US2412318A - Safety drive, braking, and control mechanism for magnetic recording devices - Google Patents

Description

Dec. 10, 1946. (:AMRAS 2,412,318

SAFETY DRIVE, BRAKING, AND CONTROL MECHANISM FOR MAGNETIC RECORDING DEVICES Filed Aug. 10, 1942 3 Sheets-Sheet 1 M2 v/lv Cannons.

Dec. 10, 1946. M. CAMRAS 2,412,318

SAFETY DRIVE, BRAKING, AND CONTROL MECHANISM FOR MAGNETIC RECORDING DEVICES Filed Aug. 10, 1942 3 Sheets-Sheet 3 M42 v/u Gene/0s.

Patented Dec. 10, 1946 SAFETY DRIVE, B

G, AND CONTROL BAKIN MECHANISM FOR MAGNETIC RECORDING DEVICES Marvin Camras, Chicago, 111., assignor to Armour Research Foundation. Chicago, 111., a corporation of Illinois Application August 10, 1942, Serial No. 454.216

15 Claims.

This invention relates to improvements in safety drive, braking and control mechanism arranged to facilitate proper operation of a machine or other device in which the invention is embodied, and insure that operation in a manner tending to prevent any injury to the machine or device. the invention being highly desirable for use in connection with magnetic recording devices, although the invention will have other uses and purposes as will be apparent to one skilled in the art.

For the purpose of clarity, by way of example only and not by way of limitation, the present invention will be described herein in association with a magnetic recording device, the invention, of course, being built in as a part of the operating mechanism of the recording device. It will be appreciated, however, that mechanism of the character comprising this invention may be used as a salient part of other devices, especially those utilizing electrical apparatus and wherein reverse motion is frequently desired.

In magnetic recording devices, wherein an elongated recording medium such as a paramagnetic wire or tape is wound from one reel to another, and frequent reversals in the direction of travel of the recording medium are desired, it is highly desirable to have suitable braking means so that when a stop is made, motion of the recording medium ceases as expeditiously as possible. Likewise, when a quick reversal in direction is desired, it is essential that the various moving parts in the apparatus come to rest or substantially to rest before the reverse drive takes effect so as to eliminate jerking which might cause injury to the apparatus.

In magnetic recording devices of this character, rectifying and other forms of vacuum and thermionic tubes are frequently utilized in the magnetizing and reproduction circuit. Such tubes require a warming up period before they are adequately eflective to produce the required results. It is therefore desirable in a device of this character to provide means to prevent proper operation of the device before the tubes are hot so as not to waste the magnetic medium and probably ruin a recording or a reproduction.

With the foregoing in mind, it is an important object of the instant invention to provide safety mechanism including a braking arrangement which stops all operating parts of a device very quickly and without undue jerks.

Another object of the invention resides in the provision of safety mechanism involving a braking arrangement which requires no extra parts to eflect a positive braking action.

A further feature of the invention resides in the provision of safety mechanism including a reverse drive mechanism in which the drive connections are automatically utilized as braking means when the mechanism is stopped.

It is also an object of this invention to provide a switching arrangement for use in connection with a device involving vacuum tubes, the arrangement being such that the device cannot be operated until the tubes are ready to perform their functions.

A further feature of the invention resides in the provision of a switching arrangement for use in a magnetic recorder involving vacuum tubes, and employing locking means responsive to the passage of current through one of the tubes to hold the switch means in position to eflect operation of the entire device.

Still another feature of the invention resides in the provision of a switching arrangement including a double-throw switch with means associated to automatically lock the switch in closed position, and the switch being so constructed that it may be opened and closed in the opposite direction without affecting the locking means.

A further object of the invention resides in the provision of safety mechanism involving a control switch which is held in closed position by means responsive to the energization of a power tube, and which automatically resumes zero or open position upon the breaking of the electrical circuit through the apparatus,

The invention also seeks the provision of a control switch for a magnetic recorder or other device, which switch effects the movement of the mechanical parts of the device, and which switch automatically assumes open position when the current to the device is opened by a master switch or otherwise.

Still another feature of the invention resides in the provision of safety mechanism involving a switching arrangement coupled with a braking arrangement so that the braking arrangement automatically operates when the switch is open so as to stop all of the movable parts of the mechanism as expeditiously as possible.

Also a feature of the invention resides in the provision of a switching and braking arrangement for use in a. magnetic recorder of a device where reverse motion is frequently desired, which arrangement makes it impossible to acquire reverse motion by throwing a switch to the opposite side without substantially stopping all 3 moving parts by automatic action of braking means.

Further, the invention seeks the provision of a safety arrangement embodied in a magnetic recording device where reverse motion is available, which arrangement is designed to prevent proper operation of the device in either direction before the vacuum tubes utilized in the device are ready to perform their functions, and which arrangement automatically provides a positive and exceedingly rapid but gentle braking action whenever the moving parts of the apparatus are stopped Or reversed in direction.

