GB2133761A - A stacking and conveying apparatus for pallets - Google Patents

Abstract

The apparatus has two spaced apart chain conveyors (1,2) arranged in the same conveying line, each provided on both sides with a transfer mechanism (9,10,11,12). The apparatus also comprises two stack conveyors (18,19). Each transfer mechanism comprises a lifting table and gripper means carried by two arms (13, 14) which are arranged in parallelogram fashion and driven by a common drive (4,4') to perform a swinging motion between two end positions. Conveyor members of the stack conveyors are formed as bushed roller chains having chain link pins provided with rollers for guiding pallet stacks. Each stack conveyor is provided at each of its ends with means for transferring pallet stacks on to or from the lifting tables. <IMAGE>

Description

SPECIFICATION A stacking and conveying apparatus for pallets The invention relates to a stacking and conveying apparatus for pallets. It is used in the manufacture of products in the technical or oxide-ceramic industry, as for example extruded ferrite aerial rods.

The production process for such ceramic products involves a relatively high expenditure for manual labour. Acertain mechanisation is indicated by the solution which is disclosed in Patent Specification No.

70 810 ofthe German Democratic Republic. In this latter, the moulded articles extruded from a pistontype extrusion press are laid on pallets guided approximatelyverticallyon a horizontal conveyor. For fixing the position of the said articles, these latter are produced over-size and rest overthe rims or edges of the pallets.

The drying also takes place in this position.

This apparatus provides neither a possibility of stacking the pallets, nor is it possible to handle moulded articles extruded in a firm or rigid plastics.

The productivity of such an apparatus remains as a whole relatively low and does not offer any possibility offurtherautomation.

What is known from Patent Specification No. 77 920 ofthe German Democratic Republic is an apparatus used with rough or coarse ceramics and used for transporting pallets loaded with moulded bricks.

The pallets made ready on a rollertrackwith conveyors are brought into a stacking arrangement after being loaded with moulded bricks. This arrangement comprises a plafform which can be raised and lowered hydraulically and also a support construction, on which rollers are likewise provided as a continuation of the roller track. A stack formation is established from below by the lifting platform and the locking pawls or catches arranged on the support construction. The stack of pallets thus formed is conveyed by means of a sliding platform with draining and outlet means into a continuous drier. The displacement of the pallet stacks within the drier is effected by means of a sliding machine.Atthe outlet end of the drier, another sliding plafform transfers the stack of pallets into an unstacking device. This latter consists essentially of a lifting platform and a movable transfer gripper or grab, which always takes up the topmost pallet from the pallet stack and transports itto the unloading station. After the unloading, which can be done manuallyoralsowith a movablegrab of known construction, the empty pallets are brought to the vicinity of the loading position by means of a gravity conveyor arranged parallel to the roller track. By means of a transverse transporter having loading magnets and movable overthe gravityconveyor and rollertrack, the empty pallets are picked up and deposited on the rollertrackfor being once again charged with fresh moulded bricks.

This apparatus, which can be used effectively in the rough ceramic field with bricks ortiles of large format shows an extensive automation in connection with the stacking, conveying and unstacking of bricks. A use or transfer ofthe solution as referred to for the manufacture of products of relatively small format in the technical or oxide ceramic industry is not available, because of the substantial differences in dimensions, and also only a slight productivity would be obtainable.

The usual extruded diameters with oxide ceramic products are in the region of 5to 20 mm, so that brick-like moulded articles have, for example, a weight which is two to three hundred times greater. In addition, ceramic moulded articles produced in a stiff or rigid form require extremely careful handling,to reliably avoid any damage thereof. This requirement can not be achieved with the known apparatus.

It is the object ofthe invention to achieve a substantial improvement in the productivity in con nection with the manufacture of the technical or oxide-ceramic products by automated handling and conveying of pallets or pallet stacks.

The invention has for its object to ensure a development favourable as regards movement in connection with the stacking and conveying ofthe pallets, with which the conveyors are to transport the pallet stacks continuously through a drier and atthe same time are to be constructed so as to compensate for discontinuities as regards the shaping apparatus and following apparatus.According to the invention, the object as stated is achieved by the fact that two chain conveyors, which are known perse, guarantee an always horizontal position of the pallets and are arranged in oneconveyorlinebutspacedfrom one another, are each provided on both sides with a transfer mechanism connected by stacking conveyors, the transfer mechanisms comprising a lifting table and also pivotable parallelogram-like arms with gripping means which can be driven by a common revolving cranked slide drive, which in its turn is equipped with gripping and centering elements, the conveyor members of the stacking conveyors being formed as bushed roller chains and their lengthened chain link pins being provided in pairs with rollers or runners,whiletheexternal Iinksofthe bushed roller chains have arranged thereon driver members with flanged rollers for receiving and guiding the pallet stacks, and in addition the stacking conveyors are each provided at the end with straight-link cranked rocking gears, through the straight-link arms of which, constructed as drivers, the pallet stacks are able to be pushed on or withdrawn from the lifting tables ofthe transfer mechanisms and the stacking conveyors.

