WO1991015940A1

WO1991015940A1 - Handling systems for lamellae

Info

Publication number: WO1991015940A1
Application number: PCT/GB1991/000564
Authority: WO
Inventors: Alan William Lucas
Original assignee: Alan William Lucas
Priority date: 1990-04-10
Filing date: 1991-04-10
Publication date: 1991-10-17
Also published as: EP0525025A1

Abstract

A handling system for lamellae, such as printed circuit boards in the course of production, comprises a pair of conveyors (54, 55) having aligned holders (62) to receive outer portions of the lower edges of the lamellae to hold the lamellae arranged generally vertically in a parallel array. Between the conveyors is a lift platform (75) on which a rack (90) is longitudinally movable. The rack has two rows of rack holders (92, 93) to hold central portions of the lower edges of the lamellae. Lamellae can be transferred from the conveyors to the rack by raising the platform (75) whereupon the rack, carrying the lamellae, can be moved out from between the conveyors (arrow 91), for example onto a truck or ball conveyor (95). In an alternative arrangement, the rack is carried by the forks of a lift truck. In a further alternative, there is a single conveyor (101) and a pair of racks (102, 103) which pass along either side of the conveyor.

Description

1 Handling Systems for Lamellae

-*»

3 This invention relates to handling systems for

4 lamellae. While the invention is particularly suitable

5 for use with systems for handling printed circuit board

6 blanks during the production process and before the application of components thereto, the invention may be applied to handling systems for other lamellae in the form of rigid or semi-rigid sheets, plates, cards or the like; the invention is particularly concerned with systems whereby such lamellae are held at only one edge to avoid damage to the broad surfaces of the lamellae or, for example, to fragile or uncured coatings thereon. In the production of printed circuit boards, rigid or semi-rigid substrates are subjected to various manufacturing processes. In some of these processes at least one surface of the finished or semi-finished board is provided with a coating; before this coating fully hardens, it can be damaged by contact with another board, with handling means or with anything else. The processes are semi-continuous and the boards may be carried on a conveyor slowly through a processing station. Devices have been produced for accumulating boards from the conveyor and holding them in a compact but non-touching arrangement, for example prior to removal to another operating station or while a coating thereon hardens. In one such accumulator there is a continuous conveyor; the surface of the conveyor is provided by a plurality of parallel slats or profiles which extend across the conveyor and each of which is generally U-shaped in section. The bottom of the U is attached to drive chains of the conveyor with the opening of the U extending upwardly when the U is travelling along the upper pass of the conveyor and the U has a flared mouth. At each end of the conveyor, the drive chains pass around sprockets so that adjacent slats are fanned out and, when halfway round the sprockets, the mouth of the U faces horizontally. As each slat reaches the horizontal position at the receiving end, a printed circuit board has one edge inserted in the slat so that, as the conveyor continues to move, the slat is gradually transferred from a horizontal position to an approximately vertical position and travels in this position along the conveyor towards the opposite end. Printed circuit boards may be fed into the slats by hand or there may be an input conveyor directing boards to the slats. The upper pass of the conveyor may be sufficiently long to enable the machine to accumulate 50 to 100 boards or more. Unless the boards are to be directed to a delivery conveyor (in which case they may be returned to the horizontal at the discharge end of the conveyor) , the boards have to be removed one by one by hand and may then be transferred by an operator into storage racks. This handling is time consuming and unless it is done with care damage can be done to the delicate boards. Machines are available having a swinging and translating arm which mechanically removes boards one by one from a conveyor to a stack but this is expensive and does not avoid the problem of damage to the boards by contact with other boards. According to the broadest aspect of the present invention a system for handling lamellae arranged generally vertically in a parallel array comprises first supporting means for first parts of the lower edges of the lamellae, a pair of second supporting means for second and third parts of the lower edges of the lamellae lying outwardly from the said first parts, and means for moving the first supporting means vertically relative to the second supporting means to transfer the lamellae from one of the supporting means to the other. The system may take various forms but, when it is applied to accumulator conveyors of the general construction described above, it is possible to employ a central vertically movable rack with a pair of conveyors lying on opposite sides of the rack or, alternatively, a central conveyor with a rack in two parts movable together vertically and lying on opposite sides of the conveyor. Thus, according to a second aspect of the invention, a handling system for lamellae comprises: a) an accumulator comprising a pair of continuous conveyors arranged side by side and with a gap between them, the conveyors having aligned pairs of conveyor holders to hold spaced outer parts of the lower edges of lamellae extending between pairs of holders on the two conveyors, b) a rack having a width less than the spacing between the conveyors and rack holders spaced to be aligned with the holders on the conveyors to hold inner parts of the lower edges of the lamellae between the said outer parts, and c) elevating means for changing the relative elevations of the conveyors and the rack for raising the rack from a position in which the rack holders are below lamellae held by the spaced outer parts in the conveyor holders to a position in which the rack holders hold the inner parts of the edges of the lamellae with the outer parts disengaged from the conveyor holders. Also, according to a third aspect of the invention, a handling system for lamellae comprises: a) an accumulator comprising a continuous conveyor having conveyor holders to hold inner parts of the lower edges of lamellae, b) a pair of racks spaced apart by a distance greater than the width of the conveyor and having rack holders which are so located that the rack holders on one rack are aligned with those on the other rack and are able to be aligned with the conveyor holders, and