有三种结构。 There are three structures for the transmission chain of
agricultural machinery. Sleeve roller chains, hook chains and integrated chains. Most of them work under the condition of being exposed outside and being attacked by dust, so it and their mating pair sprocket are worn out a lot. The wear of the chain will increase the pitch. If the worn chain pitch increases to the point where the chain contacts the sprocket teeth, it will bite, jam or fall off, and the chain cannot continue to work normally. The chain must be repaired or replaced. Checking the elongation of the chain after it is worn can be performed on a self-made workbench. During the inspection, a special movable caliper must be made, the measured chain should be placed in a horizontal position, and a certain load should be applied. The specific inspection data is specified in the following table.
Chain inspection data
Repair of sleeve roller chains
1. Elongated chain to half joint repair
Generally, the chain drive has a tensioning device, and some agricultural machinery does not have this structure. Due to the chain's elongation, the drive will beat and knock, and will not work properly. If the chain wear does not exceed the limit, you can remove a set of links and adjust to a proper tightness, but this will happen in practice; if you do not remove a set of links, it will be too long short. When repairing, you can modify and remove half of the chain links.
When refitting a single-row sleeve roller chain, first punch down the two cylindrical pins, remove one roller, the sleeve and the two inner links, pull the remaining two outer links into the shape shown in Figure b, and then File two arcs corresponding to the two adjacent outer links (Figure a) to avoid friction with each other after assembly. In order to facilitate installation, the rollers and bushings at the modification can be filed short and then assembled as shown in Figure c.
Schematic diagram of half-chain repair
The double-row sleeve roller chain can also be repaired with a modification similar to the above.
Another modification method is to lengthen the pin when the structure allows it (see the figure below). First remove the chain pins 1, 2, and 3 to separate the chains, and then remove the two inner links that connect the rollers b and c to make four round pads, leaving two in place of the roller b. Two are placed on the outer chain of roller d. Remove the roller c and use it after riveting with two long pins.
Schematic diagram of half-chain repair
In the picture: 1, 2, 3 a pin; 4 an inner link; 5 an outer link; 6- long pin
2. Repair of worn out-of-limit chains
After the chain wears, the pitch increases, which is mainly the result of the simple side wear of the pins and sleeves.
It can be repaired with or without disassembly according to the equipment conditions.
① Disassembly and repair
According to the repair principle of the adjustment and transposition method, turn the pins and sleeves that are worn on one side to the 180 ° position, which will restore the normal pitch again (Figure c below). For this reason, the worn out chain is completely disassembled, the damaged parts are eliminated, and the usable parts are reassembled according to the above method. In this way, about 80% of the parts can continue to be used.
Wear and adjustment of sleeve roller chain
When the sleeve roller chain is disassembled, simple special equipment should be used. The length of the two channel steels is 500 mm. The fastening screw head is welded to one side of the channel steel. The threaded handle is shaken according to the different pitch of the chain. The distance between the channel steels can be adjusted to support the chain on the channel steel. The spring force in the screw always pushes the channel steel to ensure the opening of the channel steel.
Disassembly device for sleeve roller chain
After the chain is loaded into the equipment, the small arms of the fork arm are first driven in turns with a punch, and then the inner chain and the sleeve are driven out with a die.
After the chain is disassembled, it is carefully cleaned and identified, and the available parts are selected for assembly. During assembly, the pin is clamped by a vise to twist the chain 180 °, and the sleeve installed in the inner chain is also twisted 180 °, so that the wear surface of the sleeve is opposed on the inside. In order to avoid the loose fitting of the inner chain piece and the sleeve, a punch is used to tighten the fitting place, and finally the pin is riveted to the outer chain piece.
② Repair without disassembly
This is a relatively simple repair method. It does not need to disassemble the chain, but shortens the pitch of the outer chain to restore the entire chain pitch to a normal state.
When repairing, put the chain on the fixture, and then use the high-frequency current to heat the middle part of the outer link to make it plastic. At this time, the outer link is squeezed and upset to the required pitch. In order to ensure the same processing pitch, a positioner is placed between the rollers.
The hinge part of the repaired chain link should be free to rotate by hand, and the roller can rotate freely in the sleeve. Then install it on the test bench, test run at 350-400 rpm for 20 minutes, check the operation and eliminate the problems found. The repaired chain should be soaked in waste engine oil at 80 ~ 90 ℃ for 15-20 minutes, so that the inner friction surface of the chain link can be well lubricated. Low temperature and short time
It is easy to penetrate into it. If the high-frequency oscillator is shaken during the infiltration to vibrate the chain at a frequency of 1000 to 2000 times / minute, the infiltration effect will be better, and the time can be shortened to only 2 to 3 minutes. Hang the chain after immersing it in oil, and use or store it after dripping the oil.
Hook chain repair
Hook chains commonly used in agricultural machinery have three pitches of 30, 38, and 41.3 mm. Most of them are cast with malleable cast iron, and a few are stamped with 30-gauge steel.
After the cast hook chain is used for a long time, the chain link will be scrapped after the following defects occur: ① the chain link is deformed and cracked, ② the hook head or the frame is broken, ③ the thickness of the hook head is less than 3.5 mm after the wear, and the inner side of the cross link is less than 4.5 mm.
Check the inner side of the chain link for abrasion using a homemade template. For example, for chain links with a pitch of 30 and 38 mm, the template uses two gaps of 4.5 mm and 5.5 mm to divide the inspected chain links into three groups: the chain that exceeds the limit of wear and tear passes the 4.5 mm gap, and should be selected to be scrapped and worn. Lighter chain links cannot pass through 5.5 mm notches. These types of links can continue to be used normally. They can pass 5.5 mm notches but cannot pass 4.5 mm notches, indicating that they have worn to a certain extent and their strength has weakened. In the future, only Can be used for lighter load transmission.
Check the template of the hook chain
In order to reduce the opening width of the hook head after abrasion, for the above two groups of assembled chain links, pressurizing devices of the hook chain links (as shown below) are used for pressure repair. When pressurizing, the chain links are sequentially placed on a square mandrel with a bevel, and the hand lever 4 is pressed by hand to bend the chain hook and reduce the opening. The pressurized chain link can no longer be disassembled, so a few new chain links that are not pressurized should be inserted during assembly to facilitate disassembly and assembly during use. After the overhaul, it should be carefully checked, and the broken links should be eliminated.
The copper hook chain can also be corrected after deformation. When cracks appear, they can be repaired by welding, but when cracks or stoppage defects appear at the hook head, they should be scrapped.
The repaired hook chain should be tested for 20 minutes at a speed of 300 revolutions per minute to check the quality of the repaired chain link.
Pressing device for hook chain link
Repair of integrated chains
The composite chain consists of cast frame links and steel stamped links, which are often used in flat elevators and scraper conveyors. After long-term use, the frame and the link plate at the joints of the chain will cause wear, elongation and deformation of the steel stamping chain, and the chain pitch will increase, so that it will exceed the limit.
After the length exceeds the limit, the comprehensive chain should be broken down into single pieces for inspection. If the cast chain joint journal is less than 4 mm and the thickness of the steel link working part is less than 2 mm, it should be eliminated. The remaining chain links can be reassembled. At this time, the cast frame links can be rotated through 90 °, which shortens the chain pitch and extends the service life. The assembly is carried out under a simple pressurizing device. Each hinge part of the chain after pressurization should rotate flexibly, and the bend of the stamped chain link is not broken. The repaired comprehensive chain was commissioned according to the hook chain specification. After repairing the chain, the strength of the chain link has weakened, so this chain can only be used on lighter machinery.