GB2260798A - Kinematic connecting mechanism for periodical motion between two coaxial shafts - Google Patents

Abstract

A mechanism for transforming the rotary motion of a first shaft 8 into a rotary cyclically variable output of a second shaft 9 coaxial with the first shaft 8 comprises two parallel auxiliary shafts 17, 22 respectively connected to the input and output shafts 8 and 9 via gearing 14, 16 and 15, 23, the first auxiliary shaft 17 having a radial arm 18 provided with a longitudinal guide 19 into which is slidably fitted a pin 20 associated with a crank 21 fixed to the second auxiliary shaft 22. The mechanism may be associated with an I.C. engine (see Fig 4), with the output shaft 9 being connected to the pistons (42) via diametral cranks (37). <IMAGE>

Description

KINEMATIC CONNECTING MECHANISM FOR PERIODICAL MOTION BETWEEN TWO COAXIAL SHAFTS.

This invention concerns systems for transmission and transformation of motion between rotating shafts.

The problem of transforming alternating movement into rotary movement, and vice versa, is well known and is of extreme importance in a wide field of mechanical applications.

Mention need only be made of the widespread use of engines and pumps fitted with pistons. Transformation of the alternate linear movement made by pistons into the rotating movement of a shaft is basic to operation of these machines.

In conventional piston-operated machines the piston stops twice in each cycle, namely at the upper dead position and at the lower dead position, and starts off again at a speed, and acceleration, each time in the opposite direction.

Reversal of piston movement involves severe losses of efficiency due to passive resistance and to problems related to vibration. Vibration in fact means noise and heavier wear on the mechanical parts of these machines.

Subject of the invention is a kinematic means of connection between two coaxial shafts, the purpose of which is to transform the rotary motion of the first shaft into an alternatively faster and slower rotary motion of the second shaft compared with the first. The kinematic mech any sum comprises at least two non-coaxial auxiliary shafts having parallel axes. The first auxiliary shaft is connected to the first main shaft by a means for transmitting motion while the second auxiliary shaft is connected to the second main shaft by another means for transmitting motion.

The first auxiliary shaft has a radial arm in which there is a longitudinal guide channel. In said longitudinal guide an articulated pin is fitted into a crank fixed to the second auxiliary shaft.

Rotation of the radial arm of the first auxiliary shaft causes the pin in the second auxiliary shaft to slide in the longitudinal guide on the radial arm.

In this way pin eccentricity in relation to the axis of the first auxiliary shaft increases and lessens periodically. This determines a certain oscillating motion of the second auxiliary shaft with respect to the first auxiliary shaft and, consequently, a certain oscillating motion of the second shaft with respect to the first.

Advantageously, if the first and second means of motion transmission, which connect the two coaxial shafts to the two auxiliary shafts, have complementary ratios of transmission, namely, ratios that are the same and inverse.

In this way the period of rotation and the mean angular velocity of the first and second shafts are equal.

Preferably the second means of motion transmission consist of toothed gear wheels.

In a preferred form of utilization the two coaxial shafts are the shafts of an internal combustion engine and they rotate supported by the engine block.

The first shaft is fixed to the body of the engine comprising at least one cylinder with a longitudinal axis tangential to a circumference whose centre lies on the axis of the two coaxial shafts.

To the second shaft is fixed a crank joined by a connecting rod to a piston inside the cylinder.

In this way, during rotation of the coaxial shafts and due to the oscillating movement of the second shaft in relation to the first, induced by the kinematic mechanism, piston movement inside the cylinder alternates.

Movement of the shaft fixed to the body of the engine, and of the coaxial shaft connected to the pistons, are controlled by ratchet gears or by other suitable devices, to ensure that said shafts shall move in the same direction only.

It follows that when the mixture explodes, one of the two parts - cylinder or piston according to the direct ion imposed by the ratchet gears - will be thrust foward and the other part will be compelled to follow it at a periodically varying speed.

A mushroom valve is situated at the cylinder head, said valve having a return spring controlled by a rocking lever, mounted on the body of the engine, whose free end slides on a roller against a circular cam fixed to the engine block.

