US3137429A - Biasing means for capstan pressure wheel - Google Patents

Description

June 16, 1964 FIG. I

D. L. JOSLOW 3,137,429

BIA-SING MEANS FOR CAPSTAN PRESSURE WHEEL Filed April 26, 1962 INVENTOR. DAVID L. JOSLOW ATTCFNEYS 3,137,429 BIASING MEANS FOR CAPSTAN PRESSURE WHEEL David L. Joslow, Chester, Conn., assignor to Chester Electronic Laboratories, Incorporated, Chester, Conn., a corporation of Connecticut Filed Apr. 26, 1962, Ser. No. 190,291 12 Claims. (Cl. 226-176) This invention relates to tape transport mechanisms for magnetic tape recorders and the like and of the type including a continuously rotating capstan and a pressure wheel movable into and out of a tape feeding position b with respect to the capstan at which position the tape is squeezed between the capstan and pressure wheel so as to be frictionally driven by the capstan. More particularly, this invention deals with a biasing means for the pressure wheel of such transport mechanisms for controlling the pressure at which the tape is squeezed against the capstan and for providing other desirable effects.

The general object of this invention is to provide an improved pressure wheel mechanism for a tape transport device which mechanism includes novel biasing means for controlling the pressure exerted by the wheel against the tape and capstan when the wheel is moved to its tape feeding position. 7

A more particular object of this invention is to provide a pressure wheel mechanism of the foregoing character wherein the biasing means for the pressure wheel is adjustable to vary the pressure exerted by the wheel against the tape and capstan and wherein the means for effecting such adjustment are accessible from the outside of'the tape transport housing or the like so that adjustments may be quickly and easily made.

Another object of this invention is to provide a pressure wheel mechanism adapted for operation by a solenoid motor and which mechanism allows for a suificient amount of overtravel of the solenoid plunger to permit the plunger to be drawn into its fully actuated position with respect to thesolenoid coil when upon actuation of the solenoid the pressure Wheel engages the capstan and tape before the solenoid plunger reaches such fully actuated position.

Other objects and advantages of the invention will be apparent during the course of the following description and from the drawing forming a part hereof.

The drawing shows a preferred embodiment of the invention and such embodiment will be described, but it will be understood that various changes may be made from the construction disclosed, and that the drawing and description are not to be constructed as defining or limiting the scope of the invention, the claims forming a part of this specification being relied upon for that purpose.

Of the drawing:

FIG. 1 is a fragmentary top view of a tape transport device employing a pressure wheel mechanism embodying the present invention.

FIG. 2 is a vertical sectional view taken on the line 2-2 of FIG. 1.

FIG. 3 is a vertical sectional view taken generally on the line 33 of FIG. 2.

FIG. 4 is a fragmentary sectional view taken on the line 4-4 of FIG. 3.

FIG. 5 is a fragmentary sectional view taken on the line 55 of FIG. 3.

Turning now to the drawings, FIG. 1 is a fragmentary top view of a tape transport device of the type used, for.

face member 12 in the form of a generally flat sheet and which member is shown to be and is referred to hereinafter as being horizontal. Other parts of the device are likewise shown and sometimes referred to herein as being horizontal or vertical, but it is to be understood that these terms are used only to define the relative orientations of the parts one to another and that in use the upper surface member 12 need not necessarily be horizontal.

Included in the tape transport device is a vertical capstan 14 which as shown in FIG. 2 extends upwardly beyond the upper surface member 12, passing through an opening 16 therein, and also extends downwardly through an opening 18 in a base plate 20-located some distance below the upper surface member. Suitable means (not shown) are associated with the capstan 14 for rotating the same continuously about its vertical central axis as is well known in the art. Other means (not shown) are also employed in the transport device for guiding the tape 10 along a path which passes in close proximity to the capstan 14.

Feeding of the tape 10 is accomplished by the capstan 14 in cooperation with a pressure wheel 22 located on the opposite side of the tape 10 from the capstan 14 so that the tape passes between the capstan and the pressure wheel. The, pressure wheel is supported for rotation about a vertical axis and is movable in a horizontal plane so as to be brought into and out of a tapeieeding relationship with the capstan. In FIGS. 1 and 2 the pressure wheel is shown out of tape feeding relationship with the capstan. Under this condition "the pressure wheel is spaced some distance from the capstan so that the tape 10 very lightly engages the capstan, if at all, and has no drivingforce imparted thereto. To cause feeding movement of the tape the pressure wheel 22 is moved toward the capstan 14 sothat the tape is. squeezed with some force between the capstan and the pressure wheel. The friction thereby created between the tape and capstan will cause the capstan to move the tape and this will be accompanied by rotation of the pressure wheel.

