Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
,05s~53 ,.
Prior Art
- United States:
:, .
2,890,6613,572,480 1,992,911
3,072,2223,371,890 3,399,747
:'.,,., ' :
3,414,3333,~89,252 3,~67,225
~' 1,865,7351,992,912
,, ,~ .
Italy: 423,510
; ~ Netherlands: 88,615
Germany: 802,030
Great Britain: 589,790
~;;1 This invention lies in the field of hydro-kinetic
i~ brakes for use as dynamometers, retarders for vehicles and
il:
~`~ hydromatic brakes on rotary drilling rigs. Specifically,
~ the invention is concerned with hydromatic brakes utilized
,.^`~;,
to absorb energy by the regulation or control of the fluid
~: being circulated through the brake.
It is well known in the art that such hydromatic
brakes consist of a rotor and stator which have opposing
pockets. The shape of the pockets in the rotor and stator
vary in shape from one design to the other, some being
; spherical, elliptical, or rectangular. In all of the des-
igns the operating principle is the same.
-~: As the rotor is rotated, the fluid contained in
,,, .,. - ~
~ the brake is caused to flow from the inside diameter of the
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rotor pocket to the outside diameter of the rotor
pocket. Energy is imparted to the fluid due to the
rotation of the rotor and the momentum of the fluid is
increased. If the fluid was allowed to exit from the
brake, after leaving the rotor, the power required to
increase the momentum of the fluid would be equal to the -
energy required by a hydraulic pump, and very little
power would be absorbed by the brake.
However, in a hydromatic brake, the fluid exiting
from the rotor flows across the gap between the rotor and
stator and into the stator pocket. The fluid is directed
from the outside diameter of the stator pocket to the
inside diameter of the stator. As the fluid exits from
the stator it impinges on the rotor vanes in a direction
,,
;` against the direction of rotation.
The power absorbed by the brake is due to the
momentum imparted to the fluid by the rotor, the friction
` loss of the fluid flowing in the rotor and stator pockets,
~,. . . .
~j~ and the energy of the fluid flowing from the stator into
i,!~'' 20 the rotor against the direction of rotation.
The friction loss due to the fluid flowing within ~ -
. .:.~ ~ ,. .
; the rotor/stator pockets is minimal compared to the momentum
imparted to the fluid by the rotor and the subsequent flow
of the fluid directed, as a result thereof, against the -
i....................................................................... :
rotor by the stator.
i- In most hydro-kinetic brake installations, the
. ~ .; ,
~i amount of power absorbed is controlled by the amount of
"; fluid contained in the brake, which is regulated by the
, amount of fluid flowing through the brake. The power
'~ absorption is maximum when the brake is completely full
., :
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~5~30
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of fluid and decreases as the quantity of fluid
` contained or flow rate is decreased.
The quantity of fluid or flow rate is regulated by
adjusting a valve installed in the inlet to the brake, or
, by a level tank. The brake is designed to operate full of
-- fluid with the inlet line full open. By closing a valve
in the inlet, the flow of fluid to the brake is xeduced
.
''''~! due to the orificing of the inlet by the valve and thus
j the quantity of the fluid into the brake pockets is
.
reduced. The fluid level in the tank can be reduced
~ ,,j r ~
; thus reducing the head applied at the inlet of the brake
~-` as another means of control.
,~ Of particular interest currently is the utilization
of a safe braking means for oil well drilling rigs. The
brake is attached to the hoisting drum of the rotary '`
drilling rig and is used to retard the descent of the hook
when going into the hole. Since the weight on the hook
varies, the absorption capacity of the brake must be
changed in order to retard the hook to the same velocity
for different hook weights.
- In the past, the two methods of flow regulation
and level control for regulating the absorption capacity of
~,~ the brake have been adequate, but have never been
completely satisfactory. The drilling rig is designed to
handle a maximum hook load or weight as a function of a
drilling depth. The brake is then matched to the drilling
,;,. ,,: .
~- rig by installing a brake that will retard the maximum
hook load to a safe descent speed such as 200 FPM when
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operating full of fluid.
