Title of Invention	A DEVICE FOR STITCHING STIFF, COMPLEX SHAPED AND LARGE SIZE COMPOSITE MATERIAL WITH SINGLE THREAD AND SINGLE SEAM
Abstract	A device for stitching stiff, complex shaped and large size composite material with single thread and single seam, which comprises a stitching head fitted in combination with a known computer numerically controlled bed and the said stitching head essentially consisting of a prime mover such as a geared motor, the said motor being connected by means to a thread-needle actuator and a hook-needle actuator respectively, the said actuators being connected to thread-needle and a hook-needle through actuating links and respectively, the said thread-needle and hook-needle being moveably held in position by known means and the said thread-needle and hook-needle being provided at needle end side with a movable footrest and footrest movement controller such as a solenoid actuator.

Title of Invention

A DEVICE FOR STITCHING STIFF, COMPLEX SHAPED AND LARGE SIZE COMPOSITE MATERIAL WITH SINGLE THREAD AND SINGLE SEAM

Abstract

A device for stitching stiff, complex shaped and large size composite material with single thread and single seam, which comprises a stitching head fitted in combination with a known computer numerically controlled bed and the said stitching head essentially consisting of a prime mover such as a geared motor, the said motor being connected by means to a thread-needle actuator and a hook-needle actuator respectively, the said actuators being connected to thread-needle and a hook-needle through actuating links and respectively, the said thread-needle and hook-needle being moveably held in position by known means and the said thread-needle and hook-needle being provided at needle end side with a movable footrest and footrest movement controller such as a solenoid actuator.

