US2716738A - Lampholders for tubular lamps - Google Patents

Description

Aug. 30, 1955 J. M. PlsTEY LAMPHOLDERS FOR TUBULAR LAMPS Filed Aug. 30, 1954 3 Sheets-Sheet l n ||||fv| Il uw Smm m Im/emftQV: John MPiSCLeH, ww /Mfy HiS Actftorrweg Aug. 30, 1955 Filed Aug. 50, 1954 J. M. PISTE-:Y

LAMPHOLDERS FOR TUBULAR LAMPS 5 Sheets-Sheet 2 van Aug. 30, 1955 1, M, PlsTEY 2,716,738

LAMPHOLDERS FOR TUBULAR LAMPS Filed Aug. 30, 1954 5 Sheets-Sheet 5 United States Patent O LAMPHOLDERS FOR TUBULAR LAMPS John M. Pistey, Fairfield, Conn., assignor to General Electric Company, a corporation of New York.

Application August 30, 1954, Serial No. 452,851

7 Claims. (Cl. 339-50) The present invention relates to lampholders for double-- ended electric discharge lamps of the type having preheated electrodes mounted at the ends of a tubular glass envelope. More particularly, this invention relates to lampholders for such lamps equipped with bases of the type disclosed and claimed in the co-pending applica tion of Eugene Lemmers, Serial No. 380,279, which was tiled on September 15, 1953, and is assigned to the same assignee as is the present invention.

This is a continuation-in-part application of application Serial No. 380,325, now abandoned, which was also :l

tiled on September 15, 1953. l

The novel lamp base of the Lemmers application makes possible the utilization of the usual inlead wires of the lamp electrodes as the lamp contacts or terminals, thus eliminating the need for externally protruding Contact pins. The inlead wires are recessed within an outwardly projecting, electrically insulating part of the base to protect them from accidental contact.

The principal object of the present invention is to provide a lampholder for tubular lamps having bases of the above type.

A further object of this invention is to provide such a lampholder having contacts engageable with the recessed inlead wires of the base and which are recessed in the holder to protect said holder contacts.

A further object of this invention relates to a means for insulating the recessed contacts of such a lampholder so that it is not possible to touch the live contacts with the human hand.

Still further objects and advantages of invention will appear in the following detailed description of the species thereof.

A feature of the lampholder embodying the invention is a pair of spring-pressed, closely spaced insulated electrical contacts recessed within the holder and having lamp terminal engaging portions which are divergent before a lamp base is inserted in the holder and which are moved by insertion of the projection on the lamp base into the holder, as a result of a cam action between the holder contacts and the lamp terminals, into parallel positions whereby each of said contacts makes a wiping electrical contact with a terminal of the lamp.

My invention will be better understood from the following description taken in connection with the accompanying drawings, and its scope will be pointed out in the appended claims.

In the drawings:

Figure l is a side elevational view showing the novel lampholders of the present invention and a lamp having bases of the above type mounted in the holders.

Figure 2 is a plan view on an enlarged scale showing the lampholders and the ends of the lamp partly in section with the basek at one end of the lamp partly withdrawn from its holder.

Figure 3 is a front view of the lamp base of the type accommodated by the rst species of the lampholders of ICC ha! this invention with the terminals of the lamp removed therefrom.

Figure 4 is a side elevational, partly sectional view of the lampholders shown in Figures l and 2.

Figure 5 is a front elevational View of the lampholder for the high-voltage end of the lamp having the movable plunger.

Figure 6 is a front elevational view similar to Figure S of a modified lampholder embodying my invention.

Figure 7 is a cross-sectional plan view taken on the lines 7 7 of Figure 6.

Figure 8 is a side elevational, partly sectional View similar to Figure 4 of the pair of lampholders according to the modification of Figure 6 for supporting a doubleended electric discharge lamp.

Figure 9 is a front View of the lamp base which is designed to be used with the second species of lampholders of Figures 6-8, with the lamp terminals removed.

