GB2331551A

GB2331551A - Interlock mechanism for slidable units

Info

Publication number: GB2331551A
Application number: GB9901956A
Authority: GB
Inventors: Alan Booty
Original assignee: MAINE ENGINEERING Ltd
Current assignee: MAINE ENGINEERING Ltd
Priority date: 1995-06-30
Filing date: 1995-06-30
Publication date: 1999-05-26
Also published as: GB9901956D0; AU6235296A; GB2302906A; GB2302906B; GB9513355D0; WO1997002400A1

Abstract

A unit 1 such as a filing cabinet has an interlock mechanism 5 for preventing more than a fixed number of slidable members 3 being slid with respect to a frame at a time. A plurality of vertically mounted rod members 6a, b, c are mounted so that they are vertically movable but restrained from rotation. For each slidable member 3 a cam piece 17 is mounted for rotation and for vertical movement. Means 9 on each slidable member 3 cause rotation of the cam piece 17. The rod members 6a, b, c and cam piece 17 define a continuous stack, each cam piece 17 being mounted, on a link pin 18, between the two rod members 6a, b, c in abutting relationship therewith. Cooperating cam surfaces 14 are provided on the cam piece 17 and on the rod member 6a, b, c abutting the cam piece 17 for causing vertical displacement when the cam piece 17 is rotated to thereby cause extension of the length of the stack. Stop members 8 are arranged on the frame for limiting the length so that when the fixed number of slidable members 3 have been slid, further rotation of the cam pieces 17 and extension of the stack is prevented, so that no further slidable members 3 can be withdrawn.

Description

1 2331551 1 Interlock Mechanism for Slidable Units The present invention

relates to units such as a filing cabinet or other piece of 0 furniture or equipment having a plurality of slidable units such as drawers or roll-out openings.

An interlock mechanism is required in order to prevent more than a certain number (usually one) of the slidable units being slid out of the unit at any one time, in order to prevent the unit becoming unstable and toppling onto a person operating the slidable units. A number of interlock mechanisms have been described, for example in European Patent Application No. EP-A-0 371 776 and in GB 2 271 145.

However, such known systems suffer fom the disadvantage that they are generally complicated, requiring a large number of specially shaped moving parts. There is also a risk of jamming of the parts.

It is an object of the present invention to provide a simple and reliable interlock mechanism for a unit having a plurality of slidable units.

According to the present invention there is provided a unit, such as a filing cabinet, comprising a plurality of slidable members, horizontally slidably mounted with respect to a frame, one on top of another, and an interlock mechanism for preventing more than a fixed number of slidable members being slid with respect to the frame at a time, the interlock mechanism comprising:

a plurality of substantially vertically mounted rod members which are mounted so that they are vertically movable but restrained from rotation about a vertical axis; for each slidable member, a cam piece, mounted for rotation about a vertical axis and for vertical movement; and linking means on each slidable member for linking the rotation of the respective cam piece with the sliding motion of the slidable member; the rod members and cam pieces defining a continuous stack extending substantkilly along a common vertical axis, each cam piece being mounted between two 2 rod members in abutting relation therewitli cooperating cam surfaces beinR I)rovided on the cam piece and on at least one of the Tod members abutting the cam piece, for causing vertical displacement along the common axis between the cam piece and the rod member when the cam piece is rotated about a vertical axis, to thereby cause extension of the length of the stack along the common vertical axis; stop members being arranged on the frame in the line of said common axis for limiting the length along the common axis of the stack so that when the fixed number of slidable members have been slid, further rotation of cam pieces and extension of the stack is prevented, so that no further slidable members can be withdrawn.

The inventors have found that incorporation of a cam piece rotatable about a vertical axis into the stack with the rods is a simple and effective way to arrange an interlocking mechanism, with the additional advantage that the cam surfaces on the cam piece and respective rod are always in engagement and less likely to jam than prior art apparatus.

Conveniently, the rod members comprise sections of rube of suitable diameter with end parts having the cam surfaces formed thereon inserted into the ends of the tubes. The linking means preferably comprises a suitable actuating part projecting from the side of a slidable member and a lever part projecting from the cam piece and resting in contact with the actuating part when the slidable member is in its rest position. Movement of the slidable member causes the actuating part to rotate the cam piece by way of the lever part.