Full Text	The present invention relates to a device for stitching stiff, complex shaped and large size composite material with single thread and single seam. The present invention particularly relates to a dual needles stitching device capable of providing single seam with single thread. The main usage of device of the present invention is to stitch semi-cured components of carbon or glass pre-preg, glass fibre reinforced plastics (GFRP) materials. These materials are stiff, complex in shape when laid on a shape retaining mould/support table. The position of the materials to be stitched, as placed on the shape retaining mould/support table denies the access from the bottom of the material. The commercially available conventional industrial stitching machines normally has single needle with single thread and need access from both-sides of the material. These conventional industrial stitching machines are suitable for stitching fabrics. The said machines are unsuitable for stitching stiff, complex shaped and large size composite materials. In figure 1, of the drawings accompanying this specification is shown the prior art of yarn pattern of conventional chain stitch method which requires access from both sides of the material. Reference may be made to the literature titled: Damage Tolerance of Stitched Carbon Expoxy Laminate, by Fritz Larsson, Defence Research Establishment. Materials Department, SE-172 90 Stockholm, Sweden, Revised 2 December 1996; accepted 22 May 1997. This machine has a single needle with thread capable of providing single seam stitching of dry pre-form with requirement of access from both sides. Prior art literature survey reveals a device with two needles, single thread capable of providing double seam stitch. Reference may be made to Journal of Textile and Apparel, Technology and Management, volume 2, issue 1, Fall 2001-ALTIN Naehtechnik, Germany, article titled: Recent Development in Robotic Stitching Technology for Textile Structural Composites. They have developed a stitching machine, where 3-dimensional preforms can be produced by application of two needles, single thread capable of producing two seams. In figure 2 of the drawings is shown the yarn pattern of ALTIN Naechtechnik machine, which produces a double seam. The drawbacks of this machine are: 1. It makes double seam, which is not desirable, as it may bring about increase in weight without enhancing the holding strength. 2. The needles being positioned in transverse plane to the seam direction's prohibits stitching in vicinity of stiffener/blade or any projection lying on the base material. 3. It requires wide gap on the support table for needle clearance, which deforms the shape of the material. 4. This device is incapable of providing single seam stitching. 5. The device is meant for stitching dry preforms that is flexible materials, without shape retention. From the hitherto known prior art devices covering industrial stitching machines and special purpose stitching machine as detailed above, it is clear that there is no device / machine available for providing single seam stitching of stiff, complex shaped, large size composite materials with shape retention. The main object of the present invention is to provide a device for stitching stiff, complex shaped and large size composite material with single thread and single-seam, which obviates the drawbacks as referred above. Another object of present invention is to provide a device capable of chain stitching with single seam. Yet another object of present invention is to provide a device having a dual-needle single thread. Still another object of the present invention is to provide a device capable of stitching on 3-D contour surface of cardboard, rubberized components and preform of composite materials. Still yet another object of the present invention is to provide a device wherein access required is from one side. A further object of the present invention is to provide a device which can also be used for tufting the composite materials. A still further object of the present invention is to provide a device having a -• stitching head with a thread-needle capable of protecting thread from shearing-and deposition of foreign materials. A still yet further object of the present invention is to provide a device having a stitching head capable of reciprocating movement with uniform velocity. In the present invention there is provided a device for stitching stiff, complex^ shaped and large size composite material with single thread and single seam. The device of the present invention is a dual needle stitching head consisting of~ thread-needle and hook-needle capable of providing uniform velocity reciprocating motion to enable single seam and single thread chain stitch. It also features thread release and regulating mechanism, thread cutting mechanism, thread holding mechanism and footrest and footrest controller. Stitching head is a computer-controlled unit with provision for mounting on a four-degree freedom computer numerically controlled bed. Hence, the device of the present invention consists of two main sub-systems, namely computer numerically controlled (CNC) bed having four degrees of freedom (3 linear and one rotation) and computer controlled dual needle stitching head. Both sub-systems when integrated forms the device of the present invention. In the drawings accompanying this specification, figure 3 depicts the pictorial view of the device of the present invention, wherein 'MB' is the four degree* freedom (3 linear and one rotation), computer numerically controlled machine bed and 'SH' is the computer controlled dual needle stitch head of the device of the present invention. In figure 4 of the drawings is shown parts of stitching head as depicted by 'SH' in-figure 3. The various parts shown in figure 4 are: 'GM': Geared motor capable of actuating needles. TS': Twin shaft mechanism for translating motor shaft rotation to twin shaft rotation. TN': Hollow thread-needle. 