US3292863A

US3292863A - Tank washer employing an impeller bracking means

Info

Publication number: US3292863A
Application number: US324157A
Authority: US
Inventors: Nelson William Lynn
Original assignee: Butterworth System Inc
Current assignee: Butterworth System Inc
Priority date: 1962-09-28
Filing date: 1963-09-26
Publication date: 1966-12-20
Anticipated expiration: 1983-12-20
Also published as: BE637962A; DK112427B; DE1432992A1; NL298448A; GB1023023A

Description

Dec. 2o, 1966 W. L. NELSON TANK WASHER EMPLOYING AN IHPBLLER BRAKING MEANS Filed Sept. 26, 1965 4 Sheets-Sheet 1 Patent Attorney Tec. Z, w W, L. NELSON TANK WASHER EMPLOYING AN IMPELLER BRAKING MEANS 4 Sheets-Sheet 2 Filed Sept. 26, 1965 William Lynn Nelson Inveniov f f By J/O,

Dec.. 20, i965 wv L. NELSON TANK WASHER EMPLOYING AN IMPELLER BRAKING MEANS 4 Sheets-Sheet 5 Filed Sept. 26, 1963 William Lynn Nelson lnvenior we@ 29 39% w. L.. NELSON 3,292,8@3

TANK WASHER EMPLOYING AN IMPELLER BRAKING MEANS 4 Sheets-Sheet 4 Filed Sep. 26

William Lynn Nelson By la): 0| 7 Poem Aorney United States Patent O 3,292,863 TANK WASHER EMELOYlNG AN MPELLER BRAEQNG MEANS William Lynn Nelson, Woodmansterne, England, assigner to Butterworth System, incorporated, a corporation of Delaware EFiled Sept. 26, 1963, Ser. No. 324,157 Claims priority, application Great Britain, Sept. 2S, @62, 36,958/ 62 il Claims. (Cl. 239-227) This invention relates to a method and apparatus for automatically distributing liquid under pressure, particularly apparatus for washing tanks and the like, and is particularly concerned with a method of controlling the operation of the same.

In the cleaning or washing of tanks, for example in sea-going tankers, it is common practice to employ tankwashing machines in which the washing liquid is ejected through nozzles attached to a spray head adapted to rotate whereby the jets follow a constantly changing direction and impinge against the walls of the tank at constantly changing positions. According to one form, the nozzles are caused to rotate about a rst axis e.g. a horizontal axis and the spray head is caused to rotate about a second axis perpendicular to the rst axis e.g. a vertical axis so that the jets impinge on the wall, tracing a pattern and eventually cover substantially the entire walls of the tank. Such devices are commonly driven by means of a hydraulic motor or turbine coupled to the spray head through reduction gearing and the said hydraulic motor or turbine is normally operated by the stream of fluid under pressure fed to the spray head and nozzles. With this type of equipment, it is desirable to control the speed of rotation of the spray head and the nozzles and the apparatus is usually designed to revolve at a substantially constant speed, usually 2 to 3 revolutions per minute in the case of ships tanks, but may be considerably more in the case of other types of tanks or other applications.

Such machines give satisfactory service but are relatively costly to produce and require periodical maintenance. The life of such machines is also somewhat limited, owing to wear on the gears and bearings. To overcome these diculties, it has been proposed to coustruct similar apparatus driven by the reaction from the jets issuing from the nozzles of the spray head to impart motive force to the nozzles -and/or spray head to rotate the same.

With such machines the control of the speed of rotation of the spray head and the nozzles has presented major problems, mainly by reason of the fact that the device is sensitive to small pressure changes and therefore tends to rotate too fast or too slow. Such fluctuations of speed, due to variations in pressure, will also occur with the turbine motor driven models but will be much less apparent than with the reaction driven devices.

Attempts to control the rate of rotation by the use of friction devices have not proved satisfactory and this invention has for its object to provide an improved method and means for controlling the speed of rotation of the nozzles and spray head.

The present invention accordingly comprises a method for controlling the speed of rotation of a rotating liquid distributing device operated by the stream of liquid fed to and distributed by the device comprising diverting a portion of the liquid stream fed to the device to a driven means positively connected indirectly or directly to the distributing device and adapted to be driven by the di verted portion of the liquid stream in opposition to the motion of the liquid distributing device in accordance with the amount of liquid diverted, and thereby exert a corresponding braking action on the liquid distributing, device and varying the amount of liquid diverted to the ice said driven means in accordance with the speed of rotation of the liquid distributing device to maintain the same substantially constant independent of variations in the pressure of the liquid supply. According to a further feature of the invention the amount of liquid diverted to the driven means is varied -automatically in accordance with the speed of rotation of the distributing device.

