DISPOSABLE FLASHLIGHT

Abstract: The present invention provides an easy and cheap to construct flashlight (10), intended to be disposable after the batteries (110, 120) have been drained. It is constructed from a housing (75, 85), two standard batteries (110, 120), a lamp (100) and a user-­ operable pressure switch (130). The batteries each have an end terminal (111) and a casing terminal, are so arranged that an opposite terminal of each is in direct contact with the lamp (100) and are preferably in an offset, side-by-side relationship. The pressure switch (130) is so designed that the lighting circuit is completed when pressure is employed on a deformable part of the housing (75, 85).

Description: The present invention relates to disposable flashlights comprising a housing containing a lighting circuit of a lamp, at least one battery and a biassed-open, user-operable pressure switch. Disposable flashlights are convenient where a small amount of illumination is required, temporarily. Such a situation is most commonly met at night, when attempting to insert a key in a lock, for example, or locating a small object in a clutch bag. Disposable flashlights on the market tend to be manufactured specially and are not priced sufficiently attractively to encourage disposal after use. It is not easy to further reduce the price of such flashlights without incurring losses associated with their specialist manufacture. In US-A-4,122,510, there is disclosed a flashlight comprising a casing containing two batteries and a lamp, a switch being operable by pressing on a deformable part of the casing. This light comprises a number of parts, and the lamp is connected to the batteries by wires. It has now been discovered that it is possible to make a cheap, disposable flashlight similar to that of US-A-4,122,510, but wherein the batteries are in direct contact with the lamp bulb. In a first aspect, the present invention provides a disposable flashlight according to claim 1. Due to practical considerations, it is generally preferred that the batteries lie in a side-by-side configuration. This not only reduces the overall size of the flashlight, but also places the open ends of the circuit in close proximity for switching. It will be appreciated that the batteries will usually be in an offset relationship to each other, as the generally preferred variety of lamp has a cylindrical contact terminal and an end contact terminal remote from the bulb. As direct contact with the lamp is a feature of the invention, the batteries will usually have to be offset when lying side-by-side. The batteries may be insulated from each other by physical separation or by an insulating layer covering the batteries. Where the latter option is selected, it will be appreciated that enough of the battery casing must be left exposed to allow necessary contact for the performance of the invention. For example, only that battery whose casing is in contact with the lamp need have insulation, such as a shrink wrap, but the end of the battery should be exposed to allow contact with the lamp. Physical insulation may be separation in space, or by placing a physical barrier between the two, such as a preformed wall in the housing. Ideally, the switch is made from one piece of material for simplicity and ease of manufacture, although 2- or more piece constructions are within the scope of the invention. Also from practical considerations, it is desirable that the switch have a fixed portion in contact with the free end terminal of the battery away from the lamp, and a circuit-making portion able to make contact with the free, casing terminal of the other battery. The switches of the present invention may be made, for example, from a simple metallic strip attached to the housing, one end being held in contact with the free end terminal, and the other being located in a deformable portion of the housing so that when the housing is pressed, the end of the strip is brought into contact with the casing terminal. In an alternative embodiment, the switch is formed from a resilient metal strip positioned substantially as described above, but having an independent existence from the housing. This embodiment allows the switch to be a simple assembly component, rather than having to be pre-attached to the housing. In a two-piece embodiment, the above two described switches are combined, with the fixed end being a resilient strip contacting the free end terminal and extending to form a contact with a strip located in the housing, as in the first embodiment. The housing is conveniently formed from two plastics halves, although the material used is not critical, nor the number of pieces. What is necessary is that at least a portion of one component is sufficiently deformable to allow operation of the switch. Preformed, or added, structures such as ribs and knobs may be used to reinforce, or generally modify, the resilient qualities of the deformable portion of the housing, so as to enhance performance. Apart from the necessary deformable qualities, the housing generally performs the function of retaining the various components in place. This is suitably achieved by the use of walls, bulkheads, protrusions, holes and the like which can generally be formed together with the