US1555249A - Testing apparatus - Google Patents

Description

G. W. PICKARD TESTING APPARATUfi Filed 4111-11 25, mo

Sept. 29, 1925. 1,555,249

Fig.3.

Patented Sept. 29, 1925.

UNITED STATES V 1,555,249 PATENT OFFICE. I

GRERNLEAF WHITTIER PICKARD, OF NEWTON, MASSACHUSETTS, ASSIGNOR TO WIRELESS SPECIALTY APPARATUS COMPANY, OF BOSTON, MASSACHUSETTS, A

CORPORATION OF NEW YORK.

.rnsrme APPARATUS.

I Application filed April 23, 1920. Serial No. 376,132.

To all whom it may concern:

Be it known that I, GREENLEAF W. PICK- ARD, a citizen of the United States, residing at Newton, in the county of Middlesex and State of Massachusetts, have invented cer tain Improvements in Testing Apparatus, of which the following description, in connection with the accompanying drawings, is a specification, like'reference characters on the drawings indicating like parts in the several figures.

This invention relates to distinguishing bad from good sheets of mica or other dielectric or insulating materials. The invention will be herein disclosed as embodied in apparatus designed particularly for testing dielectric elements to be used in electrical condensers. These elements are subjected to the distinguishing operation before being assembled in the condenser so that the. de fective elements can be eliminated. It can thus be definitely determined before the assembling operation is begun that only perfoot dielectric elements shall go into the con-- struction of'the'condensenand the expense and annoyance which otherwise would be caused by the presence of defective elements thus is eliminated.

The present invention has for its chief object to devise an apparatus with which such distinguishing method can be performed veryaccurately and'rapidlyand which will require a minimum of skill and care on the part of the operator. It is a further important object of this invention to devise an apparatus of this character which, in addition to performing and testing operation, will also automatically separate the dielectric electrically distinguishing operation, also will separate the defective dielectric sheets or films from the good ones by means controlled by-the presence of defects inthe bad sheets. n

I The nature of the invention will -be'readily understood from the following. description and the novel features will be particularly pointed out in the appended claims.

Referring now to the accompanying drawings, v

Figure 1 is a diagrammatic .view of an apparatus embodying the present inv ntlon;

the apparatus and Fig. 3 is a plan view of a sheet of mica to be tested.

Preliminary to a detailed description of the apparatus it should be stated that the entire surface of a mica sheet, or other dielectric element of a condenser, is not sub jected to a dielectric strain while in use. That is, the conducting elements are smaller than the'dielectric elements so that a margin is left around the entire edge of each dielectric element which is substantially free from the dielectric strain, this margin serving primarily to prevent the current from jumping around the edge of the mica sheet between the two adjacent conducting elements separated by said sheet.

In Fig. 3 M indicatesamica sheet and m the active area of the sheet; that is, the area subjected'to the dielectric strain. It is this area m which must be tested but it is not necessary to test the dielectric strength of the inactive margin, and in the present machine it is contemplated that this margin will not be tested.

The apparatus shown comprises two metal rolls 2 and 3, respectively, mounted one above the other, and rotatin on metal shafts which are supported in ame pieces 44 made of insulatin material. Thus the rolls are electrically insulated from each other at all places except at their peripheries. The rolls may be driven from any, suitable source of motive power and they are connected together by gears 5 and 6 made of insulating material such as bakelite, fibre, or the like. They are rotated in the directions indicated by the arrows in Fig. 1 and the mica sheets are fed between the rolls one at a time.

Each roll is of a length equal to one dimension of the area m so that when the sheets are run through them the opposite margins of each sheet project beyond the .ends of the rolls so that there will not be such a discharge from one roll to the other over the edges of the sheet tested as to prevent the proper testing of the sheet.