The invention also comprises an apparatus for distributing jets of liquid automatically in a constantly changing direction, for example for use in washing the walls of an enclosed space, for example .a tank, comprising a nozzle head provided with one or more nozzles for the ejection of said jets of liquid against the walls of the said tank, said nozzle head and nozzles being adapted to rotate about one or more axes, means for supplying the nozzle head and nozzles with liquid under pressure and means operated by the said liquid under pressure to cause rotation of the said nozzle head and nozzles, including controlling means connected directly or indirectly to said nozzle head and operated by a portion of the liquid feed to the nozzle head, adapted to act in opposition to the motion of the nozzle head to control its motion in accordance with the pressure and quantity of the liquid supplied to operate the controlling means and means to divert a portion of the liquid under pressure fed to the nozzle head to operate the said controlling means, automatically in accordance with the speed of rotation of the spray head or nozzles.

According to one form of the invention, the nozzle head is preferably rotated by the reaction forces of the jets of liquid issuing from the nozzles.

According to a further form of the invention, the means for controlling the rate of rotation of the nozzle head comprises a shaft positively connected at one end to the nozzle head, an impeller mounted on the other end or connected thereto through a suitable chain of gears or the like, said impeller being constructed to be driven in opposition to the motion of the nozzle head and being operated by a stream of liquid diverted from the liquid feed to the nozzle head. The shaft is preferably coaxial with the nozzle head and firmly attached thereto but may also be parallel to or at an angle to the axis of the nozzle head and positively connected thereto by a suitable train of gears. In operation the impeller is driven by the diverted liquid stream in opposition to the rotation of the nozzle head and thereby exerts a braking force on the nozzle head through the shaft and gears if any.

According to a further feature of this apparatus, a branch line is provided in the liquid feed line to the nozzle head, said branch line passing a portion of the liquid from the said feed line to Vthe controlling means and a valve is provided in the said branch line, preferably at a point between the junction of the branch line and the nozzle head in the feed line, adapted to control the amount of liquid passing through the said 'ranch line in accordance with the speed of rotation of the spray head. The valve controlling the diversion of the liquid to the driven means may also be arranged at a point between the junction of the branch line to the main line and the nozzle head.

The movement of the valve may be effected by hand or automatically or by a combination of manual and automatic means.

The lautomatic operation may be effected conveniently by the use of any of a number of devices available commercially and particularly pressure-sensitive devices actuated by the varying pressures in the feed or branch lines or the differential pressures between the branch line and the nozzle head supply line and adapted -to operate the valve to allow more liquid to pass to the controlling mechanism when the nozzles rotate too fast and vice versa. Alterna-tively a governor device operated .bearing 1a.

3 by the rotating nozzle head could be employed to control the valve.

The invention is illustrated by way of example in the Yaccompanying drawings, in which:

FIGURE l shows a vertical sectional view of one form of apparatus according -to the invention.

FIGURE 2 shows an end elevation of the apparatus shown in FIGURE 1 viewed from the righthand side and illustrating the positioning of the nozzles on the nozzle head.

FIGURE 3 shows an enlarged plan sectional view on the line B-B of FIGURE 1 of one form of valve mechanism used in the device.

FIGURE 4 shows a sectional view of one form of arrangement for controlling the setting of the valve automatically in accordance with the rate of rotation of the nozzles.

FIGURE 5 shows a section of an alternative arrangement for controlling the setting of the valve automatically in accordance with the differences in pressure in the liquid streams.

FIGURE 6 shows a vertical section of an alternative arrangement to FIGURE 1 in which the impeller is mounted on a shaft displaced from the axis of the nozzle and is connected to the nozzle head by a gear system.

Referring to FIGURE l, the figure represents the spray head in the form of a horizontal tubular member 1 having an inverted U-shaped tubular member 33 with both its

arms

31 and 32 in open communication with the interior of the horizontal tubular member through its upper wall and having its horizontal upper portion 33 communicating with and rotatable about a vertical tubular member 3 connecting with the liquid supply pipe.

