GB2356448A - Flashlight with improved reflector - Google Patents

Abstract

A flashlight comprises :- <SL> <LI>(i) a barrel for retaining at least one dry cell battery <LI>(ii) a lamp bulb; <LI>(iii) a reflector; <LI>(iv) means for holding the lamp bulb in a pre-determined position in relation to the reflector; <LI>(v) first conductive element(s) for electrically coupling a first electrode of the battery to a first electrode of the lamp bulb; <LI>(vi) second conductive element(s) for electrically coupling a second electrode of the battery to a second electrode of the lamp bulb; <LI>(vii) a switch; </SL> wherein the shape of the reflector follows that of a b-spline curve. Preferably the angle of the reflector surface changes by 5{ over every 10{ of arc as measured from the focal point of the reflector.

Description

2356448 IMPROVED LIGHTING APPARATUS

Field of the invention

The present invention relates primarily to searchlights, flashlights or torches. It is particularly applicable, but in no way limited, to lighting apparatus for providing a focused beam of bright light from a hand-held or free-standing unit.

Background to the invention 10

A wide variety of searchlights, flashlights, flashlamps and torches are already known. These terms have sometimes been used interchangeably to define outdoor lamps designed to throw a strong beam of light in a particular direction. For simplicity, in the following description, the term "flashlight" will be used as a generic term to describe any lighting apparatus, static, vehicle mounted or hand- held, which is designed to throw out a strong beam of light.

Flashlights of varying sizes and shapes are well-known in the art. In particular, certain of such known flashlights utilise two or more dry cell batteries, carried in series in a cylindrical tube serving as a handle for the flashlight, as their source of electrical energy. Typically, an electrical current is established from one electrode of the battery through a conductor to a switch, then through a conductor to one electrode of the lamp bulb. After passing through the filament of the lamp bulb, the electrical circuit emerges through a second electrode of the lamp bulb in electrical contact with a conductor, which in turn is in electrical contact with the flashlight housing. The flashlight housing usually provides an electrical conduction path to an 1 electrical conductor, generally a spring element, in contact with the other- electrode of the battery. Actuation of the switch to complete the electrical circuit enables electrical current to pass through the filament, thereby generating light which is typically focused by a reflector to form a beam of light.

The production of light from such flashlights has often been degraded by the quality of the reflector utilised and the optical characteristics of any lens interposed in the beam path. Moreover, intense light beams have often required the incorporation of as many as seven dry cell batteries in series, thus resulting in a flashlight having significant size and weight.

Efforts at improving such flashlights have primarily addressed the quality of the optical characteristics. The production of more highly reflective, well-defined reflectors, which may be incorporated within such flashlights, have been found to provide a more well-defined focus thereby enhancing the quality of the light beam produced. Additionally, several advances have been achieved in the light admitting characteristics of flashlight lamp bulbs.

Since there exists a wide variety of uses for hand-held flashlights, the development of a flashlight having a variable focus, which produces a beam of light having a variable dispersion, has been accomplished, such as described in EP0236113 and EP0313285 (Mag Instruments, Inc.).

However, despite these known developments the amount of light, measuredin LVX 25 levels, failing on a target placed a certain distance from the lens is still relatively low. Thus, a typical battery powered hand-held flashlight operating at 7.5 volts provides' 2 approximately 100 LUX at a distance of two metres from the reflector lens surface. In the case of flashlights with a light beam having a variable dispersion this figure can be varied between certain limits. However, even with the beam at its most concentrated, a typical maximum illumination is only in the region of 100 LUX at 2m. 5 This is woefully inadequate if one is using the flashlight to search an area for a fugitive, as in the case of police or the armed forces.

It is accordingly an object of the present invention to provide a flashlight having 10 improved light output and optical characteristics.

Summary of the invention

According to a first aspect of the present invention there is provided a flashlight comprising:

(i) a barrel for retaining at least one dry cell battery (ii) a lamp bulb; (iii) a reflector; (iv) means for holding the lamp bulb in a pre-determined position in relation to the reflector; (v) a substantially planar lens over the reflector; (vi) first conductive element(s) for electrically coupling a first electrode of the battery to a first electrode of the lamp bulb; (vii) second conductive element(s) for electrically coupling a second electrode of the battery to a second electrode of the lamp bulb; (viii) a switch; 3 characterised in that the shape of the reflector follows that of a b- spline curve.

