THE FIELD OF THE INVENTION

The present invention relates to a simple large-size vernier caliper for measurement, in particular to a long measuring jaw, which is applicable to a low-accuracy internal and external diameter measurement and belongs to an improved measurement tool. BACKGROUND ART

Currently, large-size vernier calipers with a measurement range of 0.5-2m are mostly applied in the machining industry. The vernier caliper has characteristics as below: generally, the vernier caliper can only measure lengths due to the limitation of the height of the measuring jaw; the vernier caliper is expensive and is more expensive in the case of customization; and the vernier caliper is cumbersome due to the use of all-metal stainless steel or measuring instrument steel. In the case of the accuracy requirement between a common vernier caliper and a straight steel ruler, a measuring instrument is required for measuring, for instance, diameters of various types of upright posts, round tables and so on.

SUMMARY

The objective of the present invention is to fill in the gaps in the prior art and provide a simple vernier caliper, which may be applied in a situation of large-size rough measurement and have advantages of easily obtained materials, good processing performance and portable use.

In order to achieve the objective, the vernier caliper according to an aspect of the present invention adopts a directly purchased straight steel ruler as a main ruler and a movable measuring jaw sliding on the main ruler as an auxiliary ruler; a fixed measuring jaw is provided with a recess into which a front portion of a zero count of the straight steel ruler is embedded; the straight steel ruler is punched; a rivet or screw connection is adopted; and a fixing position is at a place where a measuring surface of the fixed measuring jaw is aligned with a scale mark of 100mm - (1 to 5)mm on the front portion of the straight steel ruler. Moreover, round steels are embedded into the fixed measuring jaw and the movable measuring jaw and taken as internal measuring heads, and slidable and extendible steel bars are embedded into width and external diameter measuring surfaces. Numerical readings of the width and the external diameter are obtained in a vernier scale mark at a lower left notch of the movable measuring jaw, and a numerical reading of the internal diameter is obtained in a vernier scale mark at an upper right notch of the movable measuring jaw.

The fixed measuring jaw and the movable measuring jaw of the vernier caliper are formed by machining an engineering plastic sheet; recesses are formed on measuring surfaces of the fixed measuring jaw and the movable measuring jaw; and square steel bars are mounted into the recesses and parallel to each other. The square steel bars are fixed by being attracting with two or more magnetic steels for the convenience of sliding, and the magnetic steels run through the measuring jaws and are tightly fitted with the bottoms of the wear-resistant steel bar recesses. One or more magnetic steel is fixed on the movable measuring jaw to attract the straight steel ruler; the movable measuring jaw slides on the straight steel ruler with the recess thereof; the recess of the movable measuring jaw has a depth equal to a thickness of the straight steel ruler, and a width equal to a width of the straight steel ruler; and the bottom of the recess is parallel to the magnetic steel.

By utilization of the characteristic that scales are formed at both the upper end and the lower end of the straight steel ruler, reverse bevels at two notches of the movable measuring jaw cover partial scales of the straight steel ruler; vernier scale marks at the two notches respectively correspond to upper scales and lower scales of the straight steel ruler; the scale value per division is determined by measurement accuracy; a zero line at the lower left notch is 1 to 5 mm away from an outer edge; the integer plus decimal reading method of the measured value is the same as the conventional reading method; the measured width and the measured external diameter are obtained by reducing 100mm from the original reading, and the internal diameter is read by also reducing 100mm from a scale at the upper right notch, namely the distance between zero scales at the two notches is 100mm. As the fixed measuring jaw is fixed on the straight steel ruler and covers scale marks, by utilization of the characteristic of 10cm integer multiple marking of the straight steel ruler, the laser marking method may also be used to modify first number of integer multiple marks on the straight steel ruler; only two-digit integer multiples are directed; and the modified quantity is not much. The present invention has advantages of low cost, capability of being self-manufactured with one miller, capability of slideably elongating the measuring heads in the case of measuring large-diameter cylinders, light weight and long durability. BRIEF DESCRIPTION OF THE DRAWINGS

Detailed description will be given below to the present invention with references to the accompanying drawings and the embodiments.

