US3358910A - Vacuum pump - Google Patents

Description

Dec; 19, 1967 ZENJIRO ODA ETAL VACUUM PUMP Filed Nov. 15, 1965 '2 Sheets-Sheet l INVENTORS ZM/wo 0114 BY 727600 JIM/min I ATTORNEYS v I Dec. 19, 1967 ZENJIRO ODA ETAL 3,358,910

VACUUM PUMP Filed NOV. 15,- 1965 2 Sheets-Sheet 2 I HLLQ INVENTO 5 EA/J/PO DA ATT RNEYS United States Patent Office 3,358,910 Patented Dec. 19, 1967 3,358,910 VACUUM PUMP Zenjiro Oda and Tatsuo Asamaki, Tokyo, Japan, assignors to Nippon Electric Company, Limited, Tokyo, Japan, a corporation of Japan Filed Nov. 15, 1965, Ser. No. 507,727 Claims priority, application Japan, Nov. 16, 1964, 39/ 64,674 4 Claims. (Cl. 230-69) ABSTRACT OF THE DISCLOSURE A vacuum sublimation pump having a large supply of getter material in wire form therein with means for feeding the wire to a two-stage filamentary heater arrangement and a detector electrode adjacent the heater for sensing the position of the end of the getter wire.

This invention relates to a vacuum pump, and more particularly, to such a device of the type known as a getter pump.

As those knowledgeable in the art are aware, a titanium sublimation pump has recently been developed, and in the operation thereof, a getter material is sublimated in a comparatively low temperature heater. This pump is capable of producing an ultra high vacuum i.e., a pressure below 1( mm. of Hg and is further capable of producing this degree of vacuum very rapidly. Nevertheless this pump does have several disadvantages, one of these being that the internal surface of the vacuum chamber must often be exposed to contaminants such as water vapor, oil and so forth, which exist in the room air, as the getter material must be supplied from the outside in a rather short time interval of, for example, working hours. Such contamination causes the further disadvantages of reduced pump efficiency and decreased life.

Accordingly, it is an object of this invention to eliminate such disadvantages and to provide a novel pump arrangement of the type referred to herein which has a higher pumping speed, increased efiiciency and longer life.

Further objects and features of the present invention are:

(a) A getter material supply means is provided which is adapted to supply the material in a vacuum chamber in response to consumption of the getter material, so that it is now practicable to continue the pump operation for a long period of time without breaking vacuum provided that a sufficiently large amount of getter material is stored therein:

(b) Since the getter material is continuously supplied through the supply means, it is possible to raise the evaporating rate of the getter material, whether by sublimation or evaporation, and it is further possible to construct a pump with a relatively high pumping speed, such as of the order of several thousand l./s., even with a small sized pump; furthermore, since it is practical to enlarge the ratio of the evaporation speed of the getter material to the consumed electric power, the vacuum vessel will not become over-heated and accordingly this factor is not a limitation, so that a relatively high vacuum can be achieved.

(c) According to yet another feature of the invention, the getter material is purified by heating the same to a predetermined temperature before evaporation thereof, and consequently, the out-gassing rate at the time of evaporation of the material can be reduced, and for this further reason an ultra-high vacuum can easily be achieved.

(d) Contamination of the pump can now be avoided, because there is virtually no need to expose the internal parts of the pump to the air or touch it with the hands.

(e) Means are provided to detect electrically whether or not the getter material is being supplied properly, and if it is not, the supplying operation can be corrected in a safe and easy manner.

(f) The operation of the pump according to this invention can be started at an exceedingly low vacuum, because it is not provided with a structure to perform ionization of residual gas by using a hot cathode and a lattice type anode, or a structure wherein a getter material is evaporated by electron bombardment by employing a hot cathode.

Other objects and novel features of the invention will be pointed out or will occur to those skilled in the art from a reading of the following specification taken in conjunction with the accompanying drawing. In said drawing, which shows, for illustrative purposes only, preferred forms of the invention:

FIG. 1 is a front elevation of a pump arrangement according to one embodiment of the invention, with parts broken away for illustrative purposes; and

FIG. 2 is a side elevation, also with parts broken away, of the embodiment of FIG. 1.

