Abstract:
A spa jet of the type which utilizes a nozzle rotor for delivering a rotating jet of water into a spa is provided with a water-lubricated bearing for reducing frictional resistance to rotation. The rotor is supported by an inner bearing which is mounted for concentric rotation within an outer bearing in the housing. The inner and outer bearing surfaces which face each other include cylindrical side surfaces and upstream and downstream end wall surfaces defining a passage. The flow of water to lubricate the bearing surfaces is arranged to exert a net axial force that spaces at least one of the sets of end surfaces out of contact with each other to reduce friction and also lubricates and separates the cylindrical side surfaces.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to spa jets for hydrotherapy. In particular, it relates to a spa jet having a nozzle supported for rotation by a bearing in which a portion of the water flow is used to lubricate the rotating parts of the bearing. 
     In the art of hydrotherapy, it is known to utilize spa jets which direct water into the spa through one or more nozzles which rotate to distribute the water in a swirling motion against the skin of a person in the spa. Such a spa jet typically includes a housing, which communicates with an inlet connected to a pressurized source of water, and a bearing, mounted within the open end of the housing, which supports the nozzle for rotation. One such spa jet is, for example, shown in U.S. Pat. No. 5,014,372 to Thrasher et al., owned by the assignee of the present invention. 
     In the Thrasher prior art spa jet, two nozzles extend through a rotor mounted for rotation in the downstream end of the housing. The rotor is positioned between spring biased ring, at its upstream end, and a cage, at its downstream end, which has a flat bearing surface on which a nose portion of the rotor can rotate. This prior patent shows a space between a cylindrical side surface of the rotor and the adjacent internal surfaces of the housing and explains that water in this space surrounding the rotor acts as a lubricant and helps minimize the frictional forces that would otherwise resist rotation. 
     While the prior art device described may have been generally satisfactory for its intended purpose, there are respects in which improvement can be sought. In particular, it would be desirable to avoid an arrangement in which the rotor is exposed to frictional resistance to rotation against both its end surfaces. Also, the cage and the inclusion of a spring during assembly add manufacturing expense to a product where low price to the retail consumer is very important. 
     Accordingly, it is an object of the present invention to provide a spa jet, of the rotating nozzle type in which direct surface-to-surface friction at the ends of the rotor is minimized by increasing the extent to which the water itself is used to lubricate and support the rotor for free rotation. In addition, it is another objective to simplify the shapes of the parts used for ease of manufacture and to reduce the expense involved in assembling the spa jet from its components. 
     SUMMARY OF THE INVENTION 
     The present invention provides an improvement to a spa jet of the type having a housing, supplied by an upstream source of water under pressure, and a rotor within the housing which has a nozzle. The nozzle emits a water jet which exerts a turning moment about the axis that rotates the rotor thereby producing a swirling effect on the skin of a person in the spa against whom the spa jet is directed. The improvement resides in structure which mounts the rotor for low friction rotation by using a bearing which provides a layer of water which lubricates and supports the rotating parts to an increased extent. 
     More specifically, the bearing is comprised of a stationary, outer bearing mounted to the housing and a rotating, inner bearing which supports the rotor. The facing working surfaces of the two bearings are separated by an enveloping water stream that lubricates and supports the inner bearing for rotation to an increased degree. An annular space between the facing bearing surfaces will be referred to as the “bearing flow passage”. The bearing flow passage includes an axially extending cylindrical region and radially extending end regions, defined by facing parallel surfaces of the inner and outer bearings. The radial area of the upstream end surfaces defining the bearing passage exposed to water pressure is sufficiently greater than the radial area of the downstream surfaces so that water flowing through the bearing flow passage exerts a net downstream axial force urging the facing surfaces of the inner and outer bearings into at least partial contact at the downstream end. In contrast, however, the upstream facing end surfaces are moved out of surface-to-surface contact, thereby reducing the surface-to-surface mechanical friction compared to prior devices having continuous surface-to-surface mechanical contact at both axial ends. 
     The magnitude of the net axial force affects the magnitude of the rotational frictional force due to surface-to-surface contact at the downstream axial end of the inner bearing. The invention is designed to lower this friction in three complementary ways. First, the difference in areas of the radial surfaces of the inner bearing exposed to liquid pressure at its opposite axial ends is not large. Second, the pressure in the bearing flow passage is lowered relative to the pressure of the jet stream, to diminish the net axial force. Third, the downstream radial end surface or its inner bearing is relieved to reduce the extent of surface-to-surface contact. 
     As another feature of the invention, most of the parts comprise volumes of rotation which can be molded with relatively low degree of complication. This avoids the relatively higher expense of machined or cast parts that are more difficult and expensive to make than volumes of rotation. In addition, the parts are relatively easily assembled together by tabs which snap into grooves, allowing the parts to be installed by a sequence of pushing actions, thereby reducing the cost of assembly. 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view of a spa jet made in accordance with one preferred embodiment of the present invention; 
     FIG. 2 is a perspective view, partially in cross-section, of the preferred embodiment of the spa jet shown in FIG. 1, with an outer housing, shown in FIG. 1, omitted; and 
     FIG. 3 is a cross-sectional view of the preferred embodiment of the spa jet shown in FIG.  1 . 
