Abstract:
A separator for separating particles entrained in a fluid is disclosed. The separator includes a sleeve adapted to be mounted over a rotatable shaft for forming a cavity therebetween, an inlet to the cavity, an outlet to the cavity and means for imparting a centrifugal force on fluid within the cavity. The means for imparting the centrifugal force is operatively connected to the shaft so that, in use, spinning of the shaft creates the centrifugal force. In use, a slurry of fluid and particles enters the cavity through the inlet, the particles are caused to separate from the fluid by action of the centrifugal force, and the separated particles and fluid leave the cavity via the outlet with the particles tending to be closer to the sleeve than the shaft.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a separate for separating particles from a fluid. 
     BACKGROUND 
     In many marine craft, a propeller at the end of a drive shaft extends away from the craft&#39;s stem by out rigging via a bearing. The bearing is usually cooled and lubricated by water flowing through channels or grooves which extend through the bearing. When the marine vessel passes through water where sand or grit has been disturbed, the sand/grit particles can find their way into the lubricating grooves of the bearing. These particles are highly abrasive to the bearing, and result in the bearing quickly becoming worn. 
     There is therefore a need to minimise the amount of sand or other abrasive particles from entering the lubricating grooves of the bearing. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a separator for separating particles entrained in a fluid. 
     In accordance with a first aspect of the present invention there is provided a separator for separating particles entrained in a fluid, said separator including: 
     a sleeve adapted to be mounted over a rotatable shaft for forming a cavity therebetween; 
     an inlet to the cavity; 
     an outlet to the cavity opposite the inlet; and 
     means for imparting a centrifugal force on fluid within the cavity, said means operatively connected to the shaft so that, in use, spinning of the shaft creates the centrifugal force, 
     wherein, in use, a slurry of fluid and particles enters of the cavity through the inlet, the particles are caused to separate from the fluid by action of the centrifugal force, the separated particles and fluid leave the cavity via the outlet with the particles tending to be closer to the sleeve than the shaft. 
     Preferably, the cavity increases in cross-sectional area along its length from the length towards the outlet. 
     In a first embodiment, the sleeve is frustoconical in shape with the narrow end of the cone at the inlet and the wide end at the outlet, whereby the size of the cavity increases along its length from the inlet to the outlet, which causes the movement of the slurry through the cavity to slow the further it progresses along the length of the separator, thereby increasing the centrifugal action on the fluid as it moves along the length of the separator. 
     In the first embodiment, the means for imparting a centrifugal force is in the form of one or more paddles projecting from the shaft into the cavity, the paddles causing the fluid to rotate about the longitudinal axis of the shaft as the shaft spins. 
     In a second embodiment, the cavity is of a helical shape. The helix shaped cavity, acting as said means so that as it is rotated, the centrifugal force is imparted on the fluid in the cavity. Preferably, the helical shape assists in moving fluid through the cavity from the inlet to the outlet. More preferably, there is a plurality of helical shaped cavities. Preferably, there is provided a first raceway between the inlet and the helical cavities. 
     Preferably, the inlet is of a smaller area than the outlet and thereby limiting the amount of fluid that enters the cavity. 
     Preferably, the outlet includes a parting means arranged to portion an inner layer of fluid substantially devoid of the particles from an outer layer of the fluid carrying the particles. More preferably, the parting means is in the form of a blade closely encircling the shaft. Preferably, the outlet includes a chamber at the outlet end of the cavity between the sleeve and the shaft, the chamber arranged to receive a parting means for portioning an inner layer of fluid substantially devoid of the particles from an outer layer of fluid carrying the particles. 
     Preferably, the sleeve is arranged to rotate about its axis relative to the parting means. 
     Preferably, the outer layer is ejected from a first exist of the outlet. Preferably, the parting means includes a turbulence means for slowing the exit of the fluid carrying the particles from the outlet. 
     Preferably, the parting means is arranged to be fixed to a bearing. 
