GB2300026A

GB2300026A - I.c.engine coaxial inlet and exhaust valve gear

Info

Publication number: GB2300026A
Application number: GB9508185A
Authority: GB
Inventors: Peter Harrod
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-04-22
Filing date: 1995-04-22
Publication date: 1996-10-23
Anticipated expiration: 2015-04-22
Also published as: GB2300026B; GB9508185D0

Abstract

The inlet valve 37 and the tubular exhaust valve 25 are mounted in the cylinder head for operation by respective cams on a camshaft 20 against the bias of respective springs 30, 29.

Description

INTERNAL COMBU8TION ENGINE VALVE GEAR The present invention relates to internal combustion engines, and particularly although not exclusively to valve gear for a petrol or diesel engine of the four stroke type.

The conventional four stroke internal combustion engine having either 2,3,4 or 5 valves per cylinder is well known and these valve configurations are common in petrol or diesel engined vehicles which are widely available commercially. The conventional engines comprise cylinder heads having inlet and outlet passages which are arranged on the roof of the combustion chamber in side by side manner.

The conventional four valve per cylinder engines, generally provide greater power output than a twin valve per cylinder engine of comparable cylinder capacity.

The conventional four valve per cylinder engines, whilst allowing improved gas flow into and out of the combustion chamber as compared with conventional two valve per cylinder engines, are more complex than the conventional two valve per cylinder engines, involving twin cam shafts and twice as many valves as compared with the single cam shaft two valve per cylinder conventional engine.

One object of the present invention is to provide increased power for a given cylinder capacity, as compared with a conventional two valve per cylinder engine without significantly increasing manufacturing costs, as compared with the conventional two valve engine.

According to a first aspect of the present invention there is provided a cylinder head for an internal combustion engine having an outer gas passage formed concentrically around an inner gas passage.

Using this arrangement, the cross sectional area of the gas passage, in a direction transverse to the direction of gas flow, can be increased for a given combustion chamber space, as compared with a conventional two valve per cylinder combustion chamber in which the inlet and outlet passages are arranged on the roof of the combustion chamber in side by side manner.

According to a second aspect of the present invention there is provided a valve assembly for inletting and outletting gases to a combustion chamber of an internal combustion engine, the valve assembly comprising an inner valve and an outer valve, characterised in that the inner valve is arranged to open or close with respect to the outer valve such as to open or close an inner gas passage between said inner and outer valves.

Preferably, said inner passage is surrounded by said outer valve.

Preferably, the inner gas passage comprises a space between the inner valve and the outer valve.

Preferably, the inner valve is arranged to seal against the outer valve to close the inner passage.

Preferably, the outer valve is arranged to open or close with respect to a wall of said combustion chamber such as to open or close an outer passage between said outer valve and said combustion chamber wall.

Preferably, said outer passage surrounds said outer valve.

Said outer passage may be defined as comprising the space between the outer valve and a cylinder head in which the outer valve may be seated.

Preferably, the outer valve is arranged to seal against the combustion chamber wall to close the outer passage.

A mouth of said outer passage may be defined as comprising the space between a portion of the outer valve which seals against the combustion chamber wall, and a periphery of an aperture in the combustion chamber wall.

Preferably, said inner passage is arranged for the inlet of gas to the combustion chamber, and said outer passage is arranged for the outlet of gas from said combustion chamber.

Preferably, the inner valve is arranged to be carried by the outer valve as the outer valve opens and closes.

By arranging an inner valve to be carried by an outer valve as the outer valve opens or closes, the size of passages closed by the outer valve and the inner valve can be increased, for a given combustion chamber diameter as compared with a conventional two valve per cylinder arrangement where the valves and passages are arranged side by side.

Preferably, the inner valve is arranged to move with respect to the outer valve in a same direction as the outer valve moves with respect to the combustion chamber wall.

Preferably the inner and outer valve are arranged to open and close by moving in a direction parallel to a direction of movement of the piston as it moves up and down in the cylinder.

By arranging the inner and outer valves to move in the same direction as the piston, the distance of movement of the valve between an open and a closed position may be increased relative to the distance moved by an inlet or outlet valve in the conventional two valve per cylinder engine. For a given height of combustion chamber roof above the crown of the piston at the top dead centre position, the increased travel between the open and closed positions of a valve according to the present invention, may provide an increased inlet or outlet passage opening, and thereby allow an improved gas flow in and out of the combustion chamber, as compared with a conventional engine having two valves per cylinder.