At one end of the horizontal tubular member 1 is arranged a nozzle head 2 in the form of a hollow substantially cylindrical member closed at one end and having its opposite end formed with a flange member 2a closely fitting and rotatable abou-t the end 1a of the tubular member 1. The cylindrical wall of this member is provided with at least two nozzle tubes 9a, arranged symmetrically and preferably tangentially with respect to the circle of rotation of the member. Each of these tubes 9a is provided with a nozzle tip 9 suitably attached thereto, for example by coacting screw threads on the nozzle tip and tube.

The outer surface of -the flange member 2a is preferably recessed to form a shoulder portion 2c in which is fitted the hub of a bevel gear member 6, which is firmly attached coaxially to the nozzle head 2 for example by bolts 28. In the face of the flange member 2a abutting against the tubular member 1 is provided a groove 21 holding a sealing ring 21a of any desired -type to prevent leakage of liquid through the joint.

Within the horizontal tubular member 1 is arranged a horizontal shaft 13 coaxial with the axis of rotation of the nozzle head 2 having one end firmly attached to the said nozzle head, for example held by means of a pin 18 in a bushing member 14 attached to the inner side of the nozzle head 2 by bolts 25. The opposite end of this shaft passes through the tubular member 1 and is rotatably mounted in a closure member 11 firmly attached to the other end of the member 1 by means of bolts 26 and having a recessed portion in its outer face to hold a bearing 24, preferably a ball bearing, on the said shaft 13. The end of the shaft 13 is provided with a groove 16a and a retaining ring abutting against the outer surface of the bearing.

The bearing 24 is held in position in the recess by means of a ring 30 clamped against it by a cap member 12 screwed on to a .flanged portion of the closure member 11. The retaining ring prevents lateral movement of the shaft 13 and holds the nozzle head 2 firmly on its Grooves and

sealing rings

23 and 22 to prevent egress of the liquid are provided on the outer rim of the closure member 11 against the inner surface of the tubular member 1 and in the central bore abutting against the shaft 13.

On the shaft 13 at a point between the entry of the arms of the U-member is arranged an impeller 8, preferably in the form of a cylinder keyed by key or pin 17 to the shaft 13 and provided on its outer surface with a series of vanes so arranged as to tend to rotate the member 8 and the shaft 13 in the opposite direction `to the rotation of the nozzle head 2 when liquid is passed down the lefthand arm 31 of .the inverted U-member. If desired a fixed vane member may be arranged on the stream of liquid from arm 31 to direct the liquid against the vanes of the impeller 8. The horizontal portion 33 of the inverted U-member is provided at its midpoint with an upturned vertical flange member 7a which is rotatably arranged around the end of a tubular member 3, attached at its upper end to the liquid supply tube. The outer surface of this member 3 within the flange 7a is provided with a groove and sealing ring 20 abutting against the inner surface of the flanged member to prevent egress of liquid through the joint. The tubular member 3 is provided on its outer surface above the flange member 7a with an external horizontal circumferential flange member 3a against the lower face of which is attached, for example by bolts 27, a bevel gear wheel 5 coacting with the gear wheel 6 on the nozzle head. On the upper surface of this flange member 3a is provided a ball or other type of bearing 10 on which rests a gear cover 4 covering the gear wheel 5 and bolted to a flange or lugs 29a on the U-shaped member by bolts 29. This gear cover forms the support by which the entire device is rotatably suspended about the member 3. Within the horizontal portion 33 of the U-member 31, 32 and 33 is arranged a valve member 7 in the form of a hollow cylinder having a closed lower end and a major portion of the side wall cut away, as shown in FIGURE 3, leaving a member in the form of an upper ring portion 7d and a lower plate or dished portion 7g joined by a concentric, arcuate portion 7f. The circular portions of this member 7 are arranged coaxially rotatable in the lower part of the flange member 7a and in a coaxial recess 7b in the lower wall of the horizontal portion 33 of the U-shaped member. The faces of the circular portion abutting against the inner surfaces of the flange 7a and the recess 7b are provided with grooves and sealing rings 19. The lower member of the valve 7 is provided with a central shaft 7c passing through a suitable aperture in the lower wall of the part 33, ythe outer part of which shaft is adapted to be connected to a device for rotating it and the valve 7 within the member 33. As shown in FIGURE 1, the end of the shaft is shaped to engage a key so that it can be rotated by hand. In this figure, the shaft is also provided with a screw thread and nut 15 to allow it and the valve to be locked in any position. As shown in FIGURE 3, the arcuate Wall of the valve member 7 is so dimensioned that according to the position of the valve, access of the liquid to either

arm

31 or 32 of the U-member can be completely or partially closed or full access can be allowed to both

arms

31 and 32.