Referring in detail to Figure 1 of the drawings, in which like numbers denote like parts in all of the figures, the lamp has a tubular glass envelope 1 provided with bases 2 and 3 attached to its end and is supported between a pair of lampholders 4 and 5 attached to a suitable support 6 which may be part of a lighting fixture. The holder 4 is provided with a movable spring-pressed plunger 7, described in detail later herein, engaging the base 2 of the lamp. To mount the lamp in the holders the base 2 is first engaged with the plunger 7 and the lamp is then moved to the left to force the plunger 7 into the holder 4 until its base 3 can clear the holder 5, as shown in broken lines in Figure l. The lamp is then brought into line with the holder 5 and the base 3 engaged with the holder 5. The lamp is held firmly in the holders by the spring-pressed plunger 7. Removal of the lamp from the holders is accomplished by moving it to the left until its base 3 is withdrawn from holder 5, tilting the lamp to clear the holder 5 and then withdrawing base 2 from plunger 7.

The bases 2 and 3 are of identical structure and the internal parts of only the base 2 have been shown completely in Figure 2 of the drawings for conciseness in description.

As shown in Figures 2 and 3, the lamp base 2 comprises an annular metal shell 8, which is suitably made of sheet aluminum, and a disk 9 of electrically insulating material, such as an organic plastic. The disk 9 may be made of commercial plastic molding compounds, such as those comprising phenol-furfural resins or phenolic resins. The inner rim of the shell 8 is embedded in the periphery of the insulating disk 9 to mechanically join these base members, as shown in Figure 2. The base 2 is secured to the end of the glass envelope 1 by a body of basing cement 10.

The disk 9 has a raised elongated embossment 11 eX- tending across its center and projecting outwardly from the base. A passage 12 is provided in the embossed portion of the disk 9 and extends completely through the center of the disk. The metal wire current inleads 13 and 14 connected to electrode 15 and extending through the press 16 of the stem 17 of the glass envelope 1 extend through the passage 12 and constitute electric terminals for the lamp. The inleads 13 and 14 have been on1itted from Figure 3 to show details of the internal parts of disk 9.

The elongated embossment 11 on disk 9 of the base 2 has straight parallel sides and rounded ends and the central passage 12 through the disk conforms in shape generally to that of the embossment as shown in Figure 3.

The outer face of the embossment is recessed to define two cavities 18 and 19 spaced from the central passage 12 with grooves 20 connecting the passage 12 with each of the cavities 18 and 19. As shown in Figure 2, inleads 13 LJ and 14 of the lamp extend in spaced relation through the central passage 12 and the outer ends thereof are bent over in opposite directions to lie in the grooves 2t) and terminate within the cavities 1S and 19 respectively.

Preferably the inleads are anchored in the disk 9 by forcing them into recesses 20' in the bottom of grooves 2t) (Figure 3) and which extend the full length of the grooves and are dimensioned to receive and grip the inleads between their walls. The recesses 20' are shallow to expose the portions of the inleads therein. Obviously, insulating pins, `Hedges or a body of insulating cement may be inserted in the cavities 18 and 19 to anchor the ends of the inleads 13 and 14 therein and the recesses 20 may then be omitted or retained as desired. When the wire inleads are stiff enough all such anchoring means may be omitted.

As shown in Figures 2 and 3 of the drawings, the outer end portions of the wire inleads 13 and 14 lying in the grooves 20 are exposed for engagement with socket contacts, but are recessed within the base, because the depth of the grooves is greater than the diameter of the wire inleads. The passage 12 and the grooves 20 are made too narrow for the inleads 13 and 14 to be touched accidentally in ordinary handling of the lamp incident to its insertion and removal as described above. This is an important safety feature of the lamp base structure, because it eliminates the possibility of a person getting an electric shock by touching any exposed lamp terminals while at the same time being grounded. The above-de scribed base structure is disclosed and claimed in the co-pending Lemmers application referred to above.

The electrodes 15 mounted in the ends of envelope 1, only one of which is shown in Figure 2, comprises a tungsten ilament coated with electron-emissive material, such as alkaline-earth compounds, and are of the type requiring pre-heating to an electron-emitting temperature before starting of an electrode discharge between the electrodes at opposite ends of the lamp. The lamp envelope 1 contains a starting gas, such as argon, at a few millimeters pressure and a small quantity 21 of mercury which is at a pressure of about 10 microns during operation of the lamp. A coating 22 of fluorescent material is provided on the inner surface of the envelope 1 and this material is excited to luminescence by the mercury vapor discharge during the operation of the lamp. Lamps of this type may be about 8 feet in length and about 11/2 inches in diameter.

