In recent years, significant progress has been made in China's construction engineering sector. SC(D) series construction hoists, as commonly used construction machinery, play a vital role in building construction and related fields. However, during usage, a relatively common problem with construction hoists is the phenomenon of significant swaying and vibration during operation. This issue not only affects the comfort of operators but also hinders the long-term operation of the hoist, accelerates the wear rate of moving mechanical parts, reduces the service life of the machinery, and jeopardizes construction safety. The guide roller, serving as the connecting link between moving parts (such as the cage and transmission device) and fixed parts (such as the guide rail mast), if improperly adjusted or inappropriately constrained, inevitably becomes a major cause of sway and vibration in the hoist. Therefore, based on practical experience, this paper analyzes the structural characteristics of commonly used guide rollers in current construction hoists, seeks the causes of sway and vibration, and formulates corresponding improvement measures.

1. Structural Characteristics of Commonly Used Guide Rollers in Construction Hoists

The main moving parts in a construction hoist are the transmission device and the cage, both of which perform vertical movement up and down the guide rail mast via guide rollers. Guide rollers play a supporting and guiding role during equipment operation. The gap between the guide roller and the guide rail mast must be controlled within a certain range to ensure smooth operation of the hoist and prevent swaying and vibration.

Based on structural characteristics, guide rollers commonly used in construction hoists are mainly classified into two types: single rollers and swinging rollers. To maintain stable operation of the construction hoist during continuous work, except for the swinging rollers installed at the upper part of the cage, the single or swinging rollers installed elsewhere are all eccentric rollers with a certain adjustment margin. The guide roller adjusts its fit clearance with the guide rail mast by rotating the eccentric shaft sleeve. Continuous adjustment is possible within the eccentricity range. The roller is then secured using the pre-tightening force of bolts and nuts to lock the adjusted guide roller, keeping the gap between the guide roller and guide rail mast within a reasonable range of 0.5 to 1 mm. During complete machine installation and commissioning, each set of guide rollers is adjusted and the nuts are locked to ensure that loads on moving parts like the transmission device and cage are distributed as evenly as possible onto individual guide rollers, resulting in uniform and reasonable stress on all parts of the machine. The function of guide roller adjustment is to prevent excessive fit clearance caused by large geometric dimensional deviations between the guide roller and guide rail mast during transmission, thereby also avoiding geometric deviations from the guide roller's own manufacturing and assembly, which is a necessary condition for sway and vibration in the transmission device and cage of the construction hoist.

2. Analysis of Structural Defects in Commonly Used Guide Rollers of Construction Hoists

Upon detailed analysis, current guide rollers of this type have two structural defects, analyzed as follows:

(1) The adjustment of the guide roller is achieved by rotating the eccentric shaft sleeve. Although continuous adjustment is possible within the eccentricity range, the fastening relies on the pre-tightening force of bolts and nuts, which is not very effective. After installation, commissioning, and normal use of the construction hoist, following a period of normal磨合 (running-in), the nuts on the guide rollers gradually loosen. This directly leads to a gradual decrease in the fastening friction force of the bolts and nuts. When the eccentric moment on the adjusted guide roller exceeds the nut's fastening friction force, the guide roller may shift. Once the displacement of the guide roller reaches or exceeds the reasonable range of 0.5 to 1 mm for the guide roller-guide rail mast gap, the equipment not only fails to achieve reasonable load distribution during operation but also, as the gap continuously increases, the construction hoist will gradually develop significant sway and vibration.

(2) The bolts used in the guide rollers are ordinary bolts rather than reamed hole bolts. Comparatively, the manufacturing precision and material strength of ordinary bolts are inferior to those of reamed hole bolts. When guide rollers using ordinary bolts are assembled into the mounting holes machined on the transmission device or cage of the construction hoist according to fit precision requirements, a relatively large assembly gap inevitably exists, preventing effective force transmission. During continuous operation of the hoist, this assembly gap continuously expands, gradually leading to the onset of sway and vibration.

It can be concluded that after a period of normal use, the two aforementioned defects in commonly used construction hoist guide rollers cause the gap between the guide roller and the guide rail to gradually increase, while the整体 integrity also gradually weakens. Once the operating speed of the hoist coincides with the vibration frequency of the cage, continuous vibration of the cage occurs. The discomfort for occupants becomes difficult to overcome, while the wear rate of mechanical moving parts accelerates, reducing the service life of the machinery and even endangering construction safety.

3. Improvement Measures and Structural Characteristic Analysis of Guide Rollers

3.1 Improvement Measures

(1) Design a reasonable and effective bolt locking device. Integrate the eccentric shaft sleeve and bolt into a single component, and equip it with a fixed clamping plate to prevent loosening, thereby avoiding the influence of the eccentric moment generated by the guide roller's eccentric structure and preventing the phenomenon of the guide roller rotating and shifting around the eccentric axis.

(2) Increase the fit precision of the mating part between the guide roller and the moving parts (cage and transmission device). Based on the integrated design of the eccentric shaft sleeve and bolt, increase the dimensional precision requirements for the mating section that requires fit precision with the transmission device or cage of the hoist. Ensure dimensional accuracy meets the requirements for force transmission, enabling the guide roller and the moving parts of the hoist to form an effective integral unit.

3.2 Introduction to Structural Characteristics

Addressing the above issues, based on practical work experience, an improved construction hoist guide roller has been designed. This improved guide roller adopts an eccentric shaft adjustment structure, integrating the eccentric shaft sleeve and bolt of the commonly used guide roller described earlier into a single component, namely an eccentric shaft. The step at the end of the eccentric shaft is machined into a regular hexagon. The fixed clamping plate is machined with an inner hole matching this regular hexagon, allowing the eccentric shaft to be locked using the clamping plate after adjusting the gap between the guide roller and the guide rail mast to a reasonable range by turning the eccentric shaft. This improvement measure enables the eccentric shaft of the guide roller to be locked during normal use of the construction hoist, preventing displacement caused by the influence of the eccentric moment generated by the guide roller's eccentric structure.

Source: Enterprise Technology and Development, Issue 07, 2017. Authors: Mai Gang, Yin Yimin, Jiang Wei, Gu Binrong, Qin Tong.