Abstract:
A spray nozzle head is rotated directly by a turbine which is driven by the pressure of liquid at the inlet of the nozzle. The turbine is supported by a thrust bearing which also acts as a friction brake to cause the rotational speed of the nozzle head to remain substantially constant as the inlet pressure increases through a predetermined range.

Description:
This is a continuation of Ser. No. 08/667,492 filed on Jun. 24, 1996 now abandoned, which is a continuation of 08/296,818, filed on Aug. 26,1994, now abandoned. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to a rotating nozzle for spraying one or more jets of water or other fluid. 
     BACKGROUND OF THE INVENTION 
     In the cleaning of walls such as a container wall, it is necessary to use a liquid jet which impinges on the wall with a comparatively high jet force. All parts of the wall must be reached with the jet in order to achieve the desired cleaning effect. In the case of, for example, a cylindrical container, it is advantageous to use a rotating nozzle head which itself sprays the jet over the entire inner circumferential surface of the container. The cleaning fluid that flows through the nozzle is used to rotate the nozzle head. 
     To be effective, a rotating nozzle head must run slowly in order to insure thorough cleaning of the container wall rather than mere wetting of the wall. High speed nozzles produce a spray jet of fine particles which are retarded by ambient atmosphere and do not impinge on the container wall with sufficient velocity to ensure effective cleaning of the wall. Moreover, it is desirable that the nozzle head rotate at a speed that is substantially independent of the pressure of the cleaning fluid and especially when the cleaning fluid is foam. In order to provide a slowly rotating nozzle head, it is a known practice to use the cleaning fluid to drive a turbine which acts through a gear to rotate the nozzle head. The requirement for a gear makes the nozzle structure relatively expensive. 
     SUMMARY OF THE INVENTION 
     The general aim of the present invention is to provide a comparatively low cost rotating nozzle in which the nozzle head is driven directly and without a gear at a low rotational speed and in which the speed of the head in a predetermined pressure range remains relatively constant. 
     In part, the foregoing is achieved through the provision of a rotating nozzle having an axial thrust bearing with relatively slidable surfaces which act simultaneously as a friction brake, the braking action of which is controlled by the fluid pressure. Although it is not fully known as to how the friction brake automatically limits the rotational speed, it is possible that, at low pressures, a liquid friction exists in the axial gap of the two bearing surfaces of the axial bearing as a result of the liquid flowing through the nozzle. At increasing pressures, the friction is believed to convert into a dry friction by reason of increased pressure forces acting on upstream surfaces of the turbine that act to increase braking action of the axial bearing surfaces of the thrust bearing. Thus, the coefficient of friction changes in dependence on pressure and, up to an operating pressure of 0.5 bar, the rotational speed of the turbine and the nozzle head increases approximately proportionally to the pressure, there being achieved depending on construction of the nozzle a rotational speed up to about 35 r.p.m. At about 0.5 bar, the proportionality between rotational speed and fluid pressure ends. Above such pressure, the rotational speed actually begins to decline, the decrease in the rotational speed also being dependent on construction parameters of the nozzle. 
     In order not to impair the desired braking effect by the axial thrust bearing, no appreciable sealing is provided at the bearing except for the sealing effected by the bearing itself. Automatic starting of the rotating nozzle head may be achieved when the coefficient of friction in the axial thrust bearing is low and lies in the range between 0.05 and 0.15. Such coefficients of friction can be achieved if one or both axial bearing surfaces contain, for example, PTFE or a material with a comparable coefficient of friction. 
     In order to make the turbine efficient, an injector is located on the inlet side of the turbine. Inclined passages in the injector generate a generally tangential jet flow into the turbine. A very simple turbine is provided in the form of a cylindrical plate, in the outer circumferential surface of which grooves are formed to define passages. To enable the rotating nozzle head to start of itself and run with uniform angular velocity, the number of passages in the injector is aliquot of the number of passages in the turbine. 
     These and other objects and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view of a new and improved rotating nozzle incorporating the unique features of the invention. 
     FIG. 2 is a cross-sectional view taken axially through the nozzle. 
     FIG. 3 is a graph illustrating the relationship between rotational speed and operating pressure. 
