IL122745A

IL122745A - Load canceling elevator

Info

Publication number: IL122745A
Application number: IL12274597A
Authority: IL
Original assignee: Schnaidman Zulmir
Priority date: 1997-12-25
Filing date: 1997-12-25
Publication date: 1998-10-30
Also published as: IL122745A0

Description

LOAD CANCELING ELEVATOR Zulmir Schnaidman i^W ZfcH 122745/2 c:\lmenache\001mfV98039elv.doc // 10/03/98 FIELD OF THE INVENTION The present invention relates to conveyance systems generally, and, in particular, to elevators.

BACKGROUND OF THE INVENTION In any conveyance system, the load applied therein will directly affect the power requirement of the system. In an elevator system, the weight of the applied load adds to the force to be overcome, including, for example, the net weight of the elevator system itself, when the elevator is ascending; while when the elevator is descending, the weight of the applied load adds to the descending force, reducing the power requirement of the system.

When the load on a system changes frequently, and especially when these changes are in large increments rather than being smooth, as in the case of an elevator system when passengers enter and leave the elevator, it is sometimes desirable, for reasons of extending equipment lifetime and safety, for example, for the system power requirement to be constant, regardless of the load therein.

Another specific application for a load-independent operation is a system for use on the Jewish Sabbath and holidays. As is known, Halachah, or orthodox Jewish law, prohibits the actuation of electrical equipment on the Sabbath and holidays. There are elevator systems, designed for use on the Sabbath, which operate automatically, so-called "Sabbath elevators." The details of such Sabbath elevator systems are described in U.S. Patent number 4,071, 1 16 , the contents of which are incorporated herein by reference. Nonetheless, many orthodox Jews are reluctant or unable to use such elevator systems because of the above-described variations in system power requirements they cause by riding therein.

U.S. Patent number 4,071,1 16 discloses a load canceling device for conveyance systems, including elevator systems, but the device disclosed therein employs electrical measurements, signal transfer, and switching to achieve load canceling, so that problems with their use on the Sabbath remain.

SUMMARY OF THE INVENTION The present invention seeks to provide an elevator system wherein the system power requirement has no dependence on the applied load therein and which is permissible for use by orthodox Jews on the Jewish Sabbath and holidays. It is thus a further objective of the present invention to achieve this load independent operation without use of electrical means.

There is thus provided, in accordance with a preferred embodiment of the present invention, an elevator system which is configured for a maximum applied load and which includes: an elevator car which includes a chassis and a floating support arrangement mounted thereon; a selectably operable drive system for selectably raising and lowering the elevator car; a braking system for selectably applying a braking force to the elevator car, and force transfer means associated with the floating support arrangement and the braking system, wherein the floor arrangement is operative, in response to a load applied thereto, and thus, also to the elevator car, to transmit a force which results from the applied load to the force transfer means or to be displaced relative to the chassis; wherein the force transfer means is operative, in response to an input force from or to a displacement of the floating support arrangement, to provide to the braking system an output force proportional to the input force or to the displacement; and wherein, in response to the output force, the braking system is operative to further apply to the elevator car a supplementary braking force proportional to the force from or to the displacement of the floating support arrangement, thereby to counterbalance the applied load. Further in accordance with a preferred embodiment of the present invention, the braking system includes a main braking mechanism and a supplementary braking mechanism which is associated with the force transfer means for applying the supplementary braking force to the elevator car. The supplementary braking mechanism includes one or more brake piston/cylinder arrangements in association with the force transfer means and a friction apparatus operative to exert a frictional braking force on the drive system in response to the force from the force transfer means. The force transfer means may be either hydraulic or pneumatic and includes a piston/cylinder arrangement and a flexible conduit. 122745/2 In accordance with an alternative preferred embodiment of the invention, the force transfer means includes a mechanism for switching between a first mode wherein the elevator car is ascending and a second mode wherein the elevator car is descending. In the present embodiment, the supplementary braking mechanism is operative, in the absence of an applied load in the elevator car, to apply a braking force to the elevator car of a magnitude corresponding to the magnitude of a resistive force which would result from the maximum applied load when the elevator car is ascending. When the elevator is descending, the supplementary braking mechanism is operative to increase the overall braking force applied to the elevator car by an amount so as to counterbalance the downward force on the elevator car which results from the applied load. When the elevator is ascending, the supplementary braking mechanism is operative to decrease the overall braking force applied to the elevator car by an amount so as to counterbalance the downward force on the elevator car which results from the applied load.

