The present invention relates to an apparatus for manipulating in
the height and in particular setting down of a load. The invention relates particularly,
though not exclusively, to an apparatus for placing or setting down an element which
is heavy but highly susceptible to damage, such as a coupling tube in a tube column,
wherein after drilling to a depth corresponding with the length of the coupling
tube a new coupling tube is added to the drill column. This is the case for instance
in the extraction of oil and natural gas.
The screw thread connections with sealing surfaces between separate
coupling tubes in the tube column are very susceptible to damage when a coupling
tube is lowered with too great a force onto the already formed tube column. A damaged
coupling tube, or of which at least the screw thread connection, which is often
a conical screw thread connection, or a sealing surface is damaged, is written off
and cannot be used. Such coupling tubes often weight 600 kg, although their weight
varies considerably from tube to tube.
Apparatuses are known in the art for height manipulation of such loads.
These known apparatuses have the drawback that they need precise information in
advance concerning the actual weight of a load for manipulating before manipulation
of this load can take place. The changing or in any case adjusting of a setting
is required for this purpose. If this is not done, the load may be set down with
too great a force and suffer damage.
The known apparatuses also have other drawbacks in addition to this
above described lack of sensitivity. The weight of a load for manipulating is often
very great, particularly in relation to the desired sensitivity during manipulation
and in particular during setting down of the load. For this relation between great
weight and fine sensitivity no solution has yet been found in the known art.
From US-A-4.875.530 an apparatus is known according to the preamble
of claim 1. In this prior art electronics are employed for manipulating a load.
Further, US-A-5.474.142 relates to the use of pneumatic devices for
controlling the weight on a drilling bit in an automatic drilling system.
The present invention has for its object to obviate or at least mitigate
the problems and shortcomings of the known apparatuses, for which purpose an apparatus
according to the present invention is distinguished by a suspension on a lifting
device, which suspension comprises a drive, with which drive the load can be manipulated
in the height; a weighing device with which the weight of the load can be determined;
a memory connected to the weighing device for storing an initial weight of the load;
comparing means for comparing an actual weight with the initial weight stored in
the memory for the purpose of selective energizing of the drive in response to the
comparison, wherein the weighing device comprises a hydraulic weighing cylinder
and the memory comprises a hydraulic accumulator which is at least approximately
linear in a range of operating pressures.
An apparatus according to the invention is capable of manipulating
heavy loads very delicately and has no problems, within the operational range of
course, with the variation in weight of the individual loads for manipulating.
A fully mechanical/hydraulic operation of the weighing cylinder and
the memory is thus achieved without precise determination of the actual weight of
the load, but in the form of pressure storage in the memory of a value corresponding
to this weight.
It is noted that in such an embodiment the hydraulic accumulator can
very advantageously be designed as a hydraulic hose of a determined length, because
this will behave, depending on the chosen length thereof, the chosen or used type
of hose, in linear manner in said range of operating pressure, or will do so at
In order to ensure the memory operation of the hydraulic accumulator,
a closing valve can be arranged in an embodiment of the invention in a line between
the weighing cylinder and the hydraulic accumulator. The closing valve is opened
in order to determine the initial value, wherein an open connection is effected
between the weighing cylinder, the line and the hydraulic accumulator, whereafter
the closing valve can be closed. The hydraulic accumulator now retains the initial
value which can thus be used for comparison with weights of the load actually borne
by the weighing cylinder.
In another embodiment of the invention the comparing means can be
formed by a control valve connected on one side to the weighing device and on the
other to the memory. In the latterly described embodiment of a weighing cylinder
as hydraulic design for the weighing device and a hydraulic accumulator as design
for the memory, the actuators of the control valve can be hydraulic and directly
connected to respectively the weighing cylinder and the accumulator. A very simple
and reliable mechanical/hydraulic configuration is hereby also obtained. The above
stated closing valve can herein be arranged in parallel over the control valve in
the line between the weighing cylinder and the accumulator.
