Lighting device for household appliances

Abstract: A lighting device, specifically for household appliances, of the kind comprising a basic structure (2), provided with means for the screwing of a lamp (7,7A,8) and with contact and electric connection means (19,21A,21B); according to the invention additional means (3,4,5) are provided in the form of a seal to be inserted on said basic structure (2) and/or on said lamp (7,7A,8) to hermetically close for protection purposes against infiltrations one or more areas of the basic structure (2) and/or of the lamp (7,7A,8) assembled therein. In a preferred embodiment of the invention also the actuation means of the device are enclosed in an airtight housing. The lighting device according to the present invention has particular advantages for application in the field of refrigerating appliances using gas of explosive nature.

Description: The present invention concerns a lampholder device for household appliances, specifically for application in refrigerating appliances as described in the preamble of the appended Claim 1. It is known that the environmental harmfulness of the gases used so far in the refrigerating appliances has led the manufacturers of said household appliances to replace them with other equivalent less polluting gases. However, some of these new gases being used are particularly explosive by nature, hence a likely saturation of the refrigerating cell in case of a casual gas leakage may cause a deflagration risk. Such a deflagration risk increases considerably in the presence of electric circuits, due to possible sparks essentially caused by defective contacts or by the normal opening-closing operation of electric push-buttons and contacts. In the case of refrigerating appliances, the main spark source may be generated by the lighting circuit, particularly the lampholder usually located inside the cabinet of the refrigerating appliance. In fact, should the refrigerator become actually saturated with explosive gas due to a fault, any likely sparks at lampholder level could cause a deflagration. Such a sparking could be due for instance to an uncorrect lamp screwing, a damaged lamp or defective electric contacts of the lampholder. Moreover, mechanical tolerances between the lampholder seat and the lamp are usually such that they cannot warrant a correct resistance to unscrewing. As a result, the lamp may become loose due to the operating vibrations of the refrigerating appliance and generate an unsafe contact with the proper electric contact blades of the lampholder. It should also be mentioned that even screwing manually the lamp in the lampholder may disconnect the electric contact between the glass bulb and the metal tang or bulb screw base; such an occurrence may cause an unsafe contact of the internal electric connections with a consequent sparking risk. Finally, it is known that the lamps equipped with E14 standard thread available on the market may differ both for their power (10/15/20 W) and different dimensions and configurations of the glass bulb. From DE-A-32 17 254 an sealing ring is provided, to be inserted on a lampholder, for hermetically closing the latter against the glass bulb of a lamp; according to this solution, a series of chambers are defined between the bulb surface and the ring, for realizing a sort of labyrinth sealing. From US-A-3,728,663 a lampholder is also known, comprising a basic structure made from thermoplastic material, a portion of which defines, in conjunction with the lamp surface, a chamber having the aim of reducing the heat transmission to the lampholder. It is the object of the present invention to solve the above inconveniences. In this frame, it is a primary object of the present invention to provide a lighting device capable of removing the explosion risks related to possible sparks originated in a household appliance. It is also an object of the present invention to provide a lampholder fitted with an airtight seal capable of fitting to the various types of available lamps and acting at the same time as a locking element against lamp unscrewing. It is a further object of the present invention to allow the conversion of a common lampholder into an airtight sealed lampholder type, suitable for other likely applications as well. These objects are obtained according to the present invention by providing a lighting device for household appliances incorporating the features of the appended claims. The features and the advantages of the present invention will become apparent from the following description and appended drawings, which are supplied only by way of non limiting example, wherein: Fig. 1 is a front view of a lampholder device according to the features of the present invention; Fig. 2 shows the lampholder device according to section A-A of fig. 1; Fig. 3 shows the lampholder device according to section B-B of fig. 1; Fig. 4 is a sectional view of a first detail of the lampholder device according to figs. 1-3; Fig. 5 shows the detail of fig. 4 according to section A-A of fig. 4; Fig. 6 is a sectional view of a second detail of the lampholder device according to figs. 1-3; Fig. 7 is a front view of the detail of fig. 6; Fig. 8 is a sectional view of a third detail of the lampholder device shown in figs. 1-3; Fig. 9 is a side view of a first lamp type with E14 thread showing max tolerance