In a further development ofthe invention, the arms ofthetransfer mechanisms are connected at the end to an H-shaped cross-member, which comprises, approximately at the point of connection of flange and web, two facing pairs of levers which can be swung horizontally through operating cylinders, the said lever pairs being equipped in theirturn with gripping and centering elementsforthe pal lets.

It is likewise a feature ofthe invention that the straight-link arms of the straight-link cranked rocking gears which carry at the end driver rollers which, with the commencement of the withdrawal of a pallet stack from the lifting table, experience a horizontal speed of zero and an acceleration to aboutthe centre point of travel and, with the pushing on of the pallet stack, have a horizontal speed synchronous with the stacking conveyor, whereas when a pallet stack is removed from the stacking conveyor and pushed on to the lifting table, the driver rollers have an opposite movement cycle.

The invention will now be explained by way of example, with reference to the accompanying di agrammatic drawings, in which: FIG. is a plan view ofthe apparatus, shown in diagrammatic form; FIG. 2 is a partial view of the transfer mechanism with lifting table; FIG. 3 shows the gripper of the transfer mechanism; FIG.4showsthe cranked slide drive ofthetransfer mechanism; FIG. 5 is a side elevation ofthe stacking conveyor with straight-link cranked rocking gear for the withdrawal of the pallet stack from the lifting table; FIG. 6 is a section ofthe stacking conveyor with a pallet; and FIG. 7 is a section A-A according to FIG. 6.

As will be seen from FIG. 1 ,the stacking and conveying apparatus consists of two chain conveyors 1,2, which are arranged spaced from one another, but in one conveyor line, these conveyors being so constructed in a manner known perse that the pallets 3,3' are constantly transported in a horizontal position. Arranged atthe facing ends ofthe chain conveyors 1,2 are cranked slide drives 4, 4', the construction ofwhich is shown diagrammatically in Fig. 4. Each of the cranked slide drives 4,4' comprises fourdriven shafts 5,5',6,6',7,7',8,8',which are arranged in pairs, each pair extending to a transfer mechanism 9, 10,11,12, and having connected thereto arms 13, l4ofa gripper 15 (Fig. 2), said arms also being arranged in pairs.The transfer mechanisms 9,10,11, l2areso arranged laterally ofthechain conveyors 1,2 thatthe grippers 15, along their path of movement 16, cover the corresponding pick-up region and set-down region of lifting tables 17 and ofthe chain conveyors 1,2. Stack conveyors 18,19 are arranged between the transfer mechanisms 10, 11 and 9, 12. With this arrangement, the stack conveyor 18 takes up the pallet stack 20 which is loaded with fresh moulded articles and conducts itthrough the drier 21.

For the purpose oftaking up ortransferring the pallet stacks 20,20' on orfrom the lifting tables 17 of the transfer mechanisms 9, 10, 11, 12, the stack conveyors 18, 19 are each equipped at their ends with a straight-link cranked rocking gear 22,22', 23,23'. By means of the stack conveyor 19 and afterthe stack has been formed by means of the transfer mechanism 12, the transporting ofthe pallet stack 20' consisting of unloaded pallets 3 is effected to the transfer mechanism 9, which in its turn deposits the pallets3 rhythmically on the chain conveyor 1.

Fig. 4shows diagrammatically the construction of the cranked slide drive 4, for the transfer mechanisms 9, A crank 25, which is mounted in a gearbox 24 and is driven by a motor (not shown), engages in a slotted arm 26.

This latter is mounted togetherwith a gearwheel 27 on a shaft 28. Through an idler 29 and a driven gear 30, the gearwheei 27 drives the driven shaft 6 and, through the driven gear 31, drivesthe driven shaft 8.

Through coupling gears 32 and 32', the driven gears 30,31 transmittheir rotational movement to the drive gears 33,34 and, therefore, to the driven shafts Sand 7. As a consequence ali four shafts 5,6,7,8 perform a synchronous reversing rotational movement in the same direction. The arms 13,14, (Fig. 2) are connected at one end in parallelogram-like formation to the driven shafts 5,6 and, with each revolution ofthe crank 25, swing to and fro through an angle of 1800 from one end position to the other. Attheir opposite ends, the arms 13,14 are linked to the gripper 15, so thatthe latter is always guided in a horizontal position.

Fig. 2 shows the position ofthe gripper 15 when a pallet 3,3' is deposited on the lifting table 17 and, in chain-dotted lines, the position atthe apex of the path of movement 16 and also when receiving a pallet 3 from the chain conveyor 1.

