Note: Descriptions are shown in the official language in which they were submitted.
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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
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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.
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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
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without departing from the spirit and scope of the invention
as hereinafter defined in the Claims.
