US2864935A

US2864935A - Apparatus for spacing and uniting parts

Info

Publication number: US2864935A
Application number: US669311A
Authority: US
Inventors: Alfred D Johnson; Floyd K Collins
Original assignee: Sylvania Electric Products Inc
Current assignee: GTE Sylvania Inc
Priority date: 1957-07-01
Filing date: 1957-07-01
Publication date: 1958-12-16
Anticipated expiration: 1975-12-16

Description

Dec. 16, 1958 A. D. JOHNSON ET AL 2,864,935

APPARATUS FOR SPACING AND UNITING PARTS Filed July 1, 1957 7 Sheets-Sheet 1 AW 03 mm EO VJ m D D E R F L A FLOYD K. COLLINS ATTORNEY Dec. 16, 1958 A. D. JOHNSON ET AL 2,864,

APPARATUS FOR SPACING AND UNITING PARTS Filed July 1, 1957 7 Shets-Sheet 2 INVENTOR ALFRED D. JOHNSON FLOYD K. COLLINS ATTORNEY 7 Sheets-Sheet 3 z W m ,m. fir l 8 4 9 T I 4 9 8 9 Q 9 w? e v L M n .E m .w mm I 4 HI M J 5% m w w INVENTOR ALFRIED 0. JOHNSON FLOYD K. COLLINS ATTORNEY Dec. 16, 1958 A. D. JOHNSON ET AL APPARATUS FOR SPACING AND UNITING PARTS Filed July 1, 1957 Dec. 16, 1958 A. D. JOHNSON ET AL APPARATUS FOR SPACING AND UNITING PARTS 7 Sheets-Sheet 4 Filed July 1, 1957 INVENTOR ALFRED D. JOHNSON FLOYD K. COLLINS ATTORNEY Dec. 16, 1958 A. D. JOHNSON ET AL 2,864,935

APPARATUS FOR SPACING AND UNITING PARTS 7 Sheets-Sheet 5 Filed July 1, 1957 INVENTOR ALFRED D. JOHNSON FLOYD K. COLLINS ATTORNEY Dec. 16, 1958 A. D. JOHNSON ET AL 2,364,935

APPARATUS FOR SPACING AND UNITING PARTS 7 Sheets-Sheet '7 Filed July 1, 1957 L. Q .L

United States Patent APPARATUS FOR SPACIN G AND UNITIN G PARTS Alfred D. Johnson and Floyd K. 'Collius, Seneca Falls, N. Y., assignors to Sylvania Electric Products Inc, a corporation of Massachusetts Application July 1, 1957, Serial No. 669,311

14 Claims. (Cl. 21978) This invention relates to apparatus for positioning parts relative to one another and aflixlng said parts to each other when so positioned. More specifically, this invention concerns itself with apparatus used to position and weld the parts of an electron gun.

It is well known to those skilled in the art of electron discharge devices that great care must be exercised during manufacture of such devices to space certaln of the electrodes relative to one another in order that an acceptable product be obtained. In the case of cathode ray tubes, it is necessary to closely control the spacing between the first grid and cathode inorder that the cutoff characteristic of such tubes be maintained within certain desirable limits.

It will therefore be appreciated that in order to manufacture tubes whose cutoff characteristic will fall within certain desirable limits, a very close check must be kept on all parts which could in any way affect the distance between the control grid and the cathode. It w.ll further, be appreciated that a check of the grid-cathode spacing oneach grid-cathode assembly after it is assembled andwelded together, but before incorporation within a tube, will result in a great sav.ng in labor and materials by not incorporating improperly spaced gridcathode assemblies into otherwise good tubes. For this reason, each and every grid-cathode assembly is ch-cked for spacing before the gun assembly operation.

In a prior method of making the grid-cathode assembly, a circular metal spacer ring of L-shaped cross section is dropped into a cylindrical metal grid cup with the flange end away from the bottom of the disc. Because of variations in the flatness of thebottom of the grid cup, a reading is then made on a dial gauge to check the distance between the inside bottom of the grid cup and the outermostsurface of the flange of the spacer. Those parts showing improper dimensions are discarded. The cathode assembly, which comprises a nickel cathode sleeve provided with an emissively coatedtop cap mounted in a substantially fiat circular ceramic, is next measured for the height of the emissive coating above the ceramic. The cathode assembly is then inseited into the grid cup. The aforementioned spacer serves to space the cathode coating a proper distance from the grid. A retainer ring having a peripheral flange is then machine pressed into the cup against the ceramic and welded thereto to thereby hold the cathode as embly rigid in the grid cup. A spacing check i then made by an air senser known as an air comparator to weed out any assemblies having an unacceptable'spacing between the grid and the cathode coating.

