US3039777A - Tuning mechanism for dictating machine - Google Patents

Description

INVENTOR.

R. E TROST 3,039,777

2 Sheets-Sheet 1 TUNING MECHANISM FOR DICTATING MACHINE June 19, 1962 Filed Nov. 19, 1956 m E i United States Patent 3,039,777 TUNING MECHANISM FOR DICTATING MACHINE Richard E. Trost, Dundee, 11]., assignor, by mesne assignments, to Victor Comptometer Corporation, Chicago,

111., a corporation of Illinois Filed Nov. 19, 1956, Ser. No. 623,017 9 Ciaizns. (Cl. 27417) This invention relates in general to dictating machines and has more particular reference to tuning mechanism for such machines.

During a transducing operation of such a machine, one or both of the transducer and record medium are so driven while they are in transducing relationship that the transducer traces or retraces on the record medium a path, the characteristic shape of which is determined by the relative movement between the transducer and the record medium. Thus in a transducing operation of such a machine, it is possible to record and reproduce signals along such a path.

The term, tuning, as used herein, means initially establishing and, when and where desired, re-establishing such relative positions of the transducer and record medium as to provide the optimum transducing relationship therebetween at the beginning of and throughout the tracing or re-tracing of such a path, whereby to promote fidelity in the translation of signal volume during a transducing operation.

Tuning usually involves the adjustment of the transducer transversely of the path being traced for bringing the tracer member of the transducer into registration or alignment with that path. In the manufacture and assembly of such a machine with the usual tuning mechanism, the relative positions of the record-medium support, hence the record medium, and the transducer involves a strict adherence to close tolerances to ensure an acceptable transducing relationship between the transducer and record medium at the beginning of a transducing operation and to promote the desired cooperation between the transducer and record medium during such an operation. If such adherence to permissible tolerances is disregarded, tuning by the usual adjustment of the tracer member transversely of the path is diflicult of achievement at the beginning of and throughout a transducing operation.

An object of the invention is the provision in a dictating machine of novel and improved tuning means for obviating strict adherence to close tolerances in the manufacture and assembly of the transducer and record medium supporting means in order to insure a proper transducing relationship between the transducer and record medium.

Another object of the invention is the provision in such a machine of tuning mechanism which is itself adjustable for varying the limits and range of the tuning adjustment.

A further object of the invention is the provision in such a machine of novel and improved tuning means for adjusting one of the transducer or record medium relative to the other of them not only transversely of the path traceable on the record medium but also in a direction transversely of that along which the transducer moves during a transducing operation, whereby to insure proper cooperation between the transducer and support for the record medium during a transducing operation.

Another object of the invention is the provision of novel and improved tuning means or mechanism which is adapted for embodiment in a magnetic belt type dictating machine.

Other objects of the invention will become apparent 'ice from the following description and the accompanying drawing which, by way of example, disclose a presently preferred embodiment of the invention.

In the accompanying drawing:

FIGURE 1 is a front elevational view of a machine embodying the features of the invention;

FIG. 2 is an end view from the right of FIG. 1;

FIG. 3 is a fragmentary View oriented according to FIG. 2, with some of the casing of the machine removed to reveal certain interior elements;

FIG. 4 is a partial sectional view, taken substantially along the lines 4-4 of FIG. 1, and drawn on a larger scale and omitting certain portions of the machine not essential to the present invention;

I FIG. 5 is a fragmentary horizontal sectional view taken approximately on lines 5--5 of FIG. 1 and drawn on a larger scale;

FiG. 6 is a rear view of certain of the elements of the interior of the machine and is taken approximately 011 lines 6-6 of FIG. 3 at a diiferent scale;

FIG. 7 is a detail view taken approximately on lines 7-7 of FIG. 4 and shown on a larger scale;

FIG. 8 is an exploded view of the tuning cam assembly; and

FIG. 9 is a large scale View of the tuning cam assembly and feed screw, taken approximately on lines 99 of FIG. 3.

While for convenience the present invention is shown as being embodied in the magnetic type of dictating machine disclosed in the co-pending United States Letters Patent application of Alfred E. Lorenz, Serial No. 408,907, filed February 8, 1954, it will be understood by those skilled in the art that the invention is not limited to such a machine but may be embodied to advantage in various types of dictating machines.

