US2486525A

US2486525A - Warp knitting machine

Info

Publication number: US2486525A
Application number: US17046A
Authority: US
Inventors: Raymond A Fuhrer; Robert H Roughsedge; Hans G Lustig
Original assignee: Celanese Corp
Current assignee: Celanese Corp
Priority date: 1948-03-25
Filing date: 1948-03-25
Publication date: 1949-11-01
Anticipated expiration: 1966-11-01

Description

Nov. A l, 1949.

Filed March 25, 1948 R. A. FUHRER ET AL WARP KNITTING MACHINE 4 Sheets-Sheet 1 R-A. Il H.ROUGHSEDGE. H-G .LU STIGr Nov. 1,1949. R, A, FUHRER-ET AL 2,486,525

WAR? KNITTING MACHINE Filed March 25. 1948 4 sheets-sheet 2 1N V EN TOR.

RA. Fur-1R ER, RHROUGHSEDGE. By H.G.LUST|G.

NOV- 1 1949- R. A. FUHRER ET AL 2,486,525

WARP KNITTING MACH INE Filed Maren 25; 1948 4 shams-sheet s j ATTORNEYS Nov. 1; 1949.

R. A. FUHRER ET AL WAR? KNITTING MACHINE Filed March 25,' 1948 4 Sheets-Sheet 4 .IN VEN TORS RA. FUHRER. RHROUGHSEDGE. BY H GLUSTIQ Patented Nov. 1, 1949` Raymond A. Fuhrer,

Roughsedge, Ramsey, N. J., New York, N. Y., assig Malverne, N. Y., Robert H.

and Hans G. Lustig,

nors to Celanese Corporation of America, a. corporation of Delaware Application March 25, 1948, Serial No. 17,046

15 Claims.

This invention relates to warp knitting machines, and relates more particularly to improved mechanism employed in connection with warp knitting machines for controlling the letoff of the thread from the warp beam.

In the usual method of producing warp knitted fabrics, that is, fabrics in which a number of warp threads are knitted together in each course, a number of warp threads are drawn oif a beam or a number of sectional beams and, on their way to the thread guides and needles, are passed over a tension element. The tension element comprises a bar carried by arms pivotally mounted to allow the bar to oscillate under variations in the tension of the warp threads. The movement of the bar is used to control the mechanism for letting off the warp threads from the warp beam or beams. In prior warp knitting machines, the bar was connected by suitable mechanism to a clutch through which was driven a warp beam, or to a mechanical brake which controlled the rotation of the warp beam.

It was found that prior methods of feeding thread from the warp beam to the knitting elements caused variations to be introduced in the tension of the thread since the feeding of the thread did not synchronize with the taking up of the thread during each knitting course. This is particularly true in Warp knitting machines operating at high speeds. It is, accordingly, an important object of this invention to control the thread let-off in a warp knitting machine so as to produce ,a uniform linear thread let-olf speed so that the thread is delivered in the exact quantity required by the knitting elements and under substantially uniform tension throughout each knitting course.

Another object of this invention is the provision of a motor for positively controlling the warp beam or beams for letting off warp threads, including an electronic control device for regulating the speed of said motor and regulating the linear let-off speed of the warp threads.

A further object of this invention is to provide in a warp knitting machine novel means, including an electronic controller, for maintaining the tension bar within predetermined limits for maintaining a predetermined range of tensions on the warp threads being fed to the knitting elements.

Other objects of this invention, together with certain details of construction and combinations of parts, will appear from the following description and accompanying drawings.

According to this invention, which will be described in connection with a two-bar warp knitting machine although it is also applicable to a one-bar warp knitting machine, the torque which rotates the warp beams is substantially transmitted by the tension of the warp threads, said tension being applied to the warp threads by the knitting elements. Between the warp beams and the knitting elements are interposed tension bars which are provided with manually adjustable springs for placing on the warp threads a tension of the magnitude required for knitting. This tension is maintained during knitting by regulating the amount of warp thread let off the beams. In this manner, a fabric is produced which is uniform asregards the size of the loops and their shape since the quantity of thread fed to each loop is uniform.

Regulation of the amount of warp threads let off the beams is effected by connecting each of the shafts on which the warp beams are mounted to a direct current motor through suitable toothed gears to a worm wheel which meshes with a worm operatively connected to the output shaft of a direct current motor. In a two-bar warp knitting machine, in connection with which the present invention is being described, there is an upper warp supply and a lower warp supply. The basic let-off speed for each warp supply is different and, therefore, a separate direct current -motor is employed for effecting the let-off of each warp supply. However, the regulation of the let-ofi speeds of both warp supplies must occur simultaneously. The control for each of said direct current motors is, as stated, electronic, providing a continuously regulated armature voltage thereon.

