Touch-signal probe

Details Touch-signal probe Touch-signal probe

1998-12-23

2001-03-06

Metjahic, Safet (Department: 2858)

Electricity: measuring and testing

Fault detecting in electric circuits and of electric components

Of individual circuit component or element

C324S1540PB, C324S756010

Reexamination Certificate

active

06198298

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a touch-signal probe adapted to be used in a coordinate measuring machine, a machine tool and the like for measuring a configuration of a workpiece. More specifically, it relates to a vibrating touch-signal probe having improved sensitivity.
2. Description of Related Art
Conventionally, a height-gauge (linear measuring machine), a coordinate measuring machine, a contour measuring machine and the like are known as a measuring machine for measuring a configuration and a dimension of a workpiece. A touch-signal probe which detects a contact to a workpiece is employed in respective machines for detecting a coordinate and a position of the workpiece.
One simple way for detecting the touch of the touch-signal probe is to provide a contact portion for touching the workpiece at a tip end of an approximately cylindrical stylus to detect an opposing force caused by the touch. On the other hand, a vibrating touch-signal probe is also used, where a vibrating/detecting element is provided to the stylus to vibrate the stylus in advance and to detect a change of the vibration according to the touch. In the vibrating touch-signal probe, the vibration is changed, restrained for example, by the workpiece when the contact portion touches the workpiece. Accordingly, the contact can be detected by monitoring the vibration of the stylus to detect the change of the vibration.
The stylus of the vibrating touch-signal probe is preferably arranged radially. Especially, the stylus is most preferably arranged crosswise.
FIG. 4
shows a conventional vibrating touch-signal probe having styluses arranged crosswise. The touch-signal probe has a pair of stylus support
3
combined in X and Y-axis direction having a stylus
2
protruded thereon, a piezoelectric element
4
provided on an upper side of the respective stylus support
3
and a probe body
5
as a probe axis having the respective stylus supports
3
attached at a tip end thereof. A contact ball
2
a
provided at a tip end of the respective styluses
2
is abutted to the workpiece while the styluses
2
are vibrated by the piezoelectric element
4
to detect vibration change.
However, the contact ball
2
a
at the tip end of the stylus
2
is provided at a different height and can not be arranged at an identical level, since the stylus
2
is combined crosswise by stacking a pair of stylus
2
. Accordingly, the vibrating touch-signal probe is difficult to use and is difficult to reduce size thereof.
In view of above disadvantage, a vibrating touch-signal probe having a contact ball at the tip end of the stylus arranged coplanar has been strongly desired. In response, the applicant has proposed a structure in which the stylus support of the touch-signal probe is vibrated on an identical level in a radial direction (Japanese Patent Application No. Hei 8-336986).
FIGS.
5
(
a
), (
b
) and FIG.
6
(
a
) shows a specific structure of the touch-signal probe proposed by the applicant.
A center of the stylus support
10
corresponds to the origin of X, Y and Z-axis. The stylus support
10
has a square X-Y plane and is a flat block. A pair of vibrating/detecting element
12
composed of a piezoelectric element is bonded to a locating projection
11
protruded on four corners of an upper and a lower surface of the stylus support
10
. A total of four styluses
13
are provided on a center of respective sides of the stylussupport, the styluses being symmetrical and corresponding to X and Y-axis directions respectively.
The stylus support
10
is supported by fitting a tip end
15
a
of a probe body
15
extending in Z-axis direction to a fitting hole
14
penetrating through the plane center of the stylus support
10
.
An insert hole
16
having sufficiently larger inner diameter than an outer diameter of the tip end
15
a
is formed at a center of respective vibrating/detecting element
12
to prevent the vibrating/detecting element
12
from being interfering with the probe body
15
.
According to the above arrangement, a cross-shaped touch sensor having the ball-shaped contact portion
13
a
at the tip end of the respective styluses
13
disposed coplanar can be obtained, of which mechanism is simple and is adapted to size reduction.
However, according to the touch-signal probe structure shown in FIGS.
5
(
a
), (
b
) and FIG.
6
(
a
), the stylus support
10
deforms to be stretched and contracted in a radial direction (diametral direction relative to a central axis line of the probe body
15
) as shown in FIGS.
6
(
b
) and
6
(
c
) when the vibrating/detecting element
12
is vibrated.
Accordingly, when the stylus support
10
is attached by fitting the probe body
15
to the fitting hole
14
, the deformation of the stylus support
10
is hindered by the fitted probe body
15
and sufficient vibration can not be maintained. In other words, though the stylus support
10
has to be sufficiently vibrated for sharply sensing the contact to the workpiece, the stylus support
10
can not be vibrated for being fitted to the probe body
15
as mentioned above. Therefore, sensing accuracy can be deteriorated.
SUMMARY OF THE INVENTION
An object of the present invention is to provide enough vibration in a vibrating touch-signal probe having a stylus vibrating in a radial direction on a same level, thereby enhancing sensitivity thereof.
For the object, an aperture for isolating a vibration of a stylus support from a periphery of a fitted position of a probe body is provided around a fitting portion provided to the stylus support.
Specifically, the touch-signal probe according to the present invention has a probe body, a stylus support provided at a tip end of the probe body, a stylus which has a contact portion for abutting the workpiece at a tip end thereof and is projected from and supported by the stylus support and a vibrating/detecting element for vibrating the stylus at a frequency approximately identical with a natural frequency of the stylus and for detecting a change in vibration with a contact of the contact portion to the workpiece.
The touch-signal probe is characterized in that a fitting portion for fitting the probe body is formed on the stylus support and in that an aperture is provided around the fitting portion to isolate a periphery of a fitted position of the probe body from the vibration of the stylus support.
According to the above arrangement, the stylus is vibrated for measurement in advance by the vibrating/detecting element through the stylus support. And the touch signal-probe is moved to abut the workpiece. When the contact portion of the stylus abuts the workpiece, the vibration of the stylus is restrained, so that the vibrating state is detected by the vibrating/detecting element to detect the contact to the workpiece.
The stylus support is vibrated at a stylus supporting portion (a portion of the stylus support outside the aperture). The vibration is absorbed by the aperture and is isolated from the periphery of the fitted position of the probe body (a portion of the stylus support inside the aperture) and the probe body. Accordingly, when the stylus support is fixed and supported by the probe body, a deformation of the stylus support is not hindered and sufficient vibration of the stylus can be obtained to conduct measurement with high accuracy without deteriorating contact sensitivity.
Further, since the stylus can be disposed on a same level, the size of the touch-signal probe can be reduced even if the stylus is supported in four directions.
The stylus supporting portion of the stylus support and the periphery of the fitted position of the probe body may preferably be opposed with the aperture therebetween and may preferably be connected by a resilient hinge which is disposed at a node of vibration of the stylus support.
According to the above arrangement, since the resilient hinge is positioned at a node of the vibration of the stylus support, the stylus support can be vibrated while the stylus support being supported relative to the peripher

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