This invention relates to a speed variator comprising a drive shaft provided with at least one pair of eccentric discs whose eccentricity can be varied, also during operation, from a neutral position of zero eccentricity to a maximum value by means of a control device incorporated in the drive shaft, the eccentricity of the respective discs being mutually opposite, while a plurality of circumferential units are arranged on a pitch circle whose centre coincides with the centreline of the drive shaft and which is located in, or in the vicinity of, a plane in which the eccentric discs can oscillate during operation, these circumferential units each comprising a crank arm which can be driven for oscillation by one of the eccentric discs, the crank arms of the respective circumferential units each being dynamically connected to an output shaft via at least one unidirectional drive system, consisting of a freewheel system, via respective intermediate shafts and a transmission with a fixed transmission ratio.

Such a device is known from Netherlands patent specification 7201494 or Italian patent specification 1 051 549.

A drawback of the known speed variator is the control device incorporated in the drive shaft. Inasmuch as this control device is of mechanical construction, the assembly thereof is very complicated. Further, the known control device is subject to wear and must therefore be checked periodically and revised if necessary. Moreover, the costs of manufacture of the known control device are high, owing to the great number of parts from which it is composed.

For some applications, the known device has the drawback that, independently of the direction of rotation of the input shaft, the output shaft always has the same direction of rotation. In order to enable the output shaft to be rotated in both directions, therefore, a separate rotational-direction reversing box must be connected to the output shaft. Apart from the additional costs which such a box brings with it,

this box has a further disadvantage in that it introduces an additional source of friction and that, further, often a friction or fluid clutch is necessary to enable the direction of motion of the output shaft to be reversed. The object of the invention is to provide a speed variator without the drawbacks mentioned above.

To that end, a speed variator of the type described in the preamble is characterized according to the invention in that the control device for the eccentric discs, incorporated in the drive shaft, is of hydraulic, pneumatic or electromechanical construction and in that the respective unidirectional drive systems are reversible in that they comprise a double-acting freewheel system which is adapted for driving the respective intermediate shafts in a first direction of drive and in a second, opposite direction of drive, the respective unidirectional drive systems being reversible only when the rotational speed of the output shaft is zero.

Inasmuch as the control device for the eccentric discs, which is incorporated in the drive shaft, is of hydraulic, pneumatic or electromechanical construction, the number of parts thereof is considerably smaller compared with the known mechanical control device and the costs of manufacture of such a control device are significantly lower. At the same time, the assembly of the control device according to the invention is considerably simpler. Further, the hydraulic, pneumatic or electromechanical control device is hardly subject to wear and accordingly the invention provides a durable, reliably operating control device. Further, in such a speed variator, the direction of rotation of the output shaft is reversible without this necessitating the provision of additional reversal stages in the form of gearwheels in the device and hence without additional friction being introduced. Moreover, the hydraulic, pneumatic or electromechanical control device makes it readily possible to couple the reversing function of the unidirectional drive systems to it.

To that end, the speed variator is characterized, according to a further embodiment of the invention, in that the hydraulic, pneumatic or electromechanical control device of the eccentric discs is coupled to the respective unidirectional drive systems in such a way that these systems are reversible only when the eccentric discs are in the neutral position. Such a provision makes it impossible for the output shaft of the speed variator to be set into motion during reversal of the unidirectional drive system. This safety measure is necessary to prevent the output shaft, in case it rotates after the unidirectional drive systems have been reversed, from tending to impart rotation to the crank arms of the circumferential units, thereby damaging the speed variator irreparably. To provide for better distribution of the power to be transmitted to the intermediate shafts, and hence to enable greater power transmission, the speed variator is characterized, according to a further elaboration of the invention, in that each circumferential unit is provided with at least two reversible unidirectional drive systems .

According to a further elaboration of the invention, the speed variator is characterized in that each reversible unidirectional drive system comprises an outer ring carrying a crank arm as mentioned and an inner ring connected to an associated intermediate shaft so as to be restrained from rotation relative thereto, while the outer ring and the inner ring, respectively by way of an inner and an outer circumferential surface thereof, at least partly share a common circumferential contact surface, which is provided with recesses which have a substantially diamond-shaped section, viewed in a side elevation of a cross-sectional plane extending perpendicularly to the centreline of the associated intermediate shaft, each recess accommodating a frame carrying two resiliently supported balls or cylinders, each frame having two fixed positions within a recess which can be set via a reversing ring, whereby in a first position one of the

balls or cylinders of the frame is pressed resiliently into a corner of the recess, which corner is bounded by the outer ring and the inner ring, while the frame keeps the other ball or cylinder clear of the walls of the recess and in a second position the other ball or cylinder of the frame is pressed resiliently into the opposite corner of the recess while the frame keeps the one ball or cylinder clear of the walls of the recess .