During engine rotation, therefore, said end of the rocking lever, when sliding along the cam, rises on reaching the raised parts and in so doing opens the valve.

Means for ignition of a fuel mixture are placed on the cylinder head.

Fixed to the body of the motor is an axial distribution disk in which there are ports, connected to the combustion chamber, in contraposition to oblong ports made on a disk coaxial with and parallel to the rotating disk fixed to the engine block. Said oblong ports are connetted to devices for feeding in the fuel mixture and for discharging exhaust gases.

In the body of the engine there is an airtight chamber communicating with the cylinders and with the feed ports so that when the pistons move downward to bottom dead centre (BDC) the mixture is compressed and transferred to the combustion chamber.

The invention clearly offers a number of advantages.

The kinematic mechanism is simple, strong and low cost.

The smaller number of gears and the light weight of rotating parts help to keep down to minimum both losses due to friction and also the mechanism 5 overall moment of inertia.

By application of the kinematic mechanism to machines with pistons and cylinders, engines or pumps can be built having rotating cylinders in which the piston follows the cylinder, accelerating and decelerating in relation to it, but never reversing the direction of rotation.

This change from an absolute alternate motion of pistons to a relative alternate motion drastically reduces losses caused by inertial forces and passive resistance, namely the negative features characteristic of engines or alternate motion machines generally.

All the above can be achieved by simple, compact and inexpensive means.

Further, since the cylinders and pistons are rotating, there is no need for heavy flywheels to increase stability of rotation.

Another point in favour of the invention is that operation of any valves there may be is simplified and more direct than is possible in machines with absolute alternate motion.

Characteristics and purposes of the invention will become still clearer from the following example of its execution illustrated by diagrammatic figures.

Fig. I Plan view of the kinematic mechanism.

Fig. 2 Side view of the kinematic mechanism.

Fig. 3 Diagram to show how it operates.

Fig. 4 Rotating internal combustion engine with two cy linders, in cross section.

Fixed to a shaft 8 is a gear 14 and fixed to a hollow shaft 9, coaxial with shaft 8, is a gear 15.

Gear 14 meshes with a gear 16 fixed to a shaft 17 whose axis is parallel to that common to the two shafts 8 and 9.

the supported shaft 17 rotates freely and, at one end, car-ries a radial arm 18. The outer side of said arm 18 contains a longitudinal guide channel 19.

Inside said guide 19 slides the head of a circular-shaped pin 20. Pin 20 is articulated on a crank 21 fixed to another shaft, 22, whose axis is parallel to that of shaft 17.

Fitted onto shaft 22 is a gear 23 that meshes with the gear 15 mounted on shaft 9.

The ratio of transmission between gears 14 and 16 is equal but is inverse to the ratio of transmission between gears 23 and 15.

In making its movement the crank, 21, describes a circle 24 (Fig. 3) while the arm 18 describes a circle 25. On circle 25, numbers progressing from I to VIII mark out arcs corresponding to one eighth of the circumference.

Allowing for the way in which the pin 20 slides eccentrically along arm 18, further arcs, from I to VIII, have been geometrically marked out on circle 24, each one corresponding to its respective arc on circle 25. While amplitude of the arcs through which arm 18 passes on circle 25 is virtually equal, that of the corresponding arcs on circle 24 will be seen to increase and decrease cyclically.

Clearly, therefore, shaft 9 tends to slow down and to accelerate in relation to shaft 8 within one period of rotation, while maintaining overall the same mean angular speed.

Fig. 4 illustrates a two-cylinder rotary internal combustion engine, numbered 30 in its totality, mounted on an engine block 31.

By means of a ball bearing 32 said block supports the hollow drive shaft 8 onto which is mounted the substantially cylindrical engine body 34 and the disk 48 opposed to another disk 52, coaxial with the first one and fixed to the engine block 31.

The engine body 34 comprises the two cylinders 35, whose position one to another is diametrically opposed, with their longitudinal axis tangential to a circumference the centre of which lies on the axis of shaft 9.