As the drill pipe, used in drilling the oil well,
is connected together, the hook load will increase from
a minimum to the maximum as the drilling depth increases. r
On most rigs, the hydromatic brake is not used until
the hook load reaches a certain value, because the
friction brake on the hoisting drum can be used to retard
and stop the hook. After a particular hook load is
reached, the hydromatic brake is engaged to retard the load
to a safe descent velocity. At this point very little
fluid is required in the brake. As the load increases, the
fluid contained in the brake is increased so that the brake
will retard the increasing hook load to the same velocity.
In order for the brake to retard a load to a constant
velocity, the quantity of fluid contained in the brake
must remain constant. In other words, the amount of
fluid entering the brake must equal the amount of fluid
exiting the brake. Should the flow out exceed the flow
into the brake, the brake speed will increase causing
,~ ,
20 the brake to run a~ay with itself and hence excessive
~`` descent velocity.
~' All of the hydromatic brakes have a minimum point ;
.. - "
of operation where for a certain light load the brake will
`"~ operate at a particular steady speed. If the speed of ;~
~` the brake is increased by reducing the amount of fluid in
;- the brake, an unsteady condition will result because the
brake cannot receive the same amount of fluid as that being
, discharged. The àbove problem is encountered on drilling
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53
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`~ rigs nowadays, due to the deeper drilling depths
and hence widex operating range of load imposed upon
the brake.
;'r When the hydromatic brake is supplied fluid by a
hydraulic pump, and the braking is controlled by a
~i; manually operated inlet valve, between the brake and
. ,
-~ the pump, another control problem arises.
; While a stand of drill pipe is being connected to
, the drill string, the hydromatic brake is not being `
` 10 rotated and is at rest. During this time, the pump fills
the brake completely with fluid. However, for the load
; on the hook, the brake must operate partially full of
fluid to obtain the descent speed desired. Thus, the brake
~f must discharge some of the fluid in order to obtain a
;~ flow balance between the inlet and outlet. During the
'~ period of discharging the excess fluid, the hook descends
~` at a slower speed than desired. To compensate for the
., I
;~j slow descent speed, at the start of the drop, the driller
,~ will reduce the opening in the inlet valve in order to
prevent the brake from filling with fluid during the rest
~``! period. Then during operation of the brake, the inlet
is restricted so that the brake cannot obtain a balance
between the flow in and out, and the load runs away
as stated before.
In order to avoid the above problems of controlling
`,~ the braking action, the brake should be controlled internally.
. By controlling the brake internally, the fluid system
outside the brake housing would not affect the control of
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the brake.
: One method of internal control that is well known
in the art, is to restrict the fluid from flowing into
the stator pockets. By eliminating the fluid from
entering the stator pockets, the fluid is not allowed to
impinge on the rotor.
In the prior art, such as DeLaMater, U.S. Patent
; No. 1,992,911, movable plates have been installed between
the rotor and stator faces. As the fluid exits from the
. :, .
~: 10 rotor, it is blocked from entering the stator by the
~; adjustable plates. To permit braking, the plates are
removed from between the rotor and stator and fluid
circulation is resumed.
~,` There are several disadvantages of the adjustable
~` plates used in the prior art. It is well known in the art
that the greater the gap between the rotor and stator
faces, less braking is achieved. For maximum braking,
` the rotor face should be as close as possible to the stator
`., face in order for the fluid to enter the stator pocket as it
exits from the rotor pocket. If the gap between the rotor ~ -
`~1 and stator is large, the fluid does not flow into the
~ ; stator pocket, instead the fluid flows out of the brake
i-` outlet and is lost.
i;, ;~,. . ~
~,
Installing the adjustable plates between the rotor
~ and stator increases the gap which will decrease the
!'''`" maximum braking when the plates are retracted.
If the plates are made thin in order to keep the
~., . ,~ .
gap at a minimum, rigidity in the plates is lost and the
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force of the impinging water will cause the plates to
bend and rub against the stator face. Thus, the
friction between the plate and stator requires considerable
force to move the adjustable plates.
