GB2250012A - Elevator - Google Patents

Abstract

A traction elevator wherein a hoisting cable 9 is passed over and partly around a driving sheave 5 of a hoist and a deflector sheave 8 and is fixed at one end to a car 10 and at the other end to a counterweight 11. A main brake 24 is provided for braking the driving sheave and an auxiliary brake 23 is provided for braking the deflector sheave. The main brake 24 and the auxiliary brake 23 are interlocked so as to be operated simultaneously. The total traction for braking with respect to the hoisting cable is thereby increased. <IMAGE>

Description

ELEVATOR BACKGROUND OF THE INVENTION The present invention relates generally to elevators and more particularly to a traction type elevator in which a hoisting cable is passed around parts of a driving sheave and a deflector sheave and is connected at one end thereof to a car suspended therefrom and at the other end to a counterweight suspended therefrom.

The majority of elevators known heretofore have been of the traction type (hereinafter referred to as elevators). As will be described more fully hereinafter, a typical elevator known heretofore comprises, essentially, a car (also called a cage or cab) for carrying a cargo load up or down a shaft or hoistway between a plurality of specific height levels, a hoist mounted in a machine room or penthouse at the top of the hoistway and being operable to hoist or lower the car by means of a main or hoisting cable connected at its one end to the upper part of the car, and a counterweight connected to and suspended from the other end of the hoisting cable to provide a counterbalancing force for the car.Another part is a deflector sheave or wheel around which is passed a part of the main cable between the hoist and the counterweight, and which functions to prevent contact between the car and the counterweight as they travel vertically in opposite directions.

The hoist comprises essentially a driving sheave fixed to and rotating with a horizontal drive shaft, an electric motor coupled by way of a speed-reducing mechanism or the like to the drive shaft to drive the driving shaft, and a brake mechanism for braking the drive shaft. The above mentioned main cable is passed around the driving sheave and is thus driven by the frictional traction therebetween. This traction functions also to keep the car at two or more preset stopping positions as a result of the operation of the brake.

A problem arises when a load imposed on the floor or platform of the car of this conventional elevator exceeds the design maximum load. In such a case, slippage and loss of traction between the main cable and the driving sheave are apt to occur, whereby the stopped position of the car becomes offset from the correct stopping position. Consequently, the hoisting work must be stopped for readjustment of the preset stopping position.

Such slippage can be prevented by increasing the traction.

Obviously the traction between the hoisting cable 9 and the driving sheave 5 can be increased by increasing the wrap-around contact angle a of the cable 9 and the sheave 5. One method which may seem to be feasible for achieving this is to increase the difference between the height positions of the driving sheave and the deflector sheave. This method, however, is disadvantageous in that the height of the ceiling of the machine room must be increased.

SUMMARY OF THE INVENTION Accordingly, an object of this invention is to provide an elevator in which the hoisting traction can be readily increased without resorting to any of a number of undesirable measures as described hereinafter.

According to the present invention, briefly summarized, there is provided an elevator of traction type in which a hoisting cable is passed over and partly around a driving sheave and a deflector sheave and is fixed at one end thereof to a suspended car and at the other end thereof to a suspended counterweight, and which is characterized in that it is provided with main brake means having brake shoes for pressing against a friction surface of a brake drum provided to rotate unitarily with the driving sheave thereby to impart a braking torque to the driving sheave and an auxiliary brake means for acting on the deflector sheave thereby to impart a braking torque thereto.

According to this invention a main brake device is provided for the driving sheave of the hoist and a similar auxiliary brake device is provided also for the deflector sheave, the two brake devices being operated with an interlocked relation. Therefore the frictional force acting between the deflector sheave and the main cable can be increased, wherein the traction force can be readily increased without increasing the height of the machine room ceiling.

BRIEF DESCRIPTION-OF THE DRAWINGS In the drawings: FIG. 1 is a side elevation showing the essential parts of one example of the elevator according to this invention; FIG. 2 is a relatively enlarged side view, in longitudinal section, of release means of a brake device; FIG. 3 is a sectional partial view showing a part of a deflector sheave and a cross section of the main cable; FIG. 4 is a schematic side view showing one example of a mechanism for interlocking the actions of the release means on the driving sheave side and the deflector sheave side; FIG. 5 is a side elevation showing the essential parts of another example of the elevator of the invention; and FIG. 6 is a side elevation showing an example of an elevator known in the prior art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As conducive to a full understanding of the present invention, the general nature, attendant problems, and limitations of the prior art relating to elevators will first be considered with reference to FIG. 6 illustrating one typical example of a traction type elevator of the prior art.

The principal parts of this elevator are a car 10 (also called a cage or cab) for carrying a cargo load up or down a shaft or hoistway (not shown), a hoist 2 installed in a machine room or penthouse 1 at the top of the shaft for hoisting or lowering the car 10 by means of a main or hoisting cable 9 connected at its one end to the upper part of the car 10, and a counterweight 11 connected to the other end of the main cable 9.

