Disclosure of Invention
The embodiment of the invention provides a method and a system for pressing a tire lens by a free cavity, and provides a method which is simpler and reduces the process cost.
In a first aspect, embodiments of the present invention provide a method for pressing a tire lens in a free cavity, including:
providing a preform;
melting the preform at a high temperature, and performing die pressing to form a lens blank, wherein the lens blank forms a preset sagittal plane shape and a preset meridional plane shape in a molten state;
cutting the lens blank to form the tire lens.
Optionally, melting the preform at a high temperature and press-molding to form a lens blank, the lens blank forming a predetermined sagittal plane shape and a predetermined meridional plane shape in the melted state, comprising:
designing the shape of the preform according to the material characteristics of the preform, melting the preform at a high temperature, and adjusting the die pressing temperature and the die pressing compression amount;
and forming the lens blank by die pressing the preform, wherein the lens blank forms the preset sagittal plane shape and the preset meridional plane shape in a molten state.
Optionally, the preform comprises a polished sphere.
Optionally, the preform includes a polished spherical cap removal body, and the polished spherical cap removal body is a part remaining after spherical caps at two ends of the sphere are removed.
Optionally, the preform comprises a polished cylinder, and the polished cylindrical outer surface may be formed by a wire drawing process.
Optionally, when the preform is molded, the axial direction of the polishing cylinder is parallel to the molding pressure direction; or,
when the preform is molded, the axial direction of the polishing cylinder is perpendicular to the pressure direction of the molding.
Optionally, the preform comprises a polished cuboid.
Optionally, the preform includes an inner and outer polished circular tube, and when the preform is molded, an axial direction of the inner and outer polished circular tube is parallel to a pressure direction of the molding.
Optionally, after cutting the lens blank to form the tire lens, further comprising:
and polishing the cut surface of the tire lens after the lens blank is cut.
In a second aspect, an embodiment of the present invention further provides a system for performing the method of the first aspect, including an upper mold core, a lower mold core, a sleeve, and a molding press, where the upper mold core and the lower mold core are disposed in the sleeve;
and the mould press presses the upper mould core downwards to deform the high-temperature molten preformed body into a lens blank.
The embodiment of the invention provides a method for pressing a tire lens by a free cavity, which is characterized in that a preform is melted at high temperature and is molded to form a lens blank, the lens blank forms a preset sagittal plane shape and a preset meridian plane shape in the molten state, and the lens blank is cut to form the tire lens. That is, unlike the conventional art in which convex and concave lenses are formed, in which only the central portion of the molded preform in contact with the upper and lower mold cores is often left, and the edge portion "scrap" in contact with the upper and lower mold cores is discarded, the working surface of the finished product is formed by the mold surface, and the working surface profile is determined by the mold surface, in the embodiment of the present invention, the central portion of the molded preform (lens blank in the present application) in contact with the upper and lower mold cores is left, and further, the edge portion of the lens blank not in contact with the upper and lower mold cores is left as a tire lens whose tread is formed in a free space by the surface tension of the molten material, that is, in a free cavity. It should be further noted that, in general, the tire lens is directly milled by a numerical control device by using a single-point diamond cutter, or is formed by pressing after a mold is machined by using the single-point diamond cutter, which has the problem of high machining cost, and in the application, the tire lens which is more expensive than the common aspheric surface lens with the rotary surface is formed by using the "leftover material" of the lens blank, so that the method is more concise and reduces the process cost.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some structures related to the present invention are shown in the drawings, not all of them.
Fig. 2 is a flowchart of a method for pressing a tire lens in a free cavity according to an embodiment of the present invention, fig. 3 is a schematic structural diagram of a preform according to an embodiment of the present invention, fig. 4 is a schematic structural diagram of a lens blank formed by the preform shown in fig. 3 in a top view, fig. 5 is a schematic structural diagram of a lens blank formed by the preform shown in fig. 3 in a side view, fig. 6 is a schematic structural diagram of a lens blank formed by the preform shown in fig. 3 in a cutting manner, and referring to fig. 1 to 6 in combination, the method for pressing a tire lens in a free cavity includes the following steps:
and S110, providing a preformed body.
The material of the preform may be, for example, low melting glass or plastic, and the lens finally formed from the preform may be a glass lens or a plastic lens.
