GB2294290A - Interlock mechanism - Google Patents

Abstract

An interlock mechanism for filing cabinets and the like is provided such that only one drawer at a time can be opened. Each drawer is associated with a locking element (3, 4, 5) which pivots as its associated drawer is opened. Pivoting of the locking element lifts locking bars above the locking element, thereby causing the drawers above the opened drawer to be locked shut. The motion of the locking element also prevents the motion of locking bars below the locking element, thereby holding the drawers below the open drawer shut. <IMAGE>

Description

INTERLOCK MECHANISM The invention relates to an interlock mechanism to prevent more than one horizontally moveable drawer, tray or storage cradle (hereinafter "drawer") in furniture or storage equipment, such as filing cabinets, being opened at once. This is particularly desirable to prevent the furniture or storage equipment tipping over and causing injury or damage.

Mechanisms which prevent more than one drawer being pulled out are well known in the art.

US-5199774, for example, discloses an interlock system which uses a cable, which is drawn taut on opening a drawer, to lock catches on the remaining closed drawers. GB-2220026-A discloses a mechanism which comprises a spring-loaded cam for each drawer, which interacts with a locking rod on opening a drawer to lock the remaining drawers. US4768844 discloses a two-position cam which is rotated when a drawer is pulled out and causes a locking bar to move to lock the remaining drawers. FR-2632004 discloses an alternative system which includes at least one rod pivoted vertically on a fixed pivot. Opening a drawer causes the rod to pivot and engage slots in the remaining drawers, thus locking them.

Many of these and other known mechanisms are "beatable", that is to say, two drawers can be pulled out at the same time, thus overcoming the anti-tilt mechanism. "Unbeatable" mechanisms which allow only one drawer to be opened are known in the art, but these are often complex, involving a large number of parts such as springs or pulleys, and fine tuning to make them work properly. They are consequently relatively expensive and require expert maintenance.

It is therefore an aim of the current invention to provide an interlock mechanism which is substantially "unbeatable", has a low cost, and is maintenance free.

The invention provides an interlock mechanism for use with furniture or storage equipment comprising a plurality of horizontally moveable drawers, the interlock mechanism comprising a plurality of rotatably mounted locking cams; and a plurality of vertically mounted locking bars; each locking cam comprising a first trap or projection which engages a projection or a trap respectively, provided by a horizontally moveable drawer in such a way that horizontal movement of an unlocked drawer, tray or storage cradle, causes the locking cam associated with the drawer to rotate; a first slot or projection which is rotatably engageable with a corresponding projection or slot provided by a first locking bar, which when engaged locks said first locking bar; and a cam surface or projection which bears against a corresponding projection or cam surface provided by or at a first end of a second locking bar and which, on rotation of the locking cam, moves said second locking bar into a locked position.

The drawer may be replaced by a horizontally moveable tray or storage cradle.

Preferably, each cam is rotatable through 90". Each locking cam may additionally comprise a stop engageable with a surface on the second locking bar when the bar is locked by the movement of another locking cam. The stop may be a trap which engages a projection on the bar. Preferably, the slot formed by the cam is curved so that it smoothly engages a projection on the first locking bar, so locking said bar in position.

Each cam may comprise a second slot or projection on each cam which interacts with a corresponding projection or slot on the vertical side of the furniture or storage equipment, so acting as a guide to limit the movement of said locking cam. This may act to limit the movement of the cam, so preventing the cam rotating too far and jamming or damaging the mechanism. The slot may be curved.

The cams are preferably made of plastic, such as nylon. This reduces the cost of producing such a system, and has the additional advantage of reducing the amount of noise produced.

In a preferred embodiment, the interlock mechanism is used in filing cabinets to prevent tilting of the filing cabinet if too many drawers are pulled out.

The same locking cams may be used for the top, middle or bottom drawers.

Furthermore, the locking mechanism of the invention can be used with drawers of different heights simply by altering the length of a locking bar.

The number of drawers may be varied, and in general terms it is possible to provide an interlock mechanism for use with furniture or storage equipment comprising N drawers arranged in sequence where N is a positive integer greater than one, the interlock mechanism comprising N pivotally mounted locking elements and N-l locking members; the Nth locking element associated with the N, drawer and the P,h locking member interconnecting the P, and (P+l)h locking elements, where P is a positive integer between 1 and (N-l), each locking element comprising: a first portion for engaging the associated drawer such that motion of the drawer between its open and closed positions causes the associated locking element to rotate; a first recess or projection for engaging a corresponding projection or recess, respectively, of the locking element extending between the locking element and the preceding locking element; and a cam surface which cooperates with the locking member extending between the locking element and the succeeding locking element such that rotation of the locking element resulting from opening of its respective drawer moves the locking member into a locking position thereby preventing rotation of the preceding and succeeding locking elements.

The invention will now be described, by way of example, with reference to the following figures.

Figure 1 shows the inter-locking mechanism for a three-drawer filing cabinet with the drawers in the unlocked position; Figure 2 shows the action of the mechanism when a middle drawer is pulled out horizontally; Figure 3 shows the action of the mechanism when a bottom drawer is pulled out; Figure 4 shows the action of the mechanism when the top drawer is pulled out; and Figure 5 shows the effect of trying to pull two drawers out at the same time.

Figure 1 shows a locking mechanism comprising first and second locking bars (1,2) in a vertical stacked relationship. These bars are preferably held in place by guidance rails attached to a vertical side of the filing cabinet (not shown). Locking elements in the form of cams (3,4,5), which are conveniently made of a plastic, such as nylon, are attached to the vertical side of the cabinet by respective pivots (6). Each cam comprises a first trap (7) which engages a projection (8) such as a pin which is mounted on an adjacent drawer, a curved slot (9) and cam surface (10). The cams additionally comprise second traps (11) and second curved slots (12) which interact with projections (13) attached to the wall of the cabinet and acts as guides for the cams.