The hoist 2 is mounted on a pair of parallel, spaced-apart beams Ib, each comprising a steel I-beam.

These beams lb are laid across and secured perpendicularly to another pair of steel I-beams la, which are supported on the floor of the machine room.

This hoist 2 comprises essentially a driving sheave 5 fixed to a horizontal shaft 4, an electric motor 3 coupled by way of a speed-reducing gear mechanism or the like (not shown) to the shaft 4 to drive the driving sheave 5, and a brake mechanism including a brake drum 6 unitarily connected in tandem with the driving sheave 5 on the shaft 4.

At a position offset from the driving sheave 5 in the longitudinal direction of the beams lb and below the height level of the driving sheave 5, a deflector wheel (or sheave) 8 is rotatably supported on a pair of bearings 7 supported by the lower parts of the beams lb.

The rotational axis of this deflector sheave 8 is parallel to the rotational axis of the driving sheave 5.

The part of the above-mentioned main cable 9 connected at its end to the counterweight 11 is passed around a portion of the deflector sheave 8.

On opposite sides of the brake drum 6 of the aforementioned brake mechanism, a pair of brake shoes 12a and 12b are disposed. These brake shoes 12a and 12b are pivotally supported at their ends on one side (lower side) by pivot pins 13a and 13b. At their free ends on the opposite side (upper side), the brake shoes 12a and 12b are connected to a brake actuating mechanism 14 for actuating the brake shoes 12a and 12b in braking and releasing actions. This brake actuating mechanism 14 comprises a stud bolt 15 fixed at one end thereof to the upper end of one (12b) of the brake shoes and slidably passed through the upper end of the other brake shoe 12a, an adjusting nut 17 in screw engagement with the other end of the stud bolt 15, and a compressed coil spring 16 fitted around the stud bolt 15 between the adjusting nut 17 and the upper end of the brake shoe 12a.

Thus the spring force of the spring 16 acts to pull together the brake shoes 12a and 12b which are thereby forced to press against the friction surface of the brake drum 6, thereby exerting a braking torque thereon and therefore on the driving sheave 5. To remove this braking torque, that is, to release the brake drum 6, a release mechanism 18 is activated. This release mechanism comprises an electromagnetic coil 19 fixed to the upper end of one (12a) of the brake shoes and an electromagnetic plunger 20 slidably disposed within the electromagnetic coil 19 and being operable to thrust outward from the coil 19 to press against the upper end of the other (12b) brake shoe.

Thus, in this elevator of the above described essential organization, when the electric motor 3 is operated, its output power drives the shaft 4, and therefore the driving sheave 5, in either the e=clockwise direction or the counterclockwise direction, whereby the vertically suspended parts of the main cable 9 are alternately wound up or unwound down.

The traction force of the main cable 9 in this operation is due to the frictional force between the driving sheave 5 and the main cable 9. Thus the main cable 9 is unwound from the sheave 5 without slippage between the main cable 9 and the outer periphery of the sheave 5. Furthermore, when the car 10 is stopped, the driving sheave 5 is being fixed by the action of the brake. At this time also, the main cable 9 does not slip because of the frictional resistance force between it and the driving sheave 5. Thus the car 10 can be stopped at any of several specific positions in accordance with commands from a control panel (not shown).

The horizontal spacing between the shaft 4 and the shaft of the deflector sheave 8, that is, their spacing distance in the left-right direction in FIG. 3 is determined at a specific value by the front-to-back dimension of the car 10 and that of the counterweight 11, this specific value being such that the car 10 and the counterweight 11 will not contact each other when alternately ascending and descending in the hoistway as described above. As a result, the wrap-around angle a of the main cable 9 wrapped around the driving sheave 5 is ordinarily in the range of 120 to 150 degrees.

An elevator of the above described organization can be applied in the form of a freight elevator in a highrise warehouse or the like. In such a case, a fork lift 21 may be used to load cargo 21a on its fork prongs onto the platform of the elevator car 10. When a fork lift 21 is thus used, there is a risk of the fork lift 21 being driven onto the car platform through carelessness of the fork lift operator. This may cause the load on the car 10 to exceed the specified maximum load of the elevator, whereby slippage occurs between the main cable 9 and the driving sheave 5, and the car 10 descends.

This error occurs, for example, when the fork lift operator mistakenly assumes that no trouble will occur as long as the weight of the cargo 21a is within the allowable load limit and does not realize that the load will increase if the front wheels of the fork lift 21 ride onto the platform of the car 10 as indicated in FIG.

6.

As a consequence, if the main cable 9 thus slips and the position of the car 10 becomes offset, the operation of the elevator must be stopped and its stopping position must be readjusted.