The above steps-describe a method of manufactur ng and space checking grid-cathode assemblies which involves an undesirable number of handling operations and often produces a condition wherein assemblies are out of specification. This'condition cannot be accurately determined before the welding operation.

It is an object of this invention to produce a method and apparatus for manufacturing grid'cathode assemblies cathode-grid assemblies between theassembling of parts 2,864,935 Patented Dec. 16, 1958 which will assure that the assembly is in accordance with specifications at the time and after the cathode assembly is fixed in position within the grid cup.

It is another'object of this'inventionto continuously keep check on the grid-cathode spacing'bymeansofiaa sensing device, so that a welder which fixes the'ca'i'hode relative to the grid will be" energized only when said spacing is withincertain limits.

It is a'further object of this invention'to-eliminate checking of the grid-cathode assemblies for spacing, asz-a separate step. 1

It is another object of thisinvention to incorporate spacing, checking and welding ofsaid assemblies inone.

continuous operation.

It is a still further object of this invention to provide a method and a machine to eliminate handlmg' ofthe and the manufactured checked product.

The features of the present invention which are believedto be novel are set forth with particularity in the appended claims. The invention, together with further objects and advantages thereof, may best be' understood, however, by reference to the-following descri tion taken in connection with the accompanying drawings, in the several figures of whichlike reference numerals indicate like elements, and in which:

Fig. 1 shows, in enlarged cross-section, the grid-cathode assembly as it appears when inserted into anxair senser adapter'head ready to be spaced and welded .by the apparatus herein described.

Fig. 2 shows in enlarged cross-section thefinished grid-cathode assembly manufactured by the presentapparatus,

Fig. 3 is -a plan view of the grid-cathode assembly shown in Fig. 2,

Fig. 4 is a plan view of a j gor adapter head hold'ng the grid-cathode assembly in placeas it would appear during spacing and welding o"erations.

Fig. '5 is an end view of the adapterhead looking int the assembly receiving end,

Fig. 6 is a section on the line 6-6 of Fig. 5.

Fig. 7 is a plan view of the adapter head receiving channel, a screw driving mechanism for advancing the adapter head toward a hollow cylindrical st p, and welder electrode actuating means, a portion of the adapter head being shown in the channel.

F g. 8 is a side view of Fig. 7.

Fig. 9 is an end view of Fig. 7 takenalong the line 99.

Fig. 10 is a front view of the space checking air senser device showing a photo-diode in secti n, that operaes in conjunction with the ind'cator of the device totrigger welding, motor stop and reverie circuits,

Fig. 11 is a fragmental side view of the mechanism shown in Fig. 10 and also showing photo-diode illuminating means,

Pg. 12 is a plan view of a three speed electrically controlled transmission drive unit for advancing the lead screw mechanism shown in Figs. 7 and 8,

Fig. 13 is a side view of aportion of Fig. 12,

Fig. 14 shows a block diagram of the various circuits use-d to carry out the objects of the invention, and

Fig. 15 is a schematic diagram of the circuits shown in block form in Fig. 14.

The apparatus by which the objectives set forth; above are carried out consists in its most elementalform of a grid-cathode assembly holding device, means for advancing at a high forward speed the holding device, with respect to a stop in order to eifect a preliminary spacing ofthe assembly, means for subsequently advancing the holdingdevice at a slower speed to effect a slower rate of change of the assembly spacing, sensing means 'affixed to one end thereof.

:cap carries an electron emissive coating 14. The cathode to stop the change of spacing at a proper time, welding means to unite the grid and cathode at the proper spacing as determined by the sensing means, and means to return the mechanism to the starting point.

Description of the device Now referring to the drawings with greater particularity, Fig. 1 shows a grid-cathode assembly. The grid member of this assembly is to be accurately spaced from, and welded in spaced relationship to, the cathode 11. The cathode comprises a metallic sleeve 12, preferably of nickel, and having a cylindrical nickel cap 13 The top flat surface of the is secured within a central opening of a circular ceramic member 15 having a recessed annular portion 16, and a plurality of apertures 17 through said annular portion. The member 15 is mounted within a spider retainer comprising an annulus 18 having resilient fingers 20 projecting from the annulus. Also projecting from the annulus is a pair of diametrically opposed securing fingers 22 which are to be welded to the wall of the grid cup 10. The grid comprises a metal cup having cylindrical walls 24 and a centrally perforated bottom 25, the exterior of the cup having wings 26 or the equivalent for later securement'to other parts of the electron gun structure. The spider retainer, which holds the ceramic mounted cathode, is slidably, frictionally engaged by the inner surface of the cylindrical metal wall 24 of grid cup 10 as clearly shown in Fig. 1. The grid-cathode assembly, with the cathode thus in adjustable relationship within the grid cup, is then ready to be inserted into a holding device and to be operated on by a sensing, spacing and welding mechanism.