While some of the more salient features, characteristics and advantages of the instant invention have been above pointed out, others will become apparent from the following disclosures, taken in conjunction with the accompanying drawings, in which:

Figure 1 is a fragmentary front elevational view of a magnetic recording device in which the present invention is embodied for illustrative P 9088 Figure 2 is a vertical sectional view cutting oil the rear wall of the casing housing the magnetic recording device, and illustrating in rear elevation mechanism embodying principles of the present invention;

Figure 3 is a fragmentary plan sectional view, with parts omitted, illustrating the salient features of the mechanism of Figure 2 in plan, and taken substantially as indicated by the line III-III of Figure 2, looking in the direction of the arrows, a schematic wiring diagram salient to the instant invention being illustrated in conjunction with the mechanical parts in this figure; and

Figure 4 is a fragmentary plan sectional view taken in substantially the same location as Figure 3, but illustrating the-switch mechanism in a different stage of operation.

As shown on the drawings:

The illustrated embodiment of this invention is shown in integral association with a magnetic recording device, including a casing I having a front panel 2, upon which front panel the major portion of the mechanism embodied in this invention is supported within the casing I. Of course, most of the mechanism is carried on the back of this front panel within the casing l, and a small amount is disposed on the front of the name] so as to be readily accessible to an opera or,

With reference now to Figure 1, it will be seen that the illustrated magnetic recording device includes a reel 3 mounted on a shaft I at one side of thefront panel 2, and a similar reel I mounted on a shaft Ii on the opposite side. On these reels 3 and I is an elongated recording medium, in the illustrated instance in the form of a relatively thin wire I, preferably only a, few thousandths of an inch in diameter so as to provide substantial recording time capacity and still maintain the apparatus generally compact and of small overall size.

The wire, of course, may be wound ofl the reel 3 on to the reel 5 in the forward or recording and reproducin direction, and likewise oil the reel 5 and on the reel 3 in the rewind direction. For example, in the use of the device the wire may be run forwardly, that is, on to the reel 5, a recording being made, and the wire may be rewound on the reel 3 to the length used in the recording, and again run forwardly to have the recording reproduced.

Assuming that the wire is moving forwardly, it first passes through a level winding member 8 associated with reel 3, through an erasing or demagnetizing head 9, thence around a guide pulley l0 through a magnetizin or recording head II, and then around a guide pulley l2 and through a level winding member l3 to the reel 5.

The reels 3 and 5 are driven by an electric motor N as seen best in Figures 2 and 3, which may be supported in any desired manner on the top of the front panel 2. The shaft l5 of this motor carries on its inner end a friction drive disk It. A pair of drive pulley members ii and I8 are arranged to bear against the friction disk II and be driven thereby. These pulley members, as best seen in Figure 2, contact the drive disk I6 from opposite sides so that drive connections to operate the reels for forward and reverse movement of the recording medium can conveniently be made. The pulley I1 is connected through a suitable chain or belt l9 to a pulley 2|) carried on the inner end of the aforesaid shaft 4 carrying the reel 3. Likewise, the drive pulley I8 is connected to a belt or chain 2| with a pulley 22 on the inner end of the shaft 8 carrying the reel 5.

The pulley I1 is rotatably mounted in the channel end 23 of a dog leg lever 2| pivoted as at 25 to a supporting socket 26 mounted on the housing of the motor ll. Likewise, the pulley I8 is carried in the channel portion 21 of a dog leg lever 28 pivoted as at 29 to a similar supporting bracket 30 on the housing of the motor. A cross spring 3| connected between the shafts of the pulleys l1 and ii tends at all times to hold both pulleys in inward position bearing against the friction disk It, as seen in Figure 2.

Of course, when both pulleys are against the friction disk It as seen in Figure 2, the apparatus will not operate since the reels 3 and 5 will be driven in the same direction, and other parts of the apparatus will tend to turn in the opposite direction at the same time. Consequently, there will be a dead stop of the reels and associated apparatus when the drive pulleys l1 and it are both in contact with the friction disk It. However, when the drive pulley l8 only is in contact with the friction disc and the drive pulley I1 is held away from the disk, as later described herein, the shaft 6 and the reel 5 are positively driven direct from the motor and the machine is operated forward in recording or reproducing direction. Likewise, when the drive pulley I8 is held away from the disk I6 and the drive pulley I1 is permitted to contact the disk, the shaft I and consequently the reel 3 are positively driven from the motor in the reverse or rewind direction. Suitable gearing may be provided between the shafts 4 and B so as to make a positive drive from one to the other, if so desired, or the tension upon the recording medium I may be relied upon to operate the other reel when one reel is being positively driven by the motor.

