US3133166A

US3133166A - Compressed air actuated electric switch

Info

Publication number: US3133166A
Application number: US854829A
Authority: US
Inventors: Thommen Hans; Reimann Robert
Original assignee: BBC Brown Boveri France SA
Current assignee: BBC Brown Boveri AG Germany; BBC Brown Boveri France SA
Priority date: 1959-10-23
Filing date: 1959-11-23
Publication date: 1964-05-12
Anticipated expiration: 1981-05-12

Description

y 12, 1954 H. THOMMEN ETAL 3,133,166

COMPRESSED AIR ACTUATED ELECTRIC SWITCE Filed Nov. 23, 1959 2- Sheets-Sheet) 1 I INVENTOR. f Hans Thomrnen BY Robert ReLmmnn 1 JW% min May 12, 1 64 H. THOMMEN ETAL 3,133,156

COMPRESSED AIR ACTUATED ELECTRIC SWITCH Filed NOV. 23, 1959 2 Sheets-Sheet 2 1 8.1 78.7% wag 17.1 4 172. k 74 A? F IG 4 INVENTOR5 HOJHS T/IOI'HFTIQFI R rt eLmamn BY 46 I M.

United States Patent ()fitice 3,133,166 Patented May 12, 1964 CUMPRESSED AER ACTUATED ELECTRIC SWITCH Hans Thommen, lladen, and Robert Reiinann, Woltlinswill, Switzerland, assignors to Aktiengesellschatt Brown,

lloveri dz Cie, Baden, Switzerland, a joint-stock company Filed Nov. 23, 1959, Ser. No. 854,829 11 Claims. (Cl. 200-148) This invention concerns an arrangement for air blast switches where the actuation of the contacts and the blasting thereof are effected by compressed air and where the explosion chamber remains under pressure in the dis connected state of the switch contacts.

The actuation of the air blast switches is effected by means of main disconnection and connection valves which are connected to a compressed air tank cooperating with the switch. For effecting disconnection of the switch contacts a disconnection valve is opened and the compressed air flows into the explosion chamber which encloses the contacts. The explosion chamber is then closed by an exhaust valve through which compressed air can at first issue as long as the are burns. The compressed air remains then in the chamber and keeps the contacts apart. In order to reconnect the switch contacts a connection valve is operated so as to connect the explosion chamber with the outside air and the compressed air can then escape to atmosphere. Due to the drop of the pressure in the explosion chamber, the switch contacts are then reclosed. Since the chamber is directly connected with the compressed air tank in the disconnected state, no pressure loss can occur. But this has the disadvantage that ii the pressure decreases in the tank the explosion chamber also loses compressed air and the switch can close accidentally. Such a pressure loss can also occur if defects exist in the entire compressed air plant. In order to avoid this, check valves have been provided on the compressed tank which close when the pressure in the compressed air plant is lower than in the tank. But complete security against accidental connection of the switch is not ensured either, if defects appear in the control lines to the main valve andin the compressed air tank.

in order to increase the safetyof these switches, it is therefore suggested according to the invention to use separate compressed air tanks for blasting the switch contacts and actuating the main disconnection and connection valves, to provide a check valve at each compressed air tank, and to close the disconnection valve immediately after disconnection of the switch contacts.

The following detailed description and accompanying drawings provide a more detailed understanding of the invention.

In these drawings:

FIG. 1 is a somewhat schematic illustration of one embodiment of the invention showing the separate compressed air tanks and associated check valves;

FIG. 2 is a view similar to FIG. 1 illustrating a modification wherein auxiliary valves are used in conjunction with the disconnection and check valves;

FIG. 3 is also a view similar to FIG. 2 but wherein the disconnection valve is provided with a pair of auxiliary valves arranged in series, such auxiliary valves being responsive respectively to pressure drops in the explosion chamber and compressed air tank; and

FIG. 4 is also a schematic view illustrating the invention as applied to an air blast switching structure comprising a plurality of switch contacts arranged in series.

