JPH0210824Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a one-way gear braking device, and in particular, the invention relates to a one-way gear braking device that controls the rotation of the gear that drives the reel stand of a video tape recorder (hereinafter referred to as VTR) in only one direction. It relates to a mechanism that applies a large load only to rotations in one direction.

[Technical background of the invention] Conventionally, as a mechanism for applying a load torque to the rotation of a reel stand of a VTR, etc., a lever 3 is rotatably supported on a support shaft 2 on the outer periphery of a reel stand 1, as shown in FIG. A soft brake 4 provided at one end of the
A method that utilizes the frictional force between the soft brake 4 and the outer periphery of the reel stand 1 by pressing the lever 3 with the urging force of a spring 5 provided on the opposite side of the soft brake 4 has been widely used. In this case, the braking force is differentiated by making a difference between the load torque for rotation of the reel stand 1 in one direction and the load torque for rotation in the opposite direction. On the other hand, in order to keep the winding torque constant, as shown in FIG. Mechanisms configured to be driven by meshing small gears 8 have also been widely used. In this case, the reel stand 1 was able to rotate independently, and a constant torque was transmitted from the large gear 7 to the reel stand 1 via the sliding portion 6.

Further, a mechanism as shown in FIG. 8 has been proposed as a mechanism that applies a small load torque to the forward rotation of the reel stand 1 and a large load torque to the reverse rotation. In the figure, a lever 10 rotatably supported by a shaft 9 is provided at one end with a semicircular convex portion 10a that slides on the outer peripheral surface of the reel stand 1, and the other end of the lever 10 is A gear portion 10b that meshes with the large gear 7 is formed, and when the reel stand 1 rotates in the forward direction (arrow A), the gear portion 10b of the lever 10 disengages from the large gear 7, and the convex portion 10a
The braking is only due to the load torque due to the sliding resistance between the reel stand 1 and the outer peripheral surface of the reel stand 1, and when the reel stand 1 rotates in the opposite direction (arrow B), the gear part 10b of the lever 10 meshes with the large gear 7, causing a large The rotation of the gear 7 is stopped, and the load torque for rotating the reel stand 1 is determined by the sliding resistance of the sliding part 6 between the reel stand 1 and the large gear 7, the outer peripheral surface of the reel stand 1, and the convexity of the lever 10. Part 10a
The load torque has become large due to the sum of the sliding resistance between the

[Problems with the Background Art] In the conventional gear one-way braking device constructed as described above, shown in FIG. 6, the load torque is applied by the biasing force of the spring 5. It was difficult to keep it within a certain range. In addition, in the mechanism shown in FIGS. 7 and 8, the load torque when the reel stand 1 rotates in the forward direction A is applied directly to the reel stand 1, so the winding torque may become smaller than the required value or the sliding may occur. The load torque fluctuates due to flaws or deformation of the surface 10a or the incorporation of foreign matter, and as a result, the winding torque also fluctuates, making it impossible to obtain the desired performance of the reel stand 1, which is a drawback.

[Purpose of the invention] The present invention was made in view of the above circumstances, and its purpose is to provide a one-way braking device for gears that has a simple structure and can guarantee rotational performance of the reel stand. be.

[Summary of the invention] This invention provides a small gear that meshes with a large gear coaxially supported through a sliding part and a reel stand of a VTR, etc., and makes contact with this small gear via the sliding surface and rotates coaxially. A gear part that meshes with a large gear is provided at one end of the movably supported lever, and by applying a load only to the large gear, the winding torque of the reel stand is stabilized to achieve the intended purpose. This is what was done.

[Embodiment of the invention] An embodiment of the one-way gear braking device according to the invention will be described below with reference to the drawings.

An embodiment of the present invention is shown in FIGS. 1 and 2. In this figure, parts that are the same as those of the conventional example shown in FIGS. 6 to 8 are indicated by the same symbols. A large gear 7 is provided at the bottom of the reel stand 1 so as to be rotatable coaxially through a sliding portion 6 with a constant load torque.
This large gear 7 is meshed and driven by a small gear 8 driven by a drive source (not shown). The large gear 7
is meshed with another small gear 12 which is rotatably supported by the shaft 11, and a lever 13 is attached to the shaft 11 so as to be able to rotate on the same axis while sliding with the small gear 12.
is provided. At one end of this lever 13,
A gear portion 13a that meshes with the large gear 7 is formed. The shaft 11 is fixed to a support 14, and a spring 15 is provided along the shaft 11 between the support 14 and the lever 13, urging the lever 13 against the small gear 12. There is pressure contact.