dimensions; Fig. 10 is a side view of a second lamp type with E14 thread showing min tolerance dimensions. With reference to the above figures, 1 indicates a lampholder device as a whole, which is part of the lighting device according to the present invention, specifically suitable for application in refrigerating appliances. Said device 1 comprises a basic structure 2 consisting of a standardized lampholder type, known as such, where said structure 2 has a kind of nut-screw to lock a lamp and the related contact and electric connection elements; according to the present invention, some additional components are related to this, basic structure 2 as indicated by 3, 4 and 5 in the various figures, each one of them capable of warranting a different protection degree to the device according to the present invention. Specifically, 3 indicates a first seal made of flexible material, such as rubber, forming the main element of a protection system for the device according to the present invention. Said first seal 3 is suitable to hermetically enclose the area where a likely loosening of the glass bulb 7 from the screw base 8 of a lamp assembled on the structure 2 may occur. As best shown in Fig. 5, the first seal 3 has a breakthrough area or section for the lamp screw base 8 with teeth 9 made of the same material as seal 3. Said teeth 9 are so configurated in their dimensions and orientation to allow an easy screwing of the lamp and oppose on the other hand an unscrewing of the lamp 7-8 inserted in the structure 2. As said above, the seal 3 is manufactured from flexible material and comprises a first upper lip termination 10, which fits flexibly to the various dimensions and configurations of the lamp bulb screwed in the lampholder to obtain a gastight sealing right on the bulb side. To this purpose, the device 1 according to the present invention is shown schematically in figs. 2 and 3 as if it were housing two lamps of different type, corresponding to those illustrated in figs. 9 and 10. The larger bulb shown in fig. 9 is indicated with 7, whereas the smaller bulb for the lamp of fig. 10 is indicated with 7A. In the same figures, 6 and 6A indicate the joining area between the lamp bulb and the screw base. As shown in figs. 2 and 3, said termination 10 is fit to take different positions according to the bulb geometry of the lamp in use. The seal 3 also comprises a second lower termination 11 as clearly shown in the enlarged detail of Fig. 4. Said second termination 11 fits flexibly to the screw base 8 upon screwing and is suitable to ensure gastightness right on the screw base 8 side facing the lampholder. Therefore, said terminations 10 and 11 are delimiting an intermediate chamber 12 shown in figs. 2 and 3, to protect the joining area 6 or 6A between the bulb 7 or 7A and the lamp screw base 8 against a possible explosive gas infiltrations. As previously explained, said area is particularly at risk due to a possible loosening of the bulb from the screw base with a consequent sparking within the live electric wires. Said terminations 10 and 11 pressing the external profile also aid to avoid any unwanted loosening of the lamp. As best seen from Fig. 4, the seal 3 comprises a throat 13 towards the outside to insert the seal 3 with interference on the structure 2. In particular, both surfaces 14 and 15 opposite the throat 13 are fit to perfectly adhere to the structure 2, thus obtaining a subsequent seal against withdrawal. Said seal can eventually be improved by bonding the parts together or adding an outside band, which is not shown. The seal 3 also has a peripheral seat 16 to fasten a second element 5 of the device according to the present invention, as it will be further described. 20A and 20B indicate two flat surfaces obtained on the external and internal surface of the seal 3, respectively. Said flat surfaces 20A and 20B represent the supporting points of a special assembly tool - not shown in the figures - which provides an axial thrust for the seal 3 to be inserted on the structure 2 without the risk of damaging the parts. In the above figures 4 indicates a second seal made of flexible material, which is fit for insertion in the lower side of the basic structure 2. As best seen in Figs. 6 and 7, to this purpose said second seal has two slots 17 and 18, whose dimensions are slightly smaller than the ones of the electric connection terminals of the structure 2, indicated with 19. Then the seal 4 can be inserted on the lampholder lower side with the terminals 19 forced in the slots 17 and 18. As a result, the seal 4 is gastight by adhering to the terminals 19 and to the structure 2, isolating the area where the electric contact elements 21A and 21B of the lamp are shown, assuring a second degree of protection in agreement with the device according to the invention. Finally, 5 indicates a third seal or outside housing made of transparent flexible material, such as silicone, which allows a third degree of protection against the risk of cracking for the lamp glass bulb 7 or 7A. In the practice said outside housing 5 configurated as a cap is inserted over the bulb 7 or 7A and on the first seal 3. In particular, the outside housing 5 has a termination 5A configurated as an O-ring type seal, fit to engage the peripheral seat 16 of the first seal 3. Therefore the housing 5 can be inserted over the lamp bulb