c) elevating means for changing the relative elevations of the conveyor and the racks for raising the racks from a position in which the rack holders are below lamellae held by the said inner parts in the conveyor holders to a position in which the rack holders hold outer parts of the lower edges of the lamellae with the inner parts disengaged from the conveyor holders. Thus, put simply and referring particularly to the invention in its second aspect, in operation of the handling system each lamella is held at two points along its lower edge in the two spaced conveyors and, when lamellae are to be removed, the rack is positioned in the gap between the two conveyors the relative elevations are changed, preferably by raising the rack, so that parts of the lower edges of the lamellae between the two conveyors enter the rack holders and on further elevation of the rack they will be lifted clear of the conveyor. The rack containing the removed lamellae can then be taken away. While the conveyor holders are preferably of the construction described above, i.e. are of U-shaped cross section, the rack holders may consist of no more than slots formed in the rack. The elevating means may take various forms; for example it may simply be a lift positioned between the two conveyors on which a rack may be positioned and from which the rack may be manually removed after it is filled with lamellae; preferably the elevating means comprises a wheeled truck or cart having a projecting lift such as a pair of forks on which the rack may be positioned and inserted between the two conveyors from one end. According to a fourth aspect of the present invention, an accumulator for lamellae comprises a pair of continuous conveyors providing a pair of parallel spaced horizontal runs, the conveyors having aligned pairs of conveyor holders to hold pairs of first parts of the lower edges of lamellae extending between pairs of holders on the two conveyors with second parts of the lower edges of the lamellae downwardly exposed. According to its fourth aspect, the invention thus provides an accumulator (which may be generally similar to the accumulators already known and described above) but with a pair of spaced parallel conveyors instead of the single conveyor previously provided, thus providing access to the central portion of the lower edges of lamellae in the conveyors so that the lamellae may be removed either by hand or by means of a rack as described above. The invention may be carried into practice in various ways and three handling systems for printed circuit boards will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a plan view of the first system; Figure 2 is a side elevation of the first system; Figure 3 is an end elevation of the first system taken from the right in Figures 1 and 2 and with the feed conveyor omitted; Figure 4 is an end elevation of one of the slats or conveyor holders of the system shown in Figures 1 to 3 and to a larger scale; Figures 5, 6 and 7 are respectively a plan view, a side elevation and an end elevation, all to a larger scale, of the rack comprising part of the system shown in Figures 1 to 3; Figure 8 is a plan view, similar to Figure 1, of the second handling system; Figure 9 is a side elevation, similar to Figure 2, of the second handling system; and Figure 10 is a plan view, similar to Figures 1 and 8, of the third handling system. The core of the first system shown in Figures 1 to 7 of the drawings comprises an accumulator which is similar to accumulators already known for the purpose of accumulating printed circuit boards during the course of manufacture and comprising a stand 1 carrying a pair of housings 2 and 3 which contain bearings and drive means for a pair of conveyors 4 and 5. Each conveyor comprises a pair of chains (not shown) which at each end pass round sprockets, those at the feed end being mounted on a drive shaft 6 common to the two conveyors and those at the discharge end being mounted on coaxial but spaced lay shafts 7 and 8 which are supported at their inboard ends by vertical longitudinal plates 9,10 supported on cross members 11. Each of the conveyors carries a plurality of parallel conveyor holders 12 which are of the constant cross section shown in Figure 4 and thus comprise a base or bight 13, which is secured to links from the two conveyor chains of the respective conveyor, and two limbs 14,15 with outwardly flared outer portions 16,17 to provide a mouth 18 leading to a slot 19 to receive an edge of a printed circuit board. The system being described includes an optional feed conveyor 21 comprising a plurality of conveyor belts 22 by which printed circuit boards received from a processing station are fed in a line to the accumulator with small gaps between successive boards. Operation of the system as so far described is as follows. As the leading board is advanced by the feed conveyor 21 its leading edge will enter the mouth 18 and subsequently the slot 19 of that conveyor holder of each of the conveyors 4 and 5 which is facing horizontally at the time. At this time the two conveyors 4 and 5 are stationary. A sensor detects that entry of a board into the conveyor holders and causes the conveyors 4,5 to index forward one pitch so that the next succeeding conveyor holders reach the horizontal position at which time the conveyors stop. The next board is now able to enter the succeeding conveyor holders while the previous board will have been elevated into a position in which it is above the feed conveyor 21 and inclined upwardly from its lower edge. Boards continue to be entered into succeeding conveyor holders and on each movement of the conveyors they are inclined more and more steeply to the horizontal until they reach the horizontal passes of the conveyors when they are held in approximately vertical planes. The boards travel along the conveyors towards the discharge ends. The construction of the device so far described is the same as that of the previously available accumulators with the exception that with previous accumulators there is only a single conveyor and the conveyor holders or slats 12 extend right across the device. The system which is shown in Figures 1 to 7 and is constructed according to the invention includes a lightweight manually operable lift truck or cart 25 having a wheeled base 26, a vertical frame 27 extending upwardly from one end of the base and having handles 28 by which the cart can be moved around, and forks 29 mounted on a carriage 31 (Figure 3) which can be moved up and down the vertical frame 27 by a drive (not shown) comprising a vertical screw mounted on the frame 27 and drivable by a crank handle and a nut on the carriage 31 cooperating with the screw. Finally, the system comprises a rack 40 comprising a pair of U-shaped side members 41,42 joined