Further in accordance with the present preferred embodiment of the invention, the force transfer means further includes two branches on the flexible conduit and a shutoff valve on each branch. Each branch is associated with a brake piston/cylinder arrangement, and each of the two brake piston/cylinder arrangements is oriented to exert a force in a direction opposite to that exerted by the other. In the present embodiment, the friction apparatus includes a lever associated with the two brake piston/cylinder arrangements, a spring arrangement, and a friction mechanism to exert a frictional braking force on the drive mechanism. The spring arrangement and friction mechanism are operative, , in the absence of any force from the two brake piston/cylinder arrangements, to exert the maximum applied load braking force to the drive system; and the shutoff valves, the lever, the spring arrangement, and the friction mechanism are operative, when the elevator is descending, to increase the braking force exerted on the drive system by a magnitude so as to counterbalance the downward force on the elevator car which results from the applied load, and when the elevator is ascending, to decrease the braking force exerted on the drive system by a magnitude so as to counterbalance the downward force on the elevator car which results from the applied load.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be more fully understood and appreciated from the following detailed description, taken in conjunction with the drawings, in which: Figure 1 is a schematic illustration of an elevator system constructed and operative in accordance with a first preferred embodiment of the present invention; and Figure 2 is a schematic illustration of an elevator system constructed and operative in accordance with a second preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION Referring now to Figure 1, there is seen a schematic illustration of an elevator system, referred to generally as 10, constructed and operative in accordance with a first preferred embodiment of the present invention. Elevator system 10 includes elevator car 3, bi-directional drive motor 4, drive motor axle 5, support cable drive wheel 6, support cable 7, and counterweight 8; which are typical components of a standard elevator system as is known in the art. Drive motor 4 raises or lowers elevator car 3 by turning, backwards or forwards, axle 5 and drive wheel 6, which bears and drives support cable 7, which is attached to elevator car 3 and counterweight 8. Drive motor 4 and its associated components are typically located in a machine room (not shown) in the upper part of an elevator system 10.

In accordance with the present invention, elevator car 3 has a floating support arrangement, which in the present embodiment is a floating floor 1 1 which is displaced in response to an applied load 9, shown strictly by way of example as passengers, in car 3. Floor 1 1 is connected to piston/cylinder arrangement 12 which converts the displacement into a force proportional to the weight of applied load 9, which is transmitted, for example, hydraulically or pneumatically, by flexible tube 13 to a brake piston/cylinder arrangement 14 located in the machine room of elevator system 10. In accordance with the present embodiment of the invention, brake piston/cylinder arrangement 14 activates a brake shoe 16 which applies a frictional force to brake wheel or drum 15 which is mounted on drive motor axle 5. Floor 1 1, piston/cylinder arrangements 12 and 14, brake shoe 16, and brake drum 15 are arranged so that the braking force they apply counterbalances the force resulting from applied load 9 in car 3. It should be noted that, in the present embodiment, floating floor 1 1 and piston/cylinder arrangement 12 are shown strictly by way of example, but that another floating support and force conversion arrangement, for example a complete chamber with a piston/cylinder arrangement connected to the ceiling thereof, could be employed in an alternative embodiment of the present invention.

It will thus be appreciated that in a case wherein elevator car 3 is descending, the weight of applied load 9 produces a moment, via support cable drive wheel 6, on drive motor axle 5 which is counterbalanced by the resistive moment produced by brake drum 15 in response to the displacement of elevator car floor 1 1 in response to the same applied load 9. It will be appreciated by persons skilled in the art that, as a result of this counterbalancing, the energy supplied by drive motor 4 when elevator car 3 is descending will be the same for a load 9 of any weight. It is worth noting that, in the present embodiment, this counterbalancing is continuous and automatic and is achieved strictly by mechanical devices, with no electrical devices and no switching.

It is further worth noting that, in the present embodiment, brake shoe 16 and drum 15 are included in elevator system 10 strictly by way of example, and that some other braking mechanism, such as a mechanically activated disc brake, or an energy storage brake as is known in the art, could be employed in an alternative embodiment of the present invention. Further, in the present example, brake shoe 16 and drum 15 are supplementary to a main braking mechanism (not shown) of elevator system 10, which would be included in any prior art elevator system. In an alternative embodiment of the present invention, however, the counterbalancing braking force described above could be applied via a main braking mechanism with no need for a supplementary braking mechanism 16 and 15.

Referring now to Figure 2, there is seen a schematic illustration of an elevator system, referred to generally as 20, constructed and operative in accordance with a second preferred embodiment of the present invention. Elevator system 20 includes the same typical components of a standard elevator system as is known in the art as elevator system 10 shown in Figure 1. These standard components may be of similar structure, and serve a purpose similar to those described in with respect to Figure 1 , and are thus not specifically described herein.

In accordance with the present embodiment, elevator car 3 has a floating floor 21 which is displaced in response to an applied load, shown strictly by way of example as passengers 9, in car 3.