Selective operation of the reels 3 and 5 is controlled by a switch arrangement including a double-throw operating handle 22 extending through a decorative mounting plate 22 on the front of the panel 2, as seen in Figures 1 and 4. This switch arm carries an integral disk 34 thereon which is pivoted to a U-shaped relatively heavy supporting frame 25 as indicated at 26. The supporting frame is, of course, attached to the plate 33 and held stationary by virtue of the attachment of the plate to the front panel 2. The disk 34 is provided with an outwardly extending lug carrying a pivot pin II which extends a distance on either side of the lug. Above the lug the pivot pin is in position to engage the flared end 88 of a lever 39 which is pivoted as indicated at 49 (as seen in dotted lines in Figure 4) to a fixed cross member 4| on the frame 95. This lever 99 is bent upwardly as indicated at 42 so that it projects outwardly over the top of an insulation block 49 carried by the frame 39. In its projecting portion, the lever is twisted as seen at 42 so as to lessen the width of the lever in that portion thereof which extends between the upper ends of the aforesaid dog leg levers 24 and 29. The forward end of the lever 39 is provided with a centrally disposed notch 49 for engagement with the pivot pin 31 when the lever is in a neutral position. On each side of this notch the lever is provided with an obliquely disposed cam surface 48 around which the pivot pin 91 may ride when the arm 32 is thrown in either direction to cause a corresponding pivotal movement of the lever 39 about the pivot point 49. By virtue of the relatively free engagement between the pivot pin 91 and the flared end 39 of the lever, and the pivot point 40, the outer end of the lever beyond the twist 44 is moved in the same direction as the handle 32.

Assuming now that the handle 32 is pushed to the right from the position seen in Figure l to the position seen in Figure 4. The inner end of the lever 39 also moves to the right, and with reference to Figure 2 it will be seen that this lever then will push the upper end of the dog leg lever 24 and elevate the drive pulley H from the friction disk It, permitting the machine to be positively driven forward by engagement with the friction disk It with the drive wheel l8. Likewise, if the handle 32 is moved beyond center in the opposite direction, the lever 39 will push the upper end of the dog leg lever 29 and elevate the drive pulley l9 oil the friction disk Ii, permitting the machine to be positively driven in the reverse direction by virtue of the engagement of the friction disk It with the drive pulley l1.

Assuming now that the machine is operating forwardly, namely with the switch handle 32 in the position seen in Figure 4, and it is desired to reverse the direction of the machine, it is a simple expedient to move the handle 32 through the neutral position and throw it in the opposite direction. A sudden reversal of motion of the parts of the apparatus, it being realized that there are many more operating parts to the magnetic recorder than there are illustrated in the drawings, may result in injury to some part of the device. It is obviously desirable to stop or very nearly stop the operation of all moving parts before they are driven in the reverse direction, and obviously such stopping should not be by virtue of a suddenly applied reverse drive alone. To avoid any injury caused by sudden reverse driving action on the moving parts, and likewise to avoid any unnecessary winding of the recording medium I, my novel braking arrangement automatically comes into action upon a movement of the handle 32 to neutral position. It will be especially noted. however, that the instant the handle 92 and likewise the lever 39 reaches neutral position the spring 3| pulls both drive pulleys l1 and I8 into engagement with opposite portions of the friction disk 19. Consequently, there is an instantaneous braking action which very quickly, but nevertheless gently, slows all moving parts of the machine to a stop or very nearly to a stop before the drive pulley II is elevated away from the friction disk It to permit a positive drive through the drive pulley I! in a reverse direction. If the switch handle 92 is moved in a normal reasonable manner, there will be a dead stop of the moving parts by virtue of the braking action prior to any drive action in the reverse direction.

It will further be especially noted that the braking arrangement is so coupled with the driving arrangement that no extra parts whatever are needed to effect the braking action. Such action occurs automatically whenever the switch handle 32 reaches neutral position.

The switch arrangement governs the energizetion of the motor l4. With reference to Figures 3 and 4, it will be seen that a plurality of contact members, in the illustrated instance four, indicated by numerals 41, 49, 49 and 50, are carried by the insulation block 43 and project through both sides of the block. Each of these numbers has an inwardly turned outer end as indicated at I on member 41 so as to extend toward an adjacent switch arm. Two switch arms of the leaf spring type are provided, a switch arm 52 extending between contact members 41 and 4B, and another switch arm 53 extending between contact members 49 and 50. These switch arms are also carried by the insulation block 43 and project on both sides of the block. Each switch arm carries a contact stud 54 therein for abutment with either one of its respective pair of contact members. As indicated at 59, each of the switch arms is bent inwardly in the form of a lateral V to provide a flow between the switch arms of sufficient width to accommodate a roller 58 carried by the pivot stud 91 on the opposite gisde of the lug holding that stud from the lever It will be seen from Figure 3 that when the switch handle 32 is in neutral position the roller it rests between the flared end portions of the switch members -52 and 53 and both of these switch arms are out of contact with any of the contact members 41, 49, 49 and 50. The switch arms are held in that open circuit position by virtue of the roller 55 hearing against the upper end of these arms. The arms themselves are in the nature of leaf springs, and tend to move inwardly so that were it not for the roller 96 the switch arm 52 would always be in contact with the upper end of the contact member 48 and the switch arm 53 would always be in contact with the upper end of the contact member 49.

