JPS5974897A - Drive for cable hoisting drum - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a drum hoist or winch, particularly of the type used for raising and lowering platforms and scaffolding.

Drum hoisting rocks and drive mechanisms for hoisting operations are used to raise and lower scaffolding used for cleaning window glass outside tall buildings, and to raise and lower mine cars and elevator compartments inside mines and buildings. are known. A typical drive mechanism is a drum roller mounted on a support frame having a shaft connected to a gear mechanism connected to a reduction gear and a drive motor. Since damage to a single tooth on the drive wheel will render the hoist inoperable, it is common to provide a brake on each drum to avoid failure of the control of the hoisting drum.

For this reason, the drive mechanism often has a complicated structure and is expensive to manufacture.

Regulations usually require that the hoisting cable be wound on the drum in a single layer. This means that for a 152.4 m (500 ft) building with a scaffold suspended by four cables, at least 609.6 m (2000 ft)
ft) of cable wrapped around the drum in a single layer. Even making the system more compact with multiple drums instead of one large drum increases the cost of the gear train for the multiple drum system and makes individual emergency braking systems for each drum very expensive. 0 Integrity for multiple drum assemblies should the gear train fail due to damage to a single gear component and some emergency braking systems may be complex enough to require careful maintenance. Consideration becomes important.

It is known to use mechanical linkages to enable simultaneous movement of two spaced apart rotatable objects. For example, U.S. Pat. No. 3,229,807 discloses a mechanical linkage system that incorporates a pair of spaced apart pivot shafts with cam members together with interconnecting links;
In this device, the eccentricity of the cam member is sufficiently small that both the lever and the manual rotation means must be moved in the same direction to allow movement of the lever.

At least one cam lug mounted eccentrically on the shaft such that it overlaps the shaft, and a similar cam lug housing or additional shaft mounted on a second shaft supported at a distance from the first shaft. A coupling body interconnected by an internal linkage device was envisaged on the upper cam projection. A hoisting drum mounted concentrically on at least one of the drive or driven axes rotates with the other axle for hoisting or releasing one or more cables for raising and lowering the cable-coupled scaffold.

In particular, the drive device of the invention for simultaneously rotating a plurality of hoisting drums comprises at least two parallel shafts spaced apart and rotatably supported in a frame.

a drum mounted concentrically on at least one shaft for winding and housing a cable; and at least one circular cam protrusion mounted eccentrically on each shaft so as to overlap said shaft with the same eccentricity relative to the axis of each shaft. and internal link plates rotatably interconnected to the cam projections of each shaft, such that rotation of one of the shafts simultaneously rotates the other shaft thereby transmitting vibrational motion to the link plates. ing. One or more circular cam projections mounted eccentrically on each shaft overlap the shafts. The two cam projections, mounted eccentrically on each axis, are preferably angularly displaced, ie approximately 90° out of phase with respect to each other. Three cam lobes mounted eccentrically on each axis are out of phase with each other by an angle of about 120 degrees, and four or more cam lobes are similarly angularly out of phase with each other.

Each cam protrusion has the same diameter and has the same degree of eccentricity with respect to the axis LL% of each shaft.

The cam projection drive system of the present invention preferably uses three equally spaced cam projections mounted on each shaft and attached directly to the drum end flange. These cam protrusions are made large enough to overlap the shaft and are placed closer to each other compared to a normal drive mechanism mounted independently outside the drum drive shaft to avoid interference with the link to the shaft. Actuate the drive link plate inside the end of each shaft adjacent the drum end flange. The link plates connected directly to the drum through the cam projections provide maximum safety during the joint use of the eight drive clusters, establishing uniform power transmission.

The combined body of eight cam protrusions attached to the shaft is
A similar method in which each cam protrusion is shifted in phase angle by 120° with respect to the adjacent cam protrusion, has the same degree of eccentricity with respect to the axis of the shaft, and is mounted on a second shaft supported at a distance from the first shaft. 0 on each of said drive or driven shafts interconnected with cam lugs or additional on-shaft cam lugs arranged in a manner that provides reliable and uniform rotation of one or more shafts by the drive shaft; Concentrically mounted hoisting drums can be rotated to hoist and release one or two pairs of cables on the drum together to raise and lower the cable-connected scaffold.

