Abstract:
A guide bushing mountable in a supporting sleeve in the deck of a blast hole drill for guiding a drill string extending through the sleeve, the bushing having a tubular core providing a cylindrical axial bore adapted to receive and guide the drill string, the core having a flange by which it is supported in the supporting sleeve, and in which a resilient, elastomeric cushion mounted on the exterior of the core serves to cushion transverse movements of the bushing within the supporting sleeve. Preferably, the bushing is formed of two halves fastened together by hinges, so that it can be opened and laterally installed around the drill string.

Description:
This is a continuation of application Ser. No. 793,082, filed Feb. 28, 1977, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a guide bushing for guiding a drill string of a blast hole drill, and more particularly to such a guide bushing that is mountable in the deck or table of the blast hole drill. 
     2. Description of the Prior Art 
     Heretofore, guide bushings of the foregoing character have been available to the industry. In one type, such guide bushings have been made entirely of metal and, hence, have been extremely noisy in operation and have transmitted excessive vibrations to the blast hole drill in which they have been installed. Although relatively inexpensive, such metal bushings have not had long service life, and have tended to rapidly wear the drill string. 
     U.S. Pat. No. 3,951,470 to McLean discloses a guide bushing for a blast hole drill that improves upon the prior metal bushing. This patented bushing employs ball bearings. It is much more costly than the prior metal bushing, yet it is not very quiet in operation, and is understood to have a relatively short service life. 
     SUMMARY OF THE INVENTION 
     Objects of the invention are to provide a guide bushing for guiding the drill string of a blast hole drill, the guide bushing being relatively simple in construction, and inexpensive to manufacture, yet exhibiting a long and useful service life while operating in a quiet manner, dampening vibrations set up by the rotating drill string. 
     In accordance with the invention, there is provided a guide bushing mountable in a supporting sleeve in the deck of a blast hole drill for guiding a drill string extending through the sleeve, said bushing comprising: rigid cylindrical tubular core means providing a cylindrical axial bore adapted to receive and guide the drill string, said core means adapted to be disposed in the sleeve and around the drill string; means for mounting said core means substantially coaxially in the sleeve whilst allowing relative transverse movements between said core means and the sleeve; and resilient, elastomeric cushion means mounted on the exterior of said core means and adapted to coact with the interior wall of the sleeve to cushion said relative transverse movements. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
     FIG. 1 is a vertical sectional view of a portion of the deck structure of a blast hole drill showing, in elevation, a guide bushing in accordance with the invention installed therein; 
     FIG. 2 is a partial sectional view taken along the line 2--2 of FIG. 1 looking in the direction of the arrows, with the deck structure omitted for the sake of clarity; 
     FIG. 3 is a sectional view taken along the line 3--3 of FIG. 1 looking in the direction of the arrows; and 
     FIG. 4 is a plan view of the guide bushing and deck structure shown in FIG. 3. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings, there is shown a guide bushing, designated by the general reference numeral 11, embodying the present invention. In FIGS. 1, 3 and 4, the guide bushing 11 is shown disposed in a vertical cylindrical sleeve 12, sometimes called a guide bushing bucket, the sleeve being open at the top 13 and at the bottom 14. The sleeve is welded into a circular opening 15 in the deck plate 16 of a blast hole drill, such as the blast hole drill disclosed in U.S. Pat. No. 3,944,300 to Learmont et al. The sleeve 12 projects slightly above the deck plate 16 and provides a rim 17 that extends above the deck plate 16. The guide bushing 11 has, at its top, outwardly extending flange means 18 that rest on the rim 17 to thereby support the guide bushing in the sleeve. Alternatively, the top 13 of sleeve 12 may be positioned flush with the top of the deck plate 16, in which case the flange means 18 will rest in part on the deck plate and in part on the rim 17. 
     Dependent from the flange means 18 is a rigid cylindrical tubular core means 19. This core means and the flange means 18 are made of metal, preferably iron or steel. The core means and flange means may be cast or fabricated, for example. Especially if cast, the core means and flange means may be monolithic. 
     A bore 21 within the core means provides a rotary shaft opening for loosely journalling and vertically guiding a drill string S, as shown in phantom lines in FIG. 1, and which may be embodied in a blast hole drill, such as that disclosed in the aforementioned McLean patent. In order to perform these functions efficaciously, the metal that forms the interior wall of the core means should have good bearing properties with respect to the metal of which the drill string is made. 
     In the preferred embodiment shown in the drawings, it is seen that the core means with its flange means is assembled from two identical half-pieces. One of the half-pieces has a core portion 19a and a flange portion 18a, and the other has a like core portion 19b and a like flange portion 18b. 
     The core portions of the half-pieces abut each other along pairs of opposed vertical faces, the respective abutting pairs of faces being located 180° apart. One of the pairs of faces consists of a face 22a on the core portion 19a and an abutting face 22b on the core portion 19b. The other of the pairs consists of a face 23a on the core portion 19a and an abutting face 23b on the core portion 19b. 
     As best seen in FIG. 4, the flange portion 18a has an end 24 and the flange portion 18b has an end 25 that are circumferentially spaced from each other to provide a notch 26 that extends radially and outwardly from the abutting faces 22a, 22b, and in alignment with them. A diametrically opposite notch 27 is provided between circumferentially separated other ends 28 and 29 of the flange portions 18a and 18b, respectively. 