The speed of each direct current motor, and therefore the let-off speed of each warp supply, is effected by means of a variable reactor electronically connected to the motor and a reactor bar operatively connected to the tension bar. The movement of the tension bar causes the reactor bar to vary the air gap of the magnetic field of the coil of the variable reactor. The difference between the voltage drop of the variable reactor and a fixed reactor electrically connected thereto triggers a gas-filled tetrode tube. The ring of this tetrode tube, through suitable electric and electronic connections, causes additional voltages to be placed on the direct current motor armature, thus increasing the speed thereof to an extent depending upon the frequency with which the reactor bar enters the effective field of the variable reactor.

When the let-off speed is equal to or greater than the knitting speed, i. e. when the tension on the tension bar is below the present amount,

the reactor bar will not enter the reactor field; accordingly, the tetrode tube will not fire and the speed of the let-off motor will be reduced.

Means are provided adjacent to the reactor bar for stopping the operation of the direct current or let-off motors as well as the motor for operating the knitting elements when the tension on the warp threads is so great as to approach the breaking point of said warp threads. This means comprises two limit switches, one on each side of the reactor bar and a finger movable with said reactor bar for operating said limit switches.

rEhe invention will now be described in greater detail with reference to the accompanying drawings, wherein Fig. l is a side elevational tion, of a warp knitting invention,

2 is a view showing in top plan the reactor and reactor bar as attached to the warp knitting machine,

Fig. 3 is a front elevational view of the elements shown in Fig. 2,

Fig. l is a detailed view on an enlarged scale oi" the gearing and motor arrangement for regulating the amount of warp threads let ofi the beams,

Fig. 5 is a cross-sectional gearing arrangement as operatively connected to the warp beam shaft and to the shaft of the direct current motor, and

Fig. G is a circuit diagram showing the electrical and electronic connections of one of the motor controls.

Like reference numerals indicate like parts throughout the several views of the drawings.

In Fig. l, warp threads li and 6 are shown taken from warp beams 'l and 8, respectively, each of which is maintained on a shaft, such as shaft 9, suitably supported on frame I8 of a two-bar warp knitting machine. The frame IG also supports guide rods II and l2 and tension devices, generally indicated by reference numerals I3 and I4, with which elements the warps 5 and 6 are in contact on their way to the knitting elements, generally indicated by reference numeral I5. The knitting elements, as is well understood in the art, are operated by means of suitable elements operatively connected to the cam shaft IG which is rotated by an alternating current motor Il, see Fig. 6, normally placed on the hoor supporting the warp knitting machine at the rear thereof. Motor Il is supplied with S-phase, standard cycle alternating current from supply lines, generally indicated by reference numeral I 8.

The tension devices I3 and I4 each comprises a rod I8 pivotally mounted in and extending through bosses 2l in the frame It of the warp knitting machine. Rod I 9 extends laterally across the machine and adjacent its ends has xed thereto an arm in one extremity of which is fixed, as by means of a set screw 23, a tension bar The rearwardly extending portion of arm 22; is provided with an opening for the passage therethrough of a rod 25, the lower end 26 of which is connected at 2? to machine frame I8. Rod has mounted thereon a compression spring ttl. This spring acts between arm 22 and lock nuts threaded on rod and so resists downward movement of the tension bar 24 under the tension oi the warp threads. The degree of resistance to the downward movement of the tension bar Ml, and thus the amount oi tension placed on the warp threads, may be adjusted by movement of the lock nuts 29.

View, partly in secmachine embodying this View showing the The knitted fabric 3I passes over guide rod 32, under roller 33 and on to take-up roller 34.

The means for controlling the rate of let-oil of warp threads will now be described, particularly in connection with the circuit diagram shown in Fig. 6.

As indicated above, 3-phase, standard cycle, alternating current from supply lines I8 supply the current of motor Il of the warp knitting machine. Leads 35 and 36 from the alternating current power supply conduct current from one phase of the 3-phase supply lines to primary coil 3l' of transformer 38. Transformer 38 will eventually provide the power for a direct current motor 33 consisting of armature 40 and its field 48, the function of which will hereinafter be described, after it is properly controlled and modined in the circuits to be described.