In the above stated embodiment with hydraulic actuators of a control
valve etc., the control valve can comprise a control piston enclosed on both sides
between flexible membranes in a control cylinder, and the actuators can be open
connections to respectively the weighing cylinder and the accumulator which act
on the membranes, wherein the drive can be energized subject to pressure differences
over the control valve and connections for opening herein. In the configuration
of the control valve with membranes which enclose the actual control valve in flexible
manner, very controlled movements of the control valve in the control cylinder are
possible without the very abrupt connection transitions usual in the known art.
So-called "overshoot" problems are hereby prevented and a very controlled operation
of the drive is realized.
A further embodiment has the feature that the memory is adapted to
retain therein a weight decreased by a predetermined quantity. A downward movement
caused by the drive is hereby ensured, independently of a separate crude movement
mechanism which can remain limited to the function of movement over large distances,
wherein the drive according to the invention takes over displacement. In an embodiment
with a hydraulic weighing cylinder and a hydraulic accumulator the memory can comprise
a pressure amplifier connected to the accumulator. The desired decrease in the weight
to be retained in the memory can then be adjusted therewith. The predetermined quantity
by which the weight is to be decreased preferably corresponds to a desired and/or
allowable contact force during moving or setting down of the load. Herein the desired
or allowable contact force is with certainty not exceeded.
Further embodiments are defined in the dependent claims and comprise
a hybrid system of hydraulics and pneumatics, a drive designed as double-action
hydraulic cylinder connected to at least one hydraulic source of medium under pressure
or the like, etc.
The invention will be further elucidated hereinbelow on the basis
of an embodiment thereof and with reference to the annexed drawing, in which:
- fig. 1 shows a partly cut-away perspective view of a drilling tower with an
apparatus according to the present invention;
- fig. 2 shows a detail of the manner in which coupling tubes are mutually connected
in the drilling tower of fig. 1 to form a tube column;
- fig. 3 is a schematic view of a part of an apparatus according to the present
- fig. 4 is a schematic view of substantially a whole apparatus according to the
- fig. 5 shows a view in cross-section of a component of the apparatus shown in
fig. 4; and
- fig. 6 shows a detail of the component of fig. 5 in a first operational situation
Fig. 1 shows a drilling tower 1 in which an apparatus 10 according
to the present invention is arranged. The drilling tower serves for assembly of
a tube column 8 consisting of coupling tubes 2 which are provided in the manner
shown in fig. 2 with a conical screw thread for mutual connection thereof.
The drilling tower comprises a coupling 5 for engaging individual
coupling tubes 2, wherein coupling 5 hangs from a suspension 4 which forms an explicit
component of the present apparatus according to the invention. Suspension 4 comprises
in the manner shown in fig. 3 a weighing device in the form of a weighing cylinder
9 and a drive in the form of a double-action hydraulic cylinder 11. Weighing cylinder
9 and double-action cylinder 11 are connected by means of a line bundle to a housing
7 for other components of apparatus 10, which is shown substantially in its entirety,
albeit schematically, in fig. 4. Safety cable 12 in fig. 3 is intended to prevent
a hazardous situation occurring, for instance in the case hydraulic pressure should
fall away unexpectedly or in the case of other failure wherein coupling 5, possibly
with a coupling tube 2 thereon, comes to hang on safety cable 12 instead of on suspension
Line bundle 6 runs from suspension 4 to housing 7, in which is arranged
a control valve 13 as shown schematically in fig. 3 and in fig. 4. Fig. 5 and 6
are representations of an actual embodiment of such a control side 13, the operation
and function of which will be further explained below with reference to these figures.
