Abstract:
A fully extendible drawer unit utilizes two pairs of, in each case, three rails which can be pushed into one another. On the carcass rail is positioned a differential roller, which allows the intermediate rail to be moved along when the drawer starts to be pulled out at a lower speed than the drawer and the drawer rail. A coupling lever ensures that the intermediate rail is still pushed along even when the drawer rail has already left the differential roller and that this happens synchronously.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to the field of drawer units and more particularly to fully extendible drawer units and couplings therefor. 
     BACKGROUND OF THE INVENTION 
     Fully extendible chests of drawers, abbreviated extendible chests of drawers, are known in many embodiments and, if there is to be full extension with over-extension, i.e. the drawer can be pulled completely out of the carcass, they have respectively three rails, namely a carcass rail, a drawer rail and in between an intermediate rail relatively movable with respect to both rails. In the simplest configuration the three rails are mutually connected to one another via rollers and the intermediate rail is pulled along when the drawer is pulled out. To ensure that the intermediate rail is pulled out evenly, various measures are known by which said intermediate rail is carried along, while the speed at which it is pulled out is reduced in respect of the drawer. 
     From German patent specification 674548 a guide device for a chest of drawers is known, in which the intermediate rails run on rollers comprising two steps with different diameter. By choosing an unequal diameter ratio of 2:1, for example 8:4, it is achieved that the intermediate rail remains slightly behind and when the drawer is fully pulled out there is good, even support. 
     To enable even carrying of the two intermediate rails it is proposed in CH-AS 677593 to provide the roller on the intermediate rail with a set of teeth designated to engage in a tooth rod on the carcass rail. 
     DE-A1 41 21 070 proposes, instead of a set of teeth, connecting the rails by means of a belt which runs via a differential roller and thus allows the speed gradient of the three rails relative to one another to be pre-set. 
     Because the intermediate rails are pulled out substantially evenly with the drawer, all these known embodiments enable good, even, smooth support of the latter. They are, however, characterized by a complicated construction and are consequently expensive to produce. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to create a fully extendible drawer unit which has a simple, cheaply produced construction and allows the drawer to be pulled out and pushed in gentle, without jolting and with ease of movement. A further object of the invention is to create a coupling which enables defined carrying of the intermediate rail. 
     Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become more apparent to those skilled in the art upon examination of the following, or may be learned from practice of the invention. 
     Mounting the differential roller on the front edge of the carcass rail effects constantly non-positive carrying of the intermediate rail right from the start of the pulling out movement of the drawer from the carcass. Once the rear end of the drawer, and therefore of the drawer rail, has passed the differential roller, a coupling on the intermediate rail acts on a carrier on the drawer rail and effects that the two intermediate rails synchronously with the drawer are carried further outwards, thereby guaranteeing constant, problem-free, even support and quiet running of the drawer. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The Invention is explained in more detail with the aid of an illustrated embodiment. 
     FIG. 1 shows a side view of the carcass, intermediate and drawer rails inside one another. 
     FIG. 2 shows a side view of the rear end of the drawer rail. 
     FIG. 3 shows a cross-section through the drawer rail along line E—E in FIG.  2 . 
     FIG. 4 shows a side view of the intermediate rail. 
     FIG. 5 shows a cross-section through the intermediate rail along line B—B in FIG.  4 . 
     FIG. 6 shows a cross-section through the intermediate rail along line C—C in FIG.  4 . 
     FIG. 7 shows a side view of the carcass rail. 
     FIG. 8 shows a cross-section through the carcass rail along the line D—D in FIG. 7 
     FIG. 9 shows a side, view of the rear end of the drawer rail and the intermediate rail placed therein and also the differential roller under the intermediate rail. 
     FIG. 10 shows a side view of the rear end of the drawer rail and the intermediate rail placed therein and the coupling lifted from the differential roller. 
     FIG. 11 shows a cross-section along line A—A in FIG.  10  through the three rails. 
     FIG. 12 shows a side view of the rear end of the drawer rail and the intermediate rail placed therein and also the differential roller on the carcass rail. 
     FIG. 13 shows a side view of the lever according to a further configuration of the invention before contact with the differential roller. 
     FIG. 14 shows a side view of the lever in FIG. 13 lifted by the differential roller. 
     FIG. 15 shows a side view of the three rails with a coupling lever which can be latched in from below. 
     FIG. 16 shows an enlarged representation of a cross-section, with the lever before latching in. 
     FIG. 17 shows an enlarged representation of a cross-section with the lever after latching in. 
     FIG. 18 shows a longitudinal section through the lever and the intermediate rail along line XVI—XVI in FIG.  16 . 
     FIG. 19 shows a cross-section along line XVII—XVII in FIG.  17 . 