The control device of the present invention is initiated by operating push button 4I to cause relay 42 to be energized, thus closing contacts 43, 44 and 45. When contact 43 closes, relay 46 is energized and closes

contacts

41, 48 and 49, thus putting full voltage across the knitting motor Il causing it to operate at full speed for driving the warp knitting machine. Simultaneously, contact 44 causes relay 42 to be electrically locked in so that contacts 43, 44 and 45 remain closed even after push button 4I is released. The closing of contact 45 enables relay 5I to be energized in a-manner to be hereinafter described, thus closing contacts 52 and 53 and opening contact 54. The function of these contacts will be described below.

'I'he shunt neld 40 is supplied through leads 55 (Fig. l) with current rectified by the use of a full-wave rectifier vacuum tube 56 and is controlled by a eld rheostat 5l. The current is supplied to said rectifier tube 56 by

leads

58 and 59 tapped from points GI and 62 on secondary coil 83 of transformer 38.

The closing of contact 53 causes a rectified voltage to be impressed through leads 63 (Fig. l) upon the armature 48 of direct current motor 38. This armature current is supplied by secondary coil 83 from contact taps 84 and 65. The armature current is rectified through gas-filled

tetrodes

66 and 61, the rectified current entering lead 88. From lead 88 the rectiiied current passes through junction 89, contact 53, which is now closed, through lead Id to the armature 48 of motor 3S, to junction "II, through lead II to junction l2, and back to center tap 73 of secondary transformer coil G3. The basic running voltage across the armature 40 of motor 39 is controlled by means of the bias voltage impressed on the grids of tetrodes 8G and 6l. This grid bias is basically supplied from secondary transformer coil 63, through the network generally indicated by reference numeral 'I4 which includes a transformer 15, serving to shift the phase of the grid bias voltage in relation to the plate voltage in such a manner as to give substantially constant rectified output voltage under various conditions of speed and load. This grid bias is further modiiied and controlled by a network generally indicated by reference numeral 'I6 including a transformer TI, a rectier vacuum tube i8 and a potentiometer 19. The potentiometer it controls the grid bias within the tetrodes 66 and 8l in such a manner as to control the basic running speed of direct current motor 39. The arrangement above described drives the direct current motor 39 at a predetermined constant speed which moves substantially constant for all values of motor load which may occur. The grid bias is additionally modified by an adjustable potentiometer 8| and rheostat 82 which are parts of a controlling network, generally indicated by reference numeral 83.

The speed at which the motor 39 is set to run is determined by the amount of warp threads on the warp beam. The initial basic speed at which the motor is set to run is predetermined when the \warp-beam is at full capacity. As the warp threads on the warp beam are run off, the diameter of the windings on the beam decreases. In order to keep the linear velocity of the thread being let oi the beam constant, the rotational speed of the beam must be increased. This constant linear let-ofi. speed of the warp threads is maintained as follows: 'when the tension of the yarn is slightly more than normal, the irnpedance of variable reactor 85 is increased due to a reactor arm 06 cutting deeper into the eld of said variable reactor. The reactor arm 36 is fixed to reactor bar S1 which is mounted, as by means of said screw 88, on tension element pivot arm i3 for movement therewith.

The change of impedance in the variable reactor 35 serves to control the speed of direct current moto-r 39. To this end, primary coil S9 of transformer 9| is supplied iwith current to leads 02 and 93 which are tapped in secondary coil 53 of transformer 38 at contact points 94 and 95, respectively. The secondary coil 96 of transformer 6| impresses an alternating current Voltage across a. bridge circuit, generally indicated by reference numeral 01, which consists of a fixed resistor Q3, a rheostat 93, a fixed reactor |0|, and the variable reactor 85. This bridge through resistor |02 and by-pass condenser |03 controls the grid of gas-filled tetrode 84 in such a manner that when ythe reactor arm 36 does not enter the eld of the variable reactor 85, tetrode 84 will not conduct current therethrough, but when the reactor arm 36 goes deeper into the field of variable reactor 35, the tetrode 84 will conduct current therethrough. IIhe firing of tetrode 84 causes the voltage applied upon the terminals of armature 40 of motor 39 to be increased above the preset armature voltage by a superimposed increment of voltage, the magnitude of which is controlled by potentiometer 8|. The duration of time during which these superimposed increments are supplied for each signal from tube 84 may be varied from 1/2 to 8 cycles, depending upon the setting of rheostat 62. Moreover, if a. new signal ires tetrode 84 while the circuit is still responding to a preceding signal, the succeeding voltage increments for both signals are added to one another, thus smoothing ofi all armature voltage changes gradually. This also holds true ii more than two signals pile up.

