Lubrication system for hydraulic hammer

A lubrication system for a hydraulic hammer is disclosed. The lubrication system includes a housing having a first chamber, and a control valve, disposed proximal to a first end of the first chamber, moveable from a closed position to an open position. A piston is received within the first chamber and moveable between a first position and a second position. The piston includes a first end having a cavity, and a second end facing towards a second chamber, which receives hydraulic fluid therein. In the second position, when the first chamber is filled with air in the first position of the piston, the cavity defined at the first end of the piston maintains pressure of the air less than a biasing force of a resilient member that keeps the control valve in the closed position.

TECHNICAL FIELD

The present disclosure relates to a hydraulic hammer, and more particularly to a lubrication system of the hydraulic hammer.

BACKGROUND

Hydraulic hammers are used at work sites to break up large and hard objects such as rocks and concrete before such objects can be moved away. Generally, hydraulic hammers are coupled to a machine, such as excavators or other machines. The hydraulic hammers are powered by a combination of hydraulic power and pneumatic power. The hydraulic hammers are provided with a reservoir/cartridge for supplying lubricants such as grease, to bearing surfaces in the hydraulic hammer so as to reduce friction between the moving parts. The hydraulic hammier and the cartridge are provided with a glass window so as to allow an operator to monitor the level of grease within the cartridge. However, at times, the operator may fail to do so and fail to observe that the cartridge is empty. In such situations air is pumped into the moving parts of the hydraulic hammer and may cause the hydraulic hammer to operate inefficiently.

U.S. Pat. No. 6,145,625 hereinafter referred as the '625 patent, describes a grease lubricator for construction machine is provided. The lubricator for delivering grease lubricant to lubricating locations of a machine is coupled to a grease container and has a work chamber in which a delivery piston reciprocates. To ensure that a compressible medium, such as air which has been drawn into the work chamber is rapidly expelled therefrom, the work chamber is divided by a grease return device into a compressing portion and a delivery portion. Triggered by a sufficiently high pressure level which prevails in the compressing portion and which is present only during grease delivery, an otherwise blocked return connection is established between the compressing portion and a supply port which couples the grease container to the work chamber, as long as the head of the delivery piston, in the course of its grease delivery stroke (forward stroke) is situated in the compressing portion. However, the '625 patent may not expel the air which enters through the lubricator.

SUMMARY OF THE DISCLOSURE

In one aspect of the present disclosure, a lubrication system for a hydraulic hammer is provided. The lubrication system includes a housing having a first chamber having a first end and a second end distal to the first end. The lubrication system further includes a reservoir containing a lubricant coupled proximal to the first end of the first chamber to supply the lubricant to the first chamber. The lubrication system further includes a control valve disposed proximal to the first end of the first chamber and fluidly communicated with the first chamber. The control valve is moveable from a closed position to an open position against a biasing force of a resilient member to allow flow of the lubricant to a plurality of components disposed downstream of the control valve. The lubrication system further includes a piston received within the first chamber, and moveable between a first position and a second position. The piston includes a first end facing towards the control valve, and including a cavity. The piston further includes a second end opposite to the first end and facing towards a second chamber defined at the second end of the first chamber. The second chamber is adapted to receive a hydraulic fluid therein to move the piston from the first position to the second position. In the second position, when the lubricant is received within the first chamber in the first position of the piston, a pressure of the lubricant causes movement of the control valve from the closed position to the open position to allow flow of the lubricant to the plurality of components. Further, in the second position, when the first chamber is filled with air in the first position of the piston, the cavity defined at the first end of the piston maintains pressure of the air less than the biasing force of the resilient member to keep the control valve in the closed position.

In another aspect of the present disclosure, a pump for supplying lubricant in a hydraulic hammer is provided. The pump includes a housing having a first chamber adapted to receive a lubricant therein and a second chamber adapted to receive a hydraulic fluid therein. The pump further includes a piston received within the first chamber, and moveable between a first position and a second position. The piston includes a first end facing towards a control valve disposed adjacent to a first end of the first chamber, and including a cavity defining a volume. The volume is defined based on parameters including a biasing force of a resilient member causing movement of the control valve from an open position to a closed position and a volume of the first chamber defined by the first end of the piston in the first position of the piston. The piston further includes a second end opposite to the first end and facing towards the second chamber to move the piston from the first position to the second position based on a pressure of the hydraulic fluid. In the second position, when the first chamber is filled with air in the first position of the piston, the cavity defined at the first end of the piston maintains pressure of the air less than the biasing force of the resilient member to keep the control valve in the closed position.

DETAILED DESCRIPTION

Reference will now be made in detail to specific embodiments or features, examples of which are illustrated in the accompanying drawings. Wherever possible, corresponding or similar reference numbers will be used throughout the drawings to refer to the same or corresponding parts. Moreover, references to various elements described herein, are made collectively or individually when there may be more than one element of the same type. However, such references are merely exemplary in nature. It may be noted that any reference to elements in the singular may also be construed to relate to the plural and vice-versa without limiting the scope of the disclosure to the exact number or type of such elements unless set forth explicitly in the appended claim.

