The present invention relates to a beveling wheel and method for forming a beveled lens with the beveling wheel for use with eyeglasses. One embodiment includes a prescription lens for use on an eyeglass frame having a receiving channel. The receiving channel includes a channel bottom and opposed interior wall surfaces having a first angle therebetween. The prescription plastic lens includes a prescription lens body generally defined by a peripheral edge having a bevel extending away from the edge to a vertex. The bevel has a distal portion with a second angle. The bevel is receivable within the receiving channel. At least a portion of the vertex of the bevel has an interference fit with the receiving channel bottom when held within the eyeglass frame. The first angle is greater than the second angle.
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7. A beveling wheel for use in forming a bevel on a plastic lens, the beveling wheel comprising:
an annular disk having a periphery and a central axis; and
a bevel groove disposed on the periphery of the annular disk and configured to form the bevel on the plastic lens, the bevel groove having a distal end disposed between the periphery and the central axis, the distal end comprising an angle ranging from 108 degrees to 118 degrees such that the bevel on the plastic lens contacts and forms an interference fit with a receiving channel bottom of an eyeglass frame.
1. A beveling wheel for use in forming a bevel on a plastic lens for an eyeglass frame having a receiving channel, the bevel having a vertex, the receiving channel being defined by opposed interior wall surfaces having a first angle therebetween at a channel bottom disposed at one end, the beveling wheel comprising:
an annular disk having a periphery and a central axis; and
a bevel groove configured to form the bevel, the bevel groove disposed on the periphery of the annular disk, the bevel groove having a distal end disposed between the periphery and the central axis, the distal end comprising a second angle from 105 degrees to 120 degrees that is less than the first angle such that the vertex of the plastic lens bevel contacts and forms an interference fit with the channel bottom of the eyeglass frame receiving channel.
2. The beveling wheel of
3. The beveling wheel of
5. An eyeglasses component, comprising:
an eyeglasses frame;
two plastic lenses supported by the eyeglasses frame, the lenses being formed using the beveling wheel of
6. The beveling wheel of
8. The beveling wheel of
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This application is a division of U.S. application Ser. No. 12/540,181 filed Aug. 12, 2009, now U.S. Pat. No. 8,636,360 issued Jan. 28, 2014, the disclosure of which is hereby incorporated in its entirety by reference herein.
1. Field of the Invention
The present invention relates to a beveling wheel, method for forming a beveled lens with the beveling wheel for use with eyeglasses, and a beveled lens.
2. Background Art
Reliable assembly of eyeglasses is crucial to the many wearers of prescription, safety, and/or sun glasses. It is unfortunate that lenses often fall out of eyeglass frames after a period of wearing. In some cases, this is the result of shrinkage and/or creep of a plastic material when used for the lens. Often, an opportunity for falling out is aggravated by the relative thinness of the cross-section of the eyeglass frame, such as an eye-wire frame or a frame only having a partial frame holding for retaining the lens.
Another failure mode occurs when the glass lenses crack as a result of having an interference fit of the vertex of the bevel with a bottom of a channel portion of the eyeglass frame. It is well practiced in the art to avoid cracking of the lens by having the bevel vertex not in contact with the bottom of the channel of the eyeglass frame. As such, glass lenses have always been manufactured to have bevels which will not contact the bottom of the eyeglasses frame.
Diamond beveling wheels are customarily made for use of lens edging equipment that edges the lenses to fit into eyeglass frames. These diamond beveling wheels use technology intended to form the bevel shape required for lenses made of glass. But, today 94% of all eyeglasses are made from plastic lenses using lens edging machines designed to edge plastic lens material.
It is an unfortunate consequence of using beveling wheels designed glass to edge plastic lens materials that the bevel is not fully inserted into the channel of the eyeglass frame. When the plastic lens is not fully inserted, the lens is prevented from forming an optimal interference fit between the lens and the eyeglass frame. As a result, a plastic lens is very susceptible to falling out of the eyeglass frame caused by shrinkage of the lens, loosening of the retention screws or twisting of the frames.
What is needed is a lens that can be assembled into many types of eyeglass frames to yield a more secure assembly of the eyeglass lens and frame that decreases the possibility of the lens falling out.
What is further needed is a beveling wheel which can manufacture a bevel on the lens that can overcome, at least to some degree, the issues of shrinkage, stress and cracking of the lenses.
One embodiment of the present invention comprises a prescription plastic lens for use in an eyeglass frame. The eyeglass frame has a receiving channel defined by opposed interior wall surfaces having a first angle there between. The receiving channel also has a channel bottom at one end and a channel opening at the other. The prescription plastic lens includes a prescription lens body generally defined by a peripheral edge. The peripheral edge has a bevel extending away from the peripheral edge to a vertex. The bevel has a distal portion having a second angle. The bevel is receivable within the receiving channel. At least a portion of the vertex of the bevel has an interference fit with the receiving channel bottom when held within the eyeglass frame. The first angle is greater than the second angle.