     Preferably, the parting means includes a scoop means for scooping the inner layer of fluid away from the blade to a second exit of the outlet. 
     Preferably, the scoop means is in the form of a plurality of curved channels. Preferably, the scoop means is provided with a second raceway between the curved channels and the second exit. 
     According to a second aspect of the present invention, there is provided a separator and parting means combination, the separating means as defined above and the parting means is arranged to partition an inner layer of fluid substantially devoid at particles from an outer layer of fluid carrying the particles. 
     According to a third aspect of the present invention, there is provided a separator, parting means and a bearing combination, the separator and parting means as defined above, the bearing arranged to receive the inner layer of fluid from the parting means. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     In order to provide a better understanding, preferred embodiments of the present invention will now be described in detail, by way of example only, with reference to the accompanying diagrams in which: 
     FIG. 1 is a cross sectional side view of a separator in accordance with the present invention; 
     FIG. 2 is a complete cross sectional end view of the separator as would be seen from the section X—X of FIG. 1; 
     FIG. 3 is a cross sectional side view of another embodiment of a separator in accordance with the present invention; 
     FIG. 4 is a cross sectional side view of yet another embodiment of a separator in accordance with the present invention; 
     FIG. 5 is a cross sectional side view of the separator of FIG. 4; 
     FIG. 6A is a complete cross sectional end view of the separator as would bee seen from the second Y—Y of FIG. 5; 
     FIG. 6B is a complete cross sectional end view of the separator as would bee seen from the section Z—Z of FIG. 5; 
     FIG. 7 is a cross sectional side view of a bladed portion of a collector of FIG. 5; 
     FIG. 8A is a complete cross sectional end of view of the collector as would be seen from the second S—S of FIG. 7; 
     FIG. 8B is a complete cross sectional end view of the collector as would be seen from the section T—T of FIG. 5; 
     FIG. 9 is a cross sectional side view of another embodiment of a collector in accordance with the present invention; 
     FIG. 10A is a cross sectional side view of a bladed portion of the collector of FIG. 9; 
     FIG. 10B is a cross sectional side view of a clean fluid exit portion of the collector of FIG. 9; and 
     FIG. 11 is a cross sectional side view of a bearing with a rear blade in accordance with the present invention. 
    
    
     Referring to FIG. 1, there is provided a separator  10 A which includes a sleeve  12 . The sleeve  12  is fixed to a propeller shaft  34 . An outer wall of the sleeve  12  defines a cavity  18  between the outer wall and the shaft  34 . The cavity has an inlet  14  at one end and an outlet  16  at another end. The outer wall is of a frustoconical shape with the narrow end of the cone at the inlet  14  and the wide end at the outlet  16 . The inlet  14  is of less area than the outlet  16 . The inlet  14  is a size to allow a desired amount of a slurry of water and particles to enter the cavity  18 . The outlet  16  is of a size so that separated sand particles may be layered circumferentially on the separated water so that the separated water is adjacent a lubricating groove entry  31  of a propeller shaft bearing  30 . 
     The separator is spaced a short distant before a bearing  30  on the shaft  34 . The distance may be, for example, about 1 mm. The spacing allows the sand particles to be laterally ejected from the outlet  16  as indicated by B. 
     Referring to FIG. 2, the separator  10 A includes one or more paddles or veins  20  that project from the shaft  34 . The veins may also allow the sleeve  12  to be fixed to the shaft  34  by, for example, receiving grub screws  38 . In this example, there are three veins, however any suitable number of veins may be used. 
     Referring to FIG. 3, this embodiment of the separator  10 B includes a cylindrical sleeve  12  fixed to the propeller shaft  34 . In this case the cavity  18  is in the form of at least one helix shaped channel  52 . More that one channel may be used, such as three or four, but only one is shown in the diagram for convenience. The inlet  14  is in the form of a raceway having an inwardly directed projection  50 . Only a small gap is provided between the projection  50  and the shaft  34 . This is to limit the size of the particles entering the separator  10  and to limit the intake of fluid. The raceway may be detachable from the rest of the separator. After the gap, there is a circular cavity  51  that allows the fluid to flow freely before entry into the channel  52 . The channel  52  widens slightly along its length so that there is minimal risk of particles becoming stuck in the channel and so that the flow rate of the fluid decreases. For convenience, the widening in the channel is not shown in the diagram. 
