Title:
Pump system for conveying lubricating oil
Kind Code:
A1


Abstract:
A pump system for conveying lubricating oil to a cutting chain of a chain saw is provided. The pump system comprises at least one first oil pump, wherein a quantity of oil being conveyed thereby is adjustable by an operator of the chain saw. The pump system also includes a basic oil pump that is connected in parallel to the adjustable oil pump.



Inventors:
Durr, Bernhard (Stuttgart, DE)
Application Number:
10/903343
Publication Date:
02/03/2005
Filing Date:
07/30/2004
Assignee:
Andreas Stihl AG & Co., KG (Waiblingen, DE)
Primary Class:
Other Classes:
417/248
International Classes:
F04B3/00; F04B7/06; F04B23/06; F04B49/12; F04B53/18; F16N13/04; (IPC1-7): F04B3/00; F04B5/00; F04B25/00
View Patent Images:
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Primary Examiner:
STIMPERT, PHILIP EARL
Attorney, Agent or Firm:
ROBERT BECKER IP LAW (PAGOSA SPRINGS, CO, US)
Claims:
1. A pump system for conveying lubricating oil to a cutting chain of a chain saw, comprising: at least one first oil pump, wherein a quantity of oil being conveyed thereby is adjustable by an operator of said chain saw; and a basic oil pump that is connected in parallel to said adjustable first oil pump.

2. A pump system according to claim 1, wherein a capacity of said basic oil pump is fixed.

3. A pump system according to claim 2, wherein said at least one adjustable first oil pump has a lower maximum capacity than does said basic oil pump.

4. A pump system according to claim 1, wherein said oil pumps are piston pumps having a piston portion that is rotatably driveable about a longitudinal axis thereof, wherein a circumferential inclined groove is provided on said piston portion, and wherein a control pin that is fixedly held in an axial direction in a housing of said pump system extends into said inclined groove.

5. A pump system according to claim 4, wherein a respective piston of said oil pumps is fixed in position on a common piston portion.

6. A pump system according to claim 5, wherein said pistons are monolithically formed with said piston portion.

7. A pump system according to claim 5, wherein a pump housing is provided, wherein said pistons have different diameters, and wherein said pistons are guided in a stepped cylinder bore in said pump housing.

8. A pump system according to claim 7, wherein said pump housing has a monolithic construction.

9. A pump system according to claim 1, wherein a line valve is provided for adjusting a capacity of said at least one first adjustable oil pump.

10. A pump system according to claim 9, wherein said line valve is disposed on an intake side of said adjustable oil pump.

11. A pump system according to claim 9, wherein said line valve is a control valve.

12. A pump system according to claim 11, wherein said control valve is infinitely variable.

13. A pump system according to claim 11, wherein said control valve is a rotary piston valve.

Description:

BACKGROUND OF THE INVENTION

The present invention relates to a pump system for conveying lubricating oil to a cutting chain of a chain saw.

Chain saws have a guide bar on the peripheral edge of which is guided a cutting chain having individual chain links. The pivotable connection of the chain links, as well as the cutting teeth, are subjected to high stresses during operation. To avoid excessive wear, and to achieve an improved cutting result, a lubricating oil is supplied to the cutting chain via a pump system.

A certain quantity of oil is desired depending upon the material that is to be cut. With different types of wood that are to be cut, it has been shown that different quantities of lubricating oil are expedient for a good cutting result. For this purpose, pump systems are known having oil pumps that can be adjusted by an operator, where the operator of a chain saw can adapt the quantity of lubricating oil being supplied to the material that is to be cut.

It has been shown that the capacity of an oil pump is a function of the viscosity of the oil. However, this can change during operation. For example, heating of the lubricating oil due to external influences, such as weather or a brief heating due to the operating temperature of a drive motor, can lead to a considerable reduction of the viscosity. A thereby resulting, and possibly considerable, fluctuation of the capacity is to be compensated for by the operator by regulating the adjustable oil pump. It is also desired to be able to compensate for fluctuations of the capacity when changing the type of oil.

