GB2121109A - Worm pumps for pneumatic conveyors - Google Patents

Abstract

In a worm pump, for charging pneumatically transportable bulk material into a conveyor duct, of the kind having a worm mounted on each side of a delivery housing 2 and a nonreturn valve 3 in the delivery housing, the delivery housing is constructed in the form of a spiral, as viewed in the pump cross-section. This expedient helps to reduce the friction losses which occur when bulk material is discharged from the delivery housing, and in consequence helps to reduce the energy requirements of worm pumps with twin worms. Air is supplied to the conveyor duct via air permeable walls 7, 8. <IMAGE>

Description

SPECIFICATION Worm pump with worm mounted on both sides The invention relates to a worm pump for the charging of pneumatically transportable bulk material into a conveyor duct, of the kind having a worm mounted on both sides of the pump and a nonreturn charging valve in the delivery housing.

Worm pumps are used to charge bulk materials which are to be transported in pneumatic conveying equipment. For such operations, the charging valve of the pump has to seal against the differential pressure between the conveyor duct and the surroundings. Some worm pumps have an overhung mounting and in others the conveyor worm is mounted on both sides of the pump. The present invention is concerned with this latter category of worm pumps.

In a worm pump with a worm mounted on both sides of the delivery housing, a reorientation of the direction of travel of the transported material is necessary from the conveying direction of the worm into the conveyor duct. Since most bulk materials can only be re-routed with difficulty in the compressed state, high expenditure of energy has been necessary to achieve this reorientation.

In contrast, the energy requirements of worm pumps with a worm mounted on one side only are less. However, pumps with worms mounted on both sides, such as for example that shown in DE-PS 24 56 476, have the advantage that the worm shaft is better and more securely mounted.

The object of the invention is to reduce or even eliminate substantially completely the additional bulk material resistance which occurs on discharging in pumps with a worm mounted on both sides.

In accordance with the present invention, the delivery housing, as viewed in the pump cross section, is constructed in the form of a spiral. In consequence of this expedient, the delivery head of the pump can be very small; the plug in the delivery housing likewise can be very small, and consequently the frictional losses, which arise on discharging, can be reduced to a minimum.

In the preferred embodiment of this invention, the delivery opening of the spiral housing is rectangular and in the closed position is sealed as tightly as possible on the worm circumference by a hinged nonreturn valve lying obliquely to the conveying direction.

A particular advantage of this arrangement is that the rectangular nonreturn valve which closes the delivery opening of the spiral housing lies parallel to the axis of the conveying duct connection in the open state and returns to the closed position through an angle which is less than 90".

According to a particular embodiment of the invention, a ventilation box is connected to the delivery housing behind the nonreturn valve in the conveying direction. The inner walls of the ventilation box are gas-permeable and at least a part of the delivery air is blown through these inner walls. By means of this arrangement delivery gas, normally air, can be fed to the delivered material from all sides of the pump outlet, whereby the material discharged from the worm housing can be sufficiently loosened up. When a rectangular pump outlet is provided, rectangular sinter plates or fabric can be used as loosening units.

With short conveying distances, the entire delivery air can be introduced through porous walls of the ventilation box. Both sinter plates and also fabric can be produced with various degrees of permeability to air, so that adaptation to the required quantity of delivery air is possible.

In the event of a larger quantity of delivery air being necessary, the additional delivery air can be added through a ring nozzle arranged between the delivery housing and the conveyor duct. Such a ring nozzle can be constructed both angular and round.

If required, it is also possible to use a ring nozzle with a variable air gap.

In order to further improve the discharging of the delivered material from the worm housing via the spiral delivery housing, at least one curved vane can be provided on the worm shaft in the region of the delivery opening. Both one or several vanes can be expedient here, depending on the size of the worm and the worm capacity. These vanes are used advantageously in particular in the case of worm pumps with two worm inlets and oppositely oriented worms.

The delivery housing can be placed in a horizontal outlet position or in any other conveying direction, i.e. vertically upward or at any other desired orientation, through which possibly a conveyor duct bend can be dispensed with.

It is particularly advantageous to construct the delivery housing in the upper region to be of complementary form to that of the nonreturn valve, so that the nonreturn valve can be received therein in its open state. The valve itself, in its open state, then forms the upper wall of the delivery housing.

