Patent Application
20190152013
The present invention relates to optical element processing, and more particularly to a polishing device for optical elements and a method thereof.
Conventional polishing techniques for spherical and planar optical elements are mainly high-speed polishing based on a quasi sphere center method. Devices thereof are cheap and operations are simple. However, according to the device, control of a contact pressure between a polishing disc and a work piece is inaccurate with a large floating range. Therefore, it is difficult to provide certain parameter processing. Moreover, according to conventional polishing methods, work pieces with same curvature radius and same caliber require only one polishing disc base, but work pieces with different curvature radius or different calibers require different polishing disc bases, which increases a processing cost.
Aspheric optical element has a great advantage with respect to the spherical optical element. In different areas of modern society, aspheric optical elements are greatly demanded. Therefore, how to accurately and efficiently process the aspheric optical elements has become an urgent problem to be solved.
Conventionally, mature numerical-controlled polishing technology for aspheric optical elements is mainly applied to processing of optical elements with large calibers, comprising: numerical-controlled optical surface forming technology based on small polishing disc, stress plate polishing technology, ion beam polishing technology, and magnetorheological technology. Surface accuracy of the numerical-controlled processing technologies described above is very high, and is better than λ/10. However, processing costs thereof are unacceptable for the aspheric optical elements which are more and more widely applied. Processing of aspheric optical elements with large calibers has basically gotten rid of manual methods.
For aspheric optical elements with medium or small calibers, manual processing and numerical-controlled processing are both conventionally used. Manual processing has a high requirement for worker experience. Surface accuracy of optical elements processed by experienced works with high accuracy is also up to λ/10, but efficiency is low and demands for aspheric optical elements are not satisfied. The numerical-controlled processing technology for aspheric optical elements with medium or small calibers are mainly compression molding, injection molding, etc., whose efficiency is very high. However, because of a processing principle of copy processing, accuracy is largely limited by moulds, and materials to be processed are also limited.
An object of the present invention is to provide a polishing device for optical elements and a method thereof, for increasing processing accuracy and efficiency, and lowering manufacturing costs.
A core of the present invention is a polishing method, wherein during polishing, a polishing film of the polishing tool is trimmed to form a spherical surface, a ring-like surface, a cylindrical surface, a conical surface or a plane. Contact between the polishing film and a work piece is a theoretical point-contact, line-contact or partial surface contact (the polishing film contacts not the whole work piece surface) according to a shape of a surface to be polished. A polishing pressure between the polishing tool and the work piece depends on an elastic modulus of the polishing film. Shapes of the work piece and the polishing tool, a pressing depth of the polishing tool (similar to a cutting depth when grinding), and a polishing pressure value are controlled according to a moving trace of the polishing tool relative to the work piece. The moving trace of the polishing tool relative to the work piece equals to the one during grinding. By trace control, it is ensured that the pressing depth of the polishing tool is corresponding to a required polishing pressure. A material removal mechanism is same as the one of conventional polishing methods, which depends on the polishing pressure, a relative linear speed, characteristics of the polishing film and the work piece, and a characteristic of polishing liquid.
The present invention firstly provides:
a partial surface-contacted polishing device for spherical and planar optical elements, comprising: a tool shank, and a cylinder polishing disc base; wherein the tool shank is connected to the cylinder polishing disc base and is mounted on a tool shaft of a numerical-controlled processing device, or the cylinder polishing disc base is integrated with the tool shaft for being a individual polishing device; wherein a polishing film is stuck on the cylinder polishing disc base.
Preferably, a polishing disc connecting rod is extruded from a bottom of the tool shank, for cooperating with a polishing disc fixing port hollowed at a top of the cylinder polishing disc base, wherein when the tool shank and the cylinder polishing disc base are connected and fixed, the polishing disc connecting rod is pressed into the polishing disc fixing port without interval for ensuring a coaxiality of the cylinder polishing disc base and the tool shaft.
Preferably, threaded fittings are provided on both the tool shank and the cylinder polishing disc base, the tool shank and the cylinder polishing disc base are fixed by screws. Preferably, the bolt is an inner hexagon bolt, which not only ensures connecting reliability therebetween, but also is convenient to install and maintain.
Preferably, the cylinder polishing disc base is cylinder-shaped, and a bottom thereof is arc-shaped; the cylinder polishing disc base comprises the polishing disc fixing port hollowed at the top thereof; the polishing film is stuck on an arc portion at the bottom of the cylinder polishing disc base. The polishing film is selected according to a material of the unprocessed work piece. There is no requirement for a shape of the polishing film as long as sticking is convenient and fixed.
