US2781588A - Apparatus for drying sealed containers - Google Patents

Description

Feb. 19, 1957 H. G. WARREN Erm. 2,781,538

APPARATUS FOR DRYING SEALED CONTAINERS Filed April l2. 1954 3 Sheets-Sheet l 100 600 DISTANCE -FEET INVENTORS. HORACE 6. WARREN HERR/AM E. JOHNSON A T TOR/VEV Feb. 19, 1957 H. G. WARREN ET Ax. 2,781,588

APPARATUS E' OR DRYING SEALED CONTAINERS Filed April l2, 1954 3 Sheets-Sheet 2 /4\. l 30 3/ F/G. 3. 27

TO ALARM BELL 1N V EN TORS 7 34 HORACE G. WARREN 'HERR/AM E. JOHNSON AT TOR/VE V W H. G. WARREN Er Al. 2,781,588

APPARATUS FOR DRYING SEALED CONTAINERS Feb. 19, 1957 3 Sheets-Sheet 3 Filed April l2. 1954 Qumm JNVENToRs. HORACE a. WARREN QOL WA 29u BY HERR/AM E. JOHNSON A T TOR/VE V United States Patent APPARATUS FOR DRYING SEALED CGNTAINERS Horace G. Warren and Merriam E. Johnson, Rochester, N. Y., assignors, by mesne assignments, to Consolidated Electrodynamics Corporation, Pasadena, Calif., a corporation of California Application April 12, 1954, Serial No. 422,463

8 Claims. (Cl. 34-1) This invention relates to methods of and apparatus for dehydrating containers and more specifically to apparatus for dehydrating containers carried on a conveyor and subjected to heating and evacuation.

Although the present invention may be used to dehydrate by heating and evacuation any type of container carried on a conveyor, it is particularly useful in the dehydration of hermetically sealed containers which enclose refrigeration units. In a typical refrigerator manufacturing plant the various components of refrigeration units are carried through the plant on a plant conveyor. A series of operations are performed on the components to complete the assembly of the refrigeration units as the conveyor moves through the plant. It is not unusual for the conveyor to travel several thousand feet during the assembly and processing of the units.

Normally, a refrigeration unit comprises an electric motor, a compressor unit driven by the motor, a vapor condenser, expansion coils, capillary tubing, strainers, and sometimes a drying element. In some refrigeration units the compressor and the motor are both hermetically sealed in a single container, While in other types of units the electric motor is not hermetically sealed With the compressor. In either type of assembly the compressor is provided with refrigerant discharge and return lines which extend through a sealed closure in the container Wall and connect to the vapor condenser, expansion coils, capillary tubing, strainers, etc. which are located outside the container proper. The present invention is equally suitable for dehydrating either type of refrigeration unit.

In the manufacture and assembly of the various components in the refrigeration units, moisture is unavoidably trapped in the container which seals the compressor. This happens for both types of construction, i. e., Whether the electricl motor is hermetically sealed with the compressor or not. (dehydration) from the refrigerator units is essential to Aprevent contamination of the oil used to lubricate the compressor and to prevent contamination of the refrigerant (a liquiable gas such as Freon). Any water left in the refrigeration unit tends to emulsify with the lubricating oil and decrease its lubricating properties. In addition, the presence of water in the refrigerant causes undesirable freeze-ups, i. e., local plugging due to ice formation Within the refrigerator unit takes place and prevents proper operation. For example, freeze-ups occur due to droplets of water passing throughthe capillary tube which serves as the expansion orifice Where considerable cooling takes place. It is also desirable to remove water from the interior of the refrigeration unit to avoid the possibility of internal rusting.

To avoid these difficulties, the refrigeration units are dehydrated before the lubricating oil or the refrigerant charge is added to the unit. One of the most effective ways to dehydrate a refrigeration unit, i. e., remove water from the interior of the compressor, associated coils, condenser, capillary tubing, etc. is to evacuate the Generally speaking, removal of water` container which encloses the compressor (and in some assemblies, the electric motor) and heat the entire assembly. The interior of the container is open to the interior ofthe compressor and to the compressor return and discharge lines so that evacuation of the container results in evacuation of the associated components.

