GB2207718A

GB2207718A - Auxiliary braking device for an escalator

Info

Publication number: GB2207718A
Application number: GB08814342A
Authority: GB
Inventors: Shigeharu Kitamura
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 1987-06-16
Filing date: 1988-06-16
Publication date: 1989-02-08
Anticipated expiration: 2008-06-16
Also published as: CN1030734A; GB2207718B; KR890000338A; JPH0742070B2; CN1007514B; KR940001404Y1; JPS63315483A; GB8814342D0

Abstract

An auxiliary brake for an escalator which directly arrests the motion of the axle 5 of the stair driving sprocket wheel 3 comprises a toothed wheel 12 mounted on the axle through a friction-imparting support 12c, 17, 18, a detent lever 13 engaging with the toothed wheel to arrest the motion thereof, a spring 14 urging the lever in the direction of engagement, an electromagnet 18 which draws and keeps the lever out of engagement with the toothed wheel when energized, and a damper 16 which slows down the turning motion of the lever and represses oscillation thereof. Thus, when the electromagnet is de-energized, the lever comes into engagement with the toothed wheel after a certain delay to apply the braking force to the axle. Even when only the auxiliary brake is operative, the damper ensures the engagement of the lever with the toothed wheel by curbing the oscillations thereof. <IMAGE>

Description

AUXILIARY BRAKING DEVICE FOR AN ESCALATOR BACKGROUND OF THE INVENTION 1. Field of the Invention: This invention relates to auxiliary brakes for escalators, and more particularly to such brakes which directly arrests the motion of the sprocket wheels which drive the endless chains carrying the steps for passengers.

2. Description of the Prior Art An escalator, i.e. moving stair case for transporting passengers between floors or levels in buildings and subways, etc. comprises a pair of handrails and a moving stairway. A main brake for the stairway of the escalator curbs the motions of an electric motor driving the endless chains which carry a series of steps constituting the moving stairway. Usually, an escalator also comprises an auxiliary brake which directly arrests the motions of the axle of the sprocket wheels driving the endless chains carrying the stairway, so that the stopping of the stairway is made more reliable.

Fig. 1 shows a schematic side view of a conventional escalator. The escalator shown in the figure comprises a pair of handrails 1 and a plurality of steps constituting the moving stairway for passengers which are carried by endless chains 2a.

The chains 2a are wound around and extends between driving sprocket wheels 3 situated on the upper level and driven sprocket wheels 4 situated on the lower level. The axle 5 of the stairway driving sprocket wheels 3 also carries a driven sprocket wheel 6 which is driven b an electric motor 7 through a reduction gear device 8, a driving sprocket wheel 9 and a driving chain 10. A main brake 11 is provided on the shaft of the motor 7.

When the escalator of Fig. 1 is to be stopped, the main brake 11 is activated to arrest the motion of the shaft of the motor 7, so that the braking force of the main brake 11 is transmitted through the gear 8, the sprocket wheel 9, the chain 10, and the sprocket wheel 6 to the sprocket wheel 3 to stop the motion of the sprocket wheel 3 together with that of the stairway 2 and the chain 2a. Thus, the provision of the main brake 11 alove cannot ensure reliable stopping of the escalator.Namely, if the chain 10 is broken when the escalator is stopped, the sprocket wheel 3, and therefore the stairway 2, are put in a freely movable state, which may incur a dangerous situation: in cases where the escalator is in upward movement and carries a large number of passengers, the stairway may begin to move backward in the downward direction due to the weight of the passengers; on the other hand, in cases where the escalator is in downward movement, the stairway is further acceleratd in the downward direction, which is highly dangerous. Thus, an auxiliary brake is usually provided, which directly arrests the motion of the axle 5 of the stairway driving sprocket wheel 3.

