US3696775A

US3696775A - Magnetic tape recorder particularly of the tape cassette type

Info

Publication number: US3696775A
Application number: US83817A
Authority: US
Inventors: Ernst Markart
Original assignee: SUD ATLAS WERKE GmbH
Current assignee: SUD ATLAS WERKE GmbH
Priority date: 1970-04-21
Filing date: 1970-10-26
Publication date: 1972-10-10
Anticipated expiration: 1989-10-10
Also published as: DE2019050B2; GB1304564A; CA924279A; DE2019050A1

Abstract

A magnetic tape recorder, particularly of the tape cassette type, has support spindles for the tape carrier reels, and these support spindles are provided with driving pulleys which are coupled to a rotary driving element, during forward and reverse movement of the tape, by intermediate driving gear connected with the driving pulleys. A torque responsive clutch is included in at least the intermediate driving gear connected to the support spindle operable to effect forward movement of the tape. The torque responsive clutch includes a driven member fixed to the support spindle and a driving member freely rotatable on the driven member. The driving and driven members are interconnected by a spring wire having one end conformingly fitted in a slot in one member and the other end extending into an annular recess in the other member and bent to engage detent recesses in the other member. When the two members slip over each other, they form an acoustic signal device warning that the tape has been completely unwound from one or the other of the two tape carrier reels.

Description

United States Patent Markart 51 Oct. 10, 1972 [54] MAGNETIC TAPE RECORDER FOREIGN PATENTS 0R APPLICATIONS gigg gg THE TAPE 418,665 9/1925 Germany ..274/4 [72] Inventor: Ernst Markart, Munich, Germany P im y m ne -Louis J Capozi [73] Assignee: Sud-Atlas-Werke G.m.b.I-I., Mu- Atmmey McGlew&Toren hl le x. W 4. W 57 ABSTRACT [22] Filed: 1970 A magnetic tape recorder, particularly of the tape cas- 2 App] N 83, 17 sette type, has support spindles for the tape carrier reels, and these support spindles are provided with driving pulleys which are coupled to a rotary driving [30] Forelgn Apphcatlon Pnomy Data element, during forward and reverse movement of the April 21, 1970 Germany"; ..P 20 19 050.5 tape, y intermediate driving gear eeimeeted with the driving pulleys. A torque responsive clutch is included 52 US. Cl. ..116/67 A, 64/29, 64/30 E, in at least the intermediate driving gear connected to 116/67 192/56 242/54 l 274/4 D the support spindle operable to effect forward move- [51] Int. Cl. ..G 08b 3/00 ment of the tape' The torque responsive clutch [58] Field of Search 192/56 116/67 A 67 cludes a driven member fixed to the support spindle 242/5 274/4 4 D and a driving member freely rotatable on the driven 64/29 30 member. The driving and driven members are interconnected by a spring wire having one end con- 56] Reerences Cited formingly fitted in a slot in one member and the other end extending into an annular recess in the other UNITED STATES PATENTS member and bent to engage detent recesses in the other member. When the two members slip over each 1,167,285 l/ 1916 Flogland ..64/29 other, they form an acoustic ignal device warning 2,712,448 7/1955 Schroter C that the p has been completely unwound from one 5 fi i i l' or the other of the two tape carrier reels. ezmc 3,167,267 1/1965 Crane ..274/l1 C 9 Claims, 5 Drawing Figures l\\\ \l l i m l I/ r 9 7111/11/11, 71/ i i I I 9' ,15 l

I 1o 13 l l l I lll m] PATENTEnum 10 I972 FIG.3

11 Mu e--70? ERNST HARKART WWWEM A TT ORN EYS MAGNETIC TAPE RECORDER PARTICULARLY OF THE TAPE CASSETTE TYPE BACKGROUND OF THE INVENTION In magnetic tape recorders, it is already known to rotate driving pulleys on the reel supporting spindles through the medium of switchable friction wheels in driving connection with a rotary driving element such as, for example, the drive shaft for sound recording. The purpose of rotating these driving pulleys is to wind the tape on one reel while unwinding the tape from the other reel. Such winding is effected, for example, while the tape passes in operative relation with magnetic transducer heads for recording or. replaying sound recordings, or when it is held out of operative relation with the heads during rapid forward movement of the tape or rewinding of the tape. The tape ends are secured to the reel so that, when the direction of rotation of the reels is reversed, the winding direction is automatically reversed.

in these known magnetic tape records, it has been found that the approach of the fixed tape end frequently is not recognized in time, so that the driving element continues to act on the reel carrier spindle which is held against rotation by the tape end secured thereto, even after the tape has moved beyond its end recording-reproducing position. Aside from the fact that these stresses lead to inadmissible electrical and mechanical loading of the driving element, slippage occurs on the friction wheels, and this leads to wear in certain areas of the friction surfaces. In turn, this wear has an adverse effect on the synchronism.

