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Title:
BAGGING ARRANGEMENT FOR SYNTHETIC RESIN COMPONENT PROCESSING APPARATUS
Document Type and Number:
WIPO Patent Application WO/1991/015351
Kind Code:
A1
Abstract:
Component processing apparatus for curing and/or moulding synthetic resin composites in the production of components comprises a component support (11) on which a component (15) is mounted and on which is formed at or in the region of its periphery a sealing edge (14) extending around the periphery of the support (11), and a bagging arrangement for use with the support (11) comprising a collapsible bagging blanket (8) which in use is extended across the component (15) and the component support (11) and which is tensioned to bring it into engagement with the sealing edge (14) on the support. The component support is made re-entrant beyond the sealing edge (14) to form a re-entrant zone and the blanket (8) is so formed as to receive and receives at its periphery draw means (19) by which the length of the blanket periphery can be varied from an extended length which allows the blanket (8) to be placed over the component (15) and the component support (11) and into a covering disposition in which it covers the component (15) and the component suppport (11) and in which the blanket periphery extends beyond the sealing edge (14) on the component support (11) to a reduced length which in the covering disposition of the blanket (8) brings the blanket periphery into the re-entrant zone and the blanket (8) against the sealing edge (14) on the component support (11).

Inventors:
WILSON ROBERT SAMUEL (GB)
DAVIS WILLIAM PAUL (GB)
Application Number:
PCT/GB1991/000521
Publication Date:
October 17, 1991
Filing Date:
April 04, 1991
Export Citation:
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Assignee:
SHORT BROTHERS PLC (GB)
International Classes:
B29B13/00; B29C43/10; B29C43/36; B29C70/06; B29C70/44; B29C43/12; (IPC1-7): B29C43/36; B29C67/14
Foreign References:
US4664737A1987-05-12
AU6366586A1987-08-13
EP0098527A21984-01-18
GB2196907A1988-05-11
Download PDF:
Claims:
CLAIMS
1. Component processing apparatus comprising a component support on which a component is mounted and on which is formed at or in the region of its periphery a sealing edge extending around the periphery of the support, and a bagging arrangement for use with the support comprising a collapsible bagging blanket which in use is extended across the component and the component support and which is tensioned to bring it into engagement with the sealing edge on the support, characterised by the fact that the component support is reentrant beyond the sealing edge to form a reentrant zone and that the blanket is so formed as to receive and receives at its periphery draw means by which the length of the blanket periphery can be varied from an extended length which allows the blanket to be placed over the component and the component support and into a covering disposition in which it covers the component and the component support and in which the blanket periphery extends beyond the sealing edge on the component support to a reduced length which in the covering disposition of the blanket brings the blanket periphery into the re¬ entrant zone and the blanket against the sealing edge on the component support.
2. Apparatus according to claim 1, wherein the draw means permits the blanket periphery to maintain its extended length and is contractible to bring the blanket periphery to its reduced length.
3. Apparatus according to claim 2 wherein the draw means comprises an elongate draw element which is received by the blanket along the full periphery of the blanket.
4. Apparatus according to claim 3, wherein the draw element is exposed at one or more predetermined exposed locations along the periphery of the blanket.
5. Apparatus according to claim 4, wherein the predetermined exposed location or one or more of the predetermined exposed locations is a draw location at which the effective length of the draw element can be reduced.
6. Apparatus according to claim 5 wherein the draw element is secured to the blanket at securing locations along the blanket periphery whereby a reduction in the effective length of the draw element at a draw location produces a local reduction in the length of the blanket periphery.
7. Apparatus according to claim 6 wherein the periphery of the blanket is folded back on itself and so secured as to provide a passageway for the draw element through which the draw element passes and the periphery of the blanket is cut away at the exposed location or locations to expose the draw element.
8. Apparatus according to claim 6 or 7 wherein draw locations are so arranged in spaced relation around the periphery of the blanket that reduction in the length of the draw element can be made to provide an even tensioning of the blanket over the component and the component support.
9. Apparatus according to any of claims 3 to 8 comprising a draw device at a draw location, through which the draw element passes to form an open loop at the draw location and which includes loop enlarging means whereby the loop can be enlarged to reduce the effective length of the draw element.