Figure 2 shows the mode of action of the locking mechanism when the middle drawer (14) is pulled out in a horizontal direction. Pulling the drawer (14) out produces a horizontal movement of the projection (8) which acts on a side of the first trap (7) to rotate the cam (3) in a clockwise direction as shown in the drawing. This rotation of the cam causes the curved slot (9) to engage a projection (15) on the first locking bar (1). This prevents the locking bar (1) from moving vertically. The other end of the first bar has a projection (16) which pushes on the cam surface (10) of the cam (4) below. The effect of this is to prevent the lower cam (4) moving, thus locking the lower drawer in position.

The second locking action that is produced on clockwise rotation of the middle cam (3) is effected by pushing the second locking rod (2) into a locking position. The rotation of the cam (3) causes the cam surface (10) to abut and push against a projection (17) on the second locking rod (2) thus raising the rod so that a second projection (18) engages the second trap (11) on the upper cam (5). This locks the cam (5) in position and also prevents the movement of the upper drawer.

Pushing the middle drawer back into place, re-engages the projection (8) in the first trap (7) and rotates cam (3) back in an anti-clockwise direction into an unlocked position, thus allowing another drawer to be subsequently opened.

Figure 3 shows that pulling out the lower drawer (19) causes the cam (4) to rotate in a clockwise direction. This causes the cam surface (10) of the cam (4) to push against projection (16). The first rod (1) is pushed upwardly so that it locks cam (3) through the engagement of projection (15) and trap (11). The upward motion of the first rod (1) also causes the first rod (1) to abut and lift the second rod (2). This brings the projection (18) of the second rod (2) into engagement with the trap (11) of the upper cam (5), thereby locking the upper drawer closed.

Figure 4 similarly shows the effect of opening a top drawer, causing the pin (8) to act on trap (7) causing the upper cam (5) to rotate. This causes the curved slot (9) to engage the projection (18) at the upper end of locking bar (2). This locks the locking bar (2) so that cam (3), and in turn cam (4), cannot rotate.

Figure 5 shows that if two drawers (14,20) are attempted to be moved simultaneously, they are prevented in doing so by the interaction of the projections (15,17,18) on the locking bars (1,2) preventing both of locking cams (3,5) from rotating at the same time.

Hence the interlock mechanism is an unbeatable mechanism of the invention, only allowing one drawer at a time to be pulled out.

Although a locking mechanism for a three-drawer filing cabinet, it will be appreciated that the mechanism of the invention can be used for furniture comprising more than three drawers, or for two drawers by varying the number of cams and bars.

Claims (13)

CLAIMS:

1. An interlock mechanism for use with furniture or storage equipment comprising a plurality of horizontally moveable drawers, the interlock mechanism comprising a plurality of pivotally mounted locking cams; and a plurality of vertically movable locking bars; each locking cam comprising a first trap or projection for engaging a projection or a trap, respectively, provided on an associated horizontally moveable drawer in such a way that horizontal movement of an unlocked drawer to or from a closed position causes the locking cam associated with the drawer to rotate; a first slot or projection which is rotatably engageable with a corresponding projection or slot provided by a first locking bar, which when engaged locks said first locking bar; and a cam surface or projection which cooperates with a corresponding projection or cam surface projection of a second locking bar and which, on rotation of the locking cam, moves said second locking bar into a locking position.

2. An interlock mechanism as claimed in claim 1, wherein each unlocked cam is rotatable through substantially 90".

3. An interlock mechanism as claimed in claim 1 or 2 in which, for a given cam, the first locking bar extends downwardly from the cam and the second locking bar extends upwardly from the cam.

4. An interlock mechanism as claimed in claim 3, in which each cam further comprises a stop which engages an associated first locking bar when motion of the associated first locking bar is prevented by another cam, thereby preventing rotation of the cam.

5. An interlock mechanism as claimed in claim 4, wherein the stop is a trap which engages a projection on the bar.

6. An interlock mechanism as claimed in any previous claim in which each locking cam additionally comprises a second slot or projection which interacts with a corresponding projection or slot on the vertical side of said furniture or storage equipment, so acting as a guide to limit movement of said locking cam.

7. An interlock mechanism as claimed in any previous claim wherein one or more of the slots on each cam is curved.

8. An interlock mechanism as claimed in any previous claim in which the locking cams are made of plastics.

9. An interlock mechanism as claimed in claim 8, wherein said locking cams are made of nylon.

10. An interlock mechanism for use with furniture or storage equipment comprising N drawers arranged in a sequence where N is a positive integer greater than one, the interlock mechanism comprising N pivotally mounted locking elements and N-l locking members; the N.h locking element associated with the N, drawer and the P,h locking member interconnecting the Pb and (P+l),h locking elements where P is a positive integer between I and (N-l), each locking element comprising: a first portion for engaging the associated drawer such that motion of the drawer to and from its closed position causes the associated locking element to rotate; a first recess or projection for engaging a corresponding projection or recess, respectively, of the locking element extending between the locking element and the preceding locking element; and a cam surface which cooperates with the locking member extending between the locking element and the succeeding locking element such that rotation of the locking element resulting from opening of its respective drawer moves the locking member into a locking position thereby preventing rotation of the preceding and succeeding locking elements.

11. An interlock mechanism as claimed in claim 10, in which the locking elements are arranged in a substantially contiguous manner.

12. An interlock mechanism as claimed in any previous claim when used in a filing cabinet as an anti-tilt mechanism.

13. An interlock mechanism substantially as hereinbefore described with reference to the description and/or drawings.