German ROEMHELD coupling ROEMHELD model ROEMHELD price

ROEMHELD couplings are mechanical components used to connect two shafts (driving shaft and driven shaft) in different mechanisms, enabling them to rotate together to transmit torque. In high-speed, heavy-load power transmission systems, some couplings also provide buffering, vibration damping, and improved dynamic performance of the shaft system. A coupling consists of two halves, each connected to the driving shaft and the driven shaft respectively. Generally, prime movers are connected to working machines via couplings.

ROEMHELD Coupling Introduction

Composed of two hubs and a thin-walled metal tube, joined by welding or bonding. Although many other materials are available, stainless steel and nickel are the most commonly used materials for the metal tube. Nickel tubes are produced using an electrodepositing method. This process begins by machining a solid mandrel into a corrugated shape, electroplating nickel onto the mandrel, and then chemically dissolving the mandrel to obtain a nickel bellows. This method allows precise control over the bellows wall thickness and achieves thinner walls than other manufacturing methods. These thin-walled bellows give the coupling high sensitivity and rapid response, making it ideal for applications in extremely small and precision instruments.

ROEMHELD Coupling Structure Composition

Coupling structure: The input end features a clamping collar structure, where preload is generated by clamping screws to rigidly connect the power input shaft with the clamping collar. The output end features a taper-lock structure, where tightening screws preload a cone, causing the locking sleeve to expand and fit into the inner bore of the power output shaft, forming a unified connection. The center section consists of a bellows structure, with both ends of the bellows adhesively bonded to the input and output ends.

ROEMHELD Coupling Troubleshooting

Based on the coupling structure, power is transmitted from the coupling to the power output shaft (gearbox shaft) via a taper-lock fit, and to the power input shaft via a clamping collar. Power is transmitted between the clamping end and the taper-lock end through the bellows, which is adhesively bonded to both the taper-lock end and the clamping collar. The fault location is at the interface between the clamping collar and the bellows. Two pre-deformation grooves are machined radially into the clamping collar. The groove width is approximately 2mm. On the side with the clamping screw, the groove is through in the diametrical direction but does not penetrate completely at the depth where it connects to the bellows, resulting in a sloped cross-section. The other groove does not extend through radially, but its longitudinal connection to the bellows also does not penetrate completely, resulting in a sloped cross-section. During clamping, a torque wrench is used to tighten the clamping screws to the specified value, eliminating clearance between the bore and shaft through deformation of the clamping collar to achieve a secure fit. As seen in the cross-sectional view, due to the presence of the two pre-deformation grooves, the cross-section at this location is weaker, and deformation occurs primarily at these grooves. The pre-deformation groove on the side with the clamping screw has the smallest cross-sectional area and is the weakest point. Permanent V-shaped deformation marks at its end indicate that stress in this area during clamping exceeds the yield limit of super-hard aluminum. According to the stress distribution diagram, once the bevel gear box and main gearbox are assembled and clamped, the stress value at the adhesive interface of the pre-deformation groove on the clamping screw side is 164Mpa, with a deformation magnitude of 0.027mm. During launcher operation, the coupling is subjected to alternating composite stresses, causing even greater stress and deformation at this location. If minor defects such as voids, inclusions, or flaws exist at the adhesive interface during manufacturing, micro-cracks will first form at defective areas within the region of highest stress on the coupling's adhesive surface when alternating stress exceeds the bond strength, creating fatigue initiation sites. Due to stress concentration at the crack tips, cracks gradually propagate with increasing stress cycles and prolonged exposure to constant stress. As cracks spread, the adhesive interface is progressively weakened. When cracks reach a certain size, fatigue failure occurs. The coupling functioned normally during initial testing, but as service time increased, cracks gradually propagated. Even under low loads, the coupling eventually failed. The presence of stress at the adhesive joint is a latent cause of failure. To avoid generating excessive stress when the coupling clamping collar is tightened, annular grooves are typically cut into the clamping collar for stress relief.

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