US2292846A - Electronic timer - Google Patents

Description

E. M. PRITCHARD ELECTRONIC TIMER Filed SepL' 28, 1939 Aug. 11, 1942.

3 Sheets-Sheet l ATTORNEYS Aug. 11, 1942. E. M, PRITCHARD 2,292,846

ELECTRONIC TIMER Filed Sept. 28, 1939 3 Sheets-Sheet 2 INYENTOR. Edward M. Prztch-ard ATTORNEYS Aug. 11, 1942. E. M. PRITCHARD 2,292,845

ELECTRONIC TIMER Filed Sept. 28. 1939 3 She ets-Sheet 3 igllllllllzl-c INYENTOR. E a ward M Pratt/Lard ATTORNEYS Patented Aug. ll,

, 2.29am amoraonic 'nmnn Edward M. Pritchard, New York, N. Y., assignor to The Prosperity Company, Inc Syracuse, N. Y., a corporation of New York Application September 28, 1939, Serial No. 296,957

1 Claim. (Cl.

variety of mechanical devices, such, for instance, I

as pressing machines, say laundry ironing presses; and the device may be called an electronic timer.

The invention is particularly desirable in connection with textile presses having a variety of uses, such as in l'aundries where a smooth, firm finish is imparted to damp laundered work. Such presses are ordinarily of the jaw-motion type having coasting pressing members usually called the head" and buck which open and close on the work. These presses are power driven, that is, they are usually closed by motor means which subjects the work to a high degree of ironing or finishing pressure under heat. One or both pressing jaws (head and buck) are heated, usually by steam, for ironing and finishing the work laid upon the buck.

The conditions and manner of use, with other special requirements and problems met in the textile ironing or smoothing art, comprising the laundry trade, the tailoring trade, and the clothing manufacturing industry, have come to wide- 1y distinguish the textile and apparel presses as a general class from other pressing fields.

The upper pressing head of a conventional laundry-ironing press has a metallic plated or polished surface to impart a smooth firm finish to the damp work being pressure-ironed and dried. On the other hand, the upper pressing head of a conventional garment-press usually has a cloth covered surface to aid in distributing a spray of steam applied to the dry woolen garment to dampen it for finishing purposes. The lower buck of each type of press has a padded surface acting as a yielding pad on which to effectively iron the work, which is damp when it reaches the press in the case of laundry work, and dry in the case of garment work. The ironing pad on each type of press permits the buttons, seams, and other irregularities to be depressed into the buck to equalize the pressure of the head around these parts of the work, as the head seals down and is maintained under final heavy-ironing pressure until the work is ironed. dry and finished.-

The operation of the press may be controlled in various ways, but regardless of the method of control, it is highly desirable to raise the head from the buck when the work has been dried to a desired degree, because if the head remains in contact with the work after this degree of drying has been reached, there may be danger, especially in laundry presses, of scorching the work or otherwise deleteriously aflecting it. The time required to dry the work in the press will depend on the temperature of the head as well as the amount of moisture in the work, but in the ordinary operation of a laundry where one press is being used for a particular kind of article to be ironed, this time requirement may be fairly accurately estimated, especially since the head is usually maintained at a constant temperature and the work contains a substantially constant amount of moisture.

It is therefore one of the objects of the present invention to provide an electronic timer for a press which will open the press at a predetermined time after the head moves into contact with the work.

Another object of the invention is to provide an electronic timer for a press which may be easily adjusted, by the simple turning of a knob, for any time delay within wide limits.

Another object of the invention is to providev an electronic time delay circuit which will operate on unfiltered and unrectified alternating current.

With the foregoing and other objects in view, the invention has relation to the new principles and features with the advantages disclosed herein, as now described and shown in the attached drawings, showing an example of the new combination comprising this invention, wherein:

Figure 1 is a sectional side elevational view of a conventional power-operated full-automatic textile press arranged-to be controlled electrically by the body capacity of the operator, and including the circuit diagram of my improved electronic timer.

Figure 2 is a circuit diagram showing the invention applied to a press having two-hand electric control.

Figure 3 is a schematic view of a two-hand pneumatically controlled press showing my improved electronic timer adapted for operation therewith.

The press illustrated herein has a frame I with a work table 2 under the pressing jaws, that is, under the coacting head and buck. An ironing buck or bed 3 is mounted stationary on the frame and has the usual form of padding 1 on its ironing surface. A movable ironing head 5 is carried on the forward end of a head arm or lever 6- pivoted at I on the frame. The heads and bucks of pressing machines are manufactured in a variety of shapes and sizes best suited to particular apparel and textile materials to be pressed.