-These two rolls are connected in a high potential circuit comprising the secondary 7 of an induction coil or transformer, one terminal of this secondary being connected by a conductor 8 to the roll 2 While the other terminal is connected by a conductor '9 (hrough'the primary 10 of another induction coil to the lower roll 3. .For convenience in making these-connections, the ends of the shafts on which the rolls are mounted are extended through one of'the supports 4,

as indicated at the left of Fig. 2, and spring switches designated at 17 and 18, respective-- l The switch 17 comprises a ivotedconcfilcting arm 19 carring a r0120 at its upper end and norma ly held by a spring 21 against the end ofa stop screw 22 and a spring mounted contact 17 with which arm 19 engages to close thecircuit: The other switch 18 is like the switch 17 and includes a pivoted conducting .arm 23 carrying a roll 24 at its upper end and normally held open by a spring 21. This prima circuit, therefore, is normally open. It Wlll be seen from an inspection of Fig. 2 that the rolls 20 and 24 are mounted closely adjacent to the opposite ends of the rolls 2 and 3 and that the upper edges of the rolls 20 and 24 lie just above the level of the line of con tact of the rolls 2 and 3. The distance from the line of contact of the rolls 2 and 3 with the mica sheet to the top of each roll 20 and 24 is equal to the width of the inactive margin of the mica sheets shown at m, Fig. 3. Normally both the primary and secon ary circuits are inactive since the switches 17 and 18 are open. When, however, a sheet of mica is fed between the rolls 2 and 3, the forward or leading edge of the mica sheet first engages the roll 20 and depresses it, thus closing the switch 17. When this edge of the sheet emerges from between the rolls a distance equal to the width of the margin m, Fig. 3, the roll 24- will then be moved far enough by its engagement WlthzSflld sheet to close the switch 18. At this instant, therefore, the primary circuit is closed and the interrupted current flowing therethroughcreates a high potential in the secondary circuit which potential is impressed across the sheet of mica between the rolls. That is, the rolls form, in effect, terminals for the high potential circuit. Asthe sheet is advanced by the rolls, all parts of its active area m are subjected to the potential created in the secondary circuit. But as soon as the rear or trailing edge of the sheet lgaves the roll 20, the spring 21 opens the switch 17 and thus interrupts the action of the primary, and consequently, also, the secondary circuit. The switch 18 is opened an instant later by its spring when the mica moves out of contact with it. It will be understood, of course, that the springs that operate the arms'19 and 23 are very light.

If the mica has no fault or flaw which will permit the applied potential to drive a current through the flaw, no current will flow in the secondary circuit. If, however, the sheet has a hole in it,"or for any other reason breaks down at a fault or flaw, then a current will flow throughthe" secondary circuit. This current energizes the primary coil 10 which induces a current in the secondary 27 of'a low potential circuit that also includes a relay coil 28. The energizing of this coil lifts an armature 29 thus closing a switch 30 and causin a flow of current from a battery 31 throug a's'olenoid 32.. This solenoid attracts an armature 33 on the depending end of a plate 34 which is vpivoted at 35 and normally rests against astop screw 36. Y

It will be seen that the plate 34 forms normally a continuation of an inclined apron or chute 37dow-n which. the mica sheets slide as they are ejected from between the rolls 2 and 3. If the plate 34 is in itsnormal position, these mica sheets will slide into the forward part of a receptacle 38, but if the plate 34 is tipped into its dotted line position as shown in Fig. 1', the mica sheet then will drop into the reaward part of this. receptacle. A' partition, not shown, separates the front and rear portions of the receptacle. It will thus be seen that the plate 34 is operated automatically to'separate the perfect from the imperfect sheets of mica;

the perfect sheets sliding into the forward part of the receptacle 38 and the defective sheets into the rearward part. That is, the plate 34 acts as an automatic switch or deflector to direct the perfect and imperfect sheet-s into different paths.

In case a sheet of mica under test contains a small hole or other flaw near its forward edge while the remainder of the sheet is perfect, there is danger that the switch or deflector plate 34 after being swung into its dotted line position will drop back again before the imperfect sheet is delivered due to the fact that the flow of current through the secondary circuit will be cut off at a relatively early point'in the testing of that sheet. In such an event the defective sheet -'of mica would be delivered to the forward part of the receptacle 38 with the perfect sheets. In order to prevent this action the core of coil 28 that operates the armature 29 is provided with a locking winding 40 which is in circuit with a switch 41tl1at is closed when the relay 28 is energized and is also in circuit with a battery 42 and another switch comprising the pivoted arm 19 and the stop screw 22. The latter switch is in arallel with a switch 43 in circuit with windmg 40 and normally held open by a spring 44 but arranged to be closed by a solenoid 45 in series with the switches 17 and 18 and with the battery 14.