Preferably the b-spline curve is of a form in which the angle of the reflector surface changes by substantially 50 over every 101 of arc as measured from the focal point 5 of the reflector. This provides a solid beam of light of maximum definition.

Preferably the internal surface of the reflector is coated with a highly reflective finish such as aluminiurn deposited from the vapour phase.

In a particularly preferred embodiment the lens over the reflector incorporates a reflective surface directly above the lamp bulb, said reflective surface being adapted to reflect infra-red and ultra-violet light back onto the reflector and thus back onto the lamp bulb in order to set up a feedback loop.

Preferably the reflective coating applied to the lens is the same as the coating applied to the internal surface of the reflector.

In a further preferred embodiment the reflector forms part of a head assembly which further incorporates a means for retaining the lamp bulb in a pre-determined position and a screw-threaded region for securing the head assembly to the barrel and characterised in that the head assembly, reflector, lamp bulb retainer and screw thread region is formed from a single piece of metal.

Preferably the external surface of the head assembly incorporates cooling fins adapted to assist in dissipating the heat produced by the bulb.

4 Preferably the screw threaded region incorporates a round profile internal thread to minimise the risk of cross-threading.

Preferably the lamp bulb retaining means is so sized and shaped that the lamp bulb holder is accommodated entirely within a retaining means and is held in place by an O-ring. This O-ring arrangement is a quick and simple fixing arrangement and prevents any parts getting lost while a bulb is being changed.

Preferably the lamp bulb is run at an overvoltage in order to increase light output.

This produces a significantly greater light output compared to operation at the lamp bulb's design voltage.

Preferably the flashlight further incorporates a flexible carrying strap, having a plurality of fixings, said fixings providing the strap with a number of fixing configurations. In one configuration, the strap is adapted to encircle the region of barrel incorporating the switch and wherein an aperture in the strap is adapted to pass over the switch in a close fitting manner such that, with the strap fixed in place, the switch becomes inoperable.

Brief description of the drawings

The invention will now be described by way of example only with reference to the following drawings wherein:- Figure 1 illustrates a part cross-sectional view of a flashlight incorporating embodiments of the present invention; Figure 2 illustrates a b-spline curve profile for a reflector; Figures 3 to 7 illustrate photographs of the external features of a flashlight according 5 to the present invention; Figure 8 illustrates the flashlight of figures 3 to 7 with the head assembly removed showing one method of retaining the bulb holder.

Detailed description of preferred embodiments

The invention will now be described by way of example only. These are not the only ways in which the invention can be put into practice. However, they are the best ways currently known to the Applicant.

Referring to figure 1, this illustrates a partial cross-section of a flashlight incorporating various embodiments of the invention. Whilst these embodiments are illustrated, and will be described, combined into one flashlight, it should be appreciated that they could be used singly, or in any combination, to improve the performance of a known flashlight.

Figure 1 illustrates a flashlight 10 comprising a reflector 11, a lamp bulb 13 and a lens 12. The lamp bulb 13 is held in a bulb holder 14 which sits inside a lamp bulb holder retainer 15. The reflector 11, lens 12 and lamp bulb holder retainer 15 make up a head assembly. Reflector 11 incorporates a screw threaded region 17 which corresponds to an extemal threaded region on a barrel 22, the barrel being adapted 6 to accommodate a series of dry cell batteries (not shown). Preferably the screw threads have a round profile to minimise cross-threading and the possibility of jamming should dirt get into the threads.

First and second conducting means (not shown) are provided within the barrel to electrically couple first and second electrodes on the lamp bulb to corresponding battery terminals.

Turning now to the specific details of the various embodiments, the reflector 11 is formed in a specific shape, or to be more precise, the internal surface of the reflector is formed in a specific shape. It has surprisingly been discovered that a reflective surface following a specific b-spline curve profile provides a particularly uniform, focussed light beam. One optimum type of curve is illustrated in figure 2.

In this example the angle of the reflector surface with respect to a line perpendicular to the central axis of the reflector increases cumulatively by 50 for every 100 of arc as measured from the focal point of the lens and said central axis.

