Abstract:
An apparatus for retarding rotation of a nozzle includes a hollow housing, a rotary shaft within the housing, a rotatable rotor on the rotary shaft free to move axially along the shaft, and a cam assembly coupling the rotor and shaft together in the housing such that rotor rotation on the shaft causes the cam assembly to displace the rotor axially on the shaft in a first direction. A set of springs on the shaft biases the rotor in a second direction opposite the first direction on the shaft. Finally, a viscous fluid disposed between the rotor and the housing generates a drag on rotor rotation with the shaft. Relative rotation of the rotor with respect to the shaft in conjunction with a variable gap between the rotor and housing are used to slow and thus control rotary nozzle speed.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of priority of U.S. Provisional Patent Application Ser. No. 61/880,316, filed Sep. 20, 2013, the disclosure of which is incorporated herein 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 rotational speed of such rotary nozzles. 
         [0003]    A high pressure rotary nozzle and tractor device is disclosed in US Patent Application Publications 2012/0204368 and 2012/0205405. Such nozzles and tractor devices are 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 up to 1000 rpm or more and flow rates of 2 to 50 gpm may be needed. 
         [0004]    In order to control the rotational speed of the rotary nozzle and tractor devices, there is a need for a speed control to retard the speed of the tool to keep the rpm&#39;s in a desired range for specific cleaning applications. There are several different speed control mechanisms, one of which, described in U.S. Pat. No. 5,964,414 utilizes viscous fluid within stacked radial ball bearings within a sealed bearing chamber in the body rotatably supporting the shaft. Another mechanism includes a viscous fluid confined within a thin gap that separates two components where one component is rotated and the other is stationary. This speed control style can handle a limited input torque range based on the set distance of the gap. This limit in torque range requires that other components on the rotary nozzle be changed to accommodate major variations in flow and pressure. What is still needed is an apparatus that can be utilized over a wide torque range to reliably control rotational speed. 
       SUMMARY OF THE DISCLOSURE 
       [0005]    The present disclosure directly addresses such needs. The present disclosure addresses this limited torque range by offering a solution that involves permitting the distance of the gap between relatively rotating components connected to a rotary nozzle tool to vary as a function of tool torque, affecting the rotational speed to the tool, thus increasing the operational torque range of the tool. 
         [0006]    One exemplary embodiment of such an apparatus for retarding rotation of a nozzle includes a hollow housing, a rotary shaft within the housing, a rotatable rotor on the rotary shaft free to move axially along the shaft, and a cam assembly holding the rotor and shaft together such that rotor rotation on the shaft causes the cam assembly to displace the rotor axially on the shaft in a first direction. A set of springs on the shaft biases the rotor in a second direction opposite the first direction on the shaft. Finally, a viscous fluid disposed between the rotor and the housing generates a drag on rotation of the rotor about the shaft. 
         [0007]    In one preferred embodiment, the rotary shaft and the hollow housing have complementary frusto-conical shapes. As speed increases, the cams of the cam assembly rotate and separate, causing the shaft to move forward, reducing the gap between the shaft and the hollow housing, increasing the resistive drag force of the fluid on the rotating shaft, thus slowing it down until an equilibrium is again reached between spring force and the viscous drag force on the rotor. Conversely, as speed decreases, the spring forces push the shaft rearward, closing the cams and increasing the viscous fluid volume in the gap thus decreasing viscous drag until equilibrium is again reestablished. The combination of these changes substantially increases the useable range of torques that can be handled by the speed retarding apparatus. 
         [0008]    An embodiment of a device for retarding rotational speed of a rotary nozzle in accordance with this disclosure includes a hollow housing having an internal surface portion concentric about an axis through the housing, an elongated tubular shaft having a portion rotatably carried within the housing for rotation about the axis and an end portion extending out of the housing, an elongated rotor having an exterior surface shape complementary to the internal surface portion of the housing slidably mounted on the portion of the shaft within the housing, a cam assembly coupled between the rotor and the shaft to cause axial movement of the rotor upon rotation of the rotor about the shaft, and a viscous fluid between the rotor and the internal surface portion of the housing. 
