The use and maintenance of elevator guide shoes

The use and maintenance of elevator guide shoes

At present, how to reduce noise, enhance comfort and minimize floor leveling errors in domestically produced elevators is a problem worthy of study. There are many reasons for this problem. One of the main reasons is how to choose, maintain and repair the guide boots. Inappropriate specifications of the guide shoes and the guide rails, improper assembly clearance, and wear of the guide shoe linings can all cause the car to shake or generate friction sounds, and even pose a risk of the guide shoes coming out of the guide rails.

Types of sliding guide boots

1.1 Car guide boots

Roller guide shoes can be classified into sliding guide shoes and rolling guide shoes according to their movement mode on the working surface of the guide rail.

Sliding guide boots can be further classified into fixed sliding guide boots and elastic sliding guide boots based on whether the axial position of their boot heads is fixed or floating. Fixed sliding guide shoes (also known as rigid sliding guide shoes) are shown in Figure 1(please click). There is a relatively large gap between the guide shoes and the guide rails, which will generate significant vibration and impact during movement. Therefore, they are usually used in elevators with a speed of less than 1m/s. However, due to its simple structure, good rigidity and strong load-bearing capacity, it is widely used on low-speed and large-tonnage freight elevators with a load capacity of over 3,000 kg and a speed of less than 0.5m/s. The elastic sliding guide shoe is shown in Figure 2 (please click), and it is further divided into unidirectional floating spring type and rubber spring type sliding guide shoes. For the spring-type sliding shoe with unidirectional buoyancy, it can play a buffering role in the direction perpendicular to the end face of the guide rail. However, there still needs to be a relatively large gap between it and the working surface on the guide rail side, which makes it unable to reduce the vibration and shock in the direction of the working surface on the guide rail side. The upper limit of the rated speed of the elevator with this type of guide shoe is 1.75m/s. Rubber spring-type elastic sliding guide shoes, due to the certain directionality of the shoe head, also have a certain buffering performance in the working surface direction on the guide rail side. Their working performance is superior, and the applicable speed range of elevators is also correspondingly expanded.

The initial clamping force of the shoe lining of the elastic sliding guide shoe on the end face of the guide rail is adjustable. The selection of the initial pressure mainly considers the deflection force, which is related to the rated load of the elevator, the size of the car and the position of the center of gravity. The size b in Figure 2 achieves the adjustment of the initial pressure by regulating the spring. That is to reflect the amount of compression of the spring. For the elastic movable guide shoes of domestic elevators, their values should be selected according to Table 1 (please click).

When the elastic sliding guide shoe lining wears out, the contact pressure will decrease. When the wear is not significant, the screw can be turned to adjust, pushing the shoe head forward to increase the contact pressure and ensure the smoothness of the car's operation. However, the contact pressure should not be too high, otherwise it will increase the running resistance and accelerate the wear of the shoe lining. The boot head can rotate automatically within the boot seat. When the guide rail is not installed straight or the upper and lower ends of the boot lining are unevenly worn, the slight swing of the boot head can be compensated to prevent the car from vibrating or getting stuck on the rail. Some elevator manufacturers supply two types of boot linings at the same time. One is made of cast iron and is installed inside the boot head to be used for the initial running-in of the guide rails. One type is made of nylon. After the guide rails are run-in, the user (the user unit) replaces them on. Its advantage is that it can slow down the wear of the guide shoe. The use of running-in guide rails can improve the surface roughness of the guide rails and overcome processing defects.

Rolling guide shoes, also known as roller guide shoes, are shown in Figure 3 (please click). Due to the adoption of rolling contact, they can reduce the frictional resistance between the guide shoes and the guide rails, save power, and reduce vibration and noise. They are used in high-speed elevators and mine elevators (above 2m/s). The initial pressure exerted by the rollers on the guide rail is adjusted by regulating the amount of compression of the spring. The rollers should not be skewed to the guide rail and should be in uniform contact with the working surface of the guide rail throughout the entire rim width. When the car is running, the three rollers should roll simultaneously to keep the car running smoothly.