     The previously mentioned half-pieces are joined together in assembled relation by suitable, oppositely disposed fastener means 31,32. These fastener means preferably take the form of hinges external to the core means 19. The hinge 31 has a central knuckle 33 on the core portion 19a and this knuckle is positioned intermediate an upper knuckle 34 on the core portion 19b and a lower knuckle 35 also on the core portion 19b. A hinge pin 36 is disposed in vertically aligned holes extending through the knuckles, the hinge pin having a head 37 at its upper end and a cotter key 38 at its lower end for retaining the hinge pin in the knuckles. As best seen in FIG. 4, the hinge pin 36 is aligned with the notch 26 so that it can be withdrawn from the knuckles upwardly through the notch after the cotter key 37 has been removed. The hinge pin, of course, can be reinserted into the knuckles through the notch. The hinge pin, being narrower than the notch, will easily pass through it. 
     The hinge 32 is identical to the hinge 31 described in the immediately preceding paragraph, but has its upper and lower knuckles 39,41 on the core portion 19a and its intermediate knuckle 42 on the core portion 19b. The hinge 32 has a hinge pin 43 that can be inserted into and withdrawn from the holes in the knuckles through the notch 27. 
     A pair of grips or handles 44,45 are welded or otherwise suitably affixed to the flange portions 18a and 18b, respectively, for use in manipulating the guide bushing. 
     Cushion means 46 are mounted on the exterior of the core means 19 and below the flange means 18. The cushion means are provided in two identical sections, section 46a being mounted on the core portion 19a and section 46b on the core portion 19b. The cushion means are formed of resilient material, preferably resilient elastomeric material such as natural or synthetic rubber composition having good resilience and shock absorbing qualities, and good abrasion resistance. 
     As best seen in FIG. 2, cushion section 46a has an inner portion 47 of uniform thickness that extends peripherally over the core portion 19a from the knuckle 33 in a counterclockwise direction to the knuckles 39 and 41. This inner portion 47 extends vertically from the bottom of the core portion 19a to the under side of the flange portion 18a. The inner portion 47 has radially projecting, vertical end ribs 48 and 49, and a radially projecting, vertical intermediate rib 51. The ribs are circumferentially spaced to provide flutes 52 and 53 between successive ribs. 
     The ribs 48, 49 and 51 have cylindrical lands 54, 55 and 56, respectively, that have identical radii and that extend downwardly from the tops of the ribs. The bottoms of the ribs are provided with chamfered surfaces 57, 58 and 59 that merge with the lands and with the bottom of the inner portion 47 of the cushion section 46a. The cushion section 46a may be, and preferably is, a unitary molding, cured in contact with and bonded to the outer surface of the core portion 19a. 
     The cushion section 46b, previously mentioned, is identical to the cushion section 46a, just described. It is molded, cured and bonded to the core portion 19b, and, together with the cushion section 46a, forms the cushion means 46 that substantially encircles the core means 19. The cushion section 46b has an inner cylindrical portion 61, and integral ribs 62,63,64. 
     It is seen from FIG. 2 that ribs 48,49,51, 62,63 and 64 have equal radii and project outwardly beyond the hinges 31 and 32. The hinge 31 is recessed in the space between the ribs 48 and 63, and the hinge 32 is recessed in the space between the ribs 49 and 62. Thus, the hinges are prevented by the ribs from contacting the sleeve 12, and are thereby protected from damage. 
     Referring to FIGS. 1, 3 and 4, stop blocks 65 and 66 are shown as being welded to the upper surface of the deck plate 16. The block 65 has a tapered nose portion 67 that extends into the notch 26 of the flange means. Similarly, the stop block 66 has a tapered nose portion that extends into the notch 27. The nose portions of the blocks fit loosely in the respective notches, but they do prevent the guide bushing 11 from turning in the sleeve 12 to any substantial extent. 
     The guide bushing may be installed around a drill string that extends through the sleeve 12 by removing one of the hinge pins 36 and 43 and swinging the two parts of the bushing on the other of the hinge pins so that the bushing is opened sufficiently to be passed laterally about the drill string. The two parts of the bushing are then closed around the drill string and locked by replacing the hinge pin that was removed. 
     The bushing fits loosely about the drill strings, and may be lowered into the sleeve 12 and positioned therein as shown in FIGS. 1, 3 and 4. In this position, the bushing journals the drill string as it rotates and guides it as it advances during drilling. 
     As the drill string rotates in the bushing, the bushing is free to move laterally in all directions, as permitted by the looseness of the fit between the stop blocks and the flange notches, but the lateral movements are cushioned and limited by the engagement of the lands of the resilient cushion means 46 with the interior of the sleeve 12. The resiliency of the cushion means substantially deadens the vibrations and noise of the drill string, and softens the shocks transmitted to the bore hole drill. 
     After coming out of the hole, the bushing 11 may be removed from the drill string by pulling one of the hinge pins, and swinging the halves of the bushing apart, allowing it to be removed laterally from around the drill string. 
     The preferred embodiment shown and described herein is merely examplary of the invention. In the light of the foregoing description and the drawings, changes and modifications will occur to those skilled in the art without departing from the spirit and scope of the invention as defined in the claims.