Abstract:
A sequential drawer slide is disclosed having rails that extend in a predetermined order, resulting in the weight of the drawer initially carried by multiple slides concurrently to increase the load rating of the assembly and prolong the life cycle of the drawer slide. The sequential actuation of the slide rails as the drawer is withdrawn from the cabinet is achieved by incorporating a catch between the small slide rail and the intermediate slide rail that resists extension of the small slide rail from the intermediate slide rail up to a decoupling force. If the decoupling force is greater than the force required to extend the intermediate slide rail from the large slide rail, then the intermediate slide rail and small slide rail nested therein will extend first, and the small slide rail with extend from the intermediate slide rail only after the intermediate slide rail is fully extended.

Description:
FIELD OF THE INVENTION  
       [0001]     The invention relates generally to drawer slides, and more particularly to a drawer slide with a sequential opening mechanism.  
       BACKGROUND OF THE INVENTION  
       [0002]     The use of drawer slides for file cabinets are well known. The drawer slides support the shelves or drawers in the cabinet, and extend horizontally to allow the shelves to be accessed external to the cabinet, facilitating both the retrieval and return of documents stored therein.  
         [0003]     A typical drawer slide has a plurality of nested or stacked rails that may slide against a set of bearings, especially ball bearings. The bearings are located in raceways longitudinally disposed along the slide rails. In a typical horizontal slide configuration, a first large slide rail is mounted to each inner side wall of the cabinet at the designated location for the shelf. A second, smaller slide rail is rigidly affixed to the drawer such that the drawer extends horizontally and is supported outside the cabinet by the smaller slide rail. Each slide rail includes a longitudinal track that runs parallel to the bearing raceway substantially along the length of the rail. In a three-slide configuration, an intermediate rail cooperates with the cabinet slide rail and the drawer slide rail to further extend the drawer. Although less common, additional slide members can be added to the embodiment just described.  
         [0004]     The arrangement of the slide rails can take various forms, such as a vertical stacking of the slide rails or, more commonly, a nesting of the slide rails in a telescoping arrangement. With a telescoping slide arrangement, there is typically a small slide rail (the “inner rail”) connected to the drawer that fits into the intermediate slide rail, which in turn fits into the large slide rail (the “outer rail”) affixed to the cabinet. These three rails telescope in a known manner to extend the file drawer outward from the cabinet. When the drawer is withdrawn from the cabinet, a user applies a horizontal force to a handle on the face of the drawer causing the drawer to extend outward from the cabinet in a cantilever arrangement as the slide rails expand horizontally. Because the smallest slide rail is connected to the drawer itself, when the horizontal force is applied to the drawer the small slide rail translates horizontally with respect to the intermediate slide, causing the drawer to be supported substantially by the small slide rail. During this initial movement of the drawer the intermediate slide rail remains stationary within the larger slide rail. When the small slide rail becomes fully extended within the intermediate slide rail, usually defined by a stop on the intermediate rail, the intermediate slide rail begins to translate horizontally within the large slide. If there is only one intermediate slide, then the drawer has reached its maximum horizontal displacement from the cabinet when the intermediate slide rail is fully extended from the large slide rail.  
         [0005]     One shortcoming of the above-described slide arrangement is that the smallest slide supports the entire file cabinet for the initial movement of the drawer translation. Only after the small slide is fully extended does the intermediate slide begin to extend and support some of the load. Because often times the drawer need only be partially withdrawn to retrieve a file or return a document, the small slide will be subjected to a disproportionately high percentage of total time supporting the shelve while the shelve is extended from the cabinet. Placing the entire load on the smallest slide has the effect of shortening the life cycle of the slides and limited the load rating of the drawer itself. Premature failure or wear of the slides results, necessitating replacement of the slides and can lead to the entire cabinet being scrapped at considerable cost to the user. What is needed in the art is a system that prolongs the life cycle and increases the load rating of a multi-slide arrangement.  
