Title of Invention	"A NOVEL PROCESS FOR THE MANUFACTURE OF SHAPED THERMOPLASTIC SHEETS FOR WIND SHIELDS/ WINDOWS OF VEHICLES"
Abstract	This invention describes and claims a novel process for the manufacture of thermoplastic wind shields / windows of vehicles such as aircrafts, automobiles, ships and for windows of control towers of airports and harbours. In the novel process of the present invention,distortion free,without the loss of original optical quality,clarity,isotropic and fully transparent wind shields/windows are produced by the inventive step of vacuum technique. This novel process is cost effective and has several advantages over earlier conventional processes.

Title of Invention

"A NOVEL PROCESS FOR THE MANUFACTURE OF SHAPED THERMOPLASTIC SHEETS FOR WIND SHIELDS/ WINDOWS OF VEHICLES"

Abstract

This invention describes and claims a novel process for the manufacture of thermoplastic wind shields / windows of vehicles such as aircrafts, automobiles, ships and for windows of control towers of airports and harbours. In the novel process of the present invention,distortion free,without the loss of original optical quality,clarity,isotropic and fully transparent wind shields/windows are produced by the inventive step of vacuum technique. This novel process is cost effective and has several advantages over earlier conventional processes.

Full Text	The present invention relates to a novel process for the manufacture of shaped thermoplastic sheets of wind shields / windows of vehicles. The shaped thermoplastic sheets manufactured using the novel process of the present invention will be particularly useful for wind shields/windows of vehicles such as aircrafts,automobiles,ships and windows of control towers of airports and harbour The novelty and inventive step of this invention lies in the fact that the method of manufacture of shaped thermoplastic components for wind shields/ windows of vehicles is unique by using vacuum technique. The use of this process to manufacture wind shields / windows has eliminated the drawbacks of earlier methods and this process is cost effective. In the prior art, the process of manufacturing wind shields for aircrafts as referred in US Patent 5804317 - Process for reinforcing glass objects, the standard methods used are time consuming and operator skill dependent. Reference may be made to the process followed in general aircraft industry for making wind shields of aircrafts in which acrylic sheets are thermoformed on FRP tools, by manually stretching the heated acrylic sheet around the forming tool. The drawbacks of the earlier methods are as follow: 1. The sheets after heat treating in the oven is put on the forming tools and positioned and held in tension with suitable clamping devices. By this method, the material of the sheet is not distributed properly (non-isotropy). Further, the sheets are held in tension at plurality strategic points. Till it is kept pressed against the moulds. After cooling ,the extra edges are cut. 2. The effect of the above mentioned procedure is that the sheet develops waviness, distortion and non-uniform thickness leading to non-isotropy. 3. 30 - 40% of the material is wasted in edges due to large allowances given over and above the actual required dimensions of the component desired as shown in Figure-1 of the drawings accompanying this specification. 4. Manufacturing cycle time is considerably high. 5. Visibility of Pilot / Driver is impaired due to non-isotropy which distorts the images. The main object of the present invention is to provide a novel process for the manufacture of shaped thermoplastic sheets for wind shields/windows of vehicles which obviates all the drawbacks as experienced in earlier methods. Another object of the present invention is to provide a method of manufacture of wind shield / windows of vehicles in a very short time using a novel vacuum method. Yet another object of the present invention is to provide a cost effective method of manufacture of wind shield / windows of vehicles. Still another object of the present invention is to provide a distortion free, isotropic material for wind shield / windows of vehicles. One more object of the present invention is to provide a scratch free and maximum transparent material for wind shield / windows of vehicles. Figure 1 of the drawings describes the material required for producing the thermoplastic wind shield. In the methods described earlier more material is wasted in the form of allowances R2 and R3 which are the extra areas of allowances required in the earlier methods. Figure 2 of the drawings, shows a schematic diagram of experimental set up for the process of the present invention. It essentially consists of the three parts, namely a vacuum chamber, plastic sheet and frame. Using this set up the finished shaped component is made. This is a simple method without wasting material. Accordingly, the present invention provides a novel process for the manufacture of shaped