The force with which the pressure wheel is held against the capstan during a tape feeding operation is of considerable importance since itis necessary that the wheel exert suflicient pressure on the tape to prevent slippage between the tape and capstan. On the other hand, it is also desirable that this force be held to as low a value as possible to prevent undue loads on the bearings and the like supporting the capstan. The present invention, therefore, concerns, among other things, an actuating means for moving the pressure wheel into and out of its tape feeding position and for permitting adjustment of the force exerted by the pressure wheel against the capstan so that s gh force may be selectively adjusted to an optimum v ue.

Referring to FIGS. 1, 2, and 3, the actuating mechanism for the pressure wheel 22 in the present instance includes a vertical shaft 24 supported by the base plate 20 for pivotal movement about a vertical axis. In the present case, the supporting means for the shaft 24 includes a shouldered bushing 26 which is fitted into an opening in the base plate and which rotatively receives a corresponding portion of the shaft 24. Above the bushing 26 the shaft includes a radial flange 28 defining a downwardly facing surface which seats on the shoulder of the bushing 26 to vertically support the shaft 24. The shaft 24 is 'axilaly retained in the base plate 20 by the flange 28 located above the base plate and by a snap ring 30, or the like, located below the base plate. The shaft 24 extends upwardly from the base plate 20 and passes upwardly through an opening in the upper surface member 12 and for some distance upwardly beyond said latter member. The shaft also has a lower portion which extends some-distance downwardly from the base plate.

Between the top surface member 12 and the base plate Patented June 16, 1964 portion of the actuating mechanism for the pressure wheel.

22 is therefore concealed below the surface member 12.

From the foregoing description it will be understood that by rotating the shaft 24 about its vertical axis, the pressure wheel 22 may be brought into and out of its tape feeding relationship with the capstan 14. This movement of the shaft 24 is in turn effected by an actuating member which is rotatable about the axis'of the shaft 24 and by biasing means between the actuating member and the shaft. In the illustrated case the actuating member comprises a horizontal arm 38 carried by the. lower end of the shaft 24 and movable angularlyrelative thereto and having its outer end connected through a link 46 to the plunger 42 of a solenoid motor 44. As mentioned, the actuating arm 38 is connected to the shaft 24 through a resilient biasing means which acts to tend to hold the arm 38 in a given normal angular position on the shaft 24 as defined by suitable stop means and to resist angular movement of the arm relative to the shaft away from such normal position against the biasing force. The arrangement of the stop means and the biasing means is such that the resilient movement of the arm 38 relative to the shaft 24 and away from its normal position is in the same direction as that in which the shaft is rotated to bring the pressure wheel into tape feeding relationship with the capstan. Therefore, upon movement of the actuating arm, in the direction corresponding to movement of the pressure wheel toward the capstan the actutaing arm may move relative to the shaft and against the force of the biasing means after movement of the shaft and arm 32 is arrested by the capstan.

By way of further explanation, FIG. 1 shows the actuating arm 38 in its normal position relative to the shaft 24 and relative to the arm 32 and further shows the pressure wheel 22 spaced from the capstan 14 by a distance greater than the thickness of the tape so as to be out of tape feeding relationship with the capstan. This condition is achieved when the solenoid motor is de-ener gized. If the solenoid motor is now energized the plunger 42 is drawn into the solenoid, or to the left as viewed in FIG. 1, which through the link 40 moves the arm 38 toward the left to rotate the shaft 24 in a counterclockwise direction about its central axis. This movement of the shaft 24 in turn rotates the arm 32 in a counterclockwise direction to move the pressure wheel 22 toward the capstan 14 and to squeeze the tape 10 between the pressure wheel and the capstan to cause feeding movement of the tape. As the pressure wheel reaches this tape feeding position further movement of it, the arm 32, and

the shaft 24 is prevented by the capstan. When this occurs, however, the solenoid plunger 42 is not in its fully actuated position, and therefore further movement of the plunger toward the left is obtained by movement of the actuating arm 38 in a counterclockwise direction relative to the shaft 24 and against the force of the biasing means. This permits the plunger 42 to move to its fully actuated position relative to the solenoid coil at which the solenoid draws a minimum amount of current,