The drive device of the invention for simultaneously rotating a plurality of hoisting drums preferably comprises at least two shafts spaced apart in parallel and rotatably supported in a frame, and a cable attached concentrically to at least one of said shafts. The drums for winding and storing the drums are rigidly mounted close to each other so as to overlap each shaft so that the phases are different from each other by 120°, and have the same eccentricity with respect to the axis of each shaft. eight circular cam protrusions of equal diameter, each of which is rotatably connected to the cam protrusion of each shaft so that rotation of one of the shafts simultaneously rotates the other shaft, thereby transmitting vibrational action. eight interlocking internal link plates, means for driving one of said shafts, and damping means for reducing the speed of oscillatory operation of said link plates to slow but stop the rotation of said drum. Equipped with.

The operation of three drive link plates close to each other allows the use of a novel braking device. This device acts simultaneously on the drive plate or on an extension of the drive plate, or on a shaft interconnected to the drums, and engages all drums reliably and directly. Therefore, a plurality of drums can be reliably controlled using one braking device.

One brake and one drive link plate can transmit all braking or driving power to all drums through one plate and cooperating cam.

The use of a shaft braking system, usually with frictionally engaging arrangements, provides sliding frictional action only during positive braking of the hoist and allows pre-assembly of the assembly at the factory.

Large cam lobes are not subject to high operating pressures caused by small tolerances of gear teeth. Longer life and reliability are achieved without the need for small tolerances and complex and expensive lubrication systems.

Horizontal hoists that are normally positively driven require adjustment of the suspension cables on the hoisting drum. The cam lug drive of the present invention can be used to drive an adjustment screw that is easily combined with a hoisting drum.

A multi-drum hoist with this device allows the use of smaller diameter drums to accommodate the reduction in drive torque. This low torque requirement reduces the size and cost of the primary drive used to couple the drive motor to the hoisting drum. Also, the use of multiple drum systems significantly reduces overall size compared to a single drum system.

A first object of the invention is therefore to provide a drive for a hoisting drum which is simple to operate, reliable, safe and relatively light and compact.

The present invention will be explained in detail below with reference to the drawings.

In Figures 1 and 2, a typical hoisting machine for raising and lowering scaffolding from the top of a building comprises a scaffold lO having a pair of cables 12, 14 proximate each end of the scaffold. Raise and lower the scaffold while maintaining a horizontal and fixed position. The cables 12, 14 pass over pulleys 16, 18, respectively, which are rotatably supported on support arms 20.22.

The support arm 20.22 is supported by a moving platform 24. This carriage 24 has wheels 26 for transverse rails 28 permanently fixed to the roof 80 parallel to the roof edge 82.

A hoist (not shown) rotatably mounted in the moving table 24
The cable 12.14 is wound up and accommodated in order to raise and lower the scaffold 10.

The embodiment of the invention shown in FIGS. 8-6 includes a frame 89 having spaced parallel supported side walls 40,41;
Flanges 48.45 and connecting members 47 secure side walls 40.41 to support carriage 88 as shown in FIG.

An opening 42 is provided in the side wall 40.41 in which a bearing 44 is formed for receiving an end 46, 48 of each shaft 50.52 and 54. A drum 56.58 is mounted concentrically to the shaft 50.52 by a drum end flange 60.62 attached to the shaft 50.52. Shaft 54 is provided with an externally threaded groove 64 along its length to accommodate a horizontal winder 66, which will be described in detail below.

8 cam projections 68.70 on each shaft 50.52 and 54
．． 72, which have a phase of about 1 with respect to the adjacent cams.
The angles are set to be different by 20 degrees, and the eccentricity of each shaft is set to be the same with respect to the center of the axis.

The cam protrusions 68, 70, 72 have the same diameter and are My
and install it. The cam protrusion 68 is connected to the drum end flange 6
2 or are an integral part of the drum end flange 62, the cam projections 70.72 are attached to the shaft by splines, as known to those skilled in the art, and these can be used for repair and replacement purposes. The cam protrusion can be completely removed. All the cam lugs overlap the shaft 0. The cam lugs, respectively designated by the same reference numerals 68, 70.
78, respectively. Each drive link has a circular opening 80 formed to loosely accommodate a cam protrusion for oscillating rotation. The term "internal" is used herein in reference to link, meaning a link that oscillates about an axis inside the shaft end to cause the shaft to overlap the cam projection.

