GB2468667A

GB2468667A - Tray lift comprising elevator screws

Info

Publication number: GB2468667A
Application number: GB0904547A
Authority: GB
Inventors: Matthew Hunter; Roderick Joseph Herbert
Original assignee: HERBERT R J ENG Ltd
Current assignee: HERBERT R J ENG Ltd
Priority date: 2009-03-17
Filing date: 2009-03-17
Publication date: 2010-09-22
Also published as: GB0904547D0

Abstract

Tray lift 3 comprises elevator screws 4, comprising shaft 5 mounted for rotation and helical flange 7. Flange 7 defines a first length 8 with a first pitch, and second length 9 with a second, smaller pitch. There may be a third length 11 with a third pitch greater than the second pitch. Trays 1 engaged by the flange in the first section are un-nested, whilst trays in the middle section are nested to save space. If the third length 11 is present, the trays 1 will be un-nested when they reach the top of the tray lift. Screws 4 arranged on opposite sides of tray 1 may rotate in opposing directions, and screws 4 arranged on the same side of tray 1 may also rotate in opposing directions. Lift 3 may comprise sensors to detect the arrival of a tray 1 between screws 4, or to detect the presence of a tray 1 in lift 3. An actuator may be arranged to discharge a tray 1 from lift 3, and a controller may control the rotation of screws 4 is response to a signal from one or more sensors. Tray lift 3 may be used for trays that are used with X-ray scanning apparatus in security checks, for example in airports.

Description

TRAY LIFT

Field of the Invention

The invention relates to apparatus for lifting, stacking and unstacking nestable trays and the like.

Background and Prior Art Known to the Applicant

There are a number of applications where it is required to transport trays around an environment, and in industrial and commercial settings this is often accomplished by the use of conveyor belts. In many cases the frays are nestable, i.e. one will fit partially within another. A typical working environment where this is encountered is in baggage handling and security checking situations, for example in airports. A typical situation is when passengers are proceeding through security checks using X-ray apparatus, where it is common for passengers to put small items of personal belongings such as bags, coats, small change and mobile phones into a tray which is then conveyed through an X-ray scanning apparatus. Once the passenger has passed through a full body metal detector, they retrieve their personal belongings from the tray. The trays then need to be returned to the other end of the X-ray machine for use by subsequent passengers. There is a need, therefore for automated apparatus to be able to convey the trays from one end of the scanner to the other, stacking them, and making them available for re-use.

It is amongst the objects of the present invention to attempt a solution to this and other problems.

Summary of the Invention

Accordingly, the invention provides a tray lift comprising elevator screws, each of said elevator screws comprising a shaft, mounted for rotation, and a helical flange extending therefrom, said flange arranged to define a first length of elevator screw having a first pitch, and a second length of screw having a second pitch smaller than the first pitch; and wherein said screws are arranged on corresponding opposite sides of a tray to be lifted so that the flange engages under a rim of a fray to be lifted. Preferably, at least two elevator screws are provided, to give support to either side of a fray to be lifted.

In preferred embodiments, the tray lift comprises four elevator screws, two of said screws arranged on each of two corresponding opposite sides of a tray to be lifted. In this way, the flanges of two elevator screws each side of the tray to be lifted provide support to the tray.

In an alternative preferred embodiment, the tray lift comprises one elevator screw arranged on one side of a tray to be lifted, and two elevator screws arranged on a corresponding opposite side of a tray to be lifted.

In any aspect of the invention, it is preferred that said flange is arranged to define a third length of elevator screw, adjacent said second length, and having a third pitch greater than the second pitch.

Also in any aspect of the invention, it is preferred that elevator screws arranged on corresponding opposite sides of a tray to be lifted comprise opposite-handed helical flanges, mounted for rotation in opposing directions. By arranging the screws in this way, no rotational forces are imparted to the tray.

Also in any aspect of the invention, it is preferred that elevator screws arranged on the same side of a tray to be lifted comprise opposite-handed helical flanges, mounted for rotation in opposing directions. By arranging screws in this way, frictional forces between the flanges and the rim of the fray are balanced, thereby tending to keep the tray in position within the tray lift.

Also in any aspect of the invention, it is preferred that the fray lift further comprises a sensor to detect the arrival of a fray between elevator screws.

Also in any aspect of the invention, it is preferred that the fray lift further comprises a sensor to detect the presence of frays within the tray lift.

Also in any aspect of the invention, it is preferred that the tray lift further comprises an actuator arranged to discharge a tray from the tray lift.