A double-acting drive system of this construction is simple to operate and takes up as little space as a normal single-acting freewheel system. Further, the construction of such a unidirectional drive system is simple, so that it is durable and reliable in operation. Further, the present reversible unidirectional drive system in no way introduces any additional sources of friction into the speed variator.

According to a further embodiment of the invention, it is particularly advantageous when the operation of the respective reversing rings is hydraulic, pneumatic or electromechanical, while the hydraulic, pneumatic or electromechanical control device for the pair of eccentric discs is hydraulically, pneumatically or electromechanically coupled to the operation of the reversing rings.

The coupling of the hydraulically, pneumatically or electromechanically operable reversing rings can be realized in a simple manner via a central hydraulic, pneumatic or electromechanical operating device.

In the speed variator disclosed in the Italian patent specification referred to, the eccentric discs are each formed by a circular eccentric disc connected to the drive shaft so as to be restrained from rotation relative thereto, which disc is adapted to be shifted in a direction perpendicular to the centreline of the drive shaft, while, with interposition of roller or plain bearings, at least one ring is present on each eccentric disc, which ring does not rotate and is dynamically connected to the crank arms of the respective circumferential units.

According to a further elaboration of the invention, a speed variator of the type described hereinabove is characterized in that the hydraulic, pneumatic or electromechanical control device for the pair of eccentric discs, incorporated in the drive shaft, comprises two piston/cylinder assemblies extending perpendicularly to the centreline of the drive shaft, each assembly controlling one of the pair of eccentric discs in opposite directions, the piston of the respective piston/cylinder assemblies being provided with piston rods extending on opposite sides of the piston in the direction of the centreline of the respective cylinders or precision bores, a pre-compressed spring being confined in the cylinder of the respective piston/cylinder assemblies, this spring pressing the piston into the position wherein the eccentric discs are in a neutral position, and each cylinder being connected with two channels each opening into the cylinder on opposite sides of the piston and each being connected via bores in the drive shaft with hydraulic or pneumatic pressure medium sources by means of which the position of the piston in the cylinder, and hence the eccentricity of the eccentric discs, can be controlled.

A control device of this construction is durable and reliable in operation. The piston/cylinder assemblies can be positioned in such a way that the piston rods engage the eccentric discs centrally, so that the eccentric discs can be shifted in radial direction without being pulled out of square.

Moreover, the assembly of the present control device is simple and the shaft is minimally weakened inasmuch as the space required to build in the control device is minimal.

Accordingly, the diameter of the input shaft can be made of smaller dimensions than in the known device. The spring arranged in the respective cylinders serves as a safety measure and ensures that when the pressure of the pressure medium sources falls out, the eccentric discs are pressed into

the neutral position so that no torque of the input shaft is transmitted to the output shaft.

According to a further embodiment of the invention, the channels that open into the cylinder space where the spring is disposed are connected to a first pressure medium source, and the channels opening into the cylinder space located on the other side of the piston are connected to a second pressure medium source, the first pressure medium source providing a constant basic pressure which biases the eccentric discs into the neutral position, and the second pressure medium source having a variable, controllable pressure by means of which the extent of eccentricity of the eccentric discs can be controlled.

To clarify the invention, one embodiment of the variable- speed device will be described with reference to the accompanying drawings.

Fig. 1 is a partial sectional view of an embodiment of the speed variator;

Fig. 2 is a schematic sectional view taken on line II-II of Fig. 1;

Fig. 3 is a detail of a reversible unidirectional drive system incorporated in a circumferential unit;

Fig. 4 is a detail of the sectional view shown in Fig. 2 and shows the control device for the eccentric discs, incorporated in the drive shaft; and

Fig. 5 is a detail from Fig. 1 and shows the pressure medium source connection to the channels of the control device in the drive shaft.

The drawing shows a preferred embodiment of the speed variator according to the invention. Fig. 1 shows a partial sectional view. The speed variator comprises a drive shaft 1 which is provided with at least one pair of eccentric discs 2a, 2b, whose eccentricity can be varied, also during operation, from a neutral position of zero eccentricity to a maximum value via a control device 3 incorporated in the drive shaft. The eccentricities of the eccentric discs 2a, 2b are