It has been shown that the viscosity-dependent capacity is subjected to unexpectedly high fluctuations. An at least approximately optimum oil capacity at operating temperature can, after a longer period of interruption of operation, and with the lubricating oil cooled off, result in the initially conveyed quantity of oil being too little. An excessive wear of the cutting chain can result. Similarly, if the quantity of oil conveyed is too low, the cutting result can be unsatisfactory.

It is therefore an object of the present invention to improve a pump system in such a way that a reliable lubrication of the cutting chain is ensured over a large operating range.

BRIEF DESCRIPTION OF THE DRAWINGS

This object, and other objects and advantages of the present application, will appear more clearly from the following specification in conjunction with the accompanying schematic drawings, in which:

FIG. 1 is a longitudinal cross-sectional illustration of one exemplary embodiment of an inventive pump system having two integrated pumps and two monolithically formed pistons in the lower dead center position;

FIG. 2 shows the arrangement of FIG. 1 with the piston arrangement in the upper dead center position;

FIG. 3 shows the arrangement of FIGS. 1 and 2 with the line valve closed;

FIG. 4 shows, in a cross-sectional illustration, details of the rotatable piston of the arrangement of FIGS. 1 to 3;

FIG. 5 shows the arrangement of FIG. 4 with the piston rotated by 180°;

FIG. 6 is a longitudinal cross-sectional illustration of a variation of an adjustable oil pump with a piston in the upper dead center position, set to a low piston displacement;

FIG. 7 shows the arrangement of FIG. 6 with the piston in the lower dead center position;

FIG. 8 shows the arrangement of FIG. 6 at maximum piston displacement; and

FIG. 9 shows the arrangement of FIG. 7 at maximum piston displacement and with the piston in the lower dead center position.

SUMMARY OF THE INVENTION

The pump system of the present application comprises at least one first oil pump, wherein a quantity of oil being conveyed thereby is adjustable by an operator of the chain saw, and a basic oil pump, which is connected in parallel to the adjustable oil pump.

Thus, a pump system is proposed according to which a basic oil pump is connected in parallel to at least one adjustable oil pump. In this connection, the basic oil pump conveys a basic quantity of oil that even under cold operating conditions, and a lubricating oil that has a correspondingly high viscosity, ensures a basic supply of lubricating oil to the cutting chain. By means of the oil pump that is connected in parallel and that can be adjusted by an operator, an additional quantity of oil can be supplied to the cutting chain as a function of need. In this connection, there is no adverse impact upon the basic supply via the basic oil pump. An incorrect setting of the adjustable oil pump, or even changing environmental conditions, do not lead to an undersupply of lubricating oil.

It can be expedient to make the basic oil pump adjustable. For example, by adjusting the basic oil pump it can be possible to adapt the basic capacity to a specific type of wood or to a specific type of lubricating oil, whereas via the adjustable oil pump fluctuations of the operating parameters, for example as a consequence of fluctuations in viscosity due to the temperature, are compensated for. Pursuant to an expedient further development, the capacity of the basic oil pump is fixed. This prevents the user from unintentionally making an incorrect adjustment. The adjustable oil pump advantageously has a reduced maximum capacity in comparison to the basic oil pump. Incorrect adjustments of the pump system are prevented via the appropriately small adjustment range.

Pursuant to an advantageous further development, the oil pump is embodied as a piston pump having a piston portion that can be rotatably driven about its longitudinal axis, whereby a peripheral inclined groove is provided on the piston portion into which a control pin that is fixed to a housing in the axial direction extends. The piston portion can be continuously rotatably driven, whereby via the control pin and the inclined groove, an oscillating axial movement is produced with little mechanical effort. Such a pump has a straightforward construction and furthermore has a good service life with little mechanical wear.

