Optics: eye examining – vision testing and correcting – Eye examining or testing instrument – Subjective type
Reexamination Certificate
2002-05-01
2004-02-17
Manuel, George (Department: 3737)
Optics: eye examining, vision testing and correcting
Eye examining or testing instrument
Subjective type
Reexamination Certificate
active
06692128
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to ophthalmic instruments, and more particularly to subjective ophthalmic refractors for evaluating refractive characteristics of a patient's eye.
BACKGROUND OF THE INVENTION
A subjective ophthalmic refractor typically comprises left-eye and right-eye batteries each having a defined viewing path along which an operator may selectively introduce combinations of testing lenses having known refractive properties. During examination, the patient is positioned in a darkened room with his or her eyes aligned to view a projected target chart along the viewing paths defined by the left-eye and right-eye batteries. The operator then performs well-known refracting procedures, including refraction using astigmatic charts and the Jackson cross-cylinder test. A goal of the examination procedure is to determine the sphere power, cylinder power, and cylinder axis of each eye so that a suitable pair of corrective lenses may be prescribed.
U.S. Pat. No. 2,968,213 describes an ophthalmic refractor of the prior art. FIG. 5 of the '213 patent is an exploded view illustrating the internal components of a left eye lens battery, and serves to illustrate a longstanding arrangement for mechanically coupling a pair of rotatable cylinder lens carriers
8
and
9
and an associated ring-shaped cylinder power scale
50
of the battery to an adjustment knob
20
used by the operator to set a chosen cylinder power in the viewing path of the battery. As can be seen at FIG. 1 of the '213 patent, the indicia on scale
50
can be viewed by the operator through an display window or opening
52
in the battery housing. Typically, the indicia are numerical cylinder power values from 0 to 6.00 diopters in quarter-diopter increments, and are angularly spaced at regular angular increments about a central axis of the ring-shaped scale. The mechanical interconnections from knob
20
, through cylinder power scale
50
, to the lens carriers
8
and
9
are designed such that rotation of knob
20
positions two lenses (or a lens and an empty lens cell), one from lens carrier
8
and one from lens carrier
9
, in series in the viewing path to produce a resultant cylinder power. Lens carrier
8
is a “weak” cylinder lens carrier having, for example, a blank lens cell (zero power)and four cylinder lenses ranging in power from 0.25 diopters to 1.00 diopters at quarter diopter increments. Meanwhile, lens carrier
9
is a “strong” cylinder lens carrier having, for example, a blank lens cell (zero power) and four cylinder lenses ranging in power from 1.25 diopters to 5.00 diopters at 1.25-diopter increments. Consequently, by indexing the weak cylinder lens carrier
8
five times for every one index movement of strong cylinder lens carrier
9
, a cylinder power range of 0.00 diopters to 6.00 diopters at quarter-diopter increments is possible in agreement with the indicia on scale
50
.
With continued reference to U.S. Pat. No. 2,968,213, it will be seen that adjustment knob
20
drives a shaft
21
having at its opposite end a dual gear comprising a small front gear
23
and a larger rear gear
25
. Larger gear
25
meshes with a gear
31
which is fixedly and permanently attached to driver plate
27
in coaxial arrangement therewith, whereby rotation of knob
20
and larger gear
25
produces counter-rotation of driver plate
27
. As driver plate
27
rotates about its axis, four short pegs.
39
a
-
39
d
on the driver plate successively engage weak cylinder lens carrier
8
to index only the weak lens carrier, and a fifth longer peg
40
engages both the weak and strong lens carriers
8
and
9
to index both carriers, in the manner of a Geneva mechanism. A spring-biased roller
48
′ cooperates with five circumferential detents
53
′ in driver plate
27
to allow the operator to feel each index position at adjustment knob
20
. A locking plate
37
having a recess
49
is fixedly mounted for rotation with driver plate
27
by a hub
33
and cooperates with a star wheel
47
on strong cylinder lens carrier
9
to prevent rotation of the strong cylinder lens carrier except when it is time for the strong cylinder lens carrier to index.
Meanwhile, small front gear
23
meshes with internal gear teeth on ring-shaped scale
50
to rotate the scale in coordination with the indexing of cylinder lens carriers
8
and
9
, whereby an appropriate cylinder power value marked on the scale appears through display window
52
. Scale
50
is constrained both radially and axially by three bearings
56
located at respective positions about the circumference of scale
50
.
During manufacturing assembly of an ophthalmic refractor formed in accordance with the '213 patent, it is necessary to carefully align cylinder power scale
50
such that a correct cylinder power value is precisely centered in display window
52
while dependent rotational positions of driver plate
27
and locking plate
37
are also in proper alignment for functioning of the Geneva mechanism. However, because an exact locational relationship between the internal gear teeth and the markings on scale
50
is not specified and one scale differs slightly from another in this regard, the task of centering the scale markings in the display window and achieving proper rotational alignment among the interconnected parts has involved a process of trial and error. For example, different scales
50
and other component parts in the mechanical interconnection are tried from production batches of these parts until a suitable combination of parts produces acceptable rotational alignment and centering of the scale markings.
FIGS. 2 and 3
herein help illustrate assembly of an ophthalmic refractor eye battery
111
A according to the prior art. A cylinder power scale
118
is mounted in eye battery housing
112
A, and adjustment knob shaft
124
is inserted through a provided bearing opening in the housing such that scale drive gear
126
(see small front gear
23
of the '213 patent) fixed to the shaft meshes with internal gear
130
of cylinder power scale
118
. A driver plate
127
having a gear
131
permanently fixed thereto and a locking plate
133
having a hub
135
permanently fixed thereto are fastened together in a predefined angular relationship such that an arcuate recess
159
of the locking plate is centered with respect to the longer peg
160
of the driver plate. More specifically, three angularly spaced fastener holes
145
are provided through hub
135
in set relation to recess
159
and three corresponding threaded holes
147
are provided through gear
131
in set relation to longer peg
160
, and the hub
135
is fastened to gear
131
by threaded fasteners
149
operable through access openings
151
to form a subassembly
153
comprising locking plate
133
, hub
135
, driver plate
127
, and gear
131
. This subassembly
153
is then mounted on hub stem
137
such that gear
131
meshes with a larger gear
128
(see larger rear gear
25
of the '213 patent) fixed to adjustment knob shaft
124
adjacent scale drive gear
126
. A spring-biased roller (not shown in
FIGS. 2 and 3
but equivalent to spring-biased roller
48
′ shown in the '213 patent) engages an appropriate detent
155
in driver plate
127
to set the relationship of subassembly
153
to a star wheel and lens carriers (not shown in
FIGS. 2 and 3
but equivalent to star wheel
47
and lens carriers
8
and
9
of the '213 patent). Consequently, in order for gear
131
of subassembly
153
to mesh with larger gear
128
, the adjustment knob shaft may have to rotate slightly, thereby rotating the scale drive gear
126
and scale
118
and producing an “uncentered” appearance of the corresponding scale marking in display window
122
. To correct this, different scales
118
, driver plates
127
with attached gear
131
, and locking plates
133
with attached hub
135
must be tried until a satisfactory centering is achieved.
Understandably, this assembly process is time consuming and
Hodgson & Russ LLP
Manuel George
Reichert, Inc.
Sanders John R.
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