SUMMARY OF THE INVENTION This invention relates to magnetic tape recorders, particularly of the tape cassette type, and, more particularly, to an improved reel spindle driving mechanism providing an audible indication when a tape has been substantially completely or completely unwound from one reel to which a tape end is secured.

The objective of the invention is to provide means, particularly in tape cassette type magnetic tape recorders, adapted to indicate clearly to the user that the tape end has reached its end position, and to prevent wear on the driving wheels for the reel support spindles if the drive is not shut off in time.

In accordance with the invention, this objective is obtained by a torque responsive clutch which is designed as an acoustic signal transmitter and is arranged in at least the driving train associated with the spindle supporting the tape supply reel, although such a torque responsive clutch can be arranged in the drive trains for both spindles. Preferably, the torque responsive clutch is formed by two clutch halves mounted on the reel supporting spindle, one of these clutch halves being secured to rotate with the spindle while the other clutch half serves as a preferably freely rotating friction wheel. The two clutch halves are firmly but releasably operatively connected with each other by a resilient and elastic locking pawl. With this arrangement, an effective mechanical separation is provided between the spindle carrying the reel then having the tape wound thereon, particularly during feeding of the tape, and the driving pulley associated with this spindle. The mechanical connection is closed or maintained during feeding of the tape and opens or disengages automatically when the tape is substantially completely unwound from the other reel to effectively separate the frictional connection between the driving element and the tape supporting spindle. The driving element can also be connected, for example, when the reel supporting spindle is held against rotation in the end positions by the tape tension, without causing damage to the recorder parts, such as abrasion points on the friction surfaces of the pulleys. In addition, the torque respon-- sive clutch indicates, to the user of the recorder and by a warning sound, the respective operating state, so that the user can shut off the drive of the magnetic tape recorder.

In an embodiment of the invention, that clutch half secured to the reel supporting spindle can carry, firmly clamped therein, a preformed spring wire part serving as a locking pawl, and whose free end is prestressed by bending and engages into one of a number of recesses in the other clutch half and which are arranged in circumferentially spaced relation to each other, for the purpose of transmitting torque. This spring end, when a predetermined torque is exceeded, disengages from one recess and snaps into the circumferentially following recess, or else is lifted out of the recesses by the ring sections interposed between the recesses. The recesses permit connecting the two clutch halves in any desired angular relation, while a ratchet-like alternating dipping and lifting movements of the preformed spring wire part produce a warning sound. In further accordance with the invention, instead of a preformed spring wire part, there can also be used other locking means, for example, a spring-loaded locking pin, and the underlying concept of the invention is by no means limited to a certain number, form, or arrangement of the recesses.

In a preferred embodiment of the invention, the clutch halves are arranged concentrically with each other so that the otherwise freely rotatable clutch shaft can be mounted directly on the clutch half which is secured to rotate with the reel carrying spindle. Coatings of a bearing material are provided in the area of the interengageable surfaces of the two clutch halves, and provide favorable running properties of the clutch halves on each other.

As mentioned, in addition to providing a torque responsive clutch in the driving train for that spindle then operating to feed the tape, the spindle for reverse feeding of the tape can also be provided with a torque responsive clutch designed as an acoustic signal transmitter. With such an arrangement, the tape end is indicated acoustically, to the 'user of the recorder, during both the forward run of the tape and the reverse run thereof, and the driving element and the tape reels are rigidly or releasably connected with each other to protect the recorder parts and the magnetic tape.

An object of the invention is to provide an improved reel driving arrangement for magnetic recorders.

Another object of the invention is to provide such a driving arrangement which operates to emit an acoustic signal when a tape has been completely unwound from one reel.

A further object of the invention is to provide such a driving arrangement in the form of at least one torque responsive clutch included in the drive train for at least one of the reel supporting spindles.