Fig. 2 shows a side view of a stairway driving portion of the escalator which is provided with a conventional auxiliary brake comprising a ratchet wheel 12 and a pawl 13 disengageably engaging therewith. The ratchet wheel 12 is mounted on the axle 5 through a support member which imparts frictional resistance against the rotational motion of the ratchet wheel 12 with respect to the axle 5. The lever 13 is fixed to a tongue 13a having a rotatable slide 13b resting on the chain 10 at an end thereof. Thus, if the chain 10 is broken, the tongue 13a is rotated in the clockwise direction in the figure together with the lever 12, which thus falls into engagement with a cog 12a of the ratchet wheel 12.The engagement prevents the rotational movement of the ratchet wheel 12, imparting frictional braking force to the axle 5 through the support member which mounts the ratchet wheel 12 on the axle 5.

The conventional auxiliary brake for escalators shown in Fig. 2, however, is not activated unless the chain 10 is broken.

Thus, in cases where the power transmitting members excepting the chain 10, such as the reduction gear 8, is broken, or in cases where the main brake 11 is not activated for any reason, the auxiliary brake does not operate to stop the movement of the stairway.

In view of the above-mentioned disadvantage of the auxiliary brake of Fig. 2, Japanese laid-open patent application 59-97985, for example, proposes an auxiliary brake utilizing an electromagnet. The auxiliary brake taught by this Japanese patent application comprises a ratchet wheel similar to that of the brake of Fig. 2. The pawl or the detent lever, however, is pivoted at the middle portion thereof, one end thereof turning to engage with a cog of the ratchet wheel and the portion opposite to the engaging end with respect to the pivot being urged by a helical spring in the turning direction in which the lever falls into engagement with the ratchet wheel.An electromagnet is provided to act on the same side of the lever as the urging spring, and draws and turns the lever in the direction opposite to that of engagement, and keeps the lever out of engagement with the ratchet wheel when the electromagnet is in the energized state. The electromagnet is de-energized when the auxiliary brake is activated to stop the escalator. Thus, it is ensured that the braking force of the auxiliary brake is applied to the axle of the stairway driving sprocket wheels even in cases where the power transmitting members other than the chain corresponding to the chain 10 of Fig. 2 is in failure, or in cases where the main brake is not activated or fails to prevent the motion of the shaft of the motor.

In the case of.the auxiliary brake taught by the above-mentioned Japanese patent application, however, the following problem presents itself. If the auxiliary brake, which acts directly on the axle of the sprocket wheel driving the stairway, is activated simultaneously with the main brake which arrests the motion of the motor shaft, the stairway is stopped in a very short distance due to the strong braking force of the auxiliary brake resulting from the strong frictional force against the ratchet wheel mounted on the axle of the stairway driving sprocket wheel. The short stopping distance may cause the passengers on the stairway to stumble.A further disadvantage of the auxiliary brake is that when the brake is activated, the oscillation of the detent lever of the ratchet wheel caused by the violent interaction of the lever with the ratchet wheel may result in the disengagement thereof from the ratchet wheel, making the auxiliary brake inoperative.

With regard to the first mentioned disadvantage, the abovementioned Japanese patent application teaches to provide an electronic circuit for activating the main brake before the auxiliary brake in the usual stopping of the escalator. The provision of such an electronic circuit, however, makes the control circuit of the escalator complicated. Further, such an electronic circuit is ineffective with regard to the second disadvantage mentioned above when the braking force of the main brake is inoperative.For example, when a power transmission member is in failure which transmits power from the motor to the stairway driving sprocket wheel, the electronic circuit which delays the activation of the auxiliary brake with respect to the activation of the main brake is totally ineffective in curbing the oscillation of the detent lever caused by the collision thereof with the cogs of the ratchet wheel.

SUMMARY OF THE INVENTION Thus, a main object of the present invention is to provide an auxiliary brake for an escalator of the above described type which is activated in usual as well as in emergency conditions, wherein means is provided for delaying the operation of the auxiliary brake after the activation of the main brake in usual stopping of the escalator, while the oscillation of the detent lever of the ratchet wheel is effectively repressed even in cases where the auxiliary brake alone is activated in emergency conditions.

