CA2040461A1 - Hinged mold block conveyors in tube making apparatus - Google Patents
Hinged mold block conveyors in tube making apparatusInfo
- Publication number
- CA2040461A1 CA2040461A1 CA 2040461 CA2040461A CA2040461A1 CA 2040461 A1 CA2040461 A1 CA 2040461A1 CA 2040461 CA2040461 CA 2040461 CA 2040461 A CA2040461 A CA 2040461A CA 2040461 A1 CA2040461 A1 CA 2040461A1
- Authority
- CA
- Canada
- Prior art keywords
- mold
- tunnel
- conveyor
- block
- blocks
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
- B29C49/0015—Making articles of indefinite length, e.g. corrugated tubes
- B29C49/0021—Making articles of indefinite length, e.g. corrugated tubes using moulds or mould parts movable in a closed path, e.g. mounted on movable endless supports
Landscapes
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Mechanical Engineering (AREA)
- Blow-Moulding Or Thermoforming Of Plastics Or The Like (AREA)
- Moulds For Moulding Plastics Or The Like (AREA)
Abstract
ABSTRACT
The invention concerns apparatus for molding tube utilizing a travelling mold tunnel. The tunnel is made up of mold blocks each comprising parts which are hinged together to be closeable to form the tunnel and openable to release tube from the tunnel. The opened mold blocks from the downstream end of the tunnel are returned to the upstream end to reform the tunnel about an extrusion nozzle for thermoplastic extrudate without changing the orientation of the axes of their bores so that said axes always remain generally parallel with the axis of the mold tunnel. Mold blocks removed from a downstream end of the mold tunnel are returned to the-upstream end at a speed greater than the travelling speed of the mold tunnel.
The invention concerns apparatus for molding tube utilizing a travelling mold tunnel. The tunnel is made up of mold blocks each comprising parts which are hinged together to be closeable to form the tunnel and openable to release tube from the tunnel. The opened mold blocks from the downstream end of the tunnel are returned to the upstream end to reform the tunnel about an extrusion nozzle for thermoplastic extrudate without changing the orientation of the axes of their bores so that said axes always remain generally parallel with the axis of the mold tunnel. Mold blocks removed from a downstream end of the mold tunnel are returned to the-upstream end at a speed greater than the travelling speed of the mold tunnel.
Description
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This invention ralates to apparatus having a travelling mold tunnel for the production of seamless -~
plastic tubing, especially single or double-walled corrugated tubing or ribbed tubing.
Apparatus of utilizing a travelling mold tunnel is commonly used for the production of continuous plastic tubing. The mold tunnel is formed between a pair of complementary mold assemblies each of which comprises an endless run of mold blocks which are articulately interconnected. Each mold block of one mold assembly is complementary to a respective mold block of the other mold assembly, the mold blocks cooperating in pairs along the forward run to orm an axially extending mold tunnel defining a tubular mold. The wall of the mold is dependenk on the inner face of the mold blocks and is the matter of choice.
The mold assemblies are driven in synchronism with one another so that the mold blocks circulate along the endless tracks. The mold blocks are always located similarly with respect to the direction of their movement. Thus when the direction o movement changes, the orientation of the mold blocks changes with it. For example, the mold blocks on the retùrn run are totaled 90 with respect to mold blocks on the tunnel run. The entrance to the tunnel may be located suitably with respect to an extrusion nozzle for extruding an annular parison of plastic against the mold surface of the tunnel. When the resuIting tube is required to have more than one wall, the extrusion nozzle will extrude coaxial parisons of plastic extrudate.
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This invention ralates to apparatus having a travelling mold tunnel for the production of seamless -~
plastic tubing, especially single or double-walled corrugated tubing or ribbed tubing.
Apparatus of utilizing a travelling mold tunnel is commonly used for the production of continuous plastic tubing. The mold tunnel is formed between a pair of complementary mold assemblies each of which comprises an endless run of mold blocks which are articulately interconnected. Each mold block of one mold assembly is complementary to a respective mold block of the other mold assembly, the mold blocks cooperating in pairs along the forward run to orm an axially extending mold tunnel defining a tubular mold. The wall of the mold is dependenk on the inner face of the mold blocks and is the matter of choice.
The mold assemblies are driven in synchronism with one another so that the mold blocks circulate along the endless tracks. The mold blocks are always located similarly with respect to the direction of their movement. Thus when the direction o movement changes, the orientation of the mold blocks changes with it. For example, the mold blocks on the retùrn run are totaled 90 with respect to mold blocks on the tunnel run. The entrance to the tunnel may be located suitably with respect to an extrusion nozzle for extruding an annular parison of plastic against the mold surface of the tunnel. When the resuIting tube is required to have more than one wall, the extrusion nozzle will extrude coaxial parisons of plastic extrudate.
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Such apparatus is described in U.S. patent No. 3,981,663 to Lupke, issued September 21, 1976 and U.S. patent No. 3,832,429 to Charpentier 1974. These patents describe apparatus in which the mold assemblies are arranged one above the other. Other conventional apparatus in use is described, for example in U.S. patent Nos. 3,677,676 to Hegler 1972, and 3,751,541 to Hegler 1973. The apparatus of these patents shows the mold assemblies arranged side-by--side. Both these conventional configurations of apparatus have particular problems associated with them, in that the independent mold assemblies must be carefully synchronized in operation so that the pairs of cooperating mold blocks come together precisely to form the mold tunnel. Moreover, to provide a pair of independent mold assemblies requires considerable dup]ication of machinery and equipment and, in the case of the side-by-side layout, the apparatus covers an appreciable area of floor space ~hich may be an appreciable consideration where space is limited or expensive.
Any services which must be supplied to the mold blocks must be provided in ~uplicate for each mold assembly. Such services include the provision of suction lines, hydraulic ~luid lines, possibly heating or cooling services, etc., maintenance and repair work is also duplicated for the mechanism of each endless track. U.S. Patent No. 4,439,130 issued March 27th, 1984 to Dickhut discloses the use of mold blocks which are hinged together and closed to form the mold tunnel and opened to release formed pairs of tube. This makes possible for a single conveyor but the mold blocks still change orientation with changes in their direction o~ travel.
Such apparatus is described in U.S. patent No. 3,981,663 to Lupke, issued September 21, 1976 and U.S. patent No. 3,832,429 to Charpentier 1974. These patents describe apparatus in which the mold assemblies are arranged one above the other. Other conventional apparatus in use is described, for example in U.S. patent Nos. 3,677,676 to Hegler 1972, and 3,751,541 to Hegler 1973. The apparatus of these patents shows the mold assemblies arranged side-by--side. Both these conventional configurations of apparatus have particular problems associated with them, in that the independent mold assemblies must be carefully synchronized in operation so that the pairs of cooperating mold blocks come together precisely to form the mold tunnel. Moreover, to provide a pair of independent mold assemblies requires considerable dup]ication of machinery and equipment and, in the case of the side-by-side layout, the apparatus covers an appreciable area of floor space ~hich may be an appreciable consideration where space is limited or expensive.
Any services which must be supplied to the mold blocks must be provided in ~uplicate for each mold assembly. Such services include the provision of suction lines, hydraulic ~luid lines, possibly heating or cooling services, etc., maintenance and repair work is also duplicated for the mechanism of each endless track. U.S. Patent No. 4,439,130 issued March 27th, 1984 to Dickhut discloses the use of mold blocks which are hinged together and closed to form the mold tunnel and opened to release formed pairs of tube. This makes possible for a single conveyor but the mold blocks still change orientation with changes in their direction o~ travel.
, Since the 1970's various improvements and modifications have been made to the basic type apparatus disclosed in the patents referred to but except for the manufacture of helically corrugated tube no other basic type of apparatus is known. For the production of helically corrugated pipe, a ribbon of molten thermoplastic has been wound on an advancing mandrel. It is not with this type of apparatus that the present invention is concerned.
