GB1591125A - Internal combustion engine - Google Patents

Description

PATENT SPECIFICATION ( 11) 1 591 125

tn ( 21) Application No 42233/77 ( 22) Filed 11 Oct1977 ( 19),, ( 31) Convention Application No 733962 ( 32) Filed 19 Oct 1976 in, i " ( 33) United States of America (US).

( 44) Complete Specification Published 17 Jun 1981

U ( 51) INT CL 3 F 02 B 23/08 // 17/00 r ( 52) Index at Acceptance Fi B 1 Gl A 1 G 1 K 1 G 4 A 2 A 15 2 A 1 A 2 A 1 B 9 O 2 A 1 C 2 J 10 2 J 5 2 L 3 A 1 2 L 3 BX ( 54) AN INTERNAL COMBUSTION ENGINE ( 71) We, RICHARD FLORENCIO BLASER and ANDREW ALEXANDER POURING respectively of: 1280 Graff Court, Annapolis, Maryland 21403, United States of America; and 212 Tarragon Lane, Edgewater, Maryland 21037, United States of America; both citizens of the United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be 5 particularly described in and by the following statement:-

The present invention relates to an internal combustion engine and more particularly to an improved combustion chamber design that permits control of generated pressures and temperatures during combustion of fuel in order to decrease the amount of pollutants exhausted by the engine during operation, and to achieve other advantages 10 Efficient conversion of energy into useful work has been the goal of engine designers since the creation of internal combustion engines utilizing the Otto cycle, i e, reciprocating, rotary, diesel engines and the like In view of the scarcity and high cost of engine fuels, engineers and engine designers have been grappling with the fundamental problems of exhaust emission pollutants and increased fuel economy, while striving to improve performance in these areas 15 without sacrificing engine performance and efficiency This has produced internal combustion engines that are operating in a critical compromise of fuel/air mixture composition, pressure and temperature that results in the engine generating and discharging harmful pollutants (CO, NOX and HC) in order to achieve adequate performance.

To deal with the NOX emissions designers have retarded spark timing and employed such 20 devices as exhaust gas recirculation systems, each of which measures decreases engine performance, with a resultant overall decrease in engine performance and which further cause increases in HC and CO emissions These increased HC and CO emissions must be cleared up by expensive catalytic converters which in turn require unleaded fuels.

Continued distortion of the combustion process in internal combustion engines can only 25 result in a hodge-podge of engine control devices that increase engine manufacturing cost and result in low engine performance with low fuel economy.

Realization in both industry and the government that internal combustion engines will require drastic design changes to achieve permissible government pollution standards has resulted in considerable developmental efforts to investigate the combustion process These 30 efforts have resulted in various techniques such as changing the size and shape of the combustion chamber, relocation of the spark within the combustion chamber, the use of multiple-source ignition schemes and the use of stratified charge designed combustion chambers.

Various modifications of a combustion chamber shape into a hemispherical chamber with 35 changes in conventional spark locations has reduced HC emissions but this design has mechanical manufacturing difficulties that far outweigh the benefit of reduced emissions obtained.

Another technique presently being utilized is the use of a multiplesource ignition configuration to cause creation of a torch-like flame to shoot into a homogenous-lean air/fuel 40 mixture within the combustion chamber with the torch fueled by the same fuel as the main chamber The torch ignition mixture is mechanically separated from the main chamber by an antechamber constructed in the engine head to open into the main combustion chamber.

Another popular scheme is the stratified charge engine (SC) configuration which can have numerous variations The basic idea of the SC engine involves introduction of a rich, easily 45

2 1,591,125 2 ignitable mixture in the vicinity of the spark plug and a very lean mixture throughout the rest of the chamber, so as to have a differing air/fuel ratio in various areas within the cylinder chamber, rich in some lean in others, with the resulting overall air/fuel ratio considerably leaner than stoichiometric The burning takes place in stages with a small volume of rich air/fuel mixture being ignited first to create a flame that spreads out into the combustion 5 chamber charged with very lean air/fuel mixture causing ignition of these areas more thoroughly and burning them more completely than in conventional internal combustion engines.