Pursuant to an expedient further development, a respective piston of the two pumps is fixed in position on a common piston portion, and in so doing is in particular monolithically embodied with the piston portion. To drive the two pistons, only one corresponding piston portion is required. The pump is embodied as an integral component that is compact and straightforward. Only a single drive is necessary for both pumps. In this connection, the pistons advantageously have different diameters, whereby they are guided in a correspondingly stepped cylinder bore that is provided in a pump housing that in particular has a monolithic configuration. The different pump diameters lead to different capacities for the two pumps, whereby the smaller piston diameter, in conjunction with the adjustable oil pump, leads in a desired manner to a reduced maximum conveying capacity. With a stepped cylinder bore, the sealingly guided piston having the smaller diameter at the same time also effects a sealing of the cylinder space in which the larger piston is guided. Separate sealing means are not necessary. The pump has a straightforward construction and is economical to manufacture.

For an easy adjustability of the oil conveying capacity, the arrangement of a line valve, especially on the intake side of the adjustable oil pump, can be expedient. A line valve has a straightforward construction, and due to the arrangement on the intake side prevents pressure peaks in the pump when the valve is closed. The line valve can be embodied as a control valve, by means of which an additional quantity of oil can selectively be activated or deactivated. Pursuant to an expedient further development, the line valve is embodied as a control valve that is in particular infinitely variable. For this purpose, an embodiment as a rotary piston valve is particularly suitable. The additional quantity of oil that is conveyed via the adjustable oil pump can be regulated in a finely sensitive manner. The mechanical outlay, and hence the cost, is low.

Further specific features of the present application will be described in detail subsequently.

DESCRIPTION OF SPECIFIC EMBODIMENTS

Referring now to the drawings in detail, FIG. 1, in a cross-sectional illustration, shows a pump system for conveying lubricant or lubricating oil 1 to a cutting chain of a non-illustrated chain saw. The pump system includes an oil pump 2, which can be adjusted by a user, as well as a basic oil pump 3. The two oil pumps 2, 3 each have a supply or feed conduit 24, 26, as well as a discharge conduit 25, 27. The lubricating oil 1 is drawn in via the feed conduits 24, 26, and is discharged via the discharge conduits 25, 27. The adjustable oil pump 2, and the basic oil pump 3, are connected via their pertaining feed conduits 24, 26 with the same, non-illustrated oil tank. The two discharge conduits 25, 27 lead to the cutting chain of the chain saw, which results in a parallel connection of the two oil pumps 2,3. Further adjustable oil pumps 2, for achieving a plurality of operating stages, can also be connected in parallel.

The pump system can be configured as a system having geared pumps, diaphragm pumps, or the like, and in the illustrated embodiment is embodied as a system of piston pumps. For this purpose, a piston portion 4 having a circular cross-sectional configuration is provided that is rotatable, about an axis of rotation 20, in the direction of the arrow 30. The piston portion 4 is sealingly guided in a pump housing 11, whereby in the pump housing a control pin 6 is fixed to the housing relative to the direction of the axis of rotation 20. The piston portion 4 has a peripheral inclined groove 5 into which the control pin 6 extends. The inclined groove 5 extends at an angle to a line that is perpendicular to the axis of rotation 20. Due to the rotation of the piston portion 4 in the direction of the arrow 30, an oscillating displacement or stroke of the piston portion 4 in the direction of its axis of rotation 20 is effected via the stationarily held control pin 6 that travels in the inclined groove 5. The piston portion 4 is shown approximately in its lower dead center position, from which, upon further rotation, the piston portion 4 carries out an axial movement in the direction of the arrow 19.

Monolithically formed on the piston portion 4 are two pistons 7, 8 having corresponding diameters D2, D1, whereby the diameter D1 of the upper piston 8 is less than the diameter D2 of the lower piston 7. The lower piston 7 has the same diameter D2 as does the remaining piston portion 4. The two pistons 7, 8 merge with one another in a stepped manner. In the region of the pistons 7, 8, the piston housing 11 is embodied as a corresponding cylinder 9, 10 via a stepped bore, whereby the two pistons 7, 8 are slidingly guided in the respective cylinders 9, 10 in a sealing manner in both the axial as well as the peripheral directions.

