GB2056608A

GB2056608A - Arrangement for the supply of oil from a stationary source to a rotating shaft

Info

Publication number: GB2056608A
Application number: GB8011137A
Authority: GB
Original assignee: FORKARDT P AG
Current assignee: FORKARDT P AG
Priority date: 1979-05-12
Filing date: 1980-04-02
Publication date: 1981-03-18
Also published as: DE2919180C2; JPS55152991A; ES8101729A1; IT1130418B; FR2456894A1; FR2456894B1; JPS617559B2; DE2919180A1; IT8021966A0; ES491401A0; GB2056608B

Abstract

The invention relates to an arrangement for the supply of pressure oil from a stationary pressure oil source to a rotating shaft (1). Such arrangements are used, for example, for the actuation of a rotary pressure oil cylinder forming part of a hollow chuck assembly. They comprise a pressure oil transfer housing (7) on the shaft (1), which housing is provided on the outside with at least one pressure oil connection and on its bearing surface with at least one annular transfer groove (11), which co-operates with at least one bore in the shaft for the transfer of pressure oil between the housing (7) and the shaft (1). Between the shaft (1) and the pressure oil transfer housing (7) a sealing ring (14) with a passage in the region of the transfer groove (11) is provided, and, at which at both ends is arranged respectively at least one row of roller members (15), which roll both on the bearing surface of the shaft (1) as also of the pressure oil transfer housing (7). By this means the relative motion between the rotary and stationary parts is reduced, and the friction forces decreased. <IMAGE>

Description

REFERENCE NUMERAL LIST: 1 Shaft la Annular groove lb Annular groove 2 Cylinder housing 3 Piston 4 Piston rod 5 O-Ring 6 Central bore 7 Pressure oil transfer housing 8 Pressure oil pipe 9 Pressure oil pipe 10 Connection bore 11 Transfer groove 12 Bore 12a Inlet member 13 Bore 13a Inlet member 14 Seal ring 14a Through bore 14b Through bore 15 Roller member 16 Thrust washer 17 Cirelip 18 Oil drainage groove 19 Leakage oil bore 20 Collector housing 21 Seal 22 Seal 23 Drain opening SPECIFICATION Arrangement for the supply of oil from a stationary source to a rotating shaft This invention relates to an arrangement for the supply of pressure oil from a stationary pressure oil source to a rotating shaft.

As a result of the improvement in recent years of cutting media, machine can be effected at substantially higher cutting speeds, as a result of which spindles carrying chucks have substantially increased rotational speeds. In a turning machine, such as a lathe, with a chuck of 250mm chuck diameter the rotational speed has been increased from substantially 2500 rpm to 3500 to 4500 rpm.

With such an increase in rotational speed the peripheral speeds of the arrangement for the supply of pressure oil to the rotating spindle of the machine tool also increase. In so-called hollow chuck arrangements, in which the workpieces to be machined are passed through the spindle and therefore also through the pressure oil transfer housing, a substantial increase in the peripheral speeds in the seal spaces follows since these lie on a comparatively larger diameter. The relative sliding speeds are for example increased from substantially 16m/sec to substantially 24m/sec. These high sliding speeds at the seal space of the pressure oil supply arrangement lead, however, to a substantial increase in the heating up of the supply system as a result of molecular friction of the pressure medium in the seal space.This molecular friction increases with the square of the sliding velocity but becomes linearly smaller the more the space increases.

It would also be possible, to bring about a reduction in the high molecular friction, which arises as a result of the high peripheral speed in the seal space, by increasing the leakage oil quantity. This measure is, however, impracticable, since then the leakage oil quantity must be disproportionally greatly increased, as a result of which a high pump output would be necessary, which would lead to an unfavourable overall power loss balance of which limits are set by the permissible temperature limits of the overall system.

