U.S. patent number 3,786,600 [Application Number 05/294,350] was granted by the patent office on 1974-01-22 for contour grinder.
This patent grant is currently assigned to A. Lemay Co., Inc.. Invention is credited to Joseph Thomas Bloxsom.
United States Patent |
3,786,600 |
Bloxsom |
January 22, 1974 |
CONTOUR GRINDER
Abstract
An industrial shaping system to form various articles including
eyeglass lenses. The invention specifically discloses an eyeglass
frame pattern generator and edge grinder for shaping eyeglass
lenses to fit a particular frame. A sensing wheel makes contact
with the internal frame groove which is designed to hold the lens.
The frame pattern generator controls an edge cutter by means of a
servo system to shape the lens so that it will fit into the frame
groove after the grinding operation. A computing device in the
frame pattern generator is arranged to correct for the inherent
errors generally present in all contour devices employing a tracing
mechanism and a grinding cutter where grinding is done along the
circumference of the grinding wheel.
Inventors: |
Bloxsom; Joseph Thomas
(Peekskill, NY) |
Assignee: |
A. Lemay Co., Inc. (Carmel,
NY)
|
Family
ID: |
23133034 |
Appl.
No.: |
05/294,350 |
Filed: |
October 2, 1972 |
Current U.S.
Class: |
451/240;
409/122 |
Current CPC
Class: |
B24B
17/00 (20130101); B24B 9/144 (20130101); B24B
17/10 (20130101); Y10T 409/303248 (20150115) |
Current International
Class: |
B24B
9/14 (20060101); B24B 9/06 (20060101); B24B
17/00 (20060101); B24B 17/10 (20060101); B24b
009/14 (); B23c 001/18 () |
Field of
Search: |
;51/11R,11LG,127
;90/13.9 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Simpson; Othell M.
Assistant Examiner: Watson; Robert C.
Attorney, Agent or Firm: Heilman; James M.
Claims
The embodiments of the invention in which an exclusive property or
privilege is claimed are defined as follows:
1. A contour edger for an object to be ground comprising: (a) a
sensing means for determining the size and shape of the groove
which is to retain the edge ground object, said sensing means
including a rotatable base having an axis of rotation in alignment
with the approximate center of a frame the object is to fit, a
slidable block mounted on the rotatable base, a rockable arm
mounted on said block and including a sensing wheel at the end of
the arm which makes contact with the groove in the frame, a
ferromagnetic core coupled to the slidable block by flexible means,
said core also in alignment with the axis of said rotatable base,
and a transformer having a primary winding connected to a source of
AC power and a secondary winding, both windings surrounding said
core and in alignment therewith;
b. a servomotor system connected to the secondary of said
transformer, said system including a servomotor connected to a
means for moving the object toward and away from a grinder wheel;
and
c. an edge grinding means for grinding the edge of an object to a
desired size and shape, said grinding means including a rotatable
support for the object, said support coupled to the rotatable base
for rotation in synchronism therewith, an edge grinding wheel
turned by a grinder motor, and means for moving the rotatable
support toward and away from said grinding wheel in accordance with
the variations of the sensing means.
2. A contour edger as claimed in claim 1 wherein a variable contact
arm is secured to the servomotor for rotation therewith, said arm
engaging a voltage divider whose ends are connected to a source of
direct current, said contact arm connected to input terminals of
the servoamplifier.
3. A contour edger for eyeglass lenses comprising: (a) a sensing
means for determining the size and shape of the groove which is to
retain the edge ground lens, said sensing means including a
rotatable base having an axis of rotation in alignment with the
approximate center of an eyeglass frame the lens is to fit, a
slidable block mounted on said rotatable base, a rockable arm
mounted on said slidable block, a sensing wheel at the end of the
rockable arm which makes contact with the groove in the frame, a
ferromagnetic core coupled to the slidable block by a flexible
string, said core also in alignment with the axis of said rotatable
base, and a transformer having a primary winding connected to a
source of AC power and a secondary winding, both windings
surrounding said core and in alignment therewith;
b. a servomotor system connected to the secondary of said
transformer, said system including a servomotor connected to a
means for moving the lens toward and away from a grinder wheel;
and
c. an edge grinding means for grinding the edge of an eyeglass lens
to a desired size and shape, said grinding means including a
rotatable support for the eyeglass lens, said support coupled to
the rotatable base for rotation in synchronism therewith, an edge
grinding wheel turned by a grinder motor, and means for moving the
rotatable support toward and away from said grinding wheel in
accordance with the variations of the sensing means.