The illustrated type of machine, generally described, usually comprises, as shown in FIGS. 1, 4, and 6, a transducer head A, a rod or other suitable support B therefor, a drivable carrier C for removably carrying and driving a record medium D, and a head-traversing drive connection E including a rotatable threaded shaft or feed screw F In such a dictating machine, the head A is pivotally and slidably mounted on the support B for cooperation with the record medium D on the carrier C. The

transducer head is thus swingable in a direction substantially normal to the record medium between a transducing position and a non-transducing position with respect to the record medium on the carrier C. When the head A is in its transducing position, it is movable by the head-traversing drive connection E along the support B to traverse the record medium D for recording or reproducing signals thereon. When the head is in its nontransducing position, it is manually reciprocable along the support B to position the head for a subsequent traversing of all or a portion of the record medium.

As is well-known in the art and disclosed in the abovementioned application, the illustrated dictating machine comprises suitable supporting, driving, control, amplifier, and casing means none of which per se constitutes any part of the present invention and none of which is therefore described in detail herein. It may be well, however, to point out briefly that in the illustrated machine the transducer head A is of the magnetic type; the carrier C comprises rotatable drive and tension rolls; the record medium D is an endless belt adapted to have magnetic signals recorded thereon and to have such signals reproduced by the transducer head A; the rotatable drive roll of the carrier C, the rod B, and the rotatable feed screw F are mounted parallel to one another with the rod above and slightly forwardly of the feed screw and with the drive roll forwardly of and slightly below the rod; and the driving means is adapted to rotate the carrier C and the feed screw F in timed relationship, whereby during a transducing operation the transducer head traces a helical path on the record medium with the convolutions of the path spaced transversely of the record medium. 7 As already mentioned, the carrier C includes drive and tension rolls, now designated by the reference numerals 14 and 15, respectively. The drive roll 14 is provided with a plurality of teeth or projections 16 extending radially outwardly from its peripheral surface near an end of the roll for drivinglyengaging in spaced perforations 17 in the belt along one of its margins. The tension roll 15 is mounted on a pivotally mounted arm 18 and is thus adapted to swing between an upper position shown in broken lines in FIG. 2 and a lower or belt tightening or tensioning position shown in full lines in FIGS. 1 and 2. It also is releasably positionable in an intermediate, belt receiving and removing position, by means not shown herein but shown in the Lorenz application referred to above.

The transducer head A and carriage therefor are preferably like those disclosed in the co-pending United States Letters Patent application of Alfred E. Lorenz, Serial No. 489,20l,filed February 18,1955. i Such a transducer head comprises a suitable casing 19 and a transducer therein having a tracer member 21 depending therefrom outside of the casing and being relatively thin in a direction transversely of the belt on the carrier C. The transducer head A is adapted to be mounted on a carriage 22 in such a manner that the tracer member 21, when the head A is in its transducing position, is closely adjacent the drive roll 14 for lightly engaging the record medium thereon. In the illustrated dictating machine, the engagement between the tracer member' and record medium for optimum transducing relationship 'therebetween occurs in the vertical plane including the axis of the drive roll 14.

In the illustrated embodiment of the invention the carriage 22 includes a main body portion 23 (FIG. 4) mounted for m ovement in the manner described below and serving as the means directly to which the head A is secured. The head A has a rearwardly extending arm 24 shown forconvenience as being U-shaped in cross section (FTG. 6), and'fitted to the upper flat surface 25 of the body portion 23 and secured thereto by means such as screws 26 extending through slots 27 in the arm and threaded into tapped holes in the body portion 23. The slots 27 are longitudinally aligned and longitudinally elongated relative to. the arm 24 for enabling substantial horizontal adjustment of the transducer head A in a direction transver'sely'of the axis of the drive roll 14.

The arm 24 is extended r'earwardly beyond the body portion 23 where it has a downturned end portion 28 in which is mounted an adjusting screw 29. The adjusting screw may assume any of various practical forms, such as that shown in detail in FIG. 7. The screw as here shown has a circumferential groove 31 adjacent its inner end fitted in a slot 32 formed in a plate 33 secured to the rear face of the body portion 23. The inner extremity 34 of the screw is fitted in a groove 35 formed in the rear face of the body portion 23. Upon turning the screw 29, the arm 24, with the head A mounted thereon, is moved forwardly or rearwardly according to the direction of the turning of the screw, relative to the body portion 23, the reaction being provided by the plate 33. The screws 26 are, of course, loosened preparatory to making the adjustment of the head A, after which they are tightened to lock the arm in adjusted position.