The above are a few of the more pertinent devices of the numerous proposals that have been set forth to reduce pollution and increase engine and fuel performance Each has some 10 distinct disadvantage because of its interaction with other engine parameters inherent in the Otto cycle or diesel cycle engine In view of this there has been created a need in the industry of an internal combustion engine operating on a gas cycle that has the characteristics of the Otto cycle but which has a process of combustion that is time controlled and will operate with the advantage of high compression ratio and rich fuel/air mixtures with the efficiency and 15 total fuel oxidation of the diesel without its disadvantages of high pressure, high temperature and knock tendency.

Accordingly, the present invention has been developed to overcome the specific shortcomings of the above known and similar techniques for internal combustion engines with performance, pollution characteristics, and a multifuel burning capability that is not present 20 nor possible with conventional Otto or diesel cycle engines.

The present invention, in its broadest aspect, comprises an internal combustion engine including a reciprocating piston having a working face moving within a variable volume cylinder that includes a combustion chamber, the working face of the piston being located towards said combustion chamber, and additionally comprising a fixed volume air chamber 25 located next to the working face of the piston and separated from the combustion chamber' at the upper region of the fixed volume air chamber by a circumferential gap extending between the edge of the working face of the piston and the adjacent cylinder sidewall, the gap arranged to permit continuous exchange of compression shock and expansion wave energy between the combustion and'air chambers during a combustion reaction of fuel and air in the 30 combustion chamber, the length of the air chamber extending along at least a portion of the circumference of the piston beneath its working face and the air chamber having a radially inner sidewall including a portion which slopes with respect to the cylinder side wall and extends from the piston side edge of the gap towards the bottom area of the air chamber, said inner sidewall being continuous and uninterrupted over the entire length of said air chamber, 35 and said sloping portion generally diverging away from the adjacent cylinder sidewall over its respective length.

The general purpose of the invention is to provide a device to refine the Otto cycle of present internal combustion engines to improve engine performance and minimize exhaust pollutants In such an engine, a balancing chamber or air reservoir is provided that is in 40 communication with the combustion chamber of the internal combustion engine through a carefully designed gap; this chamber and gap allows pressure exchange operation on the compression and power stroke of the piston independently of average pressure in the combustion chamber, and throughout the combustion reaction On the admission or intake stroke, air and fuel are sequentially directly admitted via a valving arrangement into the 45 combustion chamber The decrease in cylinder pressure caused by the receding piston draws the air and fuel into the combustion chamber with a non-homogeneous charge of fuel and air, that is fuel rich at the top and virtually air at the bottom As compression starts, the air,' with slight possible fuel contamination, is forced into the balancing chamber via the gap, increasing the pressure within the balancing chamber or reservoir as the pressure increases in the 50 combustion chamber by the piston moving toward TDC At ignition and burning of the locally fuel-rich mixture the reaction rate is so fast as to drive at quasi constant volume (compression) shock wave across the combustion chamber and through the gap into the balancing chamber or reservoir Simultaneously, expansion waves from the reflected shock waves propagate back across the combustion chamber causing a pressure imbalance between 55 the combustion and reservoir chambers The air in the reservoir chamber flows out into the combustion chamber through the gap for replenishing the air within the combustion chamber for sustaining complete combustion of the fuel These expansioncompression waves interact throughout the combustion event and act in an oscillatory manner to draw or pump air from the reservoir chamber into the combustion chamber a substantial number of times An 60 additional effect of the alternting expansion-compression waves is to cause stirring at the combustion zone at supersonic through sonic speeds Passage of weak shock waves into the combustion chamber will fractionate the fuel particles, effectively atomizing them for rapid combustion and thus eliminates the need of atomization of fuel by carburetors or like devices as fuel is drawn in the combustion chamber 65 1 AO 1 11 z 3-, '-'1, 3 The reservoir in the combustion chamber is formed by providing a radially extending lip centrally supported on the piston at a predetermined distance from the piston top surface.

The peripheral dimension of the lip is slightly less than the diameter of the cylinder in which the piston is disposed so as to form a narrow spaced gap or passageway between the peripheral edge of the lip and the cylinder wall surface The cap is heated by the burning gases 5 during the combustion cycle and acts as a heat exchanger to provide heating of gases in the combustion chamber during the compression cycle Fuel is fed into the combustion-chamber by means of a carburetor like or an injection like system of fuel supply via an intake manifold and intake valve arrangement An air inlet is provided to permit atmospheric air to flow directly into the combustion chamber whenever the intake valve opens preceding delivery of 10 the fuel to the combustion chamber to cause substantially fuel free air to be drawn into the combustion chamber ahead of the fuel charge.