mutually opposite. A plurality of circumferential units 4a, 4b are arranged on a pitch circle S whose centre coincides with the centreline HI of the drive shaft 1 and which is located in, or in the vicinity of, a plane in which the eccentric discs 2a, 2b can oscillate during operation. The circumferential units are each provided with a crank arm 5 which can be driven for oscillation by one of the eccentric discs 2a, 2b. The crank arms 5 of the respective circumferential units are each dynamically connected to an output shaft 9 via at least one unidirectional drive system 6, consisting of a freewheel system 6, via respective intermediate shafts 7 and a transmission 8 with a fixed transmission ratio. Mounted on each intermediate shaft 7 are two circumferential units 4a, 4b, namely one for each eccentric disc 2a, 2b. The fixed transmission ratio of the transmission 8, which in this case is formed by three gears, can be 1:1 as well as overdrive, for instance 1:2. According to the invention, the respective unidirectional drive systems 6 can be reversed inasmuch as they are provided with a double- acting freewheel system 6 which is adapted for driving the respective intermediate shafts 7 in a first direction of drive and in a second, opposite direction of drive. The control device 3 for the eccentric discs 2a, 2b, incorporated in the drive shaft is of hydraulic, pneumatic or electromechanical construction and the respective unidirectional drive systems 6 can only be reversed when the rotational speed of the output shaft 9 is zero. By coupling the hydraulic control device 3 of the eccentric discs 2a, 2b to the unidirectional drive systems 6, it can be ensured that these systems 6 can only be reversed when the eccentric discs 2a, 2b are in the neutral position. The rotational speed of the output shaft 9 depends on the extent of eccentricity of the eccentric discs 2a, 2b. When the eccentric discs 2a, 2b are in the neutral position, the output shaft 9 is stationary even when the drive shaft 1 is rotating. When the output shaft 9 continues to rotate in its normal direction of drive due to inertia forces or is caused to

rotate by the load coupled thereto (not shown) , the output shaft 9 rotates freely together with the intermediate shafts 7. The rotation of the intermediate shafts 7 is not transmitted to the crank arms 5 owing to the interposition of the freewheel clutches 6. The speed variator thus operates as a freewheel clutch. When the drive shaft 1 and the output shaft 9 have an equal speed, they can be interconnected via a fixed coupling 19, which is known per se, so as to effect a direct drive. Preferably, this coupling occurs hydraulically or pneumatically. However, a mechanical operation of this fixed coupling 19 is also possible. Such a construction is shown in the drawing and is indicated by the reference numeral 20.

In order to distribute the power transmission to the intermediate shafts 7 as well as possible, and in order to enable a large power to be transmitted to each intermediate shaft 7, each circumferential unit 4 of the speed variator comprises two reversible unidirectional drive systems 6a, 6b, and 6c, 6d, respectively. In the embodiment shown, therefore, each intermediate shaft is fitted with four reversible unidirectional drive systems 6a, 6b, 6c, 6d.

As is clearly shown in Fig. 3, which is a sectional detail of a unidirectional drive system 6 of a circumferential unit 4, each unidirectional drive system 6 comprises an outer ring 10 which carries a crank arm 5 as mentioned and an inner ring 11 which, for instance through a key 12, is connected to a corresponding intermediate shaft 7 so as to be restrained from rotation relative thereto. The outer ring 10 and the inner ring 11, via, respectively, an inner and outer circumferential surface thereof, at least partly share a common circumferential contact surface 13. Provided in the circumferential contact surface 13 are recesses 14 which are substantially diamond-shaped, viewed in a side elevation taken in a cross-sectional plane extending perpendicularly to the centreline of the corresponding intermediate shaft 7. Arranged in each recess is a frame 15 carrying two resiliently

supported balls or cylinders 16a, 16b. Within a recess 14, each frame 15 has two fixed positions which can be set via a reversing ring 17 (see Fig. 1) . In a first position, as shown, one of the balls or cylinders 16a of the frame 15 is resiliently pressed into a corner 14a of the recess 14. The corner 14a is bounded by the outer ring 10 and the inner ring 11. The other ball or cylinder 16b is kept clear of the walls of the recess 14 by the frame 15. In a second position of the frame 15, the other ball or cylinder 16b of the frame 15 is resiliently pressed into the opposite corner 14b of the recess 14 while the one ball or cylinder 16a is kept clear of the frame 15 of the walls of the recess 14.

The operation of the reversing ring 17 is for instance effected by means of a reversing arm 18 arranged in the housing of the speed variator, which reversing arm 18 can temporarily engage projections provided on the reversing ring 17. According to the invention, it is particularly advantageous when the operation of the respective reversing rings 17 is hydraulic, pneumatic or electromechanical, while the hydraulic, pneumatic or electromechanical control device 3 for the pair of eccentric discs 2a, 2b is hydraulically, pneumatically or electromechanically coupled to the operation of the reversing rings 17. Thus, via the hydraulic, pneumatic, or electromechanical operation, it can be provided that the reversing rings 17 are only operated when the eccentric discs 2a, 2b are in the neutral position and the speed of the output shaft is zero.

As shown clearly in Fig. 4, the eccentric discs 2 are connected to the drive shaft so as to be restrained from rotation and they have a circular circumferential surface. The eccentric discs are arranged to be shifted perpendicularly to the centreline of the drive shaft. On the circular circumferential surface of each eccentric disc 2, with interposition of roller or plain bearings 21, at least one ring 32 is present, which ring 32 does not rotate and is dynamically connected to the crank arms 5 of the respective

spring 26, so that the eccentric discs can be moved from the neutral position only by positive action, namely by increasing the pressure of pressure medium source 31 to above the pressure of pressure medium source 30.

It will be clear that the invention is not limited to the embodiment described but that various modifications are possible within the framework of the invention.