Floor 21 is connected to piston/cylinder arrangement 22 which converts the displacement into a force proportional to the weight of applied load 9, which is transmitted, for example, hydraulically or pneumatically, such as by a flexible tube 23 to a braking system, referred to generally as 40, in the machine room of elevator system 20 (not shown).

In the present preferred embodiment, flexible tube 23 splits at a junction 24 into two branches 37 and 38, with respective shutoff valves 31 and 32, and which communicate with respective brake piston/cylinder arrangements 33 and 34. Brake piston/cylinder arrangements 33 and 34 are each positioned and oriented to exert a force opposite to each other on lever 35, such that, as shown in the drawing, when piston/cylinder arrangement 33 extends it exerts an upward force on lever 35, and when piston/cylinder arrangement 34 extends it exerts a downward force on lever 35. Since, when piston/cylinder arrangement 33 extends, piston/cylinder arrangement 34 contracts to accommodate the upward motion of lever 35, and when piston/cylinder arrangement 34 extends, piston/cylinder arrangement 33 must contract to accommodate the downward motion of lever 35, both piston/cylinder arrangements 33 and 34 must include pressure overflow arrangements (not shown) to accommodate the fluid displaced by the above-described contraction. Lever 35 is associated with spring arrangement 36 which is linked to brake shoe 26, to control thereby the frictional braking force brake shoe 26 exerts on brake drum 25, which is mounted on drive motor axle 5.

Spring arrangement 36 is configured to cause brake shoe 26 to exert a frictional braking force on brake drum 25, in the absence of any force from either of brake piston/cylinder arrangements 3 1 and 32, to produce a resistive moment on drive motor axle 5 of a magnitude to correspond to the resistive moment, Mm, which would be produced on drive motor axle 5 by support cable drive wheel 6 when elevator car 3 bears its maximum applied load 9 when it is ascending. It should be noted that lever 35 and spring arrangement 36 are shown strictly by way of example and that any arrangement that can transmit and amplify or deamplify the force from brake piston/cylinder arrangements 33 and 34 could be employed in an alternative embodiment of the present invention.

When ejevator car 3 is descending, an automatic or "causative" switching that sets the elevator direction, such as that described in US patent 4,071,1 16 cited above, closes shutoff valve 31 and opens shutoff valve 32, thereby allowing the force resulting from load 9 on elevator floor 21 to be transmitted only via brake piston/cylinder arrangement 34 to lever 35 and spring arrangement 36 in a downward, direction, as shown in Figure 2, on brake shoe 26. Piston/cylinder arrangement 33 must contract as lever 35 moves in a downward direction, and the excess fluid in branch 37 of the flexible tube will be taken up by the pressure overflow arrangement (not shown) of piston/cylinder arrangement 33. The braking force exerted on brake drum 25 is thus increased by a magnitude to produce a moment on drive motor axle 5 to counterbalance the moment produced by support cable drive wheel 6 on drive motor axle 5 as a result of the downward force on elevator car 3 resulting from applied load 9. The net moment on drive motor axle 5 from the load and brake drum 25 will be generally equal to that produced by spring arrangement 36 in the absence of any load in elevator car 5, given as Mm above.

When elevator car 3 is ascending, shutofif valve 31 opens and shutoff valve 32 closes, thereby allowing the force resulting from load 9 on elevator floor 21 to be transmitted only via brake piston/cylinder arrangement 33 to lever 35 and spring arrangement 36 in a upward direction, as shown in Figure 2, on brake shoe 26. Piston/cylinder arrangement 34 must contract as lever 35 moves in a upward direction, and the excess fluid in branch 38 of the flexible tube will be taken up by the pressure overflow arrangement (not shown) of piston/cylinder arrangement 34. The braking force exerted on brake drum 25 is thus decreased by a magnitude to produce a moment on drive motor axle 5 to counterbalance the moment produced by support cable drive wheel 6 on drive motor axle 5 as a result of the downward force on elevator car 3 resulting from applied load 9. The net moment on drive motor axle 5 from the load and brake drum 25 will be generally equal to that produced by spring arrangement 36 in the absence of any load in elevator car 5, given as Mm above.

It will be appreciated by persons skilled in the art that, as a result of this counterbalancing, whether elevator car is descending or ascending, the energy supplied by drive motor 4 when elevator car 3 is descending will be the same for a load 9 of any weight. It is worth noting that, in the present preferred embodiment, this counterbalancing is continuous and automatic and is achieved strictly by mechanical devices, with no electrical devices and no switching.

It is further worth noting that, in the present embodiment, brake shoe 26 and drum 25 are included in elevator system 20 strictly by way of example, and that some other braking mechanism, such as a mechanically activated disc brake, or an energy storage brake as is known in the art, could be employed in an alternative embodiment of the present invention. Further, brake shoe 26 and drum 25 are supplementary to a main braking mechanism (not shown) of elevator system 20, which would be included in any prior art elevator system. In an alternative embodiment of the present invention, the counterbalancing braking force discussed above could be applied via the main braking mechanism with no need for a supplementary braking mechanism 26 and 25.

