US2018965A - Clean-up agent - Google Patents

Description

Patented Oct. 29, 1935 UNITED STATES 2,018,965 CLEAN-UP 'AGENT' John D. McQuade, Lakewood, Ohio, assignor to Kemet Laboratories Company, Inc., a corporation of New York No Drawing. Application November 10, 1933,

Serial No. 697,545 r 7 Claims.

The invention relates to clean-up agents for use in producing high vacuums, referring more specifically to clean-up agents comprising compacted comminuted metals and alloys.

To improve the vacuums of such high vacuum devices as thermionic valves, it is customary to vaporize a highly reactive material within the imperfectly evacuated device, whereby gases are adsorbed by or reacted with the active material. This active material is commonly in the form of a getter tablet, lozenge, or pill. A frequently used method of vaporizing the clean-up agent is to mount the tablet on a tab, strip, or cup of metal within the device to be evacuated, and to heat the tab and clean-up agent by inductive electric heating to the vaporizing temperature of the active material. The vaporizing operation is commonly termed flashing.

All of the metals and alloys commonly used for getters, for example, barium, magnesium, sodium, barium-magnesium alloy, bariumstrontium-magnesium, alloy, barium-aluminum alloy, barium-silicon, mischmetal, and the like, are substantially Similarly, all of the metals commonly used as supporting tabs or cups for the getters, for example, nickel and iron, are also substantially silver-colored materials.

As a result, partly of the similarity in the of the getters and supporting tabs, and partly of the diminutive size of the usual getter tablet, careful inspection is required to ascertain whether a given getter and tab assembly actually contains a getter tablet. It is not at all an un common occurrence that the getter tablet is missing from an assembly placed in an otherwise.

perfect electronic device during manufacture of with the result that the electronic device must be scrapped. A more conspicuous getter tablet would avoid most of such mishaps.

It is an object of the present invention to provide a getter tablet or pill, of the type above described, having a distinct color which renders the tablet conspicuous against a silver-colored background.

It is a further object of the invention to provide a getter tablet or pill comprising compacted comminuted metal more firmly coherent than the getters previously known. 7

A further object is to provide a getter tablet having improved stability in air.

These and other objects are attained in the present invention which provides a getter comprising comminuted active getter material and comminuted copper pressed into the form of a.

silver-colored materials.

ing operation.

more of these metals with aluminum, beryllium,

magnesium, nickel, or silicon. An alloy containing at least about 15% of the alkali metal, alkaline earth metal, or rare earth metal, is suit- 15 An alloy comprising barium and magnesium, or barium, strontium, and magnesium, is preferred. 7

The copper may be of commercial purity, but is I preferably relatively free from gases. Heating 20 the copper powder in a vacuum will yield a suitably gas-free material. Obviously, certain redtrolytically deposited finely dendritic copper.

The getter material may be mounted on the the loose getter materia in place within a preformed depression in the tab or cup; or by form- 35 ing the tabletiandthe depression in one press- Alternatively, the getter material may be formed into a tablet or pill and supported on a tab, or in a cup, by'a screen or other suitable known holding means. 40 I have found by experiment that the clean-up agent of the invention preferably comprises about 50% to of active material, such as barium-magnesium alloy, and about 25% tablets, and may be fabricated in shapes and 55 of the getter without 5.

sizes heretofore considered impossible or impracand the balance active clean-up material chosen tical to manufacture. from the group consisting of the alkali metals,

I claim: the alkaline earth metals, the rare earth metals,

1. A clean-up agent comprising a mixture of and. alloys thereof containing at least about 15% 5 comminuted copper and comminuted silver-colof the said. metals; the copper being physically 5 cred active clean-up material, the copper formseparable from the active material and being ing about 25% to 50% of the mixture; the coppresent in suflicient amount to impart a reddish per being physically separable from the active color to the clean-up agent. ,7 material and being present in sufiicient amount 5. A reddish-colored clean-up ag nt compris- 1 to impart a reddish color to the clean-up agent. ing a coherent aggregate of comminuted copper 2. A clean-up agent comprising an intimate and comminuted silver-colored active clean-up mixture of comrninuted copper and comminuted material; the copper forming about 25% to 50% active material chosen from the group consist Qf the said. aggregate and being physically sepaing of the alkali metals, the alkaline earth f rable irom the-active clean-up material.

metals, the rare earth metals, and alloys thereof- 6; A getter: assembly comprising a thin piece 15 containing at least about 15% of the said metals; or substantially silver-colored metal provided the pp forming about t0? 0f the witha-depressiomand a reddish-colored cleanmixture; the copper being physically separable upliagent containing copper and silver-colored from the active material and being present in active clean-up material firmly secured in the sufiicient amount to impart areddish color'to'the' depression, the copper forming about to 20 clean-upagent. 'T 50% of the said agent'andbeing physically sep- --3. A clean-up agentcomprisingabout 25% to arable fronrathe saidactive clean-up'material, 50% copper, the balance an alloy of barium, 7. Agetter" assembly comprising a thin piece strontium, and magnesium; the copper being of substantially silver-colored metal provided 25 physically separable from the said alloy and bewith a depression, and firmly secured in the 25 ing. present in sufiicient amount to impart a reddepression, a reddish-colored clean-up agent dish color to the clean-up agent. composed of copper and an alloy of magnesium 4. A getter assembly comprising a thin piece with an alkaline earthmetal, thercopperform: of' substantially silve -colored metal provided ing about 25% to 50% of said: agent and being with a circumscribed depression and firmly se-' physically separable fromsaidralloy. 30

cured. in the depression a reddish-colored cleanup agent containing about 25% to copper JOHN D. MCQUADE.