FIG. 1illustrates a perspective view of a portion of a hydraulic hammer10. The hydraulic hammer10includes a housing12having a first end14and a second end (not shown) distal to the first end14. The first end14of the housing12is adapted to couple to a boom assembly of a machine, such as an excavator. In an example, the first end14of the housing may be coupled to a stick of the boom assembly using a mounting bracket, The housing12is used for accommodating plurality of components, such as a power cell (not shown), a piston (not shown) and bearing components (not shown) to facilitate operation of the hydraulic hammer10. The piston is coaxially disposed within the housing12to reciprocate along a longitudinal axis of the housing12. On reciprocation, the piston strikes a work tool (not shown) coupled to the second end of the housing12and cause the work tool to vibrate to break rocks and to penetrate through a work surface.

In an embodiment, the hydraulic hammer10further includes a lubrication system18disposed within the housing12. More specifically, the lubrication system18is disposed proximal to the first end14of the housing12such that the lubricant is supplied to the plurality of components disposed downstream of the lubrication system18. The lubrication system18supplies a lubricant to the plurality of components of the hydraulic hammer10during operation of the hydraulic hammer10. The lubrication system18is in fluid communication with each of the multiple components, such as the piston and the work tool via multiple oil passages defined within housing12. The hydraulic hammer10is fluidly communicated with a hydraulic system of the machine to which the hydraulic hammer10is attached. The hydraulic system is adapted to actuate the lubrication system18during operation of the hydraulic hammer10. The constructional and operational features of the lubrication system18will be described in detail herein below.

FIG. 2illustrates a cut sectional view of the lubrication system18. The lubrication system18includes a first reservoir20and a second reservoir22for containing lubricant, such as grease. However, it should be understood that the lubrication system18may include one reservoir or more than two reservoirs. In the illustrated example, each of the first reservoir20and the second reservoir22is a grease cartridge. Upon complete consumption of the grease, either the cartridge may be refilled with grease or the empty cartridge may be replaced with a new grease cartridge. The lubrication system18further includes a first pump24and a second pump26defined within the housing12of the hydraulic hammer10. The first pump24is fluidly communicated with the first reservoir20and the second pump26is fluidly communicated with the second reservoir22to supply the lubricant from the first and second reservoirs20,22to the plurality of components disposed downstream of the lubrication system18. The lubrication system18further includes a first control valve28and a second control valve30fluidly communicated with the first pump24and the second pump26, respectively, to allow flow of the lubricant from the first and second reservoirs20,22to the plurality of components disposed downstream of the lubrication system18. Construction and structure of the second reservoir22, the second pump26, and the second control valve30are similar to the first reservoir20, the first pump24, and the first control valve28, respectively. Hence, the constructional and structural details of the first reservoir20, the first pump24, and the first control valve28are described in detail for explanation purpose of the present disclosure. The first pump24, the first reservoir20, and the first control valve28are hereinafter referred to as “the pump24”, “the reservoir20” and “the control valve28”, respectively.

FIG. 3illustrates an enlarged view of a portion “A” of the lubrication system18ofFIG. 2. Refer toFIG. 2andFIG. 3, the pump24includes the housing12having a first chamber32and a second chamber34. The first chamber32is defined as a lubricant passage within the housing12and the second chamber34is defined along a thickness of a wall36of the housing12. More specifically, the first chamber32and the second chamber34are defined within the housing12coaxially. The first chamber32includes a first end38and a second end40distal to the first end38. The reservoir20is coupled proximal to the first end38of the first chamber32to supply the lubricant to the first chamber32. The reservoir20is disposed vertically and an inlet of the reservoir is fluidly communicated with the first chamber32such that the lubricant enters into the first chamber32due to gravity. The second chamber34is defined at the second end40of the first chamber32. The second chamber34is defined as a hollow space within the wall36of the housing12. The hollow space is further covered by a cap37to define the second chamber34coaxial to the first chamber32. The second chamber34is adapted to fluidly communicate with the hydraulic system of the machine. More specifically, the second chamber34includes an opening (not shown) for fluidly communicating with the hydraulic system such that, during the operation of the hydraulic hammer10, a pressurized hydraulic fluid is supplied to the second chamber34. In an example, the hydraulic system may include a pump, which may receive a driving power from an engine of the machine to supply the pressurized hydraulic fluid to the second chamber34during operation of the hydraulic hammer10. The pressure of the hydraulic fluid within the second chamber34may be varied based on various parameters including, but not limited to, a volume of the second chamber34. In the illustrated example, the first chamber32has an inner diameter that remains constant throughout a length thereof and the second chamber34has an inner diameter greater than the inner diameter of the first chamber32. Hence, one or more step portions41are defined at a juncture of the first chamber32and the second chamber34.