         [0009]    The cam assembly preferably includes a rotor follower cam ring disposed about the shaft and fastened to the rotor. This follower cam ring has a plurality of axially extending projections. The assembly also has a progressive cam ring fastened to the shaft. This progressive cam ring has a plurality of ramps each facing one of the axially extending projections associated with the follower cam ring. 
         [0010]    The internal surface portion of the housing has a tapered shape and is preferably a frusto-conical tapered shape. The external surface of the rotor may include a peripheral helical groove and the helical groove may have a variable depth that preferably increases from one end of the rotor to an opposite end of the rotor. 
         [0011]    An embodiment of a device for retarding rotational speed of a rotary nozzle may include a hollow housing having an internal surface portion concentric about an axis through the housing, an elongated tubular shaft having a portion rotatably carried within the housing for rotation about the axis and having an end portion extending out of the housing, wherein the end portion of the shaft is connectable to a rotary nozzle, an elongated rotor having an exterior surface shape complementary to the internal surface portion of the housing slidably mounted on the portion of the shaft within the housing, a cam assembly coupled between the rotor and the shaft to cause axial movement of the rotor upon rotation of the rotor about the shaft, and a viscous fluid within the housing around the shaft and between the rotor and the internal surface portion of the housing. 
         [0012]    The internal surface portion of the housing preferably has a tapered shape. More preferably this tapered shape may be a frusto-conical tapered shape. The external surface of the rotor preferably has a peripheral helical groove that may have a variable depth that increases from one end of the rotor to an opposite end of the rotor. 
         [0013]    The device may include a spring member comprising one or more wave springs positioned between a front bearing on the shaft and the rotor. The cam assembly may include a progressive cam ring fastened to the shaft and a follower cam ring fastened to the rotor. The cam ring preferably has a plurality of ramps spaced around the ring and the follower cam ring has a plurality of projections each engaging one of the plurality of ramps. 
         [0014]    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 
         [0015]      FIG. 1  is a longitudinal side view of an assembled speed retarding device connected to a rotary high pressure nozzle. 
           [0016]      FIG. 2  is a partial section schematic diagram of the retarding device in accordance with the present disclosure shown in  FIG. 1 . 
           [0017]      FIG. 3  is a longitudinal side view of the assembled speed retarding device connected to a rotary high pressure nozzle as shown in  FIG. 1  without the outer device housing. 
           [0018]      FIG. 4  is an exploded side view of the speed retarding device shown in  FIG. 1 . 
           [0019]      FIG. 5  is an axial cross sectional view of the assembled speed retarding device shown in  FIG. 1 . 
           [0020]      FIG. 6  is a separate perspective view of the rotor utilized in the device shown in  FIGS. 1-5 . 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    An assembled exemplary embodiment of a speed controlled rotary nozzle assembly  100  in accordance with the present disclosure is shown in a longitudinal side view in  FIG. 1 . The assembly  100  includes a rotary nozzle head  102  fastened to a speed limiting apparatus or device  104  in accordance with the present disclosure. The rotary nozzle head  102  preferably has a plurality of radially offset nozzle ports  106  for generating a rotational torque about the longitudinal axis A of the assembly  100  when high pressure fluid is pumped through the assembly  100  and ejected out of the nozzle ports  106 . 
         [0022]    The speed limiting device  104  includes a tubular shaft  108  rotatably supported within a hollow housing  110 . One end of the tubular shaft  108  extends from one end of the housing  110  and is supported by a roller journal bearing  112  in the housing  110 . The rear end of the tubular shaft  108  is rotatably supported in the housing  110  by a rear roller bearing  114  mounted within the housing  110 . The rear end of the tubular shaft  108  has an end face  116  that abuts against a unitary high pressure seal cartridge  118  carried by an inlet nut  120  that is threaded into the rear end of the housing  110 . The unitary high pressure seal cartridge  118  is preferably a replaceable rotary seal, such as is disclosed in U.S. Pat. No. 8,573,599, incorporated herein by reference. This inlet nut  120  is in turn fastened to a high pressure hose (not shown). 
