U.S. patent number 3,670,460 [Application Number 05/042,125] was granted by the patent office on 1972-06-20 for tool positioning means for lens grinder.
This patent grant is currently assigned to Senoptics, Inc.. Invention is credited to Andrew H. Oldfield, Arthur F. Trott.
United States Patent |
3,670,460 |
Oldfield , et al. |
June 20, 1972 |
**Please see images for:
( Certificate of Correction ) ** |
TOOL POSITIONING MEANS FOR LENS GRINDER
Abstract
A toric lens grinding machine has means for swinging a lens
blank past a cup-shaped grinding wheel and in contact therewith,
the wheel being mounted on crossed slides. A computer device
secured to the wheel carrying slide has a transparent portion
overlying an upward beam of light fixed on the machine base. The
computer has first dial means marked in diopters for setting an
aiming tube so as to be movable along a straight line calculated to
determine the base curve of the ground lens. Second dial means
marked in diopters are provided for moving the aiming tube along
the straight line a calculated distance for determining the
cylinder curve of the ground lens. A valve connected to hydraulic
motor means for moving the crossed slides has a single lever for
moving both slides so that the wheel is moved in a single direction
determined by the direction the lever is moved so that the aiming
tube and beam of light may be quickly aligned to position the wheel
in the machine for grinding the toric lens set on the dials. The
aiming tube is illuminated and a mirror overlying the computer
device projects images of the tube and light beam on a translucent
screen at the side of the machine.
Inventors: |
Oldfield; Andrew H. (Waterloo,
NY), Trott; Arthur F. (Richmond Hill, Ontario,
CA) |
Assignee: |
Senoptics, Inc. (Waterloo,
NY)
|
Family
ID: |
21920181 |
Appl.
No.: |
05/042,125 |
Filed: |
June 1, 1970 |
Current U.S.
Class: |
451/5; 451/6 |
Current CPC
Class: |
B24B
13/043 (20130101); B24B 49/12 (20130101) |
Current International
Class: |
B24B
13/00 (20060101); B24B 49/12 (20060101); B24B
13/04 (20060101); B24b 049/12 () |
Field of
Search: |
;51/165.71,165.72,165.9,165.92,165R,124L |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Swingle; Lester M.
Claims
We claim:
1. In a machine having a head carried on a first slide, ways for
the first slide carried transversely on a second slide, and ways on
the second slide carried on the machine base, the machine having
means for viewing the slides along the ways; head positioning
means, comprising a housing secured on the first slide and having a
transparent area overlying a portion of the base, means fixed to
the base portion for projecting a beam of light upward through the
transparent area, a vertically viewable target movable over the
transparent area, means for moving the target to a preselected
position in the transparent area, the selected position being
computed for selected positioning of the head, whereby the target
is first positioned and then the slides are moved to visually align
the target with the light beam.
2. The machine defined in claim 1, the housing having means for
illuminating the target, and a mirror fixed in the housing at an
angle of 45.degree. to the transparent area, one side of the
housing including a translucent screen, whereby images reflected
from the target and light beam are viewed on the screen for
aligning target and beam.
3. In a machine having a work head and a tool head, one head being
carried on a first slide movable on first ways extending in a first
direction, the first ways being fixed to a slide movable on second
ways extending in a direction normal to the first direction, the
second ways being mounted on a fixed base, the machine having means
for moving said slides along said first and second ways, the
required adjustments of said one head on said slides being charted
as a plurality of intersections of straight lines and arcuate
curves; computer means, comprising: a box-like housing secured to
the first slide and having a transparent area overlying a portion
of the base, means fixed to said base portion for projecting a beam
of light vertically upward through the transparent area, an aiming
tube in the housing extending vertically upward and movable over
the transparent area, first indexed dial means operatively
connected for adapting the tube to be moved along any straight line
extending as charted, second indexed dial means operatively
connected to the tube for moving the tube to a point along any of
the arcuate curves as charted, the dials being indexed for
measuring the movement of the tube to positions on said straight
lines and curves; whereby the aiming tube is first positioned by
the indexed dial means to a selected position and then the one head
is positioned with respect to the other head by visually aligning
the aiming tube with the upwardly projected beam of light by moving
said one head along said ways.
