EP0120838A4

EP0120838A4 - Drive mechanism for multiple, low-speed cassette recorders.

Info

Publication number: EP0120838A4
Application number: EP19820903121
Authority: EP
Inventors: Elwood G Norris
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-09-23
Filing date: 1982-09-23
Publication date: 1985-11-07
Also published as: AU8993482A; EP0120838A1; WO1984001234A1; JPS59501645A

Abstract

A portable, two-speed cassette tape recorder operable at both standard and slow speeds of less than 1.15 cm per second and driven by an electric motor (30) of low-cost category having a motor shaft (31) rotation rate of less than 700 rpm when operated at such slow speed. Recorder operation at low speed is accomplisehed by a tape drive system having a balanced flywheel (51) and pulley drive reel (52) integrally coupled to the motor output shaft (31). A drive pulley (33) is coupled to the capstan drive wheel (34) and cassette reel drive wheel (38) to provide the desired slow speed tape movement useful for speech reproduction.

Description

DRIVE MECHANISM FOR MULTIPLE, LOW-SPEED CASSETTE RECORDERS

Background of the Invention 1. Field of the Art.

The present invention relates to a cassette tap drive system for multi-speed cassette recorders which can b switched from a normal cassette speed to a slower spee suitable for voice recording and playback. More specifi cally, the subject invention relates to a drive mechanis for a multi-speed cassette recorder which enables adjustment to a very slow speed of approximately one-fourth or less of the standard cassette speed of 4.76 mm per second, utilizing a standard drive motor with speed at less than approximately 700 rpm.

2. Prior Art.

Among the great diversities of recording equipment is the unique, specific class of . low-cost, slow-speed, portable cassette recorders primarily designed and limited to speech recording and playback. This limited capacity for speech application results from non-uniform motor control leading to distorted audio output. Although such distortions are unacceptable for music reproduction, and other similar uses where pitch variations are readily detected, such distortion for speech playback is hardly noticeable.

A primary benefit of ^' limiting cassette player use for speech only is the feasibility of reducing tape, speed

O PI and thereby extending the available recording and playback time on any particular cassette tape. By reduction of speed and increasing the number of recording tracks, a single cassette tape can be extended for hours beyond its normal length of play at standard speed of 4.76 mm per second.

Although initially such slow speed recorders seemed commercially limited for use of the blind and in other circumstances where speech reproduction was the sole object, the need for slow—speed operation is now generally recognized for recording books, doc-uments, meetings, and other activities where the speech element is of dominant interest.

In view of the growing public interest in inexpen¬ sive, long-play speech recording capability, multi-speed cassette recorders have been developed which combine both standard and slow-speed functions. Standard tape speeds are used for record or playback of music and other uses well-known for standard cassette use. Alternatively, the cassette player is adapted for switching to a slow speed where only speech quality is required. An example of such a multi-speed cassette recorder is shown in U. S. Patent No. 4,215,377 by the same inventor and entitled "Multi-Speed Tape Cassette System." This recorder embodies the use of the standard cassette speed of 4.76 mm per second and includes a switch for reducing tape speed by a factor of one-fourth. The resulting capacity of a standard cassette tape is thereby quadrupled merely by virtue of the speed reduction.

Because the slow-speed function is primarily a convenience item, the typical user is not willing to pay a high cost ^• for such features. Therefore, sophisticated cir¬ cuitry is commercially unacceptable because of the resulting high price of the recorder. For example, direct drive motors which have an 80 pole or more rating and which operate typically without the use of brushes would provide the desired slow-speed operation, but would simply be too expensive. Furthermore, the number of components would typically increase the size of the cassette recorder and defeat the portability which is required for speech-related use. Obviously, one does not wish to take large taping equipment to a seminar δr meeting, when a small pocket recorder is sufficient. Furthermore, the consumer does not_^ wish to pur¬ chase expensive circuitry for reproducing music and other high-quality recordings at very slow speeds, when the standard 4.76 mm per second can be applied with inexpensive components to develop adequate music record/playback capa- bility. Accordingly, the logical choice has been to utilize standard cassette systems with standard speed for high fidelity reproduction and slow speed for low fidelity, speech use. Since both of these objectives can be realized by inexpensive, multi-speed cassette recorders, the use of. high technology to meet this commercial need has not been a practical solution. Instead, the market required simple modifications to adapt the standard cassette recorder and fRE O PI its typical components to a slow speed use.