This invention is concerned with a specific reservoir chamber design, as will become apparent from the description to follow.

For a complete understanding of the nature and features of an embodiment of the 15 invention, reference should be made to the following detailed description taken in connection with the accompanying drawings, Figure 1 A being in accordance with the present invention, the remaining Figures being given by way of information but not forming part of the present invention, wherein:

Figure 1 is a diagrammatic representation of apparatus installed in an internal combustion 20 engine; Figures 1 A and 1 B are diagrammatic representations of pressure exchange cap shape and Figure 2 (A-G) are illustrations of the sequence of operation of a heat balanced pressure exchange engine cycle.

Referring to Figure 1, a diagrammatic representation of an embodiment of a balancing 25 chamber or reservoir formed on a piston for refining the Otto cycle of an internal combustion engine to function on a heat balanced with pressure exchange four stroke cycle is shown An engine housing or block 10 forms a chamber for a reciprocating piston 14 that is attached by means of wrist pin 13 to connecting rod 11 A crankshaft 12 is coupled to connecting rod 11 by means of a journal bearing to permit reciprocating motion of piston 14 to be transformed 30 into rotating mechanical energy that may be utilized to drive machinery, an automobile or like device, for providing work output.

The inner wall of engine housing 10, adjacent the wall of piston 14, forms a cylinder wall 36 that is in contact with rings 15 to provide a gas pressure tight seal between movingpiston 14 and cylinder wall 36 to prevent the escape of high pressure gases generated by burning fuel in 35 variable volume combustion chamber 38 Attached to engine housing 10 is cylinder head 37 forming a closed combustion chamber between the uppermost portion of housing 10 and the inner recessed portions of the head Cylinder head 37 has two ports, exhaust and intake, that open and close by means of operation of exhaust valve 23 and intake valve 28 arrangements, respectively These vales are opened and closed in time sequence with the reciprocating 40 movement of piston 14 by means of valve lifters, push rods, camshafts, and the like, not shown, to allow the internal combustion engine to operate on a four stroke cycle.

Attached to cylinder head 37 is an intake manifold 27 that forms a closed passageway for allowing the flow of fuel and atmospheric air to combustion chamber 38 An air filter 33 is provided to filter air entering a carburetor like device 29 through venturi 35, that has nozzle 45 or port 41 attached to fuel container 32 via a valve and fuel line 31 Air flowing through venturi 35 creates a vacuum to draw fuel from fuel container 32 into combustion chamber 38.

Carburetor like device 29 may be replaced by other fuel delivery devices, such as fuel injectors or like devices, known to those skilled in the art A throttle plate 34 attached to a linkage arrangement, not shown, controls the amount of vacuum through venturi 35 by 50 restricting air flow through the venturi for controlling the amount of fuel delivered to the engine An additional linkage arrangement, not shown, may be coupled to control air flow through air inlet 26 to further control the amount of atmospheric air delivered to the engine during its operation Air inlet 26, open to atmospheric air, permits a large volume of air to be delivered to combustion chamber 38 on the intake stroke of the engine prior to delivery of 55 any fuel laden air charge This air vent is positioned adjacent intake valve 28, as shown, but may be located at any position between carburetor device 29, a fuel ejector or other fuel delivering device, and the intake valve port of intake valve 28.

A spark plus 24 is attached in cylinder head 37 in a conventional manner, and operates to deliver an electric voltage to create a spark in combustion chamber 38 in proper timing 60 sequence with other engine elements to ignite fuel within combustion chamber 38, for creating power to drive piston 14.

A cap like element 19 is centrally attached to piston 14 at its surface face by means of a rivet, bolt or like fastening device This cap like portion 19 is of mushroom-like shape with a thickened cylindrical stalk-like center portion that has one of its circular face surfaces in 65 n 4 1,591,125 4 contact with the circular surface of piston 14 Integral with the other circular surface of stem-like portion 17 is a relatively thin, radially extending cylindrical lip 20 having a periphery that is spaced a predetermined distance from cylinder wall 36 to form a gap 18 The remaining exposed surface of piston 14, the dimensional height of the stem-like portion 17, and the inner surface of lip 20, form a chamber 16 open to the combustion chamber by the 5 clearance gap or passageway 18, defined by the inner cylinder wall surface and the edge of lip which may extend the entire outer peripheral distance of top 20 or some predetermined portion, thereof Chamber 16 is sealed on its lower side by means of piston rings 15 The reservoir 16 is thus formed by a portion of th top surface of piston 14, an inner surface portion of lip 20, the cylinder sidewall, and the cylindrical wall of stem element 17, and 10 communicates with the combustion chamber through the gap 18.