If the adjustable plates are moved in and out
perpendicular to the brake centerline, the brake housing
becomes quite large in order to accommodate the adjustable
plates.
.
,, Some of the brake's inlet tubes are in the vanes of
the stator and emerge at the end of the stator vane. If
the brake is being rotated and very little braking is
' desired, the adjustable plates are moved inwardly and cover
~,i the inlet tubes. Since the supply of fluid to the brake is
desired, the adjustable plates are moved inwardly and cover
the inlet tubes. Since the supply of fluid to the brake is
;~h blocked by the adjustable plates, the rotor will become dry
'~ and excessive heat will be generated due to agitation of
`~ the air in the pocket and there will be a ~run away~
:,...................................................... .
;~ condition.
~; 20 Others in the prior art have taught the adjustment
-` of the braking force by throttling the pocket circulation,
such as Italian Patent NOa 423,510 (1947), British
:~!:'S:~ Patent No. 589,790 (1947) and United States Patent No~
- 3,572,480 (1971). However, these devices are incapable
of providing adjustments to the flow rate or quantity of
fluid within the brake sufficiently to operate within the
wide range necessary for use as with drilling rig hoist
~-` equipment.
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.. ~ccording to the present invention there is provided in a hydro-
: kinetic brake means having at least a single rotor and a single stator each
with an annular liquid pocket facing each other at the same circumferential
distance from the axis of rotation and said rotor and stator spaced a selected
: distance apart, each pocket having a plurality of planar vanes extending
- radially across said pockets and tilted in said rotor in the direction of ~ -
-.~ rotation of said rotor, and tilted in the opposite direction in the stator,
, the improvement comprising: said annular pockets in said stator and said
rotor each divided by walled surfaces into inner smaller and outer larger
pockets the distance between the outer wall surface of said inner pocket and
; .
the inner wall surface of said outer pocket being constant, said inner and
outer pockets having the same curved configuration, said vanes in said outer
. pockets continuing across said inner pockets; conduit means in said vanes in :
said stator pockets, said conduit means having its liquid inlet at the back of ~:
''.,:
` said outer pockets in said stator and its liquid outlet radially located at ~ .
; :: the space between said rotor and stator within said inner pockets to provide
. . initial continuous liquid flow into said im~er pockets through the space be-
:~ tween said stator and rotor, thence into each of said outer pockets during
. rotation of said rotor; a cylindrical groove co-axial with the axis of rota-
.-` 20 tion cut through the back of the stator and the vanes in the outer pocket,
. said groove being located such that the outer perimeter of said grGove is
within the radial location of said conduit outlets; right circular cylindrical
~t :
means, located within said groove, said cylindrical means being non-rotative
,.i. :.................................................................... . -
. and adapted to axially reciprocate in said groove; said inner and outer pockets, ~.
,~:; i
.- said groove, and said cylindrical means located relative to each other such
that a tangent to the curvature of the walled outer surface of said inner
... ,. pocket and a tangent to the curvature of the walled inner surface of said outer
`~ pocket at their point of intersection with the outer surface of said cylindrical
; :;
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~ IlleallS will be perpendicular to said outer surface; and means to reciprocate said
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cylindrical means.
This brake can be attached to the power driven rotatable drum for
reeling cable used in hoisting operations on an oil well drilling derrick.
By its axial position, the cylindrical means may control the passage of fluid
radially within the outer pocket of the stator.
In one embodiment of the invention, the cylindrical slot is con-
tinued not only through the space of the outer or large pocket, but also -
through the wall of the inner or small pocket, down to the face of the small
and large pockets, so that the entire flow of liquid within both the large and -
.,,, :
small pockets can be closed or opened as desired by adjusting the axial posi-
~` tion of a cylincrical tube baffle positioned in that slot. Mechanical,
pneumatic or hydraulic means, in combination with spring means may be used to
control the axial position of this baffle in various alternative embodiments.
~ In the accompanying drawings which illustrate an exemplary embodi-
;~ ment of the present invention:
Figure 1 represents a vertical sectional view of one embodiment of
; the apparatus.