When the drive shaft 50 rotates around its axis, the cam protrusion 6
8, 70.72 rotates eccentrically with this, and the shaft 50
converts the rotation of the drive links 74, 76, 78 into oscillatory motion of the drive links 74, 76, 78, which causes the cam projections 68, 70.72 and the driven shaft 52.54 to rotate with the shaft 50, as shown most clearly in FIG.

The shaft 50 is provided with a shaft end portion 82 with a spline or a keyway, and this is accommodated in a joint 84 of a drive motor gear reduction gear 86 for normal rotation of the shaft 50.

As best seen in Figure 8.7.8, the caliper brake, designated 90, comprises a housing 92 rigidly mounted to a support frame, not shown, within which links 74,
76.78 vibrates. A pair of upper and lower parallel sliding rods 97 and 98 are attached to a pair of end plates 94 and 96 provided on the housing 92.
Install. An intermediate plate 99 rigidly connected to a pair of rods 97 and 98 has an opening 100, and a plunger rod 101 that projects into the housing 90 through an opening 102 in the plate 96 is slidably accommodated in the opening 100. do.

A compression spring 103 is installed in the housing 90 by a ring 104 so as to be concentric with the rod 101, and the seventh
The rod 101 is pressed to the right in the figure.

An over-center release 10 is provided on the outside of the housing 90.
5 and plunger rod 9 as shown in Figure 8.
Vertical movement in the direction of the arrow 8 is the plunger rod 101
, and move the rod 101 to the right.

A pair of sliding plates 1 loosely attached to a pair of rods 97.98
20 and 121 position and support friction pads or brake pads 122 and 128 in openings 119 formed in these sliding plates. A pair of brake pads 124, 12
5 are positioned in recesses 126, 127 formed in plates 99,94.

The action of rod 93 during an emergency stop by an overspeed sensitive device is known to those skilled in the art and causes rod 101 to be forced into the position shown in FIG. Stopping is achieved by frictional engagement of the brake pads on the links or their extensions.

In particular, in FIG. 3.4, the support block 106 provided on the horizontal winder 66 is screwed onto the shaft 54, so that when the shaft 54 is rotated by the connecting link, the support block 106
6 is caused to reciprocate axially along the axis 54.

Support block 106 has two spaced pairs of rollers 110
The rollers move within the channel-shaped passage 112 to maintain the block 106 in an upright position. A bracket 114 on the carriage 108 connects the cable 12 or 14 to the drum 56.58.
It supports a double grooved pulley 116 for guiding.

FIG. 5 shows another embodiment of the invention, in which a pair of spaced double grooved pulleys 116, 116' guide the cable 12, 14 onto the drum 52, which This means winding up four support cables 12.14.

FIG. 9 shows an embodiment of the present invention, in which one cam protrusion 153 is provided on each shaft 150, 151, 152, and this cam protrusion is attached to an end flange 155 of each drum. There is. As discussed above, links 158 interconnect the cam projections to the drive link.

FIG. 10 shows another embodiment, in which each
A pair of cam protrusions 160, 161 shifted at an angle of 0° are attached to shafts 162, 164, 166, and links 168.1
They are interconnected by 70.

Shafts 174, 176 of the embodiment of the invention shown in FIG.
Four cam protrusions 172 are mounted on 178. In all embodiments, the cam projection overlaps the shaft to vibrate the link inwardly of the shaft end.

FIG. 12 shows an embodiment of the invention in which four drums 131, 132, 133, 134 are simultaneously driven by the inventive drive system designated by 135. The brake 136 is connected to all drums 1 through a connecting link.
Horizontal winder 1 that effectively controls the braking of 31 to 134
38 has a pulley 139 with four grooves, and the drum 130-1
Cables 140, 1 aligned perpendicularly to each other at 34
41. Leads to 142, 143.

In another embodiment of the braking device shown in FIGS. 13-17, the braking device, designated by 200, is mounted axially on a shaft 202 (or drum shaft), which shaft 202 is connected to a first
As shown more clearly in Figures 3 and 14, the eight cam protrusions 2
04, 206, 208, and are rigidly attached to both these cam lugs and link plates 205, 207, 209 interconnecting these cam lugs to the corresponding lugs of the parallel shafts.

A hub 210 is rotatably and concentrically attached to the shaft 202 and rigidly attached to the cam protrusion 208, and is supported by the support pusher 212. The hub 210 has a support plate 214 having a friction plate 216.
and a pair of colliding plates keyed together as by the use of dowels m21g.

