US3711026A

US3711026A - Apparatus for the cleaning of conduits and containers and method of operating same

Info

Publication number: US3711026A
Application number: US00071959A
Authority: US
Inventors: W Heinrich; L Strom
Original assignee: Woma Apparatebau GmbH
Current assignee: Woma Apparatebau GmbH
Priority date: 1969-09-13
Filing date: 1970-09-14
Publication date: 1973-01-16
Anticipated expiration: 1990-01-16
Also published as: CA925658A; BE755955A; FR2061294A5; AT305815B; NL7013292A; NO130181B; DE1946500C3; JPS4933856B1; ZA706195B; ES383494A1; DE1946500B2; DK127681B; DE1946500A1; GB1288110A; SE351994B; CH514366A

Abstract

An apparatus for the cleaning of the internal surfaces of receptacles of substantially any configuration and type comprises a head rotatable about the axis of an inlet conduit for the cleaning fluid and carries at least one rotatable nozzle arrangement having tangentially oriented nozzles communicating via the head with the conduit for rotation of the nozzle member upon ejection of the cleaning fluid through the nozzles thereof. A hydraulic motor is coupled with the head for rotating the same about the conduit axis and relatively thereto, the motor being driven at an adjustable rate by fluid delivered by a hydraulic pump coupled with the nozzle box and driven thereby.

Description

United States Patent 1 Heinrich et al.

[ Jan. 16, 1973 [75] Inventors: Willy Heinrich, Rheinkamp- Repelen; Ludwig Strom, Rheinhausen, both of Germany [73] Assignee: Woma-Apparatebau Wolfgang Maasberg & Co. GmbI-l, Rheinhausen, Germany 22 Filed: Sept. 14, 1970 21 App]. No.: 71,959

[30] Foreign Application Priority Data UNlTED STATES PATENTS 3,416,732 Reiter ..239/227 6/1966 Saad ..23 /227 8/1969 Kennedy,.lr.etal ..239/227 6/1971 Bonfield ..239/227 Primary ExaminerLloyd L. King Attorney-Karl F. Ross [57] ABSTRACT An apparatus for the cleaning of the internal surfaces of receptacles of substantially any configuration and type comprises a head rotatable about the axis of an inlet conduit for the cleaning fluid and carries at least one rotatable nozzle arrangement having tangentially oriented nozzles communicating via the head with the conduit for rotation of the nozzle member upon ejection of the cleaning fluid through the nozzles thereof. A hydraulic motor is coupled with the head for rotating the same about the conduit axis and relatively thereto, the motor being driven at an adjustable rate by fluid delivered by a hydraulic pump coupled with the nozzle box and driven thereby.

8 Claims, 2 Drawing Figures PATENTEUJAII 16 ms SHEET 1 OF 2 11mm! 1| mm W/LLI HEINRICH LUDWIG STPOM INVENTORS.

: l To FIG.|

ATTORNEY PATENTEU JAN 1 6 B75 SHEET 2 or 2 FROM RESERVOIR l6 WILL/ 'HE/NRICH LUDW/G STPOM INVENTORS ATTORNEY APPARATUS FOR THE CLEANING OF CONDUITS AND CONTAINERS AND METHOD OF OPERATING SAME FIELD OF THE INVENTION The present invention relates to an apparatus for the cleaning of conduits and containers of substantially all configurations, sizes and types and, more particularly, to an apparatus having a rotatable nozzle head through which a cleaning fluid is ejected to subject the containers of surface cleaning, as well as to a method of operating such a device.

BACKGROUND OF THE INVENTION In the cleaning of conduits and containers, using a cleaning fluid (e.g. water) ejected at high pressure from a nozzle arrangement, numerous systems have been proposed to provide adequate coverage of the surface of the container by the jet emerging from the nozzle arrangement. Such systems generally include piston-andcylinder arrangements for reciprocating the nozzle head, motors for rotating same and devices for advancing the nozzle head with respect to the container, thereby spreading the stream of cleaning liquid emerging from the nozzle system.

