Steerable drive shaft

#The present invention relates to a steerable drive shaft for motor vehicles equipped with wheels each driven by a double-universal joint.

#With heretofore known constructions of vehicles having front-wheel drive or four-wheel drive (all-wheel drive), the drive of the wheels is accomplished from an axle drive shaft, both ends of which are connected with the double-universal joints. Since, however, the angular position between the drive shaft and the power-takeoff shaft of a universal joint is only possible up to a certain degree, because otherwise the universal joint will become overloaded or damaged, limits are set for the steering deflection or turning of the wheels when using a steerable drive shaft of this type.

#In the case of vehicles where the front axle is not driven it has already been possible to obtain extremely small turning circles or radii and thus an extremely favorable maneuverability of the vehicle. This is especially desirable for tractors. However when the front axle or shaft is driven difficulties exist in attaining such small turning circles, for the above mentioned reasons.

#The invention will be better understood and objects other than those set forth above, will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawing wherein the single FIGURE schematically illustrates an exemplary embodiment of the invention.

#Describing now the drawing, in the single FIGURE there is schematically illustrated a vehicle chassis of, for instance, a tractor having a four-wheel or all-wheel drive. The front wheels 1 and 2 of the tractor are turned or deflected towards the right, so that the tractor can travel through a curve about the curve center point 3. This curve center point 3 is located at a spacing a from the vehicle center or longitudinal center line 4 upon the extension of the rear shaft or axle 5. The spacing of the axles between the front wheels 1, 2 and rear wheels 15, 16 has been designated by reference characters b and the wheel spacing by reference character c.

#A single-universal joint 6 is arranged at the region of the front axle at the vehicle center line 4. Extending from such single-universal joint 6 are two drive shafts 7 and 8 which drive the double-universal joints 9 and 10, by means of which there are driven in turn the wheels 1 and 2. A connection line 13 extends through the joints 11 and 12 of both wheels 1 and 2 formed by the axle journals or steering knuckles and at the same time through the inner joints 9a and 10a of both double-universal joints 9 and 10. Both of the drive shafts 7 and 8 together with the connection line 13 enclose an angle .gamma.. The single-universal joint 6 is located in front of this connection line 13 at the vehicle center line 4, and it is for this reason that the angle .gamma. is of the same magnitude at both sides thereof. With a deflection or turning angle .alpha. of the wheel 1 located at the outside of the curve and a considerably larger deflection or turning angle .beta. of the wheel 2 located at the inside of the curve the magnitude of the angle .gamma. preferably amounts to 1/2 (.beta.-.alpha.), i.e. is equal to one-half of the difference of the different turning or deflection angles of both wheels with maximum deflection, because then the angular disposition or angling of both double-universal joints 9 and 10 at the outside of the curve and the inside of the curve is the same with maximum wheel deflection, as will be apparent from the showing of the drawing. If, for instance, the turning or deflection angle .beta. of the wheel located at the inside of the curve amounts to 60.degree. and the turning or deflection angle .alpha. of the wheel located at the outside of the curve amounts to 44.degree., then the angle .gamma. = 8.degree., i.e. one-half of the difference between 60.degree. and 44.degree.. In other words: by virtue of this arrangement the angular disposition or angling of the double-universal joint 10 located at the inside of the curve becomes smaller in relation to the turning angle of the wheel 2 by the angle .gamma. and the angular dispositon or angling of the double-universal joint 9 located at the outside of the curve in relation to the turning angle of the wheel 1 becomes larger by the angle .gamma.. In this way the possible angular disposition of both double-universal joints is completely utilized.

#The drive shaft 7 located at the left side is driven by a spur bevel gear 14 which meshes with a pinion 15. With this miter or bevel gear arrangement the axes of the pinion 15 and the spur bevel gear 14 intersect at an angle which is smaller than 90.degree. by the difference of angle .gamma. i.e. is equal to 90.degree.-.gamma..