US3776025A

US3776025A - Exhaust machine leak detector and shut off

Info

Publication number: US3776025A
Application number: US00295645A
Authority: US
Inventors: J Plescia
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1971-01-04
Filing date: 1972-10-06
Publication date: 1973-12-04
Anticipated expiration: 1990-12-04

Abstract

A leak detector, used in conjunction with an exhausting apparatus of a multiple head variety, which is responsive to a change in pressure in the evacuation system of the exhaust apparatus so that it terminates the evacuation process of the device when the device is leaking to the atmosphere. The leak detector apparatus is built into each head of the multiple head exhaust machine and operates with a variable reference pressure which is compared to the pressure of the evacuation system. Preferably, the reference pressure is varied throughout the process as the pressure in the evacuation system is similarly varied.

Description

United States Patent 1 1 Plescia Dec. 4, 1973 EXHAUST MACHINE LEAK DETECTOR AND SHUT OFF [75] Inventor: Joseph J. Plescia, Euclid, Ohio [73] Assignee: General Electric Company,

Schenectady, NY.

22 Filed: 0ct.6,1972

21 Appl. No.: 295,645

Related US. Application Data [63] Continuation-in-part of Ser. No. 103,564, Jan. 4,

1971, abandoned.

[52] US. Cl. 73/45.1, 141/65 [51] Int. Cl. G0lm 3/04 [58] Field of Search 53/7, DIG. 3;

[56] References Cited UNITED STATES PATENTS 1,710,428 4/1929 Mey 141/8 5/1956 Ott 141/83 6/1964 Breidenbach et 73/45.l

Primary ExaminerDonald 0. Woodiel Attorney-Emil F. Sos, Jr. et al.

[57] ABSTRACT A leak detector, used in conjunction with an exhausting apparatus of a multiple head variety, which is responsive to a change in pressure in the evacuation sys- 7 Claims, 3 Drawing Figures I34 ,3 "/5751 WSL PATENIEUBEB 4 ms 3.776.025

Invervtof: Joseph J. PLescia by Q His JCHLOT'TWEH EXHAUST MACHINE LEAK DETECTOR AND SHUT OFF CROSS-REFERENCES TO RELATED APPLICATIONS This is a continuation-in-part of application Ser. No. 103,564, filed Jan. 4, 1971 now abandoned.

BACKGROUND OF THE INVENTION 2. Description of the Prior Art In prior art exhaust machines, there is generally one location or head which checks for a leak in'a lamp envelope as it goes through the exhausting process. This checking station or head is usually located at one of the BRIEF DESCRIPTION OF THE DRAWINGS Other objects and advantages of the present invention will become apparent from a consideration of, the following detailed description when taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a section view through an exhaust machine showing an exhaust head and the leak detector of the invention;

last positions on a multiple head lamp-making piece of machinery. Under these circumstances, a defective envelope or leaker can go through most of the exhausting process before its defective nature is ascertained.

Because of the nature of the exhausting equipment, an example of which is more fully described in US. Pats. Nos. 2,811,992 and 2,113,798, a leaking envelope has an impact on the quality of many of the lamps on the turret at that time. This is so because all heads are connected through a rotary valve, such as the one described in US. Pat. No. 2,113,798, to the same evacuation pumps. Consequently when a defective envelope is on the turret, the central vacuum system must work against a continual leakage of atmospheric pressure and may not reach the degree of vacuum required, thereby causing defective lamps on both sides of the leaking lamp envelope.

SUMMARY OF THE INVENTION The invention provides an individual leak detector operable at each head of a multiple head exhaust machine to seal off the leaking envelope of a device, such as a lamp, mounted on the head. As the evacuation process proceeds, the decreasing pressure in the envelope iscontinually measured against a reference pressure at each station of the exhaust machine. As long as no leakage occurs, the reference pressure will maintain the exhausting cycle fully operative. Leakage will cause the exhaust pressure to rise; when this increase is compared with the reference pressure, and exceeds a specifled minimum, the reference pressure will cause the evacuation process to cease and the individual envelope is sealed off from the exhaust machine and from other envelopes.

FIG. 2 is a section view through an exhaust machine having a reference pressure manifold; and

FIG. 3 is a plan view of the bottom half of the rotary exhaust valve of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS For purposes of convenience, and not by way of limitation, the invention will be described with particular reference to leak detectors for exhaust machines of the multiple head variety used to evacuate lamp envelopes.

Referring to FIG. 1 of the drawing, a lamp envelope 111 with an exhaust tube 112 is held in exhaust head 113. Compression rubber 114 which forms an airtight seal with the periphery of the exhaust tube 112 is held in the exhaust head block 117 by the application of pressure to rubber clamp insert from the pinch clamp 116. Air and other gases are exhausted from the interior of the lamp through the exhaust tube and then through exhaust head passageways 1'18 indicated by the arrows. Plunger assembly 119 ejects the remaining end of the exhaust tube after the tube is pinched off and severed during the lamp tipping operation.

