JPH01292203A - Length measuring apparatus - Google Patents

Abstract

PURPOSE:To measure the length of a specimen accurately, by detecting positions of two edges as reference for measuring the length of the specimen using an optical type change detection means to measure the length thereof. CONSTITUTION:A laser displacement meter 2 projects a light beam outputted from a semiconductor laser device 8 to a specimen 1 and makes the light beam reflected therefrom incident into a position detector 11 to measure a change in distance to the specimen 1. On the other hand, a movement of a conveyor 3 is measured using a rotary encoder 16 to determine a movement of the specimen. An arithmetic processing means 18 computes the length of the specimen 1 from two edge positions 6 and 7 of the specimen 1 detected with a displacement meter 2 and a movement data from the rotary encoder 16. In this manner, there is no measuring errors of the edge positions otherwise caused by a change in quantity of light received by a difference in reflection factor of the specimen, thereby enabling accurate measurement of the length of the specimen.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a length measuring device, and particularly to a length measuring device suitable for measuring the length of a strip having an obliquely cut end.

(Prior Art) In the tire manufacturing process, the lengths of treads cut diagonally at both ends must be sequentially measured on the belt conveyor of an extruder. This tread is constantly being transported on a belt conveyor, and the tread length must be measured while it is being moved.Since both ends of the tread are cut diagonally, it is difficult to accurately detect the edges that serve as measurement standards. Because of this difficulty, improving the method for measuring tread length has become an important issue.

FIG. 7 is a diagram showing the configuration of a conventional tread length measuring method described in Japanese Patent Application Laid-Open No. 55-116208. In this method, a parallel light beam is irradiated onto the upper surface of the tread 31 on the conveyor 32, and a photoelectric switch 33 that is turned on only when the amount of reflected light exceeds a predetermined level is placed above the tread. As the tread moves in the direction of arrow a based on the change in thickness, the leading edge portion 34 and the trailing edge portion 35 are detected, and the amount of movement of the belt 32 during this period is detected by an encoder 36 and a counter 37.
The structure is such that the tread length is measured by measuring the tread length. However, in the reflective photoelectric switch 33 used in this method, the light emitted from the light emitting part is reflected by the object to be measured and received by the light receiving part, and the change in the amount of received light causes the switch to be in the 0N10FF state. Therefore, there is a drawback that the reflectance of the tread surface varies depending on the condition of the tread surface, the wobbling of the tread during transportation, etc., and an error occurs in the measurement of the edge position.

In addition, as another example of the method of measuring tread length,
There is one described in Japanese Patent No. 0-228906.

In this method, in order to detect the edge of the tread, a light source that emits a light beam containing light beams having different incident angles with respect to the plane that constitutes the edge is used instead of the conventionally used light source that emits a parallel light beam, and this light source The idea is to detect the edge position by placing an image sensor at the position where the tread edge is specularly reflected by the tread edge. However, even with this method,
Since the edge is configured to be detected depending on the amount of reflected light received from the light irradiated on the end face that makes up the edge,
If the cut surface of this edge is not smooth due to the sharpness of the cutting teeth of the tread, etc., there will be a difference in reflectance, making it difficult to accurately detect the position of the edge.

Further, a conventional tread length measuring device is also disclosed in Japanese Unexamined Patent Publication No. 58-173409. FIG. 8 is a diagram showing the arrangement of the measuring means at the lower end of the front edge of the tread 31 in this device. That is, in this device, the parallel light projector 38 and the line sensor camera 39 are arranged diagonally in the vertical direction with the conveyor 32 in between, and the angle α between the light beam from the projector 38 and the conveyor surface 32 is the same as the inclined surface of the front end of the tread 31. It is installed so that the angle β with respect to the conveyor surface 32 is smaller than that of the tread, and is configured to detect the edge by first cutting off the light beam with the front edge of the tread. Further, behind this front end edge measuring means, a projecting light source and a line sensor camera are installed in a direction perpendicular to the conveyor surface 32 to detect the rear end edge of the tread.