During the spacing and welding operations the gridcathode assembly is held by the specially designed adapter head holding mechanism shown in Figs. 4 to 6. The outer member of the adapter head 27, is made of a metalblock 28, which is preferably cylindrical in shape to ride in a semi-cylindrical channel guideway, as will later appear. The block 28 is closed at one end 29, the other end being threaded at 30 to receive a cylindrical flanged end member 31. A washer 32 is seated between adjoining faces of the block 28 and member 31. The member 31 is provided with an in-turned lip 33, having a recess therebeneath. Seated in the recess is an 0 ring 34, preferably of neoprene, and to effect an air tight seal around the curved edge of the grid cup 10.

At one end of the flanged member 31 and further outward from the O ring is a collar 35, having a number of bayonet slots 36, of which there are at least two and preferably three. These slots receive or grasp the wings 26 which are disposed on the periphery of the grid cup 10. The slots have tapered walls 37 which assist in making an air tight seal between the neoprene 0 ring and the grid cylinder by rotating the grid cylinder whose wings 26 rest on the tapered walls 37, to thus press the curved edge of the grid cup against the 0 ring.

Disposed coaxially within the cylindrical piece 28 and in axially slidable relation therewith is a compression cylinder 38, Fig. 6. One end of this cylinder serves as a seat for the O ring 34. The other end rests against the surface of a cam which is aflixed to a shaft 41, the latter being held by member 28. The axis of this shaft is also transverse to the cylinders 28 and 38and suitable means is provided at one end of the shaft to receive a wrench or other device in order to turn cam 40 and thereby shift cylinder 38 with respect to cylinder 28. This action will compress the O ring 34 between cylinders 38 and lip 33 thus compressing it against the outside of grid cup 10 to efliect. an air tight seal around its periphery.

The central part of cylinder 38 is provided with a bore 42 which communicates with the end of the cylinder in contact with the O ring and with a port 44, the latter being threaded to receive an air hose connection. At diametrically opposed points on the periphery of the outer cylinder 23 are guide pins 46 to maintain it in nonrotatable position when resting in the channel to be described.

Referring now to Figs. 7, 8 and 9, means are shown for reducing the grid-cathode spacing of the grid-cathode assembly and welding the assembly when said spacing is reduced to the desired dimension as indicated by appropriate sensing means. The numeral 60 indicates a base plate upon which is mounted a guideway channel 61 having a way 62, preferably half-cylindrical in crosssection, that will allow the adapter head to be conveniently received and advanced axially thereon between an advancing push-rod shaft 63 and a positioner or stop member 64 at one end of the guideway channel.

A hollow cylindrical shaft lead screw 66 is threaded into a stationary threaded support portion 68 of the guideway channel 61 and an unthreaded portion finds bearing in a support 69. The thread must have a large number of turns per inch, being desirable, so that the axial movement of the screw shaft will be slow. This is necessary since the grid-cathode spacing is of the order of several thousandths of an inch; the inertia of the various rotating driving members could easily overshoot the correct spacing if a much smaller number of threads per inch were used.

The push-rod or shaft 63 is disposed concentrically within the lead screw shaft 66 and extends beyond both ends thereof. One end of the rod 63 is adapted to engage the end 29 of the adapter head holding means 27 and is a part of the moving means which urges the adapter head along the guideway channel 61. The other end of the rod 63 is fitted with a knurled knob 70 so as to be easily grasped. The push rod is axially movable along the length of a slot 72 in the lead screw shaft wall and can move only the length of the slot due to a protruding pin 74 on the rod. An offset bayonet type slot portion 76 is also provided in order to hold the push rod in its most forward position at which point the forward end of the push rod will either be in contact with or close to the end wall 29 of the adapter head 27 as it rests in channel way 62. The sliding feature of the push rod is manual and its purpose is to provide for quick axial travel of the push rod to thereby enable immediate removal of the adapter head from the way 62 without waiting for. the relatively slow axial travel of the lead screw assembly. A similar time saving is realized between insertion of the adapter head and the subsequent operations.

At an intermediate point on the lead screw 66 there is aflixed a pulley 78. A roller 80 rides on one side of the pulley and is attached to one end of a crank arm 82. The arm 82 is fixed on an oscillatable'shaft 84 pivoted in a bearing 86, the shaft having a second crank arm 88. A simple lever arrangement also might be employed instead of the foregoing mechanism. Attached to the free end of arm 88 is a tension spring 90, which holds the roller 80 against one side of pulley 78. Backward axial travel of the lead screw and pulley forces arm 88 to actuate a limit switch 89 and forward travel allows the spring 90 to pull arm 88 against the arm of another limit switch 91 to thereby actuate the same.

