Many types of steepless speed change gears of mechanical type exist, which are generally based on the principle consisting in exploiting, in order to operate, the adhesive force of active, variously shaped surfaces kept pressed against each other; in fact, the mechanical speed change gears are normally of the friction-based type, which operate in an oil bath or in an atmosphere of oil vapours, and of the type with an either flat or "V"-shaped transmission belt. The types of speed change gears equipped with a flat transmission belt, similarly to the friction-based speed change gears, are subject to possible skidding, or slipping, of the active organs relatively to each other, which skidding and slipping can vary with relation to the transmitted torque; as a consequence, the power transmission results to be very Limited. The speed change gears of the type with "V" transmission belt use two conical pulleys, the one of which is mounted on the driving shaft, and the other is mounted on the driven shaft; each of them is constituted by two cone-shaped (or cone frustum-shaped) rotary bodies arranged axially side by side to each other with their taper being oriented in reverse directions, between which a "V" transmission belt is taut.

By varying the axial distance between each pair of

rotary cone-shaped bodies -- by shifting them in mutually opposite directions -- the two pulleys change their winding radii and to a same extent and in opposite directed, and therefore keep constant the total length of the transmission belt; as a consequeirce , to each change in opposite directions of the winding radii of the two pulleys, the ratio varies of the motion tras ission from the driving shaft to the driven shaft on which said two pulleys are respectively fastened .

In practice, also the speed change gears known from the prior art of ttie type with the "V" transmission belt do not enable high values of transmitted power to be obtained in that beyond a certain value of transmitted torque, the "V" transmission belt tends to slip on the pulleys. Furthermore, the alternate rubbing of the transmission belt inside the variable race of the pulleys causes a wearing of the same pulley to take place, which reduces the useful life thereof. The main purpose of the instant invention is of providing a steepless speed change gear in order to change the relative speed of a driving shaft and of at least one driven shaft, which speed charge has such a structure as to obviate the drawbacks which affect the speed change gears with "V" transmission belt known from the prior art, wherein said "V" transmission belt is taut between two pulleys keyed on the shafts, and, above all, such as to make it possible high values of motion transmission ratio to be accomplished and also very high powers to be transmitted, with no risk of the belt slipping of relatively to the race of the pulleys. Rnother purpose of the instant invention is of providing a steepless gear speed change of mechanical type which can operate in air, and is highly reliable. R further purpose of the finding is of providing a speed change gear of the above specified type, which is

so conceived as to have reduced outline dimensions, to be easy to be operated and suitable for being used both on fixed industrial equiment, and on mobile apparatuses, such as any types of vehicles requiring their speed to be varied within wide ranges of values. These and still other purposes, which are better set forth by the following disclosure, are achieved by means of a steepless speed change gear of mechanical tvpe of the type with "V" transmission belt, suitable for accomplishing a steepless change of the relative angular speed of at Least two shafts, the one of which is the driving shaft and the at least other one shaft is a driven shaft, in which speed change gear, according to the present invention, said two shafts are parallel to each other and each of them is provided with external splines C Longitudinal grooves) and, at the mutually opposite ends of said splines, with a disk-shaped element respectively integral with each of said shafts, with onto each one of said disk-shaped elements a group of rectilinear and equidistant arms being peripherally hinged in such a way that the arms of each one of said arm groups can be angularly divaricated in mutually specularly opposite directions, with a slide being hinged onto the free end of each of said arms, which slide is provided with a channel axially oriented relatively to its respective arm, and is externally provided with an arcuate groove axially oriented relatively to its relevant arm, which arcuate groove constitutes a sector of a pulley, and all of said arcuate grooves relevant to the one shaft and all of the arcuate grooves relevant to the other shaft constitute, each set of pulleys considered as a whole, two coplanar, variable-diameter pulleys capable of housing a "V" transmission belt, and on each of said splined shafts one cone frustum-shaped body being mounted with possibility of translation, with the taper

of each one of said cone-frustum bodies being opposite to the taper of the other cone-frustum shaped body, and on whose external surface (i.e. , on the external surface of each one of said cone-frustum bodies) rectilinear guides being slidingly housed inside said axial channels provided in said slides so as to make it possible, by means of the simultaneous shifting of said frustum-cone shaped bodies, the groove-sector bearing arms relevant to one shaft to divaricate and the arms relevant to the other shaft to simultaneously undergo an analogous movement of approaching to their own shaft, thus simultaneously performing equal changes -- of opposite sign -- in the diameters of the pulleys and therefore steepless changes being accomplished in the ratio of transmission between said two shafts.

