Abstract:
A fluid bearing nozzle assembly is disclosed that has a hollow cylindrical body, an inlet nut fastened to the cylindrical body, and a hollow tubular shaft member coaxially carried within the housing body and captured between the inlet nut and the body. The inlet nut has a stem portion extending into a central bore through the shaft member forming an inlet bearing area rotatably carrying the shaft member thereon. The shaft member has a spray head fastened thereto for rotation of the head with the shaft member. An inner wall of the housing body and an outer portion of the shaft have complementary shapes forming a regulating passage therebetween. The shaft has helical grooves that spiral around the shaft to one or both ends to impart rotation to the shaft and spray head.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of priority to U.S. Provisional Patent Application Ser. No. 61/259,944, filed Nov. 10, 2009. 
    
    
     BACKGROUND OF THE DISCLOSURE 
     A high pressure rotary nozzle device having a rotating shaft is disclosed in my U.S. Pat. No. 7,635,096, which is incorporated herein by reference in its entirety. The hollow shaft in this device rotates within a fixed housing wherein the axial force which acts upon the shaft due to the fluid pressure at the shaft inlet is balanced, eliminating the need for mechanical bearings. 
     This nozzle is particularly well suited to industrial uses where the operating parameters can be in the range of 1,000 to 40,000 psi, rotating speeds of 1000 rpm or more and flow rates of 2 to 50 gpm. The hollow shaft in this device is provided with a “bleed hole” leading from the central bore through the hollow shaft to its exterior. This allows a small portion of pressurized fluid to reach a chamber formed within the nozzle housing outside the exterior of the forward portion of the nozzle shaft. The fluid pressure in this chamber acts upon the nozzle shaft with a sufficient axial component so as to balance the corresponding axial component against the nozzle shaft created by the internal fluid pressure. This chamber, or passage has a frusto-conical tubular shape surrounding a corresponding tapered portion of the shaft which further allows the fluid to flow between the nozzle housing and the shaft to facilitate and lubricate the shaft as it rotates. 
     Because of the frusto-conical tapered shape of both the exterior surface of the shaft and the complementary interior surface of the housing, the spacing between the housing and the shaft varies slightly with axial movement of the shaft. This movement creates a self balancing effect in which the axial forces upon the shaft remain balanced and there is always some fluid flowing between the shaft and housing which helps decrease contact and resulting wear between these two components. 
     The rotation of such a nozzle is provided by the reaction forces experienced by the nozzle tip as a result of the redirection of fluid flow outward through offset angled ports in the nozzle tip offset from the longitudinal axis of the nozzle. The redirection of flow is offset from the axis of the nozzle shaft such that the reaction forces apply a torque to the nozzle shaft and tip. At such high pressures the offset angled ports are more than sufficient to provide rotation, or swivel, of the nozzle about its longitudinal axis. A small detachable jet head having a diameter smaller than the body of the nozzle can be attached at the leading end of the nozzle to provide an improved coverage pattern for the high-pressure fluid. 
     Unless the nozzle tip, i.e., the jet head, has offset angled ports, rotation of the nozzle shaft is not likely to occur. There are some applications, however, where offset angled ports are either undesirable due to a change in driving torque when pressure or flow rate is changed, and undesirable because driving rotation by this method produces very high rotation speeds (20,000-30,000 rpm). Thus there is also a need for a rotary nozzle that is axially self balanced as above described, but in which the rotary nozzle shaft is driven by a method resulting in slower rotation speeds, in a range on the order of 2000 to 4000 rpm, rather than relying on offset angled reaction forces to provide the rotational force on the nozzle shaft. 
     SUMMARY OF THE DISCLOSURE 
     A nozzle in accordance with the present disclosure provides a simplified structure which effectively balances any axial thrust force, without need for mechanical bearings, while at the same time imparting a rotational force to cause rotation of the nozzle without requiring offset nozzle ports. 
     One embodiment of such a nozzle device has a generally cylindrical overall outer shape so that it can be inserted into pipes and other tubular passages. The device has a hollow tubular housing body fastened to a high pressure inlet. Captured between the tubular body and the inlet nut is a hollow, tapered, rotatable swivel shaft. This shaft is rotatably supported on a tubular stem portion of the inlet nut. The outer surface of the shaft has a generally frusto-conical shape that tapers down toward the discharge of the nozzle device. The inner surface of the hollow shaft has a cylindrical shape complementary to the stem portion upon which it rides. The inside surface of the tubular body has a frusto-conical tapered shape complementary to the frusto-conical shape of the outer surface of the shaft such that together they form a balancing chamber or passage therebetween. 
