Patent Application
20130169023
The present disclosure relates to a bit sleeve for retaining a tool bit in a holder block. More particularly, the present disclosure relates to a bit sleeve retained in the holder using two or more compression band retainers and having a shoulder located to concentrate force applied by a removal tool along the centerline of the bit sleeve.
In the discussion of the background that follows, reference is made to certain structures and/or methods. However, the following references should not be construed as an admission that these structures and/or methods constitute prior art. Applicant expressly reserves the right to demonstrate that such structures and/or methods do not qualify as prior art.
Road milling, mining, and trenching equipment generally have blocks each having a replaceable sleeve to hold a cemented carbide-tipped bit. The sleeve is designed and made to be replaceable should it become damaged or worn. The sleeve is retained mechanically in the holder and therefore does not require burning or welding. However, the sleeve typically must be pressed into the holder, which necessitates tight tolerance machining and grinding to maintain the proper interference fit. Alternatively, the sleeve may have a metal spring retainer which can lose its resilience or become brittle and crack or break. In these cases, dust, debris, corrosion, and rust between the steel components may become a problem, increasing the forces necessary to remove the sleeve from the holder block. In some cases, threaded fasteners on the sleeve are used in lieu of a press fit or a metal retainer to secure the sleeve in the holders. However, threads often loosen due to the vibration prevalent in this type of equipment. And if the threads do not loosen they become “frozen” due to the rust and corrosion in the threaded area, and they must then be torched off.
Accordingly, there is a need in the art for a mechanism to retain a bit sleeve in a holder that both secures the bit during use and is readily removable when necessary for maintenance and/or replacement.
A bit sleeve as disclosed herein does not require a taper lock surface or a Morris taper surface, and removes the need for a tight tolerance press fit. Instead, the bit sleeve is retained within the bore of a holder block by compression bands retained in grooves on the body of the bit sleeve. The compression bands create an annular space between the bit sleeve and the bore of the block, and retain the bit sleeve in the bore by being resiliently compressed between the bit sleeve and the bore. Additionally, the compression sleeves seal the annular space to prevent intrusion of water, moisture, dust, debris, and the like, so as to inhibit the formation of rust and to prevent binding of the bit sleeve to the block.
An exemplary embodiment of a bit sleeve for holding a tool bit in a block having a bore that is at least partially tapered includes a collar, a flange, a shank, and a body adapted to be received into the bore. The collar has a front face for supporting a flange on the tool bit, the flange is located rearward of the collar and has a diameter larger than that of the collar, the shank is located rearward of the flange and has a diameter smaller than that of the flange, and the body has a front portion joined to a rear portion. The body includes a first groove in the front portion of the body configured to receive a first compression band and a second groove in the rear portion of the body configured to receive a second compression band. In one variation, the front portion of the body has a spherically-curved wall and the rear portion of the body has a straight cylindrical wall, which correspond to a front tapered portion the bore and a rear straight cylindrical portion of the bore. In another variation, the bit sleeve further includes a shoulder extending rearwardly from the flange and having a pair of rearwardly-oriented corners substantially aligned with the centerline of the bit sleeve.
Another exemplary embodiment of a bit sleeve for holding a tool bit in a block having a bore that is at least partially tapered includes a collar, a flange, a shank, and a body adapted to be received into the bore of the block. The collar has a front face for supporting a flange on the tool bit, the flange is located rearward of the collar and has a diameter larger than that of the collar, the shank is located rearward of the flange and has a diameter smaller than that of the flange, and the body has a front spherically-curved portion joined to a rear straight cylindrical portion. A first compression band is mounted in a groove in the front portion of the body, and a second compression band mounted in a groove in the rear portion of the body. When the bit sleeve is installed in the bore of the block, the first and second compression bands are compressed between the body and the bore to secure the bit sleeve within the bore.
Another exemplary embodiment of a bit sleeve for holding a tool bit in a block having a bore that is at least partially tapered includes a collar, a flange, a shoulder extending rearwardly from the flange, a shank, and a body adapted to be received into the bore of the block. The collar has a front face for supporting a flange on the tool bit, the flange is located rearward of the collar and has a diameter larger than that of the collar, and the shank is located rearward of the flange and has a diameter smaller than that of the flange. The shoulder has a pair of rearwardly-oriented corners substantially aligned with the centerline of the bit sleeve configured to be contacted by a wedge-shaped removal tool.
An embodiment of a mining machine includes a rotatable member and one or more blocks mounted on the rotatable member, each block including a bit sleeve installed in a block having a bore that is at least partially tapered. The bit sleeve includes a collar having a front face for supporting a flange on the tool bit, a flange located rearward of the collar and having a diameter larger than that of the collar, a shank located rearward of the flange and having a diameter smaller than that of the flange, and a body adapted to be received into the bore of the block, the body having a front portion joined to a rear portion. A first compression band is mounted in a groove in the front portion of the body, and a second compression band is mounted in a groove in the rear portion of the body. The first and second compression bands are compressed between the body and the bore to secure the bit sleeve within the bore.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
The following detailed description can be read in connection with the accompanying drawings in which like numerals designate like elements and in which:
The bit sleeve 10 has a bore 12 therethrough from a front face 34 to a rear face 32, the bore 12 being adapted for receiving the shank of a tool bit (not shown), for example as disclosed in
The body 30 of the bit sleeve 10 is not tapered to match the bore 102 of the block 100. In the depicted embodiment, the bit sleeve 10 includes a front portion 24 having a spherically-curved convex wall that varies from a larger diameter at a frontward end of the front portion 24 to a smaller diameter at a rearward end of the front portion 24. The bit sleeve 10 also includes a rear portion 26 having a straight cylindrical wall and a uniform diameter throughout. The front portion 24 and the rear portion 26 of the body 30 join at a junction 28.