'HIM': Hook-needle. TNACT: Mechanism to actuate the thread-needle (TN) consisting of globoidal cam-followers duly supported and capable of providing uniform velocity reciprocating motion to the thread-needle. 'HNACT: Mechanism to actuate the hook-needle (HN) consisting of globoidal cam-followers duly supported and cappele of providing uniform velocity reciprocating motion to the hook-needle. 'GDTN': Actuating link for thread-needle. 'GDHN1: Actuating link for hook-needle. 'REG': Thread release and regulating mechanism. 'FR': Footrest to keep material in position and support thread cutting and thread holding systems. 'SL': Footrest movement controller such as solenoid actuator. in figure 5 of the drawings is shown the steps of chain stitch method to make one stitch. A chain stitch method for stitching stiff and complex shaped large size composite materials has mainly six steps to form a stitch and repetition of these steps perform chain of stitch with single seam with single thread. Figure 5(a) shows thread-needle and hook-needle positioned above the materiai. Figure 5(b) shows thread-needle penetrating in the material and reaching its lower limit. Hook-needle with lag in time follows the thread- needle. Figure 5(c) shows the thread-needle starting to retract and form a loop. Due to lag in time, hook-needle passes through loop and intersects the thread-needle and reaching its bottom limit before it starts retracting. Figure 5(d) shows the thread of thread-needle is pulled by 'REG' mechanism (not shown in this figure). This action makes thread loop tight around the hook-needle. This tight thread loop seated in the slot of the hook-needle and loop is pulled above the top surface of material. Figure 5(e) shows the required length of the loop has formed on the top surface, loop is disengaged from the slot of the hook-needle. Loop is pushed in forward direction and held in position by a flap (not shown in this figure). Now thread-needle and hook-needle are moved forward by desired stitch pitch length. Figure 5(f) shows the thread-needle reach its top most limit and starting descend and passing through the loop left on the top surface of material. In this manner first stitch is completed and repeating above-mentioned steps forms a chain of stitch. The above activity of producing a single seam chain stitch is accomplished from the topside of the material. Figure 6 shows the yarn pattern produced by the device of present invention following the chain stitch method with single line seam and single thread as detailed in figure 5 of the drawings. The present invention provides a device for stitching stiff, complex shaped and large size composite material with single thread and single seam, which features a computer numerically controlled bed of four degrees of freedom (3 linear and one rotation) and a computer controlled dual needle stitching head capable of providing chain stitch to form a single seam with single thread using a thread-needle and a hook-needle with syncronised movements and also features a mechanism for thread release and regulation, thread holding and thread cutting. Accordingly , the present invention provides a device for stitching stiff, complex shaped and large size composite material with single thread and single seam, which comprises a stitching head (SH) fitted in combination with a known computer numerically controlled bed (MB) and the said stitching head essentially consisting of a prime mover (GM) such as a geared motor, the said motor being connected by means to a thread-needle actuator (TNACT) and a hook-needle actuator (HNACT) respectively, the said actuators (TNACT and (HNACT) being connected to thread-needle (TN) and a hook-needle (HN) through actuating links (GDTN and GDHN) respectively, the said thread-needle (TN) and hook-needle (HN) being moveably held in position by known means in such a manner so as to allow included angle between the needles (TN and HN) in the range of 20 degree to 90 degree and the said thread-needle (TN) and hook-needle (HN) being provided at needle end side with a movable footrest (FR) and footrest movement controller (SL) such as a solenoid actuator. In an embodiment of the present invention the prime mover (GM), such as a geared motor is provided with a single ended or a double ended common output shaft. In another embodiment of the present invention the geared motor is a servo controlled variable speed motor capable of providing output shaft with rotational movement in the range of 0 to 50rpm. In still another embodiment of the present invention, the means for connecting the said motor to the said thread-needle actuator (TNACT) and the said hook-needle actuator (HNACT) is such as crank and connecting rod, cam and follower, twin shaft mechanism capable of translating motor shaft rotation to twin shaft rotation by known means. In yet another embodiment of the present invention the thread-needle actuator (TNACT) and hook-needle actuator (HNACT) consists of globoidal cam and followers duly supported and capable of translating rotary motion to uniform velocity reciprocating motion in the range of 0 to 50 cycles. In still yet another embodiment of the present invention, the synchronised motion of the thread-needle and the hook-needle is derived by any electro-mechanical system such as software cam or hardware cam, electric/hydraulic/pneumatic actuator, linear motors and such other similar mechanisms. In yet another embodiment of the present invention there is provided at needle end side a movable footrest (FR) and footrest movement controller (SL) such as a solenoid actuator. In still yet another embodiment of the present invention the thread-needle is a> hollow tubular needle capable of allowing the thread to pass through it. In a further embodiment of the present invention the stitching head (SH) is capable of being used as a stand alone device and also for fitment onto a known positioning device. In a still further embodiment of the present invention one or more of the stitching head (SH) being fitted onto a known computer numerically controlled bed (MB) having four degrees of freedom, namely