The design ofthe gripper 15 illustrated in Fig. 3.

The arms 13, 14 are pivotally connected in pairs on an H-shaped cross member 36 attheflange ends thereof and two opposite lever pairs 35,35' which can be swung horizontally by means of operating cylinders 37,37' are arranged in the vicinity ofthe web. These levers carry atthe end a vertically directed gripping and centering element 38, which comprises a cylin drical section for centering the pallet3,3', while the end is made hook-shaped so as to engage beneath the pallet3,3'.

Fig. 3 also shows, in chain-dotted lines as regards one ofthe levers 35, the initial position on receiving the pallet 3,3'. The other levers 35,35' showthe pallet 3,3' after centering has been effected.

The basic construction of the stack conveyor 18,19 is represented in Figs. 5,6 and 7.

The conveyor 18, is mounted on a base frame 39.

Used as conveyor member is a conventional bushed roller chain 40, between the external links 41 of which are arranged driver members 42with flanged rollers 43.

In addition, the chain link pins 44 are so extended that a roller or runner45can be pushed on on both sides. The rollers 45 are in theirturn supported on a track 46 connected to the base frame 39. In this way, each external Iinkofthebushed rollerchain46formsa kind offour-wheeled truck.

Fitted on the track 46 is a spacer rail 47, which causes a lateral guiding of the rollers 45 and thus ofthe bushed roller chain 40.

As will be seen from Fig. 7, the pallet 3,3' is provided with a support rail 48, which in its turn engages in the flanged rollers 43, so thatthroughoutthe conveying of the pallet stack 20,20', a defined position thereof is given. Furthermore, with an accumulation ofthe pallet stacks 20,20', the flanged rollers 43 are ableto roll on the support rails 48, so that the bushed roller chains 40 are guided through beneath the pallet stacks 20,20'.

The conveyors 18,19 are each provided atthe end with the straight-link cranked rocking gear 22,22', 23, 23'. A double rotary crank 49 carrying out on each occasion only one revolution is mounted on the stack conveyor 18, 19 and is movably connected to straightlink arms 51 guided by a rocker 50. The straight-link arms 51 extend to beyond the lifting table 17 ofthe associated transfer mechanism 9, 10, 11, 12 and comprise at the end a cranking which is provided with a driver roller 52. It is possible therebyforthe pallet stacks 20,20' to be removed from the lifting table 17 and pushed on to the conveyors 18,19 or, conversely, to be removed from the conveyors 18, 19 and pushed ontotheliftingtable17.

The manner of operation ofthe stacking and conveying apparatus according to the invention is hereinafter described.

On the chain conveyor 1, a prepared empty pallet3 is loaded by a delivery station which is known but is not illustrated, the pallet 3' being transported by the optoelectricallycontrolled drive means ofthe chain conveyor 1 stepwise in the direction ofthe arrow.

When the loaded pallet 3' has reached the transfer position on the chain conveyor 1, i.e.the region of the transfer mechanism 10, the latter is situated in the starting position immediately above the loaded pallet 3', and the gripper device 15with gripping and centering elements 38 is opened. The gripper 15 is now lowered by the cranked slide drive 4, driving shafts 5, 6 and arms 13, 14 on to the pallet 3'. By actuation ofthe operating cylinders 37,37', the pairs of arms 35,35' are swung in the direction ofthe pallet 3', the hook-shaped gripping and centering elements 38 engaging beneath the said pallet and at the same time centering it.

With the further pivotal movement of the arms 13, 14,the pallet 3' is now guided by the gripper 15 until above the lifting table 17 ofthe transfer mechanism 10 and deposited on said table, whereafterthe gripper 15 is returned again to its starting position. Immediately after being occupied, the lifting table 17 is lowered by the height of a pallet. In synchronism with the stack formation bythetransfermechanism 10, the unstacking and preparation of the empty pallet3 by the transfer mechanism 9 is effected in the manner as already described, but with a reversed series of movements. In this case, the gripper 15 of the transfer mechanism 9, in its starting position above the chain conveyor 1, holds an empty pallet3 at the ready position.With commencement ofthe movement, the empty pallet3 is lowered on to the chain conveyor 1.

The arms 14, 13 with the gripper 15 swing until they are above the lifting table l7ofthetransfermechan- ism 9, an empty pallet3 is gripped, centered and guided until abovethechain conveyor 1,whilethe lifting table 17 is raised bythe height of one pallet.

A best possible cycle of movements with the transporting of the pallets 3,3' is assured by the use of the cranked slide drive 4,4'. The speed close to zero which occurs in the region oftheturning or reversing points permits a gentle gripping and depositing of the pallets 3,3'. In addition, the transporting movement of the pallets 3,3' is in this case several times slowerthan the return movement of the empty gripper 15.