     The inlet nut and its stem portion each has a central bore therethrough that directs fluid flow from a high pressure fluid source through the nut and stem portion and then through a spray jet head attached to the discharge end of the shaft. The rotatable swivel shaft has a plurality of passages, each extending through the shaft from the inner to the outer surface of the shaft to a circumferential channel in the outer surface. The channel joins helical grooves formed in the outer surface of the shaft. Fluid flow in these grooves during operation imparts a rotational force on the shaft causing it to rotate about the stem portion of the inlet nut. Thus this rotational force eliminates the need for providing offset angled ports in the spray head or nozzle tip. This allows driving the rotation of the shaft at a desired slower rotation speed. Since the nozzle spray is directed out of the nozzle tip in a direction that is not offset from the longitudinal axis of the nozzle, rotation speed is not dependent on the pressure and flow rate through the nozzles. This same fluid flow, before reaching and exiting the helical grooves, provides lubrication between first the stem portion of the inlet nut and the shaft and then between the inner surface of the housing and the outer surface of the shaft such that solid bearings are not required. 
     Embodiments of a fluid bearing nozzle assembly for spraying high pressure fluid in accordance with this disclosure each include a hollow cylindrical body, an inlet nut fastened to the cylindrical body, and a hollow tubular shaft member coaxially carried within the housing body and captured between the inlet nut and the body. The inlet nut has a stem portion extending into a central bore through the shaft member. The stem portion forms an inlet bearing area rotatably carrying the shaft member thereon. The shaft member has an outlet end near an outlet end of the housing body that receives a spray head fastened thereto for rotation of the head with the shaft member. The inlet nut has a central passage to conduct fluid through the inlet nut to said outlet end of the shaft member. 
     An inner wall of the housing body and an outer portion of the shaft have complementary surface shapes together forming a regulating passage therebetween. The shaft member has one or more bores communicating between the inlet bearing area and the regulating passage, wherein pressure of fluid within the regulating passage acts axially upon the shaft to counter axial force on the shaft resulting from fluid pressure acting upon an inlet end of the shaft. Furthermore, the outer portion of the shaft has at least one helical groove there-around extending from the one or more bores along a substantial portion of the outer portion of the shaft. Fluid flow through the regulating passage and the helical groove imparts a rotational torque on the shaft to cause rotation of the shaft on the stem portion of the inlet nut. 
     In one embodiment the inner wall of the housing body and the outer portion of the shaft have complementary frusto-conical shapes. In this embodiment there are one or more bores that communicate to an annular channel in the outer surface of the shaft. The shaft has two counter rotating grooves around the shaft leading from the annular channel to opposite ends of the shaft. The fluid rotate in different directions in both grooves, thereby generate torque on the shaft in only one direction. 
     In another embodiment, the inner wall of the housing body has a stepped cylindrical shape with a large diameter portion and a small diameter portion with a shoulder therebetween. In this case, the shaft has a complementary stepped cylindrical shape with a shoulder therebetween and the one or more bores communicate with the shoulder of the shaft. Here the shaft has a single helical groove that extends from the shoulder around a substantial portion of the length of the large diameter portion of the shaft. 
     In each of these embodiments, a rear face of the shaft and the inlet nut form therebetween a balancing chamber. The hollow body has one or more weep holes communicating with the balancing chamber for relieving fluid pressure from within the balancing chamber. Preferably the nozzle also includes a cylindrical shroud fastened around the hollow body that extends around a portion of the spray head. The weep holes in the hollow body communicate between the balancing chamber and a gap between the shroud and the hollow body. This shroud primarily protects the rotating spray head from damage and prevents contact between the spray head and the object or surface being cleaned from stalling rotation of the head. 
     Further features, advantages and characteristics of the embodiments of this disclosure will be apparent from reading the following detailed description when taken in conjunction with the drawing figures. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-section of the nozzle device of one exemplary embodiment in accordance with this disclosure. 
         FIG. 2  is a side view of the frusto-conical rotatable shaft removed from the nozzle device shown in  FIG. 1 . 