The lampholder 4 shown at the left of Figures 2 and 4 comprises a body portion 23 providing a housing 24 of molded urea or othei suitable insulating material having an opening through which extends the plunger 7. The plunger 7 is provided with opposite shoulders 26 which are fitted into grooves 26 in the inner side walls of the housing. The outer ends of the grooves 26 `are closed as at 25 to act as a stop means for the spring-pressed plunger 7.

The springs 27 and 28 engage studs 29 and 30 on the back wall of the housing 24 and also studs 32 and 33 welded to the transverse welding projections 34 and 35 on the flat metal contacts 36 and 37. The welding projections 34 and 35 of the contacts are urged against a transverse integral partition 33 in the plunger 7 by the springs 27 and 28 to bias the plunger outward of the housing 24.

In addition to the transverse partition 38, which acts as a stop for the contacts 36 and 37, the plunger 7 is provided with a separate longitudinally extending partition 39 of electrically insulating material which extends through a slot in partition 38 and nsulates from each other springs 27 and 28 and the contacts 36 and 37. The partition 39 is held in position in the plunger 7 by the cover plate 41 which is located between the springs 27 and 28 and fastened to the back of the plunger 7 by screws 4t).

The blade portions of the contacts 36 and 37 extend through a slot 42 in the partition 38 and into the cavity 43 in the front face of the plunger 7. The back surface 44 of the partition 38 is slanted forwardly and inwardly from its ends toward the center, as is shown in plan view at the left of Figure 2, so that the blades of the contacts 36 and 37 diverge outwardly from each other when the lamp is removed from the holders. This is shown at the right of Figure 2 where the base 3 is illustrated as partly withdrawn from holder 5.

The springs 27 and 28 in holder 4 thus serve the dual purpose of biasing the plunger 7 outward of the housing 2.1!- and biasing the outer ends of the contacts 36 and 37 outwardly from each other so that the said contacts make a positive connection with the inleads 13 and 14 of the inserted lamp base 2. The springs 27 and 28 are connected to the terminal screws 45 and 46 of the holder 4 by their portions 47 and 48 and thus also serve to conduct electrical energy to the mounted lamp.

The lampholder 5 is similar in construction to the holder 4, except that in the holder the part 9 correspond ing to the movable plunger 7 of the holder 4, while of the same structure as plunger 7, is made stationary in the housing 51B corresponding to the housing 24 by the inscrtion ot' spacers 5l and 52 in the grooves comparable to grooves 26 between the shoulders 53 on the part 49 and the wall means 54 at the opening of housing 59. The part 49 thus constitutes a hoilow plug in the housing 50 ot the holder S. The metai springs 5S and 56 corresponding to the springs 27 and 23 of the holder d are, of course, shorter in length than springs 27 and 23, but serve the same purposes and are connected to the terminal screws ofthe holder 5 in the same manner.

The cavity 43 in plunger 7 and that in plug 49 are each dimensioned to receive the embossment 11 on the bases 2 and 3 respectively with the sides of the opening of each of the cavities 43 engaging the sides of the embossments 11 to support the lamp in the holders -i and The portions of the holder contacts 36 and 37 in said cavities 43 are spaced from the rim of the cavity openings and the outer ends of the partitions 39 lie in said openings forwardly of said contacts so that the fingers of a person mounting or disrnounting the lamp while the lamp circuit may be unintentionally energized are protected from accidentally touching the electrically charged contacts of the holders 4 and 5.

As best shown in Figure 3 of the drawing, the central passage 12 in each of the insulating disks 9 of the bases 2 and 3 has a center portion 58 of increased width to receive the ends of the partitions 39 projecting into the cavities 43.

ln mounting the lamp in the holders the elnbossment 11 on the base 2 is first inserted in the cavity 43 in the face of plunger 7 of the holder 4. and the lamp is then thrust against the plunger to overcome the force of the springs 27 and 2d and to move the plunger 7 back into the housing 24 of the housing 4 a suiiicient distance to allow embossment 11 on the bese 3 to clear the holder 5. The embossment 11 on base 3 is then positioned in the cavity 43 in the face of plug 49 of holder 5 and the grip of the person mounting the lamp is released. The springs in the holders 4- and 5 clamp the lamp in position between the said holders. In Figure l of the drawing the normal position of the mounted lamp is shown in solid lines.

ln dismounting the lamp the plunger 7 is forced back into the holder 4 until the embossment 11 on the base 3 is completeiy withdrawn from the plug 49 in holder 5 and the lamp may then be removed by tiiting its end pro vided with base 3, as shown in broken lines in Figure l, and thereafter removing the base 2 from the plunger 7.