When a predeterminable stack height is formed on the lifting table 17 ofthe transfer mechanism 10, the lifting table 17 returns by a rapid return motion to the height ofthe stack conveyor 18.

The pallet stack 20 is removed from the lifting table 17 by means ofthe straight link arms 51 and driver rollers 52 ofthe straight-link cranked rocking gear 22 and pushed on to the stack conveyor 18, whereafter the driver rollers 52 return again along a curved path to their original position. It is of particular advantage thatthe driver rollers 52 accelerate the pallet stack 20 fairly uniformly and without any jerking and, during the second half of the travel, slowthe pallet stack 20 down to the transporting speed ofthe stack conveyor 18, so that the said stack 20 is taken over at synchronous speed by the said conveyor 18.

A pre-conditionforthis optimum movement cycle is the free-wheeling function associated with the flanged rollers 43, as a result of which any relative movement of the pallet stacks 20, 20' relative to the bushed roller chains 40 ofthe conveyors 18,19 can be compensated.

In the same manner, only with a reverse movement cycle the pallet stacks 20, after travelling through the drier 21, are transferred by means of the straight-link cranked rocking gear 22' on to the lifting table 17 of the transfer mechanism 11. In a manner as already described, the pal let stack 20 is now disassembled, by the transfer mechanism 11 and the pallets 3' are deposited on the chain conveyor 2, where they are emptied. The emptied pallets 3' are once again made up by the transfer mechanism 12 and on the lifting table 17 thereofto a pallet stack 20', which is pushed by means ofthe straight-link cranked rocker gear 23' by means of straight link arms 51 and driver rollers 52 on to the second stack conveyor 19 and transported by this latter in the direction ofthetransfer mechanism 9.

The straight-link cranked rocker gear 23 arranged at this end of the stack conveyor 19 pushes the pallet stack 20' on to the lifting table of the transfer mechanism 9. The cycle ofthe pallets 3,3' is in this way completed.

It is generally known that, with the production of ceramic products, no continuous working procedure is possible between the shaping and the further technological treatment.

A decisive advantage ofthe stacking and conveying apparatus according to the invention is that a compensation for discontinuity is to be achieved.

Forthis purpose, the stackconveyors 18, 19 are normally each only half occupied with pallet stacks 20, 20', this representing the buffer capacity.

For example, if the charging side ofthe apparatus decreases in output or even fails completely, the removal station can continue to operate at its normal rhythm until the drier 21 is empty. The emptied pallets can be additionally taken up bythestackconveyor 19.

On the other hand, with disruption on the removal side ofthe apparatus, the loading side with chain conveyor 1 and transfer mechanism 9,10 can continue to operate until the drier 21 or respectively the entire conveyor 18 is filled, since a sufficient number of pallet stacks 20' stand ready on the stackconveyorl9.

Claims (5)

1. Astacking and conveying apparatus for pallets comprising two horizontal chain conveyors which ensure horizontal position ofthe pallets and are arranged in one conveying line but spaced from one another and are each provided on both sides with a transfer mechanism, the apparatus further comprising stack conveyors, at least one ofthe transfer mechanisms comprising a lifting table and also swingable parallelogram-like arms provided with gripper means and driven by a common drive, the gripper means being equipped with gripping and centering means, conveyor members of the stack conveyors being formed as bushed roller chains having chain link pins, provided in pairs with rollers or runners, the bushed roller chains having external links which have arranged thereon driver members with flanged rollers for receiving and guiding pallet stacks, and in addition the stack conveyors are each provided at each end with transport means by which the pallet stacks can be pushed on orwithdrawn from the lifting tables.

2. An apparatusaccordingto Claim 1,wherein the arms are connected at one end on an H-shaped cross-memberwhich comprises, in the region ofthe connection of its flanges and web, two facing lever pairs which can be swung horizontally by operating cylinders, the said lever pairs being equipped with the gripping and centering meansforthe pallets.

3. An apparatus according to Claim 1 or 2, wherein the transport means includestraight-linkcranked rocking gears having straight-link arms which carry at the pallet-stack-engaging end driver rollers which, with the commencement ofthe withdrawal of a pallet stackfrom the lifting table, have a horizontal speed of zero and an acceleration to aboutthe centre point of travel and, with the pushing on of the pallet stack, have a horizontal speed synchronous with the associated stack conveyor, whereas when a pallet stack is removed from the stack conveyor and pushed onto the lifting table, the driver rollers have an opposite movement cycle.

4. Astacking andconveying apparatusforpallets constructed, arranged and adapted to operate substantially as herein described with reference to, and as shown in, the accompanying drawings.

5. An installation for handling pal lets including an apparatus according to any one of Claims 1 to 4.