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According to the invention, apparatus for continuous molding of thermoplastic extrudate e.g.
tube, in a travelling mold tunnel to form an elongate molding, comprises; a travelling tunnel mold assembly of adjacent mold blocks each mold block having a bore therethrough, the bores of adjacent mold blocks being aligned axially; each mold block comprising a pair pivotally connected parts whereby the parts are movable between a closed position of the block in which the bore is circumferentially enclosed, and an open position in which the parts are located with respect to each other to release elongate molding formed between them, a tunnel conveyor ~or the tunnel mold assembly to convey it horizontally and axially in a molding run between tunnel entrance and a t~nnel exit; means to open each mold ~lock as it reaches the tunnel exit; a removal conveyor arranged to move generally in the plane of the tunnel conveyor to receive and convey each opened mold block sequentially from the tunnel conveyor, each mold block being orientated with its bore parallel to the mold tunnel;
a return conveyor generally in the plane of the tunnel conveyor arranged to move hori~ontally parallel and opposite to the tunnel conveyor to receive and convey mold blocks sequentially from the removal conveyor, each mold block being orientated with its bore ' ' ' '' ~
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parallel to the mold tunnel; and an approach conve~or arranged to move horizontally and parallel to the removal conveyor, to convey mold blocks sequentially from the return conveyor, each mold block being orientated with its bore parallel to the mold tunnel;
and means to close the returned mold blocks to form the mold tunnel. The invention is ~nvisaged for use in the molding of semi-rigid plastic tube of the type used for underground drainage or for carrying electrical wiring. The cross-section of such tube is generally circular. For easy exchange of mold blocks for ones of different diameter, each mold block may be releasably carried on a mold block carrier of articulately interconnected mold block carriers.
Means may be provided to maintain the mold blocks closed on the tunnel conveyor. Such means may suitably be either guide fences to prevent the mold block parts pivoting awa~ from each other or a cam actuated latches between the mold parts.
When the cam actuated latch is provided, the latching cam may be located at the upstream end of the tunnel to engage a first cam surface of the latch to move it into a latching position as the respective mold block is conveyed on the tunnel conveyor past the cam, and an unlatching cam ma~ be located at the downstream end of the tunnel to engage a second cam surface of the latch to move it into a latching position as the respective mold block is conveyed or the tunnel conveyor past the cam. In effect, such a latch may be a toggle latch. ~nce the hinged parts of the mold blocks are unlatched, the mold blocks must physically open to release tube formed in the mold tunnel. This may be achieved through mold block opening cam means provided at the downstream end of the tunnel, adapted to interact with a cam surface of ?
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one mold block part to pivot it with respect to the other mold block part to release the tube. Once~ the tube has been released, the mold blocks may travel on the removal return and approach conveyors, in either open or closed condition. However, since the mold blocks must open to receive an extrusion nozzle into ~ ~-the tunnel, it~is convenient to maintain the mold blocks open on the removal, return and approach conveyors. At the upstream end of the tunnel, mold blocks pivotally close under gravity. Preferably, such closing is in a controlled manner and mold block closing cam means may be provided to interact with a cam surface of each mold block to close it as it moves into position as part of the mold tunnel.
A change of direction is involved between different conveyors and guide means may be provided to guide the mold blocks from one conveyor to the next.
Such guide means may comprise a curved guide rails at outer corners between each conveyor.
The hinging of the mold block parts may be by any convenient arrangement. However, two such arrangements, referred to as e~emplary, are envisaged. In both arrangement, the hinge is provided near the top of the mold block, but in one case it is right at the top, and, in the other case, it is offset from the top. In each case, one fixed part of each pair of mold block parts is, in use, attached at its base to its respective mold block carrier. In the case where the hinge is at the top of the mold block, abutting faces of the block of the fixed and movable parts distant from the hinge, lie in a plane oblique to the radius of the bore. By this means it is possible to attach the fixed part over a stable base area. Moreovsr, connection between the fixed and " ,, , :
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`` 2 ~ 6 1 movable parts on the outside of the mold block may be offset from the direct bottom, thus allowing access to latching means. In the case where the hinge is offset from the top of the mold block, the fixed and movable parts may be symmetric. The face abutting faces may be radial and offset from the bottom of the mold block diametrically opposite the hinge. When this is so, it may be necessary to lower the mold block slightly to release tube from the slightly upstanding edge of the fixed mold block. This may be achieved by making the conveyor run descend slightly. In this case, means are provided to lower the mold blocks on the tunnel conveyor to release formed tube from the face of the fixed mold part offset from the base. In any case, it may be convenient to provide ramps between conveyors.
The invention also provides a method for forming tube in a travelling mold tunnel comprising;
extruding parison of thermoplastic extrudate into a travelling tunnel mold assembly wherein each tunnel segment comprises a mold block having a bore therethrough, the bores of adjacent mold blocks being aligned axially; each mold block comprising a pair of pivotally connected parts whereby the parts are movable between a closed position of the block in which the bore is circumferentially enclosed, and an open position in which the parts are located, with respect to each other, to release ~ube formed between them; a conveying tunnel mold assembly to convey it horizontally and axially in a molding run from between a tunnel entrance and a tunnel exit; opening each mold block as it reaches the tunnel exit; returning each mold block from the tunnel exit to the tunnel entrance upstream of the tunnel return path oriented to be added to the tunnel entrance; and closing the returned mold blocks to form the mold tunnel.
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Embodiments of the invention will now be described by way of examplP with reference to the drawings in which:
Figure 1 is a perspective view of an embodiment of apparatus according to the invention;
Figure 2 shows a plan view of the general layout for another embodiment apparatus of the invention;
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Figure 3 is an enlarged view showing one example of a mold block and carrier which may be used with apparatus according to the ~:
invention, for example as illustrated in Figure l;
Figure 4 is a cross section of the mold ~.
block and carrier of Figure 3 in its closed position;
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Figure 5 is a similar cross section of the mold block of Figure 4 i.n the open position;
Figure 6 is a cross section through another mold block and carrier in the closed position and suitable for use with apparatus as illustrated in Figure l;
Figure 7 is a cross section through the block of Figure 6 in the open position;
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Figure 8 is a view of carriers, suitable for use in apparatus as illustrated in Figure 2;
Figure 9 is a view of another closed mold block in combination with a carrier as shown in Figure 8 indicating mold opening and closing mechanism; and Figure lO is a view of the mold block of Figure 9 in the open position.
In the drawings, Figure l shows a general view of apparatus embodying the invention which may comprise a tunnel conveyor 12 along which travels a tunnel mold assembly 14, segments of which are hinged ~;
mold blocks 16 of which are closed in the tunnel mold assembly over the majority of tunnel run of a conveyor 12. Each mold block 16 comprises a fi~ed half 13 and a hinged half 15 and each has a carrier block 17 which may be driven to move along the conveyor 12 in a rnanner to be described hereafter. At an upstream and of the tunnel assembly 14, an extrusion nozzle 18 enters the tunnel to extrude an annular parison l9 of thermoplastic material to form tube 20 within the tunnel. At the downstream end of the tunnel assembly, tube 20 emerges from the tunnel. Also at the downstream end of the tunnel, mold blocks 16 open hingeably to release tube 20 and are returned to the upstream end of the tunnel conveyor 12 by means of a removal conveyor 22, a return conveyor 24 and an approach conveyor 26. Conveniently, the tunnel conveyor 12 and the removal conveyor 22, the return conveyor 24 and the approach conveyor 26 are laid out in the general form of a rectangle, the upper runs of ,, , .. ... . " . . . , , ., " .~ . , .- . - .
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each conveyor being at least generally in the same horizontal plane. While the speeds of the various conveyors may be coordinated to return mold blocks to the tunnel conveyor at a suitable speed to form the tunnel assembl~ 14 on the tunnel conveyor, in a practical embodiment the tunnel conveyor comprises a stationary track along which the mold bloc~s 16 are j driven via their carriers 17. i~
On the removal, return and approach conveyors 22, 2~ and 26 the mold blocks may travel in either an open or closed condition. However, since the mold blocks must open to release tube 20, and must ba open in order to close around extrusion nozzle 18, it may normally be convenient for them to travel on at least most of the route back to the upstream end of the tunnel conveyor 12 in the open condition. Mold blocks halves may open as much as 180 to each other or even more. However, it is normally convenient that they onl~ open widely enough to release tube 20 from between them.
When assembled into mold tunnel assembly 1 on tunnel conveyor 12, it is important that the mold blocks 16 have upstream faces and downstream faces ll in contact with one another to form a closed tunnel in the longitudinal direction. It may normally be sufficient to press the mold blocks ~irmly togethe~ on this run but it may be advantageous to mechanically link the carriers, as for instance, by the illustrated tongue 100 and groove 102 connections between them as seen ~rom Figure 8. The halves 13, 15 of each mold block 16 must, on the tunnel run tightly closed about the hinge 28 so that the tunnel is also tightly closed around its circumference, and must reliably open to release tube 20. This may be achieved by various ~ .
means, for example the cam arrangemen-t 50, 5a shown in Figure 1 or the mechanism 104 shown in Figures 9 and 10 .
