Abstract:
A lubrication injector comprising a housing and a translating metering body axially moveable with respect to the housing and provided with a lubricant supply channel. The injector includes at least one translating intermediate piston radially interposed between the metering body and the housing and axially moveable with respect to the housing, the intermediate piston carrying the metering body. The intermediate piston is mounted slidable axially on the metering body. The intermediate piston and the metering body delimit at least partly a metering chamber for a lubricant in communication with the supply channel of the metering body.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a Non-Provisional Patent Application, filed under the Paris Convention, claiming the benefit of Europe Patent (EP) Application Number 14306119.0, filed on 9 Jul. 2014 (9 Jul. 2014), which is incorporated herein by reference in its entirety. 
     FIELD OF THE INVENTION 
     The present invention relates to the fields of lubrication injectors, notably those used in grease injection systems for chain conveyors. 
     BACKGROUND OF THE INVENTION 
     Chain conveyors are used in a variety of industries to move articles and require lubrication for the plates, the rollers and all the moving parts of the chain to prevent the wear. 
     Most grease injection systems for such conveyor are provided with a lubrication injector comprising a housing, a metering body disposed into the housing and a dispensing head mounted onto the body, and with a pneumatic cylinder disposed axially behind the lubrication injector. The pneumatic cylinder comprises a piston rod connected to the housing of the lubrication injector. In use, while the pneumatic cylinder runs its stroke, the dispensing head first approaches a lubrication inlet of the chain conveyor and comes into contact with the inlet, and then delivers the grease into. The delivery of grease is obtained with a sliding of the housing on the metering body under the action of the pneumatic cylinder. 
     Such current design leads to a large required space for the grease injection system. However, the available space around the chain for installing such system is always very small. 
     One aim of the present invention is to overcome this drawback. 
     SUMMARY OF THE INVENTION 
     It is a particular object of the present invention to provide a lubrication injector, notably for grease injection system, having a good compactness in the axial direction. 
     In one embodiment, the lubrication injector comprises a housing, a translating metering body axially moveable with respect to the housing and provided with a lubricant supply channel, and at least one translating intermediate piston radially interposed between the metering body and the housing and axially moveable with respect to the housing. The intermediate piston carries the metering body. The intermediate piston is mounted slidable axially on the metering body. The intermediate piston and the metering body delimit at least partly a metering chamber for a lubricant in communication with the supply channel of the metering body. 
     The intermediate piston is able to axially drive the metering body relative to the housing and is also able to axially slide on the metering body in order to reduce the volume of the metering chamber. The axial compactness of the injector is limited since the piston actuating the metering body is disposed inside the housing and radially surrounds the body. The total length of the injector is reduced with the nesting piston and body. The piston and the body form a telescopic cylinder mounted into the housing. 
     Preferably, the housing delimits together with the intermediate piston a first chamber and an opposite second chamber for an actuating fluid. 
     In one embodiment, the intermediate piston comprises passage means for the lubricant in communication with the metering chamber. The passage means may comprise at least one hole made in the thickness of the intermediate piston and opening into the metering chamber. Advantageously, the housing may comprise passage means for the lubricant in communication with the passage means of the intermediate piston. The passage means of the housing may comprise at least one hole made in the thickness of the housing. 
     In one embodiment, the lubrication injector further comprises means for setting a stroke of the intermediate piston relative to the metering body which are mounted on the intermediate piston. The setting means delimit together with the piston and the metering body the metering chamber. The axial position of the setting means relative to the intermediate piston is adjustable. Preferably, the setting means are screwed into a bore of the intermediate piston. 
     In one embodiment, the injector comprises a dispensing head mounted on the metering body and comprising an outlet orifice in communication with the supply channel of the metering body, the intermediate piston being mounted slidable axially on the metering body towards the dispensing head in order to reduce the volume of the metering chamber. 
     The lubrication injector may further comprise at least one elastic actuator axially disposed between the metering body and the intermediate piston to obtain a compression of the actuator during an axial movement of the intermediate piston on the metering body towards the dispensing head. Preferably, the metering body and the intermediate piston delimit together a space inside which is disposed the elastic actuator. In one embodiment, the elastic actuator comprises one compression spring. 