Illustratively, referring to fig. 3, the preform comprises a polished sphere, i.e., the preform may be shaped as a polished sphere having a radius r.
And S120, melting the preform at a high temperature, and performing die pressing to form a lens blank, wherein the lens blank forms a preset sagittal plane shape and a preset meridional plane shape in a molten state.
In this step, the preform is melted at a high temperature and pressure is applied to the preform in a melted state, and the portions of the preform in a melted state, which are in contact with the upper mold core and the lower mold core, are forced to deform by the pressure of the upper mold core and the lower mold core and are flattened in the pressing direction. And the contact part of the preformed body in the molten state with the upper die core and the lower die core is limited to form a preset contact surface. On the other hand, the portion of the preform in the molten state which is not in contact with the upper and lower cores (i.e., the edge of the preform in the molten state) is not formed by contact with the upper and lower cores, but is freely formed by surface tension, that is, in the free cavity.
Illustratively, referring to fig. 4 and 5, after the preform is molded to form a lens blank of thickness H (illustrated in fig. 5 as a pie of thickness H, not the letter "I" since it is labeled in fig. 5 as being flipped 90 ° along the thickness direction label "H"), the meridional nominal radius of curvature R2 is present in the meridional plane and the meridional outer edge is rounded due to symmetry. Has a sagittal nominal radius of curvature R1in the sagittal plane. In the embodiments of the present invention, since the meridional nominal radius of curvature and the meridional nominal radius both indicate the case of curvature on the meridional surface, and the meridional radius is a special case of the meridional nominal radius of curvature, both are indicated by R2, and are not distinguished from each other. The sagittal plane nominal curvature radius and the sagittal plane radius both represent curvature in the meridian plane, and the sagittal plane radius is a special case of the sagittal plane nominal curvature radius, so that the two are represented by R1 without distinction.
And S130, cutting the lens blank to form the tire lens.
In this step, the lens blank formed by the high-temperature press molding of the preform in the above step S120 is cut.
Illustratively, referring to fig. 6, the edges of the lens blank are cut to form a tire lens. In fig. 6, a plurality of small tire lenses can be cut out in the circumferential direction.
The embodiment of the invention provides a method for pressing a tire lens by a free cavity, which is characterized in that a preform is melted at high temperature and is molded to form a lens blank, the lens blank forms a preset sagittal plane shape and a preset meridian plane shape in the molten state, and the lens blank is cut to form the tire lens. That is, unlike the conventional art in which convex and concave lenses are formed, the conventional art often retains only the central portions of the molded preform in contact with the upper and lower cores, and discards the marginal portions "rim charge" in contact with the upper and lower cores, the working surface of the finished product being formed by the mold surface, the working surface profile being determined by the mold surface, whereas in the embodiment of the present invention, the central portions of the molded preform (in this case, the lens blank) in contact with the upper and lower cores are retained, and further, the marginal portions of the lens blank not in contact with the upper and lower cores are retained as a tire lens, the tire tread of which is formed in free space by the surface tension of the molten material. It should be further noted that, in general, the tire lens is directly milled by a numerical control device by using a single-point diamond cutter, or is formed by pressing after a mold is machined by using the single-point diamond cutter, which has the problem of high machining cost, and in the application, the tire lens which is more expensive than the common aspheric surface lens with the rotary surface is formed by using the "leftover material" of the lens blank, so that the method is more concise and reduces the process cost. Further, since the embodiment of the present invention and the conventional techniques do not discard the edge portions contacting with the upper mold core and the lower mold core, the edge portions not contacting with the upper mold core and the lower mold core are cut off without care or design, and the reverse technical concept is adopted to form the tire lens by using the "edge material" of the lens blank, the lens blank is melted at a high temperature and molded to form the lens blank before cutting the lens blank to form the tire lens, and the lens blank forms the predetermined sagittal plane shape and the predetermined meridional plane shape in a melted state. Namely, the preform is molded to form a predetermined sagittal plane shape and a predetermined meridional plane shape.