4. The machine defined in claim 3, including means for illuminating
the aiming tube, and a mirror fixed in the housing at an angle of
approximately 45.degree. to the transparent area, the housing
having a translucent viewing screen in one side opposite the
mirror, whereby images reflected from the aiming tube and projected
beam of light are viewed on the screen from the side of the machine
without errors of parallax.
5. In the lens grinding machine having a base, a cup-shaped
grinding wheel mounted on a tool slide movable longitudinally of
the machine on first ways, the first ways being mounted on a cross
slide movable transversely of the machine on second ways mounted on
the base, the lens blank being mounted on a work slide movable
toward and away from the wheel, the work slide being mounted on
ways pivotally mounted in the machine for swinging movement of the
blank past, and in contact with, the wheel; tool positioning means
comprising means fixed to the base for directing a small beam of
light vertically upward, framework fixed to the tool slide
outlining a horizontally extending area having at least a portion
transparent, a vertically extending aiming tube movable within the
framework horizontally to selected positions in the transparent
area, means for moving the tube over the transparent area, indexing
means on the moving means calibrated for identifying preselected
positions of the aiming tube, and means for adjusting the
longitudinal and cross slides, whereby the aiming tube is
positioned in a preselected position determined by the calibrations
of the indexing means and the tool slides are then adjusted to
bring the aiming tube into visual alignment with the upward beam of
light, the lens is then advanced to contact the grinding wheel and
is swung therepast for grinding a lens with base and cylinder
curves determined by the calibrated position of the aligned aiming
tube.
6. The machine defined in claim 5 having means for moving the tube
over the transparent area comprising: a pulley segment pivotally
secured in the framework adjacent the transparent section and
carrying a first double pulley whose axis of rotation is spaced
from the segment pivot, a second double pulley axially aligned with
the segment pivot, an arcuate track secured in the framework
adjacent the transparent section and opposite to the segment, a
carrier movable along the track and carrying a third pulley, a
first indexed dial secured to a shaft carrying a pair of dial
pulleys, cord means connecting one of the pair of dial pulleys to
the carrier for moving the carrier back and forth along the track,
other cord means connecting the other of the pair of dial pulleys
to the segment for turning the segment back and forth about its
pivot, and a second indexed dial secured to a shaft carrying pulley
means for moving the aiming tube along a straight line path between
the second segment pulley and the third carrier pulley, still other
cord means being connected to the second dial pulley means and
running over said first and second and third pulleys and being
attached to the tube, whereby the aiming tube is moved along a
straight line path by turning the second dial and the angular
direction of the line path is moved tangent to a circle determined
by the size of the segment carried second pulley by turning the
first dial.
7. The machine defined in claim 5 having means for adjusting the
longitudinal and cross slides comprising: hydraulic cylinders
having inlet and exhaust passages for moving each slide in opposite
directions, a control valve having an annular valve member
slideable in any direction on a flat valve seat, a control handle
universally mounted in the control valve for moving the member in
any direction, inlet and exhaust ports in the valve seat connected
to the inlet and exhaust passages of the respective cylinders, and
a central port in the valve seat connected to atmosphere, the inlet
and exhaust ports being disposed equiangularly about the central
port and so arranged that movement of the valve member in any one
of four polar directions connects one port to a source of fluid
under pressure for moving one slide in one direction while
connecting the opposite direction exhaust port to the central port
and movement of the valve member in a diagonal direction connects
two inlet ports to a source of fluid under pressure while
connecting the opposite direction exhaust ports to the central port
for moving the grinding wheel in a diagonal direction.
