In the current market, the connection between the dome camera core and the casing is mostly a quick-release fastener structure. Since the cameras are generally installed on the non-vibrating building and the fixed frame, the failure of the core drop is less frequent, but individual Products still have hidden dangers in this area. Therefore, it needs to be improved so as to make the product more perfect.
Fault phenomenon
In the television monitoring of large-scale modern freight terminals, it is necessary to install a dome camera at the front end of a large crane boom such as a quayside container crane and a powder handling crane. In practical applications, the installed high-speed dome cameras have been damaged in large numbers in only half a year. The monitoring system has a high failure rate and is expensive to maintain.
Failure Analysis
Through the inspection of the fast dome camera, common fault phenomena and direct causes of damage are summarized in Table 1 below.
From the above table, it can be found that the direct cause of the above-mentioned damage of the dome camera is that the design of the mechanical structure of the connection between the dome and the shell of the dome is irrational. In use, failure occurs, the core falls off, and the electrical connection is disconnected. The ball failed.
Site use environment survey According to the field survey, the quayside crane is a large-scale steel frame structure with a suspended boom. When the crane is in operation, there is a large vibration movement at the front end of the boom that installs the dome camera. Taking a quayside container crane as an example, the main destructive vibrations are:
When a container crane on the shore lifts a container, more than 30 meters long, the position of the fast ball installed at the front end of the boom will continue to produce low-frequency vertical vibrations up to 3-5 centimeters;
When the container crane moves horizontally along the quay track, the front end of the boom will continue to generate lower-frequency horizontal vibrations with an amplitude of about 10 centimeters. In this case, the personnel need to support the fixed object to stand still;
Every time the container crane is put into and out of work or horizontally along the entire coast, in order to avoid the large masts and superstructures of large freighters, the front crane must be lifted up or down before the big boom, which will generate large shock vibrations.
When the crane moves forwards and backwards along the rails, no small vibration is generated, and it is transmitted to the fastball installed at the front end of the boom.
Therefore, fast dome cameras installed at the front end of long jibs of large quay cranes are constantly subject to horizontal and vertical low-frequency and large-amplitude vibration hazards and strong impact hazards, resulting in frequent damage to dome cameras. Conventional dome cameras are difficult to adapt to such a harsh vibration environment, and it takes too much time to damage. In fact, even if some dome cameras are installed in a fixed environment, occasionally there is a problem of poor core connection and poor electrical connection.
Failure Analysis of Failure Components
The dome camera weighs 1.2 kilograms and is mounted on the core mounting plate in the camera housing through a quick-release fastener structure. The connector is used between the core mounting plate and the commercial housing of the core. For electrical connection, the specific structure of the buckle is shown in Figure 1. After inspection of the damaged fastball camera at the scene, it was found that the damaged component was the core mounting base plate and the upper core cover attached to it, both of which were broken and cut off.
The main body of the core mounting base plate is an engineering plastic component, and the design of the base of the buckle is still relatively firm. However, the core mounting baseplate is on the side of the green sign fastener, and is easily broken near the fixing point fixed with the stud of the fastball housing. Because the fixed point has a certain distance from the force axis of the hanging floor buckle, it is similar to the cantilever type; the square hole is opened in the middle of the bottom plate, and the cross section of the fracture zone is only 17mm, so the stress is concentrated here and the structure is weak. . The adverse impact of the vibration shock again causes the core mounting base plate to break, causing the camera core fastener to loosen and detach, the camera electrical connector to be loosely connected, and the camera to malfunction. Therefore, there is a structural weak point in the core mounting base plate, and in the vibration and shock environment, fatigue mechanical damage occurs and breaks or breaks.
For the same reason, the upper shell of the core is also made of engineering plastics, and the retaining ring on the outer side of the upper buckle of the shell is also relatively thin. When the equipment is installed and operated, the inner ring controls the upper core mounting base buckle and the upper core cap buckle. The actual connecting area between the retainer and the upper housing is very small, with only 5mm on both sides, which is also the weak point of the structure. Due to the adverse impact of vibration and shock, the root of the retainer is easily broken from the upper casing, and the buckle of the core mounting base plate loses the restriction of the retainer and slides outwards, resulting in the loosening of the buckle group connection, the falling of the core, and the malfunction of the camera. . Therefore, the retainer of the upper housing is also structurally weak, and is subjected to fatigue mechanical damage due to vibration and it breaks and breaks.
Is the fast-camera's buckle connection structure itself reliable? By selecting a good dome camera, the core is removed and installed directly on the core. At this time, the two buckles are normally connected as in actual use. During the experiment, the buckle group was rocked by a series of methods such as continuously moving up and down, left and right, and swinging to simulate the vibration and impact effects of the fast ball on the quay crane. As a result, it takes a long time for the buckle to accidentally disengage, but the buckle can be reconnected after reinstallation. This shows that the buckle structure of the dome ball joint has a defect in the province and cannot withstand strong vibration impact. For this reason, even if the dome camera is installed in a fixed environment, there is an occasional problem of poor core connection and poor electrical connection.