This process has been accomplished in the past by several methods, none of which is entirely satisfactory. For example, one method involves the use of a movable rack carrying an evacuating system and a vacuum manifold. The refrigerator units are taken off the plant conveyor and manually loaded onto the rack and attached to the vacuum manifold. The rack is then pushed into the oven to heat the units While they are evacuated. After the units are dehydrated, the rack is removed from the oven, the units disconnected from the vacuum pump, and replaced on the conveyor. This batch process has the disadvantage that the movement of the refrigeration units through the plant must be interrupted, and excessive time and labor are required to load and unload the units.

Another process involves the use of a stationary evacuating system which is not placed into an oven. The refrigeration units are unloaded from the plant conveyor and placed in an oven Where they are heated to a predetermined temperature. The hot units are then removed from the oven and connected to the evacuating system. The refrigeration units are evacuated for a period of time, then disconnected from the evacuating system and returned to the oven for additional heating to be followed by the subsequent evacuation. This process is repeated through several cycles until dehydration of the units is accomplished. This method has the disadvantage that the units must be handled many times to complete the dehydration.

The present invention overcomes the disadvantages of the prior systems for dehydrating containers, particularly refrigeration units, by providing apparatus which permits the containers to remain on the moving plant conveyor belt while continuous heating and evacuation of the container is performed to effect dehydration. Thus the containers are dehydrated With a minimum amount of handling and with no interruption of the movement of the conveyor belt. This results in valuable savings in time and labor.

The invention contemplates a heating chamber or oven capable of handling a plurality of containers to be dehydrated. A first or plant conveyor is arranged to pass through the chamber carrying on it a series of the containers. A second conveyor is disposed adjacent the heating chamber and substantially parallel to the first conveyor. A series of pumping units are carried by the second conveyor. A conduit (preferably movable in a slot in the chamber) is provided on each pumping unit and extends into the oven and connects the pumping unit to at least one of the containers on the first conveyor. Means for synchronizing the movement of the two conveyors is provided to maintain alignment of the pumping unit and the container or containers Which it is evacuatmg.

In a preferred form of the invention a pressurefmeasuring device or gauge is provided with each pumping unit to measure continuously the pressure developed by each unit. Conveniently, the output of the gauge is an electrical signal which is transmitted to 'a brush adapted -to make successive contact with a first bus bar disposed along the direction of movement of the second conveyor. Means responsive to the signal from the gauge are provided for automatically inactivating any exhaust unit in which the pressure is above a predetermined value.

For use in processing containers which include electric motors, the invention is provided with a second bus bar disposed along the direction of movement of the conveyor, and an electrical contact slidable along the bus bar and connected to a winding of the motor in the sealed container. Means are provided for supplying current to the motor winding through the bus bar and the electrical contact to heat the winding and aid in the drying of the container.

In the ordinary commercial use of this invention, a substantial length of the plant conveyor is at a higher temperature than the second conveyor. To prevent excessive mis-alignment of the pumping units and containers respectively carried by the two conveyors due to thermal expansion, the plant conveyor is caused to travel a greater distance while in the oven or chamber than that traveled by the second conveyor by an amount approximately equal to the increase in length of the plant conveyor `due to thermal expansion.

These and other aspects of the invention will be understood in the light of the following detailed description taken in conjunction with the accompanying drawings in which:

Fig. 1 is a schematic perspective view showing the over-all operation of the apparatus with the various bus bars and associated electrical equipment not being shown for simplicity;

Fig. 2 is a fragmentary plan view showing how the rst conveyor is caused to travel a longer path than the second conveyor to allow for thermal expansion of the iirst conveyor;

Fig. 3 is a schematic sectional elevation taken in the vicinity of line 3--3 of Fig. 4, showing the components of a pumping unit and the associated electric circuits required for its operation;

Fig. 4 is a schematic plan view showing the path traveled by the containers and the associated bus bars and electric circuits; and

Fig. 5 is a plot of container temperature versus distance traveled in the oven, showing the preferred rate of heating.

vReferring to Fig. l, a large rectangular oven or heata.

ing chamber having an entrance opening 11 and an exit opening 12 in one end, is disposed over a portion of a rst or plant conveyor 13 which is part of the assembly line in a plant; e. g., a refrigerator manufacturing plant. The oven is heated by any suitable means; c. g., Vby steam (not shown). A plurality of refrigeration unit containers 14 are hung from the plant conveyor, which is powered by a plant conveyor driving means 15 of conventional design. A second conveyor 16 in the form of an endless loop is disposed below the oven and moves in a direction substantially parallel to that part oi the plant conveyor which passes through the oven. A plurality of pumping or exhaust units 17 are carried on the lower conveyor, which is powered by a lower conveyor driving means 18 of conventional design.