    
    
     While the invention is susceptible of various modifications and alternative constructions, a certain illustrated embodiment hereof has been shown in the drawings and will be described below in detail. It should be understood, however, that there is no intention to limit the invention to the specific form disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions and equivalents falling within the spirit and scope of the invention. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As shown in FIGS. 1 and 2, the rotating nozzle  1  of the invention has a generally cylindrical housing  2  which is provided on its lower end with an external thread  3 . The housing  2  defines a continuously cylindrical chamber  4 . A bore  6  is formed through the housing  2  coaxially with the chamber and extends between the chamber and the upper end of the housing. In the bore  6  there is inserted a bushing  7 , the flange  8  of which is located in the chamber  4 . 
     The lower end of the chamber  4  is closed by a cap nut  9  which is threaded onto the body  2  and which is formed with a fluid inlet  11 . The fluid inlet is a bore with an internal thread  12  and is formed through the bottom of the cap nut  9 . 
     In the cylindrical chamber  4 , which has a constant cross section up to the vicinity of the flange  8 , there rotates a turbine  13 . The turbine  13  is a cylindrical plate whose outside diameter is slightly less than the diameter of the chamber  4 . Formed in the outer circumference of the plate are several (e.g., eight) grooves  14  of rectangular cross-section. The grooves  14  pass through the plate from its upper face  15  to its lower face side  16  and open radially outwardly. Further, the grooves  14  are obliquely inclined with respect to the axis of rotation and the coincident axis of symmetry of the turbine  13 . The angle which the long axis of each groove  14  makes with a projection of the axis of rotation of the turbine  13  lies between about 10 degrees and 40 degrees. In the example shown, the angle is 25 degrees. 
     Formed integrally with the upper side  15  of the plate forming the turbine  13  is a turbine shaft  17 . The turbine shaft  17  has, directly adjacent the turbine  13 , a relatively large diameter cylindrical section  18  which defines an annular shoulder  19  at its junction with a cylindrical section  21  of reduced diameter. The diameter of the section  21  is such that it can rotate with very little play in the bore of the bushing  7 , that bore defining a cylindrical radial bearing surface for the shaft. The length of the section  21  is such that the turbine shaft  17  extends upwardly from the housing  2  in order to make it possible to fasten a nozzle head  22  on its upwardly projecting end. 
     The axial forces arising in the operation of the nozzle  1  are absorbed by an axial thrust bearing  23  which also forms a friction brake. One bearing surface of the thrust bearing is the axially and downwardly facing surface of the flange  8 . A washer  25  is slid onto the turbine shaft  17  to the shoulder  19  and is sandwiched between the shoulder and the flange  8 . In order to keep the dry friction in the axial bearing  23  as small as possible, both the bushing  7  and the washer  25  are made of PTFE or a comparable material. The washer  25  is of rectangular cross-section and its outside diameter is about 19 mm while its inside diameter is about 13 mm and corresponds with the outside diameter of the section  21  of the turbine shaft  17 . The height of the washer  25  is about 1 mm. In addition to the bearing  6 , on the lower face  16  of the turbine  13  there is molded a further bearing formed in part by a cylindrical stub shaft  26  which is coaxial with the turbine shaft  17 . The stub shaft  26  rotates in a blind bore  27  which is formed in an insert body  28 . The insert body  28  has the form of a flat truncated cone and is seated in the lower end of the housing  2  with its smaller end facing the cap nut  9 . To prevent the insert body  28  from being pushed upwardly by the fluid pressure, its diameter is somewhat larger than that of the main section of the chamber  4  in the zone of the turbine  13 , the chamber  4  being cylindrically enlarged near its lower end to define a radially inwardly extending shoulder for holding the insert body. 
     The insert body  28  is formed with three obliquely inclined and equally spaced bores  31  which lie on a partial-circle diameter equal to the partial-circle diameter of the grooves  14  of the turbine  13 . The bores  31  are inclined in an opposite direction from and at a steeper angle than the grooves  14  and, in the example shown, the angle which the axis of each of the bores  31  makes with respect to the axis of rotation of the turbine  13  is about 55 degrees. Depending upon the angle of the grooves  14 , however, the angle of the bores could range between 15 degrees and 75 degrees. The diameter of each bore  31  is about 4 mm and is somewhat smaller than the width of each groove  14  as measured in the circumferential direction. The insert body  28  thus acts as the injector for a turbine  13 . 