Preferably, the inner valve comprises a stem valve, and the outer valve comprises a tubular sleeve.

Preferably, said stem valve comprises an elongate stem having at a lower end of thereof a valve head substantially in the form of a disc.

Preferably, said stem valve is positioned concentrically in said sleeve.

Preferably, a lower end of the tubular sleeve is arranged to seal against a perimeter of an aperture in the combustion chamber wall for closing said outer passage.

Preferably, said inner valve is arranged coaxially with said outer valve.

Preferably, the valve assembly comprises an inner valve spring arranged for urging the inner valve to close against the outer valve.

Preferably, the inner valve spring is carried by said outer valve, such that said valve spring does not move relative to said outer valve when said outer valve opens or closes.

Preferably, said tubular sleeve is provided with a set of apertures for passage of gas from a position outside said sleeve, to a position inside said sleeve.

Preferably, the valve assembly comprises an outer valve spring for urging said outer valve to close against said combustion chamber wall.

Preferably, said tubular sleeve comprises a lower end having a flared flange, an upper surface of said flared flange being arranged to seat on a corresponding seating surface of said combustion chamber, and said valve head of the stem valve being arranged to seat with an inner surface of said flared flange.

The invention includes a cylinder head for an internal combustion engine, the cylinder head comprising: a combustion chamber; a valve assembly for inletting and outletting gases to the combustion chamber, the valve assembly comprising an inner valve and an outer valve, the inner valve being arranged to open or close with respect to the outer valve such as to open or close an inner gas passage defined between said inner and outer valves; and a cam shaft for operation of said inner and outer valves.

According to a third aspect of the present invention, there is provided a cam shaft for an internal combustion engine, comprising: an elongate shaft; a plurality of eccentric cams arranged along a length of said shaft; characterised in that arranged in sequence along said cam shaft are firstly a first outer cam arranged for operating an outer valve; secondly, an inner cam arranged for operating an inner valve; and thirdly, a second outer cam, arranged for operating the outer valve.

Preferably, adjacent said first outer cam is provided a bearing surface for securing said shaft to a cylinder head and adjacent said second outer valve is a second bearing surface for securing said shaft to said cylinder head.

For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings, in which: Figure 1 shows in cut away view a cylinder head according to a first specific embodiment of the present invention as fitted to a conventional internal combustion engine block; Figure 2 shows the first specific embodiment at a compression/ignition phase; Figure 3 shows the first specific embodiment during an exhaust phase; and Figure 4 shows in plan view, a section of cam shaft, of the first specific embodiment.

Referring to figures 1 to 3 of the accompanying drawings, a cylinder head 1, according to a first specific embodiment of the present invention is shown. The cylinder head may be fitted to a conventional engine block 2 of a petrol or diesel engine.

The cylinder head comprises a combustion chamber 3, an inlet passage 4 for inletting gas to the combustion chamber an outlet passage 5 for outletting exhaust gases from the combustion chamber, or the cylinder of the block; a valve assembly 6 comprising an inner valve 37 used as an inlet valve, and an outer valve 25 used as an outlet valve; a cam shaft 20 for operating the inner and outer valve; and a spark plug 10 for igniting a fuel mixture.

Referring to figure 1, the components labelled 20-41 are as follows: cam shaft 20, inlet valve housing 21, outlet hydraulic tappet 22, outlet valve collet 23, outlet valve top spring seat 24, outlet valve 25, inlet valve top spring seat 26, inlet valve hydraulic tappet 27, inlet valve collets 28, outlet valve spring 29, inlet outer valve spring 30, inlet inner valve spring 31, outlet valve bottom spring seat 32, outlet valve outer top guide 33, outlet valve inner guide 34, inlet valve guide 35, outlet valve outer bottom guide 36, inlet valve 37, inlet valve oil seal 38, outlet valve oil seal 39, and inlet bottom spring seat 40.