It will further be appreciated, by persons skilled in the art that the scope of the present invention is not limited by what has been specifically shown and described hereinabove, merely by way of example. Rather, the scope of the present invention is defined solely by the claims, which follow.

Claims

122745/1 CLAIflflS

1. An elevator system which is configured for a maximum applied load and which includes: an elevator car having a self-weight, and including a chassis and a floating support arrangement mounted onto said chassis; a selectably operable drive system for selectably raising and lowering said elevator car; a braking system for selectably applying a braking force to said elevator car; and force transfer means associated with said floating support arrangement and said braking system, wherein said floor arrangement is operative, in response to a load applied thereto, and thus, also to said elevator car, to transmit a force which results from the applied load to said force transfer means; wherein said force transfer means is operative, in response to an input force from said floating support arrangement, to provide to said braking system an output force proportional to said input force; and wherein, in response to said output force, said braking system is operative to further apply to said elevator car a supplementary braking force proportional to said force from said floating support arrangement, thereby to counterbalance the applied load.

2. An elevator system according to claim 1, wherein said floor arrangement is further operative, in response to a load applied thereto, to be displaced relative to said chassis; wherein said force transfer means is further operative, in response to a displacement of said floating support arrangement, to provide to said braking system an output force proportional to said displacement; and 122745/1 wherein said braking system is further operative, in response to said output force, to further apply to said elevator car a supplementary braking force proportional to said displacement of said floating support arrangement, thereby to counterbalance the applied load.

3. An elevator system according to claim 1 wherein said braking system includes: a main braking mechanism for applying a braking force to said elevator car; and a supplementary braking mechanism, associated with said force transfer means, for applying said supplementary braking force to said elevator car.

4. An elevator system according to any of claims 1, 2, and 3 wherein said supplementary braking mechanism includes. at least one brake piston/cylinder arrangement in association with said force transfer means, and friction apparatus arranged in association with said at least one brake piston/cylinder arrangement operative to exert a frictional braking force on said drive system in response to said force from said force transfer means.

5. An elevator system according to claim 1 wherein said force transfer means is hydraulic means and includes a piston/cylinder arrangement and a flexible hydraulic fluid conduit.

6. An elevator system according to claim 1 wherein said force transfer means is pneumatic means and includes a piston/cylinder arrangement and a flexible air conduit.

7. An elevator system according to claim 1 wherein said force transfer means includes a switching mechanism for switching said force transfer means between a first mode wherein said elevator car is ascending and a second mode wherein said elevator car is descending. 122745/1

8. An elevator system according to any of claims 1, 2, 3, and 7 wherein said supplementary braking mechanism is operative, in the absence of an applied load in said elevator car, to apply a braking force to said elevator car of a magnitude corresponding to the magnitude of a resistive force which would result from said maximum applied load when said elevator car is ascending, and wherein said supplementary braking mechanism is operative, in said second mode, to increase the overall braking force applied to said elevator car by an amount so as to counterbalance the downward force on said elevator car which results from the applied load, and, in said first mode, to decrease the overall braking force applied to said elevator car by an amount so as to counterbalance the downward force on said elevator car which results from the applied load.

9. An elevator system according to any of claims 1 through 9 wherein said force transfer means further includes two branches on said flexible conduit and a shutoff valve on each branch, and wherein said at least one brake piston/cylinder arrangement includes two brake piston/cylinder arrangements, each associated with one of said two branches, and each oriented to exert a force in a direction opposite to that exerted by the other, and wherein said friction apparatus includes a lever associated with said two brake piston/cylinder arrangements, at least one spring associated with said lever, and a friction mechanism associated with said drive system, wherein said at least one spring and said friction mechanism are operative, in the absence of any force from said two brake piston/cylinder arrangements, to exert said maximum applied load braking force to said drive system, and 122745/1 wherein said shutoff valves, said brake piston/cylinder arrangements, said lever, said at least one spring, and said friction mechanism are operative, in said second mode, to increase said braking force exerted on said drive system by a magnitude so as to counterbalance the downward force on said elevator car which results from the applied load, and, in said first mode, to decrease said braking force exerted on said drive system by a magnitude so as to counterbalance the downward force on said elevator car which results from the applied load.

10. An elevator system according to any of claims 1 - 9, and substantially as shown and described in conjunction with either of Figures 1 - 2. 1 1. An elevator system according to any of claims 1 - 9, and substantially as shown in either of Figures 1 - 2. For the Applicant, Jeremy M. Ben-David & Co. c:\ 1 menache\001 mf\98039elv