- Figure 2 is a vertical sectional view transverse to the axis along
the line 2-2 of Figure 1.
Figure 3 represents a partial vertical section passing through the
axis showing a second type of hydro-kinetic brake control apparatus.
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- Fi~ure 4 is a third embodiment of the invention in a
brake having two rotors and stators wlth f~uid control of both
.,
stator pockets.
Figure 5 illustrates a diagram showing the load speed
versus load with the use of a dual pocket brake having control
' means for controlling the rate of flow of liquid in the large
; pockets.
Figure 6 is a schematic view of the apparatus of this
` invention as used in conjunction with a drilling rig drawworks
system.
.
Figure 7 is a partial section depicting the relationship `
- of fluid flow to the pocket flow adjustment means.
B0fore explaining the present invention in detail, it
... .
~ is to be understood that the invention is not limited in its
,~, .
~` application to the details o construction and arrangement of
parts illustrated in the accompanying drawings, since the invention
is capable of other embodiments and of being practiced or carried
j, .
; ~ out in the various ways. Also, it is to be understood that the
``~ phraseology or terminology employed herein is for the purpose o
; 20 description and not of limitation.
.,; .
Referring now to the drawings and in particular to
Figures 1 and 2, there is shown a brake indicated generally by
the numeral 10. It comprises a housing 12 and 14. There is a
. .,.~,~ .
shaft 18 journalled in bearings 17 in the portion of the housing
., .
~ ~ 12 as is described in United States Patents 3,860,097 issued
: ..................................................................... . .
~;t.~ January 14, 1975 and 3,945,473 issued March 23, 1976. A rotor 20
is supported and locked to the shaft 18. It comprises a circular ~'
.
,` assembly havinjg a large annular pock0t 30 with a back wall 31 and
~,~ a front face 34. There is a small annular
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pocket 32 with a back wall 33 having a front face in
the plane 34. Pocket 30 is identical in geometrical
~'~ shape to pocket 32 except the latter is smaller.
Preferably pockets 30 and 32 are spaced from each other
~` a subtantially constant amount. This is for the reason
to establish subtantially constant flow in the large
,:., .
, pocket, i.e. between inside wall 30 and the backside of
.
;, the small pocket 33. There is a coaxial stator 22 having
.: .
: a large annular pocket 45. The stator also has a small
,;~
annular pocket 47 with a back surface 51. The large
and small pockets in the rotor and stator are substantially
mirror images of each other, in section, as sho~n in
~` FIGURE 1.
. .
There are a plurality of vanes 40 in the rotor 42
in the stator. The vanes in the rotor are s~t at an
acute angle to the face 34 leading into the direction of
rotation of the rotor. The vanes 42 in the stator are
~` equally spaced the same as those in the rotor but are
turned at an angle opposite to those in the rotor. In
other words, liquid thrown out of the pockets by the
rotor is directed into the pockets of the stator.
~` Each vane in the stator has a conduit cored or bored
through the vane identified by numeral 28, which leads
from the back surface 22 of the stator into the face 36
of the stator. Liquid for the hydrokinetic brake enters
through the opening 24 in accordance with the arrow 25,
and flows in accordance with arrows 29 from a plenum 52
through the conduits or openings 28 to the face 36 of the
; - 12 -
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58053
stator. This is important from the standpoint that
the brake will thus be continuously supplied with
liquid no matter the location of the cylindrical flow
control member 59. It flows through the gap 38 between ~-~
the two faces 34 and 36 of the rotor and stator, so that
, it fills all the spaces within the large and small pockets.
The flow of liquid in the rotor and stator pockets is in a
radially outward direction as shown by the arrows 49 and
back in accordance with arrows 53 in the stator. The excess
.i
liquid to compensate for that which enters through opening
24 flows outward through the gap 38 between the rotor and ~
. ....
stator faces, and axially through the annular gap 54
~ between the outer circumfer~ntial face of the rotor and
'jC the inner face of the housing 12 in accordance with arrow
.. ~ .
