Abstract:
A belt buckle for vehicle safety belts has a load bearing frame and a locking mechanism thereon. A housing encloses the frame and has an insertion slot for an insert tongue acting in conjunction with the locking mechanism. To eliminate any extraneous matter that has entered into the housing through the insertion slot, a channel leads from the insertion slot through the housing and out of the housing, forming a guide for gravity assisted movement of such extraneous matter out of the housing.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a belt buckle for vehicle safety belts. 
     BACKGROUND OF THE INVENTION 
     Belt buckles generally have a load bearing frame attached to the vehicle floor or the like by means of a suitable attachment fitting, a locking mechanism arranged at the frame, and a housing which encloses the frame and which has an insertion slot for an insert tongue acting in conjunction with the locking mechanism. This insertion slot must be free and open so as not to obstruct the insertion of the tongue into the belt buckle when the safety belt is to be used. The open and unobstructed insertion slot, however, also allows the entry of extraneous matter into the inner space of the belt buckle. Examples of such extraneous matter are liquids (drinks), glass splinters (accident, break-in), fruit pips, rice grains, fibres, grit, gravel and the like. Hard matter, in particular, but also sticky liquids can impair or even impede the function of the locking mechanism. If proper locking is not achieved, the safety belt is not capable of fulfilling its protective function. Incomplete locking, also known as “pseudo-locking”, is particularly dangerous, since the vehicle occupants are unable to detect this condition. 
     SUMMARY OF THE INVENTION 
     The invention eliminates this safety deficiency inherent in all known belt buckles. 
     According to the invention, at least one channel leads from the insertion slot for the insert tongue through the housing and out of it in such a way that any extraneous matter which may have entered through the insertion slot is guided out of the housing along the channel as assisted by gravity. Whilst with conventional embodiments of belt buckles the aim was to close the insertion slot through the insert tongue ejector as completely as possible, the invention follows the opposite strategy: Having realized that it is not possible in practice to prevent the entry of extraneous matter through the insertion slot for the insert tongue, the invention makes a point of even favoring such entry of such grit particles and foreign bodies through the channel formed within the belt buckle, so that these may leave the belt buckle housing on a direct route through the channel. It is, in fact, the agglomeration of dirt and other foreign matter in the area of the insertion slot for the insert tongue that will find its way into the interior of the belt buckle housing when the tongue is inserted or the release button is pressed. 
     In the preferred embodiment of the belt buckle, the insert tongue ejector, as opposed to known embodiments where its width coincides with that of the front end of the insert tongue in order to close up the insertion slot as much as possible when the insert tongue is released, is of reduced width so as to obtain free space on both sides of the ejector for a channel for the elimination of dirt and other foreign matter. The ejector is furthermore provided with guide surfaces at its outer end in order to favor the entry of foreign matter into the two channels. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further advantages and characteristics of the invention read from the following description of several embodiments, as well as from the attached drawings, to which reference is made, showing in 
     FIG. 1 a schematic part section of a belt buckle along section I—I in FIG. 2; 
     FIG. 2 a schematic view of a narrow side of the belt buckle; 
     FIG. 3 a sectional view of a second embodiment along section III—III in FIG. 4; 
     FIG. 4 a schematic side view of the belt buckle embodiment shown in FIG. 3, and 
     FIG. 5 a sectional view along section V—V in FIG.  3 . 
    
    
     DETAILED DESCRIPTION 
     The belt buckle  10  shown in FIG. 1 serves to lock the insert tongue  12  of a safety belt not shown here. To this effect, the insert tongue  12  is pushed, from the position shown in FIG. 1, into the belt buckle  10  and is locked there by means of a conventional locking mechanism which is not shown here. A release button, also of conventional design and not shown here, serves to release the locking mechanism. The belt buckle  10  has a frame  14  which is connected to the vehicle body or to a seat within the vehicle by means of an attachment fitting  16 . 
     The sectional view of FIG. 1 furthermore shows a housing half  18  which partly surrounds the frame  14 . As with conventional belt buckles, the housing surrounding the frame  14  consists of two halves, of which only one, that is the half-housing  18 , is shown in the illustrations. An insert tongue ejector  20 , which is pre-tensioned against the insert direction of the insert tongue  12  by means of a compression spring  22 , is arranged centrally within the frame  14  of the belt buckle  10 . As the insert tongue  12  is inserted into the belt buckle  10 , the insert tongue ejector  20  is moved downwards, and the compression spring  22  is compressed. When the locking mechanism of the belt buckle  10  is unlocked by pushing the release button, the insert tongue ejector  20  pushes the insert tongue  12  out of the belt buckle  10 , so that the corresponding safety belt is released. 
