GB2545574A

GB2545574A - Seal

Info

Publication number: GB2545574A
Application number: GB1621661.6A
Authority: GB
Inventors: Gibbs Paul; Saysell David; Austin Adam
Original assignee: Romax Technology Ltd
Current assignee: Romax Technology Ltd
Priority date: 2015-12-17
Filing date: 2016-12-19
Publication date: 2017-06-21
Anticipated expiration: 2036-12-19
Also published as: GB2545574B; CN209354617U; WO2017103911A1; GB201522331D0; GB201621661D0

Abstract

A sealing arrangement for a gearbox 100 comprising a housing 108 and a shaft 102. The arrangement includes a sealing unit 106 located on the shaft between the gearbox housing and an exterior of the gearbox 110. The sealing unit has an air path 112 which flows between an interior and an exterior of the gearbox. This path changes the velocity of air moving across the unit in response to an external pressure pulse to reduce air-borne lubricant loss from the gearbox. The path may be tortuous and have one or more chambers 107 or baffles. There may also be a cyclonic air oil separator at the end of the air path. Preferably the effective distance through which the pressure pulse occurs reduces the velocity of the air sufficiently to allow time for the air-borne lubricant droplets to precipitate within the sealing unit. The arrangement may also have surfaces or pipes for recirculating caught oil into the gearbox. The invention is consider particularly relevant to high speed trains where negative pressure can be formed outside the gearbox as the train passes trackside objects, forcing gas from inside the gearbox out through the seal.

Description

Seal

Technical Field

The present invention relates to sealing arrangements for gearboxes, and in particular to seals between a rotatable member and a housing, in which there is a pressure differential between the inside and outside of a gearbox.

Background Art

Where there is an air pressure differential between the inside and outside of a gearbox, fluid, particularly lubricant or oil, will flow from high to low pressure. If the pressure difference is high, or fluctuates, oil can be ejected from the gearbox. This occurs because the oil is carried in the flow of air, or blocks the progress of the air and is then forced out with it.

Leaking oil causes many problems, including environmental contamination and reduces the amount of available lubricant inside the gearbox.

This is a particular concern for high speed trains, as a negative pressure can be formed outside the gearbox as the train passes trackside objects, tunnels or other trains, for example. The speed of the train can also create wakes, vortices and other low pressure areas near the gearbox.

Disclosure of Invention

According to an aspect of the present invention, there is provided a sealing arrangement for a gearbox comprising a housing and a shaft. The sealing arrangement comprises a sealing unit located on the shaft between the gearbox housing and an exterior of the gearbox, the sealing unit comprising an air path between an interior and the exterior of the gearbox. In use, the air path reduces a velocity of air moving across the sealing unit in response to a pressure pulse exterior to the gearbox, to reduce air-borne lubricant loss from the gearbox.

Preferably, the air path is tortuous. Preferably, the air path comprises one or more chambers. Preferably, the air path comprises one or more baffles. Preferably, the air path comprises a cyclone.

Brief Description of Drawings

The present invention will now be described, by way of example only, with references to the accompanying drawings, in which:

Figure 1 is a cross section of one embodiment of a sealing unit of the present invention;

Figure 2 is a cross section of a further embodiment of a sealing unit of the present invention;

Figure 3 is a diagrammatic representation of a cyclone device of the prior art;

Figure 4 is a cross section of a further embodiment of a sealing unit of the present invention; and

Figure 5 is a cross section of a further embodiment of a sealing unit of the present invention.

Best Mode for Carrying Out the Invention

Referring to Figure 1, which shows part of a gearbox 100 having a shaft 102 supported on one or more bearings 104, a sealing unit 106 is mounted between a gearbox housing 108 and an exterior 110 of gearbox 100 serves to prevent leakage of lubricant from the gearbox into an external environment. The sealing unit comprises passages 112 which define an air path, as shown by the arrows. Any lubricant-laden air, for example, oil-laden air exiting an inside 114 of gearbox 100 via oil seal 116 enters passage 112 between an inside 114 and an exterior 110 of the gearbox. Passage 112 is much larger in area than oil seals, typically labyrinth seals, 116 which allows the movement of large volumes of air with a low velocity, and causes oil droplets in the air flow from the gearbox to precipitate out inside sealing unit 106. In this particular example, the oil path traverses the sealing unit twice before the air exits sealing unit 106 at 120. Depending on the application and the size of the pressure pulse, an oil path may be formed which traverses sealing unit 106 just once, or which may traverse sealing unit 106 more than twice. Oil captured in sealing unit 106 can be returned to gearbox 100. This means that air exiting at 120 contains little if any oil.

