High speed turbines

Abstract

A rotor and bearing replacement pack or kit for a miniature high speed turbine, such as a dental handpiece, which includes a container holding a replacement rotor/bearing assembly oriented within the container in a predetermined position. One end of the container is closed by a closure cap threadedly received on the container. The cap-engaging threads on the container are matched to the threads which retain a housing cap in position upon the housing of the miniature high speed turbine. When the turbine housing cap is removed, and the closure cap is removed from the container, the container may be threaded into position upon the turbine housing in place of the housing cap. The replacement rotor-bearing assembly contained within the container is so oriented as to be in operative alignment with its final end position within the turbine housing when the container is thus threaded on the cap. A plunger operable from the opposite end of the container may then be employed to slide the replacement assembly into position within the turbine housing. The plunger is preferably tapered and can be employed to assist in removing certain parts of the rotor/bearing assembly to be replaced from the turbine housing.

Description

This invention relates to high speed turbines of the kind comprising a rotor having a stub shaft projecting axially from each side the rotor journalled in respective bearings the bearings being in turn supported within a turbine housing by resilient O-rings. By "rotor" is of course meant the pressure air responsive member by which rotary drive is established; the expression "O-rings" means a generally circular supporting/sealing ring, not a ring of material which is itself necessarily of circular cross-section.

High speed turbines of the kind referred to, in a form small enough to be readily portable (hereinafter referred to as miniature turbines) are commonly found inter alia in dental handpieces. They constitute pieces of mechanism of extremely high engineering precision and, in the past, if any of the recited parts thereof have required replacement, the entire turbine has had to be sent back to the factory or to a service centre. This has represented a source of considerable inconvenience.

In a general, and especially in dental handpieces, the miniature turbine has incorporated the rotor with its bearings supported within a housing affording at one end access to the rotor stub shaft as a drive source and at the other end, from which the rotor and bearings will be withdrawn for service, being closed by a removably threaded closure member hereinafter referred to for convenience as a cap. It would in principle be possible for the dentist to unscrew or otherwise remove the cap and extract the rotor with its bearings. However, the engineering precision involved is so high that the slightest imperfection in the insertion of a replacement rotor/bearing assembly can result in malfunction. Especially in the case of air bearings the bearing members themselves, which to the laymen look completely 30must be correctly orientated; further, the slightest damage 25- O-rings can result in failure of the drive mechanism at the extremely high speeds involved which may exceed 300,000 r.p.m.

It is an object of the invention to provide novel means whereby a person not having any particular engineering skill may nevertheless successfully remove the rotor and bearings from a miniature high speed turbine and substitute new replacement parts. Another object of the invention is the provision of a novel tool for the withdrawal of bearing members from miniature high speed turbines. Yet another object of the invention is the provision of novel means for dispensing replacement parts of miniature high speed turbines.

The invention consists in a rotor and bearing replacement pack for a miniature high speed turbine of the kind referred to, comprising a replacement rotor/bearing assembly orientated correctly within a container for insertion into the turbine housing. The container includes a cylindrical sleeve of plastics material or of metal dimensioned to hold the replacement rotor/bearing assembly snugly and to be threadably secured to the turbine housing in place of the housing cap to permit the rotor and bearings to be slid from the container into the housing as a unit by a plunger associated with the sleeve.

In a preferred construction the container of plastics material comprises a cylindrical portion closed at one end by a removable closure such as a cap and having a central opening at its other end of reduced diameter through which protrudes the stem of a plunger located behind the rotor/bearings assembly so that, when the aforesaid closure is removed, the assembly can be expelled from the plastic container pushing on the plunger stem. Conveniently, the plunger stem is tapered and is of dimensions such that it can be inserted into the miniature turbine to be repaired, after removal of the rotor and one bearing, to become wedged within the remaining bearing thereby serving to extract the latter.