The nature of b-spline curves is known in the branch of mathematics dealing with parametric cubic curves and surfaces. For example, such curves are described in "Fundamentals of Interactive Computer Graphics" by James D Foley and Andries van Dam published by Addison-Wesley publishing company sections 13.5 and 13.6. The entire text of this publication is hereby incorporated by reference and forms an integral part of this disclosure.

Bending or otherwise forming a sheet of metal substantially to the 3D shape described above is difficult but not impossible. It is, however, preferable to turn the 7 reflector from a solid bar of metal, such as aluminium or aluminium alloy, preferably by using a cric lathe. This provides a particularly accurate result and the internal surface of the reflector can then be polished to a highly reflective finish.

There are additional advantages of starting from a solid metal bar. First, the bulbs used in these flashlights, described below, generate a significant amount of heat which has to be.dissipated. Cooling fins 18, 19 and 20 can be turned into the outer surface of the reflector and are in direct contact with the inner surface which is being heated. If the reflector is a separate component, as in typical conventional torches, then there is inevitably an air gap between the inner reflective surface and the outer, heat dissipating surface containing the cooling fins.

The cooling fins may be formed in a wide variety of shapes and sizes depending on the amount of heat to be dissipated. They may extend proud of the general line of the head assembly or together form the profile of the profile of the outer head surface. This may depend in part on the aesthetic appeal required.

Secondly, a shoulder 25 can be formed on which the lamp bulb holder 14 sits. This provides a substantially fixed and rigid arrangement such that the bulb, when fitted, is inevitably situated accurately at the focal length of the lens.

The lamp bulb holder 14 is preferably formed from a ceramic material and incorporates in a first face connections to accommodate a bulb. The opposite face of the holder has electrical wire connections leading to the positive and negative terminals of the battery pack respectively.

8 An example of a suitable bulb is model HLX 64625. This type of bulb is normally used in a mains powered projector.

One important embodiment of the invention is the method of holding the lamp bulb holder in place within the lamp bulb holder retaining means 15. In this example the holder is held in place by an O-ring 16. The O-ring engages in a corresponding recess in the retainer 15.

The 0-ring is typically made froma heat-resistant rubber, capable of withstanding the temperatures generated by the bulb. Such 0-rings are commercially available in a variety of sizes, for example for use in hydraulic seals. Because the 0-ring nests within a recess having substantially the same profile as itself it provides a firm retaining means against movement of the lamp bulb holder, and thus the lamp bulb away from the optimum focal point of the reflector. Only when the 0-ring is prized out of its seating can the lamp bulb holder be removed.

Optionally, the retainer 15 may also be formed integrally with the other head assembly components from the solid bar of metal.

In a particularly preferred embodiment the internal surface of the reflector is coated with a highly reflective material such as aluminium. Processes for depositing highly reflective layers of aluminium ie. silvering are known to the materials specialist.

A substantially planar lens 12 covers the reflector forming a substantially water-fight seal. In a further important embodiment the lens incorporates a reflective area 22 aligned with the end of the bulb and symmetrically arranged about the central axis of 9 the reflector. The reflective surface is preferably the same coating as applied to the reflector itself. In this example it is applied to the inner surface of the lens in a small circular area in the centre of the lens. This reflected surface reflects all visible, infrared and ultra- violet radiation. This reflective radiation is directed back towards the inner reflector surface and thus back to the lamp itself. This induces a feedback loop which causes the bulb to emit more visible light and less intra-red and ultraviolet radiation than would otherwise be the case. Whilst the exact details of the mechanism of this feedback loop are not fully understood, it is believed that the reflected radiation increases the operating temperature of the bulb and decreases the output of unwanted infra-red and ultra-violet wavelengths.

In a further preferred embodiment the bulb is run at a voltage higher than its design voltage. By way of example, a photoxexon bulb such as detailed above, designed to operate at 12 volts, is run at a substantially constant running voltage of 16.75 volts. This overvoltage together with the reflector design, the feedback loop, and a highly reflective reflector coating provides an intense white light. Using a nickel metal HIT battery pack of 12 batteries in series, when fully charged, these give a 16.75 volt potential difference.

This arrangement can give an intense white light of 165,000 LUX at a surface two metres from the lens. This is approximately 1.5 times the intensity of bright sunlight.