three linear and one rotational. The novelty of the device of the present invention resides in: (i) The-stitching head,which is capable of providing chain stitching and is able to produce single seam stitch with shape retention. Hitherto known prior art stitching heads make double seam. (ii) The device is capable of providing a stitch seam in the vicinity of stiffener or projection on the base material with shape retention, unlike in other methods where it is difficult to provide stitch seam in vicinity of the stiffener or projection on the base material with shape retention. (iii) The device is capable of protecting the thread from shearing and deposition of foreign materials. The above novel features of the device of the present invention have been realized by the non-obvious inventive steps of providing mechanism toi actuate the thread and hook needles, wherein the mechanism consists of globoidal cam-followers duly supported and capable of providing uniform velocity reciprocating motion to the needles. Further, the thread-needle is a hollow tubular needle capable of protecting the thread from shearing and deposition of foreign materials. The following examples are given by way of illustration of the device of the present invention and should not be construed to limit the scope of the present invention. Example 1 The specimens were produced using unidirectional carbon prepreg material of thickness 0.15mm in orthotropic and quasi-isotropic lay-ups and stitched on the half portion. These lay-ups were cured in autoclave and specimens were cut for stitched and unstitched cases. The test results obtained were as follows: Orthotropic laminate Unstitched Stitched Ultimate Tensile Strength (MPa) (MPa) Casel 866.24 521.96 Case2 849.97 455.23 Case3 963.16 596.62 Reduction in strength = 41.26% of average. Quasi-isotropic laminate Unstitched Stitched Ultimate Tensile Strength (Mpa) (MPa) Casel 551.61 457.03 Case2 552.85 518.91 CaseS 564.38 457.03 Reduction in strength = 14.13% of average. The effect of stitching on in-plane properties of the quasi-isotropic laminate was acceptable and in line with the requirements.The effect of stitching on preforms in-plane mechanical properties of quasi-isotropic laminates were found in stitching direction and noted in prior art that tensile strength was reduced by the stitching by 20-25%. In our case the reduction was only 14.13%. The main advantages of the device of the present invention are: 1. Capable of chain stitching with single seam with single thread. 2. Having a dual-needle single thread. 3. Capable of stitching on 3-D contour surface of cardboard, rubberized components and pre-form of composite materials. 4. Access required is from one side. 5. Can also be used for tufting the composite materials, leather and stiff fabric. 6. Capable of protecting thread from shearing and deposition of foreign materials. 7. Stitching head capable of reciprocating movement with uniform velocity. 8. Can be used with more than one thread and for providing double seam. We claim: 1. A device for stitching stiff, complex shaped and large size composite material with single thread and single seam, which comprises a stitching head (SH) fitted in combination with a known computer numerically controlled bed (MB) and the said stitching head essentially consisting of a prime mover (GM) such as a geared motor, the said motor being connected by means to a thread-needle actuator (TNACT) and a hook-needle actuator (HNACT) respectively, the said actuators (TNACT/and (HNACT) being connected to thread-needle (TN) and a hook-needle (HN) through actuating links (GDTN and GDHN) respectively, the said thread-needle (TN) and hook-needle (HN) being moveably held in position by known means in such a manner so as to allow included angle between the needles (TN and HN) in the range of 20 degree to 90 degree and the said thread- needle (TN) and hook-needle (HN) being provided at needle end side with a movable footrest (FR) and footrest movement controller (SL) such as a solenoid actuator. 2. A device as claimed in claim 1, wherein the prime mover (GM), such as a geared motor is provided with a single ended or double ended common output shaft. 3. A device as claimed in claim 1, wherein the geared motor is a servo controlled variable speed motor capable of providing output shaft with rotational movement in the range of 0 to 50 rpm. 4. A device as claimed in claim 1, wherein the means for connecting the said motor to the said thread-needle actuator (TNACT) and the said hook-needle actuator (HNACT) is such as crank and connecting rod, cam and follower, twin shaft mechanism capable of translating motor shaft rotation to twin shaft rotation by known means. 5. A device as claimed in claim 1, wherein the thread-needle actuator (TNACT) and the hook-needle actuator (HNACT) consists of globoidal cam and followers duly supported and capable of translating rotary motion to uniform velocity reciprocating motion in the range of 0 to 50 cycles. 6. A device as claimed in claim 1-5, wherein the synchronised motion of the thread-needle and the hook-needle is derived by any electro-mechanical system such as software cam or hardware cam, electric/hydraulic/pneumatic actuator, linear motors and such other similar mechanisms. 7. A device as claimed in claim 1, wherein the thread-needle is a hollow tubular needle capable of allowing the thread to pass through it. 8. A device as claimed in claim 1, wherein the stitching head (SH) is capable of being used as a stand alone device and also for fitment onto a known positioning device. 9. A device as claimed in claim 1, wherein one or more of the stitching head (SH) being fitted on to a known computer numerically controlled bed (MB) having four degrees of freedom, namely three linear and one rotational. 10. A device for stitching stiff complex shaped and large size composite material with single thread and single seam, substantially as herein described with reference to the examples and figures 3 to 6 of the drawings accompanying this specification.