     In one embodiment, the housing is provided with a main tubular body comprising a bore into which is mounted the intermediate piston, and with two side plates fixed onto the body. 
     Preferably, the intermediate piston comprises a bore into which is mounted the metering body, the bore partly delimiting the metering chamber. 
     The invention also concerns a grease injection system for chain conveyor comprising at least one lubrication injector as previously defined. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The present invention and its advantages will be better understood by studying the detailed description of a specific embodiment given by way of a non-limiting example and illustrated by the appended drawings on which: 
         FIGS. 1, 2, and 3  are cross-sections of a lubrication injector according to an example of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     A lubrication injector  10  as shown on  FIG. 1  is particularly adapted for a lubricant injection system for chain conveyor. However, the injector  10  can also be used in other applications that require a limited compactness in the axial direction. 
     The injector  10 , with an axis  12 , comprises a housing  14 , a metering piston or body  16  mounted into the housing, a dispensing head  18  disposed on the metering body and adapted to spray the lubricant, and an intermediate piston  20  radially interposed between the metering body and the housing. The piston  20  supports the metering body and is axially movable with respect to the housing  14  along the axis  12 . The metering body  16  and the intermediate piston  20  each have a cylindrical form. 
     The housing  14  is provided with a tubular main body  22  and with first and second side plates  24 ,  26  each fixed to one end of the body. The body  22  comprises an axial annular bore  22   a , coaxial with the axis  12 , into which is mounted the intermediate piston  20 . The piston  20  is mounted in radial contact with the bore  22   a.    
     The intermediate piston  20  extends longitudinally along the axis  12  and through the bore  22   a  of the housing. The piston  20  comprises an annular bore  20   a , coaxial with the axis  12 , into which is mounted the metering body  16 . The body  16  is mounted in radial contact with the bore  20   a . The bore  20   a  extends on the entire axial length of the piston  20 . The bore  20   a  extends axially from a frontal rear face of the piston to an opposite frontal front face. In the illustrated example, the bore  20   a  has a stepped form. 
     The intermediate piston  20  comprises a cylinder portion  20   b  mounted in radial contact with the bore  22   a  of the nut, and a rod portion  20   c  extending axially from a front face of the cylinder portion and having a reduced diameter. In the position shown on  FIG. 1 , a rear face of the cylinder portion  20   b , which forms the rear face of the piston, axially comes into contact with the side plate  24 . A sleeve  28  is secured into the bore  20   a  of the piston and axially bears against the end of the rod portion  20   c  axially located on the side of the dispensing head  18 . 
     The side plate  24  and the bore  22   a  of the housing delimit together with the intermediate piston  20  a first chamber  30  ( FIGS. 2 and 3 ). The opposite side plate  26 , the bore  22   a  and the piston  20  delimit a second chamber  32  axially opposite to the first chamber with regard to the cylinder portion  20   b  of the piston. As will be described later, the piston  20  may be actuated by an external source of energy (not shown), for example a pneumatic source, in order to axially move with respect to the housing  14 . To this end, the side plate  24  comprises a through-hole  24   a  extending axially into its thickness and opening into the chamber  30 . A through-hole  22   b  is also provided into the thickness the body  22  and opens into the chamber  32 . The hole  22   b  extends radially. Fittings  33 ,  34  are respectively mounted into the through-holes  24   a ,  22   b  to be connected to the external source. 
     In the illustrated example, the intermediate piston  20  comprises a longitudinal groove  20   d  provided on the outer surface of the cylinder portion  20   b  and into which extends a screw  36  mounted on the body  22  of the housing. The groove  20   d  and the screw  36  form guiding means of the piston  20 . 
     The metering body  16  has a tubular shape and extends along the axis  12 . The body  16  axially protrudes outwards with respect to the piston  20  and the housing  14 . The body  16  comprises a supply channel  16   a  extending axially from a frontal rear face of the body to an opposite frontal front face. The supply channel  16   a  is coaxial with the axis  12 . 