At one end of the channel member 61, and fixed to the base plate 60, is a rectangular block 93. in this block and extending therethrough is a'cylindrical metal tube 92. The end 64 of this tube is of smaller diameter than the main portion and is adapted to engage the annular recess 16 of the cathode ceramic 15 to thus act as a stop member. Said stop member cooperates with the advance of lead screw 66 to reduce the gridcathode spacing to the desired value. As the spacing between grid and cathode is decreased, the grid cup slips ever t e l g diame er portion of tube 92.

Held with- The'block 93 has fixed to one side thereof two rectangular blocks 94, by means of bolts 95. These blocks are recessed to receive the horizontally disposed and oppositely actuated sliding members 97, which are electrically conductive. These members are confined to the blocks 94, which are electrically non-conductive, by means of straps 98, and screws 99, allowing movement only along the longitudinal axis of said members. The outer ends of the sliding members 97 are positively connected toair cylinders 100 by means of connecting

members

101, 102 and 103. The member 102 is of insulat- 'ingmaterial to isolate the Welding current from traveling into undesired paths. Affixed to the inner ends of sliding members 97 are rollers 104 which serve as welding contacts.

Cable means 105 'connect'the sliding members 97 to terminals 106 on a terminal block107 mounted on the base plate 60.

Another cable 108 is connected from a central terminal 109 on terminal block 107 to one end of tube 92. Through the tube at this end is also provided a pin 110 to prevent axial movement of the tube when it serves as a stop for the cathode portion of the grid-cathode assembly. The pin 110 also extends through member 111 which is secured to block 93 by machine bolts 112. The tube 92 is of course insulated in suitable fashions, such as by means of an insulating sleeve, not shown, or by making the block 93 of an insulating material, so that the welding current will be routed through the proper conductors. The terminals on terminal block 107 are connected to a suitable welding power transformer 280, Fig. 15.

At the proper time for welding, air pressure will be applied to cylinders 100 from a suitable air line, not shown, as will later appear. This will force rollers 104 against the wall 24 of the grid cup it; which is to be Welded to the securing fingers 22. During welding, the current will travel from the secondary of the welding transformer 280, Fig. 15, to terminal 166 on the terminal block 197, through cables 165, through sliding members 97, through rollers 104 through the wall 24 of the grid cup and the securing fingers 22, thereby welding said well and said fingers together, through tube 92, through cable 108 to terminal 1G9 and thence returning to the secondary of the welding transformer.

At some later time when the air to cylinders 100 is cut off, the springs 114, compressed against stops 115 and members 102, will retract the sliding members 97 and rollers 104 away from the Welded grid-cathode assembly.

The air cylinders 1% are connected to any air line of suitable pressure, for example 30 pounds per square inch, through a weld air solenoid 116, Fig. 15. This solenoid is actuated by the electrical control circuit to feed air pressure to the air cylinders at the proper time before welding.

The sensing device by means of which the proper gridcathcde spacing is determined is shown in Figs. 10 and 11.

basic mechanism consists of a standard air comparator. This air senser is well known in the tube manufacturing industry for reading grid-cathode spacing of cathode ray tube assemblies by means of changes in air pressure. The unit is, however, modified as shown in Figs. '10 and 11 to adapt itto carry out the purposes of this invention. The standard air comparator comprises a casing 12%} carrying a face plate 121 with a scale 122 and a movable indicating pointer 124; to assist in carrying forth the objects of the invention, a light 'ofi'the pointer so that the beam from the light source 126 willbe reflected onto the photo-diode 130 mounted in a housing 131 on a ring 132 on the peripheryof the source, mirror and photo-diode are added. The light casing 120. The peripheral location of photo-diode will depend upon the desired grid-cathode spacing. Accordingly, ring 132 may be made rotationally'adjustable about the casing by means of a tongue 134 and slot 136 arrangement to allow location of the photo diode at different points with respect to the dial. A set screw 133 is provided to fix the location ofthephotodiode at any point. Thus the photo-diode may be rendered conductive by impingement of light thereon at any desired reading of the pointer. In this way the mechanism may be employed to weld different electron gun type assemblies at their own particular grid-cathode spacings.

In order for the air senser to sense the decrease-in spacing between the cathode coating 14 and the grid cup 16, an air line is provided between the air senser and the adapter head. The air senser operates-on a pressure of about 5 pounds per square inch but it may be connected to a standard air line of higher pressure, through an appropriate pressure reduction valve, not shown. The air flow through the system will then be as follows: first through the air senser, secondly through a flexible hose connection and into the bore 42 of the adapter head, thirdly passing through the aperture in the bottom 25 of the grid cup 10, through the spacing between the cathode coating and the grid, and finally through the three holes 17 in the cathode ceramic 15, into the atmosphere. The neoprene O ring 34 in the adapter head prevents any leakage of air past the outside of the grid cup and thus insures that the entire air flow passes through the grid-cathode spacing. As this spacing is decreased, the impedance to the flow of air through the system will be increased and this increase will be sensed by the well known air senser mechanism and will actuate the pointer 124 thereon. At some predetermined position of the pointer, the light beam from the light source 126 will be reflected into the photo-diode 130 by means of the mirror 128, to actuate various circuits as will later appear. The scale 122 of the senser may be calibrated in thousandths of an inch for direct reading of grid-cathode spacing.

