The present invention relates to a cremone handle for door and window frames of the type comprising a body carrying a turnable control lever to which there is fixed in rotation a shaft bearing an operating crown wheel, and in which operatively associated to the shaft is a snap-action positioning device for positioning the aforesaid control lever.
In currently known cremone handles of this type (see for example FR-A-2 666 369), fixing of the crown wheel on the shaft operated by the turnable lever is obtained either by means of a threaded coupling, which, of course, requires the presence of an internal thread inside the shaft and a complementary thread on the crown wheel, or by means of a key inserted in an axial groove made in the shaft and engaged in a corresponding internal radial seat of the crown wheel.
Both of the above solutions entail for the producers of handles far from negligible processing costs, which reflect on the final cost of the product, and, moreover, pose problems of reliability in relation to the rigidity of the fixing between the crown wheel and the shaft. The latter drawback may bring about, in the use of the handle, more or less early onset of play which might jeopardize the precision of operation of the handle itself.
The object of the present invention is to overcome the aforesaid drawbacks.
According to the invention, this object is achieved basically thanks to the fact that the crown wheel is coupled to the shaft by means of a bayonet joint which uses the aforesaid snap-action positioning device.
Traditionally, the snap-action positioning device includes a helical spring set coaxially to the shaft between a resting element carried by the shaft itself and a reaction bushing. In this case the invention envisages that the shaft will have at least one axial groove, from which there branches off a lateral seat, and the crown wheel will be formed internally with a radial projection which can be slidably engaged in said axial groove and in said lateral seat as a result of its axial translation along the shaft against said resting element of the helical spring, followed by its angular displacement with respect to said shaft.
According to a preferred embodiment of the invention, the resting element of the helical spring is constituted by a ring having at least one axial key appendage slidably engaged in the axial groove of the shaft in order to block the crown wheel angularly following upon engagement of the radial projection of the latter within the lateral seat of the shaft.
Thanks to this idea for solving the problem, coupling between the crown wheel and the shaft actuated by the lever of the handle is obtained by constructionally simple means, which are for the most part already present in the handle, and so as to ensure in a reliable way rigidity of the torsional connection between the crown wheel and the shaft even following upon a prolonged working life of the handle.
The invention will now be described in detail with reference to the attached figures, provided purely by way of non-limiting example, in which:
With initial reference to Figure 1, the number 1 designates, as a whole, a cremone handle according to the invention basically comprising a hollow body 2, from the front side of which there projects a boss 3, in a position corresponding to which there is applied a manual control lever 4. The lever 4 is able to turn through 90° or through 180° with respect to the body 2 in order to control in rotation a shaft 5 fixed thereto, which extends within the body 2.
Fitted on the shaft 5, according to the modalities that will emerge more clearly from what follows, is a crown wheel 10, the teeth of which mesh, on opposite sides, with two rack assemblies (not illustrated), mounted so that they can slide longitudinally in mutually opposite directions within the body 2 for actuating, via respective control sliders, the closing members of the door or window frame to which the handle 1 is designed to be applied.
With reference now in greater detail to Figure 2, operatively associated to the control lever 4 is a snap-action positioning device known to the art, which has, precisely, the function of positioning said lever 4 in the different angular positions that it can assume with respect to the body 2. For the purposes of the present invention, it is sufficient to point out that the positioning device comprises a helical compression spring 6 wound around the shaft 5 and set between a reaction bushing 7, mounted stationary with respect to the body 2 and traversed coaxially in a slidable manner by the shaft 5, and a resting ring 8 carried by the shaft 5. The reaction bushing 7, which is normally made of self-lubricating plastic material is formed with slots 9, which are designed to cooperate, as a result of rotation of the lever 4, with corresponding positioning projections (not visible in the drawings)..
For fitting of the crown wheel 10 on the shaft 5, the latter is formed with one or, more conveniently, a pair of diametrically opposite axial grooves 11, each of which is in communication - at a certain distance from the free end of the shaft 5 - with a respective lateral seat 12. The crown wheel 10 is in turn made with one or, more conveniently, a pair of internal radial projections 13 which can be slidably engaged along the grooves 11 and in the corresponding lateral seats 12 of the shaft 5.
The resting ring 8, or else a bushing 14 resting against said ring or fixed to the ring 8, is able to slide on the shaft 5 and has a pair of axial key appendages 15 slidably engaged in the axial grooves 11 of the shaft 5.
There now follows a description of the modalities of fitting of the crown wheel 10 on the shaft 5 upon assembly of the cremone handle 1.
In this first step, represented in Figures 2 and 3, the crown wheel 10 is inserted axially on the free end of the shaft 5, engaging the radial projections 13 within the axial grooves 11. The crown wheel 10 is then translated axially in the direction of the handle 4, at the same time causing the resting ring 8 with the corresponding bushing 14 to move backwards as a result of the thrust of the crown wheel 10 itself or with manual aid against the action of the spring 6, until the key appendages 15 are positioned underneath the toothed lateral seats 12. The crown wheel 10 can thus be positioned axially along the shaft 5 so that the two radial projections 13 will be set in a position axially corresponding to the seats 12, as illustrated in Figures 3 and 6.
Next, the crown wheel 10 is caused to turn (in a clockwise direction, as viewed in the figures) so as to engage the radial projections 13 within the lateral seats 12 of the shaft 15 in the way represented in Figures 4 and 7.
As a result of the said rotation, the annular resting element is axially released, i.e., the corresponding axial key appendages 15 are able to slide along the grooves 11 under the action of the force of elastic return of the spring 6. As a result of this return upwards, the radial projections 13 of the crown wheel 10 are firmly blocked within the lateral seats 12 of the shaft 5 by the axial key appendages 15, which traverse the crown wheel 10. In this way, the crown wheel 10 is rendered stably fixed in rotation to the shaft 5.
From the foregoing description, it emerges clearly that the system for fitting the crown wheel 10 of the cremone handle 1 according to the invention is obtained by means of a bayonet-joint system, which uses, as elastic element of the joint, the spring 6 already present on the snap-action positioning device of the control lever 4. In this way, as compared to traditional systems, the said fitting system proves not only simpler and less expensive, but also appreciably safer and more reliable, in so far as it guarantees a firm torsional blocking without any play between the crown wheel 10 and the shaft 5, even following upon a prolonged working life of the cremone handle.
Of course, the details of construction and the embodiments may vary widely with respect to what is described and illustrated herein, without thereby departing from the scope of the present invention as defined in the ensuing claims. Thus, for example, the resting ring 8 and the bushing 14 may be made of a single monolithic piece.