Preferably, a curvature radius of the bottom, which is arc-shaped, of the cylinder polishing disc base is r1; before utilization, the polishing film stuck on the arc portion of the cylinder polishing disc base is trimmed, in such a manner that a surface section curve thereof is a precise arc with a curvature radius of r2; a height of the polishing film is h, which satisfies r2=r1+h.
A partial surface-contacted polishing method for spherical and planar optical elements, comprises steps of:
1) pressing a polishing disc connecting rod into a polishing disc fixing port, and fixing with screws, in such a manner that no interval exists therebetween;
2) sticking a polishing film on an arc-portion at a bottom of a cylinder polishing disc base with a binding agent, and trimming a curvature radius of the polishing film after the binding agent is solidified;
3) during trimming, installing a polishing device on a work piece shaft of a numerical-controlled device, and installing a trimming grinding wheel on a tool shaft of the numerical-controlled device; trimming the curvature radius of the polishing film by point-contacting, in such a manner that the curvature radius of the polishing film is identical, and is same with a curvature radius of the spherical or the planar optical element in value and opposite in direction; and
4) during utilization, installing the polishing device on the tool shaft of the numerical-controlled device, and installing an unprocessed work piece on the work piece shaft of the numerical-controlled device; during polishing, firstly inputting surface forming parameters of the unprocessed work piece and size parameters of the polishing device into a processing software, and generating a numerical-controlling file, so as to precisely position the polishing device and the unprocessed work piece by the numerical-controlled device, in such a manner that a curvature center of the polishing film coincides with a curvature center of the unprocessed work piece at any processing position; a surface of the polishing device forms ring-surface-contact with a surface of the unprocessed work piece for polishing.
Preferably, during utilization, the polishing device is installed on the tool shaft of the numerical-controlled device; the polishing device rotates around an axis of the tool shaft and swings around a swinging center B of the tool shaft; the polishing device is also movable along a horizontal direction; the unprocessed work piece is installed on the work piece shaft of the numerical-controlled device; the unprocessed work piece rotates around an axis of the work piece shaft and is movable along a vertical direction; a moving speed of the cylinder polishing disc base and a rotation speed of the unprocessed work piece are controlled by the numerical-controlled device at each processing position, in such a manner that a contacting pressure therebetween is constant at any processing position, for keeping a constant removal amount, and further achieving certain parameter processing.
Preferably, a trimming tool is a grinding wheel with an uncertain-shaped cutting blade, or a facing cutter with a certain-shaped cutting blade.
Preferably, a curvature radius of the bottom, which is arc-shaped, of the cylinder polishing disc base is r1; before utilization, the polishing film stuck on the arc portion of the cylinder polishing disc base is trimmed, in such a manner that a surface section curve thereof is a precise arc with a curvature radius of r2; a height of the polishing film is h, which satisfies r2=r1+h.
The present invention secondly provides:
a line-contacted polishing device for spherical and planar optical elements, comprising: a tool shank, and a polishing disc base; wherein the tool shank is connected to the polishing disc base and is mounted on a tool shaft of a numerical-controlled processing device, or the polishing disc base is integrated with the tool shaft for being a individual polishing device; wherein a polishing film is stuck on the polishing disc base; the polishing disc base is a profiling polishing disc base or a cylinder polishing disc base.
Preferably, a polishing disc connecting rod is extruded from a bottom of the tool shank, for cooperating with a polishing disc fixing port hollowed at a top of the polishing disc base, wherein when the tool shank and the polishing disc base are connected and fixed, the polishing disc connecting rod is pressed into the polishing disc fixing port without interval for ensuring a coaxiality of the cylinder polishing disc base and the tool shaft.
Preferably, threaded fittings are provided on both the tool shank and the polishing disc base, the tool shank and the polishing disc base are fixed by screws. Preferably, the bolt is an inner hexagon bolt, which not only ensures connecting reliability therebetween, but also is convenient to install and maintain.
Preferably, the profiling polishing disc base is a solid of revolution, a generating curve thereof is an arc with a curvature radius of r1; the polishing disc fixing port is provided at an end of the profiling polishing disc base for installing the profiling polishing disc base on the tool shank; before utilization, the polishing film is stuck on a revolution surface of the profiling polishing disc base, and a generating curve of the polishing film is precisely trimmed for being an arc with an curvature radius of r2; a height of the polishing film is h, which satisfies r2=r1+h.
