US 1469690 A
Description (OCR text may contain errors)
@ct. z, 1923.
J. 6. SMITH SEARCHLIGHT, AND THE LIKE LAMP Filed March 9, 1925 Patented Oct. 2, 1923. ii
* UNITED: s'r
JOHN-GEORGE SMITH, OF MUSWELL HILL, LONDON, ENGLAND.
LAMP, SEARCHLIGHT,'AND THE LIKE.
Application filed March 9, 1923. Serial No. 623,986.
To all whom it may concern: Be it known that I, J OHN GEORGE SMITH, a subject of the Kin of Great Britain, and resident of Muswell ill, London, England, have invented certain new and useful Improvements in or Relating to Lamps, Searchlights, and the like, of which the following is a specification. t
This invention relates tolamps, searchlights and the like, and more particularly to head-lamps such as are used on motor vehicles, and has for its object to provide a lamp that will give the desired illumination at a iven range without objectionable glare, or with the glare reduced to a minimum.
The present invention comprises a beam projecting lamp having an ordinary parabolic reflector, and a source of light arranged at ,or near the focus thereof, and also an obturator co-axially arranged in the projected beam, wherein the rays from the para bolic reflector are reflected from a co-axial conical reflector on to an annular reflector arranged to reflect them to produce the desired projected beam, the co-axial conical reflector acting as the obturator. The desired projected beam maybe, for instance, one giving at a range or distance of 200 feet a disc of illumination of 20 feet diameter.
Various embodiments of the invention are illustrated diagrammatically by the accom panying drawings, wherein:
Figure 1, is a lamp showing a double distribution of the projected rays at a given range or distance. I Figure 2, is similar lamp showing a single distribution of the projected rays at a given range or' distance. 7
Figure 3, is a similar section of a lamp having a series flectors. v
Figure 4, is a section of a modification of the lamp having theinner conical reflector and the parabolic reflector reversed.
Figure 5, is a modification of the lamp shown i1 Figure 4, with the conical reflectors of parabolic contour.
The reflectors shown in the drawings are all co-axial with the projected beam, and the parallel rays referred to herein are rays from the ordinary parabolic reflector.
In Figure 1, the invention'is shown as ,applied to a lamp having a reflector 2, of
the ordinary parabolic kind, and a source longitudinal section of a a diagrammatic section of a of concentric annular re-' I for this reason as well 'as for the fact that of light 3, a similar parabolic reflector and light is used in each of the other figures.
The parallel rays intercepting conical reflector is shown at 4, and as shown in Figure 1, this conical reflector which also forms the obturator is held in place in the centre of the lamp lass 5 by means of a. bolt and nut 6, the bolt passing through the axis of the conical reflector 4, and through a centring block 7, of wood or other suitable-material and also through ahole in the centre of the glass 5.-
A washer 8, is arranged on the outside of the glass 5, and between this washer and the glass and also between the centring block 7, and the glass 5, packing discs of soft niaterial such as felt or cloth are provided. The annular conical reflectoris shown'at 9,
and is designed at its smaller diameter to fit in the open end of the parabolic reflector 2, in any suitable manner, for. instance, in the manner in which the glass or lens is usually fitted. The larger diameter of the annular reflector 9 is formed with a recess to receive the edge of the glass disc 5, and
the glass disc is held in this recess by means of a flanged ring 10, secured by a bayonet joint or 1n any suitable manner on the periphery of the'glass receiving recess in the annular reflector 9.
In this example, the illuminating or projected beam rays are projected from an annular conical'reflector't), of which the angle ofthe cone is 90, and its smallerdiameter is equalto that of the open end ofthe parabolic reflector'2, while its larger diameter is double the size of the smaller one, so that the cross section'alarea of the beam at the lamp glass will be about three times that of the open end of the parabolic reflector, and being dividedover a greater area a considerable reduction in glare will be efl'ected all the direct .rays from the parabolic re flector do not reach the eye being intercepted by the conical reflector 4, acting as an obturator. The larger or the annular reflector 9, may, however, be of .any other size that will give an annular. base or cross section of projected beam of larger than the light opening or base of the ordinary parabolic reflector 2.