    
    
     DETAILED DESCRIPTION 
     A spa jet, according to a preferred embodiment of the present invention, is shown in FIG.  1 . The spa jet directs a rotating jet of water into the interior of a spa from an outside source of water under pressure. A rotor, having at least one jet nozzle, is supported by a bearing in which the relatively rotating parts are separated by an enveloping layer of water over most of their facing surfaces. The relative dimensioning of the radially extending portion of the bearing surfaces, the water pressure to which they are exposed, and the extent of surface-to-surface contact between radial surfaces coming into contact occur, are designed to reduce surface-to-surface friction that would interfere with the freedom of rotation. 
     Turning to FIGS. 2 and 3, the preferred embodiment of the spa jet of the present invention includes an outer housing  2  mounted within an opening through the wall  4  of a spa. The outer housing has an inlet tube  6  connected to the outside source of water under pressure by a right angle, water inlet  8  and to an air source by another right angle, air inlet  10 . The inlet tube  6  opens into a chamber wall  11  which is generally cup-shaped and terminates in an enlarged outer flange  12  positioned within the spa. The flange  12  is clamped against the spa wall  4  by an internally threaded clamping ring  14 , on the opposite side of the spa wall. The ring  14  bears against a deflector ring  16  that draws the flange  12  against the spa wall as the clamping ring is tightened onto threads on the outer housing. A resiliently deformable sealing ring  18 , between the flange and the spa wall, prevents leakage of water out of the spa. 
     The outer housing includes an inner housing  20  which includes an inlet tube  22  and a chamber wall shaped to fit snugly within the inlet tube and the chamber wall of the outer housing. The inner and outer housings are generally shaped as volumes of rotation, subject to exceptions already discussed, such as the air and water inlet parts, and are concentric about a common axis. The inlet tube  22  has an axially and radially extending slot  24  cut in its upstream end which can be rotated into or out of alignment with the water inlet port  8  to control the flow of water passing through the inlet tube  20  into the spa. An outer adjusting ring  25 , which fits over the flange  12 , and is mounted for rotation on the outer housing  2 , is directly connected to the inner housing. The adjusting ring can be rotated by hand to adjust the water flow through to the spa jet. 
     The water passing through the inlet tube  22  of the inner housing is accelerated, by passing through a convergent venturi  26 , into a mixing chamber region  28  communicating with the air inlet  10 . The accelerated water stream entrains air bubbles into the water flow and delivers a mixed flow of water and bubbles. 
     So far, the parts  2 - 28  described are the same as, or closely similar to, those described in an earlier U.S. Pat. No. 6,123,274, owned by the assignee of the present invention. The relevant disclosure of that patent, as to common features with the present invention, is incorporated herein by reference. 
     Of particular interest to the present invention is the provision of a novel bearing assembly which uses a flow of water between its relatively rotating parts to lubricate and separate them thereby reducing friction and promoting freedom of a rotor  30  in which jet nozzles are formed. One part of the bearing assembly is constituted by an outer bearing body generally designated as  32 . The outer bearing body is shaped to fit within the chamber wall  24  of the inner housing  20 . The body  32  includes a lower, generally hemispherical region with external raised ribs which conform to the inner contour of the chamber wall  24 . The body has a lower end face  34  spaced above and facing toward the downstream end of the inlet tube  22 . A central passage  35  extends axially through the body  32  to receive the aerated stream of water directed from the venturi  26 . The body  32  also has an internal, cylindrical surface  36 , concentric with the central axis of the inner and outer housing, and a radially extending upstream end wall  38  at the upstream end of the bearing surface  36 . The surface  36  is interrupted by a plurality of peripherally spaced, radially extending channels  39  (FIG.  1 ). 
     To hold the outer bearing body  32  in place, a ring  40  is mounted in the open downstream end region of the inner housing  20 . The ring  40  has a radially extending outer flange  42 , which snap fits into a mating groove extending around the interior of the inner housing, an axially extending central web  44 , and an inner flange  46 . The inner flange  46  projects inwardly beyond the bearing surface  32  to constitute a downstream end wall. The cylindrical surface  32  and the surfaces of the end walls  38  and  46  collectively define a stationary, outer bearing surface. 
     The purpose of the outer bearing is to support an inner bearing  48  for rotation. The inner bearing  48  has a ring-shaped body with a cylindrical surface facing the cylindrical surface  36  of the outer bearing. It also has radial end surfaces facing the upstream and downstream end walls  38  and  46 . These facing surfaces define a bearing flow passage. In operation, water flow is directed through the bearing flow passage to form an enveloping layer of water which lubricates and supports the inner bearing for friction reduced operation. 