10. Apparatus according to claim 9 wherein the draw device comprises a support plate and the loop enlarging means comprises a plurality of spaced pins carried by the support plate extending away from one side of the plate, and wherein the draw element is arranged to pass along the plate in a plane parallel to the plate so that it can be withdrawn on the side of the plate carrying the pins and formed into a loop by passage round one or more of the pins.
11. Apparatus according to claim 9 wherein the draw device comprises one or more guide elements for forming the draw element into a loop and the loop enlarging means comprises a member movable from a first predetermined disposition relative to the guide element or elements to a second predetermined disposition relative to the guide element or elements, wherein the draw element passes through the guide element or elements to form the loop and wherein the movable member is arranged to engage the loop to cause the loop to enlarge by movement of the moveable member from the first predetermined disposition to the second predetermined disposition.
12. Apparatus according to claim 11 wherein the moveable member includes resilient means for moving it from the first predetermined disposition to the second predetermined disposition.
13. Apparatus according to any of claims 3 to 8 , wherein the draw element is open ended with the opposite ends thereof located at a draw location where they can be drawn together in a tying operation to reduce the effective length of the draw element.
14. Apparatus according to Claim 1, wherein the draw means is arranged to maintain the blanket periphery at a reduced length and is extensible to permit the blanket periphery to extend to its extended length.
15. Apparatus according to claim 14, wherein the draw means is pretensioned to draw the blanket periphery to its reduced length and is extensible to permit the blanket periphery to take up its extended length.
16. Apparatus according to claim 15, wherein the draw means comprises an inextensible portion and an extensible portion connected thereto.
17. Apparatus according to claim 16, wherein the extensible portion comprises a spring.
18. Apparatus according to claim 16, wherein the inextensible portion is an elongate draw element of an inextensible material and wherein the extensible portion is a loop of inextensible material which is biased by a spring into a reserve loop and which is released against the action of the spring to extend the length of the draw element.
19. Apparatus according to any of claims 3 to 8, wherein the draw element is open ended with the opposite ends thereof located at a draw location where they can be held in fixed relation by attachment to the component support.
20. Apparatus according to claim 19 wherein the draw means further comprises a draw device at the draw location wherein the effective length of the draw element can be reduced by means of the draw device.
21. Apparatus according to any of claims 1 to 20 wherein the sealing edge is provided by a sealing member extending continuously around the component support at or in the region of the periphery of the support.
22. Apparatus according to claim 21 wherein the sealing member is of triangular crosssection with a base thereof gas tight bonded to the support and with an opposite apex providing a sealing edge upstanding from the support to provide an initial seal between the blanket and the support, and wherein the main seal is a slick seal along the inside inclined face of the sealing member.
23. Apparatus according to any of claims 1 to 22 wherein the component support takes the form of a flat table top supported by a substructure in such a way that the edges of the top extend beyond the substructure to provide the reentrant zone.
24. Component processing apparatus according to claim 1 and substantially as hereinbefore described with reference to any of Figs 1 to 27 and Figs 34 to 39.
25. Component processing apparatus according to claim 1 and substantially as hereinbefore described with reference to any of Figs 1 to 5 and 28 to 33. SUBSTITUTE SHEET.
Description:
BAGGING ARRANGEMENT FOR SYNTHETIC RESIN COMPONENT PROCESSING APPARATUS

The present invention relates to synthetic resin component processing apparatus and is particularly although not exclusively concerned with apparatus for curing and/or moulding synthetic resin composites in the production of components.

Vacuum bag moulding is currently employed for the moulding of complex components which cannot be made practically by other forms of moulding such as compression moulding. For the moulding process, layers of composite material which make up the component are laid up on a component support in required relative dispositions. A bagging blanket of a flexible material is placed over the assembly of layers forming the component and extends across the component support against which it is sealed along the edges of the support. A vacuum is then applied with air being withdrawn from beneath the bag and the component assembly is then subjected to any one of a variety of processing cycles, for example by curing in an oven (heat and vacuum induced atmospheric pressure only) or an autoclave (heat, pressure and in certain cases vacuum induced atmospheric pressure), dependent upon the resin materials being used. After treatment, the vacuum is released. The bagging blanket is then removed and the processed component replaced by a further component to be processed. The processed component may then be subjected to any required post curing treatment.

