JPH0711401B2 - Gauge - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

This application corresponds to the partial continuation application of pending U.S. patent application serial number 480515 filed March 30, 1983. Video recording devices are used in a wide range of commercial and entertainment purposes. An important element of such recording devices is one or more video heads used for recording or reproducing information on a suitable recording medium.

[Prior art]

The head itself is normally 0.0075 cm from the surrounding drum surface
It is a subtle mechanism that protrudes by less than (0.003 inch).
While using the storage device, the head gradually wears,
Eventually you will have to replace the head. By measuring the amount of protrusion of the head from the surrounding surface, the remaining life of the head can be estimated, and the optimum time to replace the head can be reduced without waiting for complete wear and failure. It is possible to predict.

[Problems to be Solved by the Invention]

Currently, manufacturers of some brands and types of video recording devices provide unique means of measuring the protrusion and wear of this head. In each of these cases, the manufacturer knows precisely where the head is positioned relative to the frame of the video recorder and has a unique design that provides a series of precision mounting holes for the protruding gauge of the head. Since the relative position of the heads is precisely known, the head projection gauge is simple to mount on a unique mounting stand and requires only a single point indicator. Unfortunately, for servicemen who care for more than one brand of video recording equipment, each manufacturer's head-protrusion gauge is unique and physically incompatible, so other video It cannot be used universally to measure head fatigue in recorders. Attempting to use a gauge that does not fit this way results in inaccurate measurements that over- or under-estimate head fatigue, as well as destroy subtle heads altogether, making them expensive, and in some cases May need replacement which was not needed. In particular, the heads measured as described above are typically a few thousandths of an inch wide (ie, less than 0.1 mm), very fragile like glass pieces, and small in size, and the probe (contact) Aligning the tip of the needle with this small head is much more difficult than, for example, threading a needle. Moreover, according to the conventional measurement method, since the protrusion amount of the video head is directly measured by the probe, a high pressure per unit area is applied to the surface of the head which is fragile and fragile by the tip of the measurement probe. In the area where a single probe tip measures the base circle, the drum surface is generally rounded, and direct measurement with the probe tip will change due to curvature. Therefore, the relative protrusion amount of the head based on the portion where the tape is wound is not shown, and the measurement is inaccurate. The present invention makes it possible to bring the target pad into contact with the head very easily by using a target pad that is at least as large as the head or preferably larger than the head, and use the surface of the drum as an absolute reference position. It provides a gauge that can make precise measurements without damaging the tip of the fragile head, and a unique head protrusion gauge that can be used with virtually any video recording device. With this one universal gauge, it is possible to measure the head fatigue of any brand of video recorder with very high accuracy, and in most cases not the individual universal provided by some manufacturers. It can measure at least as accurately as a gauge. The availability of such a universal gauge is due to the novel dual pivot design in which the position of the gauge does not have to be known precisely in order to make precise measurements.

[Means for Solving the Problems]

The present invention is a gauge for measuring the degree of protrusion of a head from a drum surface of a video recording device, which is a dial gauge 20.
A measuring stem 70 attached to the dial gauge 20 via a first pivot 80, a shoe 231 firmly attached to the measuring stem 70, and a second pivot 230 located in the shoe 231. A level block 221 attached to the level block 221 for free pivoting back and forth about the second pivot 230, the level block 221 engaging the drum surface. Has a side opposite to the pivot 230 arranged to allow the reference position of the dial gauge for the second pivot 230 to be determined.
1 has a target pad 301 at a first fixed distance from the second pivot 230 on the one side, and the level block 221 is targeted by a recess 280 in the level block 221. A level pad 311 separated from the pad 301 on the one side, wherein the level pad 311 is on the level block 221 opposite the target pad 301 with respect to the second pivot 230; , The target pad 301 and level pad 311 are coplanar, and thus level pad 311
Is in contact with the drum and the target pad 301 is in head contact, the dial gauge adjusts the degree of protrusion of the head from the drum based on the displacement of the second pivot 230 from the reference position due to the rotation of the level block. It is designed to be measured.