With reference now to the arrangement represented in FIG. 1, 1 denotes the air actuated switch contact arranged in the explosion chamber 2. It is connected with the main compressed air tank 4 over the supply line 3, which can be a hollow insulator, for example. The

compressed air tank 4 is in turn fed from the compressed air plant 5. The connection valve is designated with 6, the disconnection valve with 7. The two valves 6 and 7 are pneumatically operated and are of a known construction which conform generally to the disclosure in German Patent 893,982. When the connection valve 6 opens, compressed air in the explosion chamber 2 can escape to atmosphere through the valve opening 8 so that the contact 1 recloses. If the disconnection valve 7 is actuated, a connection is established between the explosion chamber 2 and the compressed air tank 4, so that compressed air flows into the explosion chamber Z'and opens the contact. The two main valves 6 and 7 are actuated from the auxiliary compressed air tank 9, the connection valve 6 being actuated over the line 10 and controlled by suitable valve means such as an electro-magnetically controlled valve 6a placed in line 10, and the disconnection valve 7 over the line 11 and controlled by suitable valve means such as an electro-magnetically controlled valve 7a placed in line 11. At both compressed air tanks 4 and 9

check valves

12 and 13 are provided so that when the pressure in the compressed air plant 5' diminishes, the pressure in the tanks can be maintained. If a defect appears in tank 4 used for the blasting, the pressure for the valve control is maintained; conversely, if a defect appears in the compressed air tank 9 used for the valve control, tank 4 used for the blasting is unaffected. The dis connection valve 7 is so designed that it closes immediately after the switch contact 1 has been disconnected. Consequently there is no direct connection with the compressed air tank 4, and the explosion chamber 2 remains under pressure even though the pressure diminishes in tank 4.

It is known to provide the check valves with an auxiliary valve which is arranged parallel to the path of flow of the check valves but which has a substantially smaller cross section. Thus a weak connection is maintained, for example, between the compressed air tank and the compressed air plant. This has the result than minor pressure losses, which are caused by normal leakages, are constantly oiiset. In the case of a major pressure loss, however, this shunt path must be completely closed. This idea can not only be applied to the check valves, as up to now, but also tothe disconnection valve 7, so that a gradual pressure loss in the explosion chamber or in the tank can be otfset. This embodiment is shown in FIG. 2. There

auxiliary valves

14 and 15 are connected parallel to the

check valves

12 and 13 respectively. The construction of the auxiliary valve 14 and the check valve 12 connected in parallel with it is conventional and is disclosed in detail in German Patent 1,002,440. Besides, the disconnection valve 7 has also an auxiliary valve 16 connected in parallel with it, the valve 16 being of the same construction as

valves

14, 15. If the pressure drops slowly in the compressed air plant, for example, if there is a defect in the compressed air tank 9, the check valve 13 closes, but the valve 15 still supplies pressure from the tank 4 into the tank 9. Only in the case of a major pressure loss will the valve 14 also close. If a minor pressure loss occurs in the explosion chamber 2, the compressed air tank 4 supplies in a similar manner compressed air through the auxiliary valve 16 andonly at a high pressure loss will the valve 16 seal the chamber from the tank.

Conversely, the auxiliary valve 16 can be made dependent on the pressure in the blast main tank 4. If the pressure drops in this tank, compressed air will flow from the explosion chamber through valve 16 into tank 4, and only at a major pressure difference will the auxiliary valve close completely, so that the pressure in the explosion chamber is maintained. This way it is possible to ofiset minor pressure losses in the tanks 4 and 9.

We can also make the valve dependent on the pressure in the explosion chamber, but make it also close when the compressed air flows in the direction to the explosion chamber. This has the result that the valve remains only open as long as the pressure in the explosion chamber is equal to the pressure in the tank. But if a pressure'difierence appears, the explosion chamber is separated from the compressed air tank 4 so that the pressure is maintained in the latter as well as in the tank 9 from which the valves 6 and 7 are pneumatically controlled.

Another improvement can be achieved by providing two auxiliary valve units l7, 18 connected in series between the main tank 4 and hollow insulator 3 leading to explosion chamber 2 and therefore also paral eling disconnection valve 7 as shown in FIG. 3. Each of these valves can be of the same construction as the

auxiliary valves

14, 15. Of these, valvel responds to a pressure loss in the explosion chamber 2, and valve 17 responds to a pressure loss in the tank 4. The response pressures in the auxiliary valves differ, however, the valve which responds to the pressure in the explosion chamber 2 receiving a lower value. The method of operation is as follows: With normal pressure in the tank 4 and in the explosion chamber 2, both