The head A is thus adjustably mounted on the carriage 22 with the tracer member 21 above the drive roll 14. By adjusting the head as just described, the tracer member is positioned for optimum transducing relationship with the record medium on the carrier C. It will be noted that such adjustment of the head A is in a direction longitudinally of the arm 24 which in turn is on a line transversely of the axis of the drive roll 14. Upon movement of the transducer head A in either direction from its position of optimum transducing relationship with the record medium, it, is moved, angularly speaking, a large amount from the vertical, radial plane of the drive roll 14. The optimum position referred to, without entering into the details of recording relation relative to the belt, is to be maintained in the manufacture of the device. It will be understood that in production methods of manufacture certain parts are permitted a relatively wide latitude in tolerance. This tolerance that may otherwise be permitted could result in relatively great misalignment of the tracer member 21 relative to the belt or record medium. However, the adjustment enabled by the screw 29 enables accurate alignment of the tracer mem her 21 relative to the belt or record medium, without the necessity for having the parts of accurate dimensions.

The carriage 22, shown in detail in the Lorenz application Serial No. 489,201 referred to above, is mounted for movement transversely of the belt and consequent movement of the transducer head A in that direction. The guide rod B which extends transversely of the machine is suitably mounted in frame elements 37 and 38 of the machine. The specific means for mounting the carriage on the guide rod includes a hub 39 receiving the guide rod and slidable thereon. Associated with the carriage 22 is means for feeding the carriage and thereby the transducer head A along the guide rod B. The carriage includes a depending arm 41 having transverse tabs 42 (FIGS. 4 and 6) receiving the hub 3% and enabling relative pivotal movement thereon. The lower end of the arm 41 has a plate 43 secured thereto which with the lower extremity of the arm 41 cooperates with the feed screw F. This feed screw, as shown in FIGS. 5 and 6, is journalled in suitable hearings in frame elements, such as the element 44 at one end and the element 45 (FIG. 9) at the other end. The plate 43 and the lower extremity of the arm 41 are on efifectively opposite sides of the feed screw F whereby the arm 41 is normally maintained or restrained by the feed screw against pivotal movement relative to the axis of the guide rod. The surfaces on the plate 43 and arm 41 that engage the feed screw do not eifect threadmg therewith for movement of the carriage, the surfaces being broad and engaging the outer extremities of the threads on the screw. The feed screw F is driven by suitable means (not shown) within the interior of the machine, but which may be the same motor that drives the drive roll 14.

A compression spring 46 reacting between a collar 47 on the screw and the adjacent frame element biases the feed screw to a position from which adjustment is made for carrying out certain of the purposes of the present invention. This position is to the left in FIG. 6 and to the right in FIG. 5. The feed screw is biased toward the direction of the beginning margin of the record medium or belt, relative to the transverse movement of the transducer head A therealong in a transducing operation. As viewed from the front, as in FIG. 1, the beginning margin of the belt is to the right and the head A moves to the left in the transducing operation. Adjacent the end 48 of the feed screw opposite the compression spring as is another collar 49 which serves as stop means for limiting the movement of the carriage in that direction, to an elfect to be described hereinbelow.

The carriage 22 in addition to the elements mentioned above includes also a depending arm 51 which may be an integral extension of the body portion 23. The lower end of this arm has mounted thereon a leaf spring 52 with a detent or latch 53 engageable with the lower end of the arm 41. This detent releasably engages either side of the arm 41 for retaining the head A in a corresponding position. The transducer head is movable from the transducing position shown in FIG. 4 to a nontransducing position raised therefrom, as by rotating the transducer head clockwise (FIG. 4) about the guide rod B. In the lower or transducing position of the unit the detent 53 engages the rear side of the arm 41 (F16. 4) and in the non-transducing position it engages the front side, in both cases releasably engaging the arm for normally retaining the transducer head A in the set position but enabling it to be moved to the opposite position when the necessary external force is applied thereto.

