US2127593A - Phonograph - Google Patents

Description

1933- -H. F. M. GRAMAN'N PHONOGRAPH Fild June 16, 1953 Q Sheets-Sheet 1 E MAX GRAMAAW Gttomeg Aug. 23, 1938.

H. F. M. GRAMANN PHONOGRAP H Filed June 16, 1933 HEINRICH EMAx GRAMANN (Ittomeg Aug. 23, 1938. H. F. M. GRAMANN PHONOGRAPH Filed June 16, 1933 3 Sheets-Sheet 5 Heme/cu l2" MAX GRAMA NN (Ittomeg Patented Aug. 23, 1938 UNITED STATES PHONOGRAPH Heinrich F. Max Gramann, Orange, N. J., as-

signor to Thomas A. Edison, Incorporated,

West Orange, Jersey N. .L, a corporation of New Application June 16, 1933, Serial No. 676,037

2 Claims.

This invention relates to phonographs and more particularly to phonographs of the business or commercial type, which are adapted to record as well as to reproduce dictation. This invention is especially directed to a novel and improved construction for back-spacing the arm or carriage which carries the recording and reproducing mechanism so as to cause repetition of any portion of the record whenever the operator of the machine so desires.

Phonographs designed for both recording and reproducing dictation are now generally so constructed and arranged that the carriage for the recording and reproducing mechanism may at any time be manually moved or spaced back with respect to the record tablet, so .as to reproduce previously recorded matter on said tablet. When a dictator, using such a phonograph for recording dictation, desires to reproduce previously dictated matter, it is necessary-first, to manually readjust the recording and reproducing mechanism to neutral position; second, to move the carriage backwardly along the record tablet a distance depending upon the amount of matter to be reproduced; and third, to set the recording and reproducing mechanism in reproducing position. The apparatus is then in condition for reproducing and the dictator may listen to the recorded matter. When the reproduction of such matter has been completed and it is desired to dictate further, it is necessary for the dictator to again manipulate the recording and reproducing mechanism to return it to the recording position. Such manipulations incident to a repeating operation in the normal use of dictating machines are distracting in addition to requiring considerable of the dictators time. Dictators may often neglect to' recondition the recording and reproducing mechanism for recording after completing reproduction and in consequence they proceed to dictate while the reproducing stylus remains in engagement with the record tablet with the result that no recording is obtained. Warning signals have been provided to warn the dictator under these circumstances, but such signals are frequently ineffective because of the concentration of the dictator on the subject of the dictation.

The primary object of this invention is to provide a novel and eifective back-spacing construction or mechanism, easily adaptable to the above described type of phonograph or dictating machine, and by which the back-spacing of the recorder-reproducer may be easily and quickly effected with'out distractive manipulation on the part of the dictator.

production of the matter recorded within the 10 v back-spaced area has been effected.

A still further object of this invention is to provide a mechanism for the purposes stated above, which can be controlled from a point remote from the phonograph proper. V

Further objects and features of my invention will be d sclosed in the following specification and appended claims.

For a clearer understanding of my invention, attention is directed to the drawings, accompany- 2o ing and forming part of this specification, wherein:

Figure 1 is a front elevation of a phonograph having a preferred embodiment of my invention applied thereto;

Fig. 2 is a top plan view partly broken away, of the phonograph of Fig. 1; I

Fig. 3 is an enlarged side elevational view, partly in section of the carriage and associated parts of the phonograph of Fig. 1, the recording and 30 reproducing mechanism being positioned for recording;

Fig. 3A is a further enlarged plan view, partly in section, of the mechanism at the rear right comer of the carriage as seen from above;

Fig. 4 is a view of the mechanism of Fig. 3 as seen from below;

Fig. 5 is a fragmental view of the mechanism carried by the carriage in the position occupied immediately after a back-spacing movement has 40 been effected;

Fig. 6 is a sectional view taken substantially on the line 6-6 of Fig. 5;

Fig. 7 is a rear elevational view, partly in section, of the carriage shown in Fig. 3;

Fig. 8 is a fragmental view of the rear portion of the carriage taken from the left-hand side as seen in Fig. 1;

Fig.9 is a cross sectional view showing in detail the feed wheel of the phonograph of Fig. 1 and its support;

Fig. 10 is an elevational view, partly in section, showing the mouthpiece of the dictating machine including the means for remotely controlling the pperation of my improved back-spacing mechanism; the electrical circuit employed to .control said mechanism being shown schematically;

Fig. 11 is a plan view of the mouthpiece of Fig. 10 as seen from above;

Fig. 12 is a section taken on line |2|2 of Fig. 11; and

Fig. 13 isan elevation, partly in section and with parts omitted, of the rear portion of the carriage and associated mechanism.