However, in this device, the lower end of the front edge cannot be accurately measured unless the optical axis angle α of the line sensor camera 39 that detects the front edge is made considerably small.
A disadvantage is that slight vertical vibrations of the leading edge can cause measurement errors. Furthermore, since two line sensor cameras are used, the device becomes expensive.

(Problems to be Solved by the Invention) As described above, in the conventional measurement method, an object to be measured is irradiated with light and an edge position is detected based on a change in the amount of received reflected light. Therefore, the edge position cannot be accurately detected due to changes in the amount of light received depending on the state of the reflecting surface, resulting in a drawback that measurement errors are likely to occur. Furthermore, in the conventional measuring device described above, a large measurement error occurs due to vertical vibration of the object to be measured, so when measuring the length of an object to be measured, such as a tire tread, being transported on a conveyor, etc. Not practical.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and to provide a stable length measuring device that is less susceptible to fluctuations in the reflectance of the surface of the object to be measured and vibrations that occur during the transportation of the object. be.

(Means for Solving the Problems) In order to achieve the above object, the length measuring device of the present invention measures the length by detecting two edges that serve as a reference for measuring the length of the object being conveyed. The length measuring device includes: an optical displacement detecting means for projecting a focused light beam onto an object to be measured, and measuring a change in distance to the object by measuring a change in the distance to the object by projecting a focused light beam onto the object to be measured; A measurement means for measuring the amount of movement of the object to be measured, a position of an edge of the object to be measured detected by processing the output signal of the optical displacement detection means, and a movement of the object to be measured detected by the measurement means. The apparatus is characterized by comprising arithmetic processing means for calculating the length of the object to be measured based on the quantity.

(Function) According to the length measuring device of the present invention described above, a condensed light beam is projected onto an object to be measured, and the reflected light beam is received to measure changes in the distance to the object to be measured. Since the length is measured by using an optical displacement detection means to detect the positions of two edges that serve as the reference for measuring the length of the object to be measured, the difference in reflectance of the object to be measured It is possible to accurately measure the length of the object without causing a measurement error in the measurement position of the edge position due to a change in the amount of received light.

(Embodiment) FIG. 1 is a diagram showing an embodiment of the length measuring device according to the present invention. The tire tread 1, which is the object to be measured, has both ends cut diagonally, and the tread length to be measured is defined as the distance between both end edges 6 and 7 on the top surface. This edge must be detected accurately. The front edge 6 of the tread 1 is configured as a line of intersection between the tread plane 5 and the front end face 4 which intersects at an obtuse angle to this plane 5. The tread 1 is conveyed in the direction of the arrow a by a conveyor belt 3, and above the conveyor belt there is a light projecting section consisting of a semiconductor laser 8 and a light projecting lens 9, and a light receiving section consisting of a light receiving lens 10 and a position detecting element 11. A laser-type displacement meter 2 is provided. In these light projecting and light receiving parts, a laser beam emitted from a semiconductor laser 8 driven by a drive circuit 12 is narrowed down by a projecting lens, diffusely reflected on the surface of the object to be measured, and a part of it is formed into a pinhole. 10a, the light is condensed by a light receiving lens 10b, and a spot image is formed on one point of the position detection element 11. In this case, in order to eliminate measurement errors in the edge position due to changes in the tread gauge, the surface to be measured by the laser beam (
The angle of incidence with respect to the conveyor belt surface or tread plane is 90°. As shown in FIG. 3, the position detection element 11 is composed of a PIN type semiconductor element, with a P layer acting as a resistance layer and electrodes provided on both sides thereof. A light receiving lens 10 is placed at one point between these electrodes.
When a focused light beam is incident, carriers generated by the incident light become a current source, and an electrical signal is output. When the measured object is displaced in the direction of the arrow in FIG. 1, that is, in the direction away from the displacement meter 2, the optical axis of the light beam incident on the light receiving lens shifts as shown by the broken line.
The image of the light spot focused on the position detection element 11 is shown by arrow C.
Move in the direction of. This movement increases the output signal obtained from one electrode and decreases the output signal obtained from the other electrode.