Substantially all of these arrangements are highly complex, use reciprocating valves, piston or cylinder arrangements and the like which are prone to break down and are expensive, and are of inordinately large size so as to render their use impractical. These disadvantages apply to systems in which the nozzle head is rotatable about an axis defined by an inlet conduit in a plane perpendicular to the latter, to arrangements in which reciprocable motion is generated by fluidoperated cylinders, either directly or through the operation of reciprocating valves, and to systems in which the nozzle head is mounted upon a rotatable housing so that the head itself is carried about an axis parallel to an inlet conduit or coinciding with the axis thereof, while the head is, in turn, rotated about an axis perpendicular to the main or housing axis. The latter system operates with a complex transmission between the rotating housing and the nozzle head, thereby rendering it difficult if not impossible to adjust the transmission ratio. Furthermore, the lack of adjustability in the latter system renders the arrangement suitable only for the strip-wise cleaning of tanks and conduits and eliminates the possibility that the device may be used for the surface cleaning of tanks of all configurations and sizes.

OBJECTS OF THE INVENTION It is, therefore, the principal object of the present invention to provide an improved apparatus or device for cleaning conduits or tanks with a cleaning fluid which is directed at elevated pressure against the wall thereof.

It is another object of the instant invention to provide an apparatus or device of the character described which has a rotating nozzle carrier or housing defining a first axis of rotation which may coincide with that of the cleaning-fluid inlet and a nozzle head mounted upon this housing for rotation about an axis perpendicular or orthogonal to that of the housing and which permits simple adjustment of the ratio of rotation between the nozzle head and the housing carrying same.

It is a further object of the invention to provide an improved device of the character described which is of simple and compact construction, which affords ease of control, which is inexpensive to maintain and construct, and which provides superior cleaning by comparison with earlier rotating-nozzle arrangements.

It is still another object of the invention to provide a method of operating a rotating-nozzle tank, container or conduit cleaner which obviates the aforementioned disadvantages and provides improved surface-type cleaning of the container.

SUMMARY OF THE INVENTION These objects and others which will become apparent hereinafter are attained, in accordance with the present invention, in an apparatus or device for the cleaning of containers, tanks and conduits of substantially all configurations, sizes and types, which comprises an inlet conduit for delivering the cleaning fluid to the device, a head rotatable relative to this conduit about a first axis which may be parallel to or coincide with the axis of the conduit and coincide with the axis of the head, and a nozzle assembly communicating with the conduit through the head and rotatably mounted thereon for rotation about a second axis substantially perpendicular or orthogonal to the axis of rotation of I the head.

The rotation axes preferably are coplanar, according to the present invention, and the nozzle assembly is driven by reaction force, i.e. by the reaction forces produced upon ejection of high pressure jets of the cleaning fluid. To this end, the nozzle assembly may have one or more tangentially oriented nozzles and is rotated in a sense opposite to the direction of flow of the liquid from the nozzle.

According to the principles of the present invention, the nozzle assembly is coupled with the head to drive the latter via a hydraulic transmission including at least one mechanically driven pump whose hydraulic outflow is supplied to a hydraulic motor coupled with the head for rotating same.

More particularly, the mechanical input of the hydraulic pump is the rotating nozzle assembly and a first transmission means operatively connects this assembly with the input member of the hydraulic pump. This first transmission means is preferably a gear drive, but may be a chain, belt or like transmission. Furthermore, a second mechanical transmission couples the output member of the hydraulic motor with the head of the device for rotating same upon hydraulic pressuriza tion of the motor, a duct network being provided between the hydraulic pump and motor to drive the latter. This network may include valve means for varying the throughflow of fluid to the hydraulic motor and, therefore, the rate of operation of the latter relative to the operating rate of the pump, thereby establishing a variable transmission ratio between the angular velocity of the nozzle assembly and the angular velocity of the head.