         FIG. 3  is a cross-section of a nozzle device of another exemplary embodiment in accordance with the present disclosure. 
         FIG. 4  is a separate side view of a rotatable shaft removed from the nozzle device shown in  FIG. 3 . 
         FIG. 5  is a rear end view of the rotatable shaft shown in  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION 
     One embodiment of a nozzle device  100 , as is shown in cross section in  FIG. 1 , has a generally cylindrical overall outer shape so that it can be inserted into pipes and other tubular passages. The device  100  has a hollow tubular body  102  fastened to a high pressure inlet nut  104 . The inlet nut  104  is fastened to the body  102  preferably via a threaded connection  106 . Captured between the tubular body  102  and the inlet nut  104  is a hollow, tapered, rotatable swivel shaft  108 . The shaft  108  is rotatably supported on a tubular stem portion  110  projecting axially out of the inlet nut  104 . The outer surface  112  of the shaft  108  has a generally frusto-conical shape that tapers down toward the discharge of the nozzle device  100 . The inner surface  118  of the shaft  108  has a cylindrical shape complementary to the stem portion  110  upon which it resides. The inside surface  114  of the tubular body  102  has a frusto-conical tapered shape complementary to the frusto-conical shape of the outer surface  112  of the shaft  108  such that together they form a balancing passage therebetween. 
     The stem portion  110  of the inlet nut  104  forms an inlet bearing area for radially supporting the shaft  108 . A spray jet head  116  is fastened to the discharge or outlet end of the shaft  108 , via conventional means such as a threaded connection, so that both shaft  108  and head  116  rotate together as an integral unit with the head  116  forming the nozzle tip. The advantage here is that various different jet heads  116  may be attached to the shaft  108  depending on the particular cleaning task to be performed. 
     The inlet nut  104  and its stem portion  110 , have a central bore  111  therethrough that directs fluid flow from a high pressure fluid source through the nut  104  into and through ports in the spray head  116 . The rotatable swivel shaft  108  has a plurality of passages  120  therethrough, each extending from the inner surface  118  of the shaft  108  to the outer surface  112  of the shaft  108 . These passages  120  exit into a preferably centrally located circumferential channel  122  in the outer surface  112 . The channel  122  joins counter-revolution helical grooves or channels  124  and  126  formed in the outer surface  118  of the shaft  108 . Groove  126  spirals in a first direction around the shaft  108  toward the discharge end of the shaft  108 . Groove  124  spirals in an opposite second direction around the shaft  108  toward the inlet end of the shaft  108 . 
     During nozzle operation, these counter-revolution helical grooves  124  and  126  act to impart a moment, or rotational force, to the shaft to rotate the shaft  108  about the stem portion  110 , and hence rotate the spray head  116 . The shaft  108  in the device  100  effectively rotates at speeds of preferably between about 2000 to 3000 rpm. 
     Finally, a tubular shroud  140  is preferably threadably fastened as a sleeve over and to the housing body  102  to protect the spray head  116  during insertion and retraction of the nozzle  100  from tubular passages or vessels into which the nozzle device  100  is inserted. This tubular shroud  140  is fixed to the body  102  and does not rotate during nozzle operation. Although not shown in  FIG. 1 , each of the threaded connections also may preferably include an elastomeric seal ring between the threaded relatively stationary parts to eliminate fluid leakage through the threaded connections between the various components. These include the threaded connections between head  116  and shaft  108 , body  102  and inlet nut  104 , and shroud  140  to body  102 . 
     During operation, high pressure fluid is introduced through the inlet nut  104  into the central bore  111  in the inlet nut  104 . This high pressure fluid passes through stem portion  110  into and through the head  116 . A portion of the high pressure fluid is redirected such that it leaks back (to the left in  FIG. 1 ) around the stem portion  110  constituting a leakage path  130  along the inlet bearing area, i.e., in the clearance region between the outer surface of the stem portion  110  and the inner surface  118  of the shaft  108 . Part of this fluid passing through leakage path  130  flows into the annular chamber  121  between the inlet nut  104  and the shaft  108 , and then out through weep holes  142  into the gap  144  between the housing  102  and the shroud  140 . This leakage fluid then flows to atmosphere via ports  145  to the open end of the shroud  140 . Another portion of the fluid in leakage path  130  is diverted outward through passages  120  in the shaft  108  to the circumferential channel  122  formed in the outer surface of the shaft  108  and thus into a frusto-conical tapered interface or balancing chamber  146  formed between the inside surface  114  of the body  102  and the outer surface  112  of the shaft  108 . 
