Telescopic mechanical transmission with angular adjustment for assembly

In order to facilitate angular phase-alignment during assembly of a telescopic cardan shaft, comprising an outer splined shaft (1)&#8212;equipped with longitudinal inner splines (11)&#8212;and an inner splined shaft (3)&#8212;equipped with longitudinal outer projections (13, 13A)&#8212;the inner splines (11) of the outer shaft (1) have a width greater than the width of the outer projections (13,13A) of the inner splined shaft (3), in order to obtain a mutual angular play of at least 60&deg;.

BACKGROUND OF THE INVENTION

The invention relates to an extendable mechanical transmission of the type which are used in agriculture in many systems for transmission of the movement between an operating machine and a driving machine; this transmission generally comprises a pair of splined shafts which are capable of sliding axially with respect to each other in order to vary the length of the transmission and which are engaged with each other angularly for transmission of the rotational movement; these transmissions have, at the two ends, two cardan joints which are connected to each one of the two splined shafts and each of which comprises a pair of fork members articulated. perpendicularly with respect to each other.

Some difficulties arise during assembly of the splined-shaft transmission between each end cardan joint and the power takeoff which is provided in the adjacent mechanism; angular engagement is envisaged between a splined hub, generally of the power takeoff or the drive system, and a splined seat provided in the external fork member of each of the end cardan joints of the telescopic cardan shaft transmission. These difficulties are clarified more fully in the text which follows and are solved by the invention in question.

OBJECTS AND SUMMARY OF THE INVENTION

The invention therefore relates to a telescopic extendable mechanical transmission with two splined shafts axially slidable with respect to each other and in particular equipped with two end cardan joints with engaging systems for coupling to adjacent mechanisms; according to the invention, the splined profiles of the two shafts are shaped so as to provide mutual angular play.

In particular, the transmission comprises an outer splined shaft equipped with inner splines and an inner splined shaft equipped with outer projections;

in this case the inner splines of the outer shaft have a width greater than the width of the outer projections of the inner splined shaft, in order to obtain a mutual angular play of at least 60 , when six projections and six splines are envisaged.

The outer shaft may be tubular with a constant thickness and one of the splines may have a depression at the entry point, while a corresponding depression is provided along one of the longitudinal projections of the inner shaft. This results in an obligatory relative position of the two shafts.

DESCRIPTION OF PREFERRED EMBODIMENT

FIGS. 1 and 2 show a conventional cardan shaft in which, however, the profiles of the two splined shafts which are slidable with respect to each other are modified according to the invention. These splined shafts are denoted by 1 in the case of the outer shaft and by 3 in the case of the inner shaft, which is tubular, whereby the inner shaft may also advantageously be tubular 5 and 7 denote generically the two end cardan joints which are associated with, respectively, the outer shaft 1 and the inner shaft 3 ; each of these cardan joints has a fork member 5 A and 7 A, respectively, which is integral with the shaft 1 and the shaft 3 , respectively, and a fork member 5 B and 7 B, respectively, which is intended for a power takeoff of the mechanism adjacent to the corresponding fork member; in particular, in FIGS. 1 and 1A , 5 C denotes the splined seat of the fork member 5 B, while 15 denotes the splined male power takeoff which forms part of the mechanism to be coupled to the fork member 5 . A similar arrangement exists for coupling of the cardan joint 7 . Normally the splined engaging profiles, such as those 5 C and 15 , have a minimum of six splines or a greater number of splines. In FIGS. 1 and 2 the cardan shaft also has, as in the conventional manner, a protection around the shafts 1 and 3 and at least partially around the cardan joints 5 and 7 .

In the working (i.e. transmission) condition, the fork members of the two cardan joints 5 and 7 have the perpendicular axes of articulation of one of the joints which are parallel to the corresponding axes of articulation of the other cardan joint. The engagements to be effected between the seat such as 5 C and the male member such as 15 may be performed easily when the profiles 5 C and 15 correspond, as shown in FIG. 1 A.

