DRIVING APPARATUS FOR PASSENGER CONVEYOR
BACKGROUND OF THE INVENTION
(i) Field of the Invention
This invention relates to a drive apparatus for a passenger conveyor such as an escalator or an electrically moving walkway and, more particularly, to a drive apparatus for a passenger conveyor which includes a belt wound between a drive pulley and an idler pulley to transmit the driving force.
(ii) Description of the Related Art
A passenger conveyor includes a drive apparatus for driving plural stair steps which are endlessly coupled to each other and move between the landing platforms and a moving handrail which moves in synchronization with the steps. The drive apparatus includes typically a belt wound between a drive pulley and an idler pulley as transmission means for transmitting the driving force from the drive pulley to the idler pulley. One used as the commonly-known transmission means is plural V belts of a V-shaped cross section are arranged side be side between the drive pulley and the idler pulley for the purpose of improving the friction coefficient of the belt, as is known from, for example, JP-A No.2004-137040 (see paragraph 0011, Fig. 1 and Fig. 2).
For example, JP-U No. S56-136061 (see the left column of Page 1, Fig. 1 and Fig. 8) describes another drive apparatus, not for use in a passenger conveyor, including
plural V-ribbed belts having four or less protrusions arranged in the lateral direction of the belt and plural pulleys having seven or more V grooves formed therein in the lateral direction of the belt. The V-ribbed belts are arranged side by side and looped over the pulleys.
In the former employing three V-belts, however, the use of three V-belts gives rise to a wider range of variations in tension from belt to belt. As a result, some of the belts transmit a driving force greater than the allowable values for driving force transmission, thus shortening the life of the belts.
On the other hand, the later is of limited specifications, in which plural V-ribbed belts having four or less protrusions arranged in the lateral direction of the belt are arranged side by side and looped over plural pulleys having seven or more V grooves formed therein in the lateral direction of the belt. When a drive apparatus of such structure is used in a passenger conveyor, it is difficult to satisfy all factors while providing a required friction coefficient. Specifically, in the drive apparatus of the passenger conveyor, a brake is provided on a rotating shaft of the idler pulley. When the belt friction coefficient is not sufficiently achieved, the belt may possibly slip during braking to bring the passenger conveyor to a sudden stop. For increasing the belt friction coefficient in related art structure, an increase in the diameter of the pulley or an increase in the number of belts is required. However, an increase in the diameter
of the pulley leads to an increase in costs and also an increase in the size of the apparatus, and therefore disadvantageously the drive apparatus is not suitable for use in the passenger conveyor. Furthermore, if the number of belts is increased to, for example, three, as in the case of the former example, the range of variations in tension from belt to belt is made wider. As a result, some of the belts transmit a driving force greater than the allowable values for driving force transmission, thus shortening the life of the belts.
SUMMARY OF THE INVENTION
The present invention has been made in the light of circumstances in the related art as described above, and provides a drive apparatus for a passenger conveyor that is capable of reliably providing a required friction coefficient without an increase in the number of belts and an increase in the size of the apparatus.
To attain this, the present invention provides a drive apparatus for a passenger conveyor which transmits a drive force to the passenger conveyor. The drive apparatus includes an electric motor, a drive pulley that is driven by the electric motor, a flywheel that is provided coaxially with the drive pulley, a brake, an idler pulley that is coupled to a rotating shaft on which the brake is mounted, and a belt that is looped over the drive pulley and the idler pulley. The belt includes either one V-ribbed belt or two V-ribbed belts having at least 12 but no
more than 18 protrusions in total arranged in the lateral direction of the belt, and a friction force of the V-ribbed belt is greater than a braking force.
In the structure provided by the present invention, as the belt looped over the drive pulley and the idler pulley, a V-ribbed belt having an arrangement of at least 12 but no more than 18 protrusions in the lateral direction of the belt is employed. Thus, a friction coefficient required by the drive apparatus of the passenger conveyor can be reliably provided without an increase in the number of belts and an increase in the apparatus size, and the friction force of the V-ribbed belt can be made greater than the driving force.
In the present invention, the two V-ribbed belts are arranged side by side in the lateral direction of the belt.
In the structure provided by the present invention, since the two V-ribbed belts are arranged side by side, an increase in the number of belts can be minimized, and also, even if a failure occurs on one of the belts, the other belt can be used to deal with the emergency.
According to the present invention, since the number of belts used is set to two, the tension variations occurring from belt to belt can be reduced, thereby achieving an increase in the life of the belt. Further, since a high friction coefficient can be provided even when the mounting space is small, it is possible to prevent an increase in the size of the apparatus and an increase in the costs. In addition, since a friction coefficient
required by the drive apparatus of the passenger conveyor is reliably provided, it is possible to prevent the belt from slipping during braking, thus achieving a smooth stop during braking, resulting in an improvement in safety of the passenger conveyor.
BRIEF DESCRIPTION OF THE DRAWINGS
An Embodiment of the present invention will be described in detail based on the following drawings, wherein:
Fig. 1 is a front view showing a drive apparatus for a passenger conveyor according to an illustrative embodiment of the present invention;
Fig. 2 is a cross-sectional view illustrating a main section of the drive apparatus taken along A-A line in Fig. 1;
Fig. 3 is a schematic structural diagram of an escalator to which the drive apparatus according to an illustrative embodiment of the present invention is applied; and
Fig. 4 is a side view of the drive apparatus according to an illustrative embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
A drive apparatus for a passenger conveyor according to an illustrative embodiment of the present invention will
be described below in detail with reference to the accompanying drawings.