         [0023]    As is shown in  FIG. 5 , speed limiting device  104  also includes a tubular rotor  130  that is carried on the shaft  108 . This tubular rotor  130  preferably has an outer surface shape  132  complementary to an inside surface  134  of the housing  110 . Preferably the complementary surface shapes  132  and  134  are tapered and more preferably frusto-conical. Preferably the outer surface  132  has a spiral helical groove  136  extending therearound from a forward to a rearward end of the rotor  130 . The depth of the helical groove increases as the groove progresses from the forward end of the device  104  to the rear of the rotor  130 . Alternatively the groove  136  may be formed in the inner surface of the housing  110  rather than on the outer surface  132  of the rotor  130 . 
         [0024]    he rotor  130  has an axial bore  138  therethrough that is sized to receive the tubular shaft  108  therethrough, and has an inwardly directed rear annular flange  140  and a forward inwardly directed annular flange  142 . These annular flanges  140  and  142  have a close tolerance to the outer radius of the tubular shaft  108 , 
         [0025]    Mounted around a front end of the shaft  108  and abutting the annular flange  142  is a stack of wave springs  144  that are free to rotate about the shaft  108 . A thrust bearing  146  around the shaft  108  is sandwiched between the wave spring stack  144  and the forward roller bearing  112 . 
         [0026]    A rotor cam ring  148  is disposed around the shaft  108  and keyed to the rotor  130  and abuts against the rear annular flange  140  of the rotor  130 . This rotor cam ring  148  is thus sandwiched between the shaft  108  and recessed within the rear end of the rotor  130  This rotor follower cam ring  148  has 3 or 4 axially extending and radially equally spaced apart projections  150  that extend rearward toward the inlet nut  120 . 
         [0027]    Also mounted on and keyed to the shaft  108  is a shaft progressive cam ring  152 . This progressive cam ring  152  has a plurality of spaced peripheral ramps  154  that each engage with one of the rotor follower cam ring projections  150 . In operation, normally the rotor and shaft rotate together as the nozzle  106  rotates. However, as the speed increases, the viscous fluid exerts a drag on the rotor  130 . Due to this drag, as the rotor  130  rotates about the shaft  108 , the projections  150  ride up or down along the ramps  154  , depending on the drag amount, to axially move the rotor  130 . As shown in  FIG. 4 , the shaft  108  and rotor  130  generally rotate together counterclockwise viewed from the rear. if the rotor  130  rotates or lags less counterclockwise as viewed from the rear of the assembly  100 , the follower cam ring  148 , fastened to the rotor  130 , is pushed to the right, moving the rotor  130  axially forward, compressing the rotor  130  against the wave spring stack  144 . 
         [0028]    Stated another way, the motion of the rotor  130  with respect to the shaft  108  is caused by the drag force that is created by viscous fluid inside of the fluid gap between the housing  110  and rotor  130  when the shaft and rotor are rotated inside of the housing  110  (or vice versa). Rotation of the shaft is initiated by the torque from the offset jets or ports  106  on the nozzle head  102  which is attached to the shaft  108 . As the rotational speed, i.e. revolutions per minute (rpm), of the tool increases, the drag force of the viscous fluid in the fluid gap increases. This puts a rotational stress between the rotor  130  and the shaft  108 . This rotational stress, or torque, between the rotor  130  and shaft  108  acts on the actuator cams  148 / 150  and  152 / 154  that interconnect them and forces the two cam rings  148  and  152  axially apart, driving the rotor  130  axially forward on the shaft  108 . 