8. The machine defined in claim 5 having means for adjusting the
longitudinal and cross slides comprising: a first hydraulic
cylinder for moving the tool slide longitudinally in one direction
and a second hydraulic cylinder for moving the tool slide in the
opposite direction, a third hydraulic cylinder for moving the cross
slide in one transverse direction and a fourth hydraulic cylinder
for moving the cross slide in the opposite transverse direction,
the control valve having a central exhaust valve port and inlet
ports equiangularly arranged around and uniformly spaced from the
central port, each cylinder having a single combined inlet and
exhaust passage connected to a respective inlet valve port of a
central control valve, the control valve having an annular valve
member normally covering all the inlet ports, the ports and valve
member being so arranged that movement of the member in any one
direction connects the inlet passage of one cylinder to a source of
fluid under pressure and connects the inlet-outlet passage of the
oppositely acting cylinder to the exhaust port and movement of the
member in a diagonal direction connects the inlet passages of two
cylinders to a source of fluid pressure for moving the wheel
carrying slide in a diagonal direction while connecting the
inlet-outlet passages of the other two cylinders to the central
exhaust port, and a universally mounted control lever for moving
the valve member in any direction.
9. In a machine having a head mounted on a first slide, the slide
being mounted on first ways for back and forth movement in one
direction, the first ways being mounted for back and forth motion
on a second slide mounted on second ways disposed in a direction
normal to the first ways; means for moving the head in any
direction, comprising: a first hydraulic cylinder mounted for
moving the first slide in one direction, a second hydraulic
cylinder mounted for moving the first slide in the opposite
direction, a third hydraulic cylinder mounted for moving the second
slide in one direction, a fourth hydraulic cylinder mounted for
moving the second slide in a direction opposite to which it is
moved by the third cylinder, a control valve having a flat seat
enclosed in a sealed chamber supplied with fluid under pressure,
the valve seat having an exhaust port centrally located in the
chamber and connected to atmosphere, inlet ports in the valve seat
equiangularly disposed around the exhaust port and equally spaced
therefrom, each cylinder having a combined inlet and exhaust
passage connected to a respective inlet port, a valve member in the
valve chamber biased against the valve seat, the member being
annular and having its central opening capped to form a separate
passage always in communication with the exhaust port, and a
control lever universally mounted in the control valve for moving
the valve member in any direction, the valve chamber, member and
ports being so arranged that movement of the control lever in one
polar direction moves the member to expose the inlet port of one
cylinder to fluid under pressure while the inlet port of the
oppositely directed cylinder is connected by the member separate
passage to the exhaust port for moving the head along one of the
ways and movement of the control lever in a diagonal direction
moves the member to expose the inlet ports of two cylinders to
fluid under pressure while the inlet ports of the oppositely
directed cylinders are connected by the member separate passage to
the exhaust port for moving the head in a diagonal direction along
both ways.
Description
BACKGROUND OF THE INVENTION
This invention relates to means for positioning a machine head
which is carried on crossed slides and relates more particularly to
machines for surface grinding toric lenses where the tool head is
supported on a first slide which is, in turn, supported on a slide
movable in a direction normal to that of the first slide.
Toric lens grinders, such as described in U.S. Pat. No. 2,589,488
to Fowler issued Mar. 18, 1952, have long been known and various
charts and devices for determining the position of each of the
crossed slides for each of the desired combinations of base curve
and cylinder curve have been used with such lens grinders. Using
such charts and position determining devices, each slide must be
first positioned according to scales provided thereon and then the
setting of at least one slide must be corrected according to the
chart or position determining device. This requires laborious and
time-consuming reference first to the slide scales and then to the
chart or device for correction.
SUMMARY OF THE INVENTION
This invention contemplates the provision of an analogue computer
carried by the head to be adjusted, the computer having an aiming
device or target which can be positioned in the computer by setting
a first indexed dial for the desired base curve and then setting a
second indexed dial for the desired cylinder curve. A reference
aiming point is provided on the base of the machine and a single
control lever is provided for operating both slides in any desired
direction for bringing the target and reference aiming point into
alignment. Once alignment has been accomplished, the head is
thereby positioned to obtain the desired base and cylinder curves
without further correction of the position of the head.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a perspective view of a machine embodying tool
positioning means according to the invention;
FIG. 2 is an enlarged perspective view of the reference aiming
point device shown in FIG. 1;
FIG. 3 is a sectional view of the concave lens computer device on
the line 3--3 of FIG. 1, certain parts being omitted or shown in
broken lines for clarity;
FIG. 4 is a side elevational view of the computer device of FIG. 1,
certain parts being omitted or broken away for clarity and certain
parts being shown diagrammatically;
FIG. 5 is a front elevational view of the computer device;
FIG. 6 is a fragmentary, diagrammatic, rear elevational view of a
portion of the computer device as viewed from the right in FIG.