This parallel arrangement of switches ensures that after the switch arm 29 has once been lifted it will be held in its raised position due to the action of the locking winding 40 as long as either switch 43 or switch 19, 22, is closed, the two Switches operating alternately. That is, if the coil 28 has been because the parts 19 and 22 will, by that time, have come into engagement and will still keep this circuitclosed. When, however, a new mica film is fed into the machine the depression of the roll 20 will break the contact between the parts 19 and 22 and the locking circuitthen will be opened, allowing the armature 29 to drop into its lower position, thus opening the switches 30 and 41 and releasingthe deflector plate 34 which will fall back against its stop 36.

To prevent the opening of the locking circuit upon the breaking of the circuit of coil 45 and the opening of. switch 43, a leaf spring 46 is'attached at oneend to member 19, and is free at its. opposite end to yieldingly engage and disengage contact 22.

When roll 20 is depressed, member 19 moves downwardly and engages contact 17 a and slightly depresses it by reason of its spring mounting. By this time, spring 46 has disengaged contact 22.

lowing in engagement therewith until spring 46 again engages contact 22. Thereafter member 19 and contact 17 separate by reason of the continued movement of member 19, this continued movement being allowed by spring 46. The switches 17 and 18 are so arranged that the potential is applied while the sheet is held between the rolls and the potential is released before the sheet is released, thus preventing discharges be- "ltween the terminals which tend to heat the mica, causing it to deteriorate. It is to be understood that other apparatus for performing this method of applying and releasing potential only while the sheet is pressed between terminals may be used.

It' will now be evident that this invention provides a very simple apparatus with the aid of which mica sheets or films can be tested very rapidly; and that the machine, in addition to testing the sheets, will automatically separate the sheets that are defective from the good'sheets. The voltage impressed across the rolls 2 and 3 can be adjusted as desired by using a suitable type of transformer or induction coil, so that the same apparatus at different times can be While the dielectric material to has been referred toabove and also in the When roll 20 is re leased, member 19raises, the contact 17 fol-' used for different lots of micas of different thicknesses.

While I have herein shown and described the best embodiment of the invention of which Iam at present aware, it will readily be appreciated that this embodiment may be modified in many particulars without departing from the spirit or scope of this invention.

be tested appended claims as mica, it will be understood that other dielectrics are the equivalent of mica so far as the present invention is concerned.

What is claimed as new. is:

1. An automaticmica-sheet flaw-detecting and selecting machine, which comp-rises two electrically conducting members constituting circuit terminals having sufficiently wide continuous conducting surface areas to engage continuously substantial widths of the opposite surfaces of an intervening.

mica sheet; .means causing an electric current to flow through a flaw in a defective intervening mica which does not cause a current to flow through a good intervening mica; mechanism moving successive micas to positions between and ejecting them from between said conducting members; and

mechanism controlled by such current flow through defective micas and segregating the good and the-bad ejected micas.

2. An automatic mica-sheet flaw-detecting. machine comprising, in combination, a

pair of electrically conducting rolls mounted to be adjacent to one another for simultaneously engaging opposite portions of the two surfaces of a.mica sheet, means for driving said rolls to cause them to feed said sheet therethrough, and a high potential circuit in which said rolls are connected and for which they form terminals, whereby a flow of current in said circuit is normally prevented by the presence of good portions of said mica sheet-between the rollsbut is permitted when a defective part of the sheet passes between said rolls.