Another object of the invention is -to provide such a driving arrangement in which the clutch comprises two parts which are firmly but releasably interconnected by a mechanical element cooperable with the clutch parts to provide an acoustic signal when slippage between the clutch parts occurs as a tape is completely unwound from one reel.

A further object of the invention is to provide such a driving arrangement in which wear of friction driving elements and damage to the tape is effectively prevented.

For an understanding of the principles of the invention, reference is made to the following description of a typical embodiment thereof as illustrated in the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 is a vertical sectional view through a magnetic tape recorder embodying the invention;

FIG. 2 is a top plan view of one clutch half;

FIG. 3 is a bottom plan view of the other clutch half or part;

FIG. 4 is a partly broken away bottom plan view of the clutch half or part shown in FIG. 2; and

FIG. 5 is an elevational view of a reel supporting spindle, for. feeding tape, provided with a torque responsive. clutch embodying the invention.

I DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, the chassis plate 1 of a magnetic tape recorder, particularly of the tape cassette type, rotatably supports a reel carrying spindle 2, for-forwarding feeding of the tape, and a reel carrier spindle 3, for reverse feeding of the tape. The upper ends of

spindles

2 and 3, projecting upwardly from chassis plate 1, carry coupling heads 4 which engage into the central openings of the tape reels to couple the spindles with the recording tape when a recording tape cassette (not shown) isattached on the upper surface of chassis plate 1.

Spindles

2 and 3 can be coupled with a rotary driving element, of the recorder, through known friction wheels which have not been shown. The friction wheels, to this end, can drive the

spindles

2 and 3 through driving wheels 6 and 7 which, in the illustrated embodiment, are secured on a common shaft with a pulley 5 acting as a flywheel mass and which, in turn, is rotated by a driving motor.

In accordance with the invention, reel spindle 2 mounts a torque responsive clutch 9 designed as an acoustic signal transmitter, this torque clutch, in its entirety, being illustrated in FIGS. 1 and 5. Torque responsive clutch 9 simultaneously serves as a driving pulley for reel spindle 2, and which can be rotated by frictional engagement with the friction drives, while reel spindle 3 has a driving pulley 8 fixedly'secured thereto. Torque responsive clutch 9 comprises two clutch halves 9' and 9", as can be seen from FIG. 1, with clutch half 9" being mounted for free rotation on spindle 2. Clutch half 9" preferably is rotatably mounted on a cylindrical extension of clutch half 9', and is held against axial displacement relative to spin dle 2 by an annularcollar 10 on an annular surface of clutch half 9, and'through the medium of a snap type clamp l l.

In order to improve the running properties of the clutch halves, the interengageable annular surfaces of the

halves

9 and 9" are provided with

respective coatings

12 and 13 of bearing materials. Clutch half 9" receives, in a groove in its circumferential or peripheral surface, an annular body 14 of a material having a high friction coefficient, such as, for example, rubber, engageable by the switchable friction driving gear to rotate spindle 2.

As clearly shown in FIG. 4, the two clutch halves 9'v and 9" are firmly, butreleasably, connected with each other by a preformed spring wire part 15 designed as a locking pawl. For this purpose, spring wire part 15 has one end bent to form an eyelet 16 which is inserted into a circular end of an arcuate recess 17 of clutch half 9 (FIGS. 3 and4), and has a free end bent to form an abutment 18, this free end having an initial stress imparted thereto. Abutment 18 is releasably engageable in recesses 19 circumferentially spaced. from each other along an inner circular or cylindrical surface in clutch half 9".

By engagement of abutment 18 of spring wire part 15 in a recess 19, clutch halves 9' and 9" are firmly, but releasably, mechanically connected with each other so that the rotation imparted by pulley 5 to drive wheel 6 can be transmitted over the intermediate drive gear to clutch half 9" and, through spring wire part 15, to clutch half or disk 9' to rotate reel supporting spindle 2. When a predetermined torque is exceeded, which occurs, for example, when spindle 2 is held against rotation by tape tension when the end of the tape is reached, free end 18 of spring wire part 15 isdisengaged from a recess 19 and travels. over the adjacent ring section 20 into the following recess 19, and so on, in order to attain a mechanical separation of the clutch halves or disks 9' and 9' By such disengagement of the operating connection between

clutch disks

9 and 9", the parts of the recorder as well as the magnetic tape itself are protected against overloads. In addition, the provision of the torque responsive clutch 9'prevents formation of abrasion spots on the friction wheels and improves the synchronous running of the recorder.