ir The superimposed voltage increments referred to in the above paragraph are created by changing the phase relation between grid potential and plate potential in gas-filled

tetrodes

66 and 61, thereby causing an additional voltage increment to be app-lied upon the ar'mature 40 of direct current motor 30. This `method of controlling the average value oi direct current by varying the phase of the grid voltages is well known to the art. The network which controls the functions described above comprises secondary coil |04 of transformer 0|, lead |26, resistors |31 and |38, potentiometer 8|, rheostat 82, capacitor |38', rectier |08, lead |05, gas-filled tetrode 84, and leads ||3 and ||2.

vMeans are provided in the control circuit for preconditioning another circuit for initially energizing relay 5|. Thus, upon the energization of primary coil 31 of transformer 38, relay |21 is energized by current taken from secondary coil 63 at taps 6|, 65 and 62, the current passing, through rectifier vacuum tube 56. The rectified current passes through junction |28 and lead |29 to normally closed contact 54, through lead |3|, relay |21, lead |32 to junction 1|, through, lead 1 to junction 12, through lead |34 to center tap 13 in secondary coil 63. Energizing the relay |21 causes contact |35 to close.

This initial energization of relay 5| is possible only when reactor arm 86 is in such relative position to the adjustable reactor 85 as to cause gas-filled tetrode 84 to fire. This arrangement insures that the direct current motor 39 will not start running lunless there is sufficient tension in the yarn to move the tension bar in a position which causes reactor arm 66 to enter the field of variable reactor 85, thus causing tetrode 84 to fire. When reactor arm 86 is in such a position the following takes place: one phase of the current from secondary :coil |04 of transformer 9| passes through lead |26, to junction |25, through lead |24, relay 5|, normally closed limit switch |23, through lead |22 to contact 45, through lead |2| to junction H9, to junction H8, through contact |35 to junction 60, through lead 68 and rectifier |08 to junction |01, through lead |06 to the plate of gas-lled tetrode B4, then passes through to the cathode of tetrode 84, through lead i3 and junction |05 back to secondary coil |04. Thus coil 5| is energized. When contact 52 is closed by the energization of coil 5| it causes said coil 5| to be sealed in by closing the circuit consisting of secondary coil |04, lead ||2 to junction |05, lead ||3 to junction ||4, current limiting resistor ||5, lead ||6 to Contact 52, lead ||1 to junction ||8 to junction H9, lead |2| to contact 45, lead. |22 through nonmally closed limit switch |23, relay 5|, lead |24 to junction |25 and lead |26 to secondary coil |04.

It is to ybe noted that the other half cycle of the alternating current going out of secondary coil |04 is cut off by the gas-filled tetrode 84. Therefore, the initial half icycle passing through relay 5| causes it to pick up and lock in through contact 52. Simultaneously, the energization of relay 5| in this sequence ca-uses normally closed contact 54 to open, thus de-energizing relay |21 and effecting the opening of contact |35.

When yarn tension becomes excessively slack due to some faulty setting of the variable elements of the control, the position of the tension bar 24 causes reactor arm to move to the right, as shown in Fig. 3, to such an extent that finger |36, attached to and movable with reactor bar 81, comes into contact with push button |31 of limit switch |23 causing the same to open momentarily. This opening of the limit switch deenergizes relay 5|, causing contact 53 to open Iwhich will slow down the speed of direct current motor 39. This slowing down of the speed of motor 39 causes the yarn tension to increase and the tension bar to be restored to its norimal operating range. The de-energization of relay 5| also causes contact 54 to close thereby energizing relay |21 to close contact |35. Contact 52 is also opened by the de-energization of relay 5| unsealing the same.

When the tension on the yarn has been restored to its initial amount, the reactor arm B6 will again cut into the field of the variable reactor 85, causing the tetrode 84 to nre and reenergize relay in the manner described above and to again place the control in normal operation. When the yarn tension becomes too great, the ringer |36 on reactor bar 81 is caused to be moved to the left, thus coming in contact with push button |4| and opens limit switch |42 to Stop the rotation of motor I1.

Push buton |38 is to permit the Warp button |39 is closed, relay 5| ing a circuit energized by secondary coil |04. The energization of relay 5| causes Contact 53 to close and impress -the rectified voltage derived from tetrodes B5 and G1, and further derived `from secondary coil 83 to be impressed across the armature terminals of motor 39.