thereby preventing overheating of the solenoid. The use 7 4 force and thereby the force exerted by the pressure wheel on the capstan when the actuating arm is moved to its fully actuated position. Also, the means for effecting such adjustment are preferably accessible from the outside of the transport device so that the pressure exerted by the pressure wheel may be readily and easily varied without the necessity of dismantling any portions of the device. As shown best in FIGS. 2, 3, and 4, the actuat ing arm 38 is carried by the lower end portion of the shaft 24 which portion is provided with two parallel flats 46, 46. The arm'38 is provided with an opening, which loosely receives the shaft 24, and has associated there'- withtwo screws 48, 48, the inner ends of which protrude some distance into the associated opening so as to provide stopmeans for limiting the angular movement of the aim.

38 relative to the shaft 24 by engagement with the flats.

In FIG. 4 the solid lines show the arm 38 in one limit of its movement relative to the shaft 24 and the broken lines show the same arm in the other limit of its movement relative to the shaft 24. It will be understood, however, that the illustrated stop means has been shown by f A way of example only and that other suitable means may be employed without departing fromthe invention. It will also be understood that in accordance with the invention it is necessary to limit the movement of the arm 38 in one direction only with respect to the shaft, suchlimit defining the normal position of the arm relative to the shaft. The shaft 24 is tubular and extending through the bore thereof is an adjusting member in the form of a bolt 50 threaded along its entire length and having a slotted head 52 at itsupper end, which slotted head serves as a meansfor rotating the bolt. Threadably received on the bolt 50 between the head 52 and the upper end of the shaft 24 is a nut 54 which in the illustratcd case is generally cylindrical in shape and includes one or more radial openings such as indicated partially at'55 for receiving a spanner wrench forv turning the. same At its lowerend the bolt 50 .ex-.

relative to the bolt. tends downwardly beyond the lower end of the shaft 24 and threadably receives two nuts 56 and 58 which are spaced some distance apart on the bolt and between.

hold the bolt 50 in any selected angular position relative to the shaft 24. The lower nut 58 serves to retain the spring 60 on the bolt 50.

The lower end of .the bolt 50 has an axial slot which receives one end 62 of the coil spring 60 to restrain the same from rotation relative to the bolt. The other end of the spring is in the form of an arm 64 which extends i outwardly from the bolt 50 and hooks partially around a downwardly extending finger 66-attached to the actu-; ating arm 38. From. this it will be appreciated that the spring 60, if under tension, tends to rotate the arm 38 relative to the bolt 50 and likewise relative to the shaft 24, assuming the shaft to be fixed relative to the, bolt.

This rotation is, however, limited by the stop means de-. 1 scribed above and shown'in FIG. 4 so that the arm 38 is held in or urged toward its normal position by the spring. The initial tension or preload in the spring will determine the amount of force required to move the arm.38 away from its normal position and this in turn will determine the pressure exerted by the pressure wheel on the capstan when the pressure wheel is moved into its tape feeding position.

The initial tension or preload exerted by the spring 60 The nut 56 serves to provide a radial abut- Therefore by holding The upper nut 54 is therefore seen to comprise a releasable locking means which may be operated to may be varied by rotating the bolt or adjusting member 50 relative to the shaft 24, this having the effect of twisting the one end 62 of the spring relative to the other end 64. This is accomplished by loosening the nut 54 to unlock the bolt from the shaft, then rotating the head of the bolt 52 to the point at which the desired tension is achieved, and thereafter retightening the nut 54 to lock the bolt in its new position relative to the shaft.

In the illustrated case this adjusting operation is easily performed through the use of a screwdriver and a spanner Wrench. The screwdriver is first entered into the slot of the bolt head 52 and the spanner wrench applied to the nut 54. The nut 54 is then turned by means of the spanner wrench to unlock the bolt 50. The screwdriver is then rotated in a counterclockwise direction until the desired amount of tension is obtained, rotation of the arm 32 and shaft 34 being prevented by engagement of the pressure wheel 22 with the capstan 14 during this operation. The nut 54 is thereafter retightened against the shaft 24 while the screwdriver is used to hold the bolt in its adjusted position.

