GB2116634A - Rotary positive-displacement fluid-machines - Google Patents

Abstract

In a Roots-type compressor the shafts 8, 9 of the rotors are supported by "rolling" bearings 10 and a lipped sealing-gland 14 associated with each bearing separates the bearing lubricating environment from an annular chamber 15, which is adjacent the rotor chamber 7 and substantially isolated therefrom by a labyrinth seal 16. The annular chamber communicates with the atmosphere through a hole (18), Fig.2 (not shown), so as to prevent the lip of the sealing gland from being subjected to excessive loads owing to negative or positive pressures transmitted from the rotor chamber past the labyrinth seal. <IMAGE>

Description

SPECIFICATION Rotary volumetric compressor of the Roots type The present invention relates to a rotary volumetric compressor of the Roots type, comprising a support structure, two rotors mounted rotatably in a chamber within the support structure, and a pair of shafts connected to the two rotors and having their ends mounted rotatably in the support structure by means of rolling bearings, in which a lipped sealing gland is provided at each end of the shafts to separate the lubricating environment of the bearing from a respective annular chamber which is adjacent the chamber of the two rotors and is isolated therefrom by a labyrinth seal.

The object of the present invention is to prevent the lips of the sealing glands from being subjected to excessive loads (which would reduce the effectiveness and/or the lifetime of the glands), as a result of the pressures or pressure drops which occur in the rotor chamber during operation of the compressor.

In orderto achieve this object, the invention provides a compressor of the aforesaid type, characterised in that the annular chamber adjacent each lipped sealing gland communicates with a respective hole formed through the support structure to the exterior.

The present invention will now be described with reference to the appended drawings, provided purely by way of non-limiting example, in which: Figure lisa partially sectioned view of a com pressor according to the present invention, and Figure 2 is a section taken on the line ll-ll of Figure 1.

In the drawings, there is shown a rotary volumetric compressor of the Roots type, generally indicated 1, usable, for example, for supercharging an internal combustion engine.

The compressor 1 comprises a support structure 2 including an externally-finned casing 3 closed at one end by a cover 4 and at the opposite end by a plate 5 and a cover 6.

The casing 3 has an internal chamber 7 housing the two rotors (not visible in the drawings) of the compressor.

The two rotors of the compressor are connected for rotation with two shafts 8,9 the ends of which are mounted rotatably within the plate 5 and the cover 4, respectively, by means of rolling bearings 10.

The shaft 8 has one end 8a projecting from the cover 6, onto which is keyed a gear wheel 11 for connection by a cogged belt to the driving shaft or cam shaft of the engine with which the compressor is associated.

The drive is transmitted from the shaft 8 to the shaft 9 through the meshing of two gear wheels 12, 13 connected for rotation with the shafts.

With each rolling bearing 10 is associated a lipped sealing gland 14 which separates the lubricating environment of the respective bearing from an annular chamber 15 adjacent the chamber 7 of the two rotors.

Each annular chamber 15 is isolated from the chamber 7 of the rotors by a double labyrinth seal 16.

In the case of the two sealing glands 14 mounted in the plate 5, each double labyrinth seal 16 is formed between the outer surface of a tubular spacer 17 (interposed coaxially of the respective shaft between the bearing and the rotor) and the surface of the hole in the plate 5 in which the spacer 17 is mounted. In the case of the sealing glands 14 mounted in the cover 4, however, each labyrinth seal 16 is formed between the outer surface of the respective shaft and the surface of the hole in the cover 4 in which the shaft is mounted.

In order to prevent the pressures or pressure drops existing in the rotor chamber 7 of the com pressorfrom being transmitted through the labyrinth seal 16 to the annular chambers 15, thereby subjecting the lips of the sealing glands 14 to excessive loads which would render the seals unreliable, each annular chamber 15 (see Figure 2) communicates with a hole 18 formed through the support structure (or, more precisely, the plate 5 or the cover 4) to open onto the outer surface 19 of the compressor.

1. Rotary volumetric compressor of the Roots type, comprising a support structure, two rotors mounted rotatably in a chamber within the support structure, and a pair of shafts connected to the two rotors and having their ends mounted rotatably in the support structure by means of rolling bearings, in which a lipped sealing gland is provided at each end of the shafts to separate the lubricating environment of the bearing from a respective annular chamber which is adjacent the (Ç) chamber of the two rotors and is isolated therefrom by means of a labyrinth seal, characterised in that the annular chamber adjacent each lipped sealing gland communicates with a respective hole formed through the support structure to the exterior.