In FIGS. 1 and 2, the numeral 1 denotes a getter material in a getter supply bank, and is supplied continuously by means of a getter supplier 10 which is one of the features of this invention. The getter material 1 is evaporated by means of an evaporation structure 30, such evaporation being effected by a power source, not shown, which supplies electric power for this purpose. The evaporated getter material adheres to the wall of a vacuum vessel surrounding the pump and traps or exhausts gas by adsorption.

In the supplier 10, the numerals 11 and 12 denote rollers for transferring the getter material 1, numeral 13 is a bearing, 14 is a driving shaft for the roller 12, 15 denotes a handle fitted to the driving shaft 14, 16 represents a supporter for an O-ring 17, 19 denotes a nut, 20 is a bushing for maintaining an air tight vacuum by. pressing the O-ring 17 against the supporter 16 by clamping with the nut 19, 18 is a screw for clamping the getter material 1 and the rollers 11 and 12, 21 is a spool of getter material in wire form, 26 a supporting member for the spool 21, 22 a rod-like getter material guide, 23 a tubular getter material guide, 24 a support arrangement for the guide 23, and 25 an insulating stone for determining the relative positions of a pair of elec trodes, as will appear. The spool 21 preferably contains a relatively large amount of getter material. This getter material is pushed forth or fed from the rollers 11 and 12 by the rotation of the driving shaft 14 and travels to the evaporation structure 30 through the guides 22 and 23. A mark 27 is provided above the handle 15 to indicate the quantity of the getter material that is fed to the evaporation structure 30. A detecting electrode 28 is connected to a lead-in electrode 29 which is electrically insulated in an appropriate manner from a flange and the remaining structure. When the getter material is sufficiently supplied, it contacts the electrode 28, establishing an electrical closed circuit by suitable circuitry, between the flange and the electrode 28, thereby effecting sensing or detection of the getter material since the same is in contact with the flange.

In the evaporation structure 30, the numerals 31 and 32 indicate heaters, 35 and 36 rod-like terminals, and 37, 38 and 39 metal fittings for clamping the heaters by screws 34. Electric .power is supplied to the heaters by means of a power source, not shown, to heat the getter material and evaporate the same as aforesaid.

The evaporation structure 30 and the driving structure for the getter material 1 are connected to a vacuum vessel 50 of the pump. The numeral 51 denotes a flange for connecting the device of this invention to a body to be exhausted, whereby the evaporation structure 30 is placed inside of such body. When such connection is made and the getter material 1 is evaporated, the resulting arrangement has a high exhaust capacity and is capable of relatively high pumping speeds. The numeral 53 represents a plate and the numerals 52 and 54 represent tubes and together these form the vacuum vessel. The numeral 55 denotes a flange for a terminal fitting assembly 60. Numeral 65 represents a paired flange for the flange 55 and is fixed to this flange by bolts, nuts and gaskets, not shown, in a vacuum. Numeral 61 denotes a connecting pipe and 63 is an insulating stone and forms a terminal sealed by sealing bodies 62 and 64 made, for instance, of material known by the trade name Kovar.

The supply of the getter material 1 can be easily replenished by adding more getter material to the spool 21, which can be taken out by detaching the paired flange 65 from the flange 55.

The pump is operated in the following manner. The assembled vacuum system is first exhausted to a vacuum of approximately torr by means of a roughing or backer pump, such as, for example, an oil rotary pump or adsorption pump. An electric current is then fed for about 80% of the operation time of this pump, or about one minute, to the heaters 31 and 32 to expel gas, and subsequently, the electric current for the heater 31 is set to a regular value.

The heater 32 is for the purpose of expelling gases, and therefore it is energized only when necessary. Thus, the getter material in the heater 32 is evaporated and the resultant gas discharged getter material is designed to be supplemented whenever the getter in the heater 31 is consumed during operation at high vacuum. After the initial expulsion of gas by the hacker pump, the roughing system is not necessary and therefore it is closed off by means of a valve or the like.

This roughing system pump has an exceedingly small pumping speed for an inactive gas, and therefore for greater speed it is preferable that it be used together with a getter ion pump, a cryopump, or other suitable pump.