thermoplastic sheets for wind shields/ windows of vehicles, which comprises; placing and fastening a flat preheated thermoplastic sheet such as herein described onto a holder frame of the desired peripheral shape, placing the said holder frame with sheet onto a vacuum chamber, applying vacuum in the range of 200 mm to 70mm Hg for a period in the range of half minute to five minutes to obtain a shaped thermoplastic sheet, allowing the resultant shaped sheet to cool at room temperature. In an embodiment of the present invention, the thermoplastic sheet used is selected from acrylic, polypropylene sheets. Description of the process of the present invention. The process of the present invention for manufacturing wind shields / windows consists of placing a thermoplastic sheet on a vacuum chamber firmly secured as shown schematically in Figure-2 of the drawings. The vacuum is applied to the extent and duration depending upon the desired shape and the material. The flow chart explains the various steps involved in the process of the present invention for manufacture of wind shields/ windows. (Diagram Removed) The shaped component is released after cooling the component at room temperature. The component is ready for fixing as a window / wind shield.The novelty of the present invention lies in the fact that a distortion free without loss of original optical quality clarity, isotropic and fully transparent wind shield/ windows is produced by an adaptive vacuum technique eliminating the drawbacks of the earlier inethods,specifically that of saving the material resulting in cost effective process for the manufacture of shaped thermoplastic sheets for windows/wind screens of vehicles. The inventive step of the process of the present invention is vacuum technique for producing shaped thermoplastic sheet. Since the sheet is not stretched at several strategic points as in earlier methods, the material is not subjected to tensile point loads applied at several points and hence there are no residual stresses in the component manufactured by the novel method of the present invention. The starting dimensions of the sheet are chosen such that after realization the shaped component, no trimming is required on the component. This is in contrast with earlier methods,wherein 30 - 40% wastage in sheet was due to the allowances in order to hold, clamp and stretching of the sheet as shown in Figure-1 of the drawings. In the earlier method, the operator's skill plays a crucial role in realizing the shape of the component. The present method is a fool proof method and the operator skill is not necessary. The non distortion of the shaped component is checked through a combination of visual and surface testing by dial gauge. Further non waviness is confirmed by establishing the absence of any visual distortion with reference to a standard reference platfonn consisting of a graphic square matrix which happens to be a standard approved procedure to qualify the front wind shield / windows of aircrafts / vehicles / other applications. The main advantages of the present invention are: 1. The process developed is simple, cost effective and there is considerable saving in material used to produce wind shield/ windows. 2. The process does not require many persons, as in earlier methods, and quality of finished product doesn't depend on operator skills. Total elimination of finishing operations after shaping such as removal of undulations (waviness) by cumbersome and elaborate manual material removal process, surface finishing by using emery of different grades and removal of surface scratches emerging as a consequence of the above mentioned processes by abrasive pastes, lapping and finally restoring the original glass and optical quality of the unshaped sheet. 3 In the new process developed, when once the component is shaped as explained, it is ready to be fit into vehicle without any post shaping operations, after visual checks, since the process developed ensures the original optical quality of the sheet at the component level and no waviness is found later. We Claim: 1. A novel process for the manufacture of shaped thermoplastic sheets for wind shields/ windows of vehicles, which comprises; placing and fastening a flat preheated thermoplastic sheet such as herein described onto a holder frame of the desired peripheral shape, placing the said holder frame with sheet onto a vacuum chamber, applying vacuum in the range of 200 mm to 70mm Hg for a period in the range of half minute to five minutes to obtain a shaped thermoplastic sheet, allowing the resultant shaped sheet to cool at room temperature. 2. A novel process as claimed in claim 1, wherein the thermoplastic sheet used is selected from acrylic, polypropylene sheets. 3. A novel process for the manufacture of shaped thermoplastic sheets for wind shields/ windows of vehicles substantially as herein described with reference to the figure-2 of the drawings accompanying this specification.