The operation of one embodiment of the present invention constructed as described above will be explained below. When the large gear 7 is rotated by the small gear 8 in the forward direction shown by the arrow A, rotational torque due to the frictional force of the sliding part 6 is transmitted to the reel stand 1, and the reel stand 1 rotates in the direction of the arrow A. do. At the same time, the small gear 12 meshing with the large gear 7 rotates in the direction of arrow A, and the lever 13, which is pressed against the small gear 12 by the spring 15, also prevents the lever 13 from rotating due to the frictional torque therebetween. If the torque is greater than the intended torque, the gear portion 13a rotates in the direction of arrow A, the gear portion 13a and the large gear 7 disengage, and move away from each other to a pre-provided stopper (not shown). Therefore, the large gear 7 can continue to rotate in the direction of arrow A.

On the other hand, when the reel stand 1 is rotating in the opposite direction shown by the arrow B, torque is transmitted via the sliding portion 6 to rotate the large gear 7 in the direction of the arrow B. Therefore, while the gear portion 13a of the lever 13 is not meshing with the large gear 7, the large gear 7 rotates in the direction of arrow B, but at the same time, the small gear 12 also rotates in the direction of arrow B, and the small gear 12 rotates in the direction of arrow B. The lever 13, which is in pressure contact with the lever 13, also rotates in the direction of arrow B.
The gear portion 13a of is brought into mesh with the large gear 7. At this time, if the gear part 13a is prevented from being repelled by the driving force of the large gear 7, the rotation of the large gear 7 is stopped by the gear part 13a. Even in this state, the reel stand 1 continues to rotate in the direction of arrow B, for example when rewinding a tape, and a torque generated by the frictional force of the sliding portion 6 is applied to the reel stand 1.

As mentioned above, when the reel stand 1 rotates in the direction of arrow A, the load generated when rotating the small gear 12 is applied to the large gear 7, and when the reel stand 1 rotates in the direction of arrow B, the large gear 7 stops, and the torque from the sliding portion 6 is applied to the reel stand 1. Here, when the reel stand 1 is to be rotated in the direction of arrow A by the small gear 8 which provides sliding force to the large gear 7, the sliding torque given to the large gear 7 is determined from the driving torque of the small gear 8 to the small gear 12. It is calculated by subtracting the load torque. If this difference becomes larger than the maximum torque generated in the sliding part 6, the large gear 7 will spin idly, and at this time, the driving torque applied to the reel stand 1 will match the torque that generates the sliding part 6, and will be at a certain constant value. Can be set to . In this way, regarding the reel stand 1, there is no increase in the load torque when rotating in the direction of arrow A, and the load torque is suppressed within a certain range when rotating in the direction of arrow B. As a result, it is possible to obtain a one-way gear braking device that applies braking only in one direction and has no adverse effect on the opposite direction.

Other embodiments of the present invention are shown in FIGS. 3 to 5.
In this embodiment, a braking piece 16 is provided coaxially with the lower surface of the small gear 12 instead of the lever 13 in the previous embodiment, and is biased upward by a spring 15 to apply a load torque. The same effect is produced by directly applying torque to the large gear 7 meshing with the large gear 7. In addition, as shown in the enlarged sectional views of FIGS. 4 and 5, the pinion 12
A spring 15 is incorporated between the shaft 11 and the shaft 11 so as to limit the rotation of the pinion 12 in one direction.
A support stand 14 to which the reel stand 1 is fixed is provided so as to be rotatable around a shaft 17, and when the reel stand 1 rotates forward, the small gear 12 and the large gear 7 are disengaged and no load is applied to the reel stand 1. You may choose not to give it.

[Effect of the invention] As described above, according to the invention, a small gear is provided which meshes with a large gear coaxially supported via a reel stand and a sliding part, and a gear is attached to one end of a lever that supports this small gear. Since the gear part and the large gear can be engaged or disengaged depending on the direction of rotation of the reel stand, the small and simple mechanism can only rotate the reel stand in one direction. The effect is great because it is now possible to apply a predetermined torque and guarantee the rotational performance of the reel stand.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway perspective view showing one embodiment of a one-way gear braking device according to the present invention, Fig. 2 is a plan view of Fig. 1, and Figs. FIG. 5 is a partially cutaway perspective view showing an embodiment, FIG. 5 is a partially enlarged sectional view of FIG. FIG. 3 is a partially cutaway perspective view. 1...Reel stand, 3...Lever, 4...Soft brake, 6...Sliding part, 7...Large gear, 8,1
2... Small gear, 10, 13... Lever, 14...
Support stand, 15...spring.

Claims (1)

[Claims for Utility Model Registration] (1) A disc that contacts a first gear driven by a drive source via a sliding part and rotates on the same axis due to frictional force, and a disc that meshes with the first gear and rotates. a second gear that is rotatably supported; a lever that is pressed against the second gear by a biasing force of a spring and is rotatably supported coaxially with the second gear; and a lever that is formed at one end of the lever. What is claimed is: 1. A one-way gear braking device, comprising: a gear portion capable of meshing with a first gear; (2) The second gear is provided on a support base whose one end is rotatably supported, and is capable of engaging and disengaging from the first gear while being braked by the biasing force of the spring. A one-way braking device for a gear according to claim 1 of the utility model registration claim.