US2583434A - Timing device - Google Patents

Description

Jan. 22, 1952 s. F. E. MEYER TIMING DEVICE 2 Sl-IEETS-Sl-XEET 1 Filed Oct. 17, 1947 mmv ox.

I Sven FE: Mg er @061; +06% 1., ATTORNEYJ EYER Jan. 22, 1952 s. F. E

TIMING DEVICE 2 Sl-lEETS-Sl-IEET 2 Filed Oct. 17, 1947 IN V EN TOR.

ATTORNEYS Patented Jan. 22, 1952 TIMING DEVICE Sven Fredrik Erhard Meyer, Stockholm, Sweden, assignor to Svenska, Lasmutter Aktiebolaget, Stockholm, Sweden, a corporation of Sweden Application October 17, 1947, Serial No. 780,525 In Sweden December 9, 1946 7 Claims. 1

My present invention mainly relates to mercury switches, and more particularly to such types hereof where the closing of a current takes place some time after the switch has been set in operation. In the prior art such time lags have been-accomplished, as far as mercury switches are concerned, by means of clock works, air brakes, thermal means or by capillary retarding means in a mercury conduit. The closest approach in the prior art to my invention is in fact the mercury capillary switch, since it offers the advantage of having no mechanical moving parts, which is also a feature of the present invention. Mercury capillaries, however, do not readily lend themselves to producing time delays having durations of more than a few minutes, owing to the fact that narrow mercur capillaries are apt to become air bound, in which case the mercury ceases to flow. Using large mercury charges will, on the other hand, lead to ungainly dimensions of, and excessive manufacturing costs for, the switches.

A gravity operated delayed action mercury switch generally consists of two receptacles, partially filled with mercury and charged with a gas inertto mercury, such as hydrogen. When provided with a mercury capillary between the receptacles the hydrogen has unrestricted access to both of the mercury levels.

In my invention I have wholly dispensed with the mercury capillary conduit, substituting for it a hydrogen capillary of a unique type, to take up, and slowly release, the pressure difference between the mercury receptacles. This design permits me-in certain embodiments of the inventionto operate the switch by thermal means instead of by gravity alone. The particulars of the invention are to be more fully explained in conjunction with the appended drawings in which:

Figs. 1, 2, 3, 4 and 5 illustrate methods of producing the aforementioned hydrogen capillary; Fig. 6 a delayed flow device in which the hydrogen capillary is put in and out of action by electro-magnetic means; Fig. 'I an embodiment of a mercury switch having a delayed breaking action; Fig. 8 a cross section of the device shown in Fig. 7; Fig. 9 a switch for delayed closing of a current; Fig. 10 a modification of the switch shown in Fig. 7; Fig. 11 a switch for delayed breaking of a current; Fig. 12 an electromagnetically operated switch for closing a current and automatically breaking it after a certain period of time; Fig. 13 a thermally operated breaking and delayed makingswitch; Fig. 14 a switch for delayed breaking action in which the mercury passes a leaf valve when tilting the switch around; and Fig. 15 a cross section of same.

A feature common for all the embodiments shown is that the hydrogen capillary is formed in and with the aid ofthe mercury itself. He-

ferring to Fig. 1 numeral I represents a glass tube, 2 a mercury charge, 3 a fiat strip of metal (such as iron), and 4 a metal wire in contact with the strip 3. Owing to the capillary of the mercury and assuming the mercury Will not wet members 3 and 5 a capillary channel will form along the members on each side of the wire, as indicated by numerals 5 and 6. These channels provide adequate passages for a gas, since they are not readily clogged by any foreign matter. Should they, however, be partiall obstructed in some way or other, the passage can be cleared by simply shaking the glass tube in which they form a part. In Fig. 2 a similar capillary passageway 9 is seen to be formed in the bottom of a sharp groove along the strip 3; in Fig. 3 is shown that a screw I2 may be used as a capillary producing member; when immersed in mercury the bottom I3 of the thread will provide a passageway for the gas to be displaced. Similarly Figs. 4 and 5 show a stranded. wire (l0 and II) resp. a wire spiral l5 wound on a larger diameter core M for producing capillaries when submerged in mercury. Referring to Fig. 4 which in actual practice is the simplest and most applicable design it has been found that the capillary gas resistance may be varied within wide limits by changing the diameter of the wires. When using wires of not more than .3 mm. diameter the flow resistance is approximately inversely proportional to the 4th power of the wire diameter.