It will be appreciated that the bagging blanket must be arranged to form with the component support an effective seal around the periphery of the support to enable an effective vacuum environment to be obtained and to

prevent the ingress of air as a result of atmospheric pressure and any pneumatic pressure applied to the assembly during an autoclave cycle and various techniques have been employed to achieve these ends.

In prior US patent No 4664737 it has been proposed to provide an upstanding sealing edge around the periphery of the component support and to bring the bagging blanket under tension over the sealing edge. The blanket of the prior proposal is provided with a skirt in the form of a net attached to and extending around the periphery of the blanket and a plurality of outstanding spaced pins are provided on the support so that when the blanket is placed over the component and the component support with the net hanging down at the periphery, the blanket can be tensioned by pulling the net over the free ends of appropriate pins and the tension subsequently adjusted if necessary by repositioning of the net on the pins. With the blanket so tensioned, an effective initial seal is provided between the sealing edge on the support and the blanket. When air is withdrawn from beneath the blanket the pressure of atmospheric air on the blanket increases the seal between the blanket and sealing edge and provides the main sealing action.

It is an object of the present invention to provide a bagging blanket for use with a synthetic resin component processing apparatus which uses means alternative to a net for tensioning and positioning the blanket.

According to the present invention, there is provided component processing apparatus comprising a component support on which a component is mounted and on which is formed at or in the region of its periphery a sealing edge extending around the periphery of the support, and a bagging arrangement for use with the support comprising a collapsible bagging blanket which in use is extended

across the component and the component support and which is tensioned to bring it into engagement with the sealing edge on the support, characterised by the fact that the component support is re-entrant beyond the sealing edge to form a re-entrant zone and that the blanket is so formed as to receive and receives at its periphery draw means by which the effective length of the blanket periphery can be varied from an extended length which allows the blanket to be placed over the component and the component support and into a covering disposition in which it covers the component and the component support and in which the blanket periphery extends beyond the sealing edge on the component support to a reduced length which in the covering disposition of the blanket brings the blanket periphery into the re-entrant zone and the blanket against the sealing edge on the component support.

In a first embodiment of the invention hereinafter to be described, the draw means permits the blanket periphery to maintain its extended length and is contractible to bring the blanket periphery to its reduced length. Preferably, the draw means comprises an elongate draw element which is received by the blanket along the full periphery of the blanket.

In a specific embodiment of the invention hereinafter to be described, the draw element is exposed at one or more predetermined exposed locations along the periphery of the blanket and the predetermined exposed location or one or more of the predetermined exposed locations is utilised as a draw location at which the effective length of the draw element can be reduced. Other exposed locations may be utilised to provide access for ancilliary equipment required for the cure assembly, such for example as vacuum lines and thermocouple leads.

TE S ^5

The draw element may, if desired, be secured to the blanket at securing locations along the blanket periphery whereby a reduction in the effective length of the draw element at a draw location produces a local reduction in the length of the blanket periphery.

In a specific embodiment of the invention hereinafter to be described, the periphery of the blanket is folded back on itself and so secured as to provide a passageway for the draw element through which the draw element passes and the periphery of the blanket is cut away at the exposed location or locations to expose the draw element. Where a plurality of draw locations are provided, they may furthermore be so arranged in spaced relation around the periphery of the blanket that reduction in the length of the draw element can be made to provide an even tensioning of the blanket over the component and the component support.

In a specific embodiment of the invention hereinafter to be described, there is provided at a draw location a draw device, through which the draw element passes to form an open loop at the draw location and which includes loop enlarging means whereby the loop can be enlarged to reduce the effective length of the draw element. The draw device may conveniently comprise a support plate and the loop enlarging means may comprise a plurality of spaced pins extending away from one side of the plate. The draw element is then arranged to pass along the plate in a plane parallel to the plate so that it can be withdrawn on the side of the plate carrying the pins and formed into a loop by passage round one or more of the pins.

In a further specific embodiment of the invention hereinafter to be described, the draw device may comprise

one or more guide elements for forming the draw element into a loop and the loop enlarging means may comprise a member movable from a first predetermined disposition relative to the guide element or elements to a second predetermined disposition relative to the guide element or elements. The draw element is then arranged to pass through the guide element or elements to form a loop and the movable member is arranged to engage the loop to cause the loop to enlarge by movement of the movable member from the first predetermined disposition to the second predetermined disposition. The movable member may advantageously include resilient means for moving it from the first predetermined position to the second predetermined position.

