GB2127091A - Drawer interlock mechanism - Google Patents

Abstract

A drawer interlock for permitting either one of two drawers mounted in a frame (12) to be slideably withdrawn from the frame but preventing both drawers from being withdrawn together. Each drawer carries a rearward projection (61, 62) adapted for engagement with a sliding member (63) on the frame (12), the arrangement being such that as either one of the drawers is withdrawn, its associated projection (61) cams the sliding member (63) to a position in which it locks the projection (62) of the other drawer against withdrawal, and that as the drawer is replaced, its plunger cams the sliding member to a position in which either one of the drawers may be withdrawn. The sliding member (63) has an aperture (69) having vertical edges (67, 68) which are engageable respectively by cam portions (71, 72) of the projections as the drawers are withdrawn or replaced and engageable by a locking notch portion (73) of the projection (62) when the drawer carrying the other projection (61) has been withdrawn from the frame. <IMAGE>

Description

SPECIFICATION Drawer interlock device This invention relates to a drawer interlock device for permitting either one of two drawers mounted in a frame to be slideably withdrawn from the frame but preventing both drawers from being withdrawn together.

Such a device is needed in circumstances where it is undersirable for two drawers to be withdrawn from a frame together. For example, if the two drawers are capable of carrying relatively heavy contents, it is possible, if both drawers were withdrawn together, that their frame would be incorrectly loaded and therefore distorted, or that the whole arrangement would become unstable and liable to tilt or topple.

The present invention is intended to provide a drawer interlock device for preventing these possibilities, and is characterised in that each drawer carries a plunger adapted for engagement with a sliding member on the frame, the arrangement being such that as either one of the drawers is withdrawn, its associated plunger moves the sliding member to a position in which it locks the plunger of the other drawer against withdrawal, and that as the drawer is replaced, its plunger moves the sliding member to a position in which either one of the drawers may be withdrawn.

A drawer interlock device according to the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is an exploded perspective view of a two-drawer assembly in which the drawers constitute the paper trays of a xerographic copying machine; Figure 2 is an exploded perspective view, seen from the rear of the assembly of Figure 1, of the drawer interlock device of the invention; and Figure 3-5 are diagramatic plan views of the essential parts of the drawer interlock device of Figure 2, for illustrating the operation of the device.

Referring to Figure 1,the main elements of the assembly shown are a main tray 1, an auxiliary tray 2 and a tray carriage 10. The assembly is mounted within a xerographic copying machine and its purpose is to supply paper, from either one of the two trays, to a friction feeder device (not shown) which feeds a sheet from the selected tray to a series of stations at which a developed image is transferred to, and fixed on, the sheet.

The feeder is stationary, and the selected tray is moved into a sheet-feeding position. As indicated by the broken lines on Figure 1, the main tray 1 is the upper tray and the auxiliary tray 2 is the lower tray.

The tray carriage 10 is supported entirely by means of vertical ball slides 11,the moving parts only of which are shown in Figure 1, the cooperating, fixed, parts being mounted on the rear frame of the machine. The ball slides 11 allow the tray carriage to move vertically up and down.

The tray carriage 10 consists of a vertical rear plate 12, a left-hand side plate 13, and a right-hand side plate 14. The left-hand side plate 13 carries a box-like container 15 along the upper part of the tray carriage 10, for housing electrical components, including an electric motor An upper left-hand slide rail 16 and a lower left-hand slide rail 17 are mounted below the container 15, and extend from front to rear of the left-hand side plate 13.

The right-hand side plate 14 carries an inner right-hand slide rail 18 and an outer right-hand slide rail 19 which both extend from front to rear of the right-hand side plate 14, and are both at the same height as the lower left-hand slide rail 17.

The main tray 1 comprises a main tray sub-frame 20 and a main paper tray 21. The main paper tray 21 is mounted for left-to-right sliding movement over the main tray sub-frame 20 by means of a ball slide 22 at the front of the tray, the rear part of the paper tray 21 sliding over nylon studs (not shown) in the sub-frame 20. The sub4rame 20 carries, on a downward extension of its left-hand edge, a left-hand slide 23, for cooperation with the upper left-hand rail 16 of the tray carriage 10, and a right-hand slide 24, for cooperation with the outer right-hand rail 19. Since the outer right-hand rail 19 is lower than the upper left-hand rail 16, a support plate 25 is provided for the right-hand slide 24, mounted below the base plate 26 of the main tray sub-frame 20 by means of extension pieces 27.

