GB2343488A

GB2343488A - Lip seal arrangement

Info

Publication number: GB2343488A
Application number: GB9925353A
Authority: GB
Inventors: Karl Frauhammer; Gerhard Meixner; Joerg Friedrich; Andreas Strasser
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1998-11-06
Filing date: 1999-10-26
Publication date: 2000-05-10
Anticipated expiration: 2019-10-26
Also published as: CH693512A5; DE19851342C1; GB9925353D0; GB2343488B

Abstract

A sealing arrangement for the radial gap (18) between two machine parts (13, 15) which are rotatable relative to one another, in particular, between a gear compartment (11) and a motor compartment (12) of an electric tool. The sealing arrangement comprises at least one lip seal (20), having a basic body and a relatively flexible sealing edge (23) which, in a sealing position, is in contact with one of the machine parts, preferable a shaft. An assembly support (27) is provided which, during assembly of the sealing arrangement (10), via projection (28), lifts the sealing edge (23) off the machine part (15). In a sealing position of the sealing arrangement (10) the projection engages radially into a recess (29) formed by a circumferential turned groove in the machine part (15). In this position the sealing edge (23) comes into contact with the machine part (15). The assembly support may comprise a projection formed on the lip seal or a separate assembly ring, Fig 3 (31), with at least one extension (32), which during assembly lies radially between the sealing lip (22) and the machine part (15). In said manner, damage to the sealing edge (23) is prevented during assembly of the sealing arrangement.

Description

2343488 Sealing arTangement

Background art

The invention relates to a sealing arrangement for the radial gap between two machine parts which are rotatable relative to one another, in particular for the seal between a gear compartment and a motor compartment of an electric tool. For said type of application, a multitude of different seals are already generally known.

In addition to sealed bearings, return systems, labyrinth seals and felt rings, rotary shaft lip seals are also known. In electric tools, where mostly the oil- or greasefilled gear compartment is to be sealed off from the motor compartment, increasing use is being made of rotary shaft lip seals, which have a good sealing function. 15 Said rotary shaft lip seals however have the drawback of relatively high friction with the associated heat output. Furthermore, rotary shaft lip seals mostly have delicate sealing edges which may easily become damaged during assembly, thereby impairing the sealing function. 20 To minimize the friction output, it is desirable to keep the diameter of the sealing face as small as possible. However, an obstacle in the way of achieving that is that, in order to prevent the sealing edge from becoming damaged during assembly of the lip seal, the sealing faces are to be set back as far as possible from the 25 hazardous regions of the shaft, such as for example the sharp-edged teeth of a motor pinion. This leads in practice to a larger diameter of the sealing faces than would actually be necessary. Thus, the advantage of simplified assembly of the 2 rotary shaft lip seals entails the drawback of an increased heat output and the associated impairment of service life and quality.

Advantages of the invention In contrast, the sealing arrangement having the features of claim I has the advantage that the design of the rotary shaft lip seal may be effected in an optimum manner without considering quality-impairing assembly conditions. The delicate sealing edge of the lip seal during assembly is lifted over the hazardous 10 regions of the shaft and only in the sealing position is lowered onto the sealing face. By virtue of said procedure it is possible to minimize the diameter of the sealing face. T'he sliding speed and the heating at the sealing edge are in said case likewise minimized, with the result that the service life and the quality may be increased. 15 Drawings Two embodiments of the invention are illustrated in the drawings and described in detail below. Figures I and 2 show a longitudinal section through a sealing 20 arrangement according to a first embodiment and Figures 3 and 4 a longitudinal section through a sealing arrangement according to a second embodiment.

Description of the embodiments a

In Figures I to 4, the seal between a gear compartment I I and a motor compartment 12 of an electric tool is illustrated as an example of the application of a sealing arrangement 10. The gear compartment I I is separated from the motor compartment 12 by a housing 13. Situated 'in the housing 13 is a through- 3 opening 14, through which a motor shaft 15 engages. The housing 13 is an external machine part and the motor shaft 15 an internal machine part of two machine parts which are rotatable relative to one another.

A fan impeller 16 for cooling a drive motor, which is not shown in the drawings, is disposed in the motor compartment 12 on the motor shaft 15. Situated on an end of the motor shaft 15 remote from the drive motor is a driving pinion 17, which is used to drive a non-illustrated gear unit of the electric tool disposed in the gear compartment 11. 10 The drive parts accommodated 'in the gear compartment I I need to be reliably lubricated with oil or grease. The sealing arrangement 10 is intended to prevent said lubricant from being able to pass from the gear compartment I I through the through-opening 14 into the motor compartment 12. 15 The motor shaft 15 in the region of its engagement through the housing 13 has a smaller diameter thari the through-opening 14, with the result that a radial gap 18 is formed between motor shaft 15 and housing 13. A rolling- contact bearing 19 and a lip seal 20 are disposed in said gap 18. The lip seal 20 substantially 20 comprises a basic body 21, which is supported radially against the throughopening 14. Connected to the basic body 21 is a sealing lip 22, which in the vicinity of its free end has a sealing edge 23 directed towards the motor shaft 15. Figures I and 3 show the sealing arrangement 10 in each case in the course of its 25 assembly. During assembly, first the rolling-contact bearing 19 and the lip seal 20 are preassembled in each case in the through-opening 14. Then the motor shaft 15 is inserted "in the direction of an arrow 24 into the through- opening 14. The 4 result, from the point of view of the sealing body 20, is therefore an assembly direction 25 counter to the direction of the arrow 24.