Although cap like element 19 is described as fastened to the piston it is to be understood that cap 19 may be integral with piston 14 and the chamber may be machined or shaped in the piston in the same manner as piston ring grooves.

Although chamber 16 is shown in Fig 1 as formed with parallel sides, the underside 42 of 15 the cap 19 is, according to this invention, sloped towards the piston top as shown in Figure 1 A to form a wedge shape balancing chamber or reservoir 16 Figures 1 A and 1 B show cap configurations and combustion chamber geometries, as well as volumes A and B of the combustion chamber at minimum volume and reservoir chamber volume, respectively.

The undersurface 42 is a radially inner sidewall portion of the chamber 16 that extends 20 downwardly and inwardly from circumferential gap 18 that extends between the working face of the piston 14 and the cylinder wall The circumferential length of the gap may be entirely around the piston, as shown, or only partially around diametrically opposed sides of the piston The sloping sidewall portion 42 is generally continuous over its length and diverges from the cylinder wall as it approaches the bottom of the reservoir chamber The wall 42 is 25 shown as being flat or planar in section, since this has been found to be advantageous in promoting pressure exchange between the combustion and reservoir chambers.

The principle of operation of the internal combustion engine operating on the heat balanced-pressure exchange cycle may be best understood by reference to Figure 2 (A through G) that illustrates the operating sequence of an embodiment of a heat balanced 30 pressure exchange engine cycle during its four stroke operation Figure 2 A illustrates piston 14 completing an exhaust stroke with the exhaust valve 23 about to close, with piston 14 moving upward forcing the flow of burned gases, depicted by arrows, out through the exhaust valve port through a passageway in exhaust manifold 22 At this point intake valve 28 is closed and no air or fuel is flowing through intake manifold passageway 27 Air vent 26 35 located adjacent the inlet valve port has allowed a charge of fuel free air at atmospheric pressure to fill the entire volume of the intake passageway in the intake manifold up to and through venturi 35 As intake valve 28 opens, best shown with reference to Figure 2 B, piston 14 positioned near top dead center (TDC) moves downwardly enlarging the space at the top of the cylinder, atmospheric air pressure and a decrease in air pressure due to the receding 40 piston draws an inflow of air filling the space in the cylinder The inflow of air first entering the combustion chamber 38 is the charge of air within the intake manifold passageway that is replenished somewhat by air vent 26 before sufficient vacuum is generated in venturi 35 to next draw a rich charge of fuel laden air into the cylinder chamber, after the air has first been admitted As the piston reaches its lowest position, bottom dead center (BDC), the cylinder 45 space has been filled with a charge varying from rich in fuel near the top to substantially fuel-free near the cap 19 and within reservoir 16.

As piston 14 reaches its lowermost point of travel within the cylinder, (BDC), the pressure inside the cylinder is still less than atmospheric pressure and additional air and fuel can enter the cylinder, even after the cylinder begins to move upward Therefore, the intake valve 26 50 does not close until the crankshaft arm 11 is a predetermined amount of travel past BDC; this is best shown by the illustration of Figure 2 C.

After the intake stroke, best shown by reference to Figure 2 D, both valves ( 23, 28) are closed and piston 14 moves upward on the compression stroke Piston 14 compresses and heats the air and fuel in the combustion and reservoir chambers Throughout the upward 55 movement of piston 14, an accumulation of air with possible slight fuel content occurs in reservoir 16 due to slight diffusion of fuel through the charge The air in reservoir 16, however, is still maintained substantially fuel-free and outside flammability limits throughout the cycle During operation of the engine, the burning gases heat cap 19 which acts as a heat exchanger and causes heating of the air and fuel charge during compression as the charge 60 flows over and around it, thus providing additional heating of the gases.