During the realizing of a connection between individual coupling tubes
2 so as to form the tube column 8 in the manner shown schematically in fig. 2, the
conical screw threads 3 of the individual coupling tubes 2 have to be protected
against damage. The slightest damage to the upper coupling tube 2 in fig. 2 is already
fatal and will result in this coupling tube 2 being written off; it can no longer
be used to construct tube column 8. Even worse still is when the lower of the coupling
tubes 2 in fig. 2 is damaged on the conical screw thread 3 thereof; the whole tube
column 8 formed up to that point must then be lifted upward in order to remove the
lower coupling tube in fig. 2, or the upper coupling tube in fig. 1, from tube column
8. Decisive here is the force with which upper coupling tube 2 is lowered onto lower
coupling tube 1 in fig. 2. This force preferably corresponds with a weight of no
more than roughly 25-30 kg. The apparatus to be further described hereinbelow is
adapted for this purpose, wherein it makes no difference how heavy the individual
coupling tubes 2 are and even variations in the weight of individual coupling tubes
2 are irrelevant.
It is noted that the above mentioned control valve 13, which is shown
schematically in fig. 3 as detail of the total apparatus 10, is a design of comparing
means for comparing an actual weight to an initial weight stored in a memory (to
be further described hereinbelow) for the purpose of selective energizing of the
drive, which in fig. 4 is a double-action hydraulic cylinder 11, in response to
The apparatus 10 according to the present invention shown schematically
in fig. 4 comprises in addition to suspension 4 a linear hydraulic accumulator 14
as memory which can be connected selectively to weighing cylinder 9 via closing
valve 15. in the opened situation of closing valve 15 an initial weight of the coupling
tube 2 forming a load is determined, although in the embodiment shown here not as
an exact value. The weight of the load on weighing cylinder 9 results in a pressure
in the chamber of this weighing cylinder 9 corresponding to the weight of the load.
Because closing valve 15 is herein open, this pressure likewise prevails in the
line 16 between weighing cylinder 9 and linear hydraulic accumulator 14 as well
as in this linear hydraulic accumulator. This takes place immediately after a load
is picked up or just before it is set down again, i.e. in the embodiment of fig.
1 before coupling tubes 2 are assembled in the manner shown in fig. 2 to form tube
column 8. After this determination of the initial weight of coupling tube 2 the
closing valve 15 is closed.
The control valve 13, which comprises hydraulic actuators 17 located
mutually opposite in the shift direction, which actuators 17 are in open connection
with respectively the chamber of weighing cylinder 9 and linear hydraulic accumulator
14, is then subjected to the same pressure from each of the actuators 17. Immediately
after closing of closing valve 15 both actuators 17 are subject to the same pressure,
whereby control valve 13, which can occupy substantially three positions, remains
in a starting position as shown in fig. 4.
It is noted that the drilling tower 1 shown in fig. 1 comprises its
own displacement mechanism 18 which serves to carry a coupling tube 2 for arranging
on tube column 8 into the vicinity of the tube column 8 already formed up to that
point. Displacement mechanism 18 is herein rendered inoperative and the double-action
hydraulic cylinder 11 in suspension 4 takes over the function of displacing the
coupling tube 2 for arranging. The distance between the load in the form of coupling
tube 2 and the destination of this load in the form of tube column 8 at which this
transition takes place depends on the operating stroke of double-action hydraulic
cylinder 11 forming the drive of apparatus 10.
It is also noted that linear accumulator 14 of fig. 4 is designed
in fig. 3 as a hydraulic hose, also designated with reference numeral 14. Such a
hydraulic hose has an at least approximately linear characteristic in the range
of operating pressures and is thus suitable for use as at least approximately linear
accumulator. Other linear hydraulic accumulators can also be envisaged, but the
embodiment of a hose is elegant and simple and takes up hardly any space, since
it can advantageously be laid along the line bundle 6 which is required anyway.