A synchronizing unit 19 is connected to the two conveyor driving means to synchronize the speed of the two conveyors. The synchronization can be done manually, but preferably it is accomplished by apparatus of the type described and claimed by R. C. Gauger and E. W. Perkins in co-pending application Serial No. 392,396, led November 16, 1953. The speed synchronizer operates to match the speed of the lower conveyor to the speed of the plant conveyor. In the event that the two conveyors get out of line more than a predetermined amount, the speed synchronizer shuts off both of the conveyor driving means and the entire operation is stopped.

Each of the exhaust units is provided with a vacuum conduit 20 which extends up into the oven through a slot -21 in 'the oven floor. A `vacuum manifold 22 carrying `four-' flexible vacuum hoses 23, 24, 25, 26 is connected tothe'upper end v`of each conduit. The end of each hose 'I ernot'e fror'n the lconduit is `provided lwith `a conventional vacuum "gurf 27 (see Fig. 3 which 'showsthe vacuuin'gun'27 connected Ywhose/24). AEach 'of the-vacuum guns is adapted to be connected to a service line 30 provided on each of the containers. A service valve 31 is provided in each of the service lines for sealing off the container after dehydration is complete. Each vacuum gun is provided with a valve which permits it to be opened and closed by a pistol grip valve handle 27A.

Fig. 2 shows in plan view how the radius of curvature of the plant conveyor in the oven is made larger than that of the lower conveyor so that the plant conveyor follows a longer path. This allows for expansion of the plant conveyor while it is in the oven. For simplicity the plant conveyor is shown as traveling the length of the oven only twice; in commercial installation the plant conveyor is arranged to travel the length of the oven several times (six in an actual installation) and the path of the lower `conveyor is similarly arranged under the oven.

Referring to Fig. 3 (which shows only a portion of the vacuum manifold, and only one of the vacuum guns and its associated hose), the lower conveyor comprises a pair of roller tracks 33, 34 spaced from each other so that a pusher-type chain conveyor 3S can travel between them. Dogs 36 are pivotally mounted on the chain and engage the center portion of the rear of a square pallet 37 which supports a pumping unit frame or cart 38. At each corner of the cart a guide wheel 39 is mounted on a bracket 40 to rotate about a vertical axis and bear against vertical guide walls 41, 42 on 'each side of the lower conveyor.

The pumping unit on each cart comprises a high vacuum pump 44 which preferably is an oil ejector diffusion pump employing an organic pump fluid (not shown) and having the usual boiler 45, heater 46, ejector tube stack 47 and diffuser tube 48. Pumping uid vapors generated in the boiler rise in the ejector stack and are discharged through a flared ejector nozzle (not shown) into the diffuser tube adjacent the intake end of the pump where the conduit 20 is connected. A conventional mechanical vacuum pump 5t) is connected to the discharge end of the high vacuum pump. An electric motor 51 drives the mechanical vacuum pump and a water pump 52 which picks up water (not shown) from a supply trough 53 disposed in a direction along the movement of the lower conveyor. The water is pumped into cooling coils 54 on the high vacuum pump and discharged into a discharge trough 55 which is disposed above and lruns parallel to the pickup trough.

The particular type of refrigeration unit illustrated has an electric motor (not shown) hermetically sealed in the container 14 with the compressor. With this arrangement the motor windings are effectively thermally insulated from the rest of the motor when the container -is evacuated and heat transfer to the winding is poor. To decrease the amount of time required to heat the windings to insure proper dehydration, the invention provides means for heating the motor windings electrically.