3;
FIGS. 7, 8 and 9 are diagrammatic views on a smaller scale of the
respective line circuit connections between the dials and the
aiming target of the computer device of FIG. 1;
FIG. 10 is a diagrammatic view similar to FIG. 3, on a smaller
scale, of a computer device for convex lenses;
FIG. 11 is a diagrammatic view of the reference aiming point,
target, and slide positioning lever of the machine of FIG. 1
showing the mode of operation;
FIG. 12 is a fragmentary, perspective view of the crossed slide
portion of the machine of FIG. 1, portions being cut away to show
the slide-operating hydraulic cylinders;
FIG. 13 is a diagrammatic view of a chart showing a plurality of
positions for lens curve settings on which the computer device of
FIG. 1 is operatively based;
FIG. 14 is a fragmentary, diagrammatic view showing the relation
between grinding tool and lens blank at two different settings for
grinding concave lenses;
FIG. 15 is a longitudinal cross sectional view of the cylinder
operating valve of the machine of FIG. 1; and
FIG. 16, on sheet 4 of the drawings, is an enlarged diagrammatic
view of the valve seat of the valve shown in FIG. 15, the valve
member seat-engaging surface being shown in broken lines.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1, the toric lens grinding machine 10 has a base
11 on which a turntable 12 is rotatably mounted. The table 12 has
ways 13 in which the lens head slide 14 is movably mounted and
slide 14 has ways 15 on which a lens head 16 is adjustably
mounted.
A lens blank 17 is shown removably mounted in a vacuum chuck 18 on
head 16 as is usual in such machines. A thickness setting wheel 19
and a thickness indicator dial 20 are also provided on head 16.
It will be understood by those familiar with the art that the lens
blank 17 is first positioned by securing head 16 on the ways 15 in
the desired position. Slide 14 is then backed off to starting
position and turntable 12 is then operated to rotate about its axis
21 to swing the blank 17 past and in contact with the tool 22 to
grind the blank. Slide 14 is then advanced and the blank is then
again swung past the tool for another pass. A micro-switch 23 is
provided to sense the completion of the cut when the desired lens
thickness is reached. Means for regulating the thickness of each
successive cut are also provided. Motors, not shown, for turning
the table 12, for pumping coolant to the tool, and for advancing
slide 14 are provided and sensing means, not shown, are provided
for reversing the turning of the table after each pass and return
so that, after the initial positioning of head 16, the grinding
operation takes place automatically.
Spaced from the turntable 12, the tool 22, in the form of a
cup-shaped, diamond impregnated grinding wheel, is rotatably
mounted, in a spatter housing 25, on a longitudinally movable slide
26 mounted on ways 27. The ways 27 form part of a cross slide 28
which is movably mounted on ways 29 on base 11 for movement
transverse the machine. The crossed slides 26 and 28, therefor can
be moved to position the tool 22 in a plurality of positions with
respect to the axis 21 of the turntable.
A motor 30, carried of slide 26, drives a shaft, not shown,
rotatable in the slide by means of a belt, not shown, and the
shaft, in turn, rotates the tool 22 by means of another belt, not
shown. The axis 31 of the tool 22 is always in the same plane as
the axis 32 of the lens blank 17 coaxially mounted in chuck 18.
Hydraulic means, seen in part at 33 and more fully hereinafter
described, are provided for moving slides 26 and 28 and a control
panel 35 is provided at the front side of machine 10. A switch 36
on the panel is provided for turning on and off the pump providing
fluid under pressure for the slide moving means and a "joy stick"
type of lever 37 is provided for controlling the movement of slides
26 and 28 as hereinafter described. Switches 38 are also provided
on the panel for controlling operation of motor 30 and the other
motors.
Above the control panel 35, a reference aiming point device 39 is
secured on a suitable bracket to the side of base 11, the device
being adapted to cast a narrow beam of light upward as a reference
aiming point. Device 39 is shown enlarged in FIG. 2 and comprises a
tube a having a light source therein at its bottom and a pair of
lenses thereabove, one of which is shown at b, for collimating the
light into a beam of parallel rays, as is usual in such devices.