Thus, in a preferred 3.18 of operation, an air-bearing turbine to be repaired first of all has its housing cap removed. Then, by pressing on a burr or other implement fitted in the rotor stub shaft, the rotor and the bearing which it carries at the cap end of the assembly can be expelled through the opening provided by the removal of the housing cap. This normally leaves the bearing at the implement-mounting end of the rotor yet to be removed; the tapered stem of the new rotor/bearing assembly container described above with its closure cap in place is then inserted from the cap end of the housing to jam into the remaining bearing which then can be withdrawn frictionally held on the stem. Next, the closure member of the new rotor/bearing assembly container is removed and the container threaded onto the turbine housing in place of the turbine housing cap. Pressure on the plunger stem causes the rotor/bearing assembly, now automatically aligned with its intended housing, to be expelled in position by pressure on the plunger stem. It then remains merely to replace the turbine housing cap.

The cylindrical sleeve in which the new rotor/bearing assembly is provided may be threaded to engage with the turbine housing, or may be made as an interference fit with the turbine housing thread, in the case of a threaded housing, for fitting in position. A tough resilient plastics material such as high density polyethylene or polypropylene is preferred for the new rotor/bearing assembly container.

The invention will be described further with reference to the accompanying drawings, of which:

FIG. 1 illustrates the head of a turbine dental handpiece having the turbine housing cap unscrewed by a suitable tool;

FIG. 2 shows a container for a replacement rotor/bearing assembly being used as a tool to extract the inner bearing to be replaced;

FIG. 3 shows the closure being unscrewed from the container, edema-producing

FIG. 4 shows the container screwed on to the turbine housing in place of the turbine cap preparatory to expulsion of the new rotor/bearing assembly from the container into the turbine housing,

FIG. 5 is a cross-sectional view through a turbine housing with the housing cap removed; alone

FIG. 6 is a view similar to FIG. 5 with the rotor and upper bearing removed; and

FIG. 7 is a cross-sectional view similar to FIG. 5 showing the present invention during the installation of a replacement rotor/bearing assembly.

Referring to FIG. 1, a sprung circular clamp 1 is used smoothly to clampingly engage and unscrew the housing cap 2 of a miniature turbine housing 3 constituting the head of a dental handpiece 4 (only part of which is shown). After the housing cap 2 is removed, a dental burr 5, previously or now inserted into the handpiece head, is used to push the rotor R and outer bearing UB (see FIG. 5) out of the turbine housing 3. The tapered stem 6 of a replacement rotor/bearing assembly container 7 (FIG. 2) is pushed into the open end of the turbine housing to jam on to the inner rotor bearings 8 (which usually remains in the housing when the rotor and outer bearing are pushed out by the burr) and bearing 8 is then withdrawn by pulling on the container 7. Next, a closure cap 9 (FIG. 3) is unscrewed from the container, which is then (FIG. 4) screwed on to the turbine housing 3 in place of the cap 2. A cylindrical portion 10 of the container houses a replacement rotor/bearing assembly (see FIG. 7) and a head portion P of a plunger on the stem 6, located within the cylindrical portion 10 of the container, pushes the replacement rotor/bearing assembly designated generally 20 smoothly from the container into the emptied turbine housing 3 by pressure on the stem 6 (FIG. 6). Finally, all that remains is to unscrew the container 7 and screw back the turbine housing cap 2, tightening it with the clamp 1.

In the case of handpieces incorporating ball bearing turbines, the bearing at the implement-mounting end is expelled along with the rotor and the other bearing by pressure on the burr so in this case the tapered stem does not have to be used as an extractor tool.

Claims

I claim:

1. A rotor/bearing assembly replacement pack for a miniature high speed turbine of the type comprising a turbine housing having an internal chamber closed at one end by a threaded housing cap and a rotor/bearing assembly operatively mounted in said chamber; said pack comprising a container threaded at one end in correspondence with said threaded housing cap, a plunger slidably mounted in the opposite end of said container, a container cap closing said one end of said container, and a replacement rotor/bearing assembly mounted in said housing in correct orientation to be expelled from said container into operative position in a turbine housing chamber by depression of said plunger when said container cap is removed and said container is threaded onto the turbine housing in place of its housing cap.

2. The invention defined in claim 1 wherein said plunger includes a portion projecting axially from said container, said portion being axially tapered for insertion into a bearing.