GB2204644A - Reversible-pump impeller - Google Patents

Abstract

The impeller has a reversible shaft 10 driven by a suitable motor or gearbox. A number of vanes 26 are connected drivingly to the shaft for rotation therewith and each vane is capable of limited pivotal movement about a pivot axis normal to the shaft. A lost motion arrangement 12, 18 is provided to cause the vanes to tilt about their pivotal axes to an alternative position each time the direction of rotation is reversed. <IMAGE>

Description

"AXIAL FLOW PUMPS" This invention relates to an axial flow pump.

A swimming pool cleaner employing an axial flow pump to exert a force on the cleaner transverse to the surface on which the cleaner runs, is in use and has been described in U.S.A. patent 4,168,557. In that cleaner there are two motors: one for driving the pump and the other for driving the traction wheels. The use of two motors increases the expense of the cleaner and complicates its design. Unfortunately a single motor cannot be employed as the drive motor for the traction wheels has to be reversible to secure random movement of the cleaner on a pool bottom.

To allow the use of only one motor a reversible axial flow pump would be an advantage.

The present invention provides a reversible pump impeller which includes a driving shaft the axis of which extends in the pumping direction, a plurality of vanes each drivingly connected to the shaft for rotation with the shaft and each mounted for limited pivotal movement about an axis transverse to the pump axis, and a lost motion arrangement which causes the leading edge of each vane to drop with respect to the pumping direction when the direction of rotation of the shaft is reversed.

In one preferred form of the invention, the shaft carries a hub member rotatably thereon and a boss fast thereon, the vanes being pivotably mounted on pivot axles radiating from the hub member and the vanes and boss having interengaging formations which constrain each vane to tilt about its pivot axle as the hub member acquires lost motion relative to the boss and shaft when the direction of rotation of the shaft is reversed. In this form of the invention, each vane may carry a tail which extends in the pumping direction and which locates in a notch in the boss so that lost motion between the hub member and the boss causes the vane to tilt about its pivot axis when the direction of rotation of the shaft is reversed.Furthermore a portion of each tail may locate in a notch in the hub member, abutment of the tail against the sides of this notch upon lost motion taking place defining limit positions for tilting movement of the vane.

It is preferred that each vane has a planar surface facing in the pumping direction and that the vane is symmetrical about a plane at right angles to the planar surface and containing the axis of pivotal movement of the vane. It is also preferred that each vane has a relatively thick central portion accommodating the pivot axle and that the vane tapers down in thickness from its central portion to its radial edges.

The pump impeller of the invention can be located in a casing having a cylindrical outer wall, a central hub and a series of radial walls connecting the hub and outer wall, the hub and the radial walls being located downstream of the impeller with the radial walls serving to guide the pumped flow in the axial direction.

In the accompanying drawings there is shown a particular axial flow impeller in accordance with the invention. In these drawings Figure 1 is an exploded perspective view of the axial flow impeller; Figure 2 is a side view of the impeller of Figure 1 during rotation of the shaft in a first direction; Figure 3 is a view similar to that of Figure 2 but during rotation of the shaft in the opposite direction; Figure 4 is a view of the impeller from the discharge end thereof; and Figure 5 is a cross-sectional view of the impeller in its casing, the section being taken at the line 5-5 in Figure 4.

The illustrated axial flow impeller has a shaft 10 which is driven by means of a suitable reversible motor or gearbox (not shown). Mounted rotatably on the shaft 10 is an annular hub member 12 which is formed with three equi-angularly spaced notches 14 and which is located axially on the shaft by a circlip 13. As illustrated by Figure 1, the notches 14 have tapering sides 16 and, as illustrated by Figure 5, they have a depth which is about half the radial thickness of the hub member 12.

Located adjacent the hub member 12 is a boss 18 which is held fast with the-shaft by means of a screw 20. The boss 18 is formed with three equiangularly spaced recesses 22 each of which has a tapering entrance section 24 and a parallel sided section 26. The shape of a recess 22 is clearly visible in Figures 2 and 3 in which a part of the skirt 24 surrounding the recess is broken away.

