Guiding sleeve for the headrests in seats of vehicles
FIELD OF THE INVENTION 
     The invention relates to a guiding sleeve for the headrests of seats of vehicles which slidably receives a rod of the headrests so as to permit adjustment of the headrests. 
     BACKGROUND OF THE INVENTION 
     The abovenoted guiding sleeves of plastic material or metal are inserted into the back rests of the seats from above. They allow the slidable accommodation of a rod of a headrest so that the height of the headrest can be adjusted accordingly. As a result of a corresponding frictional engagement or releasable lock-in position, the headrest can be adjusted to the desired height each time. According to safety regulations, the headrest for security reasons must not be removed from the back rest under a corresponding load. 
     From German Patent DE 33 01 073 a guiding sleeve has become known which, on the one hand, provides a safe locking mechanism for preventing the rod from being removed and, on the other hand, allows a simple and effective unlocking control. This is realized in that the sleeve bore at the upper end includes an extension which receives an elongated spring element. A long front side of the spring element cooperates with the rod of the headrest and with a long rear side which is supported by the wall of the extension. In the extension an unlocking element is arranged comprising two parallel spaced legs which with their ends cooperate with the ends of the spring element, while being located at the side of the sleeve bore, and are movable from a grip to the spring element and towards the longitudinal extension. 
     The known guiding sleeve necessitates that an abutment in the form of a notch or the like is arranged on the rod in the direction of load. Consequently, the rod needs to be dimensioned accordingly so as to withstand the prescribed load. Moreover, the notch needs to be dimensioned at a sufficient depth so as to ensure a safe abutment preventing the rod from being removed. Finally, the stop spring provided for use with the known guiding sleeve involves a relatively great expense for production. 
     OBJECT OF THE INVENTION 
     It is the object of the invention to provide a guiding sleeve for the headrests of seats of vehicles which allows a more suitable dimensioning of the headrest rod, with the locking spring simultaneously comprising a more simple structure. 
     SUMMARY OF THE INVENTION 
     According to the invention, at least one spring leg connected to a cross arm engages the headrest rod at the side thereof. Therefore, a lateral notch needs to be provided in the headrest rod. The resulting weakening of the cross section is thus normal to the main load direction. Consequently, the headrest rod can be dimensioned smaller which results in a saving of material and weight. 
     The inventive guiding sleeve also accommodates a more simple spring geometry which simplifies production and installation of the spring. According to a particularly preferred embodiment of the invention, there are provided two parallel spaced spring legs comprising approximately parallel leg portions which engage the headrest rod while being arranged diametrically opposite to each other. Accordingly, the unlocking element also comprises two cam surfaces which bend the spring legs apart when actuating the grip. As a result, the lock-in reliability is increased in consequence of the spring acting in a self-centering way. Moreover, there, in this way, has been provided a uniform actuating system for guiding sleeves for different head inclinations. Besides, to uniformalize the headrests in vehicles it is also possible to provide the rod with a double notch, for instance. This allows the use of one headrest for both the front and back seat. 
     According to an embodiment of the invention, provision is made for the unlocking element to be U-shaped and for the cross arm to be flush with the outer contour of the sleeve at rest. The unlocking element, for instance, may be a one-piece moulding of plastic material which is inserted into the extension through an opening provided in the extension. 
     According to a further embodiment of the invention, provision is made for the legs to comprise snap-in noses at the outside which cooperate with snap-in projections of the extensions in such a way that as a result of the pressure of the spring element the movement of the legs is limited outwardly. While inserting the unlocking element into the extension the legs are thus slightly bent towards each other so as to allow the snap-in noses to snap behind the snap-in projections and to, in this way, limit the resting position of the unlocking element. 
     To obtain a satisfactory guidance of the unlocking element, a further embodiment of the invention provides that the legs are guided by parallel spaced wall portions of the extension. The guidance takes care that, while manually imparting pressure on the unlocking element, the forces are approximately uniformly distributed on the spring element in order to prevent the spring legs from being bent up so as to be of varying width. 
     To bring the legs of the unlocking element or their snap-in noses out of engagement with the snap-in projections, according to another embodiment of the invention, provision is made for openings provided at the level of the extension and the legs of the unlocking element and face to face with the same. An object, for instance a screw driver, may be inserted through tile openings and force the legs inwardly so as to free the unlocking element from the snap-in projections. 
     According to a further embodiment of the invention, the wall of the extension comprises a recess engaging a cranked portion of the spring arm for lateral fixing. The spring arm, on the one hand, is supported by the rear wall of the extension and, on the other hand, is supported by the cam surfaces. At the side, the spring legs are engaging the rod so that the spring is safely secured. 