     The dispensing head  18  comprises a delivery channel  18   a  which communicates with the supply channel  16   a  of the metering body and which emerges at an outlet orifice  18   b . In the illustrated example, the injector  10  also comprises an annular sleeve  38  mounted on the outer surface of the metering body  16  and supporting the dispensing head  18 . The sleeve  38  is axially moveable on the body  16 . 
     The metering body  16  comprises an abutment ring  40  secured to its outer surface and radially disposed into the bore  20   a  of the intermediate piston without contact with the bore. The ring  40  forms on the body  16  a protrusion extending radially outwards. Alternatively, the body  16  and the ring  40  may be made in one part. The sleeve  28  of the intermediate piston axially bears against the abutment ring  40  in the position shown on  FIG. 1 . 
     The injector  10  also comprises first elastic return springs  42 ,  43  axially disposed between the abutment ring  40  and the intermediate piston  20 . Each spring  42 ,  43  is disposed inside a closed space delimited by the bore of piston  20  and the metering body  16 . A first end of each spring  42 ,  43  axially bears against the piston  20  and a second opposite end axially bears against the ring  40 . Each spring  42 ,  43  is coaxial with the axis  12 . In the illustrated example, each spring  42 ,  43  is a compression spring. 
     The injector  10  further comprises a second elastic return spring  44  axially disposed on the side opposite to the return spring  42 ,  43  with regard to the abutment ring  40 . The spring  44  is axially disposed between the ring  40  and the sleeve  38  of the metering body  16 . The spring  44  is disposed inside the bore of the sleeve  28  of the piston. A first end of the spring  44  axially bears against the sleeve  38  and a second opposite end axially bears against the ring  40 . The spring  44  is coaxial with the axis  12 . In the illustrated example, the spring  44  is a compression spring. 
     The injector  10  further comprises a plug  46  mounted into the bore  20   a  of the intermediate piston axially on the side opposite to the dispensing head  18  with respect to the metering body  16 . In the position shown on  FIG. 1 , the plug  46  is axially spaced apart from the metering body  16 . The plug  46  and the body  16  delimit into the bore  20   a  an interior tight metering chamber  48  for a lubricant to deliver (not shown). The lubricant may be grease or oil. The chamber  48  is delimited axially by the frontal rear face of the body  16  and a frontal front face of the plug  46 . The axial position of the plug  46  into the bore  20   a  of the piston is axially adjustable for setting a stroke of the piston relative to the metering body  16 . The plug  46  comprises an outer thread  46   a  provided on its outer surface and which engages with an inner thread  50  formed on the bore  20   a  of the piston. The plug  46  is screwed into the bore  20   a  and is coaxial to the axis  12 . 
     The plug  46  and the bore  20   a  of the piston demit together with the body  16  the metering chamber  48 . The chamber  48  is in communication with the supply channel  16   a  of the metering body. The chamber  48  is located at the entrance of the supply channel  16   a . Passage means are provided for the lubricant to pass from an external circuit (not shown) to the metering chamber  48  in order to fill the chamber and the supply channel  16   a  of the metering body. The circuit for the delivery of the lubricant may comprise a circulation pump and is connected to a fitting  52  mounted on the outer surface of the housing  14 . 
     In the illustrated example, these passage means are of several type. Firstly, there is a radial through-hole  54  made in the thickness of the housing  14 . The hole  54  extends from the outer surface of the body  22  of the housing and opens into the bore  22   a . Secondly, other passage means for the introduction of the lubricant inside the metering chamber  48  consist in a radial through-hole  56  made in the thickness of the piston  20 . The hole  56  extends from the outer surface of the piston  20  and opens into the metering chamber  48 . The hole  56  communicates with the hole  54  of the housing. 
     The housing  14  further comprises opening and closing means  58  adapted to close off the hole  54  when no lubricant is delivered by the circulation pump and to open the hole when the lubricant is delivered. In the disclosed embodiment, the opening and closing means  58  comprises a ball and a spring applying a permanent radial force on the ball to urge it against a supply conduit of the fitting  52 . 
