1. Field of the Invention
The invention relates to a lighting device, which is suitable above all for irradiating plants, in particular in greenhouses.
2. Description of Related Art
Lamps, such as discharge lamps, for greenhouses are known from the prior art, which comprise a tubular body and have an exposed lead at each end of the body to connect the lamp. For operation, these lamps are placed in special housings, which clamp the exposed leads between two spring lamellae when the housing is folded closed, and thus, produce a conductive connection.
High-power lamps, for example, 1,000 Watts, are employed for use in greenhouses. It has proven to be problematic in this case that the production of a conductive connection cannot be reliably ensured. In the event of inadequate contact of the leads with the contact lamellae of the housing, because of high (ignition) voltages, which can reach approximately 3,000 V, electric arcs arise between the contact points and result in destruction of the device. The leads can overheat and melt at contact points of the housing due to high currents at these contact points with an excessively small contact surface. Since the contact points are subjected in greenhouses to ambient air which is enriched with moisture and chemicals, for example, fertilizer salts, the conduction at these points is impaired or completely prevented by corrosion of the contact points. In addition, the susceptibility to corrosion of the contact element is additionally increased by high temperatures at the contact points. In practice, since defective lamps cannot be replaced during the vegetation period, their defect can sometimes result in significant harvest losses. Furthermore, it has proven to be problematic according to the prior art that a lamp is unintentionally inserted into a receptacle device which is not intended therefor or its orientation therein in relation to the employed reflector is incorrect, whereby the light yield is reduced or the lamp is even destroyed.
A primary object of the present invention is to devise a lighting device which has an improved lifetime over the lighting devices known heretofore, in particular in the case of use under difficult conditions having elevated humidity and temperature strain, as in greenhouses.
To solve this above-mentioned problem, a lighting device of the invention comprises a tubular lamp, on each end of which a terminal socket is provided, which has a terminal for electrically contacting of the lamp, and two terminal receptacles associated with the terminal sockets, each having a metal terminal clamp for receiving one of the terminals of the terminal socket, wherein the terminal for making electrical contact is a strip-shaped metal terminal tab and the terminal clamp has two opposing springy contact surfaces for clamping the terminal tab between them, and wherein opposing front sides of terminal socket and terminal receptacle are adapted to engage in one another in a form-fitting way in an installed state by providing a projection and a depression complementary thereto.
The advantages achieved by the invention are, in particular, that due to the special implementation of lamp sockets and terminal receptacles, and particularly, the elements which produce the electrical contact between the two, the susceptibility to corrosion is significantly reduced and a permanent electrical contact is ensured. This significantly lengthens the lifetime of the lighting device.
An advantageous embodiment allows simple contacting and avoids jamming of the lamp when it is plugged into the terminal receptacles of the lighting device.
A further advantageous embodiment of the invention makes it easier to attach the lamp in the terminal receptacles, in particular if it must be attached overhead.
Particularly reliable contacting while simultaneously avoiding wear of the terminal receptacles when the lamp is changed is achieved by a still further embodiment.
A further advantageous embodiment reduces the temperature impact on the contacts and thus further reduces their wear.
Further measures for increasing the temperature and corrosion stability and for permanent reliable contacting are achieved by another embodiment of the invention.
Further advantageous embodiments ensure correct use of the lamp and prevent the use of an unsuitable lamp.
The measure of a still further embodiment has an advantageous effect on the corrosion resistance of the contact elements.
A further advantageous embodiment allows simple and secure attachment of the lamp.
Another aspect of the invention provides a measure to further reduce the temperature and thus increase the lifetime.
Various exemplary, but non-limiting, embodiments of the invention are shown in the schematic drawings and are described in greater detail hereafter.
The invention is explained hereafter on the basis of the drawings with respect to construction and mode of operation of the illustrated invention. Identical reference numerals identify identical parts.