The annular reflector 9, can be so designed as to give an annular beam of which the central dark portion formed by theintercepting reflector 4, will be in the form of a.
cone thereby gradually decreasing in diameter until at a given distance it will disappear and the projected light will continue therefrom as one of circular cross section at the desired range... The annular reflector can be designed togive a beam of which the outer portion is of any desired divergency. In order to bring the projected beam rays to cover the same illuminated area at the desired range as would be covered by the parabolic reflector the angles and shape of the conical and annular reflectors are correspondingly designed. In the present example to effect this'object, the conical sides of the surface of the annular reflector being straight, those of the inner cone are slightly curved correspondingly, the difference be tween the angles of the conical and annular reflectors at points where they receive and reflect any particular ray, in accordance with a. well known principle, is equal to twice the an le of the beam ray to the horizontal.
n Figure 1, the beam rays in any particular plane passing through the axes of the reflectors are projected from a radial line which for a vertical plane is the line 13, 14, formed by the intersection of the plane With the annular reflector 9, so that any diametral line such as 15, 16, on the illuminated area, at the desired range will be illuminated from two oppositely disposed radial lines as 13, 14, and 17, 18, on the annular reflector 9, this will render the distribution of the light more uniform, and
. compensate to a considerable extent for inaccuracies in the reflecting surfaces and in their co axial'alignment.
The rays projected from the annular reflector 9, from any particular radius thereon may, however, be distributed over a corresponding radius of the area of the illumination as illustrated by Figure 2.
In some types of large lamps it may be desirable to reduce the depth of the conical .and annular reflectors, and this may beeffected as illustrated by they are reduced to one half the depth of those shown in Figures 1, and 2, and in the intervening space is concentrically supported an annular reflector 94, having inner and outer conical reflecting surfaces designed to give by their combined effect the same illuminated area at the desired range as given by only one pair of inner and outer reflectors.
Only one intermediate annular reflector 94, is shown, but more may be used, each constltuting on its outer side an. inner coni- Figure 3, wherein "cal reflector for thenext larger annular reflector, and on its 1nner slde an annular reflector for the next smaller conical reflector,
all the reflectors the series being designed to produce annular-beams of light which comblne to form one single beam.
These intermediate annular conical reflectors may be supported concentrically in the same plane by means of thin radial wires, or they may be supported by fastening devices passing through holes in glass of the lamp. a
The bases of the conical and annular re flectors may be arranged in or near the same plane.
In the example shown in Figures 1 to 3, some of the rays radiating directly from the source of light will pass out at an angle through the glass and may be used for local illumination near the lamp. Such direct rays may, however, be entirely out out by designing the lamp'as illustrated in Figure 4, where n the position of the parabolic reflector 2, is reversed, and the base of the annular conical reflector 9, oppositely disposed 1 forms the inner cone4, while theportion thereof without the cylindrical surface forms the annular conical reflector 9.
It will be understood from the above that the conical intercepting reflector 4, can be made of straight or curved sides and the annular reflector 9, can also be made of straight or curved sides according to the character of the beam desired, and the two can be combined and made of one piece of transparent material such as an optical glass plate or disc having its inner and outer edges of the same shape as the conical reflectors, and prepared as surfaces adapted to reflect light through the glass plate or disc.
The glass front of the casing as illustrated is a plane disc, it may, however, be an annular piece of plate glass arranged to cover the space between the bases of the inner and outer conical reflectors, and in order to facilitate cleaning is preferably made detachable in any suitable manner such as used at 1. A light projector comprising a parabolic reflector, a frusto conical reflector at and around the open end of the parabolic reflector and attached thereto and a conical reflector arranged coaxially of the parabolic and frusto conical reflectors and in the latter and.also forming an obturator, the surface of said conical reflector and obturator being parallel with the iriner surface of the frusto-conical reflector and the apex of said conical reflector and obturator being presented toward the smaller end of the pararanged around said parabolic and conical reflectors and at the open end of the former, the said conical reflector also forming .an obturator, the surface of said conical reflector and obturator being parallel with the inner surface of the frusto-conical reflector "and the apex of said conical reflectonand obturator being presented toward the smaller end of the parabolic reflector.
3. A beam pro ecting lamp comprising in combination a parabolic reflector adapted to contain thellght source of the projected beam,'a light obturator, two concentric convex con cal' reflectors, and two concentric annular concave conlcal reflectors, the five reflectors and the obturator being co-axially arranged and the convex and concave conical reflectors arranged concentrically within the annular reflector at the open end 'of the parabolic reflector, and so constructed and associated with respect'to one another that both convex conical reflectorswill act as the obturator to divide portions of the rays projected directly from the source of light by the parabolic reflector,
which will reflect the two portions of the rays to combine to form the projected beam over the edge of the obturator.
In witness whereof I 'aflix my si nature. JOHN GEORGE MITHi but each will reflectits portion of such rays radially outwards onto its adjacent annular concave reflector