Provided above the smaller piston 8 is a pump chamber 21 that is filled with lubricating oil 1 during operation, and that is delimited by the piston 8 and the pump housing 11. Opening into the pump chamber 21 on the peripheral side of the piston 8 are the pertaining feed conduit 24 and discharge conduit 25. The piston 8 is provided on the side with a recess 22 via which, in the illustrated rotational position of the piston portion 4, the pump chamber 21 communicates in a flow-guiding manner with the upper discharge conduit 25. Upon displacement of the piston portion 4 in the direction of the arrow 19, the lubricating oil 1 that is disposed in the upper pump chamber 21 is pressed out through the discharge conduit 25 and is conveyed in the direction of the non-illustrated saw chain.

The basic oil pump 3 is constructed in a manner comparable to the adjustable oil pump 2. A lower pump chamber 31 of the basic oil pump 3 is delimited by the piston 7, the pump housing 11, and on the inner side by a circumferential wall of the smaller piston 8. By means of a lateral recess 22 on the piston 7, the lower pump chamber 31 communicates in a flow-guiding manner with the corresponding lower discharge conduit 27. During the displacement of the piston portion 4 in the direction of the arrow 19, lubricating oil 1 that was previously drawn in via the lower feed conduit 26 is conveyed out of the lower pump chamber 31 and through the lower discharge conduit 25 in the direction of the arrow 29 to the non-illustrated saw chain.

The diameters of the two pistons 7, 8, or the pertaining cylinders 9, 10, are such that with a specified stroke of the piston portion 4, the adjustable oil pump 2 has a smaller maximum capacity than does the basic oil pump 3. The stroke of the piston portion 4, and hence of the two pistons 7, 8, results from the inclined position of the groove 5 in connection with the fixed mounting of the control pin 6. The feed conduit 26 and the discharge conduit 27 of the basic oil pump 3 are provided as infrequently as is the automatic control of the piston portion 4 with an adjustment device. A capacity or delivery of the basic oil pump is thus fixed. The capacity adjustment of the basic oil pump, for an adjustment with regard to the work or by the operator, can also be provided, for example via an adjustable stroke of the piston portion 4 or by throttle devices provided in the feed conduit 26 or in the discharge conduit 27.

In the upper region of the pump system, i.e. in the region of the feed and discharge conduits 24-27, the pump housing 11 is surrounded by a line or conduit housing 43. A line valve 12 is disposed in the conduit housing 43 in the region of the upper feed conduit 24. For this purpose, an approximately cylindrical valve body 23 is rotatably mounted in the conduit housing 43. In the illustrated rotational position of the valve body 23, a bore 14 that extends through the valve body 23 is aligned with the upper feed conduit 24, which is thus continuously flow-guiding. The valve body 23 has a circumferential groove 15 into which extends a locking pin 16 that is fixed in the conduit housing 43. A valve body 23 is thereby secured in the axial direction. An end face of the valve body 23 is provided with a slot 18 for receiving a screwdriver or the like. A valve body 23 can thereby be rotated if necessary, as a result of which the bore 14 can be rotated out of its aligned position relative to the feed conduit 24. As a result, on the intake side of the adjustable oil pump 2, the flow of a feed stream of lubricating oil 1 can be controlled. To limit the rotational movement of the valve body 23, the latter is provided with a stop 17. Thus, the flow quantity of the oil pump 2 can be adjusted by an operator.

FIG. 2 shows the arrangement of FIG. 1 with the piston portion 4 rotated by about 180°. Due to the engagement of the control pin 6 in the inclined groove 5, there results a relative position of the piston portion 4 relative to the pump housing 11 where the piston portion 4 is disposed approximately in the upper dead center position. The volumes of the pump chambers 21, 31 are minimal. In the illustrated rotational position, the recesses 22 face the feed conduits 24, 26, as a result of which these feed conduits communicate with the pump chambers 21, 31 in a flow-guiding manner. The discharge conduits 25, 27 are closed off by the peripheral walls of the pistons 7, 8.