Exhaust head 113 is one of a plurality of heads which are attached to turret 120. After the exhaust gases pass through the passageways 118, they enter a filter chamber 121 in which brushes 122 catch any impurities.

During the exhaust process, the exhausted gas flows into an evacuation chamber 123 and through a passageway 124 in an O-ring piston 125. The evacuated gas then enters cavity 126 which is connected to conduit 127. This conduit is secured to passageway 128 which leads to upper port 129. Trap 130 in conduit 127 filters out any impurities which pass through filter chamber 121. Passageway 131 connects lower port 132 and exhaust manifold conduit 133 which is attached to exhaust manifold 134. When the upper port 129 and lower port 132 coincide, the vacuum or low pressure appearing in exhaust manifold 134 is applied to the lamp envelope to evacuate the envelope as described. The

ports

129 and 132 constitute what is known as a rotary exhaust valve 135. Bottom portion 136 is stationary and is attached to frame 137 through support 138. Top portion 139 is rotatable and indexes along with turret which is rotated by drive shaft 140.

0-ring piston is held in casing 141 by sea] bushing 142 and bushing sleeve 143. Attached to the front of the O-ring piston 125 is nut 144 and spacer 145 which separates the nut from front diaphragm 146. On rear portion of O-ring piston 125 is a groove 147 in which is placed an O-ring 148 which contacts the wall of casing 141 when piston 125 is lowered, as shown in FIG. 1, to seal off the hollow O-ring piston. Rear diaphragm 149 is located at and supports the opposite end of the O-ring piston.

Diaphragm 146 is arranged within casing 141 such that a reference pressure cavity 150 is formed. Diaphragm 149, which is smaller in area than diaphragm 146, forms a second reference pressure cavity 151 within housing 141. Cavity 151 is at the same pressure as the reference pressure in chamber 150. The fit between bushing sleeve 143 and casing 141 is selected such that the pressure in

cavities

150 and 151 will equalize rapidly thereby giving the same reference pressure. Because diaphragm 146 is greater in crosssectional area than diaphragm 149, operation of the O- ring piston 125 will always be under control of diaphragm 146. Cavity 150 is connected to a source of reference pressureby conduit 152. Situated between the cavity and the source of pressure is a control valve 153 which regulates the reference pressure by movement of slider 154 which positions low and

high pressure passageways

155 and 156 in either the open or closed position depending upon which pressure is desired in cavity 150. Low pressure passageway 155 mates with low pressure supply tube 157a, in turn, fed by supply pipe 158a through a conventional rotary valve 159. Similarly, high pressure passageway 156 is fed by supply tube 157b and pipe 158b through the rotary valve.

The pumping down or exhausting operation of envelope 111 begins when the envelope is placed in exhaust head 1 13 with the exhaust tube 112 forming an air-tight seal with compression rubber 114; a closed system extending from the exhaust tube 112 to the exhaust manifold 134 is formed.

At the outset of turret operation, the reference pressure fed to cavity 150 from supply tube 157b is approximately 900 mm of mercury. Since the fit between bushing sleeve 143 and casing 141 is a loose fit, a second reference pressure cavity 151 will also be at a pressure of 900 mm of mercury. As can be seen from FIG. 1 of the drawings, the cross-sectional area of diaphragm 146 is greater than that of diaphragm 149 and any movement of the O-ring piston 125 will be controlled by the pressure difference between reference pressure cavity 150 and the evacuation chamber 123. When the reference pressure in

cavities

150 and 151 is 900 mm of mercury, the pressure in

chambers

123 and 126 is atmospheric or 760 mm of mercury. This pressure difference of 140 mm of mercury (900-760) causes

diaphragms

146 and 149 to flex upward and move O-ring piston upward into an open or evacuating position, as illustrated in FIG. 1, thereby allowing evacuating of the envelope in the adjacent system of passageways.

As the evacuation process continues, the pressure within the lamp envelope 111 decreases so that, when exhaust head 113 reaches the 12th station, for example, the pressure in

chambers

123, 126 and the lamp envelope has dropped from 760 mm of mercury (i.e., atmospheric) to approximately 100 mm of mercury. At this selected point in the exhaust cycle, slider 154 is moved to mate the low pressure passageway 157a with conduit 152 thereby bringing the reference pressure in

cavities

150 and 151 to a lower value chosen to be approximately 150 mm. The results are that the lower reference pressure provides a more accurate measurement and reference point as evacuation of the envelope proceeds toward complete exhaustion.