When a sensor is employed it is preferable that the tray lift further comprises a controller to control a drive arranged to rotate said elevator screws in response to signals from one or more of said sensors.

Also included within the scope of the invention is a tray lift substantially as described herein, with reference to, and/or as illustrated by, any appropriate combination of the accompanying drawings.

Brief Description of the Drawings

The invention will be described by the accompanying drawings, in which: Figures 1 and 2 show schematic cross-sectional representation of trays to be lifted in nested and un-nested configurations respectively; Figure 3 is an end elevational view of a fray lift of the present invention; Figure 4 is a top plan view of a fray lift of the present invention; Figure 5 is a schematic end elevation of a tray lift of the present invention; Figure 6 is a perspective illusfration of a tray lift of the present invention; Figure 7 is side elevational view of a fray lift of the present invention; Figures 8-10 are schematic plan views illustrating the position of elevator screws in a tray lift of the present invention; and Figure 11 is a schematic elevational view of a fray lift of the present invention.

Description of Preferred Embodiments

Figure 1 shows, in cross-section a number of trays 1 that might be used with the tray lift of the present invention. It can be seen that the trays are in a nested configuration, with the bottom portion of one tray located within the envelope of the tray below. In this configuration, the distance between the underside of the rim 2 of adjacent trays is A. Figure 2 shows, again in cross-section, the trays in a spaced-apart configuration in which the envelopes of the trays do not overlap. In this configuration, the distance between the undersides of the frays' rims 2 is given by dimension B. Figure 3 is an end elevation of a tray lift according to the present invention, generally indicated by 3. Four trays 1 are illustrated positioned within the tray lift 3.

Arranged on either side of the trays to be lifted are elevator screws 4, each comprising a shaft 5 mounted for rotation on a bearing 6, and driven by an electric motor (not illustrated) that may be controlled by a controller (also not illustrated). Around the periphery of each shaft 5 is located a helical flange 7 defining, generally, a screw-like thread around the shaft. The flange 5 is arranged to define a first length 8 of elevator screw having a first pitch, and a second length 9 elevator screw having a second pitch, smaller than the first pitch. The elevator screws 4 are spaced apart such that, in use, an extending rim 2 of the trays 1 locates on the flange 7 of each elevator screw 4. The first pitch 8 of the elevator screw 4 is so sized such that the rim-to-rim spacing B of trays to be lifted, in an un-nested configuration, as shown in Figure 2, is an integer multiple of the pitch. In this embodiment, the first region 8 has a pitch length such that two pitches of the thread is equivalent to the distance B. The pitch of the second length 9 of the elevator screws 4 is configured such that the rim-to-rim spacing of trays to be lifted, when in their nested configuration, i.e. the distance A shown in Figure 1, is an integer multiple of the pitch. Again, in this embodiment, the second region 9 has a pitch length such that two pitches of the thread is equivalent to the distance A. As the elevator screws 4 are rotated, trays are lifted up in the tray lift and move from an un-nested configuration, towards the bottom, and into a nested configuration towards the middle of the unit. In this way, more trays can be accommodated within the unit by the nesting operation that occurs. If the direction of rotation of the screws is reversed, of course, then the trays will move downwards from a nested configuration, into an un-nested configuration at the bottom. In this embodiment, the flanges 7 of the elevator screws are arranged to have opposite-handed thread configurations. This has an additional advantage in that no twisting forces are applied to the frays 1 whilst the device is in operation. Also, frictional forces between the surface of the flanges 7 and the rims 2 of the trays 1 act to draw a fray into the bottom of the fray lift.

Figure 4 illustrates a plan view of the top (in use) of a fray lift according to the present invention, generally indicated by 3. In this embodiment, there are four elevator screws 4, two of which are positioned each side of a tray 1 to be lifted. The Figure illustrates how the rims 2 of the tray locate on the flanges 7 of the elevator screws, to be supported thereupon. It can be seen in this Figure that the elevator screws 4, on each side of the tray lift are arranged to have opposite-handed pitches and to rotate in different directions. This has the particular advantage that, when a fray 1 is in position between the elevator screws 4, the rotation of the screws tends to maintain the fray in position, because the frictional forces between the flanges 7 and the rim 2 of the tray are acting in opposite directions.

Also illusfrated in this plan view, are gearboxes 10 connected to the bearings 6 to allow multiple elevator screws to be rotated by the same motor.