Preferably, the polishing disc base is a cylinder, a first end thereof is arc-shaped with a curvature radius of r3, and the polishing disc fixing port is provided at a second end thereof for installing the cylinder polishing disc base on the tool shank; before utilization, the polishing film is stuck on an arc portion at a bottom of the cylinder polishing disc base; and a section curve of the polishing film is precisely trimmed for being an accurate arc with an curvature radius of r4; the height of the polishing film is h, which satisfies r4=r3+h.
A line-contacted polishing method for spherical and planar optical elements, comprises steps of:
1) pressing a polishing disc connecting rod into a polishing disc fixing port, and fixing with screws, in such a manner that no interval exists therebetween;
2) sticking a polishing film on a bottom of a polishing disc base with a binding agent, and trimming a curvature radius of the polishing film after the binding agent is solidified;
3) during trimming, installing a polishing device on a work piece shaft of a numerical-controlled device, and installing a trimming grinding wheel on a tool shaft of the numerical-controlled device; trimming the curvature radius of the polishing film by point-contacting, in such a manner that the curvature radius of the polishing film is identical; and
4) during utilization, installing the polishing device on the tool shaft of the numerical-controlled device, and installing an unprocessed work piece on the work piece shaft of the numerical-controlled device; during polishing, firstly inputting surface forming parameters of an aspheric surface of the unprocessed work piece and size parameters of the polishing device into a processing software, and generating a numerical-controlling file, so as to control the polishing device and the unprocessed work piece by the numerical-controlled device, in such a manner that the polishing device line-contacts with the unprocessed work piece at any processing position; wherein during polishing, a contacting trace of a profiling polishing disc base and the unprocessed work piece is a portion of a meridian section curve of the unprocessed work piece, which belongs to profiling processing; a contacting trace of a cylinder polishing disc base and the unprocessed work piece is an envelope circle, which belongs to generating processing.
Preferably, during utilization, the polishing device is installed on the tool shaft of the numerical-controlled device; the polishing device rotates around an axis of the tool shaft and swings around a swinging center B of the tool shaft; the polishing device is also movable along a horizontal direction; the unprocessed work piece is installed on the work piece shaft of the numerical-controlled device; the unprocessed work piece rotates around an axis of the work piece shaft and is movable along a vertical direction; a moving speed of the cylinder polishing disc base and a rotation speed of the unprocessed work piece are controlled by the numerical-controlled device at each processing position, in such a manner that a contacting pressure therebetween is constant at any processing position, for keeping a constant removal amount, and further achieving certain parameter processing.
Preferably, a trimming tool is a grinding wheel with an uncertain-shaped cutting blade, or a facing cutter with a certain-shaped cutting blade.
Preferably, the polishing film is stuck on a revolution surface of the profiling polishing disc base, and a sticking height ensures that the polishing film is fixedly stuck and covers the whole revolution surface; or the polishing film is stuck on a bottom, which is arc-shaped, of the cylinder polishing disc base. There is no requirement for a shape of the polishing film as long as sticking is convenient and fixed.
Preferably, the profiling polishing disc base is a solid of revolution, a generating curve thereof is an arc with a curvature radius of r1; a generating curve of the polishing film after being precisely trimmed is an arc with an curvature radius of r2; and a height of the polishing film is h, which satisfies r2=r1+h; or the polishing disc base is a cylinder, a first end thereof is arc-shaped with a curvature radius of r3, a section curve of the polishing film after being precisely trimmed is an accurate arc with an curvature radius of r4; and the height of the polishing film is h, which satisfies r4=r3+h.
The present invention thirdly provides:
a point-contacted polishing device for aspheric optical elements, comprising: a tool shank, and a polishing disc base; wherein the tool shank is connected to the polishing disc base and is mounted on a tool shaft of a numerical-controlled processing device, or the polishing disc base is integrated with the tool shaft for being a individual polishing device; wherein a polishing film is stuck on the polishing disc base; the polishing disc base is a bowl-like polishing disc base or a spherical polishing disc base.
Preferably, a polishing disc connecting rod is extruded from a bottom of the tool shank, for cooperating with a polishing disc fixing port hollowed at a top of the polishing disc base, wherein when the tool shank and the polishing disc base are connected and fixed, the polishing disc connecting rod is pressed into the polishing disc fixing port without interval for ensuring a coaxiality of the cylinder polishing disc base and the tool shaft.