The blades of the contacts 36 and 3`1 of the holders 4 and 5 are cnmshaped with rounded tips and thus wipe a portion of the inleads i3 and 14 in the 'onse 2 and 3 each time the lamp is mounted and disrnounted and also malte a tirm two-surface contact with said inleads when the embossrnents 11 on the bases, which embossments constitute projections on the lamp, are fully inserted in the holders. A good electrical connection thus is established between the lamp terminals and the holder contacts on insertion of the lamp projections in the holders.

The bottom of the grooves and the walls of passage 12 provide firm support for the inleads 13 and 14 against the pressure exerted thereon by the portions of the springpressed contacts 36 and 37 within the grooves 20 and the passage 12 of the bases 2 and 3 of the mounted lamp.

Turning now to a consideration of the modification of the lampholder shown in Figures 6-8, it is seen that the high-voltage lampholder 7) shown in Figures 7 and 8 comprises a body portion 71 providing a housing 72 having an opening through which extends the plunger 73. The plunger 73 is provided with a pair of opposite shoulders 7S which are fitted into grooves 75 in the inner side walls of the housing. The outer ends of the grooves 7S are closed as at 74 to act as a stop means for the springpressed plunger 73.

The springs 76 and 77 for actuating the plunger engage studs 78 and 79 respectively on the back wall of the housing 72 and also studs 80 and 81 welded to the transverse welding projections 82 and 83 on the flat metal contacts 84 and 85 respectively. The welding projections 82 and 83 of the contacts are urged against a transverse partition 86 in the plunger 73 by the springs 76 and 77 to bias the plunger outward of the housing 72 in the same manner as taught in the previous modification.

In addition to the transverse partition 86, which acts as a stop for the contacts 84 and 85, the plunger 73 is provided with a longitudinally extending partition 87 to insulate the spring 76 and contact 84 from the spring 77 and contact 85. The partition 87 is made integral with the plunger 73 and transverse partition 86 to be located at either side ofthe partition 87.

The blade portions of the contacts 84 and 85 extend through complementary slots 8S and 89 at either side of the partition 87. The rounded tips of said blades project into the cavity 90 in the front face of the plunger 73. The back surface 91 of the partition 86 is slanted forwardly and inwardly from its ends toward the center, as is shown in the plan view of Figure 7, so that the blades of the contacts 84 and 85 diverge outwardly from each other when the lamp is removed from the holders.

The springs 76 and 77 in holder 70 thus serve the dual purpose of biasing the plunger 73 outward of the housing 72 and biasing the outer ends of the contacts 84 and outwardly from each other so that the said contacts make a positive connection with the inleads of a lamp base inserted therein. The springs 76 and 77 are connected to the terminal screws 92 of the holder 70 by their portions 93 and thus also serve to conduct electrical energy to the mounted lamp.

In the cavity in the front face of the plunger 73 there is an extension 95 of the longitudinally extending partition 87 which projects forwardly of the outermost ends of the contacts 84 and 85. The extension 95 serves to insulate the contacts from each other as well as support and guide the movement of the contacts within the plunger. As seen in Figure 6, the extension 95 is generally H-shaped in end view with the legs of the H extending outwardly to the side so that the contacts 84 and 85 slidably engage within the resultant grooves at the opposide sides of the extension. Thus, the lampholder 70 is provided with recessed contacts to eliminate shock hazards which might occur if it were possible to touch the contacts While at the same time being grounded.

The lampholder for supporting the opposite end of the lamp is similar in construction to the holder 70, Aexcept that the movable plunger 73 has been eliminated and a hollow plug 102 substituted therefor. The plug 102 is, however, a duplicate of the plunger 73 except that it is fixed within the housing 101. This is accomplished by inserting in the housing 101, corresponding to the housing 72, spacers (not shown) between the opposite shoulders of the plug 102 and the end walls of the supporting grooves comparable to the grooves of lampholder 5. The metal springs 103, corresponding to the springs 76 and 77 of the holder 70, are, of course, shorter in length than springs 76 and 77 but serve the same purposes and are connected to the terminal screws 104 of the holder 100 in the same manner. Otherwise, the holder 100 at the low voltage end of the lamp is of the same overall construction as the lampholder 5.