Each combustion chamber is provided with a single inlet valve 37 and a single outlet valve 25, the single inlet valve and single outlet valve being operated by the single cam shaft 20. Thus, for each cylinder or set of cylinders arranged in line, only a single cam shaft is used, and only one inlet valve and one outlet valve per cylinder are used.

The valve assembly comprises the inner valve 37, having an elongate stem 50 and at a lower end of the stem, a substantially disc shaped valve head 51; the outer valve 25 in the form of a substantially cylindrical tubular sleeve having an outwardly flared lower flange 53 an upper surface 54 of the flared end arranged to seal against a corresponding sealing surface at the perimeter of an aperture on the roof of the combustion chamber, and a lower surface of the flared end arranged for sealing against a perimeter surface of the valve head 51; the inlet valve hydraulic tappet 27 being substantially circular in cross section, and extending across the upper end of the inner valve stem 50; the inlet valve housing 21, which fits inside the tubular sleeve of the outlet valve, and rests on top of the cylinder head, the inlet valve is arranged to move with the outlet valve as the outlet valve moves upwards and downwards between an open and a closed position; between the inlet valve housing 21 and the inlet valve tappet 27, the inlet valve springs, comprising the inlet valve outer spring 30 and the inlet valve inner spring 31; and the outlet valve spring 29.

The tubular sleeve of the outer outlet valve comprises a plurality of cut away passages allowing passage of gases from outside of the tubular sleeve to the inside of the tubular sleeve, the space between the stem and the sleeve wall comprising the inner passage.

Also included in the valve assembly are the outlet valve collets 23, outlet valve top spring seat 24, inlet valve top spring seat 26, inlet valve collets 28, outlet valve bottom spring seat 32, outlet valve outer top guide 33, outlet valve inner guide 34, outlet valve outer bottom guide 36, inlet valve oil seal 38, outlet valve oil seal 39, and the inlet bottom spring seat 40.

Referring to figure 4 of the accompanying drawings, there is shown in plan view a segment of the cam shaft 20 as viewed from above. One segment of the cam shaft, corresponding to one cylinder only is shown, although it will be understood that the cam shaft can extend along a same main axis, having further segments similarly as shown, for operation of further cylinders.

The cam shaft 20 comprises an elongate shaft 60 having a first outer cam 61 for depressing an upper end of the tubular sleeve of the outer valve; a second outer cam 62 for depressing the upper end of the tubular sleeve of the outer valve at a position on an opposite side of the sleeve to the first position; an inner cam for depressing the inner valve tappet, the inner cam being arranged on the cam shaft between the first outer cam and the second outer cam; the first and second outer cams and the inner cam being positioned between a first bearing surface 64 for mounting the cam shaft to a cylinder head, and a second bearing surface 65 for mounting the cam shaft to the cylinder head. The cams comprise eccentric lobes which are arranged to rotate about the main axis of the cam shaft.The positioning, shape and size of the lobes are selected for optimum opening and closing of the inner and outer valves, according to the required tuning of the engine performance.

The cylinder head 1 may be fittable to an in line, "V", or boxer engine having one, two, three, four, five, six, eight or twelve cylinders, the length of the cylinder head and number of valve assemblies and cams being selected according to the number of cylinders served per cylinder head.

Operation of a single valve assembly and single cam shaft segment for firing a single cylinder will now be described as shown with reference to figures 1 to 4 of the accompanying drawings.

Figure 1 shows an inlet phase of the cylinder, in which the outer valve 37 remains in a closed position, an upper surface of the lower flange of the outer valve being sealed against the combustion chamber, closing a mouth of the outlet passage 5. In this position, the outlet valve spring urges the outlet valve away from the engine block 2, and the lobes of the inner and outer cams do not contact the upper end of the outlet valve tubular sleeve.

The inlet valve is depressed with respect to the outlet valve, such that the upper end of the stem and the inlet valve tappet 27 are depressed by the lobe of the inner cam 20, compressing the inlet valve springs and depressing the head 51 of the inlet valve such that the inlet passage 4 is open. In this position fuel gases are inlet into the combustion chamber and the cylinder, by the movement of the piston downwards.

