I see another probably more likely interpretation of "knife edge and finger stock" in this context. Look up a knife edge fuse on the internet. Presumably the socket the fuse seats in would be the finger stock.
Mike Sherman Graco Inc. > On February 5, 2019 at 2:34 PM "Schmidt, Mark" <[email protected]> wrote: > > > Please see test below: > > > > “Safety Interlocks [21 CFR 1020.40(c)(4)(i)]:Each door of a cabinet x-ray > system shall have a minimum of two safety interlocks. One, but not both of > the required interlocks shall be such that door opening results in physical > disconnection of the energy supply circuit to the high-voltage generator, and > such disconnection shall not be dependent upon any moving part other than the > door. [Note: Safety interlock is defined in 21 CFR 1020.40(b)(11).] > > > > The primary door interlock should be of conventional design. The second > door interlock must physically disconnect the energy supply circuit to the > high voltage generator. Physical disconnection means opening the energy > supply circuit by removing a piece of the circuit. This is usually > accomplished with a ‘knife-edge and finger stock’ or ‘plug and socket’ type > connection. It is good practice to assure the primary interlock will remove > power from the energy supply circuit before the physical disconnection > occurs. Relays, micro switches, and ‘safety switches’ all contain moving > parts and, therefore, cannot be used to satisfy the requirement that the > physical disconnect interlock is "not dependent on any moving part other than > the door."” > > > > Compliance Guide for Cabinet X-Ray Systems > https://www.fda.gov/MedicalDevices/ucm094358.htm > > > > > > Mark > > > > > > From: Nyffenegger, Dave [mailto:[email protected]] > Sent: Tuesday, February 5, 2019 12:31 PM > To: [email protected] > Subject: Re: [PSES] A question about FDA language and interlocking devices > > > > That seems to make more sense. I don’t know anything about X-ray > requirements but the FDA requirements laser interlocks are not specific, only > referring to “interlocks”. > > -Dave > > > > From: MIKE SHERMAN [mailto:[email protected]] > Sent: Tuesday, February 05, 2019 12:27 PM > To: [email protected] mailto:[email protected] > Subject: Re: [PSES] A question about FDA language and interlocking devices > > > > Doug -- > > > > "knife-edge and finger stock" sounds more like the gasketing around the > door to keep the radiation inside. I think you'll find similar gasketing on > doors to EMC chambers. I've not heard of this term applied to interlock > switches. > > > > Mike Sherman > > Graco Inc. > > > > > > > > On February 5, 2019 at 10:35 AM Doug Nix <[email protected] > > mailto:[email protected] > wrote: > > > > Colleagues, > > > > > > > > I had a question come my way yesterday that I need a little help > > with. Here’s the question: > > > > > > > > > > > > > > I have a customer that produces X-ray equipment. The FDA > > > requires that the door that gives access to the X-ray source must have an > > > interlock with a ‘knife-edge and finger stock’ type connection. Also the > > > FDA mentions that interlocks should be of conventional design. What is > > > understood by “conventional design”? > > > > > > > > > > > > > > My reading on this requirement is that any conventional > > electromechanical interlocking device like this: > > > > [Image result for keyed interlock switch images] > > > > will meet the basic requirements as described by the FDA as > > “knife-edge and fingerstock” connection, but I am concerned that this may > > not be at all what is meant. > > > > > > > > As always, any guidance you can offer will be welcomed and > > appreciated! > > > > > > > > Best, > > > > > > > > Doug Nix > > [email protected] mailto:[email protected] > > +1 (519) 729-5704 > > > > > > > > > > > > > > > > > - > > ---------------------------------------------------------------- > > > > This message is from the IEEE Product Safety Engineering Society > > emc-pstc discussion list. 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To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