In the first embodiment of the invention hereinbefore referred to, the draw element may alternatively be open ended with the opposite ends thereof located at a draw location where they can be drawn together in a tying operation to reduce the effective length of the draw element.

In a second embodiment of the invention hereinafter to be described, the draw means maintains the blanket periphery at a reduced length and is extensible to permit the blanket periphery to extend to its extended length.

In the second embodiment of the invention hereinbefore referred to, the draw means may comprise an inextensible portion in the form of an elongate draw element of inextensible material, and an extensible portion, such as a spring, connected thereto. The draw means may alternatively comprise an elongate draw element of an inextensible material and the extensible portion may then comprise a loop of the draw element which is biased by a spring into a reserve loop and which is released against the action of the spring to extend the effective length

of the draw element.

In yet another embodiment of the invention hereinafter to be described the draw element is open ended with the opposite ends thereof located at a draw location where they can be held in fixed relation by attachment to the component support. The effective length of the draw element may be reduced by means of a draw device at the draw location.

In the embodiments of the invention hereinafter to be described the sealing edge is provided by a sealing member extending continuously around the component support at or in the region of the periphery of the support. The sealing member is preferably of triangular cross-section with a base thereof gas-tight bonded to the support and with an opposite apex providing a sealing edge upstanding from the support to provide an initial seal between the blanket and the support, with the main seal being provided as a slick seal along the inside inclined face of the sealing member.

The component structure may conveniently take the form of a flat table top supported by a sub-structure in such a way that the edges of the top extend beyond the sub-structure to provide the re-entrant zone.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which:-

Fig 1 is a schematic perspective view of a component processing apparatus according to a first embodiment of the invention, with some parts cut away,

Fig 2 is a schematic cross-section of a part only of the apparatus shown in Fig 1,

SUBSTITUTESHEET

Figs 3, 4 and 5 are schematic views illustrating the way in which the blanket shown in Fig 1 is provided with a skirt portion which is folded back upon itself to form a passageway for a draw element for the blanket,

Fig 6 is a schematic perspective view of the blanket shown in Figs 1 to 5, illustrating a plurality of draw locations where the draw element for the blanket is exposed to provide for local tensioning of the blanket.

Fig 7 is a schematic scrap side elevation of a bagging blanket of the form shown in Fig 6, except insofar that the draw element is secured to the skirt portion of the blanket at locations between the draw locations,

Fig 8 is a schematic scrap view of a simple tensioning device for use at draw locations of the blanket illustrated in Fig 7,

Figs 9 and 10 are schematic cross-sections taken on the lines X-X and Y-Y in Fig 3 revealing the completed bond between the blanket body portion and the skirt portion,

Fig 11 is an exploded schematic perspective view illustrating an alternative attachment procedure for attaching the skirt portion to the blanket periphery,

Fig 12 is a schematic cross-section taken on the line Z-Z in Fig 11, illustrating the completed bond between the blanket body portion and the skirt portion,

Λ.

Fig 13 is a schematic perspective view of a preferred tensioning device for use at a draw location of the blanket,

Fig 14 is a schematic elevation of the tensioning device shown in Fig 13, illustrating alternative paths for the

draw element around the pins of the device,

Fig 15 is a schematic perspective scrap view of the blanket and component support illustrated in Fig 1, showing a corner location and a side draw location,

Figs 16 and 17 are schematic scrap sections of the blanket and component support shown in Fig 1, taken on the lines X-X and Y-Y in Fig 15,

Figs 18 and 19; 20 and 21; 22 and 23; 24 and 25; and 26 and 27 are schematic views of further alternative tensioning devices for use at draw locations of the blanket illustrated in Fig 1,

Fig 28 is a schematic perspective view of a tensioning device for pretensioning a draw element for use in a second embodiment of the invention,

Fig 29 is a schematic scrap section of a part of the device shown in Fig 28,

Figs 30 and 31 are schematic scrap views of further alternative tensioning devices for use in the second embodiment of the invention,

Figs 32 and 33 are schematic scrap views of adjustment devices for adjusting the length of the draw element used in the second embodiment of the invention,

Figure 34 is a schematic side elevation of part of a component processing apparatus of the form shown in Fig 1, except insofar that the draw element is open ended and the ends thereof are attached to the component support,

Fig 35 is a schematic perspective view of a simple attachment and tensioning device for use at the draw

SUBSTITUTE SHEETi

location of the blanket illustrated in Fig 34.