The light projected by the device 39 is adapted to project a spot
of light less than one-fourth inch in diameter.
A computer device 40, hereinafter described, and a housing 41
therefor are provided, the housing being secured on longitudinal
slide 26 by the housing portion 42. The computer 40 is adapted to
slide into housing 41 and to be removable like a drawer. The
computer device 40 overhangs the side of machine 10 and its outer
side or end has two adjusting dials 43 and 44, rotatable with their
respective shafts 43' and 44' (FIG. 3).
The outer side of housing 41 is provided with a translucent and
non-transparent screen 45, and a mirror 45' indicated in broken
lines in FIG. 1, is set in the housing at about 45.degree. to the
vertical, allowing the operator to view the lighted images
projected up through the computer 40 and reflected by the mirror
45' on the screen, the images being viewed in a vertical plane and
avoiding errors of parallax.
Referring now to FIG. 12, the hydraulic means 33 are shown to
comprise the hydraulic cylinders 46, 47, 48 and 49, having combined
inlet and exhaust passages 46', 47', 48' and 49' respectively.
Cylinders 46 and 47 have their respective ends connected to the
ways 27 and slide 26 so that cylinder 46 operates to move the slide
in one direction and cylinder 47 moves the slide in the other
direction. Similarly, cylinders 48 and 49 have their ends connected
to the ways 29 and slide 28 for moving slide 28 in opposite
directions. It will be understood that a pair of two way cylinders
could be used instead of the four cylinders 46-49 but the
unidirectional cylinders are preferred because of the length of
extension obtained thereby.
Referring now to FIG. 15, a valve 50, operated by the lever 37, is
shown in longitudinal section. Valve 50 comprises a cover 51, a
valve-member-enclosing middle body 52 having a valve member chamber
53 therein, and base portion 54. Seals 55 and 56 are provided
between cover 51 and middle body 52 and between the latter and base
portion 54.
A passage 57 is provided in middle body 52 connected to a source of
fluid under pressure, not shown, the passage 57 leading to the
chamber 53. Base portion 54 has a central passage 58 axially
therethrough at its center connected to a pressure fluid reservoir,
not shown, at atmospheric pressure and leads to a central exhaust
port 59 in the valve seat surface in the plane 16--16 of FIG.
15.
A circular valve member 60 is provided in chamber 53 having an
annular seat-engaging surface 61 which normally overlies four inlet
ports 62 a, b, c and d arranged equiangularly spaced around, and
equidistantly spaced from, the exhaust port 59, the ports 62a -62d
being in the four polar directions shown in FIG. 16 and only ports
62a and 62b being shown in FIG. 15.
The valve base portion 54 has four passages connected,
respectively, as shown to the ports 62a, 62b, 62c and 62d
connected, as indicated in FIGS. 15 and 16, by flexible tubing to
the combined intake and exhaust passages of the cylinders 46, 47,
48 and 49. The valve member 60 has the central opening in its
annular seat-engaging surface capped as shown to form a circular
passage 63 for connecting one of the ports 62 to the exhaust port
59 when the member is moved in any polar direction while the
opposite port 62 is uncovered, exposing it to fluid under
pressure.
Lever 37 passes through a spherical swivel member 64 rotatably
seated between cover 51 and body 52, permitting motion of the lever
in any direction, and its lower end terminates in a ball 65
engageable in a cooperating socket in member 60. A coil spring 66
normally biases the lever 37 and its ball 65 upward out of
engagement with valve member 60 and a seal 67 is provided between
swivel member 64 and the lever 37. A deliberate act of pushing the
lever downward is therefore necessary by the operator before
operating valve 50.
Four plungers 68, biased by springs 69 retained in cups 70, bear
against the valve member 60, each plunger acting in one of the four
polar directions, to normally maintain valve member 60 in its
neutral central position covering the ports 62a-62d. The periphery
of the valve member, tapered as shown, translates some of the
plunger pressure into a downward force assuring contact between the
working face of the member 60 and the port face of the valve
seat.