According to the present invention there is provided an arrangement for the supply of pressure oil from a stationary pressure oil source to a rotary shaft, said arrangement comprising a pressure oil transfer housing for mounting on the shaft, which housing has on the outside at least one pressure oil connection and on its bearing surface at least one annular transfer groove arranged to cooperate with at least one bore in the shaft for the transfer of pressure oil between the housing and the shaft, and a sealing ring between the shaft and the pressure oil transfer housing having passages in the zone of the transfer groove and at each end at least one row of roller members is arranged, which roll both on the bearing surface of the shaft as also of the pressure oil transfer housing.

An arrangement for the supply of pressure oil from a stationary source to a rotary shaft embodying the invention, will now be described with reference to the sole Figure of the accompanying drawing which shows a longitudinal section of the arrangement.

The arrangement illustrated serves for the supply of pressure oil from a stationary pressure oil source to a rotary shaft 1 for the supply of a pressure oil cylinder, of which the cylinder housing 2 is constructed in one plate with the shaft 1. The piston 3 is disposed within the cylinder housing 2, and is made integrally with a piston rod 4. The piston rod 4 is sealed in relation to the cylinder housing 2 by means of O-rings 5 and has a central bore 6. Work-pieces can be passed through this central bore 6 to a chuck, if the pressure cylinder is mounted for actuation of a chuck at the rear end of a machine tool spindle.

The supply of the pressure medium cylinder with pressure oil is effected through a pressure oil transfer housing 7, which is rotatable but is, however, axially non-displaceably mounted on the shaft 1.

Two pressure-oil pipes 8 and 9 are connected to this pressure-oil transfer housing which remains fixed during rotation of the shaft 1, which pipes each communicate by means of a connecting bore 10 with an annular transfer groove 11. While the pressure-oil passes through the pressure-oil duct 8 through the annular transfer groove 11 and a bore 12 in the shaft 1 into the cylinder housing 2 and to the front face of the piston 3, the pressure oil pipe 9 is in communication through the corresponding transfer groove 11 with a bore 13, which leads to the rear face of the piston 3.

The transfer of the pressure-oil from the annular transfer groove 11 in the bearing surfaces of the pressure-oil transfer housing 11 to the bores 12 and 13 provided with a respective radial inlet member 12a or 13a is effected not directly, but through a sealing ring 14, which is disposed between the shaft 1 and the pressure oil transfer housing 7. This sealing ring is provided with roller members 15, which are equally distributed around the ends thereof. In the embodiment illustrated, by way of example, there is at each end face of the seal ring 14 a row of roller members 15, which are in the form of cylinders and roll both on the bearing surface of the shaft and also on the pressure oil transfer housing 7.

With the aid of these roller members 15, the sealing ring 14 rotates in the sense of rotation of shaft 1, however, at approximately one half of the rotational speed. The sliding velocity, that is the relative velocity between the bearing surfaces opposite the shaft 1 of the seal ring 14 on the one hand and on the other hand in relation to the pressure oil transfer housing 7 is likewise substantially halved in this way.

In order to make possible transfer of the pressure oil from the transfer groove 11 to the radial supply openings 12a and 13a of the bores 12 and 13, the sealing ring 14 is provided with at least one passage 14a in the region of the radial supply opening 12a and at least one further passage 14b in the region of the radial inlet opening 13a. In order further to improve the oil transfer an annular groove la, 1b is provided in the region of each of these on the shaft 1 to which the supply members 12a, 13a connect.

The axial guidance of the sealing ring 14 on the shaft 1 is effected in the embodiment illustrated by way of example, by washers 16, which are mounted on both sides ofthe roller members 15. While one of these washers 16 abuts on the front face of the cylinder housing 2 the other is held by a circlip 17 on the shaft 1.

Adjacent to and if necessary also between the two transfer planes of the seal ring 14 oil outlet grooves 18 are provided, which co-operate with drainage bores 19 in the pressure oil transfer housing 7. The leakage oil from these leakage oil bores 19 and if necessary also from the end face of the seal ring 14 is collected in a collector housing 20, which is supported on the pressure oil connection housing 7 and thus through this is supported rotatably in relation to the shaft 1. This collector housing 20 has contact-free seals 21, 22 which seal with collector housing 20 on the one hand against the shaft 1 and on the other againstthe cylinder housing 2. At the underside of the collector housing 20 there is provided a drain opening 23.