A further object of the present invention is to provide such an auxiliary brake which is simple in construction, reliable in operation and low in cost.

The above objects are accomplished according to the present invention by the provision of a mechanical damper which slows down the turning motion of the detent lever and which effectively curbs the oscillations of the lever that may be caused by the collision of the lever with the cogs of the ratchet wheel especially when only the auxiliary brake is operative.

Thus, the braking device according to the present invention comprises a ratchet wheel mounted on the axle of the stairway driving sprocket wheel, a pivoted detent lever which turns to engage with the ratchet wheel to prevent the motion thereof, urging means, e.g. a helical spring, for urging the detent lever in a turning direction in which the lever engages with the ratchet wheel, an electromagnet which draws and keeps the lever in a disengaged state when it is energized, and a damper which slows down the turning motion of the lever and represses the oscillations thereof when the electromagnet is de-energized and the lever is urged by the urging means in the direction of engagement with the ratchet wheel. The ratchet wheel is mounted on the axle through a support member imparting friction against the rotation thereof with regard to the axle.

Thus, when the auxiliary brake according to the present invention and the main brake are activated simultaneously to stop the escalator in the usual service condition, the time at which the auxiliary braking force comes into effect is delayed with respect to the main braking force, so that an abrupt stopping of the escalator can be effectively avoided. More explicitly, due to the reduction of the speed of the turning motion of the detent lever by the damper, the engagement of the lever with the ratchet wheel is delayed for a certain period of time after the activation thereof by the de-energization of the electromagnet, so that the auxiliary braking force become effective only just before or after the escalator comes to a halt.When only the auxiliary brake is operative in emergency conditions, on the other hand, the damper effectively represses the oscilations of the detent lever to ensure reliable stopping of the escalator.

BRIEF DESCRIPTION OF THE DRAWINGS Further details of the invention will become more clear in the following detailed description of the preferred embodiments taken in conjunction with the accompanying drawings, in which: Fig. 1 is a schematic side view of a conventional escalator; Fig. 2 is a side view of the stairway driving portion of an escalator provided with a conventional auxiliary brake which directly arrests the motion of the stairway driving sprocket wheel; Fig. 3 is a side view of an auxiliary brake according to the present invention; Fig. 4 is a partial sectional view of the ratchet wheel of the auxiliary brake of Fig. 3, showing the section thereof along the line IV-IV of Fig. 3; Fig. 5 is an enlarged partial side view of the ratchet wheel and the detent lever of the auxiliary brake of Figs. 3 and 4;; Fig. 6 is a view similar to that of Fig. 5, but showing a modified form of the ratchet wheel and the detent lever; and Fig. 7 is a view similar to that of Fig. 4, but showing a pair of ratchet wheels in another auxiliary brake according to the present invention.

In the drawings, like reference numerals represent like or corresponding elements or portions.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The auxiliary brake shown in Figs. 3 and 4 is installed on an escalator similar to that shown in Fig. 1 at the stairway driving sprocket wheel thereof on the upper level as the conventional brake shown in Fig. 2, and comprises a ratchet wheel 12 mounted on the axle 5 of the stairway driving sprocket wheel (not shown), a pivoted detent lever 13, a helical spring 14, an electromagnet 15, and a damper 16.