As the piston reaches bottom dead centre, the inlet valve returns to the closed position and the piston then moves upwardly in the cylinder, compressing the fuel gases prior to ignition, as shown in figure 2. The outlet valve remains in the closed position, and the head 51 of the inlet valve, seals against the lower surface of the flange of the tubular outlet valve, thus closing the inlet passage, the outlet passage already being closed. In this position, the inlet and outlet springs ensure that the lower flange of the outlet valve is sealed to the wall of the combustion chamber, closing the outlet passage, and the valve head 51 of the inner valve is sealed against the lower flange of the outlet valve, closing the inlet passage. The lobes of the inlet and outlet valve cams do not depress the inner or outer valves.

At top dead centre, the fuel gases are ignited, causing movement of the piston away from the combustion chamber. When the piston reaches bottom dead centre, the outlet valve begins to open, so that when the piston returns to top dead centre, driven by the general momentum of the engine or firing of other cylinders, the exhaust gases from the combustion may be expelled via the outlet passage 5.

Referring to figure 3 of the accompanying drawings, the passage 5 is opened by depressing the outer valve sleeve, such that the flared flange of the lower end of the outlet valve moves away from the combustion chamber wall allowing escape of the exhaust gases. The inner valve is carried with the outer valve, being arranged concentrically therein. The inner valve cannot move away from the engine block as the outer valve is forced by the outer cams towards the engine block to open the outer passage, since the inlet valve head is sealed against the lower flange of the tubular sleeve, which pushes the inlet valve head towards the engine block. Thus, the inlet valve head remains sealed to the lower flange, closing the inlet passage, as the outlet passage is opened by depression of the outer valve.

Details of operation of another specific embodiment will now be described.

Application for a patent on the design of a COMBINATION VALVE SYSTEM for the INTERNAL COMBUSTION ENGINE (I.C.E) for both petrol and diesel engines.

The efficiency of an I.C.E. depends upon several factors, I am going to try to improve it in one of these.

On the four stroke engine, the valving system. MY DESIGN IN THE FUTURE WILL BE KNOWN AS THE HARRODS SYSTEM.

The object of the design is to increase the horse power from an engine without increasing the stroke or bore, (its lubric capacity), and also without increasing the costs of manufacturing as compared with the existing two valves per cylinder engines. But compared with a three or four valves per cylinder engines it would be cheaper with a possibility of more power.

The theory is simple, increase the sizes of the inlet and outlet valves, this will allow an increase in gas volume without increasing the velocity thus the R.P.M.

will increase, therefore the H.P. will increase.

The drawing P.H.I. shows section AA, BB, CC. Section AA shows both valves closed and the position TOP dead centre, this is the beginning of the firing stroke or expansion stroke.

Section BB shows the outlet valve fully opened with the piston moving upwards this is the exhaust stroke. The operation of the valve is when the cam shaft lobe pushes down the outlet hydraulic tappet, this then operates the valve. As the outlet valve operates it takes with it the inlet valve (note this is in the closed position) this motion uses both outlet and inlet valve springs.

Section CC shows the piston going downwards sucking the gases into the cylinder with the inlet valve fully opened, the "induction stroke" on this operation only the inlet springs are used.

The name and numbers of all the parts relating the combination valve are shown on section CC and the part plan of the cam shaft just below section AA.

DESCRIPTION OF THE PARTS: PART NO. 1 The inlet valve, this is similar in design to an existing inlet valve in existing engines, in material, shape specification and tolerance.

PART NO. 2 The outlet valve, this is completely new in design, this is in the form of a tube with a bell at the bottom to form the valve seat on the cylinder head and on the inside of the bell is the seat between the inlet valve and itself. Approximately half way up the tube three or more apertures are cut away, and these apertures are for the inlet gases to pass through and down the middle of the valve when the inlet valve opens. At the top of the valve on the outside is a groove for the outlet collets Part No.

6 to be seated in assembly.

PART NO. 3 The cam shaft centre line is on the same centre line as both the valves, with the inlet valve having one lobe operating it and the outlet having two lobes, the reasons for the outlet having two lobes is: 1. To give even forces onto the valve.

2. A greater wearing area on the lobes and hydraulic tappets.

The cam shaft is shown fastened into position with retaining caps split bearing and retaining cap screws Part no. 22, 23 and 24. Reason for this type of securing the shaft is for ease of assembly.

