Electrical transmission or interconnection systems – Personnel safety or limit control features
Patent
1994-04-20
1996-12-10
Scott, J. R.
Electrical transmission or interconnection systems
Personnel safety or limit control features
200600, 173170, 192129R, 307140, H01H 3500, H02H 500, H03K 1796
Patent
active
055833861
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a safety circuit in electrically operated devices, more particularly, to such a device having several interacting switch elements to enable current to flow to operate the device. These circuits are used with electrically operated devices to eliminate the risk of injury to the user in the event that the devices are handled improperly.
Such circuits generally provide that an operating current or at least a control current is directly switched. The switches themselves are usually mechanical in structure. However, it has been found that such known safety circuits have serious drawbacks and disadvantages as pointed out below.
One disadvantage is that activation requires only that one or more switches be depressed. If the user so desires, this is often done in practice, he can operate at least one switch by simply attaching insulating tape to maintain that switch in a depressed or activated state.
If larger safety devices are involved, in practice, an additional "bridge" is quite often installed by the users. If magnetic switches are involved, these are often rendered inoperative by add-on permanent magnets.
The voltages used in these devices often lie in a range that is dangerous to humans.
The mechanisms of such mechanical switches, and thus their function, are susceptible to external forces, such as atmospheric humidity, corrosion and fouling by dirt, dust or other small debris.
Because of their size, it is not always possible to position the switches optimally on the device.
According to U.S. Pat. No. 3,651,391, the embodiment in FIGS. 1 and 2 has a first sensor switch as an on-off switch, and a second sensor switch maintains the flow of current. This second switch is used solely as a safety switch.
The disadvantages of this prior art structure are rapidly apparent.
If the first switch (on-off switch) is turned on, the device can be activated unintentionally by accidentally touching the second sensor switch. There then exists a risk of injury to the user. To reduce this risk, at least one monitor must be provided in connection with the first one-off switch. Thus, this structure does not provide the safety objective according to the present invention and is, moreover, expensive.
In a second embodiment (FIGS. 5 and 6) of U.S. Pat. No. 3,651,391, two hands (body parts) are required to operate the device, one hand acutates only a first sensor switch and the other hand only a second sensor switch. In this embodiment, only the presence of the respective hand, but not its posture or position, is critical. It is not possible to require both the presence of a hand and a particular position of this hand with only one sensor switch per body part. This structure is therefore also not usable in a device that can be held and oeprated with only one hand.
This kind of contemplated safety is often circumvented by the user by short-circuiting one of the switches in order to increase the speed of the operating sequence.
According to the present invention, circumventing safety in this way is not possible. The present invention requires that the posture of each body to be predetermined.
According to a third embodiment (FIGS. 7, 8 and 9) of U.S. Pat. No. 3,651,391, two sensor switches are provided, both of which must be activated to produce a flow of current. One of the switches is provided to turn the device on and off. The second switch keeps the current flowing as long as it is touched. With this structure also, a situation can arise where the device is activated with the first swtich turned on by accidentally touching the second switch. Also, the posture of the body part here is by no means critical.
DE-PS (German Patent) 37 16 623 C1, discloses a tilt switch which allows a current to flow only if the switch reaches a certain angle of inclination. Such a tilt switch is utilized only as an auxiliary element, according to the present invention, which can replace one of the two contact elements as disclosed.
Contact elements (sensor switches) are basically known from DE 27
REFERENCES:
patent: 3651391 (1972-03-01), Vogelsberg
patent: 3737670 (1973-06-01), Larson
patent: 3787732 (1974-01-01), Larson
patent: 4211497 (1980-07-01), Montgomery
patent: 4236086 (1980-11-01), Hoebel
patent: 4493377 (1985-01-01), Gunther et al.
patent: 4584519 (1986-04-01), Groudis
patent: 4794273 (1988-12-01), McCullough et al.
patent: 4859869 (1989-08-01), Heuwinkel et al.
patent: 4965693 (1990-10-01), Aoki
patent: 5013891 (1991-05-01), Shoemaker
patent: 5039843 (1991-08-01), Muller
Meixner Hans-Werner
Voit Alexander
Jaskiewicz Edmund M.
Pi-Patente GmbH, Entwicklung und Verwertung
Scott J. R.
LandOfFree
Safety circuit in electrically operated devices does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Safety circuit in electrically operated devices, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Safety circuit in electrically operated devices will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-425909