Geometrical instruments – Distance measuring – Opposed contacts
Reexamination Certificate
2000-07-10
2003-02-18
Gutierrez, Diego (Department: 2859)
Geometrical instruments
Distance measuring
Opposed contacts
C033S830000, C033S831000, C033S679100
Reexamination Certificate
active
06519867
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a measuring device such as a micrometer for measuring length and thickness of a workpiece.
2. Description of Related Art
Conventionally, as shown in
FIG. 4
, a micrometer
100
has an approximately U-shaped frame
101
, an anvil
102
secured to one end of the frame
101
and a sleeve
110
held at the other end thereof. The sleeve
110
is composed of an inner sleeve
103
with a base end thereof being fixed to the frame
101
and an outer sleeve
105
fixed to an outer circumference of the inner sleeve
103
protruding from frame
101
. A part of an inner circumference of a tip end of the inner sleeve
103
has a plurality of slotted grooves and a female screw, and a male screw portion
104
A of a spindle
104
is screwed to the female screw. A tip end of the spindle
104
without the male screw portion
104
A is slidably fitted to a portion of the frame
101
for the inner sleeve
103
to be fixed, and the spindle
104
is held advanceable and retractable relative to the anvil
102
. One end of a thimble
106
is rotatably free-fitted to an outside of the outer sleeve
105
fitted to an outer circumference of the inner sleeve
103
, and the other end of the thimble
106
is integrally connected to the spindle
104
. A ratchet mechanism
107
freerunning when more than a predetermined load is applied to the spindle
104
is provided to a rear end of the spindle
104
.
A main scale
108
A and main scale numeral
108
B are formed on an outer circumference of the outer sleeve
105
at an even pitch along axial direction. A vernier scale
109
A equally dividing the circumference at fifty pitches and a vernier numeral
109
B corresponding to the number of the vernier scale
109
A are formed on an outer circumference of the thimble
106
in circumferential direction at an even pitch. Incidentally, the main scale
108
A is formed by engraving, printing, dichroic molding, laser marking etc. The vernier scale
109
A is, as shown in
FIG. 5
, formed on a tapered portion
106
A of the thimble
106
by engraving, printing, dichroic molding, laser marking etc.
The main scale
108
A on the outer sleeve
105
is composed of a base line
111
, a base scale
112
at 1 mm pitch and an intermediate scale
113
in the midst of the base scale
112
, where interval between the respective scales
108
A shows 0.5mm displacement. Since the thimble
106
advances and retreats for one scale distance (1 mm) of the base scale
112
of the main scale
108
A by two rotations thereof, the pitch of the thimble
106
becomes 0.5 mm. The vernier scale
109
A provided on the thimble
106
equally divides the circumference of the thimble
106
at fifty pitches. Accordingly, one scale of the vernier scale
109
A corresponds to one hundredth of one scale of the main scale
108
A. In other words, one scale of the vernier scale
109
A indicates displacement of 0.01 mm.
The displacement of the spindle
104
relative to the anvil
102
can be measured by the above main scale
108
A, the vernier scale
109
A, the main scale numeral
108
B and the vernier numeral
109
B. In other words, dimension of a workpiece held between the anvil
102
and the spindle
104
can be measured by the above arrangement.
In the above-described micrometer
100
, the vernier numeral
109
B on the thimble
106
is from 0 mm to 45 mm (ordinarily at five scale interval) and measurement value can be read directly by the vernier numeral
109
B at, for instance, from 0.0 mm to 0.5 mm section. However, when the measurement is conducted in 0.5 mm to 1.0 mm section, since the indication of the vernier numeral
109
B is 0 mm to 45 mm, 0.5 mm has to be added to the current read value to convert 0.5 mm to 1.0 mm. Accordingly, read error of the measurement arithmetic calculation.
Further, the scale of the micrometer
100
is read by reading coincidence point of the base line
111
on the outer circumference of the outer sleeve
105
with the vernier scale
109
A of the thimble
106
. At this time, since the vernier scale
109
A is formed on the tapered portion
106
A of the thimble
106
, parallax error can be caused in measurement. In other words, on both scale surfaces of the outer sleeve
105
provided with the main scale
108
A and the thimble
106
provided with vernier scale
109
A, the coincidence of the scales is read with a level difference T (according to JIS standard of not more than 0.4 mm) including end surface dimension (currently 0.25 mm) intervening therebetween, thus deviating degree of coincidence according to eye position and causing read error.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a measuring device capable of reducing read error.
A measuring device according to the present invention has: a spindle advanceable and retractable relative to a workpiece; a sleeve partly screwed to the spindle and having a main scale and a main scale numeral on an outer circumference thereof along axial direction; and a thimble rotatably provided on an outside of the sleeve and integrally connected to the spindle, the thimble advancing and retracting for one scale of the main scale by two rotations thereof, the measuring device is characterized in that a vernier scale for equally dividing circumference of the thimble in a plurality of times is provided to an inner circumference of the thimble and that at least a part of a material of the thimble having the vernier scale is translucent.
According to the present invention, since the vernier scale is on the inner circumference of the thimble substantially in contact with the outer circumference of the outer sleeve, the level difference can be reduced for the dimension of the end surface of the thimble, so that the parallax error can be reduced in reading the coincidence point of the base line of the main scale and the vernier scale.
A measuring device according to another aspect of the present invention includes: a spindle advanceable and retractable relative to a workpiece; a sleeve partly screwed to the spindle and having a main scale and a main scale numeral on an outer circumference thereof along axial direction; and a thimble rotatably provided on an outside of the sleeve and integrally connected to the spindle, the thimble advancing and retracting for one scale of the main scale by two rotations thereof, the measuring device being characterized in having a vernier scale for equally dividing a circumference of the thimble in a plurality of times in circumferential direction, first vernier numeral corresponding to indication of the vernier scale, and second vernier numeral equal to addition of respective value of the first vernier numeral and the value of the vernier scale of one rotation.
According to the present invention, by providing the second vernier numeral of the thimble as, for instance, when the main scale is 1 mm pitch, 55 to 95, there is no need for adding 0.5 mm to the current read value during measurement of 0.5 mm to 1.0 mm section and the second vernier numeral can be directly read, thus reducing read error.
A measuring device according to further aspect of the present invention includes: a spindle advanceable and retractable relative to a workpiece; a sleeve partly screwed to the spindle and having a main scale and a main scale numeral on an outer circumference thereof along axial direction; and a thimble rotatably provided on an outside of the sleeve and integrally connected to the spindle, the thimble advancing and retracting for one scale of the main scale by two rotations thereof, the measuring device being characterized in that a vernier scale for equally dividing circumference of the thimble in a plurality of times is provided to an inner circumference of the thimble; that an inner circumference of the thimble has a vernier scale for equally dividing a circumference of the thimble in a plurality of times in circumferential direction, and an outer circumference of the thimble has first vernier numeral corresponding to indication of the vernier scale, and sec
De Jesús Lydia M.
Gutierrez Diego
Mitutoyo Corporation
Oliff & Berridg,e PLC
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