The press lever I lifts the head high above the buck to fully expose the padded surface of the latter to the operator while making her lay of the work, and consequently a wide opening is afforded for the convenience of the operator. This type of press, with its wide opening head, swingable up and down in relation to the buck around the rear horizontal axis 1, is sometimes called the scissors-action".type of full automatic press. It is one of the more convenient forms by which to disclose this invention.

A conventional form of power-actuating means is shown for closing and opening the press. The motor means may perform both functions, that is the opening and closing cycle, but more generally the motor means is employed to close the press and simultaneously stretch or load a spring counter-balance, whereupon the latter performs the reverse function of opening the press and holding it open. As said before, electric or other motor means may be employed, but the example shown comprises a pneumatic motor means 9 usually operated by air pressure.

The cylinder 9 is mounted to oscillate on a frame pivot l0, and its piston Ii with connecting rod i 2 is pivotally connected at l3 to the head arm 6. Any suitable form of head counterbalancing means may be employed, and usually this takes the form of a long coil spring l4 having its inner end attached at l5 to the press frame, and its outer movable end operatively connected at It to the head arm. With the motor means 9 idle or deenergized, the tensioned spring means I 4 maintains the head in wide open position.

An air inlet and exhaust tube It communicates with the inner or closed end of the cylinder, and this usually is an air hose which flexes with the up and down movement of the cylinder. A control member, such as valve means is, is connected with the combination air inlet and exhaust tube I 3. Operation of the valve i8, that is, the opening and closing thereof, serves to admit and exhaust air to and from the cylinder 9 for the purpose of closing and opening the pressing jaws 3 and 5.

In the event an electric motor is used to drive the press, an electrical power switch will of course be employed in place of the fluid-power valve means IS. The magnetically controlled type of valve shown, that is, a solenoid actuated valve l9, has a valve stem 20 which carries a solenoid core or armature 2| adapted to be actuated by a magnet coil or solenoid winding 22. A spring 23 tends to normally raise the valve stem when the solenoid is deenergized. and the energizatlon of the solenoid returns it against the tension of the spring to its lowermost position. Thus the valve I9 is controlled by energizing and deenergizing the solenoid 22. This 15 a poppet type valve and it is found to be satisfactory for use in this new combination when a pneumatic motor means is used to operate the press.

Both the valve l9 and operating solenoid 22 may be mounted on the frame I of the pressing machine, although of course this is not essential. The showing of the valve and associated mechanism in Figure 1 is diagrammatic and not intended to illustrate the location of these parts.

An air-pressure supply conduit 24 connects with the valve housing l9 to feed air under pressure to the flexible hose Hi from a compressor and tank which have not been shown. An inlet valve head 25 is carried on the inner end of the valve stem 20 and is held open by the action of the solenoid 22, that is, unseated from its valve seat, for the purpose of connecting the air conduit 24 with the motor tube II to deliver air under pressure to the pneumatic motor 0 to close the press. During the pressing operation the inlet valve head 2! is maintained open by the solenoid to keep the air supply line 24, II open to the cylinder for urging the piston ll further on its power stroke to inch and seal the head 8 more firmly against the yielding buck pad I and to compensate or take up for any give or compression in the pad. Thus when the press is closed the motor 9 is stalled against further movement by the contact of the head with the buck, the pressure of the air continuing to urge the two together under ironing compression.

An exhaust valve head 2! acts to close an air passage between the motor 3 and an exhaust port opening to atmosphere from a valve chamber 2| when the inlet valve 25 is open, so that the compressed air is conducted from the air-supply conduit 24 to the hose l8 and motor, without escaping through the exhaust port. The inlet valve 25 and exhaust valve 21 are fixed on the valve stem 20 and work in unison. Thus one valve head is always closed when the other is open, which is to say, that when the inlet valve 25 is open, the exhaust valve 21 is closed and the press is closing or closed. Conversely, when the inlet valve 25 is closed on its valve seat, the exhaust valve 21 is open to exhaust the motor cylinder 9 through the exhaust port or passage 28 to atmosphere, and the press is open or in the act of opening.