A third arm 54 is included in the carriage and is mounted on the hub 39 by means of lateral tabs 50 having aligned apertures receiving the hub. This arm is on the same side of the feed screw F as is the arm 51 and on the outside or front side of the latter. A tension spring 55 interconnects the lower ends of the arms 54 and 41. Secured on the arm 54 is a plate-like element 56 having an edge 57 (FIG. engageable with the threads on the feed screw F for feeding the carriage and transducer head A along the guide rod B. When the head is in its transducing position the edge 57 engages the threads of the screw, and when the head is raised to non-transducing position, the edge is out of engagement with the threads, enabling free sliding movement of the carriage and head along the guide rod as when so manually manipulated.

As in the co-pending Lorenz application, Serial No. 468,907 referred to above, provision is made for tuning the dictating machine, but the tuning means in the present instance includes improvements over that disclosed in the said Lorenz application. The tracer member 21 traces a path on the belt that may be in the neighborhood of .014 inch wide. This path is of helical form, as mentioned above, brought about by the movement of the belt surface in linear direction around the rolls, and simultaneous feeding of the transducer head A in transverse direction along a path parallel with the axis of the drive roll 14. The linear speedof the belt and rate of rotation of the feed screw F may be selected for coordination to produce any desired spacing of the convolutions of the helical path, but it is desired that this spacing be on the order of inch.

After a recording or dictating operation the record medium is placed in a signal reproducing machine. This may be the same machine in which the recording or dictating operation was performed, or it may be another machine. The present machine may be utilized either for recording, or for transcribing or reproducing, but it is possible that a different machine, although similar to the present, be utilized for transcribing or reproducing. Vfheu a different machine is used for transcribing or reproducing, and normally when the same dictating machine is used for transcribing or reproducing, the record medium is removed after completion of the dictating operation and later replaced on a machine for the reproducing operation. When the record medium is so placed in the reproducing machine it is, of course, desired that the tracer member be accurately aligned with the signal path and not be misaligned relative there to in a transverse direction along the axis of the roll. This may be made necessary, for example, because of the turning of the belt end-for-end, i.e., turning it 180 degrees rotation or revolution about a transverse axis. In such case the signal path convolutions would be dis placed a distance equal to one-half spacing between the convolutions, relative to the position of the head A at the completion of the dictating operation. In order to accurately align the tracer member of the transducer with the signal path, in such case, provision is made for relative shifting movement between the record medium or belt D and the tracer member 21 in direction parallel with the axis of the roll 14. In the preferred arrangement this is accomplished by so shifting the tracer member 21, which is done by moving the transducer head A along the guide rod B. This is most effectively accomplished by shifting the feed screw F.

This shifting movement is effected by tuning cam means indicated generally at 58 (FIGS. 3, 6, 8, and 9). The parts making up the assembled cam means are best shown in the exploded view of FIG. 8 and include a disc-like element 59 which is preferably a stamping and includes a main portion 61 lying substantially in a plane and having an aperture 62 for mounting it and a tapped hole 63 ad jacent the periphery thereof. This disc-like member includes a cam element 64 at its periphery disposed at an angle to the plane of the main portion 61. This cam element is formed as by slotting the disc-like member and turning or twisting the cam portion. The cam means also includes a finger lever 65 including a plate portion 66 which engages the disc-like element 59 and has an aperture 67 for mounting it. The portion 66 has an arcuate slot 68 concentric with the axis of the aperture 67. This element also includes an arm 69 having a finger grip portion 7-1 on the outer swinging end thereof. The members 59 and 65 are fitted and secured together and to a frame element 72 of the machine by means of a screw 73 inserted through the apertures 67 and 62 and through the frame element where it is secured by suitable means such as a nut 74 over which the inner end of the screw 73 is peened. A spring washer 75 is included in the assembly for tensioning the parts to snug engagement, and a suitable spacer 75:: may be interposed for spacing the assembly relative to the frame element 72. A lock screw 76 is inserted through the slot 68 in the plate portion 66 and threaded into the hole 63 in the disc-like member 59. This screw is utilized for locking the members 65 and 59 in relative angular positions about the axis of the screw 73 in a manner described below.

The cam means 58, in assembly as described above, is mounted on the frame of the machine adjacent the end 43 of the feed screw F (FIG. 6). The feed screw has sliding engagement in its bearing supports and its end 48 is exposed through the frame element 72. The cam means is mounted in a position radially offset from the feed screw, such as below the feed screw in position for the cam element 64 to engage the end of the screw. Upon rotation of the cam means about the axis of the mounting screw 7-3 the cam element 64, being inclined at an acute angle to that axis and engaging the end of the feed screw, produces an axial shifting elfect on the screw.

