GB2240209A

GB2240209A - A variable torque type reel driving device

Info

Publication number: GB2240209A
Application number: GB9028157A
Authority: GB
Inventors: Seung-Lyul Choi; Bong-Joo Kim
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 1989-12-30
Filing date: 1990-12-28
Publication date: 1991-07-24
Also published as: KR910013130A; IT9048428A1; DE4042133A1; KR920008479B1; JPH041962A; IT1242197B; IT9048428A0; GB9028157D0; FR2658648A1

Abstract

A variable torque type reel driving device of a magnetic recording and reproducing apparatus having a reel driving means (10) for selectively operating reels according to rotation direction thereof comprises a variable torque generating means (40), provided on one shaft, a reel speed changing means (30) for changing the speed of reels. The variable torque generating means has a declined cam (42) and a felt (22) attached to a driving pulley (20) and generates the speed slip by a pulley washer with respect to a transmitting power compressed by displacement of the cam. The reel speed changing means has a clutch member (32) and a lever (54) which is operated only in a desired mode. <IMAGE>

Description

C C, 1 2 't, r 2 >:2Or A VARIABLE TORQUE TYPE REEL DRIVING DEVICE The

present invention relates generally to an idler driving mechanism for driving selectively a supply reeldisk equipped with a tape supplying reel and a take-up reeldisk equipped with a tape take -up reel in a tape recorder and, more particularly, to a variable torque type reel driving device which can be driven by a friction force in a low-speed driving mode and which, in its rotation direction, can be driven by a variable torque in a reverse picture search(RPS) mode and is driven directly by a motive power in a highspeed driving mode.

Generally, operation mode of driving a reel in a video tape recorder has the following three mode: firstly, a playback(PB) mode which drives a tape at normal speed: secondly, a forward picture search(PPS) mode which feeds forwardly (in the clockwise direction) a tape at a speed faster than playback speed of tape to search a desired picture and a reverse picture search(RPS) mode which feeds reversely (in the counter-clockwise direction) the tape at a speed faster than the playback speed of the tape to search a desired picttjre,- thirdly, a fast forward(F/F) and rewind(REW) modes which - reproducing ing) f st move forw---,dly and rever5ely withML pi ctur 1k C C Among such case, in the reverse picture search mode, tension of tape become strong and function of tape guide is deteriorated, so that variation of tape tension, such as high tension and relaxation. is Irregularly represented, thereby making the recording and reproducing of the tape impossible. Therefore, these are reprented an noises. In order to stabilize this, torque stronger than torque of rotation of the tape reel in the play-back mode is required.

For that purpose, accordingly, the control of the torque is performed in the tape operating mode. As method of controlling the torque is used a gear train method or a variable torque method. However, use of the gear train method brings about the complicated construction and the expensive cost of production. Therefore, there is recently a tendancy to generally use the variable torque method.

Referring to Fig.1 which represents a running system of video tape as an example of a video tape recorder, a reel driving section will be explained. In Fig.1, a tape T is forwardly or reversely feeded by a supply reel SR and a take-up reel TR and is also feeded at constant speed by a capstan shaft CS and a pinch roller. If a driving mechanism D is driven by rotation force of a capstan motor CM which rotates said capstan shaft CS, a reel disks RD and RD'of said s7upply reel SR and take-up-reel TR are selectively driven by a idler ID swung left or right according to rotation direction of said driving mechanism.

That is, upon clockwise driving said idler ID, said take-up reel 1 1 disk RD' is clockwise driven and also, upon counter-clockwise driving, said idler ID said supply reel disk RD is counter-clockwise driven. And, since said take-up reel disk RD' is provided at close distance from said capstan motor CM, so large driving force (torque) is not required upon clockwise running of the tape T. However, since said supply reel disk RD is provided at relatively far distance therefrom, upon the reverse picture search RPS of the tape T the remarkable load is applied, thereby requiring the driving torque stronger than in said clockwise running of the tape T. Also, in a high-speed running mode not a normal running (low- speed running), since said capstan motor CM is rotated at high speed, one of said two reel disks RD and RD' is selectively driven. At this time, however, no slip must be generated on power transmitting system (gearing system) and the motive power is transferred as it is.

Thus, according to the driving mode of the reel, the torque must be varied and also, according to the driving speed thereof, the driving state by the motive force or the frictionally-transmitting ntate of the driving force thereby must be adequately varied. Such variation is generally performed by the driving mechanism D of said idler ID.

An example of such conventional driving mechanism as described above is disclosed in Japanese laidopened Utility Model Publication No. 1-109835, which varies the torque and has the driving functions by the motive foree and by the frictionally-transmitting of this motive force. Nowever, in this construction of said conventional C_ driving mechanism, a large amount of components is required and, for especially variable torque, three felts and four springs is used. Therefore, the large loss of power is caused and the expensive cost of production is required. Also, the assembly thereof is very complicated or troublesome.

Accordingly, it is an object of the present invention to provide a simple driving mechanism and preferably one which can comprise one felt and two springs.

It is another object of the present invention to make the loss of power as small as possible.. thereby ensuring the reliable driving by the variable torque and by the motive power.

To accomplish the afore-mentioned object of the invention, there is provided a variable torque type reel driving device of a magnetic recording and reproducing apparatus comprising a reel driving means for selectively operating reels in accordance with rotation direction thereof: a variable torque generating means provided on one shaft: a reel speed changing means for changing the speed of reels.

In a preferred embodiment of the pip-sent invention d!SC-1.c)vecl herein, said variable 'Lorque generating mean--, may inclone a d(..(-, 'jine-] (,i.m, and also said variable torque gencrating n]Eiri.g the - 4 speed slip by a pulley washer with respect to a transmitting power. compressed by displacement of said declined cam.

Also, in said preferred embodiment of the present invention, said reel speed changing means may include a clutch member and a lever which operates only in a desired mode.

Further, said variable torque generating means of the reel driving device according to the present invention can include a felt attached on a driving pulley.

Thus, the present invention is intended to provide a reel driving device in which the power is transmitted by motive force in a high-speed rotation mode and by frictionally transmitted force bringing about a predetermined torque in a reverse picture search mode and which transmits the power by a variable torque according to the rotation direction thereof in a frictional driving.

Also, according to a reel driving device of the present invention, in a reverse picture search, since a guide is prensed by the displacement of a cam guide protrusion along the declined cam, at this time the speed slip is generated between the driving pulley and the rotator assembly by the pulley washer, so that the torque is generated due to the operation of a compressed spring force and the speed slip on the pulley washer, whereby the problents of the prior art 1n the reverse, r'iC'Lur(i, search mode can he - F. - C Now, the foregoing and other objects as well as advantages of the present invention will become clear by the following description of the present invention with reference to the accompanying drawings,wherein:

1 Figure 1 shows schematically a tape running system for explaining a reel driving section of a conventional video tape recorder; Figure 2 is an exploded perspective view showing a reel driving device according to a preferred embodiment of the present invention; Figure 3 is a cross-sectional view showing the assembled state of the reel driving device according to the embodiment of the present invention; Figure 4 is a partially sectional view showing schematically a part of a second rotator assembly for explaining the operation of a cam of an embodiment of the present invention; and Figure 5 is an explanatory view for explaining the operation of a clutch in high-speed running (F/F and REW) modes of the reel driving device of an embodiment of the present invention.

The invention will now be described in detail with reference to t i.be drawings.

c In Figure 2 which is an exploded perspective view showing a reel driving device according to a preferred embodiment of the present invention. all of a driving pulley 10. a frictionally-transmitting rotator 20, a first rotator assembly 30 and a second rotator assembly 40 form single assembly and are supported on a support shaft 51 mounted on a base 50.

Said driving pulley 10 has the form of a belt pulley and includes a belt groove 11 formed to load a belt 52 on outer surface thereof, a boss insert hole 12 punched in the central portion thereof and a plurality of pin insert holes 13 formed in the constant spaces at the periphery of said boss insert hole 12.

In the reel driving device of the present invention, said driving pulley can use a capstan motor for constantly feeding a general tape as a driving source.

Said frictionally-transmitting rotator 20 is provided with a double-step boss 21 which includes a large-diameter portion 23a and a small-diameter portion 21b. Said large-diameter portion 21a is inserted into said boss insert hole 12 of said driving pulley 10 so that it can be freely rotated therein. Also, on a lower side of said small-diameter portion 21b is/are formed one or plural protrusion/protrusions 21c. On the upper portion of raid frictionally-transmitting rotator 20, is attached a felt 22 which is friet.iorij-?e(l or) the lower portion of s..ijd driving Pul 1C.V jO.

On the tipper side of said driving pulley 10 are provided siad 1? C first rotator assembly 30 which comprising a transmitting-disk 31. a clutch 32 and a clutch spring 33. Said transmitting-disk 31 includes a boss latching hole 31a in which said small-diameter portion 21b and said trusion 21c thereof are fitted, a plurality of latch hooks 31b being protruded at predetermined height and a plurality of pin through-hole 31c corresponding with said pin insert hole 13.

Said clutch 32 is latched by said hook 31b of said transmitting -disk 31. Also, said clutch 32 is provided with a plurality of pins 32a which can be inserted through said pin through-hole 31c into said pin insert hole 13 thereby to be slidably moved upward and downward therein, wherein the upward movement limit of clutch 32 is up to position where said clutch 32 is latched by said hook 31b.

- Said clutch spring 33 is disposed between said clutch 32 and said transmitting-disk 31 so that said clutch 32 can be raised up to said latched position, whereby normally said pin 32a is disposed in said pin through-hole 31c of said transmitting-disk 31. However, when said clutch 32 is pressed downward, said clutch pin 32a can be moved and inserted into said pin insert hole 13 of said driving pulley 10.

On the upper side is disposed said second rotator assembly 40 which is engaged with said boss 21 of said frictionally-transmitting rotator 20 thereby to be driven by the frictional force. Also. said second rotlator a-,;nenibly 40 compri,3es a rotator body 41,:- tubillar cr hoUow cam 42, a guide 43 and a torquechanging spring 44. Said rota- i c tor body 41 has a gear portion 41a in the periphery thereof and a plurality of guide supports 41b extended down. Said cam 42 includes a boss insert hole 42a which is rotatably disposed in the hollow portion of said body 41 and in which the upper portion of said small-diameter portion 21b of said boss 21 Is inserted and a declined cam surface 42b formed in the periphery thereof. Said guide 43 includes a cam guide protrusion 43a which communicates motion to said declined cam surface 42b and a plurality of guide grooves 43b which is engaged with said guide supports 41b. Thus, said guide 43 is limited at two heights. Said spring 44 is disposed between said guide 43 and said transmitting-disk 31.

Also, in order to space out somewhat said driving pulley 10 and said transmitting-disk 31 a pulley washer 14 is provided having the small coefficient of friction therebetween.

Figure 3 shows the assembled state of the reel driving device in the reverse picture search (RPS) mode thereof, when said driving pulley 10 is driven by a belt 52, said frictionally-transmitting rotator 20 is driven by the frictional force of the felt 22 which is frictionized with said driving pulley 10 by the force of said spring 44. By this frictionallydriving force, said second rotator assembly 40 is driven. At this time, said first rotator assembly 30 is also driven by said frictionallydriving force.

In the me-Aritime, the rotator body 41 'of the second rotAt.,,)r assembly 40 is engaged with any driven member such as idler. In such 9 - cl a case, if the load of the driven member is larger than the frictional- force between said spring 44 and said felt 22, slip occurs at said felt 22. That is, said second rotator assembly 40 is driven within the predetermined range of load. At this time, in case of being driven clockwise, the cam guide protrusions 43a of the guide 43 is positioned at the upper limit of the declined cam surface 42h formed on the cam 42 as shown by a solid line in Figure 4 so that said spring 44 is not pressed, whereby the elastic force is relatively weakened. Accordingly, since, in this case, said frictionally-driving force is no large, it is proper to drive the jight load. However, in case of being driven couter-clockwise, as shown by the broken line in Figure 4 said protrusion 43a is shifted to the lower limit position of said declined cam surface 42b so that said spring 44 is compressed, thereby bringing about the large elastic force. Accordingly, since, in this case, said frictionallydriving force is relatively strong so that said driven member can be driven counter- clockwise by the resulting increased torque, the heavy load can be driven.

As shown in Figure 4, in the reverse picture search (RPS) mode, as said protrusions 43a is shifted along said declined cam surface 42b, said protrusion 43a is compressed so that the speed slip may be caused by said pulley washer 14 shown in Figure 2 between the driving pulley 10 and the driven rotator assembly. Therefore, due to operations of the compressed spring force and the speed slip between sald driven assembly and said pulley washer. Accordingly, in the reverse picture search (RPS) mode, the afore-inentioned problenis, in - 1 () - i C which the prior art has, can be dissolved.

In the meanwhile, as shown in Figure 5, on the upper side of the clutch 32 of the first rotator assembly 30 is disposed a lever shift member 54 which is operated as a lever by a slide member 53. Also. said lever shift member 54 can be operated in the high-speed running (F/F or REW) mode as a member engaged with any separate mode changing lever.

That is, since in the normally-running mode said lever shift member 54 is not operated, said first rotator assembly 30 is not driven so that the operation thereof may be disregarded. And the second rotator assembly 40 is driven by the predetermined torque from the frictionally-transmitting rotator 20. Further, in the highspeed running (F/F and REW) mode, when said clutch 32 is lowered downward by said lever shift member 54, said pins 32a are inserted through the pin through-holes 31c of said rotator 20 into the pin insert hole 13 of said driving pulley 10. Therefore, said first rotator assembly 30 is directly driven by the motive force of said pulley 10 and this motive force is transmitted to said rotator 20. Thus, said rotator 20 is driven by the motive force independent of the frictional force by said torque changing spring 44. Accordingly, all of rotators 20, 30 and 40 are driven by the motive force. When said lever shift member 54 is returned to the original position, the clutch engagement of said first rotator assembly 30 with said driving pulley 10 is released. Consequently, szdd rotator 20 and said second rotator assembly 40 are driven by the frictional force.

11 - C.

Thus. the reel driving device according to the present invention is of a variable torque type and uses method of changing the torque by increasing or reducing the pressure of the felt by a declined cam, whose operations follow:

1.

2.

In the playback mode, the torque is generated by the f elt attached to the pulley so that the run of the tape is performed at the normal speed: In the fast forward (F/F) and rewinding (REW) modes, when the lever shift member 54 presses the clutch 32 by operation of the slide member 53. the clutch pin 32a of said clutch 32 is engaged with the transmitting-disk 31. whereby the power transmitted from the driving pulley 10 is transmitted thereto without any loss: and 3. In the reverse picture search (RPS) mode, as shown in Figure 4, as said protrusions 43a is shifted along said declined cam surface 42b, said protrusion 43a in compressed so that the speed slip may be caused by said pulley washer 14 shown in Figure 2 between the driving pulley 10 and the driven rotator assembly. Therefore. due to operations of the compressed spring force and the speed slip between said driven assembly and said pulley washer. Accordingly. in the reverse picture search (RPS) mode, the afore-mentioned problems, in which the prior art has, can be dissolved.

According to the present invention, as described above, the reel driving device of video tape recorder can perform the frictionally- i 1..

j 1 C transmitting drive, by the changed torque dependent on the rotation direction. using the second,rotator assembly provided with the torque changing means and the direct drive, by the motive force, using the first rotator assembly provided with the clutch means and the auxiliary means thereof. Also, the reel driving device of the present invention can accomplish the reduction of cost price and power loss. and can increase the productivity. Also, this invention can ensure the power transmission, thereby improving the reliability of products.

While there has been described a preferred form of the invention, obviously modifications and variations may be made without departing from the scope of the invention.

C

Claims

CLAIMS:

1. A variable torque type reel driving device of a magnetic recording and reproducing apparatus comprising:

a reel driving means for selectively operating reels according to rotation direction thereof:

variable torque generating means provided on one shaft: and reel speed changing means for changing the speed of reels.

2. A variable torque type reel driving device as claimed in claim 1, wherein said variable torque generating means may include a declined cam.

3. A variable torque type reel driving device as claimed in claim 1 or 2, wherein said variable torque generating means generates the speed slip by a pulley washer with respect to a transmitting power compressed by displacement of said declined cam.

4. A variable torque type reel driving device as claimed in claim 1, 2 or 3, wherein said reel speed changing means may include a clutch rnember and a lever which is operated only in a desired mode. -

5. A variable torque type reel driving device as claimed in any preceding wherein said variable torque generating means includes a felt atttached on a driving pulley.

1

6. A variable torque type reel driving device substantially as herein described with reference to Figures 2 and 3 with or without reference to Figures 4 and 5 of the accompanying drawings.

Published 1991 at 7be Patent Office. State House. 66/71 HW Hor T Landon WC I R 47P. Further copies may be obtained from Sales Branch. Unit 6. Nine Mile Point. Cwmielinfach. Cross Keys. NI 7HZ. Printed by Multiplex techniques ltd, St Mary Cray. Kent.