According to an essential feature of this invention, the method of operating a rotating nozzle arrangement for the cleaning of containers, therefore, comprises the step of ejecting the cleaning fluid from a rotating nozzle assembly and thereby driving the latter by reaction force, displacing a hydraulic fluid, e.g. the cleaning liquid or another liquid medium, at a rate controlled by the rate of rotation of the nozzle assembly, and rotating the head carrying the nozzle assembly about its axis at a rate. controlled by the fluid displacement generated by the rotating nozzle assembly.

In structural terms, the system includes an inlet conduit, a substantially cylindrical housing mounted upon this conduit and formed with an axially extending passage communicating therewith and with at least one branch extending orthogonally to this passage, preferably along the axis of rotation of a nozzle assembly communicating with this branch and provided with a plurality of outwardly extending pipes carrying the respective nozzles, the nozzles being oriented tangentially to drive the nozzle assembly by the reaction force produced upon emergence of the jet from the nozzle.

The housing carries the hydraulic pump which is mechanically coupled with the nozzle assembly to be rotated thereby. Similarly, the housing may carry the hydraulic'motor which is connected with the pump via duct means rotatable with the housing, the output member of the motor being operatively connected with the conduit via a transmission as noted earlier. Hence, the output of the hydraulic pump is a function of the angular velocity of the rotating nozzle assembly while the rotational speedof the housing is a function of the rate at which hydraulic fluid is supplied to the latter via the pump. Since a valve is provided in the duct means, the through-put to the motor may be adjusted readily and hence the ratio of the angular velocity of the housing and the angular velocity of the nozzle assembly may be established with substantially infinite control at any rate desired for the particular cleaning task. Bothfluid pump and fluid motor are carried by the housing and rotated together therewith. The overall rotation rates are determined, therefore, by the rate at which fluid is ejected from the nozzle assembly.

The invention is based upon the surprising discovery that the strip-like cleaning of containers, tanks and the like as practiced by the devices known heretofore can be replaced by a genuine surface cleaning of the tank when the constant ratio of angular velocity of the nozzle assembly and the housing (characteristic of the prior art) is replaced by continuous control of the rotation ratio and, moreover, the control of the rate of rotation is made substantially independently. The latter is accomplished by determining empirically the optimum rate of rotation of the nozzle assembly and of the housing and establishing the transmission ratio between the two necessary to yield the appropriate housing rotation rate with the necessary velocity of the nozzle assembly. The cleaning fluid is then supplied to the latter at the rate necessary to obtain this optimum speed, whereupon the housing is driven at its optimum speed. The control of the hydraulic transmission between the nozzle assembly and the housing permits substantially any desired speed to be obtained with both the housing and the nozzle assembly, merely by adjusting the throughput of the fluid passed from the pump to the motor.

According to a more specific feature of the invention, the fluid pump is driven by a mechanical transmission from the nozzle assembly and is mounted upon the rotating housing while the fluid motor is carried bythe housing and has its output shaft mechanically linked with an angularly fixed member, e.g. the conduit mentioned earlier. While these mechanical transmissions have fixed ratios, this is not significant since the important ratio is determined by the fluid flow between the pump and motor as noted earlier.

While the valve means for adjusting the fluid flow to the hydraulic motor may be a throttle-type valve, it has been found to be advantageous to associate the fluid pump and fluid motor with a reservoir which may be carried by the housing and to use a three-way valve for bypassing or shunting fluid from the pump to the reservoir when the flow of fluid to the hydraulic motor is to be reduced. This system has the additional advantage that the pressure delivered by the pump and applied to the motor can be adjusted within a wide range to provide the desired degree of torque at the motor. Another advantage has been discovered to reside in the system described above, namely the fact that the velocity of rotation varies repeatedly as a consequence of the hydraulic slippage and the indirect forced transmission between the hydraulic pump and the hydraulic motor. The rotary movement is, therefore, augmented by oscillation which has been found to be important to a thorough cleaning of large surface in containers and the like.

