CA2402035A1

CA2402035A1 - Shock sub for absorbing torsional impact loads

Info

Publication number: CA2402035A1
Application number: CA 2402035
Authority: CA
Inventors: Michael Wawrzynowski
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-09-09
Filing date: 2002-09-09
Publication date: 2004-03-09

Abstract

A shock sub for absorbing torsional impact loads includes a tubular housing having an interior surface and an inner mandrel telescopically received within the tubular housing. The inner mandrel has an outer surface. A spiral engagement is provided between the inner surface of the housing and the outer surface of the mandrel allowing unfetterd relative rotational movement of the housing and the mandrel along a spiral guide path defined by the spiral engagement. Springs are provided for dampening relative rotation of the housing and the mandrel, such that torsional impact loads result in relative rotational movement of the housing and the mandrel along the spiral guide path, with the relative rotational movement being resisted and absorbed by the springs.

Description

TITLE OF THE INVENTION:
Shock sub for absorbing torsional impact loads FIELD OF THE INVENTION
The present invention relates to a shock sub for absorbing torsional impact loads BACKGROUND OF THE INVENTION
Excessive impact torque loads damage the cutting edges of drilling bits and overtorque toll joints. There are many shock subs which are capable of absorbing longitudinal impact loads, but not torsional impact loads.
SUN~ARY OF THE INVENTION
What is required is a torque sub capable of absorbing torsional impact loads.
According to the present invention there is provided a shock sub for absorbing torsional impact loads which includes a tubular housing having an interior surface and an inner mandrel telescopically received within the tubular housing.
The inner mandrel has an outer surface. A spiral engagement is provided between the inner surface of the housing and the outer surface of the mandrel allowing unfetterd relative rotational movement of the housing and the mandrel along a spiral guide path defined by the spiral engagement. Means are provided for dampening relative rotation of the housing and the mandrel, such that torsional impact loads result in relative rotational movement of the housing and the mandrel along the spiral guide path, with the relative rotational movement being resisted and absorbed by the means for dampening.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other features of the invention will become more apparent from the following description in which reference is made to the appended drawings, the drawings are for the purpose of illustration only and are not intended to in any way limit the scope of the invention to the particular embodiment or embodiments shown, wherein:
FIGURE 1 is a side elevation view, in section of a shock tool constructed in accordance with the teachings of the present invention.
FIGURE 1A is a cross-section view taken along section lines A-A of FIGURE 1.
FIGURE 1B is a cross-section view taken along section 70 lines B-B of FIGURE 1.
FIGURE 1C is a cross-section view taken along section lines C-C of FIGURE 1.
FIGURE 1D is a cross-section view taken along section lines D-D of FIGURE 1.
FIGURE 2 is a first end perspective view of a mandrel from the shock tool illustrated in FIGURE 1.
FIGURE 3 is a second end perspective view of a mandrel from the shock tool illustrated in FIGURE 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The preferred embodiment, a shock tool generally identified by reference numeral 10, will now be described with reference to FIGURES 1 through 3.
A shock sub for use in the drill string absorbing longitudinal and torsional impact loads, comprising the combination of inner, outer and independent telescopically related tubular elements.
Telescopic inner tubular assembly comprising:
spline mandrel 11 is connected to middle pipe 12 which is connected to seal mandrel 13 which is connected to piston 14 with seal 15.
This whole assembly is connected to the upper part of the drill string 80.
Telescopic outer tubular assembly comprising:
seal housing 20 with seals 21, connected to spiral spline housing 22, connected to spring housing 23 with rest ring 24 locked in between. Next to the spring housing 23 is the cylinder sub 25, connected to the bottom sub 26. Optional stabilizer 27 can be connected to bottom sub 26.
This whole assembly is connected directly to the drill bit.

Independent telescopically related tubular elements comprising:
torque sleeve 30 with locked spiral keys 31, thrust bearing 32, lock ring 33, retainer ring 34, belleville disc springs 35, other set of belleville disc springs 36, second thrust bearing 37, equalizing piston 38 with seals 39 and 40.
Shock absorbers have been used extensively in the drilling industry for a number of years.
Majority of them were designed to cope with the problem of the vibration.
Excessive impact torque loads could be more destructive then longitudinal loads.
Interrupted torque loads are the main cause in damaging the cutting edges of the drill bit.
Overtorqued tool joints can build excessive stress and break easily. The same could happen to the gears of the surface or downhole rotary equipment. Most of the shock tools are built as a telescopic tubular assembly sealed and oil lubricated. Interlocking splines allow for transmission of torque and axial movent between inner and outer telescopic assemblies.
Any type of elastically compressible cushion placed in between pair of opposed shoulders will set the limit to telescopic movement and will provide longitudinal absorption. If the torque load is transformed to the longitudinal load the same type of cushion can be used to absorb the torque. Transforming torque sleeve 30 is placed inside the tool.
The torque is transmitted through the set of straight splines of the spline mandrel I 1 which are interlocking with the internal splines of the torque sleeve 30. Other end of the torque sleeve 30 through the spiral keys 31 interlocks with the spiral spline housing 22. The belleville disc springs for this instance are placed between the shoulders within the telescopic outer assembly. They provide the cousion for the transmitted torque and act independently from the axial load. Substantial load of torque overcomes the friction resistance of the straight and spiral splines, moves the torque sleeve down against springs 35. Known torque load and precalculated spring elasticity will provide desirable torque absorption. Drawing 2 explains changes in the tool when the axial and torsional loads are applied. Drawing 3 and drawing 4 are showing the isometric view of the torque sleeve with the spiral keys.
In this patent document, the word "comprising" is used in its non-limiting sense to mean that items following the 30 word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article "a" does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements.
It will be apparent to one skilled in the art that modifications may be made to the illustrated embodiment without departing from the spirit and scope of the invention as hereinafter defined in the Claims.

Claims

1. A shock sub for absorbing torsional impact loads, comprising:
a tubular housing having an interior surface;
an inner mandrel telescopically received within the tubular housing, the inner mandrel having an outer surface;
a spiral engagement between the inner surface of the housing and the outer surface of the mandrel allowing unfetterd relative rotational movement of the housing and the mandrel along a spiral guide path defined by the spiral engagement; and means for dampening relative rotation of the housing adn the mandrel, such that torsional impact loads result in relative rotational movement of the housing and the mandrel along the spiral guide path, with the relative rotational movement being resisted and absorbed by the means for dampening.

2. The shock sub as defined in Claim 1, wherein the means for dampening is a spring configuration.