US2511558A - Electric lighting appliance - Google Patents

Description

June 13, 1950 P w. BAKER ELECTRIC LIGHTING APPLIANCE 2 Sheets-Sheet 1 Filed Oct. 12, 1948 Inventor PERCY WILLIAM BAKER Agent June 13, 1950 P. w. BAKER ELECTRIC LIGHTING APPLIANCE 2 Sheets-Sheet 2 Filed Oct. 12, 1948 Inventor PERCY WILLIAM BAKER Agent Patented June 13, 1950 ELECTRIC LIGHTING APPLIANCE Percy William Baker, Wroxham, England Application October 12, 1948, Serial No. 54,080 In Great BritainOctober 20, 1947 4 Claims.

The present invention relates to electric lighting appliances and is concerned in particular with a dimming device whereby the luminous intensity of the light source may be readily controlled in a convenient, simple and cheap manner.

The invention is in particular applicable to domestic lighting appliances such as table-or floor lamps. If an attempt were made to use a variable resistance for dimming purposes difiiculty-would be encountered in dissipating the heat produced in such a resistance, without part of the appliance reaching such a temperature that the possibility arises of damage to the polished surface of, for example, a table. The present invention is more especially concerned with the provision of an appliance including a dimmer in which the energy dissipated in the dimmer is reduced to a very low figure.

In accordance with the present invention a. variable or selectively adjustable capacitor is provided in the circuit to the light source. Such capacitor may be continuously variable or alternatively a series of fixed condensers may be connected into circuit by means of a suitable tapping switch.

Preferably the capacitor or capacitors and a control member are located in a hollow base of the lamp, the control member including a knob extending through the hollow base in a convenient position for operation.

In a convenient arrangement a plurality of capacitors are assembled into a block unit and a rotary control switch is provided adapted to connect one or more of said capacitors in parallel one with the other, in the circuit to the lamp. Conveniently the leads from each capacitor unit include a composition resistor of sufiicient value to prevent or minimise sparking at the switch contacts. Such switch preferably includes an "01? position and a full-on position in which the capacitors are not in circuit.

Such capacitors, when used on an alternating current supply, are chosen to have appropriate reactances to provide a suficient dimming efiect in any desired number of stages, and they serve to limit the current flowing without dissipating themselves any appreciable amount of energy.

A table lamp incorporating the features of this invention is shown by way of example on the accompanying drawings wherein:

Fig. 1 is a vertical section of the lamp with the dimming control device in the base, and

arrangement of the parts in the base.

Fig. 3 is a sectional plan showing an alternative construction of the invention.

The table lamp shown on the drawings is intended to be representative of the type of appliance to which the invention may be applied, and it comprises a base member 3 adapted to rest on a floor or table and an upright pillar 4 carrying a lamp holder 5 at the upper end, to which a lamp shade may be attached by methods well known in the art. The pillar may if desired, and as shown in Figs. 1 and 2, include a central tube 6 through which the flexible wire lead 3 passes to the lamp holder 5 and which serves to clamp the pillar l. In the said base, a rotary switch 8 of any suitable type is provided adapted to connect any of a plurality of capacitors into circuit feeding the lamp holder 5, and to provide in the fullon position a direct electrical connection from the supply to the lamp holder.

Preferably, and as shown in Figs. 1 and 2 the capacitors are incorporated into a condenser lock 9 having a metallic case which can be fastened to a separate bottom plate In secured to the underside of the base 3 by means of screws fixing into lugs II. The switch 8 is also carried by the bottom plate it and may be of the well known wafer" type, having means to locate the switch in its various working positions and including a plurality of fixed contacts i2 and a rotary contact segment I3, on a spindle l4 extended through an aperture in the upper face of the base 3 and carrying a knob I5. One end contact i2 is connected to the incoming supply lead while the other end contact i2 is connected to a common lead of the several capacitors and to one wire of the lead 1, the other wire of which goes to the other incoming lead; a connector block [6 may be used to make these connections. The intermediate contacts l2 are connected to the free leads of the several capacitors in block 9; preferably resistors H, which may be of the composition type, are included in these leads to minimise sparking at the contacts I2 when the switch is operated. The values of these resistors are only sufficient for this purpose; that is to say they are not of such a high resistance that any appreciable energy is dissipated therein and a value of about 50 to ohms would normally be chosen.

With the switch 8 in the position shown the circuit to the lamp is broken and as the segment 13 is moved in the anti-clockwise direction, in the first position one onl of the capacitors is connected into circuit resulting in only a small current being allowed to pass to the lamp. In the next position a second capacitor is connected in parallel with the former and more current is allowed to pass and so on until the segment I3 reaches the far end contact I2 when all the capacitors are short circuited and current is fed directly from the supply to the lamp. Thereby a progressive illumination is obtained as the knob I5 is turned, varying from oil to full illumination.

In the alternative construction shown in Fig. 3 the condenser block 9 is of the tubular type and is accommodated within the lower part of the pillar 4, which in this case is of a sufliciently large diameter for this purpose. Preferably the condenser block is provided with an encircling clip I8 to support the block on lugs 19 provided at the base of the pillar, the block being fixed to the lugs by means of screws 20. In this case the switch 8 of a similar construction to Figs. 1 and 2 and the leads from the switch to the condenser block are provided with resistors H. In the construction "shown in Figs. 1 and 2 the base plate 10 carries the switch and the condenser block but other methods of assembly may be adopted if desired. Thus, as also shown in Fig. 3, the switch 8 may be mounted in or on the base member 3 with the knob projecting from the upper face and the bottom plate It then merely acts as a closure member for the base member 3.

The invention is not limited to the connection of capacitors in parallel one with the other to obtain the progressive dimming action as a plurality of capacitors of progressively increasing value may be connected alternatively into circuit by the action of switch 8. Furthermore a progressively variable capacitor could also be used.

It will of course be realised that the dimming devices according to the present invention are only applicable for use on alternating current circuits although no damage would be done if they were connected to a direct current circuit as the capacitors would prevent current flow.

WhatIclaim is:

1. An electric lighting appliance for use on alternating current circuits, comprising means to support a lamp bulb, means to supply current thereto, a plurality of capacitors, switch means to control the connection of the capacitors in parallel one with the other in the lamp circuit,

and a damper resistor associated with each capacitor in the connection to the switch means.

2. The appliance according to claim 1, wherein said switch means comprise a rotary switch having a plurality of contacts, each connected to a different capacitor, and a movable contact seg ment adapted to progressively connect or disconnect said contacts one upon the other and to bring the capacitors in parallel on with the other and in series with the circuit to the light source.

3. An electric lighting appliance comprising circuit means to feed current from input terminals to a light source, a dimming control switch, said switch having a plurality of contacts and a movable segment to progressively connect or disconnect said contacts, a plurality of condensers, one terminal of each condenser being connected to one of said contacts, the other terminal of each condenser being connected to the circuit feeding the light source, the segment being also connected to said circuit means, and a low value resistor connected to a terminal of each condenser to reduce the magnitude of the circulating current between adjacent condensers when said segment is moved to connect an additional condenser, or disconnect a condenser from the connection, in parallel with at least one condenser already connected to the circuit means.

4. The appliance according to claim 3, wher in one end contact of said contacts is connected to the supply and the other end contact is connected to the light source and to a common lead for the several resistors so that one end position of the control switch is an off position while the other end position is a full on position with the resistors not in use.

PERCY WILLIAM BAKER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,749,520 Voorhoeve Mar. 4, 1930 FOREIGN PATENTS Number Country Date 413,484 Great Britain July 19, 1934

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