REMOTE e-STOP BUTTON (RSB)
This is
a safety oriented product developed by RGB Engineering for roll grinder
applications, but would have equal merit for any machine tool installation.
The idea was conceived as a result of an unfortunate and tragic accident on a
combination lathe/roll grinder in a roll rubber covering plant where the
operator was killed. He was literally crushed in the “nip” point between
the rotating roll and bed. The actual details leading up to the accident
are unclear, as he was working alone, but all indications are that he was trying
to clear some debris from under the roll, and got pulled into the converging
nip. The fact that this was a rubber roll with increased friction
(compared with metal rolls) undoubtedly contributed to the seriousness of the
event. Although not all roll grinders service rubber covered rolls,
nevertheless it is still conceivable that a similar accident could occur with
any roll; plus there are numerous other potential dangerous situations that
could cause serious injury or even death. There are problems with other
pinch points (i.e.: between the headstock and carriage), and there are openings
where an operator could wedge his foot and be trapped in the path of the moving
carriage (i.e.: in the narrow floor plate opening for the service carrier
bracket). As most roll shop personnel are aware, there are many other
potential hazardous conditions that exist on any roll grinder. This becomes an
even more serious concern when the operator is working alone in an enclosed
room, with only occasional contact with other personnel, as is sometimes the
case. It is for these reasons that RGB Engineering is offering this safety
upgrade.
Since hearing of the unfortunate accident, various devices have been designed
and tested by RGB Engineering, which has led to the development of the “RSB”
module (Remote e-Stop Button). Simply put, this is a
radio controlled transmitter/receiver unit working in conjunction with
interfacing relays a
nd
controls to engage the machine’s E-Stop circuit. The transmitter, shown
here, would typically attach to the operator’s belt or clothing (like a pager)
on a key chain, or optionally via a belt clip or pendant. Pressing the
E-stop button at any time would result in an immediate stoppage of all main
drives and controls, consistent with the normal E-stop function. In
addition, it could sound an alarm that would alert other personnel outside of
the immediate roll grinder area that an emergency situation exists.
Of course, there is always the possibility that in a panic situation the
operator may not have free access to press the button, enough time, or that the
inertial effects of the particular machine tool component may still cause injury
or death. For the accident mentioned above, it is impossible to say if such a
device would have saved the operator’s life. But there can be no argument that
it certainly provides a level of protection well beyond what exists now in most
roll grinders, or for that matter, other machine tools.
Actually, the first thought was to make this a “voice activated” device, which
would transmit a signal to the E-stop circuit any time a pre-programmed key word
or phrase was shouted by the operator. However, after extensive testing in
a roll shop environment, it has been concluded that the voice activation feature
is just not reliable enough for this application. The main problem is
sensitivity to background noise levels, requiring reprogramming (training) under
too many different background scenarios. This led to the simplified pushbutton
transmitter, which has been tested on a roll grinder in a noisy roll shop
environment without any failures or false triggers.
Please contact RGB Engineering for a quotation specific to a candidate roll
grinder, or any other machine tool. Costs will be less if current
electrical drawings showing the E-stop and permissive circuit diagrams for the
machine as installed are available. Along with the receiver unit,
interposing relays will be mounted in the main electrical cabinet. The
installation will be done by RGB Engineering’s field electrical engineer, or
optionally, by the customer.