3. An automatic mica-sheet flaw-detecting machine comprising in combination a pair of electrically conducting rolls mounted to be adjacent to one another for simultaneously engaging opposite portions of the two surfaces of a mica sheet, means for driving said rolls to cause them to feed said sheet therethrough, and a high potential circuit in which said rolls are connected and for which they form terminals, and controlling means for said circuit arranged to be operated by the forward edge of the mica sheet as the rolls draw the sheet between itself controlled by said moving mechanism;

and mechanism controlled by the current flow through defective micas and segregating the good from the bad ejected micas.

5. An automatic mica-sheet flaw-detecting and selecting machine, which comprises two electrically conducting members constituting circuit terminals having sufliciently wide continuous conducting surface areas to engage continuously substantial Widths of the opposite surfaces of an intervening mica sheet; means causing an electric current to flow through a flaw in a defective intervening mica which does not cause a current to flow through a good intervening mica; mechanism for moving successive micas to positions between and ejecting them from be- 0 tween said conducting. members; at least one of said terminals having a width less than the mica sheet whereby the sheet in testing position extends to a limited degree beyond said terminal; controlling means for said current-causing means and itself controlled by said moving mechanism; and mechanism controlled by said current floor through defective micas and segregating the good from the bad ejected micas 6. A mica testing machine comprising, in combination, a pair of rolls for simultaneously engaging opposite faces of a mica sheet, means for driving said rolls-to cause ,them to feed said sheet therethrough, and a high potential circuit in which said rolls are connected and for which they form terminals, a device movable into either one of two operative positions for controlling the path taken by the ejected mica sheets, and automatic means for shifting said device from one of said positions to the other to direct the perfect and imperfect sheets into different paths upon their discharge from be tween said rolls and for automatically holding said device in its shifted position until after the sheet for which it is shifted has passed said device.

- 7. An automatic mica-sheet flaw-detecting machine comprising, in combination, a pair of electrically conducting rolls mounted to be adjacent to one another for simultaneously engaging opposite portions of th two surfaces of a mica sheet, means for driving said rolls to cause them to feed said sheet therethrough, means for impressing a high twan -a potential across said rolls whereby a mica sheet fed between them will be subjected to a dielectric strain, a deflector normally held in position to direct the sheets ejected from between said rolls in a predetermined path, and means acting automatically upon the passage between the rolls of a dielectrically weak portion of the micasheet, to shift said deflector into a position causing the defective sheet to follow a different path.

-8. A mica testing machine comprising, in combination, a pair of rolls for simultane ously engaging opposite faces of' a mica sheet, means for driving said rolls to cause them to feed said sheet therethrough, and a high potential circuit in which said rolls are connected and for which they form ter minals, whereby a flow of current in said circuit is normally prevented by the presence of said mica sheet between the rolls but is permitted when a defective. part of the sheet passes between said rolls, a deflector normally held in'a position to direct the sheets ejected from between said rolls in a predetermined path, electro-magnetic means operative automatically upon a .flow of current through said circuit permitted by the passage of a defective sheet to shift said deflector into a position causing the ejected sheet to follow a different path, and means operative to ensure the retention of said de- Hector in its shifted position until said defective sheet has been directed into the desired path.

9. An automatically operating mica-sheet flaw detecting and selecting machine comprising, in combination, a pair of electrically conducting rolls mounted to be adjacent to one another for simultaneously engaging opposite portions of the surfaces of a mica sheet, means for driving said rolls to cause them to feed said sheet therethrough, and a high potential circuit in which said rolls are connected and for which they form terminals, whereby a flow of current in said circuit is normally prevented by the presence of said mica sh wt between the rolls but is permitted when a defective part of the sheet passes between said rolls, a deflector nor mally held in a position to direct the sheets ejected from between said rolls in a predetermined path, electro-magnetic means for shifting said deflector into a difl'erent position, and a relay controlling the operation of said electro-magnetic means and arranged to be energized by a flow of current through said high potential circuit. i

10. A mica testing machine comprising, in combination, a pair of rolls for simultaneously engaging opposite faces of a mica sheet, means for driving said rolls to cause them to feed said sheet therethrough, and a high potential circuit in which said rolls are connected and for which they form terminals, whereby a flow of current in said circuit is normally prevented by the presence of said mica sheet between the rolls but is permitted when a defective part of the sheet passes between said rolls, a deflector normally held in a position to direct the sheets ejected from between said rolls in a predetermined path, electro-magnetic means for shifting said deflector into a different position, a relay controlling the operation of said electro-magnetic means and arranged to be energized by a flow of current through said high potential circuit, and a locking circuit for maintaining said electro-nragnetic means energized after its operation has been initiated until after the testing operation on the sheet which permitted the flow of current through said circuit has been completed.