,~ 39. It then flows into the plenum 50 and out through
,~, the opening 26 in accordance with arrow 27.
~, As pointed out in the copending applications, the
,~ radial dimension of the gap 54 i'3 important in controlling
, 1,~l , .
`~` the flow of liquid through the brake. By making the control
` 20 at the outlet of the brake, it insures that the pockets will - ~
,~-` all be filled with liquid at all times, which provides for ~ -
.~ .
a stable load-speed situation. ~ -
The stator 22 is supported by a planar flange 23
~ which is clamped by means of bolts 16 between the parts 12
,":;1.!' and 14 of the housing. Suitable seals are provided between
~ the stator and the housing, so that the liquid will flow
.. . .
~, from the inlet openings 24 through the conduit 28 into the ~-
~ ,~
`~ gap 38 between the two sets of pockets, and out through
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"; the annular opening 54 and through the outlet 26.
~. There is a coaxial circular groove or slot 56 cut,, ~
, at a radius corresponding to the maximum axial dimension
of the small pocket. This is cut from the back surface 22
; of the stator to the back surface 43 of the small pocket 47.
Preferably slot 56 is located at a point within the flow
contour characteristics so as to be perpendicular with
"
;~ the flow of fluid in the outer pocket. In addition, the
slot or groove 56 is located such that the outer perimeter
of the groove is within the radial location of the conduits
28. The importance of the location of the cylindrical
groove and the cylindrical means therein so that the impinging
~` fluid flow strikes the cylinder at a right angle.
.:.
`~` Otherwise, the force of the impinging fluid would tend to
., .
` cause the cylindrical member 59 to move axially into or
,-~i; out of the slot. There is a cylindrical pipe or tube 59
~:.,
~, adapted to slide in the groove 56. This has a transverse
wall or plate 58. Spring means 64 may be provided in the
~`~ space between the stator and the wall 58 to urge the wall
outwardly, so as to provide a clear passage within the
large pocket of the stator. In the space between the plate
58 and the outer wall 14 of the housing, means are provided
opening 62 for provision of pneumatic or hydraulic fluid
into the space 60, to urge the piston axially to the left
~- so that the pipe 59 slides in the groove 56 and can block
, all or part of the cross section of the large pocket,~ so that fluid flow in accordance with arrow 52 will not
,; be possible. Upon release of penumatic or hydraulic
pressure on the plate 58, the spring forces the plate 58
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~ to the right, opening up the passage so that fluid
., ~ . .
flow 53 can resume. When there is no flow through
. ~ .
the stator pockets the braking effect of the large
stator pocket is eliminated. When the pipe 59 is ;
retracted so that liquid flow 53 can resume, then the
maximum braking provided by the large pocket i5 available.
Reference is now made to FIGURE 3 which shows a
modification of the assembly of FIGURE 1, in which the
groove 56 is cut not only through the space in the
large pocket, but through the back wall 43 of the small
pocket, as an extension 56A, down to the face 36 of the
stator. Thus, in FIGURE 3 is shown the cylinder 72
which is now of greater length, compared to that of
FIGURE 1, so that the cylinder can travel until the end 71
is flush with the face 36 of the stator. In that position
."~ ~ .
it can close off fluid flow in the stator through both
` the large and the small pockets, and minimize the braking
~;~l effort of the hydrokinetic brake"
~, The cylinder 72 of FIGURE 3 is modified from that
20shown in FIGURE 1 in that the circular Flate 58 now becomes
an annular plate 70, attached to the pipe 72. This
~`~ annular plate 70 acts as a piston in an annular space 79.
There is a fluid space 78 behind the piston 70 into S
which pressure fluid can be supplied through opening 80
to urge the piston 70 and the attached pipe 72 to the
left in opposition to the spring 74. In so doing, the
~:. -
~` pipe 72 can close off part or all of the two spaces
;~ within the large and small pockets. Various seals, such
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as "O" rings, are utilized as necessary to seal the
stator into the housing and also to seal the pistons 58
and 70 into their appropriate cylindrical operating space.