[Action]

According to the present invention, the drum is first rotated so that the head does not come in the middle, and a level block mounted on a free pivot with a limited range of movement is brought into close contact with the surface of the drum, and the basic Allows the reading of a dial gauge (displacement indicator) to be read in order to subtract the scale and rotate the drum to bring the head into the target area around the center of rotation of the free axis of the level block. Bring it into the means to allow the level block to rotate on this free pivot and press it against the measuring stem, which pivots around a separate pivot and the dial gauge needle causes the protrusion of the head. It suffices to rotate by an amount proportional to. Although the video head is much stronger in the radial direction (ie toward the center of the video drum) than perpendicular to the drum surface, the head is still quite brittle. Therefore, the force exerted on the head with the gauge of the present invention is only in a relatively strong radial direction, and is exerted by the restoring force of the dial gauge spring, thus minimizing the risk of damaging the head. In order to ensure that the user does not significantly shift the gauge and thus the reading is inaccurate, the face of the measuring block that engages the head is provided with a recess adjacent the target area means. Therefore, when measuring the protrusion of the head,
The contact of the head with the target area means is clearly visible.

【Example】

As a first embodiment of the present invention, FIG. 1 shows a general view of a universal gauge for measuring the protrusion of the head.
Universal mounting block so that the gauge can be locked in a stable position on any convenient surface of the video recorder
Provide 10. The dial gauge 20 is connected to the universal mounting block by a series of axles 30 and axle locks 40, which locks allow the dial gauge 20 to be stably positioned in any desired position. A measurement probe (contact) 50 is coupled to the dial gauge by a gauge body 60. In the main body 60, a stem 71 which can freely rotate on a stem pivot 80 is accommodated. When the measuring probe 50 moves in the X direction, the stem
71 rotates about the stem pivot 80. This movement rotates around dial gauge 20. This movement is dial
Feeling arm that is part of gauge 20 (not shown)
The dial gauge 20 which is transmitted to the stem, which indicates movement in the X direction as the needle 90 rotates, is a conventional gauge, such as a load gauge, having a fine spring (not shown) that generates a restoring force on the stem 71. It may be a gauge available from Brown and Sharp Company in Island State. As will be explained later, since this restoring force is applied to the video head itself via the measuring probe 50, it is important to keep this restoring force as low as possible, typically around 15 grams. As shown in FIG. 2, the measuring probe 50 is attached to the measuring stem 70 by a shoe 2 which is firmly attached by a fixing screw 210.
Composed of 00. The measuring stem 70 is typically a separate member, but acts as an extension of the stem 71 and is attached to its bottom. A level block 220 is housed in the shoe 200 and is free to pivot about a second pivot 230 within a limited range of travel d. The pivot axis of the second pivot 230 is parallel to the pivot axis of the stem pivot 80. A perspective view of shoe 200 is shown in FIG. Shoe 200
Has two holes 240,250 for holding the pivot 230. The two holes 240 and 250 are the third holes 2 through which the measuring stem 70 passes.
It is chosen to have a centerline perpendicular to 60. A pivot pin 235 is press fit into holes 240 and 250 so that level block 220 is free to pivot about pivot pin 235. The level block 220 itself has two recesses 28 in the flat front surface 270.
It is composed by cutting 0,290. Therefore, the recesses 280,290
Makes three pads on a flat front 270. That is, the target pad 300 and the two level pads 310, 320, all of which are arranged symmetrically with respect to the axis of rotation of the second pivot 230. FIG. 4 illustrates the method used to measure the protrusion of the head. First, the universal mounting block 10 is used to attach to a stable member of the gauge video recorder. Next, as a rough adjustment, operate the shaft 30 and the shaft lock 40 to move the measurement probe 50 from the position of the head 330 to 0.3175 cm (1
Measurement probe by bringing within 8 inches)
Position 20. Next, fine adjustment is performed to move the measurement probe 50 from the position of the head 330 to about 0.0508 cm to 0.0762 cm.
Position within (about 20 to 30/1000 inches). The target pad 300 is then moved up and down as necessary to align it with the vertical position of head 330 (ie, in the Y direction). Then, as shown in FIG. 5, the drum 340 is rotated so that the measuring probe 50 can be applied to the headless portion of the drum 340. While the measuring probe 50 is in this position, all of the three pads 300, 310, 320 are in contact with the drum 340, the measuring stem 70 moves in the X direction only by the portion indicated by the needle 90, and the drum 340 does not project the head. Set the reference position to represent and dial gauge
Set preload force for 20 springs. The drum is then manually rotated until the tip of the head 330 contacts the target pad 300 and maximum reading is obtained when the center of the head is aligned with the pad. Note that the head 330 is relatively robust in the X direction (ie, the radial direction of the drum 340), but is still very delicate. For this reason, it is important to minimize the amount of force applied to the head 330. In the design of this embodiment, only the restoring force of dial gauge 20 is applied to head 330. Head 330 once the measuring probe 50 is protruding
Upon contact with the level block, the level block may pivot about the second pivot 230 until one of the two level pads 310, 320 is stationary on the surface of the drum 340, as shown in FIG. However, this rotation has no great influence on the measurement of the protrusion of the head at the center of the measurement probe 50. At the same time, the entire measuring probe 50 is headed from the surface of the drum 340.
