GB2202005A

GB2202005A - Pump

Info

Publication number: GB2202005A
Application number: GB08705895A
Authority: GB
Inventors: Thomas Fielder Fuggle; John Barry Westwood
Original assignee: SSP PUMPS; SSP PUMPS Ltd
Current assignee: SSP PUMPS; SSP PUMPS Ltd
Priority date: 1987-03-12
Filing date: 1987-03-12
Publication date: 1988-09-14
Anticipated expiration: 2007-03-12
Also published as: GB2202005B; GB8705895D0

Abstract

A rotary lobe pump for pumping chocolate has a rotor housed in a rotor housing 2 and attached to a shaft 14 passing through said rotor housing 2, the shaft being sealed by means of a composite seal which comprises a labyrinth seal ring 6, a lip seal ring 7 and a mechanical seal 10, the annular chamber formed between the lip seal and mechanical seal being filled with an edible grease and the mechanical seal being operative to prevent leakage of said grease from said chamber. <IMAGE>

Description

"PUMP" This invention relates to a pump, and more particularly, a pump for pumping chocolate or similar foodstuffs.

Previous chocolate pumps have been unsatisfactory in that mechanical shaft seals have failed after a very short time. Cocoa butter separates out of the chocolate and shows as a yellow fat on the atmosphere side of the seal.

This is followed by precipitation of residual "burnt" sugar in the form of carbon deposits which causes rapid failure of the seal faces and leakage of pumped chocolate.

Alternatively, pumps have been manufactured having packed-gland type seals. However, no suitable packing material has been found and the packing material has invariably leaked causing degradation of leaking chocolate and rapid seal failure. The abrasive effect of the carbon and sugar deposits in the chocolate is emphasized by the fact that the pump is kept at a sufficiently elevated temperature to keep the chocolate fluid and pumpable.

Whereas prior to the present invention rotary pumps pumping chocolate at pressure have had their seals fail regularly after 2 to 3 days use, pumps embodying the present invention have been found to operate leak free for many months when under test.

According to the present invention, there is provided a pump having a ureter housed in a rt6f hôlleing and attached to a drive shaft passing through said rotor housing, the shaft being sealed to the housing by means of first and second seal means having an annular chamber formed therebetween such annular chamber being filled with an edible grease, the second seal means being operative to prevent leakage of said grease from said chamber to the exterior of the pump.

In order that the invention may be more readily understood, the following is given merely by way of example with reference to the accompanying drawing, in which the sole figure shows an axial section of the pump shaft seal.

The preferred chocolate pump is a rotary lobe pump although other types of pump may be used. The rotor 15 is fitted on a shaft 14 passing out through rotor housing 2. An optional sleeve 5 on the shaft is sealed by an 0-ring 13 and extends through a shaft seal to prevent leakage of the pumped chocolate. Instead of using the sleeve 5 as illustrated the sleeve may be omitted with the sealing means to be described engaging directly with the shaft instead of with the sleeve on the shaft. The seal is a composite seal housed in a housing 1 which is attached to the pump rotor housing 2 by means of studs 3 and nuts 4.

Chocolate which may leak along the shaft sleeve 5 from inside the rotor housing 2 first passes a labyrinth header ring 6 before encountering a resilient lip seal 7. The lip seal 7 is held by a retaining ring 8 and is kept in sealing engagement with the sleeve 5 by a garter spring 9. At the atmosphere side of the composite seal there is a mechanical seal 10 having a rotary portion sealed to the sleeve 5 by a rotary 0-ring 11 and a stationary portion of the seal sealed to the housing 1 by a stationary 0-ring 12. The rotary portion comprises a ring 16 having a sealing sliding engagement with the stationary portion and also includes a resilient rotary element 18 which is under compression to urge the ring 16 into sealing engagement with the stationary portion of the seal.The element 18 and ring 16 both have apertures engaged by grub screws 17 dimpled to the sleeve 5 to ensure the rotary portions of the seal will rotate with the shaft. The element 18 has a radially extending flange held in sliding engagement with an annular projection from the lip seal retainer 8. An annular chamber is formed between the lip seal 7 and the mechanical seal 10 and is packed with an edible grease. A suitable grease is sold under the name MOBIL GREASE FM2. The annular chamber is refillable with the grease via grease nipples 13 or other grease devices suitably placed around the housing 1. The grease will not leak past the mechanical seal 10, nor does it have a degrading effect on the seal. The chocolate is unable to displace the edible grease which acts as a buffer and thus the pump is reliably sealed even when the chocolate has caused some wear of the labyrinth header ring 6 and the lip seal 7.

Claims

1. A pump having a rotor housed in a rotor housing and attached to a drive shaft passing through said rotor housing, the shaft being sealed to the housing by means of first and second seal means having an annular chamber formed therebetween, such annular chamber being filled with an edible grease, the second seal means being operative to prevent leakage of said grease from said chamber to the exterior of the pump.

2. A pump according to claim 1, wherein first seal means comprises a first seal ring and a lip seal, the chamber being located between the lip seal and the second seal means.

3. A pump according to claim 2, wherein said first seal ring is a labyrinth seal ring.

4. A pump incorporating a seal constructed and arranged to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.

4. A pump according to any one of the preceding claim, wherein the second seal means comprises a mechanical seal.

5. A pump according to claim 4 wherein said mechanical seal has a rotary portion sealed to the shaft by a rotary 0-ring and a stationary portion sealed to the housing by a stationary 0-ring.

6. A pump according to any preceding claim which is a rotary lobe pump suitable for pumping chocolate.

7. A composite shaft seal having first sealing means comprising a labyrinth header ring and a lip seal, and second sealing means comprising a mechanical seal ring, a chamber defined between said first and second sealing means being filled with an edible grease.

8. A seal according to claim 7 wherein said mechanical seal comprises a rotary portion sealed to the shaft by means of a rotary 0-ring and a stationary portion sealed to the seal housing by means of a stationary 0-ring.

9. A seal substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.

10. A pump incorporating a seal according to any one of claims 7, 8 or 9.

Amendments to the claims have been filed as follows CLAIMS

1. A pump having a rotor housed in a rotor housing and attached to a drive shaft passing through said rotor housing, the shaft being sealed to the housing by means of first and second seal means having an annular chamber formed therebetween, said first seal means comprising a labyrinth seal ring and a lip seal, the chamber being located between the lip seal and the second seal means which itself comprises a mechanical seal, and said annular chamber being filled with an edible grease, the second seal means being operative to prevent leakage of said grease from said chamber to the exterior of the pump.

2. A pump according to claim 1, wherein said mechanical seal has a rotary portion sealed to the shaft by a rotary O-ring and a stationary portion sealed to the housing by a stationary O-ring.

3. A pump according to either preceding claim which is a rotary lobe pump suitable for pumping chocolate.