The phonograph is of well known construction and comprises a base 4 having upright standards 3, 1 and 1'. A mandrel for supporting a record tablet A is carried by a shaft 2 joumaled in the standard 3. The mandrel shaft 2 is connected through a suitable clutch 9, I0 to a drive pulley 5 which in turn is connected by a belt 8 to a driving motor (not shown). A feed screw 20, driven from the mandrel shaft by gears 22, 23 is provided for moving a carriage |3 transversely of the record tablet A. A pair of guide rods I1, l8 supported by the standards 1, 1' are provided for slidably supporting the carriage I3. Guide rods I1 and I8 are supported in the standards 1 and 1' so that they are freely rotatable,- but are restrained against longitudinal movement.

The carriage l3 supports a sound box l4 and control mechanism for shifting the sound box into recording, reproducing or neutral position by actuation of a control lever 65. The sound box and control mechanism therefor are of well known construction and are substantially the same as those described in detail in U. S. Patent to N. H. Holland, No. 1,420,316, entitled Phonographs and issued June 20, 1922. The sound box comprises a frame 32 having a downwardly extending lug 39 to which is pivotally secured a casing 42 having a sound chamber and a diaphragm 4|. The frame 32 comprises a neck 33 for attachment of an elbow 34 forming the end of a flexible speaking tube 35. Connection is made between neck 33 and the easing 42 by means of a sliding tube 45. The casing 42 is provided with a tab 42 for coaction with the control mechanism. A stirrup 55 is secured to the diaphragm 4| and carries a recording stylus 56. A floating weight 48 positioned below the casing 42 is likewise pivotally secured to the lug 39. The floating weight 48 is provided with a central hole 4| through which the recording stylus 56 and the stirrup 55 may pass. An advance ball 80, which may be made of sapphire and which has a spherical surface preferably of a radius large in comparison with the radius of the recording and reproducing styli, is provided on the floating weight for coaction with the record under certain conditions. The floating weight also carries a reproducing stylus arm 58 pivotally secured at 60 and carrying a reproducing stylus 59. The end of the stylus arm 58 opposite to that carrying the stylus, lies at all times within the stirrup 55. The floating weight 48 is also provided with a tab 48 for coaction with the control mechanism.

The control mechanism comprises a pair of lifting dogs 1| and 12 arranged for rotary movement around the guide rod i1. When the control lever is shifted to the forward or recording position (Fig. 3) both of the lifting dogs.1| and 12 are moved in a counterclockwise direction until they are entirely clear of the tabs 48' and 42' with which they respectively coact. Under these conditions the floating weight 48 will move downwardly until the advance ball 80 contacts the record surface and the casing 42 will likewise move downwardly until the recording stylus 56 is also in contact with the record surface. The advance ball 80 contacts the record surface somewhat in advance of the recording stylus 56 and in consequence, when the mandrel is rotated to cause the recording stylus to cut a phonographic groove in the surface of the record tablet, the advance ball rides on the uncut portion of the record tablet in advance of said stylus. If sound waves impinge upon the diaphragm 4|, the depth of the engraving will be varied in accordance therewith and a phonographic record will be made.

When the control arm 65 is shifted to the neutral position both the lifting dogs 1| and 12 are rotated in a clockwise direction and coact with their respective tabs 48 and 42' to lift both the floating weight 48 and casing 42 and also the styli 56 and 59 entirely clear of the record.

When the control arm 65 is moved to its rear or reproducing position, the lifting dog 12 remains in its upper position thus holding the casing 42 against the frame 32 as in the neutral position. The lifting dog 1| however is then again rotated downwardly or in a counterclockwise direction and thereby allows the floating weight to move downwardly away from the casing 42. Under these circumstances the rear end of the reproducer stylus arm 58 is held within the stirrup 55 and as a result the reproducing stylus arm 58 is rotated in a counterclockwise direction so that the reproducing stylus 59 will engage the record grooves. When such contact occurs, the advance ball is out of contact with the record surface and the mass of the floating weight serves to bias the reproducer stylus into its record engaging position. As the mandrel is rotated the stylus is vibrated by the record groove and this vibration is transmitted by the arm 58 to the stirrup 55 and consequently to the diaphragm 4|, thereby producing sounds corresponding to the engraving on the record. The mechanism whereby the prescribed motions of the lifting dogs 1| and 12 are attained is described in the above mentioned Holland patent and is not therefore described herein. The recording and reproducing mechanism is shown in reproducing position in Fig. 5.