In another embodiment of the present invention, a beveling wheel for use in forming a bevel on a plastic lens for an eyeglass frame is provided. The eyeglass frame has a receiving channel defined by opposed interior walls having a first angle between them at a channel bottom disposed at one end of the receiving channel. The beveling wheel includes an annular disk having a periphery and a central axis. The beveling wheel also includes at least one bevel groove for use in forming the bevel. The bevel groove has a distal end comprising a second angle less than the first angle. When the bevel is retained in the receiving channel of the eyeglass, the vertex of the bevel contacts at least a portion of the channel bottom.
Another embodiment of the present invention includes a method for forming a beveled lens for use with eyeglasses having a lens retention structure including a bottom. The method includes shaping a plastic lens blank generally defined by a first peripheral edge to form a bevel protruding away from a second peripheral edge. The bevel includes a securing structure capable of being in contact with the bottom of the lens retention structure when supported within the lens retention structure.
Reference will now be made in detail to presently preferred compositions, embodiments and methods of the present invention, which constitute the best modes of practicing the invention presently known to the inventor. But, it should be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for any aspect of the invention and/or as a representative basis for teaching one skilled in the art to variously employ the present invention.
Except in the operating examples, or where otherwise expressly indicated, all numbers in this description indicating dimensions, angles, material properties, or uses are to be understood as modified by the word “about” in describing the invention's broadest scope. Practice within the numerical limits stated is generally preferred. Figures may not necessarily be to scale. Also, unless expressly stated to the contrary:
An interference fit of a bevel on a plastic lens to a bottom of a receiving channel of an eyeglass frame provides a relatively secure assembly with regard to lenses falling out. The assembly is particularly secure when a bevel height of the bevel on the plastic lens is greater than a depth of a groove of the eyeglass frame by an amount exceeding a typical shrinkage and/or creep dimensional change associated with polymeric materials used in a lens body for a lens. Use of plastic for a lens allows an interference fit between a vertex of the bevel and a receiving channel of the eyeglass frame. Unlike a glass lens, the plastic lens is not readily susceptible to cracking when a vertex of the glass bevel comes in prolonged contact with the receiving channel bottom of the eyeglass frame. The prolonged contact in at least one embodiment may be more than a day. In another embodiment the prolonged contact may be more than a month. In yet another embodiment, the prolonged contact may be more than a year.
The depth of the bevel groove 18, in at least one embodiment, may range from 0.25 mm to 1.1 mm. In another embodiment, the depth of the bevel groove 10 may range from 0.4 mm to 1 mm. In at least one other embodiment, the depth of the bevel groove 10 may range from 0.45 mm to 0.75 mm. It should be understood that the bevel wheel 10, while illustrated as shown in
The bevel groove 18 may be angularly shaped such as a V-groove. The angle 22, θ1, of the bevel groove 18, may have an angle ranging from 100° to 130° at the distal end 20, such as an apex of the V. In another embodiment, the angle of the bevel groove 22 may range from 105° to 120°. In yet another embodiment, the angle of the bevel groove 22 may range from 108° to 118°. The periphery 14 of the beveling wheel 10 may have an abrasive surface 24, such as tungsten carbide or polycrystalline diamond. The abrasive surface 24 may also line the bevel groove 18. It should be understood that the abrasive surface 24 of the periphery 14 may employ the same or different abrasive from the abrasive surface in the bevel groove 18 without exceeding the scope of the invention. The abrasive surface 24 is capable of shaping a plastic lens body.
Turning now to
When bevel 50 is glass and contacts the retention structure 42, the prior art bevel 50 may crack. When bevel 50 is a thermoplastic composition, such as when bevel 50 is a polycarbonate material, compression on the apex of the bevel tends to lessen the chance of stress on the lens as the softer bevel easily deforms, absorbing the pressures that would have created stress in a lens that was fitted into a frame such as an eyewire. The eyewire, as commonly known in the art, typically uses larger lens bevel designs, which contact larger areas of the non-deformable cross-section. When bevel 50 is a thermoset plastic composition, such as CR-39 by PPG, the thermoset material generally shrinks with age as a crosslinking process used in manufacturing the thermoset material continues. The thermoset bevel can tolerate moderate stress when the bevel 50 is initially compressed in the eyewire frame. Birefringence rings may be evident in the plastic lens within 10 mm of the bevel 50. As shrinkage occurs, the stress is relieved, but using the embodiments of the invention, the lens remains secure in the eyewire frame, but the birefringence may diminish in intensity and size.