All this is well known in the art. While the operation
of the piston 70 and cylinder 72 in the slot 56 is shown ;~
as pneumatic or hydraulic ln combination with a spring
- return, the operation can be entirely mechanical by -~ ;
means of levers operating the pipe 72 and 59, as would be
knowledgeable to the man skilled in the art. -~
Comparison of FIGURES 1 and 3 illustrates that in
a single rotor and stator system, a single cylinder and pipe
..
can be used to control the flow either in the large pocket
, alone or in both the large pocket and the small pocket of
the stator.
Referring now to FIGURE 4 there is shown an embodiment
similar to that of FIGURB 1 except that there are two
rotors 120, 120A spaced apart, facing each other, and
two stators 122, 122A supported in the space between the
two rotors, with the faces of the stators 136 and 136A
at the desired gaps 138, 138A, from the two rotor faces.
The stators are spaced apart back to back and in the space
.
- between them ~here is cut two axial circular grooves 156
~;
and 156A between the back surfaces of the large pockets of
~; the stators and the back surfaces of the small pockets.
; There are two pipes 206 and 206A mounted on pistons 208
: and 218. Both pistons are in a single cylinder, face to
face, so that pressure fluid applied through an opening
;.; ;
200, 202 to the cylindrical space 204, which is in the
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form of an annular cylinder, can move the two pistons
; and their cylindrical pipes 206 and 206A, simultaneously
outwardly, against the restraint of helical springs 214
and 222, respectively, to control the flow of liquid
in the stator pockets. of course the grooves 156, 156A
can be cut through the large pocket space only, or through
, . ~ .
both the large and small pocket spaces.
~ One pipe 206 is attached, as by welding, to an
; annular plate 208, which forms a piston. The piston ``~
carries also a smaller tubular member 210. The tubular ~;
; . , ,
; member 210 and the fixed cylindrical portion 222 provide
~-; an annular cylinder for the piston 218 carrying the pipe ;
206A in the second stator. The helical springs 214 and
.. ,~ , .
~`' 222, which are guided by the rings 216 and 224, provide `
the restraint, and the force to retract the pistons when
the pressure fluid is removed from the space 204.
.~;. .
;!"".: In the operation of a hydrokinetic brake the stability
of operation is improved if the pockets, both the large
~!
. ` ., . : .
s' and small, are filled with liquid at all times and the
~ 20 outlet control of flow accomplished by means of the annular
, ~ .
gaps 154 and 154A. As the rotor rotates, the liquid in
the rotor pockets is thrown radially outwardly in
~` accordance with arrows 149 and 149A, as in a centrifugal
!`'l pump. If the flow channel within the stator large
; pockets and small pockets are open, the flow from the
~` rotor goes into the pockets of the stator and flows
radially inwardly in accordance with arrows 153, 153A.
, ~ It is the impact of the liquid from the stator into the
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rotor pockets, with the consequent generation of
turbulence and heat, that represents lost energy,
.,
;~ and restraint to the movement of the rotor, that is,
:...................................................................... :
the braking effect. ~owever, if there is no flow
through the stator pockets, this heat generation is
:- reduced to a minimum, ana simply involves the friction
:`,.
involved in the flow of liquid into the rotor and out
:
through the control yaps 154, 154A. Therefore, by
. .
controlling the rate of flow of liquid in the stator
pockets, the amount of braking effort can be varied
with the entire brake in a stable operation.
~.
As shown in FIGURE 1 it is possible to make the
~ control element, that is the coaxial pipe and groove,
!,",~'~' operate only through the space within the large pocket,
` or as in FIGURE 3 the operation of the flow control
element can be activated through the large pocket and also
:
the small pocket, giving a maximum control of braking effort.
i, ~,
Referring now to FIGURE 5 there is shown a diagram in
which the ordinate represents load speed, that is the
, ..;
`~i 20 speed of the lifting hook in a rotary drilling apparatus for
example, while the abscissa represents the hook load, that
is the load supported by the drilling cables. FIGURE 6 is
i a schematic ishowing the brake 10 attached via shaft 18,
;:
. coupling 300 to drum 302. The drum contains spiral wrapped
, ~
wire line 304 which is directed by way of a sheave atop a
., :
:~-; drilling derrick down to a hoisting hook and/or elevator for
.