The alignment of the mold blocks 16 on the tunnel conveyor 12 is also important so that the extrusion nozzle 18 is accurately centered in the tunnel ~or accuracy in molding the tube 20.
Conveniently, a track 30 is provided on tunnel conveyor 12 for engagement with a corresponding part 31 of each carrier 17 for guidance and location of mold block 16. The track 30 may be in the form of an upstanding rail to cooperate with a groove 31 shaped slot 31 o each mold block. The rail 30 may house a source of suction and suction passages 33 through carrier 17 may connect suction ports 35 o the rail 30 with suction passages 37 in the mold block 16 leading to its interior. The provision of suction to the interior of the tunnèl may be provided in a similar manner to that described in any of U.S. patent No. 4,319,872 or Canadian patent No. 1,083,765, these patents are directed to a travelling mold comprising mold blocks through which suction may be applied, , although all of the patents are limited to the use of two conveyor systems, one for each of two runs of half mold blocks. Nevertheless, th~ provisions of suction means within guides for the mold blocks may be regarded as similar.
Suitably the carriers 17 "wrap around" the track 30 at its edges, or around an additional edge tracks 39, by means of an inwardly extending flange 41, to prevent accidental disengagement of the carriers 17 and blocks 16. The length o the tunnel conveyor and the length of the tunnel assembly 14 should be suficient for extruded annular ,. .. - : .
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.: , thermoplastic parison to set into tube 20 of sufficient rigidity or th~ removal of mold blocks 16 without permanent distortion of the tube. Cooling plugs, and other forming means for the inside surface of the tube may be provided in a conventi-onal manner supported on an inner core extending coaxially from the extrusion nozzle. For simplicity, such devices are not illustrated. However, additional cooling means is possible on the outer surface of the mold, as for example, by ribs 106 on its outer surface as shown in Figure 9. Cooling water may be flowed over the exterior of the closed mold tunnel assembly to aid cooling and drain channels 108 may be provided for the water.
When the mold assembly has remained closed over a sufficient length ~or the tube to set, the mold blocks may be opened by hinging each of them about its hinge 28. Once open, the blocks may be removed from the tube, for example, orthogonally therefrom along removal conveyor 22. While, as already commented, the speeds of the various conveyors should be coordinated, there is no particular reason for accurate alignment of the mold blocks 16 in tunnel formation on any of the removal conveyor 22, the return conveyor or the approach conveyor.
In practice, it is convenient that removal conveyor 22 runs at an angle of slightly more than 90 to the tunnel conveyor and that mol~ blocks are located on it with their tunnel axis not quite aligned with the directional axis of conveyor 22. Thus, the orientation of mold blocks 16 is the same as on tunnel conveyor 12 so that they are set at a slight angle on conveyor 22. On tunnel 12 mold blocks 16 more in the direction of the tunnel axis. Whereas, on conveyor ~7 ; :
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-- 2~0~1 - lZ -they move in a direction at slightly greater than 90 to the tunnel axis of each block 16.
It is convenient to remove the mold blocks 16 in a direction parallel with the upstream faces and the downstream faces 17 and, although sufficient guidance means should be provided to prevent them falling off the conveyor, there is no need for accurate guide means such as track 30. The guidance means may conveniently ~e chains 110. The provision of a guide rail 32 extending alongside removal conveyor 22 and, at least partially, alongside tunnel conveyor 12 may be useful in some instances.
When a tongue 100 and groove 102 linkage is provided between mold blocks carriers 17 (See Figure 8) on the tunnel run, this linkage must be disconnected to allow the carriers 17 with their associated blocks 16 to travel essentially edge to edge on the removal run rather than face to face.
The linkage may comprise a rail of T-shaped cross section or, as illustrated an aligned pair of lugs 100 o~ T-shaped cross section on one tunnel face of a carrier, e.g. the downstream face 11 and a corresponding T-shaped groove 102 in the other face.
When travelling in the tunnel direction the T-groove 102 interlocks the T-rail 100 to hold faces of ad~acent blocks in register. However, when a block 16 and its associated carrier 17 are subjected to an approximate gO change of direction without change of orientation, as indicated, for example, by the arrow A
in Figure 8, (or in the 180 direction), then T-members 100 will slide out of T-grooves 102 to unlatch the carriers and allow them to move away in the new direction.
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~ rhe movement of carriers 17 ~and hence blocks 16) on the tunnel conveyor may be by means of driven sprocket wheels 32 which mesh with lugs 112 provided on one, or as illustrated both, sides of carriers 17. Such sprocket wheels 32 at the upstream of the tunnel run may conveniently drive the entire tunnel train of carriers 17 and mold blocks 16.
Movement of the carriers and mold blocks on removal 22, return 24, and approach 26 conveyors may be by any convenient means. However, it is to be noted that similar sprocket wheels may be used on the return run and chains 110 which may run on sprocket wheels 114 driven in any convenient manner. For additional ease in transition from one direction to another, where one conveyor adjoins another conveyor travelling in a different direction, ramps may be provided in the conveyors.
Even when the apparatus is used for molding pipe of small diameter, the thickness between its faces is usually considerably less than the width of ~ -the block across the horizontal diameter of the mold tunnel. In fact, the apparatus is suitable for the molding of large diameter tube and, for mold blocks for molding large diameter tube, the difference between the thickn0ss of the block and the width of the block is considerable.
Since the blocks move in the direction of their thickness on the closed mold tunnel run on tunnel conveyor 12 and in the general direction of their width on the removal and approach conve~ors 22, 26, it is clear that the speed of conveyors 22 and 26 will be greater than that of the mold blocks on tunnel conveyor 12 at least by an amount sufficient to ., , ' : ~ .. ' '': ' ~ ;
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accommodate the difference between their thickness and their width.
An important feature of the invention is, however, the provision of a return conveyor 24 which moves at a speed greater than that of the mold blocks 16 and carriers 17 on tunnel conveyor 12.
The speed of blocks 16 and carriers 17 on tunnel conveyor 12 is dictated by the length of the conveyor, the speed of extrusion, the thickness and diameter and cooling conditions of the molded tube and on other parameters. On tunnel conveyor 12 the mold blocks 16 must lie with adjacent faces in contact to form the tunnel. On the return conveyor 24, however, these parameters do not apply and, therefore, a mold block 16 and carrier 17 may be peeled of the downstream end of the mold tunnel, speeded up and returned to the upstream end of the mold tunnel, at much greater speed than that of blocks on the tunnel conveyor 12.
Thus, for example, the mold tunnel may comprise ten mold blocks 16 on respective carriers 17, the length of the mold tunnel is 100 inches, each mold block having a thickness of 10 inches and width of say 50 inches. In this case, the distance of the removal, return and approach conveyors 22, 24, 26 is at least 50 + 100 + 50 inches. In practice, of course~ it will be more than this so that there is room for operating machinery between the tunnel and return conveyors 12, 24. In fact, it is emphasized that the numbers chosen for exemplification are only numbers chosen for simple calculation rather than examples of practical speeds and dimensions which may be used.
. . ' ' ' ' ~ ~ ' ~ . , ~ ,, , ' . . . ! . , .' ', In the example it will be seen that the total length of the return runs is 200 inches and the length of the tunnel run is 100 inches. If the speed of a block on tunnel conveyor 12, is 1 inch per minute it will take 10 minutes for a block 16 to move sufficiently far along tunnel conveyor 12 to allow the addition of another block 16 at that end.
If the average speed of block on the removal, return and approach conveyors is 22, 24, 26 is 10 inches per minute, it will take only 20 minutes for a block 16 to peel off the downstream end of the tunnel, and travel to the upstream end for readdition to the tunnel.
It may seem that unlike the systems of the prior art in which there were as many blocks on a return run as on a tunnel run, the present invention may offer the advantage of utilizing a lesser number of blocks on the removal, return and approach runs as on the tunnel run. This may result in reduction in manufacturing costs, material costs and running costs of equipment. Any such savings are of considerable importance in the provision, supply, and running of the heavy machinery necessary ~or the molding of large diameter pipe.