     According to a yet further embodiment of the invention, the free ends of the spring legs are bent outwardly to allow an easier actuation and the bent off end portion extend at approximately the same angle as the ramp-like cam surfaces. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Various other objects, features, and attendant advantages of the present invention will be more fully appreciated from the following detailed description when considered in connection with the accompanying drawings, in which like reference characters designate like or corresponding parts throughout the several views, and wherein: 
     FIG. 1 is a longitudinal section through a guiding sleeve according to the invention as shown in FIG. 2 and taken along line 1--1 of FIG. 2, with the rod and spring element removed for purposes of clarity. 
     FIG. 2 is an enlarged section through the guiding sleeve of FIG. 1 taken along line 2--2. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The guiding sleeve shown in FIG. 1 is generally indicated by the reference number 10. It comprises a cylindrical hollow sleeve portion 11 as well as a head 12 radially projecting from the sleeve portion 11. As appears from FIG. 2, the head comprises an approximately circular outline. Within the area of the head 12 a cylindrical bore 13 of the sleeve portion 11 is provided with an approximately rectangular extension 14 which at 15 is narrowed to the diameter of the bore 13 again. The recess or extension 14 is limited by a rear wall 16 and by side wall portions 17, 18. An opening 19 extending over the entire width of the head 12 is provided opposite to the rear wall 16. A spring element 20 is arranged within the extension 14. It is substantially U-shaped and comprises an arm 21 which with a cranked central portion 22 engages a recess 24 at the inside of the rear wall 16. On both sides of the recess 24 the arm portion 21 is fully supported by the rear wall 16. Two spring legs 26, 28 are connected to the cross arm 21 and comprise portions 30, 32 converging away from the ends of the cross arm 21 and changing into parallel leg portions 38, 40. At their ends the leg portions 38, 40 comprise portions 42, 44 which are curved outwardly. A rod 43 of a headrest adapted to be inserted into the guiding sleeve 10, which in FIG. 2 is shown in section only, comprises notches 46, 48 which are arranged diametrically opposite to each other and functioning as abutments which shall prevent the rod 43 from being removed from the sleeve 10. In the other areas the rod 43 is circular. As soon as the rod 43 is moved upwardly the two leg portions 38, 40 lock into notches 46, 48 and prevent the rod 43 from being further removed. For this purpose, the spring legs 26, 28 are pretensioned towards each other. 
     Besides, a locking element 50 is inserted into the extension 14 which comprises two parallel legs 52, 54 which at one end are connected to each other by means of an arm 56. The straight outer surfaces of the legs 52, 54 towards the extension 14 in the front area are dimensioned so as to allow the legs to be guided by the corresponding inner wall portions of the side walls 17, 18. The legs 52, 54 in their rear end portions comprise snap-in noses 58, 60 which snap behind snap-in shoulders 62, 64 as soon as the unlocking element 50 has been completely inserted into the extension 14. The unlocking element 50 at its outer surface which has been adapted to the circular outline of the head 12 comprises a recess 66 into which a finger can be inserted for pressing in the unlocking element 50 as shown by the dotted line. 
     The arm 56 of the unlocking element 50 at its inner surface comprises two ramp-like cam surfaces 70, 72 engaging the curved end portions 42, 44 of the spring 20. In this way, the unlocking element 50 is kept at its shown position, that is, a close fit of the snap-in noses 58, 60 with the snap-in shoulders 62, 64. If, however, the unlocking element 50 is pressed into the extension 14, the cam surfaces 70, 72 cause the spring legs 26, 28 to bend apart, as shown in FIG. 2, so as to allow the rod 43 to be easily removed from the guiding sleeve 10. The rear wall 16 has been provided with two openings 36, 37 which are arranged opposite to the ends of the legs 52, 54. The ends of the legs 52, 54 comprise lateral oblique surfaces so that any object inserted through the openings 36, 37 and engaging the oblique surfaces is capable of deforming the legs towards each other in order to bring the snap-in noses 58, 60 out of engagement with the snap-in shoulders 62, 64. In this way, the unlocking element 50 and also the spring 20 can be easily removed from the extension 14. It goes without saying that the length of the cross arm 21 is smaller than the distance between the wall portions 17, 18 in the area of the opening 19. 
     Finally, it should be mentioned that in the drawing according to FIG. 1 only the sleeve itself but not the spring 20 is shown. 
     Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described herein.