Abstract:
An automatic lubrication apparatus is designed and intended to be mounted on a hydraulic tool and can be driven by a hydraulic-pressure medium, in particular on a hydraulic hammer, and includes a lubricant pump incorporation a pump element. The pump element of the lubricant pump is cyclically impacted by a cam, and the cam is operatively connected to a hydromotor from which torque is transferred so as to produce synchronous rotation.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority from European Patent Application Number 04023633.3 filed Oct. 4, 2004, the contents of which are hereby incorporated by reference in their entirety. 
       BACKGROUND OF INVENTION 
       [0002]    The present invention relates to an automatic lubrication apparatus for hydraulic tools associated with heavy machinery, particularly heavy machinery used for construction and excavation. 
         [0003]    The present invention relates to an automatic lubrication apparatus which is designed and intended to be mounted on a hydraulic tool that can be driven by a hydraulic-pressure medium and is in particular a detachable component of a construction machine, which is designed to be mounted on a hydraulic hammer of an excavator, such that the lubrication apparatus sends lubricant from a lubricant reservoir through a lubricant conduit to one or more sites to be lubricated, and comprises a lubricant pump including a pump element against which a cam cyclically impacts. 
         [0004]    Automatic lubrication means for hydraulic tools associated with a construction machine are sufficiently well-known. 
         [0005]    However, parts of such conventional lubrication means are disposed centrally in the construction machine, which is advantageous in that this position is less exposed to oscillation and is more protected, but presents the disadvantage that very long leads are needed, and more effort is required to exchange the hydraulic tool for another hydraulic tool, and to remove or attach the existing hydraulic tool. 
         [0006]    Given this background, the document WO 02/33309 A1 has already proposed a lubrication apparatus designed and intended to be mounted on a hydraulic hammer that can be driven by a hydraulic-pressure medium and is a detachable component of an excavator, according to the structure described at the outset. This previously known apparatus, however, has the disadvantage that in this case the eccentric device that drives the pump element is driven by linear reciprocating movement of the free end of a selector piston that is part of a progressive distributor, with an intervening freewheel mechanism. The result is a relatively jerky movement of the eccentric, because only the movement of the selector piston in the direction to drive the eccentric forward can be used, whereas in the phase of retraction of the piston the eccentric comes to a halt. Even the forward movement of the selector piston is irregular. 
       SUMMARY OF THE INVENTION 
       [0007]    It is the objective of the present invention, in contrast, to create an automatic lubrication apparatus of the kind cited at the outset in which a more uniform driving of the pump element is ensured. 
         [0008]    This objective is achieved by the characteristics of the present invention. Advantageous further developments are given in the subordinate claims. 
         [0009]    A central idea of the present invention resides in the fact that the eccentric device (earn) driving the pump element is itself driven by a hydromotor, in a synchronized manner so that the torque is transmitted directly. Therefore, in contrast to the state of the art, the movement of the cam is not continually interrupted but rather proceeds uniformly. Because a hydromotor is distinguished by relatively high synchronization properties and direct torque transmission while driving, the cam is also driven in a synchronized manner. On the whole, therefore, a substantially more uniform transport of lubricant is ensured, which is useful in particular in view of the considerable acceleration and vibration forces that can act when a lubrication apparatus is fixed to a hydraulic tool. Because in accordance with the invention the cam is driven by a continuously operated hydromotor, a long-term operation is ensured even if the acceleration forces are of an order of magnitude equal to several times the acceleration due to gravity. 
         [0010]    According to a first embodiment of the invention the pump element comprises a displaceably seated pump piston against which the cam strikes, and a spring to pull the pump piston back towards the cam. As a result, the pump piston is constantly kept in contact with the cam, so that the back and forth movement of the pump piston is made as uniform as possible. 
         [0011]    In an alternative embodiment the pump element likewise comprises a displaceably seated pump piston forced into contact with the cam, but in such a way that both the forward and the backward movements of the pump piston are brought about by the cam itself. 