Preferably, threaded fittings are provided on both the tool shank and the polishing disc base, the tool shank and the polishing disc base are fixed by screws. Preferably, the bolt is an inner hexagon bolt, which not only ensures connecting reliability therebetween, but also is convenient to install and maintain.
Preferably, the polishing disc base is the bowl-like polishing disc base which is cylinder-shaped, and a bottom thereof is arc-shaped; the bowl-like polishing disc base comprises the polishing disc fixing port hollowed at the top thereof; the polishing film is stuck on an arc portion at the bottom of the bowl-like polishing disc base; wherein a curvature radius of the bottom of the bowl-like polishing disc base is r1; a surface section curve of the polishing film after being trimmed is a precise arc with a curvature radius of r2; a height of the polishing film is h, which satisfies r2=r1+h.
Preferably, the polishing disc base is the spherical polishing disc base which is spherical-shaped or partly spherical-shaped; the spherical polishing disc base comprises the polishing disc fixing port hollowed at the top thereof; the polishing film is stuck on a spherical surface; wherein a curvature radius of spherical polishing disc base is r3; a curvature radius of the polishing film after being trimmed is r4; and a height of the polishing film is h, which satisfies r4=r3+h.
A point-contacted polishing method for aspheric optical elements, comprises steps of:
1) pressing a polishing disc connecting rod into a polishing disc fixing port, and fixing with screws, in such a manner that no interval exists therebetween;
2) sticking a polishing film on a polishing disc base with a binding agent, and trimming a curvature radius of the polishing film after the binding agent is solidified;
3) during trimming, installing a polishing device on a work piece shaft of a numerical-controlled device, and installing a trimming grinding wheel on a tool shaft of the numerical-controlled device; trimming the curvature radius of the polishing film by point-contacting, in such a manner that the curvature radius of the polishing film is identical; and
4) during utilization, installing the polishing device on the tool shaft of the numerical-controlled device, and installing an unprocessed work piece on the work piece shaft of the numerical-controlled device; during polishing, firstly inputting surface forming parameters of an aspheric surface of the unprocessed work piece and size parameters of the polishing device into a processing software, and generating a numerical-controlling file, so as to control the polishing device and the unprocessed work piece by the numerical-controlled device, in such a manner that the polishing device contacts with the unprocessed work piece at a P point of any processing position; wherein the P point coincides with an aspheric meridian section curve relative to a moving trace of the unprocessed work piece.
Preferably, if the unprocessed work piece is convex and is to be externally polished, trimming an external arc of the polishing film; if the unprocessed work piece is convex and is to be internally polished, trimming an internal arc of the polishing film; i3 the unprocessed work piece is concave, trimming the external arc of the polishing film, or trimming the external arc and the internal arc of the polishing film. A trimming tool is a grinding wheel with an uncertain-shaped cutting blade, or a facing cutter with a certain-shaped cutting blade. There is no requirement for a shape of the polishing film as long as sticking is convenient and fixed.
Preferably, during utilization, the polishing device is installed on the tool shaft of the numerical-controlled device; the polishing device rotates around an axis of the tool shaft and swings around a swinging center B of the tool shaft; the polishing device is also movable along a horizontal direction; the unprocessed work piece is installed on the work piece shaft of the numerical-controlled device; the unprocessed work piece rotates around an axis of the work piece shaft and is movable along a vertical direction; a moving speed of the cylinder polishing disc base and a rotation speed of the unprocessed work piece are controlled by the numerical-controlled device at each processing position, in such a manner that a contacting pressure therebetween is constant at any processing position, for keeping a constant removal amount, and further achieving certain parameter processing.
Preferably, a curvature radius of the bottom of the bowl-like polishing disc base is r1; a surface section curve of the polishing film after being trimmed is a precise arc with a curvature radius of r2: a height of the polishing film is h, which satisfies r2=r1+h; wherein a curvature radius of spherical polishing disc base is r3; a curvature radius of the polishing film after being trimmed is r4; and a height of the polishing film is h, which satisfies r4=r3+h.
The present invention has advantages as follows.
1) According to the present invention, the curvature radius of the polishing film is able to be accurately trimmed.
2) According to the present invention, the tool shank is independent and universal, thereby reducing the processing cost of the polishing device.