     A portion of the fluid in channel  122  diverges and flows outward in opposite spiral directions through this balancing chamber  146 , first forward along helical groove  126  to exit the nozzle  100  around the head  116  and also rearward along helical groove  124  to the clearance space that forms annular chamber  121  between the inlet nut  104  and the rear face of the shaft  108 . This portion of the fluid then joins the portion of leakage  130  from along the stem  110  and passes through weep holes  142 , then passes out through ports  145  and the shroud  140  to atmosphere. 
     During operation, the shaft  108  becomes axially dynamically balanced on the stem  110  such that mechanical bearings are not required. The lubricity of the fluid flowing through these leakage paths  130  and through the balancing chamber  146  sufficiently supports and lubricates the shaft  108  and attached spray head  116  such that bearings are not required. Furthermore, the fluid flow through the helical grooves  124  and  126  provides the rotational torque necessary to rotate the shaft  108  and its attached spray head  116 . This torque generating function is performed by the leakage fluid flow. Therefore offset nozzle tips are not necessary to rotate the nozzle head  116  as in previous designs. However, where higher rotational speed is desired, offset nozzle tips may be advantageously employed. 
     Another exemplary nozzle device  200  is shown in  FIG. 3 . The nozzle device  200  operates in a similar manner to device  100 . The device  200  has a hollow tubular body  202  fastened to a high pressure inlet nut  204 . The inlet nut  204  is fastened to the body  202  preferably via a threaded connection  206 . Captured between the tubular body  202  and the inlet nut  204  is a hollow cylindrical, rotatable swivel shaft  208 . 
     This shaft  208  is separately shown in side view in  FIG. 4 , and in a rear end view in  FIG. 5 . The shaft  208  is rotatably supported on a tubular stem portion  210  of the inlet nut  204  that projects axially from the main body of the inlet nut  204 . The outer surface  212  of the shaft  208  has a first cylindrical portion  213  and a reduced diameter cylindrical portion  214  forming an annular shoulder  215  therebetween. The inside surface  214  of the tubular body  202  has a shape complementary to the stepped cylindrical shape of the outer surface  212  of the shaft  208  such that together they form a balancing passage therebetween. 
     The inner surface  218  of the shaft  208  forms a straight bore that has a cylindrical shape complementary to that of the stem portion  210  upon which it resides. A rear end, or inlet view, of the shaft  208  is shown in  FIG. 5 . The central bore  218  is surrounded by an annular recess forming part of the balancing chamber  221 . The interior sides of this recess around the bore  218  are straight so as to form a hexagonal nut shape used to hold the shaft  208  during assembly and disassembly of the shaft  208  to the spray head  216 . 
     The stem portion  210  of the inlet nut  204  forms an inlet bearing area for radially supporting the shaft  208 . A spray jet head  216  is fastened to the discharge or outlet end of the shaft  208 , via conventional means such as a threaded connection, so that both shaft  208  and head  216  rotate together as an integral unit with the head  216  forming the nozzle tip. The advantage here is that various different jet heads  216  may be attached to the shaft  208  depending on the particular cleaning task to be performed. 
     The inlet nut  204  and its stem portion  210 , has a central bore  211  therethrough that directs fluid flow from a high pressure fluid source, through the nut  204 , the bore  211 , and then into and through ports  217  in the spray head  116 . The rotatable swivel shaft  108  has a plurality of passages  220  therethrough, preferably at least two, each extending from the inner surface  218  of the shaft  208  to the outer surface  212  of the shaft  208 . These passages  220  exit into an annular space or chamber  222  formed between the shoulder  215  and a complementarily shaped inner shoulder surface  223  of the housing  202 . The single helical groove  224  communicates with this space  222 . Groove  224  spirals around the shaft  208  from the space  222  toward the inlet end of the shaft  208 . The direction of the helical groove  224  determines the direction of rotation of the shaft  208 , and hence the rotary spray head  216 . For example, if the groove  224  spirals clockwise from the space  222  around the shaft  208  toward the inlet end of the shaft  208 , then rotation will be counterclockwise. 