220. Support plate 214 is rigidly attached to hub 210 and discs 218, 220 are slidably attached for rotation on hub 210. The shaft 202 abuts a compression plate 224 having a friction disk 226 against the disk 220.
The plate 224 is slidably attached to the hub 21 through the shell.
The compression plate 224 is pressed against the disk 220 by a plurality of compression springs 225 coaxially attached to bolts 228 screwed into the same gap. The spring 225 is compressed between the ring 230 and the compression plate 224 at a predetermined setting, thereby causing the disks 218 and 220 to compress the M friction disk 216.
．． 226 collide with each other and are connected by friction, so the disk 218
, 220 normally rotate together with the hub 210.

Disc 220 has a plurality of equally spaced cams or cam projections 282 formed around the periphery of disc 220, and disc 218 has a plurality of dog figures 284 defining notches 286 around the periphery and corresponding to cam projections 232. Sensitive actuation device 2 rotatably attached to a shaft 240 placed on a stationary bracket 241
88 is pressed clockwise in FIG. 13 by the tension spring 242 so that the cam follower member 2441 supported on the cam arm 248 rests on the cam protrusion 282. Since the cam follower member 244 is placed on the cam protrusion 282, the cam follower member 244 is lowered on the opposite side of the cam protrusion 232, and the engaging roller 246 is aligned with the notch 236 in the housing that rotates the sensitive actuation device 238 in the opposite direction. The sensitive actuator 288 is moved against the shaft 24 against the spring force of the spring 242 to
16, the engagement roller 246 passes through the notch 236 and FIG. 284.

The tension in spring 242 is increased by axial movement of a threaded bolt 250 coupled to spring 242 such that cam follower 244 moves along protrusion 282 up to a predetermined rotational speed of shaft 202 .

As the rotational speed of shaft 202 and disk 220 increases, the inertia of vibration-sensitive actuator 238 causes cam follower 243 to move away from the surface of cam protrusion 232, which in turn causes engagement roller 246 to dog, as shown in FIG. Contact the approaching surface of Figure 234. The acute angle defined by the face of notch 286 completely accommodates engagement roller 246. Disk 218,2
20 is prevented from rotating further and then the friction disk 2
16.226 to the plates 214, 224, and this frictional resistance is transferred to the hub 210 and the cam protrusion 204.20.
6.208, the information is transmitted to the drive device through the interconnection of the link plates 205, 207, and 209, and the hoisting state is stopped smoothly and quickly.

Limit switch 260 at the same time as the positive braking action caused by sensitive actuator 238 in the position shown in FIG.
opens. Limit switch 260 is sensitive actuator 288
is electrically connected to the hoisting drive motor by an associated actuating device 267.

Therefore, the rotation of the hoisting drum is stopped by cutting off the hoisting drive motor.

[Brief explanation of the drawing]