The pump24further includes a piston42received within the first chamber32. The piston42is adapted to be movable between a first position ‘F1’ and a second position ‘F2’ (as shown inFIG. 4). The piston42includes a first end44and a second end46opposite to the first end44. The first end44of the piston42further includes a cavity48defining a volume ‘V’. The second end46of the piston42faces the second chamber34and is disposed within the second chamber34against a biasing force of an elastic member50. In the illustrated example, the elastic member50is a compression spring. One end of the elastic member50rests against the step portion41defined between the first chamber32and the second chamber34and another end is attached to a flange47provided at the second end46of the piston42. As such, the piston42is moved from the first position ‘F1’ to the second position ‘F2’ against the biasing force of the elastic member50. Further, movement of the piston42from the first position ‘F1’ to the second position ‘F2’ is controlled based on the pressure of the hydraulic fluid supplied to the second chamber34and the biasing force of the elastic member50. The elastic member50also enables movement of the piston42from the second position ‘F2’ to the first position ‘F1’ when the hydraulic fluid is relieved from the pressure at which the piston42is moved from the first position ‘F1’ to the second position ‘F2’. The volume ‘V’ of the cavity48is defined based on parameters including, but not limited to, the biasing force of the resilient member51and a volume of the first chamber32defined by the first end44of the piston42in the first position ‘F1’ of the piston42. The cavity48is also designed in such way to maintain structural rigidity of the piston42by considering various dimensional characteristics of the piston42including, but not limited to, a length of the piston42and an outer diameter of the piston42.

The control valve28of the lubrication system18is disposed proximal to the first end38of the first chamber32. The control valve28is further in fluid communication with the first chamber32. In the illustrated example, the control valve28is a check valve. The control valve28is adapted to be movable from a closed position to an open position against a biasing force of a resilient member51to allow flow of the lubricant to the plurality of components disposed downstream of the control valve28. In an example, a valve opening is defined at the first end38of the first chamber32and the valve opening is normally closed by the control valve28in the closed position of the control valve28. The control valve28is normally seated within the valve opening against the biasing force of the resilient member51. In the illustrated example, the resilient member51is a compression spring. In the open position, the control valve28moves against the biasing force of the resilient member51to allow flow of the lubricant to the plurality of components disposed downstream of the control valve28.

FIG. 4illustrates a sectional view of a portion of the lubrication system18having the piston42disposed at the second position ‘F2’. During operation of the hydraulic hammer10and the machine, the hydraulic fluid is supplied to the second chamber34at desired pressure. As a force developed within the second chamber34due to the desired pressure of the hydraulic fluid becomes greater than the biasing force of the elastic member50, the piston42starts moving from the first position ‘F1’ to the second position ‘F2’. During the movement of the piston42from the first position ‘F1’ to the second position ‘F2’, the lubricant stored in the first chamber32gets pressurized. As a force developed within the first chamber32due to the pressure of the lubricant becomes greater than the biasing force of the resilient member51, the control valve28displaces from the closed position to the open position to allow the lubricant to flow towards the plurality of component of the hydraulic hammer10. When the pressure of the hydraulic fluid is relieved within the second chamber34, the elastic member50causes the piston42to move back to the first position ‘F1’. Such continuous movement of the piston42between the first position ‘F1’ and the second position ‘F2’ supplies the lubricant to the components of the hydraulic hammer10during operation thereof. Over a period of time, the lubricant present in the reservoir may be completely consumed, which an operator may fail to notice.

FIG. 5illustrates a sectional view of a portion of the lubrication system18having the piston42disposed at the second position ‘F2’, when the reservoir20is empty. In operation, when the second chamber34fails to receive the hydraulic fluid therein or a force developed within the second chamber34due to the pressure of the hydraulic fluid becomes less than the biasing force of the elastic member50, the piston42moves to the first position ‘F1’. In the first position ‘F1’, air present in the reservoir22enters into the first chamber32due to a vacuum created by the piston42within the first chamber32.

When the piston42moves from the first position ‘F1’ to the second position ‘F2’, the air received within the first chamber32in the first position ‘F1’ of the piston42gets compressed. Further, the air contained within the volume of the first chamber32defined by the first end44of the piston42is compressed within the cavity48of the piston42. However, a force developed within the cavity48of the piston42due to the pressure of the air is less than the biasing force of the resilient member51. As the force caused due to the compression of the air within the cavity48is less than the biasing force of the resilient member51, the control valve28continues to stay in the closed position. Thus, the control valve28prevents flow of air to downstream of the control valve28, when the reservoir22becomes empty.

Various embodiments disclosed herein are to be taken in the illustrative and explanatory sense, and should in no way be construed as limiting of the present disclosure.

INDUSTRIAL APPLICABILITY

The present disclosure provides the lubrication system18for the hydraulic hammer10. The second chamber34and the resilient member51aids in moving the piston42from the first position ‘F1’ to the second position ‘F2’. In addition, the cavity48provided at the first end44of the piston42aids in retaining the control valve52in the closed position, and prevents transfer of air into the hydraulic hammer10when the reservoir is empty.