[0001 ] HYDRAULIC ELEVATOR SAFETY APPARATUS

FIELD

[0002] There is described a safety apparatus intended to prevent a free fall of an elevator car of a hydraulic elevator in the event of a loss of hydraulic pressure due to a single bottom cylinder failure.

BACKGROUND

[0003] A hydraulic elevator has an underlying hydraulic cylinder which serves to raise and lower the elevator car. It was once assumed that a leak of hydraulic fluid would merely result in the elevator car slowly descending. There have now been some catastrophic failures due to hydraulic cylinder failures as a result of rust and hydraulic line ruptures. These have resulted in serious injuries and, in some instances, loss of life. One solution which has been proposed is to provide a sensor in combination with an overspeed valve which will slow the descent of an elevator car if an unacceptable rate of descent is sensed, as is illustrated and described in U.S. Patent 6,059,071 (Gilliland et al). The overspeed valve only provides protection against some types of failures, it not protect against hydraulic cylinder failure. Another solution which has been proposed are various devices which prevent telescoping movement of the hydraulic cylinder, as is illustrated and described in U.S. Patents 3,995,534 (Rastetter); 6,039,151 (Ringel et al); 6,179,094 (Seggebruch et al); 6,206,145 (Cable et al); and 6,478,123 (Seggebruch et al). One such device which prevents telescoping movement of the telescoping cyclinder is currently being marketed by Adams Elevator under the Trademark "Life Jacket". There will now be described an alternative solution.

SUMMARY

[0004] There is provided a hydraulic elevator safety apparatus for an elevator having a hydraulic cylinder which moves an elevator car up and down a vertical shaft. The apparatus includes a stop assembly that moves with the elevator car and consists of a stop lever, at least one elevator stop carried by the stop lever and a stop lever support which is secured to the frame of the elevator car. The stop lever is pivotally secured to the stop lever support to define a fulcrum. The lever pivots about the fulcrum between an inoperative position and an operative position. In the inoperative position, the elevator stop is disengaged allowing the elevator car to move downwardly unimpeded. In the operative position, the elevator stop engages to prevent downward movement of the elevator car. A stop lever biasing spring biases the stop lever into the operative position. A stop lever hold-down assembly is provided that does not move with the elevator car and includes a hold-down support and a hold-down lever pivotally secured to the hold-down support and movable between a stop lever retention position and a stop lever release position. A cable guide is mounted to the hold-down lever. A follower cable is provided having a first end secured to the stop lever and a second end secured to the elevator car. The cable extends around the cable guide of the hold-down lever, such that the cable moves around and is guided by the cable guide as the car goes up and down. As long as the hold-down lever is maintained in the stop lever retention position, the cable exerts a force upon the stop lever to overcome the force of the stop lever biasing spring and maintain the stop lever in the inoperative position. A pressure monitoring hydraulic actuator is provided which includes a hydraulic cylinder and a piston movable in the hydraulic cylinder. The piston has a piston rod connected to the hold-down lever. Movement of the piston in a first direction moves the hold-down lever to the stop lever retention position. Movement of the piston in a second direction, opposed to the first direction, moves the hold-down lever to the stop lever release position slackens the cable. A hydraulic connection is maintained between the hydraulic lifting cylinder for the elevator car and the hydraulic actuator. As long as hydraulic pressure is maintained at operating levels, the piston of the hydraulic actuator is urged in the first direction to maintain the hold-down lever in the stop lever retention position. Upon a loss of hydraulic pressure, the piston of the hydraulic actuator moves in the second direction to the stop lever release position and slackens the cable, whereby the biasing force of the stop lever biasing spring moves the stop lever into the operative position with the elevator stop engaging to prevent downward movement of the elevator car.

[0005] As will hereinafter be described, in most installations an elevator car travels along guide rails. It is, therefore, preferred that the stop lever support is mounted to the frame of the elevator car in proximity to one of the guide rails. When the stop lever is in the inoperative position the elevator stop is positioned in parallel spaced relation to the one of the guide rails and moves along the guide rails with the elevator car. When the stop lever is in the operative position the elevator stop frictionally engages the one of the guide rails to develop a rapidly increasing pressure on the guide rails during a stopping interval and thereafter prevent further downward movement of the elevator car. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] These and other features will become more apparent from the following description in which reference is made to the appended drawings, the drawings are for the purpose of illustration only and are not intended to be in any way limiting, wherein:

[0007] FIG. 1 is a side elevation view of a hydraulic elevator safety apparatus.

[0008] FIG. 2 is a schematic hydraulic diagram for the hydraulic elevator safety apparatus illustrated in FIG. 1.

DETAILED DESCRIPTION

[0009] A hydraulic elevator safety apparatus generally identified by reference numeral 10, will now be described with reference to FIG. 1 and FIG. 2.

Structure and Relationship of Parts:

[0010] Referring to FIG. 1, safety apparatus 10 is illustrated as it would appear installed in a pit 102 of a vertical shaft 104 of a hydraulic elevator 100. There is illustrated elevator car guide rails 106 and frame 108 of the elevator car. Although not illustrated, it will be understood that the elevator car is positioned on frame 108 and that there is a single hydraulic lifting cylinder also positioned in pit 102 moves frame 108 up and down vertical shaft 104. [001 1] A stop assembly, generally identified by reference number 12, moves with the elevator car. Stop assembly 12 includes a stop lever 14. An elevator stop 16 is carried by stop lever 14. A stop lever support 18 is secured to frame 108 of the elevator car. As is illustrated, stop lever 14 is pivotally secured to stop lever support 18 to define a fulcrum 20. Stop lever 14 pivots about fulcrum 20 between an inoperative position and an operative position. In the inoperative position, elevator stop 16 is disengaged allowing the elevator car to move downwardly unimpeded. In the operative position, elevator stop 16 engages to prevent downward movement of the elevator car. A stop lever biasing spring 22 biases stop lever 14 into the operative position.