It should be further noted that the shape of the preform affects the sagittal plane shape and the meridional plane shape of the formed tire lens, and the shape of the preform needs to be precisely designed and modified for many times to ensure that the tire lens with the preset sagittal plane shape and the preset meridional plane shape is finally formed. Further, the inventive concept of the present application is directed to manufacturing a tire lens, and the remaining portion of the cut lens blank after cutting the edge thereof to form the tire lens is not the focus of attention, and in some embodiments, the remaining portion of the cut lens blank after cutting the edge thereof to form the tire lens can be used as a conventional lens, and in other embodiments, the remaining portion of the cut lens blank after cutting the edge thereof to form the tire lens cannot have the performance required of a conventional optical element and needs to be discarded.
Illustratively, when the preform mass is small enough that the influence of gravity is small enough relative to the surface tension of the molten preform, the sagittal plane may be made to form a symmetrical arc (arc or non-arc) of nominal radius R1.
Illustratively, the preform comprises a polished sphere having a radius r less than or equal to 10 mm. Further, the radius r of the polished sphere can also be less than or equal to 5mm to further reduce the effect of gravity on surface tension.
Fig. 7 is a flow chart of another method for pressing a tire lens by a free cavity according to an embodiment of the present invention, and referring to fig. 7, the method for pressing the tire lens by the free cavity comprises the following steps:
and S210, providing a preform.
S220, designing the shape of the preform according to the material characteristics of the preform, melting the preform at a high temperature, and adjusting the die pressing temperature and the die pressing compression amount.
The material properties of the preform refer to the properties of the material of the preform, in particular its physical properties, such as young's modulus, poiserime ratio, viscosity, melting point, conversion temperature, etc. For example, the preform may be made of glass or plastic. When the preform is made of low-melting glass, glass materials with different refractive indexes and different Abbe coefficients can be respectively used. The shape of the preform may be various, and may include, for example, a sphere in the above examples, and in other embodiments, the preform may have other shapes, which will be further described below.
In the step, the shape of the preform is designed according to the material characteristics of the preform, and correspondingly, the molding temperature and the molding compression amount are adjusted, so that the edge of the lens blank molded and formed in the subsequent step finally forms a preset sagittal plane shape and a preset meridian plane shape, and the surface shape requirement of the formed tire lens is finally met.
And S230, forming a lens blank by die pressing the preform, wherein the lens blank forms a preset sagittal plane shape and a preset meridional plane shape in a molten state.
And S240, cutting the lens blank to form the tire lens.
In the embodiment of the present invention, step S120 in the above embodiment is subdivided into: designing the shape of the preform according to the material characteristics of the preform, melting the preform at a high temperature, and adjusting the die pressing temperature and the die pressing compression amount; and forming the lens blank by die pressing the preform, wherein the lens blank forms the preset sagittal plane shape and the preset meridional plane shape in a molten state.
Fig. 8 is a schematic structural view of another preform according to an embodiment of the present invention, fig. 9 is a schematic structural view of a lens blank formed from the preform shown in fig. 8, and referring to fig. 8 and 9, the preform includes a polished cylinder, which can be formed by a conventional polishing process or a wire drawing method. That is, the preform may be cylindrical in shape, with the radius of the cylindrical surface of the cylinder being designated as r. The height of the cylinder is marked h.
Alternatively, referring to fig. 8 and 9, when the preform is molded, the axial direction of the polishing cylinder is parallel to the pressing direction of the molding. That is, the preform is flattened by applying pressure in the height direction of the cylinder, and the resulting wafer is shown in fig. 5, which is not described herein.
Fig. 10 is a schematic structural view of another preform provided in an embodiment of the present invention, fig. 11 is a schematic structural view of a lens blank formed from the preform shown in fig. 10, and referring to fig. 10 and 11, the preform includes a polished rectangular parallelepiped, that is, the preform may have a polished rectangular parallelepiped shape. As a specific example, the preform may further include a cube (the cube is a specific rectangular parallelepiped). The side lengths of the sections of the cuboids are marked as a and b respectively, and the height of the cuboid is marked as h. Polishing the cuboid means polishing the cuboid.
Fig. 12 is a schematic structural view of another preform according to an embodiment of the present invention, fig. 13 is a schematic structural view of a top view of a lens blank formed from the preform shown in fig. 12, fig. 14 is a schematic structural view of a side view of the lens blank formed from the preform shown in fig. 12, and referring to fig. 12 to 14, the preform includes a polished cylinder, and the polished cylinder can be formed by a conventional polishing process or a wire drawing method. When the preform is molded, the axial direction of the polishing cylinder is perpendicular to the pressing direction of the molding. That is, the preform is flattened by applying pressure in the direction of the cylindrical surface of the polishing cylinder. The radius of the cylindrical surface of the polishing cylinder is denoted r and the length of the polishing cylinder is denoted l. The polished cylinder is the polished cylinder.
