Reusable vacuum bag for making laminated articles

A vacuum bag assembly used in making laminated articles having layers of composite materials and thermosetting resins that are formed and adhesively bonded together. The assembly includes a forming tool on which the composite materials and the thermosetting resins may be positioned. The composite materials have edges well spaced from edges of the forming tool. A vacuum bag is positioned over the composite material and the forming tool. The vacuum bag includes a flexible mat, having an irregular surface contiguous with the composite materials. The flexible mat also has edges well spaced from the edges of the forming tool. The vacuum bag also has a continuous flexible suction channel having an inner arch-like surface and an outer arch-like surface positioned between the edges of the flexible mat and the edges of the forming tool. The suction channel is attached to the flexible mat by a flexible connecting flange. Further, the flexible connecting flange, the outer surface of said suction channel, the edges of the flexible mat and the forming tool define the walls of an airspace positioned in between the flexible mat and the suction channel. The airspace is in pneumatic communication with the irregular surface of the flexible mat.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a vacuum bag, and more particularly to a 
reusable vacuum bag used to remove air over the surface of an area. 
2. Background Information 
Vacuum bags have long been used in industry on laminated articles comprised 
of composite materials that are adhesively bonded together. To make a 
composite or laminated article, oriented fiber layers with applied 
thermosetting resin are stacked upon a forming surface portion of a 
forming tool. A plastic bag sheet is then placed over the composite or 
laminated article. A double-sided sealing tape, such as chromium tape, is 
then continuously applied between the plastic bag sheet and the periphery 
of the forming tool. Thus, a volume defined by the plastic bag sheet and 
the forming tool is sealed off. A vacuum source in pneumatic communication 
with a space between the forming tool and the plastic bag sheet is used to 
draw a vacuum in the sealed off volume so that the plastic bag sheet is 
firmly pressed against the forming tool thereby forming the materials to 
the shape of the forming surface. The above steps are repeated to produce 
the composite or laminated article having a number of plies. Sheets of 
honeycomb core can also be laid upon or between layers of composite 
material to produce panels of various shapes and sizes. An additional step 
of heating the composite or laminated article while under pressure in an 
oven or pressurized autoclave oven can be used to cure the adhesive resins 
in and between the plies of the laminated materials. The above system may 
be used to produce a light-weight, high-strength laminated article that is 
capable of being used as an aircraft component. 
Unfortunately, vacuum bags that use the a plastic bag sheet and the sealing 
tape are not very durable and cannot be used to apply more than a few 
layers of laminates before they are discarded and replace. Accordingly, 
when a given composite or laminated article is produced, a skilled worker 
must fashion the vacuum bag and then attempt to use it for as many 
operations as possible. Fabricating a vacuum bag for each article in a 
production run is time consuming and expensive. A large number of used 
vacuum bags must be thrown away adding unwanted solid waste. Consequently, 
there has long been a need for a method that employs a durable or reusable 
vacuum bag for laying-up a laminated article. Further, there is a need for 
a reusable vacuum bag that can be fashioned to any shape or size, and that 
is easy to use and does not require bulky edge support or edge fastenings. 
More particularly, there is a need for a reusable vacuum bag assembly that 
can form an airtight seal with a forming tool such that the periphery of 
the vacuum bag secures itself to the forming tool with an airtight seal 
when a vacuum is drawn in the vacuum bag. 
SUMMARY OF THE INVENTION 
In accordance with one aspect, the present invention relates to a vacuum 
bag assembly used in making laminated articles having layers of composite 
materials and thermosetting resins that are formed and adhesively bonded 
together. The assembly includes a forming tool on which the composite 
materials and the thermosetting resins may be positioned. The composite 
materials have edges well spaced from edges of the forming tool. A vacuum 
bag is positioned over the composite material and the forming tool. The 
vacuum bag includes a flexible mat, having an irregular surface contiguous 
with the composite materials. The flexible mat also has edges well spaced 
from the edges of the forming tool. The vacuum bag also has a continuous 
flexible suction channel having an inner arch-like surface and an outer 
arch-like surface positioned between the edges of the flexible mat and the 
edges of the forming tool. The suction channel is attached to the flexible 
mat by a flexible connecting flange. Further, the flexible connecting 
flange, the outer surface of said suction channel, the edges of the 
flexible mat and the forming tool define the walls of an airspace 
positioned in between the flexible mat and the suction channel. The 
airspace is in pneumatic communication with the irregular surface of the 
flexible mat.

DETAILED DESCRIPTION OF THE INVENTION 
FIG. 1 shows a vacuum bag assembly 10 including a vacuum bag 35 and forming 
tool 20. The forming tool 20 includes a substantially flat base 30 and a 
forming surface (not shown). The vacuum bag 35 comprises a flexible mat 
40, a continuous suction channel 50, and connecting flange members 60 
which are bonded to the suction channel 50 and the flexible mat 40. A 
vacuum line 70 leads to a vacuum source 71 and is connected to the 
flexible mat 40 with a fitting 72. 
As can be seen in FIG. 1, the suction channel 50, the connecting flange 
members 60 and the base plate 30 are fashioned to negotiate corners around 
the periphery of the vacuum bag 35. These corners are formed by cutting 
the various sections at appropriate angles and then bonding the resulting 
pieces together using compatible, flexible adhesives. 
As shown in FIG. 2, the vacuum bag 35 comprises the flexible mat 40, the 
suction channel 50 and the connecting flange members 60. The flexible mat 
40 has a substantially smooth upper surface 42 and a lower surface 43 that 
is embossed by a system of interconnecting channels 44. The system of 
interconnecting channels 44 provides a path for air to flow under the 
flexible mat 40. The smooth upper-surface 42 of the flexible mat 40 forms 
an air-tight seal with the fitting 72 and the vacuum line 70. In this way, 
the vacuum source 71 and the vacuum line 70 are in pneumatic communication 
with the system of interconnecting channels 44 embossed in the lower 
surface 43 of the flexible mat 40. 
