SLD (Safety Lowering Device)

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The BMS SLD is an ultra safe lowering device for rope rescue. Constructed of high strength metals, primarily stainless steel, it is designed for many years or trouble free operation in urban fire and rescue environments. Initially conceived for single rope rescue from the roofs of tall buildings, the SLD can be used to lower up to 600 Lbs. in an easy and secure fashion on 12 to 15 mm static kern-mantle and laid rescue rope as well as heat resisting fiber ropes.

The SLD is comprised of two main sub-assemblies, a 3 bar “U” frame rack (B, D,&E) and an un-loader device used to spread the bars to allow rope to pass through the SLD when under load. Unlike the traditional brake bar rack the rope is reeved through the device from the end of the rope since none of the bars swing open from the frame. This feature eliminates the possibility that the rope can become detached from the SLD either in use or in transit. As you can see from the drawing, when loaded, the bars move closer together providing additional friction arresting movement of rope through the device. The greater the load on rope the greater the holding force exerted on the rope by the SLD. This configuration, with un-loader detached from A, by itself makes an excellent belay device capable of catching loads up to 600 lbs with minimal shock loads by allowing limited slippage. With the addition of the un-loader subassembly to the device the bars can now be spread under load allowing the rope to move through the SLD at an easily controllable rate. Should the operator let go of the Ball Knob Handle (C) the SLD returns to a locked-off condition immediately stopping rope movement satisfying the tenants of the “Whistle Test” (the device auto-locks when unattended). In the drawing above it should be noted the Ball Knob Handle (C) is in the lowest friction position. When loaded the Ball Knob Handle (C) swings up and to the left effectively locking-off the SLD. Moving Ball Knob Handle down and to the right spreads bars allowing rope to pass through the SLD with excellent control.

When more than one individual will require lowering it is important to be able to reset the system quickly. This might be critical during high-rise a fire event when multiple rescuers would be required to be lowered sequentially. After each lowering the unloaded rope can be easily pulled through the device with out de-rigging the device from the rope allowing quick resets. This feature also allows any slack in the system that may appear during the evolution to be quickly taken up by the operator maintaining an effective belay on the rescuer while connected to the system. Conversely if slack is required it can be easily fed out by spreading the bars of the SLD with the un-loader. Over the next several months BMS hopes to commit this design to production.

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    Carroll Bassett
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