     Finally, a tubular shroud  240  is preferably threadably fastened as a sleeve over and to the housing body  202  to protect the spray head  216  during insertion and retraction of the nozzle  200  from tubular passages or vessels into which the nozzle device  200  is inserted. This tubular shroud  240  is fixed to the body  202  during nozzle operation and does not rotate. 
     At the rear of the swivel shaft  208  in the space between the inlet nut  204  and the shaft  208  are a pair of weep holes  226  that lead from this space through the housing  202  into an annular gap  228  between the housing  202  and the shroud  240 . The space between the inlet nut  204  and the shaft  208  forms a balancing chamber  221 . Fluid that enters this gap  228  then flows to the atmosphere behind the rotary head  216  through passages  232  in the housing  202 . 
     The threaded connections between the housing  202  and the shroud  240  includes two elastomeric seal rings  250 . These outer seal rings  250  see only low pressure leak water. An inner seal ring  250  is provided around the rear end portion of the spray head  216  between the threaded connection to the shaft  208 . This seal ring  250  sees full high operating fluid pressure. These seal rings  250  prevent fluid leakage past the threaded connections during high pressure operation of the nozzle device  200  and ensure that all the fluid flows either through the useful passages and leakage paths as described herein or through the spray head directly. 
     During operation, high pressure fluid is first introduced through the inlet nut  204  into the central bore  211  in the inlet nut  204 . This high pressure fluid passes through stem portion  210  into and through the head  216 . A portion of the high pressure fluid is redirected such that it leaks back (to the left in  FIG. 3 ) around the stem portion  210 , constituting a leakage path  230  along the inlet bearing area, i.e., in the clearance region between the outer surface of the stem portion  210  and the inner surface  218  of the shaft  208 . 
     Part of this fluid passing through leakage path  230  flows into the balancing chamber  221  between the inlet nut  204  and the shaft  208 , and then out through weep holes  226  into the gap  228  between the housing  202  and the shroud  240 . This leakage fluid then flows through passages  232  to atmosphere via the open end of the shroud  240 . Another portion of the fluid in leakage path  230  is diverted forward and outward through the passages  220  in the shaft  208  to the space  222 . From the space  222 , most of this portion of leakage fluid then flows through the helical groove  224  to the balancing chamber  221 . A small portion of leakage fluid flows toward the head  216  through the annular clearance space between the reduced diameter portion  214  of the shaft  208  and the housing  202 . 
     During operation, the shaft  208  becomes axially dynamically balanced on the stem  210  such that mechanical bearings are not required. The lubricity of the fluid flowing through these leakage paths  230  and through the balancing chamber  221  sufficiently supports and lubricates the shaft  208  and attached spray head  216  such that bearings are not required. Furthermore, the fluid flow through the helical groove  224  provides the rotational torque necessary to rotate the shaft  208  and its attached spray head  216 . This torque generating function is performed entirely by the leakage fluid flow. Therefore offset nozzle tips are not necessary to rotate the nozzle head  216  as in previous designs. However, where high rotational speed is desired, offset nozzle tips may also be advantageously employed in these embodiments, since the head  116  and  216  are interchangeable with other head designs. 
     Balancing in this embodiment  200  occurs because, as the fluid pressure in the space  222  exerted by the leakage fluid increases, an axial force pushes the shaft  208  rearward, or to the left in  FIG. 3 . When this occurs, the rear end of the shaft  208  partially closes off the weep holes  226 . This reduces the leakage rate, which in turn increases the axial pressure acting on the left end of the shaft  208  in opposition to the axial force exerted in space  222  until a balance between the axially opposing forces is achieved. 
     In this embodiment  200 , it is therefore the interaction of the rear face of the swivel shaft  208  with the opening to the weep holes  228  that actually regulates the balancing of axial forces during nozzle operation. The presence of the helical groove  224  determines the direction of and speed of rotation of the swivel shaft  208 . The dimensions of the space between the shaft  208  and housing  202 , and the inner wall of the shaft  208  and the outer wall of the stem  210  are such that a clearance of between 0.0005 and 0.0010 is preferred. 
     In accordance with the features and benefits described herein, the present invention is intended to be defined by the claims below and their equivalents.