11. A mica testing machine comprising, in combination, a pair of rolls for simultane;

ously engaging oppositevfaces of a mica sheet, means for driving said rolls to cause them to feed said sheet therethrough,, a high potential circuit in which 'said rolls are connected and for which they form terminals, whereby a flow of current in said circuit is normally prevented by the presence of said mica sheet between the rolls but is permitted when a defective part of the sheet passes between said rolls, a deflector normally held in-a position to direct the sheets sheet, means ejected from between said rolls in a predetermined path, electro-ma'gnetic means operative automatically upon a flow of current through said circuit permitted by the passage of a defective sheet to shift said defiector into a position causing the ejected sheet to follow a different path, and a looking circuit for said electro-magnetic meansl operative to ensure the retention of said deflector'in its shifted position until said defective sheet has been sired path, said locking circuit includinga switch arranged to be operated by thepresentation ofthe next sheet of mica to said rolls to open said locking circuit and thereby enable said deflector to return to its original position.

12. An automatically operating mica- .sheetfiaw-detecting and selecting machine,

which comprises a pair ofelectrically conducting members constituting circuit terminals having sufficiently wide continuous connism controlled by said current flow through d between two circuit terminals having-wide ducting surfaces to engage continuously substantial widths of the opposite surfaces of the mica-sheet; means causing anelectric current to How through a flaw in adefective mica between said conducting members which does not cause a' current to flow through a good mica so located; means for ejecting. the 1micas successively from between said conducting members ;'and mechadefective micas and segregating the goo and the badejected micas.

13. A testing apparatus comprising, in

directed into the de-.

combination, two electrically conducting members mounted to engage simultaneously opposite faces of a sheet of mica, a high potential circuitconnected to said members and for which the members form terminals, a primary circuit supplying powerto said high potential circuit, and controlling means for said primary circuit normally, holding the latter circuit open but mounted and arranged to be .operated to close said circuit upon the presentation of a mica sheet in testing position.

l4. A ,m1ca testing machine comprising, in combination, a pair of rolls for simultaneously engaging opposite faces of a mica sheet, means'for driving said rolls to cause them to feed said sheet therethrough, and a high potential circuit in which said rolls are connected and for which they form terminals, switch operating elements controlling said circuit and maintaining it normally inactive but mounted and arranged to be engaged by both the leading and trailing edges of saidmica sheet whereby saidcircuit is inactive whenever either one of sai elements is not engaged bya mica sheet.

15. A mica testing machine comprising, in combination, a pair of rolls for simul taneously engaging opposite faces of a mica for driving said rolls to cause them to feed said sheet therethrough, a high potential circuit in which said rolls are connected and for which they form terminals, and two normally open switches connected in series and controlling said circuit, said switches having operating elements mounted, respectively, one in front of and the other behind the line of contact of said rolls with the mica sheet whereby both of said elements are engaged by the sheet as it is fed through the rolls;

16. A mica testing machine comprising, in combination, a pair of rolls for simultaneously engaging opposite faces of a mica sheet, means for driving said rolls to cause them to feed said sheet therethrough, ahigh potential circuit in which said rolls are mounted and for which they form terminals, a primary circuit supplying'power to saidhigh potential circuit, and two switches connected in said primary circuit-in series with each other,omeans for normally holding said switches open, an operating element for each of said switches, said elements being located one in front of and the other behind the line of contact of said rolls with the mica sheet whereby they are operated to close the switches by their contact with said sheet.