A pair of leads 58, 59 on the container are connected to the electric motor running windings (not shown) and extend down the outside of the vacuum conduit and are attached to two brushes 60, 61 respectively, carried by the cart. These brushes are adapted to make sliding contact with a series of bus bars 62, 63, 64, 65 disposed along the direction of movement of the lower conveyor (see Fig. 4).

A conventional thermocouple gauge 66 is installed in Athe lowerportion of the conduit to measure the pressure therein. The output of the thermocouple gauge is connected -to -a brush 67 which is adapted to make intermittent sliding contact with a series of bus bars r68, 69, 70, 71, '72, 73, '74, 75, 76 disposed along the directionv of movement of the lower conveyor (se'e Fig. 4).

,'Fig. 4 shows most -clearly thel path traveled by the exhaust carts and the refrigeration units and the various electrical circuits which are actuated as the refrigeration units and exhaust are carried through 'the oven. Like l reference numerals are used to indicate like parts referred to previously.

Bus bars 110, 111 are disposed at the entrance of the oven and are contacted by the brushes 60 and 61, respectively, connected to the windings of each motor. The bus bars 110, 111 form the contacts of a continuity check circuit indicated schematically at 114 in Fig. 4 as an ammeter 11S in series with a voltage source 116 and the bus bars. if the continuity circuit indicates that the motor windings `do not form a complete circuit, that particular refrigeration unit is removed from the conveyor for inspection to determine the source of trouble.

A pair of bus bars 78, 79 are supplied line voltage from a source S0; bus bar 78 is grounded. Brushes 61, 81 carried on each exhaust cart make continuous sliding contact with bus bars 78, 79 respectively. These brushes supply power to the heater for the high vacuum pump on each exhaust cart and power for the electric motor on each exhaust cart. A trigger switch 82. is carried on each exhaust cart and controls the supply of power to the heater.

Power is supplied to each of bus bars 62, 63, 64, 65 from the secondary windings 84, 85, 86, 87 respectively of a transformer 89, as indicated by the wiring of Fig. 4. The iirst bus bar 62 contacted by the brush 60 (which is connected to refrigeration unit motor windings) is supplied the highest voltage of all these bus bars. Each succeeding bus bar is supplied with progressively less voltage. This arrangement permits the motor windings to be brought up to the desired temperature as rapidly as possible without endangering the motor by overheating. By the time the motor has been carried past the end of the last bus bar 65, the motor windings are practically at the ambient oven temperature and require no additional electrical heating.

Pour conventional voltage-, sensitive switches 90, 91, 92, 93 of the low limit contact meter type are connected between ground and bus bars 62, 63, 64, 65 respectively to monitor the voltage applied to each of the bus bars. It is essential that the proper voltage be maintained on each bus bar to achieve the proper rate of heating of the motor windings. The relay coil terminals of each of the voltagesensitive switches are connected to measure the voltage applied to the associated bus bar, and the contact terminals of each of the voltage-sensitive switches are connected in series to a relay 94 which controls a main starter switch 95.

As long as the proper voltage is applied to each of the bus bars 62, 63, 64, 65, current flows through the contact terminals oi' the Voltage-sensitive switches and holds the relay 94 closed.

If the voltage in any of these bus bars should fall below a predetermined amount, the series circuit through the voltage-sensitive switches is opened and the relay 94 is actuated to turn off the main starter switch. This cuts olf the power to the master drive, speed synchronizer and slave drive to stop both of the conveyors. The power to the bus bars is also cut oli to prevent overheating of the motor windings while the refrigeration units are stationary within the oven. The power to the bus bars 78 and 79 is not cut oi, so that the pumping units continue to operate.

The rst bus bar 68 contacted'by the brush 67 (connected to the thermocouple gauge in the vacuum conduit) is located within the oven an arbitrary distance from the oven entrance which is suicient to allow the pumping units to reduce the pressure of a normal container or group of containers to a desired value. If, for any reason, a pumping unit has failed to reduce the pressure to a desired value, a conventional pressure-sensitive switch 96 of the contact meter type operates to actuate a solenoid 97 and turn on an alarm bell. The solenoid (see Fig. 3) actuates the trigger switch as shown by the dotted lines and turns olf the heater under the high vacuum pump boiler. A limit switch 93, immediately following the bus 6 bar 68, operates a conventional resetting means 99 of the electrical or mechanical type which resets the solenoid and turns oi the alarm bell.