housing piece. The pieces of the housing may be joined by conventional means, such as snap fitting, gluing or sonic welding, for example. It will be appreciated that, while the whole housing may be deformable, especially when made of plastics material, it is only necessary that a portion of the housing be deformable. Generally, it is known that flashlights assembled from preformed components must allow for variation in the components themselves. As such, a further feature of the present invention is the provision of suitable biassing means as required to ensure continuing contact between the various components. Such biassing means may be in the form of springs, for example, or may rely on the the general resilience of the casing, if appropriate. The latter may be effected by the use of ribs, or slightly insufficient space may be provided in the housing for a particular component. In either instance, the housing has to be deformed to accommodate the relevant component(s), thus ensuring a tight fit. The type of lamp used is not important, provided that it can be retained by the housing in some way. One preferred variety of lamp has a chamfered bulb, allowing retention of the lamp by provision of a hole in the housing smaller than the maximum width of the bulb. Thus the bulb is sufficiently exposed to provide illumination, but is still held in the casing. An alternative lamp has a retention collar forming part of the cylindrical contact. Thus a hole can be provided as before, but the whole of the bulb may be allowed to protrude, the collar holding the lamp in place. In an alternative aspect of the present invention, there is provided a flashlight, comprising a flashlight housing, a pair of batteries inside the housing, and a lamp. Each battery has a terminal disposed on an end thereof, and the battery casing of each battery also acts as a terminal. First means are provided for securing at least a portion of the lamp within the flashlight housing. The flashlight further comprises second means for retaining the batteries in an offset side-by-side relationship within the housing and in a relationship with respect to the lamp such that a central contact terminal of the lamp contacts a first terminal of a first of the batteries and a cylindrical contact of the lamp contacts a second terminal of the second of the batteries, where the polarity of the second terminal is opposite the polarity of the first terminal. In addition, third means are provided for electrically insulating the casings of the batteries from each other while they are in their offset side-by-side relationship, and fourth means are provided for electrically connecting the batteries so that current flows through the lamp. The fourth mean is rendered operative when force is applied to a portion of the flashlight housing that has at least limited flexibility. The flashlight described herein requires only a very few parts, and can be automatically assembled, thus making it very low in cost. It is therefore possible to market the flashlight as being disposable after the cells are discharged. A specific embodiment of the invention will now be described in more detail with regard to the accompanying drawings, in which: Figures 1A and 1B respectively show upper and lower perspective views of the flashlight disclosed herein; Figure 2 shows an exploded perspective view of the flashlight of Figure 1, illustrating the components of the flashlight and the internal configuration of each of the flashlight housing halves; Figure 3 shows a plan view of the arrangement of the internal components of the flashlight in one housing half; Figure 4 shows a sectional view of the flashlight shown in Figure 1A, taken along Section line 4-4, and; Figure 5 shows a sectional view of the flashlight shown in Figure 1A, taken along Section line 5-5. Figures 1A and 1B show the external configuration of a flashlight 10, which generally comprises a housing 20 defined by a top surface 70 and a bottom surface 80. Surfaces 70 and 80 are joined by sidewalls 30 and 40, rear wall 50 and front wall 60. Housing 20 can be formed in other shapes than that shown in the figures, such as oval or rectangular, depending upon the designer's aesthetic preferences and the requirements for proper and efficient functioning of the flashlight. The geometry of housing 20 is interrupted by a notch 21 that accommodates a tab 22. Tab 22 defines a hole 23 so that flashlight 10 can be conveniently attached to a key chain or the like. Alternatively, a tab or other projection (not shown) can be affixed to rear wall 50 and a hole can be defined in the tab or projection for the same purpose. The preferred location for tab 22 is as shown in the figures, since it allows easier manipulation and orientation of flashlight 1 for illumination of a keyhole or the like. The housing is formed form two halves 75 and 85, which are joined along a parting line 90 that divides sidewalls 30 and 40, rear wall 50 and front face 60. Figure 2 shows housing halves 75 and 85 after being separated along parting line 90. Depending upon the particular shape of housing 20, parting line 90 can also be located at a position that tends to make it less visible, such as at the intersection of two surfaces that define portions of the housing 