Preferably, biasing means are provided for urging the rod members and the cam pieces into contact with one another. The biasing means may comprise a weight and in a particularly simple embodiment, the weight of the individual parts is sufficient to bias them into contact. However, a spring may be used for additional biasing action.

Biasing means urging the rod members and cam pieces into contact along the common vertical axis will also urge the cam pieces into their rest positions through the action of the cam surfaces provided on the cam pieces and respective rod members. Rotation of the cam pieces back to the rest position and hence shorteaing of the stack when a slidable me:-,.ber is withdrawn can be pre-.-mted by arrangizg ae actuator i permanent contact with the lever part or by a detent.

1 p 3 In a particularly preferred embodiment, a detent provided for releasably fixing the cam piece with respect to the respective rod member when these parts have been rotated with respect to one another. In this manner, the actuator part need only be in contact with the lever part for sufficient time to move the cam piece from a rest position to a position in which the detent fixes it with respect to the respective rod member. The detent should be such that when the slidable member is returned, the actuator part again acts on the lever releasing, the detent and allowing the cam piece and rod member to return to their rest positions.

The cam surfaces preferably comprise abutting helical surfaces extending helically around the common axis. A detent may be provided as above by corTesponding helix sections of opposite pitch to the cam surfaces.

Preferably, cam surfaces are provided on the top and the bottom of each cam piece so that a relatively large extension of the stack can.be achieved when the cam piece is rotated. It also eases and simplifies installation, as the cam pieces may then be essential-ly symmetical.

The invention will be farther described by way of example only with reference to the accompanying drawings in which:

Figure I is a schematic elevation view of a unit according to the present invention; Figure 2 shows a detail of the interlocking mechanism in its rest position; Figure 3 shows a detail of the interlocking mechanism in its extended position; Figures 4a - 4c show top, side and end views of the actuator parts; Figures 5a - 5b show views of a rod member end piece; Figures 6a - 6b show views of the cam piece; and Figure 7 shows a link pin.

Detailed DescriLtion of the Drawings Figure I shows a filing cabinet according to the present invention.

The cabinet is generally designated as 1. The cabinet comprises a frame 2 which is not shown in detail. Three drawers 3 are shown. They are slidably mounted in the frame by arrangements shown schematically at 4. The skilled person will be 0 4 aware of suitable designs of frame, drawer and arrangements 4 for use with the present invention.

An interlock mechanism 5 is shown schematically. It comprises four rod members 6a, b, c, d. Rod member 6a bears against a stop means 7 at the bottom of the frame. Rod member 6d is retained spaced from a stop member 8 by a predetermined distance x. Each drawer 3 is provided with an actuator 9, the actuators being shown engaging cam pieces 10, 11 and 12 as will be described hereinbelow. Withdrawal of any drawer 3 causes actuator 9 to rotate cam piece 10 in such a manner as to cause displacement between the cam piece and the respective rod members abutting it so that the length of the stack of rod members and cam pieces is extended by a distance x. Further withdrawal of a drawer 3 is prevented, as the rod member 6d now bears against stop member 8. Means, not shown, are provided for supporting the rod members 6a, 6b, 6c, 6d for vertical movement along a common axis but for preventing rotation of the rod members about the cornrn on axis.

The cam pieces 10, 11 and 12 are substantially identical and will be described with reference to cam piece 10, shown in Figures 2, 3 and 5 below. The cam piece 10 has a lever part 13. In its rear position (shown in Figure 2) the lever part extends to the rear of the frame 1. The cam piece 10 has, at each end, a helical surface 14 interrupted in the middle by a helical surface 15 of reverse pitch. The helical surface has a peak 16. Preferably, as shown in Figure 5, this pattern of peak 16, helical surface 14 and reverse helical surface 15 occurs twice around the circumference of the cam piece. An exactly corresponding surface is formed in end pieces 17 which are shown fixed into the rod members 6d and 6c. In the rest position, the respective helical surfaces rest snugly against each other in an abutting relationship.