         [0012]    Regarding the drive mechanism, the hydromotor can preferably make operative connection with the cam by way of a worm gearing, in which case the worm gearing can engage an off-centre gearwheel coupled coaxially to the cam so that its rotation is reliably transmitted. 
         [0013]    According to another preferred aspect of the present invention, within the lubricant conduit, in particular inside the pump element, a nonreturn valve is provided to prevent the transported lubricant from flowing backwards. 
         [0014]    According to a special aspect of the present invention, within the lubrication apparatus a lubricant-reservoir connection is provided, which is designed to be used both with commercially available cartridges and with a press-tube. As a result the lubrication apparatus in accordance with the invention can be employed by many users in a wide variety of countries, with no restrictions. 
         [0015]    It is also useful for a pressure-regulating valve to be provided within the lubricant conduit, in particular inside the pump element, so that a desired maximal pressure can be specified for the lubricant conduit and/or the lubrication site. 
         [0016]    In an embodiment that is favourable with respect to mounting and maintenance technology, the hydromotor is removably attached as a separate unit to the lubricant pump, by way of a plurality of bolts. This makes it extremely easy to exchange the hydromotor. 
         [0017]    According to a special aspect of the present invention, the hydromotor comprises a main axis A oriented orthogonally to the axis B of the cam. In particular, the main axis A of the hydromotor can be oriented parallel to the direction of movement of the pump piston in the lubricant pump. 
         [0018]    So that the amount of lubricant to be transported can be adjusted, a flow-control valve is provided by means of which the stream of hydraulic fluid, in particular hydraulic oil, can be set to a desired flow velocity. 
         [0019]    A typical range of lubricant transport values for the lubrication apparatus in accordance with the invention extends from 0.5 to 1.5 cm 3 /min, preferably from 0.8 to 1.3 cm 3 /min. The amount transported per stroke, in a special embodiment of the invention, is between 0.15 cm 3 /stroke and 0.20 cm 3 /stroke, preferably about 0.18 cm 3 /stroke. 
         [0020]    Furthermore, a display device can also be provided on the lubrication apparatus, so that the actual level to which the lubricant reservoir is filled can be read out. Such a display device can display the current filling level continuously and/or make it possible to see that the filling level has fallen below a minimal residual level. Such a filling-level display can be implemented purely visually, by a viewing window, a scale, a display rod actuated when the piston approaches a press-tube and/or a cartridge, and/or it can be implemented by electrical transmission means through which a filling-level signal is sent to an evaluation device. 
         [0021]    In the following the invention is explained in greater detail, also with respect to additional characteristics and advantages, with reference to the description of exemplary embodiments, assisted by the attached drawings, wherein 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]      FIG. 1  shows a excavator equipped with a hydraulic hammer having its own lubrication apparatus, 
           [0023]      FIG. 2  shows an embodiment of a lubrication apparatus according to the invention in partial sectional view, 
           [0024]      FIG. 3  is an enlargement of part of  FIG. 2 , 
           [0025]      FIG. 4  is a sectional view through the lubrication apparatus illustrated in  FIG. 2 , along the line TV-Ui in  FIG. 2 , 
           [0026]      FIG. 5  is a partial cross-sectional view of the lubrication apparatus according to  FIG. 2 , as seen orthogonally thereto, 
           [0027]      FIG. 6  shows an embodiment of the lubrication apparatus according to the invention that is modified with respect to the embodiment according to  FIG. 2 , 
           [0028]      FIG. 7  is a perspective view of the embodiment of the lubrication apparatus according to  FIG. 2 . 