In order to drive the lead screw shaft 66 at the proper speed in the forward and reversedirections, a special three speed transmission drive assembly, see Figs. 12 and 13, is employed. The assembly is enclosed in a housing 200. The input shaft 202 extends from one side of the housing through the opposite side and is fitted with a pulley 204 for belt connection to another pulley, not shown, on a suitable driving means, as for example, an electric motor. The output shaft 206 is disposed at right angles to the input shaft and on a different level. It extends from one end of the housing, through the opposite end and is fitted with pulley 208. This pulley has teeth as does pulley 78 on the lead screw for positive driving action by means of a toothed belt between them.

Associated with the output shaft 206 are standard magnetic

clutch drive mechanisms

210, 232 and 214 and a magnetic brake 216. The

clutches

210 and 212 when actuated through energization of appropriate circuits allow a gear arrangement to turn the lead screw shaft 66 at fast forward and slow forward speeds, respectively, of 48 and 16 revolutionsper minute. The clutch 214 allows for a reverse speed of 64 revolutions per minute. The gear trains which produce these speeds are: (1) fast f-orwardinput shaft 202 via a spur gear 218 which drives a spur gear 220 fixed on a shaft 222 on which a worm'224 is also fixed, to drive a clutch body 226; (2) slow forward-input shaft 202 via a spur gear 230 which drives a spur gear 232 fixed on a shaft 234 on which a worm gear .236 is also fixed, to drivea clutch body 238; (3) reverseinput shaft 202 via a worm 242 which drives a clutch body 244. The

clutch bodies

226, 238 and 244 continuously rotate in close proximity to their

mating elements

228, 240, and 246.

' discharge type.

respectively, which latter elements are fixed to output shaft 206. Various circuits actuate the various standard clutches at different times to cause the appropriate clutch body to drive its mating portion. The circuit arrangement is so designed that if one clutch be actuated, no other can be actuated unless and until that one clutch has been deenergized, thus avoiding damage to the assembly unit. The magnetic brake arresting means likewise cannot be actuated if any other clutch beenergized.

The circuit for automatically carrying out the steps of the invention is shown in block form in Fig. 14. The photo-diode 130 and its cooperating light source 126 is shown in conventional circuit arrangement in Fig. 15. The photo-diode 130 is connected by a plug 249 and socket 251 and a cable to the input circuit of photo-diode amplifier 252; by this means the lamp 126 is also con nected to a low voltage power transformer 253. A sensitive relay 274 is connected in the output circuit of tube 255 and controls the action of relay 275.

A welding circuit in block 258, is of the condenser The welder, located on the base plate 60, receives its power from the control circuit by means of a plug 259, socket 261 and cable arrangement, Fig. 15. When relay 278, is actuated, the circuit comprising the primary of the welding transformer 280 in series with power storage condenser 282 and heat control resistor 284 is complete, thus discharging condenser 282.

The various magnetic clutches on the transmission drive assembly are connected by a plug 305, socket 307 and cable arrangement, to the control circuit of Fig. 15. This means also affords connection to limit

switches

89 and 2;, push button start switch 306 and the weld air solenoid A timing circuit 256 includes a relay 286, capacitor 288, resistor 290 and a rectifier 292. This timer assists in actuating the welder at the proper time.

To operate the various circuits a power supply having a full wave rectifier 294 and a half Wave rectifier 296 is employed to supply direct current. The circuit includes a conventional high voltage transformer 297 and filter circuits.

The operation of the system is made possible by means of a magnetically actuated stepping switch 298 having seven positions and six circuits or banks, four shorting and two non-shorting. Counting from the left, the first three banks are shorting, four and five are non-shorting, and six is shorting. The various circuits actuated by the advancement of the switch contacts will be described under the description of operation to follow. A relay coil 300 is provided as a part of the switch, with an interrupting contact 301, to actuate the switch to subsequent positions. A push-button 302 is provided, however, to manually advance the step switch when desired. Main power to the entire circuit is controlled by a single pole single throw switch 304.

