The invention relates to a machine such as an inter¬ nal combustion engine and/or compressor or pump compris¬ ing a metal housing, at least one cylindrical bore which is arranged in this housing and- which can be closed on both ends by a cylinder cover fixable to the housing, feed(s) and discharge connected to each of both ends of each cylindrical bore for supplying fuel mixture, air and fuel, air or liquid, respectively for discharging combus¬ tion gases, compressed air or pressure liquid, in each cylindrical bore at each of the ends a chamber is bounded by the wall of the bore, the cylinder cover and a closed end wall of a hollow piston reciprocally movable along a predetermined stroke and enclosed by a piston skirt, at least one passage recessed in the skirt in lengthwise direction of the piston and having a length which corre¬ sponds with the stroke and which during the movement of the piston can always correspond with an opening in the wall of the cylindrical bore in the housing, sealing means between the piston skirt and the wall of the cylin- drical bore and comprising means for coupling a rotatable shaft or the like to the piston consisting at least of a piston rod fixed thereto on one side inside the cavity of the piston and pivotally connected to a link rod and/or a crank of a crankshaft, wherein at least one of the means extends through the passage and the opening.

Such a machine is known from the Netherlands publi¬ cation 8800036 or the European patent application 454627.

These known machines have the drawback that the housing and/or the pistons with associated mechanisms are complex, particularly since the cylinder does not have a constant bore and slots are formed in the piston skirt over a considerable part of its length at two mutually opposing zones to allow passage of moving parts which convert the translation of the piston into rotation of the crankshaft and due to the use of complicated trans-

missions between the crankshaft mechanism and the shaft for rotating connected thereto, such as rotating housing parts inside which the piston moves, gear transmissions mounted on the housing, auxiliary pistons and the like, the engines are thereby costly, the manufacture requires much expert knowledge and, due to the many rotating components which have to be geared very precisely to each other, the engines are susceptible to breakdown, wherein repair and maintenance are costly and must be provided by experts.

The invention provides an engine, pump or compressor which is of simple structure, entails comparatively low cost and can be serviced by an average mechanic .

For this purpose the engine according to the inven- tion is characterized in that the diameter of the bore is 1-5 times larger than the stroke, the piston rod, crank and associated part of the crankshaft and the balance weights are arranged within the inner dimension of the cavity of the piston, the corresponding openings in the housing are cylindrical and have a smaller diameter than the greatest length of the passages in the piston skirt, the crankshaft is mounted in the cylindrical openings of the housing and the position of the mounting of the crankshaft is fixed relative to the housing. A robust and operationally reliable engine is provided by the compact structure with simple and straightforward components. A preferred variant of the engine, compressor or pump according to the invention is characterized in that the passage in the piston skirt has a shorter length than the corresponding opening in the housing.

With this embodiment it is nevertheless possible with a relatively small opening in the piston wall to transmit a large moment to the crankshaft. The link rod is connected to the piston rod. This preferred embodiment is improved further in that the passage in the piston skirt and the opening in the housing extends outward into a second housing part arranged connecting onto the hous¬ ing, the link rod is mounted at its other end on the crank of a crankshaft, the link rod is supported pivotal- ly between both ends using an intermediate support and

the link rod is mounted for displacement in lengthwise direction on piston rod and/or intermediate support and/or on the crank.

With the improvement according to this variant of the construction of the engine according to the invention it is possible, making use of the levering action, to influence the force exerted by the link rod on the crank by the choice of the position of the intermediate sup¬ port, whereby it is possible to- apply a large moment with a relatively small engine.

The link rod must of course be dimensioned for the bending stresses caused therein and the bearings must be designed for the bearing pressures which occur, but these specifications fall within the technical knowledge of the engine constructor.

A further advantage of this variant is that the crank/piston rod mechanism is disposed at a further distance from the combustion chambers, wherein there is less danger of overheating thereof. The machine according to the invention is particu¬ larly suitable as a combustion engine which is flushed with compressed air and the combustion gases are com¬ pressed prior to being fed to the combustion chambers. The efficiency of the combustion engine can be greatly improved in this manner.

In a further developed embodiment of the combustion engine, by pre-flushing an engine with two-stroke action with compressed air for a short time and thereafter further filling it with the compressed combustible mix- ture the utility of the two-stroke engine is increased and a small engine can deliver great power.

That in the very compact engine a comparatively large amount of heat is developed will be apparent, although with a good cooling of the housing and optional additive cooling of the motor oil the surplus heat can be discharged.

The invention therefore improves in simple manner the method of compression and supply of the compressed gases to the combustion chambers .

Due to the over-square arrangement of the piston- cylinder combination the hollow space inside the piston is sufficiently large to accommodate a crank-piston rod mechanism without additional slots in the piston and local widenings of the cylinder being necessary with the extra operations associated therewith and the dangers of fouling. Particularly in the variant of the engine ac¬ cording to this variant of the invention the ratio diame¬ ter cylinder : stroke will be chosen in the order of magnitude of 2 : 1, preferably 2.2 : 1. When the chamber is used as pre-compressor this ratio can be chosen even larger, wherein the stroke volume must also be adapted to the desired amount of pre-compressed gas.