4. A contour edger as claimed in claim 3 wherein the flexible
string is threaded through an axial hole in a shaft which turns the
rockable arm.
5. A contour edger as claimed in claim 3 wherein said primary and
secondary windings are positioned in axial alignment with the
movement of the core.
6. A contour edger as claimed in claim 3 wherein said servomotor
system includes an amplifier coupled between the transformer
secondary winding and the servomotor.
7. A contour edger as claimed in claim 3 wherein the servomotor is
coupled to the support for the eyeglass lens by a rack and
pinion.
8. A contour edger as claimed in claim 6 wherein said servomotor
system includes a demodulator which receives an alternating voltage
from the transformer secondary winding and delivers a direct
current to the amplifier.
9. A contour edger as claimed in claim 3 wherein a variable contact
arm is secured to the servomotor for rotation therewith, said arm
engaging a voltage divider whose ends are connected to a source of
direct current, said contact arm connected to input terminals of
the servoamplifier.
Description
BACKGROUND OF THE INVENTION
Eyeglass lenses or other objects are generally furnished by a
supplier such as a lens grinder in a standard size which is
designed to be larger than any of the frames in current use. It is
then the duty of the local optometrist or optician to fit the frame
owned or selected by the wearer. In the past a large number of
metal patterns were available, each pattern having the shape and
size of a particular frame groove. The pattern was secured to a
profile and the lens edged to the desired shape and size. The
invention hereinafter will be referred to as applied to
eye-glasses. However, it is equally applicable with small
modification to various other articles of manufacture.
During recent years, the number of frame shapes has increased to
such an extent that it is no longer feasible to stock all the
pattern shapes. The present invention uses no patterns but instead
derives the shape and size of the lens from the frame lens opening
itself.
The invention comprises two principal parts; a frame pattern
generator and a lens edger. The frame pattern generator derives
information from the eyewire lens opening and this information is
used to position a servosystem coupled to the lens edger for the
proper shaping of the lens to fit the eyewire lens opening.
The coordinate system used for the frame pattern generator is
analoguous to the coordinate system used for the lens edger. If the
scale and origins of the two systems are equal, as they are in the
present invention, then any geometrical shape will have identical
shape and size in the two systems.
The frame is securely mounted on a platform, and a small sensing
wheel on the end of a rockable lever is run around the eyewire
groove, and a grinding wheel, coupled to the sensing wheel, edges
the lens to the desired shape along the circumference of the
grinding wheel. In other simple coupling mechanisms of this type,
an error is always introduced where the grinding is done along the
circumference of the grinding wheel. The rockable lever, holding
the sensing wheel, is continuously positioned from the line of
motion of the principal axis and these angular settings compensate
for the errors, in this type of grinding operation.
The present invention also includes a sliding support for the
rockable lever, this support being mounted on linear ways secured
to a platform which is fixed to a rotary shaft whose axis is
aligned with the approximate center of the eyeglass eyewire lens
opening. A string is secured to the movable portion of the sliding
support and is threaded through an axial hole in the rotary shaft,
terminating on a magnetic core. This core is movable between two
electric windings, one of which is supplied with a steady
alternating current from an external power source. The second
winding acts as the secondary winding of a transformer and its
available current depends upon the position of the movable core.
The terminals of the second winding are connected to a servosystem
having an output servomotor which controls the position of the lens
with respect to the edge grinding wheel.
One of the features of the invention is the use of an eyeglass
frame with an eyeglass pattern generator which can be coupled to a
lens edge grinder to grind the edge of a lens so that the lens can
be fitted into the lens opening of the eyewire.
Another feature of the invention is the eyeglass frame pattern
generator which converts tracing information which is used to
control a servosystem for positioning the lens edger.