Operation of the device Operation of the apparatus is as follows: A ceramic mounted cathode, held within the spider 18, is inserted a short distance into grid cup 10, see Fig. 1. This gridcathode assembly is next inserted into the recess of the adapter head 27 against the neoprene O ring 34, see Figs. 4, 5 and 6. Turning the assembly several degrees will engage the wings 26 on the grid cup with the tapered walls 37 of slots 36 on the adapter head, thus holding the assembly firmly in position. Turning cam 40 via a suitable wrench applied to the end of the shaft 41 then effects an air tight seal between the 0 ring and the outside of grid cup 10.

The assembly must be inserted in such a position that the securing fingers 22 on the spider retainer 18 are in line with the guide pins 46 on the adapter head, so that said fingers will be under the weld rollers 104 for the welding operation. The adapter head is next laid in the semicylindrical adapter head channel way 62, see Figs.

' diode, thus activating the latter.

7, 8 and 9, so that the annular recess 16 of cathode ceramic 15 either engages or is in close proximity to stop 64 at one end of the channel way. The push rod 63 iS then advanced and turned manually until its pin 74 engages the offset slot 76 in lead screw 66. The push rod is thus fixed against axial movement with respect to the lead screw. 7

The switch 304, Fig. 15, having been previously thrown, the circuits are energized for automatic operation. It will be assumed that an assembly has just been spaced and welded and the step switch will therefore be in position #1, the brake clutch 216 thus being energized. Also, the limit switch 89 will be in closed position and limit switch 91 will be open, by reason of the reverse travel of lead screw shaft 66. Details of the operation ofthe device are best understood with reference to the various step switch positions.

Step switch posiliOn #1 .The series of automatic operations is now started by operating the push button switch 3%. This energizes the step switch coil 300 which advances the step switch to position #2.

Step switch position #2.In this position, bank #1 o the step switch feeds power to the motor which drives the three speed transmission unit; it remains energized for all positions of the step switch from position 2 to position 6 inclusive. Bank #4 energizes the magnetic clutch 210 which allows the motor to drive the lead screw shaft at the fast forward speed of 48 R. P. M. This will advance the grid-cathode assembly in the adapter head traveling along the guideway 62, toward stop 64. After the cathode ceramic abuts said stop, the grid-cathode spacing will uniformly decrease.

Bank #5 establishes a circuit path to the step switch coil 300 through limit switch 91, Figs. 7 and 8, so that when the lead screw shaft 66 actuates said limit switch by means of the pulley and oscillatable shaft arrangement 78, 8t), 82, 84 and 88, said coil will advance the step switch to position #3.

Step switch position #3.Bank #2 energizes the primary of transformer 253 which supplies current to photodiode lamp 126. It also connects power to the weld air solenoid 116 which supplies air pressure to air cylinders 109 thus forcing weld rollers 104 into contact with the grid cup, or with tube 92 if the cup wall 24 has not yet advanced far enough to be between the rollers and the tube. These conditions are maintained for

positions

3, 4 and 5 of the step switch. Bank 3 connects B-lpower to the output circuit of the photo-diode amplifier tube 255; this condition also remains for

positions

3, 4 and 5 of the step switch. Bank 4 connects power to the low forward magnetic clutch 212 on the three speed transmission, through the relay 2'75, allowing the lead screw shaft 66 to now be driven at the slow forward speed of 16 R. P. M. The high speed forward clutch is deenergized when the step switch leaves #2 position, thus preventing damage to the transmission assembly. Bank #5 establishes an open circuit to the step switch coil 300, through the open contacts on relay 275; the step switch will not be advanced to the next position until relay 275 is actuated.

At this point the lead screw 66 continues to be advanced' at the slow forward rate of 16 R. P. M., continuously decreasing the grid-cathode spacing. The air flowing through the grid aperture will therefore be increasingly impeded as the cathode moves closer to the aperture. This will alter the pressure and rate of air flow through the air senser. As the grid-cathode spacing approaches the desired value, which is previously determined by t-he setting of photo-diode on the periphery of the air senser, see Figs. 10 and 11, the pointer 124 will begin to move. When the pointer reads the proper spacing, the light from lamp 126 will, as previously described, be reflected from the mirror 128 into the photo- This will change the grid bias on tube 255, increasing its current flow and actuating relay 274 and in turn closing relay 275. The

closing of'relay 275 accomplishes the following: (a) .relay contactor #1 applies B+ to the welding circuit, thus chargingthe welding discharge condenser 282, (b) relay contactor #2 disconnects the low forward speed magnetic cuitis provided to delay the step switch a short time before the 'step switch is advanced to the weld firing position. Bank #5 connects power'to the timing circuit and bank #4 establishes a circuit, through open relay 286 to'the stepswitch coil 300. The condenser 288 of thetiming' circuit comprising relay 286, condenser 288, res'istor'290and rectifier 292 acts as a short circuit when 'power is first applied to the-circuit by bank #5, and relay 286, therefore, which is in parallel with the condenser 288 cannot close. In a short time, however, the condenser charges, there is now a voltage drop across it and the relay closes. Thisapplies the voltage from bank #4 to the step switch coil'300 to advance it to position #5.