When the switch handle 32 is thrown in the position seen in Figure 4, the roller 56 forces the switch arm 53 into contact with the contact member 99, and leaves the switch arm 52 free to contact with the contact member 49, as clearly seen in Figure 4. If the switch handle 92 is thrown in the opposite direction, the switch arm 52 will be forced into contact with the member 41, and the switch arm 53 will be permitted by its own resiliency to contact the member 49. With reference to Figure 3, wherein a schematic wiring diagram is shown, it will be seen that the motor is connected to the switch arrangement with a pair of line conductors 51 and 5B which may lead from any suitable source of electrical energy. Line wire 59 is connected directly to a motor terminal by conductor 59. Line wire 51 is connected by a conductor 69 to the switch arm 52. A conductor 9| leads from the outer motor terminal to both contact members 41 and 48.

with the switch handle 32 in the forward position as seen in Figure 4, current may travel through conductor 60, the switch arm l2, contact member 48, conductor 6| to the motor, and out of the motor through conductor to line wire 88. When the switch handle 32 is thrown in the opposite direction, contact will be made between the switch arm 52 and the contact member 41, and the current will flow through conductor 60, the switch arm 52, contact member 41, conductor ll to the motor, and from the motor to line wire 58 through conductor 59. It will thereuponbe seen that the motor is operated at all times in the same direction regardless of which direction the switch handle 32 may be thrown.

It will also be noted from Figure 3 that the circuit through the motor I4 is closed by the switch arm 52 at about the same time that one or the other of the drive pulleys l1 and I8 is elevated ofl' the friction disk It. In other words, it is impossible to operate the motor I! more than an instant with both drive pulleys in contact with the friction disk 16. As soon as the handle 32 is moved sufficiently to establish contact between the switch arm 52 and either of the members 41 or III, one of the dog leg levers 24 and 28 must be pivoted so as to elevate its respective drive pulley by means of the lever 39 which will be operated in unison with the switch arm 52 by movement of the handle 32.

The magnetic recording deviceillustrated in the drawings preferably embodies a compound electrical circuit including a number of vacuum tubes in association with the recording and the loud speaker elements, not shown in the drawings. The use of such tubes necessitate a slight warming up period for the device before it is ready to either record or reproduce a previously made recording. It is not desirable, therefore, to have the moving parts, especially the reels 3 and 5, operating until the machine is ready for either recording or reproduction. Otherwise, a recording might be partially omitted, the reproduction partially omitted, and a definite wastage of recording medium 1 due to unnecessary windins. as well as a wastage of time. It is therefore desirable to prevent energization of the motor I until the tubes embodied in electrical circuit of the recording device are sufllciently hot to adequately perform their function.

To this end, means are provided to restore switch handle 32 to neutral circuit open position until the tubes in the magnetic recording device are sufllciently hot. These means include a transversely disposed lever 62 pivoted as at 63 to the end of the fixed cross bar 4| which projects beyond the frame 35. The pivot point is near but spaced inwardly from one end of the lever 82 as seen clearly in Figures 3 and 4. A tension spring '4 is anchored at one end to the projecting end of the lever 62, and at the upper end to a suitable anchoring member 55 attached to the frame 35. This tension spring tends to pivot the lever so that the larger portion on the opposite side of the pivot point 63 is thrown inwardly to the position seen in Figure 3. Such pivotal movement is limited by the engagement of a link lli pivoted at one end to the lever 62 as indicated at '1, and provided with an enlarged aperture 6| (Figure 3) adjacent its other end, through which aperture the aforesaid stud 31 projects. This aperture 8! is preferably considerably larger than the stud 11 so that there is play of the link I relative to the shank of the stud 31.

When the switch handle 32 is thrown from neutral position, the stud or pin 31 carries the end of the link It along therewith and consequently pivots the major portion of the lever 82 outwardly to the position seen in Figure 4. The lever 82 will assume the position seen in Figure 4 regardless of which direction the switch handle 32 may be thrown. Any movement of the switch handle 32 out of neutral position is, of course, in opposition to the action of the spring 54, and if there is nothing to hold the lever 82 in its pivoted position as seen in Figure 4, the spring 64 will promptly pivot the lever back to its position seen in Figure 3, and the link 68 by virtue of its engagement with the pin or stud II will promptly hold the switch handle 32 back to neutral position and prevent its remaining in either of its circuit closing positions.