10. As shown in Figures 2 through 5, the components of the flashlight 10 comprise lamp 100, first battery 110, second battery 120, contact arm 130 and biassing means 140, with the components being assembled in housing half 85 (Figure 3). Each of first battery 110 and second battery 120 is cylindrical and has a central terminal 111 located along the central axis of the battery and at one end thereof. The central terminal 111 is insulated from the battery's conductive casing since the conductive casing acts as the battery's second terminal. The cells are preferably of standard size, with sizes AAAA, AAA, AA or N for example being suitable, as are equivalent cells sizes of other chemical systems. AAAA alkaline cells are suitable for use with the present embodiment. Lamp 100 comprises a clear or translucent lamp bulb 102 joined to a lamp base 104. Lamp base 104 further comprises a cylindrical, electrically conductive contact 106 that terminates in and is electrically insulated from a central, electrically conductive contact 108. Means are provided for keeping batteries 110 and 120 electrically isolated from each other in the housing 20. Such means can be, for example, one dividing wall, or a plurality of dividing walls 152 and 154, which are integrally fastened to the inside of bottom surface 80. In addition, ribs 200 are formed in housing half 85 and are located a distance from dividing walls 152 and 154 that is smaller than the diameter of battery 110, thereby yielding an interference fit that securely holds battery 110 in housing half 85. Similarly, ribs 230 and 232, which are formed in housing half 85, are located a distance from dividing walls 152 and 154 that is smaller than the diameter of battery 120, thereby yielding an interference fit that securely holds battery 120 in housing half 85. A semicircular cutout 160 in housing half 85 corresponds to a similar cutout in housing half 75 to provide an aperture 170 to allow light from lamp bulb 102 to be projected from housing 20. In the present embodiment, lamp bulb 102 is configured so that the portion distal from lamp base 104 necks down to a diameter narrower than the portion proximate lamp base 104. This configuration allows the portion of lamp bulb 102 distal from lamp base 104 to protrude through aperture 170. A chamfered seat 180 located about the periphery of aperture 170 mates with the necked-down portion of lamp bulb 102. A plurality of ribs 192 and 194 (Figures 2 and 3) are respectively located in housing half 85. The distance between ribs 192 and 194 is less than the diameter of lamp base 104, thereby yielding an interference fit that securely holds lamp 100 in housing half 85. As shown in Figures 2 and 3, cutout 160 and a plurality of projections, or ribs, 190, cooperate to locate the central contact 108 of lamp 100 over the central terminal 111 of first battery 110. It has been found that, with commercially available lamps, the distance from central contact 108 to the intersection of bulb 102 and a lamp base 104 can vary up to one-eighth of an inch (c. 3.2mm), and that the overall length of the lamp can also vary significantly. In order to accommodate these variations, it is preferable to include in housing 20 means for biassing the central contact 108 and the central terminal of battery 110 toward each other. In the present embodiment biassing means 140 is located between first battery 110 and that portion of rear wall 50 as is included in housing half 85. Biassing means 140 urges terminal 111 of battery 110 toward central contact 108, while seat 180 prevents further movement of lamp 100. As a result, central contact 108 is placed firmly in physical and electrical contact with the central terminal 111 of first battery 110, despite significant variations in the dimensions of lamp 100. Biassing means 140 can take any of a variety of forms although in the present embodiment, it is made from strip of resilient material, such as copper plated steel, bent through a U-shaped arc and pressed into the gap between first battery 110 and the inner surface of that portion of rear wall 50 on housing half 85. In that gap, biassing means 140 also can be, for example, a V-shaped strip of resilient material, a resilient ball, a disk, or a string. As an alternative, biassing means 140 can be a resilient washer placed between lamp 100 and casing 20. However, if lamps having reasonably uniform dimensions can be obtained, it is possible to dispense with such biassing means. Referring to Figure 2, there is shown resilient and electrically conductive contact arm 130, which has a first portion 133 integrally joined to a second cantilevered arm portion 137. First portion 133 in the specific embodiment has the same U-shaped configuration as biassing means 140. Aside from being resilient and conductive, it is preferable for contact arm 130 to be made from a corrosion resistant material such as copper plated steel. To make contact arm 130, it is preferable first to form it form a strip of material, rather than to blank it from a sheet, and then form first portion 133 by bending one end of 133 through an arc of 180°. First portion 133 is pressed into the gap between the central terminal 111 of second battery 120 and a bulkhead 210. Bulkhead 210 is integrally joined