     The injector  10  also comprises opening and closing means  60  adapted to close off the supply channel  16   a  of the metering body. Under the effect of the pressure applied by the lubricant inside the channel  16   a , the channel is closed. In the disclosed embodiment, the opening and closing means  60  are mounted into the supply channel  16   a  of the body and comprises a ball and a spring applying a permanent axial force on the ball to urge the ball against a plug of the dispensing head. 
     In use, from the position shown on  FIG. 1 , the piston  20  is actuated by the external source of energy which conveys a fluid into the hole  24   a  and the chamber  30  of the housing. With the effect of the pressure applied by the fluid on the rear face of the piston  20 , the piston moves axially jointly with the metering body  16  towards the outside. The piston  20  and the metering body  16  moves axially together until the dispensing head  18  comes into contact with a lubrication inlet of the chain conveyor (not shown) to lubricate. During this first approach step, the piston  20  axially drives the metering body  16  as shown on  FIG. 2 . There is no axial relative movement between the body  16  and the piston  20 . 
     With the contact between the dispensing head  16  of the injector and the chain conveyor, the collar  38  supporting the head axially moves on the metering body  16  towards the piston  20  since the fluid still exerts a pressure on the rear face of the piston and some lubricant already fills the supply channel  16   a  of the metering body. The spring  44  is axially compressed between the ring  40  of the body and the collar  38 . The means  60  opens the supply channel  16   a  of the metering body. 
     Then, the piston  20  axially slides on the metering body  16  towards the head  18  under the pressure applied on the piston. The piston  20  axially translates with respect to the body  16  until the plug  46  axially abuts against the body as shown on  FIG. 3 . The front face of the plug axially comes into contact against the rear face of the body  18 . The elastic springs  42 ,  43  are axially compressed between the ring  40  and piston  20 . 
     During the axial movement of the piston  20  on the body  16 , the volume of the metering chamber  48  is reduced. The plug  46  of the piston exerts an axial pressure on the lubricant located into the chamber  48  which is conveyed inside the supply channel  16   a  of the metering body. This leads to a dispersing of the lubricant already present into the supply channel. 
     Then, the external source of energy conveys the fluid into the chamber  32  of the housing and not anymore into the chamber  30 . With the effect of the pressure applied by the fluid on the front face of the cylinder portion  20   b  of the piston, the piston moves axially jointly with the metering body  16  towards the inside of the housing  14 . Simultaneously, since the dispensing head  18  is not anymore in contact with the chain conveyor, the spring  44  releases the stored energy during the compression and exerts an axial force on the sleeve  38  which axially slides on the metering body  16  towards the outside. The means  60  close the supply channel  16   a  of the metering body with such translation. The springs  42 ,  43  also release the stored energy and exert an axial force on the ring  40  of the metering body. The body  16  axially slides into the bore  20   a  of the piston towards the outside. Thus, the rear face of the metering body  16  is axially spaced apart from the plug  46  of the piston and the metering chamber  48  recovers its initial volume. The external source of energy is then stopped when the piston  20  abuts against the side plate  24  as shown in the position illustrated on  FIG. 1 . 
     The disposition of an intermediate piston mounted inside the housing of the injector and the mounting of the metering body into the piston enable to limit the axial compactness of the injector. The total length of the injector is limited with the piston and the metering body which are axially nested into the housing. Otherwise, with the structure as illustrated in the example shown on the Figures, the injector is easily adaptable to the configuration of the chain conveyor. A first type of chain conveyor is called “chain conveyor moving to the right” and a second type is called “chain conveyor moving to the left”. The mounting of each plate either on one side or on the other side of the housing is chosen according to the type of the associated chain conveyor. 
     Although the invention has been illustrated on the basis of a lubrication injector having a plug which is axially movable along the intermediate piston in order to set the stroke of the piston, it should be understood that the invention can be applied with a plug having another design or with a piston deprived of such movable plug.