Failure analysis caused by loose screws of different projectors

Failure analysis caused by loose screws of different projectors

Date:2022-05-17
When the projector is working, the screw is one of its important parts, and all screws are also needed for fixing. There are many kinds of screws on the projector. If the screw is loose during the use of the projector, what kind of failures will it cause?
1. Fixing screw of the feeding gear
It is used to fix the film supply gear on the film supply sprocket shaft, and pull the film at a certain linear speed, so that the film gate completes the projection.
If it is slightly loose, the end of the screw will not be separated from the platform on the axle, which will cause the axial clearance of the feeding gear to be too large. The working corners of holes 1, 3 or 2 and 4 are scratched, which also increases the instability of the film.
If it is relatively loose, the end of the screw may be separated from the platform on the axle, causing the film supply gear to lose rotation, or even unable to pull the film at all, becoming a passive rotation like a pulley, so that the upper buffer bend disappears quickly, forming an intermittent gear directly from the The film supply box forcibly pulls the film, which destroys the normal operation of the film. At this time, the screen image is severely shaken and cannot be viewed, and there is serious mechanical noise, which can easily cause damage to the film.
2. Receiving gear fixing screw
It is used to fix the take-up gear on the sprocket shaft, so as to drive the film to run regularly when the take-up gear rotates.
If it is slightly loose, the end of the screw is not separated from the platform on the axle, which will cause the axial clearance of the take-up gear to be too large, which will easily cause the non-working angle of the 1, 3 or 2, 4 positions of the film hole to be picked. hurt.
If it is loose, the end of the screw will come off the platform on the axle, and the gear will no longer work. Because the take-up gear belongs to the brake gear, once it loses the braking effect, the speed of the take-up device to rewind the film is much higher than the normal projection (456mm/sec) line speed, which will make the lower buffer bend disappear quickly, or even force it. Pulling the film to the intermittent gear will cause the screen image to shake severely, making it impossible to watch; and it will generate large mechanical noise (especially for projectors using pressing tiles), and it is very easy to cause damage or breakage of the film.
When the fixing screw of the feeding gear or the receiving gear is loose, the flat surface of the end of the fixing screw exposed outside the gear may be higher than the working circumference of the gear teeth and touch the picture of the film, causing damage to the film. The length of the screw is 6mm, and it cannot be replaced and lengthened at will.
3. Intermittent gear fixing screw
It fastens the intermittent gear to the cross axle with through screws and nuts so that the intermittent gear regularly pulls the film.
Because it uses a through screw, whether it is slightly loose or large, the gear will generally not lose rotation. At this time, although it can still pull the film, because the screw has a large gap in the nail hole, the intermittent gear cannot stop at the same position in each cycle, which is easy to cause the film to shake seriously at the gate or even unable to Watch, and produce large mechanical noise, and easily damage the film.
The screws and nuts of the intermittent gear must be fixed on the platform of the gear body to prevent loosening or displacement. In order to reduce the weight of the intermittent gear and reduce its inertia during operation, the original screw and nut should be used for fixing, and the larger one should not be used arbitrarily.
4. Fixing screws of the tile bracket
There are two of them, and they have the same function, that is, to fix the pressing tile bracket on the lower end of the film door cover to maintain the correct position of the pressing tile and its bracket, that is, to leave no less than 0.15mm between the pressing tile bracket and the film. The gap; make the tableting tile have a pressure of 20-40g on the film passing through the intermittent gear.
If only one of them is slightly loose, the impact is not large. If both of them are loose, it will cause the pressure change of the pressing tile to the intermittent gear, which will cause the film to shake at the film gate, and there will be mechanical noise; even the film will be dislodged at the intermittent gear, which will damage the film's perforation. This phenomenon is more obvious when twisting the frame adjuster to correct the wrong frame; in addition, it will also change the gap between the pressing tile bracket and the film, and even make the film run close to the bracket, causing scratches on the film body.
5. Intermittent oil box oil blocking screw
It is used to fill the oil filling hole on the intermittent oil box and prevent the lubricating oil in the oil box from overflowing. Because of its short length, not much twist depth, and easy sliding.