Fig 36 is a schematic perspective view of a device which enables the draw element to be tensioned by attaching only one free end of the draw element to the component support,

Fig 37 is a schematic elevation of part of the apparatus shown in Fig 1, except insofar that one free end of the draw element is attached to the component support by means of the devices illustrated in Figs 35 and 36, and

Fig 38 is a schematic side elevation of part of a component support suitable for use with the bagging arrangements illustrated in Figs 34 and 37.

Referring first to Fig 1, a component processing apparatus is shown comprising a component support lay-up structure 11 including a flat component support plate 12 supported by a base 13. The component support plate 12 carries in the region of its periphery a sealing member 14 which extends fully around the plate 12 but which is shown partly cut away in Fig 1. A component 15 for processing is mounted on the support plate 12 within the bounds of the sealing member 14. A blanket 8 also shown partly cut away includes a body portion 16 which is spread over the component 15 and the entire surface of the support plate 12 and a skirt portion 17 which extends over the edges of the four sides of the support plate 12.

As best seen in Fig 2, the blanket body portion 16 drapes over the sealing member 14 and the skirt portion 17 of the blanket extends over the edge of the support plate 12 along all four sides of the plate 12. As shown in Fig 2, the skirt portion 17 is folded back upon itself to form a passageway 18 extending for the full length of the blanket periphery for reception of a draw element 19.

The draw element 19 can be tensioned in a manner hereinafter to be described to draw the skirt portion 17 beneath the support plate 12 and into a re-entrant zone 10 formed by the projection of the support plate 12 beyond the base 13 which supports it.

The blanket body portion 16 may be made from any one of the variety of different materials and is preferably made from an elastomeric material, giving it high tensile strength, the ability to stretch and retract rapidly with full recovery to its original dimensions and good tear resistance. The skirt portion 17 may also be made from any one of a large number of fabrics provided they are tear resistant and both drapeable and flexible. It may furthermore be of any weave provided it can be stitched and must be resistant to continuous use at the temperatures to be used in the processing of the component. Suitable yarns for the material forming the skirt portion 17 are aromatic polyamides such as No ex and Kevlar (Registered Trade Marks) , oxidised polyacrylonitrile (PAN) , fibreglass, linen, nylon and polyester. The yarn for stitching must have a high tensile strength and resistance to heat and abrasion eg Kevlar or a polyester.

The draw element 19 may be in the form of a rope and manufactured from any of a variety of materials provided it is flexible, heat resistant and has a high breaking strain. Such materials include Nomex, nylon (multi-filament or mono-filament) , Kevlar, steel cable/chain or specially reinforced solid rubber/hollow hose, for example, in silicone, and may be even some form of belting/strapping in any materials.

Referring now to Figs 3 to 5, the skirt portion 17 may be secured to the periphery of the blanket body portion 16 by arranging for perforations 20 in the skirt portion 17

SUBSTITUTE SHEET

and securing it to the periphery of the blanket 16 by bonding using a bonding strip 21 as shown. The skirt portion 17 is, as shown, then folded back on itself to form a double ply edge 22 shown in Fig 5, which is then double stitched to the main body of the skirt portion 17 to form the passageway 18.

The blanket 8 illustrated in Fig 1, 2 is also shown in Fig 6, from which it will be seen more clearly that the skirt portion 17 is cut away at draw locations 22 and 23 along one side of the blanket and at a draw location 24 along an adjacent side of the blanket.

Additionally, the skirt portion 17 on the side remote from the draw locations 22 and 23 is similarly cut away at corresponding draw locations, while a further draw location is provided on the side of the blanket opposite the draw location 24. Furthermore, the skirt portion 17 is interrupted at corner locations 25, 26, 27 and 28 to facilitate the draping of the skirt portion 17 over the edges of the support plate 12.