The two bearings of the mounting shaft of the nonreturn valve are advantageously mounted eccentrically, thereby to facilitate the adjustment of the valve to achieve a problem-free sealing surface between the valve and the delivery housing.

If at least the part of the delivery housing which is constructed of complementary form to the nonreturn valve is made so as to be penetrable by air, then during the conveying, a quantity of air will flow through this region, to help prevent dust accumulating in this space and obstructing the nonreturn valve in its movement.

In the case of worm pumps with a worm mounted on both sides and with only one worm inlet, a disc can be fitted on the worm shaft in the delivery opening in the diameter of the worm channels, which disc on the reverse side has additional, narrow, curved vanes. By this means. it is possible to avoid the stuffing box in front of the worm end bearing being directly loaded by the full pressure of the conveyed material.

These vanes, the disc and the reverse vanes can also be firmly connected with the last worm vane, i.e. the worm end vane, and consequently can be quickly interchangeably mounted so as to be force-locking onto the worm shaft as a wearing part.

An embodiment of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 shows the delivery housing of a worm pump of this invention in cross section; Figure 2 shows the worm and the delivery housing in longitudinal section; and Figure 3 shows in cross section a modified delivery housing provided with curved vanes.

Referring to the drawings, bulk material to be conveyed is pressed, with the aid of the worm 1, into the delivery housing 2. Until a sealing plug of conveyed material has formed in the delivery housing 2, the nonreturn valve 3 prevents the recoil of delivery air from the conveying duct via the conveyor worm to the conveyed material discharge.

In the delivery housing 2, the conveyed material has to change its direction of conveyance by 900.

The spiral-shaped wall 4, and in the embodiment of Figure 3 the curved vanes 5, facilitate the reorientation operation. In Figure 1 the nonreturn valve 3 is also to be seen in its raised i.e. open state as indicated by the dotted outline; here it becomes clear that the surface 6 of the nonreturn valve 3 in the raised state conforms to the shape of the upper wall of the delivery housing. A ventilation box having an upper air-permeable wall 7 and air-permeable lower and side walls 8 and 9 communicates with the housing 4 behind the valve 3. Through the upper wall 7 air arrives both into the space behind the nonreturn valve and also into the conveying chamber. Through the remaining walls 8 and 9, delivery air arrives exclusively into the conveyor duct. In the case of a particularly large requirement for delivery air, additional delivery air can be blown into the conveyor duct through the ring nozzle 10 which is provided downstream of the ventilation box.

Claims (11)

1. A worm pump for charging pneumatically transportable bulk material into a conveyor duct and having a worm mounted on both sides and a nonreturn valve in the delivery housing of the pump, characterized in that the delivery housing is constructed in the form of a spiral as viewed in the pump cross-section.

2. A worm pump according to Claim 1, characterized in that the delivery opening of the spiral housing is rectangular.

3. A worm pump according to Claim 2, characterized in that a hinged, rectangular nonreturn valve is provided to seal the delivery opening of the spiral housing, the valve in its open position lying parallel to the axis of the conveyor duct connection and moving to its closed position through an angle which is smaller than 90 .

4. A worm pump according to any preceding claim, characterized in that the delivery housing is connected to a ventilation box, the inner walls of which are permeable to air and through which at least a part of the delivery air is adapted to be blown.

5. A worm pump according to Claim 4, characterized in that a ring nozzle for additional delivery air is provided downstream of said ventilation box.

6. A worm pump according to any preceding claim, characterized in that at least one curved vane is mounted on the worm shaft in the region of the delivery opening.

7. A worm pump according to Claim 3,or any one of Claims 4-6 when appendant to Claim 3, characterized in that the upper region of the delivery housing is of complementary shape to that of the nonreturn valve whereby in its open state the valve is received therein.

8. A worm pump according to Claim 7, characterized in that the nonreturn valve is hinged from an eccentrically-mounted shaft.

9. A worm pump according to Claim 7 or Claim 8, characterized in that at least a part of said upper region of said delivery housing is permeable to air.

10. A worm pump according to Claim 6, characterized in that in the delivery opening of the worm shaft in addition a disc is fitted in the diameter of the spiral channels, which on the reverse side has additional, narrow, curved vanes.

11. A worm pump substantially as hereinbefore described with reference to Figures 1 and 2 or Figure 3 of the accompanying drawings.