2. A rotary volumetric compressor as constructed and arranged substantially as hereinbefore described and as shown in the figures of the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (2)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Rotary volumetric compressor of the Roots type The present invention relates to a rotary volumetric compressor of the Roots type, comprising a support structure, two rotors mounted rotatably in a chamber within the support structure, and a pair of shafts connected to the two rotors and having their ends mounted rotatably in the support structure by means of rolling bearings, in which a lipped sealing gland is provided at each end of the shafts to separate the lubricating environment of the bearing from a respective annular chamber which is adjacent the chamber of the two rotors and is isolated therefrom by a labyrinth seal. The object of the present invention is to prevent the lips of the sealing glands from being subjected to excessive loads (which would reduce the effectiveness and/or the lifetime of the glands), as a result of the pressures or pressure drops which occur in the rotor chamber during operation of the compressor. In orderto achieve this object, the invention provides a compressor of the aforesaid type, characterised in that the annular chamber adjacent each lipped sealing gland communicates with a respective hole formed through the support structure to the exterior. The present invention will now be described with reference to the appended drawings, provided purely by way of non-limiting example, in which: Figure lisa partially sectioned view of a com pressor according to the present invention, and Figure 2 is a section taken on the line ll-ll of Figure 1. In the drawings, there is shown a rotary volumetric compressor of the Roots type, generally indicated 1, usable, for example, for supercharging an internal combustion engine. The compressor 1 comprises a support structure 2 including an externally-finned casing 3 closed at one end by a cover 4 and at the opposite end by a plate 5 and a cover 6. The casing 3 has an internal chamber 7 housing the two rotors (not visible in the drawings) of the compressor. The two rotors of the compressor are connected for rotation with two shafts 8,9 the ends of which are mounted rotatably within the plate 5 and the cover 4, respectively, by means of rolling bearings 10. The shaft 8 has one end 8a projecting from the cover 6, onto which is keyed a gear wheel 11 for connection by a cogged belt to the driving shaft or cam shaft of the engine with which the compressor is associated. The drive is transmitted from the shaft 8 to the shaft 9 through the meshing of two gear wheels 12, 13 connected for rotation with the shafts. With each rolling bearing 10 is associated a lipped sealing gland 14 which separates the lubricating environment of the respective bearing from an annular chamber 15 adjacent the chamber 7 of the two rotors. Each annular chamber 15 is isolated from the chamber 7 of the rotors by a double labyrinth seal 16. In the case of the two sealing glands 14 mounted in the plate 5, each double labyrinth seal 16 is formed between the outer surface of a tubular spacer 17 (interposed coaxially of the respective shaft between the bearing and the rotor) and the surface of the hole in the plate 5 in which the spacer 17 is mounted. In the case of the sealing glands 14 mounted in the cover 4, however, each labyrinth seal 16 is formed between the outer surface of the respective shaft and the surface of the hole in the cover 4 in which the shaft is mounted. In order to prevent the pressures or pressure drops existing in the rotor chamber 7 of the com pressorfrom being transmitted through the labyrinth seal 16 to the annular chambers 15, thereby subjecting the lips of the sealing glands 14 to excessive loads which would render the seals unreliable, each annular chamber 15 (see Figure 2) communicates with a hole 18 formed through the support structure (or, more precisely, the plate 5 or the cover 4) to open onto the outer surface 19 of the compressor. CLAIMS

1. Rotary volumetric compressor of the Roots type, comprising a support structure, two rotors mounted rotatably in a chamber within the support structure, and a pair of shafts connected to the two rotors and having their ends mounted rotatably in the support structure by means of rolling bearings, in which a lipped sealing gland is provided at each end of the shafts to separate the lubricating environment of the bearing from a respective annular chamber which is adjacent the (Ç) chamber of the two rotors and is isolated therefrom by means of a labyrinth seal, characterised in that the annular chamber adjacent each lipped sealing gland communicates with a respective hole formed through the support structure to the exterior.

2. A rotary volumetric compressor as constructed and arranged substantially as hereinbefore described and as shown in the figures of the accompanying drawing.