The feeding and back-spacing mechanism, with the exception of the feed screw 20, is mounted on the rear portion of the carriage |3. The construction of the back-spacing and feeding mechanism is identical with that described in my copending application Serial No. 375,367, filed July 2, 1929. The carriage l3 at its rear end is in the form of a hollow channel having side walls 90 and 9| and a boss 93. A tube 94 having an internal diameter of the proper size to receive the rear guide rod I8 is fitted into suitable holes in the boss 93 and in the side wall 9| and is secured against movement therein. The tube 94 extends entirely across the space intervening the side walls of the carriage l3 and forms a pivotal mounting for a U-shaped member comprising a rear portion 96 and two side arms 4 and H5. The lower portion of the member 96 is bent inwardly (see Fig. 8) to form a mounting bracket 96'. Mounting bracket 96' is drilled to receive a threaded portion of a shouldered stud 91 which is secured to the bracket by a nut I04. A tubular member 98 comprising a Worm gear 99 and having a gear wheel 2| fixed thereto, is rotatably mounted on the stud 91 and is held against longitudinal movement thereon by a screw ||l| (see Fig. 9). The gear wheel 2| is arranged for engagement with the feed screw 20 and acts under certain conditions as a feed nut. A leaf spring 1 adjustably secured to the side-wall 9| of the carriage coacts with a pin 6 secured in the side arms 4 and I15 to bias the gear wheel 2| into engagement with the feed screw 20. The worm gear 89 meshes with a worm I rotatably mounted on the tube 84. By reason of the frictional resistance in the worm and gear connection, the gear wheel 2| is locked against movement and thereby serves in the same fashion as the more uspal form of feed nut when' the carriage is being fed across the record by the feed screw. A ratchet wheel III is secured concentrically to the worm I00. Adjacent the ratchet wheel I II a cam I is mounted for rotation on the tube 94. A pawl I08 is pivotally mounted on the cam I05 and is biased into engagement with the ratchet wheel I I I by means of a coil spring H0. The cam I05 carries an inwardly extending pin I06 which passes through a short circumferential opening I0'I in the tube 94 and into a longitudinal slot I06 in the rear guide rod I8. Adjacent the standard I (see Figs. 1 and 2) the back rod I8 is provided with an arm I24 to the outer end of which a connecting lever I23 is rotatably fastened. The opposite end of the connecting lever I23 is secured to an armature I22 designed to coact with a magnet coil I2I. When the magnet I2I is energized the armature I22 will be drawn upwardly opposite the core of the magnet which will cause a rotary motion to be imparted to the back rod I8. When such rotary motion occurs, the cam I05 will be rotated because of the engagement of pin I06 in slot I06 and the worm I00 will simultaneously be rotated by reason of the engagement of the pawl I08 with the ratchet wheel III. Such rotation of the worm I00 will cause the worm gear 99 and the gear wheel 2| to be rotated and a back-spacing motion of limited extent is thereby imparted to the carriage, the feed screw then acting as a rack and the gear wheel 2| as a pinion. When the magnet coil I2I is de-energized, the armature I22 drops down, thus restoring the cam I05 to its original position. The pawl I08 slides back over the ratchet III, leaving the worm in the position to which it was moved during the back-spacing operation. If a back-spacing motion of greater extent is desired, the magnet coil I2I may be suc cessively energized and de-energized, thus imparting a step by step back-spacing motion to the carriage which may be continued to accomplish any desired extent of backward movement.