In approaching the original problem of developing both standard and slow (one quarter) speed versatility in a single cassette recorder, numerous problems were encoun- tered. Although the prior art disclosed the use of separate idler wheels mounted for engagement with the tape drive capstan, such embodiments did not prove successful. For one reason, the motor drive requirements of switching from one idler wheel to a second idler wheel to provide slow speed was not well-suited for standard cassette components and resulted in increased costs and mechanical and electrical problems in producing an acceptable multi-speed recorder. See, for example, U. S. Patent No. 4,170,029 entitled "Multiple Speed Drive Mechanism For Cassette Recorders" by Donald D. Kahn for disclosure of separate idler wheels whose engagement provides the switch in tape drive speed.

It was determined by the subject inventor that the required cassette recorder format for a multi-speed cassette recorder of the type described above should conform substan- tially to the design of standard cassette recorders which utilize a single pulley and capstan drive. Speed adjustment by mechanical means did not appear well-suited for this type of device. Instead, a single pulley drive system was deemed appropriate, with motor speed adjustment being provided to change the rotation speed of the pulley between normal and slow speed performance.

Initially, attempts for slow-speed operation were made by the inventor by reducing motor speed from the standard 2,400 rpm to a one-quarter speed of 600 rpm. It was discovered, however, that the conventional motor in a portable cassette player failed to operate under those conditions. Instead, inaudible sound reproduction occurred, with jerking and jumping of the tape . and motor. WOW and flutter increased to 1?₀ or more during slow speed applica¬ tion. In order to develop the desired reduced speed, the inventor discovered the necessity of increasing the motor rpm to its upper limit (i.e., 3,000 rpm) and then applying a voltage drop to reduce motor speed by one-quarter to an approximate value of 750 rpm. It was discovered that conventional motors for cassette players of this type would effectively operate for speech reproduction at the approxi- mate 750 rpm range,, whereas 600 rpm was non-operational.

Accordingly, the two-speed cassette player, as illustrated in U. S. Patent No. 4,215,377, operated at approximately 3,000 rpm to give linear tape drive of 4.76 mm per second. The motor speed was then reduced by one-fourth to 750 rpm to provide a corresponding quarter speed cassette tape movement. In effect, the solution to achieving slow speed cassette playback of speech quality was initially accomplished by avoiding the non-operational range of appro¬ ximately 600 rpm. Instead, motor speed was increased to overcome this failing and thereby enable development of a single pulley drive on a capstan in a conventional tape drive format. The conventional mechanical system for driving economy-type cassette recorders is illustrated in U. S. Patent No. 4,170,029 of Kahn and 4,193,100 by James S. Bagley and Gary J. Van Norden. In each of these disclosures, as well as the standard commercial cassette recorders available in the marketplace, the cassette tape drive system comprises a motor with a pulley which transfers the rota¬ tional motion from the motor to a capstan drive assembly. A typical configuration for the capstan drive assembly is a shaft with a tape drive disc or roller which contacts the cassette tape and moves the tape at the rate of speed of the rotating face of the capstan roller. Tape movement is accomplished by trapping the cassette tape against the capstan drive roller by a pinch roller which prevents tape slippage when properly engaged. Consequently, as the capstan rotates in response to the single pulley and motor, the cassette tape is pulled at the same speed. Essentially, the rotational speed of the capstan roller is converted to linear speed in the tape movement prior to contact by tape recording, playback, or erase heads.

Typically, the capstan assembly includes a fly¬ wheel which is mounted on the capstan to stabilize rota¬ tional movement as developed by the driving motor. Accor¬ dingly, it is the capstan system which operates to directly control the tape speed in all phases of record, playback, and erase modes.

It is apparent that the capstan assembly and other moving parts which may be coupled to the pulley of the moto represent a substantial load for the drive motor. Further¬ more, it is apparent that the operation of the cassett player in both normal and slow speed modes is clearly 5 dependent upon motor operation.