Means are provided, however, to hold the lever 82 in its pivoted position as seen in Figure 4, so that the handle 32 may remain in either circuit closing position, and these means are directly responsive to the functioning of a vacuum tube associated with the magnetic recording device. Unless that tube is hot the holding means do not function.

With reference to Figure 2 it will be seen that the lever 82 is stepped downwardly as indicated at 89 so that the end of this lever projects into the short oscillatory path of a pivoted armature Hi responsive to the energization of a relay II supported on a bracket 12. This relay may be of any suitable construction, including a frame I3, the usual coil and iron core, with a portion of the frame 14 bent as seen in Figures 3 and 4 to limit the outward movement of the armature Ill when the relay is de-energized. This outward movement of the armature is caused by a spring 15 anchored at one end to a part of the frame and at the other to a projecting portion of the armature I0 which is pivotally associated with the frame.

The entire electrical circuit of the magnetic recording device is not necessary to be illustrated herein. Therefore, in Figure 3 that portion of the electrical circuit essential to the operation of this invention is diagrammatically illustrated in association with the mechanical parts.

The electrical circuit and apparatus includes a suitable power transformer T6 with the primary 11 thereof connected across the line wires 51 and 58. A secondary winding 18 in the transformer 16 is connected at opposite ends through conductors 19 and to the plate BI and 82 of a power tube 83 which, in the illustrated instance, is in the form of a full wave rectifying tube. A second secondary winding 84 is connected through conductor 85 to the cathode 86 of the tube ill from one end, and from the other end of this winding a conductor 81 leads to a terminal of the coil in relay ll. Of course, the cathode 86 is connected across the coil 84, such connection being completed by conductor 88 leading from the upper side of the cathode to the conductor 81. The other terminal on the coil of relay II is connected through conductor 89 to a load 80, which load in the illustrated instance is shown merely diagrammatically in the nature of a resistance, but in actual practice this load may be other electrical elements in a complete compound circuit of the magnetic recording device. A conductor 9| leads from the load Oil to a tap 92 on the secondary transformer winding 1!. A condenser is preferably connected between the conductors l1 and SI, and a choke coil 84 is provided in the conductor 81 to insure smooth and direct current reaching the relay.

The aforesaid switch arm 88 is connected through conductor 88 to conductor II, and a conductor 98 leads from the contact member 80 to recording apparatus so that when the circuit is closed between the switch arm 88 and the contact member 50 the recording apparatus is energized. This same circuit may provide energization also for a loud speaker system to reproduce a previous recording, and it is not necessary to show such circuit connections in connection with the instant invention. In similar fashion, a conductor 81 leads from the contact member 88 preferably to a speaker short arrangement, so that the loud speaker will be shorted out during rewinding of the recording medium I.

It will also be seen that when current is flowing through the line wires 81 and 58, and the power tube 88 or other tubes in the load 88 become sufilciently hot to perform its functions, the relay II will be energized and drive the armature 18 toward the relay coil, which will be to the left as seen in Figure 3. With all of the other apparatus in the position seen in Figure 3, the armature will abut the end of the lever 82 and not be able to reach the coil on the relay. After the power tube is heated and the relay is energized, a throwing of the switch handle 82 in either direction results in a pivotal movement of the lever 62 toward the panel 2, and this pivotal movement takes the lever out of the path of the relay armature Ill permitting this armature to engage the relay coil and fall in behind the end of the lever 62 to the position seen in Figure 4. Thus, the switch arrangement is held by the relay in closed position. It will be noted, as explained above, that the switch handle 82 cannot be leftin either forward or reverse position without the relay preventing the lever 52 from Jerking the switch handle 82 back to neutral position by virtue of the action of the spring 84. In this way, it is impossible in ordinary operation to energize the apparatus and cause a travel of the recording medium 1 before the magnetic recording device is capable of performin a recording or reproducing function.

Another feature of the operation of the mechanism embodied in this invention should be especially noted. As long as the power tube 88 is energized, the relay will be energized and the amature Ill will be held over in the position seen in Figure 4 after the switch handle 82 has once been thrown in either direction. Now, even though the lever 62 is held in its pivoted position by the relay armature 10, the switch handle 82 may be moved to neutral position and thrown in the opposite direction without disturbing the lever 82. This movement of the handle 82 is enabled by virtue of the flared head portion 88 of the lever 89. and also by virtue of the enlarged aperture 88 in the lever 66, this aperture being sufllciently large to permit relative movement between itself and the inner stud 31 on the end of the lever 82 sufliciently for the lever to be thrown completely in either direction, regardless of the fact that the lever 82 is held by the relay in pivoted position. By virtue of the inclined edge surfaces 46 on the lever head 88 and by the pressure exerted on the roller 58 by the switch arms 82 and 53, the switch handle 82 will remain in either operating position until it is manually moved through neutral position to the other operating position.

