the pump is in the position of  FIG. 2 ; 
         FIG. 3  is a longitudinal sectional view of the pump in  FIG. 1  in a third generic work position; 
         FIG. 3 a    is a sectional view of the enlarged portion of  FIG. 1  when the pump is in the position of  FIG. 3 ; 
         FIG. 4  is a longitudinal sectional view of a second embodiment of hydraulic pump, according to the invention, in a first rest position; 
         FIG. 4 a    is a sectional view of an enlarged portion of the pump in  FIG. 4 ; 
         FIG. 5  is a longitudinal sectional view of the pump in  FIG. 4 , in a second position in which the pump is partially actuated; 
         FIG. 5 a    is a sectional view of the enlarged portion of  FIG. 5 ; 
         FIG. 6  is a longitudinal sectional view of the pump in  FIG. 4  in a third generic work position; 
         FIG. 6 a    is a sectional view of the enlarged portion of  FIG. 6 ; 
         FIG. 7  is a sectional view of a possible application of a hydraulic brake according to the invention; 
         FIG. 8  is a front view of the application of  FIG. 7 ; and 
         FIG. 9  is an exploded view of a hydraulic brake shown in  FIGS. 7 and 8 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings, numeral  1  indicates in the whole a hydraulic pump for hydraulic servo actuators such as calipers of disc brakes, according to the present invention. 
     In particular, shown in the attached figures is the preferred but non-limiting embodiment of a pump  1 . 
     The pump  1  comprises a containment body  2  which delimits thereinside a cylindrical cavity  3  able to hold fluid and be in fluid communication, via a suitable conduit  4 , with a hydraulic servo actuator, for example a brake caliper of a type known per se and not to be illustrated in greater detail. 
     Usually, the caliper is connected to the conduit  4  of the pump  1  via a hose, not shown, anchored for example at one or more points of the frame and/or at the yoke of the motorcycle. 
     A piston  5  is mounted in the cylindrical cavity  3  and is axially movable therein, under control of actuation means  6  connected to the piston  5  and operated by the driver, to push the fluid in the conduit  4  so as to cause a clamping of the pads onto the disc brake. 
     More in particular, the actuation means  6  comprise a rod  7  projecting by a first end  2   a  of the containment body  2  and exhibiting a first end  7   a  thereof connected to the piston  5 , preferably through a ball joint  8 . 
     A second end  7   b  of rod  7 , opposite to the first  7   a , can be engaged in a manner known per se to an actuation member, not shown, mounted in proximity of the motorcycle&#39;s footboard. 
     The piston  5  comprises a sealing means, such as a gasket  9  being slid into abutment against an inner surface  10  of the cylindrical surface  3  to ensure fluid sealing. 
     The pump  1  also comprises a fluid compensating reservoir  12  in fluid communication with the cylindrical cavity  3 , and means  13  for closing or opening the connection between the reservoir  12  and said cylindrical cavity  3 . 
     With reference to the embodiment shown in  FIGS. 1-3   a , said means  13  for closing or opening the connection between the reservoir  12  and said cylindrical cavity  3  comprise a closing device  14  movable in consequence of the displacement of piston  5  between a position for the opening and one for the closing of a port  15  allowing communication between said reservoir  12  and said cylindrical cavity  3 . 
     Advantageously, the reservoir  12  is substantially aligned with said cylindrical cavity  3 , and the port  15  opens up onto the top  16  of the cylindrical cavity  3  and lies in a position axially opposite to the first end  2   a  of the containment body  2 . The reservoir  12  develops therefore by the opposite side of rod  8  along the axis “X”, longitudinally to the cylindrical cavity  3 , to the piston  5  and to the same rod  7 . Moreover, as illustrated in this embodiment, also the compensating reservoir  12  is delimited by the containment body  2  which, therefore, includes as a whole both the pumping unit, cylinder  3 -piston  5 , and the reservoir  12 . 
     The conduit  4  for communication with the hydraulic actuator opens up onto a side wall  17  of the containment body  2  and is in proximity of the top  16  of cavity  3  and the port  15 . A connector  18  of known type is installed in said conduit  4 , and the pipe (not shown) feeding the fluid to the caliper is mounted on said connector  18 . 
     The piston  5  is movable between a rest or retracted position in which it lies close to the first end  2   a  of the containment body  2 , and an active or advanced position in which it lies close to the top  16  of the cavity  3 . 
