AU776477B2 - Sealing of cylinder heads - Google Patents

Description

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Applicant(s): RAIL PARTS LIMITED Invention Title: SEALING OF CYLINDER HEADS o* *o The following statement is a full description of this invention, including the best method of performing it known to me/us: 2 SEALING OF CYLINDER HEADS This invention relates to a method of sealing cylinder heads to cylinder linings, and to completed assemblies of cylinders and engines, having such sealed cylinder heads and liners.

BACKGROUND TO THE INVENTION Particularly where large engines are used, for example in locomotive or marine installations, the banks of cylinders have separate cylinder heads. The cylinders themselves are most often supplied with separate liners to allow for wear replacement. Typically in the diesel locomotive industry, such a liner is inserted from the bottom of a cylinder jacket and bolted tight to seal up against the abutting end of a cylinder head.

These engines are almost invariably water cooled, :and the sealing between the cylinder head and cylinder 20 liner is critical. If water leaks into the cylinder, the •resultant hydraulic pressure can ruin the crank system.

oo :In an earlier patent application in South Africa the applicant disclosed a method of sealing a cylinder head to a cylinder liner in which a cylinder head had a •g 25 head end and a cylinder end for fitment against a cylinder liner. The cylinder liner had a cylinder head end with o•annular formations thereon for location within an annular groove in the end face of the cylinder head side.

grog o* To provide better sealing between cylinder and head than had been achieved prior to the time of that earlier application, and particularly where refurbishment of a cylinder and/or head took place, the applicant proposed that a cylinder head be fitted to a cylinder liner, the walls of a groove in the head be machined away and a new ring section provided. This was done by building up welding, or by welding a ring to the head, and machining.

A corresponding annular rebate was provided on the inner wall of the liner by machining, to receive the ring as an insert therein. The ring was provided with external screw threading at a position removed from the free end.

Complimentary screw threading was provided on the inner surface of the annular rebate, and a matching annular portion, at the innermost portion of the annular rebate, was provided to match the ring portion. The matching annular portion and ring portion were dimensioned to create an interference fit. The interference fit was attained by machining the ring portion and the annular portion of the rebate.

To create an interference fit, the diameter of the ring portion was made to between 0,10 and 0,20mm greater than the diameter annular portion. The ring 2 0 portion was copper plated to a thickness of between 5 and 8 micrometers to 20 provide an anti fretting surface.

In use, the cylinder head was fitted in sealing manner to the liner by heating the "liner to approximately 2500 C, and cooling the cylinder head to approximately minus 300 C. The parts were then rapidly screwed together and the differential 25 heat expansion and contraction allowed the interference fit to be obtained.

The method enables cylinders and their liners of the type described to be provided with a relatively inexpensive method of sealing.

OBJECT OF THE INVENTION While the method of sealing between the components has proved satisfactory both for new and refurbished cylinder heads and cylinder liners, it is the object of the present invention to provide added security to the assembly in the event of any possible leakage formed or developed between the liner and the cylinder head.

SUMMARY OF THE INVENTION According to this invention there is provided an assembly of a cylinder head and cylinder liner for a large internal combustion engine wherein the liner and cylinder head are screwthreaded together by means of screwthreads provided partway along a rebate in the liner and on a ring extending from the cylinder head the ring terminating in a circular flange characterized in that the rebate and flange are engaged in an interference fit and a seal located between the components at an end of the screwthreads.

A further feature of this invention provides for the seal to be in the form of an 0- 20 ring of heat resistant material providing rubber like properties.

The invention also provides the seal to be located in a groove at the inner end of the screwthread in the cylinder liner.

BRIEF DESCRIPTION OF THE DRAWINGS One embodiment of the invention is described below, by way of example only, and with reference to the accompanying drawing in which: FIG.1 is a cross-sectional view of part of an assembled cylinder head and liner.

5 DETAILED DESCRIPTION OF THE INVENTION As illustrated a cylinder head for a large diesel locomotive is connected to a cylinder liner by means of interengaging screw-threads The ring projecting from the cylinder head terminates at its free end in a circular flange The flange engages with an interference fit in the end of a rebate in the end of the bore in the cylinder liner The thread in the liner extends inwardly from its free end to that part of the rebate in the bore of the cylinder liner providing the interference fit with the circular flange At the inner end of the screwthread in the liner a groove is provided to locate an O-ring seal of heat resistant rubber or rubber-like material.

Conveniently the material can be that sold under the trade name "Viton" which is a fluroelastomer manufactured by o DuPont Dow.

oooo The components are assembled in the manner S 20 described in our specification above referred to but with :the O-ring located in the groove to be engaged by S: the ring This additional sealing between the assembled components has proved to be very effective even when a 25 leakage path has been deliberately made through the interference fit. Thus increased security is provided in a .simple and inexpensive manner.

!°It will be understood that the O-ring seal could be provided at the opposite end of the screwthreads S 30 provided that it remains, in use, adequately protected by the engine water jacket.

For the purposes of this specification it will be clearly understood that the word "comprising" means "including but not limited to", and that the word "comprises" has a corresponding meaning.

It is to be understood that, if any prior art publication is referred to herein, such reference does not 5a constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country.

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Claims (3)

1. An assembly of a cylinder head and cylinder liner for a large internal combustion engine wherein the liner and cylinder head are screwthreaded together by means of screw threads provided partway along a rebate in the liner and on a ring extending from the cylinder head, the ring terminating in a circular flange characterized in that the rebate and flange are engaged in an interference fit and a seal located between the components at an end of the screwthreads.

2. An assembly as claimed in claim 1 in which the seal is in the form of an O- ring of heat resistant material providing rubber like properties.

3. An assembly as claimed in claim 1 or 2 in which the seal is made of "Viton". An assembly as claimed in any one of the preceding claims in which the S 20 seal is located in a groove at the inner end of the screwthread in the cylinder liner. ooooo An assembly of a cylinder head and a cylinder liner of a large internal combustion engine substantially as described with reference to the 25 accompanying drawing. Dated this 23rd day of July 2001 RAIL PARTS LIMITED S. By their Patent Attorneys GRIFFITH HACK Fellows Institute of Patent and Trade Mark Attorneys of Australia