Each of the bus bars 69, 70, 71, 72 which are succes sively contacted by brush 67 are connected to a fourpoint strip chart recording potentiometer 100 located on a main control panel 101. These strip chart recordings provide a permanent record of the progress of evacuation of each of the exhaust carts as they move under the oven.

Bus bar 73 located within the oven near the oven exit is connected to a conventional voltage-sensitive switch 102 of the contact meter type which operates an alarm bell 103 if the pressure in the exhaust units is above a predetermined amount. The voltage-sensitive switch 102 does not operate to turn oi the high vacuum pump heater on the cart. Bus bar 73 is immediately followed by a limit switch 104 which operates a conventional resetting means 105 of the electrical or mechanical type which turns off the alarm bell.

Bus bars 74, 75, 76 disposed in series outside the oven exit along the direction of conveyor movement are contacted by the brush 67 on each exhaust cart. Bus bars 74, 75, 76 are connected to indicating meters 106, 107, 10S respectively to provide a pressure check on any exhaust cart which actuates the alarm bell 103.

The refrigeration units connected to the exhaust cart which actuate the alarm bell are disconnected from the vacuum manifold sequentially and the indicating meters are observed to determine which of the refrigeration units was permitting the leak. This is readily determined because the pressure as indicated by .the thermocouple gauge will begin to decrease immediately when the faulty refrigeration unit is disconnected from the vacuum manifold.

An actual operation of the apparatus is as follows: The oven (16 feet high, 36 feet wide, and 137 feet long) was maintained at a temperature of about 300 F. plus or minus 5, with steam at 110 p. s. i. g. The plant conveyor followed a winding path within the oven (the slot in the oven floor followed the path of the conveyor) so that the length of the path traveled by the plant conveyor within the oven was about 800 feet. For this particular installation the refrigeration units were of the type in which the electric motor was hermetically sealed with the compressor in a single container.

The exhaust manifold provided at the top of the exhaust conduit was provided with four flexible exhaust hoses and each was connected to an individual refrigeration unit container at the oven entrance after the continuity check of the motor windings had been made. The conveyor speed through the oven was about 62/3 feet per minute, so that the dehydration of each unit was completed in two hours. The speed of the lower conveyor carrying the exhaust units was synchronized to Kthat of the plant conveyor by a speed synchronizer described in co-pending application Serial No. 392,396, led November 16, 1953, by R. C. Gauger and E. W. Perkins. The bus bar 68 was located about 44 feet inside the oven from the oven entrance, this being about the proper distance required for a pumping unit to reduce the pressure within the four refrigeration units connected to it to about 1000 microns of mercury. As mentioned above, if the thermocouple gauge indicated a pressure above this Value, a solenoid was actuated and an alarm bell was turned on. The solenoid tripped a trigger switch to turn off the heater on the ejector pump. This prevented damage to the pump Huid which would occur if the pump uid were continuously heated at a pressure above about 1000 microns of mercury.

The bus bar 62 was 46 feet 8 inches long and applied 90 volts to the running windings of the electric motors. No voltage was applied to the starting windings because the starting condenser was not installed at this point in the process. Therefore, the windings were heated but the motor did not operate. As the refrigeration units were carried on through the oven, the voltage applied to the motor windings was reduced stepwise by bus bars 63, 64, 65 (26 feet, 8 inches; 40 feet; and 220 feet long, respectively) and nally discontinued altogether at the end of bus bar 65. This resulted in a heating curve of the shape shown in Fig. 5, the objective being to raise the temperature of the motor windings to that of the oven as rapidly as possible without causing the temperature of the motor windings to exceed about 295 F. Temperature in excess of this value is likely to damage the insulating material in the motor.

