Drawer guide
TECHNICAL FIELD 
     The present invention relates to drawer guides of the typed used to support a drawer in a cabinet body. 
     BACKGROUND ART 
     Such guides typically include a cabinet body rail for connection to a cabinet body, a drawer rail for connection to a drawer, a center rail and carriages with rolling means acting between the rails. The design of such guides is intended to ensure that when the drawer is pulled out of the cabinet body, the center rail is entrained in order to ensure maximum possible support of the drawer. This is referred to as differential withdrawal. It is important here to synchronize the withdrawal movement of the drawer with the withdrawal movement of the center rail in order to accomplish the required differential withdrawal. This may be achieved by means of a closed traction means such as a cable or chain which runs over guide rollers located at front and rear ends of the center rail. 
     A drawer guide of the kind mentioned above is described in German Utility Model 1 966 323. 
     There is also known a drawer guide in which there are upper and lower carriage assemblies, wherein in a cabinet body rail a lower carriage cooperates with a center rail and an upper carriage cooperates with a guide rail on the drawer side. The traction means is however different from that in German utility model 1966323, particularly on account of the fact that a total of four carriage assemblies rolling over different tracks are needed and the ends of the traction means are connected to the cabinet body rail and drawer rail. 
     OBJECTS OF THE INVENTION 
     It is therefore an object of the invention to provide a drawer guide of the kind mentioned above which provides with substantially lower production costs, a simpler arrangement which operates more reliably. 
     Another object of the invention is to provide a drawer guide in which differential withdrawal is reliably achieved. 
     A further object of the invention is to provide a drawer guide in which the traction means does not need to be directly connected to the cabinet body rail or drawer rail. 
     SUMMARY OF THE INVENTION 
     The foregoing objects are met in accordance with the present invention by the provision of a drawer guide for supporting one side of a drawer with respect to a cabinet body including a cabinet body rail for connection to a carcass, a drawer rails for connection to a drawer, a center rail, first and second carriages both with rolling means acting between the rails, a guide roller at opposite end regions of the center rail, a closed traction means with an upper run and a lower run, wherein said first carriage is arranged in load-transmitting relationship between said drawer rail and said center rail and said second carriage is arranged in load-transmitting relationship between said cabinet body rail and said center rail and wherein said traction means runs over said guide rollers and each of said runs of traction means is connected to a different one of said carriages at each of said carriage&#39;s ends so as to synchronize displacement of said center rail as said drawer rail is displaced relative to said carcass rail. 
     An essential characteristic of the invention is that the guide rollers over which the traction means is guided are arranged at the front and rear ends of the center rail and that the traction means is attached to upper and lower carriages at mutually opposed ends of the carriage. 
     With this arrangement, there is provided the essential advantage that when the drawer is pulled out of the cabinet body, the center rail is now entrained precisely by half the distance of withdrawal with synchronous movement, wherein gentle withdrawal of the drawer from the cabinet body is ensured and at the same time the drawer is also fully supported in its withdrawn position by the carriage assembly on the center rail. 
     It is preferred if the rolling means includes several rolling bodies such as rollers and the rollers are arranged one above the other and form corresponding running planes for engagement of the center rail which is entrained between the carriage assemblies, each carriage being carried by these rollers. Lateral guiding rollers may also be provided for maintaining the distance between the carriages or between the carriages and the rails, in order to ensure lateral guiding of the rail assembly. This lateral guiding may alternatively be provided by the rolling means. 
     A wire cable is preferably used as the traction means, but other traction means can be used instead, e.g. plastic cables and the like. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The invention is described in more detail below with reference to the accompanying figures showing only one embodiment. Further characteristics essential to the invention and advantages of the invention are apparent from the figures and the description thereof. The figures show: 
     FIG. 1: a schematic section through a drawer guide according to the invention in the pulled-out state, 
     FIG. 2: the same view as FIG. 1 in the pushed-in state, 
     FIG. 3: section through the line III--III in FIG. 2. 
    
    
     DETAILED DESCRIPTION 
     Drawer rails 2 are attached on each side to a drawer 1 which is connected to a frame 9. For simplicity&#39;s sake, in the description below only one drawer guide is described, because that located on the opposite side of the drawer is of exactly identical construction. 
     The drawer rail 2 forms an approximately C-shaped profile in which is arranged an upper carriage 3. Only the upper and lower rollers of the carriage in FIG. 3 are shown, the carriage itself not being shown for simplicity&#39;s sake. The rollers are rotatable in a manner known in the art or held freely guided in a corresponding carriage body. 
     The center rail 4 constructed as a U-profile engages by a first bent arm 4a of the U between the upper 3a and lower 3b roller assemblies of the upper carriage 3. 
     The lower assembly of the drawer guide is similar to the upper assembly described above. On a cabinet body 14 a cabinet body rail 10 is arranged which is also approximately C-shaped. A lower carriage 5 with upper 5a and lower 5b roller assemblies rolls along in the cabinet body rail 10. A second bent arm 4b of the center rail 4 is rollingly and slidably engaged by the lower carriage roller assemblies 5a and 5b. 
     The center rail 4 is provided at its front and rear ends with a guide rollers 12 and 11 respectively which are mounted rotatably on the center rail. Over the guide rollers 11 and 12 is guided a traction means 8 which is connected by connection means 3a to the upper run 8a of the traction means at the front and rear ends of the upper carriage 3. The lower run 8b of the traction means 8 is connected by connection means 5a to the front and rear ends of the lower carriage 5. 
     This simple assembly operates reliably. When the drawer 1 is pulled out of a carcass in the direction of the arrow 6, the upper carriage 3 is smoothly and reliably entrained as far as the mid point of the drawer rail 2. Thus the drawer is optimally supported via the carriage 3 and the center rail 4 on the cabinet body rail 10. 
     At the same time the center rail 4 is supported relative to the cabinet body rail 10 via the carriage 5 which runs into the rear portion of the center rail 4. 
     In the pushed-in state (FIG. 2), the two carriages 3, 5 are located approximately one above the other. 
     With this description of the invention in detail those skilled in the art will appreciate that modifications may be made to the invention without departing from the spirit thereof. Therefore it is not intended that the scope of the invention be limited to the specific embodiments. Rather it is intended that the scope of the invention be determined by the scope of the appended claims. The invention should be considered as extending to any novel combination of claims or features disclosed in the specification or abstract.