Inside measuring instrument

Abstract

There is provided a thin-bottom type bore gauge having damping unit between a gauge head and a head main body part, and a long life. A head part of a bore gauge includes a head main body part, a measurement spherical face at one end face, and a gauge head slidably provided by penetrating an inside and an outside of the head main body part. The gauge head a spring holding groove carved in a circumferential direction at the other end side, and a compression coil spring is interposed between the spring holding groove and an inside end face of the head main body part.

Claims

1. A head part of an inside measuring instrument which measures an inside of a measurement target object, the head part comprising: a head main body part; and a gauge head which includes a measurement spherical face on one end face and is slidably provided by penetrating an inside and an outside of the head main body part, wherein the gauge head includes a spring holding groove carved in a circumferential direction in the gauge head at the other end side of the gauge head opposite the measurement spherical face, and a compression coil spring is positioned around the gauge head with an end of the compression coil spring being positioned within the spring holding groove, the compression coil spring being interposed between the spring holding groove and an inside end face of the head main body part.

2. The head part of the inside measuring instrument according to claim 1, wherein the compression coil spring includes a diameter which accepts the gauge head inside thereof, and a diameter of an end turn part corresponding to the other end of the gauge head is smaller than other parts so as to be fitted on the spring holding groove.

3. The head part of the inside measuring instrument according to claim 1, further comprising: a rod which is movable in a direction orthogonal to a moving direction of the gauge head; and a cam provided between the other end of the gauge head and the rod, and rotatably supported about an axis by the head main body part, wherein end faces or wholes of the gauge head and the rod are ceramic.

4. A head part of an inside measuring instrument which measure an inside of a measurement target object, the head part comprising: a head main body part; a gauge head which includes a measurement spherical face on one end face and is movably provided by penetrating an inside and an outside of the head main body part, the gauge head including a spring holding groove carved in a circumferential direction in the gauge head at the other end side of the gauge head opposite the measurement spherical face; a compression coil spring is positioned around the gauge head with an end of the compression coil spring being positioned within the spring holding groove, the compression coil spring being interposed between the spring holding groove and an inside end face of the head main body part; a rod which is movable in a direction orthogonal to a moving direction of the gauge head; and a cam provided between the other end of the gauge head and the rod, and rotatably supported about an axis by the head main body part, wherein end faces or wholes of the gauge head and the rod are ceramic.

5. An inside measuring instrument comprising a head part according to claim 1.

6. The inside measuring instrument according to claim 5, further comprising: biasing means for biasing the rod in a direction toward a cam, wherein biasing force of the compression coil spring is the same as biasing force of the biasing means or more, and the head part further includes: a rod which is movable in a direction orthogonal to a moving direction of the gauge head; and the cam provided between the other end of the gauge head and the rod, and rotatably supported about an axis by the head main body part.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is an external view of a bore gauge;

(2) FIG. 2 is an enlarged view of a head part;

(3) FIG. 3 is a cross-sectional view of the head part;

(4) FIG. 4 is an exploded perspective view of the head part;

(5) FIG. 5 is a diagram for explaining a problem;

(6) FIG. 6 is a cross-sectional view of the present exemplary embodiment;

(7) FIG. 7 is a diagram illustrating a gauge head of the present exemplary embodiment; and

(8) FIG. 8 is a diagram illustrating a third compression coil spring.

DETAILED DESCRIPTION

(9) A first characteristic of an exemplary embodiment of the present invention is that a third compression coil spring is interposed between a head main body part 300 and a gauge head 400 (see FIG. 6). Before the specific configuration of an exemplary embodiment of the present invention is described, a problem in the case where a common coil spring 50 is simply provided will be described with reference to FIG. 5.

(10) As illustrated in FIG. 5, when the coil spring 50 is to be simply interposed between the head main body part 300 and the gauge head 400, the following problem occurs.

(11) When the coil spring 50 is to be interposed between the head main body part 300 and the gauge head 400, a flange 410 for holding a spring can be provided on the gauge head 400, as illustrated in, for example, FIG. 5. Thus, the diameter of the gauge head 400 needs to be increased to provide the flange 410, and an excessive space is to be secured below the measurement axis, which is undesirable considering the purpose to measure a shallow hole.