Prior to the present invention, motor speed has been regulated by electronic control circuitry to adapt the typical cassette recorder for slow speed operation. Numerous variations of motor speed control circuitry exist within the ° state of the art and develop a corresponding variance to the price range of consumer products of this type. Such electro¬ nic regulation generally tends to increase the price of the recorder beyond that which the consumer is willing to pay and consequently discourages the use of a single cassette _5 player for both record and playback function.

What is needed, therefore, is an economical multi- speed cassette recorder adapted for normal speed and slow speed use wherein conventional cassette components can be utilized to avoid increasing costs and size of the cassette 0 recorder. This need arises, in part, from prior art use of electronic control circuitry to reduce motor speed for conventional cassette drive motors. The need for more costly and complex motor adjustments have resulted from the appar¬ ent limitation wherein reduction of the standard 2,400 rpm 5 of the cassette drive motor to 600 rpm or less creates mechanical problems which prevent adequate operation of the system. Based on the foregoing prior art summary, there¬ fore, the solutions available for developing slow, multi- speed cassette performance have been to (i) increase the cost and sophistication of electronic circuitry, (ii) in- crease the cassette player costs by use of high performance motors, or (iii) to increase the voltage applied to the motor to raise its rpm to its upper limit for standard play, thereby enabling a reduction in speed to yield an rpm output substantially greater than the non-operative 600 rpm value cassette drive system.

OBJECTS AND SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a slow-speed tape recorder and playback device ideally suited for voice reproduction and capable of cas- sette tape delivery at a speed less than 4.76 millimeters per second.

It is a further object of the subject invention to provide a method of converting a non-functional cassette tape drive system where rotational motion of the motor is less than 700 rpm, to an acceptable voice reproduction cassette tape drive system without the need of switching to a more expensive or sophisticated motor.

It is yet another object of this invention to provide a single pulley, cassette tape drive system capable of operation at motor rotation speeds approximately within the range of 600 rpm to 700 rpm, with minimum levels of

Wow and Flutter distortion. TS^R-^E

OMP^ It is a still further object of the present invention to provide a cassette tape recorder and playback device capable of operating at a cassette tape speed of approximately one millimeter per second -in voice reproduc- tion and playback.

It is yet another object of this invention to

" provide a cassette tape, recorder and playback device having a single pulley cassette tape drive system including a variable speed control switch for continuously adjusting cassette tape drive speed from a range of approximately .80 millimeters per second to 1.15 millimeters per second.

These and other objects are realized in a cassette tape recorder and playback device which conforms to an economy line of cassette recorders designed for voice reproduction at extremely slow speeds which substantially extend the record and playback capability with respect to record and playback time. The device includes at least one record/playback head for applying or detecting magnetic signals on a cassette tape and at least one erase head for cancelling the signal. A conventional mechanical .shifting device is utilized for contacting the respective record/ playback and erase heads at the active surface of the cassette tape. The recording device includes electronic circuitry for interconversion of electromagnetic signals and audio output signals to provide record and playback capa¬ bility to the device. A -single pulley, cassette tape drive system is provided with a conventional electric motor which typically carries limiting operational characteristics wherein the tape drive system develops non-unifor tape movement leading to unsatisfactory levels of Wow and Flutter distortion and audio output when the drive system operates at motor output shaft rotation rates less than 700 rpm, and specifically in the approximate rate of 600 rpm. The cassette tape drive system is adapted for such slow-speed operation at rates less than 600 rpm by use of a balance flywheel integrally coupled to. the output motor shaft. The flywheel enables the cassette tape driv system to overcome non-uniform tape movement and improve audio output to an acceptable output signal suitable for vocal reproduction. In addition, the cassette tape recorder and playback device includes a single pulley drive belt for converting motor rotational motion to linear cassette tape movement against the record/playback and erase heads. Motor control elec¬ tronic circuitry is coupled to the tape drive system for applying a predetermined current to the motor to establish tape movement at a uniform rate less than 4.76 millimeters per second. The motor control circuitry and other electric power requirements are satisfied by a power source coupled to the system and motor electronic circuitry for enabling operation of the cassette recorder and playback device.