valves

17, 18 are open. If the chamber pressure drops, the compressed air tank at first supplies compressed air over both valves. A compensation thus takes place. The valve 17 remains open as long as the pressure in the tank 4 remains unchanged. When the pressure in the tank 4- drops, however, the valve 17 at first shuts off the air supply. The pressure in the explosion chamber 2 now drops faster and the valve 18 closes, too. In the meantime, however, the pressure in the tank 4 rises again, due to the supply, so that the valve 17 opens again. The connection to the explosion chamber 2 is still interrupted, however, since the valve 18 is still closed. In case the pressure drops in the compressed air tank, without any defect in the explosion chamber, the valve 17 closes after a slight pres 'sure drop already so that the compressed air is maintained in the explosion chamber.

In all these arrangements the supply of the compressed air must naturally be stopped when the switch receives a connecting order. This is also done by the auxiliary valve which depends on the pressure in the explosion chamber. Since the pressure escapes when the switch is closed, the auxiliary valve also responds and interrupts the connection with the tank.

Of particular advantage is the suggested arrangement in switches with multiple interruption arranged in series. In the case of defects in an explosion chamber or in the tanks, only the defective parts are then separated and the rest of the switch remains in order. Even if the point of interruption closes accidentally in an explosion chamber, due to a pressure loss, the other points of interruption and the entire switch still remain open. As shown in FIG. 4, several points of interruption 2.1, 2.2 are fed separately through hollow insulators 3.1 and 3.2. Each insulator has an arrangement with disconnection valve and bridging Valve. The figure shows by way of example two auxiliary valves connected in series. The disconnection valves are designated with 7.1 and 7.2. Parallel to them are arranged the auxiliary valves 171 and 18.1 and 17.2 and 18.2 respectively. When the pressure drops in the tank 4, the valves 17.1 and 17.2 respectively close, starting from a certain pressure, and the explosion chamber remains under pressure. But if a pressure loss occurs in an ex plosion chamber, for example, chamber 2.1, compressed air will at first be supplied from the tank 4. Only starting from a certain pressure in the explosion chamber will the supply be stopped, since the valve 18.1 closes. The other explosion chamber 2.2 remains unaffected, however, and is ready for switching. Even if the contact in the explosion chamber 2.1 should close accidentally, the entire switch still remains open.

The above described arrangement has the advantage that the explosion chamber remains under pressure if losses occur in the compressed air plant or in the compressed air tanks and that accidental switching can be avoided. Even if the compressed air tank 9 completely loses its pressure, there is no influence on the switch. It remains in the position which it had before the pressure loss in tank 9. In the case of defects in one explosion chamber, the other chambers and the control are not affected. Due to the auxiliary valves it is possible to take into account slow pressure losses. The safety of the air blast switches is thus further increased by these arrangements.

We claim:

1. A compressed air actuated electric switch comprising a pair of contact means spring loaded to a closed position and which are actuated to open position and blasted by compressed air, an explosion chamber within which said contact means are located, a main compressed air tank, a conduit between said main tank and said explosion chamber, a disconnection valve disposed in said conduit and controlling How of compressed air between said tank and explosion chamber to actuate said contact means to open position, said contact means being maintained in said open position so long as the pressure of said compressed air remains in said explosion chamber, a connection valve for discharging the compressed air from said explosion chamber to eliect reclosure of said contact means, an auxiliary compressed air tank for supplying compressed air for actuating said disconnection and connection valves, said disconnection valve being reclosed after opening of said contact means to maintain the pressure of said compressed gas in said explosion chamber, a source of'compressed air for said main and auxiliary compressed air tanks, feed lines between said compressed air source and said main and auxiliary compressed air tanks, and check valves in said feed lines.

2. A compressed air actuated electric switch as defined in claim 1 and which further includes a pressure responsive auxiliary valve arranged in parallel with said disconnection valve, the free cross section of said auxiliary valve being a fraction of the free cross section of said disconnection valve.

3. A compressed air actuated electric switch as defined in claim 2 wherein said auxiliary valve is adjustable with respect to its actuating pressure.

4. A compressed air actuated electric switch as defined in claim 2 and wherein said auxiliary valve is re sponsive to the pressure in said explosion chamber, said auxiliary valve being opened only in the event of a minor loss in pressure in said explosion chamber to admit compressed air thereto from said main compressed air tank.