       SUMMARY OF THE INVENTION  
       [0006]     The present invention provides a sequential extraction of the drawer slide rails that results in the weight of the drawer initially carried by both the combination of the intermediate and small slide rails concurrently, thereby increasing the load rating of the assembly and prolonging the life cycle of the drawer slides. The sequential actuation of the slide rails as the drawer is withdrawn from the cabinet is achieved by incorporating a catch or other impediment between the small slide rail and the intermediate slide rail that resists extension of the small slide rail from the intermediate slide rail up to a separation force J. As long as force J is greater than the force required to extend the intermediate slide rail from the large slide rail, then the intermediate slide rail (and small slide rail nested therein) will extend first, and the small slide rail with extend from the intermediate slide rail only after the intermediate slide rail is fully extended. The catch between the small and intermediate rails can be achieved by an interfering contact between the small and intermediate slides where the frictional forces of the contact resists separation of the two slide rails up to a separation force J friction . Alternate catches may be based on the deflection of an interfering member or other force generating mechanisms in additional to the frictional force achieved by the embodiment discussed below.  
         [0007]     In a first embodiment, the impediment may be a V-shaped notch formed in the channel of the small slide rail that interferes with a detent block on the intermediate slide rail, resisting extension of the small slide rail within the intermediate slide rail. The frictional force needed to overcome the interference of the V-shaped notch against the detent block need not be large, rather it simply needs to be of sufficient magnitude that the intermediate slide rail extends before extension of the small slide rail. When the drawer is returned to the cabinet, the small slide first retracts into the intermediate slide again following the sequential expansion in reverse, once again ensuring that the shelf is supported by the combination of the intermediate and small slide rails for one half of the travel of the drawer. The insertion of the drawer into the cabinet forces the V-shaped notch or other protrusion over and past the detent or other frictional member resetting the mechanism for the next sequential extraction. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  is front view, partially in shadow, of an embodiment of the multiple rail slide of the present invention;  
         [0009]      FIG. 2  is an elevated perspective view of the small rail of the embodiment of  FIG. 1 ;  
         [0010]      FIG. 3  is an elevated perspective view of a portion of the small rail of the embodiment of  FIG. 1  engaging the detent of the intermediate rail;  
         [0011]      FIG. 4   a  is a front view of the detent mechanism of  FIG. 3 ;  
         [0012]      FIG. 4   b  is a side view of the detent mechanism of  FIG. 3 ;  
         [0013]      FIG. 4   c  is an elevated, perspective view of the detent mechanism of  FIG. 3 ;  
         [0014]      FIG. 5  is a magnified view of encircled portion of  FIG. 1 ;  
         [0015]      FIG. 6  is a front view, partially in shadow, of the embodiment of  FIG. 1  with the intermediate slide rail extended from the outer slide rail; and  
         [0016]      FIG. 7  is a front view, partially in shadow, of the embodiment of  FIG. 1  with the slide fully extended. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0017]      FIG. 1  illustrates a three piece telescoping slide  10  comprising three rails, an outer rail  20 , an intermediate rail  25 , and an inner rail  30 . The slide is used to support a file shelf or drawer in a file cabinet, and extend the drawer horizontally outward from the cabinet to access files, documents, and the like. The respective rails telescope from within each other in a well known manner to support the drawer outside of the cabinet. A cabinet will typically include three or more such drawers, with slides on each side supporting each drawer. That is, each drawer will typically have a left slide and a right slide mounting the drawer to the inside walls of the cabinet. While this disclosure may refer to the slide as singular in some references, it is to be understood that the slides are usually used in pairs to provide the support for each drawer.  
