Integral bit retention system

Abstract

A percussion bit assembly includes a percussion bit having an upper, elongated bit shank, a lower bit head, and a bit skirt disposed intermediate the bit shank and the bit head. The percussion bit has an axial bore extending longitudinally through at least the bit shank and the bit skirt and at least one receptacle extending radially outward from the lower portion of the axial bore. A bit retainer includes at least one longitudinal member and at least one lateral member. The longitudinal member extends longitudinally within the axial bore of the percussion bit from an upper end portion, mounted within the upper portion of the axial bore, to a lower end portion disposed in the lower portion of the axial bore. The lateral member extends laterally from a radially inner end portion connected to the lower end portion of the longitudinal member to a radially outer end portion mounted in the receptacle.

1 . A percussion bit assembly for downhole boring operations comprising: 
 a percussion bit including an upper, elongated bit shank, a lower bit head, and a bit skirt disposed intermediate the bit shank and the bit head; the percussion bit defining an axial bore extending longitudinally through at least the bit shank and the bit skirt, the axial bore having upper and lower portions; the percussion bit also defining at least one receptacle extending radially outward from the lower portion of the axial bore; and    a bit retainer including at least one longitudinal member and at least one lateral member; the longitudinal member extending longitudinally within the axial bore of the percussion bit from an upper end portion, mounted within the upper portion of the axial bore, to a lower end portion disposed in the lower portion of the axial bore; the lateral member extending laterally from a radially inner end portion, connected to the lower end portion of the longitudinal member, to a radially outer end portion mounted in the receptacle.    
   
   
       2 . The percussion bit assembly of  claim 1  wherein the percussion bit defines first and second circumferentially spaced receptacles, the upper portion of the percussion bit axial bore defines a circumferential shelf, and the bit retainer includes a pair of retainer bars; each of the retainer bars including a longitudinal portion and a lateral portion defining the longitudinal and lateral members; a radially outer end portion of each lateral portion being received in one of the receptacles; the upper end portion of each longitudinal portion having a tab extending radially outward therefrom, the tabs being supported on the shelf of the percussion bit axial bore.  
   
   
       3 . The percussion bit assembly of  claim 2  wherein the bit retainer also includes upper and lower spacers, the upper spacer being positioned proximate to the upper end portions of the retainer bars and the lower spacer being positioned proximate to the lower end portions of the retainer bars, whereby the upper and lower spacers prevent radial movement of the tabs and the lateral portion of the retainer bars.  
   
   
       4 . The percussion bit assembly of  claim 3  wherein the lower end portion of each retainer bar includes a protrusion extending radially inward into the axial bore, the lower spacer being supported on the protrusions of the retainer bars.  
   
   
       5 . The percussion bit assembly of  claim 4  wherein the lower spacer is an H-shaped member defining a pair of oppositely disposed indentations and an axial opening, the lower end portion of the longitudinal portion of one of the retainer bars being received in each of the indentations.  
   
   
       6 . The percussion bit assembly of  claim 3  wherein the upper spacer is a substantially cylindrical member, having a wall defining an axial opening and a pair of oppositely disposed indentations extending radially inward into the opening.  
   
   
       7 . The percussion bit assembly of  claim 6  wherein the upper end portion of the longitudinal portion of one of the retainer bars being received in each of the indentations,  
   
   
       8 . The percussion bit assembly of  claim 7  wherein the upper spacer is supported on the shelf of the percussion bit axial bore.  
   
   
       9 . The percussion bit assembly of  claim 1  wherein the at least one receptacle extends radially outward into the bit skirt.  
   
   
       10 . The percussion bit assembly of  claim 1  wherein the at least one receptacle extends radially outward into the bit head.  
   
   
       11 . The percussion bit assembly of  claim 1  wherein the at least one receptacle extends radially outward at an obtuse angle from the axial bore and lateral member extends at an obtuse angle from the lower end portion of the longitudinal member.  
   
   
       12 . The percussion bit assembly of  claim 1  wherein the at least one receptacle extends radially outward at an obtuse angle from the axial bore and lateral member includes an upper segment that extends substantially parallel to the longitudinal member and a lower segment that extends at an obtuse angle from the upper segment.  
   
   
       13 . The percussion bit assembly of  claim 12  wherein the at least one receptacle extends through the bit skirt into the bit head.  
   
   
       14 . The percussion bit assembly of  claim 1  wherein the at least one receptacle extends radially outward at an acute angle from the axial bore and lateral member extends at an acute angle from the lower end portion of the longitudinal member.  
   