Another feature of the invention is the adaptability of the
eyeglass frame pattern generator whereby a wide range of shapes and
sizes can be employed.
Another feature of the invention is the use of the plane polar
coordinate system whereby the polar angle is generated by a motion
which is common to the frame pattern generator and the lens
edger.
Another feature of the invention is the use of a rockable tracing
arm which follows the lens groove in the eyewire when the groove is
a three dimensional curve.
Still another feature of the invention is the use of a linear
variable differential transformer coupled between the pattern
generator and the servosystem whereby the direct electrical
connections between these components is eliminated.
Another feature of the invention is the mechanism for removing the
weight of the mechanical computer from the sensing wheel.
Another feature of the invention is the use of a mechanical
computer mechanism whereby the proper projection component on the
radius vector is obtained for the control information to the
servosystem for positioning the lens edger.
Another feature of the invention is the positioning mechanism for
the mechanical computer mechanism.
Other features and additional details of the invention will be
disclosed in the following description, taken in connection with
the accompanying drawings.
BRIEF DESCRIPTION OF THE FIGURES
FIG. 1 is a perspective view of a portion of the device showing the
frame sensing table, the rotary sliding support, the container
which houses the lens holder, and the motor for the angle
drive.
FIG. 2 is a detailed side view of the sensing wheel, the mechanical
computer, and the sliding support. Some parts are shown in
section.
FIG. 3 is a schematic diagram of connections showing the coupling
means between the sensing wheel, the mechanical compensator, the
servoamplifier, the servomotor, and the edge grinding wheel. The
feedback generation and control connection are shown in this
figure.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the figures, an eyeglass frame 10 is secured to a
table 11 by a clamping mechanism 12. The table 11 is secured to a
supporting means 13. The lower portion of support 13 forms the top
of a container 15 which houses the motor for the angular drive and
a lens holder.. Between table 11 there is a base 16 which includes
four linear ball bushings 17 supporting two parallel shafts 18.
The mechanism can be operated in either one of two modes since the
basic requirement depends upon the relative motion of the eyeglass
frame and the sensing wheel, also the relative motion of the lens
and the edge grinding wheel. In the following description the
device will be described as a rotary sensing means and a rotary
lens. It is to be understood that similar results can be achieved
if the eyeglass frame, along with supports 11 and 13, are rotated
about a common axis. In this case, the grinding wheel will also
move around the lens which will be stationary.
The parallel shafts 18 are connected to a bridge type block 20
secured to both shafts by set screws 21. It is evident that block
20 and the two shafts 18 can be moved horizontally in the linear
bushings 17, this movement controlled by the sensing device
composed of wheel 32, shaft 31, in bearing 29, arm 30, shaft 28,
and linear bearing 27. The movement is transmitted by a flexible
string 23 to a ferromagnetic core 22 positioned within a
transformer winding 26. The string 23 is threaded around a pulley
24 and its upper end is secured to a ring 25 on the lower part of
block 20. In this manner the movement of block 20 is coupled to the
core 22 and winding 26.
Block 20 supports the rotatable linear bearing and a short vertical
shaft 28. The linear ball bearing 27 permits a vertical movement of
shaft 28 as well as a rotary motion. The vertical motion is
necessary to allow for frame grooves which may not be entirely
positioned in a horizontal plane. The top end of the shaft 28 is
secured to a short lever arm 30 which carries a sensing shaft 31
and sensing wheel 32. The sensing wheel in one embodiment was
one-eighth inch in diameter and is designed to track in eyewire
grooves 33 of the eyeglass frame 10. The core 22 holds the sensing
wheel 32 in contact with groove 33 by means of its weight via
string 23, pulley 24 and ring 25.