by transverse rods 43,44. The upper part of the rack has a plurality of vertical slits 45 extending across the bight of the U and partway down each side, the spacing of the slots which constitute rack holders being the same as the spacing of the conveyor holders 12 on the conveyors 4 and 5. As can be seen in Figure 1, the rack 40 has a width such that it can be positioned between the vertical plates 9 and 10 between the conveyors 4 and 5 and, because the sprockets of the conveyors 4 and 5 at the discharge end are mounted on short lay shafts rather than a shaft extending right across between the two conveyors, can be entered into the accumulator from the discharge end. Operation of the complete system is as follows. Printed circuit boards are accumulated on the conveyors 4 and 5 in the manner described above. When a sufficient number of boards have been accumulated, the cart 25 is moved into the position shown in Figures 1 to 3 with a rack 40 in position on the forks 29. Either by manipulation of the cart of by adjusting the position of the rack 40 on the forks 29, the rack is positioned beneath the lower edges of the boards to be removed and the forks are then elevated from the position shown in dotted lines in Figure 2 to the position shown in full lines in Figure 2. As the rack 40 reaches the lower edges of the boards these lower edges will enter the slots 45 in the rack and as the rack continues to rise the boards will be lifted out of the conveyor holders 12 on the conveyors 4 and 5 and will become supported in the slots or rack holders 45 of the rack 40. Once the boards are clear of the conveyor holders 12 the cart 25 may be removed. It is preferable for the rack to make contact with the lower edges of the boards at a time when the conveyors 4,5 are stationary but it will be possible to make the rack holders with flared mouths similar to those of the conveyor holders and/or mount the rack 40 on the forks 29 in such a way that it can move freely on the forks to adjust its position to the positions of the boards on the conveyors and can move with the boards as the conveyors move. For example the upper surfaces of the forks 29 may be formed by rollers or the rack 40 may have rollers by which it is supported on the fork 29. Although the apparatus shown in Figures 1 to 7 has been described primarily in relation to its unloading function, i.e. removing boards from a conveyor by which the boards are supplied to the apparatus it will be apparent that the apparatus may be operated in reverse as a loader. In this mode, a rack containing boards will be brought to the accumulator on the cart, the rack is lowered between the conveyors so that the boards are transferred from the rack to the conveyors and then the boards may be delivered one by one to a delivery conveyor; for example, the conveyors 4,5 may be driven in the opposite direction to that previously described and the boards taken away on the conveyor 22. Turning now to the system shown in Figures 8 and 9, there is an accumulator which is essentially the same as that shown in Figures 1 and 2 and comprises a pair of conveyors 54 and 55 carrying conveyor holders 62 and an optional feed conveyor 71. Between the two conveyors 54,55 there is a horizontal lift table 75 which can be raised and lowered by a hydraulic ram 76. The upper surface of the lift table 75 carries two rows of freely rotatable trapped balls 77 on which a rack 90 can move longitudinally in the direction of the arrows 91. The rack is provided with two rows 92,93 of rack holders which have the same spacing as the conveyor holders 62 on the conveyors 54 and 55. The rack has depending side flanges 95 which lie parallel to the longitudinal edges of the lift table 75 to guide the rack longitudinally of the lift table. It will be seen that the lift table 75 extends to the left as seen in Figures 8 and 9 beyond the left hand ends of the conveyors 54,55 by a distance equal to the length of the rack 90 so that one rack may be parked on this part of the table while another rack (not shown) is positioned between the conveyors 54,55. Thus (when the system is being used to fill the racks 90) a full rack may be removed from the left hand end of the lift table when convenient while a second rack is in position between the two conveyors while these conveyors are in operation. The full rack can be removed in various ways; for example, it is possible to use a lift truck similar to that shown in Figures 1 and 2 but having a platform 95 in the form of a ball conveyor; alternatively a fixed ball conveyor may extend to a adjacent the lift table 75. It will be apparent that racks may be slid off the lift table 75 onto the platform 95 or vice versa. In both of the systems already described there is a pair of conveyors and a rack is positioned between the conveyors for the transfer between the two conveyors and the rack of the lamellae such as printed circuit boards. However the reverse arrangement is possible and such a system is shown in Figure 10. This is generally of the same construction as the system shown in Figures 1 to 7 but, instead of having two conveyors, only a single conveyor 101 is provided while two racks 102 and 103 mounted on a lift cart 104 can be located on either side of the conveyor 101. Thus, when the system is being used to load printed circuit boards into the holding means constituted by the racks 102,103 the boards are delivered flat and in succession by, for example, the optional infeed conveyor 105 and the central parts of the leading edges of the boards are received in the holders of the conveyor 101 and the boards are transferred into the vertical position and moved along by the conveyor 101. At an appropriate time, the cart 104 is moved into the position shown in Figure 10 and the racks 102,103 are elevated so that outer portions of the lower edges of the boards are received in the holders of the racks 102,103 and the boards are lifted from the holders on the conveyor 101. The cart 104 may then be removed with the boards carried by the racks 102,103. It is of course possible to operate in the reverse direction so that boards held in the racks 102,103 can be transferred to the conveyor 101. While in the arrangement shown the racks 102,103 are permanently secured to the forks of the cart 104 to ensure rigidity and alignment of the holders of the racks with each other and with the holders of the conveyor 101 when required, it will be apparent that the racks may be movable on the forks of the cart 104 provided some form of anchoring means is provided and in this case the two racks are preferably rigidly interconnected at their left hand ends as seen in Figure 10 although it will not be possible to connect their right hand ends as this would prevent passage of the racks alongside the conveyor 101.