PART NO. 4 The inlet housing. The function of the housing is to retain and guide the inlet valve. The body of the housing is circular with a hole bored in its centre for the inlet valve guide part no. 18, it is also machined out to house the inlet inner and outer valve springs, seats, hydraulic tappets and seals. The housing is located to the cylinder head very accurately with a spigot recess and is retained in position with four housing screws part no. 25.

Recesses are ut into the top of the housing so to allow the rotation of the lobes of the cam shaft and the inlet hydraulic tappet to pass through.

In this design hydraulic tappets are used, it can be designed with rocker arms and an auxiliary shaft.

Preference is given to the hydraulic tappets as less parts are required.

PART NO. 5 Outlet hydraulic tappet is in the form of an annulus.

PART NO. 6 Outlet valve collets. These are conventional type of collets except they are fairly large in diameter these will return the assembly of the outlet valve, outlet spring and seats in position on the cylinder head.

PART NO. 11 Inlet hydraulic tappet is more conventional in design in the form of a disc. NOTE:- The same oil feed operates both tappets as their are aperture in the outlet valve and inlet valve housing, thus pressure is maintained throughout the full cycles, this oil also lubricates all the moving parts.

The following part no.s are all conventional in design and materials: 7, 8, 9, 10, 12 to 27 inclusive.

The design as shown in the drawing P.H.1. is only in a general form. When detail designing of a working system is done small modifications are most likely.

EXAMPLE The valve seats the diameter of the valves these changes will be determined by calculations and practical test, to achieve the best results for the required engine.

The compression ratio works out about 10:1 on the example on the drawing. This is fairly high considering that when the valve is fully opened it does not infringe the top of the piston at top dead centre, so if the cam shaft drive belt breaks no damage is done. With this design very high compression ratio can be achieved thus raising the brake mean effective pressure and therefore raising the H.P., but the valves will infringe on the piston at top dead centre if the cam shaft drive belt breaks.

It is important that the assembly of the system is simple and is as described in the following steps:1. The outlet valves top and bottom outer guides part no.s 20 and 21 are inserted into position into the cylinder head part no. 27.

2. The outlet valve part no. 2 is inserted into the cylinder head.

3. The outlet valve oil seal, bottom spring seat outlet valve spring and the top spring outlet valve are placed into position, the spring is compressed retaining the valve to the head then the outlet valve collets par no. 6 are placed into position.

Compression device released the collets retain all the parts in position.

4. The outlet hydraulic tappet part no. 5 can now be placed into position.

5. The inlet valve guide part no. 18 and the outlet valve inner guide part no. 19 are fitted to the inlet housing part no. 4.

6. The inlet valve housing is now inserted into the outlet valve from the top, this is then fastened into position onto the head by four housing screws part no. 25.

7. The inlet valve part no. 1 can now be inserted into the housing, the inlet valve oil seal part no. 17, inlet bottom valve spring seat part no. 16, the inlet inner and outer valve springs parts no.s 14 and 15, and the inlet valve top spring seat are placed into position, the springs are compressed retaining the valve to the head, then the inlet valve collets part no. 13 are placed into position, the spring compression device is released the collets retain all the parts in position.

8. The inlet hydraulic tappet part no. 11 can now be placed into position.

9. The cam shaft can now be fitted.

10. The head can now be fitted to the engine block.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. A Cylinder Head for an Internal Combustion Engine having Outer Gas Passages formed - concentricity around an Inner Gas Passage.

2. A valve assembly for inletting and outletting gases to a combustion chamber of an internal combustion engine, the valve assembly comprising of an inner valve assembly characterised in that the inner valve is arranged to open or close an inner gas between the inner and outer valves; and a cam shaft for operation of said inner and outer valves.

3. An internal combustion engine valve gear as described herein with reference to Figures 1-4.

4. A valve assembly as claimed in Claims 1 or Claim 2 the inner gas passage comprises of space between the inner valve and the outer valve (4 in figure 2).

5. A valve assembly as claimed in Claim 1 or Claim 2 where the inner valve is arranged to seal against the outer valve to close the inner passage (4 in figure 4).

6. An outer valve as claimed in Claim 1 or Claim 2 with respect to the wall of said combustion chamber such as to open or close an outer passage between said outer passage between said outer valve and combustion chamber wall.