     As can be seen from FIG. 2, the belt buckle  10  has an insertion slot  24  for both the insertion and the ejection of the insert tongue  12 . The frame  14  of the belt buckle  10  is made up of two parallel plates  26  and  28 , between which the insert tongue ejector  20  is movably arranged. The plates  26  and  28  are arranged at a distance from each other which essentially corresponds to the thickness of the insert tongue  12 , making sure that it is guided between the plates  26  and  28  in a safe way. When the insert tongue  12  is not inserted, that is in the condition illustrated in the Figures, the insertion slot  24  is open and dirt and foreign bodies are free to enter into the insertion slot  24 . 
     Such foreign bodies  30  are shown in FIG.  1 . The foreign bodies  30  enter the inside of the belt buckle  10  via the insertion slot  24 . Channels  32  lead from the insertion slot  24  through the belt buckle  10 , and the intruding foreign bodies  30  are made to travel through these channels  32  and consequently through the belt buckle  10  in the direction of the arrow indicated in FIG.  2 . Since the foreign bodies  30  are conveyed through the belt buckle  10  to be then expelled from it, no jamming of the locking mechanism can occur and malfunctions of the belt buckle  10 , in particular the condition of pseudo-locking, are prevented. 
     As is shown again in FIG. 1, the foreign bodies  30  which have entered through the insertion slot  24  are made to move along the channel  32 , assisted by their gravity and by the vibration of the vehicle, and are then conveyed through the channel  32  and expelled from the belt buckle  10  and the housing of the belt buckle, respectively, through an opening  34  of the housing, which is essentially opposite the insertion slot  24 . The channels  32  are formed between the parallel plates  26  and  28  of the frame  14  and on both sides of the insert tongue ejector  20 . To this end, the insert tongue ejector  20  is made relatively narrow with respect to the width of the insertion slot  24 , which corresponds essentially to the width of the insert tongue  12 . At its end facing the insert tongue  12  and the insertion slot  24 , respectively, the insert tongue ejector  20  is rounded and therefore provided with guide surfaces  36  which open out into the channels  32 . Any foreign bodies  30  that enter are guided sideways by these guide surfaces  36  and into the channels  32 . Embossments  38  are provided in the parallel plates  26  and  28  of the frame on both sides of the insert tongue ejector  20 . By these embossments  38 , guide surfaces  40  are formed between the plates  26  and  28 , so that the channels  32  in the area of the insert tongue ejector  20  are delimited by its lateral surfaces  42 , the facing inner surfaces of the plates  26  and  28 , as well as by the guide surfaces  40  formed by the embossments  38 . The embossments  38  extend not only over the area of the insert tongue ejector  20 , but further through the belt buckle  10  and thereby delimit the channels  32  also in their further extension. The channels  32  are then delimited in the lower area of the belt buckle  10  by the lateral surfaces  44  of the attachment fitting  16  and by the guide surfaces  46  formed on the plates  26  and  28 . Once the foreign bodies  30  have passed the belt buckle  10  through the channel  32 , as shown in FIG. 1, these then leave the housing of the belt buckle  10  adjacent to the attachment fitting  16 . In order to ensure that even fairly large foreign bodies, such as apple pips or glass splinters, are able to leave the belt buckle  10  through the channels  32 , the channels  32  are designed to have a cross section of approximately 4 mm 2  to 10 mm 2 . 
     A further embodiment of the belt buckle according to the invention, similar in design to the belt buckle shown in FIGS. 1 and 2, is illustrated in FIGS. 3 to  5 . Here, the belt buckle  50  also has a frame consisting of two parallel plates  52  and  54  which are connected to a vehicle structure by means of an attachment fitting  56 . The belt buckle  50  has a plastic housing consisting of two housing halves, of which only one housing half  58  is shown in the illustrations. Channels  62  are formed on each side of the movably provided insert tongue ejector  60  positioned between the plates  52  and  54 , through which channel any foreign bodies  64  which have penetrated the belt buckle  50  are once more expelled, gravity assisted, from the belt buckle  50  and its housing. The plates  52  and  54  have embossments  66  in the area of the insert tongue ejector  60  which act as lateral limits to the channel  62 , so that the channel  62  is of width b. The width b of the channel  62  also remains essentially constant within the further extension of channel  62  through the belt buckle  50 , since the embossment  66  is followed by an angled sheet metal lug  68 , forming an integral part of plate  52  and constituting a further guide surface to delimit the channel  62 . 
     In the lower section of the belt buckle  50 , the channel  62  is delimited in its longitudinal direction by a ramp  70  formed to the housing half  58 , which extends from the housing half  58  to the plate  54  through the plate  52  and the channel  62 . As can be clearly seen from FIG. 4, the ramp  70  is positioned at an angle to the longitudinal direction of the channel  62 , so that any foreign bodies  64  moving along the channel  62  are deflected from the longitudinal direction of the channel  62  and are expelled from the housing of the belt buckle  50  through an opening  72  provided in the housing half  58  in the direction indicated by an arrow in FIG.  4 .