This body forms an airtight chamber 49 communicating with the cylinders 35 and has round it a cavity 50 filled with cooling liquid. Shaft 8 is coaxial with, and inside, shaft 9 and is fixed to diametral cranks 37 joined by connecting rods 40 to the gudgeons of the two pistons 42.

The combustion chambers 43, formed of cylinders 35 and pistons 42, are connected by ducts 51, on the heads 36 of the cylinders 35, to two ports 44 made in the rotating disk 48.

Said ports 44 are opposed to the oblong ports 54 situated on a disk 52, coaxial with the first, and fixed to the engine block 31, for discharge of combustion gases and for drawing in combustion fuel by means that are not shown here for the sake of simplicity.

Two spark plugs 53 are screwed onto the heads 36 of cylinders 35.

Two mushroom valves 45 with return springs 55 and worked by two rocking levers 46, pass through the ducts 51.

A circular cam 38 is fixed to the engine block 31 and the free ends of the rocking levers 46 slide along said cams.

When the rocking levers reach a raised part 39 in the cam, the valves 45 are found to open.

Clearly therefore we have formation of two rotating complexes: the first comprising the hollow drive shaft 9 and motor body 34 with cylinders 35, the airtight chamber 49, the rocking levers 46 and distribution disk 48, while the second comprises the shaft 8 with cranks 37, connecting rods 40 and pistons 42.

Said complexes are connected by the toothed gear wheels 15 and 14 to the kinematic mechanism illustrated in Figs.1 to 3.

The toothed gear wheel 14 is fixed to the shaft 8 and the toothed gear wheel 15 is fixed to the hollow shaft 9.

As the ratio between gears 14 and 16 of the kinematic mechanism is 2:1, it is evident that for each turn of the com plexes the kinematic mechanism concerned makes two turns.

Ratchet gears and other suitable devices (not included for simplicity in the figures) allow the above two complexes to rotate in one direction only, namely that corresponding to rotation of the cylinders 'before' the pistons.

The engine functions as follows.

When the spark plugs 53 ignite, the mixture compressed in the combustion chambers 43 by the cylinders 42 explodes provoking forward movement of the first complex with the cylinders 35 followed by the second complex with the pistons 42.

Since, at the time of explosion, the kinematic mechanism seen in Figures 1 to 3 occupies the position indicated by dotted lines 18' and 21' of the arms 18 with guides 19 and 21 and pin 20, it is clear that, as rotation proceeds, the second complex with the pistons rotates at a rapidly decreasing speed, the effect of this being to detach the pistons further and further from the bottom of the cylinders and enlarge the combustion chamber. This continues until the arms 18 and 21 reach the position shown in Figs.

1 and 2. On passing beyond this position, movement of the cranks 37 is quickened so that each piston reaches the bottom of the cylinder and the combustion chamber is recreated.

By means of the kinematic mechanism referred to, a relative alternate movement is thus set up between cylinder and piston even if cylinder and piston never move backward.

According to whether a four-stroke or a two-stroke engine is concerned, two alternate strokes of the piston will obviously be required, or else only one.

Since the ratio between the toothed gear wheels fixed to the engine's complexes and to those forming part of the kinematic mechanism is 2:1, the relative alternate strokes of the pistons will naturally be two per turn so that, for each turn, one cycle will be set up for four-stroke operation and two cycles for two-stroke operation.

The number of cycles per turn may of course be varied as desired by altering the ratio of transmission between the engine and the kinematic mechanism.

The air-tight chamber 49 may act as a pump seeing that it can be made to communicate with the combustion chamber and therefore when the pistons are moving down towards the BDC they can determine compression of the fuel mixture brought into the chamber through special ports and so its transfer into the combustion chamber.

Discharge of exhaust gases is made through the mushroom valves 53 and the circular ports 44 created on the rotating disk 48 and communicating with the combustion chamber, ports which lie in opposition to the oblong ports 54 made on the fixed disk 52 mounted on the engine block.

