Locking mechanism for a lever-arch type file

Abstract

 A locking mechanism for a lever-arch type file comprises a base plate (1), a pair of first arch elements (2) rigidly fixed to and upstanding from the base plate and a pair of second arch elements (3) pivotally mounted on the base plate for movement relative to the first arch elements between an open position and a closed position. A leaf (8)spring mounted on the base plate acts permanently to bias the second arch elements (3) towards the open position. Inter-engaging teeth (9) on the first and second arch elements hold the second arch elements (3) in the closed position against the action of the spring (8).

Description

[0001] The invention relates to loose leaf files and in particular to a locking mechanism for a lever-arch type file.

[0002] In a type of loose leaf file known generally as a ring-binder, loose sheets are held in the file on snap-openable rings. The rings are in two movable halves which are both connected to a spring plate so that the rings can snap open and snap closed. One problem with this type of file is that the rings can burst open if a large number of sheets is being held.

[0003] In another type of loose leaf file known generally as a lever-arch file, loose sheets are held in the file by openable arches. The arches each comprise a first fixed element and a second movable element which is moved towards the fixed element under the action of a lever acting against a spring. The lever passes an over-centre position such that the movable elements are locked in the closed position.

[0004] The present invention provides a locking mechanism for a file of the lever-arch type wherein the lever is dispensed with and in order to hold the arch elements in the closed position against the action of the spring, they are provided with engagement elements.

[0005] Accordingly, the invention provides a locking mechanism for a lever-arch type file comprising: a base plate; a pair of first arch elements rigidly fixed to and upstanding from the base plate; a pair of second arch elements pivotally mounted on the base plate for movement relative to the first arch elements between an open position and a closed position; a spring mounted on the base plate and permanently acting to bias the second arch elements towards the open position; and engagement elements on the first and second arch elements adapted to hold the second arch elements in the closed position against the action of the spring.

[0006] This provides several advantages over the prior art. Firstly there is a saving in that the lever set is not required. Secondly, the base plate can be made narrower. Thirdly, the base plate can be made thinner.

[0007] Embodiments of the invention are described below with reference to the accompanying drawings, in which:

Figure 1 is an isometric view of a locking mechanism for a lever-arch type file in the closed position;

Figure 2 is an isometric view of the locking mechanism in the open position;

Figure 3 is an exploded view of the locking mechanism;

Figure 4 is a side view of the locking mechanism in the closed position;

Figure 5 is a plan view of the locking mechanism in the closed position;

Figure 6 is a cross-sectional view of the locking mechanism in the closed position taken along the line VI-VI in Figure 5;

Figure 7 is a cross-sectional view of the mechanism in the open position;

Figures 8, 9 and 10 are end views of locking mechanisms showing how the present invention permits the use of a smaller base plate; and

Figures 11 and 12 are side views of locking mechanisms showing forces acting thereon.

[0008] The locking mechanism shown in Figures 1-7 comprises a generally rectangular metal base plate 1, a pair of first arch elements in the form of pillars 2 which are rigidly fixed to two comers of the base plate and are upstanding thereon and a pair of second arch elements 3. The second arch elements are integrally formed with each other and are connected by a bar 4 which has outer portions 5 extending generally parallel to one side of the base plate and a central cranked portion 6. The outer portions 5 of the bar 4 are held on the base plate by curved tabs 7 which permit pivotal movement of the bar about the longitudinal axis of the outer portions 5. The second arch elements 3 are thus pivotally mounted on the base plate for movement relative to the pillars 2 between an open position (shown in Figures 2 and 7) and a closed position (shown in figures 1 and 6). In the embodiments shown, the first arch elements 2 have an upright portion 21 and a short angled portion 22. The second arch elements 3 have an upright portion 31, a curved portion 32 and a short angled portion 33.