The main paper tray 21, which feeds paper to the right, has an upstanding front wall 28 and a left-hand side wall 29. A movable corner piece 30 is mounted for left to right sliding movement on a slide 31. On the left-hand side wall 29, an elongated catch member 32 is formed, with an upstanding outer portion that extends from about the mid-portion to the rear end portion of the side wall 29. The upstanding outer portion of the catch member 32 is for engagement with a notch 33 in a rack 34 that is mounted for sliding left-to-right movements in the container 15. The rack is engaged by a pinion that is driven by a motor 35.When the main tray 1 is in the 'home' position in the tray carriage 10, i.e. when it has been slid to the rear of the carriage 10 as far as it will go, the upstanding outer portion of catch member 32 engages in notch 33, enabling the motor 35 to drive the paper tray 21 to the left or the right.

In order to prevent the main paper tray 21 from moving to the right other than when it is in its 'home' position, a groove 44 is formed along the right hand vertical side of the container 15. Groove 44 extends from the front of the container 15 to a point approximately mid-way between the front and rear of container 15, terminating just in front of the rack 34. The upstanding portion of catch member 32 and the groove 44 are arranged such that during withdrawal and re-insertion of the main tray 1, catch member 32 and groove 44 are slidingly interlocked.

Once the main tray 1 is fully home, however, catch member 32 has passed completely through groove 44, and is engaged only by notch 33 of rack 34.

The auxiliary tray 2 includes a platform 36 for supporting copy paper sheets between upstanding front plates 37 and a slideable corner piece 38.

Corner piece 38 is arranged for left-to-right sliding on slide 39. A left-hand slide 40 is carried by a downwardly extending side plate 41 at the left-hand edge of the platform 36, and a right-hand slide 42 is carried by a downwardly extending plate 43 mounted inwardly of the right-hand edge of platform 36. Left-hand slide 40 cooperates with the lower left-hand rail 17 of the tray carriage 10, and right hand slide 42 cooperates with the inner right-hand rail 18 of carriage 10.

Copy paper sheets can be fed out from either tray at the choice of the operator. If sheets are to be fed from the main tray, the main paper tray 21 is moved to the right over the main tray sub-frame 20 by means of motor 35. The tray carriage 10 is elevated to bring the top right-hand edge of the stack of sheets in the main paper tray 21 into the feeding position relative to a paper feeder (not shown) situated in a fixed position above the trays. If sheets are to be fed from the auxiliary tray, the main tray 21 is moved to the let over the main tray sub-frame 20, and the tray carriage 10 is elevated to bring the top right-hand edge of the stack of sheets in the auxiliary paper tray 2 into the feed position. In order to change back to the main tray, the tray carriage 10 is lowered, the main tray is moved again to the right, and the tray carriage 10 is elevated again.

When replenishment of either tray is required, the tray in question may be simply pulled out, on its slides, to the front of the machine. This is only permitted once the main tray 21 has been moved fully to the left and the trays have been lowered from the feed position. In order to load paper, the operator will open the front door, which will break the machine interlock and send a signal by way of the machine logic to the motor which elevates and lowers the tray carriage 10. When the trays have come to rest, either one of them can be withdrawn by the operator. The operatorwill load paper towards the front right-hand corner of the required tray, and set the inboard corner piece 30 or 38 to lock the paper in position.In the front right-hand corner of each tray, there is a registration corner piece, which is moved out of the way whenever the tray is inserted into the machine.

On closing the front door of the machine, the interlock is remade, and on selection of a paper tray, the required tray is moved into the feed position.

When the machine is in the standby mode, it is always set to feed paper from the main tray. This is achieved by a time-out feature that resets the machine to the main tray mode if no copies are made within 90 seconds of completing the previous job, The drawer interlock device of the present invention prevents the operator from pulling out both trays together, and will be described with reference to Figure 2. The main tray sub-frame 20 and the auxiliary tray 2 carry respectively on their rear walls a main tray interlock plunger 61 and an auxiliary tray interlock plunger 62, the plungers projecting horizontally rearwards from their trays. The plungers are arranged to cooperate with an interlock slide 63 which is mounted, by means of retaining tabs 64, for left/right sliding movements over rear plate 12 of the tray carriage 10.The slide 63 is in the form of a generally rectangular frame, with top and bottom rails 65, 66 and vertical side posts 67 and 68. These top rails and side posts define an aperture 69 through which the plungers 61 and 62 can pass. The edges of side posts 67 and 68 adjacent to the aperture 69 are thickened to provide retaining members for latching notches (to be described below) formed in the plungers 61 and 62. An aperture 70 in the rear plate 12 is provided between the retaining tabs 64 for alignment with aperture 69 of slide 63, the plungers passing through aperture 70 in order to cooperate with slide 63.