Referring to Fig. 6 numeral 26 is a U-bent glass tube partially filled with mercury 21. Numeral 28 represents a thin wire corresponding to I in Fig. 1, in one end attached to the glass (at 29), in the other end fastened to a piece of iron armature 30, 3|, magnetically cooperating with the electromagnet 32, 33. As long as the electromagnet is not in action a loop (at 34) forms in wire 28, causing the mercury to contact the wire from all sides, thus preventing any gas to pass from the right to the left gas chambers of the U-tube. As soon, however, as the magnet is energized the wire 28 will be stretched along the inner tube wall, causing capillaries to be formed in analogy with Fig. 1. Thus the mercury 21 will slowly equalize itself between the two U- tube branches. Any electrical lead-ins are omitted in this figure.

In Figs. '7 and 8, which represent a practical embodiment of the invention, is shown a glass.

vessel having two chambers 60, 6|, partially separated by recess 62. In its neutral (horizontal) position (0-0) the bottom 61 is offset at a slightly higher level than that of the left one,

causing a step to be formed at 63. The step 63 together with the wall 62 acts as a valve or trap for the mercury permitting it to flow without resistance from the righthand to the lefthand chamber but permitting flow in the opposite direction under the control of the gas flow through the capillary passage only. The conformation of the glass vessel is such that the mercury will flow from the right hand chamber 6| to the left hand chamber 68 in a relatively thin layer due to the ofiset at 63 forming a weir leaving a passage for gas adjacent the lowermost portion of the constriction 62. Due to the existence of the gas passage a very rapid flow of mercury from the right hand chamber to the left hand one occurs. On the other hand, when the tube is tipped so that its center line coincides with the line II of Figure 7, the mercury completely fills the constricted passageway so that there is no space for the passage of gas other than that space provided by the capillary passageways formed by the twisted wires 68. Consequently, the fiow of mercury from the left hand chamber to the right hand chamber is retarded. In the tube a stranded wire 68, of the type shown in Fig, 4, is carried from one gas space to the other, through the mercury filling 86. The tube is further provided with two electrical lead-ins, 64 and 65. The tubes operating position is indicated by the center line II. It will be assumed, then that all or most of the mercury was previously transferred to the left chamber, as indicated in the figure, causing electrical contact to be formed between 64 and 65. By gravity the mercury then slowly flows into the right chamber at a rate determined by the hydrogen flow along the capillary formed by 88. Eventually the contact between 64 and 65 will break. In any given switch the time lag may be varied within wide limits by choosing a corresponding slope of the center line II. Re-settin the switch is accomplished by tilting it along centerline I where the mercury will freely run towards the left, unobstructed by the barrier 62.

In Fig. 9, showing a glass vessel I8, II, a trap- I ping or valving step I3, a barrier I2, and a stranded wire H the operation is essentially the same as in Fig. 7, except that the switch is built for a delayed closing action (between lead-ins I4 and In Fig. 10, which resembles Fig. 7 except for the proportions, the glass tube is designated by I8'I9, the gas barrier by 88, the trapping or valve forming step by 82, the stranded wire by 81, and the lead-ins by 85, 86. built to be operable, i. e. re-set, without tilting. By curving the bottom of the right chamber, as indicated by 82 and by adjusting the height of dam 8| the switch may be re-set by being moved back and forth in a longitudinal direction.

Curving the chamber bottom at 82 permits the mercury pool 83 to perform a pendulum-like motion along the bottom of the tube, which will assist reloading of the left chamber with mercury. The switch is primarily intended to be used as a safety cut-out for electric irons where itwill keep the current on incessantly as long as the iron is kept in'motion and will break the current only after the iron has been at a standstill for some 4 or 5 minutes.

