Plummer blocks

Plummer blocks Two additional features are now available on the SKF SNA rolling bearing plummer block range. One is a grease escape valve for more economic operation in high speed transmission applications. The other, for particularly arduous applications, is a new housing made of spheroidal graphite cast iron with solid feet for mounting purposes. The new grease escape valve plummer block is designated SNA-V. It is similar to the standard design, but fitted with a grease nipple situated so that the grease enters the housing at the opposite side to the sleeve locknut. To prevent grease forcing its way out of the entry side of the housing a V-ring is mounted inside the housing to act as a return valve. The V-ring has a hole in the lip through which a small quantity of grease passes during relubrication to lubricate the seal lips. Surplus grease is allowed to escape on the locknut side of the housing where the locknut assists expulsion past the V-ring lip. Grease spraying is avoided by the insertion of a guard in the seal groove of the housing. The new housing variant is designated SSNAD. It will be available in all the sizes and seals can be selected from the same range as for the standard housings. The housings will be delivered without drilling holes in the base. They can be drilled to provide four bolt holes of the same size and in exaclly the same positions in the base as with the previous SSN housing type. Skefco Ball Bearing Co Ltd, Leagrove Road, Luton, Bedfordshire, England

of probes used within SKF. In Fig 5 the fight transmitting and receiving fibre bundles are divided and mounted in an angle to each other. In Fig 6 the transmitting and receiving fibres are randomly mixed and the probe is mounted perpendicularly to the surface. A project is now running at the SKF European Research Centre to investigate the properties of these types of probes and to optimize the design for different bearing surfaces and forms. No definite results have been obtained, but from previous experience the divided probe probably has better resolution, while the mixed probe can be easier to apply. The electric signal from the fight sensitive detector is amplified and divided into two channels. In the first channel the total reflected fight is measured and too rough or too dark surfaces are sorted out. In the second channel the signal is differentiated and only fast variation in the reflected light is detected and components with surface faults such as dark spots, flats, cracks, etc are sorted out. Fig 7 shows a typical electric signal from a roller with a small crack. The resolution of a well designed fibre optic probe is in most cases better than a trained human eye. There are, however, surface faults that are difficult to detect, such as faults very near the end of a roller and continuous line faults around a roller, etc. Fig 8 shows a probe made for surface fault detection of complete bearings. The probe has mixed transmitting and receiving fibres and is divided into 12 parallel channels. This device has been incorporated into an apparatus (Fig 9) for inspection of complete bearings. The capacity of this apparatus is about 1200-1500 bearings per hour, depending on size.

CURVED SURFACESIN ENGINEERING Cambridge, March 1972 Proceedings of a conference organized jointly by the IPC journal Computer Aided Design and the CAD Centre, Cambridge. This volume contains thirteen papers reviewing computer methods for the design and manufacture of engineering curved surfaces. Applications covered include numerically controlled machining; aircraft design; shipbuilding; design and production of plastics and glassware.

ISBN 0 902852 10 8 Price £5.00 Available in August from: IPC Science and Technology Press Ltd, (ref: ADCAP 21 T ), IPC House, 32 High Street, Guildford, Surrey, England.

SKF European Research Centre, Plettenburgerweg, Postbus 50, Jutphass (Gemeente Nieuwegein), Netherlands

TRIBOLOGY October 1972

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