       
    
    
     DESCRIPTION OF THE INVENTION 
       [0029]    In  FIG. 1  a typical case of application of the lubrication apparatus in accordance with the invention is illustrated. To a construction machine  30 , which here is represented specifically as an excavator, a hydraulic tool  15  is attached by way of an extension arm or boom  31 . The tool  15  is equipped with a lubrication apparatus  32  according to the invention. The hydraulic hammer (chisel) is exposed to high mechanical loads and must be supplied with heat-resistant special lubricant. The following exemplary embodiments of the lubrication apparatus according to the invention, illustrated as specific structures, are also designed to be used with special lubricants having a large component of solid materials, e.g. copper chisel-paste, or to be used with EP2 fat. 
         [0030]    The lubrication apparatus  32  in accordance with the invention is installed in the hydraulic tool  15  or its carrier device itself; which eliminates long lubricant conduits to the construction machine. Furthermore, owing to the direct installation of the lubrication apparatus  32 , the chisel and lubrication apparatus can be attached as a complete unit to any excavator, because there is no need for installation in the excavator. The lubrication apparatus according to the invention is not negatively affected by the considerable vibrations and/or accelerations of the hydraulic hammer. 
         [0031]    The lubrication apparatus according to the invention must merely be connected to the hydraulic-fluid system of the construction machine  30  by way of a high-pressure tube, in order to supply the lubrication apparatus  32  with energy. A lubricant pump  12  of the lubrication apparatus  32  is driven by a hydromotor  14 , which is connected to the hydraulic circulation of the construction machine  30 . For example, following actuation of the foot switch for the hydraulic tool  15 , which is situated in the driver&#39;s cabin, the lubrication apparatus  32  is also supplied with hydraulic fluid to drive the hydromotor  14 , so that a lubricant transport is initiated as desired. 
         [0032]    A specific preferred embodiment is explained in the following, with reference to  FIGS. 2 to 5 . The embodiment of the lubrication apparatus  32  in accordance with the invention shown here is of modular construction; comprising a unit that incorporates the above-mentioned hydromotor  14  (hydromotor unit) as well as an adjacent unit that comprises the lubricant pump  12  with a cam  13  as well as a pump element  11  lubricant-pump unit). 
         [0033]    The unit comprising the lubricant pump  12  contains, firstly, a block-shaped basic body  33 , to the outer wall of which, by way of several bolts  16 , is attached the hydromotor unit  14 , which also comprises a cover  65  that can be removed for maintenance purposes. 
         [0034]    In the basic body  33  are mounted the above-mentioned cam  13 , which is rotatable about a main axis B, as well as the above-mentioned pump element  11 , which can be moved linearly in a direction perpendicular to the main axis B of the cam  13 . The cam  13 , seated in two pivot bearings  34 ,  35 , is housed in a cam recess  37 , the open end of which can be closed by a cover  36 . The pump element  11  is enclosed within a pump-element bore  38 , which opens at one end into the cam recess  37 . A lubricant-reservoir connection  24  communicates with the pump-element bore  38  by way of a connecting bore  39 . The pump-element bore  38  additionally comprises a lubricant-outlet opening  40 , to which a lubricant conduit  22  is connected to transport lubricant to a lubrication site  23 . 
         [0035]    By way of the lubricant-reservoir connection  24  various kinds of lubricant reservoir  21  can be attached; the one shown in the sectional view according to  FIGS. 2 and 3  is a cartridge  26 , whereas in the sectional view according to  FIG. 6  a press-tube  25  is attached to serve as lubricant reservoir  21 . 
         [0036]    According to a particular aspect of the present invention the lubricant-reservoir connection  24  is designed for use both with a press-tube  25 , as shown in  FIG. 6 , and with a commercially available cartridge, as shown for example in  FIGS. 2 and 3 . For this purpose, in the basic body  33  there is provided a pot-shaped recess  41  having a bottom surface  42  away from which the above-mentioned connecting bore  39  extends, towards the pump-element bore  38 . At the circumference of the bottom surface  42  a circular gasket  43  is provided, so that a press-tube  25  (cf.  FIG. 6 ) or adapter  27  (cf.  FIGS. 2 and 3 ) can be inserted onto a sealed seating. The adapter  27  itself is provided with a cartridge connector  44  and likewise comprises a circular gasket  45  to provide a seal against the cartridge  26 . The adapter  27  can be screwed firmly, by way of an internal bore  46 , into an internally threaded section  48  within the connecting bore  39 . 