Glow discharge tube |40 is placed across lead 68 to lead |26. The glowing of said tube |40 indicates the ring of tetrode 84.

In order to halt the operation of the entire system, a push button |42 is supplied, the opening of said push button causing, through Suitable worm and shaft are housed in a casing |53 mounted on the housing We` and the casing of motor 39.

and the worm. This makes for a worm-gearing which is self-locking. Accordingly, the worm Wheel cannot drive the Worm so that, when the .motor is, not rotating the worm, the worm wheel is braked or locked by friction. However, the rotation of the worm by the motor 39, which opcrates continuously during the knitting operation causes the amount of warp threads to be let off therefrom, which amount is suillcient to maintain the position of the tension bar, or tension bars, and, therefore, the tension on the warp threads within predetermined limits.

It is to be understood that the foregoing detailed description is merely given by way of illustration and that many variations may be made therein without departing from the spirit of our invention.

Having described our invention, what we desire to secure by Letters Patent is:

1. In a warp knitting machine wherein the torque for rotating a warp beam is transmitted nected to said warp beam, and electronic means operated by said reactor arm for continuously electronic means operated by said reactor arm for continuously controlling the speed of said motor.

pass on their way to said knitting elements, a reactor arm movable by said tension bar, a motor, gearing, including a self-locking Worm Wheel and worm, operatively connecting said warp beam, and electronic means operated by said reactor arm for continuously controlling the speed of said motor.

5. In a warp knitting machine wherein the torque for rotating a warp beam, mounted on a shaft of said machme, is transmitted by the tenand electronic means operated by said reactor arm :for continuously controlling the speed of said motor so as to cause said Warp threads to be let oli Warp beam to maintain the position of said tension bar within predetermined limits.

6. In a warp knitting machine wherein the torque for rotating a warp beam, mounted 0n a shaft of said machine, is transmitted by the tenn sion of the warp threads applied by the knitting elements, means for controlling the let-ofi of the warp threads from said warp beam, said means comprising a movable tension bar over which the warp threads pass on their way to said knitting elements, a reactor arm movable by said tension bar, a gear fixed to said shaft, a motor, gearing, including a worm wheel and worm, connecting said motor and said gear on said shaft, and electronic means operatedvby said reactor arm for continuously controlling the 'speed of said motor so as to cause said warp threads to be let off said warp beam in an amount sufficient to maintain the position of said tension bar within predetermined limits.

7. In a warp knitting machine wherein the torque for rotating a warp beam is transmitted by the tension of the warp threads applied by the knitting elements, means for controlling the let-oil of the warp threads from said warp beam, said means comprising a movable tension bar over which the warp threads pass on their way to said knitting elements, means for adjusting the position of said tension bar, a reactor arm movable by said tension bar, a' motor operatively connected to said warp beam, and electronic means operated by said reactor arm for continuously regulating the armature voltage applied to said motor.

8. In a warp knitting machine wherein the torque for rotating a warp beam, mounted on a shaft of said machine, is transmitted by the tension of the warp threads applied by the knitting elements, means for controlling the let-off of the warp threads from said warp beam, said means comprising a movable tension bar over which the warp threads pass on their way to said knitting elements, means for adjusting the position of said tension bar, a reactor arm movable by said tension bar, a gear iixed to said shaft, a motor, gearing connecting said motor and said gear on said shaft, and electronic means operated by said reactor arm for continuously regulating the armature Voltage applied to said motor so as to cause said warp threads to be let oi said warp beam in an amount suiilcient to maintain the position of said tension bar Within predetermined limits.

9. In a two-bar warp knitting machine wherein the torque for rotating the warp beams is transmitted by the tension of the warp threads applied by the knitting elements, means for separately controlling the let-off ci the warp threads from said warp beams, said means comprising movable tension bars over which the warp threads pass on their way to said knitting elements, a reactor arm movable by each of said tension bars, a motor operatively connected to each of said warp beams, and electronic means operated by each of said reactor arms for separately and continuously controlling the speed of each of said motors.