     An overhanging extension  20  of the sleeve  12  provides an outlet chamber  17  which forms part of the outlet  16 . Within the outlet chamber  17  there is provided a collector  40  in the form of a blade  54  that surrounds the shaft  34  to portion the separated “clean” fluid from fluid still carrying the particles. In this application only a small amount of fluid is required to lubricate the bearing  30 , therefore only a small amount of clearance is required between the blade  54  and the shaft  34 . However this may vary for other applications. The partitioning of the outlet  16  by the collector  40  provides a means of “peeling” off the inside “clean” fluid which exists the separator through a clean fluid exit  24  of the outlet  16 . Meanwhile the remaining fluid and particles are ejected out of a particle ejection slit  19  of the outlet  16 . 
     Referring to FIG. 4, in this embodiment of the separator  10 C, the sleeve  12  is shorter in length than in the embodiment of FIG.  3  and has three channels  52 . The extension  20  is longer to accommodate a more sophisticated from of the collector  40 . The shaft  34  is shown in phantom. In this embodiment, the collection  40  is longer and includes a plurality of grooves  72 . 
     FIG. 5 shows the separator  10 C without the collector  40 . At the front  11  of the separator the sleeve  12  is chamfered (at  13 ) to assist in streamlining. FIGS. 6A and 6B show the height of the three channels  52  increase along the length of the sleeve  12  so that the area of the channels  52  correspondingly increase along the length of the sleeve  12 . 
     FIG. 7 shows the collector  40  of FIG. 5 in isolation. The grooves  72  extend from the edge  68  of the blade  54  to a raceway  74 . The raceway  74  distributes “clean” fluid that has passed through the grooves  72  so that it may enter the bearing which fits within a collar section  76 . The collar section  76  is fixed to the bearing  32  by a grub screw  80 . 
     The collector  40  is fixed to the bearing  32  and thus does not spin with the shaft  34  and sleeve  12 . The orbiting fluid is more easily scooped when the direction of rotation of the helical shaped grooves  72  are opposite to the direction of rotation of the channels  52 . Where the blade  54  narrows to a thickness equal to the height of the grooves  72 . The grooves  72  create gaps in the blade  54 . The parts of blade between the gaps are finger-like. These fingers further assist is scooping the “clean” fluid into the grooves  72 . A curved surface  62  of the blade  54  extending away from the blade edge  68  parts the particles from the “clean” fluid. 
     Due to the shaft  34  spinning inside the collector  40 , adequate clearance  73  is required between the inner surface of the collector  40  and the shaft  34 . It is however, envisaged that in some applications the collector  40  may be fixed to the shaft  34  rather than the bearing  30 . In this case, the grooves  72  are preferably in the same direction as the channels  52 . 
     FIGS. 8A and 8B show the grooves  72  extending through the collector  40  between the edge  68  and the raceway  74 . The clearance  73  between the shaft  34  and inner surface of the collector  40  can be clearly seen. 
     FIG. 9 shows an alternative form of the collector  40 A which includes a bladed portion  44  and a clean fluid exit portion  44 . These are shown coupled together. 
     FIG. 10A shows the bladed portion  44 , which includes the blade  54  that encircles the shaft  34  by a narrow gap  73 . The bladed portion  44  also includes a step  45  for connecting to the clean fluid portion  46 . An outer surface  63  of the step extends from the curved surface  62 . 
     FIG. 10B shows the clean fluid exit portion  46 , which includes the plurality of grooves  72  that extend from a front  60  of the portion  46  to the raceway  74 . The grooves  72  are helical in shape so as to sweep the fluid therethrough. Alternatively they may be straight and parallel with the shaft  34 . 