It moves in the X direction by a protrusion distance P of 30. Therefore, the measurement stem 70 rotates about the stem pivot 80 by the angle A, transmits the distance P to the dial gauge 20, and is read out in the unit of micrometer or 0.0254 cm (10/1000 inch). To do so. At the maximum reading, the needle 90 actually corresponds to the distance P plus the level display, and it is easy to convert this to the protrusion distance P by subtracting the level display. Measuring the displacement of the video head involves a very small horizontal displacement of the head 330. This is converted into rotation of the stem 70 and read out by the dial gauge 20. Especially the 4th
As shown, in response to the target pad 300 displacing a distance P, the measuring stem 70 pivots by an angle A. However, if Y is the vertical distance from the stem pivot 80 to the contact point between the head 330 and the target pad 300, and tanA = P / Y, an error in Y causes a corresponding read error. To minimize this source of error, the width of the target pad 300 is limited to a "target area" 360 of about 0.125 cm (0.05 inch). This is a leveling pad for the target pad 300 with recesses 280,290.
Achieved by separating from 310,320. The recesses 280, 290 that make up the target pad 300 help the user to see when the target area 360 is properly aligned with the head 330. In addition, the recesses 280, 290 should be selected to be deeper than the maximum protrusion P of the new head 330 (eg, about 0.05 cm (0.02 inch)) to provide the user with a positive indication of misalignment, ie, , The dial gauge 20 will always show P = 0 when the video head is not in contact with the target area 360, giving the user a clear "wrong" result, indicating that a misalignment has occurred. It is preferable to select FIG. 6 shows a second embodiment of the present invention.
The claims of this application are in accordance with this second embodiment. In this case, the measurement probe
It has a level block 221 that has only two pads, a pad 301 and a level pad 311. This second embodiment also uses the same universal mounting block used in the first embodiment. In this second embodiment, the upper drum 342
And a lower drum 341, the upper drum being slightly larger than the lower drum, and is particularly suitable for video recording devices. However, this design also works with video recording devices where the drum dimensions are the same. In such a drum, it is typical to provide a pair of heads such as heads 331 and 332 that are vertically overlapped with each other. The measurement when the second embodiment is used is performed in the same manner as the first embodiment. That is, the drum 34
Touch 2 to determine the reference position, then turn the drum and hit the target pad 301 to one head so that the corner of the level pad 311 contacts the drum. Level block 221 between level pad 311 and target pad 301
The concave portion 280 provided in the head 331 makes a gap with respect to the head 332 while measuring the protrusion degree of the head 331. Lines 302 are scored on the target pad to aid in proper alignment with the head. FIG. 7 shows diagrammatically the measuring method which shows the relationship of the various dimensions involved. In this figure, L represents the length of the horizontal arm of the level block relative to the axis 230, B represents the vertical dimension from the axis 230 to the horizontal arm corresponding to the level pad 311, and C represents the horizontal dimension from the axis 230 to the target pad 301. It represents the vertical dimension up to the arm. FIG. 7 shows the state of the device when measuring the degree of protrusion of the head 332. It is shown that the head projects a distance P. This corresponds to the level block rotating by an angle θ and displacing a distance X. At this time, the total distance between the drum surface and the pivot 230 is (X + L). At the same time, this should equal the distance P plus some incremental distance Q. Distance Q corresponds to the distance of pivot 230 from the end of head 332. That is, X + L = P + Q (1) It can be proved from the simple triangle method that: Q = (C ² + L ² ) ^1/2 + cos (a + θ) Q = (C ² + L ² ) ^1/2 (cos a cos θ−sin a sin θ) Substituting this into equation (1) Therefore, the equation (2) is simplified as the following equation. This is a quadratic equation of P, and the distance X, L,
It can be easily solved with C and B. Here, in the particular case of interest, P is typically much smaller than (C + B) or L. As a result, the formula (3) becomes very simple as follows. P≈X (1 + C / B) (4) This is irrelevant to L. From the above description of the first embodiment, the displacement X corresponds to the rotation of the stem 70 by the angle A, and thus Y is the length of the stem 70 from the pivot point 80 to the point 231 (see FIG. 7). , And for a small angle A, X≈Y tamA. At this time, equation (4) can be rewritten as follows. P≈Y (1 + C / B) tanA (5) From the equation (5), once the angle A is determined, the protrusion degree of the head is a simple function of the length Y, lengths B and C of step 70. Yes, it is as easy as calibrating the dial gauge 20 so that the protrusion of the head can be read directly. Specific length B,
C and Y can be selected from a wide range depending on what aspect of the device is to be optimized. However, there are some important points to keep in mind when making this choice. First, the proper distance C should be chosen so that the spring return force of the dial gauge is sufficient to keep both the target and level pads in engagement with the drum. From a mechanical point of view, the force exerted by the head on the target pad exerts a unidirectional torque on the level block, which is counterbalanced by the torque produced by the force of the drum acting on the level pad.
Therefore, the distances B and C determine the magnitude of the force on each pad. Second, the larger the ratio of C to B, the lower the sensitivity of the dial gauge, and thus the C to B such that sufficient sensitivity is guaranteed to obtain an accurate reading of the dial gauge. You should choose an appropriate ratio of. Third, it is necessary to reduce the overall spring force to reduce the risk of damaging the fragile video head. When using a standard 1/10 reading (ie (1/10000 inch) dial gauge, the optimum shape is Y = 1.016 cm (0.4 inch), B = 0.8255 cm
(0.325 inch) and C = 0.3556 cm (0.14 inch). In the second embodiment, in order to measure the eccentricity of the drum, the displacement of the stem 70 is not determined by the equation (5) but is simply determined by X = Y tanA. Please note that the scale is set.

【The invention's effect】

As described above, in the gauge according to the present invention, by using the target pad, the target pad can be brought into contact with the head very easily, and the surface of the drum can be used as an absolute reference position. Precise measurement can be performed without damaging the tip of the fragile head. Also, with the above configuration, the force applied to the head is only in a relatively strong radial direction, and is exerted by the return force of the dial gauge spring, thus minimizing the risk of damaging the head. You can In addition, the face of the measuring block which engages the head is provided with a recess adjacent the target area means, in order to ensure that the user does not significantly shift the gauge and thus the reading is inaccurate. Therefore, when measuring the degree of protrusion of the head, it is possible to make an accurate measurement because it is clearly visible that the head is in contact with the target area means. Furthermore, it can be generally used to measure head fatigue of other video recording devices that are not physically compatible.

[Brief description of drawings]

FIG. 1 is a general view of a preferred embodiment of the universal head protrusion gauge of the present invention, FIG. 2 is a detailed view of a measuring probe used in FIG. 1, and FIG. 3 is a shoe shown in FIG. FIG. 4 is a side view showing a state in which the measuring probe of FIG. 2 is used, FIG. 5 is a plan view of a drum of a typical video recording device, and FIG. 6 is a second view of the present invention. FIG. 7 shows an embodiment, and FIG. 7 is a schematic view of a second embodiment illustrating various lengths of this apparatus.

[Explanation of symbols]

 20 …… Dial gauge 71 …… Measuring stem 80 …… Stem Axis 200 …… Main body 220 …… Level block 230 …… Axis

Claims (1)

[Claims] 1. A gauge for measuring the degree of protrusion of a head from the surface of a drum of a video recording apparatus, comprising: a dial gauge 20; and a measuring stem 70 mounted on the dial gauge 20 via a first pivot 80. , A shoe 231 fixedly attached to the measuring stem 70, and a level block 221 attached to a second pivot 230 located in the shoe 231, the level block 221 comprising the second pivot 230. Mounted freely pivotable back and forth around, the level block 221 has one side opposite the pivot 230 arranged to engage the drum surface, whereby A dial gauge reference position for the second pivot 230 is determined, and the level block 221 is further targeted to a position a first fixed distance from the second pivot 230 on the one side. A pad 301, and the level block 221 also has a level pad 311 separated from the target pad 301 by a recess 280 in the level block 221 on the one side, wherein the level pad 311 Is located on the level block 221 on the opposite side of the target pad 301 with respect to the second pivot 230, and the target pad 301 and the level pad 311 are in the same plane, so that the level pad 311 is When in contact with the drum and head contact with the target pad 301, the dial gauge measures the protrusion of the head from the drum based on the displacement of the second pivot 230 from the reference position due to the rotation of the level block. A gauge characterized by doing so.