     Fluid flows from the fluid inlet  11  to the passage bores  31  through a gap  32  between the insert body  28  and the bottom of the cap nut  9 . From the chamber  4 , the fluid flows through transverse bores  33  which are formed in the turbine shaft  17  in the larger diameter section  18  thereof. The transverse bores  33  communicate with a blind bore  34  which opens upwardly out of the upper end of the shaft. 
     The nozzle head  22  comprises a tubular piece  35  slipped on the upper end portion of the turbine shaft  17  and secured thereto by suitable means. The nozzle head also includes a ring  37 , hexagonal in cross section, which is slipped onto the tubular piece  35  down to a shoulder  36  thereof. The tubular piece  35  is received in a coaxial bore  38  of the ring  37 , the midportion of the bore being enlarged as indicated at  39 . In order to hold the ring  37  against the shoulder  36 , a nut  40  is screwed onto the upper closed end of the tube  35 . 
     In the ring  37 , a plurality (e.g., three) of relatively wide bores  41  lead to the outside and are arranged in such a way that they have no component or only a slight component in the circumferential direction. The flow connection between the bore  34  and the fluid outlets  41  occurs through the interior space of the tube  35  as well as through transverse bores  42  in the tube. 
     In operation of the rotating nozzle  1 , fluid to be sprayed is supplied under pressure into the fluid inlet  11 . From there, the fluid flows through the gap  32  adjacent the lower surface of the insert body  28  to the three obliquely running bores  34  which generate three fluid jets. These fluid jets have an axial component in the direction of the turbine  13  and also a component in the circumferential direction since the bores which form the passages  31  are inclined at the angle mentioned of 55 degrees with respect to the axis of rotation. As a result, the fluid flowing out of the passages  31  acts circumferentially against the appropriate walls of the grooves  14 , whereby the turbine  13  is set in rotation. The fluid flowing through the grooves  14  passes into the zone of the chamber  4  between the turbine  13  and the axial bearing  23 . According to pressure relations, a very small part of the fluid passes into the gap of the axial bearing  23  and brings about a fluid lubrication there. By far the greater part of the fluid flows, however, through the radial bores  33  into the bore  34  and from there into the tube  35 . The fluid then flows through the transverse bores  42  toward the nozzle outlets  41 . Since the turbine shaft  17  is integral with the turbine  13  and since the nozzle head  22  is held against turning on the shaft, it revolves with the turbine  13 . 
     The rotational speed at which the turbine  13  rotates depends on the particular angle the grooves  14  make with respect to the axis of rotation of the turbine shaft  17  and also on the particular angle the passage bores  31  likewise make with respect to the axis of rotation. Further, the rotational speed is influenced by the distance which the lower side  16  of the turbine is spaced from the opposing flat side of the insert body  28 . The greater the gap, the lower the rotational speed. A favorable dimension for the gap width is about 1.6 mm, while the outside diameter of the plate forming the turbine  13  is about 32 mm and its thickness is about 8 mm. The cross-sectional area of each outlet bore  41  is approximately 3 mm 2  and presents the essential flow-limiting resistance. All the other flow resistances are less in total than the flow resistance evoked by the outlets  41 . 
     In a nozzle  1  dimensioned in this manner, there is obtained the rotational speed characteristic curve shown in FIG. 3 when the nozzle is supplied with water at room temperature. As is shown, as the pressure rises to about 0.5 bar, the rotational speed of the nozzle head  22  rises proportionally to the pressure to a value of about 37 r.p.m. In the pressure range of between about 0.5 bar and 1.0 bar, the speed curve reverses, and further increases in pressure first lead to a reduction of the rotational speed. For example, when the pressure reaches about 10 bar, the speed of the nozzle head  22  decreases to about 30 r.p.m. Only with a further increase in pressure does the speed again increase. Accordingly, as is evident, the nozzle  1  is a slowly running nozzle and, in the optimum range of its operating pressure, namely between 0.5 bar and 15 bar, no pressure-proportional changes in rotational speed occur. Upwardly from a pressure of 15 bar, the speed increases only insignificantly until the pressure reaches 20 bar. In practical application of such a nozzle, namely, the cleaning of containers, the speed is approximately constant since, for a pressure variation of 1:10, there is in contrast a speed variation of only 1:1.2. It is possible, therefore, without appreciably changing the rotational speed of the nozzle, to rinse the container walls with jets of significantly different pressure.