   
       15 . The percussion bit assembly of  claim 1  wherein the bit skirt has an outer surface; the receptacle is a transverse bore extending from the outer surface on a first side of the bit skirt, through the axial bore, and into an opposite, second side of the bit skirt; the longitudinal member is a retainer tube having a lower end portion defining oppositely disposed, first and second openings; and the lateral member is a pin; the pin having a first end portion positioned in a segment of the transverse bore in the first side of the bit skirt, a middle portion extending through the openings of the retainer tube lower end portion, and a second end portion positioned in a segment of the transverse bore in the second side of the bit skirt.  
   
   
       16 . The percussion bit assembly of  claim 15  wherein the upper portion of the percussion bit bore defines a circumferential shelf and a upper end portion of the retainer tube has a circumferential collar extending radially outward therefrom, the collar being supported on the shelf.  
   
   
       17 . The percussion bit assembly of  claim 16  wherein the transverse bore and the openings of the retainer tube each have an inside diameter; the first end portion of the pin includes outer and inner segments, the outer segment extending from the outer surface of the first side of the bit skirt to an intermediate position between the outer surface of the first side of the bit skirt and the axial bore, the inner segment extending from the intermediate position to the axial bore; the second end portion of the pin, the middle portion of the pin, and the inner segment of the first end portion of the pin have a substantially uniform outside diameter which is smaller than the inside diameters of the transverse bore and the openings of the retainer tube, and the outer segment of the first end portion of the pin has an outside diameter selected for frictional engagement between the outer segment of the first end portion of the pin and the transverse bore.  
   
   
       18 . The percussion bit assembly of  claim 16  wherein the bit retainer also includes a plug; the segment of the transverse bore in the first side of the bit skirt includes outer and inner portions, the outer portion extending from the outer surface of the first side of the bit skirt to an intermediate position between the outer surface of the first side of the bit skirt and the axial bore, the inner portion extending from the intermediate position to the axial bore; the transverse bore and the openings of the retainer tube each have an inside diameter and the pin has a substantially uniform outside diameter which is smaller than the inside diameters of the transverse bore and the openings of the retainer tube; the first end portion of the pin being disposed in the inner portion of the segment of the transverse bore in the first side of the bit skirt and the plug being fixedly mounted in the outer portion of the segment of the transverse bore in the first side of the bit skirt.  
   
   
       19 . The percussion bit assembly of  claim 1  wherein the bit skirt has an outer surface; the receptacle is a transverse bore having a first segment extending from the outer surface on a first side of the bit skirt to the axial bore and a second segment extending from the axial bore to the outer surface on an opposite, second side of the bit skirt; the longitudinal member is a retainer tube having a lower end portion defining oppositely disposed, first and second openings; and the lateral member is substantially identical first and second pins; the transverse bore and the openings of the retainer tube each have an inside diameter; each pin having outer and inner segments; the inner segment of each pin having an outside diameter which is smaller than the inside diameters of the transverse bore and the openings of the retainer tube; the outer segment of each pin having an outside diameter selected for frictional engagement between the outer segment of the pin and the transverse bore; the first and second pins being disposed in the first and second segments of the transverse bore, the outer segment of each pin extending from the outer surface of the bit skirt to an intermediate position between the outer surface of the bit skirt and the axial bore, the inner segment extending from the intermediate position through a one of the openings of the retainer tube.  
   
   
       20 . The percussion bit assembly of  claim 19  wherein the inner segment of each pin extends a distance into the bit bore.  
   
   
       21 . The percussion bit assembly of  claim 20  wherein said distance is substantially equal to ¼ inch.  
   
   
       22 . A percussion bit assembly for downhole boring operations comprising: 
 a percussion bit including an upper, elongated bit shank, a lower bit head, and a bit skirt disposed intermediate the bit shank and the bit head;    the percussion bit defining an axial bore extending longitudinally through at least the bit shank and the bit skirt, the axial bore having upper and lower portions; the upper portion of the axial bore defining a circumferential shelf;    the percussion bit also defining a plurality of circumferentially spaced receptacles, each receptacle extending radially outward from the lower portion of the axial bore; and    a bit retainer including a plurality of retainer bars and upper and lower spacers; each of the retainer bars including a longitudinal segment and a lateral segment; the longitudinal segment extending longitudinally within the axial bore of the percussion bit from an upper end portion to a lower end portion; the upper end portion of each longitudinal portion having a tab extending radially outward therefrom, the tabs being supported on the shelf of the percussion bit axial bore; the lateral segment extending laterally from a radially inner end portion, connected to the lower end portion of the longitudinal segment, to a radially outer end portion; the outer end portion of a one of the retainer bars being disposed within each of the receptacles; the upper spacer being positioned proximate to the upper end portions of the retainer bars and the lower spacer being positioned proximate to the lower end portions of the retainer bars, whereby the upper and lower spacers prevent radial movement of the tabs and the lateral segments of the retainer bars.    
   