[0012] In FIG. 1, elevator stop 16 is illustrated as a pair of cooperating wedges 16a and 16b. It will be appreciated that the configuration of elevator stop 16 may vary. Stop lever support 18 is mounted to frame 108 of the elevator car in proximity to one of guide rails 106. When stop lever 14 is in the inoperative position, wedges 16a and 16b of elevator stop 16 are positioned in parallel spaced relation to guide rail 106. When stop lever 14 is in the operative position, wedges 16a and 16b frictionally engages guide rail 106 to develop a rapidly increasing pressure on guide rail 106 during a stopping interval and thereafter prevent further downward movement of the elevator car.

[0013] A stop lever hold-down assembly, generally identified by reference numeral 24, is positioned in pit 102 and does not move with the elevator car. Hold-down assembly includes a hold-down support 26 and a hold-down lever 28 pivotally secured to hold-down support 26 and movable between a stop lever retention position and a stop lever release position. A cable guide 30 is mounted to hold-down lever 28. Cable guide 30 is in the form of a sheave and includes cable retainers 32. [0014] A follower cable 1 10 is provided having a first end 1 12 secured to stop lever 14 and a second end 1 14 secured to frame 108 of the elevator car. Cable 110 extends around cable guide 30 of hold-down lever 28. Cable moves around and is guided by cable guide 30 as the elevator car goes up and down. As long as hold-down lever 28 is maintained in the stop lever retention position, cable 1 10 exerts a force upon stop lever 14 to overcome the force of stop lever biasing spring 22 and maintain stop lever 14 in the inoperative position.

[0015] A pressure monitoring hydraulic actuator is provided, generally identified by reference 34. Hydraulic actuator includes a hydraulic cylinder 36, and a piston 38 movable in hydraulic cylinder 36. Piston 38 has a piston rod 40 which is connected to hold-down lever 28. Movement of piston 38 in a first direction, indicated by arrow 42, moves the hold-down lever 28 to the stop lever retention position. Movement of piston 38 in a second direction opposed to the first direction, as indicated by arrow 44, moves hold-down lever 28 to the stop lever release position and slackens cable 1 10. It is preferred that a piston biasing spring 46 be provided to bias piston 38 in the second direction. [0016] There is a hydraulic connection, in the form of a feed line 48 indicated by arrow 48, between the hydraulic lifting cylinder (not shown in FIG. 1) for the elevator car and hydraulic actuator 34. Referring to FIG. 2, there is illustrated a preferred hydraulic circuit. Single hydraulic lifting cylinder is identified by reference numeral 120. Hydraulic lifting cylinder 120 receives hydraulic fluids for its normal operation through feed line 122 which is connected to a hydraulic pumping unit (not shown). A pair of pressure monitoring hydraulic acutators 34 are illustrated. The reason two are illustrated is that it is preferred to have a pair of elevator stops each acting upon opposed guide rails. Hydraulic actuators 34 are connected to hydraulic lifting cylinder 120 by feed lines 48, so that they share pressure with hydraulic lifting system 1 12. It is viewed as desirable to include a manual shut off valve 50 on each of feed lines 48, to isolate hydraulic acutators 34 for purposes of servicing and testing. In order to make provision for testing, there should also be a testing connection line 52 with a testing valve 54. Shut off valve 50, testing connection line 52 and testing valve 54 allows for connection of equipment to vary the pressure in feed line 48 and test operation of safety apparatus 10 without involvement of hydraulic lifting cylinder 120.

Operation:

[0017] Referring to FIG. 1, as long as hydraulic pressure is maintained at normal operating levels, piston 38 is urged by hydraulic pressure in the first direction to maintain hold-down lever 28 in the stop lever retention position. As long as hold-down lever 28 is maintained in the stop lever retention position, cable 1 10 exerts a force upon stop lever 14 to overcome the force of stop lever biasing spring 22 and maintain stop lever 14 in the inoperative position. When stop lever 14 is in the inoperative position, wedges 1 a and 16b of elevator stop 16 are positioned in parallel spaced relation to guide rail 106. [0018] Upon a loss of hydraulic pressure, piston 38 moves in the second direction to the stop lever release position, slackening cable 1 10. The movement of piston 38 in the second direction is accelerated by piston biasing spring 46 which biase piston 38 in the second direction. The slackening of cable 1 10 results in the biasing force of stop lever biasing spring 22 moving stop lever 14 into the operative position. When stop lever 14 is in the operative position, wedges 16a and 16b frictionally engages guide rail 106 to develop a rapidly increasing pressure on guide rail 106 during a stopping interval and thereafter prevent further downward movement of the elevator car.

Variations:

[0019] There are a variety of ways in which the elevator stops may be configured. The preferred manner is a guide rail engagement with the operating force derived entirely from pressure applied on the guide rails through eccentrics, rollers, wedges, or similar devices. It is preferrable to avoid introducing any medium that might limit the braking force.

Cautionary Warnings:

[0020] If the elevator stop is to engage the guide rails, the guide rails must be installed in the elevator pit in a manner that can withstand the forces experienced during stopping.

[0021] In this patent document, the word "comprising" is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article "a" does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements.

[0022] The scope of the claims should not be limited by the illustrated embodiments set forth as examples, but should be given the broadest interpretation consistent with a purposive construction of the claims in view of the description as a whole.