GB2171377A - Displacement systems - Google Patents

Abstract

Seed trays (2) are moved along a path (4) by a reciprocatable rod (14) which carries a series of engagement assemblies (16) mounted thereon at spaced intervals. Each assembly (16) includes a finger (26) having a first portion (26a) which projects transversely of the path (4) from one side of the path and a second portion (26b) inclined in the general direction of the path (4) in the upstream sense. The second portion of the finger is arranged to engage the inner walls of the trays (2) to propel the tray (2) along the path in response to reciprocation of the rod (14). The assemblies are either mounted so as to rotate relative to the rod to allow the fingers to ride back over the trays, or are fixed on the rod, which itself is caused to rotate by cams (60), (Fig. 4, not shown). <IMAGE>

Description

SPECIFICATION Displacement systems The present invention relates to displacement systems for displacing individual articles such as containers.

In the field of horticulture, machines have been proposed for automatically planting seeds in seed trays. Such machines have involved the use of endless belt conveyors for carrying the seed trays through a series of different work stations in order that a succession of operations can be carried out.

In such machines, the conveyor belt must be displaced intermittently to allow the necessary operations to be carried out step by step. Thus, for example, when seeds are placed in the individual compartments of a multi-row seed tray, the tray must be kept stationary while each row of seeds are planted and, following planting, be stepped on to allow the next row of seeds to be planted.

The intermittent operation of an endless belt to effect such a motion from a seed tray can be difficult to achieve and will subject the conveyor to a high degree of strain. Furthermore, such conveyor systems are bulky and do not lend themselves to being readiiy relocated; a requirement which often arises when such machines are used in a greenhouse complex.

It is an object of the present invention to provide an improved displacement system.

According to the present invention there is provided a displacement system for displacing a succession of articles along a predetermined path, the system comprising a track arranged to be located along side the path, means for causing the track to reciprocate in a direction parallel to said path, and a plurality of article engaging means secured to said track to reciprocate with said track, said engaging means extending transversely of said path for engaging an upstream face of a said article to urge the article along the path when the track moves in the downstream direction, and said engaging means being arranged to move relative to the or each downstream face of the article when the track moves in an upstream direction.

Advantageously said track comprises an elongate rod of circular cross-section.

Preferably the engaging means comprises a support member constrained against axial movement relative to said rod, but being angularly movable about the axis of said rod, and a finger secured to said support member, said finger having a first portion extending transversely of said path and a second portion extending both in the downstream direction and downwardly towards the floor of said path whereby, when in operation, the free end of said second portion is arranged to engage the upstream face of a said article when the rod is displaced in said downstream direction, and to pivot up and over the downstream face of said article when the rod is displaced in the upstream direction.

Preferably the rod is supported on an elongate member of L-shaped cross-section; the upstanding arm of the L lying between the rod and the path and acting to limit the angular displacement of the finger about the rod.

The means for displacing the rod comprises a pair of piston and cylinder arrangements, one at each end of the rod.

According to the invention, there is further provided a valve arrangement for controlling the supply of air to a piston and cylinder assembly, the arrangement being arranged to supply air to two chambers controlling the movement of a piston, the arrangement having a change-over piston for switching the supply of air between the two chambers and means for monitoring the expulsion of air from that chamber, which during that part of the cycle is not supplied with air, to cause the changeover piston to change over the supply to the other chamber when the expulsion of air from the monitored chamber has dropped below a predetermined rate.

A seed tray displacement system embodying the invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which: Figure 1 is a plan view of the system; Figure 2 is a fragmentary section through the system but to an enlarged scale; Figure 3 is a longitudinal section through one of the piston and cylinder arrangements of Figure 1; Figure 4 is a longitudinal section through a modified system; and Figure 5 is a valve arrangement for controlling the operation of the system.

As shown in Figures 1 and 2, a seed tray displacement system is arranged to convey a succession of seed trays 2 along a path 4.