Therefore, since the difference between the two signals increases in one polarity, it is possible to measure a change in the position of the object to be measured. That is, two voltage signals converted into direct current (
A position signal that does not depend on the amount of reflected light can be obtained by calculating the position signal (A - B) and the light amount signal (A + B) from (A and B) and further dividing by (A7B)/(A + B). It will be. With this configuration, until the tread 1 moving in the direction of arrow a is conveyed below the laser displacement meter 2, the laser beam is first projected onto the surface of the conveyor belt 3, and the laser beam is projected onto the surface of the conveyor belt 3, The specularly reflected light is reflected and enters the position indicated by the broken line in FIG. 1, and as described above, an electric signal is outputted according to the distance between the conveyor surface and the light projecting section. Next, as the tread 1 moves, when the front end surface 4 of the tread l comes to a position where the laser beam is projected, the front end surface 4 is inclined with respect to the incident light beam of the laser beam, so As shown in Figure 2, most of the reflected light from the laser beam is reflected toward the front of the tread, and almost no light enters the light receiving section. The laser displacement meter 2 is designed so that its output voltage becomes, for example, zero when the amount of light incident on the light receiving section is extremely small, and therefore a laser beam is projected onto the front end surface 4 of the tread 1. During this period, the output of the laser displacement meter is zero. Furthermore, the tread 1 is transported,
When the laser beam reaches the position where it is projected onto the upper surface of the tread 1, it is reflected as shown by the solid line in FIG. 1, and an electrical signal is output according to the distance between the front surface of the tread and the light projecting section.

FIG. 4 is a graph showing the output voltage of the laser displacement meter 2 when a laser beam is projected onto the conveyor surface 3, the tread front end surface 4, and the tread upper surface 5, respectively. As described above, when the laser beam is projected onto the front end face 4, the output is zero. If the output voltage is set so that the output voltage is positive when it is projected onto the conveyor surface 3, and the output voltage is negative when it is projected onto the tread top surface 5, then if the threshold value is set to a slightly negative position, the output The position of the tread front edge 6 can be detected when the voltage changes from zero to negative.

When the tread 1 is further conveyed and the tread rear edge 7 passes below the light projecting part, the laser beam is projected onto the conveyor surface again, and at that point the output voltage changes to positive again, so the position of the rear edge 7 is detected. be done.

In the length measuring device according to the present invention, an A+nm/pulse rotary encoder 16 is further provided at one end of the conveyor. The number of pulses emitted from the rotary encoder and shaped by the pulse shaping circuit 16 is measured, and the number of pulses is expressed as A (mm).
Find the tread length l by multiplying by -0, that is, measure the number of pulses emitted by the rotary encoder while the laser beam is projecting on the upper surface 5 of the tread 1 (from the front edge 6 to the rear edge 7) And then e
Then, the tread length l is determined by β=Axe (mm).

FIG. 5 (A>(B) is a diagram showing the second embodiment of the present invention. In this embodiment, in addition to the device described in the first embodiment, a photoelectric switch 19 is installed behind the conveyor belt. Although not shown here, the laser displacement meter 2 is installed above the front part of the conveyor belt 3, and is connected to the photoelectric switch 19 and the laser displacement meter 18. The distance between the two is set longer than the standard length of the tread.The rotary encoder attached to the front of the conveyor generates a pulse of A (mm)/pulse as in the first embodiment. Here, the position of the trailing edge 7 of the tread 1 is detected by the photoelectric switch 19, and the tread 1 is measured from that moment until the position of the leading edge 6 of the tread is detected by the laser displacement meter 2. If the amount of movement is X and the number of pulses generated from the rotary encoder 16 during that time is e, then x = exA (mm).The distance between the photoelectric switch 19 and the displacement meter 2 is constant, and this When B(+n+n), the tread length l can be determined by the formula n=B (mm) - eXA (+nm).