Full Text

The present invention relates to a device for stitching stiff, complex shaped and large size composite material with single thread and single seam. The present invention particularly relates to a dual needles stitching device capable of providing single seam with single thread.
The main usage of device of the present invention is to stitch semi-cured components of carbon or glass pre-preg, glass fibre reinforced plastics (GFRP) materials. These materials are stiff, complex in shape when laid on a shape retaining mould/support table. The position of the materials to be stitched, as placed on the shape retaining mould/support table denies the access from the bottom of the material.
The commercially available conventional industrial stitching machines normally has single needle with single thread and need access from both-sides of the material. These conventional industrial stitching machines are suitable for stitching fabrics. The said machines are unsuitable for stitching stiff, complex shaped and large size composite materials.
In figure 1, of the drawings accompanying this specification is shown the prior art of yarn pattern of conventional chain stitch method which requires access from both sides of the material.
Reference may be made to the literature titled: Damage Tolerance of Stitched Carbon Expoxy Laminate, by Fritz Larsson, Defence Research Establishment. Materials Department, SE-172 90 Stockholm, Sweden, Revised 2 December 1996; accepted 22 May 1997. This machine has a single needle with thread capable of providing single seam stitching of dry pre-form with requirement of access from both sides.

Prior art literature survey reveals a device with two needles, single thread capable of providing double seam stitch. Reference may be made to Journal of Textile and Apparel, Technology and Management, volume 2, issue 1, Fall 2001-ALTIN Naehtechnik, Germany, article titled: Recent Development in Robotic Stitching Technology for Textile Structural Composites. They have developed a stitching machine, where 3-dimensional preforms can be produced by application of two needles, single thread capable of producing two seams. In figure 2 of the drawings is shown the yarn pattern of ALTIN Naechtechnik machine, which produces a double seam. The drawbacks of this machine are:
1. It makes double seam, which is not desirable, as it may bring about increase
in weight without enhancing the holding strength.
2. The needles being positioned in transverse plane to the seam direction's
prohibits stitching in vicinity of stiffener/blade or any projection lying on the
base material.
3. It requires wide gap on the support table for needle clearance, which deforms
the shape of the material.
4. This device is incapable of providing single seam stitching.
5. The device is meant for stitching dry preforms that is flexible materials,
without shape retention.
From the hitherto known prior art devices covering industrial stitching machines and special purpose stitching machine as detailed above, it is clear that there is no device / machine available for providing single seam stitching of stiff, complex shaped, large size composite materials with shape retention.
The main object of the present invention is to provide a device for stitching stiff, complex shaped and large size composite material with single thread and single-seam, which obviates the drawbacks as referred above.

Another object of present invention is to provide a device capable of chain stitching with single seam.
Yet another object of present invention is to provide a device having a dual-needle single thread.
Still another object of the present invention is to provide a device capable of stitching on 3-D contour surface of cardboard, rubberized components and preform of composite materials.
Still yet another object of the present invention is to provide a device wherein access required is from one side.
A further object of the present invention is to provide a device which can also be used for tufting the composite materials.
A still further object of the present invention is to provide a device having a -• stitching head with a thread-needle capable of protecting thread from shearing-and deposition of foreign materials.
A still yet further object of the present invention is to provide a device having a stitching head capable of reciprocating movement with uniform velocity.
In the present invention there is provided a device for stitching stiff, complex^ shaped and large size composite material with single thread and single seam. The device of the present invention is a dual needle stitching head consisting of~ thread-needle and hook-needle capable of providing uniform velocity reciprocating motion to enable single seam and single thread chain stitch. It also features thread release and regulating mechanism, thread cutting mechanism, thread holding mechanism and footrest and footrest controller. Stitching head is a computer-controlled unit with provision for mounting on a four-degree freedom