10. In a two-bar warp knitting machine wherein the torque for rotating the warp beams is transmitted by the tension of the warp threads applied by the knitting elements, means for separately controlling the let-off oi the warp threads from said warp beams, said means comprising movable tension bars over which the warp threads pass on their way to said knitting eiements. an oscillating reactor arm movable by each of said tension bars, two direct current motors, gearing connecting each of said motors to its respective warp beam, and electronic means operated by Ll l) each of said reactor arms for separately and continuously controlling the speed of each of said motors.

l1. In a two-bar warp knitting machine wherein the torque .for rotating the warp beams is transmitted by the tension of the warp threads applied by the knitting elements, means for separately controlling the let-off of the warp threads from said warp beams, said means comprising movable tension bars over which the warp threads pass on their way to said knitting elements, an oscillating reactor arm movable by each of said tension bars, two direct current motors, gearing, including a worm wheel and worm, connecting each of said motors to its respective warp beam, and electronic means operated by each of said reactor arms for separately and continuously controlling the speed of each of said motors.

l2. In a two-bar warp knitting machine wherein the torque for rotating the warp beams is transmitted by the tension of the warp threads applied by the knitting elements, means for separately controlling the letoii` of the warp threads from said warp beams, said means comprising movable tension bars over which the warp threads pass on their way to said knitting elements, an oscillating reactor arm movable by each of said tension bars, two direct current motors, gearing, including a self-locking worm wheel and worm, connecting each of said motors to its respective warp beam., and electronic means operated by each of said reactor arms for separately and continuously controlling the speed of each oi said motors.

13. In a two-bar warp knitting machine wherein the torque for rotating the warp beams, each mounted on a shaft of said machine, is transmitted by the tension of the warp threads applied by the knitting elements, means for separately controlling the let-off of the warp threads from said warp beams, said means comprising movable tension bars over which the warp threads pass on their way to said knitting elements, means for adjusting the position of said tension bars, a reactor arm movable by each of said tension bars. a gear fixed to each oi said shafts, two direct current motors, gearing com necting each of said motors to its respective gear on said shafts, and electronic means operated by said reactor arm for separately and continuously controlling the speed of each of said motors so as to cause said warp threads to be let off each oi said warp beams in an amount sufficient to maintain the position of said tension bars within predetermined limits.

14. In a two-bar warp knitting machine wherein the torque for rotating the warp beams, each mounted on a shaft of said machine, is transmitted by thetension of ,the warp threads applied by the knitting elements, means for separately controlling the let-off of the warp threads from said warp beams, said means comprising movable tension bars over which the warp threads pass on their way to said knittting elen ments, means for adjusting the position o said tension bars, a reactor arm movable `by eachof said tension bars, a gear xed to each of said shafts, two direct current motors, gearing, including a worm wheel and worm, connecting each of said motors to its respective gear on said shafts, and electronic means operated by said reactor arm for separately and continuously regulating the armature voltage applied to each of said motors so as to cause said warp threads to be let off each of said warp beams in an amount 1 l sufcient to maintain the position of said tension bars within predetermined limits.

15. In a two-bar warp knitting machine rotating the Warp beams,

CTI

movable tension bars over which the warp 10 threads pass on their way to said knitting eleadjusting the position of said RAYMOND A. FHRER. ROBERT H. ROUGHSEDGE. HANS G. LUSTIG.

REFERENCES CITED The following references are of record in the file of thx patent:

UNITED STATES PATENTS Number Name Date 2,032,176 Kovalsky Feb. 25, 1936 2,430,022 Lambach Nov. 4, 1947 2,430,639 Jaques Nov. 11, 1947 2,450,470 Dion Oct. 5, 1948 Certificate of @orrecton Patent No. 2,486,525 November 1, 1949 RAYMOND A. FHRER ET AL.

it is hereby certified that error appears in the printed specioation of the above numbered patent requiring oorreotion es follows:

Column 7 ine 9, for boton 138 reed button 139 and that the said Letters Patent should De reed with this correction therein that the same may conform to the record of the oase in the Patent Ooe.

Signed and sealed this 2nd dey of May, A. D.1950.

[sum1 THOMAS F. MURPHY,

Assistant Commissioner of Patents.

Certificate of Correction Patent No. 2,486,525 November 1, 1949 RAYMOND A. FHRER ET AL.

It is hereby certified that error appears in the printed epecication of the above numbered patent requiring correction es follows:

Column 7, line 9, for buton 138 reed button 189 and that the said Letters Patent should be reed with this correction therein that the same may conform to the record of the case inthe Patent Olice.

Signed and sealed this 2nd day of May, A. 134950.

[Sv-Ll THOMAS F. MURPHY,

Assistant Uommzssz'oner of Pateta.