Using control valve 13 one or no connection is made selectively between
a source 19 of medium (air or hydraulic fluid) under pressure and one of two pumps
20, which are each connected to one side of the double-action hydraulic cylinder
11 which forms the drive for movement of the load in the form of coupling tube 2
in the direction away from or toward the already formed tube column 8, in any case
in the latter part of this relative movement. In the intermediate position of control
valve 13 shown in fig. 4, no connection has been realized between source 19 and
motors 20. The drive in the form of double-action cylinder 11 is thus not energized,
which corresponds with equal pressures on both actuators 17 and indicates that the
actual weight measured at a determined moment by weighing cylinder 9 is still equal
to the initially measured weight of load 2. This intermediate position can also
be forced, irrespective of the prevailing pressures, using an immobilizing means
further described hereinbelow with reference to fig. 5 and 6.
Once load 2 has been carried with displacement mechanism 18 into the
proximity of its destination, displacement mechanism 18 is rendered inoperative,
whereafter operation of the drive 11 of the embodiment of the invention begins.
Prior thereto the pressure prevailing in linear accumulator 14 is reduced by a value
with a pressure amplifier 44, this value corresponding with an allowable and safe
contact force between coupling tubes 2 and the already formed tube column 8. The
initial weight determination, closing of closing valve 15 and decrease of the pressure
in linear accumulator 14 can take place respectively immediately after pick-up,
whereafter the displacement mechanism 18 is set into operation while an above mentioned
immobilizing means is energized. Alternatively, the pressure in the linear accumulator
can be decreased with pressure amplifier 44 only at the place of destination, and
even the initial determination can take place there.
After closing of closing valve 15 the pressure in linear accumulator
14 is reduced in the following manner. The pressure amplifier comprises a cylinder
45 with a plunger-piston combination 42 therein, control connections 40, 41 and
a single-stroke pump head 43. By energizing control connection 40 and de-energizing
control connection 41 from the situation shown in fig. 4 a predetermined quantity
of fluid or oil corresponding with the stroke of plunger 42 is extracted from accumulator
14, this being accompanied by a pressure decrease in the accumulator. In a released
state of the immobilizing means referred to above and further described below, the
control valve is then subjected to a higher pressure on the actuator 17 connected
to the weighing cylinder. As a consequence the control valve 13 shifts to the right
from the position shown in fig. 4 and the upper of the pumps 20 in fig. 4 is energized
for a downward movement of cylinder 11, and therewith the load 2.
The downward movement of cylinder 11, and therewith load 2, comes
to an end when coupling tube 2 comes to rest on the already formed tube column 8.
With a continuing movement of cylinder 11 the weight with which coupling tube 2
rests on tube column 8 increases and the weight borne by weighing cylinder 9 thus
decreases. When the pressure associated with this decrease in weight borne by weighing
cylinder 9 has decreased by practically the same value as the pressure decrease
on the side of linear accumulator 14 caused by pressure amplifier 44, the situation
shown in fig. 4 is restored and the control valve re-assumes the position shown
here, whereafter the driving by cylinder 11 is stopped.
When the load in the form of coupling tube 2 comes into contact with
tube column 8, the weight borne by weighing cylinder 9 decreases. As a result the
pressure balance over control valve 13 is restored, whereby the control valve re-assumes
the position shown in fig. 4. By properly selecting the pressure decrease to be
brought about in the accumulator by pressure amplifier 44, for instance on the basis
of the quantity of fluid (oil) to be extracted from accumulator 14 by pressure amplifier
44 by controlling the stroke volume of pressure amplifier 44, the pressure decrease
associated with the contact force of coupling tube 2 on tube column 8, wherein the
movement is stopped, can be readily determined in advance.