7. An outer passage surrounds the outer valve as claimed in Claims 1 or Claims 2, defined as comprising the space between the outer valve and the Cylinder Head (5 of figure 2).

8. An outer valve is arranged to seal against the combustion chamber wall to close the outer passage as claimed in Claims 1 or Claims 2, the mouth of the outer passage may be defined as the space between a portion of the outer valve which will seal against the combustion chamber wall and the periphery of the aperture in the combustion chamber wall (25 of figure 1).

9. An inner passage is arranged for the inlet of gas to the combustion chamber and the outer passage is arranged for the outlet of gas from the combustion chamber as claimed in Claims 1 or Claims 2, as shown in figure 2 inner passage is item 4 and the outer passage is item 5.

10. An inner valve as claimed in Claims 1 or Claims 2 is arranged to be carried by the outer valve as the outer valve opens and closes by arranging an inner valve to be carried by an outer valve as the outer valve opens or closes, the size of passages closed by the outer valve and the inner valve can be increased for a given combustion chamber diameter as compared with a conventional two valve per cylinder arrangement where the valves and passages are arranged side by side (37 of figure 1).

11. An inner valve as claimed in Claims 1 or Claims 2 is arranged to move with respect to the outer valve in the same direction as the outer valve moves with respect to the combustion chamber wall (37 of figure 1).

12. An inner and outer valve as claimed in Claims 1 or Claims 2 are arranged to open and close by moving in a direction parallel to the direction of movement of the piston as it moves up and down in the cylinder, arranging the inner and outer valves to move in the same direction as the piston, the distance of movement of the valve between an open and a closed position may be increased relative to the distance moved by an inlet or outlet valve per cylinder engine.

13. An inner and outer valve as claimed in Claims 1 or Claims 2 for a given height of combustion chamber roof above the crown of the piston, at the top dead centre position the increased travel between the open and closed positions of this valve according to the present invention, may provide an increased inlet and outlet passage opening, and thereby allow an improved gas flow in and out of the combustion chamber.

14. An inner valve comprises a stem valve (poppet valve), and the outer valve comprises a tubular sleeve as claimed in Claims 1 or Claims 2, the stem valve comprises a blowgate stem having at the lower end of the of a valve head substantially in the form of a disc, (37 of figure) the stem of the valve is positioned concentricity in said sleeve, the lower end of the tubular sleeve in arranged to seal against a perimeter of an aperture in the combustion chamber wall for closing the outer passage, (25 of figure 1) and the inner valve is arranged continually with the outer valve.

15. A cam shaft for operation of the inner and outer valve, as claimed in Claims 1 or Claims 2, the elongated shaft as plurality of eccentric cams arranged along its length the first outer cam for operating the outer valve the second for operating the inner valve and the third outer cam operating the outer valve, adjacent to the first outer cam is provided bearing surface for securing the shaft to the cylinder head and also adjacent to the second outer valve is a second bearing surface for securing the shaft to the cylinder head.

16. A inlet housing as claimed in Claims 1 or Claims 2, rotating and guide to the inlet valve and outlet valve, the body of the housing is circular with a hole bored in it's centre for the inlet valve guide part no. 18 it is also machined out to house the inlet inner and outer valve springs, seats, hydraulic tappets and seals. The housing is located to the cylinder head very accurately with a spigot recess and is retained in position with four housing screws part no.

25. Recesses are out into the top of the housing so to allow the rotation of the lobes of the cam shaft and the inlet hydraulic tappet to pass through.

17. An outlet valve hydraulic tappet as claimed in Claims 1 or Claims 2 is in the form of an annulus.

18. An inlet valve hydraulic tappet as claimed in Claims 1 or Claims 2 is more conventional in design in the form of a disc.