The annular disk-shaped ratchet wheel 12 has a plurality of cogs 12a formed on the circumference thereof each having an engaging surface 12b, and is mounted on the axle 5 through a friction imparting support. Thus, a disk-shaped flange 17 fixedly secured to the axle 5 has formed on an inner side surface thereof an annular projection 17a having a plurality of circumferentially evenly spaced through-holes extending in the axial direction of the axle 5. An auxiliary annular disk 18 having a plurality of through-holes corresponding to the holes 17b of the flange 17 is mounted to the flange 17 by means of the bolts 19 extending through the holes 17b and 18a. Each bolt 19 has formed on the end portion thereof an axially extending bore 19 having a helical female thread to which cylindrical male screw rod 20 is screwed in.The rod 20 carries a fastening tube 21 having a flange 21a and sliding on the inner surface along the side surface of the rod 20. A nut 22 is screwed onto the male screw rod 20 to press the auxiliary annular disk 18 against the flange 17 by the resilience of the helical spring 23 placed around the bolt 19 between the auxiliary annular disk 18 and the fastening tube 21 which slides along the side surface of the rod 20 to be pressed against the spring 23. The annular disk-shaped ratchet wheel 12 has an inner annular portion of reduced thickness on each surface of which annular friction-imparting lining 12c is fixed. The wheel 12 is fitted into the annular disk-shaped gap formed between the opposing surfaces of the flange 17 and the auxiliary annular disk 18.The linings 12c may be made of any ordinary material for brake linings such as metallic type materials, asbestos-type materials or the like.

Thus, the ratchet wheel 12 is held between the flange 17 and the auxiliary disk 18 through the intermediary of the friction-imparting linings 12c, and the pressure applied to the ratchet wheel 12 can be adjusted by the screwing in and out of the nuts 22. Between the inner circumferential surface of the ratchet wheel 12 and the outer side surface of the projection 17a opposing thereto a low friction lining 24, made for example of a fluorocarbon resin sheet, is inserted.

The detent lever 13 is pivotly mounted on the pin 13d and turns in the direction shown by an arrow A to engage with an engaging surface 12b of a cog 12a of the ratchet wheel 12 which rotates in the anti-clockwise direction B in Fig. 3 when the escalator is in downward movement. The helical spring 14 is held between the holder ring 14a and the upper surface of the flat plate-shaped portion 13e of the lever 13 situated opposite to the end 13c thereof with respect to the pin 13d, by means of a rod 14b extending through the spring 14 and the through-hole formed in the flat plate-shaped portion 13e of the lever 13. The holder ring 14a is fixed on an upper end portion of the rod 14 which is fixedly secured to the support table 25 through a support member 14c.Thus, the spring 14 urges the lever 13 in the direction of engagement A in which the end 13c of the lever 13 engages with a cog 12a of the ratchet wheel 12.

The electromagnet 15 positioned on the top of the table 25 draws the lever in the direction opposite to the direction of engagement A through a plunger 15a and a connection pin 15b when it is energized. The pin 15b operatively couples the plunger 15a and the lever 13 at a position thereof between the pin 13d and the urging spring 14. Thus, the energized electromagnet 15 keeps the end 13c of the lever 13 out of engagement from the cogs 12a of the ratchet wheel 12 when the auxiliary brake is not activated. A small-sized electromagnet is sufficient provided that the turning force of the electromagnet 15 acting on the lever 13 is greater than the sum of the turning force of the spring 14 and the frictional force developing between the end 13c of the lever 13 and a cog 12a of the ratchet wheel 12 when the engagement is to be released.

The damper 16 is operatively coupled to the extreme end portion of the lever 13 situated opposite to the engaging end 13c with respect to the pivot pin 13d. The damper 16 may be of the dashpot type, the shock damper type or the like in which energy can be calculated and selected by the time to be delayed, and which, by dissipating the energy, reduces the speed of the turning motion of the lever 13 and'represses the oscillations thereof.