Utilization of the subject invention enables oper- ation of an otherwise non-functional cassette tape recorder, where slow-speed operation at motor shaft rotation rates of less than 700 rpm would result in excessive levels of flutter and WOW distortion, making the cassette unit un¬ acceptable even for voice reproduction. By utilization of a balanced flywheel coupled integrally, to the motor output shaft, tape movement can be reduced to a range of .80 to 1.15 millimeters per second, enabling an increase of up to 5 times the standard tape time available from a cassette tape. Accordingly, the subject invention provides an additional alternative to the three previously listed options for obtaining acceptable slow-speed use for cassette tape voice reproduction systems. This fourth option has the benefit of minimal expense, maintenanc of minimal size for the tape recorder unit, minimal modification requirements to elec¬ tronic circuitry within the conventional cassette tape recorder design, and improved availability for commercial use to a broader range of markets.

These objects and other benefits of the subject invention can be better understood by. reference to the following detailed description, taken in combination with the attached drawings. * DESCRIPTION OF THE DRAWINGS

Figure 1 shows a perspective vi<*w of mechanical parts of the subject invention, with block-type diagram of electrical circuitry and related components.

Figure 2 shows a side, plan view of the mechanical parts of the subject invention shown in Figure 1;

Figure 3 is an enlarged view of the electric motor with the flywheel attachment shown in cross-section, mounted

O to the electric motor output shaft; -

Figure 4 shows a graphical representation of operating characteristics of a conventional, low-cost motor commonly applied to the class of cassette tape recorders falling within the subject matter of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

It is well-recognized in the cassette recorder industry that established classifications exist for low-cost and high-cost cassette recorders, respectively. Within the low-cost, portable recorder classification, adaption to a slow tape speed lower than one-fourth reduction, has been heretofore unsuccessful. Although such desired slower speed for vocal reproduction cassette recorders is feasible by upgrading the quality of mechanical motor drive systems, the resulting cost increases are clearly undesirable from a marketing point of view. Accordingly, the present invention is considered to fall within the specific field of cassette

^" recorder and playback devices which utilize an inexpensive electric motor as part of its tape drive system. Illustrative of this type of low-cost motor is the

Mabuchi RM-050-09220 manufactured by the Mabuchi Motor

Company, Ltd. with headquarters in Japan. This type of motor is a low-input motor primarily operated on battery power source. It is typically used in audio mechanisms such as tape recorders, record players, and the like. The armature is three-pole and utilizes brushes and bearings for current flow. Such design is basic in the industry and is well-known

^^E OMP to those skilled in the art.

As has previously been stated, the primary problem with low-speed operation (below 700 rpm) for the typical motor of this category is its lack of ability to maintain a uniform tape speed velocity. A standard cassette tape advances at 4.76 millimeters per second, and has sufficient speed to permit some motor speed variation without dis¬ torting audio output. However, when the tape speed is reduced by a factor of four or more, for example to a speed of 1.0 millimeter per second, the low-cost motors jerk and create virtually inaudible audio output, unless other fac¬ tors - are introduced to increase torque or rpm speed of the motor.

For example, with respect to the subject Mabuchi motor represented by the characteristics of Figure 4, standard speed (without load) is 2400 rpm. Reduction of motor speed by one quarter to 600 rpm fails to yield sufficient torque to maintain constant tape speed. Conse¬ quently, distortion occurs in the form of Wow and Flutter At maximum efficiency with an"rpm speed of 1700, the motor produces only 1.6 g.cm torque. This is noted from the peak of the efficiency curve /^ , where torque is shown along the X axis in a Cartesian coordinate system, and the efficiency ( ϊl ) current (I), and motor speed (N) in rpm, are shown respectively along the Y axis.

When the subject operational characteristics shown in Figure 4 are considered with a reduction in rpm, it is clear by the drastic fall in the performance curve at point 10 that efficiency falls at an extremely rapid rate between 750 rpm and 600 rpm. Based on these operational characteris¬ tics, it is not surprising that inexpensive motors such as this class represented fail to provide adequate response at low rpm. Indeed, one skilled in the art would not anticipate that this type of low-cost motor would effectively operate at speeds of less than 700 rpm.