By means of the sealing ring in accordance with the invention, of which the movement relative to the shaft and to the pressure oil transfer housing is adjusted in dependence upon the value of the resistances in the sealing space, the molecular friction generated therein is substantially reduced and correspondingly the lower frictional effect leads to reduced heat generation. Bythis means an uhndesirable heating up of the supply arrangement is avoided in spite of a substantial increase in rotational speed, so that the energy losses connected therewith and the damaging effects on the precision of the machine tool are overcome.The resultant doubling of the sealing space by use of the arrangement of the sealing ring in accordance with the invention, for this reason does not have a negative effect on the loss balance, since by the reduction in the frictional effect at a predetermined speed, the supply arrangement remains cooler, whereby the viscosity of the pressure oil increases, so that the leakage oil quantity with increase in the sealing space is reduced and in relation to the known arrangements, overall, it is expected that approximately the same values will be achieved. Furthermore, the advantage arises, that the two rows of roller members provide a concentric space between the shaft and the pressure oil transfer housing, so that the sealing ring can float freely.

Whilst with the separate arrangement of the sealing ring and roller members guided in a cage the speed of the sealing ring adjusts itself a slip speed corresponding to the value of the sealing space resistance, in an alternative construction at least one row of roller members is connected with the sealing ring, for example, in such a way that the cage of this roller member row is rigid with the sealing ring or the sealing ring is constructed at its rim as a cage for the roller members. In this alternative the speed of the sealing ring corresponds to the rotational speed ofthe roller bearing cage. The sealing ring rotates relatively to the shaft and respectively to the pressure oil transfer housing at approximately one half of the rotational speed of the shaft.

The sealing ring can be guided in the axial direction aditionally by means of the roller members and/or the thrust rings or washers. These thrust rings or washers can also be arranged to provide axial guidance of the pressure oil transfer housing.

The pressure oil transfer housing is mounted, as shown, within the collector housing, which is sealed at both sides of the pressure oil transfer housing in relation to the shaft by means of seals. In this way an especially favourable and advantageous circulation of the drainage oil is achieved. A constructionally simple mounting of the collector housing is achieved by supporting it on the pressure oil transfer housing on the shaft in a rotatable manner. The seals are contact-free in orderto reduce frictional losses.

Claims

1. An arrangement for supply of pressure oil from a stationary pressure oil ~source to a rotary shaft, said arrangement comprising a pressure oil transfer housing for mounting on the shaft, which housing has on the outside at least one pressure oil connection and on its bearing surface at least one annular transfer groove arranged to cooperate with at least one bore in the shaft for the transfer of pressure oil between the housing and the shaft, and a sealing ring between the shaft and the pressure oil transfer housing having passages in the zone of the transfer groove and at each end at least one row of roller members is arranged, which roll both on the bearing surface of the shaft as also of the pressure oil transfer housing.

2. An arrangement according to claim 1, wherein at least one row of said roller members is connected with the sealing ring.

3. An arrangement according to claim 1 or claim 2, wherein the sealing ring is guided in the axial direction by means of the roller members and/or by means of thrust washers.

4. An arrangement according to claims 1 to 3, wherein the thrust washers serve also for the axial guidance of the pressure oil transfer housing on the shaft.

5. An arrangement to any one of the preceding claims wherein the pressure oil transfer housing is arranged as a whole within a collector housing which is sealed at both sides of the pressure oil transfer housing in relation to the shaft by means of 4 seals and is provided with a drainage oil connection.

6. An arrangement according to claim 5, wherein the collector housing is rotatably mounted on the shaft through the intermediary of the pressure oil transfer housing.

7. An arrangement according to claim 5 or claim 6, wherein the seals are formed as contact-less seals.

8. An arrangement for the supply of pressure oil from a stationary source to a rotary shaft substantially as herein before described with reference to the accompanying drawing.

9. 9. A hollow chuck incorporating an arrangement according to any one of the preceding claims.