US2359500A

US2359500A - Sealing-in method

Info

Publication number: US2359500A
Application number: US176910A
Authority: US
Inventors: Arthur J White
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1937-11-27
Filing date: 1937-11-27
Publication date: 1944-10-03
Anticipated expiration: 1961-10-03

Description

I Oct. 3, 1944. A. J. WHITE SEALING-IN METHOD Original Filed Nov. 27, 1957 Inventor: Arthur J. White b W 9 His A ttorneg. I

Patented Oct. 3, 1944 SEALING-IN METHOD Arthur J. White, Cleveland Heights, Ohio, assignor-to General Electric Company, a corporation of New York Application November 27, 1937, Serial No. 176,910

Renewed January 11, 1940 7 Claims.

My invention relates to an improved method of sealing together the ends of tubular glass members, and more particularl to a method of sealing glass stems in the bulbs or envelopes of electric lamps or similar devices.

Stems for electric lamps and similar devices generally comprise a glass stem tube having one end fused around a portion of one or more leadin wires extending through the tube, the other end of said tube being flared or flanged outward. The stem is sealed in a bulb or envelope by inserting it therein and then applying gas flames to fuse the open end or neck portion of said bulb or envelope and the flange on said stem to seal them together.

The above method has the disadvantage in some instances that the gas flames distort a considerable portion of the bulb or envelope adjacent to the seal. This may be objectionable for several reasons, one of which is that the subsequently attached base may not be properly seated on the bulb. Moreover, the gas flames may, in some instances, adversely affect the lead-in wires extending from the stem.

One of the objects of the present invention is to provide a new and improved method of sealing a stem in anenvelope which will obviate the above-mentioned disadvantages and will seal a stem in an envelope without distortion of the portion of the envelope adjacent to the sealed joint. Another object is to provide a method by which the stem is quickly and efliciently sealed in the envelope to produce a hermetical seal free from cracks. Other objects and advantages of my invention will appear from the following descripof the lamp with a base attached thereto.

According to my invention, the method of sealing consists generally in placing a stem with its flanged end resting on a disc or ring of a material which is capable of being heated by induction and will not adhere to the fused glass, such as carbon. The envelope is then placed over the stem with its open end or neck portion resting on the flange or adjacent thereto. .The .said disc or ring is then heated to a high degree by induction to cause the adjacent ends of the stem and envelope to be fused and sealed together by conduction and radiationof heat from the said disc or ring. Pressure may be applied at the opposite end of the envelope, if desired, to press the fused ends of the envelope and stem thereagainst.

Referring to Fig. 1, the lamp illustrated therein in process of assembly comprises a tubular glass envelope l0 having a stem l l at its upper end (shown as already sealed in), and another stem I2 at its lower end about to be sealed in. The

said stem I2 is of the so-called tipless variety and comprises a glass stem tube 13 and an exhaust tube [4 which are fused at their upper ends to form a mass of glass [5 enclosing portions of lead-in wires ill-i6, there being an axial opening I'l through the said mass of glass formed by blowing through the said exhaust tube 54. An electrode l8, consistingpreferably of a coiledcoil of tungsten wire coated with an electron emissive material such as barium and/or, strontium oxide, is secured at its ends to the inner ends of the lead-in wires l6l6. It is very desirable that the stemsbe as short as possible in order that the electrodes Ella-l8 may be close to the ends of the envelope l0. Therefore, in making the stem l2 it is held in an upright position and the upper ends of the stem tube 13 and exhaust tube M are heated to fusion by gas flames, causing them to collapse and flow down along the lead-in wires lB-IB to form the solid mass of glass 15. While the glass mass I5 is stillplastic, air pressure is applied to the exhaust tube ill to blow the opening 11, there being no compression or pressing of the glass mass i5 by a pair of jaws at any time as is the usual present practice. Air-is also blown into the space between the exhaust tube l4 and stem tube l3 to round out the joint therebetween, thereby eliminating sharp corners which may lead to cracks. During the flowing of the glass downward along the lead-in wires !6--I6, the said wires are coated with a layer of glass, and breaking off this coating leaves a clean surface, free from oxide, to which the ends of the electrode l8 may be readily welded. The stem II is made in the same manner except, of course, that the exhaust tube I4 is omitted. This method of making the stems is described and claimed in my application No. 176,909, of even date, now Patent 2,128,173. Of course, stems made according to standard practice may be used if desired.