     Because the surface area of the radial upstream end face of the inner bearing  48  exposed to the flow of water through the bearing flow passage is larger than the corresponding downstream surface, the pressure of water exerts an axial force urging the facing radial surfaces of the inner bearing and the upstream endwall apart. This obviates surface-to-surface friction between them during operation. 
     This axial force urges the inner bearing into surface-to-surface contact with at least a portion of the downstream end wall  46 . Various design features have been incorporated to reduce the frictional effect where the surface contact occurs. First, the axial force urging the inner and outer bearings together has been reduced by lowering the pressure of the water traveling through the bearing flow passage relative to the pressure of the main water stream passing through the spa jet to the spa nozzles. This is achieved by upstream flow inlets  47  to the bearing flow passage from the central passage  35 . The flow inlets collect water from a region of the main flow which is at its peripheral edge rather than from the central region of the flow which is traveling more rapidly. The inlet flow passages are narrow, in terms of length to diameter, causing a pressure loss as liquid travels along them to reach the bearing flow passage. Specifically, the inlet passages comprise a plurality of bores, within the hemispherical portion of the bearing body, extending from a point adjacent the upstream end of the central passage  35  to a radially outward region of the bearing flow passage constituting the portion between the end wall  38  and the opposing radial end surface of the inner bearing. Water also enters the annular region of the bearing flow passage from its opposite radially inner end via a peripheral channel  50  between the inner and outer bearings. The pressure losses which occur through the arrangement described lower the pressure in the bearing flow passage. 
     There are other features which contribute to lower the net axial force urging the inner bearing  48  into contact with the downstream end wall  46 . The area of the downstream annular and surface of the inner bearing  48  exposed to fluid pressure is equal to a substantial fraction of the area of the upstream and surface. Because the pressure force of the water passing around the inner bearing acts in opposite axial directions at opposite ends of the inner bearing, the axial forces subtract from each other to reduce the net axial pressure urging the inner bearing  48  against the downstream end wall  46 . 
     These described features complement each other in reducing the magnitude of the rotational friction on the inner bearing  48 . 
     The inner bearing housing  48  supports the rotor  30  for rotation. The rotor  30  has a cylindrical lower body  60  which forms a non-rotating fit within the interior of the inner bearing  48 , extending axially into the spa jet in the region surrounded by the adjusting ring  35 . The rotor  30  has two slanted axial bores  64   a  and  64   b , which are symmetrically offset in opposite directions and on opposite sides of the central axis of rotation, at a symmetrical radial offset to the axis of rotation. They produce two complementary, diametrically spaced inclined jets, which have additive turning moments, thereby rotating the rotor in the same direction. Both nozzles,  64   a  and  64   b , at their upstream end, receive water directly from the central passage  35  through the body  32 . 
     To provide an outlet for the water flowing through the bearing flow passage, the ring  40  and the downstream radial end surface of the inner bearing  48  are provided with concentric axially-extending cylindrical rims  66  and  68 , respectively. The rims are spaced apart to define an annular outlet passage between them which communicates with the bearing flow passage and allows water to flow into the interior of the spa. These are a plurality of radially spaced notched openings  78  in the ring  40 , at the junction between the web  46  and to the rim  66 , to enable flow between the bearing flow passage and interior of the outlet passage  76 . The notches and the outlet passage together constitute a flow outlet. The notches also reduce the surface-to-surface frictional contact between the downstream radial end surfaces. 
     The inner bearing  48  is manufactured as a hollow annular part of U-shaped cross section. Specifically, it has axially extending, cylindrical inner and outer side walls,  72  and  74  joined at the downstream end by a radially extending end wall  76 , from which the rim  68  projects (FIG.  2 ). The inner and outer walls are spaced apart by peripherally spaced solid webs  75  (FIG. 2) to maintain the dimensional shape and sizing of the inner bearing. 
     Manufacture of the spa jet herein discussed is intended to facilitate high volume, low cost manufacture and to reduce the assembly indicated, in order to reduce the price to the ultimate retail user of a spa jet. Many of the parts described, notably the inner housing  20 , the bearing bodies  32  and  36 , are volumes of rotation, which may be produced by molding equipment at a lower manufacturing costs than parts made by more expensive techniques, such as machining, casting, or other more complicated procedures. These parts are equipped with a variety of resilient tabs projecting from their peripheral surfaces, which snap into mating slots in the complementary parts into which they fit. The parts described, the outer body, the inner housing, the outer housing, and the rotor are all joined together essentially by relative axial pushing and turning motions. As a result, manufacturing can be a relatively non-complicated procedure, capable of producing the spa jets in volume at significant manufacturing cost savings. 
     Although references have been made in the foregoing description to a preferred embodiment, persons of ordinary skill in the art of designing spa jets will recognize that insubstantial modifications, alterations, and substitutions can be made to the preferred embodiment described without departing from the invention as claimed in the accompanying claims.