In the compact embodiment indicated by Fig. 11 in which numeral 88 designates an outer glass vessel, 98 an inner glass vessel open at the bottom, 89 a glass member uniting 88 and 98, 9I a stranded wire, 92 and 93 electrical lead-ins, and 94 a. mercury charge, the operation is essentially the same as'in Fig. 7. The switch is set in operation by being turned through 'a 360 angle in an anticlockwise direction when the major part of the mercury chargeaccumulates in the inner The device is r glass vessel 90, closing the electrical contact between 92 and 83. After a period of time the mercury level in the inner tube drops below the bottom end of rod 93, causing the current to be interrupted.

In Fig. 12 numeral 91 designates a glass tube, 98, 99 and I88 three separate lead-ins, I8I a glass sleeve surrounding and insulating member I88 from mercury except at the top, I82 an iron core guided in the glass tube at I83 and I84 and having a recess I85 at the bottom. Numeral I86 indicates a mercury filling, I81 a stranded wire which extends from the bottom of recess I85 to the top guide I83; I88 is an electromagnetic coil. When the coil is energized the iron core I82 is pulled upwardly to the extent that its lower edge leaves the mercury. When the coil current is interrupted the iron core I82 drops down into the position shown, causing the outer mercury level to establish contact with 99. The gas filling which is trapped in space I85 will simultaneously prevent the inner mercury level from contacting rod I88. Owing to the capillary gas leakage along the stranded wire the mercury levels will tend to equalize, which in due time will cause the electrical connection between 98 and 99 to break, and the contact between 98 and I88 to be established. The device thus constitutes a dual purpose time switch.

In Fig. 13 numerals I89 and H8 represent the left and right members of a V-shaped glass tube, partly separated by a barrier III. In the bottom of the glass tube is provided a step II2 adjoining a cup II 'i having a lead-in H6. The cup is filled with a small quantity of mercury II5, whereas the main mercury filling is designated by II3. Numeral I II shows a second leadin. In the right chamber is provided a heater resistance I28 having lead-ins H8 and H9. A stranded wire I2I passes from one chamber to the other. It should be observed, however, that the wire portion in the left chamber ends at a point which is at times covered with mercury, which is what the figure indicates. Assuming the two mercury levels to be at the same height at the outset, there will be electrical contact between terminals III; and Ill. The wire strand in the left chamber will in this position extend slightly above the mercury surface. On passing a current through the heater resistance I28 the surrounding hydrogen gas will rapidly expand, displacing the mercury towards the left and causing the contact at I I2 to break. At the same time the left tip of the wire strand will be covered by mercury, closing off the capillary passage. Obviously the contact at II2 will remain broken as long as the heater resistance is in operation and until the right chamber has had time to cool down sufficiently to permit the surrounding gas to contract. Once the contraction has proceeded far enough to uncover the left tip of the wire strand the two gas spaces have a means of communication, permitting full pressure equalization. The object of the wire strand arrangement as described is mainly to establish such communication when the device is at rest; any tendency of the gas to get unevenly absorbed or adsorbed in either of the gas spaces, which would otherwise render the device irregular or inoperative, will thus be efiectively counteracted by the gas equalization through the capillary conduit. In Figs. 14 and 15 numeral I38 designates a vertically disposed glass vessel divided into an upper chamber I3! and a lower chamber I32 by means of a sheet steel partition I33. Sald partition is kept in position by a supporting wire I42. In the partition which need not fit very snugly in the glass is provided a trickle aperture" I34 the diameter of which should be around 3 millimeters, a smaller wire aperture I35, and a larger valve aperture I36, the latter being covered with a thin gage metal flap valve I31. From the top end of the glass tube two contact rods I33 and I39 are depending, the latter equipped with a steatite end covering I40. A stranded wire I4I leads from the top to the bottom of the glass tube through the wire aperture I35. The device is partially filled with mercury.

It is set in operation by being turned upside down and then returned to the position shown. On turning it upside down the mercury will flow without appreciable restriction through the flap valve aperture I36, collecting in the upper chamber and establishing contact between terminals I38 and I39. It does not, however, readily flow back into the lower chamber owing to the capillary action in the valve, in the apertures and around the rim of the partition I33. Except for a small quantity which immediately runs through to create the required gas pressure difference between the lower and the upper gas spaces the mercury would perpetually remain above the partition, were it not for the gas capillary created by the stranded wire. Owing to the gas leakage through the capillary, however, the mercury will slowly trickle down through the aperture I34, which in time causes the electrical contact to break around member I40.