The operation of the auxiliary brake of Figs. 3 and 4 in the usual service condition of the escalator is as follows. The escalator moving in downward direction is stopped by activating the main brake, such as the brake 11 shown in Fig. 2, and the auxiliary brake of Figs. 3 and 4 simultaneously. The main brake acts instantaneously on the motor shaft of the escalator to decelerate the motion of the moving stairway. The auxiliary brake according to the present invention, however, becomes operative after a certain delay just before or after the escalator comes to a halt. Themechanisim of the delayed action of the auxiliary brake is as follows. When the electromagnet 15 is de-energized at the activation of the auxiliary brake, the lever 13 is urged in the direction of engagement A by the urging spring 14.However, the damper 16 slows down the turning speed of the lever 13 to delay the engagement of the end 13c of the lever 13 with a cog 12a of the ratchet wheel 12 rotating in the anti-clockwise direction B in Fig. 3. When the lever 13 finally engages with the ratchet wheel 12, the rotation of the ratchet wheel 12 is thereby prevented and the frictional force developing between the frictional linings 12c and the opposing surfaces of the flange 17 and the auxiliary annular disk 18 co-operate to stop the stairway of the escalator reliably.

When the main brake is inoperative, however, the lever 13 turns in the direction A and comes to engage with the ratchet wheel 12 rotating in the direction B at a high speed. Even in such emergency cases, due to the repression of the oscillations of the lever 13 by the damper 16, the end 13c of the lever 13 is ensured to engage reliably with a cog 12a of the ratchet wheel 12. Thus, the friction developing between the frictional linings 12c and the opposing surfaces of the flange 17 and the auxiliary annular disk 18 rotating with the axle 5 stops the rotation of the axle 5 and the movement of the stairway of'the escalator with high reliability.

The delay time passing between the de-energization of the electromagnet 15 and the engagement of the lever 13 with the ratchet wheel 12 depends on the rotational position of the ratchet wheel 12 at the time of engagement. Thus, the length of time between the de-energization of the electromagnet 15 and the coming into effect of the auxiliary braking force varies according to the relative position of the ratchet wheel 12 at the time of activation of the auxiliary brake. However, the brake of Figs. 3 and 4 is capable of stopping the escalator moving in downward direction and of preventing the reversal of motion of the escalator moving in upward direction with high reliability.

On the other hand, when the escalator is started to set the stairway again in motion, the electromagnet 15 is energized to turn the lever 13 in the direction opposite to the direction of engagement A to keep the lever 13 out of engagement from the ratchet wheel 12.

Referring now to Fig. 5, the relationship of the ratchet wheel 12 and the lever 13 of the brake of Figs. 3 and 4 is described in greater detail. The pivot pin 13d of the lever 13 is positioned on the tangent line t of the outer circle of the ratchet wheel 12 which is drawn from the apex of the engaging cog 12a of the ratchet wheel 12, so that the reaction of engagement of the end 13c with the surface 12b of the cog 12a on the pin 13d is minimized. Further, the angle e formed between the engaging surface 12a and the radius n passing through the center 0 of the ratchet wheel 12 and the base of the engaging surface 12b of the cog 12a must be greater than zero, because the end 13c of the lever 13 must be disengaged from the cog 12a when the escalator is to be started.However, it is necessary that the relation, tan e < p holds, wherein p is the coefficient of friction of the end 13c of the lever 13 and the surface 12b of the cog 12a, so that a reliable engagement of the lever 13 with a cog 12a of the ratchet wheel 12 is ensured when the escalator is to be stopped.

The ratchet wheel and the detent lever of Figs. 3 through 5 is effective only for arresting the motion of the ratchet wheel in the direction B. Thus, the above-described ratchet mechanism can be used only for stopping the escalator moving in one direction (in the case of the brake of Figs. 3 through 5, downward direction). Fig. 6 shows a geometry of the ratchet wheel and the detent lever which is capable of arresting the motion of the ratchet wheel in the clockwise as well as in the anti-clockwise direction. The ratchet wheel 12 of Fig. 6 is formed on the circumference thereof with a plurality of trapezoidal cogs 12a each of which have a pair of engaging side surfaces 12b which are inclined with respect to the radii of the ratchet wheel 12 in a similar way as the surfaces 12b of the ratchet wheel 12 of Figs. 5.The lever 13 pivoted to the pin 13d has a trapezoidal projection 13e having corresponding engaging side surfaces at the engaging end 13c thereof which can drop into a recess formed between adjacent cogs l2a. Thus, when the -auxiliary brake is activated and the lever 13 is turned in the direction A, the lever is capable of arresting the motion of the ratchet wheel 12 in the clockwise direction B' as well as the anti-clockwise direction B. The ratchet configuration of Fig. 6 can thus be used to stop the motion of escalators moving both in the downward and upward direction.