19. An outlet valve collets as claimed in Claims 1 or Claims 2 are of conventional design large in diameter.

20. An inner valve collets as claimed in Claims 1 or Claims 2 are of conventional design.

21. An inlet inner valve spring as claimed in Claims 1 or Claims 2 is of conventional design.

22. An inlet outer valve spring as claimed in Claims 1 or Claims 2 is of conventional design.

23. An outer valve spring as claimed in Claims 1 or Claims 2 is of conventional design.

24. An outer valve bottom spring seat as claimed in Claims 1 or Claims 2 is of conventional design.

25. An outer valve top spring seat as claimed in Claims 1 or Claims 2 is of conventional design.

26. An inlet valve top spring seat as claimed in Claims 1 or Claims 2 is of conventional design.

27. An inlet valve bottom spring seat as claimed in Claims 1 or Claims 2 is of conventional design.

28. An outlet valve outer top guide as claimed in Claims 1 or Claims 2 is of conventional design.

29. An outlet valve outer bottom guide as claimed in Claims 1 or Claims 2 is of conventional design.

30. An outlet valve inner guide as claimed in Claims 1 or Claims 2 is of conventional design.

31. An inlet valve guide as claimed in Claims 1 or Claims 2 is of conventional design.

32. An inlet valve oil seal as claimed in Claims 1 or Claims 2 is of conventional design.

33. An outlet valve oil seal as claimed in Claims 1 or Claims 2 is of conventional design.

34. A camshaft retaining cap screw as claimed in Claims 1 or Claims 2 is of conventional design.

35. A camshaft retaining cap as claimed in Claims 2 or Claims 2 is of conventional design.

36. A camshaft bearing as claimed in Claims 1 or Claims 2 is of conventional design.

37. An inlet valve housing screw as claimed in Claims 1 or Claims 2 is conventional in design.

38. A cylinder head bolt as claimed in Claims 1 or Claims 2 is conventional in design.

39. A spark plug as claimed in Claims 1 or Claims 2 is conventional in design,

40. A cylinder head for an Internal Combustion Engine as herein described and illustrated in the accompanying drawings.

39. A spark plug as claimed in Claims 1 or Claims 2 is conventional in design.

Amendments to the claims have been filed as follows 1. On an Internal Combustion Engine the cylinder head as all arrangement of a valve assembly comprising co-axially aligned inlet and exhaust valve mechanism actuated by single cam shaft, the size and arrangement of the valves will increase the revs per minute of the engine without increasing the mean gas velocity through the valves, the valve assembly is slightly offset from the centre line of the piston and crankshafl to allow for the spark plug to be fitted into file cylinder head.

2. The valve assembly as claimed in Claiiiis 1 comprising of an inner valve assembly and a outer valve assembly characterised in that the inner valve is arranged to open or close an mnet gas passage and the outer valve to open of close the outer gas passage and a cam shaft (20 of figure 1) for operation of said inner and outer alves.

4. A valve assembly as claimed in Claims 1 or Claim 2 the inner gas passage comprises @@ space between the inner valve and the outer valve (4 in figure 2).

5. A valve assembly as claimed in Claim 1 or Claim 2 where the inner valve is arranged to seal against the outer valve to close tlle inner passage (4 in figure 4).

6. An outer valve as claimed in Claim i or Claim 2 with respect to the wall of said combustion chamber such as to open or close an outer passage between said outer passage between said outer valve and combustion chamber wall.

8. An outer valve is arranged to seal against the combustion chamber wall to close the outcr passage as claimed in Claims 1 or Claims 2, the mouth of the outer passage may be detined as the space between a portion of the outer valve which will seal against the combustion chamber wall and the periphery of the aperture in the combustion chamber wall (25 of figure 1).

10. an inner valve as claimed in Claims 1 or claims 2 is arranged to be carried by the outer valve as the outer valve opens and closes by arranging an inner valve to be carried by an outer valve as the outer valve opens or closes, the size of passages closed by the outer valve and the inner valve an be increased for a given combustion chamber diameter as compared with a conventional two valve per cylinder arrangement where the valves and passages are arranged side by side (37 of figure 1).

11. An inner valve as claimed in Claims 1 or Claims 2 is arranged to move with aspect to the outer valve in the same direction as the outer valve moves with respect to the combustion chamber wall (37 of figure 1).

12. An inner and outer valve as claimed in Claims 1 or Claims 2 are arranged to open and close by moving in a direction parallel to the direction of movement of the piston as it moves up and down in the cylinder, arranging tlle inner and outer valve to move iu the same direction as the piston, tlle distance of movement of the valve between an o@ Qi11 and a closed position may he increased relative to the distance moved by an inlet or outlet valve per cylinder engine.