The-short delay achieved by means of a condenser of the order of 300-400 microfarads is all that is needed to dela'y theswitch advance the desired time.

Step switch: position #5.In this position, bank #6 applies -A.' C.*voltage to relay 278, closing it and thereby discharging the weld'storage condenser through the gridcathode assembly. The fingers 22 of the retainer ring 18 are now firmly welded to the wall 24 of grid cup at the proper gridcathode spacing. Bank #5 energizes the step actuating coil 300, advancing the step switch to position"#6.

Step "switch position #6.In thisposition the photodiode light 126 and the weld air solenoid 116 are cut out by bank #2. The rollers 104 are therefore retracted from grid-cathode assembly. Bank #3 deenergizes the photo-diode amplifier tube 255. The brake is now off since thezrelay275, now open, 'deenergizes the magnetic brake clutch 216.

' Bank #4 energizes the reverse magnetic clutch 214 and the lead screw shaft is now driven in reverse speed at 64 'R. P..M.

Bank #5 establishes a circuit through open limit switch 89 so that when .the .lead screw shaft 66 hastraveled far enough in the reverse direction to close it, see Fig. 8, a voltage will be again applied to step switch coil 300 to advance the step switch to position #7. In its reverse travel, the lead screw 66 first opens limit switch .91 and then, .a shortdistance further, closes limit switch 89, thus advancing .the step switch to position #7.

.Position'#7 merelyreturns thestep switch to position #1 ready to repeat the sequence of operations.

The push-rod 63, Figs. 7 and 8, may now be retracted, the completed grid-cathode assembly removed from the adapter head, and a new assembly loaded therein for the next operation.

Thus is disclosed a novel apparatus and method for manufacturing and space checking grid-cathode assemblies which eliminates a great number of disadvantages of the prior art. While certain aspects of the invention have been described with particularity, it is apparent that various changes and modifications may be made without departing from the spirit of the invention or the scope of the appended claims.

Having thus described the invention, what is claimed as new is:

1. Apparatus for automatically positioning two parts of an electron gun with respect to each other comprising means for holding-said parts, a positioner engaged by one of 'said parts to restrain it against motion, meansfor engaging the second part and moving it with respect to the first part, means for sensing the relative displacement between said parts, and means under control of the sensing means for arresting the motion of said moving means.

2. Apparatus for automatically positioning two parts of an electron gun with respect to each other comprising means for holding one of said parts, means for moving the second part with respect to the first part at a relatively fast rate of speed, means under control of said moving means for changing the rate of speed from said fast rate to a slower rate, sensing means for sensing the relative displacement of said parts, and means under control of the sensing means for disabling the forward motion of said moving means.

3. Apparatus for automatically positioning'two parts of an electron gun with respect to each other comprising means for holding one of said parts, means for moving the second part with respect to the first part at a relatively fast rate of speed, means under control of said moving means for changing the rate of speed from said fast rate to a slower rate, sensing means for sensing the relative displacement of said parts, means under control of the sensing means for disabling the forward motion of said moving means, and means also under control of the sensing means for etfecting a rapid reverse movement of the moving means.

4-. Apparatus for automatically positioning two parts of an electron gun with respect to each other comprising means for holding one of said parts, means for moving the second part with respect to the first part at a relatively fast rate of speed, means under control of said moving means for changing the rate of speed from said fast rate to a slower rate, sensing means for sensing the relative displacement of said parts, means under control of the sensing means for disabling the forward motion of said moving means, and means for manually moving that portion of the moving means which is engageable with the holding means.

5. Apparatus for automatically positioning two parts of an electron gun with respect to each other comprising means for holding one of said parts, means for moving 'the second part with respect to the first part at a relatively fast rate of speed, means under control of said moving meansrfor changing therate of speed from said fast rate to a slower rate, sensing means for sensing the relative displacement of said parts, means under control of the sensing means for disabling the forward motion of said moving means, and means for manually advancing and retracting at least a portion of the moving means respectively toward and away from the holding means.

6. Apparatus for automatically positioning two parts of an electron gun with respect to each other comprising means for holding one of said parts, means for moving the second part with respect to the first part at a relatively fast rate of speed, means under control of said moving means forchanging the rate of speed from said fast rate toa slower rate, sensing means for sensing the relative displacement of said parts, means under control of the sensing means for disabling the forward motion of said moving means, and means also under control of said sensing means for arresting the forward motion of said moving means.