This is a far brighter light than known flashlights of a comparable size can produce Turning now to further details of the invention, the on-off switch is in the form of a toggle switch. Moving the switch in one direction turns on the light and the switch remains displaced in that direction. The light remains on until the switch is returned manually to its original setting. Moving the switch in the opposition direction, against the action of a spring, caused the light to come on momentarily so long as the switch is held in that displaced position. It is thus possible to signal with the flashlight or provide illumination for a short period.

The flashlight also incorporates a flexible handle 30 which incorporates some important features. These are illustrated in figures 3 to 8 inclusive. Collars 31 and 32 at opposite ends of the barrel provide anchoring points for the handle in a first configuration. This is the typical carrying configuration and is illustrated in Figure 3.

However, a further fixing point 33 enables the handle to be attached to the flashlight in a second configuration in the form of a carrying loop. This configuration is illustrated more clearly in figures 5, 6 and 7. The collars and handle are preferably made of metal. However, any suitable material, including synthetic plastics materials, as selected by the materials specialist may be used.

A further important feature of the handle is an aperture 34 close to the fixing nearest to the reflector. This aperture is designed to fit over the switch 21 when the handle is in a third configuration. The handle is designed to wrap substantially around the collar nearest to the reflector and in this configuration the switch becomes inoperable. This is a particularly useful safety feature because it means that the flashlight cannot be turned on accidentally.

Figure 8 illustrates the -lamp holder retaining means and demonstrates a further important embodiment of the invention. Once the head assembly is unscrewed from the barrel this reveals the O-ring 16 holding the lamp holder in place. The O-ring is easily removed using any pointed tool to prise is from its recess. However, it will be 11 appreciated that the wires connecting the bulb holder to the battery pass through the O-ring and prevent the O-ring from becoming lost. The O-ring is too small to pass easily over the bulb holder and thus remains loosely sifting around the conducting wires. Once the bulb has been replaced and the lamp bulb holder replaced into its retainer then the O-ring is simply passed up the wires and repositioned into the recess. There are therefore no parts which can be damaged or mislaid during the process of changing a bulb. This contrasts with the general arrangement inside a torch or flashlight in which there are numerous components which have to be separated and put to one side while the bulb is replaced. These can easily be mislaid and the flashlight then becomes useless until replacement(s) are obtained.

In summary, an improved flashlight has been developed with a variety of novel features. These can be applied equally well to handheld, battery operated units or larger, static units powered by mains electricity. The principles apply equally well to vehicle mounted or mobile units. In this context the term vehicle has a very broad meaning and includes any form of land, sea or air conveyance.

The present application describes a new flashlight unit which includes the following features:

1. The unit produces a uniform beam of light with no rings or dark spots contained within the light because of the bulb and reflector coating used. It also creates a very white light at about 165,000 LUX.

2. The efficiency of the unit is enhanced by means of feeding back the infra-red and ultra-violet wave lengths from the reflector to the glass then back to the 12 reflector and back to the bulb element. This can be described as a feedback loop.

3. The reflector is designed to maximise the output on a photo xenon bulb running at 16.75 volts (it is designed to run at 12 volts) with the circular coating on the glass as well as the reflector coating to produce the desired beam shape and colour.

4. It uses a. Ni metal hid battery pack containing 12 cells in series. When fully charged they reach 16.75 volts. It is also extremely compact for its power and light output.

The key features are:- The head is machined from solid round bar, because of the heat and the reflector shape. It also has grooves cut in it for cooling.

It uses a round profile internal thread so that it cannot be cross threaded and also will not jam up because of dirt fouling the ends etc.

At the rear internal of the head of the bulb holder housing is machined from solid stock and then bored to allow the holder to enter in, then this in turn allows the head to rotate while the body and bulb stay stationary.

This arrangement also allows the unit to be dismantled with no special tools and also no parts can be lost. It can only be put together in two ways and both are correct.

The bulb and holder (holders are ceramic) are held in place by a heatproof 0- ring at the back of the head assembly, stopping the bulb and holder coming out the rear of the unit, locating it at the correct distance and allowing free movement to turn independently.