         [0037]    Hence if the adapter  27  is previously inserted, either a press-tube  25  or a commercially available cartridge  26  can be used in the lubricant pump, whichever is preferred. 
         [0038]    In the following, the structure and function of the pump element  11  are described in greater detail, The pump element  11  is driven by the cam  13 , making contact with a cam surface  49  that encloses the cam. When the cam  13  rotates, the cam surface  49  pushes a pump piston  17  of the pump element  11  forward in a cyclic manner, during which process the pump piston  17  is kept in contact with the cam surface  49  by means of a spring  18 , so that the pump piston  17  consequently carries out a uniform back-and-forth movement as the cam  13  is rotated. When the spring  18  pulls the pump piston  17  back into a retracted position, lubricant is simultaneously sucked through the connecting bore  39  into a pump volume  50  within the pump element  11 . Then when the pump piston  17  is pushed forward by the cam surface  49 , it presses the lubricant against a nonretum valve  20 , so that it passes out of the pump volume  50  through the lubricant outlet opening  40  into the lubricant conduit  22  and hence onto the lubrication site  23 . 
         [0039]    In order to ensure that the pressure in the lubricant conduit  22  and hence at the lubrication site  23  does not exceed a desired maximal pressure, downstream of the nonreturn valve  20  there is disposed a pressure-control valve  28  that can be adjusted to a desired maximal pressure by means of a set-screw  51 . 
         [0040]    In the following the driving mechanism for the cam  13  is discussed in greater detail. Hydraulic fluid made available at the construction machine, in particular hydraulic oil, flows through a hydraulic-fluid inlet  52  into the hydromotor  14 , where it drives a first hydromotor shaft  53  that in turn, by way of a first gearwheel  54  nonrotatably fixed to the shaft, rotates a second gearwheel  55  so as to drive a second hydromotor shaft  56 ; subsequently the fluid emerges from the hydromotor  14  through the hydraulic-fluid outlet  58 . The second hydromotor shaft  56  is axially connected to, and transmits torque to, a worm-gear arrangement  19 . The worm gearing  19  projects out of the housing of the hydromotor  14  and extends into a drive bore  57  of the basic body  33 , engaging a cam-side gearwheel  29  that transmits the torque to the cam  13  and hence rotates it. 
         [0041]    Owing to the construction described above, a very uniform driving of the cam  13  is ensured. 
         [0042]    In  FIG. 7  a perspective view of the lubrication apparatus  32  according to  FIG. 2  is shown. The flow-control valve  59  of the hydromotor  14  is covered by a sealing cap  61 . The entire lubrication apparatus  32  can be attached to a hydraulic tool  15  by fixation screws  64 . Because of the considerable accelerations and vibrations here, fixation of the lubrication apparatus to the hydraulic tool or a carrier device for that tool is very critical. To secure the fixation screws  64  against loosening, special security disks can be used. In addition, the threads of the two fixation screws  64  can be coated. Lubricant conduits leading to lubrication sites can be connected to a plurality of lubricant connections  60 . 
         [0043]    Within the basic body  33  a monitoring aperture  62  is provided, which opens into the pot-shaped recess  41 . When transparent cartridges are used, this enables their filling level to be monitored. In the illustrated case a press-tube  25  has been inserted into the recess  41 . Furthermore, a display device  63 , here represented specifically by a rod, can be provided, which moves forward when the filling level of the cartridge or press-tube is low, thereby signalling this low filling level and hence notifying the operator that it will soon be necessary to exchange the cartridge or fill the press-tube.