Figure 1 is a perspective view of a conventional hoisting device used to raise and lower scaffolding for cleaning windows of tall buildings.
FIG. 8 is a partially cutaway perspective view of the drive mechanism in a preferred embodiment of the present invention; FIG. 4 is the book shown in FIG. 8; FIG. 5 is a cross-sectional view taken along line 5--5 of FIG. 4 showing the winding of a pair of hoisting cables on the drum by broken lines; FIG. 6 is a partially cutaway side view of an embodiment of the invention; A side view showing the internal link plate interconnecting the axle cams in the device shown in FIG. 4, and FIG. An end view of one embodiment; FIG. 8 is an end view corresponding to FIG. 7 showing the braking device in the actuating braking position; FIG. 9 is an end view showing one cam protrusion on each shaft. FIG. 10 is a side view of yet another embodiment of the invention showing a pair of cam projections on each shaft; FIG. 11 is a side view of a further embodiment of the invention showing a pair of cam projections on each shaft; FIG. FIG. 12 is a front view of an embodiment of the invention with four hoisting drums; FIG. 18 is a perspective view of another embodiment of the braking device; Figure, 14th
The figure is a sectional view of the braking device taken along line 14-14 in FIG. 13, FIG. 15 is a side view of the braking device shown in FIG. 18, and FIG.
Figures 1 and 17 are side views showing the operation of the sensitive actuator. 10...Scaffolding 12, 14...Cable 16.18...Pulley 20, 22...Support arm 24...Moving platform 26...Wheel 28...
・Horizontal rail 30... Rooftop 32... Edge
38... Support carrier 39... Frame 40.41... Side wall 43.45... Flange 47... Connecting member 50.52.54...
Shafts 56, 58... Drums 60, 62...
Drum end flange 64...Male thread groove 66...Horizontal winder 68, 70, 72...Cam protrusion 74
．． 76.78... Drive link 80... Circular opening 8
2...Shaft length part 84...Joint 86...Reducer 90...Caliper brake 92...Housing 98...Plunger rod 94, 9
6... End plate 97, 98... Parallel sliding rod 9
9... Intermediate plate 100... Opening 101...
・Plunger rod 108...Compression spring 1
04...Link 105...Over center release 106...Support block 108...Transport platform 110...Roller 112...Groove type passage 11
4... Bracket 116, 116... Double grooved pulley 119... Opening 120, 121.
...Sliding plates 122, 128, 124, 125...
・Brake pads 126, 127... recess 13
1,132.133.134...Drum 185...Drive device 186...Brake 138...Horizontal winder 189...Pulley 140, 141,
142, 143... Cables 150, 151,
152...Shaft 158...Cam protrusion 155...
End flange 158... Link 160.161...
・Cam protrusion 162, 164, 166...shaft 168,
170...Link 172...Cam protrusion 174
．． 176.178...Axle 200...Brake device 202...Axle 204, 206,
208...Cam protrusion 205.207, 209...Link plate 210...Hub 212...Support bush 2
14...Support plate 216...Friction disk 218
, 220... Collision control disk 224... Compression plate
225... Compression spring 226... Friction disk 228... Bolt 232... Cam protrusion
234...dog tooth 236...notch
238...Sensitive actuation device 240...Axis
241... Stationary bracket 242... Tension spring 243... Cam arm 244... Cam driven member 246... Engagement roller 250... Bolt 260...
Limit switch 262...actuating device.

Claims (1)

Claims: 1. A drive device for a plurality of hoisting drums that are rotated simultaneously, comprising at least two shafts spaced apart in parallel and rotatably supported on a frame, and at least one of the shafts.
A drum that is attached concentrically to the book and houses the cable wound therein, and a drum that is attached separately to each said shaft so that the phase differs from each other by 120 degrees and has equal diameters so as to have the same eccentricity with respect to each said shaft. three circular cam bases and three rotatably interconnecting cam protrusions on said shaft such that rotation of one of said shafts simultaneously rotates the other shaft, thereby transmitting vibrational action; a link plate, means for driving one of said shafts, and damping means for reducing the speed of vibrational operation of said link plate to slow or stop rotation of said drum. Features a cable hoisting drum drive device. 2. Each of said link plates is an elongated plate, said link plates having at least two circular holes formed to rotatably accommodate said cam projections for vibrational operation. The drive device according to item 1. 3. A drive system according to claim 1, wherein said control means comprises a caliper brake adapted to compress said link plates together in frictional engagement. 4. The drive device according to claim 3, wherein the control means is located at at least one end of the link plate. 5. Claims in which the three circular cam protrusions rigidly attached to each of the shafts are attached close to each other, whereby the link plates are operatively attached close to each other so as to perform vibrational operation. The drive device according to item 1. 6. The drive device according to claim 1, wherein the three circular cam protrusions rigidly attached to each of the shafts are attached to each other to form an integral structure. 7. The frame includes a pair of spaced apart structural members having bearings for supporting the shaft, and an additional shaft rotatably supported on the frame in spaced relation parallel to the other shaft; A winder having a threaded groove formed on the surface of the additional shaft and engaged with the additional shaft, and a means for guiding the winder to reciprocate on the shaft are out of phase with each other. three circular cam protrusions with equal diameters are rigidly attached to the additional shaft so as to differ by 120° and have the same eccentricity with respect to the axis, and the link plate is connected to the cam protrusions on the other shaft. 2. The drive device according to claim 1, wherein the drive unit and the additional cam protrusion are interconnected. 8. The control means is mounted on one shaft and has a hub rigidly attached to the cam protrusion so as to be able to rotate together with the cam protrusion, and the cam means and the rotation stopper are rotatably mounted on the hub. and a friction plate is rigidly attached to the hub so as to be able to rotate together with the hub, and the friction plate is engaged with the cam means and the rotation stopper means by a friction engagement so that they are normally coupled and rotate together. a responsive actuator adapted to be rotatably mounted on the cam means and the rotation stop means and operatively engaged with the cam means and the rotation stop means, such that the sensitive actuation device is connected to the predetermined hub; When the rotational speed exceeds the predetermined rotational speed, the engagement of the actuating device with the rotation stop means completely stops the cam means and the rotation stop means. The drive device according to claim 1, wherein the drive device is capable of stopping rotation with the attached cam protrusion. 9. The hub is mounted concentrically on the one shaft, the one shaft is parallel to the at least two shafts and rotatably supported, and the hubs are provided with hubs having a phase difference of 120 degrees from each other. Three circular cam protrusions of equal diameter and the same eccentricity are rigidly attached to the axes of the at least two axes, and the circular cam protrusions are connected to corresponding circular cam protrusions on the at least two axes by link plates. 9. A drive device according to claim 8, which is interconnected to the cam protrusion. 10 The cam means and the rotation stop means are provided with a pair of control disks mounted together for combined rotation, a plurality of equally spaced cam protrusions are formed around one of the disks, and a plurality of equally spaced cam protrusions are formed around one of the disks; A dog tooth having a notch is formed around the plurality of cam protrusions to correspond to the plurality of cam protrusions, and the sensitive actuating device is provided with a cam driven member and an engaging roller that protrude from the device, and the sensitive actuating device is rotated. The cam driven member is movably mounted and biased in the rotational direction, thereby pressing the cam driven member against the cam protrusion until the rotational speed of the control disk reaches a predetermined rotational speed. When the rotation speed of the control disc reaches a predetermined rotation speed or higher, the cam driven member leaves the surface of the cam protrusion, seats the engaging roller on the dog tooth, and the disc further rotates. 10. The drive device according to claim 9, wherein the friction disk stops rotation of the hub and the cam protrusion attached thereto. 11 A first friction disk mounted on a support plate rigidly attached to the hub in order to ensure rotation together with the hub, and a second friction disk mounted on a pressure plate attached to the hub in order to rotate simultaneously with the hub. a friction disk, the pressure disk having means for pressing the friction disk of the platform 2 towards the first friction disk; 11. The drive device according to claim 8, 9 or 10, wherein the pressure plate is brought into frictional engagement with a control disk therebetween. 12 A shaft having a concentrically mounted hub, a cam means and a rotation stopper rotatably mounted on the hub, and a shaft that rotates the hub so as to cause frictional engagement between the cam means and the rotation stop means. a pair of spaced apart friction disks removably mounted, one of said friction disks being mounted on a support plate rigidly attached to said hub to ensure rotation of said friction disk with said hub; The other friction disk is mounted on a pressure plate attached to the hub so as to be able to rotate together with the hub, and the friction disk attached to the pressure plate is pressed toward the first friction disk. and a sensitive actuator operatively engaged with the cam means and the rotation stop means is rotatably mounted on the cam means and the rotation stop means, whereby the rotational speed of the hub is adjusted to a predetermined rotation speed. The sensitive actuation device moves according to the cam means until the rotational speed of the hub reaches the predetermined rotational speed or more, and the sensitive actuation device engages the rotation stop means, so that the cam means and the rotation stop means are engaged with the rotation stop means. A shaft braking device characterized in that the shaft braking device is configured to reliably stop the hub and the rotation of the cam protrusion attached to the hub. 18 a pair of control discs mounted together for coupled rotation, comprising said cam means and rotation stop means, one of said discs having a plurality of equally spaced cam protrusions formed around said disc; a plurality of dog teeth constituting a notch formed around the periphery to correspond to the cam protrusion, the other side of the sensitive actuating device is provided with a cam driven member and an engaging roller that protrude from the sensitive actuating device; is rotatably attached and biased in the rotational direction, thereby pressing the cam driven member against the cam protrusion until the rotational speed of the control disk reaches a predetermined rotational speed. When the rotational speed of the control disk reaches or exceeds the predetermined rotational speed, the cam driven member separates from the surface of the cam protrusion, causing the engaging roller to sit on the dog tooth, and the disk moves in accordance with the cam projection. 13. The shaft braking device according to claim 12, wherein further rotation is prevented and the M friction disk stops the rotation of the hub and the cam protrusion attached thereto.