For a short rsum of the operation of the presout invention, let it be assumed that it is desired to start the magnetic recording device and move the recording medium I in the forward direction for the purpose of taking a recording. Line wires 81 and 88 may be energized by the throwing of any suitable master switch. The switch handle 82 may then be moved from neutral position to the position seen in Figure 4, but if sumcient time has not elapsed for the power tube 88 or other tubes in the load 88 to become hot. the relay II will not be energized, and the action of the control lever 82 will immediately throw the switch handle 82 back to neutral position and prevent operation. However, if sufllcient time has elapsed for the vacuum tubes to become hot, the relay will lock the lever 82 in its pivoted position. as seen in Figure 4, and the mechanism will operate forwardly.

After a suitable recording has been made, it may be desirable to listen back to the recording. To this end, the switch arm 82 is then moved to neutral position and thence onwardly to reverse position opposite to that seen in Figure 4. This movement may be accomplished, as above explained, despite the fact that the lever 82 is still being held in pivoted position by the relay armature.

It should be noted, however, that as the handle 82 is moved from the position in Figure 4 to the opposite position for reverse winding, that handle will, by virtue of the notch 45 in the head of the lever 89, hesitate in neutral position if it is reasonably actuated by the operator, and if the operator moves the lever with excess rapidity, nevertheless the lever must pass through neutral position. At the time the lever reaches neutral position the springs 8i pull both drive pulleys i1 and I8 into contact with the friction disk l6 and the automatic brake action takes effect almost instantaneously to rapidly but gently slow down the moving parts, so there will be no injurious jerk when the parts start moving in the reverse direction. Likewise, there will be no material winding of the recording element 1 in the forward direction due to momentum. if the handle 82 is moved very slowly from forward position to reverse position.

If after rewinding has been accomplished, it is desired to listen to the rewound recording, it is a simple expedient to again move the switch handle 32 to forward position, and again as the handle reaches intermediate position the automatic braking action takes effect and the parts are slowed down so that any injurious jerk is eliminated, and the machine may be operated forwardly to reproduce the recording. The forward motion, likewise, may be made despite the fact that the relay armature is still holding the lever 82 in pivoted position.

It should be further noted that if at the end of a forward or reverse of the recording medium I, the source of power to the machine is cut off by opening the circuit through line wires 51 and 58, the relay will automatically become deenergized. Therefore, if the handle 82 has been locked in either forward or reverse position, that handle will be immediately shaped back to neutral position by the action of the relay armature and the lever 62, the automatic braking action will at once take effect, and only a negligible amount of the wire I will move after the circuit has been broken.

From the foregoing, it is apparent that I have provided novel safety mechanism for use in a device having operating parts in general like those 11- of a magnetic recording device, as well as other devices wherein reverse motion may frequently be desired. The mechanism effectively prevents operation of the entire device before that device is ready to perform its function by virtue of the heating of tubes or for some other reason. It should be noted that upon failure of the line voltage for any reason the switch is returned to neutral position and the automatic braking action become effective at once. The mechanism also provides an instantaneous braking action whenever the device is stopped or whenever it is desired to reverse direction. No extra parts are utilized in order to afford that braking action. The mechanism also includes a novel arrangement between switch means and drive means operating in conjunction to provide the braking action, and to prevent any movement of the apparatus prior to the time when the apparatus is ready to perform its functions. It will further be noted that the invention is simple in construction, economical. highly durable, positive in its action, and may be manipulated with extreme facility.

It will. of course, be understood that various details of construction may be varied through a wide range without departing from the principles of this invention, and it is, therefore, not the purpose to limit the patent granted hereon otherwise than necessitated by the scope of the appended claims.

I claim as my invention:

1. In a device having movable parts operable both in forward and reverse directions and embodying an electrical circuit, a vacuum tube in said electrical circuit, means for driving said parts, a control handle movable to cause operation of said means, resilient means tending to hold said control handle in inoperative position, and mechanism directly responsive to current flow through said tube for holding said handle in operative position against the action of said resilient means.

2. In a device having movable parts operable both in forward and reverse directions, a driving arrangement for forward movement. a drivins arrangement for reverse movement, a main drive for actuating both said arrangements, means urging both said arrangements toward engagement with said main drive at all times, and a double-throw lever for selectively moving either of said arrangements out of engagement with said main drive against the action of said means.