Although in the present instance the adjusting member 59 has been shown to be provided with a slotted head 52 for receiving a screwdriver and the locking member 54 has been shown in the form of a nut adapted for use with a spanner wrench, it will be understood that the invention is not necessarily limited to this particular design of these elements. If desired, each of these parts may, in fact, be made of such a size and shape as to be directly manipulable by the hands of a user without the need for tools.

The invention claimed is:

1. In a tape transport device having a capstan located adjacent the path of tape travel and supported for rotation about its central axis, the combination comprising a shaft supported for rotation about an axis fixed relative to and disposed parallel with said capstan axis, an arm fixed to said shaft and having a pressure wheel supported thereon for rotation about an axis fixed relative to said arm in parallel relationship with said capstan axis which pressure wheel is moved toward said capstan and into tape feeding relationship therewith as said shaft is moved angularly in a first direction and is moved away from said capstan as said shaft is moved angularly in the oppo site direction, an actuating member supported for pivotal movement about the axis of said shaft and relative to said shaft, stop means for limiting said pivotalrnovement of said actuating member in said opposite direction relative to said shaft, biasing means for urging said actuating member in said opposite direction and toward its limited position relative to said shaft and for resiliently resisting movement of said actuating member in said first direction relative to said shaft whereby upon movement of said actuating member in said first direction said actuating member may move relative to said shaft and against theforce of said biasing means after movement of said shaft and arm is arrested by said capstan.

2. The combination as defined in claim 1 further characterized by said actuating member comprising an arm loosely carried by said shaft, and means connected with said arm and including a solenoid motor for moving said latter arm about said axis of said shaft between actuated and unactuated positions.

3. The combination as defined in claim 1 further characterized by said biasing means comprising a spring, and means for selectively adjusting the preload of said spring without changing said limited position of said actuating member relative to said shaft to vary the amount of force required to move said actuating member relative to said shaft and away from said limited position.

4. The combination as defined in claim 3 further characterized by said tape transport device having a top surface member, said pressure wheel being located above said top surface member and said actuating member being located below said top member, and said means for selectively :adjusting the preloadof said spring in: cluding parts located above said'top surface member which parts are manually operable to effect said adjust ment. a v 5. In a tape transport device ,having a capstan located adjacent the path of tape travel and supported for rotation about a vertical axis, the combination comprising a hollow shaft supported for rotation about a vertical axis spaced from said capstan axis, an arm fixed to said shaft and having a pressure wheel supported thereon for rotation about a vertical axis also spaced from said capstan axis and which pressure wheel'is moved toward said capstan and into tape feeding relationship therewith as said shaft is moved angularly in a first direction andv is moved away from said capstan as said shaft is moved angularly in the opposite direction, an actuating member supported for pivotal movement about the axis of said shaft and relative to said shaft, stop means for limiting said pivotal movement of saidactuating member. in said opposite direction relative to said shaft, an adjusting member extending vertically through the bore of said shaft and having means atits upper end for rotating the same relative to said'shaft,'meansfor releasably locking said adjusting member in various selected angular positions relative to said shaft, and a torsion spring having one end fixed relative to said actuating member and its other end fixed relative to said adjusting member and which spring is arranged so asv to resiliently urge said actuating member in said opposite direction relative to said shaft when said adjusting member is angularly locked to said shaft and the initial tension of which spring may therefore be varied by varying the angular position of said adjusting member relative to said shaft.

6. The combination defined in claim 5 further characterized by said adjusting member having a threaded portion adjacent its upper end end, and said releasable locking means including means defining an abutment on the lower end portion of said adjusting member which abutment is engageable with the lower end of said shaft and said releasable locking means also including a locking member threadably received on said threaded portion of said adjusting member which locking member by being threaded in one direction or another on said adjusting member is movable axially of said adjusting member and into and out of a position at which said locking member engages the upper end of said shaft and clamps the latter between itself and said abutment to prevent angular movement of said adjusting member relative to said shaft.

7. The combination as defined in claim 5 further characterized by said actuating member comprising an arm loosely received on a corresponding portion of said shaft for pivotal movement relative to said shaft.

8. The combination as defined in claim 5 further characterized by said torsionxspring comprising a helical coil spring surrounding said adjusting member adjacent the lower end thereof.

9. The combination as defined in claim 5 further characterized by means connected with said actuating member and including a solenoid motor having a plunger for tmoving said actuating member about said axis of said shaft between actuated and unactuated positions corresponding to actuated and unactuated positions respectively of said plunger, said actuating member in being moved from said unactuated position to said actuated position being movedtin said first direction to an extent greater than that necessary to bring said pressure wheel into tape feeding relationship with said capstan so that said actuating member is moved relative to said shaft against the force of said spring.

