GB2233625A - Mechanical handling device - Google Patents

Abstract

A mechanical handling device for stacking and unstacking a plurality of substantially identical articles (e.g. crates) comprises a conveyor 3; means 4 for holding an article at an entry point on the conveyor; a table 5 adjacent to the conveyor which serves to lift and support an article or a stack of articles; parallel arms 6', 6'' each pivotally connected at one end to a point on said table and pivotally connected at the other end to a fixed pivot point, the arms being driven for rotation about the fixed pivot points to cause the table to describe a generally circular path whilst remaining substantially horizontal throughout; means 15, 16 for driving the arm; a releasable gate 8 for holding an article or stack of articles at an exit position; means 7 for engaging the sides of an article or of the lowermost one of a stack, to enable it to be supported independently of said table and of said conveyor; and means for controlling the sequential operation of the components of the device. <IMAGE>

Description

MECHANICAL HANDLING DEVICE The present invention-relates to mechanical handling devices and, more particularly but not exclusively, is concerned with devices for stacking or unstacking similar articles, such as crates.

Current stacking devices often have pneumatic lift cylinders which have to operate quickly and with large impact forces so as to achieve desired stacking/ unstacking rates. However, in cold environments, such as refrigerated factories, the cylinders are prone to seizure due to freezing.

One such mechanical stacking device is disclosed in GB 1574036. The device disclosed in this document has a lever for lifting and lowering which is actuated by a piston ram. The lever has engaging means which sequentially engages, lifts/lowers, and disengages articles so as to stack/unstack the articles.

It is an object of embodiments of the invention to provide a device which avoids or ameliorates the limitations of the above described devices.

According to an aspect of the invention there is provided a mechanical handling device for stacking and unstacking a plurality of substantially identical articles, e.g. crates, which device comprises: a conveyor; retaining means for holding an article at an entry position on said conveyor; a table disposed adjacent to said conveyor for lifting and supporting an article or a stack of articles; at least one arm, the or each arm being pivotably connected at one end to a respective point on said table and pivotably connected at the other end to a respective fixed pivot point, whereby rotation of the arm/s about the fixed pivot point/s causes (each part of) the table to describe a generally circular path, the table remaining substantially horizontal throughout; means for driving the arm/s; a gate for holding an article or a stack of articles at an exit position;; means for engaging the sides of an article, or of the lowermost of a stack of articles, whereby said article or stack of articles can be supported independently of said table and of said conveyor; and means for controlling the sequential operation of the components of the device.

In one embodiment of the invention, the table comprises two separate table portions. These table portions may be disposed on either side of the conveyor.

Each table portion, in certain embodiments, may have two arms to control movement of the table. The conveyor in certain embodiments may be formed of two spaced apart belts. The distance between the belts may be reduced in the table region; this may be desirable in embodiments which have two separate table portions.

In an alternative embodiment, the table comprises a single portion, this may be disposed between two parallel belts of the conveyor.

The retaining means in some embodiments may be a spring loaded lever, a pawl or any such device. In some embodiments the gate may be a swing-type gate having two halves which swing outwardly to open when necessary.

Alternatively, the gate may have a single member or have a sliding mechanism for opening and closing.

There are advantages of embodiments of the present invention such as an increased stacking/unstacking capacity. This is because as the arm/s rotate continuously in one direction, the table moves continually, allowing the crates to enter the device in an almost continuous manner as opposed to designs where pneumatic raising/lowering, stopping/starting operations are needed.

For a better understanding of the present invention and how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings in which: Figure 1 shows a stacking/unstacking device embodying the present invention; and Figure 2 shows part of the underside of the device of Figure 1.

Figures 3 to 8 sequentially shows various operational stages of the device of Figure 1.

Figure 1 shows a stacking/unstacking device 1 for use with, for example, crates 2. The device 1 has a conveyor 3 with a stop 4 located so as to be able to hold the crates at an entry position 10 on the conveyor 3. A table 5 is provided adjacent to the conveyor 3 which can lift and support a single crate 2 or a stack of crates. The table 5 is in the form of two portions 5' and 5", the portions being placed one on either side of the conveyor 3. Movement of the table portions 5' and 5" are controlled by two arms 6 (see Figure 3) pivotally attached to each table portion 5' and 5" at respective points 13' and 13". The other ends of the arms 6 are attached to fixed pivotal points 14 and 14t (Figure 3 shows the two table portions with the further portion being dotted in. For clarity these features have been omitted from Figures 4 to 8).Further support members 7 are provided so as to support the crates, in particular when the crates are in an elevated position and are no longer supported by the table 5. Gates 8 are provided at an exit to the conveyor so as to help support the crates and to allow the stack to be removed from the conveyor 3 when appropriate.

The movement of the arms 6 is controlled by a drive motor 15 which causes one arm 6' on each table portion 5' and 5" to rotate about the fixed points 14' and 14".

The other arm 6" on each table portion 5' and 5" is forced to rotate as 6' causes the table portions 5' and 5" to rotate. The distance between the sets of fixed points 14' and 14", 13' and 13" is the same. In the illustrated embodiment, movement is caused by the motor driving a belt 16 which in turn causes the arms 6 to rotate. Movement of the arms 6' allows both portions to be lifted, lowered etc. simultaneously. In an alternative embodiment (not illustrated), motor 15 acts directly on the leading arm 6" via a close-coupled gear box.