     In greater detail, the closing device  14  comprises a stem  19  connected to the piston  5  and developing within the cylindrical cavity  3  along the longitudinal axis “X”. The stem  19  is movable through the communication port  15  during the motion of piston  5  between the rest position and the active position. 
     A body  20  is slidingly and sealingly mounted around the stem  19 , and elastic means  21  having preferably the form of a spiral spring are interposed between the piston  5  and body  20  to push the same body  20  toward a distal end  19   a  of stem  19 , opposite to piston  5  and against a peripheral edge  15   a  of the communication port  15 . 
     As best visible in  FIG. 1 a   , the said distal end  19   a  has a relief  22  against which the body  20  is made to abut being pushed by the spring  21  preferably with the interposition of a spacer  20   a . The body  20  is provided with a first gasket  23  mounted on an inner radial portion of same body  20  and put in sliding contact with the stem  19 . A second gasket  24  is installed on a portion of the same body  20  in facing relationship with the surface  16  of cylindrical cavity  3  and surrounding the distal end  19   a  of stem  19 . Ancillary elastic means  26  defined, in this non-limiting example, by a turn of a second spiral spring, are interposed between the body  20  and the peripheral edge  15   a  of communication port  15  and are able to move the body  20  away from said port  15 . 
     When the piston  5  lies in the rest position ( FIGS. 1 and 1   a ), the distal end  19   a  of stem  19  is close to the port  15 , and the body  20  being pushed by the spring  21  lies in contact with the relief  22 . In such position, the second gasket  24  of body  20  is spaced apart from the peripheral edge  15   a  of port  15 , so as to delimit an annular passage between the cylindrical cavity  6  and the reservoir  12 . 
     The thrust exerted by the driver through the rod  7  determines firstly a united movement of piston  5 , stem  19  and closing body  20 , thereby counteracting the second spiral spring  25 . The second gasket  24  is pushed against the peripheral edge  15   a  of port  15  and shuts off the communication between the cylindrical cavity  3  and the reservoir  12  ( FIGS. 2 and 2   a ). Once the communication between the cylindrical cavity  3  and the reservoir  12  is shut off, the thrust exerted by piston  5  is cause for a pressurization of the fluid present in the cavity  3  without influencing the fluid held in the reservoir  12 . 
     The further advancement of piston  5  in opposition to the first spring  21 , causes a translation of stem  19  within the body  20 , which remains almost steady with respect to the containment body  2 , the stem  19  entering partially into the reservoir  12  ( FIGS. 3 and 3   a ). 
     Upon disengaging the rod  7 , the first spring  21  is of help in bringing the piston  5  back to the rest position, and the second spring  25  pushes the closing body  20  and re-opens the port  15 . 
     To compensate for the reduction of volume, as determined by the introduction of the stem  19  into the reservoir  12  ( FIGS. 3 and 3   a ) and the wear of the pads, the pump  1  comprises also a movable wall  26  delimiting the reservoir  12  and preferably defined by an elastic membrane. In the illustrated embodiment, said wall  26  is elastically deformable between a first position in which it lies for moving close to the port  15 , and a second position in which it lies for moving away from said port  15 . 
     More in particular, the pump  1  comprises an elastic capsule  27  inserted into a housing of the containment body  2 , which housing delimits the reservoir  12  at the bottom, that is close to port  15 . The capsule  27  defines the movable elastic wall  26  at the bottom and is advantageously closed on top, that is, in proximity of a second end  2   b  of the containment body  2 , by a plug  28 . 
     Finally, a lower plug  29  closes a side opening  30  formed in the containment body and leading into the reservoir  12 . Such opening  30  has the function to control the level of fluid within the same reservoir  12 . 
     Described herebelow with reference to  FIGS. 4-6   a  is a second embodiment of a pump according to the present invention. 
     Advantageously, also in this embodiment the reservoir  12  is generally lined up with the cylindrical cavity  3 . 
     The reservoir  12  develops therefore by the opposite side of rod  8  along the longitudinal axis “X” shared by the cylindrical cavity  3 , the piston  5  and the same rod  7 . 
     Moreover, as illustrated in this preferred embodiment, also the compensating reservoir  12  is advantageously delimited by the containment body  2  which, therefore, includes, as a whole, both the pumping unit, cylinder  3 -piston  5 , and the reservoir  12 . 
