Skyjack has been testing a form of secondary guarding for scissor lifts for the past six months or so and is now preparing to put it into production, initially as an option within the Europe, Middle East and Africa region.
The system, dubbed the ‘SGLE’ (Secondary Guarding Lift Enabler) comprises a shrouded control box plus an anti-tamper enable button on the side of the control box. In order to raise the platform both the joystick and the button must be depressed - if either is released the machine will stop. The design requires two hand operation and obliges the operator to adopt an upright posture away from the guardrails, helping reduce the chances of entrapment against over head obstacles.
Lowering the platform or driving are both activated without the need to use the enable button.
The system will be officially launched at the ARA/Rental show next month and will be available on all of Skyjacks scissor lift models as well as its vertical mast type lifts. It will also be available as a retrofit kit.
The system was designed in response to requests from a number of UK contractors and rental companies that work with them. UK rental company AFI has been involved with the development and has been trialling and evaluating the system since last year.
While the danger of entrapment against overhead obstacles when using scissor lifts is significantly lower than it is with boom lifts – which is already relatively low – one or two people still die each year (globally) from injuries sustained by the involuntary raising of a scissor lift platform into an overhead beam, or other obstacle.
The first example that we are aware of occurred almost 20 years ago during the construction of a new Intel plant in Israel. A man using a small scissor lift died after he was crushed against an overhead beam after he was pressed against the joystick controller. The lift was fitted with a timed enable button that had to be pressed in order for the joystick to work. The design, which replaced the foot pedals or triggers in use at the time – left the controls live for a number of seconds after it was pressed and for as long as the controller remained in use, specifically to eliminate the need for two handed control.
In this case the operator had pressed the enable button, raised the platform and must have come into contact with a beam just behind him, pushing him forward onto the joystick and control box, thus keeping the lift function operating with nothing he could do to reverse the situation.
As a result of the incident Intel stopped all work and then demanded that all such machines be changed/modified before they were allowed to be used again and timed activated enable buttons such as this became rare.
Lest anyone think that this new enable system from Skyjack is similar to that earlier system think again, it is totally different in that it is tamper proof and requires the finger to remain on the button at all times when lifting, At the same time the shroud stops a person’s chest being pressed against the joystick.
The solution is elegant, simple and relatively inexpensive, and having tried the device it certainly appears to be effective, without causing undue hassle or inconvenience to the well trained and experienced operator. It is also not an entirely new concept, German built scissor lifts often used this two handed approach in the pre CE days of the late 1980s and early 1990s.
It would not surprise me to see this concept be widely adopted by other manufacturers as end users adapt to it and request machines they rent to be equipped with it.