When the average speed of the removal, return and approach conveyors 22, 24, 26 are greater that that of the blocks 16 on the tunnel conveyor 12, it is thought that return conveyor 24 may conveniently run faster than the removal and approach conveyors 22, 26.
The position of hinge 28 and the comparative size of the mold block parts which are hinged together , - 16 - 2~
about the hinge are a matter of choice. However, it is found that the apparatus may of~er advantages for the molding of large diameter tube. For example, tube diameter greater than 12" is moldable using the method and apparatus according to the invention.
As shown in Figures 1, 3, 4, 5, 9 and 10 the hinge of each mold block 16 is located at the top of a mold block 16 and connects mold block parts 13, 15 each of which comprises roughly half the mold block 16 although a~y convenient propor-tion may be chosen.
When hinge 28 is at the top of the mold block, it is preferable to shape the fixed part 13 ~conveniently referred to as halves~, fixed half 13, so that it includes the whole of the base of the mold block which connects with carrier 17 in any conventional manner. Thus the guide blocks may suitably have the shape illustrated in Figures 3, 4 and 5. These guide blocks have faces 42, 43 adjoining the hinge 28 which are flush with each other when the guide block is closed to lie radially of the mold tunnel. These blocks also have faces 44, 45 which are flush with each other when the guide block is closed and spaced apart from one another when the guide block is open. These faces, when the guide block is closed, lie in a plane which is oblique to the radius of the tunnel.
~ guide block as shaped from two assymetric sectors as shown in Figures 3, 4 and 5 is advantageous in some respects in that it is easy to remove from the formed tube 200 As shown, with the hinge at the top most point of the block and the opening of the tunnel at the lower most point of the tunnel, the block is easily withdrawable from the tube in a direction ~ ~ . . .
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orthogonal to it, for e~ample, on the removal conveyor 22. When the block has this shape, there is no interference or dragging on the tube 20 when the opened block ]6 is pulled away from it.
Another desirable shape of mold block is shown in Figures 6 and 7. In this case, the two halves 13, 14 of the block 16 are symmetric and thus have advantages in manufacture. The hinge 28 is offset from the top of the mold block and fixed half 13 is attached carrier 17. In this case, both pairs of faces ~2, 43 and 44, 45 are radial to the tunnsl when the mold block is closed. However, because the hinge 28 is offset from the uppermost point of the mold block, the lower opening point of th~ mold block is not coincident with the lowermost point of the tunnel. Thus when an attempt is made to pull the mold block away from formed tube 20, it will tend to drag the tube 20 with it if is pulled in a strictly horizontal direction. In this case, it is desirable to adjust the level of removal conveyor 22 to be slightly lower than that of tunnel conveyor 21. The dif~ere~ce in height between tunnel conveyor 12 and removal conveyor 22 may be the same as the difference in height between the lower opening point 46 of the mold block and the lowest point of the tunnel 47. The conveyors 12, 22, 24 and 26 may all be in the same generally horizontal plane. Any slight reduction in height of conveyor 22 is being very slight and may be regarded as being within the same general horizontal plane as the upper runs of the other conveyors.
From conveyor 22 the mold blocks 16 and carriers 17 are transferred to return conveyor 2~
which may, as shown, run parallel and opposite to the direction of tunnel conveyor 12. On return conveyor . .~ .
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24, the mold blocks 16 and carriers 17 are again travelling in the direction of the tunnel axis and will probably, due to the speed, be close together in tunnel formation and, again linked through T-bars 100 and T-grooves 102. There is, however, no theoretical need to ensure that they fit tightly together with their upstream and downstream faces in tight flush fit. Nor is there a need to provide for accurate alignment of the tunnel. Therefore, for conveyor 24, there is no need to provide a track similar to track 3~.
At the end of conveyor 24 the mold blocks change direction again onto approach conveyor 26 in a similar manner to the changes of direction before described. When on approach conveyor 26, at least when approachi~g extrusion nozzle 18, it is important that the mold blocks be in open position, it is possible to start closing the mold blocks before they r~ach extrusion nozzle 18, provided there is sufficient clearance between the hinged half 14 and `
the extrusion nozzle as the mold moves into position for the start of another mold tunne:L run.
As the open mold block 16 approaches the beginning of the mold tunnel conveyor 12 and the e~trusion nozzle 18, it may be closed by any convenient means.
One means of openin~ and closing the mold blocks 16 is shown in Figure 1. A cam track 50 ma~
be provided following the general layout of conveyors 12, 22, 24, 26. Cam track may be of C-section to accept and retain the heads of 60 mushroom lugs 52 (exteriors) outNardly from hinged half 14 of each mold block. Along the tunnel conveyor 12, a continuous ~, .. ..
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cam track 50 opens inwardly and is located at a height lateral of the conveyor 12, as to maintain the mold blocks closed. As the downstream end of conveyor 12 approaches, cam track 50 rises to hingedly raise each mold hal~ 14 and open the mold block 16. The path of cam track 50 follows the track of the leads 60 of the mushroom lugs 52 and, as the mold blocks 16 changes -direction onto the removal conveyor, twists so that it opens downwardly. The cam track 50 may rise to hingedly raise the mold half 18 through 180 but this is not necessary. It may be easier to only open the mold block 16 sufficiently for removal of tube 20.
The cam track 50 may be maintained at this height over the removal conveyor 22, the return conveyor 24 and the approach conveyor 26. At the downstream ena of the approach conveyor 26, the cam track descends to close the mold block 16 and twists to open again towards the tunnel conveyor 12.
A preferred manner of opening and closing the mold blocks 16 is illustrated in Figures 8, 9, and 10, which illustrate a mold block 16 and a carrier 17 having mold opening mechanism carried by the carrier.
This mold opening mechanism comprises screw threaded vertical spindle 34 carried in an upstanding framework side 36 of carrier 17. At its lower end spindle 34 carries sprocket wheel 38 geared to actuating sprocket wheel 40.
Actuating sprocket wheel 40 may be powered by any convenient means such as an electric motor or other motor. Alternatively, at least on the tunnel run, a rack 46 may be provided so that motion of the carriers past the rack 46 will engage wheel 40 or 38 to turn spindle 34.
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2 ~ 6 :~ i Turning of spindle 34 in the direction shown by arrow B in Figure 9 will lower block 48 engaged on the spindle 34. Block 48 has an axle 62 projecting to either side of it carrying one end of an articulated arm 64, comprising a member 65 hinged to hinged mold block half 14, a member 66 hinged to fixed mold block - .
half 13, a rigid link 67 pivotally connected at its ~; , respective ends to members 65 and 66, and a member 68 pivotally connected at one end to member 66 and link 678 and, at the other end to block 48.
As block 48 descends spindle 34 the action of articulated arm 64 is to open mold block as shown in Figure 10.
The outer surface of mold blocks 16 may have cooling ribs 70.
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According to the invention, apparatus for continuous molding of thermoplastic extrudate e.g.
tube, in a travelling mold tunnel to form an elongate molding, comprises; a travelling tunnel mold assembly of adjacent mold blocks each mold block having a bore therethrough, the bores of adjacent mold blocks being aligned axially; each mold block comprising a pair pivotally connected parts whereby the parts are movable between a closed position of the block in which the bore is circumferentially enclosed, and an open position in which the parts are located with respect to each other to release elongate molding formed between them, a tunnel conveyor ~or the tunnel mold assembly to convey it horizontally and axially in a molding run between tunnel entrance and a t~nnel exit; means to open each mold ~lock as it reaches the tunnel exit; a removal conveyor arranged to move generally in the plane of the tunnel conveyor to receive and convey each opened mold block sequentially from the tunnel conveyor, each mold block being orientated with its bore parallel to the mold tunnel;
a return conveyor generally in the plane of the tunnel conveyor arranged to move hori~ontally parallel and opposite to the tunnel conveyor to receive and convey mold blocks sequentially from the removal conveyor, each mold block being orientated with its bore ' ' ' '' ~
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parallel to the mold tunnel; and an approach conve~or arranged to move horizontally and parallel to the removal conveyor, to convey mold blocks sequentially from the return conveyor, each mold block being orientated with its bore parallel to the mold tunnel;
and means to close the returned mold blocks to form the mold tunnel. The invention is ~nvisaged for use in the molding of semi-rigid plastic tube of the type used for underground drainage or for carrying electrical wiring. The cross-section of such tube is generally circular. For easy exchange of mold blocks for ones of different diameter, each mold block may be releasably carried on a mold block carrier of articulately interconnected mold block carriers.