Frequently, during the assembly stage, phase-alignment is required between the profiles, such as that 5 C of the fork member 5 B and/or such as that of the fork member 7 B, and the corresponding profiles such as that 15 for the seat 5 C and such as the corresponding profile for the seat of the fork member 7 B. Sometimes angular adjustment of the power takeoffs adjacent to the splined shaft is not easy or possible and coupling is more complicated. The invention instead allows this coupling to be performed with extreme ease, as described below. Considering that which is illustrated in FIGS. 2 and 2A , if it is not possible to rotate the male member 15 , coupling may be performed by imparting to the cardan joint 5 and to the outer shaft 1 a rotation so as to bring the splined profiles 15 and 5 C into phase-alignment. When the splined profiles such as 15 and 5 C have a number of splines greater than six, it is sufficient to be able to rotate the shaft 1 and the cardan joint 5 through an angle of less than 60 .

Sometimes it is not possible to obtain this possibility of angular play, if the other cardan joint, such as 7 in FIGS. 2 and 2A , is already engaged with the male member of the machine adjacent to said other joint and if this male member is not free to rotate.

In order to obtain with ease the required adjustment also in the above mentioned case, according to the invention, differentiation between the splines and the projections of the shaft 3 and the splines and the projections of the shaft 1 (compared to the normral geometry which envisages an exact geometric similarity between the cross sections of the two splined shafts such as 1 and 3 ) is envisaged.

In particular, on the one hand the outer splined shaft 1 having the conventional form with three internal splines 11 distributed uniformly over the circumference and with a notable transverse width is envisaged, as can be seen in particular in FIGS. 3 , 4 and 5 . On the other hand the inner splined shaft 3 (which may also be tubular, but which may also be solid if necessary) has three external longitudinal projections 13 , 13 , 13 A, each of which has a width much smaller than the width of the splines 11 of the outer shaft 1 . As a result, a free angular play between the shaft 3 and the shaft 1 by an amount which can even be as much as at least 60 is possible, as can be clearly seen from the comparison between FIGS. 6C , 7 C and 8 C. As envisaged in conventional solutions, in order to ensure a positive engagement between the two telescopic splined shafts 1 and 3 , a limited depression 11 A of the inner spline 11 of the shaft 1 may be formed and a depression 13 B of the longitudinal projection 13 A with respect to the other two projections 13 of the inner splined shaft 3 is correspondingly provided; as a result the engagement between the two shafts 1 and 3 can occur only in the region of the depression 11 A and the depression 13 B as can be clearly seen in FIG. 4 .

The functions of what has been described may be clearly understood by considering FIGS. 6A to 8 C. The set of three figures, FIGS. 6A , 6 B and 6 C, illustrates schematically the conditions in which it is possible to achieve uniformity of engagement without angular adjustment during assembly of the cardan joint 5 with the power takeoff to be combined with the fork member 5 B. In fact, considering the left-hand parts when viewing FIGS. 1 and 2 and considering also FIGS. 1A and 2A , compared to FIGS. 6A , 6 B and 6 C, it can be noted that the splined profile 15 may be engaged with the splined-profile cavity 5 C, the two profiles being in the corresponding angular conditions shown in FIG. 6 C which correspond to those shown in FIG. 1 and also in FIGS. 3 and 4 . When a difference in angular position of the profile 15 is encountered, as shown in FIG. 7A , with respect to the condition considered in FIG. 6A , with an angular deviation which in the drawing is by way of example 20 , it is easy to perform engagement of the fork member 5 B with which the splined cavity 5 C is associated, because the assembly consisting of the shaft 1 and the cardan joint 5 may be displaced by 20 with respect to the assembly consisting of the shaft 3 and the fork member 7 , as clearly shown when considering FIGS. 7B and 7C compared to FIGS. 6B and 6C , this resulting in the possibility of said assembly being coupled with the mechanism having a profile 15 which is out of alignment by 20 . This possibility may be extended up to a relative angular deviation varying from nearly zero up to nearly 60 When the number of splined profiles is greater than six, the maximum deviation is reduced.

On the other hand the functional capacity of the transmission, with the shafts 1 and 3 shaped according to the invention instead of with profiles which are exactly the same as each other, remains unchanged except for the initial play which it may have for the possibility of engagement between the splines of the shaft 1 and the projections of the shaft 3 .

It is understood that the drawing shows only a simplification provided only by way of a practical demonstration of the invention, the forms and arrangements being able to be varied without, however, departing from the scope of the idea which underlies the invention itself. Any presence of reference numbers in the accompanying claims has the purpose of facilitating reading of the claims with reference to the description and the drawing and does not limit the scope of protection represented by the claims.