More particularly, in order to secure the simultaneous translation of said cone-frustum shaped bodies externally provided with guides, a sleeve or ring body is provided, which is coaxial with each shaft and is externally integral with the cone-frustum shaped body, and on each one of said translatable sleeves a fLange element is applied, which fLange element is linked with a the ram of one single hydraulic piston, or the like, which is suitable for simultaneously shifting both of said sleeves and therefore both of the relevant cone- frustum bodies, along their respective shafts. Further characteristics and advantages of the present invention will be clearer from the following disclosure in detail of a preferred, non-limitative form of practical embodiment thereof, made by referring to the thereto attached drawing tables, supplied for merely exemplifying and non-limitative purposes, in which: Figure 1 shows a plan view of a steepless speed change gear suitable for varying the angular speed of a driven shaft relatively to the angular speed of a driving shaft, accomplished according to the instant invention;

Figure 2 shows a plan view of one of the two shafts of

Figure 1 with a slide-bearing arm and the relevant arcuate belt-bearing sector;

Figure 3 shows a front view of the external surface of a cone-frustum body bearing a plurality of rectilinear guides ;

Figure 4 shows a front view of a disk-shaped body bearing arms suitable for divaricating to a fan-shaped configuration and intergal with groove-bearing slides bearing grooves suitable for housing a cogged "v ^* " transmission belt; and

Figures 5 and 6 respectively show a side view and a o front view rotated at an angle of 9fi> , of the ram- piston control system which controls the configuration of the speed change gear according to the preceding figures .

Referring to such figures, the speed change gear according to the present finding is constituted by a driving shaft 1, mounted on its relevant revolutionary supports 1a-1b, and a driven shaft 2 with its relevant end supports 2a-2b; said shafts are parallel to each other.

The portion of each one of said shafts comprised between the relevant opposite revolutionary supports is provided with splines (i.e. , longitudinal grooves) ⁽ Figures 1 and 2), so as to show an external tooting 3 and respectively 3a, having a sunburst-like shape, i.e. , the shape of a toothed pinion.

Onto the end of the driving shaft, and in the nearby of the revolutionary support 1a, a disk-shaped element 4 is coaxially keyed. Said disk-shaped element has the outline of a cap. In an analogous way, a similar disk- shaped, cap-like disk element is keyed ontto the opposite end of the driven shaft 2. Said two disk- shaped elements 4 are hence specularly opposite to each other, and both of them are provided with protruding

elements 5, spaced from each other in similar ways and oriented parallel to the respective shaft. Onto said protruding elements 5 rectilinear rods or arms 7 are hinged in 6. Said rods or arms 7 can be clearly seen in Figure 4. They can oscillate from a position parallel to the respective shaft to a position angularly spaced apart from said shaft. Rt the end of the arms 7, which is opposite to the end at which they are hinged onto the element 4, prismatic elements 9 are hinged in β (Figure 1). Said prismatic elements 9 have the shape of slides or runners, each of which is provided with a prismatic axial channel 10, of substantial trapezoidal shape (Figure 4), the longitudinal axis of which is parallel to the respective arm 7.

On each prismatic slide 9 two divergent side walls 11- 11a are provided on the external side. Said divergent side walls 11-113 are arcuate in a circle-arc fashion, with their ideal centre being on the axis of the respective shaft 1 and 2. Inside the groove deifned by said side walls radial teeth 12-12a are provided. Each pair of divergent side walls 1l-11a defines a trapezoidal groove which defines a swinging circle sector at the end of its relevant arm 7. The whole of the trapezoidal grooves formed by the pairs of side walls 11-11a define, relatively to each one of the two shafts 1 and 2, a pulley, whose diameter can change as a consequence of the increase or decrease of the angle of opening of the arms 7 relatively to their own shaft. R one can see from Figures 1-2 and 4, inside the grooves of the two pulleys, which -- as it will be better clarified in the following -- will be contained always on the same plane perpendicular to both shafts, a cogged "V" belt 13 is housed, which is suitable for transmitting the movement from the driving shaft 1 to the driven shaft 2. In order to allow the arms 7 of either of the shafts to

get divaricated while the arms relevant to the other shaft are approached to said other shaft, a cone- frustum shaped body, respectively 14 and 14a is mounted with possibility of translation on the sunburst-like toothing 3 and respectively 3a of the two arms. Each of said cone-frustum shaped bodies 14 and 14a has centrally on the minor base -- a circular, toothed opening 15 (Figure 3) which performs the function of getting inmeshed with the splines 3 arranged in a sunburst-like fashion of the two shafts. On the external conical surface of the bodies 14-I4a, rectilinear trapezoidal guides 16 are provided in relief, so as to slidingly enter, in a substantially dove-tail shaped arrangement, the grooves 10 of the slides 9.