Full Text

The present invention relates to a novel process for the manufacture of shaped thermoplastic sheets of wind shields / windows of vehicles. The shaped thermoplastic sheets manufactured using the novel process of the present invention will be particularly useful for wind shields/windows of vehicles such as aircrafts,automobiles,ships and windows of control towers of airports and harbour
The novelty and inventive step of this invention lies in the fact that the method of manufacture of shaped thermoplastic components for wind shields/ windows of vehicles is unique by using vacuum technique. The use of this process to manufacture wind shields / windows has eliminated the drawbacks of earlier methods and this process is cost effective. In the prior art, the process of manufacturing wind shields for aircrafts as referred in US Patent 5804317 - Process for reinforcing glass objects, the standard methods used are time consuming and operator skill dependent. Reference may be made to the process followed in general aircraft industry for making wind shields of aircrafts in which acrylic sheets are thermoformed on FRP tools, by manually stretching the heated acrylic sheet around the forming tool.
The drawbacks of the earlier methods are as follow:
1. The sheets after heat treating in the oven is put on the forming tools and positioned and held in tension with suitable clamping devices. By this method, the material of the sheet is not distributed properly (non-isotropy). Further, the sheets are held in tension at plurality strategic points. Till it is kept pressed against the moulds. After cooling ,the extra edges are cut.
2. The effect of the above mentioned procedure is that the sheet develops waviness, distortion and non-uniform thickness leading to non-isotropy.
3. 30 - 40% of the material is wasted in edges due to large allowances given over and above the actual required dimensions of the component desired as shown in Figure-1 of the drawings accompanying this specification.
4. Manufacturing cycle time is considerably high.
5. Visibility of Pilot / Driver is impaired due to non-isotropy which distorts the images.
The main object of the present invention is to provide a novel process for the manufacture of shaped thermoplastic sheets for wind shields/windows of vehicles which obviates all the drawbacks as experienced in earlier methods.
Another object of the present invention is to provide a method of manufacture of wind shield / windows of vehicles in a very short time using a novel vacuum method.
Yet another object of the present invention is to provide a cost effective method of manufacture of wind shield / windows of vehicles.
Still another object of the present invention is to provide a distortion free, isotropic material for wind shield / windows of vehicles.
One more object of the present invention is to provide a scratch free and maximum transparent material for wind shield / windows of vehicles. Figure 1 of the drawings describes the material required for producing the thermoplastic wind shield. In the methods described earlier more material is wasted in the form of allowances R2 and R3 which are the extra areas of
allowances required in the earlier methods.
Figure 2 of the drawings, shows a schematic diagram of experimental set up for the process of the present invention. It essentially consists of the three parts, namely a vacuum chamber, plastic sheet and frame. Using this set up the finished shaped component is made. This is a simple method without wasting material.
Accordingly, the present invention provides a novel process for the manufacture of shaped thermoplastic sheets for wind shields/ windows of vehicles, which comprises; placing and fastening a flat preheated thermoplastic sheet such as herein described onto a holder frame of the desired peripheral shape, placing the said holder frame with sheet onto a vacuum chamber, applying vacuum in the range of 200 mm to 70mm Hg for a period in the range of half minute to five minutes to obtain a shaped thermoplastic sheet, allowing the resultant shaped sheet to cool at room temperature.
In an embodiment of the present invention, the thermoplastic sheet used is selected from acrylic, polypropylene sheets.
Description of the process of the present invention.
The process of the present invention for manufacturing wind shields / windows consists of placing a thermoplastic sheet on a vacuum chamber
firmly secured as shown schematically in Figure-2 of the drawings. The vacuum is applied to the extent and duration depending upon the desired shape and the material.
The flow chart explains the various steps involved in the process of the present invention for manufacture of wind shields/ windows.
(Diagram Removed)
The shaped component is released after cooling the component at room
temperature. The component is ready for fixing as a window / wind shield.The novelty of the present invention lies in the fact that a distortion free without loss of original optical quality clarity, isotropic and fully transparent wind shield/ windows is produced by an adaptive vacuum technique eliminating the drawbacks of the earlier inethods,specifically that of saving the material resulting in cost effective process for the manufacture of shaped thermoplastic sheets for windows/wind screens of vehicles. The inventive step of the process of the present invention is vacuum technique for producing shaped thermoplastic sheet. Since the sheet is not stretched at several strategic points as in earlier methods, the material is not subjected to tensile point loads applied at several points and hence there are no residual stresses in the component manufactured by the novel method of the present invention.
The starting dimensions of the sheet are chosen such that after realization the
shaped component, no trimming is required on the component. This is in
contrast with earlier methods,wherein 30 - 40% wastage in sheet was due to
the allowances in order to hold, clamp and stretching of the sheet as shown in
Figure-1 of the drawings. In the earlier method, the operator's skill plays a
crucial role in realizing the shape of the component. The present method is a
fool proof method and the operator skill is not necessary.
The non distortion of the shaped component is checked through a
combination of visual and surface testing by dial gauge.
Further non waviness is confirmed by establishing the absence of any visual
distortion with reference to a standard reference platfonn consisting of a
graphic square matrix which happens to be a standard approved procedure to
qualify the front wind shield / windows of aircrafts / vehicles / other
applications.
The main advantages of the present invention are:
1. The process developed is simple, cost effective and there is considerable
saving in material used to produce wind shield/ windows.
2. The process does not require many persons, as in earlier methods, and
quality of finished product doesn't depend on operator skills.
Total elimination of finishing operations after shaping such as removal of undulations (waviness) by cumbersome and elaborate manual material removal process, surface finishing by using emery of different grades and removal of surface scratches emerging as a consequence of the above
mentioned processes by abrasive pastes, lapping and finally restoring the
original glass and optical quality of the unshaped sheet.
3 In the new process developed, when once the component is shaped as explained, it is ready to be fit into vehicle without any post shaping operations, after visual checks, since the process developed ensures the original optical quality of the sheet at the component level and no waviness is found later.

