Abstract:
A speed retarding device for a rotary nozzle includes a hollow cylindrical housing and a rotatable tubular shaft rotatably carried by the housing. The shaft has an enlarged drag sleeve portion carried in the housing and a shaft end extending through at least one end of the housing to receive a rotary nozzle thereon. A pair of support bearings support the drag sleeve portion of the shaft in the housing. An annular inner seal between each of the support bearings and the drag sleeve portion defines a cavity within the housing receiving a viscous fluid confined within the cavity. The support bearings are separated from the cavity confining the viscous fluid and an outer annular seal on the shaft adjacent each support bearing prevents environmental contamination such as water and debris from entry into the support bearings.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of priority of U.S. Provisional Patent Application Ser. No. 62/024,408, filed Jul. 14, 2014 bearing the same title, which is hereby incorporated by reference in its entirety. 
     
    
     BACKGROUND OF THE DISCLOSURE 
       [0002]    The present disclosure is directed to high pressure fluid rotary nozzle systems. In particular, embodiments of the present disclosure are directed to an apparatus for retarding the speed of rotation of such rotary nozzles. 
         [0003]    High pressure water jet cleaning devices utilizing reaction force rotary nozzles tend to rotate at very high speeds. In many applications it is desirable to slow down such rotary nozzle speed to maximize usable lifetime of the rotary nozzle and effectively improve the cleaning efficiency of such nozzles. A speed reducing device fastened to the shaft of such rotary nozzles is often utilized to retard rotation of the nozzle. Typical viscous fluid speed reducing devices utilize a viscous fluid flowing along a tortuous flow path in a confined space around the rotating shaft to generate a drag on the nozzle shaft. 
         [0004]    Typically the operational lifetime of the speed reducing device is limited by the longevity of the bearings and the medium such as a viscous fluid utilized to produce the speed retardation. As an example, the useful lifetime without maintenance of conventional viscous speed retarders is on the order of 40-60 device operating hours. A typical retarder device has a bearing supported shaft connected to the rotary nozzle such that the shaft rotates with the nozzle. A generally cylindrical housing contains the two support bearings supporting the rotating shaft and contains the retarding mechanism. One such retarding mechanism has a series of roller bearings immersed in a viscous fluid within the housing and between end support bearings that are also immersed in the viscous fluid. Another exemplary conventional retarder is a Warthog WG-1 by Stoneage Inc. This retarder has end support bearings sandwiching a large diameter drag sleeve fastened to or integrally formed around the shaft in the housing instead of utilizing a series of bearings in the viscous fluid. These support bearings and the drag sleeve are immersed in the viscous fluid contained within the cylindrical housing. Together the support bearings and the retarding drag sleeve are contained between two shaft seals, sealing the shaft to the housing, and preventing escape of the viscous fluid. Thus the end support bearings and the drag sleeve in the WG-1 are immersed in viscous fluid and function together to retard the speed of the rotating nozzle. 
         [0005]    As the retarder rotates in the housing, the viscous fluid is circulated (pumped) within the fluid chamber by a helical groove around the outer surface of the drag sleeve portion of the shaft and through a series of axially extending bores through the drag sleeve portion of the shaft. Additionally, the helical groove serves to uniformly distribute the fluid above the drag sleeve and through the end bearings. In the immersed bearing system, drag is created as a function of the fluid viscosity, the bearing geometry, the surface area of the drag sleeve and the gap size between the drag sleeve and the cylindrical housing. This implementation of a viscous fluid retarder creates drag, and also eventually degrades the viscosity of the viscous fluid. Once the viscous fluid degrades during operation, the rotary nozzle speed increases substantially, frequently audibly indicating to an operator that the viscous fluid needs to be changed. The retarder and nozzle then must be removed from service, disassembled, cleaned and flushed, reassembled and new viscous fluid installed. This is inconvenient to the operator, takes maintenance down time and can result in increased maintenance costs over the life of the tool. Therefore what is needed is a viscous retarder device that has a substantially improved operational lifetime in order to solve these problems. 
       SUMMARY OF THE DISCLOSURE 
       [0006]    The present disclosure directly addresses such needs. An apparatus in accordance with the present disclosure is a speed reducing or limiting device for a rotary nozzle that exhibits an operational lifetime between maintenance periods of many times that of conventional viscous retarder devices. This remarkable longevity increase is achieved by isolating the shaft support bearings from the viscous fluid in the retarding cavity of the device. 
         [0007]    An exemplary embodiment of a retarder in accordance with the present disclosure includes a hollow generally cylindrical housing that carries an elongated shaft having a retarding portion between forward and rear support bearings. Each of the support bearings is isolated from the retarding portion of the elongated shaft within the housing by an annular seal. A conventional viscous fluid material such as gear oil or silicone fills the housing around the retarding portion of the shaft between the two annular seals. 
         [0008]    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 
         [0009]      FIG. 1  is an axial cross sectional view through a retarder device in accordance with the present disclosure fastened to a rotary nozzle head. 