DESCRIPTION OF THE DRAWING SPECIFIC DESCRIPTION In the drawing, there is illustrated an apparatus for the cleaning of the internal surfaces of receptacles and containers of substantially any type, the apparatus comprising a rotatable head or housing I mounted upon an angularly fixed conduit 4 serving to connect the apparatus to a source of cleaning liquid at high pressures. The fitting 4 has an internal cavity 4a which communicates with that of a tube 11, the latter forming a bearing rotatably supporting the head 1. The internal passage 11a of the tube 11 is provided with a pair of radial ports 11b (one of which is seenin FIG. 2) which communicate with an annular gap 30 formed by an axially open recess 31 provided in the housing 1 which has, as illustrated, a generally cylindrical configuration. The mouth of this cavity and the tube 11 are closed by a plug 32 which prevents the escape of high-pressure fluid. A pair of seals of the O-ring and gland type are provided at 33 and 34, to surround the tube 11 at axially opposite sides of the ports 1 lb.

The annular chamber 30 communicates with a pair of

radial passages

35 and 36 formed in a housing or head 1 and aligned along an axis 5 which is orthogonal or perpendicular to the axis of rotation 6 of the head. The term radial as used with respect to the passages 35 is to be understood as referring to the relationship between these passages and passage 11a and axis 6.

The

passages

35 and 36, of course, are axially aligned, while lying at right angles to the axis 6. The axes 5 and 6 may be coplanar as will be apparent from FIG. 2, the common plane being the plane of the paper.

The rotatable head 1 is also formed with a pair of

tubular bosses

37 and 38 extending in opposite directions along the axis 5 and hence coaxially surrounding the

passages

35 and 36, the bosses having shoulders as represented at 39. At their extremities remote from the central portion of the housing or rotatable head 1, the

bosses

37 and 38 are provided with a pair of diametrically opposite ports 40 and 41 (FIG. 2) communicating with the

respective passage

35 or 36 and opening into an annular space 42 defined around the

respective boss

37 or 38 by a hub 43 rotatably mounted thereon. Each hub forms part of a rotatable nozzle carrier or head, generally designated at 2, which is rotatable about the axis 5 and carries a pair of radially outwardly extending

pipes

44 and 45 welded to the hubs and rotatable therewith in planes P and P which are perpendicular to the axis 5 but parallel to one another and to the axis 6.

In the embodiment illustrated, two such nozzle assemblies 2 are provided upon the head 1, it being noted that the system may accommodate any number of such assemblies, the head 1 being formed with a

corresponding boss

37 or 38 upon which the assembly isjournaled to prevent escape of fluid in the region of the hub a pair of

seals

46 and 47 are disposed within the chamber 42, circumferentially surrounded at

boss

37 or 38, and axially flank the

ports

40 and 41 while sealingly engaging the cylindrical inner surface of the hub 43 and permitting free rotation of the latter while confining the ,high pressure liquid. While only two nozzles are shown to be mounted on each hub, it will be appreciated that any number of angularly equispaced nozzles can be used. Each of the

pipes

44, 45 of the respective nozzle 3 communicates via a

radial aperture

49, 50 in the hub with the annular compartment 42 and hence receives the cleaning fluid at high pressure.

At their outer ends, the

pipes

44, 45 are bent substantially at right angles at 51 and 52, as illustrated in FIG. 1, in opposite directions with respect to the plane P" defined by the axes 5 and 6. The nozzles 3, formed at these bent extremities of the pipes, are of frustoconical configuration to increase the velocity of the jets ejected therefrom. It has been found to be advantageous to orient the corresponding nozzles of the assemblies in opposite senses to that the assemblies are rotated in opposite senses as well. To facilitate the movement of the apparatus in the container, the nozzles 3 are formed with cylindrical outer peripheries 53 projecting beyond the remainder of the head 1 and the apparatus carried thereby, thereby limiting the possibility of damage to the head structure (see FIG. 2).