     FIG. 11 shows the bearing  30  with a rear blade  90 . There is a raceway  92  that allows fluid that has passed through the lubricating channels  32  to collect and then exit the bearing as shown by D. The rear blade  90  is useful when the shaft is spinning in reverse. Due to the narrow opening between the blade and the shaft  34 , it will act as a simple sieve discouraging particles to travel the wrong way into lubricating grooves  32 . 
     The method of use and operation of the present invention will now be described with reference to the accompanying drawings. 
     A marine craft is propelled forward by propeller  36  mounted on the propeller drive shaft  34 . In the first embodiment, the forward motion causes a slurry of water and sand and possibly other particles to enter the inlet  14  as shown by arrows A. In the second embodiment the helical shape of the channel draws the water and particles into the inlet  14 . Large particles are prevented from entering the raceway by the projection  50 . 
     When the slurry of water and particles enters the cavity  18  either the veins  20  or the helical shaped channels cause the slurry to spin with the rotation of the shaft  34 . The slurry continues to move along the length of the separator  10  either by forward motion, venturi effect described below or the helical shape. As the slurry moves along the length of the separator the widening of the cavity presents an increasing area to the slurry. This causes the flow of the slurry to slow. At the same time, the slurry is orbiting the shaft. Due to the orbiting motion, a centrifugal force acts upon the particles causing them to move closer to the sleeve than the water. This may be more pronounced in the second embodiment where the length of the cavity  18  is greater than the distance between the inlet and outlet due to its helical shape. 
     The particles move along the inside surface of the sleeve until they reach the outlet  16 . Movement of the sand particles may be assisted by the sloping of the inside of the sleeve. In the second and third embodiments, the blade  54  provides a physical partition between the inner “clean” water and the outer slurry. The particles are ejected from the separator as shown by arrow B. Some of the separated clean water may enter the lubricating grooves  32  of the bearing  30  at C. The remainder of the water will also exit the separator with the sand at B. The ejection of the particles and water may cause a venturi effect which causes the slurry to be sucked into and through the cavity  18 . Once the water entering the bearing has passed through the bearing grooves  32  it exits at D. 
     The bearing may be provided with a collector  40  in the form of a projection  42  that projects a short distance into the separator as shown in FIG.  1 . This is thought to assist in the uptake of the separated water into the bearing and also assist in the ejection of the sand particles and corresponding venturi effect. The collector  40  also acts as a partition. The blade  54  in FIG. 3 may be considered a more somewhat sophisticated form of this. The collector in the third embodiment is an even more sophisticated form of partition. 
     An escape passage between the collector  40  and the extension  20  leads from the outlet chamber  17  to the ejection slit  19 . Within the escape passage there is a turbulence means in the form of a series of circumferencial grooves  66  in the outer surface of collector  40 . These grooves  66  create turbulence in the slurry of particles and remaining fluid. The turbulence slows down the slurry flow so that the venturi effect of the ejected particles does not create a suction strong enough to draw fluid in through the bearing  34 . In addition, the turbulence reduces the possibility of particles becoming trapped. After the grooves  66  is an exit chute  64  that opens to the exterior of the separator  10 C and forms the ejection slit  19 . 
     It will be clear to those skilled in the art that the present invention has at least the advantage of reducing the occurrence of said entering the lubricating grooves of the bearing, thereby reducing the wear on the bearing. 
     Modifications and variations will be apparent to those skilled in the art, such as the number of views, the length of each vein or the number of helical channels may vary; the length of the separator may vary provided that the slurry is caused to orbit the shaft and thus introduce the centrifugal separating effect on the sand particles or the form and complexity of portion may also vary. It is envisaged that the separator may find application other than for minimising the amount of abrasive particles entering the lubricating grooves of a propeller shaft bearing. Such other applications may require further modifications. Such modifications and variations are intended to be within the scope of the present invention, the nature of which is to be determined from the foregoing description.