5. A compressed air actuated electric switch as defined in claim 2 and wherein said auxiliary valve is responsive to the pressure in said explosion chamber, said auxiliary valve being open only so long as the pressures in said explosion chamber and main tank are equal and being reclosed as soon as a pressure differential therebetween arises and compressed air starts to fiow'through said auxiliary valve in the direction of said explosion chamber.

6. A compressed air actuated electric switch as defined in claim 2 and wherein said auxiliary valve is responsive to the pressure in said main compressed air tank, said auxiliary valve being opened only in the event of a minor loss in pressure in said main compressed air tank to readmit compressed air thereto from said explosion chamher.

7. A compressed air actuated electric switch as defined in claim 1 and which further includes a pressure responsive auxiliary valve arranged in parallel with said disconnection valve and having a free cross section which is a fraction of the free cross section of said disconnection valve, said auxiliary valve being constituted by a pair of valve units connected in series between said main tank and said explosion chamber, one of said valve units being responsive to the pressure in said explosion chamber and the other valve unit being responsive to the pressure in said main tank.

8. A compressed air actuated electric switch as defined in claim 7 wherein said auxiliary valve unit which responds to the pressure in said explosion chamber is set for actuation at a pressure lower than the actuation pressure of said valve unit which is responsive to the pressure in said main tank.

9. A compressed air actuated electric switch as defined in claim 7 wherein said auxiliary valve unit responsive to the pressure in said explosion chamber closes upon actuation of said connection valve to discharge compressed air from said explosion chamber.

10. A compressed air actuated electric switch comprising a plurality of series connected pairs of contact means spring loaded to a closed position and which are actuated to open position and blasted by compressed air, an explosion chamber individual to and enclosing each said pair of contact means, a main compressed air tank, a conduit between said main tank and each said explosion chamber, a disconnection valve disposed in each said conduit and controlling flow of compressed air between said tank and said explosion chambers to actuate said pairs of contact means to open position, said pairs of contact means being maintained in said open position so long as the pressure of said compressed air remains in said explosion chambers, a connection valve for each said explosion chamber for discharging the compressed air therefrom to effect reclosure of the corresponding pair of contact means, an auxiliary compressed air tank for supplying compressed air for actuating said disconnection and connection valves, each said disconnection valve being reclosed after opening of the corresponding pair of contact means to maintain the pressure of said compressed air in the corresponding explosion chamber, a source of compressed air for said main and auxiliary compressed air tanks, feed lines between said compressed air source and said main and auxiliary compressed air tanks, and check valves in said feed lines.

11. A compressed air actuated electric switch as defined in claim 10 and which further includes a pressure responsive auxiliary valve arranged in parallel with each said disconnection valve, the free cross section of each said auxiliary valve being a fraction of the free cross section of the corresponding disconnection valve.

References Cited in the file of this patent UNITED STATES PATENTS 2,748,226 MacNeil May 29, 1956 2,786,119 Forwald Mar. 19, 1957 FOREIGN PATENTS 759,175 Great Britain Oct. 17, 1956 1,002,440 Germany Feb. 14, 1957 1,003,321 Germany Feb. 28, 1957 1,026,395 Germany Mar. 20, 1958 1,155,295 France Nov. 25, 1957 551,071 Belgium Sept. 29, 1956

Claims

1. A COMPRESSED AIR ACTUATED ELECTRIC SWITCH COMPRISING A PAIR OF CONTACT MEANS SPRING LOADED TO A CLOSED POSITION AND WHICH ARE ACTUATED TO OPEN POSITION AND BLASTED BY COMPRESSED AIR, AN EXPLOSION CHAMBER WITHIN WHICH SAID CONTACT MEANS ARE LOCATED, A MAIN COMPRESSED AIR TANK, A CONDUIT BETWEEN SAID MAIN TANK AND SAID EXPLOSION CHAMBER, A DISCONNECTION VALVE DISPOSED IN SAID CONDUIT AND CONTROLLING FLOW OF COMPRESSED AIR BETWEEN SAID TANK AND EXPLOSION CHAMBER TO ACTUATE SAID CONTACT MEANS TO OPEN POSITION, SAID CONTACT MEANS BEING MAINTAINED IN SAID OPEN POSITION SO LONG AS THE PRESSURE OF SAID COMPRESSED AIR REMAINS IN SAID EXPLOSION CHAMBER,