In fact, the inventor himself discovered that a one-fourth reduction in tape speed could not be successfully accomplished except by increasing the motor speed to its maximum rpm (3000) and then effecting a one-fourth reduction to obtain 750 rpm. Furthermore, the inventor has discovered that a reduction to less than one-quarter speed (for example, one—fifth the standard speed equal approximately to 1.0 millimeter per second) fails to develop an audible sound acceptable in vocal reproduction.

Despite the apparent inadequacy of such -motors for cassette tape drive systems running at a tape speed of less than 1.2 millimeters per second (wherein the electric motor is running at less than 700 rpm) , it has now been discovered that the same non-operational speed ranges become opera¬ tional with the present invention applied. In other words, the same motor which failed to produce an audible, accep- table vocal reproduction at motor speeds less than 700 rpm and corresponding tape speed below 1.2 millimeters per second, can be converted to a functional, fully acceptable

OMP vocal reproduction recording device by mechanical modifica tion of the motor output.

This invention is embodied in Figure 1 which show basic mechanical components of a cassette tape recorder, with electrical components in block diagram form. Th cassette tape 11 is shown with its direction of emplacemen within the cassette recorder coming from the bottom of th page. Although the normal orientation of the machine show in Figure 1 would be inverted such that the cassette would be inserted from the top, the subject figure is shown i opposite orientation to disclose the basic components of the cassette tape drive system.

As with a standard cassette tape recorder, Figure 1 discloses a record/playback head 12 which is illustrated to be engaged against the cassette tape 13 wound on reels within the cassette body 14. To maximize available time for recording and playback, a double track or stereo head may be utilized and switched for single track operation to double the available time for use. In other words, if the tape speed was reduced to one-fifth the standard speed of 4.76 millimeters per second, use of a stereo or dual track record/playback head in a single track mode doubles this one-fifth reduction in tape speed to yield available taping time of ten times the tape capacity in standard, stereo mode.

Likewise, an erase head 15 is provided and is appropriately wired to provide single or dual erase capacity for the respective tracks recorded on the tape 13. The re¬ cord/playback head 12 and erase head 15 are usually mechani¬ cally ganged with a rubber, compression roller 16 which operates to impress the cassette tape 13 against the capstan drive shaft 17. This mechanical combination 12, 15 and 16 is typically engaged against the cassette and tape by a mechanical lever 18 and associated hardware which enables the displacement of the respective heads and compression wheel into engagement of the cassette or retraction when not in use.

Other mechanical levers (not numbered) are shown in common orientation with lever 18 and represent other well-known operating modes or switches, such as record, pause, rewind, etc. This mechanical hardware is not specifi- cally shown in the figures in view of its well-known nature to those skilled in the art.

In addition to standard mechanical features of a cassette tape recorder as set forth above, a complete unit requires system electronic circuitry 20 which is coupled to the record/playback and erase heads, and other necessary points of circuit connection for interconversion of electro¬ magnetic signals to and from the taping surface of the cassette tape 13 for appropriate amplification and direction to audio output. Further discussion of the specific compo- nents of system electronic circuitry is deemed unnecessary, in view of the well-developed nature of this subject. Figure 1 shows the circuitry 20 coupled to the respective record/ playback and erase heads in a graphic manner via item 21.

The circuitry is powered by a power source 2 coupled via circuit wires 23. This power source 22 typicall provides ^* power for motor control electronic circuitry 2 which maintains motor speed at appropriate levels as th tape recorder is switched from standard play to slow spee (.80 to 1.15 millimeters per second tape speed). Connecting wires 26 are graphic representations of circuitry coupling between the system electronic circuitry 20 and motor control circuitry 24. Such graphic representations are intended to cover conventional circuit arrangements for maintaining record and playback capability in standard and slow-speed operation. Therefore, further disclosure is deemed unneces¬ sary. ^* The primary focus of the subject invention is in connection with the cassette tape drive system comprised of an electric motor 30 having a rotary output shaft shown in dashed lines as item 31. Again, the components of the motor are well-known and fall within the category of low-cost motors typically applied to the portable cassette tape recorder industry. The specific motor represented in Figure 1. is Mitsumi 7610. In fact, it is to be understood that the subject motors falling within the scope of this invention have limiting operational characteristics which develop non-uniform tape movement (leading to unsatisfactory levels of flutter and WOW distortion in audio output) when shaft rotation falls below 700 rpm.