In Figure 1 there is shown a capacity responsive control for the press. Such a device is provided with an electrode which has an alterable capacity to ground. The operator moves into the field of the electrode increasing the capacity to ground and changes a circuit connected with the electrode so as to open the press. When she moves away from the electrode, the reverse change in its capacity to ground ail'ects the circuit to cause the press to close.

In the particular arrangement illustrated, the capacity electrode may take the form of a rod electrode 30 which may be insulatedly mounted upon the head 5 in spaced relation thereto. Another rod electrode 3| may be insulatedly mounted on the table 2 and spaced a short distance therefrom. These two electrodes 30 and 3i may be connected together by means of a wire 32 which leads to the capacity control circuit enclosed in the housing 33. This capacity control circuit is not shown in detail, as it does not form any part of the present invention,

The capacity control unit 33 may have an output relay 34 which is so connected to the circuit that it will be de-energized when the operator is in the vicinity of the electrodes 30 and 3i, and it will be energized when the operator moves away from these electrodes. The relay 34 may have an armature 35 which controls two pairs of contacts. The contacts 36 and 31 are open, as shown, when the relay is deenergized. The contacts 38 and 33 are closed when the relay is deenergized. The contact 31 may be connected to one side 42 of the volt, 60 cycle, alternating current power mains by means of a wire 43. The contact 38 may be connected by means of a wire 44 to a contact 45 forming part of a relay 48 connected in the timer circuit and which will be later described. Another contact 41, normally engaging the contact 45, may be connected directly to the solenoid 22 which controls the operation oi the valve IS. The other side of the solenoid 22 may be connected by means of a wire 43 to the other wire 43 of the power mains. The purpose of the contacts 33 and 33 will be described later.

When the relay 34 of the capacity control unit 33 is deenergized, as in Figure 1. no current will flow through the solenoid 22 and therefore the valve stem 20 will be in the position shown, held there by the spring 23. In this position of the valve, the exhaust is open and the head is raised and maintained in its raised position by the tension of the spring l4. However, when the relay 34 is energized, as by the operator stepping away from the vicinity of the electrodes 30, 3|, current is supplied to the solenoid 22 from the power main 42, the wire 43. contacts 31 and 35, the wire 44, and contacts 45 and 41 of the relay 45, while the wire 48 completes the circuit to the other side 49 of the power mains. With this arrangement, the press is controlled by the presence or absence of the operator. When she steps in front of the press, it opens; when she steps away from the press, it closes.

The time delay circuit may be enclosed as a v unit in a housing 5|, shown in dot and dash lines in Figure 1. The circuit may comprise a thermionic tube 52, the input circuit of which produces the timing effect while the output circuit contains a controlling device for affecting the operation of the press. This tube 52 may be of the heater type and may have a heating filament 53, a cathode 54, a control grid 55, a screen grid 56, and an anode 51.

Operating voltages for the tube 52 may be supplied irom a transformer 50 having a primary winding Bl, which may be connected directly to the power mains 42 and 49, and a secondary winding 52. One end of the secondary winding 62 may be connected by means of the wire 63 to one end of the filament 53, and the other end of the secondary winding 62 may be connected by means of the wire 54 to one coil terminal of the relay 46. The other coil terminal of the relay 45 may be connected directly to the anode 51 of the tube 52. A condenser 65 may be connected across the coil terminals of the relay 46 to store up and smooth out the sixty cycle impulses which pass through the tube 52 to energize the relay.

The screen grid 55 may be connected to a tap 58 on the secondary winding 62 which will give the screen grid a suitable operating potential below that of the anode. connected to the other side of the filament 53 and also, by means of the wire 61. to another tap 53 on the secondary winding 62. This tap 68 is sufllciently spaced from the end of the secondary connected to the wire 63 to produce a suitable voltage between the tap 68 and the end of the secondary to energize the filament 53.

Separate secondary windings may be used. if desired, for the transformer in place of the single winding 62 shown, but in such case the separate windings would be connected together in the manner shown to efifectively form a single winding.