(12) Furthermore, if the coil spring 50 is interposed between the head main body part 300 and the gauge head 400, a holding part 350 of the gauge head 400 needs to be shorten to provide the coil spring 50. Then, the gauge head 400 may unstably function.

(13) Moreover, if a partial protrusion, such as the flange 410, is provided on the gauge head 400, the machining man-hour is considerably increased (the cutting amount is increased). There may be various ideas if the gauge head 400 and the head main body part 300 could be more intricately machined. However, it is undesirable that the labor and cost for machining in the trend of falling prices.

(14) Due to the above problem, although the thin-bottom type bore gauge 100 has the problem of the life, damping means has not been provided between the gauge head 400 and the head main body part 300.

(15) Exemplary embodiments of the present invention will be illustrated and described with reference to reference signs assigned to elements in the drawings.

First Exemplary Embodiment

(16) A first exemplary embodiment of the present invention will be described.

(17) As illustrated in FIG. 6, the first characteristic of the present exemplary embodiment is that a third compression the coil spring 500 (see FIG. 6) is interposed between a head main body part 300 and a gauge head 400.

(18) The present exemplary embodiment is illustrated in FIGS. 6 to 8.

(19) In FIG. 6, the head main body part 300 includes a first hole 321 and a second hole 322 orthogonal to the first hole 321. At the crossing point of the first hole 321 and the second hole 322, the diameter of the first hole 321 is enlarged, and a cam 330 is disposed in a space formed thereby. The space will be referred to as a cam disposition space 325.

(20) The gauge head 400 is slidably inserted to one side of the second hole 322 interposing the cam 330. Thus, the hole of the second hole 322 at the side where the gauge head 400 is disposed will be referred to as a gauge head hole 323. Note that, the inner face of the gauge head hole 323 is equivalent to a holding part 350 which holds the gauge head 400.

(21) In the head main body part 300, the edge of the opening at the other side of the gauge head hole 323 is an end face 324 perpendicular to the axial line of the gauge head hole 323. The end face 324, which will be apparent from the later description, is an end face for holding the spring and will be referred to as a spring holding end face 324.

(22) FIG. 7 is a diagram illustrating the gauge head 400 of the present exemplary embodiment.

(23) The gauge head 400 has a columnar shape as a whole, and includes a measurement spherical face 430 on one end face and a cam contacting face 440 on the other end face. The cam contacting face 440 is brought into contact with the cam 330. The gauge head 400 includes a groove line 450, which is carved in the circumferential direction, at the other end side. The groove line 450, which will be apparent from the later description, is the groove for holding the spring and will be referred to as a spring holding groove 450.

(24) Note that, a part to be engaged with the lock plate 340, such as a long groove 420, is not required in the present exemplary embodiment.

(25) When the gauge head 400 is inserted into the gauge head hole 323, the spring holding groove 450 protrudes to the other side more than the spring holding end face 324. Then, the third compression coil spring 500 is attached between the spring holding groove 450 and the spring holding end face 324.

(26) FIG. 8 is a diagram illustrating the third compression coil spring 500. In FIG. 8, the end turn part at the right side (one side) is brought into contact with the spring holding end face 324, and the end turn part at the left side (the other side) is engaged with the spring holding groove 450. The end turn part at the right side (the one side) will be referred to as a first end turn part 510, and the end turn part at the left side (the other side) will be referred to as a second end turn part 520.

(27) The diameter of the third compression coil spring 500 is slightly larger than that of the gauge head 400, and the gauge head 400 is neatly accommodated inside the third compression coil spring 500. However, the diameter of the second end turn part 520 is smaller than the other parts, and the second end turn part 520 is fitted on the spring holding groove 450.

(28) In the above described configuration, the third compression coil spring 500 biases the gauge head 400 to the other side by receiving the reaction from the spring holding end face 324. In other words, the third compression coil spring 500 biases the gauge head 400 in the direction opposite to the protruding direction, that is, in the direction in which the gauge head 400 is retracted. While a first compression coil spring (not illustrated) biases a spindle (not illustrated) or a lower rod 210 in the protruding direction (downward), the third compression coil spring 500 biases the gauge head 400 in the direction opposite to the force direction of the first compression coil spring (not illustrated).