Means may be provided to maintain the mold blocks closed on the tunnel conveyor. Such means may suitably be either guide fences to prevent the mold block parts pivoting awa~ from each other or a cam actuated latches between the mold parts.
When the cam actuated latch is provided, the latching cam may be located at the upstream end of the tunnel to engage a first cam surface of the latch to move it into a latching position as the respective mold block is conveyed on the tunnel conveyor past the cam, and an unlatching cam ma~ be located at the downstream end of the tunnel to engage a second cam surface of the latch to move it into a latching position as the respective mold block is conveyed or the tunnel conveyor past the cam. In effect, such a latch may be a toggle latch. ~nce the hinged parts of the mold blocks are unlatched, the mold blocks must physically open to release tube formed in the mold tunnel. This may be achieved through mold block opening cam means provided at the downstream end of the tunnel, adapted to interact with a cam surface of ?
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one mold block part to pivot it with respect to the other mold block part to release the tube. Once~ the tube has been released, the mold blocks may travel on the removal return and approach conveyors, in either open or closed condition. However, since the mold blocks must open to receive an extrusion nozzle into ~ ~-the tunnel, it~is convenient to maintain the mold blocks open on the removal, return and approach conveyors. At the upstream end of the tunnel, mold blocks pivotally close under gravity. Preferably, such closing is in a controlled manner and mold block closing cam means may be provided to interact with a cam surface of each mold block to close it as it moves into position as part of the mold tunnel.
A change of direction is involved between different conveyors and guide means may be provided to guide the mold blocks from one conveyor to the next.
Such guide means may comprise a curved guide rails at outer corners between each conveyor.
The hinging of the mold block parts may be by any convenient arrangement. However, two such arrangements, referred to as e~emplary, are envisaged. In both arrangement, the hinge is provided near the top of the mold block, but in one case it is right at the top, and, in the other case, it is offset from the top. In each case, one fixed part of each pair of mold block parts is, in use, attached at its base to its respective mold block carrier. In the case where the hinge is at the top of the mold block, abutting faces of the block of the fixed and movable parts distant from the hinge, lie in a plane oblique to the radius of the bore. By this means it is possible to attach the fixed part over a stable base area. Moreovsr, connection between the fixed and " ,, , :
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`` 2 ~ 6 1 movable parts on the outside of the mold block may be offset from the direct bottom, thus allowing access to latching means. In the case where the hinge is offset from the top of the mold block, the fixed and movable parts may be symmetric. The face abutting faces may be radial and offset from the bottom of the mold block diametrically opposite the hinge. When this is so, it may be necessary to lower the mold block slightly to release tube from the slightly upstanding edge of the fixed mold block. This may be achieved by making the conveyor run descend slightly. In this case, means are provided to lower the mold blocks on the tunnel conveyor to release formed tube from the face of the fixed mold part offset from the base. In any case, it may be convenient to provide ramps between conveyors.
The invention also provides a method for forming tube in a travelling mold tunnel comprising;
extruding parison of thermoplastic extrudate into a travelling tunnel mold assembly wherein each tunnel segment comprises a mold block having a bore therethrough, the bores of adjacent mold blocks being aligned axially; each mold block comprising a pair of pivotally connected parts whereby the parts are movable between a closed position of the block in which the bore is circumferentially enclosed, and an open position in which the parts are located, with respect to each other, to release ~ube formed between them; a conveying tunnel mold assembly to convey it horizontally and axially in a molding run from between a tunnel entrance and a tunnel exit; opening each mold block as it reaches the tunnel exit; returning each mold block from the tunnel exit to the tunnel entrance upstream of the tunnel return path oriented to be added to the tunnel entrance; and closing the returned mold blocks to form the mold tunnel.
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Embodiments of the invention will now be described by way of examplP with reference to the drawings in which:
Figure 1 is a perspective view of an embodiment of apparatus according to the invention;
Figure 2 shows a plan view of the general layout for another embodiment apparatus of the invention;
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Figure 3 is an enlarged view showing one example of a mold block and carrier which may be used with apparatus according to the ~:
invention, for example as illustrated in Figure l;
Figure 4 is a cross section of the mold ~.
block and carrier of Figure 3 in its closed position;
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Figure 5 is a similar cross section of the mold block of Figure 4 i.n the open position;
Figure 6 is a cross section through another mold block and carrier in the closed position and suitable for use with apparatus as illustrated in Figure l;
Figure 7 is a cross section through the block of Figure 6 in the open position;
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Figure 8 is a view of carriers, suitable for use in apparatus as illustrated in Figure 2;
Figure 9 is a view of another closed mold block in combination with a carrier as shown in Figure 8 indicating mold opening and closing mechanism; and Figure lO is a view of the mold block of Figure 9 in the open position.
In the drawings, Figure l shows a general view of apparatus embodying the invention which may comprise a tunnel conveyor 12 along which travels a tunnel mold assembly 14, segments of which are hinged ~;
mold blocks 16 of which are closed in the tunnel mold assembly over the majority of tunnel run of a conveyor 12. Each mold block 16 comprises a fi~ed half 13 and a hinged half 15 and each has a carrier block 17 which may be driven to move along the conveyor 12 in a rnanner to be described hereafter. At an upstream and of the tunnel assembly 14, an extrusion nozzle 18 enters the tunnel to extrude an annular parison l9 of thermoplastic material to form tube 20 within the tunnel. At the downstream end of the tunnel assembly, tube 20 emerges from the tunnel. Also at the downstream end of the tunnel, mold blocks 16 open hingeably to release tube 20 and are returned to the upstream end of the tunnel conveyor 12 by means of a removal conveyor 22, a return conveyor 24 and an approach conveyor 26. Conveniently, the tunnel conveyor 12 and the removal conveyor 22, the return conveyor 24 and the approach conveyor 26 are laid out in the general form of a rectangle, the upper runs of ,, , .. ... . " . . . , , ., " .~ . , .- . - .
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each conveyor being at least generally in the same horizontal plane. While the speeds of the various conveyors may be coordinated to return mold blocks to the tunnel conveyor at a suitable speed to form the tunnel assembl~ 14 on the tunnel conveyor, in a practical embodiment the tunnel conveyor comprises a stationary track along which the mold bloc~s 16 are j driven via their carriers 17. i~
On the removal, return and approach conveyors 22, 2~ and 26 the mold blocks may travel in either an open or closed condition. However, since the mold blocks must open to release tube 20, and must ba open in order to close around extrusion nozzle 18, it may normally be convenient for them to travel on at least most of the route back to the upstream end of the tunnel conveyor 12 in the open condition. Mold blocks halves may open as much as 180 to each other or even more. However, it is normally convenient that they onl~ open widely enough to release tube 20 from between them.
When assembled into mold tunnel assembly 1 on tunnel conveyor 12, it is important that the mold blocks 16 have upstream faces and downstream faces ll in contact with one another to form a closed tunnel in the longitudinal direction. It may normally be sufficient to press the mold blocks ~irmly togethe~ on this run but it may be advantageous to mechanically link the carriers, as for instance, by the illustrated tongue 100 and groove 102 connections between them as seen ~rom Figure 8. The halves 13, 15 of each mold block 16 must, on the tunnel run tightly closed about the hinge 28 so that the tunnel is also tightly closed around its circumference, and must reliably open to release tube 20. This may be achieved by various ~ .
means, for example the cam arrangemen-t 50, 5a shown in Figure 1 or the mechanism 104 shown in Figures 9 and 10 .
The alignment of the mold blocks 16 on the tunnel conveyor 12 is also important so that the extrusion nozzle 18 is accurately centered in the tunnel ~or accuracy in molding the tube 20.
Conveniently, a track 30 is provided on tunnel conveyor 12 for engagement with a corresponding part 31 of each carrier 17 for guidance and location of mold block 16. The track 30 may be in the form of an upstanding rail to cooperate with a groove 31 shaped slot 31 o each mold block. The rail 30 may house a source of suction and suction passages 33 through carrier 17 may connect suction ports 35 o the rail 30 with suction passages 37 in the mold block 16 leading to its interior. The provision of suction to the interior of the tunnèl may be provided in a similar manner to that described in any of U.S. patent No. 4,319,872 or Canadian patent No. 1,083,765, these patents are directed to a travelling mold comprising mold blocks through which suction may be applied, , although all of the patents are limited to the use of two conveyor systems, one for each of two runs of half mold blocks. Nevertheless, th~ provisions of suction means within guides for the mold blocks may be regarded as similar.