A discharge tube 1 is situated in the interior of a tubular, light-transmitting protective tube 3. A terminal socket 5 is located at each of the two ends of the light-transmitting protective tube 3. Apart from the implementation of the terminal sockets 5, the lamp according to the invention fundamentally corresponds to the typical prior art. A flat, plate-shaped terminal tab 4 protrudes in the radial direction from each terminal socket 5 toward the protective tube 3. The terminal tabs 4 are connected via power lines 2 to the an electrode situated in the interior of discharge tube 1. Electrical contact with the opposing contact surfaces 7 in the terminal receptacle 6, which comprises metal plates, for example, is produced via the terminal tab 4 when it is plugged into the terminal socket 5. The advantage is achieved by plugging or inserting the terminal tab 4 between the contact surfaces 7 that adhering contaminants or oxide layers are rubbed off of the contact surface upon insertion, whereby the resistance and the temperature at the contact point are reduced.
The temperature of the contact elements, i.e., terminal tab 4 and terminal clamp having the contact surfaces 7, can be reduced in that their cross section which is available for electrical conduction is designed in accordance with the employed power. Preferably, the minimal line cross section of the contact elements is therefore at least twice as large as the cross section of one of the electrodes in the discharge tube 1 of the lamp. The cross section is the maximum cross section of the electrode in the discharge tube. The temperatures at the contact point and in the contact elements as a whole may thus be kept low, whereby fusing is prevented and corrosion is reduced.
The contact surfaces 7 and the terminal tab 4 can comprise a corrosion-inhibiting metal, for example, gold or nickel, and/or can be at least partially coated therewith, for example, solely on the contact points which are subjected to the corrosive atmosphere. In addition, the terminal tabs 4 and/or the contact surfaces 7 can be manufactured from a soft metal or coated using such a metal. This has the advantage that the contact resistance between terminal tab 4 and contact surface 7 can be significantly reduced and good contacting can be ensured.
In addition, a mechanical pre-tension can be applied to the opposing contact surfaces 7, which causes the two contact surfaces 7 to be pressed toward one another. The outermost ends of the contact surfaces, which protrude in the direction toward the terminal tab 4, preferably run away from one another again, in order to make it easier to insert the terminal tab between them. The opposing contact surfaces 7 thus have a wedge-shaped opening or widening at their ends for inserting the terminal tab 4. In addition, the terminal tab 4 can be wedge-shaped, so that the terminal tab 4 can be inserted more easily between the contact surfaces 7 and increasingly presses them apart as it is inserted. This has the advantage that a contact having low resistance and high contact surface area is ensured between the terminal tab 4 and the contact surfaces 7. The contact surfaces 7 are preferably connected to one another at their rear ends, from the side facing away from the receptacle side for the terminal tab 4, and form a terminal clamp having two contact surfaces.
Both the terminal socket 5 and also the terminal receptacle 6 are expediently manufactured from a temperature-stable, high-strength, and/or abrasion-resistant material. Both preferably comprise ceramic.
The terminal receptacles 6 are preferably situated at a suitable distance on a carrier 9. In addition, a heat dissipation plate 10 is expediently situated on a carrier, in order to dissipate the heat formed in lamp operation. However, a suitable heat dissipation device can alternatively or additionally be situated at another point, for example, on the contact surfaces 7 and/or on the terminal receptacle 6. In particular, the terminal receptacle 6 and/or the terminal socket 5 can comprise cooling ribs in order to dissipate the heat still better. In addition, the terminal receptacle 6 or the terminal socket 5 can be situated on a metal which has good heat conduction properties, for example, an aluminum plate or an aluminum carrier. This has the advantage that heat which arises at the contacts between the terminal tab 4 and the contact surfaces 7 or due to the discharge tube 1 is effectively dissipated and corrosion of the contact points can be prevented. It has been shown that a temperature reduction by approximately 20° C. results in doubling of the lifetime of the components.