computer numerically controlled bed. Hence, the device of the present invention consists of two main sub-systems, namely computer numerically controlled (CNC) bed having four degrees of freedom (3 linear and one rotation) and computer controlled dual needle stitching head. Both sub-systems when integrated forms the device of the present invention.
In the drawings accompanying this specification, figure 3 depicts the pictorial view of the device of the present invention, wherein 'MB' is the four degree* freedom (3 linear and one rotation), computer numerically controlled machine bed and 'SH' is the computer controlled dual needle stitch head of the device of the present invention.
In figure 4 of the drawings is shown parts of stitching head as depicted by 'SH' in-figure 3. The various parts shown in figure 4 are:
'GM': Geared motor capable of actuating needles.
TS': Twin shaft mechanism for translating motor shaft rotation to twin shaft rotation.
TN': Hollow thread-needle. 'HIM': Hook-needle.
TNACT: Mechanism to actuate the thread-needle (TN) consisting of globoidal cam-followers duly supported and capable of providing uniform velocity reciprocating motion to the thread-needle.
'HNACT: Mechanism to actuate the hook-needle (HN) consisting of globoidal cam-followers duly supported and cappele of providing uniform velocity reciprocating motion to the hook-needle.

'GDTN': Actuating link for thread-needle.
'GDHN1: Actuating link for hook-needle.
'REG': Thread release and regulating mechanism.
'FR': Footrest to keep material in position and support thread cutting and thread holding systems.
'SL': Footrest movement controller such as solenoid actuator.
in figure 5 of the drawings is shown the steps of chain stitch method to make one stitch. A chain stitch method for stitching stiff and complex shaped large size composite materials has mainly six steps to form a stitch and repetition of these steps perform chain of stitch with single seam with single thread. Figure 5(a) shows thread-needle and hook-needle positioned above the materiai.
Figure 5(b) shows thread-needle penetrating in the material and reaching its lower limit. Hook-needle with lag in time follows the thread- needle.
Figure 5(c) shows the thread-needle starting to retract and form a loop. Due to lag in time, hook-needle passes through loop and intersects the thread-needle and reaching its bottom limit before it starts retracting.
Figure 5(d) shows the thread of thread-needle is pulled by 'REG' mechanism (not shown in this figure). This action makes thread loop tight around the hook-needle. This tight thread loop seated in the slot of the hook-needle and loop is pulled above the top surface of material.
Figure 5(e) shows the required length of the loop has formed on the top surface, loop is disengaged from the slot of the hook-needle. Loop is pushed in forward

direction and held in position by a flap (not shown in this figure). Now thread-needle and hook-needle are moved forward by desired stitch pitch length.
Figure 5(f) shows the thread-needle reach its top most limit and starting descend and passing through the loop left on the top surface of material.
In this manner first stitch is completed and repeating above-mentioned steps forms a chain of stitch. The above activity of producing a single seam chain stitch is accomplished from the topside of the material.
Figure 6 shows the yarn pattern produced by the device of present invention following the chain stitch method with single line seam and single thread as detailed in figure 5 of the drawings.
The present invention provides a device for stitching stiff, complex shaped and large size composite material with single thread and single seam, which features a computer numerically controlled bed of four degrees of freedom (3 linear and one rotation) and a computer controlled dual needle stitching head capable of providing chain stitch to form a single seam with single thread using a thread-needle and a hook-needle with syncronised movements and also features a mechanism for thread release and regulation, thread holding and thread cutting.
Accordingly , the present invention provides a device for stitching stiff, complex shaped and large size composite material with single thread and single seam, which comprises a stitching head (SH) fitted in combination with a known computer numerically controlled bed (MB) and the said stitching head essentially consisting of a prime mover (GM) such as a geared motor, the said motor being connected by means to a thread-needle actuator (TNACT) and a hook-needle actuator (HNACT) respectively, the said actuators (TNACT and (HNACT) being connected to thread-needle (TN) and a hook-needle (HN) through actuating links (GDTN and GDHN) respectively, the said thread-needle (TN) and hook-needle (HN) being moveably