(29) Note that, the first compression coil spring (not illustrated) is stronger than the third compression coil spring 500.

(30) In the above described configuration, while a thin bottom is maintained, it is possible to interpose the third compression coil spring 500 between the gauge head 400 and the head main body part 300. As the employed third compression coil spring 500, the diameter thereof is not fixed, but the diameter of the second end turn part 520 is small. For example, when a coil spring having a fixed diameter is used, the spring holding flange 410 needs to be provided on the gauge head 400 as illustrated in FIG. 5, and a thin bottom cannot be maintained. In contrast, a coil spring having a small diameter of the second end turn part 520 is employed in the present exemplary embodiment, the spring is held by the circumferential groove (spring holding groove) 450 at the gauge head 400 side accordingly. Thus, it is possible to provide damping means between the gauge head 400 and the head main body part 300 while a thin bottom is maintained.

(31) Furthermore, the end turn part (the second end turn part 520) is engaged with the spring holding groove 450, which leads to more excellent space efficiency as compared to the case where, for example, the spring is held by the spring holding flange (see 410 in FIG. 5) and to securing the length of the holding part 350 as a result. Thus, the gauge head 400 stably functions.

(32) The third compression coil spring 500 prevents the gauge head 400 from popping out, and a lock plate (stopper) is not required in the present exemplary embodiment. The working distance limit of the gauge head 400 is regulated by an elastic member which is the third compression coil spring 500, and the components (the lock plate 340 and the gauge head 400) do not collide with each other, which leads a long life and improvement of measurement precision.

(33) Since the lock plate 340 is not required, a bottom face 302 of the head main body part 300 does not need to receive large force. Thus, it is possible to thin the bottom face 302 of the head main body part 300 accordingly.

Modified Example 1

(34) In the above exemplary embodiment, it has been described that the first compression coil spring (not illustrated) is stronger than the third compression coil spring 500.

(35) Conversely, the third compression coil spring 500 may be stronger than the first compression coil spring (not illustrated). In this case, the gauge head 400 is being retracted in the normal state. Thus, after the head part 200 is inserted into a hole or a groove which is a measurement target object W, the spindle (not illustrated) (or the lower rod) is slowly pressed down, and the measurement spherical face 430 is brought into contact with the measurement target object W.

(36) Alternatively, the third compression coil spring 500 and the first compression coil spring (not illustrated) may have the substantially same strength.

(37) Alternatively, the first compression coil spring (not illustrated) may not be provided. As long as the third compression coil spring 500 is provided, the spindle (not illustrated), the lower rod 210, and the gauge head 400 function in response to the movements of each other.

Modified Example 2

(38) It is preferable that the cam contacting face 440 of the gauge head 400 and the cam contacting face 220 of the lower rod 210 are formed of materials having high hardness, such as ceramic. Not only the end faces but also the wholes of the gauge head 400 and the lower rod 210 may be formed of ceramic. When the third compression coil spring 500 is provided similarly to the above exemplary embodiments, the lower rod 210 and the gauge head 400 push each other interposing the cam 330 therebetween. Thus, the force applied to the cam contacting face 440 of the gauge head 400 and the cam contacting face 220 of the lower rod 210 becomes larger accordingly. Then, it is preferable that the cam contacting face 440 of the gauge head 400 and the cam contacting face 220 of the lower rod 210 are formed of materials having high hardness and excellent wear resistance. Furthermore, when the wholes of the lower rod 210 and the gauge head 400 are formed of materials having high hardness, such as ceramic, the wear of the whole sliding face is reduced, and the life of the bore gauge 100 is to be longer.

(39) Note that, the ceramic is only required to have high hardness and excellent wear resistance, and a component material itself is not limited.

(40) As an example, it is preferable that a sintered body having zirconia (ZrO2) or alumina (Al2O3) as the main component, and the hardness is HV 1200 or more.

(41) Note that, the present invention is not limited to the above exemplary embodiments, and a configuration appropriately modified without departing from the spirit belongs to the technical scope of the present invention.