In the embodiment of the invention shown in Fig 6, the draw element 19 is shown threaded through the passageways 18 formed in the skirt portion 17, with the two free ends appearing at the corner location 25. With this arrangement, the blanket 16 is placed, as shown in Fig 1, over the component 15 and the support plate 12 and the free ends of the draw element 19 drawn together and secured to bring the skirt portion under the support plate 12 as shown in Fig 2. Tensioning devices hereinafter to be described are then used at the draw locations along the sides of the blanket 16 to provide a full and even tensioning of the blanket 16 so that it bears down in sealing contact with the sealing member 14 for its full extent around the periphery of the support plate 12. The draw element 19 may be made from any

material which can withstand the treatment/cure environment and may range from steel to a lightweight composite.

In an alternative embodiment of the invention illustrated in Fig 7, the draw element 19 is held captive in sections of the passageway 18 at locations 29 between adjacent draw locations so that when the draw element 19 is tensioned at an intermediate location, say location 30, the tensioning effect on the blanket 16 is localised. In this way localised adjustments of the tensioning of the blanket 16 can be made simply by adjustment of individual tensioning devices at the different draw locations. A simple form of tensioning device is illustrated in Fig 8 and comprises a collar 31 through which the draw element 19 is passed to produce a loop 32, the draw element 19 being increasingly tensioned by drawing more of the draw element 19 through the collar 31. This simple device has the feature that the draw element 19 can be easily tensioned and quickly released.

The attachment of the skirt portion 17 to the blanket body portion 16 as illustrated in Fig 3 produces a secure bond as illustrated in Figs 9 and 10, with the blanket body portion 16, the skirt 17 and the bonding strip 21 being bonded together using an elastomeric sealant or adhesive 33. Alternatively, attachment of the skirt portion 17 to the blanket body portion 16 may be achieved as illustrated in Figs 11 and 12 where an additional reinforcing strip 9 of an elastomeric material is interposed between the outer strip 21 and the blanket body portion 16, with the end of the skirt portion 17 being arranged to pass over it and to be folded back against the lower face of it to form a secure attachment when the assembly is bonded together by the sealant 33.

Referring now to Fig 13, a tensioning device 34 is shown

which comprises a flat plate 35 carrying a plurality of spaced pins 36 secured to the plate and extending from one face thereof. The plate 35 has also secured to it a guide plate 136 mounted on pillars 37 which space vertical portions of the guide plate 136 from the face of the plate 35 and space the horizontal top portion of the guide plate 136 from the upper edge of the plate 35.

In use, the device 34 shown in Fig 13 is presented to the draw element 19 at a draw location of the blanket body portion 16 so that the draw element 19 engages under the guide plate 136 and can then be pulled down over the front face of the plate 35 and passed in a loop around one or more of the pins 36 thereby tensioning the draw element 19 at the draw location. As best seen in Fig 14, the draw element 19 can be arranged to take any one of a number of paths around the pins 36 to provide for a wide range of loops of different sizes to permit adjustment of the tension in the draw element 19.

The plate 35 and the pins 36 may be manufactured from a number of materials eg. steel, aluminium, reinforced nylons etc ie. any material able to withstand the cure cycle and exhibit the required mechanical properties.

As best seen in Fig 15, the skirt portion 17 of the blanket is arranged to be cut away at corner locations of the blanket and a corner-piece 161, preferably of elastomeric material, is inserted to fill the cut away corner locations to enable proper seating of the blanket body portion over the support plate 12 and even tensioning of the blanket body portion over the sealing member 14. As will be seen from Fig 16, the edge of the blanket at the corner locations is strengthened by a reinforcing strip 38 which is bonded to the blanket using an elastomeric adhesive.

S UB STITUTESHEET

A variety of different tensioning devices for tensioning the draw element 19 will now be described with reference to Figs 18 to 27. All require the draw element 19 to pass in the form of an open loop through the device and provide means for extending the length of the loop to draw in the draw element 19 and reduce its length at the appropriate draw location of the blanket, thereby bringing the element 19 under tension so that it is drawn into the re-entrant zone 10 beneath the support plate 12 as shown in Fig 2.