Obviously the devices described above may within the scope of the invention be varied in a large number of ways. It is possible, e. g., so to modify the device shown in Fig. 11 that it operates with its axis horizontally disposed and so that it performs a delayed making, rather than breaking, action. In the device shown in Figs. 14 and 15 a valve ball, perforated or solid, may be substituted for the flap valve. Other variations, applicable in several of the embodiments shown, consist in producing the capillary by non-metallic means such as paper, string, etc.

I claim:

1. A delay switch comprising, in combination, an insulating enclosure having a constriction forming two chambers, said enclosure being filled with gas and mercury, the bottom wall of one chamber being offset upwardly, said offset being spaced from the constriction to facilitate rapid flow of mercury from one chamber to the other, said constriction preventing rapid flow from said other chamber to said one chamber, and a gas capillary extending through the mercury from one chamber to the other, said capillary determining the rate of flow of mercury from said other chamber to said one chamber.

2. A delay switch comprising, in combination, an insulating enclosure having a constriction forming two chambers, said enclosure being filled with gas and mercury, the bottom wall of one chamber being ofiset upwardly, said offset being spaced from the constriction to facilitate rapid flow of mercury from one chamber to the other, said constriction preventing rapid flow from said other chamber to said one chamber, a gas capillary extending through the mercury from one chamber to the other, said capillary determining the rate of flow of mercury from said other chamber to said one chamber, and a plurality of contacts extending through said enclosure into contact with the mercury therein when the major portion of the mercury is in one of said chambers.

3. A delay switch comprising, in combination, an insulating enclosure having a constriction forming two chambers, said enclosure being filled with gas and mercury, the bottom wall of one chamber being ofiset upwardly, said offset being spaced from the constriction to facilitate rapid flow of mercury from one chamber to the other, said constriction preventing rapid flow from said other chamber to said one chamber, a gas capillary comprising a stranded wire extending through the mercury from one chamber to the other, said capillary determining the rate of flow of gas from said one chamber to said other chamber and thereby determining the rate of flow of mercury from said other chamber to said one chamber, and a plurality of contacts extending through said enclosure into contact with the mercury therein when the major portion of the mercury is in one of said chambers.

4. A delay action switch comprising, in combination, an insulating enclosure of generally cylindrical form, a partition wall forming two chambers with a restricted passageway therebetween, a constriction in the opposite wall of said enclosure adjacent said partition, the bottom wall of said enclosure being lower on one side of said last mentioned constriction than on the other, mercury and gas in said enclosure, said mercury normally lying in one of the said chambers, said restricted passageway serving to cause rapid flow of a thin layer of mercury from one chamber to the other, said first mentioned constriction preventing rapid flow from the other chamber to the one, contacts extending through said enclosure into contact with said mercury when the mercury is in one of said chambers, and a capillary passing from one chamber to the other through said mercury to thereby permit slow interchange of gas between the two chambers and slow flow of mercury from said other chamber to said one chamber.

5. A device as claimed in claim 4 characterized in that the flow of mercury in either direction is initiated by imparting to the said enclosure a tipping movement about a transverse axis located between the chambers.

6. A device as claimed in claim 4 character ized in that said partition has a substantial linear dimension longitudinally of the enclosure and said constriction in the opposite wall is adjacent one end of said linear dimension.

7. A device as claimed in claim 4 characterized in that the mercury is caused to flow into said one chamber during horizontal movement of the enclosure parallel to its own longitudinal axis and is permitted to flow slowly into the other chamber upon the cessation of such movement.

SVEN FREDRIK ERHARD MEYER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,676,752 Walker July 10, 1928 1,797,974 Brandall Mar. 24, 1931 2,206,436 Spencer July 2, 1940 2,373,557 Goodman Apr. 10, 1945 FOREIGN PATENTS Number Country Date 446,420 Germany June 30, 1927

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