When a drawer 3 is withdrawn, lever part 13 is rotated. Rod member 6c and 6d and their corresponding ends 17 are unable to rotate. Accordingly, the cam surfaces 14 act against one another causing a displacement of the rod members 6e and 6d with respect to the cam piece 10. Each rod member is moved by a distance x/2, so that the total displacement is x. It should be noted that rod 6c remains at essentially the same height, cam piece 10 is rais ed by distance x/2 and rod member 6d is moved by a distance x. When the cam piece is rotated through a specific distance, the peak 16 of C the cam piece comes to rest between the helical surface 14 and the reverse-pitch part 1 of rod members 6c and 6d, so that the cam piece 10 and rod members are releasably restrained from rotation with respect to one another. This permits further withdrawal of the drawer 3 so that actuator 9 ceases to be in contact with lever arm 13. When the drawer is returned, it will act upon lever part 13, moving the peak 16 up the reverse pitch helical surface 15 and then back down the helical surface 14 so that the parts are returned to the rest position shown in Figure 2.

A pin 18 is slidably received in a bore passing through the end pieces 17 and the cam piece 10. The pin assists in keeping these parts axially aligned. - Figures 4a, 4b and 4c show end, side and bottom views, respectively, of an actuator 9 for attachment to a drawer 3.

Figures 5 a and 5b show top and side views respectively of a cam piece 10.

Figures 6a and 6b show top and side views respectively of an end piece 17 for engagement in a rod member 6a, b, c or d.

Figure 7 shows the pin 18.

A spring may be provided in the space between the top of rod member 6d and the stop 8, in order to place the stack of rod members and cam Pieces under load. A coil spnnp, may be used which is such that the compression distance between its rest position and the position in which the coils of the spring touch one another so that no furffier compression is possible, is x.

t 6

Claims

Claims: 1. A unit, such as a filing cabinet, comprising a plurality of

shdable members, horizontally slidably mounted with respect to a frame, one on top of another, and an interlock mechanism for preventing more than a fixed number of slidable members being slid with respect to the frame at a time, the interlock mechanism comprising: a plurality of substantially vertically mounted rod members which are mounted so that they are vertically movable but restrained from rotation about a vertical axis; for each slidable member, a cam piece, mounted for rotation about a vertical axis and for vertical movement; and linking means on each slidable member for linking the rotation of the respective cam piece with the sliding motion of the slidable member; the rod members and cam pieces defining a continuous stack extending substantially along a common vertical axis, each cam piece being mounted on a link pin between two rod members in abutting relation therewith, cooperating cam surfaces being provided on the cam piece and on at least one of the rod members abutting the cam piece, for causing vertical displacement along the common axis between the cam piece and the rod member when the cam piece is rotated about a vertical axis, to thereby cause extension of the length of the stack along the common vertical axis; stop members being arranged on the frame in the line of said cornmon axis for limiting the length along the common axiS of the stack so that when the fixed number of slidable members have been slid, further rotation of cam pieces and extension of the stack is prevented, so that no further slidable members can be withdrawn.
2. A unit according to claim 1, in which the rod members comprise sections of tube of suitable diameter with end parts having the cam surfaces formed thereon inserted into the ends of the tubes.
3. A unit according to claim 1 or 2, in which, the linking means comprising an actuating part projecting from the side of a slidable member and a lever part projecting from the cam 7 piece and resting in contact with the actuating part when the slidable member is in its rest position, whereby, in use, movement of the slidable member causes the actuator to rotate the cam piece by way of the lever part.
4 A unit according to claim 1, 2 or 3, in which biasing means are provided for urging the rod members and cam pieces into contact with one another.
A unit according to claim 4, in which the biasing means comprise a weight.
6. A unit according to claim 4 or 5 in which the biasing means comprises a spring.
7. A unit according to any preceding claim, in which a detent is provided for releasably fixing the cam piece with respect to the respective rod member when these parts have been rotated with respect to one another.

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8. A unit according to any precedin,; claim, in which the cam surfaces comprise abutting helical surfaces extending helically around the common axis.
9. A unit according to claim 8 as appendant to claim 7, in which the detent is constituted by corresponding helix sections of opposite pitch to the cam surfaces.
10. A unit according to any preceding claim, in which cam surfaces are provided on the top and bottom of each cam piece.
11. A unit according to any preceding claim, wherein each respective link pin is received in a bore passing through a respective cam piece and the ends of adjacent rod members, to allow at least one of the rod members to slide with respect to the cam piece.
12. A und', substantially as, described herein with reference to the accompanying drawings.