Enclosed high-pressure electric discharge lamp structure with cable terminal

The double-ended lamp has a base at each end, one of which is connected to cable. To prevent scattering of the high-pressure lamp bulb in case of explosion for example due to improper handling before installation, it is enclosed within a transparent protective tube, secured at its ends by caps slipped over the respective bases. To hold the caps and hence the tube in place, and prevent rolling of the bulb enclosed by the tube in the tubular end caps, the connecting cable is passed out of one end base from the side and it is of such length that it can be stretched adjacent the tube enclosure of the lamp to the other base, to be there fastened by a cable connector to the base pin terminal by a wing nut, or the like.

The present invention relates to protection of a double-ended, 
high-pressure electric discharge lamp, and more particularly to protection 
against shattering and explosion of such a lamp which has a connecting 
cable permanently secured at one end to the lamp, the other end of the 
lamp having a plug or pin with a separable screw-on connection stud. Prior 
to use the lamp is enclosed in a protective transparent tube of insulating 
material, secured in caps slipped over both ends of the lamp through 
central openings formed in the caps. 
It is known to provide high-pressure lamps which have a socket at each end, 
each socket having a central connection pin. For protection prior to 
installation in electrical fittings, the lamps are usually enclosed in 
transparent tubings to surround the light bulb. End caps at the basis hold 
the tube in place. The base pin provided at each end of the lamp protrudes 
through a central opening in the respective cap. The caps are held on the 
tubular protective covering by a rigid metal strap which is slipped over 
the caps externally and surrounds the base pins. The tight grip of the 
tube in the caps, by means of the strap, prevents the lamp components from 
being scattered if the lamp bulb should, per chance, explode. The strap 
has an additional function: It acts as an anti-roll restraint to prevent 
the tubular lamp, and its bases, from rolling off a support surface, for 
example from rolling off a table on which it has been placed, and hence 
breaking upon falling. 
Double-ended, a high-pressure electric discharge lamps are also known in 
which the base at one end of the lamp does not have a base pin, but rather 
is provided with a securely and permanently attached connecting cable. 
It is an object of the present invention to provide high-pressure, 
explosion-protected discharge lamps which require lesser number of parts, 
are easy to make and are easily assembled and locked together for 
shipment. 
SUBJECT MATTER OF THE PRESENT INVENTION 
Briefly, the connecting cable is securely attached to one of the lamp 
bases, and then passed close to and along the outer wall surface of the 
protective tube in stretched condition to extend to the base pin at the 
other end of the lamp, where it is detachably connected to the terminal 
bolt or pin of the other base, for example by a wing nut. It is laterally 
inserted into the base, preferably as the connection at the anode end of 
the lamp and connected inside the base with the electrode rod by 
soldering, and additionally clamped therein, for example by a compression 
connector. The connection lug on the cable is preferably open-ended so 
that, after shipment, it can be readily removed by loosening the wing nut 
from the other connecting terminal, that is from the pin or bolt. The tube 
protecting the lamp is made of transparent plastic. The cable which is 
attached to the lamp during shipment and handling, prevents rolling off of 
the lamp from flat surfaces during handling and shipping. 
The assembly has the advantage that no additional material or strap is 
required to lock the protective covering in place; the cable which serves 
as a lead connection serves this purpose before installation of the lamp 
in its receiving socket. The length of the cable is so selected that it 
extends, with its connector lug, just from one base to the other, closely 
fitting and tightly stretched along the protective tube. Thus, the caps 
are reliably fixed on the protective tube during shipment and, upon 
fracture of the lamp under high pressure, component parts are prevented 
from being expelled about. The lamp, simultaneously, is prevented from 
rolling on a surface.

A high-pressure xenon discharge lamp 1 has an anode 2 and a cathode 3, and 
is supplied with bases 4, 5. Base 5, at the cathode end of the lamp, is 
provided with a central threaded connection bolt or pin 6. The lamp is 
enclosed within a protective housing which is formed as a tube 7 of 
transparent plastic. Tube 7 is held in place by caps 8, 9, slipped over 
the ends of the tube. Caps 8, 9 are likewise made of plastic, closing off 
the tube 7. Each of the caps 8, 9 is formed with a central opening. Cap 9, 
at the cathode end of the lamp, has a somewhat smaller opening than cap 8 
at the anode end. Through this smaller opening of cap 9 extends the pin 6. 
Connecting cable 10 is laterally connected in base 4; it is rigidly 
pinched or clamped in a connecting lug 11 and soldered to the electrode 
rod extending from the anode to the base 4. To facilitate assembly, the 
cap 8 is formed with a lateral notch at the edge of the central opening so 
that the clamp extension or nipple 11 can be passed therethrough. 
In accordance with a feature of the invention, the cable 10 is so 
dimensioned that it is held straight and under tension and lies tightly 
adjacent tube 7, extending up to the bolt 6. The cable is terminated in an 
open-ended cable terminal 12 which fits around the terminal bolt 6, to 
which it is secured by a wing nut 13. A washer 14 is interposed between 
the cap 9 and the wing nut 13. 
To install the lamp 1, the cable 10 is detached from pin 6, and cap 9 is 
removed from tube 7. The lamp 1, still enclosed within tube 7, is then 
screw-fitted with its pin 6 in a standard receiving socket and tube 7, 
interconnected with cap 8, is removed by withdrawal from the free end of 
the lamp 1. Cable 10, rigidly connected to lamp base 4, is thereafter 
connected to the other pole of the voltage source (not shown).