As shown in Figure 1, each seed tray, which is advantageously of an expanded polystyrene or vacuum formed plastics material, is divided into a plurality of individual compartments. The compartments are filled with a seeding compost, dibbled to produce a seed pocket, a seed is then placed in each compartment and covered with a covering material, whereafter the contents of each compartment may be watered down. Each of these operations is conducted at a different station (not shown) and the system to be described is arranged to step the trays along a path through each station in turn. Because the system displaces the trays in discrete steps, the operation at each station is carried out on the trays on a row by row basis.

The system includes an L-shaped support member 6 which is arranged to be secured on a bench or work table 8 defining the path 4 along which the trays 2 are to be displaced. The surface of the table 8 preferably has a low coefficient of friction to allow the trays 2 to readily slide therealong.

The L-shaped support member 6 is arranged to extend along side the path 4. A pair of piston and cylinder arrangements 10 and 12 are secured one at one of the two opposite longitudinal ends of the support member 6.

An elongate rod or track 14 is coupled to, and supported between, the two pistons of the piston and cylinder arrangements 10 and 12 so as to be reciprocatable by the arrangements along an axis extending parallel to the path 4. The L-shaped support 6 has an upstanding limb 6a which lies between the rod 14 and the path 4. The upper extremity of the limb 6a lies above the level of the rod 14.

A series of engagement assemblies 16 are mounted on the rod 14 at spaced intervals.

Each assembly 16 includes an annular member 18 which is threaded onto the rod 14 and which has a fastening bolt 20 by means of which it can be secured to the rod 14 at a selected location.

A support member 22 has a U-shaped slot which is engaged by the annular member 18. The support member 22 has a bore along an axis which passes through the U-shaped slot and the bore is engaged by the rod 14. In this manner the support member is free to pivot about the axis of the rod 14 but is constrained from sliding along the rod 14 by the annular member 18.

The support member 22 also has a transversely extending bore which receives a finger 26. A fastening member 24 is provided to secure the finger to the support member 22. The finger has a first portion 26a which extends transversely to the axis of the rod 14 to project over the upper extremity of the upright limb 6a of the L-shaped member and a second portion 26b which is bent at right angles to the first portion in the downstream direction of the path and is inclined downwardly towards the work table 8.

Because the centre of gravity of the support member 22 and finger 26 is to the left hand side of the rod 14 as viewed in Figure 2, the support member and finger will pivot about the axis of the rod 14 until the movement of the finger 26 is limited by engagement with the L-shaped member 6.

The piston and cylinder assembly 10 is shown in more detail in Figure 3.

The cylinder 28 of the assembly 10 is held by a clamp arrangement 36 in the form of a split cylinder which is secured to the L-shaped member 6 and can be opened up or closed down by a simple screw arrangement 40. This allows the cylinder to be axially repositioned relative to the L-shaped member as desired to increase or decrease the stroke of the rod 14.

The cylinder 28 has an air inlet 34 and houses a piston 30. A bail 32 of resilient material is located between the cylinder head and a projection 30a on the head of the piston. The ball acts to cushion the impact of the piston on the cylinder head. At the opposite end of the piston there is provided a recess for accommodating the free end of the rod 14.

The piston and cylinder arrangement 12 is similar to the arrangement 10.

In operation the L-shaped member 6 carrying the two piston and cylinder arrangements 10 and 12, together with the associated rod 14 and support assemblies 16, is secured in position along side a desired path for the seed trays 2. The cylinders of the piston and cylinder arrangements 10 and 12 are positioned to effect a desired length of stroke for the rod 14 and then they are clamped in place.

Similarly, the support assemblies 16 are appropriately spaced along the rod 14 and then locked in position. A series of seed trays are positioned in abutment with the upstanding limb 6a of the support member 6. The angular position of each finger 26 is then adjusted so that the lower extremity of the second portion 26b of the finger 26 lies below the tops of the outer and inner partition walls of the seed tray when the upper portion 26a of the finger rests on the L-shaped member.