Suitably the carriers 17 "wrap around" the track 30 at its edges, or around an additional edge tracks 39, by means of an inwardly extending flange 41, to prevent accidental disengagement of the carriers 17 and blocks 16. The length o the tunnel conveyor and the length of the tunnel assembly 14 should be suficient for extruded annular ,. .. - : .
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.: , thermoplastic parison to set into tube 20 of sufficient rigidity or th~ removal of mold blocks 16 without permanent distortion of the tube. Cooling plugs, and other forming means for the inside surface of the tube may be provided in a conventi-onal manner supported on an inner core extending coaxially from the extrusion nozzle. For simplicity, such devices are not illustrated. However, additional cooling means is possible on the outer surface of the mold, as for example, by ribs 106 on its outer surface as shown in Figure 9. Cooling water may be flowed over the exterior of the closed mold tunnel assembly to aid cooling and drain channels 108 may be provided for the water.
When the mold assembly has remained closed over a sufficient length ~or the tube to set, the mold blocks may be opened by hinging each of them about its hinge 28. Once open, the blocks may be removed from the tube, for example, orthogonally therefrom along removal conveyor 22. While, as already commented, the speeds of the various conveyors should be coordinated, there is no particular reason for accurate alignment of the mold blocks 16 in tunnel formation on any of the removal conveyor 22, the return conveyor or the approach conveyor.
In practice, it is convenient that removal conveyor 22 runs at an angle of slightly more than 90 to the tunnel conveyor and that mol~ blocks are located on it with their tunnel axis not quite aligned with the directional axis of conveyor 22. Thus, the orientation of mold blocks 16 is the same as on tunnel conveyor 12 so that they are set at a slight angle on conveyor 22. On tunnel 12 mold blocks 16 more in the direction of the tunnel axis. Whereas, on conveyor ~7 ; :
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-- 2~0~1 - lZ -they move in a direction at slightly greater than 90 to the tunnel axis of each block 16.
It is convenient to remove the mold blocks 16 in a direction parallel with the upstream faces and the downstream faces 17 and, although sufficient guidance means should be provided to prevent them falling off the conveyor, there is no need for accurate guide means such as track 30. The guidance means may conveniently ~e chains 110. The provision of a guide rail 32 extending alongside removal conveyor 22 and, at least partially, alongside tunnel conveyor 12 may be useful in some instances.
When a tongue 100 and groove 102 linkage is provided between mold blocks carriers 17 (See Figure 8) on the tunnel run, this linkage must be disconnected to allow the carriers 17 with their associated blocks 16 to travel essentially edge to edge on the removal run rather than face to face.
The linkage may comprise a rail of T-shaped cross section or, as illustrated an aligned pair of lugs 100 o~ T-shaped cross section on one tunnel face of a carrier, e.g. the downstream face 11 and a corresponding T-shaped groove 102 in the other face.
When travelling in the tunnel direction the T-groove 102 interlocks the T-rail 100 to hold faces of ad~acent blocks in register. However, when a block 16 and its associated carrier 17 are subjected to an approximate gO change of direction without change of orientation, as indicated, for example, by the arrow A
in Figure 8, (or in the 180 direction), then T-members 100 will slide out of T-grooves 102 to unlatch the carriers and allow them to move away in the new direction.
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~ rhe movement of carriers 17 ~and hence blocks 16) on the tunnel conveyor may be by means of driven sprocket wheels 32 which mesh with lugs 112 provided on one, or as illustrated both, sides of carriers 17. Such sprocket wheels 32 at the upstream of the tunnel run may conveniently drive the entire tunnel train of carriers 17 and mold blocks 16.
Movement of the carriers and mold blocks on removal 22, return 24, and approach 26 conveyors may be by any convenient means. However, it is to be noted that similar sprocket wheels may be used on the return run and chains 110 which may run on sprocket wheels 114 driven in any convenient manner. For additional ease in transition from one direction to another, where one conveyor adjoins another conveyor travelling in a different direction, ramps may be provided in the conveyors.
Even when the apparatus is used for molding pipe of small diameter, the thickness between its faces is usually considerably less than the width of ~ -the block across the horizontal diameter of the mold tunnel. In fact, the apparatus is suitable for the molding of large diameter tube and, for mold blocks for molding large diameter tube, the difference between the thickn0ss of the block and the width of the block is considerable.
Since the blocks move in the direction of their thickness on the closed mold tunnel run on tunnel conveyor 12 and in the general direction of their width on the removal and approach conve~ors 22, 26, it is clear that the speed of conveyors 22 and 26 will be greater than that of the mold blocks on tunnel conveyor 12 at least by an amount sufficient to ., , ' : ~ .. ' '': ' ~ ;
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accommodate the difference between their thickness and their width.
An important feature of the invention is, however, the provision of a return conveyor 24 which moves at a speed greater than that of the mold blocks 16 and carriers 17 on tunnel conveyor 12.
The speed of blocks 16 and carriers 17 on tunnel conveyor 12 is dictated by the length of the conveyor, the speed of extrusion, the thickness and diameter and cooling conditions of the molded tube and on other parameters. On tunnel conveyor 12 the mold blocks 16 must lie with adjacent faces in contact to form the tunnel. On the return conveyor 24, however, these parameters do not apply and, therefore, a mold block 16 and carrier 17 may be peeled of the downstream end of the mold tunnel, speeded up and returned to the upstream end of the mold tunnel, at much greater speed than that of blocks on the tunnel conveyor 12.
Thus, for example, the mold tunnel may comprise ten mold blocks 16 on respective carriers 17, the length of the mold tunnel is 100 inches, each mold block having a thickness of 10 inches and width of say 50 inches. In this case, the distance of the removal, return and approach conveyors 22, 24, 26 is at least 50 + 100 + 50 inches. In practice, of course~ it will be more than this so that there is room for operating machinery between the tunnel and return conveyors 12, 24. In fact, it is emphasized that the numbers chosen for exemplification are only numbers chosen for simple calculation rather than examples of practical speeds and dimensions which may be used.
. . ' ' ' ' ~ ~ ' ~ . , ~ ,, , ' . . . ! . , .' ', In the example it will be seen that the total length of the return runs is 200 inches and the length of the tunnel run is 100 inches. If the speed of a block on tunnel conveyor 12, is 1 inch per minute it will take 10 minutes for a block 16 to move sufficiently far along tunnel conveyor 12 to allow the addition of another block 16 at that end.
If the average speed of block on the removal, return and approach conveyors is 22, 24, 26 is 10 inches per minute, it will take only 20 minutes for a block 16 to peel off the downstream end of the tunnel, and travel to the upstream end for readdition to the tunnel.
It may seem that unlike the systems of the prior art in which there were as many blocks on a return run as on a tunnel run, the present invention may offer the advantage of utilizing a lesser number of blocks on the removal, return and approach runs as on the tunnel run. This may result in reduction in manufacturing costs, material costs and running costs of equipment. Any such savings are of considerable importance in the provision, supply, and running of the heavy machinery necessary ~or the molding of large diameter pipe.
When the average speed of the removal, return and approach conveyors 22, 24, 26 are greater that that of the blocks 16 on the tunnel conveyor 12, it is thought that return conveyor 24 may conveniently run faster than the removal and approach conveyors 22, 26.
The position of hinge 28 and the comparative size of the mold block parts which are hinged together , - 16 - 2~
about the hinge are a matter of choice. However, it is found that the apparatus may of~er advantages for the molding of large diameter tube. For example, tube diameter greater than 12" is moldable using the method and apparatus according to the invention.
As shown in Figures 1, 3, 4, 5, 9 and 10 the hinge of each mold block 16 is located at the top of a mold block 16 and connects mold block parts 13, 15 each of which comprises roughly half the mold block 16 although a~y convenient propor-tion may be chosen.
When hinge 28 is at the top of the mold block, it is preferable to shape the fixed part 13 ~conveniently referred to as halves~, fixed half 13, so that it includes the whole of the base of the mold block which connects with carrier 17 in any conventional manner. Thus the guide blocks may suitably have the shape illustrated in Figures 3, 4 and 5. These guide blocks have faces 42, 43 adjoining the hinge 28 which are flush with each other when the guide block is closed to lie radially of the mold tunnel. These blocks also have faces 44, 45 which are flush with each other when the guide block is closed and spaced apart from one another when the guide block is open. These faces, when the guide block is closed, lie in a plane which is oblique to the radius of the tunnel.