When the aspect ratio l/R of the cylindrical blank is large enough, R2in fig. 13 tends to infinity, and the extruded tire lens surface degrades into a cylindrical surface with only a sagittal radius R1, which is a special form of tire lens.
Fig. 15 is a side view of a lens blank formed from the preform shown in fig. 3, with reference to fig. 3-5 and fig. 15, and taking a sphere as an example of the preform, the sphere is pressed into a circular cake with a cross-sectional center diameter D and semicircular sides (in an ideal state), a radius R1 of the sagittal plane is equal to half of the thickness H, a radius R2 of the meridional plane, a volume Vb of the spherical preform, and the volume of the circular cake (i.e., the lens blank) formed after flattening is Vt, wherein Vb is equal to Vt. Due to the rotational symmetry of the sphere and the round cake, the volume relation of the sphere and the round cake can be obtained from the sectional graph, and the following specific requirements are met:
2*(R2-R1)*H+π*R1 2 =π*r 2 wherein the operator "+" denotes multiplication.
Thus, for a given sphere radius r and height H of the pie body, one can obtain:
R1=H/2,
R2=π*(r 2 -(H/2) 2 )/(2*H)+H/2。
in fact, the sagittal plane is not generally semicircular, and when the oblate volume is integrated by numerical calculation, multiple combined solutions of the nominal radius R1 and the radius R2 can be obtained under the condition of the specified preform volume Vb and the specified thickness H.
Fig. 16 is a schematic structural view of another preform according to an embodiment of the present invention, fig. 17 is a schematic structural view of a lens blank formed by the preform shown in fig. 16, and referring to fig. 16 and 17, the preform includes a polished spherical cap body, which is a portion remaining after spherical caps at two ends of the sphere are removed (in order to ensure symmetry, the rise heights of the spherical caps at the two ends are consistent). As illustrated in fig. 16 and 17, a plurality of polished spherical cap bodies, and a plurality of lens blanks formed after the polished spherical cap bodies are molded. And polishing the spherical cap removing body, namely the polished spherical cap removing body.
Exemplarily, referring to fig. 16 and 17, a truncated spherical body with radius R1, an oblate body extruded with sagittal radius R11, meridional radius R21; a spherical-removed crown body with a radius R2, and an oblate body with a sagittal plane radius R12 and a meridian plane radius R22 is extruded; a spherical-removed crown body with a radius R3, and an oblate body with a sagittal plane radius R13 and a meridian plane radius R23 is extruded; a truncated spherical body with a radius R4, an oblate body pressed with a sagittal radius R14 and a meridional radius R24. For the preform, r1 < r2 < r3 < r4, h1 > h2 > h3 > h 4. Where h1 is the height of the deglobulated crown with radius r1, h2 is the height of the deglobulated crown with radius r2, h3 is the height of the deglobulated crown with radius r3, and h4 is the height of the deglobulated crown with radius r 4. For the lens blanks formed after molding, there are R11 < R12 < R13 < R14, R21 > R22 > R23 > R24.
Illustratively, referring to fig. 16, the truncated ball is used as a preform, pressed into a disk of fig. 17, and then cut as shown in fig. 6 to obtain a tire mirror as shown in fig. 1, wherein R2 is 5.31mm, R1 is 0.835mm, X is 4.0mm, Y is 1.47mm, and the center thickness (not shown) is 1.50 mm. The adopted preform material is low-melting glass, the refractive index of the glass is 1.81, the Abbe coefficient is 40.99, the Young modulus is 11506, and the Poisson ratio is 0.3.
Fig. 18 is a schematic structural view of another preform according to an embodiment of the present invention, fig. 19 is a schematic structural view of a top view of a lens blank formed from the preform shown in fig. 18, fig. 20 is a schematic structural view of a side view of the lens blank formed from the preform shown in fig. 18, and referring to fig. 18 to 20, the preform includes an inner and outer polished circular tube body, and the inner and outer polished cylindrical surfaces thereof may be formed by a conventional polishing process or a wire drawing method. When the preform is molded, the axial direction of the circular tube body is parallel to the pressure direction of the molding. That is, the preform is flattened by applying a pressure in the cross-sectional direction of the tubular body.
