Core Lifter Assembly

Abstract

A core lifter assembly includes a combination of a core lifter ring and a core lifter case. The ring has an axially extending portion of an outer generally frusto-conical configuration having an included taper angle β. The included taper angle β is also the taper angle of the outer circumferential surface of the ring. The included taper angle β may in alternate embodiments be ≧6°; ≧7°; ≧8°; or ≧10°. In one embodiment an upper limit of the included taper angle β may be about 30°. Thus in one embodiment the included taper angle β may be expressed by the relationship: 30°≧β≧6°. Further, the angle β may comprise any sub range within the aforementioned range of 6-30°. However in other embodiments the taper angle may exceed 30°.

1 - 39 . (canceled) 
     
     
         40 . A core lifter for a core drill comprising: at least one core lifter ring having at least one axially extending portion having an outer generally frusto-conical configuration formed with an included taper angle β≧6°. 
     
     
         41 . A core lifter according to  claim 40  wherein each core lifter ring has N axially extending portions with each portion having an outer generally frusto-conical configuration formed with an included taper angle β≧6° wherein N is an integer ≧I. 
     
     
         42 . The core lifter according to  claim 40  wherein the included taper angle satisfies 30°≧β≧6°. 
     
     
         43 . The core lifter according to  claim 41  wherein the included taper angle satisfies 30°≧β≧6°. 
     
     
         44 . The core lifter according to  claim 40  wherein one or more of the axially extending portions comprises a plurality of circumferentially alternating and generally axially extending grooves and splines formed on an inner circumferential surface or an outer circumferential surface of the one or more axially extending portions. 
     
     
         45 . The core lifter according to  claim 44  wherein the grooves (a) extend parallel to the central axis of the ring; or (b) follow a spiral path between axially opposite ends of their corresponding axially extending portion; or (c) extend to and reach a large outer diameter end of their corresponding axially extending portion; or (d) extend to and reach a small outer diameter end of their corresponding axially extending portion. 
     
     
         46 . The core lifter according to  claim 40  comprising a core lifter case in which the at least one core lifter ring is slidably retained. 
     
     
         47 . The core lifter according to  claim 46  wherein the core lifter case comprises a tapered section for each axially extending portion, with each tapered section configured to engage a corresponding axially extending portion to cause a change in diameter of the core lifter ring associated with the axially extending portion in response to axial displacement of the associated core lifter ring relative to the tapered section. 
     
     
         48 . A core lifter for a core drill comprising a core lifter ring having opposite downhole and uphole ends spaced by an axial distance X, an interior circumferential surface having a substantially constant major diameter for the axial distance X, and an outer circumferential surface, wherein the interior circumferential surface and outer circumferential surface are configured to form a half angle θ≧3° for at least a portion of the distance X in at least two circumferentially spaced locations and wherein at the locations a wall of the ring decreases in thickness in a direction from the uphole end to the downhole end. 
     
     
         49 . A core lifter for a core drill comprising a core lifter ring having opposite downhole and uphole ends spaced by an axial distance X, an interior circumferential surface having a substantially constant major diameter for the axial distance X, and an outer circumferential surface, wherein the interior circumferential surface and outer circumferential surface are configured to provide the ring with a half angle θ≧3° for at least a portion of the distance X wherein a wall of the ring decreases in thickness in a direction from the uphole end to the downhole end for the corresponding portion of the distance X. 
     
     
         50 . The core lifter according to  claim 48  wherein the half angle satisfies 15°≧θ≧3°. 
     
     
         51 . The core lifter according to  claim 49  wherein the half angle satisfies 15°≧θ≧3°. 
     
     
         52 . The core lifter according to  claim 48  wherein the portion of the distance X is X/N where N is an integer ≧I and wherein the ring comprises N number of integrally formed portions. 
     
     
         53 . The core lifter according to  claim 52  wherein the outer circumferential surface of the ring for one or more of the N portions has a radius that is constant in a circumferential direction for any location along the central axis and continuously decreases in an axial direction from the uphole end to the downhole end. 
     
     
         54 . The core lifter according to  claim 52  wherein one or more of the N portions comprises a plurality of circumferentially spaced recesses on the outer circumferential surface whereby an outer circumference of the ring in one or more of the N portions comprises alternating grooves and sloped splines wherein the angle θ is a measure of an angle of slope of the spline relative to a line co-axial with a central axis of the ring. 
     
     
         55 . The core lifter according to  claim 41  further comprising between mutually adjacent axially extending portions one or more transition zone extending from a small diameter end of one of the axially extending portions to a larger diameter end of the other axially extending portions. 
     
     
         56 . The core lifter according to  claim 55  wherein the one or more transition zone comprises (a) a tapered transition zone having a substantially frusto-conical circumferential surface; or (b) a cylindrical transition zone having a substantially cylindrical circumferential surface; or (c) a tapered transition zone having a substantially frusto-conical circumferential surface and a contiguous cylindrical transition zone having a substantially cylindrical circumferential surface. 
     
     
         57 . The core lifter according to  claim 55  wherein mutually adjacent axially extending portions are arranged in a manner such that a small diameter end of one axially extending portion is located immediately adjacent a large diameter end of an adjacent axially extending portion and a stepwise transition is formed between the one axially extending portion and the adjacent axially extending portion. 
     
     
         58 . The core lifter according to  claim 47  wherein each lifter ring comprises between mutually adjacent axially extending portions one or more transition zone extending from a small diameter end of one of the axially extending portions to a larger diameter end of the other axially extending portions and wherein the lifter case is provided with an intervening surface portion for each transition zone of an associated core lifter ring, each intervening surface portion being configured to match a corresponding transition zone of a core lifter ring associated with the transition zone to facilitate axial displacement of the associated core lifter ring. 
     
     
         59 . The core lifter according to  claim 44  wherein a wall of the core lifter ring is formed of substantially uniform thickness for the axial length of each of the grooves.