The parts of the mechanism thus far described are each separately old in the art. It will be seen that the mechanism provides manual control for the positioning of the recording and reproducing mechanism, as well as means whereby the carriage may be back-spaced. In order to throw the gear wheel 2| out of engagement with the feed screw 20 when the control lever 65 is moved into the neutral position wherein the carriage I3 should be freely movable along the guide rods, a plunger 8| having a rounded head 84 is provided for coaction with a roller 84 (see Fig. 3). When the lever 65 is moved to neutral position the roller 84' pushes the plunger 8| backwardly. A push rod 8| secured to the plunger 8| coacts with the upper end of the rear portion 96 of the U-shaped member which carries the feed wheel 2| and its associated parts. It will be seen that when the plunger 8| moves backwardly under the influence of the roller 84', the portion 96 and consequently the feed wheel 2| will be rotated in a clockwise direction around therear guide rod I8 and against the tension of the spring I II, thus serving to disengage the gear wheel 2| from the feed nut 20. When the control lever is in either the recording or reproducing position the spring II'I moves the plunger 8| forward and causes the gear wheel 2| toengage the feed screw 20.

In order to make the operation of this mechanism automatic it is essential that when a backspacing operation is performed the recorder and reproducer mechanism be simultaneously thrown into reproducing condition. In order to accomplish this an auxiliary lifting dog I 36 having a projecting nose I 31 is pivotally mounted adjacent the lifting clog I2 in such a way that the projecting nose may also coact with the tab 42' on the casing 42 (see Figs. 3, 4 and 5). The lifting dog I36 is freely rotatable and may be moved independently of the lifting dog 12. A pin I35 is arranged for coaction with a suitable shoulder on the lifting dog I36. The pin I35 is secured to a disk I35 concentric with the lifting dog I36 and is similarly mounted for rotation within a boss I5 on the carriage I3. A coil spring I40 connected between the disk I35 and the outer wall of the boss I5 serves to bias the disc and consequently the pin I35 to a point where the nose I31 of the lifting cam I36 is below and clear of the lifting tab 42'. A connecting rod I3I is pivotally secured to the pin I35 by a suitably drilled U-shaped member I34. The connecting rod |3I passes to the rear of the carriage and is supported in a bearing formed in an L-shaped bracket I4I secured to the inner side of wall 90 of the carriage. The rear end of the connecting rod I3I is arranged for coaction with a top portion I30 of a bail having side arms I28 and I29. The ball is pivoted on one side by a pivot screw I25 passing through the arm I28 and secured in the arm H4, and on the other side by a short shouldered stud I26 passing through the arm I28 and secured in the arm II5. A screw I50 threaded in the stud I26 holds the arm I29 in place. A coil spring I33 around the pivot screw I25 biases the bail toward the rear of the carriage. The arm I28 of the bail is provided with a roller I32 for coaction with the nose of the cam I 05. It will therefore be seen that when the back-spacing mechanism is operated and the cam I05 rotated, a forward motion will be imparted to the bail which will in turn strike the end of the connecting rod I3I and move the auxiliary lifting dog I36 in a clockwise direction thus lifting the casing 42 upwardly and conditioning the recorder-reproducer mechanism for reproducing (see Fig. 5).

However as soon as the back-spacing mechanism returns to its normal position the recorderreproducer mechanism would likewise tend to return to the recording position. In order to maintain the mechanism in reproducing position, the connecting rod I3I is provided with a notch I3I' for coaction with a latching pawl I42. The pawl I42 is pivoted on the L-shaped bracket MI by a shoulder screw I43 and is biased into contact with the connecting rod I3I by a coil spring I44.

As soon as the connecting rod I3I has been moved forward during a back-spacing movement, the latching pawl I42 falls into the notch I3I' and retains the connecting rod I 3| in its forward position and thus maintains the sound box in its reproducing position.

The latching pawl I42 has a lower extended portion I45 which in normal operation abuts against a pin I46 carried by a marker plate I41. The marker plate M1 is supported on the back rod I8 adjacent the carriage I3. It is provided with an enlarged collar I48 carrying a pin I5| for engagement with the slot I06 in the back rod -I8 whereby it is maintained correctly positioned. It is also provided with a suitable frictioning device comprising an adjustable spring I49 and a plunger I49 housed in a well in the collar I48. When the carriage is in the recording position and is moving forward normally the marker plate is pushed along by the side wall 9| of the carriage. By reason of the contact between the pin I46 and the lower end I45 of the latching pawl, the marker plate maintains the upper or latching end of the pawl I42 completely out of contact with the rod I3I. However, when a back-spacing motion is imparted to the carriage the marker mechanism is not moved backwardly with the carriage and as a result the latching pawl is then free to fall into the notch I3I and thereby to maintain the recording and reproducing mechanism in reproducing condition. When all of the recorded matter has been reproduced, the lower end of the latching pawl I42 will again engage the pin I46 and, upon slightly further advance of the carriage, will withdraw the latching pawl from the notch I3I and allow the connecting rod I3I to move backwardly under the urging of the coil spring I40. The casing 42 will thereupon be released and will drop down until the recording stylus 56 again engages the record and conditions the machine for recording.