Figure 5 illustrates, in a schematic end elevation, a tray lift 3 according to the present invention. In this embodiment, the elevator screws 4 have helical flanges 7 that are arranged to define three regions of differing thread pitch. As before, there is a first region 8 having a thread pitch having an integer number of threads equal to the spacing A of trays to be lifted when in an un-nested configuration; in this embodiment, there is one pitch equivalent to the distance B. There is also a second region 9 in which the thread pitch is arranged to correspond to the distance A in Figure 1, i.e. the rim-to-rim spacing of trays in a nested configuration. Finally there is a third region 11 adjacent to the second region 9, in which the thread pitch is again spaced such that an integer number of thread pitches is equal to the distance B in Figure 2, being the rim-to-rim spacing of frays in an un-nested configuration. It can also be seen that the thread pitches on each of the elevator screws 4 are arranged to be opposite-handed, and to rotate in opposing directions. In this way, when the elevator screws 4 are rotated as illusfrated, the trays 1 move progressively from the bottom to the top of the elevator screws 4 starting in an un-nested configuration, progressing towards a nested configuration in the middle of the fray lift, and emerging at the top of the fray lift again in an un-nested configuration.

This arrangement of differently-pitched helical flanges along the elevator screws allows trays to be introduced in a horizontal fashion (i.e. from the side, as illustrated) at one end of the fray lift, to be fransported upwards through a nested configuration, and to be un-nested when they reach the top of the tray lift whence they may be removed from the lift, again in a generally horizontal, sideways fashion. Again, rotation of the elevator screws may be effected in the opposite direction allowing trays to be moved from the top to the bottom of the fray lift.

Figure 6 illusfrates, in perspective view, an embodiment of a tray lift of the present invention, generally indicated by 3. This Figure illusfrates a tray lift 3 having four elevator screws 4, two of which are arranged on either side of the long access of frays 1 to be lifted. It can be seen that the elevator screws arranged on the same side of the tray to be lifted comprise opposite-handed helical flanges, and are mounted for rotation in opposing directions. Also, elevator screws arranged on corresponding opposite sides of the tray to be lifted 1 also comprise opposite-handed helical flanges mounted for rotation in opposing directions. The use of opposite-handed flanges on corresponding opposite sides of the trays prevents rotational forces being applied to the frays 1 when they are introduced into the tray lift. Likewise, the use of opposite-handed flanges on the same side of the trays 1 provides a stabilising force to the trays 1 when in the position illustrated in Figure 6, because the frictional forces between the flanges 7 of the elevator screws 4 and the rim 2 of the trays 1 are acting in opposite directions.

Also illustrated in Figure 6 are gearboxes 10 arranged to transmit rotational forces from a motor (not illustrated) to each of the elevator screws 4. Connection between each of the bearings 6 and gearboxes 7 is effected by shafts 12, only partially illusfrated, for clarity.

In this way, all four of the elevator screws may be operated by a single motor.

Figure 7 is a side elevation view of a tray lift 3 according to the present invention. This again illusfrates the elevator screws 4 having three regions 8, 9, 11 of differing thread pitches. In this embodiment, two thread pitches of region 8 correspond to the rim-to-rim spacing of the trays 1 in the un-nested configuration as illustrated in Figure 2. Region 9, two thread pitches of the elevator screws 4 are equivalent to the rim-to-rim spacing A of trays in a nested configuration, as illustrated in Figure 1. Finally, in region 11, two thread pitches are again equivalent to the rim-to-rim spacing of frays in an un-nested configuration (B) as illustrated in Figure 2.

Figures 8-10 illustrate in schematic plan view, alternative arrangements of elevator screws 4 disposed around a tray 1 to be lifted.

In Figure 8, four elevator screws 4 are used, two of which are disposed on either side of the tray 1. The tray 1 may be introduced between the elevator screws from the side in the direction illustrated by arrow C. When in position, the screws 4 may be rotated in the directions indicated in Figure 8 to lift the tray. It can be seen that the elevator screws 4, located on the same side of the tray, are configured to rotate in opposing directions, and elevator screws 4 located on corresponding opposite sides of the tray 1 to be lifted are also configured to rotate in opposing directions.

Figure 9 illustrates an alternative embodiment having three elevator screws 4, two of which are disposed on one side of a fray 1 to be lifted and the third is located on the opposite side of the tray, approximately in between the two other elevator screws 4. Such an arrangement provides support for the fray at three points, and reduces the number of elevator screws needed to operate the tray lift 3.

