AU2006203631B2 - Lubrication means for a spline - Google Patents

Abstract

The invention relates to a lubrication means for a spline 11 comprising at least one groove 14 in at least one of the abutting faces of a pair of splines I1 to act as a reservoir for lubrication fluid to provide lubrication to each spline face. Such grooves or channels 14 allow for retention of 5 lubricating fluid such as oil and therefore acts to minimise surface wear and provides a cooling effect. 11 11_1111 14 ii 11 Figure Ia Figure lb

Description

Regulation 3.2 AUSTRALIA PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT ORIGINAL Name of Applicant: Sandvik RC Tools Australia Pty Limited Actual Inventor: Brian Thomas Sanfead Address for Service: C/- MADDERNS, 1st Floor, 64 Hindmarsh Square, Adelaide, South Australia, Australia Invention title: LUBRICATION MEANS FOR A SPLINE Details of Associated Provisional Application No: 2005904562 dated 23 August 2005 The following statement is a full description of this invention, including the best method of performing it known to us.

This invention relates to providing a lubrication means for a spline and in particular to providing lubrication between the working faces of an engaged spline set. BACKGROUND OF THE INVENTION 5 Splines are used in numerous applications to provide a drive coupling while at the same time allowing longitudinal movement along the axis of rotation. The invention will have general application in relation to splines regardless of the field of use, however for ease of description, the invention will be described in relation to its use in respect of down hole percussive hammers. 10 However, it should be realised that the scope of the invention is not to be confined to this particular application. The drill bit of a percussive down hole hammer for both normal and reverse circulation, is conventionally provided with a splined shank. This shank locates within a drive sub with the drive 15 sub being threadably engaged to the end of a hammer barrel. The use of the spline between the drill bit and drive sub enables rotation of the drill bit as the hammer rotates while at the same time allowing longitudinal movement of the drill bit with respect to the hammer. There is generally significant clearance between the drive sub spline and the spline on the shank of 20 the drill bit. This clearance allows a small amount of rotation of the dill bit with respect to the drive sub. As a result, when the hammer rotates in any given direction, contact will be between one side of each individual spline of the drive sub and a single corresponding side of a drive sub spline. Driving forces including relative movement between the drive sub and the drill bit can be 25 considerable so that damage resulting from high contact loads is a significant problem. This damage can be reduced, and therefore the life of a drill bit and drive sub is extended, if adequate lubrication is provided between the contacting surfaces of the spline. However, because of the close fit normally provided between these contacting surfaces, it is very difficult to maintain 30 effective lubrication particularly when the drill bit is operated continuously over an extended period. One solution for ensuring adequate lubrication is to stop the drilling process and to lift the hammer off of the bottom of the hole which will result in disengagement of the spline surfaces to allow 35 coating with lubricant that is entrained within the compressed air supply that drives the hammer. 2 However, this practice is time consuming and results in a loss to the driller through reduced drilling rates. Accordingly, it is an object of this invention to provide a means for enabling lubrication between 5 the contacting faces of a spline and to thereby reduce the need for interrupting the drilling process as is currently required. Other objects and advantages of the present invention will become apparent from the following description, taken in connection with the accompanying drawings, wherein, by way of illustration 10 and example, an embodiment of the present invention is disclosed. SUMMARY OF THE INVENTION Accordingly, in one aspect, the invention is a lubrication means for a pair of splines comprising at 15 least one groove in at least one of the abutting faces of the pair of splines to act as a reservoir for lubrication fluid to provide lubrication fluid to each spline face. In one form, there is provided one or a number of short or longitudinal grooves that are positioned or extend along the length of the working faces of one of the spline sets. The grooves can generally 20 extend along the length of the spline, be positioned across the longitudinal axis of the spline or be a combination of both. Such grooves will work to retain lubrication fluid and, in the case of continuous elongate grooves, may provide a conduit for transfer of lubricating fluid along the length of the spline while the adjacent faces of the spline are abutting. 25 In addition to longitudinal grooves, other orientations of grooves or surface channels may be used. For example, the invention may comprise a number of grooves or channels angled with respect to the longitudinal axis and spaced along the length of each spline face. Further, such angled grooves or channels may form cross-hatching along the length of the face. In addition to straight grooves or channels, they may be formed in a serpentine shape or any other form of irregular shape along the 30 length of the spline face. The grooves or channels may also terminate on the face of the spline so that they form blind or interrupted channels for retention of lubricating fluid. The grooves or channels can be formed in the faces of one of the spline sets or both. It may also be formed in only one side of each spline in the case of only one drive direction. For example, in the 35 case of a down hole hammer, the grooves may be formed on the driven side of the splines of the drill bit only. Alternatively, they may be formed within the splines of the drive sub only and finally, 3 the grooves or channels can be formed in both spline sets. In