It will be apparent that the head 2 shown in elevation in FIG. 1 ejects cleaning-water jets in the direction of arrows A and B, i.e. tangentially with respect to the orbit of the nozzles and through the reaction force will drive the nozzles angularly about the axis 5 in the clockwise sense (arrow C).

According to the principles of the present invention, the or each nozzle assembly 2 is fixed, e.g. by bolts 54 to a gear 14 which is rotatable together therewith about the axis 5 upon the rotatable head 1. The gears 14 form, with gears 15, fixed-ratio mechanical transmission driving respective hydraulic pumps 7. The latter are carried by plates 55 bolted at 56to the housing 1 and have input shafts 57 carrying the pinion gears 15. Hence the nozzle assemblies 2 are rotated at a rate determined by the pressure and quantity of the cleaning fluid delivered to the nozzles and drive the pumps 7 at a rate likewise proportional to the quantity of cleaning fluid dispensed by the apparatus.

The head or housing 1 is, in turn, provided with a hydraulic motor 8 and, preferably, carries this motor via a support plate 58 best seen in FIG. 1. The motor 8 has an output shaft 59 rotatable about an axis parallel to the axis 6 and carrying a pinion gear 13 which meshes with the fixed sun gear 12 bolted at 60 to the fitting 4. Hence, hydraulic pressurization of the motor 8 will drive shaft 9 and cause its gear 13 to orbit the angularly fixed gear 12 at a rate determined by the throughflow of this hydraulic motor. Furthermore, since the gear 12 is coaxial with members 4 and 11 and is angularly fixed, the motor 8 must orbit the axis 6 and thereby carries the housing 1, together with the nozzle heads 2, therearound. The transmission 10, like transmissions 9, is a mechanical fixed-ratio transmission.

The hydraulic pump 7 and the hydraulic motor 8 are connected in a fluid circuit with a reservoir 16, diagrammatically illustrated in FIG. 1 with the remainder of the ducts connecting the pumps and motors and mounted upon the head 1. From the pump 7, a discharge line 17 delivers the high-pressure fluid to the motor 8 via a throttle valve 20 and a three-way valve 21, the intake of pump 8 being represented at 61. From the three-way valve 21, a further passage 18 extends to a reservoir 16 and the latter is also provided with a branch 19 from the outlet side of motor 8. The input to the pumps 7 is represented by a line 62 deriving from the reservoir 16. In place of a three-way valve 21, however, a bypass valve may be provided in shunt across the pump to regulate the net fluid flow through the motor. It will be apparent that the

valves

20 and 21 determine the throughflow of the fluid displaced from the pump 7 to the motor 8 and, therefore, the transmission ratio between the rotary nozzle assemblies 2 and the rotary housing 1 and through this transmission ratio is in finitely adjustable. The speed of the nozzles assemblies, however, is determined by the rate at which the cleaning fluid is ejected from the nozzles.

We claim:

1. An apparatus for the cleaning of containers, conduits and the like comprising:

conduit means connected to a source of a cleaning liquid under pressure;

a head mounted on said conduits for rotation about a first axis;

at least one nozzle assembly mounted on said head for rotation about a second axis generally perpendicular to said first axis and having at least one nozzle directed tangentially for rotation of the nozzle assembly about said second axis with ejection of a jet of said liquid from said nozzle;

passage means in said head and said assembly communicating between said conduit means and said nozzle for delivering said liquid to the latter;

a hydraulic pump mounted on said head and driven by said assembly for dispensing a hydraulic medium;

a hydraulic motor having an output shaft;

means mechanically connecting said head with said shaft for rotating said head about said first axis; and

duct means connecting said pump with said motor for delivering said medium to the latter for positively driving said motor at a predetermined ratio with respect to said pump.

2. The apparatus defined in claim 1 wherein said duct means includes at least one valve for controlling the flow of fluid between said pump and said motor and thereby establishing the transmission ratio between said assembly and said head.

