What Is a Bed Hoist?

A hoist is a light and small lifting device that uses a drum to wind a steel wire rope or a chain to lift or pull heavy objects, also known as a winch. The hoist can lift heavy objects vertically, horizontally or obliquely. The hoist is divided into three types: manual hoist, electric hoist and hydraulic hoist. At present, electric hoists are mainly used. It can be used alone or as a component of lifting, road building and mine hoisting machinery. It is widely used due to its simple operation, large amount of rope, and easy displacement. Mainly used for material lifting or leveling of construction, water conservancy projects, forestry, mines, docks, etc.

Hoists include construction hoists,

The hoist converts electrical energy into mechanical energy through the electric motor 1, that is, the motor's rotor rotates and outputs it through the V-belt 2,

National reference standards for construction hoists:
GB1102 round stranded wire rope GB3811 crane design specification GB5972 practical code for inspection and scrapping of steel wire rope for lifting machinery GB6947 construction hoist test specification and method GBJ232 electrical installation installation construction and acceptance specification JJ12.3 general technical requirements for construction machinery welding parts JJ15 general construction machinery assembly Technical conditions

First, the precautions when using the hoist:

1. The wire ropes on the reels should be arranged neatly. If overlap and oblique winding are found, they should be stopped and re-arranged. It is strictly forbidden to pull by hand or foot during rotation

The scale of national transportation infrastructure and urban construction is getting larger and larger, and the size and power of hoisting machines used in construction projects are getting larger and larger, and the traction speed is getting faster and faster. Correspondingly, the key transmission parts of the hoisting machine are open gears. The size of the auxiliary structure is getting larger and larger, and the noise of the hoist is also getting higher and higher under the condition of high power and high speed operation, but this is not allowed by national standards. The national standard of building hoist GB1955-2002 stipulates that the qualified hoist noise limit is no more than 85dB (A) outside the machine and no more than 88dB (A) near the ear of the operator. When the traction force of the hoist is small and the speed is low, the noise is far below the standard limit, and the control is also easy; but when the traction speed is high and the traction force is large, to ensure that the noise does not exceed the standard, design, technology, materials, and quality Take effective measures in various aspects such as inspection. 1 Existing problems: There are many ways for the source of hoist noise, but it is essentially the result of impact and vibration. Generally, it is caused by the poor meshing quality of the gear and the unstable movement, which results in instantaneous acceleration during the movement. We have an 80kN fast slipping hydraulic control hoist with a wire rope traction speed of 30m / min and a motor power of 55kW. The machine noise is generally within the standard range, but occasionally the noise exceeds the standard. A few machines fail the factory inspection. I feel unable to get started when eliminating noise. Because the drawings and process flow based on machine manufacturing are the same, since most products are qualified, we should exclude unreasonable design and process factors.

Noise source analysis and control

1. Chassis We believe that the design and manufacturing of the chassis may cause noise: The chassis uses a box-shaped structure, and not all welds are continuously welded. The length, height, and position of the welds on each chassis are different, and there are large individual differences in chassis rigidity. Some have a resonance effect, and the machine is amplified if there is a little vibration noise; The chassis is welded from steel and does not have shock absorption and muffling functions. If its natural frequency is close to the gear meshing frequency, it may cause individual machines to be caused by weak gear vibrations. Large co-oscillations cause the noise value to rise. We conducted separate experiments for the above possibilities, but through three experiments, we found that the noise level is weakly related to the chassis structure, stiffness, frequency and other factors, and the noise level is strongly related to the moving parts. Therefore, the chassis design structure and manufacturing quality are not the reasons for the excessive noise .

2. Bearing clearance Some people think that since the noise is accompanied by the reel assembly and the transmission, it may be caused by the large clearance of the reel sliding bearing. We select the fit clearance of the reel parts to ensure that the clearance between the bearing hole and the main shaft meets the requirements of the drawing, and test after assembly. During the test, a variable frequency motor was used to adjust the speed, and the effect of speed on noise was observed. A large number of test results show that the speed has the highest impact on noise. The higher the drum speed, the greater the noise value and the more intense the machine vibration. The gap is next. The larger the gap between the spindle and the sleeve, the louder the noise. Minimal impact on noise. If the machine's original noise is very low, the speed and the change in the size of the spindle clearance will not produce excessive noise, which indicates that the excessive noise is not caused by the large bearing clearance.

During the design of the hoist, it is necessary to avoid the phenomenon of random ropes and bite ropes. A hoist with a cam rope mechanism is proposed. The drum is a key design component. Traditional design methods mostly determine it by experience. thickness. ^[2]

The hoist has the advantages of large carrying capacity, stable and reliable hoisting, and a wide range of operating speed. It is widely used, but due to the lack of awareness and effective methods of safe use of the hoist, it often causes production accidents. ^[3]

Hoist installation position

1. Set up an operating shed and ensure that the operator can clearly see the commander and the dragged or hoisted objects. During the construction process, the buildings, scaffolding, and materials and components stacked on site should not affect the driver's monitoring of the entire process within the operating range. When operating the shed in a hazardous work area, the top should meet the requirements of the protective shed.

2. The foundation is solid. The hoist should be as far away from the dangerous working area as possible, choose a place with a high terrain and solid soil. The ground anchor should be locked with the wire rope and the hoist base, and the front should be piled to prevent the hoist from moving and overturning.

3. Reel direction. The reel is aligned with the center of the guide pulley. The distance from the reel to the first guide pulley is as follows: the slotted roll should be greater than 15 times the width of the roll, and the slotless roll should be greater than 20 times to prevent rolls. When the drum is running, the wire ropes are staggered with each other and the guide wheel flange and the wire rope are worn.

Hoist operator requirements

1. The hoist driver should take professional training and hold a certificate to work. When working, focus on the work. When there are obstacles in the line of sight, clear them in time. Do not operate when the signal is unclear.

2. Before operation, it should be idling to confirm that the electrical, braking, and environmental conditions are good before operation. Operators should understand the main content and workload of the shift in detail.

3. The driver shall not leave the post when the suspended objects are not completely on the ground. Items must be lowered to the ground when resting or suspended. After work, cut off the power and close the switch box.

4. The driver should always pay attention to the operating conditions and the wear of the wire rope. When the load change is raised for the first time, it should be stopped for 0.5m above the ground, and then continue to rise when there is no problem.

5. When using a single-cylinder hoist, the brake must be used to control the descending speed. The brake cannot be applied too quickly and suddenly, and it must be slowly dropped.

6. It is prohibited to use a toggle-type switch to prevent collision and misoperation.

7. The wire rope should be regularly coated with butter and placed in a dedicated channel to prevent rolling and tipping, which will damage the strength of the wire rope.

8. When the rated pulling force of the hoist is greater than 125KN, a rope arranging device should be provided. The wire rope on the drum should be kept at least 3 ~ 5 turns, and the end of the wire rope should be fixed and reliable.

9. The distance from the outer edge of the drum to the outermost wire rope should not be less than 1.5 times the diameter of the wire rope

10. During the operation, no one shall span the hoisting wire rope being operated.