For the above-mentioned problem of structural weakness and structural defects, it can be inferred that the root cause of the problem lies in the defects in product design and manufacturing.
ways to improve
For the core mounting base plate, the structural strength of the weak point of the member is reinforced. Reinforce ribs are provided at the joint between the concave hole of the round screw and the plane of the bottom plate; the material thickness of the entire bottom plastic member is thickened to ensure the fastness of the member, thereby decomposing stress concentration points and avoiding fatigue failure of the member. It is also possible to replace the core mounting base plate with metal components to improve the structural fastness.
One of the functions of the original damaged core upper cover buckle outer retainer is to lock the buckle connection of the upper core mounting bottom plate. The retainer actually has a certain distance from the buckle connection point, the locking effect is not good, and the impact itself is not small. Therefore, the method of increasing the strength of the weak point by simply increasing the connection area between the retainer and the base body is not the best improvement method, and cannot fully solve the defect that the fast ball core installation buckle will be accidentally released. A more reasonable method is to improve the ball comprehensively. Core installation buckle structure.
According to the analysis of the structure of the fast-ball buckle of FIG. 1 , there is a certain gap between the right side of the buckle of the core mounting base plate and the left side of the core decorative plate. When the ball buckle retainer breaks or the ball base mounting plate breaks and breaks, the buckle of the ball core mounting base plate easily slides to the gap on the right side, so that the buckle set is accidentally disengaged, the core ball falls off, and the camera malfunctions. In addition, even if the member is not broken, the snap-on retainer of the upper core cover as a snap-connected locking device is far from the fastening point, and the locking effect is poor, and the buckle-slipping of the core mounting base plate cannot be completely and reliably restricted. To the right of the gap, so that the buckle group accidentally released, will also lead to the above-mentioned failure phenomenon. Secondly, the rigidity of the core mounting base plate and the buckle itself is not enough, and the clearance of the structural fit is too large and the like may also cause accidental disengagement of the core mounting buckle group. Therefore, there are many factors that cause accidental disengagement of the dome camera mounting fasteners.
According to the above-mentioned defects of the buckle connection, a new fast ball core quick-release type buckle structure is improved and designed. The specific structure is shown in the figure, and the structure of the buckle fastening and disassembly device is shown in the figure. The main structural changes of the new fast ball core quick-release fasteners include:
Removed the original core on the shell buckle retainer and core buckle decorative plate;
The design increase is made of metal and includes a buckle closure for the button receiving hole;
The ball buckle is designed to be a floating form. It can be rotated to achieve convenient dismantlement of the ball core, and can also float left and right, cling to the right side, and increase the width of the buckle.
The new buckle baffle device is bent to the left, filling in the gap between the original buckle and the decorative plate. At the same time, the buckle of the core is always tight to the right side. Extruded by both sides, the buckles of the core buckles can be inserted into the snap holes of the core installation base plate smoothly and reliably, and the fasteners of the core mounting base plate will not slide to the right side. problem. In addition, the width of the ball buckle fastener is increased, and the button extends into the buckle baffle receiving hole to ensure that the two buckle faces of the buckle are completely in contact with the front face. When working, the forces are coaxial with each other and perpendicular to the fastening surface and cannot accidentally knock off the buckle. In this way, the new buckle baffle and the floating form core buckle actually constitute a reliable locking safety device, even in the shock and vibration environment, the fast ball camera buckle set will not accidentally disengage the failure, thus, completely Eliminate the hidden dangers of fastball cameras.
If the vibration of the actual use of the environment is very large, if necessary, you can use the safety screw to fasten the dome camera directly on the chassis. At the same time, the internal structure of the core should also meet the anti-vibration requirements.
For fast dome camera monitoring cameras that are to be used in vibrating environments, mechanical vibration reduction and vibration isolation devices may also be added to protect the equipment in an all-round way. The built-in mechanical vibration-reducing and vibration-isolation device in the camera is especially effective in improving the image shake and will be better than the software-based image stabilization.
The connection between the dome and the casing of the existing dome camera adopts a quick-release fastener structure. Since the cameras are generally installed on the non-vibrating building and the fixed frame, the failure of the core is less likely to occur, but individual products There is still such a hidden danger. Therefore, there is a need to improve structural design and strictly control materials and production processes. For the imitation products, we should fully grasp the product's structural principles, and take into account the gap between our material properties and production processes, and we should correct and improve the design. At the same time, we will carry out the necessary vibration fatigue test and quality test of impact test on the fastball products to detect hidden defects in time. Safety ropes must be installed during installation and maintenance of the dome to prevent accidents.
Chemical Mechanical Seal
Mechanical Seal,Pump Seal,Oil Seal
Longshen Seal Manufacture (Wuhan) Co., Ltd , http://www.topstarseal.com
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Packing: 150g~1000g/