Because the body 30 does not have a tapered shape to match the taper of the bore 102, the bit sleeve 10 must be retained in the bore 102 by another mechanism. As shown in
Both compression bands 52, 54 are made from a resilient abrasion-resistant material that is not susceptible to corrosion or rust, for example, a nylon composite material. In one variation, the compression bands 52, 54 are made from a nylon composite material including glass in the composite. Preferably, the nylon composite material includes about 10% to about 50% glass, and more preferably about 30% glass. The material of construction of the compression bands 52, 54 enables the bit sleeve 10 to be installed into and removed from the bore 102 with relative ease (i.e., without binding or seizing) while providing a secure fit that prevents the bit sleeve 10 from walking out of the bore 102 as a result of the vibration imparted by the tool bit. Further, the resilience or compliance of the compression bands 52, 54 enables the fit tolerance between the body 30 and the bore 102 to be wider than is typically required for a compression fit, which reduces manufacturing costs and scrap. Also, because the compression bands 52, 54 are retained in the grooves 36, 38, respectively on the body 30, there are no separate parts that can be potentially lost or damaged.
The spherically-curved surface of the front portion 24 is configured, in combination with the front compression band 52, to carry the loads and forces transmitted from the tool bit through the bit sleeve 10 and into the block 100. At the same time, front compression band 52 maintains a space between most of the front portion 24 and the bore 102, thereby allowing only a small contact area between the spherically-curved surface of the front portion 24 and the tapered bore 102. The small contact area substantially prevents the bit sleeve 10 and the block 100 from locking together.
When a new bit sleeve 10 is installed in the bore 102 so that the compression bands 52, 54 are seated in the bore 102, as shown in
In the depicted embodiment of
The front compression band 52 is preferably located entirely within the bore 102 with a front edge of in alignment with, or near alignment with, the front face 106 of the block 100. Similarly, the rear compression band 54 is preferably located entirely within the bore 102 with a rear edge in alignment with, or near alignment with, the rear face 104 of the block 100. The front band 52 seals the front end of an annular space 110 between the body 30 and the bore 102, and the rear band 54 seals the rear end of the annular space 110, so as to substantially prevent water, moisture , dust, debris, and the like from entering the annular space 110. Consequently, the outer surface of the body 30 and the inner surface of the bore 102, both typically made from steel, are prevented from rusting and seizing together.
The compression bands 52, 54 reduce wear on the bore 102 by absorbing most or all of the vibration imparted to the bit sleeve 10 by the tool bit, and by substantially keeping the bit sleeve 10 from contacting the surface of the bore 102. Additionally, the spherically-curved surface of the front portion 24 of the body 30 can mate with the taper of the bore 102, even if the bore 102 is worn, since contact is essentially at a point (where the spherical curve of the body 30 is tangent to the taper of the bore 102) rather than along mating surfaces. This is in contrast to a conventional bit sleeve arrangement having a tapered body mating with a tapered bore. As disclosed herein, the bit sleeve 10 will also be able to seat tightly against the top surface 106 of the block 100.
In the depicted embodiment, the bit sleeve 10 further includes a shoulder 20 that is stepped to extend rearwardly from the flange 18. The shoulder 20 is convexly curved and includes two rearwardly-oriented corners or steps 21 each situated substantially on the centerline of the bit sleeve 10. The corners 21 provide contact points or surfaces for a removal tool 200.
For removal of the bit sleeve 10 from the block 100, as shown in
During removal of the bit sleeve 10, the shank 22 is positioned between the two prongs 201 of the fork-shaped removal tool 200 and the sloped face 202 of each prong 201 contacts the corners 21 of the shoulder 20. As each wedge-shaped prong 201 is inserted further, or is pried against the corresponding corner 21 of the shoulder 20, the prong 201 exerts force on the bit sleeve 10 that is primarily along an axial direction of the bit sleeve 10. In particular, the positioning of the corner 21 on the shoulder 20 to be substantially aligned with the centerline of the bit sleeve 10 substantially prevents the removal tool 200 from creating forces that would skew the bit sleeve 10 and make it more likely to bind in the bore 102. Thus, the removal tool 200 enables the bit sleeve 10 to slide straight out of the bore 102.
Although described in connection with preferred embodiments thereof, it will be appreciated by those skilled in the art that additions, deletions, modifications, and substitutions not specifically described may be made without department from the spirit and scope of the invention as defined in the appended claims.