Referring now to FIG. 16, it will be seen that when the annular
working face 61 of the valve member is moved in any one of the four
polar directions one of the ports 62, for example toward 62a, then
62a will be connected by the circular passage 63 at the center of
the valve member to the exhaust port 59 while the opposite port,
62b in the example, will be uncovered and exposed to the hydraulic
fluid under pressure to the chamber 53. In the example given above,
cylinder 47 will be extended and cylinder 46 will be collapsed,
moving slide 26 in the direction it is shown extended in FIG. 12.
Movement of valve member 60 in the opposite direction moves the
slide in the opposite direction. Movement of the valve member in
either of the other two polar directions results in movement of
slide 28.
It will also be apparent that, when valve member 60 is moved in any
diagonal direction, two adjacent ports 62 will be connected to the
exhaust port 59 and the opposite two adjacent ports 62 will be
uncovered and subjected to pressure to move slides 26 and 28, the
tool 22 being carried in a diagonal direction.
Referring again to FIG. 1 and assuming that the near side of the
rim of the cup wheel tool 22 is the working side, the tool is shown
positioned to the left of the axis of swing 21 of the turntable. If
the slide 26 is extended until toll 22 passes the axis 21 extended
and the lens blank 17 is then swung past in contact with the tool a
concave lens is ground. The base curve, in the common plane of axes
31 and 32, is determined by the distance of the tools grinding edge
from the axis 21 where it intersects the common plane.
The cross curve or cylinder, the curve in the plane normal to the
common plane, is determined by the curvature of the wheel 22 and
the angle at which axis 32 of the lens makes with the wheel during
grinding. This is illustrated in FIG. 14 which shows the tool 22 as
viewed from the back of the machine of FIG. 1. If the tool 22 is
withdrawn to the other side of the Y-Y' axis of FIG. 14, a convex
lens is generated, the cross curve being ground by the interior of
the tool wheel rim. Axis 31 of the tool 22 is always parallel to
the X-X' axis on the same side thereof. Curvature of the base and
cylinder curves are conventionally measured in diopters, the
reciprocal of the lens focal length expressed in meters.
Conventionally, prescriptions for changes in the curvatures vary by
one-eighth diopter increments and over 1,400 combinations of base
and cylinder curves are commonly prescribed. Over the years,
however, charts for obtaining the most advantageous positions of
the tool 22 for each combination of base and cylinder curves have
been made. Such charts take the form of a succession of arcs 71 and
straight lines 72, illustrated in FIG. 13, the diopter settings
being at their intersections.
The straight lines are found to be tangent to a circle 73 centered
at the axis 21 where it meets the common plane of axes 31 and 32
and whose radius may be computed from the diameter of the wheel
tool 22 and the radius of curvature of its rim or lip. The arcs are
found to be centered not at the center 21 by rather at the points
of tangency of the lines 72 with the circle 73. If the lines 72 and
arcs 71 are drawn at 10 diopter intervals, for example,
intersections at one-eighth diopter intervals may be accurately
found by interpolation.
Referring now to FIG. 3, the computer device 40 is shown as having
a floor 75 and a front wall 76 in which the dial operated shafts
43' and 44' are rotatably mounted. A relatively small pulley 77 is
fixed to the shaft 43' and a relatively large pulley 78 is fixed to
the shank of pulley 77 so that both pulleys are operated by turning
dial 43.
The dial shaft 44' is secured to a rotatable member 79 on which a
first pulley 80 is rotatably mounted and a second pulley 81 is
fixed. Pulley 80 carries a pin 82 projecting through an arcuate
slot 83 in pulley 81 and a spring 84 continually biases pulley 80
with respect to pulley 81, as shown in FIG. 5, so that pulley 80
may act as take-up pulley for pulley 81.
Four pillars or posts 85, secured to the floor 75, support a cover
86 of a transparent material such as plastic, best shown in FIG. 4,
the cover having side and back and walls extending down to the
floor 75.
The floor 75 has a generally triangular portion 87, substantially a
segment of a circle in outline, of glass or other transparent
material, and supported on the portion 87, an aiming tube 88, best
seen in FIG. 4, is movable in any direction by means now to be
described. The tube 88 is vertically disposed and rests on radially
projecting feet 89.