~ guide block as shaped from two assymetric sectors as shown in Figures 3, 4 and 5 is advantageous in some respects in that it is easy to remove from the formed tube 200 As shown, with the hinge at the top most point of the block and the opening of the tunnel at the lower most point of the tunnel, the block is easily withdrawable from the tube in a direction ~ ~ . . .
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orthogonal to it, for e~ample, on the removal conveyor 22. When the block has this shape, there is no interference or dragging on the tube 20 when the opened block ]6 is pulled away from it.
Another desirable shape of mold block is shown in Figures 6 and 7. In this case, the two halves 13, 14 of the block 16 are symmetric and thus have advantages in manufacture. The hinge 28 is offset from the top of the mold block and fixed half 13 is attached carrier 17. In this case, both pairs of faces ~2, 43 and 44, 45 are radial to the tunnsl when the mold block is closed. However, because the hinge 28 is offset from the uppermost point of the mold block, the lower opening point of th~ mold block is not coincident with the lowermost point of the tunnel. Thus when an attempt is made to pull the mold block away from formed tube 20, it will tend to drag the tube 20 with it if is pulled in a strictly horizontal direction. In this case, it is desirable to adjust the level of removal conveyor 22 to be slightly lower than that of tunnel conveyor 21. The dif~ere~ce in height between tunnel conveyor 12 and removal conveyor 22 may be the same as the difference in height between the lower opening point 46 of the mold block and the lowest point of the tunnel 47. The conveyors 12, 22, 24 and 26 may all be in the same generally horizontal plane. Any slight reduction in height of conveyor 22 is being very slight and may be regarded as being within the same general horizontal plane as the upper runs of the other conveyors.
From conveyor 22 the mold blocks 16 and carriers 17 are transferred to return conveyor 2~
which may, as shown, run parallel and opposite to the direction of tunnel conveyor 12. On return conveyor . .~ .
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24, the mold blocks 16 and carriers 17 are again travelling in the direction of the tunnel axis and will probably, due to the speed, be close together in tunnel formation and, again linked through T-bars 100 and T-grooves 102. There is, however, no theoretical need to ensure that they fit tightly together with their upstream and downstream faces in tight flush fit. Nor is there a need to provide for accurate alignment of the tunnel. Therefore, for conveyor 24, there is no need to provide a track similar to track 3~.
At the end of conveyor 24 the mold blocks change direction again onto approach conveyor 26 in a similar manner to the changes of direction before described. When on approach conveyor 26, at least when approachi~g extrusion nozzle 18, it is important that the mold blocks be in open position, it is possible to start closing the mold blocks before they r~ach extrusion nozzle 18, provided there is sufficient clearance between the hinged half 14 and `
the extrusion nozzle as the mold moves into position for the start of another mold tunne:L run.
As the open mold block 16 approaches the beginning of the mold tunnel conveyor 12 and the e~trusion nozzle 18, it may be closed by any convenient means.
One means of openin~ and closing the mold blocks 16 is shown in Figure 1. A cam track 50 ma~
be provided following the general layout of conveyors 12, 22, 24, 26. Cam track may be of C-section to accept and retain the heads of 60 mushroom lugs 52 (exteriors) outNardly from hinged half 14 of each mold block. Along the tunnel conveyor 12, a continuous ~, .. ..
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cam track 50 opens inwardly and is located at a height lateral of the conveyor 12, as to maintain the mold blocks closed. As the downstream end of conveyor 12 approaches, cam track 50 rises to hingedly raise each mold hal~ 14 and open the mold block 16. The path of cam track 50 follows the track of the leads 60 of the mushroom lugs 52 and, as the mold blocks 16 changes -direction onto the removal conveyor, twists so that it opens downwardly. The cam track 50 may rise to hingedly raise the mold half 18 through 180 but this is not necessary. It may be easier to only open the mold block 16 sufficiently for removal of tube 20.
The cam track 50 may be maintained at this height over the removal conveyor 22, the return conveyor 24 and the approach conveyor 26. At the downstream ena of the approach conveyor 26, the cam track descends to close the mold block 16 and twists to open again towards the tunnel conveyor 12.
A preferred manner of opening and closing the mold blocks 16 is illustrated in Figures 8, 9, and 10, which illustrate a mold block 16 and a carrier 17 having mold opening mechanism carried by the carrier.
This mold opening mechanism comprises screw threaded vertical spindle 34 carried in an upstanding framework side 36 of carrier 17. At its lower end spindle 34 carries sprocket wheel 38 geared to actuating sprocket wheel 40.
Actuating sprocket wheel 40 may be powered by any convenient means such as an electric motor or other motor. Alternatively, at least on the tunnel run, a rack 46 may be provided so that motion of the carriers past the rack 46 will engage wheel 40 or 38 to turn spindle 34.
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2 ~ 6 :~ i Turning of spindle 34 in the direction shown by arrow B in Figure 9 will lower block 48 engaged on the spindle 34. Block 48 has an axle 62 projecting to either side of it carrying one end of an articulated arm 64, comprising a member 65 hinged to hinged mold block half 14, a member 66 hinged to fixed mold block - .
half 13, a rigid link 67 pivotally connected at its ~; , respective ends to members 65 and 66, and a member 68 pivotally connected at one end to member 66 and link 678 and, at the other end to block 48.
As block 48 descends spindle 34 the action of articulated arm 64 is to open mold block as shown in Figure 10.
The outer surface of mold blocks 16 may have cooling ribs 70.
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Claims (23)
1. Apparatus for continuous molding of thermoplastic extrudate in a travelling mold tunnel to form an elongate molding, comprising;
a travelling tunnel mold assembly of adjacent mold blocks each mold block having a bore therethrough, the bores of adjacent mold blocks being aligned axially;
each mold block comprising a pair of pivotally connected parts whereby the parts are movable between a closed position of the block in which the bore is circumferentially enclosed, and an open position in which the parts are located with respect to each other to release elongate molding formed between them;
a tunnel conveyor for the tunnel mold assembly to convey it horizontally and axially in a molding run between a tunnel entrance and a tunnel exit;
means, to open each mold block as it reaches the tunnel exit;
a removal conveyor arranged to move generally in the plane of the tunnel conveyor to receive and convey each opened mold block sequentially from the tunnel conveyor, each mold block being orientated with its bore parallel to the mold tunnel;
a return conveyor generally in the plane of the tunnel conveyor arranged to move horizontally parallel and opposite to the tunnel conveyor to receive and convey mold blocks sequentially from the removal conveyor, each mold block (16) being orientated with its bore parallel to the mold tunnel;
and an approach conveyor generally the plane of the tunnel conveyor arranged to move horizontally and parallel to the removal conveyor, to convey mold blocks (16) sequentially from the return conveyor, each mold block being orientated with its bore parallel to the mold tunnel;
means to close the returned mold blocks to form an upstream end of the mold tunnel;
the removal, return and approach conveyors being operable at on average speed greater than that of the mold blocks on the tunnel conveyor and being adjusted to return a mold block to add to the upstream tunnel assembly; and
a travelling tunnel mold assembly of adjacent mold blocks each mold block having a bore therethrough, the bores of adjacent mold blocks being aligned axially;
each mold block comprising a pair of pivotally connected parts whereby the parts are movable between a closed position of the block in which the bore is circumferentially enclosed, and an open position in which the parts are located with respect to each other to release elongate molding formed between them;
a tunnel conveyor for the tunnel mold assembly to convey it horizontally and axially in a molding run between a tunnel entrance and a tunnel exit;
means, to open each mold block as it reaches the tunnel exit;
a removal conveyor arranged to move generally in the plane of the tunnel conveyor to receive and convey each opened mold block sequentially from the tunnel conveyor, each mold block being orientated with its bore parallel to the mold tunnel;
a return conveyor generally in the plane of the tunnel conveyor arranged to move horizontally parallel and opposite to the tunnel conveyor to receive and convey mold blocks sequentially from the removal conveyor, each mold block (16) being orientated with its bore parallel to the mold tunnel;
and an approach conveyor generally the plane of the tunnel conveyor arranged to move horizontally and parallel to the removal conveyor, to convey mold blocks (16) sequentially from the return conveyor, each mold block being orientated with its bore parallel to the mold tunnel;
means to close the returned mold blocks to form an upstream end of the mold tunnel;
the removal, return and approach conveyors being operable at on average speed greater than that of the mold blocks on the tunnel conveyor and being adjusted to return a mold block to add to the upstream tunnel assembly; and
2. Apparatus as claimed in claim 1 in which the number of mold blocks present at any time on the combined removal, return and approach conveyors is less than that of the mold tunnel assembly.