Since the extension 95 in the cavity 90 of the plunger 73 and the comparable extension in the plug 102 are larger than rthe central portion 58 of the passage 12 in the lamp base 2 it is clear that only the lampholders 4 and 5 are to be used with the lamp base 2. In Figure 9 is shown the lamp base that is designed to engage within the lampholders 70 and 100 of Figures 6-8. The

-lamp lbase 110 is mostly the same as lamp base 2 with a metal shell 111, a plastic disk 112, the oval embossment 113, central passage 114, and a deep recess leading to the passage 114 in order to accommodate the extension 95 -of the lampholder. The inleads of the lamp are brought in through the back of the base 110 and folded to lie in the grooves 115 in the same manner as taught in the lamp base 2 of Figure 2.

Consequently, having shown and described two species of lampholders embodying my invention, it will be readily apparent to those skilled in this art that I have devised a means to eliminate shock hazards by using recessed contacts in the lampholder to cooperate with recessed terminals in the lamp bases. By so doing it is impossible for a person to touch either one of the two contacts in the lampholders with the hand. If the person were grounded he would not experience a high-voltage surge through his body. This is accomplished without forfeit-ing good electrical contact between the lampholder and the lamp base because of the novel shape of the lampholder contacts and their relative positions in the lampholders.

Modifications of this invention will occur to those skilled inthis art, and it is to be understood, therefore, that this invention is not limited to the particular embodiments disclosed but that it is intended to cover all modifications which are within the true spirit and scope of this invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A lampholder comprising walls defining an openended housing, a hollow contact support member mounted in said housing, said member having a transverse partition recessed lfrom its outer end and defining with the walls of said member an outwardly opening cavity, the surface of said partition facing away from said cavity having inwardly slanting portions, and said partition having a contact-receiving slot therethrough, said holder comprising also a pair of flat spaced electrical contacts extending through the slot in said partition and terminating within said cavity, the forward end portions of said contacts being cam-shaped and the rearward ends thereof having transverse portions, and springs mounted within said housing and 4biasing said contact outwardly with their transverse portions pressed against the said slanted surface portions of said partition to hold said contacts in outwardly divergent positions, and a longitudinally extending partition mounted within the said support member to insulate each spring and contact from the other, whereby a wiping electrical contact is made between said holder contacts and the terminals of a lamp base suitably shaped to engage the cam-shaped ends of said contacts and thereby to cause displacement of said cont-acts from their divergent positions into parallel positions against the force of said springs on insertion of a lamp base into the cavity of said contact support member.

2. A lampholder comprising walls defining an openended housing, a contact-supporting hollow plunger extending through the opening in said housing and springs within said housing biasing said plunger outwardly against a limit means on said housing, said plunger having a transverse partition recessed from its outer end and defining with the walls of said plunger an outwardly opening cavity, the surface of said partition facing away from said cavity having inwardly slanting portions, and said partition having a contact-receiving slot therethrough, said holder comprising also a pair of at spaced electrical contacts extending through the slot in said partition and terminating within said cavity, the forward end portions of said contacts being cam-shaped and the rearward ends thereof having transverse portions, the said springs within said housing engaging the transverse portions of said contact and pressing said portions against the said slanted surface portions of said partition to hold said contacts in outwardly divergent positions, and a longitudinally extending partition mounted within the said plunger to insulate each spring and contact from the other, the outer end of said lastmentioned partition terminating beyond the outermost ends of the said contacts, whereby a wiping electrical con tact is made between said holder contacts and the terminals of a lamp base suitably shaped to engage the camshaped end of said contacts and thereby to cause the displacement of said contacts from their divergent positions into parallel position against the force of said springs on insertion of a lamp base into the cavity of said plunger.