3. The apparatus defined in claim 2, wherein a respective mechanical fixed-ratio transmission is connected with said pump and with said motor.

4. The apparatus defined in claim 3 wherein said duct means includes a reservoir carried by said head for supplying said medium to said pump and means for splitting the flow of said medium from said pump between said reservoir and said motor.

5. Theapparatus defined in claim 4 wherein the lastmentioned means includes a three-way valve.

6. The apparatus defined in claim 5 wherein said head is provided with a central passage along said first axis and said conduit means includes a tube rotatably mounting said head and communicating with said passage, a pair of oppositely extending generally radial tubular bosses formed with'bores communicating with said passage and extending along said second axis and means for securing said motor to said head, said motor having a shaft rotatable about an axis offset from but parallel to said first axis; said apparatus comprising two such nozzle assemblies, each of said assemblies having a hub rotatably mounted upon a respective one of said bosses and defining an annular compartment communicating with the respective bore, a plurality of outwardly extending pipes communicating with the respective compartment, and nozzles formed at the ends of each of said pipes directed rearwardly with respect to the sense of rotation of the respective assembly, the mechanical transmission connected with said pump including a gear coupled with said assembly and entrained thereby about said second axis and a pinion meshing with said gear and connected with said pump; said transmission connected with said motor including a gear fixed to said conduit means and centered upon said first axis, and a pinion mounted upon said motor shaft and meshing with the gear fixed to said conduit means; and said duct means including respective ducts connecting the fluid outlet of said motor and said three-way valve with said reservoir.

7. An apparatus for the cleaning of containers, conat least one nozzle assembly mounted on said head for rotation about a second axis generally perpendicular to said first axis and having at least one nozzle directed tangentially for rotation of the nozzle about said second axis with ejection of a jet of said liquid from said nozzle;

passage means in said head and said assembly communicating between said conduit means and said nozzle for delivering said liquid to the latter; a hydraulic pump mounted on said head and driven by said assembly for dispensing a hydraulic medium;

a hydraulic motor operatively connected with said head for rotating same about said first axis; duct means connecting said pump with said motor for delivering said medium to the latter, said duct means including at least one valve for controlling the flow of fluid between said pump and said motor and thereby estabishing the transmission ratio between said assembly and said head, and a respective mechanical fixed-ratio transmission connected with said pump and with said motor, said duct means including a reservoir carried by said head for supplying said medium to said pump and a three-way valve for, splitting the flow of said medium from said pump between said reservoir and said motor. 8. The apparatus defined in claim 7 wherein said head is provided with a central passage along said first axis and said conduit means includes a tube rotatably mounting said head and communicating with said passage, a pair of oppositely extending generally radial tubular bosses formed with bores communicating with said passage and extending along said second axis and means for securing said motor to said head, said motor having a shaft rotatable about an axis offset from but parallel to said first axis, said apparatus comprising two such nozzle assemblies, each of said assemblies having a hub rotatably mounted upon a respective one of said bosses and defining an annular compartment communicating with the respective bore, a plurality of outwardly extending pipes communicating with the respective compartment, and nozzles formed at the ends of each of said pipes directed rearwardly with respect to the sense of rotation of the respective assembly, the mechanical transmission connected with said pumpincluding a gear coupled with said assembly and entrained thereby about said second axis and a pinion meshing with said gear and connected with said pump; said transmission connected with said motor including a gear fixed to said conduit means and centered upon said first axis, and a pinion mounted upon said motor shaft and meshing with the fear fixed to said conduit means; and said'duct means including respective ducts connecting the fluid outlet of said motor and said three-way valve with said reservoir.