The outer radius of the circular tube body is rout, the inner radius of the circular tube body is rin, the height of the circular tube body is H, when pressure is applied, the outer cylindrical surface of the circular tube body is located in an outer free cavity, the inner cylindrical surface of the circular tube body is located in an inner free cavity, the circular tube body is formed by surface tension, the tire shape or the bracelet shape with the thickness of H is obtained after the circular tube body is pressed, namely, the outer free cavity is formed, the surface of the tire surface is a tire surface with a convex arc sagittal plane R1out and a convex sub meridian plane R2out, the inner free cavity is formed, the tire surface is a tire surface with a convex arc sagittal plane R1in and a concave sub meridian plane R2in, the tire surface is cut by an area 7 in the drawing, namely, a bright convex-concave tire surface is obtained, and then the opposite rectangular cut surface of the tire surface is polished, so that the convex-concave tire lens is obtained.
Optionally, after cutting the lens blank to form the tire lens, the method of free-cavity pressing the tire lens further comprises: and polishing the cut surface of the tire lens after the lens blank is cut. In embodiments of the invention, the tire lens is a part of the lens blank (see fig. 6) because the tire lens has no cut surface before it is cut to form the tire lens. After the tire lens is cut and formed, a cut surface of the tire tread opposite to the tire tread is a new light transmission surface, and it is necessary to perform a polishing process on the cut surface of the tire lens after cutting the lens blank.
Fig. 21 is a schematic view of a system for free-cavity compression of a tire lens according to an embodiment of the present invention after a preform is placed, and fig. 22 is a schematic view of a system for free-cavity compression of a tire lens according to an embodiment of the present invention when a lens blank is formed, and referring to fig. 21 and 22, the system for free-cavity compression of a tire lens includes an upper mold core 1, a lower mold core 3, a sleeve 2, and a molding press (not shown), and the upper mold core 1 and the lower mold core 3 are placed in the sleeve 2. The upper die core 1 and the lower die core 3 are precisely matched with the sleeve 2in the radial direction. In addition, the sleeve 2 also plays a role in axially limiting the upper die core 1. The mold press presses the upper mold insert 1 to deform the high temperature molten preform into a lens blank.
Illustratively, as shown in fig. 21 and 22, when the molding surface is a plane, that is, the lower surface of the upper core 1 and the upper surface of the lower core 3 are planes, the (spherical) preform is pressed into a tire-shaped wafer 5.
Fig. 23 is a schematic view showing a structure of a tire lens formed by cutting a lens blank formed of the preform shown in fig. 12, and referring to fig. 12, 13 and 23, a tire lens is obtained by cutting a portion having a predetermined length L and a width W from a side surface of the lens blank. The thickness H of the tire lens is obtained by die pressing, and then the plane H W is polished, so that the finished tire lens with one H W rectangular light passing surface and one tire tread is obtained.
With respect to R1 and R2, the two limiting cases are: when R1 ═ R2, the tire tread is the surface of revolution (spherical); when R2 is infinite, the tire tread is cylindrical (cylindrical or non-cylindrical).
Exemplarily, referring to fig. 23, R2 is infinite, R1 is 0.225mm, H is 0.42mm, W is 4.0mm, and L is 0.3 mm. The adopted preform material is low-melting glass, the refractive index of the glass is 1.81, the Abbe coefficient is 40.99, the Young modulus is 11506, and the Poisson ratio is 0.3.
FIG. 24 is a schematic view of another free-cavity compression tire lens system with a preform disposed therein according to an embodiment of the present invention. The system for free-cavity compression of a tire lens can be made as a mold with multiple cavities, i.e., at least two preforms are placed simultaneously and at least two lens blanks can be molded from the at least two preforms to improve the work efficiency.
Further, referring to fig. 24, the working surface of the mold core (including the upper mold core 1 and the lower mold core 3) may be not a plane but a structure having the recess 6 for fixing the preform, which is within the protection scope of the present invention.
It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious modifications, rearrangements, combinations and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.