13. An inner and outer valve as claimed in Claims 1 or Claims 2 for a given height ol combustion chamber roof above the crown of the piston, at the zO) dead centre position the increased travel between the open and closed positions of this valve according to the present invention, may provide an increased inlet and outlet passage opening, and thereby allow an improved gas flow in and out of the combustion chamber.

14. An inner valve comprises a stem valve @poppet valve), and the outer valve comprises a tubular sleeve as claimed in Claims 1 or Claims 2. the stem alve comprises a blowg:ite sleni having at the lower end of the of a valve head substantially in the form of a dise, (37 of figure) the stem of the valve is positioned concentricity in said sleeve. the lower end of the tubular sleeve ill arranged to seal against a perimeter of an apeitwe in the combustion chamber wall for closing the outer passage, (25 of figure 1) and the inner valve is arranged continually with the outer valve.

15. A cam shaft for operation of the inner and outer valve, as claimed in Claims 1 or China 2.

the elongated shaft as plurality of eccentric cams arranged along its length the first outer can for operating the outer valve the second for operating the inner valve and the third outer cam operating the outer valve, adjacent to the first outer cam is provided bearing surface for securing the shaft to the cylinder head and also adjacent to the second outer valve is a second bearing surface for ecur the shaft to the cylinder head.

16. A inlet housing as claimed in Claims 1 or Claims 2, rotating and guide to the inlet valve and outlet valve, the body of the housing is circular with a hole bored in it's centre for the inlet valve guide (35 of figure 1) it is also machined out to house the inlet inner and outer valve springs, seats, hydraulic tappets and seals. The housing is located to the cylinder head vey accurately with a spigotrecess and is retained in position with four housing screws' Recesses are out into the top of the housing so to allow the rotation of the lobes of the cam shaft and the inlet hydraulic tappet to pass through.

17. An outlet valve hydraulic tappet (22 of figure 1) as claimed in Claims 1 or Claims 2 is in the form of an annulus.

18. An inlet valve hydraulic tappet (27 of figure 1) as claimed in Claims 1 or Claims 2 is more conventional in design in the form of a disc.

19. An outlet valve collets (23 offigure 1) as claimed in Claims 1 or Claims 2 are of conventional design large in diameter.

20. An inner valve collets (28 of figure 1) as claimed in Claims 1 or Claims 2 are of conventional design 21. An inlet inner valve spring (31 of figure 1) as claimed in Claims 1 Claims 2 is of conv@ntions) dssion.

22. An inlet outer valve spring (30 of figure 1) as claimed in Claims I or Claims 2 is of conventional design.

23. An outer valve spring (29 of figure 1) as claimed in Claims 1 or Claims 2 is of conventional design.

24. An ouler valve bottom spring scat (32 oi figure i) as claimed in Clainis 1 or Claims 2 is of conventional design.

25. An outer valve top spring seat (24 ol figure 1? as claimed in Claims 1 or Claims 2 is is of conventional design.

26. An inlet valve top spring seat (26 of figure 1) as claimed in Claims 1 or Claims 2 is of conventional design.

27. An inlet valve bottom spring seat (10 of figure 1) as claimed in Claims 1 or Claims 2 is of conventional design.

28. An outlet valve outer top guide (33 of figure 1) as claimed in Claims 1 or Claims 2 is of conventional design.

29. An outlet valve outer bottom guide (36 of figure 1) as claimed in Claims 1 or Claims 2 is of conventional design 30. An outlet valve inner seal (34 of figure 1) as claimed in Claims 1 or Claims 2 is of conventional design 31. An inlet valve guide (35 of figure Ij afi claimed in Claims 1 or Claims 2 is ofconventional design.

32. An inlet valve oil seal (38 of figure 1) as claimed in Claims 1 or Claims 2 is of conventional design.

33. An outlet valve oil seal (32 of figure 1) as claimed in Claims 1 or Claims 2 is of conventional design.

34. A camshaft retaining cap screw as claimed in Claims I or Claims 2 is of conventional design.

35. Acamshaft retaining cap (60 of figure 4) as claimed in Claims 2 or claims 2 is of conventional design.

36. A camshaft bearing (64 offigure 4) as claimsd in C1Rims 1 or Claims 2 is of conve2ltional design 37. An inlet valve housing screw as claimed in Claims 1 or Claims 2 is conventional in design.