3. In a device having movable parts operable both in forward and reverse directions, a main drive, a,forwa-rd driving arrangement, a reverse driving arrangement, a double-throw control to selectively cause operation of either drive arrangement by said main drive, and means arranged to automatically bring both said arrangements into operative connection with said main drive whenever said control reaches neutral position.

4. In a device having a pair of spaced reels with an elongated member therebetween to be wound from one to the other in either direction, a main drive member, a forward drive member operatively connected with said reels, a reverse drive member operatively connected with said reels, 9. control element arranged to selectively cause operation of either the forward or reverse drive members by said main drive member. and resilient means constantly and automatically urging both the forward and reverse drive members toward engagement with said main drive member at all times, said resilient means becom- 12 ing fully effective to establish engagement between said forward and reverse drive members with the main drive member when said control element reaches neutral position.

5. In a magnetic recording device wherein a recording medium travels in either direction between a pair of spaced reels, a friction drive member, a forward drive member operatively connected to actuate said reels and move the recordin medium forwardly, a reverse drive member arranged to actuate the reels in the opposite direction, resilient means constantly urging both said forward and reverse drive members into engagement with said friction drive member, and a control element arranged to selectively move either of said forward or reverse drive members out of engagement with said friction drive against the action of said resilient means.

6. In a magnetic recording device wherein a recording medium travels in either direction between a pair of spaced reels, a friction drive member, a forward drive member operativcly connected to actuate said reels and move the recordin medium forwardly, a reverse drive member arranged to actuate the reels in the opposite direction, resilient means constantly urging both said forward and reverse drive members into engagement with said friction drive member, acontrol element arranged to selectively move either of said forward or reverse drive members out of engagement with said friction drive against the action of said resilient means, an electrical circuit including a vacuum tube governing the entire operation of the recording device, means constantly tending to hold said control element in neutral or inoperative position, and holding means directly responsive to current flow through said tube to lock said control element in either operative position.

'7. In a magnetic recording device wherein a recording medium travels in either direction between a pair of spaced reels, a friction drive member, a pair of drive pulleys engageable with said friction drive member, one of said pulleys being connected to actuate the reels in one direction and the other pulley being connected to actuate the reels in the opposite direction, resilient means connecting said pulleys and constantly urging both pulleys into engagement with said drive member, and a control element arranged to selectively move either pulley out of engagement with said drive member against the action of said resilient means.

8. In a device having movable parts operated by an electric motor and including a circuit involving a vacuum tube. a control handle for governing the energization of said motor, means tending to hold said handle in inoperative position, and holding mechanism directly responsive to ourrent'flow through said tube for locking said handle in operative position against the action of said means.

9. In a device having operating parts controlled by an electrical circuit including a vacuum tube, a drive motor, a switch member for controlling the energization of said motor, means tending to hold said switch member in inoperative position, and a relay lock in said circuit directly responsive to current flow through said tube to hold said switch in circuit closing position against the action of said means.

10. In a device having movable parts operable in both forward and reverse directions and controlled by an electrical circuit including a vacuum tube, driving mechanism, a switch arrange- 13 ment of the double-throw type to selectively operate the driving mechanism for forward o reverse operation, means associated with said switch arrangement tending at all times to hold the 13. In a device embodying movable parts operable both in forward and reverse directions and having an electrical control circuit including a vacuum tube, driving mechanism operable in switch arrangement in neutral position, and an either forward or reverse directions, a braking electrical holding device directly energizable by arrangement, tending at all times to prevent opcurrent flow through said vacuum tube to hold eration of said driving mechanism, control means said switch arrangement in either operative poto negative the braking arrangement, and elecsition against the action of said means. trical means responsive to current flow through 11. In a device having movable parts operasaid tube arranged to prevent eifectlve operation ble in both forward and reverse directions and of said control means until such current how is controlled by an electrical circuit including a vacestablished. uum tube, driving mechanism, a switch arrange- 14. In a magnetic recording device, a pair of ment of the double-throw type to selectively opspaced reels, a recording medium on said reels, erate the driving mechanism for forward or re- 15 means including an electrical circuit embodying verse operation, means associated with said switch an element which must first become heated bearrangement tending at all times to hold the fore operating efficiently for magnetizing said switch arrangement in neutral position, an elecmedium, drive means for said reels, 3, control trical holding device directly energizable by curmember to Cause actuation of S d v me ns. rent flow through said vacuum tube to hold said means tending 0 hold d Co l member at switch arrangement in either operative position 115 6 in inoperative Position, and an Electrical against the action of said means, and the conholding d e responsive to said element when nection between said switch arrangement and heated efllcienb Op n to 106k a d 00nsaid means being such that the switch arrangel member n op ra v p t n a t he ment may be thrown in the opposite direction 5 action of the Se ond Said means. while said holding device remains in effective In mflgnetic recording device. 8- p r operation. spaced reels carrying an elongated recording me- 12. In a device having movable parts operable dium Which y travel f 0116 l to the in both forward and reverse directions and conother n either direction. drive me s to actuate trolled by an electrical circuit i cl din avaeuum said reels in either direction, a movable control tube, driving mechanism, a double-throw control for governing t Operation f d drive means. handle, a pivoted switching lever h ifi a flared restraining means tending to hold said control end for loose engagement with said handle to be n inOpBmtlVe Position, means t effect a doperated thereby to govern the operation of said g on said medium includin n electrical driving mechanism in either direction, a spring ul a vacuum tube in said circuit. and holding urged member tending at all times to hold said means responsive t curr nt fl w hro h said control handle in neutral position, and an electrivacuum tube t lock said control in pe at ve cal holding device energizable by current flow position against the action of d st a n n through said tube to lock said spring urged 'memmeansber in inoperative position to permit said handle 40 MARVIN CAMRAS- to be thrown in either direction and reversed while said holding device remains in effective operation Disclaimer 2,412,318.-Mom'n 00mm, Chicago, Ill. Sum! D ncnsmsn ron Mmrm'ric Rnconnmo DEVICES.

