Shift device for a change speed gearbox
Shifting assembly for a change speed gearbox includes axially displaceable shift rods and pivotably displaceable shift rockers for actuating respective gear wheel clutches. Locking elements in the form of linear pins and pivotal members are abuttingly engaged with the respective shifting mechanisms so as to assure locking of all other shift rockers and shift rods when one of the shift rockers and shift rods is moved to a clutch actuating position.
In a shift device of this general type described in German Patent Document DE 41 18 931 A1, the pivotably movable locking element is constructed in the form of a two-armed locking lever which is pivotably mounted on the gearbox casing at a central point located between its two lever ends. On its one lever arm it has a recess for engagement of the linearly movable locking element and interacts with its other lever end by means of a locking cam with a corresponding mating cam contour of the shift rocker.
In such a way that the locking cam is held, in the neutral position of the shift rocker corresponding to the disengaged state of the gear wheel clutch, in engagement with the mating cam contour on the shift rocker by means of a restoring spring which acts on the locking lever–and, on the other hand, when the shift rocker is activated into a gear speed position corresponding to the engaged state of the other gear wheel clutch, the locking cam is pivoted by the mating cam contour into its other end position in which it is no longer the recess of the locking lever but rather its locking face which is congruent with the geometric axis for the movements of the linearly movable locking element. When an additional shift rocker is used in this known shift device, a second two-armed locking lever which interacts with the second shift rocker and an intermediate locking linkage which interacts with both two-armed locking levers and also with the first shift rocker must be provided, so that this known shift device requires a complicated design.
German Patent Document DE-A 21 32 736 also discloses a shift device for change speed gearboxes of vehicles having three shift rods to be locked, in which shift device cylindrical spring-loaded locking elements are arranged between the shift rods, the locking elements being axially displaceably secured in a bearing hole of the gearbox casing, and in which shift device the shift rods are arranged in the form of a triangle.
In order to be able to lock in each case two shift rods at the same time and only release one for shifting gears–the required shift means and their bearing being easy to manufacture, being arranged in a space-saving fashion and being intended to permit reliable locking–in this known shift locking device the arrangement is effected in such a way that the locking elements are displaceably mounted in a bearing hole, connecting two shift rods, of the gearbox casing, the locking elements being provided with sloping faces at one end in the region of a further locking hole which opens into the bearing hole at a right angle, and a sphere which interacts with the sloping faces of the locking elements being inserted into the locking hole.
Finally, German Patent Document DE 29 30 151 A1 also discloses a change speed gearbox of the countershaft type, in which three shift rods arranged parallel to the gearbox shafts are mounted axially displaceably in a gearbox casing which is connected to a clutch casing using flanges, of which shift rods two are connected fixedly in terms of movement in each case to the fork shaft of an associated linearly movable shift fork and the third is connected in an articulated fashion to the fork shaft of an associated shift fork which is mounted so as to be pivotable in relation to the gearbox casing.
An object on which the invention is based is to provide a shift device of the type mentioned above which is both distinguished by a simple design of the locking mechanism and can be easily extended for use by more than one shift rocker and/or shift rod.
This object is advantageously achieved according to the preferred embodiments of the invention by providing a shifting assembly comprising a first axially displaceable shift rod operable to actuate a first gear wheel clutch, a first pivotably displaceable shift rocker operable to actuate a second gear wheel clutch, a first pivotably movable locking element carried by the first shift rocker, and a first linearly movable locking element extending transversely to, and selectively lockingly engaging with the first shift rod, wherein said first pivotably movable locking element and first linearly movable locking element are configured to assure locking of the first shift rocker against actuation of the second clutch when the first shift rod is actuating the first clutch and locking of the first shift rod against actuation of the first clutch when the first shift rocker is actuating the second clutch.
In shift devices constructed according to the invention, the number of the totality of gear wheel clutches for the gearbox shafts does not preclude utilization of the novel locking assembly arrangement.
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