With a further rotation of the piston portion 4 in the direction of the arrow 30 there is effected a downward displacement in the direction of the arrow 32. The volumes of the pump chambers 21, 31 consequently increase, as a result of which lubricating oil 1 is drawn in via the feed conduits 24, 26.

A continuous rotational drive of the piston portion 4 in the direction of the arrow 30 results in an oscillating displacement of the piston portion 4 in the direction of the arrow 19 (FIG. 1) or the arrow 32 (FIG. 2). In conjunction with the alternating flow-guiding communication of the pump chambers 21, 31 via the recesses 22 either with the feed conduits 24, 26 or with the discharge conduits 25, 27, there is effected a cyclical operation of the two oil pumps 2,3.

FIG. 3 shows the arrangement of FIG. 1 with the line valve 12 closed. The valve body 23 is rotated by 90° relative to the position shown in FIG. 1. The bore 14 is transverse to the upper feed conduit 24, as a result of which the latter is closed. The feed of lubricating oil 1 through the upper feed conduit 24 into the upper pump chamber 21 is interrupted. The adjustable oil pump 2 conveys no lubricating oil 1, while the basic oil pump 3 conveys lubricating oil 1 through the lower discharge conduit 27 in the direction of the arrow 29 to the cutting chain.

The valve body 23 is rotatable in an infinitely variable manner, as a result of which an infinitely variable throttling effect can be established by means of a freely selectable relative rotation of the bore 14 relative to the feed conduit 24. The line valve 12 is thereby an infinitely variable control valve. Due to the illustrated rotatable valve body 23, the control valve 13 is embodied as a rotary piston valve. It can also be expedient to provide a linearly displaceable valve body 23, a butterfly valve, an adjustable orifice plate, or the like. A control valve that can be switched into two or more prescribed positions can also be expedient.

In the illustrated embodiment, the pump system is embodied as an integrated system of the two oil pumps 2, 3 with a common pump housing 11, conduit housing 43, and monolithic piston portion 4. Two separate oil pumps 2, 3 having a different or the same construction can also be provided. For example, with a separated configuration of the two oil pumps 2, 3, the basic pump 3 can have a fixed stroke or displacement, and the adjustable oil pump can have a variable displacement, of the corresponding piston 7, 8. A configuration corresponding to that of FIGS. 6 to 9 can, for example, be suitable for this purpose.

The schematic cross-sectional illustration of FIG. 4 shows the arrangement of FIG. 2 in the region of the upper piston 8. In the illustrated rotational position of the piston 8, which is rotatably driveable in the direction of the arrow 30, the feed conduit 24 communicates in a flow-guiding manner with the lateral recess 22 of the piston 8. At the same time, the discharge conduit 25 is closed off by the peripheral wall of the piston 8. With a downward movement of the piston 8, lubricating oil 1 (FIG. 2) flows in the direction of the arrow 33 to the recess 22, and from there into the upper pump chamber 21 (FIG. 2).

FIG. 5 shows the arrangement of FIG. 4 with the piston 8 rotated by 180°. The feed conduit 24 is closed off by the peripheral wall of the piston 8. The discharge conduit 25 communicates in a flow-guiding manner with the recess 22. With an upward movement of the piston 8, lubricating oil 1 flows out of the upper pump chamber 21 (FIG. 1) via the recess 22 and through the discharge conduit 25 in the direction of the arrow 28.

The schematic illustration of FIG. 6 shows a further embodiment of an oil pump, the capacity of which can be adjusted. The illustrated oil pump can be utilized by itself or in a pump system pursuant to FIGS. 1 to 5. The details for the control of the oil flow via the rotatable piston portion 4, although not shown in detail here, can be embodied similar to that of FIGS. 1 to 5.

