keeping them running
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Ron Cater Roller shutters are convenient —except when they jam! So a more robustly made design made by the Dover Roller Shutter Co which has several attractive features should arouse interest among hauliers.
A great problem with roller shutters is distortion, either of the shutter-slats or of the body. When a unit jams it may defy all attempts to open it or be severely damaged in the process—whatever the outcome. an additional expense.
The new Dover shutter—the Nytherm--incorporates extruded light alloy slats which are 10in deep: the extrusions are 1.25in. wide and the sections have a stiffening rail running the full length of the slats. The units can support a 2cwt load imposed on a 12ft length without suffering any permanent distortion. Even when, during a test, the loadirt was made dynamic by bouncing it up and down there was still no permanent distortion.
An extremely rigid track is used in which precision-made roller-races carrying nylon runner-wheels operate. Each wheel has a load capacity of 750Ib and will continue to run free at whatever angle the load is applied. This feature coupled with the rigid structure of the shutter overcomes jamming caused because the body has racked or because the load has fallen back against it.
The Dover shutter, because of its smooth back and robust construction, can be levered open without detriment should a load spill against it.
Weather-sealing is by neoprene-rubber mouldings which fit snugly into slots provided in the extruded sections. A unique cam-operated top slat firmly closes the extreme top of the body-opening and loads the seals against the bodywork preventing any ingress of water.
Other seals fitted longitudinally between the slats are arranged to fold as the shutter rolls over the curve in the track. Wherever the shutter is exposed to the weather the angle of these seals is such that rain water is deflected down the front of the slat. The open backs of the slats are closed by light alloy sheet, the inner meeting edges of which are sealed by two-sided adhesive tape.
The growing demand for frozen food is increasing the demand for insulated and refrigerated bodywork. In the past the insulation properties of shutters have not been good and coupled with other shortcomings this has prevented their extensive use. By utilizing foamed polyurethane, Dover Shutters have produced a very well insulated unit. The foam is either pre-formed and then cut and inserted into the slats or it is foamed in situ. A further insulation is achieved by spraying an elastomer to a thickness of 0.375 in. onto the back panel of the shutter. To provide adequate articulation of the slats the elastomer coating is • cut along the line of the slat joints.
Practical tests carried out on the insulation qualities of the shutters so treated have shown these to be quite good. For instance, working on a rig on which the shutter section represented 25 per cent of the area exposed to an ambient temperature of 72deg F, drops of only 1 deg F per hour have been recorded from an internal temperature of 40deg F.
Operators interested in the Dover Nytherm shutter unit should contact the Dover Roller Shutter Co Ltd, Wheaton Road, Witham, Essex; telephone Witham 3636.