Figure 2 E illustrates the initiation of combustion with piston 14 near TDC and both valves closed Piston 14 has compressed the air/fuel charge to give greater force to the expanding gases when combustion (ignition of the fuel) takes place At this point, a spark ignites the fuel of the charge and it reacts with immediately available oxygen with an explosive force tending 65 1,591,125 1,591,125 5 to drive piston 14 downward and expand the combustion chamber as the pressure in the combustion chamber increases The pressure increase at quasi-constant volume (combustion) generates and drives compression (pressure) shock waves across the combustion chamber and into reservoir 16, via passageway 18, momentarily compressing the air in the reservoir 16 against its internal walls Simultaneouslyv the expansion waves created by 5 interaction of reflected shock waves and the combustion front propagate in a reverse direction into the space between the top of cap 19 and cylinder heat 37 momentarily decreasing the pressure in combustion chamber 38, particularly near the gap A pressure imbalance in the gap area occurs due to the shock compression of the very lean substantially fuel free air in reservoir 16 to pressure greater than local pressure in combustion chamber 38, 10 causing the air within chamber 16 to flow out via passageway 18 into combustion chamber 38, in which a pressure imbalance has occurred This condition is illustrated with reference to Figure 2 F which shows outflow of the heated shock compressed air from reservoir 16 via passageway 18 into combustion chamber 38 during the compression event The pressure imbalance condition occurs as a time dependent process and even though the average 15 pressure in the combustion chamber may be higher than the average pressure in the reservoir chamber The nature of the interaction of shock and expansion waves is such that the pressure imbalance is expected to be localized along the gap area 18.

The interaction of the reservoir and the combustion chamber is crucially important for proper heat balanced-pressure exchange engine operation To provide the necessary oscillat 20 ing action of the compression and expansion waves during combustion of the fuel as they successively interact within the combustion zone and to provide a pumping action to force substantially fuel free air from chamber 16 requires certain dimensional interrelationship of combustion chamber volume A (at minimum volume), reservoir chamber volume B and passageway 18 (Figures 1 A and 1 B) for a particular engine configuration In an internal 25 combustion engine the volumetric balancing ratio of B/A is normally in a range of from 20 to 3 The passageway opening 18 should be 05 to 200 in ( 1 27-5 08 mm) measured across its narrow dimension The lower value typical for standard size cylinder of automobile engines, the higher value typical for compression ignition engines The gap, however, must be capable of permitting controlled passage of the oscillating shock waves into and out of the reservoir, 30 to permit controlled pressure imbalances to occur across the gap, and to control the rate of flow of oxygen through the gap from the reservoir chamber in response to the fluctuating pressure imbalances, so that oxygen will be supplied to the combustion chamber in controlled amounts entirely throughout the combustion event, quite independently of overall average pressure conditions in the combustion chamber, or piston position, in the manner of a 35 pumping action.

Table 1 sets forth the pressures and temperatures present at designated stages in Otto and Heat Balanced Combustion cycles, illustrating exemplary pressures and temperatures extant at the given stages, where: y is the compression ratio; B 3 is the volumetric ratio of balancing chamber volume to combustion chamber minimum volume; condition d is at start of com 40 pression; condition b is at ignition; and condition c is at maximum cylinder pressure.

TABLEl

45 Otto Cycle Heat Balanced Cycle y= 8 /3 = O y= 8 8 = 43 Psia TO R Psia TO R 50 a 14 7 600 14 7 600 a b 240 1200 240 1200 b c 1000 4980 670 3070 c 55 A two-stroke engine cycle that has a similar combustion cycle as the four stroke but that requires only one revolution of the crankshaft can also be modified to operate on a heat balanced cycle In a two-stroke engine, the compression stroke of the working piston draws a 60 fresh supply of air into the crankcase On the next compression stroke this air is compressed in the combustion chamber and fuel is later injected into the combustion chamber A cap structurally similar to the one described above operates in the same manner to sustain combustion during the burning of fuel-air charge in the combustion chamber to cause the engine cycle to be refined to a heat balanced cycle 65 6 1,591,125 6 As can be seen from the above description, the present invention provides an apparatus and techniques for providing control of pressure and temperature in the operation of a reciprocating internal combustion engine of spark or compression ignition and two or four stroke configuration in a refined thermodynamic cycle by providing a balancing chamber and gap parameters that have a relationship with the combustion chamber volume of the engine 5 Variation of these parameters within certain limits will allow an engine to operate on a balanced heat cycle that has many of the advantages of both the Otto and Diesel cycles with few or none of their disadvantages In particular an engine operating on a balanced cycle has better operating engine performance, overall engine speed and load conditions, better fuel economy and less emission of pollutants These are some of the advantages not found in the 10 prior art technique and devices mentioned above.