13 The charging jacks use two diodes, this allows for the charging current'to flow in but you cannot short-circuit the jacks from themselves when in use. (it stops the current flowing back from the batteries, if it were dropped in water or a metal object was inserted into both jack sockets at the same time).

e The switch is a standard arrangement.

0 The battery packs contain a thermistor (temperature sensor) which is used during charging, to limit the heat built up in the cells.

0 The battery packs are then sealed in the body, by means of expanding foam at both ends, this provides shock as well as water proofing.

9 The end cap of the body is fitted by one way seal. A groove "top har type section has an O-ring fitted to it, the body has an internal groove in it, and a shoulder in it.

0 When the end cap is fitted it compresses the O-ring and when it is located the 0 ring expands into the grooves, the shoulder also has sealant on it, which in turn stops the cap from rotating.

0 To remove this unit you have to use great pressure from the inside to force it out.

0 The leather work performs the following functions: the front strap has the foles for the switch and the charging jacks; it also has a one way poper on it. this performs two functions (1) To lock the switch in transit so that it cannot be turned on.

(2) When reversed it forms the belt clip or hanging clip.

0 If the leather strap is stretched out to the bottom of the torch then it becomes a carrying handle for the unit.

Because of the two raised sections for the leatherwork they also stop the whole unit from slipping out of your hand in both directions.

14 0 The leather rings also provide for the flashlight to be elevated from the charger. This allows for the cooling of both the charger and the battery pack in the flashlight. It also stops both units from being scratched.

Claims (13)

Claims

1. A flashlight comprising:

(i) a barrel for retaining at least one dry cell battery (ii) a lamp bulb; (iii) a reflector; (iv) means for holding the lamp bulb in a pre-determined position in relation to the reflector; (v) first conductive element(s) for electrically coupling a first electrode of the battery to a first electrode of the lamp bulb; (vi) second conductive element(s) for electrically coupling a second electrode of the battery to a second electrode of the lamp bulb; (vii) a switch; wherein the shape of the reflector follows that of a b-spline curve. 15

2. A flashlight as claimed in Claim 1 wherein the b-spline curve is of a form in which the angle of the reflector surface changes by substantially 50 over every 100 of arc as measured from the focal point of the reflector.

3. A flashlight as claimed in Claim 1 or Claim 2 in which the internal surface of the reflector is coated with a highly reflective finish.

4. A flashlight as claimed in any of Claims 1 to 3 in which there is a lens over the reflector and said lens incorporates a reflective surface directly above the lamp bulb, said reflective surface being adapted to reflect infra-red and ultra-violet light back onto the reflector and thus back onto the lamp bulb in order to set up a feedbackloop.

IT 16 A flashlight as claimed in Claim 4 wherein the reflective coating applied to the lens is the same as the coating applied to the internal surface of the reflector.

6. A flashlight as claimed in any preceding Claim wherein the reflector forms part of a head assembly which further incorporates a means for retaining the lamp bulb in a pre-determined position and a screw-threaded region for securing the head assembly to the barrel and characterised in that the head assembly, reflector, lamp bulb retainer and screw thread region is formed from a single piece of metal.

7. A flashlight as claimed in Claim 6 wherein the external surface of the head assembly incorporates cooling fins adapted to assist in dissipating the heat produced by the bulb.

8. A flashlight as claimed in Claim 6 or Claim 7 wherein the screw threaded region incorporates a round profile internal thread to minimise the risk of crossthreading.

9. A flashlight as claimed in any of Claims 6 to 8 inclusive wherein the lamp bulb retaining means comprises a lamp bulb holder adapted to buff against a shoulder on the reflector, the lamp bulb holder being held in place by an o-ring.

10. A flashlight as claimed in any preceding Claim wherein the lamp bulb is run at an overvoltage in order to increase light output.

11. A flashlight as claimed in any preceding Claim which further incorporates a flexible carrying strap said strap incorporating fixings at each end of the strap providing the strap with a number of fixing configurations.

12. A flashlight as claimed in Claim 11 wherein, in one configuration, the strap is adapted to encircle the region of barrel incorporating the switch and wherein an aperture in the strap is adapted to pass over the switch in a close fitting manner such that, with the strap fixed in place, the switch is inoperable.

13. A flashlight substantially as herein described with reference to and as illustrated in any combination of the accompanying drawings.

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