Allowable Pinching Force

[Farhan_Fraser]

We design and manufacture a machine in which an operator must position film between two jaws. In some applications the operator must hold the film while the jaws close or reposition the bag after the jaws have closed. This can represents a significant safety hazard. I redesigned all our machines to move away from a foot pedal control, however this limits functionality

We see machines being sold for this application with a foot pedal to operate the jaws. I wonder how this is achieved without guarding or double palm buttons to keep the operator out of the way of the closing jaws. Here is an example:

https://www.youtube.com/watch?v=trz1zDW8Yqs

In doing some research, I found Specification EVS-EN 417-7:2006+A1:2008 with the following statement in section 5.2.2.1.2 Safety by Design:
The moving parts can be considered safe by design if the force exerted does not exceed 75N or 150 N if the movement is automatically reversed if resistance is encountered.

Does anybody know if there is an equivalent spec with this information applicable to North America?

Thanks in advance.

 

[3DDave]

How much force is required?

I would think about using a pull-cable/spring return foot pedal such that the jaws are operated by a series spring to limit the force to the required amount and then a stop to take any greater pedal force. Mostly people won't pinch their fingers if they are supplying the force.

If it's to be automatic I would have a leading set of jaws that have to close first, lightly spring loaded, with position switches to sense if they fail to close to bag thickness before the main jaws close. They could be polycarbonate if seeing the heated jaws is required.

Is that standard number the correct one? All I find is a reference to non-refillable gas cylinders.

 

[dvd]

Reacted over a small area, like part of a fingernail, that 75 N would be painful.