Electric lamp and discharge devices: systems – Combined load device or load device temperature modifying... – Plural circuit elements
Patent
1989-12-01
1991-05-21
Pascal, Robert J.
Electric lamp and discharge devices: systems
Combined load device or load device temperature modifying...
Plural circuit elements
315 52, 315200R, H05B 3700
Patent
active
050178334
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a pilot light assembly for indicating the status of an electrical device powered at mains voltage.
2. Description of Prior Art
One application is in an electrical limit switch, where it is ususal to provide a pilot light to indicate the "on" state of the switch. In the past, this has generally been done by means of a neon lamp connected across the appropriate terminals of the switch. The neon lamp is usually secured to a cover member and connected to the switch terminals by flying leads. Assembling such an arrangement can be awkward and we have found that it commonly happens that, after the flying leads have been connected, the cover member (which can be of heavy construction for safety reasons) is dropped by the assembly person. The resulting strain on the leads can cause bad joints or fracture the wire.
SUMMARY OF THE INVENTION
One object of the present invention is to provide a pilot light assembly which can be wired in circuit independently of its being mounted to a cover or other support, and readily secured to or removed from the support after wiring.
Another object of the invention is to provide a pilot light assembly which is entirely solid state, while having dimensions small enough to fit into a restricted space, e.g. the space available in an existing limit switch for a neon indicator.
The invention is defined in the appended claims.
Embodiments of the invention will now be described, by way of example only, with reference to the drawings, in which:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional side view showing one form of assembly in accordance with the invention in position on a supporting panel;
FIG. 2 is a cross-sectional side view of a housing of a modified embodiment in disassembled condition;
FIG. 3 shows part of the housing of FIG. 2 with components mounted thereon; and
FIGS. 4 to 6 are circuit diagrams of alternative circuitry for the assembly .
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1, a housing 10 comprising a generally cylindrical plastics moulding has a central projecting portion 12 formed with an exterior screw thread 14 and an end window 16. Conveniently, the entire housing 10 is moulded from a transparent or translucent material to form the window 16 integrally. The housing is mounted on a supporting panel 18 by screwing the projecting portion 12 into a correspondingly threaded hole 20 such that the surface of the window 16 lies flush with or just above the outer surface of the panel 18. The panel 18 may be, for example, part of the cover of a limit switch.
IF required by the particular application, sealing may be provided by a gasket 22 trapped between the panel 18 and a shoulder 24 formed on the housing 10.
A printed circuit board (pcb) 26 is positioned within the housing 10 and mounts a light-emitting diode (LED) 28 extending into the hollow interior volume of the projecting portion 12, which is of a shape and size corresponding substantially to that of the LED 28, so as to be visible through the window 16. Circuit components to be described are mounted on the opposite surface of the pcb 26, flying leads 30 being provided for connecting the assembly to the circuit to be monitored.
The volume indicated at 32 is filled with a potting compound, e.g. epoxy resin, to encapsulate the components and secure the pcb 26 in position.
An identification label 33 is attached to the outside of the panel 18. This is suitably a self-adhesive plastic label with a clear area through which the LED 28 may be viewed. The label 33 also provides additional sealing.
FIGS. 2 and 3 show a modified embodiment in which like parts are denoted by like reference numerals. The housing 10 is formed in two parts 10a,10b which can be snap-fitted together by teeth 34 engaging in notches 36, thus enabling mounting and wiring to be carried out separately.
FIG. 4 shows the circuit arrangement for use with d.c. power. Since the LED 28 requires a low operating voltage (typically 1.8V) and the c
REFERENCES:
patent: 4725759 (1988-02-01), Tachikawa
Elektronik, vol. 34, No. 14, Jul. 12, 1985 (Munich, DE), H. Zeltwangen; "SMD-Technik in kleineren und mittleren unternehmen", pp. 43-70.
Clarke Geoffrey
Harris Geoffrey J.
Femal Michael J.
Pascal Robert J.
Square D Company
LandOfFree
Pilot light assembly does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Pilot light assembly, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Pilot light assembly will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-240698