and enclose it completely to warrant the required airtightness. Also the housing 5 based on the type of lamp inserted in the structure 2 can aid to avoid any unwanted lamp loosening. Finally, actuation means of the device 1 are provided according to the invention, located on a doorpost of the cabinet containing the refrigerating appliance. The purpose of said actuation means, which may consist eg. of a push-button switch - not shown in the figure for simplicityís sake - is to detect the opening and closing of the door and consequently control the switching on and off of the lamp screwed in the lampholder. Assembly and operation of the device according to the present invention is as follows. The seals 3 and 4 are inserted over the basic structure 2 consisting practically of a substantially standardized lampholder type as mentioned above. In particular, the seal 4 is forced on the electric connection terminals 19 of the lampholder through the slots 17 and 18 to warrant gastigthness on that side and specifically in the electric contacting area 21, whereas the seal 3 is inserted over the part where the lamp will be fastened through the throat 13, using the above mentioned assembly tool. Then the lamp is screwed as usual in the lampholder. Due to the existing seal 3, at least a part of the lamp screw-base 8 is located within the teeth 9 suitable to hinder a loosening of the lamp. Independently from the lamp dimensions, lip termination 10 of the seal 3 warps flexibly against the lamp bulb 7 or 7A to warrant the sealing on that side. The second termination 11 of that same seal 3 warrants on the other hand a gastightness in the lower side of the joining area 6 between the lamp bulb and the screw base. Thus, a gastight chamber 12 is practically formed between lip termination 10 and termination 11 to protect against a likely loosening of the bulb from the screw base. Finally, the outside housing 5 made of transparent flexible material is inserted over the lamp and fits to the bulb 7 or lamp 7A geometry. Said housing 5 is fastened through its end section 5A having the form of an O-ring seal, which mates with the relevant peripheral seat 16 of the seal 3; as a result a further protection related to the possibility of a lamp bulb cracking is warranted. In case of a lamp replacement, it will be enough to remove the housing 5A, unscrew the lamp to be replaced, screw on the new lamp and assemble the housing 5A back again. It should be noticed that teeth 9 are provided to hinder any unwanted lamp unscrewing; to this purpose both the seal 3 and teeth 9 are designed to require at least 0.3 N.m unscrewing torque. Obviously, this does not hinder a manual unscrewing of the lamp. According to the above description the characteristics of the present invention appear quite obvious and also its advantages are clear. One of the main advantages according to the present invention is the possibility of converting a conventional lampholder (2) in an airtight lampholder (1) in a rather simple and low-cost manner, whose application is especially beneficial in the field of the refrigerating appliances, and which is suitable to warrant three different airtightness degrees: for the electric contacts between lampholder and lamp, for the joining area between lamp bulb and screw base, for the lamp bulb. At the same time, the special design of this same device according to the present invention avoids the risk of casual lamp unscrewing; on the other hand its gastightness and resistance to undesired loosening does not hinder a replacement of the lamp. Also the advantages of the present invention appear clear in terms of design simplification and manufacturing standardization, since the manufacturer can use the same lampholder basic structure 2 both for the applications that do not require airtight sealing and for those where such a sealing is required. To this purpose it should also be mentioned how the device can flexibly fit the various geometrical configurations of the lamps available, i.e. using the same components all time. Finally, it is obvious that many changes and modifications are possible to the lampholder device described only by way of example, without departing from the novelty spirit of the innovative idea. As said above, in the case of refrigeration appliances the main sparks source can be represented by the lighting circuit, which besides the lampholder also has a push-button switch located on the doorpost of the refrigerator cabinet. Therefore, if the refrigerator is saturated with explosive gas, also the likely sparks due to the closing of said push-button may cause a deflagration when opening the door. Therefore, a special advantageous embodiment of the present invention is provided with an airtight push-button whose electric contacts are isolated from the sorrounding environment by an adequate airtight housing enclosing them. It is also clear that the device described above by way of example can find application in other fields other than refrigeration, i.e. wherever an airtight protection on one or more lampholder areas is required; for instance, the device described herein can be used on washing-machines, such as laundry-washers, eg. for lighting inside the washing tank, i.e. with the purpose of isolating the electric parts of the lighting system inside the washing tank and avoid humidity and water infiltrations.