Claims

1. An apparatus for the cleaning of containers, conduits and the like comprising: conduit means connected to a source of a cleaning liquid under pressure; a head mounted on said conduits for rotation about a first axis; at least one nozzle assembly mounted on said head for rotation about a second axis generally perpendicular to said first axis and having at least one nozzle directed tangentially for rotation of the nozzle assembly about said second axis with ejection of a jet of said liquid from said nozzle; passage means in said head and said assembly communicating between said conduit means and said nozzle for delivering said liquid to the latter; a hydraulic pump mounted on said head and driven by said assembly for dispensing a hydraulic medium; a hydraulic motor having an output shaft; means mechanically connecting said head with said shaft for rotating said head about said first axis; and duct means connecting said pump with said motor for delivering said medium to the latter for positively driving said motor at a predetermined ratio with respect to said pump.

5. The apparatus defined in claim 4 wherein the last-mentioned means includes a three-way valve.

6. The apparatus defined in claim 5 wherein said head is provided with a central passage along said first axis and said conduit means includes a tube rotatably mounting said head and communicating with said passage, a pair of oppositely extending generally radial tubular bosses formed with bores communicating with said passage and extending along said second axis and means for securing said motor to said head, said motor having a shaft rotatable about an axis offset from but parallel to said first axis; said apparatus comprising two such nozzle assemblies, each of said assemblies having a hub rotatably mounted upon a respective one of said bosses and defining an annular compartment communicating with the respective bore, a plurality of outwardly extending pipes communicating with the respective compartment, and nozzles formed at the ends of each of said pipes directed rearwardly with respect to the sense of rotation of the respective assembly, the mechanical transmission connected with said pump including a gear coupled with said assembly and entrained thereby about said second axis and a pinion meshing with said gear and connected with said pump; said transmission connected with said motor including a gear fixed to said conduit means and centered upon said first axis, and a pinion mounted upon said motor shaft and meshing with the gear fixed to said conduit means; and said duct means including respective ducts connecting the fluid outlet of said motor and said three-way valve with said reservoir.

7. An apparatus for the cleaning of containers, conduits and the like comprising: conduit means connected to a source of a cleaning liquid under pressure; a head mounted on said conduits for rotation about a first axis; at least one nozzle assembly mounted on said head for rotation about a second axis generally perpendicular to said first axis and having at least one nozzle directed tangEntially for rotation of the nozzle about said second axis with ejection of a jet of said liquid from said nozzle; passage means in said head and said assembly communicating between said conduit means and said nozzle for delivering said liquid to the latter; a hydraulic pump mounted on said head and driven by said assembly for dispensing a hydraulic medium; a hydraulic motor operatively connected with said head for rotating same about said first axis; duct means connecting said pump with said motor for delivering said medium to the latter, said duct means including at least one valve for controlling the flow of fluid between said pump and said motor and thereby estabishing the transmission ratio between said assembly and said head, and a respective mechanical fixed-ratio transmission connected with said pump and with said motor, said duct means including a reservoir carried by said head for supplying said medium to said pump and a three-way valve for splitting the flow of said medium from said pump between said reservoir and said motor.

8. The apparatus defined in claim 7 wherein said head is provided with a central passage along said first axis and said conduit means includes a tube rotatably mounting said head and communicating with said passage, a pair of oppositely extending generally radial tubular bosses formed with bores communicating with said passage and extending along said second axis and means for securing said motor to said head, said motor having a shaft rotatable about an axis offset from but parallel to said first axis, said apparatus comprising two such nozzle assemblies, each of said assemblies having a hub rotatably mounted upon a respective one of said bosses and defining an annular compartment communicating with the respective bore, a plurality of outwardly extending pipes communicating with the respective compartment, and nozzles formed at the ends of each of said pipes directed rearwardly with respect to the sense of rotation of the respective assembly, the mechanical transmission connected with said pump including a gear coupled with said assembly and entrained thereby about said second axis and a pinion meshing with said gear and connected with said pump; said transmission connected with said motor including a gear fixed to said conduit means and centered upon said first axis, and a pinion mounted upon said motor shaft and meshing with the fear fixed to said conduit means; and said duct means including respective ducts connecting the fluid outlet of said motor and said three-way valve with said reservoir.