If there is a slight loosening, it will cause a small amount of lubricating oil to seep out and contaminate the parts, but it will not have a big impact; if there is a large amount of loosening, it will force the lubricating oil to seep more seriously under the action of the intermittent parts. , Not only pollutes the parts and the film, but also makes the oil storage in the oil box decrease rapidly, and the related parts in the oil box are accelerated wear due to insufficient lubrication. In addition, due to the reduction of oil volume and oil pressure in the oil box, the lubrication of the active connection between the 31 tooth wheel and the axle is also affected.
Of course, the lubricating oil of the intermittent oil box overflows and seeps, and there are other parts and reasons besides the oil filling hole, and it is also related to the viscosity of the oil used, the seasonal cold and heat conditions at that time, and the temperature conditions of the screening venue. This will not be repeated here.
6. Intermittent oil box sliding pressure plate screw
There are three screws in total, respectively corresponding to three T-shaped sliding pressure plates, which fix and clamp the intermittent oil box on the machine plate and maintain a certain sliding property. This allows for staggered frame adjustments during projections. I have encountered a projectionist who intentionally loosened the screw to reduce the resistance of misalignment. This approach is wrong. Because changing the size of the resistance when adjusting the wrong position can only be achieved by increasing or decreasing the thickness of the steel paper pad under the three T-shaped sliding pressure plates.
If one of the three screws is only slightly loose, it is not easy to detect, and it is irrelevant. If several screws are loose to varying degrees, the resistance of the frame adjuster will be very small when the frame adjuster is twisted, and automatic displacement will occur during the projection, resulting in misalignment.
In addition, if several screws are loose, the intermittent device will be inclined to one side under the action of the motor belt and the heavy driving pulley, which will deteriorate the perpendicularity between the intermittent gear and the machine plate, and even affect the To the stability of the film at the gate; the film hole is injured to varying degrees.
7. Cross car tightening ring fixing screw
It has two same functions, small size and light weight. It is used to fix the tight ring on the cross axle to control the axial clearance of the cross car (cum intermittent gear), so that it is not larger than 0103mm. For the head screw, the tip of the end should be pushed into the groove on the cross axle to avoid sliding. The axial clearance of intermittent gear can be realized by adding or removing steel pads on the shaft.
If it is loose, it will cause the intermittent gear to produce large axial clearance and mechanical noise, and it is easy to cause the film to be picked.
8. Motor transmission pulley fixing screw
It fixes the pulley on the motor shaft, the speed of the pulley is high (2880 rpm); the transmission power is large, (the rotating power of the whole machine is transmitted through this wheel), and it is easy to loosen. If it is loose, the light will make the machine speed unstable, and the heavy will make the machine slow down or even stop, making it impossible to perform the projection.
9. Shader gear fixing screw
It is used to fix the 23-tooth shutter gear on the shaft of the shutter, to control the inner and outer positions of the 31-tooth shutter connecting gear and the axial clearance of the shutter, and to make the shutter rotate regularly under the drive of the synchronizing gear.
It generally has little effect if it is slightly loose. However, due to the high speed of the shutter (24 rpm), it is easy to change into a large loosening, or even the screw comes out by itself, causing the shutter to make a trace, and as a result, the speed is reduced or stopped, and the built-in fireproof plate is automatically closed. and other failures, making the screening impossible.
10. Active pulley fixing screw
It is used to fix the driving pulley on the notched axle of the intermittent device. The functions are: drive the supply and take-up gears and the shutter to rotate through 15 teeth and other transmission gears; drive the intermittent gear to rotate through the intermittent device; control the axial clearance of the notch wheel. Because the speed of the driving pulley is high, the weight is heavier, and because the film is pulled intermittently, the load is uneven, so the fixing screw is easy to loosen.
If the screw is slightly loose, it will increase the axial clearance of the driving pulley and increase the running noise of the machine. If there is large loosening, the intermittent device will stop and the intermittent gear will stop working. At this time, because the supply and take-up gears can still work normally, the upper buffer bend will increase rapidly, the lower buffer bend will disappear rapidly, and even the film hole will be broken and the film will be broken.
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