As shown in FIG. 3, the suction channel 50 has a "cup like" cross-section 
and includes a raised flat center portion 52, an inside leg 54, and in 
outside leg 56. The connecting flange members 60 comprises a spacer member 
62 and a flange member 64. In an alternative embodiment, the connecting 
flange members 60 may comprise a single piece member (not shown). The 
connecting flange members 60 are airtight, and are bonded in an airtight 
manner to the smooth upper surface 42 of the flexible mat 40 at one end 
and to center the center portion 52 of the suction channel 50 at the other 
end. 
The embossed lower surface 43, as shown in FIG. 3, of the flexible mat 40, 
is in continuous contact with the base plate 30. The suction channel 50 is 
spaced away from an outer edge 45 of the flexible mat 40. Further, the 
connecting flange members 60 are continuously bonded to the suction 
channel 50 and the spacer member 62, and the spacer member 62 is 
continuously bonded to the flexible mat 40. The inside leg 54 and the 
outside leg 56 of the suction channel 50 are in continuous contact with 
the base plate 30. 
As shown in FIG. 4, the inside leg 54 of the channel member 50, the 
connecting flange member 60, the spacer member 62, the outer edge 45 of 
the flexible mat 40, and the base plate 30 define a closed air space 80, 
which is disposed around the vacuum bag between the flexible mat 40 and 
the suction channel 50. The air space 80 and the system of air channels 44 
define a vacuum volume of the vacuum bag 35. 
FIG. 4 shows the flexible suction channel 50 being flattened against the 
base plate 30 by surrounding air pressure and by the vacuum formed in the 
closed space 80 so that the pressure of the air under channel 50 is 
substantially equal to the air pressure in the system of channels 44 and 
the closed air space 80. Should outside air leak between the outside leg 
56 of the suction channel 50 and the base plate 30, the resulting higher 
air pressure under the suction channel 50 relative to that in the vacuum 
volume will urge the inside leg 54 of the suction channel away from the 
base plate 30 thereby allowing the leaked air to escape into the vacuum 
volume and thus reestablishing the vacuum under the suction channel 50. In 
this way, while a vacuum is drawn against the vacuum bag, the suction 
channel 50 continues to firmly adhere to the base plate 30 allowing the 
flexible mat 40 of the vacuum bag 35 to press a laminated composite 
article down upon the forming surface of the forming tool 20. 
For simplicity, the base plate 30 as shown in FIGS. 1-4 has been 
represented as a substantially flat member. An embodiment of the present 
invention can be fashioned to conform to tooling surfaces that are simply 
or even unusually contoured as long as such surfaces do not have drastic 
discontinuities or abrupt corners which would prevent the suction channel 
50 from maintaining continuous contact with the forming tool 20. 
In the preferred embodiment, the suction channel 50 is made from an 
extruded silicone rubber material having a "shore A" durometer rating of 
45 to 50. The material properties of the suction channel 50 are critical 
because the material must be flexible enough to deflect under pressure but 
strong enough to exert forces sufficient to promote the suction channel 50 
to firmly adhere to the base plate 30. Also, in the preferred embodiment, 
the connecting flange members 60 and the flexible mat 40 are made from 
flexible silicone rubber. As can be readily understood by those skilled in 
the art, all of the silicone rubber material chosen for the components of 
the vacuum bag 35, including the adhesives that bond them together, can be 
chosen to withstand conditions of a pressurized heating process so that 
the vacuum bag of the present invention may be used in the production of 
high-strength, light-weight composite components for aerospace vehicles. 
The following describes the operation of the vacuum bag assembly of the 
present invention. Initially, a build-up of laminated cloth layers (not 
shown) are placed with applied adhesives over the forming surface (not 
shown) and are extended out onto the flat surface of the base plate 30. A 
removable non-stick plastic sheet (not shown) covers the laminated cloth 
build-up. 
After the layer or layers of the composite material along with the applied 
adhesives have been laid on the forming surface of the forming tool 20 and 
covered by the non-stick plastic layer, the operator places the vacuum bag 
35 over the forming tool 20. The vacuum bag 35 is positioned to completely 
cover the build-up of the cloth layers and to substantially cover the 
forming tool 20. The operator then smoothes out the vacuum bag 35 to 
ensure that the suction channel 50 is in continuous contact with base 
plate 30. The operator activates the vacuum source which causes the vacuum 
bag 35 along with the suction channel 50 to pull down and adhere to the 
forming tool 20. The vacuum bag 35 pulls down onto the forming tool 20, 
and then it stretches to conform to the forming surface of the forming 
tool 20 providing an evenly distributed pressure to the layers of the 
composite material laid on the forming tool 20. These same steps can be 
repeated for an article placed in a pressurized oven except that instead 
of applying a vacuum with the vacuum line 70, the vacuum line 70 is placed 
in pneumatic communication with a lower pressure volume outside the oven, 
drawing gases and creating a relative vacuum in the vacuum bag assembly. 
Except as otherwise disclosed herein, the various components shown in 
outline or block form are individually well known and their internal 
construction and their operation is not critical either to the making or 
the using of this invention. 
While a detailed description above has been expressed in terms of specific 
examples, those skilled in the art will appreciate that many of the 
configurations could be used to accomplish the purpose of the disclosed 
apparatus. Accordingly, it will be appreciated that various equivalent 
modifications of the above-described embodiments may be made without 
departing from the spirit and scope of the invention. Therefore, the 
invention is to be limited only by the following claims.