As the subject invention has been described and explained solely as an example in no way limited to this and for a presentation of its essential features, numerous variations may be made to it according to industrial,commercial or other needs and it may also be included in other systems and means without thereby leaving its sphere of operation.

It is therefore understood that, in applying for patent rights, every equivalent use of its concepts is included as well as every equivalent product executed and/or in operation according to any one or more of the characteristics set forth in the following claims.

Claims (11)

1. Kinematic mechanism to connect two coaxial shafts for transforming the rotatory motion of the first into an alternating accelerated and retarded motion of the second shaft in relation to the first, characterized in that it comprises at least two auxiliary shafts having parallel axes, the first auxiliary shaft being connected to the above first coaxial shaft by means of a first part for transmission of the motion and the second auxiliary shaft being connected to the above second coaxial shaft by means of a second part for transmission of the motion, and in that, on the first auxiliary shaft, there is a radial arm with a longitudinal guide in it into which is fitted a pin articulated onto a crank fixed to said second auxiliary shaft so that, due to rotation of the radial arm of the first auxiliary shaft, the pin on the second auxiliary shaft slides in the radial arm's longitudinal guide, periodically increasing and reducing its eccentricity with respect to the axis of the first auxiliary shaft determining a relative oscillating motion of the second auxiliary shaft in relation to the first auxiliary shaft and consequently a relative oscillating motion of the second shaft with respect to the first shaft.

2. Kinematic mechanism as in claim 1, characterized in that said auxiliary shafts are parallel to the coaxial shafts.

3. Kinematic mechanism as in claim 1, characterized in that said first and said second part for transmission of motion connecting said two coaxial shafts to said two auxiliary shafts have complementary ratios of transmission, namely equal and inverse, so that the period of rotation and the mean angular velocity are the same for both.

4. Kinematic mechanism as in claim 1, characterized in that said first and said second part for transmission of motion are toothed gear wheels.

5. Kinematic mechanism as in claim 1, characterized in that said two coaxial shafts are those of an internal combustion engine and rotate supported on the engine block, that said first shaft is fixed to the body of the engine comprising at least one cylinder whose axis lies at a tengent to a circumference the centre of which is on the axis of said two coaxial shafts, that fixed to said second shaft is a crank joined by means of a connecting rod to a piston inserted in said cylinder, so that during rotation of the coaxial shafts, due to the effect of the oscillating motion of the second shaft in relation to the first, induced by the kinetic mechanism, piston movement inside the cylinder alternates.

6. Kinematic mechanism as in claim 5, characterized in that the shaft fixed to the body of the engine and the coaxial shaft connected to the pistons are subjected to action by ratchet gears, or other devices suitable for making said shafts move in one direction only so that when the mixture explodes one of the two parts, cylinder or piston according to the direction imposed by the ratchet gears, will be thrust forward and the other compelled to follow it at a periodically varying speed.

7. Kinematic mechanism as in claim 5, characterized in that the cylinder head carries a mushroom valve with return spring controlled by a rocking lever pivoted on said engine body, whose free end slides on a roller against a circular cam fixed to said engine block so that, during rotation of the body of the engine, said end of the rocking lever, sliding on the cam, rises up on reaching the raised parts causing the valve to open.

8. Kinematic mechanism as in claim 5, characterized in that the cylinder head carries on it means for igniting a fuel mixture.

9. Kinematic mechanism as in claim 5, characterized in that an axial distribution disk is fixed to the body of the engine, said disk having in it ports connected to the combustion chamber said ports being opposed to oblong ports made in the disk coaxial and parallel to the rotating disk, fixed to the engine block, said ports being connected to devices for feeding in the fuel mixture and for discharging combustion gases.

10. Kinematic mechanism as in claim 5, characterized in that the body of the engine comprises an airtight chamber communicating with the cylinders and with the fuel supply ports so that when the pistons move down towards the BDC the mixture is compressed and transferred to the combustion chamber.

11. Kinematic mechanism substantially as herein described with reference to the accompanying drawings.