In the mechanism just described it will be seen that the recording and reproducing mechanism is returned to recording condition at substantially the same point along the record as that at which the back-spacing motion was started. Such an arrangement might result at times in cutting out a small portion of the groove already recorded or might shift the recording and reproducing mechanism into recording position before the reproduction had been entirely completed. For this reason it is preferable to allow a slight space to intervene before the recording and reproducing mechanism is again conditioned for recording. In order to accomplish this, the stud I26 on which the arm I29 is pivoted is provided with a camming surface I52 on its outward end. A member having a complementary camming surface I53 is secured to the marker plate I41 by a screw I50. It will therefore be seen that whenever a back-spacing movement is imparted to the carriage, and the marker plate I41 is rotated upwardly by reason of its pin and slot connection with the back rod I8, the marker plate will be cammed to a position slightly in advance of the farthest point of advance of the carriage. Under these conditions when the carriage again moves up to the marker plate and the recording and reproducing mechanism is again conditioned for recording by coaction of the marker plate with the pin I46, there will be a slight gap left between the finish of the previous recording and the start of the succeeding recording.

The .mechanism above described is available for operation as described as long as the dictation is continued, providing means for repeating .and subsequently restoring the mechanism to recording condition whenever desired. However whenever a cylinder is removed from the mandrel and a new cylinder placed thereon it is necessary to move the control lever 65 into the neutral position and to move the entire carriage backwardly toward the starting position. Under these circumstances it is necessary to also retract the marker plate I41 so that it will always be available in connection with the operation of repeating portions of the dictated matter. In order to insure the return of the marker plate I41 with the carriage, a bracket I69 carrying a pawl I58 pivoted on a screw I59, is secured to the mounting bracket 96'. When the control lever 65 is in recording position the pawl I58 is clear of the marker plate I4'I (see Fig. 3) and the relative movement of the carriage and the' marker plate is not restricted. However, as soon as the control lever 65 is thrown into neutral position wherein the mounting bracket 96 and the feed screw are rotated about the guide rod I8 in a clockwise direction as seen in Fig. 3, the pawl I58 will be moved inwardly and over the plate I41 as shown in Fig. 3A, so that if the carriage is retracted it will serve to carry the marker plate I4'I along. As soon as the control lever is again moved in the recording position the pawl I58 is again moved out of the way of the marker plate. A spring IIiI serves to bias pawl I58 to the operative position shown and also permits the pawl to ride over the plate M1 in the event said pawl should be positioned rearwardly thereof by reason of improper operation of the machine and the carriage should then be advanced, with the arm 65 set in neutral, for the purpose of restoring said pawl to its normal position in advance of plate In the construction shown the feed wheel 2| is held against rotation under normal operating conditions by the frictional engagement of the worm wheel 99 with the worm I00. However under some circumstances there may be a certain amount of back-lash or lost motion in the connection of the feed wheel to the carriage and this is very undesirable during the recording operation when it is essential to have the groove engraved upon the record tablet very accurately. For this reason it may be desirable to provide a frictional braking mechanism which will prevent any such lost motion. Such a braking mechanism may comprise a pulley I mounted on the sleeve 98 which carries the gear wheel 2|. A brake band I99 is secured at one end to a pin I92 fixed in bracket 96 andencircles the brake drum I90. The brake band I99 is secured atits other end to another pin I93 fixed in a plate I94 rotatably mounted on the sleeve 98 adjacent the brake drum I90. The plate I94 has a short extending arm I95 adapted to cooperate with a short arm I95 of a bell crank I9! (see Figs. 4, 7 and 8). Bell crank I9? is pivoted on a pin I98 carried by a bracket I99 secured to the mounting bracket 96. The long arm of the bell crank is provided with a short finger 292 adapted to bear against the peripheral surface 203 of the cam I05. The shape of the cam is such that when the mechanism is in normal operating condition a considerable tension is maintained on the spring band I99 thus preventing any play or lost motion of the gear wheel 2I. However as soon as a back-spacing motion ,is initiated, the cam I05 moves a slight distance and recedes from finger 202 to release the tension upon the spring band I90 so that the gear wheel 2I is free to roll along the feed screw and thus cause the backspacing movement described above.