[0009] A steel leaf spring 8 is mounted on the base plate and acts permanently on the cranked portion 6 of the bar 4 to bias the second arch elements 3 towards the open position. The arch elements 3 can be moved by hand against the action of the spring 8 to the closed position. Engagement elements in the form of interlocking teeth 9 are formed at the free ends of the first and second arch elements 2, 3 in the angled portions 22, 33 and are adapted to hold the second arch elements 3 in the closed position against the action of the spring. To move arch elements 2, 3 into and out of engagement with each other it is necessary to bend at least one of them slightly out of its normal vertical plane to enable the teeth 9 to hook together or unhook from each other. Since the second arch elements 3 are longer than the first arch elements 2, most of the bending is accommodated by the second arch elements.

[0010] As shown in the drawings, the teeth on the arch elements 2, 3 are oriented such that the second arch elements 3 must be bent slightly towards each other (as indicated by the arrows in Figure 4) to enable the teeth 9 to hook and unhook. This is the most convenient arrangement since opening of the arch can be easily achieved using one hand to squeeze the arch elements 3 together. Another orientation may alternatively be provided, however, in which the second arch elements 3 are bent in the same direction as one another to effect unhooking of the teeth. This can also be effected one-handedly.

[0011] The base plate 1 is stamped out of a single piece of metal and incorporates an upstanding curved tongue 10 which forms a stop for the cranked portion 6 of the bar 4 and thus for the second arch elements 3 when they are moved to the open position. In this position, the cranked portion 6 is urged against the underside of the tongue 10 by the spring 8. The tabs 7 and tongue 10 are integral with the base plate but the spring 8 is a separate element which is fitted onto the base plate.

[0012] One of the major advantages of the invention is explained by reference to Figures 8-9. Figure 8 shows a prior art mechanism in which a lever 12 carrying a roller 13 is installed at the centre of the base plate. The roller acts on a cranked portion of the arm connecting the second arch elements to move them to the closed position against the action of a spring. The lever passes to an over-centre position to lock the second arch elements in the closed position. If the lever set is removed, as in the case of the present invention and as shown in Figure 9, the width W of the base plate can be reduced by about 10 mm as shown in Figure 10.

[0013] A further advantage is explained with reference to Figures 11 and 12. In the closed condition, a traditional lever-arch mechanism as shown in Figure 11 suffers the pressure from the lever and the elasticity of the spring. To guarantee the locking function of the lever, the above-mentioned pair of reverse forces F have to be designed inclined other than vertical. As a result, the base plate suffers unbalanced forces and has to be made thick to avoid being deformed by these unbalanced forces.

[0014] As shown in enclosed Figure 12, in the absence of the lever set and related pressure from it, the base plate of the lever-arch mechanism of the present invention suffers smaller forces F'. In addition, with no more need to guarantee the locking function of the lever, the new mechanism is designed to suffer vertical and balanced forces. Thus, the base is unlikely to be deformed and can be made thinner.

Claims

1. A locking mechanism for a lever-arch type file comprising:

a base plate (1);

a pair of first arch elements (2) rigidly fixed to and upstanding from the base plate;

a pair of second arch elements (3) pivotally mounted on the base plate for movement relative to the first arch elements between an open position and a closed position;

a spring (8) mounted on the base plate and permanently acting to bias the second arch elements (3) towards the open position; and

engagement elements (9) on the first and second arch elements adapted (2, 3) to hold the second arch elements in the closed position against the action of the spring.

2. A locking mechanism as claimed in Claim 1, wherein the base is stamped from a single piece of metal and incorporates an upstanding curved tongue (10) which acts as a stop for the second arch elements (3) in the open position.

3. A locking mechanism as claimed in Claim 1, wherein the second arch elements (3) are integrally formed and are connected by a cranked bar (4) which engages the stop (10) when the second arch elements are in the open position.

4. A locking mechanism as claimed in any preceding claim, wherein the engagement elements (9) are in the form of interlocking teeth formed at the ends of the arch elements and wherein the teeth are so orientated that the second arch elements must be bent slightly towards each other to effect engagement and disengagement.

5. A locking mechanism as claimed in any one of Claims 1-3, wherein the engagement elements (9) are in the form of interlocking teeth formed at the ends of the arch elements and wherein the teeth are so orientated that the second arch elements must be bent in the same direction as one another to effect engagement and disengagement.

Drawing