17. The method of applying a flaw-detecting difference. of electrical potential to the opposite surfaces of a dielectric sheetcontinuous conducting surfaces continuously engaging substantial widths of the opposite surfaces of the sheet, which consists, after locatmg the sheet between the terminals, in

I successively pressing the terminals into firm engagement with the sheet and relieving the sheet from such terminal-compression, causing such pressing and release of the sheet to effect the application and the discontinuance respectively of the flaw-detecting potential to the terminals.

18. Apparatus for distinguishing good mica sheets from similar sheets possessing minute defects not readily observable,,comprising a pair of electrically conducting members having sufiiciently wide continuous surfaces to engage continuously substantial widths of opposite mica faces; m"chanism moving successive micas to positions between said conducting members; and means controlled by said moving mechanism and operating while a mica is between said conducting members, and causing the application of such a potential difference to said conducting members as will cause a current to flow through a defect in a defective mica but not through a good mica.

19. An automatically operating machine for detecting flaws in dielectric sheets which comprisis a pair'of electrically con ducting members constituting circuit terminals having sufficiently wide continuous conducting surface areas to engage continuously substantial widths of the sheet; means for moving the sheets to positions between and ejecting them from between said terminals; means controlled by the sheet in its movement and connecting the terminals in their circuit; means associated with.

said circuit for causing the application of such potential difference to said terminals as will causea current to flow through a defect in a defective mica but not through a good mica; and means automatically returning said connecting means to its normal disconnecting position upon further movement of said sheet but prior to the ejection thereof.

20. An automatically operating micasheet flaw-detecting machine, which comprises a pair of sheet-feeding rolls mounted to e normally in peripheral contact with one another; means for rotating the rolls to feed the mica sheet between them; and means for subjecting the mica sheet to a high electric stress while it is being fed by said rolls.

21. An automatically operating micasheet flaw-detecting machine, which comprisesa pair of sheet-feeding rolls mounted to be normally in peripheral contact with one another; means for rotating the rolls to feed the mica sheet between them; insulating supports for the ends of said rolls and between which the sheet passes while being fed between the rolls; and means for subjecting the mica sheet .to a high electric stress while it is beingifed by said rolls.

22..An automatically operating machine for detecting flaws in a mica sheet, which comprises two conducting members constituting circuit terminals having sufiiciently wide and continuous conducting surfaces to engage continuously a substantial portion of the width of the sheet; and in ans, operated by movement of said sheet and only when the sheet is in such engagement with .both terminals, to appl and remove, suc-' cessively, a difl':rence 0 electrical potential between said terminals and the opposite surfaces of the sheet.

23. An automatically operating micasheet, flaw-detecting machine, which comprises rotatable sheet-feeding vmeans; and means, operating while the sheet is being fed by said means, causing an electric current to flow through a flaw in a defective mica sheet which does not cause a current to flow through a good mica sheet.

24. Apparatus for distinguishing and segregating good mica sheets and similar sheets possessing minute defects not otherwise observable, said apparatus comprising two electrically conducting members haw ing sufiiciently wide continuous surfaces to engage continuously substantial widths of opposite mica faces; mechanism moving successive micas'to positions between and e ecting th'm from between sald conduct-.

ing members; means controlled by said moving means and operated when a mica is engaged by and between said conducting members and applying such a potential difference to said conducting members as will cause a current to flow through a defective mica "but not through a good mica; and mechanism' controlled by such current flow through defective micas and segregating the good and the bad ejected micas.

'25. Apparatus for distinguishing good mica sh'ets from similar micas possessing minute defects not readily observable, said apparatus comprising two members having relatively movable electrically conducting mica-engaging surfaces; mechanism moving a mica-engaging surface of at least one of said conducti members toward the other into position to engage a mica between them;- means applying to said conducting surfaces such an electrical potential difference as to cause a flowof current-through a defect in a defective mica but not through a good mica; a switch controlling said poten'tial applying means; and mechanism controlled by continued operation of said conducting member moving means while the mica is engag'd by said conducting surfaces, and operating said switch to cause operation of said means for applying potential difierence. Y

In testimony whereof I have name to this specification.

' GREENLEAF WHITTIER PICKARD.

signed my

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