' As long as the pressure in

cavities

150 and 151 is greater than that in

chambers

123 and 126, the evacuation process continues. However, if a leak exists in the envelope 11 1 or for that matter anywhere in the closed system from envelope 111 to vacuum manifold 134, there will be a corresponding increase in the gas pressure in

chambers

123 and 126 and in the vacuum system from the lamp envelope 111 to manifold 134. When such an increase of pressure exceeds the reference pressure in

cavities

150 and 151 by about 50 mm mercury, the

diaphragms

146 and 149 are flexed downward and thereby move the O-ring piston into a closed position. When this occurs, the O-ring 148 forms an air-tight seal with the wall of casing 141 and exhaust conduit 127 is sealed off to terminate the exhaust process.

As a result, the leaking envelope and exhaust head are isolated on an individual basis throughout the complete exhaust cycle as the turret rotates and thus do not adversely effect the exhaust operation being performed on other envelopes and exhaust heads carried by the turret, from the exhaust manifold 134.

The advantages of the invention are these. An individual leak detection operation is performed at each head. Great sensitivity is obtained by varying the reference pressure because the detector responds to relatively small changes in pressure. Moreover, detection of a leak can occur on a continual basis at any point in the exhaust cycle, as the turret revolves through one cycle of operation, as distinct from prior multiple head exhaust machines where a single check for leakage was made at a single selected point in the cycle.

Another embodiment utilizing the varying reference pressure leak detector is illustrated in FIGS. 2 and 3. The exhaust process is performed through a conduit connection shown in FIG. 2 at 160. One end of conduit 160 is connected to a device similar to trap and exhaust conduit 127 of FIG. 1, the other end to upper port 169 of rotary valve 170. Lower exhaust port 171 of rotary valve 170 (FIG. 2) is connected by passageway 172 and conduit 173 to exhaust manifold 165.

There are three

other exhaust manifolds

166, 167 and 168 shown in FIG. 3 similarly connected to conduit through rotary exhaust valve 170. Valve is attached to frame 174, similar to frame 137 in FIG. 1, through support 175 which is turned by a drive shaft 176 similar to that shown at 140 in FIG. 1.

The top of lower exhaust port 171 is shown in FIG. 3. There are 48 of these lower exhaust ports which are connected to 48 exhaust heads (not shown) through a rotary exhaust valve and piping mechanism such as the one illustrated in FIG. 1.

Reference chamber 150 is connected by conduit to upper port 177 of rotary valve 170. Upper port 177 communicates to lower port 178 which is connected to reference pressure manifold 161 by conduit 179. The top of lower port 178 is shown in FIG. 3. 48 top portions of the lower port for the reference pressure are shown in FIG. 3, one for each index station of the turret. Also shown in FIG. 3 are three additional

reference pressure manifolds

162, 163, 164 which are connected to the appropriate ones of lower ports 178 so that the different reference pressures appearing in these manifolds are connected to reference

pressure chambers

150 and 151 in a manner similar to that of manifold 161 as shown in FIG. 2.

Although there are a total of 48 vacuum openings (171) in the rotary valve and a total of 48 reference pressure openings (178) shown in FIG. 3, this number of openings or stations may be greater or less depending upon the number of index stations specified in the turret design.

For purposes of illustration only, a typical cycle will now be described with reference to FIGS. 2 and 3 by giving the reference pressures and the pressures in the envelope or the exhaust system. In positions 1 through 7, the heads are used for lamp loading; consequently, the pressure in the exhaust system is atmospheric or 760 mm of mercury and the reference pressure is 900 mm of mercury. At stations 8 through 12 envelopes can also be loaded into the exhaust head 113 as the evacuation process begins. At station 12 the pressure within the lamp envelope 111 and the vacuum system has been reduced from 76.0 to 1 10 mm. The reference pressure at station 11 is 900 mm and at station 12 is reduced to 150 mm, this being greater than the 110 mm exhaust pressure thereby keeping the exhaust system open.

Stations 13 through 20 are exhausted through vacuum manifold 166. The pressure within the envelope and exhaust system is reduced from 80 mm at station 13 to approximately 25 mmat station 20. Reference pressure manifold 163 tests for leaks at stations through 19. As the envelope pressure is being reduced from 80 to 25 mm, the reference pressure goes from 150 mm at station 14 to 100 mm at station 19. Exhaust stations 21 through 28, part of exhaust manifold 167, reduced the envelope pressure from 25 mm to approximately 2.7 mm. Reference pressure manifold 164, which is connected to stations through 35 on the rotary valve 135, is at a pressure of 40 mm so that a variation in envelope pressure of approximately 15 to 37% mm would activate the leak detector and curtail the exhausting process. 7

It is evident that numerous modifications will become apparent to those skilled in the art without departing from the spirit and scope of this invention. Further, as this invention may be advantageously employed regardless of the particular type of exhausting equipment or container to be exhausted, the description hereinabove set forth is not intended in a limiting sense but merely descriptive of the invention as defined in the appended claims.