The control grid55 of the tube 52 may be connected to the cathode 54 through two resistances 1i and 12 which are in series with each other, the resistance 1| being adjacent the control grid and the resistance 12 being adjacent the cathode. The resistance 1| is preferably made adjustable by a slidable contact arm 13 which may be manually controlled by means of a knob 14. Rota tion of the knob 14 will slid the contact arm 13 The cathode 54'may be r along the resistance 1| to change the resistance to any desired value. Between the contact arm 13 and the control grid 55 I connect a condenser "15, the; charging and discharging of which proin Figure 1, and that the relay 34 of the capacity control unit is therefore in the position shown, with the contacts 38 and 39 engaging each other, the grid 55 will be connected to the end of the secondary winding 62 through the combination of resistance 1| and condenser 15. Thus an alternating current potential will be applied to the control grid 55 which, because of its rectifying characteristic, will build up a negative potential and thus charge the condenser 15. The negative potential on the control grid 55 will reduce the plate or anode current of the tube 52 to a minimum, with the result that there will not be sufflcient anode current to operate the relay 43. Hence the contacts 45 and 41 of the relay 46 will be in engagement with each other, as shown, and the circuit to the solenoid 22 will be closed, with the exception of'the contacts 36 and 31 of the relay 34, which will be open.

If then the operator steps away from the press, thus causing the capacity control circuit 33 to energize the relay 34, the closing of contacts 38 and 31 will energize the solenoid 22, move the valve stem 20, so as to open the inlet valve 25 and opened which breaks the direct circuit between the grid and secondary 62. The negative charge on the control grid 55 now begins to leak oil as the condenser 15 gradually discharges through the resistance 1|. Eventually this charge on the control grid 55 will leak ofi to such an extent that the plate or anode current of the tube will be increased sufficiently to operate the relay 45 and open thecontacts 45 and 41. The time required for this action to take place will depend on the value of the resistance 1|, which may be ad- Justed by means of the knob 14. Opening the contacts 45 and 41 will break the circuit through the solenoid 22. This permits the valve 25 to be closed by the tension of the spring 23, thus shutting ofi the supply of air to the cylinder 9 and opening the exhaust, so that the piston I I may be returned to its inner position by the spring 14. which at the same time swings the arm 6 about the pivot 1 and raises the head 5.

Inasmuch as the operator is still away from the vicinity of the electrodes 30 and 3i, the relay 34 will remain energized which will keep the contacts 38 and 39 separated. This will keep the condenser 15 discharged and maintain the potential of the control grid 55 positive enough to keep the relay 45 energized, and th s will keep the press open. When, however, the operator returns to the press, her presence in the vicinity of the electrodes 30 and 3| will cause the capacity control circuit to respond and deenergize the relay 34, thus opening the contacts 35 and 31 and again closing the contacts 38 and 39. Closing the contacts 39 and 39 will again cause the grid to be connected to the end of the secondary 92 which will quickly build up a negative charge on the control grid 99 to release the relay 49 and close the contacts 49 and 41. The circuit is now restored to the condition illustrated in Figure 1, with the press open and the relay 34 deenergized by the presence of the operator.

It will be obvious that some articles will require less-time to finish in the press than others, because 01 the particular weight of the material and the amount of moisture present. Where the work being done by a particular press is uniform, the timer may be accurately set to release the press at the proper time. However, it may be desirable durin a particular run of the press to finish some smaller article which would take less time to finish than the time predetermined by the set of the timer controlknob 14. In such case, operator need only approach the vicinity of the electrodes 39 and 3| to cause the relay 94 to open the energizing circuit of the solenoid 22 so that the press will open before the timer relay 49 has operated. Closing of the contacts 39 and 39 by the release of the relay 34 as the operator steps into the vicinity of the electrodes 39 and 9| will again negatively charge the control grid 99 and maintain the relay 49 in its deenergized position.

In Figure 2 the invention is shown applied to a press having another type of electrical control wherein two push button switches 89 and 9| must be depressed simultaneously, one by each hand of the operator, in order to operate the press. To this end, these switches 99 and 8| may be connected in series between one side 82 1 the 110 volt, 60 cycle, power main and a third push button switch 93. The latter switch is normally held closed but may be opened by manually depressing the button associated therewith. The

switch 93 is connected to one side of the solenoid 22, while the other side thereof is connected to the contact 41 on the relay 49 which forms the controllin device for the timing circuit contained inhousing 5|. The other contact 49 associated with the relay 49 is connected to the other wire 99 of the power supply main. The transformer of the timing circuit (not shown in this figure), may also be connected to the power supply mains 92 and 95 by means of the wires 99 and 91, respectively. This timing circuit may be identical with that described in connection with Figure 1.