In Figs 18 and 19, it will be seen that the tensioning device shown comprises a body portion 40 with two depending arms 41 and 42 which are spaced apart as shown and are joined together at their lower ends by a bridge piece 43. The body portion 40 include bores 44 and 45 and in use of the device the draw element 19 is arranged to pass down through the bore 44, round the bridge piece 43 and then back up through the bore 45 to form an open loop. As shown in Fig 19, the device further includes a pivotal arm 46 which can be turned by a handle 47 through a quick release ratchet mechanism (not shown) from a position shown in Fig 18 in which it lies within the bounds of the plates 41 and 42 and parallel thereto up to a position at right angles thereto as illustrated in Fig 19. The loop in the draw element 19 formed in the device can thus be enlarged by turning the handle 47, thereby reducing the effective length of the draw element and bringing it under the tension required to hold the blanket in place on the support plate 12 and to provide an initial seal, between the blanket and the sealing member 14.

In the tensioning device illustrated in Fig 20 and 21, the draw element 19 is arranged to pass through an opening 48 at one side of a body portion 49 of the device, then pass along a channel 50 on the end of a

c-

displaceable arm 51 pivoted at 52 on the main body portion 49 and then upwardly through a further opening 54 formed on the other side of the body portion 49. The arm 51 is resiliently biased by a spring 53 away from the body portion 49 of the device. The draw element 19 is thus reduced in length at the draw location by the formation of the loop within the device and tensioned by the biasing action of the pivotal arm 51.

A further alternative tensioning device is illustrated in Figs 22 and 23 and comprises an arm 54 having a boss 55 pivotal on a shaft 56 which carries at its ends collars 57 and 58 through which the draw element 19 is passed as shown. The arm 54 is extended by a screw-threaded shaft 59 carrying a shoe 60 having a channel 61 and the draw element 19 is as shown in Fig 23, arranged to pass from the collar 57 through the channel 61 and back through the collar 58. A reduction in the effective length of the draw element 19 is then achieved by the provision of the loop within the device, which can be set by an appropriate axial adjustment of the shaft 59 which is screwed into the arm 54.

The tensioning device illustrated in Figs 24 and 25 is of the same general form as that shown in Figs 22 and 23, except insofar as the boss 55 is replaced by a yoke 62 which is pivotal on the shaft 56 carrying the collars 57 and 58. The tensioning arm 54 can then be removed from the shaft 56 to release the draw element 19 and be repositioned when further tensioning of the draw element is required.

The tensioning arm 54 of the device shown in Figs 24 and 25 may if desired be replaced by a modified tensioning arm 54' shown in Figs 26 and 27. In this modification a shoe portion 64 is adjustably threaded on the end of a shaft 65, a head 66 of which is slidably arranged within

a counterbore 67 in the arm 54 ' , which also encloses a biasing spring 68 which normally holds the shaft 64 in the position shown in Fig 26. Such spring loading of the shoe portion 64 enables the arm 54 * carrying the yoke 62 to be displaced along the shaft 64 effectively to shorten the tensioning arm and facilitate removal of the arm from the support shaft 56.

In a second embodiment of the invention now to be described, the skirt portion 17 of the blanket carries a draw element 19 which is pretensioned to draw the periphery of the skirt portion 17 into the re-entrant zone 10 and beneath the support plate 12 as shown in Figs 1 and 2 and is extensible to enable the skirt portion 17 to be extended to enable it to be drawn over the support plate 12 when the blanket body portion 16 is placed over the component 15 and the support plate 12. The blanket 8 with its skirt portion 17 and the draw element 19 may conveniently take the form described with reference to Figs 1 to 12, except insofar as the draw element 19 is arranged as a continuous element extending for the full periphery of the skirt portion 17 and is formed into a reserve loop by a tensioning device, which may take any one of a number of different forms, three of which are illustrated in Figs 28 and 29, Fig 30 and Fig 31.

