An apparatus for transforming a reciprocating movement to a rotating movement, or vice versa, is known from the Swedish laid out publication 433.393, which discloses an axial-to-rotary transforming apparatus, in which an endless cog belt is actuated by a reciprocatally moving slide and comprising a ratchet wheel having three cog segments provided at an angle of 120" from each other and each having a few cogs for co-operation with the cog belt, and which cog wheel is adapted to rotate a certain distance at each end position, whereby the cogs change contact from one cog belt path to the other cog belt path.

A disadvantage with said apparatus is that the cog belt is moving at the moment when the ratchet wheel changes contact between the two cog belt paths, whereas the slide is still standing. This leads to the appearance of a non desired play in the rotary movement. Also, said known apparatus is not formed so that it can be used in combination with a pneumatic piston-cylinder apparatus.

In the present invention the driving takes place from the shaft end of the reciprocatable motor, and the drive force from the cylinder controls the

change of operation while the piston rod is moving, and therefore there will be very little, if any, interruption in the drive function. When the coupling means of the yoke has come into engagement with the drive drive belt the engagement force is determined by the magnitude of counter force emanating from the output shaft or shafts, that is by the actual load on the output shaft or shafts. This is accomplished in that one or more ratchets or pawls of the coupling means clamps the drive belt safely against the inner surface of the yoke. The greater counter force is applied to the output shaft the greater force is applied between the pawl or pawls and the yoke. Thanks to this construction it is possible to provide a fully effective function even using a smooth of only slightly fluted drive belt, for instance a reinforced drive belt having a rough surface, or even a conventional V-belt.

Thus, according to the invention the piston rod end of the reciprocatable motor is connected to a yoke which surrounds the two paths of the drive belt, which yoke encloses two opposed ratchet/pawl means, whereby one of said ratchet means provides a fixed clamping of a first one of the drive belt paths between said ratchet/pawl means and the inner surface of an outer frame of the yoke at the active expelling stroke of the piston, and thereby a driving of drive belt, corresponding to the expelling stroke of the reciprocatable motor, and in which the other ratchet/pawl means, at the return stroke of the piston, provides a driving against the second drive belt path, whereby the drive belt will move in one and the same direction at both piston movement directions, and whereby the shafts of the two pulleys will rotate in one and the same direction.

In a preferred embodiment of the invention the inner sides of the yoke frame are formed with a friction increasing surface, for instance a fluted or otherwise formed inner surface. Also the drive belt can be formed with a friction increasing outer surface, for instance a fluted outer surface. The invention also includes the possibility of forming the inner sides of the yoke with inner cog segments and the forming the outer side of the drive belt with outer cogs. Normally it is, however, quite sufficient to use a drive belt not having any cogs, even a V-belt.

The characterizing feature of the invention is that the output shafts of the pulleys are formed with gears which are surrounded by a drive wheel having inner cogs or teeth and which is driven by the gears of the pulleys, and the shaft of which acts as a final shaft of the apparatus. Thereby said final

shaft of the apparatus gets a strongly reduced rotation speed and thereby exerts a correspondingly high torque transmittance.

The large output drive wheel acts as a type of fly wheel which overbridges the siight interruption in the driving appearing when the reciprocatable axial motor changes direction from expelling movement to retraction movement. Thereby the output wheel gets an even and practically constant rotation speed.

Now the invention is to be described more closely in connection to the accompanying drawings which show a couple of embodiments of the invention. In the drawings figure 1 shows an embodiment of an apparatus according to the invention, for sake of clearness in a partly cut open condition.

Figure 2 shows an alternative embodiment of a twin system comprising two pneumatic axial motors. Figure 3 is a cross section view along line Ill-Ill of figure 1. Figure 4 is a partial view in an enlarged scale of the drive system of the apparatus including the yoke, and figure 5 shows how the yoke has been rotated 180" along its longitudinal axis, thereby providing a reversing of the actuation direction of the drive belt.

For the sake of simplicity the axially reciprocatable motor will in the following be referred to as a pneumatic motor. It is, however, to be understood that the specification, claims and drawings also include other types of motors like gas motors or hydraulic motors.

The apparatus shown in figure 1 comprises a pneumatic axial-to-rotary motor which co-operates with a large output wheel, and which apparatus comprises a pneumatic piston-cylinder arrangement 1 having a stationary cylinder 2 and a reciprocatable piston rod 3. The cylinder 1 carries, at the free end thereof, a pulley 4 mounted in a pulley holder 5. A second pulley 6 is mounted in a stationary pulley holder 7 spaced from the pneumatic piston- cylinder arrangement 1. Each of the first pulley 4 and the second pulley 6 is mounted on a rotary output shaft 8 and 9, respectively, and each said output shafts carries a gear (cog wheel) 10 and 11, respectively. An endless belt 1 2 extends over the two pulleys 4 and 6, which belt 1 2 can be a cog belt, a reinforced smooth belt, a V-belt, a chamfered or otherwise treated belt, preferably formed with an outer surface having a friction increasing surface covering. The belt operates with an upper and a lower drive belt path 1 2a and 1 2b, respectively.