The speaking tube comprising the flexible tube 35 serves as a sound conduit and is terminated in a mouthpiece 36. The mouthpiece preferably of moulded insulating material, is provided with a clutch controlling switch which comprises a switch box I89 and a cover I83 therefor, the cover being pivoted by a screw and bushing I84. The switch cover is normally biased outwardly and when in this position the clutch is disengaged. Upon pressing the switch cover I 83 downwardly the clutch is engaged and the mandrel ro- 75 tated. The construction of the clutch and clutch controlling mechanism is of itself no part of this invention and may be of the type described in Patent No. 1,380,486, to S. G. Langley, dated June 7, 1921, and entitled Controlling device.

In addition to the clutch controlling switch, a second switch is provided within a casing I10 on the speaking tube for controlling the repeating mechanism described herein. This switch comprises a finger-piece "I of insulating material pivoted in the casing I10 by pins I12. Fingerpiece I'll carries a metallic connecting arm I11 adapted, when the finger-piece IN is rocked in either direction to make contact and establish a circuit between a pair of double-ended contacts I14, I15, thus establishing a circuit through conductors I20. a battery I20 and magnet coil I2I, whereby the repeating mechanism on the phonograph is actuated. A coil spring I13 serves to bias the finger-piece "I to its central or upright position. It is to be noted that the motion required to actuate the repeating control switch is at right angles to that required for the clutch control switch, thus avoiding any confusion as to function. Furthermore closure of the repeating control switch is accomplished by movement of finger-piece I 1| in either direction so that succestlve actuations of the back-spacing mechanism may be quickly effected by rapid oscillation of the finger-piece. It is intended that the finget-piece I" be moved by the index finger which may be done without moving the hand from its normal position about the clutch control switch. The operation of the machine is as follows: When it is desired to dictate, a record tablet A is placed on the mandrel, the carriage is moved to the beginning of the tablet and the control lever 65 moved into recording position. The operator then dictates into the mouthpiece, maintaining the switch cover I 83 of the clutch control depressed as long as'he is speaking into the machine. If during the course of the dictation he should be interrupted and upon returning desire to listen to the last portion of the matter already dictated, or if he should desire to make changes in the matter dictated, or if for any other reason it is necessary that he listen to the Previously dictated matter, he rocks or oscillates the finger-piece Ill, closing and opening the circuit of the repeat magnet coil [2| one or more times, thus causing any desired number of back-spacing movements of the carriage as described hereinbefore. During this back-spacing operation, the recording and reproducing mechanism will be conditioned for reproducing and upon completion of the back-spacing motion he may cause the mandrel to rotate by depressing the switch cover I 83, whereupon the carriage will again move forward and the matter dictated will be reproduced. When the carriage has traveled a slight distance past the end of the dictated matter, the recording and reproducing mechanism will be automatically restored to the recording condition and he may proceed with his dictation. The extent of the back-spacing motion depends upon the number of oscillations given to the fingerpiece "I, one back-spacing operation being performed for each closure of the switch I11, I14, I15. It isto be understood that if more than one back-spacing operation is performed, the operations subsequent to the first one will merelyn'esuit in further retraction of thecarriage, the other necessary functions having been performed with the first back-spacing operation.

Having thus described my invention, I claim:

1. Ina phonograph, a carriage, a feed screw, carriage advancing means comprising a rotatable feed nut mounted on said carriage for coaction with said feed screw, means to lock said feed nut against play relatively to said carriage during an advancing movement, back-spacing mechanism for said carriage, said mechanism being adapted to cause rotation of said feed nut to cffeet backspacing movement, and means asso- 1 ciated with said mechanism to render said looking means inoperative during a back-spacing operation.

2. In a phonograph, a sound box, a feed screw, sound box advancing means comprising a gear wheel mounted for coaction with said feed screw, braking means to eliminate play in said feed wheel when it acts as a feed nut during advancing movement of the sound box, sound box backspacing mechanism comprising means to rotate said gear wheel whereupon it coacts with said feed screw as a pinion on a rack to eifect backspacing, and means associated with said backspacing mechanism for rendering said braking means inoperative during operation of said backspacing mechanism.

HEINRICH -F. MAX GRAMANN.

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