For other centre to centre spacing Lx, the permitted weight T can be calculated using the following approximated formula: perm. Fzul.[N] = F[N] + 0.5 F( L(mm) -1) Maximum operating temperature permitted + 80°C, for short periods + 100°C Lx(mm) Monobloc-Bellhousings with noise damper acc. to VDMA 24 561 It’s a well known fact, that manufacturers of hydraulic accessories have no influence at all upon the noise characteristics of a pump. The influencing of airborne, structure borne and liquid sound is incumbent on the pump design engineer himself. The noise characteristics of a pump – consisting of basic frequency and harmonic waves – can become very annoying when the structure borne noise of the hydraulic unit and the integrated elements of the machine are combined. The flow vibration of a pump combined with it’s pressure vibration, can cause a particularly unpleasant resonance of the structure, which in itself cannot always be calculated, even by means of a sound pressure level monitoring in form of a dB(a) value. In order to prevent the reproduction of this vibration into other integrated elements of the structure, it is necessary to isolate the structure borne noise. This is achieved by the use of flexible drive couplings, flexible connections on pipe work and also by the use of bellhousings with integrated noise / vibration reduction flanges. Damping flanges of this type consist of an elastomeric element, which isolates the metallic contact between the pump and other elements of the hydraulic unit. Our associate company, Raja-Lovejoy manufactures and distributes damping flanges for the reduction of noise within hydraulic units. With many years of experience within this field, a monobloc bellhousing system with integrated noise damping has been developed, (top left drawing, page 39), which offers a simples solution against conventional solutions. The connection between the noise damping ring and the bellhousing is of moulded design using a form conclusive and vulcanised elastomer compound and is designed to avoid rotation and radial wind up. The design provides a noticeable improvement in stiffness, resulting in a tensile strength of 56 kN, (based upon a monoblock bellhousing with a motor flange diameter of 300mm and is suitable for use with an electric motor with frame size D132). The higher stiffness results in reduced shaft misalignment and increases the service life of the drive coupling. The noise damping effect of the monobloc bellhousing is effected by the installation as well as the noise characteristics of the pump. The more annoying the pumps noise the higher the damping degree will be. The spectrum of sound level reduction generally lies between 3 dB(a) in the case of less noisy pumps (Fig. 1) and more than 10 dB(a) by pumps (Fig. 2), which produce higher levels of noise. Pump Drive Components RV Series Bellhousing (VDMA Std.) Permitted Load for Damped Bellhousings 37 #DriveLineHarmony www.jbj.co.uk/couplings.html
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