The arm 69 and finger piece 71 project through a slot 77 in a portion 78 of the machine casing, which then is exposed to the front of the machine for easy access by the operator. The slot 77 defines the range of swinging movement of the arm, by engagement of the arm with the ends of the slot. Upon movement of the finger piece 71 and arm in downward direction the cam element 64 effects axial shifting movement of the feed screw F in inward direction (to the right, FIG. 6), and upon movement of the finger piece in upward direction the camming effect is removed and the compression spring 46 shifts the feed screw in the opposite or outward direction. The extent of shifting of the feed screw is preferably an extent at least as great as the transverse spac ng between adjacent convolutions of the signal path on the belt. In the case mentioned above the spacing is approximately inch. Obviously, any desired spacing may be utilized but regardless of the magnitude of the spacing, provision is preferably made for shifting the feed screw, and consequently the transducer head A, an extent at least as great as mentioned so that upon shifting the head in one direction or another it may be made to register accurately with the signal path.

It is desired that in addition to the tuning operation described, as by shifting the feed screw F, adjustment be made in the cam means 58 for properly positioning the range of shifting movement of the transducer head relative to the range of movement of the arm 69. In manufacturing methods, as was explained above, considerable latitude and tolerance is permissible from the standpoint of most considerations. However, it is desired to provide for alignment of the tracer member 21 transversely of the belt with particular regard to the starting position thereof or along the beginning margin of the belt, which in this case is the righthand margin as viewed in FIG. 1. Stop means is provided for limiting the movement of the tracer member to such beginning position. This stop means preferably consists of the collar 49 on the feed screw (FIGS. and 6) against which the carriage abuts. The desired relation is that when the unit is moved to the beginning position in which the carriage abuts the collar 49, the tracer member 21 is in the desired alignment relative to the beginning margin of the belt. Due to ordinary manufacturing tolerances, such alignment may not be accurately achieved in mass production assembly of machines. The adjustment between the members 65 and 59 enables accurate alignment of the character mentioned without the necessity of precision in fabricating the parts or assembling them. The cam element 64 has an angular dimension substantially greater than that required for the necessary shifting of the feed screw. In the present case this angular dimension is on the order of twice that actually required for the purpose mentioned. For any given setting of the disc-lire element 59, the feed screw F and transducer assume a definite position. The arm 69 is limited in its movements by the ends of the slot 77 and because of the tolerances mentioned above, the range of movement of the arm 69, as determined by the slot, may not be positioned, in angular relation to the cam element 64, for properly positioning the transducer head A adjacent the beginning margin of the belt. In such case the lock screw 76 may be loosened and the elements 65 and 59 relatively shifted angularly about the axis of the mounting screw 7 3 to a new position for positioning the cam element 64 with relation to the range of movement of the arm 69 so that the tracer member 21 is properly aligned with the beginning margin of the belt at the desired point in the range of movement of the arm 69. Thereafter the lock screw 76 is tightened for locking the members 65 and 59 in the new relative angular position.

This adjustment of the cam means eliminates the necessity for adjusting the transducer head A relative to its carriage in transverse direction. It is desired that the tracer member 21 constantly assume a position in a plane perpendicular to the axis of the drive roll 14 and this relation may be maintained While adjusting the parts for aligning the tracer member 21 with the beginning margin of the belt, by means of the cam means 58. Additionally, the tracer member 21 may be adjusted relative to the carriage in direction transversely of the axis of the drive roll 14 without interfering in any way with the adjustments made by the cam means 58.

It is thought that the invention and its attendant advantages will be understood from the foregoing description, and it will be apparent that various changes may be made in the form, construction and arrangement of the parts without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the form hereinbefore described and illustrated in the drawing being merely a preferred embodiment thereof.