    
    
     DETAILED DESCRIPTION 
     Reference numeral  1  in FIGS. 1 and 7 represents a carcass rail  1 , on whose rear end  3  a buffer stop  5  and on whose front end  7  a two-step differential roller  9  are rotatably positioned. In the region of the differential roller  9  the upper edge of the carcass rail  1  runs tangentially to the apex of the differential roller  9 . The differential roller  9  comprises a groove  11  with the larger diameter and a groove  13  with the smaller diameter. As an example, seven holes  15  serve to guide through screws to attach the carcass rail  1  to a carcass inner wall (not illustrated). The lower leg  17  of the carcass rail  1  in the example illustrated runs level and at a right angle to the base leg  19 . The upper leg  20  forms a downwardly concave groove  21 . The concave groove  21  ends at a distance in front of the end  7  (FIG.  7 ). The distance enables the rear roller  23  on the intermediate rail  25  to be inserted from above into the space between the lower leg  17  and the upper leg  20  of the carcass rail  1 . Preferably two pull-stops  27  are moulded onto the lower leg  17 , for example in the form of bosses forming a temporary buffer for the rear roller  23  of the intermediate rail  25 . The rear roller  23  on the intermediate rail  25  protrudes beyond the lower leg  17  thereof. 
     The intermediate rail  25  further comprises a front roller  31  which protrudes beyond the upper edge  34  of the intermediate rail  25 . A buffer stop  33  can also be constructed at the rear of the intermediate rail  25 . In the cross-sections according to FIGS. 5 and 6 of the intermediate rail  25  it can be seen that rear roller  23  located at the bottom is preferably rotatably attached in an off-set region  35  of the base leg  37  of the intermediate rail  25 . This enables the roller  23  to come to rest in the plane of the base leg  37 , thereby making it possible for the structure to be narrow. On the upper edge of the base leg  37  a c-shaped rail  39  with a lower flat running face  41  and a concave upper guide device  42  is constructed or attached. The c-shaped rail  39  extends only over the rear half of the intermediate rail  25 . The latter serves to guide the single roller  43  in the region of the rear edge of the drawer rail  45 . This comprises a plate  46 , designated to adjoin the drawer, on whose lower edge a leg  49  is constructed, on which the floor of the drawer (not illustrated) comes to rest and can be attached. On the upper edge of the drawer rail  45  a guide track  47  is mounted, which forms a guide and running face for the front roller  31  on the intermediate rail  25 . In the central region of the plate  46  of the drawer rail  45  a carrying rail  51  with a running face  53  directed downwards is attached. The latter comes into contact with the groove on the large diameter  11  of the differential roller  9  when the drawer is partially pushed into the carcass (compare situation in FIG.  11 ). 
     A one-armed lever  55  is further pivotably coupled to a pin  57 . The lever  55 , which acts as a coupling, comprises a hook-shaped end  69 , formed from an outer lug  61  and an inner lug  63 . A leading or sliding face  65  and the flank  67  adjoin the lugs  61  and  63 . The sliding face  65  is located between the end of the lever  55  and the lug  61 ; the flank  67 , which is inclined at an obtuse angle to the sliding face  65 , extends in the direction of the pin  57 . The sliding face  65  and the flank  67  are located in a region protruding laterally beyond the surface of the lever  55 . 
     On the lower edge of the lever  55  is further constructed a curve running at an obtuse angle, whose function will be explained in the functional description. Attached to the drawer rail  45 , on the carrying rail  51 , is a cam  69 , into which the lever  35  can be latched. In the proximity of the pin  57  additionally attached to the lever  55  is a trigger  71 , which penetrates a recess  73  in the intermediate rail  25 . 
     The mode of operation of the fully extendible drawer unit is explained in more detail below. When the drawer is pulled out the differential roller  9  is set in motion by the carrying rail  51  attached to the drawer rail  45 , the running face  53  of said carrying rail  51  being supported on the larger diameter  11  of the differential roller  9 , thereby also setting in motion the intermediate rail  25 , which rests on the smaller diameter  13  of the differential roller  9 . The speed of movement of the intermediate rail  25  corresponds to the ratio of the two diameters on the differential roller  9 . The intermediate rail  25  is supported while the drawer is being pulled out on the one hand from below by the differential roller  9  (there by the smaller diameter  13 ) on the lower edge  26  and prevented from tilting by the rear roller  23  attached to the intermediate rail  25 , which runs inside the carcass rail  1 . The roller  23  is herein supported in the concave groove  21  of the upper leg  20  and is also guided laterally by the groove  21 . The drawer itself, which is attached to the two drawer rails  45 , is supported on the pull-out side, i.e. at the front, on the front roller  31  of the intermediate rail  25 . The roller  31  is herein guided in the guide track  47  of the drawer rail  45 . To prevent the drawer from tipping the rear roller  43  of the drawer rail  45  is supported on the rail  39  of the intermediate rail  25 . 