FIGURE 4 illustrates one form of arrangement for automatic control of the valve 7. According to this arrangement, a horizontal lever arm 34 is fixedly attached to the shaft of the valve 7 so that rotation of the arm rotates the valve. The outer end of the said arm 34 is provided with a slot 35 in which rides a pin 36 carried on a sliding member 37 of a centrifugal governor. This member is carried on a shaft 38 suitably mounted on the exterior of the device and having at one end a pinion gear 39 engaging a further gear 6b mounted on and rotating with the nozzle head 2. This may conveniently be formed on the gear 6 already provided thereon. On this shaft 38 is aflixedly mounted the fixed member 4t) of the centrifugal governor. This fixed member 40 is rotatable with the shaft 38 and is provided at spaced intervals with a plurality of hinged arms 41 each hingedly attached to a separate ball or weight member 42, each of which is in like manner hingedly connected by arms 43 to the sliding member 37. These arms 43 are attached to a member 44 attached to sliding member 37 freely rotatably about the shaft 38 and slidable therealong together with the sliding member 37 and adapted to slide the member 37 to and fro along the shaft 33 and thus adjust the position of the valve 7 in accordance with the speed of the governor which is, in turn, controlled through the gears 6 and by the rate of rotation of the nozzle head 2.

FIGURE 5 shows diagrammatically an alternative method of operating the arm 34 attached to the shaft 7c and operated by the differential pressures in the

arms

31 and 32 of the U-shaped member, that is, on either side of the impeller device. In this arrangement, a shaft 3S is suitably mounted parallel to the horizontal tube member 1 to be slidable to and fro and having a pin 36 riding in the slot 35 in the arm 34. Each end of this shaft is attached to a piston or bellows 45 in a closed chamber 46, the closed ends of which are connected by

pipes

47 and 48, in open communication with the

arms

31 and 32 of the tubular member. As the differential pressures between the two arms varies, so the pressures in cylinders 46 is varied accordingly and therewith, the arm 38 is caused to move to and fro under the action of the pistons or bellows and so actuate the arm 34 to operate the valve 7 in accordance with the differences of pressures in the two

arms

31 and 32.

FIGURE 6 illustrates an alternative form of the FIG- URE 1 in which the shaft 13 bearing the impeller 8 is laterally oset with respect to the axis of rotation of the nozzle head and is operated by a pinion gear 13a coacting with a further gear 6a bolted on to the said nozzle head and suitably within the gear wheel 6 already provided thereon.

According to this modification, the horizontal tubular member 1 is provided with a lower recessed portion below the center part of the U-members 31-33 and the

limbs

31 and 32 of the U-member are extended downwardly to this lower portion so that, in effect, the horizontal tube 1 is stepped down below the horizontal portion of the U- member. In the outside wall of this stepped-down portion adjacent the nozzle head, is provided an aperture 49 and a sleeve bearing member 50 forming a bearing for the shaft 13, the other end of which is mounted rotatably in the opposite wall in a manner similar to that shown in FIGURE l. Valve 7 is provided in similar manner as shown in FIGURE l and operated in any suitable manner, for example as shown in FIGURES l, 4 and 5.

In operation, the stream of liquid under pressure is supplied through the member 3 and valve 7 to the horizontal portion 33 of the inverted U-member. In accordance with the position of valve 7 part of the liquid stream is passed down arm 32 to the nozzle head 2. The liquid under pressure issuing through the nozzle tips 9 attached to the nozzle head 2 cause the latter to rotate under the reaction forces set up by the jets issuing from the nozzles. As shown in the drawings, this will be clockwise. With the nozzle head 2, is rotated the shaft 13, either direct as shown in FIGURE l, or through the train of gears 6a and 13a shown in FIGURE 6 and the impeller S is thereby rotated. When the nozzle head 2 rotates above a desired speed, the valve 7 is operated either manually as shown in FIGURE l or automatically for example as shown in FIGURES 4 and 5 to allow an increase in the amount of the uid passing down member 3 to pass into member 31 and thus directly through to the impeller 8, which owing to the formation of the vanes, tends to turn this in a counterclockwise direction (viewed from FIG. 2) opposite to that of the nozzle head 2, thus exerting a braking action on the rotation thereof.

