US 2516993 A
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Description (OCR text may contain errors)
Aug. 1, 1950 H. HOLT 2,516,993
FOCUSING ELECTRIC LAMP Filed ma 26, 1945 I 23 6 22 l/ 2/ l3 l4 l5 F/GZ I n ventor 13 //oZ Altorney Patented Aug. 1
assignor togfildham & Son Limited, Denton,
H ,near Manchester, England, a British company Application May 26, 1945, Serial Nol 595,965
In Great Britain July 12, 1944 3 Claims.
This invention relates to electric lamps with bulbs provided with two filaments, either of which may be brought into operation by a switch. Such lamps are usually provided with reflectors, and the distribution of light intensity in the beam from the lamp depends on the position of the filament along the axis of the reflector. It is desirable to be able to vary the distribution of light intensity by moving the bulb along the axis of the reflector and, further, for a given distribution, the position of the bulb generally has to be different according to which of the two filaments is in operation. The movement of the bulb along the axis of the reflector will be termed focussing.
The object of the invention is an improved construction of lamp having a combined switch and focussing device.
According to the invention, a member is adapted to slide in the lamp case in a direction parallel to the axis of the reflector, a bulb holder is attached to the sliding member so as to move with it and a two-way switch is mounted on the member. The switch knob may be movable in one direction to focus the bulb and in another way to operate the switch.
In the accompanying drawings, which show by way of example one way of carrying out the invention, as applied to a portable battery lamp:
Figure 1 is a sectional elevation of the lamp and the upper part of the lamp case, and
Figure 2 is an underneath view correspondto Figure 1, showing the lamp and lamp case in section, and
Figure 3 is a section on the line A--A of Figure 2, showing a switch contact piece.
The lamp I is attached to the lamp case 2, containing the battery. The bulb 3 having two filaments passes axially through the reflector 4 and enters the bulb holder 5, which is adapted to slide in holes in the wall 6 of the lamp I and the adjacent wall of the lamp case 2. A member I, consisting of a plate with depending forked end 8, is adapted to slide beneath the upper wall of the case 2, being pressed against it by the spring 9 on the bolt III fixed to the case 2. The depending end 8 is forked to enter the groove II in the bulb holder 5, and to embrace the bulb holder and to make electrical contact therewith. Thus the sliding plate I is supported at one end by the spring =9 and bolt III and, at the other end by the bulb holder which, in turn, is supported by the walls of the lamp I and lamp case 2.
A rotary two-way switch is fixed to the underside of the plate I and consists of an insulating :block I2, two fixed contact pieces I3, and a movable contact piece I4 which is fixed to the metal rod I5 carrying a switch knob I6 outside the case 2. A bush I5a tight on the rod I5 prevents electrical contact with the plate I.
The plate I is slotted at I! to receive the bolt Ill and the case 2 is slotted at I8 to receive the bush I5a, whereby the plate, with the bulb and bulb holder, can be slid to the right from the position shown in full lines to the position shown in dotted lines at I, Figure 1. The plate is thus adapted for movement for focussing the bulb in the reflector.
The contact pieces I3 are preferably resilient and formed with a depression I 9 (Figure 3), into which the movable contact piece I4 may enter, as shown in Figure 3. Thereby the switch is yieldingly held in either of its two on positions, and the switch knob I6 is adapted to serve as a handle to move the plate I to focus the bulb without risk of unintentional turning to open the switch. The construction provides simple .means for switching on either of the two filaments of the bulb and :for focussing it, and both operations may be effected by means of the single knob projecting from the case, while there is no opening in the wall of the case through which dirt can enter.
As indicated in Figure 2, the contact pieces I3 are connected by wires 20, 2I, to contacts 22 in the bulb holder which in turn engage the contacts 23 of the two lamp filaments, hence each filament can be placed in circuit by rotating the switch knob I6 so as to bring the contact piece I4 onto the corresponding contact piece I3 the circuit being completed from the battery through the contact pieces I4 and I3, the leads '20, 2|, a contact 22, a contact 23, the selected filament, the bulb cap, the bulb holder 5, the plate I and back to the battery.
1. An electric lamp comprising a lamp case, a reflector supported by the lamp case, a bulb holder mounted for movement along the axis of the reflector and including a twin circuit socket for operatively receiving a twin filament bulb, a focussing member engaging the bulb holder and being supported in the lamp case for movement axially of said reflector, a two-way switch supported by the focussing member, electric connections between said switch and said socket to establish twin circuits, and an operating element operatively connected with said switch and said focussing member for selectively 3 operating said switch to establish a selected circuit :Eor the bulb and for operating said focussing member to selectively focus the resultant illumination produced by the bulb.
2. An electric lamp according to claim 1, wherein said focussing member comprises a slide, a fork depending from one end of the slide to straddle the bulb holder, a slot in the other end of the slide, a fixed guide extending inwards from the lamp case and cooperating with said 10 slot, and resilient means carried by said guide to frictionally engage said other end of the slide against the inside of said casing to hold the focussing member in selected focussing position.
3. An electric lamp according to claim 1, wherein said operating element is rotatable rela- 4 tive to said switch and focussing member to or erate the switch, said operating element also being movable longitudinally of said reflector axis to operate said focussing member.
REFERENCES CITED The following references are of record in the file of this patent:
UNITED STATES PATENTS Number Name Date 1,584,539 Hopkins May 11, 1926 1,906,268 Horowitz May 2, 1933 5 2,245,793 Kurlander June 17, 1941