Two methods have heretofore been considered for overcoming this problem. The first method is the socalled double-wrap method, which comprises winding the main cable 9 two times around the driving sheave 5 to increase the wrap-around angle a and thereby to increase the traction. The second method comprises increasing the difference between the height positions of the driving sheave 5 and the deflector sheave 8 thereby to increase the wrap-around angle a.

In the above first method, not only must the widths of the driving sheave 5 and the deflector wheel 8 be widened, but the diameters of the shafts 4 and 8a thereof must also be increased. By the second method, the height of the ceiling lc of the machine room 1 must be increased. Moreover, the positioning and installation of the hoist 2 becomes difficult. Yet, the wrap-around angle a does not increase appreciably, and the effectiveness of this method is low.

The present invention overcomes the above described problem by providing an elevator having an auxiliary brake device 23 for applying braking torque to the deflector sheave 8 as shown in FIG. 1.

In FIG. 1, those parts which are the same as or equivalent to corresponding parts in FIG. 6 are designated by like reference numerals. In the example of the elevator of the invention shown in FIG. 1, the driving sheave 5 is provided with a main brake device 24, while the deflector sheave 8 is provided with the auxiliary brake device 23. These brake devices 23 and 24 have the same construction, which will now be described with respect to the auxiliary brake device 23.

A brake drum 25 is coaxially fixed to the shaft 8a of the deflector sheave 8. A pair of brake shoes 26a and 26b are disposed on opposite peripheral sides of this drum 25. These brake shoes 26a and 26b at their ends on one side (lower side as viewed in FIG. 1) are pivotally supported on respective pins 27a and 27b. The other free ends of these brake shoes 26a and 26b are provided with means 28 for applying braking force. This braking force applying means 28 comprises a stud bolt 29 fixed at its one end to one (26b) of the brake shoes near its free end and slidably passed through the other brake shoe 26a, an adjusting nut 31 screwed onto the other end of the stud bolt 29, and a compression spring 30 interposed between the adjusting nut 31 and the other brake shoe 26a. The spring force of the spring 30 acts to pull the pair of brake shoes 26a and 26b toward each other.The brake shoes 26a and 26b are thereby pressed against the friction surface of the brake drum 25, whereby braking torque is applied to the deflector sheave 8.

This braking torque is removed, that is, the brake drum 25 is released, by operating a release means 32. As shown in FIG. 2, this release means 32 has a frame 33 fixed the free end of one brake shoe 26a and enclosing an electromagnetic coil 19 fixed thereto. An electromagnetic plunger 20 is slidably inserted in the interior of the electromagnetic coil 19 to undergo advancing and retracting movement in the axial direction thereof. The front or outer end of this plunger 20 abuts against the free end of the other brake shoes 26b. The rear or inner end of this plunger 20 abuts against a retaining plate 35. A compression spring 34 is interposed between the retaining plate 35 and an inner wall surface of the frame 33. This spring 34 functions to eliminate play or backlash between the plunger 20 and the brake shoe 26b when the electromagnetic coil 19 is not energized.

FIG. 3 is a fragmentary sectional view taken along a plane passing through the axis of the deflector sheave 8.

This deflector sheave 8 is provided around its peripheral surface with a U-shaped cable groove 36 formed therein.

Along the central part of the bottom of this cable groove 36 is formed an undercut groove 37 communicating with the cable groove 36 and extending deeper toward the axis of the deflector sheave 8. This undercut groove 37 functions to produce a great frictional force between the surface of the cable groove 36 and the hoisting cable 9.

In the above described example, it is desirable that the main brake device 24 on the driving sheave side and the auxiliary brake device 23 on the deflector sheave side be controlled simultaneously. This can be accomplished by simultaneously operating the release means 18 and the release means 32.

When the car 10 is to be stopped at a certain height position in the elevator of - the above described mechanical organization, a command signal is transmitted from an elevator control panel (not shown). In response to this signal, a switch (also not shown) operates to deenergize simultaneously the electromagnetic coils of both brake devices 24 and 23. Accordingly, the two brake devices 24 and 23 operate to stop simultaneously the driving sheave 5 and the deflector sheave 8.

The total frictional force between the cable 9 and the driving sheave 5 and the deflector sheave 8 is increased by the frictional force of the wrap-around contact angle ss of the deflector sheave 8 and the cable 9 in comparison with the frictional force between the cable 9 and only the driving sheave 5 in the conventional elevator. This increase is approximately 1.2 to 1.5 times. Therefore, in comparison with the conventional elevator, the traction in the elevator of this invention is greater.

Furthermore, the auxiliary brake device 23, which is additionally installed, is mounted in the space above the deflector sheave 8, which space has heretofore not been used. Thus there is no necessity of increasing the height of the machine room. Since the installation of this auxiliary brake device can be carried out by locally adding parts, the parts can be readily mounted irrespective of whether they are already installed existing parts or whether they are parts to be newly mounted.