:- raising and lowering the drill pipe, not shown, but well
,ii~,~
~ known in the art. The hoist drum is driven by a power
. . .
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plant 306 by either a low speed drive 308 and clutch
310 or high speed drive 312 and clutch 314. Water from
a supply tank 320 is pumped via conduit 322 to the inlet
of the brake 10 with the outlet conduit 324 returned to
., .
~ tank 320. Most rigs include a fluid pressure supply
.:; ,
- (air in this instance) 330 which is controlled by the
driller by valve 332 to connection, e.g. 62 of FIG~RE 1
,., for operating the movable plate 58 into the stator ~ ~-
pockets. The purpose of the hydrokinetic brake in that
application is to provide a restraint on the rotation of
~; the cable drum, so that the load supported by the hook or
; .
;~ elevator will move no faster than a selected speed of say
200 feet per minute, over a selected range of load, that is,
from 75,000 to 200,000 pounds.
,,
; The small pocket alone is adequate for braking the
hook when the loads are less than 75,000 pounds. The
.::
' portion of the characteristic labelled 240 (solid line)
~ represents the speed of the hook as the load increases from '
`'; 15,000 up to 75,000 pounds, while the speed varies from 90
`~ 20 feet per minute to 200 feet per minute. It has been
decided that the speed of 200 feet per minute is the
f.;. : ~
, selected operating speed. It is clear that if the small
:, .
pocket is used alone, that, as the load increase~ above
` 75,000 pounds, the hook speed will increase in accordance
with the dashed extension 242 of the characteristic of
~.,; ~, .
,~ the small pocket section. This is undesired. The large
.~........................................................................ .
pocket has been closed off by the control means 332 during
-, the time that hook loads are less than 75,000 pounds, that
;;- :.
`,;~ is, for the conditions of characteristic 240 up to the point 246. ~
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As the load increa~es beyond 75,000 pounds, the control means
is retracted, permîtting an increasing amount of liquid flow
through the large pockets. This movement of the control is
synchronized with the load so that the characteristic load
speed remains at about 200 feet per minute, up to a point 248,
corresponding to a load of 200,000 pounds. At this point the
control means are completely withdrawn from the large pocket
space, and no further control o liquid flow is possible.
Consequently, as the load increases beyond 200,000 pounds the
speed of the hook increases beyond 200 feet per minute in
accordance with characteristic 252. The characteristics 250
. .. .
~ and 252 represent the speed versus load characteris~ics with
., .
both small and large pocket sections operative.
It would be possible to extend the portion 244 to
the left, and maintain a 200 feet per minute speed for lesser
~ .
~ ;~ loads than 75,000 pounds, by the embodiment of Figure 3, by
i .
closing off part of the flow in the small pocket.
Referring to Figure 3 the end portion 71 o the
. "
` ~ pipe 72 can be square as shown, or it can be rounded into any
: .
c 20 selected shape, so as to minimize the turbulence due to the
: .
flow of liquid around the end of the pipe as it partially
projects into the liquid ~low in the large pocket.
Reference is made to United States Patents 3,860,091
;,
~` and 3,945,473 for further details of the construction of the
:~ hydrokinetic brake. It will be clear that while this embodi-
` ment of the invention, namely, the axially moving coaxial pipe
` operating in slots through
~ i .
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: the space of the large pocket and the small pocket of
the stator is shown applied to the type of brake disclosed
,;. in the referenced applications, this feature of control of ~. .
. flow by the use of annular small and large pockets and a
~- control pipe can be applied to any other type of
i: hydrokinetic brake. -
.~- An important aspect of the invention is the placement
` of the cylindrical pipe 59 relative to the flow of
liquid. As shown in FIGURE 7 the perimter is to be
located relative to the pocket so as to be perpendicular
to the flow as shown by the arrows and thus balance the
; forces on the cylindrical pipe 59. ~ -
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