Referring to Figure 2, which shows another embodiment of a sealing unit 106 between a gearbox housing 108, and an external environment 110, in which sealing unit 106 comprises one or more chambers 107 having a large-volume (compared to normal labyrinth seals) chamber(s) that allow a pressure differential across the unit. Chambers 107 act to damp out any pressure pulse coming from outside, keeping the velocity of the air nearer to the gearbox closer to its original state. This means that air exiting at 120 contains little if any oil.

The oil path is shown as being first in one direction and then in another direction. Other arrangements are also possible, for example the passages may move the air in a circular direction as in a cyclone device shown in Figure 3. This has a vortex chamber 300, an air input 302, an air output 304 and an output for particulate matter, such as drops of oil, 306.

Referring to Figure 4, which shows another embodiment of a sealing unit 106 between a gearbox housing 108, and an external environment 110, in which sealing unit 106 comprises vortex chamber 300 of the kind shown in Figure 3. Passage 112 is connected to input 302 of the vortex device, which causes air escaping the gear box to move in a vortex. Oil-free air exits at 120, and recovered oil is collected at 122 and can be returned to the gearbox. This means that air exiting at 120 contains little if any oil.

Referring to Figure 5, which shows another embodiment of a sealing unit 106 between a gearbox housing 108, and an external environment 110, in which sealing unit 106 comprises one or more baffles 502. These serve to slow the airflow and cause oil droplets to precipitate out of the airflow.

The key thing is that the passageways in the sealing unit act to change the velocity of air passing through them so that the quantity of oil carried in the air is reduced as the velocity of the air is reduced.

The present invention differs from prior art seals as follows: 1) There is a tortuous path for the air. The oil is suspended in the air, or “fired” with air pressure. By providing a tortuous path the velocity of the air is changed locally, allowing the momentum of the oil to carry it out of the airflow. 2) There are large-volume (compared to normal labyrinth seals) chamber(s) that allow a pressure differential across the unit. These act to damp out any pressure pulse coming from outside, keeping the velocity of the air nearer to the gearbox closer to its original state. 3) Baffles are used in conjunction with the chambers to further damp the airflow and catch oil on its way out 4) Openings to the outside and to the gearbox (with or without normal seals) are much larger in area than labyrinth seals. This is to allow the movement of large volumes of air with a low velocity. 5) Because of the larger clearances and chambers these units do not require precision machining and can be easily retro-fitted.

The invention includes surfaces and a pipe(s) for recirculating the caught oil into the gearbox.

Industrial Application

The sealing arrangement can be used in any application where a non-contact oil seal is required and pressure differences/fluctuations are expected.

Increasing the effective distance through which the pressure pulse occurs reduces the velocity of air through the sealing unit, which allows time for air-borne air droplets to precipitate within the sealing unit.

Claims

1. A sealing arrangement for a gearbox comprising a housing and a shaft, the sealing arrangement comprising: a sealing unit located on the shaft between the gearbox housing and an exterior of the gearbox, the sealing unit comprising an air path between an interior and the exterior of the gearbox; wherein, in use, the air path changes a velocity of air moving across the sealing unit in response to a pressure pulse exterior to the gearbox, to reduce air-borne lubricant loss from the gearbox.

2. A sealing arrangement according to claim 1, in which the air path is tortuous.

3. A sealing arrangement according to claim 2, in which the air path comprises one or more chambers.

4. A sealing arrangement according to any preceding claim, in which the air path comprises one or more baffles.

5. A sealing arrangement according to any preceding claim, in which the air path comprises a cyclone.

6. A sealing arrangement according to any preceding claim, in which the effective distance through which the pressure pulse occurs reduces the velocity of air through the sealing unit, allowing time for air-borne air droplets to precipitate within the sealing unit.