FIG. 1 is a perspective view of an embodiment of the present invention.

FIG. 2 is a plan view of a fixed measuring position of the large-size vernier caliper as shown in FIG. 1.

FIG. 3 is a partial enlarged perspective view of numerical readings at the measuring position as shown in FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

In the embodiment as shown in FIG. 1 , the dimension of the purchased straight steel ruler 6 is 2000x40x2mm, and the straight steel ruler is made of a ferritic stainless steel material which can be attracted by a magnet. When the length is more than 1 m, a material , deformation should be considered. A ruler body is drilled and riveted with a channel steel 7 formed by bending a sheet or a 40x40 finished aluminum profile. A U-shaped recess is formed at the rear of the fixed measuring jaw 3; a round reel 4 is directly pressed on the straight steel ruler 6; the fixed measuring jaw 3 and the channel steel 7 are formed together by riveting with a rivet 5; and a round steel 4 is also embedded into the movable measuring jaw 9 and taken as an internal diameter measuring head. Moreover, recesses are formed on measuring surfaces of the fixed measuring jaw 3 and the movable measuring jaw 9; the bottom of the recess and a slotted hole are communicated with each other; a square magnet 2 is tightly fitted in the slotted hole; a slideable square steel bar 1 made of high-speed steel 5x5x200mm is embedded into the recess; and a chamfer angle is formed on the top of the square steel bar 1 ; and a measured position is grinded into an inclined plane. The fixed measuring jaw and the movable measuring jaw are manufactured by milling 12mm polyformaldehyde (POM) sheets, including the process of marking vernier lines. The round steel 4, i.e., the internal measuring head, is made of Φ6 hard-drawn wrought stainless steel wire. FIG. 2 is a plan view of an operating measuring position of the vernier caliper. The double dot dash line of the measuring head is an extendible maximum size, for ensuring that the square steel bars 1 are attracted by two magnetic steels 2; and the distance from the measuring head as illustrated to the end surface of the straight steel ruler 6 is the theoretic maximum radius for the measurement of the external diameter. The measured width and the measured external diameter are 300, and the internal diameter is 400. When the movable measuring jaw 9 is attached to the fixed measuring jaw 3, a zero scale mark on the vernier is aligned with a 10cm scale mark on the straight steel ruler 6, and the outer size of the two round steels 4 is 100. In the embodiment, one round magnetic steel 8 is tightly fitted on the movable measuring jaw 9 to attract the straight steel ruler 6 and make it slide in the recess.

The enlarged perspective view in FIG. 3 illustrates the relation between scale values of the straight steel ruler 6; a digital scale portion covered by the movable measuring jaw 9 is indicated by dotted lines; and an edge distance between a zero scale mark at the lower left notch and the movable measuring jaw 9, namely the distance between the measuring surface of the fixed measuring jaw 3 and a 10cm scale mark of the straight steel ruler 6, is 1.5mm. The reading of the zero scale mark at the lower left notch aligned with a 40cm scale mark of the straight steel ruler 6 is 300mm, and the reading of the zero scale mark on the upper right notch aligned with a 50cm scale mark of the straight steel ruler 6 is 400mm, that is, reducing 100mm from the actual reading, which can be conveniently remembered. The accuracy of the vernier caliper in the embodiment is 0.1 mm. As illustrated in FIG. 3, scales on the vernier of the movable measuring jaw 9 are obtained by dividing scales of the straight steel ruler 6 with the length of 19mm into 10 equal parts, namely 1.9mm per division, so that the difference of every two divisions between the main ruler and the auxiliary ruler is 2-1.9 = 0.1 mm. The n ^th scale mark on the vernier is aligned with a scale mark on the main ruler; the decimal value of the measured dimension is nxO.lmm; and the sum of the integer and the decimal is the measured value. The foregoing is only one preferred embodiment of the present invention. It should be noted that various deformations and improvements can be made by those skilled in the art without departing from the principle of the present invention and should also fall within the protection scope of the present invention.