     The roller  31  on the intermediate rail  25  is preferably positioned in such a way that the guide track  47  does not rest on the roller  31  when the drawer is pushed in and the roller  31  does not take on a supporting function until the drawer is pulled out. In this manner it is guaranteed that initially, when the drawer is pulled out, the drawer rail  45  rests almost exclusively on the differential roller  9 , thereby setting this in motion. To guarantee that the intermediate rail  25  is carried along even if the drawer rail  45  has already left the region of the differential roller  9 , the lever  55  is provided. If in the process of pulling out the drawer, at the latest when the carrier  69  reaches the flank  67  of the coupling lever  55 , the coupling lever  55  is lifted and the carrier  69  passes through under the lug  64  (FIG. 10) until it reaches the flank of the lug  61  and latches in. The intermediate rail  25  is now carried along synchronously to the end, i.e., until the drawer is fully or over pulled out (FIG.  12 ). The large lug  61  is located, with respect to the smaller lug  63 , in front and downwards, so that—if the coupling lever  55  is lifted from the differential roller  9  by the curve  60 —the carrier  69  cannot come unlatched. 
     In the configuration of the invention according to FIGS.  13 / 14  the sliding face  65  and the flank  67  end at the same height, i.e. the lugs  61  and  63  are located at approximately the same height. 
     On the other hand, as soon as the drawer rail  45  is pulled out sufficiently far, the lever  55  turns clockwise under its own weight and latches into the lug  61 . From this time on the intermediate rail  25  is pulled out with the drawer at the same speed as the drawer rail  45 . The action of the differential roller  9  on the intermediate rail  25  lapses at this time, as the drawer rail  45  is no longer supported on the larger diameter  11 . 
     At the end of the pulling out process the rear roller  23  of the intermediate rail  25  pushes against the rear pull-out stop  27 . If the drawer is pulled out of the carcass for cleaning purposes or for other reasons, the drawer can be pulled out over the top of the pull-out stop  27  by overcoming the resistance thereof. If the roller  23  has overcome the pull-out stop  27  the drawer still cannot fall out, however, because it is still secured by the lever  55 . With the trigger  71  the lever  55  can be lifted and the drawer fully released. 
     Attaching the drawer takes place in the reverse order. The intermediate rail  25  with the roller  23  is placed on the lower leg  17  of the intermediate rail  25 . This is made possible because the upper leg  20  is not taken as far as the differential roller  9 . After the roller  23  has been inserted, the intermediate rail  25  is supported with its lower edge on the small diameter  13  of the differential roller  9  and the roller  31  is supported in the groove  21 . The drawer rail  45  is placed with the roller  43  on the running face  41  and then pushed in until the upper leg  47  of the drawer rail  45  is resting on the roller  31  of the intermediate rail  25 . When the drawer rail  45  is pushed in, the sliding face  65  of the lever  55  on the insertion side slides upwards on the cam  69  and pivots the lever  55  in a counter clockwise direction. Then the cam  59  latches into the lever  55  and the intermediate rail  25  is thereby pushed backwards synchronously with the drawer rail  45  until the curve  60  begins to rest on the differential roller  9  and is lifted by the latter. The lifting causes the lever  55  to be released from the cam  69 , and the drawer rail  45  with the drawer begins to move relative to the intermediate rail  25  and with the latter arrives in a fairly large overlap until at the end of the pushing in process all three rails  1 ,  25 ,  45  are substantially located above or inside one another. 
     In a further particularly advantageous configuration of the invention the lever  155  acting as coupling is again coupled to a pin  157  and is held substantially horizontal by a peg  158 , which engages in a recess  160  in the intermediate rail  25 , in the non-engaged position, i.e. when the drawer is pushed in. A stopper  164 , which reaches through a recess  162  in the intermediate rail  25 , is constructed on the lever  155  in the region of the lug  161 . Said stopper is located with minimal play inside the recess  162  when the lever  155  is out of engagement with the cam  169  on the intermediate rail  25 . The stopper comes into contact with the intermediate rail  25  as soon as the cam  169  presses with impact or with great force against the stopper  164 . Preferably the lever  155  is connected to the intermediate rail  25  via the pin  157  with play, to enable the stopper  164  to fit closely in the orifice  162 . 
     When the drawer is pulled out, the lever  155  slides with the leading face  165  onto the groove  13  with the smaller diameter and is lifted by it. The cam  169  herein comes into contact with the stopper  164  and is held by it. The contact of the lever  155  with the cam  169  takes place spring elastically, because a slot  172  is constructed on the lever  155  running parallel to its lower edge  170 . Owing to the high elasticity of the material of which the lever  155  is made—it is preferably made of a plastics material—the narrow bridge  174  springs inwards when it is in contact with the groove  13  above the differential roller  9 . So as to be able to remove the drawer completely from the guide device, the lever  155  can be pivoted by pressing the stopper  164  downwards by hand, and in fact against the elasticity of the bridge  174 , until the cam  169  can be guided out above the lug  163 . The flank  166  adjacent to the lug  163  is inclined to the horizontal, so that, when the drawer is pushed in, the cam  169  can move safely out of its latched position when the lever  155  is no longer being pressed upwards. 
     Because the lever  155  can be actuated by means of the smaller diameter on the differential roller  9 , it is possible substantially to reduce the total height of the three co-operating guide rails  1 ,  25 ,  45 . 
     The lever  155  can also be placed on guide rail devices which diverge in construction from those described in this invention.