When the two piston and cylinder arrangements are operated in push-push configuration, the rod 14 is caused to reciprocate.

Reciprocation of the rod 14 on the forward stroke causes the downstream extremities of the fingers 26 to engage the upstream face of a partition or wall of a seed tray and to displace the seed tray in the downstream direction. On the return stroke of the rod 14, the underside of the lower portion of each finger 26 will engage the next upstream wall or partition of the seed tray and be lifted up to pass over the wall and thereafter fall into the space just upstream of the wall passed. This lifting action of the finger is permitted by virtue of the fact that the support 22 can freely pivot about the rod 14.

On the next forward stroke of the rod 14, the seed tray 2 will again be displaced in the downstream direction.

In this way, each seed tray 2 is displaced in discrete steps along a path extending along side the L-shaped support 6. It will be appreciated that the system provides a versatile and compact arrangement for displacing seed trays from the side thereof, without significantly obscuring the area above the seed tray. This, therefore, does not significantly impede any operations which may have to be carried out on the seed tray from above.

In a modification shown in Figure 4, parts similar to those in Figure 2 are similarly referenced. In this system, instead of relying on the seed trays themselves to raise the fingers 26, a separate mechanism is used. This separate mechanism involves the use of a bar 50 of square external cross-section, which bar has a central bore that receives the rod 14. The bar 50 is secured to the rod 14 by a split pin 52. The bar 50 supports a cam follower 62 having a projecting portion 62a engaging a cam 60. The cam 60 is coupled to a piston and cylinder arrangement 56 which is supported on the work bench 8 by a support post 54.

In addition, in this modification, each support member 22 is locked to the rod 14 against relative rotation so that when the rod 14 rotates so also does each support 22.

In operation, the centre of gravity of each support 22 and associated finger 26 is such that it will cause the rod 14 to rotate in an anti-clockwise sense (as viewed in Figure 4) until the projection 62a engages the cam 60. As the rod 14 reciprocates the rod 14 and the fingers 26 will thus be held in a fixed attitude. If now during an appropriate part of the stroke the piston and cylinder arrangement 56 is actuated, the cam 60 will be displaced downwardly and thus in turn will cause the cam follower 62 and the rod 14 to be angularly displaced in a clockwise sense as viewed in Figure 4. The result is that the fingers 26 are raised. When the piston and cylinder arrangement is deactuated, the fingers 26 will again fall to their former positions.

By linking the piston and cylinder arrangement 56 for synchronous operation with one or other of the piston and cylinder arrangements 10 and 12, the fingers can be raised for the duration of either the forward stroke of the rod 14 or its return stroke.

A pneumatic valve arrangement for controlling the piston and cylinder arrangements 10 and 12 is shown in Figure 5. As shown, a valve 66 has an inlet 68 supplied with compressed air from a source 70. A pair of outlet ports 72 and 74 are coupled to the piston and cylinder arrangements 10 and 12 respectively.

The valve 66 has a central chamber 76 housing a central piston 78 and two lateral chambers 80 and 82, each housing a respective lateral piston 84 and 86. Each lateral chamber 80 and 82 communicates with the central chamber 76 through a respective opening 81 and 83 which can be closed off by a respective lateral piston 84 or 86. Each lateral chamber 80 and 82 has a restricted vent 85 and 87 and is coupled (on the other side of the piston 84, 86 to the central chamber 76) to a respective one of the ports 74 and 72.

The central piston 78 is provided with four axially spaced O-rings 100 which define channels providing selective coupling between the inlet 68, two restricted outlets 88 and 90 and two main outlets which feed respective ones of the two ports 72 and 74. The central piston 78 has an axial through bore 102 and a radial bore 104 which provides communication between the axial bore 102 and the central channel defined by the O-rings 100.

In operation, with the central piston 78 in the position shown in Figure 5, air is supplied under pressure from the source 70 through the central channel around the piston 78 to the outlet which communicates with the port 74. This supply of air is also fed through the radial bore 104 and the axial bore 102 into both lateral chambers 80 and 82 via the openings 81 and 83. The air supply to the port 74 is also fed to the rear face of the piston 84 so as to urge the piston 84 to close the opening 81.