The arms 6 move so as to keep the planar upper surfaces 12' and 12" of the table substantially horizontal throughout movement. When the table 5 is in its highest position the four arms 6 are vertically upright as in Fig. 4. As the arms move through 900, the arms 6 become linearly aligned still keeping the table horizontal. Further rotation of the arms causes the table 5 to be lowered (Figure 5). To this end the distance between the fixed pivot points 14' and 14" must be larger than the length of the arms 6 so that this position can be achieved.

The conveyor may advantageously be in the form of two synchronised belt portions (Figure 2). The distance between the belt before entering the table region is such that a crate would be substantially supported by the conveyor. As the belts enter the table area the distance between the belts decreases. The conveyor 3 is still able to transport the crates whilst also allowing the table to support the crates when appropriate without disturbing the conveyor. In an alternative embodiment (not illustrated), a single table portion is disposed between two belt runs which are at a fixed separation from one another (i.e. they do not come together in the table region as shown in Figure 2).

The gates 8 may be of a swing construction such that at an appropriate time the gates swing open to allow the crates to leave the device. Alternatively, a sliding type of mechanism may be more appropriate.

The stop may be in the form of a spring-loaded hook, pawl or any such suitable construction.

The control means for the device 6 are provided by a microprocessor unit (not shown) which is able to coordinate the operation of the device. Alternative embodiments may have mechanical control means.

The support members 7 may be in the form of rod which can engage the crates through holes in the sides of the crate. It alternatively may in the form of a support plate adapted to be moved between the table portion 5' and 5" so as to support the crates when the portions are removed.

Operation of the device 1 will now be described with reference to Figures 3 to 8.

As shown in Figure 3, stop 4 allows a pair of crates 2 to enter the device 1. The crates are transported by the conveyor 3 until the crates abut against the gate 8 which holds the crates at the exit position 9.

The arms 6 (Figure 4) start to rotate about the fixed points 14 and hence cause the table 5 to move in a generally upward direction. As a result of the movement of the table and the resistance of the gate 8, the crates are raised. The support members 7 then operate to support the crates in the raised position.

The arms 6 (Figure 5) continue to rotate hence causing the table to be lowered leaving the crates in the raised position supported by members 7. The arms 4 continue to rotate to move the table through its lowest position. At the same time the stop allows two more crates to enter the device 1 until they abut against the gate 8.

The arms 6 (Figure 6) continue to rotate and cause the table to lift the second pair of crates which are now under the first pair of crates, the support members 7 having been withdrawn when the first pair of crates are supported by the second pair of crates. When the table 5 reaches its highest position, the support members 7 again operate to hold the second pair of crates which in turn support the first pair of crates.

At the same time, the stop 4 allows another pair of crates to enter the machine.

The above sequence of operations continue until the desired number of crates have been stacked.

When the final pair of crates are in position (Figure 7) the table 5 lifts the full stack, members 7 being withdrawn. The gate 8 opens (Figure 8) and the arms 4 continue to rotate so as to allow the table to lower the stack down into the conveyor 3. The stack is thus removed. The stop 4 does not allow another pair of crates to enter. Meanwhile, the operation can recommence.

There are many variations on the above described embodiments of the present invention. In particular in the design of the table may be varied. For example the table may be in the form of a U-shape with the pivot arms arranged in the inside of the U. The form of the pivot arms may also be varied. For example, the two table portions may be connected by two rods perpendicular to the direction of movement of the conveyor. These rods may be connected to two pivot arms to cause the rotation of the table. The number of arms may be altered to for example 1 or 3. The advantages of stability accorded with the use of two arms are not as good as with just one arm. The crates may enter the device singly, in twos or any other suitable number. This will depend on the size of the crates as well as that of the device.

Claims (8)

1. A mechanical handling device for stacking and unstacking a plurality of substantially identical articles, e.g. crates, which device comprises: a conveyor; retaining means for holding an article at an entry position on said conveyor; a table disposed adjacent to said conveyor for lifting and supporting an article or a stack of articles; at least one arm, the or each arm being pivotably connected at one end to a respective point on said table and pivotably connected at the other end to a respective fixed pivot point, whereby rotation of the arm/s about the fixed pivot point/s causes (each part of) the table to describe a generally circular path, the table remaining substantially horizontal throughout; means for driving the arm/s; a gate for holding an article or a stack of articles at an exit position;; means for engaging the sides of an article, or of the lowermost of a stack of articles, whereby said article or stack of articles can be supported independently of said table and of said conveyor; and means for controlling the sequential operation of the components of the device.

2. A device as claimed in claim 1, wherein said table is arranged to be moved continuously during operation of the device.

3. A device as claimed in claim 1 or 2 wherein two arms are provided.

4. A device as claimed in claim 3 wherein the distance between the respective points on said table is the same as the distance between the fixed pivot points.

5. A device as claimed in claim 1, 2, 3 or 4 wherein the table is formed of two separate portions.

6. A device as claimed in claim 5 wherein the table portions are disposed adjacent each side of the conveyor.

7. A device as claimed in claim 5 or 6 wherein each table portion has two arms.

8. A mechanical handling device as hereinbefore described with reference to and as shown in the accompanying drawings.