As best seen from figures 4 and 5 the two belt paths 1 2a and 1 2b are surrounded by a yoke 1 3 which is fixed anchored at the outer end of the piston rod 3 and which is formed with an upper frame part 1 4a and a lower frame part 1 4b inside which frame parts the belt paths 1 2a and 1 2b are slidable. Inside the yoke there is a double acting ratchet means comprising an upper, angularly formed ratchet or pawl 1 5 which is rotatable about a pin 1 6 which is mounted at the end of the yoke located closest to the piston rod 3, and a second, angularly formed ratchet or pawl 1 7 which is rotatable about a pin 1 8 which is mounted adjacent the opposite end of the yoke. The ratchets or pawls 1 5 and 1 7 are biassed in opposite directions by a double acting spring 1 9 which is mounted between said pawls.

Due to the shape and the location of the pivot axis place of the pawls 1 5 and 1 7 the upper pawl 1 5 will, upon expelling of the piston rod 3, be forced into engagement with the inner side of the upper belt path 1 2a by the piston rod 3 of the pneumatic motor with a pressure which is proportional to the load which is applied to the output shaft or shafts 8 and 9, and which is increased to the same extent that the load on the rotation shaft is increased.

The belt path 1 2a is thereby pressed against the inner side of the upper yoke frame part 1 4a and is kept clamped thereto. As mentioned above the belt can be formed with a friction increasing surface covering, and the inner side of the outer frames 1 4a and 1 4b can be fluted of correspondingly formed with a friction increasing surface. The lower pawl 1 7 will, at the same time, slide free of force, against the inner side of the lower belt path 1 2b.

When the piston rod 3 has completed a stroke outwards of the cylinder 2 and changes direction thereby starting its retraction movement the lower ratchet or pawl 1 7 is correspondingly pressing the lower belt path 1 2b into contact with the lower outer frame part 14b, and the upper pawl 1 5 is, free of force, training over the lower belt path 1 2b.

It is possible to make use of other types or ratchets or pawls, in particular positively controlled pawls which, in dependence on the force of the pneumatic axial motor, forces the belt into engagement with the yoke parts, thereby providing a slip free and safe driving.

By forming the yoke rotatable about its longitudinal axis it is possible to invert the direction of movement of the drive belt. In figure 4 is shown that the drive belt is operated in the clockwise direction (see the arrows at the belt paths 1 2 and 1 2b). It is also indicated with the arrow of rotation that the yoke can be rotated, namely over an angle of 1800, and in figure 5 the yoke is

rotated accordingly whereby the belt is driven in the inversed direction, that is in counter clockwise direction as indicated with the arrows of the drive belt paths 1 2a and 1 2b in figure 5. In both cases only the function upon expelling of the piston rod 3 is shown.

In the very moment of inversing the movement of the piston rod 3 the drive force on the drive belt 1 2 is interrupted for a very short moment, namely at the moment when the drive force changes from being caused by one pawl 1 5 to being caused by the second pawl 1 7. For many purposes such short lack of drive force is of no practical importance, especially not in the case illustrated in the drawings, in which the rotatable shafts are co-operating with a large outer ring which acts as a type of fly wheel and in which some some fly wheel effect overbridges said lack of drive force.

For eliminating, however, eventual problems depending on such short moments of lack of drive force on the drive belt 1 2 the apparatus may, as shown in figure 2, be formed with two or more pneumatic axial motors which act in common on the output shafts 8 and 9 and on the shaft 21 of the outer ring 20, but in which the yokes 1 3 and 13' of the respective axial motors are displaced a slight distance in relation to each other on the drive belts 12, 12'.

This has an effect that the changing between expelling and retracting operation of the piston rods 3 and 3' foliow at different times for the respective axial motor, whereby the rotated shafts 8 and 9 are constantly subjected to drive force, either from the drive belt 1 2 of one axial motor or from the drive belt 12' of the other axial motor, or from both drive belts at the same time.

In figure 2 is shown that the pneumatic axial motors are mounted parallelly to each other. Alternatively it is possible that arrange the axial motors opposed to each other or at any desired angle in relation to each other.

For providing a very high torque of the output shaft the apparatus is formed so that the gears 10 and 11 on the shafts 8 and 9 are surrounded by a large wheel 20 having inner teeth which co-operate with the gears 10 and 11 of the axial motor or motors, and the output shaft 21 of which gets a strongly gear reduced rotational speed and a corresponding possibility of transferring high torques.

There is a possibility of taking out force from both gears 10 and 11 and from the output shaft 21 of the large fly wheel 20. Alternatively, or in combination therewith, there is also a possibility of taking out force by means

of an outer belt 22 extending over the outer surface of the large fly wheel 20.

REFERENCE NUMERALS 1 piston-cylinder arrangement 2 stationary cylinder 3 piston rod 4 pulley 5 pulley holder 6 pulley 7 pulley holder 8 output shaft 9 output shaft 10 gear 11 gear 12 belt (12a, 1 2b) 13 yoke 14 frame (14a, 14b) 1 5 ratchet, pawl 16 pin 1 7 ratchet, pawl 18 pin 19 spring 20 outer ring 21 shaft 22 outer belt