An actuating switch for starting the operation of the timing circuit may be made to automatically operate by the movement of the press arm 9. To this end, a movable switch lever 9| is pivoted at 92 on the press frame and has a contact 93 which is in engagement with a fixed contact 94 when the press is open. A lever or arm 99 may be attached to the head arm 9 of the press in such a manner that an adjusting screw 99a on the arm '99 may engage the movable end of the switch lever 9| when the press is closed to cause it to open the contacts 93 and 94. Contacts 93 and 94 are connected, respectively, by wires 99 and 91 to the timer control circuit or unit 9|, these wires taking the place of wires 19 and 11 in the arrangement of Figure 1.

The two push button switches 99 and 9| may be shunted by a locking switch 99 comprising contacts I99 and NI, a wire I92 being used to connect the contact |9| to the supply main 92 and the wire I93 being used to connect the contact I99 with a point in the circuit between the switch 99 and the switch 93. The contacts I99 and IN may also be associated with the lever 9| and arranged to be opened or separated when the lever is in its normal position and to be closed when the lever is moved by the movement of the arm 9 in swinging the head 9 upon the buck 9. In other words, the switch contacts I99 and |9| are open when the press is open and are closed when the press is closed.

With the arrangement Just described, assuming the press to be open, there is no circuit through the solenoid 22, the switch contacts I99 and |9| being open and the two switches 99 and 9| being open. When the operator desires to close the press, she depresses both buttons 99 and 9| which closes both of these switches and causes current to flow from the main 92, through switches 9| and 99, and switch 93, which is normally closed, through the solenoid 22 and through contacts 49 and 47, which are closed, to the other side 99 of the power mains. The switch contacts 49 and 41 are closed because the contacts 99 and 94 are closed, and hence the grid oi the timing circuit tube is negatively biased, as described in connection with Figure 1, and the relay 49 is deenergized.

Current flowing through the solenoid 22 operates the valve |9 to admit air under pressure into the cylinder 9 and starts the press moving towards its closed position. The operator still has her hands on the control switches 99 and 9|. but when the press reaches a point near its closed position, the lever 99 on the arm 9 comes in contact with the lever 9| to swing this lever so as to close contacts I99 and 9|. This forms a locking circuit for the solenoid 22 which takes the control of the press away from the operator, and the operator may remove her hands from the control buttons 99 and 9|, the press remaining closed because these manual control switches are shunted by the contacts I99 and Ill which are now closed.

At this time the initiation oi. the timer circuit has already taken place, for when the press 45,reached the closed position, the contacts 93 and 94 were opened and this broke the circuit between the grid and secondary (Figure 1) of the timer circuit, so as to permit the condenser 19 to slowly discharge. When the condenser 19 has been sufliciently discharged, which will take a certain period oi time depending upon the value of the resistance 1|, the relay 49 will operate and open the contacts 49 and 41. The circuit through the solenoid 22 will then be broken and the press will open. v

When the press reaches its open position, the contacts I99 and 9| will have separated and the contacts 93 and 94 will have moved into engagement with each other. This causes the circult to be made between the control grid 99 of the tube 92 and the end of the secondary winding 92 oi. the timer circuit again and causes the grid to immediately build up a negative potential which reduces the current of the tube sufficiently to deenergize the relay 49 and permit the contacts 49 and 41 to close. The press will now remain open because the switches 99 and II and the contacts I99 and MI will be open, and every- ,thing will be in readiness for the press to close aacaue will open the circuit through the solenoid and bring the press to its open position where it will stay because of the open'contacts I and IN.

The invention may also be applied to a press having iull pneumatic two-hand control. A conventional form of such press and control, with this invention applied thereto, is shown diagrammatically in Figure 3. A cylinder I06 and piston I01 are similar'to the cylinder 9 and piston II shown in Figure 1. A pair or manually con-' trolled push buttons I08 and I09 may be arranged and so spaced in a known manner, on the front or the press, that they must be depressed simultaneously by the two hands of the operator when it is desired to close the press.

The two-hand buttons I08 and I09 control the admission of air under pressure to the cylinder I06, and each button controls an exhaust valve connected with the cylinder. Air is delivered to a valve housing IIO, operatively associated with the button I09, by an air supply pipe III. A valve stem II2 reciprocates in the housing H0 'and carries an inlet valve head II3 normally urged against its seat II4 by a spring II5. This normally closed position of the inlet valve II3 prevents air pressure from reaching a passage II6 connected by an air pipe III with the inlet end or the cylinder I06.