A segment of a pulley 90 is pivotally mounted on a post 91 secured
to the floor 75. Post 91 also rotatably carries an upper pulley 92
and a lower pulley 93. Another pair of pulleys 94 and 95 tangent to
pulleys 92 and 93 respectively, are carried on a second post 96
carried on pulley segment 90 inward from post 91, as best seen in
FIG. 6.
Farther inward from post 91, along the curved edge 97 of the
transparent portion 87 of the floor, an arcuate track 98 is secured
to floor 75 and a carriage 99 is movable along the track. A pulley
100, mounted on a horizontally disposed axis substantially tangent
to the arcuate side of floor portion 87, is mounted on carriage
99.
Referring now to FIG. 7, means for moving the carriage 99 comprises
a non-stretchable cord 101, such as braided copper wire as used in
a draftsman's board to operate a straight edge parallel to one edge
of the board, secured at 102 to pulley 78. The cord 101 runs from
the top of pulley 78 to a pulley 103 disposed at an angle, as shown
in FIG. 3, around the pulley 103 and around the upper pulley 104 of
a pair of pulleys 104, 105 at the back of device 40, as best seen
in FIG. 6, and along an appropriate groove in track 98 to the
carriage 99 to which it is secured. From carriage 99, the cord 101
extends along track 98 and around pulley 106 at the end of the
track. From pulley 106 cord 101 extends over a conventional
tensioning device 107 and then through a tube 108 and around the
pulley 78 back to the point of fastening at 102.
The tensioning device 107 is shown in FIG. 3 as comprising a first
pulley 107' rotatable on a post 109. A second pulley 110 is
rotatably carried on an arm 111 which is also rotatable on post
109, the arm being passed by a spring, not shown, in the direction
of the arrow 112. Cord 101, like the other cords hereinafter
described, is shown in FIG. 3 in broken lines for clarity of
illustration.
Referring now to FIG. 8, means for rotating the pulley segment 90
comprises another cord 115 secured at 116 to the smaller pulley 77,
passing several turns around the pulley 77 and then around pulley
117 which is disposed at an angle like pulley 103 but spaced
therefrom. From pulley 117, cord 115 extends under cord 101 to the
pulley 105 below pulley 104 (FIG. 6), around pulley 105 to another
pulley 118, rotatably secured to floor 75 adjacent the segment 90,
around pulley 118 and around the pulley segment 90 to which it is
secured at 119. The segment is biased in a counter-clockwise
direction by a spring, diagrammatically shown as a leaf spring 120
in FIG. 8. Segment 90 is therefore turned clockwise by turning
shaft 43' and turned counter-clockwise by spring 120 when shaft 43'
is turned in the other direction.
It will now be apparent that turning dial 43 counter-clockwise
moves the segment 90 and carriage 99 both in one direction and,
when the dial 43 is turned in the other direction, segment and
carriage move in the opposite direction. Pulleys 77 and 78,
however, are of different diameters carefully chosen to give a
straight line between carriage 99 and the tangent pulley 92 the
desired tangent relation around the segment pivot 91.
Referring now to FIG. 9, means for moving the aiming tube 88 along
the straight line determined by the position of segment 90 and
carriage 99 comprises a third cord 121 having one end secured to
the dial-44-operated pulley 81, wound partially around pulley 81,
and then extending around an angularly disposed pulley 122 at the
front corner of floor 75. From pulley 122 the cord extends to the
upper pulley 123 of a pair of pulleys 123-124 at the back of floor
75, best seen in FIG. 4.
From pulley 123, cord 121 extends around pulley 94 on the segment
90, as shown in FIG. 3, thence back and partially around pulley 92,
in the reverse direction, to the aiming tube 88 to which it is
secured. From aiming tube 88, the cord extends over the pulley 100
on carriage 99 and then back through aiming tube 88, through which
it now passes freely, to the pulley 93, below pulley 92, as best
seen in FIG. 6, and around pulleys 93 and 95, in the path indicated
in FIG. 3. From pulley 95, cord 121 then runs around pulley 124,
under pulley 123, and around a horizontally disposed pulley 125,
adjacent pulley 122, and thence around the pulley 80 where it is
fastened, the spring 84 causing the last named pulley to act as a
take-up pulley.