OMPI

/fa WIP The rotational motion of the motor 30 is converted to linear cassette tape movement against the record/playback and^*erase heads by means of a single pulley 33 which follows a rotational path around the motor shaft 31, the capstan drive wheel 34 and the cassette reel drive mechanism 35.

As has been previously stated, cassette tape 13 is captured between the capstan shaft 17 and compression wheel 16. The rotation of the capstan drive wheel 34 causes common rotation of the capstan shaft 17, which thereby regulates tape movement across the respective record/playback 12 and erase 15 heads.

The cassette reels 37 and 38 are powered by the single pulley 33 as it rotates drive wheel 38. This drive wheel 38 is coupled to a geared transmission wheel 39 which is capable of selectively engaging cassette drive wheels 40 and 41. The operation of this system maintains the cassette tape in a tense span from the respective cassette reels 37 and 38 across the capstan shaft 17, record/playback head 12, and erase head 15. As has been previously stated, the foregoing components have regularly been applied to standard speed and slow-speed cassette recorders. However, because of inadequate motor torque and efficiency, operation below 700 rpm and 1.2 millimeters per second tape speed has not been available. The present inventor has discovered that integral attachment of a balanced flywheel 50 to the motor output shaft 31 can convert the subject cassette recorder to an operable system suitable for vocal reproduction within the previously non-operable ranges. Accordingly, without modifi¬ cation of motor characteristics as represented in Figure 4, and without requirement of electronic circuitry modifica- tions such as increasing rotational speed of the motor to maximum levels, the unexpected and surprising results are achieved strictly by mechanical adaption.

The flywheel applied to the motor output shaft 31 must have sufficient mass to develop a required inertial force necessary to complement, motor torque to develop an opera¬ tional system. This flywheel should be at least 15 grams in weight, and usually will not exceed 150 grams. The most preferred range of flywheel mass for the type of motor represented as used in Figure 1 is 20 to 40 grams. It is important that the flywheel be integrally coupled to the motor output shaft to ensure . no free movement of the flywheel independent of the motor shaft 31.

The flywheel configuration 50 illustrated in the fi¬ gures includes its primary mass unit 51 and the drive belt reel 52. This reel may be composed of separate wall elements 52a and 52b on opposing sides of a belt drive surface 52c, or the combination can be substituted by a single element performing the same function.

The mass unit 51 of the flywheel 50 may be of any weighted material such as brass or comparable metals. The specific weight of the mass unit 51 is best optimized by empirical evaluation of the specific motor utilized in the cassette recorder. For example, each motor of different manufacturer and design will have varying performance char¬ acteristics. Because of the extreme variation of motor efficiency in the range of 600 to 700 rpm, empirical derivation of optimum flywheel weight is necessary. Numerous methods are available within the state of the art for adjusting weight in a balanced flywheel and measuring audio output and other factors for optimization.

In addition, other geometric configurations of the subject flywheel are envisioned. For example, the relative positioning of the drive belt 33 and mass element 51 may be reversed. Likewise, the reel configuration 52 may be modi¬ fied without departing from the precepts of the subject invention. It will also be apparent to those skilled in the art that other cassette tape drive systems having differing component configurations of the cassette reel drive and capstan shaft drive are possible.

Accordingly, the specific example and structure set forth in the figures is only to be considered exemplary. As shown in Figure 3, for example, the motor 30 is mounted to a cassette chassis 36, with appropriate spacing for proper tension on the pulley or drive belt 33.