3. Apparatus as claimed in claim 2 in which means are provided to maintain the mold blocks closed on the tunnel conveyor.
4. Apparatus as claimed in claim 3 in which the means comprises a cam actuated latch between the mold parts.
5. Apparatus as claimed in claim 3 in which the cam actuated to maintain the mold blocks closed comprises a cam channel slidably engaging a lug of each mold block.
6. Apparatus as claimed in claim in which the cam channel is continuous and is located at a height above the conveyors to maintain mold blocks closed during travel along the tunnel conveyor and open on the removal, return and approach conveyors.
7. Apparatus as claimed in claim 2 in which the means to open the mold block and the means to close the mold blocks comprises a rotatable screw threaded spindle on each mold block carrier, a member screw threadedly engaging the spindle for axial adjustment of its location thereon by rotation of the spindle , and articulated linkage between said member and the respective mold block (16) pivotally connected parts for opening and closing of the mold blocks a dependance on the axial location of said member.
8. Apparatus as claimed in claim 7 in which the spindle is driven in an opening direction for the mold blocks by a gear wheel engaging a rack located on the tunnel conveyor.
9. Apparatus as claimed in claim 2, in which one fixed part of each pair of mold block parts is, in use, attached at its base to its respective mold block carrier, and is provided with a hinge (28) at the top of the mold block for pivotal connection with the other movable part (15) of said pair.
10. Apparatus as claimed in claim 9 in which abutting faces of the fixed and movable mold block parts distant from the hinge lie in a plane oblique to the radius of the bore.
11. Apparatus as claimed in claim 2 in which one fixed part of each pair of mold blocks is, in use, attached at an attachment point of its respective carrier, and is provided with a hinge offset from the top of the mold block for pivotal connection with the other movable part of said pair.
12. Apparatus as claimed in claim 11 in which abutting faces distant from the hinge of the fixed part and the movable part (15) are offset from the base of the mold block and radially arranged and diametric with hinge faces of the fixed and movable parts.
13. Apparatus as claimed in claim 12 in which, at the downstream end of the tunnel and downstream of the means to open each mold block, means are provided to lower the mold blocks on the tunnel conveyor to release formed tube from the face of the fixed mold part offset from the base.
14. Apparatus as claimed in claim 2 in which the tunnel conveyor comprises a fixed guide and drive means are provided to drive mold blocks to move over the guide.
15. Apparatus as claimed in claim 14 in which the drive means comprise a drive sprocket wheel sequentially engaging drive tugs projecting from each mold block carrier.
16. Apparatus as claimed in claim 2 in which engagement means are provided for sliding engagement of adjacent mold blocks on the tunnel conveyor.
17. Apparatus as claimed in claim 16 in which the engagement means comprises for each mold block, a groove along one of a leading edge and a tracking edge of each mold block carrier and a tongue adapted to make with the groove of the other of the leading and tracking edges.
18. A method for continuous molding of thermoplastic extrudate in a travelling mold tunnel to-form an elongate molding, comprising;
extruding a parison of thermoplastic extrudate into a travelling tunnel mold assembly of adjacent mold blocks each mold block having a bore therethrough, the bores of adjacent mold blocks being aligned axially;
each mold block (16) comprising a pair pivotally connected parts (13, 15) whereby the parts are movable between a closed position of the block in which the bore is circumferentially enclosed, and an open position in which the parts are located, with respect to each other, to release elongate molding (20) formed between them;
conveying the tunnel mold assembly horizontally and axially in a molding run from between a tunnel entrance and a tunnel exit;
opening each mold block as it reaches the tunnel exit;
returning each mold block on a return path from the tunnel exit to the tunnel entrance upstream of the tunnel return path, the mold block being oriented with its bore parallel to the tunnel axis during travel on the return path to be added to the tunnel entrance, the average speed of mold blocks on the return path being greater than that of mold blocks in the tunnel assembly, the following steps;
removing opened mold blocks from the tunnel conveyor onto a removal conveyor (22) generally running in the plane of the tunnel conveyor, and receiving and conveying each opened mold block sequentially from the tunnel conveyor (12), each mold block being orientated with its bore parallel to the mold tunnel; and transferring the opened mold blocks (16) from the removal conveyor to a return conveyor generally in the plane of the tunnel conveyor running horizontally parallel and opposite to the tunnel conveyor, and receiving and conveying mold blocks sequentially from the removal conveyor, each mold block being orientated with its bore parallel to the mold tunnel;
transferring the mold blocks from the return conveyor to an approach conveyor (26) generally in the plane of the tunnel conveyor running horizontally and parallel to the removal conveyor, receiving and conveying mold blocks sequentially from the return conveyor, each mold block being orientated with its bore parallel to the mold tunnel;
and closing the returned mold blocks to form the mold tunnel.
extruding a parison of thermoplastic extrudate into a travelling tunnel mold assembly of adjacent mold blocks each mold block having a bore therethrough, the bores of adjacent mold blocks being aligned axially;
each mold block (16) comprising a pair pivotally connected parts (13, 15) whereby the parts are movable between a closed position of the block in which the bore is circumferentially enclosed, and an open position in which the parts are located, with respect to each other, to release elongate molding (20) formed between them;
conveying the tunnel mold assembly horizontally and axially in a molding run from between a tunnel entrance and a tunnel exit;
opening each mold block as it reaches the tunnel exit;
returning each mold block on a return path from the tunnel exit to the tunnel entrance upstream of the tunnel return path, the mold block being oriented with its bore parallel to the tunnel axis during travel on the return path to be added to the tunnel entrance, the average speed of mold blocks on the return path being greater than that of mold blocks in the tunnel assembly, the following steps;
removing opened mold blocks from the tunnel conveyor onto a removal conveyor (22) generally running in the plane of the tunnel conveyor, and receiving and conveying each opened mold block sequentially from the tunnel conveyor (12), each mold block being orientated with its bore parallel to the mold tunnel; and transferring the opened mold blocks (16) from the removal conveyor to a return conveyor generally in the plane of the tunnel conveyor running horizontally parallel and opposite to the tunnel conveyor, and receiving and conveying mold blocks sequentially from the removal conveyor, each mold block being orientated with its bore parallel to the mold tunnel;
transferring the mold blocks from the return conveyor to an approach conveyor (26) generally in the plane of the tunnel conveyor running horizontally and parallel to the removal conveyor, receiving and conveying mold blocks sequentially from the return conveyor, each mold block being orientated with its bore parallel to the mold tunnel;
and closing the returned mold blocks to form the mold tunnel.
19. A method as claimed in claim 19 in which the speeds of each of the removal, return and approach conveyors is greater than that of the tunnel assembly.
20. A method as claimed in claim 19, including latching the mold blocks closed on the tunnel conveyor.
21. A method as claimed in claim 20, in which the mold blocks are opened at the tunnel exit by a cam channel slidably engaging a lug of each mold block the channel rising to lift the respective mold block part and thereby open the mold block.
22. A method as claimed in claim 21, in which the mold blocks are maintained open on the removal, return and approach conveyors.
23. A method as claimed in claim 22 in which mold blocks (16) are opened and closed through rotation of a screw threaded spindle acting to adjust the axial location of a member in screw threaded engagement therewith, through articulated linkage with the respective mold block parts.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2040461 CA2040461A1 (en) | 1991-04-15 | 1991-04-15 | Hinged mold block conveyors in tube making apparatus |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2040461 CA2040461A1 (en) | 1991-04-15 | 1991-04-15 | Hinged mold block conveyors in tube making apparatus |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2040461A1 true CA2040461A1 (en) | 1992-10-16 |
Family
ID=4147402
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2040461 Abandoned CA2040461A1 (en) | 1991-04-15 | 1991-04-15 | Hinged mold block conveyors in tube making apparatus |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2040461A1 (en) |
-
1991
- 1991-04-15 CA CA 2040461 patent/CA2040461A1/en not_active Abandoned
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| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Dead |