The impeller of the invention also includes three vanes 26 each of which is mounted pivotally with respect to the hub member 12 by means of a radial pin 28. The inner end of each pin 28 locates in a hole in the hub member 12 and the vanes are rotatable on the shanks of the pins. Each vane has one planar surface 30 and a relatively thick central portion 32 through which the pin 28 passes. The vanes taper down in thickness from the central portion to their radial edges 34 as is clear from Figures 2 and 3. Each vane is symmetrical about a plane 26 which contains the axis of the relevant pin 28 and which is at right angles to the planar surface 30.

At the inner end of each vane there is a cranked tail 38. A first portion 40 of each tail is located in a notch 14 in the hub member 12 while a second portion 42 extends in the axial direction in a recess 22 in the boss 18. The tapering nature of the notches 14 and entrance sections 24 permits limited side-to-side movement of the tails. Figure 5 shows that there is a small clearance between each portion 42 and the base of the recess 22.

Figure 5 illustrates the impeller casing 44 which has a cylindrical wall 46, a central annular hub 47 and a series of radial walls 48 connecting the hub and the wall 46. The overall diameter of the impeller is slightly less than the internal diameter of the cylindrical wall 46.

In use, the impeller and casing are submerged in the liquid which is to be pumped. With the driving motor rotating the shaft in the direction of the arrow 50 in Figure 2 and with vanes rotating as a result of the action of the recesses 22 on the tails, the vanes have the orientations seen in Figure 2. If the driving motor is now reversed, lost motion between the hub member 12 and the boss 18 causes them to tilt about the axes of the pins 28 to the orientations seen in Figure 3. The provision of the planar surfaces 30 and the symmetrical nature of the vanes results in a continuation of the axial pumping action with no change in the impeller's performance.

The fully tilted positons of the vanes are determined by abutment of the tails 38 with the sides 16 of the notches 14. It will be appreciated that the leading radial edge 34L of each vane drops down with respect to the pumping direction each time the shaft is reversed.

An impeller and casing of the kind described above can be fitted to a pool cleaner of the kind discussed initially and will perform its pumping action irrespective of the direction of rotation of the motor and shaft.

The casing serves the important function of preventing the pumped liquid from spiralling as it leaves the impeller vanes and therefore prevents corkscrewing of the pool cleaner as it moves about on the floor of a swimming pool.

Claims (9)

CLAIMS:

1.

A reversible pump impeller which includes a driving shaft the axis of which extends in the pumping direction, a plurality of vanes each drivingly connected to the shaft for rotation with the shaft and each mounted for limited pivotal movement about an axis transverse to the pump axis, and a lost motion arrangement which causes the leading edge of each vane to drop with respect to the pumping direction when the direction of rotation of the shaft is reversed.

2.

The pump impeller of claim 1 in which the shaft carries a hub member rotatably thereon and a boss fast thereon, the vanes being pivotably mounted on pivot axles radiating from the hub member and the vanes and boss having interengaging formations which constrain each vane to tilt about its pivot axle as the hub member acquires lost motion relative to the boss and shaft when the direction of rotation of the shaft is reversed.

3.

The pump impeller of claim 2 in which each vane carries a tail which extends in the pumping direction and which locates in a notch in the boss so that lost motion between the hub member and the boss causes the vane to tilt about its pivot axis when the direction of rotation of the shaft is reversed.

4.

The pump impeller of claim 3 in which a portion of each tail locates in a notch in the hub member, abutment of the tail against the sides of this notch on lost motion taking place defining limit positions for tilting movement of the vane.

5.

The pump impeller of any one of the preceding claims in which each vane has a planar surface facing in the pumping direction and in which the vane is symmetrical about a plane at right angles to the planar surface and containing the axis of pivotal movement of the vane.

6.

The pump impeller of any one of the preceding claims in which each vane has a relatively thick central portion accommodating the pivot axle and in which the vane tapers down- in thickness from its central portion to its radial edges.

7.

The pump impeller of any one of the preceding claims when located in a casing having a cylindrical outer wall, a central hub and a series of radial walls connecting the hub and outer wall, the hub and the radial walls being located downstream of the impeller with the radial walls serving to guide the pumped flow in the axial direction.

8.

An axial flow pump which includes an impeller according to any one of the preceding claims.

9.

A pump impeller substantially as herein described with reference to the accompanying drawings.