With this configuration, it is possible to calculate the tread length immediately when the front edge 6 of the tread is detected by the displacement meter 2, and therefore, it is possible to calculate the tread length immediately after the front edge 6 of the tread is detected by the displacement meter 2. Therefore, it is possible to calculate the tread length immediately after the front edge 6 of the tread is detected by the displacement meter 2. This has the advantage that the selection, etc. can be done quickly.

FIGS. 6(A) and 6(B) are diagrams for explaining a third embodiment of the present invention. In this embodiment, the tread length is measured with the tread plane 5 facing downward as shown in FIG. The conveyor belt 3 that conveys the tread is divided into two so that the laser beam is projected onto the tread plane.In this case, the upper end 20 of the tread 1 is located at the laser spot position. Until the laser beam is inserted into the tread, the laser beam passes between the divided belts and is not reflected, so the output voltage of the laser displacement meter shows zero as shown in Figure 6 (B). Even if a laser beam is projected onto the end face 4 constituting the edge, the output of the laser displacement meter will still be zero because the reflective surface is inclined with respect to the laser beam as described in the explanation of Embodiment 1.Tread When the laser beam is projected onto the plane 5, the voltage output will be negative and the position of the leading edge 6 of the tread can be detected.

After passing the trailing edge 7 of the tread, the laser beam passes through the belt again, so the output becomes zero again and the trailing edge position can be detected. The method for calculating the tread length is the same as in Example 1 described above, but
Of course, a photoelectric switch may be provided at the rear of the conveyor and the calculation may be performed using the method described in the second embodiment.

In the case of this embodiment, since the laser beam is projected from below the tread plane, the distance from the displacement meter 2 to the tread plane 5 is always constant and is not affected by the tread gauge. This configuration has the advantage that the edge position measurement accuracy is higher than that of configuration 1. However, since the laser beam is projected upward, there is a high risk of the laser beam entering the eyes of the measurement worker, and safety measures are required to prevent this, and because a two-part belt conveyor is used. There are disadvantages such as higher costs.

(Effects of the present invention) As explained above, according to the present invention, the cut surface of a tire tread or the like can be cut without being affected by changes in the reflectance of the surface of the object to be measured or vibrations generated during transportation of the object to be measured. It is possible to detect the position of an oblique edge, and the length of the object to be measured can be accurately measured.

[Brief explanation of the drawing]

1 and 2 are diagrams showing the structure of the first embodiment of the present invention, FIG. 3 is a diagram showing the structure of the position detection element used in the present invention, and FIG. 4 is a diagram showing the structure of the position detection element used in the present invention. A graph showing the output voltage of the laser displacement meter, Fig. 5 (A> and (B)) a diagram showing the configuration of the second embodiment of the present invention, and Fig. 6 (A) and (B) A diagram showing the configuration of the third embodiment of the invention, and FIGS. 7 and 8 are diagrams for explaining the conventional tread length measuring method and device. 1. Tire tread 2. Laser displacement meter 3
... Conveyor surface 4 ... Edge i surface 5 ... Tread plane 6.7 ... Edge death ... Semiconductor laser 11 ... Position detection element 16 ... Rotary encoder 18 ... Arithmetic processing means Representative Patent Attorney Oki Sugimura Figure 3 Figure 4 LiyF Etsuji Aibata
Figure 5 (A) (B) Figure 7 t)

Claims (1)

[Claims] 1. In a length measuring device that measures the length of an object to be measured by detecting two edges that serve as a reference for measuring the length of an object to be measured, a focused light beam is projected onto the object to be measured, and then an optical displacement detection means for measuring a change in distance to an object to be measured by receiving a reflected light beam; a measurement means for measuring the amount of movement of the object to be measured; and an output signal of the optical displacement detection means. and calculation processing means for calculating the length of the object to be measured based on the detected position of the edge of the object to be measured and the amount of movement of the object to be measured detected by the measuring means. Characteristic length measuring device.