1f, for any reason (e. g. work stoppage on some portion of the plant conveyor in another part of the plant) during the process the two conveyor belts got out of synchronization by more than a predetermined amount (nine inches), the speed synchronizer automatically shut ofi the power applied to the driving means for the plant and lower conveyors and stopped both conveyors.

if the voltages applied to each of bus bars 62, 63, 64, 65 dropped below a predetermined Value, the voltagesensitive switch associated with the respective bus bar tripped relay -t and the power supplied to drive the plant and lower conveyors was turned off. The power to the bus bars 62, 63, 64, 65 wasalso turned off by this operation to prevent overheating of the motor windings while the refrigeration units were stopped within the oven.

As each refrigeration unit came out the oven exit, its service valve was closed and the associated vacuum hose disconnected from it. The unit then continued on the same conveyor belt through the plant assembly line,lcolm plete dehydration having been eiected without having to tal/te the refrigeration unit off of the conveyor. After being disconnected from the dehydrated refrigeration units, each pumping unit was carried by the lower conveyor across the front of the oven to the oven entrance where it was connected to four more refrigeration units entering the oven entrance.

If a refrigeration unit came out of the oven which had not been evacuated to the required low pressure (SO microns of Hg), the alarm bell 103 was sounded and all refrigeration units attached to the associated pumping unit were checked to determine which one was faulty. The faulty unit was rejected and the other units were processed agam.

The apparatus of this invention provides the advantage of continuous pumping and heating of the containers, which has not been feasible with other schemes now practiced by the refrigeration industry. These advantages, when combined with the automatic controls and application of voltages to the motor windings on the control, .result in a uniform process which produced 150 dehydrated containers per hour. The above described apparatus reduced the required time for this rate of production from approximately eight hours to two hours, and furthermore, the operator requirements were reduced from about fourteen to a maximum of four manhours.

As mentioned above, the apparatus of this invention is equally suited for evacuating containers associated with refrigeration units in which it is not necessary to apply heating voltage to the motor windings. The application ot heating voltage may not be necessary for either one of two reasons: (l) The motor is so mounted within the container thermal conductivity between the container and the motor is sufficiently high so as not to require the application of heating voltage to insure heating oi the motor windings; or (2) the electric motor is located exterior of the container.

ln either type of arrangement the container and associe-.tc refrigeration unit components can be heated and evacuated continuously in much the same manner as described previously, except that heating voltage is not idl.

applied to motor windings; or an alternate procedure may be used as follows:

Conventional evacuating means are connected to the containers through their service valves to impose a preliminary or rough vacuum on the containers while they are carried by the plant conveyor, but before they are heated. The service Valves on the containers are then closed and the containers are disconnected from the rough vacuum system. The containers are then passed through an oven to subject the containers to a preheat period of approximately two hours while they are under the static vacuum previously imposed by the rough vacuum system. In the preheat period the motor windings come up to substantially the same temperature as the container, so that even in assemblies in which the motor is sealed in the container with the compressor, there is no need for heating voltage to be applied to the motor windings.

The containers are then connected to the apparatus shown in Figs. 1 through 4 and are evacuated continuously to a final evacuation in a manner similar to that described previously, except that no heating voltage is applied to the electric motor windings.

Conveniently, the same oven is used to preheat the containers and also to heat the containers while they are being evacuated continuously.

We claim:

lplniapparatus Afor evacuating and drying sealed containers, the combination which comprises a heating chamber capable of holding a plurality of the containers, a. first conveyor passing through the chamber and upon which'a series of the containers is carried through the chamber, a second conveyor disposed adjacent the heating chamber and substantially parallel to the first conveyor in its path through the chamber, a series of pumping units carried by the second conveyor and disposed adjacent the chamber, means for synchronizing the movement of the two conveyors, and a conduit on each pumping unit connecting it to at least one ot the containers on therst conveyor and movable in a slot in the heating chamber.

V2. Apparatus according to claim 1 in which the tirst conveyor is disposed to travel a greater distance while in the chamber than the distance traveled by the second conveyor by an amount substantially equal to the increase in length of the first conveyor in the chamber due tol thermal expansion of the tirst conveyor.

3. Apparatus according to claim l, which includes means Afor automatically measuring the pressure in each pumping unit during the drying, and means for inactivating any pumping unit in which the pressure exceeds a predetermined value.

