WO1995029029A1 - Hydraulic bushing with axially displaceable pressurizing means at the rear of the bushing - Google Patents

Abstract

Hydraulic bushings (1) are generally provided with a peripheral flange in which a pressurizing means (3, 4, 5) is arranged. A desire has been expressed to eliminate the peripheral flange. According to the present invention this is made possible by placing the pressurizing means (3, 4, 5) in the rear end (6) of the bushing (1).

Description

Hydraulic bushing with axially displaceable pressurizing means at the rear of the bushing

Hydraulic bushings of various types are known, for instance, through Swedish patent 460,264 and 500,552. From the machining aspect the known constructions have the limitation that the flange part with pressurizing means is usually too large when machining must be performed in narrow work pieces such as aluminium components for the aircraft industry. They are also too heavy which will place increased demands at high rpm on both design and material.

The need for slim tool designs for both low and high rpm has increased in recent years, with the advent of improved machining equipment with extremely good spindle stability.

The use of machining tools in which coolant is supplied through the tool shaft to the machining part of the tool has increased, thereby influencing the design.

Current machining technology tends towards 40,000 rpm at ISO 40 cone or equiva¬ lent.

The above-mentioned problems are solved according to the present invention by placing the pressurizing means axially in the rear portion of the bushing, i.e. the part to be inserted in the part of the holder, that is to transmit rotary movement to the bushing. The pressurizing means can be influenced so that a unit can perform an axial movement parallel to the axis of the bushing, thereby influencing the bushing system. The unit suitably constitutes a body provided with threading that cooperates with a thread in a cavity where the unit is localized.

To enable coolant to be supplied to the machining part of the machining tool and to minimize unbalance, the solution has been selected to provide a channel system outside and close beside the pressurizing means. Hydraulic bushings are often manufactured by specialist companies and are fitted on a holder part by another company that adapts the construction to the requirements of the market. It must therefore be possible for the bushing to be fitted either directly to the holder by means of a screw joint or to be welded, soldered or in some other way secured to the holder. Screw joints are not accepted for certain purposes where high speed is necessary, and some other connection means must therefore be used.

The bushing construction can be designed to have two attachment parts, one of which locks inwardly against the machining tool and the other one which locks outwardly towards the holder part, both hydraulic bushing parts being influenced by the same pressurizing means and where the circuits can be separated from each other when necessary. The method offers extremely good centering and secure locking. If no screw joint is used the construction is secured to the holder part by means of welding, soldering or some other equivalent method.

The present invention will be described in more detail with reference to the accompanying drawings in which

Figure 1 shows a known bushing with holder part having tangential pressur- izing means in the flange of the bushing.

Figure 2 shows a bushing according to the present invention, for attachment to the holder part by means of a screw joint and with coolant supplied axially,

Figure 3 shows a bushing according to Figure 2 secured to the holder part by means of a screw joint, and

Figure 4 shows a bushing with one hydraulic bushing clamping inwardly to retain a machining tool and one hydraulic bushing clamping out¬ wardly against the holder part, both being influenced by the same pressurizing means and with coolant being supplied axially. The two pressurizing circuits may be separated from each other, not shown here.

Figures 2, 3 and 4 show a bushing with a cavity 2. A tubular channel 10 is arranged inside the cavity wall, of the same type as channel 11 in Figure 1. The channel 10 is in communication with a supply channel 9 which is in turn in communication with a space 11 for pressure medium. In this latter space is an axially movable body 4, provided with a sealing ring and valve ball 3. The body 4 can be influenced by a second body 5 provided with external threading that cooperates with threading arranged in the cavity in which said second body is located. By subjecting the second body 5 to a screwing movement, therefore, the pressure medium in the tubular channel 10 and the space 11 can be influenced, thereby displacing the wall of the cavity in radial direction. The second body 5 is influenced solely from behind with the aid of a suitable tool, e.g. a tee wrench. 8 indicates the part of the holder able to transmit a rotary movement to the bushing 1. Coolant supplied axially through the holder part 8 is supplied to the bushing 1 through one or more axial, helically or otherwise shaped channels (7) in the shaft part 6 enabling coolant to reach the cavity in order to cool the machining part of the machining tool if this is provided with internal cooling channels.

Besides the parts described in Figures 2 and 3, Figure 4 shows a shaft part 6 in the form of a hydraulic bushing clamping outwardly against the holder part 8. Using the same pressurizing means 3, 4, 5, the wall of the space 2 is placed under pressure in order to clamp the machining tool, and also the wall of the shaft part 6 in order to clamp it against the holder part 8.

The two circuits 10 and 13 can be separated from each other with the aid of some form of stop device. This is not shown in Figure 4.

Claims

1. A hydraulic bushing (1) to receive and retain a machining tool, in which the cavity (2) to receive the machining tool is preferably provided with an inflexible bottom, the inner wall of the cavity (2) is arranged to be radially flexible via a tubular space (10) inside said inner wall, which tubular space can extend beyond the length of the cavity (2) and which space (10) contains a pressure medium to be influenced by pressurizing means (3, 4, 5) that preferably includes an axially displaceable unit (5) and that suitably utilizes a thread arrangement, c h a r a c t e r i z e d in that said pressurizing means (3, 4, 5) are arranged in the shaft part (6) of the bushing (1), which is intended to secure the bushing (1) to the holder part (8) and which transmits a rotary movement to the bushing (1) and in that the displacement direction of said unit (5) is parallel with the axis of the bushing (1 ) and can be influenced externally.

2. A hydraulic bushing as claimed in claim 1 , c h a r a c t e r i z e d in that the cavity (2) is in communication with one or more channels (7) running through the shaft part (6) and beside the pressur- izing means (3, 4, 5), and communicating with coolant supply means through the holder part (8).

3. A hydraulic bushing as claimed in claim 1 , c h a r a c t e r i z e d in that the shaft part (6) containing the pressurizing means (3, 4, 5) has an exterior wall which is flexible radially outwards via a tubular space (13) in the outer part of the shaft (6) and which is influenced by an axial displacement of the pressurizing means (3, 4, 5) and which, upon being placed under pressure, locks the shaft part (6) against the holder part (8) and in that at the same time a machining tool is firmly secured to the tool holder through the circuit (10) so that, after being placed under pressure, the circuit (13) can be temporarily or permanently separated from the circuit (10) by some form of demarcating means. A hydraulic bushing as claimed in claim 3, characterized in that the cavity (2) is in communication with one or more coolant channels (7) running through the shaft part (6) and beside the pressurizing means (3, 4, 5), said channels (7) also communicating with coolant supply means through the holder part (8).