Geometrical instruments – Distance measuring – Opposed contacts
Reexamination Certificate
1998-03-09
2001-01-23
Hirshfeld, Andrew H. (Department: 2859)
Geometrical instruments
Distance measuring
Opposed contacts
C033S831000
Reexamination Certificate
active
06176021
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a micrometer. Particularly, it relates to a micrometer which is designed to reduce the cost and weight.
2. Description of the Related Art
As shown in
FIG. 10
, a micrometer comprises an almost U-shaped main body
101
, an anvil
102
held at an end portion of the main body
101
, a spindle
104
screwed into the other end portion of the main body
101
through an inner sleeve
103
to move toward and away from the anvil
102
, an outer sleeve
105
placed and fixed onto the outside of the inner sleeve
103
, a thimble
106
rotatably covered on the outside of the outer sleeve
105
and integrally connected with the spindle
104
, and a ratchet mechanism
107
which slips when an excess load is applied on the spindle
104
, and is provided at the rear end of the spindle
104
.
On the outer circumferential surface of the outer sleeve
105
, a graduation
108
of a main scale is formed at a predetermined pitch along the axial direction, and on the outer circumferential surface of the thimble
106
, a graduation
109
of a vernier scale is formed at a predetermined pitch along the circumferential direction. By these graduations
108
,
109
, the amount of displacement of the spindle
104
to the anvil
102
can be measured. In other words, dimensions of the object which is held between the anvil
102
and the spindle
104
can be measured.
However, since the main body
101
of the conventional micrometer is molded by casting, there is a disadvantage that the production costs are high. The processes of producing the main body comprise following steps of: making a mold having a cavity which is equivalent in size and shape as that of the main body; pouring a molten sintered alloy or ductile iron (FCD400) into the cavity; taking out the casting from the split mold after cooling the molten metal; sintering the casting; removing the burrs on the casting; and boring holes on the casting to press fit the anvil
102
and the inner sleeve
103
. Therefore it needs much expense in time, effort and cost.
In addition, such castings being heavy in weight, it also brings up a disadvantage of spoiling the handling properties and operability, when it is used as a micrometer which performs measuring while holding it in one hand.
Besides, when the measurement is carried out with supporting a part of the main body
101
by hand, the heat of hand is directly transferred to the main body
101
, resulting in the thermal expansion of the main body
101
. Therefore the measures to get rid of the influence become necessary. Conventionally, as one of the measures for this point, a cover
110
has been attached with screws on the portion of the main body
101
where it is gripped by hand. However, it results in, not only an increase in weight and size but also the increase in time and labor for the attachment and cost of it.
It is an object of the present invention to provide a micrometer which enables it to reduce the cost and the size.
It is another object of the present invention to provide a micrometer which can restrain the influence of thermal expansion caused by the heat of hand.
SUMMARY OF THE INVENTION
In a micrometer having a main body which has an anvil at one end portion and holds a spindle being able to move toward and away from the anvil at the other end portion through an inner sleeve, the micrometer according to the present invention is characterized in that the main body has a frame formed by bending metal plate stamped out in a designated size and shape, an anvil holding portion to hold the anvil at one end portion on the flame, and an inner sleeve holding portion to hold the inner sleeve at the other end portion on the flame, both holding portions being processed by bending.
Preferably, light and highly rigid material, such is cold-rolled steel (SPC-C) should be used as the metal plate. The use of the flame formed by the bending process of such metal plate enables it to reduce the cost and weight compared with the conventional article of a cast metal obtained by casting, while restraining the deformation caused by the measuring pressure, in other words, maintaining the rigidity required for the measurement.
When a metal having a similar linear expansion coefficient to that of the spindle is used as the metal plate, the elongation of the frame will be approximtely equal to the elongation of the spindle under the temperature change of the working environment. Therefore, the measurement with a high precision can be maintained without any deviation from the base point.
Since the anvil holding portion and the inner sleeve portion are prepared through a bending process of the frame of the present invention, the conventional hole boring process which is required to press fit the anvil and the inner sleeve, becomes unnecessary. Therefore it becomes possible to reduce the cost on this point, too.
In the above structure, the outer surface of the frame can be either covered with resin or coated with a coating agent.
It is preferable to use, as a resin, a glass-fiber reinforced engineering plastic, such as polyphenylene sulfite (PPS) and the like, which has small thermal conductivity, similar linear expansion coefficient to the frame, and excellent tenacity, heat resistance, burning resistance, and chemical resistance. As for a coating material, it is preferable to use a substance having the same properties as that of the above resin. By using such resin and coating material, it is possible to improve the rigidity, and at the same time, since the temperature of a hand does not directly transfer to the frame when the frame is gripped with a hand during measurement, it is also possible to restrain the influence of the thermal expansion caused by the heat of hand while the weight reduction is ensured.
As for a covering method of the outer surface of the frame with resin, the resin can be molded through the injection molding, using the frame as an insert part. In more detail, after the frame is set in a cavity of the mold, the resin can be injected on the periphery of the frame. According to the aforementioned method, while the anvil holding portion and the inner sleeve holding portion of the frame are holding the anvil and the inner sleeve respectively, the frame and the anvil and the inner sleeve are unitedly combined with one another by the resin.
By providing a first circular projection whose outer diameter is almost equal to the inner diameter of the inner sleeve holding portion of the frame, a second circular projection whose outer diameter is shorter than the outer diameter of the first circular projection and which has a bumpy outer surface, and a circular tread whose outer diameter is shorter than the outer diameter of the second circular projection, on the outer circumferential surface of the inner sleeve, it is possible to decide the position relating to the frame through the first circular projection, and it is also possible to ensure the connectivity in the radial direction through the second circular projection, and the connectivity in the thrust direction through the circular tread.
The frame can be made with one sheet of a metal plate, but it is desirable to use several sheets of the metal plates, for example, a pair of the frame elements, which are formed through a bending process of the metal plate stamped out in a designated shape and size, placed one upon another. By taking this way, the rigidity of the frame can be further enhanced and the frame can be easily produced because what is required is only several sheets of the frame elements stamped out with a press machine and the like, and put one upon another.
In order to enhance the rigidity of the frame, it is desirable to provide a rib on the frame element. It is preferable to form the rib along the outer circumferential edge of the frame element.
When providing a convex portion on one frame element, and a concave portion on the other frame portion, a pair of the frame elements can be placed one upon the other with high precision in positioning by simpl
Fujimitsu Tohru
Hamano Chikashi
Mishima Toshihiko
Nakata Kiyohiro
Sato Hajime
Hirshfeld Andrew H.
Mitutoyo Corporation
Oliff & Berridg,e PLC
Smith R. Alexander
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