Although this invention has been described with respect to a particular embodiment thereof, it is not to be so limited, as various modifications are possible. For instance, the evaporating means need not necessarily be a coil heater, as a cylindrical or other suitable type will be satisfactory for the purpose. Also, the heater temperature for evaporation may be selected as necessary. As to the driving mechanism, it may be either of the manual or automatic type as necessary or desired. Further regarding the getter material, the same may be supplied in various different shapes and forms such as powder, short rod, ball shape, etc. The supplying structure should also, of course, conform with the type of material. Although the amount of the getter material being supplied is indicated by the mark 27 or the detecting electrode 28, it is desirable that a reflecting mirror be installed at a suitable location so as to more easily allow continuous observation of the condition of the heaters.

Also, the electric heating current for evaporating the getter materials can be continuous or pulsating, but it is desirable that the ratio (amount of evaporation) (mean consumed electricity) be large. To make this ratio large and to maintain purification of the getter material are most important factors in obtaining an ultra-high vacuum with the pump of this invention. Accordingly, in order to operate the device for a long period, i.e., of the order of a year, without breaking vacuum, it is essential that the heater 32 be placed in a chamber which communicates with another vacuum pump. In this manner, a getter material which is baked out in a separate vacuum chamber to remove occluded gas, may be conducted into the heater 31.

Further, the getter material may be replenished, without breaking vacuum, by providing a side chamber in the apparatus, to supply a getter material to the spool Whenever the getter material is used up. In this connection, see the article, especially FIG. 2, by Mr. Ito and Mr. Ishii, on page 134, in the Journal of the Vacuum Society of Japan, vol. 7, No. 4, 1964.

While the foregoing description sets forth the principles of the invention in connection with specific apparatus, it is to be understood that the description is made only by Way of example and not as a limitation of the scope of the invention as set forth in the objects thereof and in the accompanying claims.

What is claimed is:

1. In a vacuum sublimation pump wherein evacuation of gas is achieved with the aid of evaporation of a getter material, the combination comprising:

means for continuously feeding getter material from a getter supply bank,

a first filamentary type heater for continuously melting said getter material in a chamber,

a second filamentary type heater adjacent said first heater for periodically melting an additional amount of getter material to supplement the amount of such material vaporized by said first heater,

means for sensing the presence or absence of said getter material in the region of said melting means Whereby the same may be controlled to insure the continuous supply of said material to said melting means,

said sensing means including a contact electrode positioned to be engaged by said getter material,

and means for allowing the getter material in said getter supply bank to be replenished without breaking vacuum in said chamber, whereby said pump may be continuously operated for extremely long periods of time.

2. The invention described in claim 1 wherein said means for melting includes said two heaters spaced in tandem relationship along the path of travel of said getter material between the getter supply bank and said contact electrode.

3. The invention described in claim 1 wherein said getter supply bank includes a spool of getter material in Wire form, said combination further including a pair of rollers for feeding said getter material to said melting means.

4. The invention described in claim 1 which further comprises means including a flange between Said getter supply bank and said melting means for enclosing said latter means within a vessel to be maintained at a high vacuum.

References Cited UNITED STATES PATENTS 2,954,156 9/1960 Meyer 23069 3,056,740 10/1962 Holland et a1. 230-69 3,249,291 3/1966 Ackley 23069 FOREIGN PATENTS 859,915 1/1961 Great Britain.

OTHER REFERENCES German printed application, 1,055,747, February 1957.

DONLEY J. STOCKING, Primary Examiner.

WILLIAM L. FREEH, Examiner.

Claims (1)

1. IN A VACUUM SUBLIMATION PUMP WHEREIN EVACUATION OF GAS IS ACHIEVED WITH THE AID OF EVAPORATION OF A GETTER MATERIAL, THE COMBINATION COMPRISING: MEANS FOR CONTINUOUSLY FEEDING GETTER MATERIAL FROM A GETTER SUPPLY BANK, A FIRST FILAMENTARY TYPE HEATER FOR CONTINUOUSLY MELTING SAID GETTER MATERIAL IN A CHAMBER, A SECOND FILAMENTARY TYPE HEATERR ADJACENT SAID FIRST HEATER FOR PERIODICALLY MELTING AN ADDITIONAL AMOUNT OF GETTER MATERIAL TO SUPPLEMENT THE AMOUNT OF SUCH MATERIAL IN THE REGION OF SAID MELTING MEANS WHEREMEANS FOR SENSING THE PRESENCE OR ABSENCE OF SAID GETTER MATERIAL IN THE REGION OF SAID MELTING MEANS WHERE-

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