           [0010]      FIG. 2  is an exploded perspective view of the retarder device shown in  FIG. 1  separated from the rotary nozzle. 
           [0011]      FIG. 3  is an exploded perspective view of the retarder device and nozzle head shown in  FIG. 1  showing each subcomponent in assembly sequence. 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    An exemplary embodiment of a retarder device  100  in accordance with the present disclosure connected to a rotary nozzle  200  is shown in sectional view in FIG.  1 . The retarder device  100  includes a tubular shaft  102  carried within a generally cylindrical tubular housing  104 . The shaft  102  has a distal end  106  fastened to the nozzle  200  and an opposite end  108  coupled with an inlet nut  110  that is connected to a high pressure fluid hose (not shown). 
         [0013]    This cylindrical housing  104  also carries within it a first support bearing  112  and a second support bearing  114  which together rotatably support the shaft  102 . Each of the bearings  112  and  114  is sandwiched between a pair of shaft seals  116  and  118 , 
         [0014]    The shaft  102  also has a retarding sleeve portion  120  between the two shaft seals  118 . This sleeve portion  120  is preferably an integral part of the shaft  102  and has a large diameter outer cylindrical surface  122  sized to closely fit within the housing  104 . This surface  122  has a peripheral helical groove  124  that extends from one end to the other of the sleeve portion  120 . The sleeve portion  120  further has a plurality of axially extending bores  126  spaced around the axial bore  128  through the shaft  102 . 
         [0015]    The sleeve portion  120  is captured on the shaft  102  within the housing  104  by the front and rear inner seals  118 . A pair of threaded ports  130  permits filling the space within the housing  104 , and around and within the sleeve portion  120 , with a high viscosity fluid such as silicone fluid having a kinematic viscosity within a range of 200 to 60,000 cSt, and more preferably within a range of 200 cSt to 15,000 cSt. The speed range of the retarder  100  is determined by the viscous fluid viscosity and the high pressure fluid applied to the nozzle  200 . The retarding capacity of the retarder  100  is determined by the viscous fluid viscosity, the cylindrical surface  122  length and outer diameter, and the gap between the cylindrical surface  122  and the housing  104 . This retarding capacity serves to resist the torque generated by the nozzle  200  when high pressure fluid such as water is applied. The resulting net forces dictate the rotational speed of the nozzle  200  relative to the retarder  100 . There are additional secondary retarding forces, operating torque from the high pressure seal, intrinsic bearing drag and shaft seal drag. However, these forces are essentially fixed as a function of the design and the reasonable life of the related parts. These forces are intended to be dominated by the retarding mechanism and the nozzle torque. 
         [0016]    The front and rear outer seals  116  keep water and external contaminants out of the bearings  112  and  114 . The inner seals  118  keep viscous retarder fluid out of the bearings  112  and  114 . Separation of the bearings  112  and  114  from the viscous fluid accomplishes two things. First, the bearings  112  and  114  are free to rotate the shaft  102  without drag of the viscous fluid and utilizing their own optimal lubricating medium, which tends to increase the bearing lifetime. Second, the seals  118  prevent the bearings from degrading the viscous fluid due to bearing shear forces exerted on the viscous fluid. An alternative embodiment may be implemented utilizing sealed bearings to isolate the bearing components and lubricant from the viscous fluid and retarding mechanism. 
         [0017]    The bearings  112  and  114  may be sealed bearings. Alternatively open bearings may be utilized that are packed with grease. Grease zerk fittings or oil bath fittings could also be installed in the housing  104  to accommodate such an open bearing configuration. 
         [0018]    The isolated bearing innovation of the present disclosure resulted from lengthy testing performed on conventional viscous fluid retarders. A custom made tool tester was utilized to control various permutations of input torque, speed and temperature on a conventional retarder configuration. It was found that the conventional retarder configuration lasts, on average, about 40 hours on this tester. The failure mode was a speed runaway resulting from viscosity change in the fluid. By analyzing the viscous fluid before and after speed runaway, it was learned that the rolling contact of the bearings shears the molecules of the silicone viscous fluid at a rate that is a function of the rotary nozzle speed. This shearing results in a steady and predictable reduction in fluid viscosity and relatedly an increase in tool rotation speed. 
         [0019]    By separating the bearings  112  and  114  from the viscous fluid via an extra set of inner seals  118  and containing each bearing  112  and  114  also with a set of shaft outer seals  116 , an average of 1000 hours or more of useful lifetime between maintenance intervals for the retarder  100  was established based on test and measurements performed on the aforementioned tool tester. Such a drastic improvement of lifetime manifests a gross improvement in the tool&#39;s performance. 
         [0020]    More consistent, sustainable rotational speed can also be achieved by removing the primary means for viscous fluid degradation (bearings) from the retarding mechanism. The rotational speed becomes predictable as a function of part geometry and fluid viscosity. Therefore the retarder  100  can be characterized such that users can install fluid of different viscosity (within a recommended range of viscosities) to achieve different rotational speeds for a given nozzle rotational torque. Removing the bearings from the braking mechanism also permits the retarder to reliably function at higher speeds. In the prior device, the immersed bearings served to multiply harmful shear characteristics due to their geometry and higher speed operation could not be sustained due to the revolution dependent breakdown of fluid viscosity. Removing the bearings from the retarding mechanism results in more consistent retarding. When the mechanism is reduced to a drag sleeve, cylindrical housing and viscous fluid, the retarding capability is more reliable and predictable. 