The valve stem II2 also carries an exhaust valve head IIB which, in its normally closed position, keeps open the valve passage II6 to the atmosphere through anexhaust port H9. The pipe III is also connected to another pipe I22 which leads to a second valve chamber I23 operatively associated with the button I08. This valve chamber I23 contains a valve stem I24 which carries an exhaust valve head I25 controlling the opening and closing of an exhaust port I26 in the valve chambento exhaust the air from the pipe I22 to the atmosphere when the valve stem I24 is in its normal position.

In order for air from the pipe III to be delivered to the cylinder I06, both the valve stems H2 and I24 must be pushed inwardly, the first to push the valve II3 away from its seat H4 and to force the valve head H8 against its seat to close the compartment H6, and the second to close the exhaust port I26 so as to prevent air from passing from the pipe I22 out through the valve chamber I23.

These valve stems I24 and H2 may be controlled by the push buttons I08 and I09. To this end, each of the push buttons may be provided with a. bell crank I30 which may be pivoted at I3I to a. portion of the frame of the machine and may have one arm provided with a roller I32 adapted to engage the back of the push button. The other arm of the bell crank may be provided with a roller I33 adapted to engage the end of a lever I34 which is pivoted at I35 to some part of the frame of the machine. Thissame end of the lever I34 engages one of the valve stems I24 and H2, as the case may be, so that rotation of the lever about its pivot point forces the valve stem into its particular valve housing. The lever I34 may be provided with a suitable cam surface to engage the end of the valve stem. A spring I36 may be attached between a portion of the frame and a portion of the bell crank adjacent the roller I33 to urge the bell crank in the opposite direction so as to push the button outwardly.

The bell crank I30 and lever I34, associated with both of the buttons I06 and I09, are exactly alike and both work in exactly the same manner to force the associated valve stem inwardly-when the button is depressed.

Means are provided to take the control of the press away from the operator when the head of the press has reached a certain predetermined position in the closing direction. To this end, the cylinder I06 may be provided with an opening I36 near the outermost position of the piston and arranged to be uncovered by the piston as it approaches its outermost position. A pipe I40 may connect this opening with a diaphragm housing I4I rorming a part or the valve housing IIO. This diaphragm housing may have a diaphragm I42 mounted therein on one side of which is a compartment I43 into which the pipe I40 opens. On the other side of the diaphragm I42 may be provided a plunger I44 which bears against the diaphragm and extends through an opening in the housing to engage the free end of the associated lever I34. Similarly, a diaphragm housing I45 may form part of the valve housing I23 and may contain a diaphragm I46 having a compartment I41 on one side thereof into which the pipe I40 may be connected. A plunger I49 may engage the other side of the diaphragm I46 and may pass outwardly through the housing to contactwith the free end of the associated lever I34.

When the buttons I08 and I09 have been depressed so as to close the exhaust valves I25 and II8 respectively and open the inlet valve II3, air

passing through the pipe III is free to enter the 6 lower end of the cylinder I 06 through the pipe III. The piston then starts to move outwardly to close the press, and when the press head is nearly closed and the piston moves beyond the port I39, air under pressure is introduced to the diaphragm compartments I41 and I43 through the pipe I40. The pressure on the side of these diaphragms causes the ,plungers I48 and I44 to move outwardly, thus holding the levers I34 in the position which they originally assumed by the action of the buttons. At this tim the removal of the operators hands from the buttons will cause the buttons to move ouwardly to assume their normal position, urged by the springs I36, but the valve stems I24 and H2 will be held at their innermost position by the levers I34 which in turn are held by the diaphragms I46 and I42. The press is thus maintained in its closed position regardless of the fact that the operator has removed her hands from the control buttons.

In order to open the press again, an exhaust valve housing I50 is provided in which may be mounted a valve stem, I5I carrying a valve head I52. The valve head I52 may be held by means of a spring I54 against an exhaust port I53 which is open to the atmosphere. A lever I55 is pivotally mounted at I56 in such a manner that it maybe moved in a certain direction to force the valve stem I5I inwardly against the tension of the spring I54 and move the valve head I52 to uncover the exhaust port I53. A pipe I51 may connect the interior of the valve housing I50 with the pipe I40.

When the operator Wants to open the press, she need only move the lever I55 to open the exhaust port- I53. This will relieve the pressure in the pipe I40 which is acting against the diaphragms I46 and I42, so that the spring H5 in the valve housing IIO may move the valve stem I I2 and close the inlet valve I I3, and at the same time open the exhaust port II9, so that the air in the cylinder may pass out through this port to close the exhaust port I53, but when the solenoid is energized, the valve stem I5I will "be pulled against the tension of the spring I54 to open the exhaust port I53.