Claims: A lighting device, in particular for household appliances, able to receive a lamp having a glass bulb (7,7A) and a screw base (8), comprising a basic structure (2), provided with means for the screwing of the lamp and with contact and electric connection means (19,21A,21B), additional means (3,4,5), in the form of seal to be inserted on said basic structure (2) for hermetically closing one or more areas of the basic structure (2) and/or of the lamp assembled therein, for protection purposes against infiltration, wherein said additional means (3,4,5) comprise at least a first seal (3) made of flexible material and having at least two portions ( 10 ,11) which delimit, in conjunction with said lamp, a hermetic chamber (12), a first one (10) of said portions (10, 11) flexibly fitting to said glass bulb (7,7A) for thereby realizing a first airtight seal on the lamp, characterized in that said chamber (12) is provided for hermetically enclosing the joining area (6,6A) between said glass bulb (7,7A) and said screw base (8), after the lamp has been assembled in the basic structure (2), a second one (11) of said portions (10,11) flexibly fitting to said screw base (8) for thereby realizing a second airtight seal on the lamp. A device according to claim 1, characterized in that said additional means (3,4,5) are also provided for avoiding undesired unscrewing of the lamp (7,7A,8) assembled in the basic structure (2). A device, according to claim 2, characterized in that said first seal (3) has a passage zone or section for the screw base (8) of lamp, said passage zone comprising teeth (9) whose dimensions and orientation are so configured for allowing an easy screwing of the lamp and opposing resistance to the unscrewing of the lamp. A device, according to claim 3, characterized in that said passage zone or section is defined below said second portion (11). A device, according to claim 1, characterized in that said first seal (3) has a throat (13) for the fastening on the basic structure (2), the fastening of the two elements being in particular improved through bonding and/or by the addition of an external band. A device, according to claim 1, characterized in that said additional means (3,4,5) comprise a second seal (4) fit for hermetically enclosing the zone of the electric contacts (21A,21B) between the lamp and the basic structure (2). A device, according to claim 6, characterized in that said second seal (4) has at least a slot (17,18) for its forced insertion on at least one electric connection terminal (19) of the basic structure (2), said second seal (4) adhering onto said terminal (19) and to the basic structure (2) for obtaining the required airtight seal. A device, according to claim 1, characterized in that said additional means (3,4,5) comprise an external housing (5), in particular made of transparent flexible material, such as silicone, for hermetically enclosing the bulb (7,7A) of the lamp assembled in the basic structure (2). A device, according to the claim 8, characterized in that said external housing (5) is inserted over the lamp bulb (7,7A) to fully enclose it, and partially on said first seal (3), said external housing (5) having in particular a termination (5A) apt at engaging a peripheral seat (16) defined on said first seal (3). A device, according to claim 9, characterized in that said external housing (5) is operative for avoiding unwanted lamp unscrewing. A device, according to one or more of the previous claims, characterized in that a lamp actuating switch is provided, in particular to detect the opening and closing of a door and consequently to control the switching of said lamp, the electric contacts of said switch being insulated from the surrounding environment through an airtight housing enclosing them. Use of the device according to one or more of the previous claims for illuminating the inside of refrigerating appliances or washing machines. A refrigerating appliance, having a cabinet and a refrigeration circuit, live operating electric means being provided within the cabinet, which comprise a lighting device according to claim 1 and preferably also a lamp actuating switch, the refrigeration circuit using a gas capable of explosion under determined fault conditions of the appliance, characterized in that said electric means are enclosed in relevant airtight housings which hinder the gas eventually seeped from the refrigeration circuit to reach any live electric parts of said electric means.

Inventors: BELFIORE STEFANO, CERRUTI DANIELE, GADINI COSTANZO, SIMONELLI DIEGO, BELFIORE, STEFANO, CERRUTI, DANIELE, GADINI, COSTANZO, SIMONELLI, DIEGO
Applicants: ELTEK SPA, ELTEK S.P.A.
Application year: 1996
Main classification: F21V31
IPC codes: F21V31, F21V25, F21S8, F25D27, H01R33