7. Apparatus for automatically positioning and welding two parts of an electron gun with respect to each other comprising means for holding and advancing both of said parts, a positioner engaged by one of said parts to restrain it against further motion, means for moving the holding means for continuing to advance the second part thereby varying the spacing between said parts, means for sensing said variation in spacing, and means under control of said sensing means when said spacing attains a predetermined value for arresting the relative motion of the parts and for welding said parts to each other.

8. Apparatus for automatically positioning and welding two parts of an electron gun withrespect to each other comprising meansforholding and advancing both of said parts, a positioner-engaged by one of saidparts to restrain it against further motion, means for moving the holding means for. continuing to advance the second part thereby varying the spacing between said parts, means for sensing the relative. displacement between said parts, means under control of the sensing means for arresting the motion of said moving means, and a movable welder electrode also under-control of said sensing means mounted to move toward and away from said parts to thereby weld said parts together.

9. Apparatus for automatically positioningand welding two parts of an electron gun with respect to each other comprising, a guideway, means for holding said parts in said guideway and for advancing both of said parts therealong, a positioner at one end of said guideway and engageable by one of saidparts to restrain it against motion, means for moving the second part with respect to the first part to vary the spacing between said parts, means for sensing said variation in spacing between said parts, and means under control of said sensing means when said spacing reaches a predetermined value for arresting the relative motion of said parts, for welding said parts to each other, and for reversing the movement of said moving means.

10. Apparatus for automatically positioning and welding two parts of an electron gun with respect to each other comprising a guideway, means for holding said parts in said guideway and for advancing both of said parts therealong, means for moving said holding means along said guideway, a positioning means at one end of said guideway engageable by one of said parts to restrain it against motion to thereby effect a change in spacing between said engageable part and said other part, means for changing the rate of advance of said holding means and one of said parts, means for sensing the change of spacing between said parts, and means under control of said sensing means for disabling and arresting the motion of said moving means, for welding said parts to one another, and also for effecting a direction of movement of said moving means away from said positioning means.

11. Apparatus for automatically positioning and welding two parts of an electron gun with respect to each other comprising means for holding and advancing both of said parts, a positioner engaged by one of said parts to restrain it against further motion, means for moving the holding means for continuing to advance the second part thereby varying the spacing between said parts, means for sensing said variation in spacing, and means under control of said sensing means when said spacing attains a predetermined value for disabling and for arresting the forward motion of said moving means, for welding said parts to one another, and also for causing said moving means to travel in a direction opposite to said forward motion.

12. Apparatus for automatically positioning two parts of an electron gun with respect to each other comprising means for holding said parts, a positioner engaged by one of said parts to restrain it against motion-means for moving the second part with respect to the first'part, said moving means including a first axially movable hollow shaft having a first slot in an axial directionin'the wall of said shaft and a second slot portion at one end of said first slot portion at an angle thereto and communicating therewith, a second shaft disposed coaxially within said first shaft and extending beyond both ends of said first shaft and movable therein, said secondjshaft having a pin extending above the surface thereof and ada ated to ride in said first and second slots of said first shaft, and means to drive said first and second shafts in an axial direction.

13. Apparatus for automatically positioning twog parts of an electron gun with respect to each other and one of which parts is perforated and for determining the spacing therebetween comprising a positioner engaged by one of said parts to restrain it against motion, means for moving the second part with respect to the first part, a holding means for said parts including a first member having an inturned flange portion, and grasping means exterior of said flange portion for holdinglsaid parts,

.with the perforated part within the flange portion, a second member within the first member. and in telescopic relation therewith, a compressible ring between an end of said second member and said flange, means for longitudinally moving said second member with respect to said first member to compress said ring and form an air tight seal around said perforated part, a passageway extending longitudinally through the second member and terminating in an air outlet at the said end of said second member, said passageway extending to an air inlet port near the other end of said second member, air pressure .sensing means, and an air line between said sensing means and said air inlet port.

14. Apparatus for automaticallypositioning two parts of an electron gun withrespect to each other comprising holding means for said parts, a positioner engaged by one of said parts to restrain it against motion, means for moving the second part with respect to the first part, including a rotatable shaft connected to drivesaid holding means and having a helical screw surface adapted to engage a mating screw surface in a fixed member'to thereby impart a component of axial travel to the shaft,

a pulley secured to said shaft, means to drive said "pulley, a lever having a roller mounted on one arm thereof and riding on' a side of said pulley, means acting on said lever to hold said roller in contact with said pulley, and a switch in the path of movement of the other arm of said lever to be actuated thereby to control the movement of the pulley driving means.

References Cited in the file of this patent UNITED STATES PATENTS I 2,266,566 Poole Dec 16,1941 2,380,357 Ziebolz Iuly'lO, 1945 2,581,997 Beggs "Jan; 8, 1952 2,585,533 Bryant et al Feb. '12, 1952 2,611,676 Pohle Sept. 23, 1952