10. In a tape transport device having a capstan located adjacent the path of tape travel and supported for rotation about a vertical axis, the combination comprising a hollow shaff supported for rotation about a vertical axis spaced from said capstan axis, an arm fixed to said shaft and having a pressure wheel supported thereon for rotation about a vertical axis also spaced from said capstan axis and which pressure wheel is moved toward said capstan and into tape feeding relationship therewith as said shaft is moved angularly in a first direction and is moved away from said capstan as said shaft is moved angularly in the opposite direction, an actuating arm loosely supported on the lower end portion of said shaft for relative pivotal movement about the axis of said shaft, stop means for limiting said pivotal movement of said actuating arm in said opposite direction relative to said shaft, an adjusting member extending vertically through the bore of said shaft and beyond the upper ends thereof and having means at its upper end for rotating the same relative to said shaft, means for releasably locking said adjusting member in various selected angular positions relative to said shaft, and a helical coil spring axially retained on and surrounding one end of said adjusting member and having one end fixed relative to said actuating arm and its other end fixed relative to said adjusting member and which spring is arranged so as to resiliently urge said actuating arm in said opposite direction relative to said shaft when said adjusting member is angularly locked to said shaft and the initial tension of which spring may therefore be varied by varying the angular position of said adjusting member relative to said shaft.

11. The combination defined in claim 10 further characterized by said adjusting member comprising a bolt, threaded along substantially its entire length, and'said releasable locking means comprising upper and lower members threadably received by said bolt and ,engag'eable respectively with the upper and lower end surfaces of i said shaft.

12. The combination as defined in claim 11 further characterized by said means for rotating said adjusting member comprising a slotted head on said bolt.

References Cited in the file of this patent UNITED STATES PATENTS Lakso Jan. 8, i957

Claims (1)

1. IN A TAPE TRANSPORT DEVICE HAVING A CAPSTAN LOCATED ADJACENT THE PATH OF TAPE TRAVEL AND SUPPORTED FOR ROTATION ABOUT ITS CENTRAL AXIS, THE COMBINATION COMPRISING A SHAFT SUPPORTED FOR ROTATION ABOUT AN AXIS FIXED RELATIVE TO AND DISPOSED PARALLEL WITH SAID CAPSTAN AXIS, AN ARM FIXED TO SAID SHAFT AND HAVING A PRESSURE WHEEL SUPPORTED THEREON FOR ROTATION ABOUT AN AXIS FIXED RELATIVE TO SAID ARM IN PARALLEL RELATIONSHIP WITH SAID CAPSTAN AXIS WHICH PRESSURE WHEEL IS MOVED TOWARD SAID CAPSTAN AND INTO TAPE FEEDING RELATIONSHIP THEREWITH AS SAID SHAFT IS MOVED ANGULARLY IN A FIRST DIRECTION AND IS MOVED AWAY FROM SAID CAPSTAN AS SAID SHAFT IS MOVED ANGULARLY IN THE OPPOSITE DIRECTION, AN ACTUATING MEMBER SUPPORTED FOR PIVOTAL MOVEMENT ABOUT THE AXIS OF SAID SHAFT AND RELATIVE TO SAID SHAFT, STOP MEANS FOR LIMITING SAID PIVOTAL MOVEMENT OF SAID ACTUATING MEMBER IN SAID OPPOSITE DIRECTION RELATIVE TO SAID SHAFT, BIASING MEANS FOR URGING SAID ACTUATING MEMBER IN SAID OPPOSITE DIRECTION AND TOWARD ITS LIMITED POSITION RELATIVE TO SAID SHAFT AND FOR RESILIENTLY RESISTING MOVEMENT OF SAID ACTUATING MEMBER IN SAID FIRST DIRECTION RELATIVE TO SAID SHAFT WHEREBY UPON MOVEMENT OF SAID ACTUATING MEMBER IN SAID FIRST DIRECTION SAID ACTUATING MEMBER MAY MOVE RELATIVE TO SAID SHAFT AND AGAINST THE FORCE OF SAID BIASING MEANS AFTER MOVEMENT OF SAID SHAFT AND ARM IS ARRESTED BY SAID CAPSTAN.

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