01.06.2018

MEC unveils anti entrapment for scissors

MEC has announced details of a new overhead protection device for slab electric scissor lifts, that it is calling ‘Proactive Platform Safety System of PPSS for short.

The device, which is based on a system that it has been using on its boom lifts for the past year or so, is designed to alert the scissor lift operator to the proximity of any overhead obstacles or hazards with the aim to avoid collision and entrapment.

The PPSS system emits an ultrasonic ‘cone of safety’ to detect objects above the machine operator, it begins detecting obstacles four metres above the platform floor, with the alarm beginning to sound via a ‘beep’ when an object is identified within the cone.
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One of the ultrasound beam generators on a MEC boom lift

The frequency of the beeps increases as the object becomes closer, just as you might find on a car reversing alarm. When a pre-set safe distance is reached the frequency of alarm beeps becomes constant and the machine lift function stops automatically. An override button allows the operator to deliberately move closer to the object in order to find the perfect working height.
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The PPSS system emits a cone shaped ultrasonic beam which detects objects up to four metres above the platform floor

The PPSS system aims to provide a proactive warning to reduce the risk of an overhead collision or entrapment. The company says that the “unique” 45 degree orientation of the lift control handle is designed so that any forward/downward movement will cause the machine to lower in the case that contact was made with an overhead obstacle which pushed the operator onto the controls.
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An overhead view shows how the operator falls within the beam area

Vertikal Comment

The pace of anti-collision systems such as this for scissor lifts is gathering pace rapidly, with all manor manufacturers working on systems that might help.
They follow the earlier introduction by some companies of shielded control panels, and an attempt by UK rental company Kimberly to introduce a switch activated wrist rest device in 2015, that it called ‘SkySecure’.

Then at Conexpo last year JLG demonstrated its ‘No Touch’ proximity device on a scissor lift – initially aimed at the aviation market, with beam emitters that can be set to warn and prevent contact in various directions, depending on the application.

Later in the year Skyjack added the ‘Lift Enabler’ an extra enable button on the controls that obliges two hand operation, causing the operator to stand over the controls rather than lean over the guardrails while moving, as well as helping stop lift or drive functions should an entrapment situation arise.

At the ARA in February, GMG demonstrated a “radar” type system on a scissor lift control box that worked in a similar way to this device from MEC, while Skyjack demonstrated a prototype of a similar multi beam system. Genie showed a more mechanical system at Vertikal Days a few weeks ago, the ‘Lift Guard Contact Alarm’ that attaches to the lift’s guardrails, while Snorkel unveiled a pressure activated safety frame/shroud around its controller dubbed Snorkel Guard. So, it looks as though secondary guarding will quickly become a feature on all scissor lifts, the question is will it be standard – or optional?

A full review of such systems will be included in the slab electric scissor lift feature in the next Cranes & Access magazine – due out in two weeks time.