If no use is being made of pressure amplifier 44 and valve 15 closes,
as soon as load 2 hangs still and is then pulled on, the weight borne by weighing
cylinder 9 becomes greater and the pressure therein increases, together with the
pressure on the left-hand actuator 17 of control valve 13, whereby control valve
13 in fig. 4 will (again) shift to the right. The upper of the pumps 20 is hereby
set into operation to energize the drive in the form of double-action cylinder 11
in the direction of a downward displacement of load 2. When the load is moved downward
in helical movement by the drilling tower crew, the drive 11 assists herein. For
the intended connection to a tube column 8 the crew need exert hardly any force
and the drive helps the crew in bringing about a positioning of coupling tube 2
which is in any case correct in height relative to tube column 8 in the coupling
Conversely, it is the case that if the crew pushes the coupling tube
upward, the weight borne by weighing cylinder 9 decreases, the control valve 13
shifts to the left and the lower of the motors 20 in fig. 4 is set into operation.
Under the influence of the pressure exerted by this pump 20 the cylinder 11 will
retract and carry coupling tube 2 upward.
In the influencing of the drive in this manner a threshold force associated
with the design of the apparatus must however be overcome, although the cylinder
(to be further described below) of control valve 13 preferably exhibits as little
friction as possible so as to avoid the phenomenon of stick-slip.
In fig. 4 overflows in the form of sequencing valves 21 are arranged
between pumps 20 and the drive in the form of double-action cylinder 11. In the
shown configuration this prevents a so-called overshoot occurring at a transition
between movement and standstill of cylinder 11.
The upper of the sequencing valves 21 shown in fig. 4, which co-acts
with upper pump 20 to energize the drive in downward direction, can be set to 50
bar for this purpose, while the lower sequencing valve 21 associated with upward
movement of the drive in the form of cylinder 11 can be set to 210 bar.
The load 2 on suspension 4 also causes a pressure in the moving cylinder
11 in the lower chamber thereof. When control valve 13 takes up a position shifted
to the right relative to fig. 4, a valve 39 closes in a connection between the sequencing
valve 21 functioning as overflow and the upper pump 20, and this pump 20 comes into
operation. The pressure rises until it is sufficient in the lower part of the chamber
of cylinder 11 to cause opening (e.g. at 210 bar) of the sequencing valve 21 associated
with lower pump 20 and also functioning as overflow. Only then does the cylinder
begin the downward movement, this without stick-slip. Once coupling tube 2 has come
to rest with a desired contact force on tube column 8 in the above described manner
and control valve 13 returns to the starting position thereof shown in fig. 4, the
upper pump 20 stops and valve 39 is opened. The load 2 is pulled up slightly by
the pressure then prevailing in the lower part of the chamber of cylinder 11, whereafter
a balance also prevails once again in the upper part and the lower part of the chamber
of cylinder 11. This raising is sufficient to compensate for the inertia of the
system 10 and the inertia of load 2. The sequencing valve 21 associated with upper
pump 20 and functioning as overflow has the function of damping this latterly described
Adjustment of the overflow pressure at the sequencing valves 21 takes
place by adjusting the spring force of the sequencing valves.
It is noted that in the embodiment shown in fig. 4 the control valve
13 is connected to a pneumatic source 19. When control valve 13 is in a position
wherein one of the pumps 20 is set into operation, a converter 22 is arranged in
each case as control for the relevant one of the pumps 20.
It is further noted that for energizing of the drive in the form of
double-action cylinder 11 in upward or downward direction a hydraulic or pneumatic
circuit (not shown) is additionally provided, which operates directly on the desired
pump 20 or once again via converters 22, for instance to induce an up and/or downward
displacement of load 2 on drive 11 irrespective of the set and possibly decreased
initial weight and/or the actual weight. Converters 22 can be compressors. Processing
of the additional circuit for direct influencing of the operation of drive 11 in
the diagram of fig. 4 is well within the competence and reach of the average skilled
person, certainly after study of the foregoing, so that further description thereof
Fig. 5 shows in sectional view an embodiment of a control valve 13
and fig. 6 shows a view of this control valve 13 in a shifted position thereof.
Control valve 13 comprises in fig. 5 a valve 23 shiftable in practically
frictionless manner in cylinder 24 to which five connections 25-29 are connected.