         [0029]    Thus, the multi-stacked wave return spring  144  serves to oppose the cam actuation, exerting a force attempting to return the rotor  130  back to its original rest position. Once the viscous rotational drag force is great enough, the force in the cams overcomes opposing return spring force, the rotor  130  begins to rotate about the shaft  108  and the cam mechanism drives the rotor  130  forward, i.e, to the right in  FIG. 4 , on the shaft  108  and thus into the housing  110 . Once the force exerted by the cams matches the spring force, the device  104  reaches equilibrium and the rotor  130  stays in a stationary position. 
         [0030]    In addition, as the rotor  130  moves forward during rotation of the rotor and shaft together, its taper and the internal taper of the housing  110  come closer together, causing the fluid gap between the rotor  130  and the housing  110  to become smaller until the rotor  130  engages the thrust bearing  146 . Viscous drag force is inversely proportional to this gap size; therefore, as the fluid gap decreases, the viscous drag force increases and serves to maintain the tool speed within a specified range. By changing the spring rate of the return spring stack  144 , the desired speed range of the tool, i.e. device  104 , can be adjusted. If the spring rate is reduced, it takes less force to overcome, and the rotor  130  will move forward sooner causing the tool to rotate slower. Inversely, if the spring rate is increased, the tool will rotate faster. The rotor  130  has a limited range of motion and is stopped by the thrust bearing  146  at a minimum gap position preventing any mechanical interference between the rotor  130  and the housing  110 . Furthermore, engagement of the rotor  130  with the thrust bearing  146  prevents the follower cam projections  150  from moving beyond the ramps  154  on the progressive cam ring  152  fastened to the shaft  108 . 
         [0031]    At the forward end of the housing  110  is an annular seal ring  156  around the shaft  108  that prevents ingress of contaminants into the housing  110 . A similar annular seal  158  is press fit into the inlet nut  120  at the rear end of the housing  110  so as to prevent high pressure water or other fluid from entering the housing  110  around the rear end of the shaft  108 . This seal ring  158  also prevents viscous fluid  160  in the housing  110  from escaping. A threaded port  162  closed by a threaded plug  164  permits filling of the cavity within the housing  110  with the viscous fluid  160 . A preferred viscous fluid in one exemplary embodiment of the retarder device of the present disclosure is a pure silicone fluid having a viscosity of 2000 cSt. 
         [0032]    A separate perspective view of the rotor  130  is shown in  FIG. 6 . This rotor  130  is a frusto-conical sleeve that has inwardly directed flanges  140  and  142  which ride against the shaft  108  as described above. Preferably a single helical groove  136  spirals around the tapered exterior surface  132  of the rotor  130 . As can readily be seen in  FIGS. 5 and 6 , the depth of this groove  136  deepens as it approaches the rear of the rotor  130 . In addition, the rotor  130  has a plurality of radially spaced bores  166  that extend parallel to the central axis through rotor  130 . These bores  166  provide a return path for fluid flowing rearwardly through the gap between the housing  110  and the rotor  130  such that during rotary nozzle operation there is a constant circulation of fluid within the device  104 . 
         [0033]    Many changes may be made to the device, which will become apparent to a reader of this disclosure. For example, the rotor  130  may be configured with or without a helical external groove as is shown in  FIG. 6 . Such a helical groove may be a single groove as shown. Alternatively a set of helical grooves may be formed on the outer surface of the rotor. The purpose of the helical groove(s) is to help pull the viscous fluid into the thin gap between the housing and rotor components, which increases the efficiency of this speed control style. The cam ring assembly  148 / 152  may be separate elements as shown or may be integrally incorporated into the return spring stack  144 . The device  104  may also be configured to permit external adjustment of the initial spring compression thereby providing multiple operational rpm ranges for the given torque range and without disassembly of the speed retarder apparatus. 
         [0034]    All such changes, alternatives and equivalents in accordance with the features and benefits described herein, are within the scope of the present disclosure. Such changes and alternatives may be introduced without departing from the spirit and broad scope of my invention as defined by the claims below and their equivalents.