SUBSTITUTE SHEET

Claims

Claims :

1. A system for handling lamellae arranged generally vertically in a parallel array, the systems comprising first supporting means for first parts of the lower edges of the lamellae, a pair of second supporting means for second and third parts of the lower edges of the lamellae lying outwardly from the said first parts, and means for moving the first supporting means vertically relative to the second supporting means to transfer the lamellae from one of the supporting means to the other.

2. A handling system for lamellae comprising: a) an accumulator comprising a pair of continuous conveyors arranged side by side and with a gap between them, the conveyors having aligned pairs of conveyor holders to hold spaced outer parts of the lower edges of lamellae extending between pairs of holders on the two conveyors, b) a rack having a width less than the spacing between the conveyors and rack holders spaced to be aligned with the holders on the conveyors to hold inner parts of the lower edges of the lamellae between the said outer parts, and c) elevating means for changing the relative elevations of the conveyors and the rack from a position in which the rack holders are below lamellae held by the spaced outer parts in the conveyor holders to a position in which the rack holders hold the inner parts of the edges of the lamellae with the outer parts disengaged from the conveyor holders.

3. A handling system for lamellae comprising:

' ^~~ ~ * a) an accumulator comprising a continuous conveyor having conveyor holders to hold inner parts of the lower edges of lamellae, b) a pair of racks spaced apart by a distance greater than the width of the conveyor and having rack holders which are so located that the rack holders on one rack are aligned with those on the other rack and are able to be aligned with the conveyor holders, and c) elevating means for changing the relative elevations of the conveyor and the racks from a position in which the rack holders are below lamellae held by the said inner parts in the conveyor holders to a position in which the rack holders hold outer parts of the lower edges of the lamellae with the inner parts disengaged from the conveyor holders.

4. A handling system as claimed in claim 2 in which the elevating means comprises a lift positioned between the two conveyors.

5. A handling system as claimed in claim 2 or claim 3 in which the elevating means comprises a wheeled truck having a projecting lift insertable between the conveyors.

6. A handling system as claimed in any of claims 2 to 5 in which the conveyor holders are of U-shaped cross-section.

7. A handling system as claimed in any of claims 2 to 6 in which the rack holders consist of slots formed in the (or each) rack.

SϋDET.TUTΞ SHEET

8. An accumulator for lamellae comprising a pair of continuous conveyors providing a pair of parallel spaced horizontal runs, the conveyors having aligned pairs of conveyor holders to hold pairs of first parts of the lower edges of lamellae extending between pairs of holders on the two conveyors with second parts of the lower edges of the lamellae downwardly exposed.