4. In apparatus for evacuating and drying `sealed containers enclosing motors having windings, the combination which comprises a heating chamber capable of holding a plurality of the containers, a rst conveyor passing through the chamber and upon which a series of the containers is carried through the chamber, a second conveyor disposed adjacent the heating chamber and substantially parallel to the rst conveyor, a series of pumping units carried by the second conveyor, means for synchronizing the movement of the two conveyors, a conduit on each pumping unit connecting it to at least onevof the containers on the rst conveyor, the conduit being movable in a slot in the heating chamber, a bus bar disposed along the direction of movement of the conveyors, an electrical contact slidable along the bus bar and attached to the winding of a motor in each sealed container, and means for supplying current to the winding through the bus bar and the electrical contact toY heat the windings and aid in the drying.

5v. In apparatus for evacuating and drying sealed containers enclosing motors having windings, the combination which comprises a heating chamber capable of holdinga plurality of the containers, a iirst conveyor passing through the chamber and upon which a series of the containers is carried through the chamber, a second conveyor disposed below the heating chamber and substantially parallel to the portion of the first conveyor within the chamber, a series of pumping units carried by the second conveyor and disposed below the chamber, means for synchronizing the movement of the two conveyors, a conduit on each pumping unit connecting it to at least one of the containers on the first conveyor and movable in a slot in the bottom of the heating chamber, a bus bar disposed along the direction of movement of rthe conveyors, an electrical contact slidable along the bus bar and attached to the winding of a motor in each selected container, and means for supplying current to the winding through the bus bar `and the electrical contact to heat the winding and aid in the drying.

6. In apparatus for evacuating and drying sealed containers containing motors having windings, the combination which comprises a heating -chamber capable of holding a plurality of the containers, a rst conveyor passing through the chamber and upon which a series of the containers is carried through the chamber, a second conveyor disposed below the heating chamber and substantially parallel to the first conveyor, a series of pumping units carried on the second conveyor and disposed below the chamber, means for synchronizing the movement of the two conveyors, a conduit on each pumping unit connecting it to at least one of the containers on the rst conveyor and movable in a slot in the bottom of the heating chamber, a plurality of bus bar-s disposed along the direction of movement of the conveyors and carrying a variety of electrical voltages, an electrical contact Vslidable along the bus bars and attached to the windings of a motor in each sealed container, and means for supplying varying amounts of current to the winding through the bus bars and the electrical Contact to heat the winding and aid in the drying.

7. Apparatus according to claim 6, which includes means for measuring the individual voltages on the bus bars and for stopping both conveyors and cutting off the supply of current to the bus bars if the voltage on any of the bars drops below a predetermined value for that particular bar.

8. In apparatus for evacuating and drying sealed c011- tainers, the combination which comprises a heating chamber capable of holding a plurality of the containers, a tirst conveyor passing through the chamber and upon which a series of the containers is carried through the chamber, a preliminary evacuating means Idisposed adjacent the first conveyor for imposing a static vacuum or the containers before they are carried into the heating chamber by the rst conveyor, means for subjecting the containers to a preliminary heating while under the static vacuum, a second conveyor disposed adjacent the heating chamber and substantially parallel to the irst conveyor in its path through the chamber, a series or' pumping units carried by the second conveyor and disposed adjacent the chamber, means for synchronizing the movement of the two conveyors, and a conduit on each pumping-unit connecting it to at least one of the preheated containers on the first conveyor and movable in a slot in the heating chamber.

References Cited in the tile of this patent UNITED STATES PATENTS 544,373 Patterson et al Aug. 13, 1895 1,757,205 Morris May 6, 1930 2,l06,445 Wade Jan. 25, 1938 2,223,588 Watson et al Dec. 3, 1940 2,277,030 Anderson Mar. 24, 1942 2,281,079 Rollins Apr. 28, 1942 2,485,609 Koster et al. Oct. 25, 1949 2,532,315 Johnson et al. Dec. 5, 1950 2,546,004 Kinn Mar. 20, 1951 2,557,621 :Touborg June 19, 1951 FOREIGN PATENTS 1,553 Great Britain 1905 8,613 Great Britain 1905

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