3. A lampholder comprising walls dening an openended housing, a contact-supporting hollow plunger extending through the opening in said housing, and springs within said housing biasing said plunger outwardly against a limit means on said housing, said plunger having a transverse partition recessed from its outer end and defining with the walls of said plunger an outwardly opening cavity, the surface of said partition facing away from said cavity having inwardly slanting portions and said partition having a contact-receiving slot therethrough, said holder comprising also a pair of fiat spaced electrical contacts extending through the slot in said partition and terminating within said cavity, the forward end portions of said contacts being cam-shaped and the rearward ends thereof having transverse portions, the said springs within said housing engaging the transverse portions of said contacts and pressing said portions against the said slanted surface portions of said partitions to hold said contacts in outwardly divergent positions, and a longitudinally extending partition mounted within the said plunger to insulate each spring and contact from the other, the outer end of said last-mentioned partition terminating beyond the outermost end of the said contact, whereby a wiping electrical contact is made between said holder contacts and the terminals of a lamp base suitably shaped to engage the cam-shaped end of said contacts and thereby to cause displacement of said contacts from their divergent positions into parallel positions against the force of said springs on insertion of a lamp base into the cavity of said plunger.

4. A lampholder comprising walls defining an openended housing, a hollow contact support member telescopically arranged with said housing, said member having a transverse partition recessed from its outer end and defining with the walls of said member an outwardly opening cavity, and a pair of contact-receiving slots formed through said partition to lie within a common plane, and a longitudinally extending partition between the said slots in the rear of the said support member to form separated chambers, said holder comprising also a pair of spaced electrical contacts extending through the said slots in said partition and terminating within said cavity, the forward end portions of said contacts being cam-shaped of rounded shape and the rearward ends thereof having transverse portions, and a member formed within said cavity between said slots to insulate said contacts from each other as well as to support them in their movement, and a spring mounted within each of the said separated chambers of the support member and biasing said contacts outwardly through the said slots, whereby a wiping electrical contact is made between said holder contacts and the terminals of a lamp base suitably shaped to engage the ends of said contacts.

5. A lampholder comprising walls defining an openended housing, a hollow contact support member mounted in said housing, said member having a transverse partition recessed from its outer end and defining with the walls of said member an outwardly opening cavity, and a pair of contact-receiving slots formed through said partition to lie within a common plane, and a longitudinally extending partition between the said slots in the rear of said support member to form separated chambers, the rear surfaces of said transverse partition within the said separated chambers being forwardly inclined to each other inwardly of the sides of the support member, said holder comprising also a pair of flat electrical contacts extending through the said slots in said partition and terminating within said cavity, the forward end portions of said contacts being cam-shaped and the rearward ends thereof having transverse portions, and a spring mounted within each of the said separated chambers of the support member and biasing said contacts outwardly through the said slots to hold said contacts in outwardly divergent positions, and an extension member of said longitudinal partition formed within said cavity between said slots to insulate said contacts from each other, whereby a wiping electrical contact is made between said holder contacts and the terminels of a lamp base suitably shaped to engage the camshaped end of said contacts and thereby to cause displacement of said contacts from their divergent positions into parallel positions against the force of said springs on insertion of a lamp base into the cavity of said support member.

6. in a lampholder as recited in claim 5 wherein the outer end of the said extension member formed within said cavity extends beyond the outermost ends of the said contacts so that the contacts are in effect recessed within the contact support member.

7. A lampholder comprising walls defining an openended housing. a contact-supporting hollow plunger extending through the opening in said housing, said plunger having a transverse partition recessed from its outer end and defining with the walls of said plunger an outwardly opening cavity. and a pair of contact-receiving slots formed through said partition to lie within a common plane. and a longitudinally extending partition between the said slots in the rear of the plunger to form separated chambers. and springs within each of said chambers biasing said plunger outwardly against a limit means on said housing, the rear surfaces of said transverse partition within the said separated chambers beinginclined forwardly toward each other from the sides of the plunger, said holder comprising also a pair of Hat spaced electrical contacts extending through the said slots in said partitions to hold said contacts in outwardly divergent positions, and a member formed within said cavity between the said slots to insulate said contacts from each other as well as to support them in their movement, the outermost end of said last-mentioned member extending beyond the outer ends of the contacts so that the contacts are in effect recessed within the said plunger` the forward end portions of said contacts being cam-shaped whereby a wiping electrical contact is made between said holder contacts and the terminals of a lamp base suitably shaped to engage the cam-shaped end of said. contacts and thereby to cause displacement of said contacts from their divergent positions into parallel positions against the force of said springs on insertion of thc lamp base into the cavity of said plunger.

No references cited.

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