The drive belt 33 is mounted on reel 52 close to the axis of the motor output shaft 31 to enhance the maintenance of momentum with respect to the motor rotation. This is contrary to standard mounting techniques in connection with the drive belt on the capstan drive wheel 34. It has been noted by the inventor that such mounting techniques greatly enhance the ability of such a cassette unit to operate at low speeds, despite normal inoperability caused by only slight variations in rpm. For example, a cassette recorder without the subject motor shaft flywheel developed .5 percent WO /Flutter at standard speed (4.76 millimeters per second). Without the flywheel attached, reduction of the motor speed by more than one-quarter (below 700 rpm) resulted in increased WOW/Flut- ter exceeding one percent. Speech was unintelligible and motor operation was sporatic and jerking. With the addition of the subject flywheel to the motor shaft in accordance with the present invention, WOW/Flutter was reduced back to .5 percent, the same level as realized at standard speed without the flywheel. This surprising and unusual result enables the same- cassette recorder which was unacceptable because of WOW and Flutter in excess of one percent to now be utilized for .vocal, reproduction. This improvement is realized without complicated mechanical adjustments and without extensive electrical regulation which has previously been required to obtain the same results.

OMP

Claims

I claim:

1. A cassette tape recorder and playback device capa¬ ble of an operating tape speed less than one-fourth the 5 standard cassette tape speed of 4.76 mm per second, said device comprising: a) at least one record/playback head (12) for » applying or detecting electromagnetic signals on a cassette tape (13); 10 b) at least one erase head (15) for cancelling said signal on the tape;

-c) means (18) for mechanically contacting said respective record/playback and erase heads to the cassette tape; 15 d) system electronic circuitry (20) coupled to the record/playback and erase heads for interconversion of said electromagnetic signals to audio output signals, to provide record and playback capability; e) a single pulley cassette tape drive system 20 including:

(i) an electric motor (30) with a rotary output shaft (31), said motor having limiting operational characteristics which develop nonuniform tape movement leading to unsatisfactory 25 levels of Wow and Flutter distortion in audio output at shaft rotation rates less than 700 rpm; (ii) means (33, 34, 13, 16) for converting motor rotational motion to linear cassette tape movement against the record/playback and erase heads; (iii) said tape drive system further being characterized by and comprising a balanced fly¬ wheel (50) integrally coupled to the motor output shaft;

(f) motor control electronic circuitry (24) for applying a predetermined current (45) to the motor to establish tape movement at a uniform rate less than 4.76 mm per second; and

(g) a power source (22) coupled to the system and motor electronic circuitry to enable operation of the cassette recorder and playback device.

2. A cassette tape recorder and playback device as defined in Claim 1 wherein the flywheel (50) coupled to the motor output shaft is further characterized by having a weight ranging from approximately 15 grams to 150 grams, the specific value within said range being empirically iden¬ tified for optimal operation for a specific electric .motor. 3. A cassette tape recorder and playback device as defined in Claim 1 wherein the means for converting motor

• rotation motion to linear cassette tape movement is charac¬ terized by a single pulley (33) mounted at the motor output shaft between the electric motor and a primary mass unit (51) of the flywheel coupled thereto.

4. A cassette tape recorder and playback device as defined in Claim 1 wherein the weight of the flywheel coupled to the electric motor output shaft is approximately 20 to 40 grams.

5. A cassette tape recorder and playback device as defined in Claim 1 wherein the tape drive system is further characterized by switching means (55) for adjusting cassette tape speed from a standard speed of approximately 4.76 mm per second to a slow speed range between approximately 0.80 mm per second to 1.15 mm per second.

6. A cassette tape recorder and playback device as defined- in Claim 5, further characterized by electronic adjustment means (24) for providing variable speeds over the slow speed range of 0.80 to 1.15 mm per second.

7. A cassette tape recorder and playback device as defined in Claim 5, wherein the slow speed of the cassette tape is approximately .95 mm per second.

O PI 8. A cassette tape recorder and playback device as defined in Claim 1 wherein the balanced flywheel is charac¬ terized by a primary mass unit configured as a circular disc (51) and having most of the weight of the flywheel, said flywheel further characterized by a reel (52) integrally attached to the primary mass unit and having a common axis of rotation and means for attachment to the motor output shaft (31), said reel being adapted with a surface and configuration adapted to drive a pulley contacted thereat as part of said means for converting rotational motion to linear tape motion.