The operation of this portion of the device is evident from the
above description. The frame 10 is secured to table 11 by clamps 12
and the sensing wheel 32 is placed in groove 33. Then a motor 36
(FIG. 3) is started and, acting through a gear reduction box 37,
both the lens 43 is rotated and shaft 40 is turned at the same
speed. Shaft 40 acts through a gear box 41 to turn vertical shaft
42 and the sensing and computing device at the same speed. Gear box
41 is equipped with an optional reversing mechanism so that shaft
42 may be set to turn in the same direction as shaft 38 in which
case the device will shape the lens so that it will fit in the
eyeglass frame being sensed. If the gear box 41 is reversed, the
sensing mechanism will rotate in the opposite direction and the
lens will be ground to fit the other eyeglass frame.
As shaft 42 rotates about its axis, the sensing wheel moves around
groove 33, and the arm 30, which carries the sensing wheel, changes
its angular position so that arm 30 is always perpendicular to the
tangent of the groove at the point of contact with the wheel
32.
The purpose of the mechanical computer is to obtain the projection
of the position of the sensing wheel 32 in groove 33 along the
direction of travel of rods 18 as well as projecting the eyewire
groove onto the horizontal plane. The distance from the axis of
shaft 28 to the edge of sensing wheel 32 nearest to the axis of
shaft 28 as measured along lever arm 30 is equal to the radius of
the grinding wheel 52. The axis of shaft 28 is analgous to the
center of the grinding wheel. The distance from the line passing
through the axis of shaft 28 to the geometric axis of the eyewire
lens opening (and perpendicular to them) will be called the
principal radius. Similarly, the distance from the line passing
through the center of the grinding wheel to the axis of the glass
lens holder in the lens edger (and perpendicular to it) will be
called the secondary radius. The lens edge grinder has its axis
positioned along the secondary radium by a distance equal to the
length of the principal radius.
The extremum values of the positions of the sensing wheel 32
correspond to the points of grinding of the lens on the grinding
wheel. Lever arm 30 projects these positions on the principal
radius (whose direction of travel of rods 18) and the displacements
of rods 18 are measured by the displacements of core 22 relative to
winding 26. The core 22 transfers a measured amount of magnetic
flux to the secondary winding 44 (see FIG. 3) and the result is
applied to demodulator 45. The core 22 rotates when the base 16 is
turned. Because the displacement of core 22 is sensed by
electromagnetic field coupling, the electronic circuitry remains
stationary in space and does not participate in the rotary motion
of plate 16.
The servosystem shown in FIG. 3 contains components well known in
the art. The components used and the complete servosystem have been
described in a book "Electronic Instruments" by Greenwood, Holdam
and Macrae, published by McGraw-Hill in 1948, incorporated herein
by reference. The winding 44 applies a variable AC to the
demodulator 45. The demodulator 45 provides full wave rectification
to the imput signal and applies a direct current input to the
servoamplifier 46. The output of the amplifier 46 is applied over
conductors 47 to a direct current motor 48. This output motor turns
gear 50 and rack 51 to move the lens system toward or away from an
edge grinding wheel 52. The complete motor system moved by rack 51
includes the motor 36, the gear box 37, and the lens 43. These
components may be secured to a common base 53 which moves on a
slide or rollers (not shown). The grinding wheel 52 is mounted on
the end of a shaft 54 turned at relatively high speed by a motor
55.
The servomotor shaft which turns gear 50 also turns a contact blade
56, the end of which makes contact with a circular resistor 57.
Resistor 57 is supplied with direct current from terminals 58 and
as the contact blade 56 moves along resistor 57, the DC potential
on it and its connecting conductor 60 varies in accordance with the
blades position.
When the servosystem is operated, the motor 48 turns clockwise or
counter clockwise depending upon the polarity of the DC potential
on conductors 47. As the motor 48 turns, the potential on conductor
60 is varied until this potential is equal to the DC voltage
applied to the input of the servoamplifier 46 by the demodulator
45. When this balance is attained, both the input and output
voltages of the servoamplifier are balanced and the grinding wheel
52 is correctly positioned to remove the desired amount of glass
from the lens 43.
Many other mechanical and electrical modifications and variants
will be readily apparent from a reading of the above, and all are
within the concept of the invention as described and claimed.
While my invention has been described in detail as applied to an
eyeglass frame, it should be understood that the apparatus could be
used for many other industrial purposes all within the disclosed
inventive concept.
* * * * *