3) According to the conventional spherical and planar optical elements polishing techniques, an entire surface of a polishing disc contacts with a work piece, which is spherical or planar contact, and depends on swinging of the polishing disc to achieve disorder polishing. According to the present invention, the polishing disc is cylinder-shaped. During polishing, ring-surface-contact is formed. By trimming the polishing film, polishing discs with same sizes are applicable to work pieces with different curvature radii.
4) According to the conventional polishing techniques, a quasi sphere center method is utilized. A polishing disc is surface-contacted with a work piece and polishes with a profiling method. According to the present invention, the polishing disc is line-contacted with the work piece, which means that during polishing, a contacting trace of the polishing disc and the work piece is a closed or a non-close curve. Because of rotation of the work piece, a desired surface is obtained.
5) According to the present invention, the polishing discs, especially the bowl-like polishing disc, are universal. By trimming the polishing film, polishing discs with same sizes are applicable to work pieces with different curvature radii.
6) According to the present invention, the moving speed of the polishing disc base and the rotation speed of the unprocessed work piece are controlled by the numerical-controlled device at each processing position, in such a manner that the contacting pressure therebetween is constant at any processing position, for keeping a constant removal amount, and further achieving certain parameter processing.
Element reference: 1—tool shank: 2—cylinder polishing disc base; 3—polishing film; 4—screw; 5—trimming grinding wheel; 6—unprocessed work piece; 7—profiling polishing disc base; 8—spherical polishing disc base; 9—work piece; 11—polishing disc connecting rod; 12—bowl-like polishing disc base; 21—polishing disc fixing port; 31—enternal arc; 32—internal arc; 100—polishing device.
Referring to preferred embodiments, the present invention is further illustrated.
Referring to
Accordingly, the embodiment 1 provides a surface-contacted polishing device for spherical and planar optical elements.
Preferred embodiment 1:
Referring to
A polishing film 3 is stuck on an arc portion at a bottom of the cylinder polishing disc base 2. The polishing film 3 is selected according to a material of the unprocessed work piece 6. There is no requirement for a shape of the polishing film 3 as long as sticking is convenient and fixed. The polishing film 3 is stuck on the arc portion at the bottom of the cylinder polishing disc base 2 by a binding agent, and a sticking height ensures that the polishing film 3 is fixedly stuck.
During installing, the polishing disc connecting rod 11 is pressed into the polishing disc fixing port 21. Preferably, screws 4, which are inner hexagon bolts, are used for fixing, in such a manner that no interval exists therebetween. One side of the polishing film 3 is applied with the binding agent for being stuck on the arc-portion at the bottom of the cylinder polishing disc base 2. Preparation is finished after the binding agent is solidified.
After installing as above, the polishing film 3 of the polishing device 100 is trimmed. The polishing device 100 is installed on a work piece shaft of a numerical-controlled device, and a trimming grinding wheel 5 is installed on a tool shaft of the numerical-controlled device. A curvature radius of the polishing film 3 is trimmed by point-contacting, in such a manner that the curvature radius of the polishing film 3 is identical, and is same with a curvature radius of the spherical or the planar optical element in value and opposite in direction for improving positioning accuracy and processing accuracy.
Preferred embodiment 2:
Preferred embodiment 3:
It should be understand that, no matter in the preferred embodiment 1, 2 or 3, a contacting area between the polishing film 3 and the unprocessed work piece 6 is relatively small. Therefore, the polishing film 3 is easy to be worn out, but the polishing device 100 has certain universality, which means that by precisely trimming the curvature radius of the polishing film 3, the polishing device 100 is suitable for polishing elements with different calibers and curvature radius.
An embodiment 2 of the present invention:
A line-contacted polishing device for spherical and planar optical elements is provided.
Preferred embodiment 4:
Referring to
A polishing film 3 is stuck on an arc portion at a bottom of the profiling polishing disc base 7. The polishing film 3 is selected according to a material of the unprocessed work piece 6. There is no requirement for a shape of the polishing film 3 as long as sticking is convenient and fixed. The polishing film 3 is stuck on a revolution surface of the profiling polishing disc base 7 by a binding agent, and a sticking height ensures that the polishing film 3 is fixedly stuck and covers the whole revolution surface.
During installing, the polishing disc connecting rod 11 is pressed into the polishing disc fixing port 21. Preferably, screws 4, which are inner hexagon bolts, are used for fixing, in such a manner that no interval exists therebetween. One side of the polishing film 3 is applied with the binding agent for being stuck on the revolution surface of the profiling polishing disc base 7. Preparation is finished after the binding agent is solidified.