to the inside of bottom surface 80, to dividing wall 154, and to the inner surface of that portion of sidewall 30 on housing half 85. Accordingly, first portion 133 performs a function similar to biassing means 140, in that it urges battery 120 away from rear wall 50, and also maintains firm electrical contact between the central terminal 111 of battery 120 and cantilevered arm portion 137. It is of course also possible to form contact portion 133 into a V-shape or any other shape suitable to perform the function just described. It should also be noted from the figures that the location of bulkhead 210 in cooperation with first portion 133 results in offsetting second battery 120 along its axis relative to first battery 10 such that batteries 110 and 120 are in an offset side-by-side relationship. As a result, the casing of second battery 120, which acts as the battery's second terminal, overlaps cylindrical contact 106 of lamp 100. In additon, referring to Figure 3, ribs 190 and ribs 232, located on the inner surface of that portion of sidewall 40 contained on housing half 85, cooperate to urge together cylindrical contact 106 and the casing of second battery 120, so as to yield physical and electrical contact between these two members. Apart form serving to bias battery 120, first portion 133 of contact arm 130 also provides support for second cantilevered arm portion 137. Referring to Figure 3, it can be seen that cantilevered arm portion 137 extends diagonally over dividing wall 154 and terminates over first battery 110. Although cantilevered arm portion 137 is biassed away from first battery 110, application of a sufficient amount of force to cantilevered arm portion 137 causes it to flex and thereby contact the casing of battery 110. This contact results in a closed circuit being created so that current can flow from the first central terminal of first battery 110 to the second terminal of battery 120 via central contact 108 and cylindrical contact 106 of lamp 110, and then from the first central terminal of second battery 120 to the second terminal of battery 110 via first portion 133 and second cantilevered arm portion 137 of contact arm 130. This current flow of course illuminates lamp 100. The biassing of cantilevered arm portion 137 away from first battery 110 can result simply from the inherent resiliency of the material comprising contact arm 130. However, due to the relatively long length of contact arm 130 and the desire to fabricate contact 130 from relatively thin strip material for reasons of cost, it is preferable to provide means for biassing second cantilevered arm portion 137 away from first battery 110. An effective embodiment of such means is depicted in Figure 2, which shows a support tab 155 integrally attached to and projecting above dividing wall 154. Support tab 155 serves to hold cantilevered arm portion 137 away from first battery 110, and since it shortens the moment arm from the free end of arm portion 137, tab 155 also serves to increase the amount of force needed to cause cantilevered arm portion 137 to flex and contact the casing of battery 110. Figures 2 and 3 show positioning block 212, which is approximately located against that end of battery 120 having central terminal 111. Positioning block 212 prevents any substantial movement of battery 130 toward rear wall 50, as could occur when flashlight 10 is inadvertantly dropped by the user. Without positioning block 212, such movement could cause first portion 133 to be deflected beyond its elastic limit, thereby deforming first portion 133 and possibly breaking the contact between first portion 133 and central terminal 111 of battery 120. A similar function is performed by tab 237, which is located as shown in Figure 2 inside housing half 75. When housing halves 75 and 85 are mated, tab 237 approximately rests against that end of battery 110 not having central terminal 111. Tab 237 prevents any substantial movement of battery 110 toward rear wall 50 when flashlight 10 is dropped, which could cause biassing means 140 of the type shown in the drawings to deform, thereby possibly breaking the contact between central terminal 111 of battery 110 and central contact 108 of lamp 100. From the drawings, it can be seen that after assembly, cantilevered arm portion 137 is disposed under top surfaces 70 of housing 20. The portion of top surface 70 disposed over cantilevered arm portion 137 should be of at least limited flexibility (as by making the portion from a slightly resilient material) so that when pressure is applied to top surface 70, that surface deforms somewhat (as shown in Figures 4 and 5), which causes cantilevered arm portion 137 to flex and contact the casing of battery 110, thereby lighting lamp 100. To achieve the desired limited flexibility and also for reasons of cost, it is preferred to make housing 20 from a somewhat resilient plastic. The housing 20 in the preferred embodiment is suitably made from a copolymer of propylene such as "Polyfort" (A. Schulman, Akron, Ohio, USA). The amount of force and deformation needed to close the lamp circuit is affected by tab 242 and projection 244 which, as shown in Figure 2, are located in housing half 75. When housing halves 75 and 85 are assembled, tab 242 rests