In co-pending Application No 42225/77 (Serial No 1591124) there is described and claimed a time dependent process for carrying out an energy conversion cycle involving converting chemical energy into thermal potential by utilizing the pressure waves generated during the rapid reaction of a combustible fuel in the presence of oxygen and using the 15 thermal potential for producing useful work in the combustion chamber of a piston type internal combustion engine operating over periodic cycles that each include an intake, compression, expansion (work producing) and exhaust event, characterized by, for each cycle:

(a) supplying air alone into a combustion chamber of the engine during the initial portion 20 of the intake event while the volume of the combustion chamber is increasing; (b) adding fuel into the combustion chamber during a later part of the cycle, the total quantity of fuel being selected to provide a reaction that will rapidly produce a predetermined thermal potential and a predetermined maximum pressure in the combustion chamber; 25 (c) increasing the temperature of the total quantity of air and fuel admitted during the cycle by compressing at least the air during the compression event; (d) partially isolating a portion of the initially supplied air from substantially all of the later supplied fuel during the cycle by placing a portion of the initially supplied air in a reservoir chamber located adjacent the combustion chamber, said reservoir chamber com 30 municating with the combustion chamber through a narrow gap that permits transmittal of pressure gradients between the combustion and reservoir chambers, and maintaining the isolated portion of air in the reservoir chamber free from substantial contamination with fuel throughout the cycle; (e) igniting the fuel in the combustion chamber to initiate its rapid reaction with immedi 35 ately available oxygen near the end of the compression event, therebygenerating a continuous series of pressure shock and expansion waves that traverse the combustion chamber and intersect the gap to produce pressure differentials between the combustion and reservoir chambers independently of the total pressure in the combustion chamber and continuing throughout the reaction; 40 (f) permitting and promoting by combustion and reservoir chamber geometry, and gap configuration, the cyclic rapid rebound and reentry of the shock waves across and through the gap at a rate to cause controlled pumping of oxygen into the combustion chamber from the reservoir chamber due to the said pressure differentials between the chambers throughout the combustion event; 45 (g) permitting expansion of the combustion chamber during the expansion (work producing) event; (h) exhausting the combustion chamber near the end of the expansion event.

Claims (1)

1. WHAT I CLAIM IS:-

   1 An internal combustion engine including a reciprocating piston having a working face 50 moving within a variable volume cylinder that includes a combustion chamber, the working face of the piston being located towards said combustion chamber, and additionally comprising:

   a fixed volume air chamber located next to the working face of the piston and separated from the combustion chamber at the upper region of the fixed volume air chamber by a 55 circumferential gap extending between the edge of the working face of the piston and the adjacent cylinder sidewall, the gap arranged to permit continuous exchange of compression shock and expansion wave energy between the combustion and air chambers during a combustion reaction of fuel and air in the combustion chamber, the length of the air chamber extending along at least a portion of the circumference of the piston beneath its working face 60 and the air chamber having a radially inner sidewall including a portion which slopes with respect to the cylinder sidewall and extends from the piston side edge of the gap towards the bottom area of the air chamber, said inner sidewall being continuous and uninterrupted over the entire length of said air chamber, and said sloping portion generally diverging away from the adjacent cylinder sidewall over its respective length 65 1,591,125 7 1,591,125 7 2 An internal combustion engine as claimed in Claim 1, said piston having an upper compression sealing ring, and wherein the air chamber has a generally flat, radially extending bottom wall located just above the compression sealing ring, and said sloping sidewall portion is generally planar and extends between the said bottom wall and the piston side edge of said gap to thereby define a wedge-shaped cross section of said air chamber 5 3 An internal combustion engine substantially as hereinbefore described with reference to and as illustrated in Fig 1 A of the accompanying drawings.

   For the Applicants:POTTS, KERR & CO, 10 Chartered Patent Agents, 15, Hamilton Square, Birkenhead, Merseyside, L 41 6 BR.

   and 15 27, Sheet Street, Windsor, Berkshire SL 4 1 BY.

   Printed for Her Majesty's Stationery Office, by Croydon Printing Company Limited, Croydon, Surrey, 1981.

   Published by The Patent Office, 25 Southampton Buildings, London, WC 2 A IAY, from which copies may be obtained.