held in position by known means in such a manner so as to allow included angle between the needles (TN and HN) in the range of 20 degree to 90 degree and the said thread-needle (TN) and hook-needle (HN) being provided at needle end side with a movable footrest (FR) and footrest movement controller (SL) such as a solenoid actuator.
In an embodiment of the present invention the prime mover (GM), such as a geared motor is provided with a single ended or a double ended common output shaft.
In another embodiment of the present invention the geared motor is a servo controlled variable speed motor capable of providing output shaft with rotational movement in the range of 0 to 50rpm.
In still another embodiment of the present invention, the means for connecting the said motor to the said thread-needle actuator (TNACT) and the said hook-needle actuator (HNACT) is such as crank and connecting rod, cam and follower, twin shaft mechanism capable of translating motor shaft rotation to twin shaft rotation by known means.
In yet another embodiment of the present invention the thread-needle actuator (TNACT) and hook-needle actuator (HNACT) consists of globoidal cam and followers duly supported and capable of translating rotary motion to uniform velocity reciprocating motion in the range of 0 to 50 cycles.
In still yet another embodiment of the present invention, the synchronised motion of the thread-needle and the hook-needle is derived by any electro-mechanical system such as software cam or hardware cam, electric/hydraulic/pneumatic actuator, linear motors and such other similar mechanisms. In yet another embodiment of the present invention there is provided at needle end side a movable footrest (FR) and footrest movement controller (SL) such as a solenoid actuator.

In still yet another embodiment of the present invention the thread-needle is a> hollow tubular needle capable of allowing the thread to pass through it.
In a further embodiment of the present invention the stitching head (SH) is capable of being used as a stand alone device and also for fitment onto a known positioning device.
In a still further embodiment of the present invention one or more of the stitching head (SH) being fitted onto a known computer numerically controlled bed (MB) having four degrees of freedom, namely three linear and one rotational.
The novelty of the device of the present invention resides in:
(i) The-stitching head,which is capable of providing chain stitching and is able to produce single seam stitch with shape retention. Hitherto known prior art stitching heads make double seam.
(ii) The device is capable of providing a stitch seam in the vicinity of stiffener or projection on the base material with shape retention, unlike in other methods where it is difficult to provide stitch seam in vicinity of the stiffener or projection on the base material with shape retention.
(iii) The device is capable of protecting the thread from shearing and deposition of foreign materials.
The above novel features of the device of the present invention have been realized by the non-obvious inventive steps of providing mechanism toi actuate the thread and hook needles, wherein the mechanism consists of globoidal cam-followers duly supported and capable of providing uniform velocity reciprocating motion to the needles. Further, the thread-needle is a hollow tubular needle capable of protecting the thread from shearing and deposition of foreign materials.

The following examples are given by way of illustration of the device of the present invention and should not be construed to limit the scope of the present invention.
Example 1
The specimens were produced using unidirectional carbon prepreg material of thickness 0.15mm in orthotropic and quasi-isotropic lay-ups and stitched on the half portion. These lay-ups were cured in autoclave and specimens were cut for stitched and unstitched cases. The test results obtained were as follows:
Orthotropic laminate Unstitched Stitched
Ultimate Tensile Strength (MPa) (MPa)
Casel 866.24 521.96
Case2 849.97 455.23
Case3 963.16 596.62
Reduction in strength = 41.26% of average.
Quasi-isotropic laminate Unstitched Stitched
Ultimate Tensile Strength (Mpa) (MPa)
Casel 551.61 457.03
Case2 552.85 518.91
CaseS 564.38 457.03
Reduction in strength = 14.13% of average.
The effect of stitching on in-plane properties of the quasi-isotropic laminate was acceptable and in line with the requirements.The effect of stitching on preforms in-plane mechanical properties of quasi-isotropic laminates were found in stitching direction and noted in prior art that tensile strength was reduced by the stitching by 20-25%. In our case the reduction was only 14.13%.

The main advantages of the device of the present invention are:
1. Capable of chain stitching with single seam with single thread.
2. Having a dual-needle single thread.
3. Capable of stitching on 3-D contour surface of cardboard, rubberized
components and pre-form of composite materials.
4. Access required is from one side.
5. Can also be used for tufting the composite materials, leather and stiff fabric.
6. Capable of protecting thread from shearing and deposition of foreign materials.
7. Stitching head capable of reciprocating movement with uniform velocity.
8. Can be used with more than one thread and for providing double seam.