It will now be apparent that dial 44, when it is turned moves the
aiming tube 88 back and forth, toward and away from the carriage
99. It will also be apparent, now, that dials 43 and 44 may have
indicia marked thereon, as shown at 126 and 127 in FIG. 1, an index
mark 128 and 129 being provided adjacent the respective dials. The
indicia or scales 126 and 127 are appropriately marked in diopters
and the base curve may first be set by the dial 44, the cylinder
curve then being set by dial 43.
Referring again to FIG. 4, parts not shown in FIG. 3 include a
bracket 130 secured on pulley segment 90 which supports a small
mirror 131 at 45.degree. to the vertical. The top of aiming tube 88
is beveled at 45.degree. and a transparent mirror or light beam
divider of glass 132 is secured to the top of the tube 88 for
reflecting upward light from mirror 131. A collimated light source,
not shown, projecting the image of a circle is secured in housing
41 above the computer device 40 and directs light down in the
direction of arrow 133, in FIG. 3. The light reflected toward the
glass 132 which reflects the light upward in the direction of arrow
134, to the 45.degree. mirror in housing 41 and thence to screen
45. Since screen 45 is not transparent, an image is formed on the
screen which can be superimposed on the circular image from light
source 39, thus eliminating parallax errors caused by an observer
not viewing the screen at precisely right angles to the screen.
It will now be apparent that the base and cylinder curves for the
desired toric lens may be set by the dials 44 and 43 and aiming
tube 88 is thereby positioned so that when slide 26 and device 40
are moved to a position with aiming tube 88 directly over the
reference aiming point device 39, the tool 22 is positioned with
respect to the swing axis 21 to grind the desired toric lens.
Aiming tube 88 is approximately one-fourth inch in diameter,
slightly larger than the collimated spot of light from source 39,
so that very accurate positioning of slide 26 may be obtained.
The slide 26 is moved by the single lever 37 for moving tool 22 in
any desired direction. When the operator views the screen 45, he
views the light spot image from the beam of light from aiming point
39 in the mirror 45' and also views the annular light spot image
projected by illuminated aiming tube 88 in the mirror. By moving
lever 37, the operator can quickly align the projected images of
reference point 39 and aiming tube 88. Two of the aiming tube legs
89 may be connected a cross the tube, thereby forming a cross-hair
aiming spot with cord 121 passing through the tube which aiming
spot is projected on screen 42 as a shadow.
With the particular connections shown in FIG. 16 between the slide
cylinders and the ports 62 and lever 37 moves oppositely to the
working surface of the valve member 61, so the operator moves the
lever 37 in the direction he wishes to move the reference aiming
point 39 with respect to the aiming tube 88, as indicated by the
arrows 135 and 136 in FIG. 11.
When the images of reference point 39 and tube 88 are concentric,
the tool 22 is positioned. The operator then adjusts the slide 14
for grinding the desired lens thickness, adjust the lens head 16 on
ways 15 so that the lens blank 17 will contact the tool 22, swings
the lens head 16 about axis 21 and adjusts the stops for
automatically swinging the lens blank past the tool. The motors are
then started by the buttons 38 an grinding takes place
automatically.
It will be understood that the computer device 40 is for concave,
or minus diopter, lenses only. When a convex lens is to be ground,
however, the device 40 is removed from housing 41 and a convex, or
plus diopter, computer device 40', as shown in FIG. 10, is
substituted. The device 40' has the same parts as device 40 but
they are arranged as a mirror image from side to side, as
shown.
Since convex lenses are ground with the tool 22 to the left of axis
21, as shown in FIG. 1, another reference aiming point device, like
that shown at 39, is provided located secured to the side base 11
below the housing 40 as shown in FIG. 1.
The machine is not necessarily limited to grinding opthalmic
lenses. For lenses of higher power than are normally used for
opthalmic purposes as, for example, instrument lenses, another
computer device, similar to the computers 40 and 40' but covering a
different range of lens curves, may be substituted.
* * * * *