The sealing lip 22 sticks out viewed in assembly direction 25, axially rearwards and at the same time is inclined towards the motor shaft 15. The sealing lip 22 is of a flexible construction so that it may yield radially outwards during the insertion movement of the shaft 15.

To prevent the sealing edge 23 of the sealing lip 22 from being damaged by teeth 26 of the driving pinion 17 during insertion of the motor shaft 15, the sealing arrangement 10 is provided with an assembly support 27. In the first embodiment according to Figures I and 2, the assembly support 27 is formed by a projection 28 which, viewed in assembly direction 25, hes axially in front of the sealing edge 23 and is directed substantially radially inwards. The projection 28 is of an is annular design. It may however alternatively be subdivided into a plurality of segments.

As the motor shaft 15 is assembled by being inserted through the throughopenmig 14, the projection 28 is supported against the driving pinion 17, wherein the sealing edge 23 is simultaneously lifted off the motor shaft 15 and damage to the sealing edge 23 is thereby prevented. As soon as the sealing arrangement 10 has reached its sealing position as shown in Figure 2, the projection 28 engages into a radial recess 29 in the motor shaft 15, with the result that the sealing edge 23 then comes into sealing contact with the motor shaft 15. To said end, the sealing edge 23 is in a known manner preloaded 'in a radially inward direction by a spring lock washer 30. The recess 29 preferably takes the form of a circumferential turned groove.

The embodiment illustrated in Figures 3 and 4 differs from the first embodiment only in respect of the construction of the assembly support 27. Otherwise, identical and identically acting parts are denoted by the same reference characters.

In Figures 3 and 4, the assembly support 27 is formed by a separate assembly ring 3 1, which has an extension 32 projecting radially inwards. Said extension 32 is markedly longer than the radial width 'in the gap 18 so that, during insertion of the motor shaft 15 and assembly of the sealing arTangement 10 in assembly direction 25, the extension 32 is bent axially rearwards and lies radially between motor shaft and sealing lip 22, with the result that the sealing edge 23 likewise lifts off the driving pinion 17.

Whereas in the first embodiment according to Figures I and 2 a special sealing body 20 with a suitable projection 28 on the sealig lip 22 is required, in the second embodiment according to Figures 3 and 4 a conventional lip seal may be is used. In both cases, after assembly the assembly support 27 may remain in the appliance without causing any disruption.

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Claims

1. Sealing arrangement for the radial gap (18) between two machine parts (13, 15) which are rotatable relative to one another, in particular for the seal between a gear compartment (11) and a motor compartment. (12) of an electric tool, having at least one lip seal (20) provided with a sealing edge (23), which in a sealing position of the sealing arrangement (10) is in contact with one of the machine parts (13, 15), preferably with an internal machine part (15) in the form of a shaft, and having an assembly support (27) which, during assembly of the sealing arrangement (10), lifts the sealing edge (23) off the machine part (15), wherein the assembly support (27) in the sealing position of the sealing arrangement (10) engages radially into a recess (29) in the machine part (15), with the result that the is sealing edge (23) then comes into contact with the machine part (15).

2. Sealing arrangement according to claim 1, characterized in that the sealing edge (23) is disposed on a sealing lip (22) of the sealing body (20), and that the lip seal (20) has a basic body (2 1), to which the sealing lip (22) is connected.

3. Sealing arrangement according to claim 2, characterized in that the sealing lip (22) sticks out viewed in assembly direction (25), axially rearwards from the basic body (21) and is inclmied substantially radially mwards and is flexible relative to the basic body (2 1).

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4. Sealing arrangement according to claim 3, characterized 'in that the assembly support (27) is formed by a projection (28), which is formed on the lip seal (20) and lies, viewed in assembly direction (25), axially in front of the sealing edge (23).

5 5. Sealing arrangement according to claim 3, characterized in that the assembly support (27) is formed by a separate assembly ring (3 1), which is disposed, viewed in assembly direction (25), axially in front of the lip seal (20) and which has at least one extension (32), which during assembly of the sealing arrangement (10) lies radially between sealing lip (22) and machine part (15).

6. A sealing arrangement substantially as herein described with reference to the accompanying drawings.

6. Sealing arrangement according to claim 1, characterized in that the recess (29) is formed by a circumferential turned groove.