At the same time, the lifting and dipping movement of wire end 18 into recesses 19, and the cooperation of end 18 with the interposed ring sections 20, produces an acoustic signal which indicates, to the user of the recorder, that the tape end has been reached so that the user is warned to shut off the drive of the recorder. It goes without saying that the coupling forces exerted by spring wire part 15 are selected to be correspondingly smaller than the driving force.

While While, the embodiment shown in the drawing, only reel supporting spindle 2 is provided with a torque responsive clutch, it is within the purview of the invention to provide another torque responsive clutch for reel supporting spindle 3, and which also serves as an acoustic signal transmitter. This insures mechanical protection for the recorder parts and the tape during reverse movement of the tape, and also indicates acoustically that the end of the tape has been reached during such reverse movement.

While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is:

1. In a magnetic tape recorder, particularly of the tape cassette type, with tape carrier reels attached on support spindles having driving pulleys, which are coupled to a rotary driving element during forward and reverse movement of the tape, by intermediate driving gear connected with the driving pulleys: the improvement comprising a torque responsive clutch included in at least the intermediate driving gear connected to the support spindle operable to effect forward movement of the tape; said torque responsive clutch being designed as an acoustic signal generator which generates an acoustic signal responsive to the tape being completely unwound from one reel.

2. In a magnetic tape recorder, as claimed in claim 1, said torque responsive clutch comprising two clutch disks mounted on the support spindle, and including a first clutch disk fixedly connected with the support spindle and a second clutch disk freely rotatable on the support spindle; and resilient elastic means firmly, but releasably, interconnecting said clutch disks for conjoint rotation.

3. In a magnetic tape recorder, as claimed in claim 2, said resilient elastic means comprising a releasable locking pawl mounted on said first clutch disk and engageable with said second clutch disk.

4. In a magnetic tape recorder, as claimed in claim 3, said releasable locking pawl comprising a preformed spring wire part having one end fixed to said first clutch disk and having a free end releasably engageable with cooperating formations on said second clutch disk.

5. In a magnetic tape recorder, as claimed in claim 4,

said spring wire part having a prestressed free end formed as a releasable abutment engageable with circumferentially spaced recesses in a cylindrical surface of said second clutch disk, said recesses being separated by interposed ring sections of said second clutch disk; said prestressed free end, when the torque on said clutch exceeds a predetermined value, being disengaged from a recess, in which it is then engaged, by the adjacent interposed ring section and engaged in following recesses in succession; said engagement and disengagement providing an acoustic signal indicating that the tape has been completely unwound from one reel.

6. In a magnetic tape recorder, as claimed in claim 2, said second such disk being mounted concentrically and rotatably on said first clutch disk; and means retaining said second clutch disk against axial displacement relative to the support spindle. v

7. In a magnetic tape recorder, as claimed in claim 6,

a coating of bearing material on that surface of at leastv one clutch disk engageable with a cooperating surface on the other clutch disk.

8. In a magnetic tape recorder, as claimed in claim 7, respective coatings of bearing material being provided on both interengageable surfaces of the clutch disks.

9. In a magnetic tape recorder, as claimed in claim 1, respective torque responsive clutches included in the intermediate driving gear connected to both support spindles, and serving, independently of each other, as acoustic signal generators.

Claims

5. In a magnetic tape recorder, as claimed in claim 4, said spring wire part having a prestressed free end formed as a releasable abutment engageable with circumferentially spaced recesses in a cylindrical surface of said second clutch disk, said recesses being separated by interposed ring sections of said second clutch disk; said prestressed free end, when the torque on said clutch exceeds a predetermined value, being disengaged from a recess, in which it is then engaged, by the adjacent interposed ring section and engaged in following recesses in succession; said engagement and disengagement providing an acoustic signal indicating that the tape has been completely unwound from one reel.

6. In a magnetic tape recorder, as claimed in claim 2, said second such disk being mounted concentrically and rotatably on said first clutch disk; and means retaining said second clutch disk against axial displacement relative to the support spindle.

7. In a magnetic tape recorder, as claimed in claim 6, a coating of bearing material on that surface of at least one clutch disk engageable with a cooperating surface on the other clutch disk.