approximately against battery 110 and projection 244 overlies cantilevered arm portion 137. Thus, as pressure is applied to top surface 70, tab 242 tends to prevent deflection of that portion of top surface 70 between tab 242 and front wall 60. The net result is to increase the amount of force needed to close the lamp circuit relative to the case where tab 242 is omitted. Also, when pressure is applied to top surface 70, projection 244 urges cantilevered arm portion 137 against battery 110 to close the lamp circuit. Thus the presence of projection 244 results in the need for less deformation of top surface 70 to close the lamp circuit relative to the case wherein projection 244 is omitted. In addition, since top surface 70 in the preferred embodiment is curved, dimensional variations in cantilevered arm portion 137 could change the amount of deflection needed to close the lamp circuit. Projection 244 thus serves to avoid this potential problem. To assemble flashlight 10, components 100, 110, 120, 130 and 140 are press-fit into their appropriate locations in housing half 85, either manually or by use of automatic assembly equipment. Housing half 75 is then placed over half 85. Proper positioning of the housing halves is aided by pin 280 of housing half 85, which engages bore 285 in housing half 75, and by pin 290 of housing half 75, which engages bore 295 in housing half 85. Proper positioning of housing halves 75 and 85 is further aided by providing, for example, a step joint between the housing halves, as illustrated by Figures 4 and 5, or by a tongue and groove joint. After the housing halves are properly positioned, they are permanently fastened and sealed, as by ultrasonic welding. In lieu of using dividing walls 152 and 154, it is possible to cover either cell 110 or cell 120 with an insulative covering, such as a shrink film, at least in the region where they are likely to make contact. If such insulating means is employed, there of course should be no insulative covering in the regions where cell 120 contacts cylindrical contact 106, and where cantilevered arm portion 137 contacts battery 110.

Claims: A flashlight (10) comprising a housing (75), (85) having a deformable portion and containing a lighting circuit of a lamp (100), two batteries (110), (120), each having a central contact terminal (111), being located in the housing (75), (85) in a side-by-side relationship and facing in opposite directions, the casings of the batteries being insulated from each other, and a biassed-open, user-operable pressure switch (130) comprising a resilient, conductive contact arm (137) electrically connected to the free central contact terminal (111) of one battery (120), the arm extending over the casing terminal of the other battery (110) and under the deformable portion of the housing so as to be operable thereby, characterised in that the lamp (100) has a lamp bulb (102) fastened to a base section (104) comprising a first cylindrical contact terminal (106) terminating in and insulated from a second central contact terminal (108), the batteries being in such a relationship with respect to the lamp (100) that the second central contact terminal (108) of the lamp (100) contacts the first terminal (111) of a first of the batteries (110) and the first cylindrical contact (106) of the lamp contacts the casing of the second of the batteries (120) A flashlight according to Claim 1, further comprising one or two biassing means (133, 140) acting against one or both free battery terminals respectively. A flashlight according to Claim 2, wherein the biassing means (133, 140) are leaf springs. A flashlight according to Claim 2 or 3, wherein the switch (130) is in electrical contact with the biassing means (133) acting on the free central contact battery terminal (111). A flashlight according to any of Claims 2 to 4, wherein the biassing means (133) is formed integrally with the switch (130). A flashlight according to any preceding Claim, further comprising at least one projection (232), (190) inside the housing to urge the cylindrical contact (106) of the lamp (100) toward the casing of the relevant battery (120). A flashlight according to any preceding Claim, wherein the casings of the batteries (110), (120) are electrically insulated from each other by means of a dividing wall (152), (154) located in the flashlight housing. A flashlight according to any of Claims 2 to 8, further comprising means (155) for biassing the contact arm (137) away from the battery casing. A flashlight according to Claim 8, wherein the biassing means (155) comprises a support tab that urges the contact arm (137) away from the battery casing. A flashlight according to Claim 9, wherein the support tab (155) is mounted on the dividing wall (154). A flashlight according to any preceding Claim, wherein the lamp bulb (102) is configured so that a portion distal from the base section necks down to a diameter narrower than a portion proximate to the base section, and the housing has an aperture (180) having a chamfered seat about its periphery that mates with the necked-down portion of the lamp bulb (102).

Inventors: AMTHOR, HELMUT KASPER
Applicants: EVEREADY BATTERY COMPANY, INC.
Application year: 1987
Main classification: F21L7
IPC codes: F21L4