The terminal receptacle 6 and the terminal socket 5 are preferably implemented such that they engage with one another in a complementary way. The areas pressing against one another expediently run diagonally inward or outward, in order to provide the largest possible support surface, without terminal receptacle 6 and terminal socket 5 having to be enlarged unnecessarily. For example, the terminal receptacle 6 can have a recess in the form of a truncated cone or truncated pyramid on the connection side with the terminal socket 5. Correspondingly, the terminal socket 5 can have a complementary bulge or projection in the form of a truncated cone or truncated pyramid on the connection side with the terminal receptacle 6. On the one hand, the advantage is thus achieved that the lamp can easily be guided into the provided contact position when it is plugged in and, on the other hand, a high degree of form fit is achieved using small insertion forces, which seals the connection between terminal socket and terminal receptacle. This prevents corrosive substances in the ambient air from touching the contact surfaces and damaging them.
In addition, sealants can be situated on the terminal receptacle 6 and/or the terminal socket 5, which seal the gap between both parts. In particular, the surfaces of the terminal receptacle 6 or the terminal socket 5 can partially be equipped with inlaid or glued-on, preferably temperature-resistant, permanently elastic materials, such as O-ring seals made of Viton or rubber, for example. Pyramidal surfaces can also be entirely or at least partially implemented as a sealing lip using permanently elastic material. However, flat sealing material and/or sealing lips can also be attached to the terminal receptacle 6 or the terminal socket 5, which comprise Teflon, for example. The seal at the connection point can thus be improved further.
Terminal receptacles 6 and terminal sockets 5 are preferably implemented such that the lamp can only be inserted into the receptacle in a single orientation. This is expediently achieved via a special shaping of the corresponding parts. A manufacturing-related asymmetry of the lamp can be the reason for a specific orientation of the lamp in the receptacle. However, through a suitable reflector, this asymmetry can be compensated for such that it does not cause irregular illumination of the irradiated surface. This presumes a specific arrangement of the lamp adapted to the reflector implementation, however. This predefined orientation is ensured by special shaping of the connection areas of lamp and receptacle. The shape coding can additionally ensure that only a suitable combination of lamp and ballast, reflector, and lighting device is used. The two terminal receptacles 6 can each have recesses, for example, which differ from one another in size and/or shape. Correspondingly, the two terminal sockets 5 can each have projections which are complementary to the recesses. In one variant, the footprints of the two terminal receptacles 6 or terminal sockets 5 can each be implemented differently from one another. For example, the number of the corners of the footprints and/or the edge lengths can differ. The orientation of the terminal tab 4 to the terminal socket 5 can also differ depending on the side of the lamp, in order to prevent the terminal tab from being plugged into the wrong terminal socket. In particular, the illustrated terminal tabs 4 can be situated rotated and/or offset in parallel in the terminal socket 5 in comparison to the lamp longitudinal axis. Furthermore, each of the two terminal tabs 4 can be shaped differently from one another. This also applies accordingly for the terminal clamps 21.
In order to prevent the lamp from falling out of the lighting device, at least one holding device is provided for holding the lamp in the receptacle. This holding device can comprise a catch device, for example, which is provided on the terminal socket and/or on the terminal receptacle. These mounting devices can be implemented, for example, by a tongue-and-groove element, in which a corresponding lug of the terminal socket 5 engages in a matching recess in the terminal receptacle 6 and catches therein or vice versa. The holding device can also be integrated in the terminal tab and/or contact elements, however, and comprise a groove or protrusion in the terminal tab 4 and a correspondingly shaped raised area or a recess in a contact surface 7, so that these catch in one another. Spring elements 11 are also possible, as shown in
The power supply of the devices and a connection to a suitable ignition circuit or a ballast device are ensured via corresponding power lines 8. The arrangement fundamentally corresponds to the prior art, so that it does not have to be described in greater detail here.
The terminal socket 5 shown in
A good form fit is achieved and the connection point is sealed by the embodiments shown of the terminal socket 5 and the terminal receptacle 6. Corrosive substances are thus prevented from entering the terminal receptacle.
All seal arrangements shown can be combined suitably with various forms of the terminal receptacle 6 and the terminal socket 5 such that a seal of the connection point between terminal socket 5 and terminal receptacle 6 results. A still better seal of the connection point in relation to corrosive substances in the ambient air is achieved by the arrangements shown of the seal.
Number | Date | Country | Kind |
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10 2010 018 535.3 | Apr 2010 | DE | national |