The timer unit 5|, which may be exactly the same as that shown in detail in Figure 1, may have a relay I62 which may correspond to the relay 46 in Figure 1, but which may have contacts I60 and I64 which are normally open and close only when the relay is energized, these contacts thus acting oppositely from the contacts 45 and 41 of Figures 1 and 2. The press arm 6 may also be provided with a lever 65 which may engage a movable contact I 65 to move it away from a contact I66 when the press is in its closed position, the contacts I65 and I 66 being normally in engagement with each other when the press is open. Contacts I65 and I66 constitute the starting switch for the timer unit and may be connected, respectively, by wires I61 and I68 to the timer unit, these wires corresponding to wires 16 and I1 in the timer circuit of Figure 1.

The transformer primary of the timer unit may be connected directly to the 110 volt alternating current power supply mains I69 and I10. The solenoid I6I may have one end connected by moved to close the exhaust port I63 and place the whole system in condition again for closing of the press by the operation of the control buttons I06 and I06. 7

The timer unit 5| may be mounted in any convenient place on the frame of the machine, preferably where the adjusting knob 14 may be easily reached by the operator. It will be understood that the knob 14 may be provided with a graduated scale so that the operator may set the timing as desired for a particular run of work to be done.

From the above description, it will be evident that I have provided a new electric timing device which may be adjusted for any desired time delay and which will actuate an independent circuit when such predetermined time has elapsed. The invention lends itself particularly to the timing of pressing machines, such as laundry presses, and may be set to effectively open the press at any predetermined time after it has been closed. At the same time, the timing circuit will not interfere in any way with the normal operation of the press, whether controlled entirely electrically or by pneumatic control mechanism, and may be applied to any ex- I isting press with a minimum of changes in the means of a wire ill to the power supply main I66 while the other end of the solenoid may be connected by means of a wire I12 to the contact I64 of the relay I62. The other contact I63 of the relay I62 may be connected to the other power supply main I10.

With the arrangement shown, operation of the pneumatic control buttons to close the press is in accordance with the description already given. When the press is open, the contacts I65 and I66 will be in engagement with each other which will produce a sufllcient negative charge on the control grid of the timing tube 52 to keep the relay I62 deenergized and thus keep the solenoid I6I deenergized by the separation of contacts I63 and I64. After the press has been closed in the manner already described, the contacts I65 and I66 are separated by the action of the lever 95, which permits the charge to leak of! of the control grid of the timing tube and eventually causes the relay I62 to be energized, thus closing the contacts I63 and I64. This produces a current in the solenoid I6I which pulls the armature I60 towards it and moves the valve stem I5I against the tension of the spring I54, which opens the exhaust port I53 and performs the same function that the operator does when she moves the lever I55. This will open the press, and when the contacts I65 .and I66 come into engagement again, the relay I62 of the timer will be immediately deenergized, so that the armature I60 and valve stem I5I may be various parts thereof.

This invention is presented to fill a need for improvements in electric timer circuits. It is understood that various modifications in structure, as well as changes in mode of operation, assembly, and manner of use, may and often do occur to those skilled in the art, especiallyafter benefiting from the teachings of an invention. Hence, it will be understood'that this disclosure is illustrative of preferred means of embodying the invention in useful form by explaining the construction, operation and advantages thereof.

What is claimed is:

An electric timer comprising a thermionic tube having an anode, a control grid and a cathode, means to apply an alternating voltage between said anode and said cathode, a condenser and a resistance connected in series between said control grid and said cathode, said resistance being adjacent said cathode, means to apply an alternating voltage across said resistance whereby said condenser is charged because of the rectifying action of said control grid, thus charging said control grid negatively, means to gradually discharge said condenser whereby said control grid is caused to approach cathode potential, and a relay connected in the anode circuit of said tube; in combination with a work circuit having a normally closed switch therein openable by the relay when energized, a control switch in the work circuit in series with the relay operated switch and being normally open, and a normally closed switch openable by the closing of the control switch and connected in the grid circuit, whereby when the control switch is closed, said switch in the grid circuit is opened and the work circuit remains closed until the relay is de-energized and the relay switch opened.

EDWARD M. PRI'I'CHARD.

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