The cone-frustum shaped body 14 is mounted on the shaft 1 with its taper being opposite to the taper of the body 14a mounted on the shaft 2; such a specular arrangement makes it possible the arms 7 of the driving shaft to get, e.g. , divaricated by means of the shifting of the body 14, while the arms 7 of the driven shaft are approached to the same shaft during the shifting of the body 14a (Figure 1).

Thus, at each axial and simultaneous shift of the two bodies 14-14a along their respective axes, a change of equal extent and of reverse direction takes place in the diameter of the two pulleys defined by the arcuate grooves 10 of the slides 9; furthermore, the pulleys remain always contained on one plane perpendicular to the axis of the shafts, so that the belt remains always uniformly taut and housed inside a race (constituted by the set of equally spaced apart grooves on each pulley ⁾ , the shape and size of which remains always constant .

In order to accomplish the simultaneous displacement of the two cone-frustum bodies 14-14a along their

β respective shafts, a drive/control device is provided, of the type of a hydraulic piston/ram system, or the like, as shown in Figures 5 and 6. Such a device is constituted by two equal arms 17- 7a, parallel to each other and divaricated at an angle to each other, which are connected by an arm 1θ, arranged parallel to the shafts 1 and 2 (as schematically shown in short-dashed line in Figure 1) and connected with the stem of the ram of a hydraulic piston 19, or the like.

Rt the end of the arms 17-17a a cylindrical, openabte flange 20 and respectively 20a is provided integral with said arm. Said flanges 20-20a are inserted around the cylindrical groove 21 and respectively 21a (Figure 1) of two sleeves respectively integral with the major base of the mutually opposite cone-frustum shaped bodies 14-14a, and are capable of sliding -- together with these latter -- along the shafts 1 and 2. The stationary supports 1b and 2a for the respective shafts 1 and 2 constitute the stroke limits for the respective cone-frustum shaped bodies 14-14a in the position in which the arms 7 are parallel to the respective shafts, and the disk-shaped bodies 4 constitute the opposite stroke limits for the same cone-frustum bodies 14-14a. From the above, and from what can be clearly seen in the figures, it will be clear that by suitably acting on the hydraulic piston 19 the two cone-frustum shaped bodies 14-14a, so as they are shown in Figure 1, (i.e. , with the body 14 being moved to its right-end stroke limit and therefore with the arms 7 being parallel to the shaft 1, and with the opposite body 14a being also moved to its right-end stroke limit and therefore with the arms 7a being divaricated to their largest angle) are simultaneously shifted to the left and the continuity of the translation causes on the driving shaft 1 a divarication of the sLides 9 with their

relevant arcuate belt-bearing sectors while the body 14a, which has its external longitudinal guides 16 directed in the opposite direction to those of the body 14, causes on the driven shaft 2 a movement of approaching to the same shaft of the slides 9. The result is that on the driving shaft 1 the pulley constituted by the circular sectors progressively and continuously increases in diameter, while the pulley of the driven shaft 2 correspondingly decreases, also progressively and continuously, in diameter, with the extent of said decrease being the same as of said increase.

Inasmuch as the respective diameter of each of the two pulleys increases and decreases simultaneously to a same extent, the belt running around said pulleys remains always taut and housed inside a continuous and constant race, with the advantage that it does not undergo any wear caused by a rubbing against the side walls 11-11a of the same race.

Therefore, it is obvious that the change in the diameter of the two pulleys causes a continuous change to occur in the ratio of transmission of movement from the driving shaft to the driven shaft.

In practical embodiments, to the speed change gear as disclosed hereinabove, structural and functional changes of equivalent character may be supplied without departing from the scope of protection of the same finding .

So, e.g., with the arms 7 of the driving shaft, as well as with the arms of the driven shaft two slides 9 parallel to each other can be associated, so as to be capable of analogously driving a third (and a fourth) driven shaft, having the same structure as of the driven shaft indicated with the reference numeral 2 in Figure 1. Finally, the transmission belt, of cogged type, enables

very high powers to be transmitted, with no risk of slipping, in that it can get inmeshed with the teeth 12-12a of each race sector 9.