We claim:
1. A device for stitching stiff, complex shaped and large size composite material
with single thread and single seam, which comprises a stitching head (SH) fitted
in combination with a known computer numerically controlled bed (MB) and the
said stitching head essentially consisting of a prime mover (GM) such as a
geared motor, the said motor being connected by means to a thread-needle
actuator (TNACT) and a hook-needle actuator (HNACT) respectively, the said
actuators (TNACT/and (HNACT) being connected to thread-needle (TN) and a
hook-needle (HN) through actuating links (GDTN and GDHN) respectively, the
said thread-needle (TN) and hook-needle (HN) being moveably held in position
by known means in such a manner so as to allow included angle between the
needles (TN and HN) in the range of 20 degree to 90 degree and the said thread-
needle (TN) and hook-needle (HN) being provided at needle end side with a
movable footrest (FR) and footrest movement controller (SL) such as a solenoid
actuator.
2. A device as claimed in claim 1, wherein the prime mover (GM), such as a
geared motor is provided with a single ended or double ended common output
shaft.
3. A device as claimed in claim 1, wherein the geared motor is a servo controlled
variable speed motor capable of providing output shaft with rotational movement
in the range of 0 to 50 rpm.
4. A device as claimed in claim 1, wherein the means for connecting the said
motor to the said thread-needle actuator (TNACT) and the said hook-needle
actuator (HNACT) is such as crank and connecting rod, cam and follower, twin
shaft mechanism capable of translating motor shaft rotation to twin shaft rotation
by known means.
5. A device as claimed in claim 1, wherein the thread-needle actuator (TNACT)

and the hook-needle actuator (HNACT) consists of globoidal cam and followers duly supported and capable of translating rotary motion to uniform velocity reciprocating motion in the range of 0 to 50 cycles.
6. A device as claimed in claim 1-5, wherein the synchronised motion of the
thread-needle and the hook-needle is derived by any electro-mechanical system
such as software cam or hardware cam, electric/hydraulic/pneumatic actuator,
linear motors and such other similar mechanisms.
7. A device as claimed in claim 1, wherein the thread-needle is a hollow tubular
needle capable of allowing the thread to pass through it.
8. A device as claimed in claim 1, wherein the stitching head (SH) is capable of
being used as a stand alone device and also for fitment onto a known positioning
device.
9. A device as claimed in claim 1, wherein one or more of the stitching head (SH)
being fitted on to a known computer numerically controlled bed (MB) having four
degrees of freedom, namely three linear and one rotational.
10. A device for stitching stiff complex shaped and large size composite material
with single thread and single seam, substantially as herein described with
reference to the examples and figures 3 to 6 of the drawings accompanying this
specification.

Documents:

261-del-2003-abstract.pdf

261-del-2003-claims.pdf

261-del-2003-complete specification (granted).pdf

261-del-2003-correspondence-others.pdf

261-del-2003-correspondence-po.pdf

261-del-2003-description (complete).pdf

261-del-2003-drawings.pdf

261-del-2003-form-1.pdf

261-del-2003-form-19.pdf

261-del-2003-form-2.pdf

261-del-2003-form-3.pdf

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Patent Number

217572

Indian Patent Application Number

261/DEL/2003

PG Journal Number

38/2008

Publication Date

19-Sep-2008

Grant Date

27-Mar-2008

Date of Filing

10-Mar-2003

Name of Patentee

COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG, NEW DELHI-110001, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	RAM SINGH VERMA	NATIONAL AEROSPACE LABORATORIES, AIR PORT ROAD, BANGALORE-560017,INDIA.
2	JAYASANKAR SOMASUNDARAN NAIR	NATIONAL AEROSPACE LABORATORIES, AIR PORT ROAD, BANGALORE-560017,INDIA.

PCT International Classification Number

D05B 1/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA