FI72820C - Non-destructive method and apparatus for inspecting tires. - Google Patents

Description

72820

Non-destructive test method and apparatus for inspecting tires

This invention relates generally to a test piece non-destructive method and apparatus for inspecting rubber rings. Such an inspection technique may also be combined with conventional grinding operations in accordance with the present invention.

This invention relates to some mechanical structural solutions for such equipment.

There has long been a strong need to provide a cost-effective, efficient, non-destructive test (NDI) test for rubber outer tires. There are obvious safety benefits to be gained from such technology if it is to be implemented efficiently and quickly. There are also potential economic benefits. For example, in tire retreading operations, a defective tire carcass can be discarded before more money and time is spent if the defective individual can be accurately, efficiently, and quickly detected.

In fact, the need for an improved NDI method and equipment for testing outer tires is so great that the U.S. Army Department, U.S. Pat. The Army Materials and Mechanics Research Center has published special symposia to cover this area alone in 1973, 1974, 1976, and 1978. Documents for the first three symposia have now been published and are available from U.S. Department. National Technical Information Service. Each includes a complete chapter on ultrasound testing of the tire, as well as other chapters dealing with different testing methods (e.g., holographic, infrared, X-ray).

There are also many prior patents relating generally to the use of ultrasonic waves for non-destructive testing of a test piece on pneumatic rubber rings. Examples of 2,72820 of these patents are U.S. Patents 2,345,679, 2,378,237, 3,336,794, 3,604,249, 3,815,407, 3,882,717 and 4,059,989.

There are also several prior patents relating to mechanical structures for attaching or otherwise physically treating pneumatic outer rings during various types of testing or manufacturing processes. Examples are U.S. Patents 2,695,520, 3,550,443, 3,948,094 and 4,023,407.

Although a very large number of different non-destructive ultrasonic tests have been performed on tires in the past in accordance with these prior patents, they all have shortcomings and have not been able to achieve widespread acceptance in commercial practice.

Prior art tire mounting mechanisms have generally included axially movable tire mounting rings for rapid mounting and inflation of the tire under test. In previous NDI machines, the ultrasonic transmitter has been placed inside a rotatable inflated ring, although these have only been fixed or manually adjustable mounting arrangements. Other NDI machines have included an articulated transmitter mounting arrangement with an unfolded, unfilled test tire. Until now, however, there has been no viable mechanical arrangement for the rapid placement of ultrasonic transducers along the wall of a inflated test ring, which at the same time would facilitate rapid tire attachment / removal operations and also protect transducers from physical inconvenience and damage.

It has now been discovered that these prior attempts to ultrasonically inspect outer tires without destroying a specimen can be greatly improved and made more commercially viable.

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According to the invention, there is provided a non-destructive tire testing apparatus having an acoustic ultrasonic transmitter and an acoustic ultrasonic receiver mounted opposite the inside and outside of a relatively movable inflated tire wall to obtain and display the condition of the portion of the tire wall thus tested, which apparatus is known to be opposite. adapted to grip tightly to the respective edges of the ring with the ring positioned therebetween and adjustable transmitter mounting means mechanically mounted between said retaining rings to pull said transmitter radially toward the center of the circular retaining rings when the ring is mounted between said retaining rings and removed therefrom to push away from the center of the circular mounting rings and towards the tread wall to the fixed active position for the period.

There is also provided a non-destructive tire testing method using an acoustic ultrasonic transmitter and an acoustic ultrasonic receiver mounted opposite the inside and outside of a relatively moving inflated tire wall to obtain and display the condition of a portion of the tire wall thus tested. engage tightly in opposite circular retaining rings with the ring interposed therebetween and that said transmitter is pulled radially toward the center of said circular retaining rings when the ring is mounted between and removed from said retaining rings, and that said transmitter is pushed radially away from the center of said circular retaining rings and tread wall to a stationary active station for the test period.

The use of an inflated tire in a preferred embodiment has been found to help maintain the actual surface of the rotating tire and thus avoid variations that could otherwise be caused by "throwing" the tire or some other axial movements of the tire walls during rotation. An air-filled tire is also useful in that it helps to at least partially stress the walls of the tire as they are during normal use and to open leaks through the walls of the tire so that they can be detected by ultrasonic detection as air passes through them. A pressure of approximately 35 kPa is required to maintain a stable air-filled tire structure.

However, it has been found that improved signal transmission and improved overall performance are obtained if the ring is inflated with air in the pressure range of approximately 100-125 kPa.

It is preferred, although not necessary, that the tread of the tire being inspected be first ground to obtain a uniform surface, which reduces erroneous defects that might otherwise be caused by tread patterning and / or uneven wear points or patterns in the tire tread. In this connection, it should be mentioned that the tire grinding apparatus and the present method can be used as a combined, comfortable and efficient overall operation. In any case, since such a grinding operation is inevitably included in the tire retreading operation, this combination is particularly attractive when the tire carcasses are inspected in preparation for retreading.

This is also described in the FI application. A preferred exemplary embodiment of the present invention also includes special mechanical properties for automatically moving the acoustic transducers to and from the operating position relative to the walls of the inflated ring. During tire attachment and detachment, the acoustic transmitters are retracted both radially and axially relative to the at least one tire retaining ring or flange for the purpose of both facilitating tire installation and detachment operations and protecting the acoustic transmitters from possible physical damage. During or after inflating the tire, these acoustic transmitters are moved radially outwardly inside the inflated tire to an operating position relative to the inner surface of the walls of the tire 5,72820. At the same time, the system of acoustic receivers is moved radially inwards towards the outer surfaces of the walls of the inflated ring to the desired operating position.

In a preferred exemplary embodiment, the relative axial movement of the acoustic transmitters relative to the tire mounting flange or ring is accomplished by spring loading the tire mounting ring so as to move axially away from the acoustic transmission, exposing them during inflating Such a spring load also helps the tire rims to fit correctly on the mounting flanges or rings during the tire mounting and inflation operations.

Reference is also made to the parent application FI patent application 801189 and to FI patent applications 85 3500 and 85 3502.

The foregoing and other objects and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings of a preferred exemplary embodiment thereof.

Figures 1 and 2 are perspective views of a combined NDI / grinder constructed in accordance with the present invention.

Figure 3 is a block diagram of the invention shown in Figures 1 and 2.

Figure 4 is a block diagram of ultrasonic NDI circuits that may be used in the NDI / grinder of Figures 1-3 or in a machine having only NDI capability.

Fig. 5 is a detailed sectional view of the fixed spindle of the embodiment of Figs. 1 and 2 and the transmitter mounting arrangement used in the embodiment of Figs. 1 and 2.

Figures 1 and 2 are thus two perspective views of a preferred exemplary embodiment in which a grinding and NDI machine is combined. As will be appreciated, the machine's NDI properties of the 72820 can be used if desired without the ability to grind.

The larger mechanical components of the machine are mounted on an open frame 100 with a fixed spindle 102 and an axially movable spindle 104 facing each other on the same horizontal axis 106.

Conventional circular ring mounting rings or flanges 108 and 110 are attached to the rotatable outer ends of the spindles 102 and 104 for mounting an air-filled ring 112 therebetween. The conventional pneumatically operated tire lifting mechanism 114 is preferably used to assist the operator in lifting and pivoting the tire between and out of the mounting rings 108 and 110 during tire fitting and removal.

The mounting ring 108 and thus the wheel ring 112 is driven by a two-horsepower DC motor 116 through a reduction gear 118. A tire surface speed of approximately 183 m per minute is preferred for grinding operations, while a much lower speed of approximately 12 m per minute is preferred for NDI operations. The mandrel 104 and thus the mounting ring 110 is pushed axially forward and retracted by the pneumatic cylinder 120. During the tire mounting operation, the mounting ring 110 is retracted by the cylinder 120 to allow the ring 112 to be lifted into place on the mounting ring 108. The mounting ring 110 is then pushed against the ring 112 filled with air to the desired pressure through the center of the mandrel 102.

A conventional rotating tire grinding grid 200 is mounted on a vertical base 202 located at the rear of the machine, as seen in Figure 2. The rasp 200 is guided by a conventional panel 204 to move transversely along the desired grinding path 206 and horizontally toward and away from the ring.

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Control is provided by a conventional control mechanism, including a joystick used to control the pneumatic cylinder 208, guide screws, and associated drive motors, and the like. The grinding grinder 200 is rotated by a separate motor mounted on a stand 202. The grinding mechanism itself is of the conventional type marketed, e.g., by Bandag Inc., e.g., Buffer Model No. 23A.

The system (row) 16 of acoustic ultrasonic receiving transducers 210 is located above and around the outer walls of the ring 112. The receivers 210 preferably include a conically formed collimator and / or focusing tube to help limit the receiving field of each individual transducer to a relatively small and unique area across the ring wall. The receivers 210 may conveniently be individually or in groups canned in polyurethane foam or the like to assist in mechanically securing the receivers to their desired positions, to help protect the receivers, and to help isolate the receivers from interfering external acoustic signals. The row of receivers 210 is radially set to the operating position by the air cylinder 212 with the hydraulic control cylinder connected, for the purpose of determining the radially advanced operating position for the receivers 210.

A block diagram for a combined tire grinding / NDI machine and associated electrical and pneumatic circuits is shown in Figure 3. The electric motor and pneumatic cylinder controllers 300 are quite conventional and are therefore not described in detail. The user inputs, marked to the left in Figure 3, are made directly or indirectly by the user with conventional electrical switches, relays, air valves and / or fluid control valves.

When the machine is in operation, the wheel ring is placed in the lifter 114 and lifted into position between the mounting rings 108 and 110. Preferably, the predetermined pointer point 8 72820 of the ring is aligned with the pointer point on the flange 108. The fastening apparatus is then coupled by causing the flange 110 to move into the ring 112 so as to pinch the ring flanges together in preparation for inflating the tire. The tire is then inflated to the desired set pressure value. As will be explained in more detail below, the flange 108 is spring loaded so that during attachment and inflation of the ring it is caused to move axially outward against the spring load (e.g., approximately 5 cm). This facilitates the ring filling process and at the same time exposes the ultrasonic transmitter located inside the ring from a relatively protected position so that it can then be pushed outwards into the operating position below the row of receivers 210. A locking switch activated by air pressure and / or physical movement of the flange 108 can be used to prevent the transmitter from protruding prematurely before it is exposed from its protected position.

In the grinding mode, there is no need to push the transmitter out. The drive motors of the grinding tarasp are activated and controlled in a conventional manner (e.g. with a joystick and conventional push-button controls) to grind the tread of the tire as desired. It is preferred, although not necessary, to grind the tire to a substantially flat tread before the NDI operation is performed. Such grinding is believed to prevent possible erroneous indication indications that could be caused by normal tread patterns and / or uneven tire surface wear.

When the user selects the NDI mode, the ultrasonic transmitter inside the inflated ring 112 is pushed into the operating position and the row of receivers 210 is lowered into the operating position by the pneumatic cylinders associated with the row.

The speed of the same 2-horsepower DC motor, which operates the tire at a surface speed of approximately 180 m per minute during grinding operations, can be reduced with conventional electrical circuits to operate the tire at a speed of approximately 12 surface meters per minute during the NDI mode. After the tire movement has reached a serious state, the user can activate 9,72820 radar input switches for the ultrasonic NDI circuits 302.

The tire walls are then ultrasonically inspected during one full revolution of the wheel to produce a display 304 that can be interpreted directly or indirectly by a human to indicate the condition of the tire (e.g., satisfactory for further grinding and retreading, suspicious or unsatisfactory). If the condition in question is indicated, the tire may be discarded or further refined and then retested.

The ultrasonic NDI circuits 302 are shown in more detail in Figure 4. The outputs 16 of the ultrasonic receiver 210 are amplified and multiplexed into eight signal processing channels AH by the circuits 402 shown in more detail in Figure 5. Each signal processing channel then provides AVS gain (automatic gain control). an analog-to-digital conversion signal processing circuit 404. The resulting digitized outputs are presented on a conventional eight-bit data bus 406 connected to a conventional microprocessor CPU (e.g., an 8080 type eight-bit processor) 408. The CPU 408 is also connected via a conventional address bus 4 data memory 412, programmable read only memory (PROM) 414, and system interface circuit 416, shown in detail in Figure 8. Display interface 418 (shown in detail in Figure 10) is directly connected to data memory banks 412. to provide a CRT-type oscilloscope display.

The system interface 416 provides the necessary gating and other control signals to the signal processing circuit 404 and also provides HIGH CHAN multiplexing signals to the preamplifier circuits 402 and the transmitter drive circuits and the multiplexing circuit 422 used to operate the plurality of ultrasonic transmitters. The operation of the entire system is synchronized to the rotational movements of the ring 112 by a rotating pulse generator 424 which is driven directly by the ring (e.g., geared to the reduction stage). The rotating pulse generator 10 72820 424 produces 1024 pulses per revolution in pin RPGX and 1 pulse revolution in pin RPGY.

Acoustic ultrasonic transmitting crystals 500 and 502 are housed within an air-filled ring 112 secured between flanges 108 and 110, which in turn are rotatably mounted on spindles 102 and 104. Electrical wires supplied by transmitters 500 and 502 are passed through a fixed spindle 102 to transmitter activation circuits. The filling air is likewise passed through the center of the spindle 102 as are the pneumatic lines and / or other control connections for pushing out and retracting the transmitters.

The exemplary ultrasonic transmitters 500 and 502 have a radiation field substantially comprising a sector of approximately 90 °. For this reason, they are mounted at a 90 ° angle to each other in a block 504, which may be formed of, for example, polyvinyl chloride plastic. It has been found that acceptable operation does not result if the transmitters are too close to or too far from the inner surfaces of the ring. In a preferred exemplary embodiment, the transmission crystals 500 and 502 are approximately 5 cm from the inner surfaces of the ring, although this optimal distance can be varied considerably (e.g., plus or minus approximately 2.5 cm).

The in-line receiving transducers 210 are arranged in an arc that generally corresponds to the shape of the outer side of the ring wall.

Here, too, it has been found that acceptable operation does not result if the receivers are too close to or too far from the outer walls of the ring. Preferably, the receivers are no closer than approximately 2.5 cm from the outer surface of the ring, but are preferably 14-22 cm from the opposite transmitter crystal. The receiving transducers 210 each preferably use a conically shaped collimator and / or focusing tube »as detailed in Figure 12. These tubes are preferably machined from polyvinyl chloride plastic and also help

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11 728 2 0 to match the impedance of the transducer crystal surface used to the acoustic impedance of the ambient air.

A moderately high ultrasonic frequency is used to help avoid interference from erroneous surrounding acoustic signals and to achieve improved resolution by using shorter wavelength acoustic signals while avoiding ultra-high frequency acoustic signals and associated problems. Frequencies above 40 kHz are recommended, 75 kHz is currently the preferred preferred frequency.

In more detail, the fixed mandrel 102 and the associated transmitter mounting arrangement are shown in section in Figure 5. The transmission crystals 500 and 502 are oriented at a 90 ° angle to each other from the surface of the PVC mounting block 1500. The block 1500 is in turn attached to a retractable rod 1502 connected to the piston of the pneumatic cylinder 1504.

As shown in Fig. 5, the pneumatic cylinder 1504 has pulled the transmission crystals 500 and 502 back to a protected area bounded by an annular plate 1506 attached to the tire mounting flange 108. The tire mounting flange 108 is rotatably attached to a fixed mandrel 102 by a ball bearing assembly 1508 and 15. the coupling is kept airtight by a rotating sealing composition 1512. The center of the mandrel 102 is hollow to pass through the electrical conductors of the pneumatic control line 1514 and the transmitter.

The rotating flange 108 and the composition associated therewith are loaded by a spring 1517 toward its axially extended position, as shown in Figure 5. However, the flange 108 can be axially displaced against the spring force to the position shown in phantom in the figure. In a preferred exemplary embodiment, such movement begins when the flange 108 is subjected to a horizontal force of approximately 680 kg (14 kPa). A sliding joint 12 72820 allowing this movement is also kept airtight by the O-ring 1516. In the exemplary embodiment, no axial movement greater than approximately 5 cm is allowed until the spring force is sufficient to resist further movement even when the ring is inflated to approximately 100-125 kPa.

When the flange 108 is moved to the left, as shown in phantom in Figure 5, against the force of the spring 1517, the exposed transmitters 500 and 512 and the pneumatic cylinder 1504 can be activated to push the transmitter unit to the position shown in phantom in Figure 5 for a functional measurement period. Suitable locking switches activated by the pressure inside the inflated ring and / or the physical axial position of the flange 108 can be used to ensure that the pneumatic cylinder is not inadvertently activated to push the transmitters outward and to be damaged while the transmitters 500 and 502 are still enclosed by the flange 1506 and protected.

Claims (13)

Apparatus for non-destructive testing of tires, comprising an ultrasonic acoustic transmitter (500, 502) and an ultrasonic acoustic receiver (.210), which are mounted opposite each other on the inside and outside of a relative movable wall (112), respectively. an inflated tire for generating and imaging (520) a measurement value with respect to the condition of the thus-tested portion of the tire wall, characterized by centrally arranged circular rings (108, 110), which are arranged to sealingly abut the corresponding edges of the tire, when placed between them, and adjustable mounting means (1504, 1502, 1500) of the transmitter, which are mechanically mounted between said rings for pulling the transmitter radially in the direction of the center of the circular rings during mounting and disassembly of the wheel between respective rings mentioned and for advancing the transmitter radially away from the center of the circular rings and in the direction of the tire tread to a phase t active mode during a test cycle. f 2) Apparatus according to claim 1, characterized by tire inflating means (102) for inflating the tire after being retained by said rings, at least one ultrasonic acoustic receiver (210) arranged for operation outside the tire, at least one ultrasonic acoustic transmitter (500, 502) arranged for operation within the tire, said receiver and transmitter being fixed in relation to each other and in relation to the outside frame of the apparatus during a test cycle, characterized in by a plurality of ultrasonic acoustic receivers (210), arranged in a grouping substantially consistent with a cross-sectional contour of the exterior of the tire, and adjustable mounting means (212) for the receiver, which are arranged for retraction of the receivers radially away from the circular rings during tire assembly and disassembly. between the respective rings and for projecting the recipients radially in the direction of the circular the below rings are. mäteykei. 18 72820 41 Test apparatus according to any one of claims 1-3, characterized in that the transmitter is located approximately 5.1 + 2.5 cm from the inside of the deck wall and that the receiver is arranged approximately 14.0 - 21.6 cm. from the transmitter, during a measurement cycle. Test apparatus according to any of claims 2-4, characterized in that said inflating means (102) are arranged for opening the tire to approximately 1, 034 - 1, 241 bar. Apparatus according to any one of claims 1-5, characterized by means (1516) for enabling relative movement of the transmitters with respect to at least one of the rings in a direction which is substantially perpendicular to them. wherein said adjustable mounting means for the transmitter, when in its radially retracted position, is also axially displaced relative to one of said rings to thereby facilitate the mounting operation of the tire without damaging the transmitter. Apparatus according to claim 6, characterized. of tire inflation means for inflating the tire to a pressure of at least 0.345 bar after being engaged with said rings. Apparatus according to any one of claims 1-7, characterized by means (212) for radially withdrawing the receiver from said circular rings during mounting and disassembly of the tire between the respective rings and for advancing the receiver radially in the direction of said circular rings during a measurement cycle. A method of non-destructive testing of a tire using an ultrasonic acoustic transmitter (500, 502) and an ultrasonic acoustic receiver (210) mounted on each other on the inside and outside of a relative moving wall (112). ) to an inflated tire in and for the production and calibration (420) of a measured value with respect to the well-tested portion of the tire wall condition li