We Claim:
1. A novel process for the manufacture of shaped thermoplastic sheets for wind shields/
windows of vehicles, which comprises; placing and fastening a flat preheated
thermoplastic sheet such as herein described onto a holder frame of the desired
peripheral shape, placing the said holder frame with sheet onto a vacuum chamber,
applying vacuum in the range of 200 mm to 70mm Hg for a period in the range of half
minute to five minutes to obtain a shaped thermoplastic sheet, allowing the resultant
shaped sheet to cool at room temperature.
2. A novel process as claimed in claim 1, wherein the thermoplastic sheet used is selected
from acrylic, polypropylene sheets.
3. A novel process for the manufacture of shaped thermoplastic sheets for wind shields/
windows of vehicles substantially as herein described with reference to the figure-2 of
the drawings accompanying this specification.

Documents:

1122-del-2000-abstract.pdf

1122-del-2000-claims.pdf

1122-del-2000-correspondence-others.pdf

1122-del-2000-correspondence-po.pdf

1122-del-2000-description (complete).pdf

1122-del-2000-drawings.pdf

1122-del-2000-form-1.pdf

1122-del-2000-form-19.pdf

1122-del-2000-form-2.pdf

1122-del-2000-form-3.pdf

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Patent Number

216783

Indian Patent Application Number

1122/DEL/2000

PG Journal Number

13/2008

Publication Date

31-Mar-2008

Grant Date

19-Mar-2008

Date of Filing

08-Dec-2000

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG, NEW DELHI-110 001, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	RAJA MANURI VENKATA GOPALA KRISHNA RAO	NATIONAL AEROSPACE LABORATORIES, BANGALORE, INDIA
2	C. PRAGALATAAN	NATIONAL AEROSPACE LABORATORIES, BANGALORE, INDIA
3	S.S.DESAI	NATIONAL AEROSPACE LABORATORIES, BANGALORE, INDIA

PCT International Classification Number

B29C 47/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA