US3651899A

US3651899A - Brake device in tape recorder

Info

Publication number: US3651899A
Application number: US24219A
Authority: US
Inventors: Tetsuji Yoshii
Original assignee: Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Holdings Corp
Priority date: 1969-10-07
Filing date: 1970-03-31
Publication date: 1972-03-28
Anticipated expiration: 1989-03-28
Also published as: JPS5028806B1; NL146915B; BE748363A; DE2015582A1; CA932675A; FR2048369A5; DE2015582B2; NL7004701A; GB1309270A

Abstract

A brake device in a tape recorder which includes a brake band entrained on a braked drum for movement in the direction of the braked drum, whereby one end portion of the brake band engages stop means in accordance with the direction of rotation of the braked drum to thereby provide a slack end portion of the brake band, while the other end portion of the brake band provides a tight portion to which is imparted a spring force having a predetermined characteristic.

Description

United States Patent Yoshii [4 1 Mar. 28, 1972 [54] BRAKE DEVICE IN TAPE RECORDER [72] Inventor: Tetsuji Yoshii, Neyagawa, Japan [73] Assignee: Matsushlta Electric Industrial Co., Ltd.,

Osaka, Japan 221 Filed: Mar.3l,197 0 [21] Appl.No.: 24,219

[30] Foreign Application Priority Data Oct. 7, 1969 Japan ..44/80056 [52] US. Cl. ..l88/77 R, 188/171 [51] Int. Cl. ..Fl6d 49/00, B60t 13/04 [58] Field of Search ..188/77 R, 166, 171

[56] References Cited UNITED STATES PATENTS 998,976 7/1911 Moody ..188/171 2,641,338 6/1953 Findley ..188/171 X 3,092,345 6/1963 Clayton et a1 ..l88/77 X FOREIGN PATENTS OR APPLICATIONS 563,517 9/1923 France ..188/77 592,187 4/1925 France ...188/77 184,585 6/1907 Germany 188/77 966,666 8/1957 Germany 188/77 961,185 6/1964 Great Britain 188/166 Primary Examiner-Duane A. Reger Attorney-Stevens, Davis, Miller & Mosher [5 7] ABSTRACT A brake device in a tape recorder which includes a brake band entrained on a braked drum for movement in the direction of the braked drum, whereby one end portion of the brake band engages stop means in accordance with the direction of rotation of the braked drum to thereby provide a slack end portion of the brake band, while the other end portion of the brake band provides a tight portion to which is imparted a spring force having a predetermined characteristic.

2 Claims, 10 Drawing Figures P'A'TENTEU MAR28 1972 SHEET 1 BF 4 PR/OR ART 2 PR/ORART FR/CT/ON COEFF/C/ENT mwmsk mikqmm IN VENTOR BY yow w h ATTORNEYS PATENTEDmza m2 3, 651,899

sum u 0F 4 3.1 E /OM10; 4,2

BRAKE DEVICE IN TAPE RECORDER This invention relates to a brake device used with the reel bed or the like in a tape recorder.

Generally, in the reel bed or the like of a tape recorder, a different braking force (or different directivity of the braking force) is required in accordance with the direction of rotation of the reel bed. Usually, the suitable directivity ratio for the braking force is 2 l in accordance counter-clockwise the variation in the amount of the tape wound on the reels, and it is required that a pair 'of such reel beds be arranged symmetrically to each other so as to ensure the smooth rotation thereof without causing the tape to be slack or broken in use. According to the prior art the braking operation has usually been mostly accomplished by the press contact of a friction shoe with the braked drum of the reel bed.

For example of the prior art brake device is shown in FIG. 1. In this device, a brake band 15 has one end thereof connected to a spring 17 through a lever 16 and the other end connected to a pivotally mounted shaft 18. The braking torque provided by a such brake device for the counterclockwise rotation of the reel bed 1 is expressed by the following equation:

Hence, the directivity ratio between the two braking torque is thus:

MBN/MBRZBLH T represents the tension in the tight end portion of the brake band during the counter-clockwise rotation of the reel bed, T the tension in the slack end portion of the brake band during the clockwise rotation of the reel bed, T the tension, in the slack end portion of the brake band during the clockwise rotation of the reel bed, the angle of contact of the brake band with the braked drum (FIG. 2 relates to the case where 0 180), p. the coefficient of friction between the braked drum and the brake band, R the radius of the braked drum, M the braking torque during the counter-clockwise rotation of the reel bed, and M the braking torque during the clockwise rotation of the reel bed.