It will be understood that this braking action can be varied by controlling the amount of liquid allowed to pass down the arm 31 by the positioning of the valve 7.

The operation of the device can also be arranged to a substantially constant rate of rotation of the nozzle head and spray head at any desired rate by adjusting the valve manually to achieve the desired speed and then further adjusting the valve manually or automatically or by both means periodically when the speed of rotation of the nozzles deviates from the desired rate. For various reasons it will be preferred to effect the main speed control manually and to effect the subsequent controls rendered necessary by fluctuations in the operating conditions automatically when required.

The rotation of the nozzle head 2 also rotates the gear 6 which coacts with the gear 5 mounted on the member 3 and causes the spray head to rotate about the axis of the fixed gear 5, so that circular motion in two planes is imparted to the nozzles 9.

While this invention has been described with respect to an apparatus driven by the reaction of the liquid issuing from the nozzles, it will easily be seen that it could be also applied to similar devices operated by the liquid stream supplied to the device.

The apparatus of the invention, when used with reaction driven spray heads, has the advantage that it eliminates the necessity of complicated gearing and high speed bearings and its construction is comparatively simple.

' Tests have shown that by simply closing or opening the control valve in a device adapted for cleaning ships tanks, the speed of the nozzle head can be varied from 2 to 3 to ll revolutions per minute and maintained at a substantially constant speed throughout a relatively wide range of pressure variations in the liquid feed line. By use of this device, it will thus be possible to provide a nozzle head with given nozzle sizes having a variable speed range. While the device has been described particularly with respect to a reaction driven machine, it can equally be applied to a machine driven by a liquid motor 0r turbine operated by the liquid stream to the nozzles, although in such cases, the variation and speed due to fluctuations in the liquid pressures is much less evident than in the simple reaction driven devices.

What is claimed is:

1. An apparatus for distributing jets of liquid in continuously changing direction, e.g. for use in washing the walls of a closed space, e.g. a tank, comprising a nozzle head provided with one or more nozzles for the ejection of said jets, said nozzle head and nozzles being adapted to rotate about one or more axes, means for supplying the nozzle head and nozzles with liquid under pressure and means operated by the said liquid under pressure to cause the said nozzle head and nozzles to rotate in a predetermined first rotational direction, braking means xedly connected to said nozzle head operated by a portion of the liquid fed to the nozzle head and adapted to continuously apply a resisting torque to said nozzle head in a second, predetermined rotational direction in opposition to the rst rotational direction of said nozzle head to retard its motion in accordance with the pressure and quantity of liquid supplied to operate it and means to divert a portion of the liquid under pressure fed to the nozzle head to operate the said braking means in accordance with the speed of rotation of the said nozzle head to maintain a desired speed thereof substantially independent of variations in the pressure of the liquid supply.

2. Apparatus as claimed in claim l wherein the means for rotating the nozzle head comprises the reaction force exerted by the jets issuing from the nozzles.

3. Apparatus as claimed in claim 2 wherein the braking means for controlling the rate of rotation of the nozzle head comprises a shaft positively connected at one end to the nozzle head and an impeller connected thereto, said impeller being constructed to operate in torque opposition to the motion of the nozzle head and being operated by a stream of liquid diverted from the liquid fed to the nozzle head.

4. Apparatus as claimed in claim 3 wherein a branch line is provided in the liquid feed line to the nozzle head,

said branch line passing the liquid to the said braking Ameans and a valve is provided adapted to control the amount of liquid passing through said branch line in accordance with the speed of rotation of the nozzle head.

5. Apparatus -as claimed in claim 4 wherein the valve is provided at the junctions of the branch line and the main feed line.

'6. Apparatus Ias claimed in claim 5 wherein the said valve is operated by a pressure sensitive device in accordance with the uctuations of pressure in the supply of liquid to the nozzle head.

' 7. Apparatus as claimed in claim 5 wherein the valve is operated by a governor device in accordance with the uctuations of the speed of rotation of the nozzle head.

8. Apparatus as claimed in claim 2 wherein the braking means for controlling the rate of rotation of the nozzle head includes a reduction gear means, a shaft connected Ito said gear means, and an impeller upon said shaft, said impeller being constructed to operate in torque opposition to the motion of the nozzle head and being operated by a stream of liquid diverted from the liquid fed to the nozzle head.