     The conduit  4  in communication with the hydraulic actuator opens up onto a side wall  17  of the containment body  2  and is close to the top  16  of cavity  3 . 
     A connector  18  is installed in such conduit  4  by means of known mechanisms, and the hydraulic connection (not shown) which feeds the fluid to the caliper is mounted on said connector  18 . 
     Also in this solution provision is made for the piston  5  to be movable between a rest or retracted position in which it lies close to the first end  2   a  of the containment body  2 , and an active or advanced position in which it lies close to the top  16  of cavity  3 . 
     More in particular, the means  13  for closing or opening the connection between the reservoir  12  and the cylindrical cavity  3  also comprise a stem  19  united to the piston  5  and developing within the cylindrical cavity  3  along the longitudinal axis “X”. 
     The stem  19  is movable during the motion of piston  5  between the rest position ( FIGS. 4 and 4   a ) and the active position ( FIGS. 6 and 6   a ). 
     In particular, in proximity of the end  19   a  of stem  19 , away from piston  5 , the stem  19  comprises a plurality of conduits  36 ,  37  for the passage of the fluid from the compensating reservoir  12  to the cylindrical cavity  3 . As best visible in  FIG. 4 a   , the stem has a main conduit  36 , generically oriented mostly in the directions parallel to the axis “X”, with which other secondary conduits  37  are connected. 
     This embodiment also comprises two further sealing means, for example two gaskets  31 ,  32 , the first  31  of which is preferably mounted slidingly and sealingly around the stem  19 , while the second  32  is mounted with interference on the top  16  of the cylindrical cavity  3 . 
     The pump also comprises elastic means  34  preferably in the form of a spiral spring, which are interposed between the piston  5  and the second gasket  32 , to facilitate the return of piston  5  to the rest or retracted position and to keep the gasket  32  in place. 
     When the piston  5  is in the rest position ( FIGS. 4 and 4   a ), the secondary conduits  37  on the distal end  19   a  of stem  19  are so disposed as to put in fluid contact the compensating reservoir  12  with the cylindrical cavity  3 . 
     The generic thrust onto the rod  7  first determines the movement of piston  5  in conjunction with the stem  19 . The secondary conduits  37 , being formed inside the stem  19 , move along with the latter, thereby missing the fluid communication with the cylindrical cavity  3 . 
     Once the fluid communication has been shut off, the thrust exerted by the piston  5  is used for putting the fluid in the chamber  3  under pressure, with no effect on the fluid contained in the reservoir  12 . 
     The further advancement of piston  5  in opposition to the spring  34 , causes a translation of stem  19  within the body  20  by partially penetrating into the reservoir  12  ( FIGS. 6 and 6   a ). 
     Upon releasing the operating force on the rod  7 , the spring  34  is of aid in bringing the piston  5  back to the rest position; thereby re-establishing the fluid communication between the reservoir  12  and cavity  3  through the main conduit  36  and the secondary conduits  37 . 
     Also in this embodiment, in order to compensate for the reduction of volume, as determined by the introduction of the stem  19  into the reservoir  12  ( FIGS. 6 and 6   a ), the pump  1  comprises also a wall  26  delimiting the reservoir  12  and being preferably defined by an elastic membrane. 
     In the illustrated embodiment, said wall  26  is elastically deformable between a first position ready for moving close to the port  15 , and a second position ready for moving away from said port  15 . 
     More in particular, the pump  1  comprises an elastic capsule  27  inserted into a housing of the containment body  2 , which housing delimits the reservoir  12  at the bottom. 
     The capsule  27  defines the movable elastic wall  26  at the bottom and is closed on top, that is, in proximity of a second end  2   b  of the containment body  2 , preferably by a plug  28 . 
     Finally, advantageously, a lower plug  29  closes a side opening  30  formed in the containment body and leading into the reservoir  12 . 
     Described herebelow with reference to  FIGS. 7-9  is a possible application of a hydraulic pump  1 , according to the present invention, for making a hydraulic brake for a bicycle or motorcycle. 
     In this embodiment, the actuation means  6  of pumps  1  comprise the rod  7  driven by a brake&#39;s lever  40  apt to be operated by the user&#39;s hand. 
     As it is known, the hydraulic brakes for cycles and motorcycles can be fixed by means of suitable fastening members  48  to a handlebar  35  so as to allow the user, having one hand on a knob  41  of the handlebar, to act on the lever  40  in order to move it close to the same knob  41  and thus operating the hydraulic brake. 