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

1. In a mechanism for detecting and stopping evacuation of gas from an envelope upon leakage of the envelope the combination of i a. holding means for supporting said envelope,

b. a source of low pressure for evacuating the envelope,

c. means for connecting said low pressure source to said holding means and envelope including a hollow casing, a movable diaphragm separating said easing into separate evacuation and pressure chambers and a hollow piston carried by said diaphragm for transmitting said low pressure to said evacuation chamber on one side of said diaphragm in one position and movable to a second position to seal off said low pressure source, d. and a source of reference pressure higher than said low pressure connected to said pressure chamber 5 on the other side of said diaphragm to maintain said piston in said one position, leakage of gas in said envelope causing the low pressure in said evacuation chamber to increase with respect to said reference pressure and thereby deflecting said diaphragm against the action of said reference pressure to move said diaphragm to its second position whereby said piston seals off said evacuating low pressure source. 2. In a mechanism for detecting and stopping evacua- 15 tion of gas from any one or more of a number of lamp envelopes mounted on an exhaust machine upon leakage of any envelope at any one of a plurality of work stations comprising, in combination:

a. a rotating turret provided with a plurality of means for supporting, evacuating and moving the envelopes through a series of work stations,

b. a source of low pressure and means for connecting said source to each of said supporting and evacuating means to evacuate the envelopes at selected ones of said work stations,

c. a source of reference pressure different than said low pressure,

(1. means located at each of said supporting and evacuating means to compare the evacuative pressure in the envelope with the reference pressure,

e and means responsive to the difference between the evacuative pressure and the reference pressure caused by leakage of a single envelope to seal off the low evacuative pressure from such envelope.

3. The mechanism of claim 2 wherein said means to compare said evacuation pressure with said reference I pressure is a hollow air-tight casing divided into two compartments by a pressure responsive material.

4. The mechanism of claim 2 wherein said means responsive to the difference between the evacuation pressure and the reference pressure constitutes a movable piston engaging a wall of a housing to seal off the low evacuative pressure from the housing and envelope.

5. The mechanism of claim 2 wherein a means is provided to vary the pressure values of the source of said reference pressure. I

6. The mechanism of claim 5 wherein said means for varying said reference pressure is .a slider with two passageways for transferring from one source of reference pressure to another. I v

7. The mechanism of claim 5 wherein said means for varying said reference pressure is a plurality of manifolds having different reference pressures.

Claims

1. In a mechanism for detecting and stopping evacuation of gas from an envelope upon leakage of the envelope the combination of a. holding means for supporting said envelope, b. a source of low pressure for evacuating the envelope, c. means for connecting said low pressure source to said holding means and envelope including a hollow casing, a movable diaphragm separating said casing into separate evacuation and pressure chambers and a hollow piston carried by said diaphragm for transmitting said low pressure to said evacuation chamber on one side of said diaphragm in one position and movable to a second position to seal off said low pressure source, d. and a source of reference pressure higher than said low pressure connected to said pressure chamber on the other side of said diaphragm to maintain said piston in said one position, leakage of gas in said envelope causing the low pressure in said evacuation chamber to increase with respect to said reference pressure and thereby deflecting said diaphragm against the action of said reference pressure to move said diaphragm to its second position whereby said piston seals off said evacuating low pressure source.

2. In a mechanism for detecting and stopping evacuation of gas from any one or more of a number of lamp envelopes mounted on an exhaust machine upon leakage of any envelope at any one of a plurality of work stations comprising, in combination: a. a rotating turret provided with a plurality of means for supporting, evacuating and moving the envelopes through a series of work stations, b. a source of low pressure and means for connecting said source to each of said supporting and evacuating means to evacuate the envelopes at selected ones of said work stations, c. a source of reference pressure different than said low pressure, d. means located at each of said supporting and evacuating means to compare the evacuative pressure in the envelope with the reference pressure, e. and means responsive to the difference between the evacuative pressure and the reference pressure caused by leakage of a single envelope to seal off the low evacuative pressure from such envelope.

3. The mechanism of claim 2 wherein said means to compare said evacuation pressure with said reference pressure is a hollow air-tight casing divided into two compartments by a pressure responsive material.

5. The mechanism of claim 2 wherein a means is provided to vary the pressure values of the source of said reference pressure.

6. The mechanism of claim 5 wherein said means for varying said reference pressure is a slider with two passageways for transferring from one source of reference pressure to another.