It will be seen from Figs 28 and 29 that the draw element 19 is arranged to pass over a jockey pulley 69 carried by a backing plate 70, then beneath and around a plunger 71 and then over a second jockey pulley 72. As will be seen from Fig 29, the plunger 71 is carried on a shaft 73 having a piston element 74 which rides in a housing 75 which is closed by a top 76 and which houses a coil spring 77, the arrangement being such that the plunger 71 is biased downwardly by the spring 77 from a seated position on the base of the housing 75, causing a reserve loop 78 to be formed in the draw element 19 and bringing

the draw element 19 under tension so that with the skirt portion 17 of the blanket in position, as shown in Figs 1 and 2 the skirt portion is drawn into the re-entrant zone beneath the plate 12 and the blanket body portion 16 into contact with the sealing member 14 on the top plate 12. The draw element 19 can be lengthened by reducing the extent of the reserve loop 78 against the action of the spring 77 and the arrangement is made such that the extension provided enables the skirt portion 17 to be passed over the edge of the top plate 12.

The tensioning device illustrated in Figs 28 and 29 allows not only for the effective lengthening of the draw element 19 but also allows for adjustment of the actual length of the element 19 throughout the life of the blanket.

An alternative tensioning device for use in the second embodiment of the invention is illustrated in Fig 30 and comprises a body 79 which supports leaf springs 80 and 81 which carry collars 82 and 83. In use, the draw element 19 passes through the collar 82, through a channel on the body 79, across the top of the body 79, then downwardly through a further channel in the body 79 and finally through the collar 83.

The springs 80 and 81, in the disposition shown in Fig 30, hold the draw element 19 at a reduced length in which it brings the skirt portion 17 of the blanket into the re-entrant zone beneath the plate 12 and the body portion 16 of the blanket into engagement with the sealing member 14. The placing of the blanket with the skirt portion 17 extending over the edge of the plate 12 can then be achieved by extending the effective length of the draw element 19 by flexing the leaf springs 80 and 81 outwardly.

In yet a further alternative tensioning device illustrated in Fig 31, the draw element 19 has opposite ends connected together by a coil spring 84 which holds the draw element 19 at a length in which it draws the skirt portion 17 of the blanket into the re-entrant zone beneath the support plate 12. The placing of the blanket on the component 15 with the skirt portion 17 extending over the edge of the support plate 12 can then be achieved simply by extension of the coil spring 84.

The two tensioning devices described with reference to Figs 30 and 31 do not, however, allow for adjustment of the actual length of the draw element 19 during the life of the blanket and adjustment devices for this purpose may be provided as illustrated in Figs 32 and 33.

In the embodiment of the invention illustrated in Fig 34, the free ends of the draw element 19 appear at draw location 90. Each free end of the draw element 19 is attached to the base 13 of the component support by means of a clip 91 which anchors the free end of the draw element to the edge of an airflow aperture 92 in the component support base 13.

Fig 35 illustrates a clip 91 suitable for attaching a free end of the draw element 19 to the component support base 13. The clip 91 has a head portion 93 for engaging the edge of the airflow aperture 92 and a lockable collar portion 94 which enables the draw element to be further tensioned when the free end of the draw element is secured to the component support base 13.

Since most component supports have a base 13 which incorporate apertures to allow airflow and facilitate access to the underside of the component, the free ends of the draw element 19 may be attached to the component support base 13 by making use of those apertures, without

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requiring modification of the component support base 13. However, under certain circumstances, when suitable sites are not available in the base 13 of the component support, the free ends of the draw element 19 may be anchored to special anchor handles fixed to the component support base 13.

Fig 36 illustrates a device which allows the draw element 19 to be attached to the component support base 13 by anchoring only one of the free ends of the draw element. A ring 95 is secured to one free end of the draw element and the other free end of the draw element is passed through the ring 15.

In the embodiment of the invention illustrated in Fig 37, the device illustrated in Fig 36 is secured to one free end of the draw element 19 and the other free end of the draw element 19 is anchored by means of clip 91 to the edge of aperture 92 in the component support base.

Fig 38 illustrates a component support suitable for use in all embodiments of the invention hereinbefore described.

The bagging arrangement according to the present invention, although operating according to a different principle, has all the advantages of the blanket arrangement proposed in US patent No 4664737 together with the following advantages:-

1. No modification or addition to the cure/mould support structure need be made.

2. A more uniform load distribution can be provided on the elastomeric blanket with less risk of the securement system being torn away (or disbonded) from the blanket during a critical cure cycle.

3. Manufacturing costs can be reduced by the use of off-the-shelf materials in the manufacture of the blanket.

4. The pretensioned bagging arrangement according to the second embodiment of the invention is simpler and easier to apply.

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