Measuring and testing – Instrument casing
Reexamination Certificate
1997-09-22
2001-02-27
Williams, Hezron (Department: 2856)
Measuring and testing
Instrument casing
C033S517000, C206S305000
Reexamination Certificate
active
06192755
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a dial gauge case, which can be utilized for a usual dial gauge for magnifying a stroke or displacement of a spindle with a magnifying mechanism such as a rack-and-pinion assembly.
2. Description of the Prior Art
A usual dial gauge magnifies a stroke or displacement of a spindle having a probe or measuring pin provided at an end with a pinion-and-rack assembly or like magnifying mechanism, and displays the magnified stroke or displacement as a corresponding rotation of a pointer.
Such a dial gauge permits even a very small displacement of the probe to be confirmed as a great rotation of the pointer, thus permitting high accuracy measurement.
FIGS. 10 and 11
show a well-known dial gauge
10
.
The illustrated dial gauge
10
comprises a dial gauge case
40
, which accommodates a dial gauge mechanism including a scale board
20
and a pointer
30
, and a spindle
50
penetrating a peripheral wall
41
of the case
40
.
A cylindrical stem
60
projects outward from the peripheral wall
41
, and accommodates the spindle
50
.
The stem
60
protects the spindle
50
, and serves a mounting portion to be mounted in a support which supports the dial gauge
10
.
The inside of the dial gauge case
40
is as shown in FIG.
12
. In the case
40
and the stem
60
, bearings
42
and
64
are provided such that they face each other in the direction of sliding of the spindle
50
, thus permitting smooth sliding of the spindle
50
.
In the above usual dial gauge
10
, the case
40
is fabricated as a one-piece casting of zinc, and the bearings
42
and
64
are fabricated by using bronze or like material having satisfactory frictional properties.
In the assembling of the dial gauge
10
, therefore, it is necessary to mount the bearings
42
and
64
in the peripheral wall
41
and the stem
60
, respectively, giving rise to the problem that the efficiency of dial gauge manufacture is reduced with increased number of parts and increased number of assembling steps.
It is conceivable to fabricate the case
40
and bearings
42
and
64
altogether as a one-piece molding of bronze. Doing so, however, results in an extreme increase of the material cost of the case
40
.
The invention seeks to solve the above problems, and it has an object of providing a dial gauge case, which permits reducing the number of dial gauge components and improving the efficiency of dial gauge manufacture without greatly increasing the material cost of the dial gauge.
SUMMARY OF THE INVENTION
The invention features a dial gauge case, which has a bottom and a peripheral wall surrounding the bottom, the bottom and the peripheral wall defining a recess for accommodating a dial gauge mechanism therein, the peripheral wall being provided with a pair of bearings for slidably supporting a spindle of the dial gauge, the peripheral wall and the bearings being formed together as a one-piece molding of a plastic material.
According to the invention, with the peripheral wall and the bearings formed together as a one-piece molding, the number of components involved in the assembling of the dial gauge can be reduced, thus simplifying the operations of assembling the peripheral wall and the bearings and improving the efficiency of the dial gauge manufacture.
In addition, since the peripheral wall is obtained from a plastic material, the material cost of the dial gauge is not greatly increased, and the weight thereof can be reduced.
The plastic material is preferably a reinforced plastic, which is obtain by reinforcing a synthetic resin composed of polyphenylene sulfide (hereinafter referred to as PPS) with a member of the group consisting of carbon fiber, glass fiber, potassium titanate whisker and aluminum borate whisker.
By using PPS, a case having high heat resistance and high wear resistance is obtainable, and by reinforcing PPS with carbon fiber or the like, a case having high mechanical strength is obtainable.
Carbon fiber, potassium titanate whisker or aluminum borate whisker used as reinforcing material, not only improves the mechanical strength of the case, but also functions as a frictional material. It is thus possible to obtain bearings, which permit satisfactory sliding and are also excellent in wear resistance.
The plastic material used as the bearing material is obtained by reinforcing PPS with carbon fiber, potassuim titanate whisker or aluminum borate whisker. A reinforced plastic, used for the remainder of the case is obtained by reinforcing PPS with glass fiber.
The glass-fiber-reinforced plastic is used for the case portion and not the bearings, allowing a minimum amount of expensive reinforcing material such as carbon fiber to be used thus reducing the material cost of the case.
Where a stem accommodating a spindle is provided on the dial gauge case, a bearing is suitably provided at the stem end or the inside of the stem.
With the bearing provided at the stem end, no bearing need be provided at the free end of the stem, thus permitting simplification of the dial gauge assembling as described before in connection with the prior art. With one of the bearings provided inside the stem, on the other hand, it is possible to provide a sufficient distance between the pair of bearings, so that the spindle can be supported more reliably.
Where one of the bearings is provided inside the stem, the stem is formed with one or more holes in the vicinity of its stem end for coupling the peripheral wall and the bearing through the hole or holes.
With a hole or holes formed in the stem end, synthetic resin is led through the hole or holes to the stem. It is thus possible to readily fabricate the case with the bearing formed inside the stem. Thus, the distance between the pair of bearings in the direction of sliding of the spindle can be set to be sufficiently large for supporting the spindle in the bearings more reliably.
Moreover, with the peripheral wall and the bearing coupled together through the hole or holes provided in the stem end, the stem is mechanically connected to the case, and it is possible to reliably preclude detachment of the stem from the peripheral wall.
The invention also features a method of manufacturing a dial gauge case, which has a bottom and a peripheral wall surrounding the bottom, the bottom and the peripheral wall defining a recess for accommodating a dial gauge mechanism therein, the peripheral wall being formed together with a pair of cylindrical bearings for slidably supporting the spindle as a one-piece molding, the method including fabricating the cylindrical bearings from a reinforced plastic obtained by reinforcing a synthetic resin composed of a polyphenylene sulfide with a member of the group consisting of carbon fiber, potassium titanate whisker and aluminum borate whisker, and molding the case from a plastic material with the bearings set in a die by insert molding, thereby making the peripheral wall and the bearings integral with one another.
With the bearing fabricated form the material different from that of the case and made integral with the case when molding the case, it is possible to use an expensive reinforcing material such as carbon fiber only for the bearing, which should provide for improved sliding property, while using inexpensive glass fiber for the remainder of the case. The expensive reinforcing material such as carbon fiber thus can be used only in a minimum necessary amount, thus permitting reduction of the material cost of the case.
REFERENCES:
patent: 3226836 (1966-01-01), Bond
patent: 3338103 (1967-08-01), Lohrs et al.
patent: 4489496 (1984-12-01), Mizuno et al.
Ishii Munenori
Shinohara Toshiyuki
Cygan Michael
Mitutoyo Corporation
Oliff & Berridg,e PLC
Williams Hezron
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