Device for the Protection of a Transmission Joint in Agricultural Vehicles

The present invention concerns a device for the protection of a transmission joint in agricultural vehicles, more especially for a homokinetic joint that is known in the field as "wide-angle joint" and allows the transmission shaft to be inclined up to an angle of about 80.degree. compared to the motor-shaft or the drive-shaft.

The field of the invention is that of transmission means for agricultural vehicles and the related protection devices of the transmission means as a whole, and especially of the joints for such means. This field is subject to the European standards EN 1151, EN 292 and EN 294 that prescribe operating tests and safety criteria and for this reason the sale of these transmissions means is subject to the issuance of certificates by competent authorities.

The prior art comprises:

i) a so-called "non integral protection", or open protection, in which a single casing body protects the perimeter of the joint, but leaves an opening through which a foreign body may reach rotating parts (see for example the European Patent n.degree. 0 154 216 held by the same applicant). If one considers that the foreign body might be a person's hand, it is clear why such a protection is dangerous. This form of protection is fitted into a perimetral groove of the disc between the two yokes of the coupling where it is held in position by chainlets, and is a conical piece with the greater aperture facing the transmission shaft so that there are no problems when the shaft inclines, for example when the tractor goes round a bend.

ii) a so-called "semi-closed petal protection" comprising a main casing that covers the whole joint around the perimeter and an auxiliary casing that covers the end of the transmission shaft that connects to the joint. The space between the two casings, set at a certain distance from one another, allows relative movements between the same casings when the transmission shaft inclines and is closed by a series of plastic "petals" that have their external margins fastened within the main casing and their internal margins loose, but touching the auxiliary casing. This solution offers a certain amount of protection and the possibility of high inclinations of the transmission shaft, but has its main drawback in the fact that, because the "petals" are elastic, they may bend even under a weak pressure allowing a foreign body to reach the rotating parts of the transmission means.

In the following description we shall define as--proximal connection means--or also--proximal yoke--the joint means connected to the motor shaft or to the drive-shaft (these shall both conventionally be defined as--motion shaft--); as--distal connection means--or also--distal yoke--the joint means connected to the transmission shaft; as--disc--or--intermediate means--the means that connects the two previously named connection means. Furthermore, the term--casing(s)--is intended as the part or parts of the protection device that, fastened around the joint in a certain way, is of tubular, cylindrical, conical or funnel shape, in order to continuously cover the entire perimeter of the joint or part of it and is conveniently spaced from it. Generally, these casings are conveniently made of deformable plastic materials or mixes of natural or synthetic rubbers.

It is understood that the device may be suited to protecting both the motion shafts. Therefore we shall term--proximal end--that of any part connected to the motion shaft and--distal end--that of any part adjacent the transmission shaft.

The invention overcomes the above stated drawbacks and, as characterized in the claims, is a protection device comprising: a) a first casing that has its proximal end conventionally fixed to a ring slidingly engaged in a groove of the device central means and the distal end bears an extension folded inwards, up to the adjacency of the distal connection means, said casing has a first part that covers the central means and the connections between the central zone and the distal connection means and a second part that covers the distal connection means and the related end of the transmission shaft, the connection between said two parts being realized by means of a section that is able to elastically deform under the action of the transmission shaft that inclines compared to the motion shaft so that the second part inclines compared to the first part; b) a second casing, fixed to a ring slidingly engaged in a groove of the distal connecting means, that extends from outside towards the inside of the first casing, adjacent to the inside wall of the latter; c) a third casing, fixed to the perimeter of the proximal end of the first casing, in order to perimetrally cover the part of the proximal connection means connected to the intermediate means.

The main advantage of the invention is that it offers a complete and safe protection against the accidental or intentional entry of a foreign body in the joint zone; the first casing effectively prevents the entry of a foreign body especially in the region of the connection between the intermediate connection means and the distal connection means, that is the most dangerous, while the second casing cooperates with the extension folded inwards from the second end of the first casing to effectively prevent the entry of a foreign body in the region in which the distal connection means is connected to the end of the transmission shaft.

The invention is explained in detail below with an example of embodiment and with reference to the attached drawings, in which:

FIG. 1 is a longitudinal unit view partly sectioned,

FIG. 2 is a first partly sectioned longitudinal view,

FIG. 3 is a second partly sectioned longitudinal view, and

FIG. 4 is a third partly sectioned longitudinal view.

FIG. 1 shows: the proximal yoke 1, solid with the motor shaft, not shown, connected to disc 2 and the distal yoke 3 solid to the transmission shaft 4 and a first casing 5 fixed to the ring 6 engaged so as to slide within a perimetral groove of the disc 2. this casing 5 is in a single piece and bears a first part 7 that covers disc 2 essentially up to the zone where the latter is connected to the distal yoke 3 and bears a second part 8 that covers the remaining part of the distal yoke 3 and the zone in which the latter connects to the transmission shaft 4. The connection between parts 7 and 8 of casing 5 is realized with a deformable Z shaped section 9 that allows the part 8 to incline compared to part 7 when the distal yoke 3 and the transmission shaft 4 incline compared to the motor shaft. Extension 10 of casing 5 is folded towards the inside and towards the proximal part of the casing in order to collaborate with a second casing 11 that is fixed to a ring 12 slidingly engaged in a groove of the dital yoke 3 and that is extended into the first casing ending with a radial extension 13 so that, even if a foreign body should pass the obstacle set by extension 10, the second casing with its extension 13 will avoid any contact with rotating parts. Another purpose of the second casing 11 is to afford an adequate engagement seat to the pipe 15 that protects the transmission shaft 4 along its entire length. A third casing 14 is fixed to the external perimeter of the proximal end of the first casing in order to protect the connection zone between the proximal yoke 1 and disc 2.

FIG. 2 shows another way to realize deformable section 9'. Casing 5' is a single piece of conveniently elastic plastic material. The deformable section has an S shape especially suited to the purpose. The apertures 16 on the proximal end of the casing serve to engage the latter on the ring 6, by means of appropriate extensions, not shown, so that the latter bears in correspondance with the same apertures.

FIG. 3 shows a part of the upper half of a casing 5" in one piece in order to illustrate yet another way to realize said deformable section 4" shaped like bellows.

FIG. 4 shows part of the upper half of a casing 50 in order to illustrate yet another way to realize a deformable section 9"' with a connecting element between the two parts 70 and 80 of the casing that is realized in two parts. These parts are joined by the pre-formed Neoprene S-shaped deformable section 17 fixed to their perimeter by means of rivets 18.