         [0018]     The innermost rail  30  slides longitudinally within the intermediate rail  25 , which in turn slides longitudinally within the outermost rail  20 . The inner rail  30 , as shown in  FIG. 2 , has a planar front panel  35  extending longitudinally with upper traverse edge  40  and lower traverse edge  45  extending perpendicular thereto forming a substantially “C” shaped beam. On the outer surface  55  of each traverse edge  40 , 45  of the inner rail  30  is a concave recess  50  extending substantially the longitudinal length of the inner rail  30 . Each concave recess  50  forms half of a ball bearing raceway that cooperates with a complimentary concave recess on the inner surface  60  of traverse upper and lower edges  65 ,  70  of the intermediate rail  25  as shown in  FIG. 7 . The front panel  35  includes a plurality of apertures  75  for use with a bracket (not shown) to secure the slide  10  to a retractable drawer, where fasteners (not shown) pass through the apertures  75  and corresponding holes in the bracket and drawer in a known manner. At a distal end  72  of the inner rail  30  is a flap  80  that cooperates with a detent  100  on the intermediate rail  25  to define the closed or withdrawn position. That is, when the slide  10  is retracting from its telescoped or extended position the inner rail  30  stops translation with respect to the intermediate rail  25  when the flap  80  contacts with the arcuate bumper  85  of the detent  100  of the intermediate rail  25 . The arcuate bumper  85  has some resiliency to absorb some of the energy of the moving drawer so that the drawer does not bounce off the intermediate rail  25  with substantial force.  
         [0019]     Spaced a short distance from the distal end  72  of the inner rail  30  is a “V” shaped notch  95  projecting inwardly from the upper traverse edge  40  at an inner surface  54  (see  FIG. 5 ). The “V” shaped notch is adjacent and proximal to the longitudinal position of the detent  100  of the intermediate rail  25  when the slide is contracted so that the end flap  80  and “V” shaped notch  95  border the detent  100 . The “V” shaped notch  95  has a vertical dimension such that the apex  97  extends into a path defined by the movement of a bypass surface  105  of the detent  100  as the intermediate rail  25  moves with respect to the inner rail  30 . In other words, the movement of the inner rail  30  with respect to the intermediate rail  25  causes the V-shaped notch  95  to come in contact with the bypass surface  105  of the detent  100  on the intermediate rail  25 . The frictional interference of the “V” shaped notch  95  with the by pass surface  105  of the detent  100  can be overcome by a supplemental horizontal force J corresponding to the frictional force resisting the movement of the “V” shaped notch across the surface of the bypass surface (see  FIG. 3 ). After the “V” shaped notch of the inner rail travels across the bypass surface  105 , the supplemental force J is eliminated and the inner rail  30  will move freely within the intermediate rail  25 .  
         [0020]     The detent  100  of the intermediate rail  25  is shown in  FIG. 4   a - c.  The energy absorbing arcuate bumper  85  extends from a substantially planar base  110 . Extending from the base  110  are outwardly directed fingers  115  defining channels  120  for receiving the respective traverse edges  40 , 45  of the inner rail  30 . Thus, when the inner rail  30  is in proximity with and parallel to the intermediate rail  25 , the upper edge  40  and lower edge  45  of the inner rail  30  are disposed in the channels  120  defined by fingers  115   a,b.  The detent  100  further includes angled tabs  130  that locate the detent  100  on the intermediate rail  25  by cooperating with mating slots  145  on the intermediate rail.  
         [0021]     Disposed on the detent  100  along on upper portion of the base  110  is a substantially rectangular stop  150  that supplies the bypass surface  105  for the sequential opening of the rails. The stop  150  includes a preliminary contact surface  155  defined by a proximal end surface that is adjacent to the V shaped notch  95  ( FIG. 5 ) when the slide is fully retracted. When a force is applied to the drawer to withdraw the drawer from the cabinet, the horizontal force applied to the drawer is transferred to the small rail(s)  30  to which it is attached. Unlike the prior art slides that would allow the inner rail to fully extend before translation of the intermediate rail would initiate, in the present invention the initial movement of the inner slide  30  causes the V-shaped notch  95  to bear against the contact surface  155  of the stop  150  on the detent  100  of the intermediate rail  25 . By orienting the bypass surface  105  parallel to the direction of travel of the inner rail, a predictable force to overcome the friction between the V-shaped notch and the bypass surface is established. The force required to overcome the interference of the V shaped notch  95  with the stop  150  (i.e., the initial deflection of the stop plus the friction resisting the movement of the notch dragging across the bypass surface  105  of the stop, referred herein as force J) is greater than the ordinary force required to move the intermediate rail  25  within the outer rail  20 . Accordingly, the horizontal force applied to the drawer is transferred through the inner rail  30 , across the sequential release mechanism, to the intermediate rail  25 , causing it to slide within the fixed outer rail  20 .  