Figure 10 illustrates, again in plan view, a yet further embodiment of the invention. In this embodiment, two elevator screws 4 are disposed on opposite sides of the tray 1 to be lifted, and a third elevator screw is located at an end region of the tray 1. In this embodiment, the elevator screws on either side of the tray are arranged to rotate in opposite directions and to generally draw the tray into the tray lift in the direction illustrated by arrow D. Frictional forces between the flanges 7 of the elevator screws 4 and the rim 2 of the tray 1 biases the tray 1 against the third elevator screw 4 located at an end region of the tray, thereby not only providing support for the tray, but also holding it in position within the tray lift. In this embodiment, the handedness and direction of rotation of the elevator screw located at the end of the tray may be such that the elevator screw can rotate in either direction, as required. Furthermore, if this third elevator screw is made shorter than then two side elevator screws, then the frictional forces will act to automatically discharge the tray from the tray lift when it reaches the top.

Figure 11 illustrates, in schematic elevational view, an embodiment of the invention. In this embodiment, trays 1 are delivered to a base region of the fray lift 3 by means of a conveyor 13. A sensor 14 is provided to detect the arrival of a tray within the bottom region of the tray lift. The sensor 14 may comprise, for example, a micro-switch, actuated by the arrival of a tray, an optical sensor e.g. in which the fray 1 breaks a beam of light or any other such proximity sensor. Once the fray 1 is in position at the bottom of the tray lift, a controller (not illustrated) triggers rotation of the elevator screws to lift the tray up the tray lift a distance equivalent to the rim-to-rim spacing of the trays in an un-nested configuration, thereby freeing a space for a subsequent tray 1 to be delivered to the bottom of the tray lift. The controller can then stop the rotation of the screws to await the arrival of a subsequent tray.

As trays progressively arrive at the base of the tray lift and are lifted by the elevator screws, the varying pitch region of the elevator screws position the trays in a nested configuration within the main body of the tray lift, as illustrated. For clarity, some trays have been omitted from this illustration. A second sensor 15 is also provided to detect the presence, position or number of trays 1 within the body of the tray lift.

Located towards the top of the tray lift 3 is a linear actuator 16 that can be triggered by the controller to push a tray out of the tray lift and on to a pair of rails 17 located either side of the tray where the trays may be supported by their rim regions 2.

The tray sensor 15 may be used to detect whether there is a tray present at the uppermost region of the tray lift and, if not, the controller can trigger rotation of the elevator screws 4 to lift any trays within the lift to the top region, where they can be delivered on to the rail 17 by the actuator 16. In this way, trays are always available at the top of the lift for use.

Claims

CLAIMS1. A tray lift comprising elevator screws, each of said elevator screws comprising a shaft, mounted for rotation, and a helical flange extending therefrom, said flange arranged to define a first length of elevator screw having a first pitch, and a second length of screw having a second pitch smaller than the first pitch; and wherein said screws are arranged on corresponding opposite sides of a tray to be lifted so that the flange engages under a rim of a tray to be lifted.
2. A tray lift according to Claim 1 comprising four elevator screws, two of said screws arranged on each of two corresponding opposite sides of a tray to be lifted.
3. A tray lift according to Claim 1 comprising one elevator screw arranged on one side of a tray to be lifted, and two elevator screws arranged on a corresponding opposite side of a tray to be lifted.
4. A tray lift according to any preceding claim wherein said flange is arranged to define a third length of elevator screw, adjacent said second length, and having a third pitch greater than the second pitch.
5. A tray lift according to any preceding claim wherein elevator screws arranged on corresponding opposite sides of a tray to be lifted comprise opposite-handed helical flanges, mounted for rotation in opposing directions.
6. A tray lift according to any preceding claims wherein elevator screws arranged on the same side of a tray to be lifted comprise opposite-handed helical flanges, mounted for rotation in opposing directions.
7. A tray lift according to any preceding claim further comprising a sensor to detect the arrival of a tray between elevator screws.
8. A tray lift according to any preceding claim further comprising a sensor to detect the presence of trays within the tray lift.
9. A tray lift according to any preceding claim further comprising an actuator arranged to discharge a tray from the tray lift.
10. A tray lift according to any of claims 7 and 8, further comprising a controller to control a drive arranged to rotate said elevator screws in response to signals from one or more of said sensors.
11. A tray lift substantially as described herein, with reference to, and/or as illustrated by, any appropriate combination of the accompanying drawings.