1946. Disclaimer filed Mar.

Foundation Illinois Imh'mta of Hereby enters this disclaimer to claims 9, i4 and 15 of said patent.

[Wim'al Gazelle May 4, 1948.]

ms, Bnnmo, AND Comm.

th Patent dated Dec. 10,

Twh I 3 68, Research 13 ment of the double-throw type to selectively operate the driving mechanism for forward o reverse operation, means associated with said switch arrangement tending at all times to hold the 13. In a device embodying movable parts operable both in forward and reverse directions and having an electrical control circuit including a vacuum tube, driving mechanism operable in switch arrangement in neutral position, and an either forward or reverse directions, a braking electrical holding device directly energizable by arrangement, tending at all times to prevent opcurrent flow through said vacuum tube to hold eration of said driving mechanism, control means said switch arrangement in either operative poto negative the braking arrangement, and elecsition against the action of said means. trical means responsive to current flow through 11. In a device having movable parts operasaid tube arranged to prevent eifectlve operation ble in both forward and reverse directions and of said control means until such current how is controlled by an electrical circuit including a vacestablished. uum tube, driving mechanism, a switch arrange- 14. In a magnetic recording device, a pair of ment of the double-throw type to selectively opspaced reels, a recording medium on said reels, erate the driving mechanism for forward or re- 15 means including an electrical circuit embodying verse operation, means associated with said switch an element which must first become heated bearrangement tending at all times to hold the fore operating efficiently for magnetizing said switch arrangement in neutral position, an elecmedium, drive means for said reels, 3, control trical holding device directly energizable by curmember to Cause actuation of S d v me ns. rent flow through said vacuum tube to hold said means tending 0 hold d Co l member at switch arrangement in either operative position 115 6 in inoperative Position, and an Electrical against the action of said means, and the conholding d e responsive to said element when nection between said switch arrangement and heated efllcienb Op n to 106k a d 00nsaid means being such that the switch arrangel member n op ra v p t n a t he ment may be thrown in the opposite direction 5 action of the Se ond Said means. while said holding device remains in effective In mflgnetic recording device. 8- p r operation. spaced reels carrying an elongated recording me- 12. In a device having movable parts operable dium Which y travel f 0116 l to the in both forward and reverse directions and conother n either direction. drive me s to actuate trolled by an electrical circuit i cl din avaeuum said reels in either direction, a movable control tube, driving mechanism, a double-throw control for governing t Operation f d drive means. handle, a pivoted switching lever h ifi a flared restraining means tending to hold said control end for loose engagement with said handle to be n inOpBmtlVe Position, means t effect a doperated thereby to govern the operation of said g on said medium includin n electrical driving mechanism in either direction, a spring ul a vacuum tube in said circuit. and holding urged member tending at all times to hold said means responsive t curr nt fl w hro h said control handle in neutral position, and an electrivacuum tube t lock said control in pe at ve cal holding device energizable by current flow position against the action of d st a n n through said tube to lock said spring urged 'memmeansber in inoperative position to permit said handle 40 MARVIN CAMRAS- to be thrown in either direction and reversed while said holding device remains in effective operation Disclaimer 2,412,318.-Mom'n 00mm, Chicago, Ill. Sum! D ncnsmsn ron Mmrm'ric Rnconnmo DEVICES.

1946. Disclaimer filed Mar.

Foundation Illinois Imh'mta of Hereby enters this disclaimer to claims 9, i4 and 15 of said patent.

[Wim'al Gazelle May 4, 1948.]

ms, Bnnmo, AND Comm.

th Patent dated Dec. 10,

Twh I 3 68, Research

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