         [0022]     As the intermediate rail  25  extends in a cantilevered manner away from the outer rail  20 , the weight of the shelf is supported by the combination of the inner rail  30  and the intermediate rail  25 . The structural capacity of this combination is significantly greater than the weight bearing capacity of the inner rail alone. For a standard one hundred pound rated full extension slide, the sequential extension of the intermediate and inner rails can increase the load capacity to approximately one hundred forty to one hundred fifty pounds, resulting in a fifty percent increase in load capability. This also has a significant impact on the life cycle of the slide  10 , and particularly the wear of the inner slide rail  30  which no longer bears the full weight of the drawer during the initial stages of extraction. This increase in life cycle and load capacity is a function of the sequential slide actuation and is not found in the prior art.  
         [0023]     Once the intermediate rail  25  is fully extended ( FIG. 6 ), an additional force J is necessary to further move the drawer away from the file cabinet. The force J is defined as the amount of force required to overcome the sequential actuator—in this case the force required to overcome the interference of the V-shaped notch  95  with the contact surface  105  of the stop  150 . When this incremental force J is applied, the further extraction of the drawer is achieved as the V-shaped notch passes across the contact surface, after which only the normal extracting force is required to fully open the drawer ( FIG. 7 ). The fully extended position is set by the engagement of a wedge shaped detent (not shown) on the front panel  35  of the inner rail at a proximal end  74  that engages the beveled edge  175  of the detent  100  to arrest further extension of the inner rail  30  from the intermediate rail  25 .  
         [0024]     The rails are preferably made of a metal such as steel to support the loads of the cantilevered shelves. The detent  100  is preferably formed of a hard polymer or plastic with some give, such that the interference with the V-shaped notch will cause the detent to yield and permit passage when the required force J is applied.  
         [0025]     The sequential opening of the slide  10  is shown in  FIGS. 1, 6  and  7 . Initially fully retracted, the inner rail  30  is seated within the intermediate rail  25 , which in turn is seated within outer rail  20 . Applying an outward horizontal force to the drawer initially will tend to cause the attached inner rail  30  with move within the intermediate rail  25 . However, the movement of the inner rail  30  is arrested by the interference of the V-shaped notch  95  with the stop  150  on the detent  100  of the intermediate rail  25 . As a result, as shown in  FIG. 6  the inner rail  30  and intermediate rail  25  initially extend together from within the outer rail  20 . Thus, up to and including the extended position of the slide  10  as shown in  FIG. 6 , the drawer is supported by the combination of the inner rail  30  and the intermediate rail  25 . Further applied force J will cause the V-shaped notch to deflect the detent  100  slightly cause the notch to drag across the bypass surface  105  until it separates from the detent  100 . This permits the inner rail to then extend unhindered from the intermediate rail until the slide is fully extended as shown in  FIG. 7 . When the drawer is returned to the cabinet, the V-shaped notch of the inner rail is forced back across the bypass surface  105  of the detent to reset the mechanism for the next use.  
         [0026]     While the above described embodiments disclose a frictional engagement of the detent with a protrusion of the cooperating rail, it may be appreciated that the invention is not limited to the above described embodiments for one of ordinary skill in the art would recognize that the sequential slide can be achieved by various mechanisms. For example, the force J required to overcome the movement of the inner slide rail within the intermediate slide rail can be prescribed by the deflection of one member on the inner rail interfering with a member of the intermediate rail during relative translation. Alternatively, the frictional force can be developed in various ways besides that disclosed, and is not limited to a V-shaped notch with a flat surface. The release of the inner rail from the intermediate rail could also require a manual actuation, such as depressing a button to eliminate an interfering member. Therefore, it is to be understood that the invention is not limited to those embodiments described above, but rather is includes all scope as defined by the claims appended hereto.