As one measure for causing the main brake device 24 and the auxiliary brake device 23 to act simultaneously, the movement of the release means 18 on the side of the main brake device 24 can be transmitted to the side of the auxiliary brake device 23 by means of a flexible actuating wire. One example of means for such a measure is shown in FIG. 4.

More specifically, the rear end 38a of a flexible actuating wire 38 is connected to the rear end of the electromagnetic plunger 20 of the release means 18 on the side of the main brake device 24. The front end 38b of the flexible actuating wire 38 is connected to one of a pair of drivers 40a and 40b coupled together by a pin 39.

In another example of the elevator according to this invention as shown in FIG. 5, the deflector sheave 8 is provided with an auxiliary brake device 40. This brake device 40 has a short arcuate shoe 47 for contacting and separating from the periphery of the deflector sheave 8.

The wrap-around contact angle ss of the cable 9 and the deflector sheave 8 is less than the contact angle a of the cable 9 and the driving sheave 5, being of the order of 1/2 to 1/5 of the angle a. For this reason, the required braking torque of this brake device 40 can be reduced, and its construction can be made relatively simple.

This auxiliary brake device 40 has a bracket 41 fixed to structure lb supporting the hoist 2 and the deflector sheave 8. This bracket 41 slidably supports a shoe holder 42, which thereby can undergo horizontal advancing and retracting moyement toward and away from the periphery of the deflector sheave 8. The shoe holder 42 supports at its working and the above mentioned brake shoe 47. An adjusting nut and a locking nut, constituting together a double nut 43, are screwed onto the other end of the shoe holder 42. Between this double nut 43 and the bracket 41 is fitted under compression a compression spring 44. Thus, the spring force of this spring 44 acts to separate the brake shoe 47 away from the peripheral surface of the deflector sheave 8.

Furthermore, the electromagnetic coil of a solenoid 45 is fixed to the shoe holder 42, and the outer end of the solenoid plunger 46 abuts against the fixed bracket 41. Thus, when the solenoid 45 is energized to thrust its plunger 46 outward, the brake shoe 47 is advanced to apply braking force to the deflector sheave 8. By connecting in parallel the electromagnetic coil of the solenoid 45 and the electromagnetic coil 19 on the side of the driving sheave 5, the main brake device 24 and the auxiliary brake device 40 can be operated simultaneously thereby to apply braking torque simultaneously on their respective sheaves 5 and 8.

Claims (8)

WHAT IS CLAIMED IS:

1. In an elevator wherein a hoisting cable is passed over and partly around a driving sheave and a deflector sheave and is fixed at one end thereof to a car and at the other end thereof to a suspended counterweight, the improvement comprising in combination therewith a main brake having brake shoes for pressing against a friction surface of a brake drum provided to rotate unitarily with said driving sheave thereby to impart a braking torque to the driving sheave and an auxiliary brake for acting on said deflector sheave thereby to impart a braking torque thereto.

2. An elevator according to claim 1 in which said auxiliary brake comprises a brake drum having a friction surface and connected to said deflector sheave to rotate unitarily therewith, a pair of brake shoes disposed on opposite sides of said brake drum, each brake shoe having one pivotally supported end and another free end, spring means for acting on the free ends of said brake shoes thereby to press the brake shoes against the friction surface of said brake drum, and release means for acting.

on the brake shoes and pressing the same, counter to the force of said spring means, away from the brake drum thereby to release the brake drum.

3. An elevator according to claim 1 in which said auxiliary brake comprises a brake drum having a friction surface and connected to said deflector sheave to rotate unitarily therewith, a brake disposed in the vicinity of said friction surface to be pressed thereagainst, spring means for pressing said brake shoe against said friction surface, and release means for acting on the brake shoe and pressing the same, counter to the force of said spring means, away from the brake drum thereby to release the brake drum.

4. An elevator according to claim 2 or 3 in which said release means is a solenoid type mechanism comprising an electromagnetic coil and a plunger inserted in a slidable state in the electromagnetic coil.

5. An elevator according to claim 1 in which said deflector sheave has around the periphery thereof a Ushaped cable groove for receiving therein said hoisting cable passed around the deflector sheave, and, along the central part of the bottom of this cable groove, is formed an undercut groove extending deeper toward the axis of the deflector sheave and communicating with the cable groove.

6. An elevator according to claim 1 in which said main brake and auxiliary brake have respective release means which are coupled by a mutually interlocking linking mechanism.

7. An elevator according to claim 6 in which said linking mechanism comprises a flexible actuating wire.

8. An elevator substantially as hereinbefore described with reference to Figures 1 to 4, or Figure 5 of the accompanying drawings.