   
       23 . A percussion bit assembly for downhole boring operations comprising: 
 a percussion bit including an upper, elongated bit shank, a lower bit head, and a bit skirt disposed intermediate the bit shank and the bit head;    the bit skirt having an outer surface; the percussion bit defining an axial bore extending longitudinally through at least the bit shank and the bit skirt and a transverse bore having a first segment extending from the outer surface on a first side of the bit skirt to the axial bore and a second segment extending from the axial bore to a position intermediate the axial bore and the outer surface on an opposite, second side of the bit skirt; the axial bore having upper and lower portions; the upper portion of the axial bore defining a circumferential shelf; and    a bit retainer including a retainer tube and a pin; the retainer tube extending longitudinally within the axial bore of the percussion bit from an upper end portion to a lower end portion; the upper end portion having a circumferential collar extending radially outward therefrom, the collar being supported on the shelf; the lower end portion defining oppositely disposed, first and second openings; the pin having a first end portion positioned in the first segment of the transverse bore, a middle portion extending through the openings of the retainer tube lower end portion, and a second end portion positioned in the second segment of the transverse bore; the bit retainer also including a pin retaining element.    
   
   
       24 . The percussion bit assembly of  claim 23  wherein the transverse bore and the openings of the retainer tube each have an inside diameter; the first end portion of the pin includes outer and inner segments, the outer segment extending from the outer surface of the first side of the bit skirt to an intermediate position between the outer surface of the first side of the bit skirt and the axial bore, the inner segment extending from the intermediate position to the axial bore; the second end portion of the pin, the middle portion of the pin, and the inner segment of the first end portion of the pin have a substantially uniform outside diameter which is smaller than the inside diameters of the transverse bore and the openings of the retainer tube, and the outer segment of the first end portion of the pin has an outside diameter selected for frictional engagement between the outer segment of the first end portion of the pin and the transverse bore, whereby the outer segment of the first end portion of the pin is the pin retaining element.  
   
   
       25 . The percussion bit assembly of  claim 23  wherein the first segment of the transverse bore includes outer and inner portions, the outer portion extending from the outer surface of the first side of the bit skirt to an intermediate position between the outer surface of the first side of the bit skirt and the axial bore, the inner portion extending from the intermediate position to the axial bore; the transverse bore and the openings of the retainer tube each have an inside diameter and the pin has a substantially uniform outside diameter which is smaller than the inside diameters of the transverse bore and the openings of the retainer tube; the first end portion of the pin being disposed in the inner portion of the first segment of the transverse bore; the pin retaining element being a plug fixedly mounted in the outer portion of the first segment of the transverse bore.  
   
   
       26 . A percussion bit assembly for downhole boring operations comprising: 
 a percussion bit including an upper, elongated bit shank, a lower bit head, and a bit skirt disposed intermediate the bit shank and the bit head; the bit skirt having an outer surface; the percussion bit defining an axial bore extending longitudinally through at least the bit shank and the bit skirt and a transverse bore having an inside diameter, a first segment extending from the outer surface on a first side of the bit skirt to the axial bore, and a second segment extending from the axial bore to the outer surface on an opposite, second side of the bit skirt; the axial bore having upper and lower portions; the upper portion of the axial bore defining a circumferential shelf; and    a bit retainer including a retainer tube and substantially identical first and second pins; the retainer tube extending longitudinally within the axial bore of the percussion bit from an upper end portion to a lower end portion; the upper end portion having a circumferential collar extending radially outward therefrom, the collar being supported on the shelf; the lower end portion defining oppositely disposed, first and second openings, the first and second openings each have an inside diameter; each pin having outer and inner segments; the inner segment of each pin having an outside diameter which is smaller than the inside diameters of the transverse bore and the openings of the retainer tube; the outer segment of each pin having an outside diameter selected for frictional engagement between the outer segment of the pin and the transverse bore; the first and second pins being disposed in the first and second segments of the transverse bore, the outer segment of each pin extending from the outer surface of the bit skirt to an intermediate position between the outer surface of the bit skirt and the axial bore, the inner segment extending from the intermediate position through a one of the openings of the retainer tube.