For sealing in the stem 12, I have illustrated in Fig. 1 an apparatus comprising a support 'rod or block I 9 of refractory insulating material, such as sillimanite, having a disc or ring 20 of material which is capable of being heated by induction and will not adhere to glass, preferably carbon. placed on its upper end. The stem I2 is placedwith its flanged end 2| resting on the disc 20 in abutting relation therewith, the exhaust tube II and lead-in wires l8i8 extending into an axial opening 22 in the supp rt rod IS. The envelope I is then clamped in the jaws of a holder 3| and it is lowered until the reduced open end or neck portion 23 thereof rests on the flange 2|. A coil 24, which is connected to a suitable source 32 of high frequency current, is then slowly raised by a lever 33, for example,

o as to surround the disc 20, thereby heating the said disc by induction to a very high degree and causing .the envelope neck 23 and flange 21 to be fused and sealed together. Pressure is preferably applied to the envelope l0 during the sealing operation, for example, by a suitable weight 25. By this method of sealing the neck 23 of the envelope is not distorted, nor is the shoulder 26 distorted, nor is any portion of the short stem l2 distorted. The envelope in and stem l2 are permitted to remain on the disc 20 for a short period after the current flow to coil 24 has been interrupted so that the sealed joint is annealed.

By making the flange 2| large enough to extend a short distance beyond the neck 23 of the bulb, as shown in Fig. 1, a small head 21 may be formed at the sealed joint which may be desirable for preventing the base from being pulled oil the envelope. In Fig. 2, I have illustrated one form of base comprising a shell 28 of insulating material which is butted against the shoulder 26 and is attached to'the neck 23 of the envelope by cement 29, the bead 21 being embedded in said cement. Since the shoulder 26 is undistorted, the bases 28 of diflerent lamps are always uniformly mounted and the overall lengths of the lamps are held within close limits. Each of the bases 28 is in this instance provided with a pair of pins 30-30 to which are connected the lead-in wires l6-l6.

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

1. The method of sealing a glass stem tube to the glass envelope of an electric lamp or similar device which comprises placing adjacent ends of said stem tube and envelope against a disc of material which is capable of being heated by induction and will not adhere to glass and then heating said disc by induction to cause a portion of the generated heat to flow by conduction to the abutting ends of said stem tube and envelope to fuse them together.

2. The method of sealing a glass stem tube to the glass envelope of an electric lamp or similar device which comprises placing adjacent ends of said stem tube and envelope against a disc 01' carbon and then heating said disc by induction to cause a portion of the generated heat to flow by conduction to the abutting ends of said stem tube and envelope to fuse them together.

3. The method of sealing a glass stem tube having a flanged end to the end of the glass envelope of an electric lamp or similar device which comprises positioning said stem tube with its flanged end in abutting relation with a disc of material which is capable of being heated by induction and will not adhere to glass, placing said envelope over said stem tube with its end pre ing against the said flanged end of said stem tube, and then heating said disc by induction to cause a a portion of the generated heat to flow by conduction to the abutting ends of said stem tube and envelope to fuse them together.

4. The method of sealing adjacent ends of glass tubes together which comprises arranging said tubes one within another with their adjacent ends against a disc of material which is capable of being heated by induction and will not adhere to glass and then heating said disc by induction to cause a portion of the generated heat to flow by conduction to the abutting ends of said tubes to fuse them together.

5. The method of sealing adjacent ends of glass tubes together which comprises arranging said tubes one within another with their adjacent ends in contact and at least one of them abutting against a disc of material which will not adhere to glass and then heating said disc to cause a portion of the generated heat to flow by conduction to the said ends of said tubes to fuse them together.

6. The method of sealing adjacent ends of glass tubes together which comprises arranging said tubes one within another with their adjacent ends in contact and at least one of them abutting against a disc of material which will not adhere to glass and then heating said disc electrically to cause a portion of the generated heat to flow by conduction to the said ends of said tubes to fuse them together.

7. The method of sealing a glass stem tube to the glass envelope of an electric lamp or similar device which comprises placing adjacent ends of said stem tube and envelope in contact with each other and the end of one of them against a disc of material which will not adhere to glass and then heating said disc to cause a portion of the generated heat to flow by conduction to the said ends of said stem tube and envelope to fuse them together.

' ARTHUR J. WHITE.