Connection 26 leads to source 19, while connections 25 and 27 lead to a reservoir
or simply a discharge. Connections 28 and 29 are on the other hand connected to
pumps 20 in fig. 4. Due to the form of the piston or valve 23 in cylinder 24, in
the position thereof shown in fig. 5 there is no connection between connections
25-27 and connections 28 and 29. If on the other hand piston or valve 23 shifts
to the right, a connection is brought about from source 19 via connection 26 along
valve 23 and via connection 28 to the upper of the pumps 20 in fig. 4. The reverse
situation is shown in fig. 6, where valve 23 is displaced to the left under the
influence of a higher pressure on the right-hand side corresponding with linear
hydraulic accumulator 14. The lower of the pumps 20 is set into operation to energize
drive 11 in upward direction.
Valve 23 is enclosed in the line of cylinder 24 between auxiliary
pistons 30 which, due to an assembly of a centring ball 32 and a pin 33, exert a
centring action on valve 23 to prevent jamming thereof.
On the side of the auxiliary pistons 30 opposite valve 23 are arranged
membranes 31. These latter are made of flexible material. On the side of membranes
31 opposite auxiliary pistons 30 there prevail pressures such as are supplied to
actuators 17. Membranes 31 have a very favourable effect on the displacement characteristics
of valve 23. Valve 23 progresses through gradual and even movements and does not,
as a known valve, shoot from the one extreme position thereof to the other. The
membranes also form a very effective medium separation, wherein the medium supplied
via actuators 17 remains absolutely separated from the medium used to bring about
selective connections between connection 26 in particular and connections 28 and
The threshold force described with reference to fig. 4 which must
be overcome by a member of the crew of drilling tower 1 during manual manipulation
of the coupling tube to cause the apparatus according to the invention to follow
and to assist or enhance this manipulation is caused partly by the elasticity and
resilience of membrane 31. Other factors are the active surface of weighing cylinder
9 which itself preferably exhibits the smallest possible resistance associated with
friction, the active surface of auxiliary pistons 30, the volumetric expansion value
of the at least approximately linear accumulator 14, and measures in apparatus 10
associated with suppressing or preventing "stick-slip", etc. These are therefore
design parameters in which the average skilled person will be proficient without
any inventive work, particularly after studying the foregoing, for instance by varying
the parameters such as the flexibility of the used membranes, the length of the
hose 14 applied as accumulator etc.
Control valve 13 further comprises an immobilizing means. This is
formed by immobilizing pistons 34 which are disposed outwardly relative to valve
23 on the side of the membranes 31 opposite thereto. Immobilizing pistons 34 are
connected to a piston rod 35 which are each provided with a head 36 with which the
active region of membranes 31 can be covered. By introducing medium under pressure
via connections 37 the immobilizing means is energized and valve 23 is efficiently
enclosed in stationary manner in the starting position thereof shown in fig. 5.
The immobilizing means can be rendered inoperative by removing the pressure from
connections 37 and/or by introducing a (higher) pressure via connections 38. In
the released situation of the immobilizing means the heads 36 on immobilizing pistons
34 are detached from membranes 31 but form a stop for bounding the outward movement
of valve 23, as shown in fig. 6.
The present invention is described by way of example in the foregoing,
but is not limited thereto. The invention is defined in the appended claims. Within
the thereby defined scope of protection many alternative embodiments are possible
which will occur to the skilled person after examination of the foregoing. A hybrid
system of a pneumatic and a hydraulic circuit does not therefore have to be used,
but the whole apparatus as shown in fig. 4 can have a hydraulic design. It is even
possible for drives and weighing devices to be used other than hydraulic ones. Even
an electric motor can thus be used as drive with a load cell for the weighing device,
wherein not the actual weight determined by the load cell but only a precise determination
of the initial weight in relation to the weight at a later moment is important.