     More in particular, the lever  40  is hinged, free to rotate, onto the containment body  2  through a relevant pivot  39  supported by a projection  52  of same body  2 . 
     Advantageously, the rod  7  may exhibit a device  44  for adjusting the travel of lever  40  in correspondence of the end  7   b  of same rod  7 . In this type of known-per-se adjusting device  44 , the end  7   b  of rod  7  is externally threaded and engages into a corresponding internal thread of a cylinder  46 . 
     By rotating the rod  7 , it is possible to adjust the distance, under rest condition, between the lever  40  and the knob  41 . 
     The hydraulic pump  1  is interposed between the handlebar  35  and the lever  40 . 
     In particular, the compensating reservoir  12  is closed by a respective plug  38  which is kept under pressure onto a gasket  43  via a small collar  45  screwed onto the handlebar  35  by respective fastening elements  48 . 
     More in particular, a portion  2   c  of the containment body  2 , and the small collar  45  are so shaped as to be able to embrace the handlebar  35  and be coupled stably thereon. In this embodiment, a flexible cable  42  is fitted onto the connector  18  and is able to deliver the fluid to a hydraulic servo actuator such as a brake caliper. 
     Also shown in  FIG. 7  is the arrangement of the main conduit  36  having connected thereto the secondary conduits  37  formed inside the stem  19  and moving solid therewith. 
     Referring now to  FIGS. 8 and 9 , it can be seen that the hydraulic pump comprises a containment body provided with holes  49  normally closed by screws  29 , said holes being used for a visual control of the fluid inside the reservoir  12  or for the drainage thereof. 
     The example of  FIGS. 7-9  has been given with reference to the embodiment of the pump  1  shown in  FIGS. 4-6   a . However, it is understood that other embodiments of the pump  1  can be constructed, in particular of the type illustrated in  FIGS. 1 to 3 . 
     Advantageously, a brake for bicycles and motorcycles as illustrated in  FIGS. 7-9  exhibits a shape of “radial” type, that is, with the axis “X” of the pump&#39;s piston being substantially perpendicular to the axis “Y” of handlebar  35 , so that the brake is characterized by an advantageous lever ratio which allows the user, the breaking force being equal, to act with lesser force onto the lever  40  than in the case of different brakes, such as axial” pump-type, for example. 
     At the same time, a brake according to the invention has the reservoir  12  lined up with the cylinder of pump  1  and disposed between the cylinder and the handlebar  35 . 
       FIG. 9  is an exploded view of the brake of  FIGS. 7 and 8 , showing in particular the shape of end  2   c  of body  2  complementary to the handlebar  35  for the fixing of the semicircular collar  45  above described. 
     Preferably, in the embodiment of  FIG. 9 , also the plug  38  of reservoir  12  is shaped complementarily to the handlebar  35 , against which it is compressed through a clamping action exerted by the fastening members  48  between the portion  2   c  of body  2  and semicircular small collar  45 . 
     Also viewable in  FIG. 9  is the shape of the main body  2  having an open portion  2   d  into which there are inserted a main gasket  51 , a spiral spring  21 , the stem  19  and a pack of sealing elements  50 , in this order. 
     The rod  7  is inserted, as already shown in  FIG. 7 , inside the pack of sealing elements  50 , with the end  7   a  being engaged into a corresponding cavity  52  of stem  19 . 
     The invention solves the problems encountered in the prior art and achieve the proposed objects. 
     In fact, the total volume and the weight of the pump, according to the invention, are remarkably reduced with respect to those of a traditional pump. 
     Such characteristics make it possible to assemble the pump in the most suited positions, for example on motorcycles or bicycles, so as not to hamper the movements of the driver and to concentrate the masses at such positions as to minimize the inertias and maximize the performance of the means in question. 
     Moreover, the means  13  for closing or opening the connection between the reservoir  12  and the cylindrical cavity  3 —besides conferring the pump the compact construction which is provided with—allow closing with extreme rapidity the said connection and increasing the readiness and efficacy of the braking. 
     The invention thus conceived is evidently suited for industrial application; the same invention can also be subjected to several modifications and changes falling within the scope of the inventive idea; moreover, all the parts may be replaced by other elements technically equivalent. 
     While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.