German JAKOB coupling, JAKOB model, JAKOB price

JAKOB coupling slider is ring-shaped, made of steel or wear-resistant alloy. Cross-slider couplings are suitable for transmissions with lower speeds and higher torque transmission. Slider couplings consist of two shaft hubs and a center slider. The center slider, as a torque-transmitting element, is usually made of engineering plastic; in special cases, other materials such as metals can be selected.

JAKOB coupling introduction

Gear couplings have small radial dimensions and high load capacity. They are often used for shaft system transmissions under low-speed, heavy-load conditions, such as in metallurgy, mining, and lifting/transport industries, and are also suitable for petroleum, chemical, and general machinery industries. High-precision gear couplings that have undergone dynamic balancing can be used for high-speed transmissions, such as gas turbine shaft systems. Since drum-tooth gear couplings offer greater angular compensation than straight-tooth gear couplings, drum-tooth gear couplings are widely adopted both domestically and internationally, while straight-tooth gear couplings should be avoided where possible. Gear couplings are a type of movable rigid coupling. They transmit torque and rotational motion between the two halves of the coupling through the meshing of internal and external teeth, suitable for connecting coaxial shaft systems, and possess certain capability to compensate for relative displacement between the two shafts. Its structure is shown in Figure One. It mainly consists of an internal gear ring, a gear shaft sleeve, and end covers. Generally, for smaller-sized gear couplings, the end cover and internal gear ring can be formed as a single unit. Due to their compact structure, high load capacity, wide operating speed range, and reliable operation, gear couplings are widely used in various mechanical industries such as metallurgy, mining, lifting/transport, petroleum, and shipbuilding.

JAKOB coupling classification

Gear couplings can be divided into three types based on the axial tooth profile of the external gear sleeve: straight-tooth gear couplings, drum-tooth gear couplings, and special drum-tooth gear couplings. Regardless of the type, the internal gear ring and the involute straight internal gear are identical except for differences in the selection of the tip clearance coefficient. For straight-tooth gear couplings, the axial tooth blank of the external gear sleeve can be machined into straight and arc shapes, while the pitch circle and root circle are straight. The meshing form of this coupling is exactly the same as the internal and external tooth meshing of involute cylindrical gears. Relative displacement between the two shafts is compensated by increasing the side clearance of the internal and external teeth, but the compensation amount is limited. For drum-tooth gear couplings, the tooth top of the external gear sleeve is machined into an arc, meaning the tooth blank is machined into a spherical surface. In the cross-section at the tooth center plane and tangent to the pitch cylinder, the teeth form a drum shape, hence the name drum-tooth coupling. Its characteristics are: 1) High load capacity; calculated based on bending strength, the torque transmitted is increased by 15～30% compared to straight-tooth gear couplings under the same conditions; 2) Reasonable structure and reliable performance; since the tooth sides are drum-shaped, contact conditions are improved when the shaft axes are at a certain angle, thereby reducing contact stress, eliminating load concentration at the tooth ends of straight-tooth couplings (i.e., eliminating edge crushing), and improving operational performance. 3) Good compensation performance; the drum-shaped tooth profile of the external gear sleeve increases the allowable relative offset between the connected shafts. The maximum allowable inclination angle can reach 6 degrees, with a general recommendation of 1.5°～2.5°.

JAKOB coupling troubleshooting

1) Misalignment of gear couplings: Coupling misalignment is classified into angular misalignment, parallel misalignment, and combined misalignment. Angular misalignment occurs when there is wobble on the coupling face, causing the centerlines of the two half-couplings to form an angle, which generates excitation forces during rotation and induces vibration response. Parallel misalignment occurs when the centerlines of the two half-couplings are not collinear, but remain parallel at a certain distance, generating vibration response during rotation. Combined misalignment is the most common misalignment phenomenon in actual rotating machinery, involving both angular misalignment and parallel misalignment, representing a combination of the two. During the manufacturing process, the end face may not be perpendicular to the centerline, or the centerline of the end face bolt holes may not be concentric with the journal, due to reasons such as processing or measurement. During the installation process, tightening the connection bolts (gear sleeve bolts) causes deformation of the rotating shaft, resulting in significant runout at the journal. Sometimes, differences in the tightening force of the circumferential connection bolts of the coupling can also cause conditions similar to wobble on the coupling face. During operation, if operating conditions change drastically, such as during load application, when the load reaches a certain value (i.e., the shaft system torque increases to a specific level), mutual dislocation of the coupling occurs, changing the alignment state of the shaft system, and causing a sudden change in the vibration response of the rotor connected by the coupling. A large instantaneous change in shaft system torque impacts the coupling transmitting the torque, causing mutual dislocation of the coupling, and changing the alignment state of the shaft system. 2) Torsional vibration: The torsional vibration of gear couplings has been analyzed and studied, mainly using the Fourier series solution method, with clearance, damping, and excitation force as parameters, A nonlinear analysis was conducted on the torsional vibration of shaft systems connected by gear couplings; Extensive tests were carried out on the axial vibration of shaft systems connected by gear couplings, and the main causes of axial vibration were qualitatively explained, indicating that axial vibration is mainly caused by misalignment and friction on the tooth surfaces, and significant axial displacement will occur when there is no axial restoring force or thrust bearing. Vibration analysis is one of the techniques for predicting coupling misalignment, as it can determine the trend of gradual changes in equipment condition, but when determining whether a piece of equipment is in a misaligned state, it is necessary to refer to a large amount of historical data and cases, and to distinguish whether the issue lies with the bearings, lubricating oil, or coupling, or with the connection and fixation, so it has certain limitations. Infrared thermography can, when equipment condition is poor, differentiate overheated areas such as bearings, motor housings, and couplings, and determine the alignment error of the coupling, and when combined with other predictive techniques such as vibration analysis, the effect will be better. Tests were conducted on high-speed rotating turbine generators and blowers, providing a brief explanation of the bending vibration caused by gear couplings; Bending vibration tests were performed on shaft systems connected by gear couplings under different parameter conditions such as unbalance, lubrication conditions, clearance, errors, and load; In addition, Yamauchi, Someya, and others conducted a nonlinear analysis of the bending vibration of half-coupling systems under the action of dry friction on the tooth surfaces, The vibration of gear couplings is mainly related to the misalignment between internal and external gears and tooth surface friction, and special attention must be paid to the lubrication of tooth surfaces in high-speed rotation conditions.

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