When using roller guide shoes, it is not allowed to apply lubricating oil to the working surface of the guide rail to avoid slipping. The sliding guide shoes need to be lubricated with oil to reduce frictional resistance. Usually, the oil box is placed at the top of the two upper guide shoes as shown in Figure 4(please click). The lubricating oil in the oil box is evenly applied to the working surface of the guide rail through felt to achieve the purpose of automatic lubrication.

1.2 Pair of heavy guide boots

The structure of the counterweight guide shoe is simpler than that of the car guide shoe. See Figure 5(please click). The two sides of the boot lining are clamped with Angle steel, which is installed on the counterweight frame. Depending on the manufacturing materials, there are two structural forms of boot linings (Figure 5).

2. Maintenance and inspection of guide boots

2.1 Faults and Troubleshooting of Guide Boots

When an elevator shakes or makes friction sounds during operation, there are many reasons for this. Here, we only propose the possible causes and troubleshooting methods from the perspective of faults in the guide shoes.

If foreign objects get stuck in the oil groove of the boot lining, they should be removed and the boot lining cleaned.

2) The boot lining is severely worn, causing the metal covers at both ends to rub against the guide rail. The boot lining should be replaced.

3) If the gap between the working surfaces of the guide rails on both sides of the hoistway is too large, the guide shoes should be adjusted to maintain a normal top clearance.

4) If the shoe lining is unevenly worn or severely worn, it should be replaced or the side lining of the inlaid type shoe lining should be adjusted, and the guide spring of the guide shoe should be adjusted to make the pressure of the four guide shoes uniform.

5) If the rollers of the rolling guide shoes are unevenly worn, the rollers of the rolling guide shoes should be replaced or repaired.

Rolling guide shoe

2.2 Maintenance and Inspection of guide boots

The gap between the side of the boot lining of the car guide shoe and the guide rail is 0.5 to 1mm. The elastic sliding guide shoe lining has no gap with the top surface of the guide rail, and the adjustment range of the guide shoe spring does not exceed 5mm. The gap between the lining of the fixed sliding guide shoe and the top surface of the guide rail is 1 to 2mm. The gap between the lining of the counterweight guide shoe and the top surface of the guide rail shall not exceed 2.5mm. The gap between the rollers of the rolling guide shoe and the guide rail surface is 1 to 2mm.

2) Run the car and the counterweight at the same level and check the guide shoes on the upper part of the car and the counterweight. Swing the car or counterweight frame back and forth to both sides to check the size of the side clearance and the wear of the shoe lining. You can also inspect the hardness or softness of the springs. If the top gap is too large, you can remove the boot lining and add a gasket on the top surface to adjust it. For those with excessive side clearance, if it is an inset shoe liner, the side shoe liner bolts can be screwed in to adjust the side clearance properly. For integral boot linings, gaskets can be added to the side and back of the boot linings for adjustment, making the gap on one side slightly larger. However, due to structural reasons, the effect is not as good as that of the inset type. Therefore, a good approach is to replace the boot linings with new ones.

Check the tightness of the guide shoes to the car frame and the counterweight frame. Use spring washers to prevent the nuts from loosening.

3) Severe wear of the boot lining, excessive clearance or skewed installation can cause the car to "bite the road" during driving. The "track biting" phenomenon can be identified by the following signs: there is a narrow and bright mark on the side of the guide rail, and in severe cases, the mark has burrs. The side of the boot lining is flared and has burrs. During the operation of the car, especially when starting and leveling the floor, it veers off course and twists. The reasons for the occurrence of "rail biting" are: the guide rail is twisted, skewed or loose. The upper and lower guide shoes are not aligned properly and the clearance with the guide rail is inconsistent. The car frame is deformed or the boot seat bolts are loose. The shape of the boot lining is too small and wobbles inside the boot toe.

4) Always pay attention to the lubrication of the guide rails and promptly remove the dirt inside the boot linings. The working surface of the guide rail of the sliding guide shoe should be cleaned as per regulations. Add oil once a week and clean it once a year. If there is an automatic oiling device, use HJ-40 lubricating oil; if there is no automatic oiling device, use calcium-based grease. No lubricating oil is applied to the working surface of the rolling guide shoe guide rail, but the working surface should be clean. There should be no obvious slippage of the roller during operation. The rolling guide shoe bearings should be lubricated with calcium-based grease once a month and cleaned every six months.