After installing as above, the polishing film 3 of the polishing device 100 is trimmed.
Preferred embodiment 5:
Preferred embodiment 6:
According to the preferred embodiment 6, the cylinder polishing disc base 2 is cylinder-shaped, wherein an advantage of a shape thereof is that polishing discs with same sizes is suitable for polishing work pieces with different calibers and curvature radii. A processing principle thereof is same with the one of grinding, which belongs to profiling processing. A contacting trace of the cylinder polishing disc base 2 and the unprocessed work piece 6 is an envelope circle.
An embodiment 3 of the present invention:
Preferred embodiment 7:
Referring to
A polishing film 3 is stuck on an arc portion at a bottom of the cylinder polishing disc base 2. The polishing film 3 is selected according to a material of the unprocessed work piece 6. There is no requirement for a shape of the polishing film 3 as long as sticking is convenient and fixed. The polishing film 3 is stuck on the arc portion at the bottom of the cylinder polishing disc base 2 by a binding agent, and a sticking height ensures that the polishing film 3 is fixedly stuck.
During installing, the polishing disc connecting rod 11 is pressed into the polishing disc fixing port 21. Preferably, screws 4, which are inner hexagon bolts, are used for fixing, in such a manner that no interval exists therebetween. One side of the polishing film 3 is applied with the binding agent for being stuck on the arc-portion at the bottom of the cylinder polishing disc base 2. Preparation is finished after the binding agent is solidified.
After installing as above, the polishing film 3 of the polishing device 100 is trimmed. The polishing device 100 is installed on a work piece shaft of a numerical-controlled device, and a trimming grinding wheel 5 is installed on a tool shaft of the numerical-controlled device. A curvature radius of the polishing film 3 is trimmed by point-contacting. If the unprocessed work piece 6 is convex and is to be externally polished, trimming an external arc 31 of the polishing film 3; if the unprocessed work piece 6 is convex and is to be internally polished, trimming an internal arc 32 of the polishing film 3; if the unprocessed work piece 6 is concave, trimming the external arc 31 of the polishing film 3, or trimming the external arc 31 and the internal arc 32 of the polishing film 3. After treatment, the curvature radius of the polishing film 3 is identical, which improves positioning accuracy and processing accuracy.
Preferred embodiment 8: Referring to
According to the preferred embodiment 8, the spherical polishing disc base 8 is spherical, whose advantage is that a position range of the P point is larger than the one of the preferred embodiment 7, in such a manner that a linear speed range of the P point is also larger for improving polishing. According to the preferred embodiment 8, a convex element is only able to be externally polished, which is different from the preferred embodiment 7.
It should be understand that, no matter in the preferred embodiment 7 or 8, a contacting area between the polishing film 3 and the unprocessed work piece 6 is point-contact. Therefore, the P point and nearby areas will be continuously worn out, which will lower processing accuracy. At that moment, a position of the P point on the polishing film 3 may be changed or the polishing film 3 may be trimmed again for regaining the processing accuracy. Preferably, the position of the P point is changed, because by trimming, an arc shape of the polishing film 3 is a standard circle, which means that a distant between the P point and an arc center is certain at any position on the arc. By changing the position of the P point, the polishing film 3 will not be trimmed again and again, which improves a coefficient of utilization thereof. After several changing, the polishing film 3 must be trimmed again for ensuring the process accuracy.
One skilled in the art will understand that the embodiment of the present invention as shown in the drawings and described above is exemplary only and not intended to be limiting. It will thus be seen that the objects of the present invention have been fully and effectively accomplished. Its embodiments have been shown and described for the purposes of illustrating the functional and structural principles of the present invention and is subject to change without departure from such principles. Therefore, this invention includes all modifications encompassed within the spirit and scope of the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201320123105.7 | Mar 2013 | CN | national |
| 201320123777.8 | Mar 2013 | CN | national |
| 201320124181.X | Mar 2013 | CN | national |
This is a Divisional application of the U.S. application Ser. No. 14/772,307, filed Sep. 2, 2015, which claims priority under 35 U.S.C. 119(a-d) to CN 201320123777.8, filed Mar. 19, 2013; CN 201320124181.X, filed Mar. 19, 2013; and CN 201320123105.7, filed Mar. 19, 2013.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 14772307 | Sep 2015 | US |
| Child | 16261582 | US |