In at least one embodiment, the plastic bevel 38 is substantially free of a crazing zone, including whitening or birefringence band, within 10 mm of the vertex 60 of the bevel, when held within the eyeglass frame 34. In other embodiments, the plastic bevel 38 is substantially of the crazing zone or birefringence band within 5 mm of the vertex 60 of the bevel, when held within the eyeglass frame 34.
The bevel angle 62, θ2, may be less than the angle of retention structure angle 64, θ3, in order to assure that the bevel's vertex 60 can come in contact with retention structure's vertex 58 to form the interference fit when the lens 36 is assembled with the eyeglass frame 34. In at least one embodiment, the bevel angle 62 may range from 100° to 130°. In another embodiment, the bevel angle 62 may range from 105° to 120°. In yet another embodiment, the bevel angle 62 may range from 108° to 118°.
It should be understood that the bevel 38 of lens 36 may not necessarily be an isosceles triangle as schematically illustrated in
Referring now to
One or more of the vertices 82 or 84 may contact a bottom 90 of the retention structure 42. It should be understood that a connecting material may be between either of the vertices 82 or 84 and the bottom 90 without exceeding the scope of the invention.
It should be understood that while a right frustum is illustrated in
Further, it should be understood that the bevel 38 may have almost any shape provided that there are no undercuts to the bevel 38. A two-dimensional cross-sectional view of the bevel 38 has one axis of symmetry or less in at least one embodiment.
Referring back to
A receiving channel 104 of the retention structure 42 has a height 102, h2, may be less than the height 100, h1, of bevel 38 in at least one embodiment of the invention. In another embodiment, the height 102, h2, of the receiving channel 104 of the retention structure may be greater than 0.24 mm. In at least one other embodiment, the height 102, h2, of the receiving channel 104 of the retention structure 42 may range from 0.24 mm to 1.09 mm. In at least another embodiment, the height 102, h2, of receiving channel 104 of retention structure 42 may range between 0.34 mm to 0.99 mm. In yet another embodiment of the invention, the height 102, h2, of the receiving channel 104 of the retention structure 42 may range from 0.44 mm to 0.74 mm.
A prescription lens body for use in preparing the lens 36, onto which bevel 38 is disposed, may be composed of any plastic used for prescription lenses. Non-limiting examples of plastic for the prescription lens body may include a crosslinked homopolymeric allylic molecule, a polymer copolymeric system including at least one allylic molecule, a polycarbonate-containing polymer, a selectively crosslinked urethane-based polymer, and a polymer having a refractive index ranging from 1.56 to 1.7. An example of the homopolymeric allylic molecule includes allyldiglycolcarbonate such as PPG CR-39 thermoset. An example of a selectively crosslinked urethane-based polymer includes a quasi-thermosetting polymer, such as Trivex provided by PPG. In another embodiment, the polymer may have a refractive index ranging from 1.6 to 1.7. In yet another embodiment, the polymer may have a refractive index ranging from 1.67 to 1.7.
The lens body may be formed using a plastic shaping process including abrading, casting in a mold, milling, injection molding, adhering, using material additive methods, such as stereolithography, and combinations thereof.
It should be understood that the bevel 38 may also be formed on a lens body using a plastic shaping process, including abrading, casting in a mold, milling, injection molding, adhering, using material additive methods, such as stereolithography, and combinations thereof. It should be further understood that the plastic shaping processes may yield net shape bevels, near net shape bevels, and/or bevels requiring use of a secondary process, such as a machining process with the beveling wheel of at least one embodiment of the present invention.
The beveling wheel portions 110 and 112 may be joined together along the annular disk faces 126 and 128 to define a bevel groove comprised of the inwardly directed angled surfaces 122 and 124.
A bevel groove angle such as the bevel groove defined by the inwardly directed angled surfaces 122 and 124 may range from 100° to 130° in at least one embodiment of the invention. In another embodiment of the invention, the bevel groove angle may range from 105° to 120°. In another embodiment of the invention, the bevel groove may range from 108° to 118°. It is understood that while the bevel wheel is illustrated as having only two portions, bevel wheels may be constructed with a plurality of portions including some that are only portions of the inwardly directed angled surfaces 122 and 124 without exceeding the scope of the invention.
Turning now to
Turning now to
In
In
Abrasive surfaces, such as surfaces 24, 204, and/or 208, in at least one embodiment, may have compositions of materials having hardness ranging from 4 to 10 on the Moh's hardness scale. In another embodiment, abrasive surfaces may have compositions of materials having a hardness greater than 9.
It is also understood that in at least one embodiment, the abrasive surface may include a portion of a cutting media may be partially in a grinding matrix without departing from the scope of the invention. In another embodiment, the cutting media may fully encapsulated in the grinding matrix.
While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention.
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