I claim:

1. A dictating machine comprising a belt of magnetic material, a pair of rolls disposed on spaced parallel axes for mounting the belt for movement through a linear path about said axes including a curved portion, a magnetic transducer, a carriage mounting said transducer and movable for moving said transducer between a transducing position and a non-transducing position relative to said belt, feed means for moving said carriage and thereby said transducer uniformly transversely of the direction of movement of said belt, when the transducer is in transducing position, for tracing a helical path on the belt, said carriage including an arm rigidly supporting said transducer and slidable longitudinally in a straight line lying in a plane perpendicular to said axes and, when the transduced is in transducing position, tangent to a circle concentric with said curved portion of said path, means mounted on said carriage for adjustably moving said arm and transducer along said line, and means for shifting the transducer a limited distance transversely of said helical path, relative to any position of the transducer due to said uniform transverse movement, a distance at least as great 8 as the distance between adjacent convolutions of said helical path.

2. In a dictating machine, a belt of magnetic material, means for moving the surface of the belt in a linear path about a transverse axis, a magnetic transducer having a transducing position relative to said belt, feed means for uniformly moving the transducer transversely of the direction of movement of the belt when the transducer is in transducing position to trace a helical path on the belt, means for producing shifting movement of the transducer a limited distance transversely of said helical path other than the uniform transverse movement, when the transducer is in transducing position, and including a movable actuating element indirectly engageable with said transducer and a finger lever for moving the actuating element, said actuating element being operable through a range sufficient for shifting the transducer a distance at least as great as the spacing between adjacent convolutions of said helical path, said finger lever being movable through a range sufficient for operating said actuating element through its range and being releasaoly secured thereto for adjustment relative thereto to any position within a range equivalent to the range of movement of the actuating element.

3. The invention set out in claim 2 in which said actuating element is mounted for rotary movement and said finger lever is swingable about a common axis with the actuating element.

4. The invention set out in claim 2 in which the feed means includes a feed screw parallel with said axes, the actuating element is mounted for rotary movement and has a cam element engaging the feed screw and operative for axially shifting it in response to rotary movement of the actuating element, and said finger lever is swingable about a common axis with the actuating element.

5. The invention set forth in claim 2 in which stop means is provided on said feed means for limiting movement of the transducer in one direction for locating it at a predetermined position relative to a beginning margin of the belt.

6. In a dictating machine, a belt of magnetic material, means for moving the surface of the belt in a linear path about a transverse axis, a magnetic transducer having a transducing position relative to said belt, feed means for uniformly moving the transducer transversely of the direction of movement of the belt when the transducer is in transducing position to trace a helical path on the belt, means for producing relative shifting movement between said belt and transducer a limited distance in direction transversely of said helical path other than the uniform transverse movement, when the transducer is in transducing position, and including a movable actuating element indirectly engageable with the shiftably movable one of said belt and transducer and a finger lever for moving the actuating element, said actuating element being operable through a range sufficient for causing said shifting movement a distance at least as great as the spacing between adjacent convolutions of said helical path, said finger lever being movable through a range sufiicient for operating said actuating element through its range and being releasably secured thereto for adjustment relative thereto to any position within a range equivalent to the range of movement of the actuating element.

7. A dictating machine comprising a belt of magnetic material, a pair of rolls disposed on spaced parallel axes for mounting the belt for movement through a linear path about said axes including a curved portion, a magnetic transducer, a carriage mounting said transducer and movable for moving said transducer between a transducing position and a non-transducing position relative to said belt, feed means for moving said carriage and thereby said transducer uniformly transversely of the direction of movement of said belt, when the transducer is in transducing position, for tracing a helical path on the belt, said carriage including an arm rigidly supporting said transducer and slidable longitudinally of the arm in a straight line lying in a plane perpendicular to said axes and, when the transducer is in transducing position, tangent to a circle concentric with said curved portion of said path, and means mounted on said carriage for adjustably moving said arm and transducer along said line.

8. The invention set out in claim 7 wherein said ad ustable moving means includes a screw reacting between said arm and another portion of said carriage, and the construction includes means for locking the arm, and thereby the transducer, in adjusted position.

9. The invention set out in claim 2 in which the means for moving the surface of the belt is operable for so moving it selectively in each of opposite directions,

and in which means is included for moving the transducer when in transducing position conjointly with the belt in each corresponding opposite direction.

References Cited in the file of this patent UNITED STATES PATENTS 2,683,038 Saliba Jan. 6, 1954 2,702,710 Conrad Feb. 22, 1955 2,729,453 Camras Jan. 3, 1956 2,802,905 Taris Aug. 13, 1957 2,864,892 Perkins Dec. 16, 1958 FOREIGN PATENTS 746,243 Great Britain Mar. 14, 1956

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