the case of a drill bit or drive sub that is driven in both directions, the grooves can be formed in both sides of each spline. A further aspect of the invention is a milling tool for forming the grooves or channels within the spline 5 face. In this aspect of the invention, a milling tool is provided with raised cutting portions, which form a groove or channel of the required width and depth. A number of these ridges can be spaced along the tool depending on the required number of grooves or channels to be formed in the spline surface. In a further aspect, the invention may be said to reside in a lubrication means for a pair of splines D comprising at least one groove extending substantially lengthwise along at least one of the abutting faces of the pair of splines, so as to enable the transfer of lubrication fluid along at least a substantial portion of the length of the abutting faces of the pair of splines. In a further aspect, the invention may be said to reside in a percussive down hole hammer comprising 5 a splined drive sub comprising driving splines abutting driven splines on a drill bit, at least one of a pair of abutting faces of the pair of splines comprising at least one groove extending substantially lengthwise along the spline so as to enable the transfer of lubrication fluid along at least a substantial portion of the length of the abutting faces of the pair of splines. o In a further aspect, the invention may be said to reside in a drill bit for a percussive down hole hammer comprising driven splines, each driven spline having a working face for abutment with a driving spline and comprising at least one groove extending substantially lengthwise along the working face so as to enable the transfer of lubrication fluid along at least a substantial portion of the length of the face. 25 In yet a further aspect, the invention may be said to reside in a drive sub for a percussive down hole hammer comprising driving splines, each driving spline having a working face for abutment with a driven spline and comprising at least one groove extending substantially lengthwise along the working face so as to enable the transfer of lubrication fluid along at least a substantial portion of the length of the face. 30 BRIEF DESCRIPTION OF THE DRAWINGS In order to fully understand the invention, a preferred embodiment is described below. However, it will be realised by persons skilled in the art that the invention is not to be restricted to the features 5 described in this embodiment and that other variations that would be apparent a skilled addressee are to be included within the scope of the invention. 4 The embodiments are illustrated in the accompanying drawings in which; Figure Ia and l b show a first embodiment of a lubrication means, and Figures 2 and 3 show a second and third embodiment of the lubrication means. 5 In the following description, like reference characters designate like or corresponding parts throughout the several views of the drawings. DETAILED DESCRIPTION 10 Figures la, lb, 2 and 3 illustrate a drill bit 10 (without carbide inserts in the face of the drill bit) which comprises a shank 12 and a drill bit head 13. The shank 12 has a number of splines 11 which engage with corresponding splines of a drive-sub (not drawn). 15 The splines 1I and corresponding splines of the drive-sub enable rotation of the drill bit 10 and also enable it to move longitudinally with respect to the drive-sub. As seen in figures 1 a and 1 b, serpentine grooves 14 are formed in the driven side face of each spline 11. The groove 14 extends from the upper section of the spline and extends downwardly to 20 terminate the position towards the lower end of the spline I I which corresponds to the lowest point of engagement of the drive-sub. Preferably, the drive-sub splines also have similar grooves formed in each working face of its spline. However, this is not essential to the invention as a single groove 14 acts both as a conduit as 25 well as a lubrication reservoir to direct lubricant to the working faces of the splines while at the same time enabling fresh lubrication to refill the reservoir of the groove 14. Figures 2 and 3 show alternatives where figure 3 shows a straight line groove 16 and in the case of figure 2, a number of short length grooves 15 form a cross-hatched pattern. 30 Other shapes of longitudinal grooves and short length or grooves located across or along the spline I I will still be within the scope of this invention. Such grooves or channels allow for the retention of lubricating fluid such as oil which therefore acts 35 to minimise surface wear that would otherwise result. In addition to lubrication, the lubricating fluid has a significant cooling affect as a result of reduced friction between the contacting faces. 5 Accordingly, the invention will provide a means of allowing some lubrication to be provided which will assist in extending the durability and life of drill bits and drive subs under continuous drilling operations and assist in preventing damage associated with lack of lubrication that in turn leads to 5 catastrophic failure. Throughout the specification and the claims that follow, unless the context requires otherwise, the words "comprise" and "include" and variations such as "comprising" and "including" will be understood to imply the inclusion of a stated integer or group of integers, but not the exclusion of 10 any other integer or group of integers. The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement of any form of suggestion that such prior art forms part of the common general knowledge. 15 It will be appreciated by those skilled in the art that the invention is not restricted in its use to the particular application described. Neither is the present invention restricted in its preferred embodiment with regard to the particular elements and/or features described or depicted herein. It will be appreciated that various modifications can be made without departing from the principles of 20 the invention. Therefore, the invention should be understood to include all such modifications in its scope. 6

