Internal combustion engine

A two-stroke internal combustion engine having at least two cylinders which are aligned, each cylinder having a piston. The pistons are rigidly attached to each other by means of a piston rod which is provided with a carrier and exhaust valves, the valves being slidably arranged on the piston rod, and exhaust ducts which are provided for each cylinder at the ends facing each other. The facing ends also having valve seats. Intake ports having pressure controlled check valves are provided in each cylinder at the distal ends, and each combustion chamber is on the side of the piston which faces the other piston. The exhaust ducts are arranged in a guide for the common piston rod.

The present invention concerns an internal combustion engine, more 
particularly a piston engine of the type disclosed in the introduction to 
the subsequent independent claim 1. 
Primarily, the engine is intended for use in operations requiring a 
reciprocating motion, such as a hydraulic pump, a piston compressor, foil 
etc. but it can also be used to transfer the reciprocating motion to a 
rotating motion by means of a conventional crank mechanism. 
Internal combustion engines in various designs have been suggested to a 
relatively large extent, even if not all have found practical application 
for various reasons, such as high production costs, many moveable parts, 
high fuel consumption, poor efficiency, extensive space requirements etc. 
According to Swiss Patent Publication No. 640.600 an engine is, admittedly, 
known which overcomes some of the above-mentioned drawbacks. The engine 
has two moveable pistons which are rigidly attached to each other by means 
of a piston rod. However, said engine has been provided with combined 
scavenge pistons and valves on the piston rod. On ignition in one of the 
combustion chambers, the piston and the scavenge piston are pushed in the 
same direction. When the piston reaches the exhaust ports in the cylinder 
wall, the piston rod opens up ducts for scavenging with the air/fuel 
mixture, this being a form of cross-scavenging. The flow section for the 
scavenging mixture is very limited, however, while the scavenging pressure 
seems too low, combined with a short time lapse for opening between the 
valve effective parts, which leads to poor gas exchange and lower 
efficiency. Also, the negative pressure built up on one side of the 
scavenge piston seems very restricted, so that the supply of fresh charge 
will be negligible. 
The object of the present invention is to provide an engine of simple 
construction with few moveable parts, a high degree of efficiency, low 
fuel consumption, and limited space requirements, where also the 
above-mentioned disadvantages according to the prior art are avoided. This 
is achieved by means of two moveable pistons which are rigidly attached to 
each other by means of a piston rod, which rod, according to the 
invention, is provided with a carrier and exhaust valves, said valves 
being provided slideably on the piston rod, and exhaust ducts which are 
provided for each cylinder at the ends facing each other. These ends also 
have valve seats. The cylinders are also provided with intake ducts where 
pressure controlled check valves have been placed, the ducts leading into 
intake ports which have been arranged in each cylinder at the ends turned 
away from each other. Each of the combustion chambers pertaining to the 
engine are on the side of the piston which faces the other piston. The 
pistons may be provided with one or more valves in order to increase the 
charge supply further. It is advantageous to have the intake ducts of the 
engine connected to an overcharging device, however, this is not 
essential. At the same time, the pistons themselves are acting as scavenge 
pistons, the scavenging being longitudinal scavenging with good control of 
the gas exchange process.

The engine has two cylinders 6 which are aligned. In each of the cylinders 
there is a moveable piston 4, said pistons being rigidly attached to each 
other through a piston rod 5, a carrier 7 being attached to the piston rod 
5. The valve head 8' of the exhaust valves 8 communicable with exhaust 
ducts 3 is slideably arranged on the piston rod 5. Each exhaust valve head 
8' can be seated against a valve seat 8" which is arrranged at the end of 
a cylinder 6 that faces the other cylinder 6. The exhaust valve head 8' 
has devices (not represented in the drawing) for temporarily locking the 
valve head 8' to the piston rod 5, for instance by means of a per se known 
spring catch action device which may consist of a spring-loaded ball held 
in the valve head and co-acting with a groove along the circumference of 
the piston rod. In this way, the valve head 8' is held in a certain 
position on the piston rod 5 until the parts are mutually exposed to a 
force sufficiently strong to push the ball out of engagement with the 
groove, thereby freeing the valve to move relative to the rod. As an 
alternative way of keeping the valve in a desired position, a suitable 
spring 10 may be arranged between the piston 4 and the valve head 8'. 
Moreover, the engine is provided with intake ducts 2 having check valves 
2a, each duct leading into an annular chamber 2b at the ends of the 
cylinders not facing each other. The combustion chambers pertaining to the 
engine have been marked 1. The pistons 4 may be provided with one or more 
valves 9 in order to improve the charge supply to the combustion chamber 
should the engine be overcharged. The pressure built up in the engine, 
causing the reciprocating motion of the pistons, may be taken out as 
output at B. 
In one of the end positions of the pistons (as shown in the drawing), the 
exhaust valve head 8' seals against the valve seat 8" principally because 
of the compression pressure exerted on the valve. In the alternative 
embodiment the spring 10 assists in pressing the valve 8 against the valve 
seat 8". In this position a compressed air/fuel mixture is ignited in one 
of the combustion chambers 1, driving the piston 4, the piston rod 5 and 
the carrier 7 upwards. The check valve 2a in the intake duct 2 will be 
closed. The exhaust valve 8 remains closed until the carrier engages with 
the valve head 8' and pushes this from the valve seat 8", thereby opening 
for discharge of the combustion products. The medium over the piston 4 is 
compressed until the piston passes the intake duct 2, and subsequently 
escapes to the underside of the piston via the annular chamber 2b, 
assisting to drive the combustion product out through the open exhaust 
valve 8 in the exhaust ducts 3. At the same time, the valve 2a in the 
intake duct is opened for supply of fresh charge to the cylinder 6. The 
fresh charge is supplied to the combustion chamber 1 until the piston 4 
again passes the intake duct 2 on its way down. In the case of 
overcharging, if the piston 4 is provided with refill valves 9, these will 
be open until the compression pressure exceeds the charge pressure. The 
charge is compressed until the piston unit reaches its end position ready 
for a new work sequence. 
The lower piston works correspondingly, except that the working stroke 
starts when the other piston has gas exchange. In this manner, the engine 
acts according to the two-stroke principle. 
It is significant that the engine can function through its work cycle 
without any extra devices such as counterbalancing devices like for 
instance flywheels, counterweights etc.