The foregoing equations (2) and (4) correspond to curves a and b of FIG. 2, respectively, which indicates that the value of M or braking force during the counter-clockwise rotation of the reel bed is greatly varied with the variation in the friction coefficient ;1.. It is also apparent from the equation (5) that the directivity ratio is increased in terms of exponent. For example, if n is coefficient, the initial friction coefficeint, B the braking force during the counter-clockwise rotation of the reel bed and A the braking force during the clockwise rotation, as shown in FIG. 2, then the directivity ratio is approximately 2 1, whereas if the friction coefficient is varied to a, 0.5, the braking forces during the respective rotations will be 13 and A and accordingly the directivity ratio between these braking forces will be sharply increased from 2 l to 4.5 I.

With the prior art brake device, the friction coefficient thus tends to increase with the use of the device. Especially with the band type brake device, the braking force provided thereby varies approximately in proportion to a value having the friction coefficient as the exponent thereof and such variation affects the directivity ratio so greatly that the latter increases even up to a ratio two or three times as high as an initially set value. More specifically, if the initially set directivity ratio is 2 1, the ratio will be increased to 4 1 l to 6 l, and

such a great increase in the directivity ratio results in breakage, dilation or other damage of the tape during use.

It is an object of the present invention to provide a brake device which comprises a brake band entrained on a braked drum, spring means connected to the ends of said brake band,

and stop means separately provided adjacent to said ends of said brake band, whereby one end portion of said brake band engages one of said stop means in accordance with the direction of rotation of said braked drum so as to provide a slack portion of said brake band which is free from any spring force while the other end portion of said brake band provides a tight portion to which is imparted a spring force having a predetermined characteristic.

It is another object of the present invention to provide a brake device which comprises a brake band entrained on a braked drum, said brake band having their ends connected to a lever at two points therein, and resilient means interconnecting said lever and a fixed portion in such a manner that the end of said resilient means connected to said lever lies at apoint which divides the distance between said two points of said lever, said resilient means being designed so as to exert a component of force on the tight portion of said brake band during the rotation of said braked drum in either direction.

According to the present invention, the brake band entrained on the braked drum is movable in the direction of rotation of the braked drum, whereby one end portion of the brake band engages stop means to provide a slack portion of the brake band in accordance with the direction of rotation of the braked drum while the otherend portion of the brake band provides a tight portion to which is imparted a spring force having a predetermined characteristic. Thus, as the friction coefficient increases during the operation of the brake band, the tension in the slack portion of the brake band approaches zero so that the braking force is determined only by the spring force exerted on the tight portion of the brake band substantially without being affected by the variation in the friction coefficient. This leads to the provision of a highly stable and novel brake device.

With the prior art brake device, it has been impossible to predetermine or foresee the limit of the variation in friction coefficient. In contrast, according to the present invention, the friction coefficient can always be limited within a predetermined allowable value so that any inconvenience resulting from too great a variation in the friction coefficient may be completely prevented. Also, such an allowable limit and the directivity ratio are determined only be the selection of the resilient forces for two springs, and this leads to the elimination of the need to pay minute attention to the materials forming the brake band and braked drum, the workmanship of such members, the value of coefficient of friction therebetween and other factors. Moreover, any variation in the friction coefficient during the use of the brake device may be substantially negligible. Thus, the brake device according to the present invention is very excellent in working life and stability of performance as well as simple and easy to manufacture, and thus it eliminates the drawbacks peculiar to the prior art brake device.

The invention will now be described by way of example in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic front view showing an example of the brake device according to the prior art;

FIG. 2 is a graph for illustrating the relation between the friction coefficient and braking forces provided by the device of FIG. 1;

FIG. 3 is a schematic front view showing an example of the brake device according to the present invention;

FIGS. 4 and 5 are similar front views but showing the device of FIG. 3 in different operative positions;

FIG. 6 is a graph for illustrating the relation between the friction coefficient and braking forces provided by the device of FIG. 3;

FIGS. 7 to 9 are schematic front views showing another example of the brake device according to the present invention, and illustrating the device in variousoperative positions; and

FIG. 10 is a schematic front view showing the brake device of FIGS. 7 to 9 as applied to the reel device in a tape recorder.

Referring to FIG. 3 which shows an example of the brake device according to the present invention, there is seen a reel bed 101 and a brake band 102 entrained on a braked drum provided by the reel bed 101. One end 103 of the brake band 102 is secured to an arm 107 at one end thereof. The arm 107 has a spring 105 connected thereto and is pivotally mounted by means of a shaft 106. The arm 107 is normally urged by the spring 105 so as to engage stop means 108. The other end 104 of the brake band 102 is connected to a spring 109 by means of a lever 110 mounted for pivotal movement about a shaft 112. The resilient force of the spring 109 is selected to be at a lower level than that of the spring 105 so that the brake band 102 is normally urged by the spring 105 so as to maintain the lever 110 slightly disengaged with stop means 111. The slight disengagement between the lever 110 and stop means 111 allows the brake band 102 to move in the direction in which the braked drum is rotated. This arrangement is such that either the arm 107 or the lever 110 is automatically and selectively engaged with the stop means 108 or 111 in accordance with the direction of rotation of the braked drum. An electromagnet 113 is provided to release the brake during the operation, and this electromagnet is provided with a plunger having a pin 1 14 studded at the lower end thereof.

Description will now be made of the operation of the abovedescribed brake device.

FIG. 3 shows the brake device in a braking position. If the brake releasing electromagnet 113 is energized with the brake device in this position, the plunger is raised by the electromagnet so that the pin 114 studded in the plunger engages the lever 110 to rotate the lever counter-clockwise and thereby release the brake as shown in FIG. 4. When the reel bed 101 is rotating counter-clockwise, a braking force in the counterclockwise direction as indicated by an arrow b is imparted to rotate the brake band 102 together with the braked drum in the direction b so as to engage the lever 110 with the stop means 111. Thus, the spring 109 has its resilient force nullified while the other spring 105 alone is at work, whereby there is established the relation as expressed by the aforementioned equation (4), which vmeans the same characteristic as that shown by a curve a" in FIG. 6. If a braking force is imparted to the reel bed 101 when it is rotating in the clockwise direction as indicated by an arrow a in FIG. 3, the arm 107 then engages the stop means 108 to nullify the resilient force of the spring 105 and leave the spring 109 alone at work. Thus, there is established the relation of the equation (4) as in the abovedescribed case of the counter-clockwise rotation, to thereby provide the same characteristic as that shown by the curve a.

Accordingly, in the same way as in the case of the equation (4),.the braking torque for the counter-clockwise rotation of the reel bed 101 (i.e. the case of FIG. 5) will be expressed as:

Similarly, the braking torque for the clockwise rotation ITe. the case of FIG. 3) will be expressed as:

:I-Ience, the brake device of the present invention has the directivity ratio expressed as follows:

0* 1 7 MBN 1 M BR 0 1) E TgR This means that the directivity ratio of th e "Brake deviceis determined only by the tensions T and T of the

springs

105 and 109, thus resulting in the characteristic curves b" and a" as shown in FIG. 6, which relates to the case where 0 equals 180.

Referring to FIG. 7, there is shown another embodiment of the present invention. This alternative example includes a braked drum 201 rotatably mounted on a shaft 202. A brake band 203 is entrained peripherally of the braked drum 201 and has the ends thereof secured to a lever 204 at 205 and 206. Resilient means 207 is provided between the lever 204 and a fixed portion 209 to interconnect them. One end of the resilient means 207 is secured to the lever 204 at a point 208 which divides the distance between

thepoints

205 and 206 into a desired ratio a b and the other end of the resilient means a la secured to a b portion 209. Stop pins 210 and 21 1 are provided to restrict the movement of the lever 204.

In the normal position of the FIG. 7 device, if the force of the resilient means 207 is represented by T components of force T and T exerted on the

respective points

205 and 206 in the lever 204 will be:

If a braking force is imparted to the braked drum 201 when it is rotating in the clockwise direction A as shown in FIG. 8, then the component of force T will be:

T, T e. 9

where T represents the tension produced in the slack end portion of the brake band 203 during the rotation of the braked drum 201 in the direction A, e the base of natural logarithm, p. the coefficient of friction between the braked drum 201 and the

brake band

203, and 0 the angle of contact of the brake band 203 with the braked drum 201. As a result, there is provided the following braking torque M If, on the other hand, the braked drum 201 is rotated in the counter-clockwise direction B, the lever 204 will be slightly rotated for disengagement from the stop pin 210 and for engagement with the other stop pin 211. In this position the braking torque M will be expressed as:

T represents the tension produced in the slack portion of the brake band 203 during the rotation of the braked drum 201 in the direction B.

The characteristics of the braking forces thus derived by the equations (13) and (16 are shown in FIG. 6, which indicates that the braking forces increase with the increase of the friction coefficient p. but they converge for the predetermined values of LR and ER. Therefore, as shown by the curves in FIG. 6, there is provided a much less variable, stable braking characteristic. The directivity ratio between the braking forces can be derived from the previous equations (13) and 16) as follows:

a MB -l- TOR a FIG. shows the braking device of the present invention as applied to the reel mechanism of a tape recorder. Numeral 212 denotes a plunger type electromagnet having a braking rod movable integrally therewith. Movement of the braking rod 213 controls the release of the brake band 203.

As has been described above, the brake device of the present invention comprises a brake band entrained on a braked drum and having their ends connected to a lever at two points thereof, and resilient means interconnecting the lever and the fixed portion of a tape recorder. The end of the resilient means connected to the lever is located at a point which divides the distance between the aforesaid two points of the lever into any desired ratio, so that a component of force is exerted on the brake band during the rotation of the braked drum in either direction. This arrangement results in the following advantages:

a. For any variation in'the friction coefficient, there is obtained a less variable braking force showing a stable braking characteristic; and

b. The directivity of the braking force is not affected at all by the friction coefficient, but is always maintained at a predetermined ratio.

Thus, the present invention provides an ideal brake device which is free from any trouble such as breakage of the tape and which is simple in construction as shown in the foregoing embodiments.

What is claimed is:

l. A brake device, comprising:

a brake band fitted to the contour of a braked drum:

an arm having one end connected with one end of said brake band, said arm being pivotally supported at the other end thereof;

a lever having one end connected with said other end of said brake band, said lever being pivotally supported at the center thereof;

a first spring means having one end connected to said one end of said arm and having the other end fixed stationary;

a second spring means having one end connected to said one end of said lever and having the other end fixed to a stationary member;

wherein said first and second spring means are arranged such that when the brake device is shifted into a braking position said brake band is pressed against the braked drum due to the tension of both said spring means;

a first stop means fixed near said arm and said first spring means, said first stop means being spaced at a predetermined distance from said arm; and

a second stop means fixed near said lever and said second spring, said second stop means being spaced at a predetermined distance from said lever, whereby one end portion of said brake band is hindered from further movement when at least one of said arm and said lever engages one of said corresponding stop means in accordance with the direction of rotation of said braked drum to provide a slack portion of said brake at said one end which is free from any spring force while the other end portion of said brake band provides a tight portion to which is imparted a predetermined spring force.

2. A brake device, comprising:

a brake band fitted to the contour of a braked drum;

a lever having its ends connected to ends of said brake band,

respectively;

resilient means interconnecting said lever and a fixed point of said brake device such that the end of said resilient means connected to said lever lies at a point which divides the distance between said ends of said lever and such than when said brake device is shifted into a braking position said brake band is pressed against said braked drum due to the tension of said resilient means; and

first and second stop means respectively fixed to stationary means near said ends of said lever and spaced at predetermined distances from said ends,

whereby said resilient means exert a component of force on the tight portion of said brake band during the rotation of said braked drum in eigher dirsctign.

Claims

1. A brake device, comprising: a brake band fitted to the contour of a braked drum: an arm having one end connected with one end of said brake band, said arm being pivotally supported at the other end thereof; a lever having one end connected with said other end of said brake band, said lever being pivotally supported at the center thereof; a first spring means having one end connected to said one end of said arm and having the other end fixed stationary; a second spring means having one end connected to said one end of said lever and having the other end fixed to a stationary member; wherein said first and second spring means are arranged such that when the brake device is shifted into a braking position said brake band is pressed against the braked drum due to the tension of both said spring means; a first stop means fixed near said arm and said first spring means, said first stop means being spaced at a predetermined distance from said arm; and a second stop means fixed near said lever and said second spring, said second stop means being spaced at a predetermined distance from said lever, whereby one end portion of said brake band is hindered from further movement when at least one of said arm and said lever engages one of said corresponding stop means in accordance with the direction of rotation of said braked drum to provide a slack portion of said brake at said one end which iS free from any spring force while the other end portion of said brake band provides a tight portion to which is imparted a predetermined spring force.

2. A brake device, comprising: a brake band fitted to the contour of a braked drum; a lever having its ends connected to ends of said brake band, respectively; resilient means interconnecting said lever and a fixed point of said brake device such that the end of said resilient means connected to said lever lies at a point which divides the distance between said ends of said lever and such than when said brake device is shifted into a braking position said brake band is pressed against said braked drum due to the tension of said resilient means; and first and second stop means respectively fixed to stationary means near said ends of said lever and spaced at predetermined distances from said ends, whereby said resilient means exert a component of force on the tight portion of said brake band during the rotation of said braked drum in either direction.