The use of the machine as hydraulic pump or as compressor also means an improvement in the known pumps and compressors, particularly also due to the high pres¬ sures which can be reached and larger quantities of compressed gas and pressure liquid to be delivered.

Mentioned and other features of the invention are elucidated hereinbelow with reference to a schematic drawing. Schematically in the drawing: fig. 1 shows a longitudinal section through an embodiment of the machine as internal combustion engine in four-stroke arrangement according to the invention, wherein the crank-piston rod mechanism is accommodated inside the inner wall of the piston skirt; fig. 2 shows a section of the piston assembly of the engine of fig. 1 drawn in side view; fig. 3 shows a section along the line III-III of fig. 2, wherein the cylinder halves are drawn separated from each other; fig. 4 shows a section through a variant of the engine of fig. 1 embodied as two-stroke engine, wherein the engine has a combustion chamber and a gas compression chamber; fig. 5 shows a section of an embodiment of the engine of fig. 4 embodied as double two-stroke engine; fig. 6 shows an assembly of a plurality of cylin¬ der/piston combinations of a variant of the engine of fig. 4 and 5;

fig. 7 shows a four-stroke multi-piston engine as according to fig. 1, wherein a cylinder/piston combina¬ tion is embodied as air compressor; fig. 8 shows a sketch of the dimension ratios in an engine as according to any of the fig. 2-6.

Shown in fig. 1 as an embodiment of the engine according to the invention is a cylinder/piston unit of a four-stroke boxer engine.

Housing 1 with cylindrical- bore 2 is closed on both sides by cylinder covers 3 and 4. In the cylinder covers are arranged inlet valves 5 and outlet valves 6, in addition to sparking plugs 7.

A piston 11 consisting of cylinder halves 9 and 10 mutually connected with connecting means 8 is reciprocal- ly movable in the cylindrical bore.

Piston 11 is connected pivotally by means of a pin 12 to a piston rod 13 which is pivotally connected on the other side to a crank 14 with crank webs 16 of a crank¬ shaft 15 which is mounted through the opening 18 in the piston in a crankshaft bearing arranged in housing 1.

On the housing is arranged a crankcase 17 with motor oil 20 which is pressed by a pump 19 to the locations in the engine which must be lubricated.

In the machines according to the invention the valves are preferably operated by electronically con¬ trolled valve lifters 21, although a valve lifter system with cam shafts, tappets and valve lifters or the like may of course also be applied.

The crank travels through a path 22 when piston 11 is moved reciprocally.

Fig. 2 and 3 show details of the piston halves 9 and 10, the opening 18 and crankshaft 15 with crank 14 and crank webs (with balance weights) 16.

The engine of fig. 4 is a variant of the engine of the preceding figures, wherein in a connecting block 23 of piston 111 a pin 121 is mounted pivotally and for movement over a predetermined distance in horizontal sense relative to block 23. In this variant the piston rod 131 moves through opening 27 in the housing 1' pro- vided with cooling spaces 28 into a second housing part

29, which piston rod 131 is embodied in this variant as a lever which can swivel on support shaft 24 and engages on the other end round the pin 25 of a rocker lever 26 movable over a predetermined distance in horizontal sense, which lever is connected on the other side to the crank 141 of crankshaft 151.

Connected to the crankshaft is a flywheel 30 on which can be arranged a gear rim with a starting motor. The engine is embodied as two-stroke engine with a com- bustion chamber 31 and a compressed air chamber 32.

Air is drawn into compressed air chamber 32 through filter 33 via inlet valve 34 and, during downward move¬ ment of piston 111, compressed and pressed via delivery valve 35 though pressure conduit 36 to pressure vessel 37. This latter communicates via the compressed air feed 38 with the pressure space 39 above the electronically controlled compressed air valve 40.

When the piston is almost in the lowest position and combustion chamber 31 begins to communicate via ports 42 with the combustion gases outlets 43, the spring-loaded compressed air valve 40 is opened so that fresh com¬ pressed air flows into combustion chamber 31 and pushes combustion gases out of combustion chamber 31. When the piston thereafter compresses the fresh air and is almost at the end of the stroke, fuel is sprayed into combustion chamber 31 via fuel injectors 41. When the fuel is oil and the compression in the combustion chamber is suffi¬ ciently high, the injected fuel will ignite in the air strongly heated by the compression. When a lesser com- pression takes place and petrol or the like is injected, an electronically controlled sparking plug will be re¬ quired to generate a spark at the correct moment to cause ignition of the mixture in combustion space 31.

In the case of petrol as fuel it is of course also possible tc form a combustible mixture and carry it into the pressure space 39.

In such an engine it is less necessary to supply highly compressed air and it is advantageous to apply a double-action two-stroke engine.