As shown in Fig. 3, the passenger conveyor, for example, an escalator 1 includes a frame unit 2 which is made up of an upper horizontal frame 2A, a middle slope frame 2B and a lower horizontal frame 2C and bridged between the top and bottom landings, a drive sprocket 3 journalled in the upper horizontal frame 2A, an idler sprocket 4 journalled in the lower horizontal frame 2C, a step chain 5 endlessly looped over the drive sprocket 3 and the idler sprocket 4, plural steps 6 which are coupled to the step chain 5 and have step plates horizontally held at all time on the return run, balustrade panels 7 respectively erected along positions of the frame unit 2 corresponding to the opposing sides of the steps 6 in the lateral direction, moving handrails 8 respectively moved by being guided along the peripherals of the balustrade panels 7, and a drive apparatus including units for driving the step chain 5 and the moving handrails 8.
The drive apparatus 9 transmits the power to drive mechanisms of the step chain 5 and the moving handrails 8 through a power transmission chain 10. As shown in Fig. 1 and Fig. 4, the drive apparatus 9 includes an electric motor 11, a gear system 12 which is a power transmission path, and a brake 14 which is attached to an input shaft 13 of the gear system 12 to apply a braking force. The driving force of the electric motor 11 is transmitted to the input shaft 13 of the gear system 12 through a belt 17
which are looped over a drive pulley 15 of the electric motor 11 and an idler pulley 16 of the gear system 12. Then, the driving force is transmitted to the drive sprocket 3 through the power transmission chain 10 which is wound on a pulley 19 secured to the output shaft 18 of the gear system 12. A flywheel 21 is fixed to the drive shaft 20 of the electric motor 11. In addition, an auto tensioner 22 is provided on at least one side of the belt 17 for maintaining a uniform tension of the belt 17.
As shown in Fig. 1 and Fig. 2, the belt 17 is made up of two V-ribbed belts 17a, 17b. Each of the V-ribbed belts 17a, 17b has six protrusions arranged in the lateral direction of the belt. Also, the drive pulley 15 and the idler pulley 16 over which the V-ribbed belts 17a, 17b are looped have grooves formed therein in positions corresponding to the protrusions of the V-ribbed belts 17a, 17b (note that the grooves formed in the idler pulley 16 are not shown in Fig. 2, but the idler pulley 16 also has the same grooves formed therein as the drive pulley 15).
In the illustrative embodiment, since the belt 17 looped over the drive pulley 15 and the idler pulley 16 is made up of the V-ribbed belts 17a, 17b having 12 protrusions in total arranged in the lateral direction of the belt, the frictional force of the V-ribbed belts 17a, 17b can be made greater than the braking force. As a result, when the brake 14 is activated, the inertial force of the flywheel 21 can be transmitted to the driven side
without allowing the V-ribbed belts 17a, 17b to slip, thus bring the passenger conveyor to a gentle stop.
According to the illustrative embodiment, since the number of V-ribbed belts 17a, 17b used is set to two, the tension variations occurring from belt to belt can be reduced to achieve an increase in the life of the belt. Further, since the V-ribbed belts 17a, 17b can have a high friction coefficient even when the mounting space is small, an increase in the size of the apparatus and an increase in the costs can be prevented. In addition, since a friction coefficient required by the drive apparatus of the passenger conveyor is provided, the V-ribbed belts 17a, 17b can be prevented from slipping during braking, thus achieving a smooth stop during braking, resulting in an improvement in safety of the passenger conveyor. Furthermore, since the number of V-ribbed belts 17a, 17b is set to two, not only an increase in the number of belts can be minimized, but also, even if a failure occurs on one of the belts, the other belt can be used to deal with the emergency. Since the provision of the auto tensioner 22 makes it possible to maintain a uniform tension of the V-ribbed belts 17a. 17b, an increase in the interval between adjustments to belt tension can be achieved.
In the illustrative embodiment, as shown in Fig. 1 and Fig. 2, the belt 17 is made up of the two V-ribbed belts 17a, 17b each of which has six protrusions arranged in the lateral direction of the belt, but the present invention is not limited to this embodiment. The number of
belts may be one and the total number of protrusions formed on the V-ribbed belts may be arbitrarily set within a range from 12 to 18. The reason why the number of protrusions is here set to 12 or more is that 12 protrusions are necessary to obtain a predetermined friction coefficient required by the drive apparatus of the passenger conveyor. The reason why the number of protrusions is set to 18 or less is that, if the number of protrusions exceeds 18, this causes an increase in view of the space required for winding the belts. A required number of protrusions ranges from 12 to 18 in total. Accordingly, in the case of using one belt, at least 12 but no more than 18 protrusions may be formed in one belt. When two belts are used, at least 12 but no more than 18 protrusions in total may be formed in the two belts. In addition, the illustrative embodiment has been described using an escalator as an example of the passenger conveyor, but it should be understood that the present invention can apply to a drive apparatus for a motorized walkway.
It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alternations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.

What is Claimed is:
1. A drive apparatus for a passenger conveyor which
transmits a drive force to the passenger conveyor,
comprising:
an electric motor,
a drive pulley driven by the electric motor,
a flywheel provided coaxially with the-drive pulley,
a brake,
an idler pulley coupled to a rotating shaft on which the brake is mounted, and
a belt looped over the drive pulley and the idler pulley,
wherein the belt includes either one V-ribbed belt or two V-ribbed belts having at least 12 but no more than 18 protrusions in total arranged in the lateral direction of the belt, and a friction force of the V-ribbed belt is greater than a braking force.
2. The drive apparatus for a passenger conveyor
according to claim 1, wherein the two V-ribbed belts are
arranged side by side in the lateral direction of the belt.