Claims (16)

1. A lubrication means for a pair of splines comprising at least one groove extending substantially lengthwise along at least one of the abutting faces of the pair of splines, so as to enable 5 the transfer of lubrication fluid along at least a substantial portion of the length of the abutting faces of the pair of splines.

2. The lubrication means according to claim 1, wherein the or each groove is elongate. 10

3. The lubrication means according to either of claims 1 or 2, wherein the or each elongate groove has a serpentine shape.

4. The lubrication means according to either of claims 1 or 2, further comprising a plurality of grooves. 15

5. The lubrication means according to claim 4, wherein adjacent grooves intersect.

6. The lubrication means according to claim 5, wherein said grooves form a cross-hatch pattern. 20

7. The lubrication means according to claim 2, wherein the elongate groove is straight.

8. The lubrication means according to any one of the preceding claims, used on the splines of a drill bit. 25

9. The lubrication means according to claim 8, further comprising a drive-sub that engages the drill bit, wherein the abutting faces of splines that engage the drill bit splines also have at least one groove to act as a reservoir for lubrication fluid. 30

10. A percussive down hole hammer comprising a splined drive sub comprising driving splines abutting driven splines on a drill bit, at least one of a pair of abutting faces of the pair of splines comprising at least one groove extending substantially lengthwise along the spline so as to enable the transfer of lubrication fluid along at least a substantial portion of the length of the abutting faces of the pair of splines. 35 7

11. A drill bit for a percussive down hole hammer comprising driven splines, each driven spline having a working face for abutment with a driving spline and comprising at least one groove extending substantially lengthwise along the working face so as to enable the transfer of lubrication fluid along at least a substantial portion of the length of the face.

12. A drive sub for a percussive down hole hammer comprising driving splines, each driving spline having a working face for abutment with a driven spline and comprising at least one groove extending substantially lengthwise along the working face so as to enable the transfer of lubrication fluid along at least a substantial portion of the length of the face.

13. A lubrication means substantially as herein described with reference to the accompanying drawings.

14. A percussive down hole hammer substantially as herein described with reference to the 5 accompanying drawings.

15. A drill bit substantially as herein described with reference to the accompanying drawings.

16. A drive sub substantially as herein described with reference to the accompanying drawings. 8