Mounted on a free end of the piston portion 4 is a gear wheel or pinion 36 having an inclined toothing. The gear wheel 36 is provided for engagement in a drive worm, as a result of which the piston portion 4 can be rotatably driven about its axis of rotation 20 in the direction of the arrow 30. The piston portion 4 is rotatably and longitudinally displaceably mounted in the pump housing 11. The control pin 6 extends into the inclined groove 5, whereby from the rotational movement in the direction of the arrow, an oscillating displacement of the piston portion 4 is effected in the direction of the double arrow 44.

In the illustrated embodiment, the control pin 6 is displaceably embodied in the direction of the double arrow 35 in a radial direction relative to the axis of rotation 20. For this purpose, the control pin 6 is provided with a shaft 38, which is longitudinally displaceably mounted in the housing 11. The longitudinally displaceable mounting can be effected, for example, via a non-illustrated thread. With a rotation of the control pin 6, for example at a head 39, a radial displacement of the control pin 6 in the direction of the double arrow 35 can be effected.

Disposed at that end of the shaft 38 that faces the piston portion 4 is a spherical portion 37 that extends into the inclined groove 5. In the axial direction, and on the sides, the inclined groove 5 is delimited by essentially planar groove walls 41, 42 that extend parallel to one another and are inclined relative to a line that is perpendicular to the axis of rotation 20. The spherical portion 37 extends in an essentially play-free manner, or with little play, between the groove walls 41, 42, which results in an automatic control of the piston portion 4 in a direction of the double arrow 44.

A rotational movement of the piston portion 4 in the direction of the arrow 30 results, in an oscillating manner, in a change of the inclined position of the groove walls 41, 42 relative to the spherical portion 37. Due to the spherical surface, a rolling movement of the groove walls 41, 42 along the spherical portion 37 is effected in a wear-reducing manner.

The control pin 6 is shown in a radial position in which the spherical portion 37 is disposed close to the axis of rotation 20. From FIG. 7 it can be seen that with a rotation of 180°, in conjunction with the inclined position of the groove walls 41, 42, the piston portion 4 carries out a displacement h1.

FIG. 8 shows the arrangement of FIG. 6 with thecontrol pin 6 displaced radially outwardly. In this connection, the spherical portion 37 is disposed approximately in a ball-receiving means 40 of the pump housing 11, whereby, however, it still extends into the inclined groove 5. From the increased radial spacing of the spherical portion 37 relative to the axis or rotation 20, there is effected in conjunction with the inclined position of the groove walls 41, 42, in the illustrated upper dead center position of the upper pump chamber 21, a reduced volume relative to the volume of FIG. 6. In the illustrated embodiment, the end face of the piston 8 rests approximately against the pump housing 11.

FIG. 9 shows the arrangement of FIG. 8 with the piston portion 4 rotated by about 180°. In this connection, the piston portion 4 is disposed in the lower dead center position, whereby from the increased radial spacing of the spherical portion 37 relative to the axis of rotation 20 there results an increased displacement h2 in comparison to the position of FIGS. 6 and 7. In the illustrated lower dead center position, the volume of the upper pump chamber 21 is thus greater than in the lower dead center position of FIG. 7 where the control pin is displaced inwardly. The stroke or displacement space resulting from the displacement h1 or h2 thus increases approximately linearly relative to the radial spacing of the spherical portion 37 from the axis of rotation 20. The conveying capacity of the illustrated oil pump is therefore approximately a linear function of the displacement space, and hence is adjustable via the radial position of the control pin 6 relative to the axis of rotation 20.

The control pin 6 can also be displaced radially outwardly to such an extent that the spherical portion 37 is disposed entirely in the ball-receiving means and thus no longer extends into the inclined groove 5. This makes it easy to assemble or disassemble the piston portion 4.

With regard to the remaining features and reference numerals, the arrangement of FIGS. 6 to 9 corresponds to the arrangement of FIGS. 1 to 5.

The specification incorporates by reference the disclosure of German priority document 103 35 280.5 filed 01 Aug. 2003.

The present invention is, of course, in no way restricted to the specific disclosure of the specification and drawings, but also encompasses any modifications within the scope of the appended claims.