Meanwhiie, the air from port 74 actuates the piston and cylinder arrangement 12 to effect the displacement of the rod 14. As a result of this displacement, the force is also transmitted to the other piston and cylinder arrangement 10 to cause air to be expelled therefrom into the port 72. This air pressure is communicated to the rear face of the piston 86 which is thus moved to close the opening 83 providing communication between the lateral chamber 82 and the central chamber 76.

This state persists until the rod 14 reaches the end of its stroke whereupon no further air is expelled from the arrangement 10. As a consequence, the pressure holding the piston 86 against the opening 83 which communicates with the main chamber 76 ceases, and the pressure in the main chamber 76 displaces the piston 86 to a point at which it can escape from the lateral chamber 82 through the vented outlet 85.

This produces a pressure imbalance on opposite sides of the central piston 78 and as a consequence the central piston 78 becomes displaced to the right as viewed in Figure 5, until the central channel defined by the O-rings 100 provides communication between the inlet 68 and the port 72.

The supply of air under pressure to the two piston and cylinder arrangements is now reversed and as a consequence the rod 14 is caused to effect its return stroke. It will be appreciated that at the end of the return stroke the central piston 78 will again be displaced, this time to the left hand side (as viewed in Figure 5) as a result of a pressure imbalance on opposite sides of the central piston 78.

It will thus be seen that the pneumatic valve arrangement automatically switches the supply of air between the two piston and cylinder arrangements at the end of each forward and return stroke. This switching action is totally independent of the length of each stroke which as hereinbefore described can be adjusted.

It will also be appreciated that while the pneumatic valve arrangement has been described as controlling the displacement system of Figures 1 to 4, it can of course be used for other purposes.

Claims (9)

1. A displacement systemfor displacing a succession of articles along a predetermined path, the system comprising a track arranged to be located along side the path, means for causing the track to reciprocate in a direction parallel to said path, and a plurality of article engaging means secured to said track to reciprocate with said track, said engaging means extending transversely of said path for engaging an upstream face of a said article to urge the article along the path when the track moves in the downstream direction, and said engaging means being arranged to move relative to the or each downstream face of the article when the track moves in an upstream direction.

2. A system according to Claim wherein said track comprises an elongate rod of circular crosssection.

3. A system according to Claim 1 or Claim 2 wherein the engaging means comprises a support member constrained against axial movement relative to said rod, but being angularly movable about the axis of said rod, and a finger secured to said support member, said finger having a first portion extending transversely of said path and a second portion extending both in the downstream direction and downwardly towards the floor of said path whereby, when in operation, the free end of said second portion is arranged to engage the upstream face of a said article when the rod is displaced in said downstream direction, and to pivot up and over the downstream face of said article when the rod is displaced in the upstream direction.

4. A system according to Claim 3 wherein the rod is supported on an elongate member of Lshaped cross-section; the upstanding arm of the L lying between the rod and the path and acting to limit the angular displacement of the finger about the rod.

5. A system according to Claim 3 or to Claim 4 wherein the means for displacing the rod comprises a pair of piston and cylinder arrangements, one at each end of the rod.

6. A valve arrangement for controlling the supply of air to a piston and cylinder assembly, the arrangement being arranged to supply air to two chambers controlling the movement of a piston, the arrangement having a change-over piston for switching the supply of air between the two chambers and means for monitoring the expulsion of air from that chamber, which during that part of the cycle is not supplied with air, to cause the changeover piston to change over the supply to the other chamber when the expulsion of air from the monitored chamber has dropped below a predetermined rate.

7. A system according to any one of Claims 1 to 5 including a valve arrangement according to Claim 6.

8. A valve arrangement substantially as hereinbefore described with reference to the accompanying drawings.

9. A seed tray displacement system substantially as hereinbefore described, with reference to the accompanying drawings.