         [0021]    Another improvement in the speed retarder  100  in accordance with the present disclosure is the inclusion of replaceable centralizer vanes  210 . Conventional retarder designs such as Stoneage&#39;s WG retarder devices have historically had radial fins welded to a separate cylindrical sleeve that installs to the exterior surface of the housing of the retarder. These radial fins must be replaced together with the cylindrical sleeve, 
         [0022]    In the retarder  100  shown in  FIGS. 1-3 , the housing  104  is a cylindrical tube provided with six axially extending exterior slots  202 . The rear end of the housing  104  is closed by the threaded inlet nut  110 . The front end of the housing  104  is closed by a front end nut  206 . The front end nut has a peripheral annular rearwardly facing recess  208 , shown in  FIGS. 1 and 3 . The inlet nut  110  closing the housing  104  is fitted with a removable annular rear end cap  204 . This rear end cap  204  similarly has a forwardly facing annular recess  212  (visible in  FIG. 1 . The rear end cap  204  is fastened to the inlet nut  110  by a series of six threaded fasteners  214  such as Torx® bolts. 
         [0023]    Each of the vanes  210  is a plate having a generally equilateral trapezoidal shape preferably made of a hardened steel material. Vanes made of a plastic or composite material may alternatively be utilized. These vanes  210  are captured within the slots  202  and the vane ends are captured within the recesses  208  and  212 . The vanes  210  may be removed and replaced without disassembly of the retarder  100 , simply by removing the fasteners  214  and removing the end cap  204 . The vanes  210  can then simply slip out of the slots  202  and a new vane or vanes  210  installed. 
         [0024]    Another improvement in the speed retarder  100  in accordance with the present disclosure is the inclusion of a hardened face seal pair  300  between the inlet nut  110  and the rear end  108  of the rotary shaft  102 . This seal pair  300  comprises two elements: a nut flanged tubular high pressure rear face seal  302  that fits within a hexagonal recess in the inlet nut  110 , and a nut flanged tubular shaft high pressure front face seal  304  that fits within a complementary hexagonal recess in the proximal end  108  of the shaft  102 . These seals  302  and  304  are held in their respective recesses via O-rings  306  and biased toward each other via a wave spring  308  around the stem portion of each seal  302  and  304 . These high pressure seals permit rotation of the shaft  102  relative to the inlet nut  110  with minimal high pressure water leakage. 
         [0025]    The seal pair  300  permits the inlet nut  110  to be removed from the assembled retarder  100  for high pressure face seal  300  maintenance and/or centralizer vane  210  replacement without disturbing the bearing  114  and inner seal  118  and thus violating the integrity of the viscous fluid cavity within the housing  104  containing the viscous fluid. Similarly, the front end nut  206  may be removed from the housing  104  without violating the integrity of the bearing  112 , inner seal  118 , and integrity of the viscous fluid cavity within the housing  104 . 
         [0026]    Another improvement in the speed retarder of the present disclosure is a series of features designed to permit removal of the nozzle  200  without any additional disassembly of the retarder  100 . A hex key, Torx® tool, rod or screwdriver having the appropriate shaft diameter can be inserted into the retarder  100  front end nut  206  at the hole  207 . When the shaft  102  is properly clocked relative to the front end nut  206 , the inserted tool will engage a slot  209  in the shaft  102  and lock the shaft  102  to the front end nut  206 . Once the tool has been properly inserted and shaft  102  locked, an open end wrench can be applied to the flats on the front end nut  206  and similarly to the flats on the nozzle  200  to remove the nozzle  200  from the shaft  102  of the retarder  100 . An entry portion of the hole  207  may be threaded and plugged with a complementary set screw to prevent debris from filling and stopping the shaft from rotation during tool operation. 
         [0027]    Many changes may be made to the device, which will become apparent to a reader of this disclosure. For example, the helical groove  124  may have an Acme thread profile, a buttress thread profile, or a 55 degree or 60 degree thread profile. The seals  302  and  304  may have a shape other that hexagonal as described above. They may have any shape to fit in complementary recesses in the inlet nut  110  or in the proximal end  108  of the shaft  102 . Although the rear face of the nozzle  200  is shown flush with the front face of the nut  208 , there is a gap therebetween as the nozzle  200  rotates with the shaft  106 . The nozzle  200  may be further spaced from the nut  208  than as shown and its rear face may be tapered outward so as to prevent collection of debris between the two rotating surfaces. All such changes, alternatives and equivalents in accordance with the features and benefits described herein, are within the scope of the present disclosure. Any or all of such changes and alternatives may be introduced without departing from the spirit and broad scope of my disclosure and invention as defined by the claims below and their equivalents.