Geometrical instruments – Distance measuring – Opposed contacts
Reexamination Certificate
1999-10-29
2001-10-30
Bennett, G. Bradley (Department: 2859)
Geometrical instruments
Distance measuring
Opposed contacts
C033S831000
Reexamination Certificate
active
06308433
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a micrometer. More specifically, it relates to a micrometer of which spindle moves at a high speed.
2. Description of the Related Art
Some micrometers move the spindle thereof at a higher speed than the conventional ones.
As shown in
FIGS. 1 and 2
, such micrometers include a frame
1
having an anvil
2
, a spindle
3
advanceable relative to the anvil
2
of the frame
1
, an inner sleeve
4
disposed on the frame
1
coaxially with the spindle
3
, an outer sleeve
5
rotatably fitted to an outer circumference of the inner sleeve
4
, a thimble
7
rotatably provided on an outside of the outer sleeve
5
through a ratchet mechanism
6
, a driving means
8
for advancing and retracting the spindle
3
relative to the anvil
2
in accordance with rotation of the thimble
7
, a displacement sensor
9
for detecting displacement amount of the spindle
3
, and a display
10
for displaying detected value detected by the displacement sensor
9
. Reference numeral
12
indicates a power on-off switch.
The driving means
8
includes an engage pin
21
projectingly provided on a rear end of the spindle
3
through a connecting member
20
, a slit
22
formed on a circumference of the inner sleeve
4
along an axial direction of the spindle
3
for movably guiding the engage pin
21
in the axial direction of the spindle
3
, and a spiral groove
23
formed in spiral on an inner circumference of the outer sleeve
5
around the center of the spindle
3
for engaging the engage pin
21
. The pitch of the spiral groove
23
is extremely wider than a conventional screw pitch, which is, for example, approximately ten to twenty times as wide as the screw pitch of the conventional micrometer (ordinarily 0.5 mm pitch).
The displacement sensor
9
has a sensor
26
including a scale
24
formed along a longitudinal direction of the spindle
3
and a detector
25
fixed to the frame
1
spaced apart at a predetermined gap. The displacement sensor
9
converts signal detected by the sensor
26
into a number of pulse signals corresponding to a movement displacement amount of the spindle
3
and counts the pulses.
When the outer sleeve
5
is rotated by rotating the thimble
7
, the spindle
3
is advanced and retracted in the axial direction thereof through an engage pin
21
engaging the spiral groove
23
of the outer sleeve
5
. At this time, since the pitch of the spiral groove
23
is ten to twenty times as large as the conventional screw pitch, the spindle
3
can be moved approximately ten to twenty times as fast as the conventional one.
Accordingly, even in alternately measuring workpiece having dimension difference, the spindle
3
can be moved at a high speed, thereby efficiently conducting measurement.
According to the above-described high-speed micrometer, since the pitch of the spiral groove
23
, i.e. a lead, is large, fluctuation of thrust (thrust force: measurement force) of the spindle
3
according to deviation of driving force (force for rotating the thimble
7
) can be restrained. On the other hand, when a user's hand is released from the thimble
7
while the workpiece is sandwiched by the anvil
2
and the spindle
3
, the spindle
3
can be backed by the rotation of the outer sleeve
5
. This is made possible since a larger rotating force operates on the outer sleeve
5
than the conventional micrometer by virtue of a counterforce provided by the workpiece.
When the spindle
3
is backed, the movement is detected by the displacement sensor
9
, which result in a change of displayed value on the display
10
.
SUMMARY OF THE INVENTION
An object of the present invention is to solve the above problem inherent to the conventional high-speed micrometer and to provide a micrometer capable of high-speed and highly accurate measurement even when the spindle is backed by the counterforce by the workpiece.
A micrometer according to the present invention has a frame including an anvil, a spindle advanceably provided relative to the anvil, a sleeve provided on an outside of the spindle on the frame rotatably around a central axis of the spindle, a driving means for advancing and retracting the spindle relative to the anvil in accordance with a rotation of the sleeve, a displacement sensor for detecting a displacement amount of the spindle, and a display for displaying detected value detected by the displacement sensor, the driving means including a spiral groove on either one of the sleeve or the spindle around a center of the spindle and an engage pin provided on the other one of the sleeve and the spindle for slidably engaging the spiral groove, and a lead of the spiral groove being not less than 5 mm. The micrometer is characterized in further comprising: a moving direction discriminator for discriminating a moving direction of the spindle; a minimum value renewal holder for newly displaying detected value detected by the displacement sensor when the moving direction discriminator judges that the spindle advances in an advancing direction relative to the anvil and also for holding displayed value on the display when the moving direction discriminator judges that the spindle moves in a retracting direction relative to the anvil and the retraction amount of the spindle from the displayed value newly displayed on the display is less than a set amount; and a minimum value hold releaser for displaying the detected value detected by the displacement sensor on the display when the moving direction discriminator judges that the spindle is moving in a retracting direction relative to the anvil and when the retraction amount of the spindle from the displayed value newly displayed on the display is not less than the set amount.
According to the above arrangement, the detected value detected by the displacement sensor is newly displayed onto the display when the spindle moves in the advancing direction relative to the anvil. In other words, when the spindle advances toward the anvil, the minimum value is automatically newly displayed.
During the measurement process, when the spindle moves in a retracting direction relative to the anvil, the retraction amount, i.e. retraction amount of the spindle from updated minimum value is within a range of the set amount, the displayed value on the display is held. In other words, the minimum value is maintained. Accordingly, when the spindle is backed by a rotation of the sleeve caused on account of large lead of the spiral groove, the displayed value is not changed, thereby achieving high-speed and highly accurate measurement.
On the other hand, when the retraction amount of the spindle is more than the set amount, the detected value detected by the displacement sensor is displayed on the display. In other words, the minimum hold status is released. Accordingly, the minimum hold status can be released in a series of ordinary measurement operation without accompanying special switching operation, thereby achieving superior operability.
In the above, a setting means for selectively setting the set amount may preferably be provided.
By providing the setting means, since the set amount can be selectively established, the minimum hold release condition can be changed according to measurement condition. Accordingly, since the minimum hold status is not released unpreparedly, the displayed value can be securely read.
REFERENCES:
patent: 3484942 (1969-12-01), Toubhans
patent: 3758956 (1973-09-01), Nakata
patent: 4255861 (1981-03-01), Nakata et al.
patent: 4561185 (1985-12-01), Sakata et al.
patent: 4578868 (1986-04-01), Sasaki et al.
patent: 4738030 (1988-04-01), Backlund et al.
patent: 5433016 (1995-07-01), Tachikake et al.
patent: 5495677 (1996-03-01), Tachikake et al.
patent: 5829155 (1998-11-01), Takahashi et al.
Hayashida Shuuji
Nakadoi Tetsuya
Otsuka Takahiro
Sasaki Kouji
Tachikake Masahiko
Bennett G. Bradley
Mitutoyo Corporation
Oliff & Berridg,e PLC
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