A9. Means for controlling the speed of rotation of a Arotating liquid distributing device driven by the stream Vof liquid distributed, said means comprising adjustable means for diverting a portion of the liquid stream fed to the distributing device, and means for passing the said diverted portion of liquid through a driven means connected to said liquid distributing device, said driven means being ladapted to be driven by the diverted liquid to continuously produce a resistive torque in opposition to the motion of the distributing device to exert a braking action on the said distributing device in accordance with the amount of diverted liquid.

10. Means for controlling the speed of rotation of a 3 rotating liquid distributing device driven by the stream of liquid distributed, said means comprising means for diverting a portion of the liquid stream fed t-o the distributing device, and means for passing the said diverted portion of liquid through a driven means connected to said liquid distributing device, said driven means being adapted to be driven by the diverted liquid to continuously produce a resistive torque in opposition to the motion of the distributing device to exert a braking action on the said distributing device in accordance with the amount of diverted liquid, and means for varying the amount or' liquid diverted to the driven means in accordance with the speed 0f rotation of the liquid distributing device to thereby maintain the speed of rotation substantially constant independent of variation in pressure of the liquid supply.

11. Apparatus in accordance with claim 10 including in addition means for directing the liquid diverted through said driven means back to the main liquid feed stream to be subsequently distributed by said distributing device.

References Cited by the Examiner UNITED STATES PATENTS 479,249 7/1892 Cuthbert 239-227 1,779,983 10/1930 Roach 239-252 1,943,152 l/1934 Weiss 239-l 1,950,712 3/1934 Coles et al. 239-252 2,084,585 6/1937 Keith 239-227 2,392,408 1/1946 Radonich 239-1 2,681,250 6/1954 Metcalf et al. 239-227 2,784,034 3/1957 Metcalf 239-252 X 2,865,672 12/1958 Guinard 239-252 2,917,243 12/1959 Lione 239-227 FOREIGN PATENTS 623,780 5 1949 Great Britain.

M. HENSON WOOD, IR., Primary Examiner.

EVERETT W. KIRBY, Examiner.

D. L. MOSELEY, V. C. WILKS, Assistant Examiners.

Claims

1. AN APPARATUS FOR DISTRIBUTING JETS OF LIQUID IN CONTINUOUSLY CHANGING DIRECTION, E.G. FOR USE IN WASHING THE WALLS OF A CLOSED SPACE, E.G. A TANK, COMPRISING A NOZZLE HEAD PROVIDED WITH ONE OR MORE NOZZLES FOR THE EJECTION OF SAID JETS, SAID NOZZLE HEAD AND NOZZLES BEING ADAPTED TO ROTATE ABOUT ONE OR MORE AXES, MEANS FOR SUPPLYING THE NOZZLE HEAD AND NOZZLE WITH LIQUID UNDER PRESSURE AND MEANS OPERATED BY THE SAID LIQUID UNDER PRESSURE TO CAUSE THE SAID NOZZLE HEAD AND NOZZLES TO ROATE IN A PREDETERMINED FIRST ROTATIONAL DIRECTION, BRAKING MEANS FIXEDLY CONNECTED TO SAID NOZZLE HEAD OPERATED BY A PORTION OF THE LIQUID FED TO THE NOZZLE HEAD AND ADAPTED TO CONTINUOUSLY APPPLY A RESISTING TORQUE TO SAID NOZZLE HEAD IN A SECOND, PREDETERMINED ROTATIONAL DIRECTION IN OPERATION TO THE FIRST ROTATIONAL DIRECTION OF SAID NOZZLE HEAD TO RETARD ITS MOTION IN ACCORDANCE WITH THE PRESSURE AND QUANTITY OF LIQUID SUPPLIED TO OPERATE IT AND MEANS TO DIVERT A PORTION OF THE LIQUID UNDER PRESSURE FED TO THE NOZZLE HEAD TO OPERATE THE SAID BRAKING MEANS IN ACCORDANCE WITH THE SPEED OF ROTATION OF THE SAID NOZZLE HEAD TO MAINTAIN A DESIRE SPEED THEREOF SUBSTANTIALLY INDEPEDENT OF VARIATIONS IN THE PRESSURE OF THE LIQUID SUPPLY.