Covers are found on the housings of industrial gear units for various reasons including the closure of an opening used in the assembly of the internal components, or the closing of a bearing bore. Additionally covers may offer openings in the housing for, for example, inspection or adjustment of the internal components or to provide for connection of accessories.

Furthermore in gear units which are required to run under lubrication covers are necessary in order to close the housing against the escape of lubricant and the ingress of water or contaminants.

Conventionally in such gear box housings the closure of orifices has involved mechanical means of securing covers such as bolting, screwing, clamping or shrink fitting. Where the cover is round it is possible to utilise internal or external screw threading.

With such conventional closures it has been necessary to provide the mating surfaces on the cover and the housing with either a high degree of surface finish or shape conformity or alternatively to provide gasketing in addition to the mechanical clamping.

In either case the mechanical preparation of mating surfaces or provision of an extra gasket component adds to the time and expense of manufacturing the finished gear unit.

It is an object of the present invention to provide an improved method of retaining a cover to a housing which can mitigate the above disadvantages and provide for easier assembly.

A co-pending PCT patent application filed by this Applicant on the same day as this application provides a different solution to the above mentioned problems.

In accordance with one aspect of the present invention there is provided a method of retaining a cover interiorally within an orifice in a machine housing and sealing a gap therebetween comprising providing a first peripheral extending groove in a radially outward facing surface of the cover and a second peripheral extending groove in a confronting radially inward facing surface of the housing, applying an expandable solidifiable sealing material into at least one of the peripheral extending grooves, positioning and temporarily holding the cover within the orifice such that the first and second grooves confront each other and then expanding the sealing material to fill both grooves and to occupy at least in part space between the cover and the housing such that the cover is retained and sealed in the housing by mechanical interlock of the expanded sealing material interposed between them.

By a solidifiable sealing material is meant a material which is substantially rigid when'set'.

The invention is particularly applicable where the machine is a gear unit and particularly a multi-stage gear unit. Such machines contain oil as a lubricant and the invention may retain and seal a cover to the housing of the gear box either above or below the oil level. Furthermore the housings of such machines are generally of cast metal and the housing surface contacted by the sealing material may be a moulded surface i. e. it is not necessary to provide a machined surface for contact by the sealing material. The invention is applicable to gear unit designed for power applications ranging from 0.5 horsepower to 4000 horsepower.

Further aspects of the invention will become apparent from the following description, given by way of example only, of embodiments of the invention in conjunction with the following schematic drawings in which:- Figure 1 shows a cover retained in position within an orifice of the housing of a gear box; Figure 2 is a section view taken along A-A'in Figure 1; Figure 3 is a sectional view showing the profile of the interior, radially inward facing peripheral surface of the orifice in the housing ; Figures 4 shows a sectional profile of the radially outward facing peripheral surface of the cover; Figure 5 shows the sealing material in position in a groove on the peripheral surface of the cover; Figure 6 shows a sectional scrap view of the cover positioned within the orifice in the housing prior to expansion of the expandable sealant material ; Figure 7 is a sectional scrap view showing the sealing material in an expanded state, and Figure 8 shows another embodiment of the invention.

Shown in the Figures 1 and 2 is a circular orifice 1 formed in the wall 2 of a cast metal gearbox housing. Retained within the orifice is a circular cover 3 having a diameter just slightly less than the diameter of the orifice such that there exists a small gap g between the two.

As can be seen in Figure 3 and 4, the radially inwardly facing peripheral surface 4 of the orifice in the housing is provided with a shallow groove 5, whilst the radially outermost peripheral surface 6 of the cover 3 is provided with a shallow groove 7. The shallow grooves 5,7 are positioned on their respective surfaces such that when the cover in positioned within the orifice, with the surfaces 4 and 6 confronting each other, the grooves 5,7 are opposite each other, i. e. they are also confronting.

In the next step of the invention a quantity of an expandable sealing material 8 is put into the groove 7 in the cover in sufficient quantity to substantially fill this groove as shown in Figure 5. Suitable materials for the expandable sealant material include the commonly available structural polystyrene foaming products which expand a short time after application or may include elastomeric materials containing blowing agents which may be activated chemically or by heat or by time to set firm.

The cover is then positioned within the orifice in the housing such that the two shallow grooves 5,7 confront each other and the cover is temporarily held in this position by any suitable means such as adhesive tape.

In the final step of the method the expandable sealant material is caused to expand in volume by suitable means such that it spans the gap G between the confronting surfaces 4,6 and further expands into the shallow groove 5 provided in the wall of the housing.

With the solidifiable sealing material in a solidified conditions the cover 3 is thereafter retained within the orifice in the housing 2 by the mechanical interlock provided by the solidified expanded sealing material disposed within and across the two confronting grooves as shown in Figure 7.

In a preferred feature of the present invention, instead of the confronting peripheral surfaces 4,6 of the housing and the cover respectively having a plane cylindrical profile they are each stepped to provide a confronting portion which is inclined at an angle to the remaining main portion. One such example of this is shown in Figure 6. The inwardly facing surface 4 of the housing 2 is provided with shoulder portion 9 whilst the outward facing surface 6 of the cover 3 is provided with a form matching shoulder portion 10. In this embodiment both shoulder portions 9, 10 are substantially perpendicular to their respective main portions of faces 4,6 but they need not necessarily be so.

Provision of an inclined portioned to the confronting surfaces as shown assists in correctly locating the cover within the orifice by preventing the cover from being inserted too far towards the interior of the housing.

In a further preferred aspect of the invention a rubber gasket or O ring 11 is disposed between the confronting surfaces of the housing and cover in a position inwardly of the peripheral extending grooves. Such a sealing ring may further improve the correct positioning of the cover within the orifice, and provide the necessary temporary retaining means and ultimately contribute to the seating of the gap.

Figure 8 shows a further embodiment of the invention wherein the confronting surfaces of the cover and housing each have a frusto-conical form rather than cylindrical.