Referring now to Figures 3,4 and 5, the relative positions of the plungers 61 and 62 and the slide 63 are shown, with the main (upper) tray 1 withdrawn (Figure 3), with both trays in their home position (Figure 4), and with the auxiliary (lower) tray 2 withdrawn (Figure 5). During the following explanation, the terms "left" and "right" will be taken as being for a viewer situated behind the tray assembly ie., as shown in Figures 2-5.

As shown in Figure 3, the main tray 1 has been withdrawn, which has caused the interlock slide 63 to move to the right. When both trays were in the home position (as shown in Figure 4), the interlock slide 63 was in a central position. As the main tray was withdrawn, however, the sloping portions 71, 72 of the main tray plunger 61 cooperated with the vertical side posts 67 and 68 of the interlock slide 63 to cause the slide to move to the right. As the interlock slide 63 moved to the right, the thickened portion of the left-hand side posts 67 engaged in notch 73 in the auxiliary tray plunger 62. This engagement of the plunger 62 by the slide 63 prevents the auxiliary tray from being withdrawn.

As the main tray is re-inserted, sloping portions 71 and 72 of the main tray plunger 61 re-engage the side posts 67 and 68 of the slide 63, moving the slide 63 back to its central position (Figure 4). This causes the post 67 to dis-engage the noch 73 in the auxiliary tray plunger 62, to allow withdrawal of either tray.

If now the auxiliary tray is withdrawn (Figure 5) the sloping portions 74,75 of the auxiliary tray plunger 62 engage the vertical posts 67, 68 of slide 63, and cause the interlock slide 63 to move to the left. This causes the main tray plunger 61 to be locked by engagement of the latching notch 76 in the main tray plunger 61 by the right-hand side post 68 of slide 63.

On re-insertion of the auxiliary tray, its plunger 62 re-engages the slide 63, and returns it to its central position.

In order to locate the slide 63 accurately, and to positively retain it in its desired location, a spring clip and ramp arrangement is used. The spring clip 77 (Figure 2) is secured at one end, by way of a spacer 78, to the rear plate 12 of the tray carriage, and terminates at its other end in a U-shaped catch portion 79. The outer radius of catch portion 79 engages a ramp 80 formed along the top rail 65 of the slide 63. Ramp 80 includes two protrusions 81 which define between them a valley 82. When the slide 63 is in its central position, catch portion 79 of spring clip 77 engages the valley 82 and when the slide 63 is moved either to the left or the right, the catch portion 79 rides over the appropriate protrusion 81 to assist in retaining the slide 63 in its left- or right-hand position. The spring clip prevents unwanted movements of the slide 63 due, for example, to machine vibrations.

The interlock device described above includes a single aperture interlock slide, with the interlock plungers engaging opposite side posts of the slide.

Alternatively, a slide may be used which has two apertures, one for each plunger. The apertures in such a slide may be spaced apartto accommodate the two plungers, e.g., with an appreciable vertical spacing between them.

Claims (3)

1. A drawer interlock device for permiting either one of two drawers mounted in a frame to be slideably withdrawn from the frame but preventing both drawers from being withdrawn together, characterised in that each drawer carries a plunger adapted for engagement with a sliding member on the frame, the arrangement being such that as either one of the drawers is withdrawn, its associated plunger moves the sliding member to a position in which it locks the plunger of the other drawer against withdrawal, and that as the drawer is replaced, its plunger moves the sliding member to a position in which either one of the drawers may be withdrawn.

2. The device of claim 1 wherein the sliding member has an aperture having vertical edges which are engageable respectively by engagement portions of the plungers as the drawers are withdrawn or replaced and engageable by a locking notch portion of the relavent plunger when the drawer carrying the other plunger has been withdrawn from the frame.

3. The device of claim 1 or claim 2 including a spring clip for cooperating with a ramp arrangement on the sliding member for retaining the sliding member in the optimum position for preventing withdrawal of one drawer when the other is withdrawn, or in the position in which either drawer may be withdrawn.