Fig. 7 shows another embodiment of the ratchet wheel support structure, in which a pair of ratchet wheels 12 are mounted on the flange 17 by a fastening bolt 26 and a nut 27, the outer annular portion of the flange 17 being pressed between the opposing step-formed recesses of the pair of ratchet wheels 12 through the friction-imparting linings 12c fixed thereto. The pair of ratchet wheels 12 may be comprised in an auxiliary brake similar to that of Figs. 3 and 4, which, however, comprises a detent lever of enough thickness to engage with both ratchet wheels 12. Otherwise, the brake incorporating the ratchet wheels 12 of Fig. 7 may be constructed similarly as the brake of Figs. 3 and 4.

Claims

CLAIMS:

1. A braking device for an escalator having a sprocket wheel driving an endless chain carrying a plurality of steps for passengers comprising: a toothed wheel mounted coaxially with the sprocket wheel and coupled thereto through coupling means which impart frictional resistance against rotation of the sprocket wheel relative to the toothed wheel, a stop member movable into and out of engagement with the toothing of the toothed wheel for preventing or permitting rotation of the toothed wheel.

means for moving the said member into and out of engagement with the toothed wheel8 and damping means for reducing the speed of movement of the said member and damping oscillations thereof when the said member is moved in the direction of engagement with the toothed wheel.

2. A braking device for an escalator having a sprocket wheel driving an endless chain carrying a plurality of steps for passengers, comprising: a toothed wheel mounted on an axle of said sprocket wheel through a support member which imparts frictional resistance against a rotational motion of said toothed wheel with respect to the axle of said sprocket wheel: a pivot lever having an end engageable with said toothed wheel to prevent a rotational motion of said toothed wheel; urging means for resiliently urging said pivot lever in a direction of engagement in which the end of said pivot lever engages with said toothed wheel; electromagnet means for drawing said pivot lever in a direction opposite to the direction of engagement when it is in an energized state: and damper means for mechanically reducing the speed of a turning motion of said pivot lever and repressing an oscillation of said pivot lever when said electromagnetic means is de-energized.

3. A braking device for an escalator as claimed in claim 2. wherein said urging means. electromagnetic means, and damper means are operatively coupled to a side of said pivoted lever which is situated opposite to the end thereof engageable with said toothed wheel with respect to a pivoting point of said pivot lever.

4. A braking device for an escalator as claimed in claim 2 or 3 further comprising a motor operatively connected to drive said sprocket wheel, wherein said damper means operates such that said pivot lever is brought into engagement wth said toothed wheel in a delayed relation to the braking of said motor.

5. A braking device for an escalator as claimed in claim 2, 3 or 4 wherein said urging means comprises a spring.

6. A braking device- for an escalator as claimed in claim 2, 3, 4 or 5 wherein said toothed wheel is mounted on the axle of said sprocket wheel through a flange fixed to the axle and a friction lining.

7. A braking device for an escalator as claimed in any of claims 2 to 6, wherein said toothed wheel is formed on its circumference with a plurality of cogs engageable with the endof said pivot lever.

8. A braking device for an escalator as claimed in any of claims 2 to 6 wherein said toothed wheel is formed on its circumference with a plurality of recesses engageable with the end of said pivot lever.

9. A braking device for an escalator, substantially as herein described with reference to Figures 3 to 5, Figure 6 or Figure 7 of the accompanying drawings.