US3346073A - Safety brake tripping system for elevators - Google Patents

Description

Filed May 6, 1966 R. F. MARTIN SAFETY BRAKE TRI'PPING SYSTEM FOR ELEVATORS 5 Sheets-Sheet 1 F I6. IA

INVENTOR v RICHARD E MART/N Oct. 10, 1967 R. F. MARTIN 3,346,073

SAFETY BRAKE TRIPPING SYSTEM FOR ELEVATORS Filed May 6, 1966 5 Sheets-Sheet 2 Q'qu'u A A j, 32 32 "1'' El 37 7 30 30 J I 3/ F 6. 2 3/ l 22 0a. 10, 1967 R, F, MARTW 3,346,073

SAFETY BRAKE TRIPPING SYSTEM FOR ELEVATORS Filed May 6, 1966 5 Sheets-Sheet 5 /3 r W W 53 Oct. 10, 1967- R. F. MARTIN 3,346,073

SAFETY BRAKE TRIPI ING SYSTEM FOR ELEVATORS Filed May 6, 1966 5 Sheets-Sheet 4 Oct. 10, 1967 MART|N 3,346,073

SAFETY BRAKE TRIPPING SYSTEM FOR ELEVATORS Filed May 6, 1966 5 Sheets-Sheet 5 #fiv Fl 6. M

United States Patent Office 3,346,073 SAFETY BRAKE TRTPPING SYSTEM FOR ELEVATORS Richard F. Martin, Rock Island, 111., assignor to Montgomcry Elevator Company, a corporation of Delaware Filed May 6, 1966, Ser. No. 548,222 6 Claims. (Cl. 187-90) ABSTRACT OF THE DISCLOSURE Tripping mechanism for an elevator safety brake, in which a shaft that rotates at a speed directly proportional to the speed of the elevator is provided with acceleron1 eter means which trips the safety brake if the rate of ac celeration of rotation of the shaft exceeds a predetermined maximum value.

Elevator systems always include an over speed control which has a tripping device to set car brakes on the elevator car guide rails in the event of motor failure or a breakage in the hoisting cables for the car. The over speed control is a safety device which is divorced from the hoisting motor and cable apparatus to set the car brakes on the guide rails independently of the operating controls for the elevator.

It is old in the art to employ flyballs which, in the event of excessive speed of the elevator car, operate on the basis of centrifugal force to move a shaft that operates through levers to shut down the elevator motor and set the brakes on the elevator guide rails. Such speed controlled flyball tripping devices include massive balls or discs connected to a rotating shaft by pivoted link arms. The shaft rotates in direct proportion to the speed of descent of the elevator car.

The tripping device must, of course, be set to trip the brake at a speed higher than the fastest possible down travel of the car in normal operation. On cars which operate at a maximum speed of 300 to 400 f.p.m. the conventional flyball actuated device is adequate; but it has been discovered that in higher speed elevators, which may travel at 500 to 800 f.p.m., conditions develop in flyball units that cause them to lag and trip at a dangerously high speed. Instead of tripping the brake, for example, at 950 f.p.m. on a car designed for 800' f.p.m. the flyball may not trip the brake until the car reaches 1300 to 1500 f.p.m.; and this, of course, creates a dangerous situation that far exceeds state safety specifications. To the best of my knowledge, the reason for this behavior of flyball devices has not heretofore been known.

The flyballs are on a shaft which rotates constantly when the elevator is in motion, and if an elevators normal operating speed is 800 f.p.m., the rotational speed of the flyballs is quite high. I have now discovered that at speeds of rotation produced by an elevator speed in excess of about 500 f.p.m., the flyballs tend to lag behind a radial disposition with respect to the shaft on which they are mounted, and this flexes the flyball links enough to cause binding in the link pivots. The result is a frictional drag which requires higher centrifugal force to move the flyballs than should theoretically be required, so the elevator speed necessary to move the flyballs out from the shaft is far greater than would be expected. The effect, of course, tends to be cumulative if a malfunction causes the elevator car to approach a free fall condition. Thus the car reaches an unsafe speed before the balls are able to move enough to trip the brake mechanism.

The device of the present invention is designed for use either as an accessory added to the rotating shaft of a flyball device, or as a new and improved safety brake Bfitfifilli Patented Oct. 10, 1967 tripping system for newly installed elevators. Briefly, the

. shaft of the tripping assembly and the other of which is an inertia member of relatively large mass journalled on the shaft so that upon acceleration of the shaft the inertia member may lag behind the fixed member. The resulting relative movement between the two members trips the safety brake on the elevator car.

The principal object of this invention, therefore, is to provide an elevator safety brake tripping device which is operated by excessive acceleration of the elevator car rather than by excessive speed.

Another object is to provide a tripping device which sets the brakes on a high speed elevator before it can reach a dangerous rate of descent.

Still a further object of this invention is to provide a safety brake system of the character described which includes means for adjusting the rate of acceleration at which relative movement of the relatively movable members occurs.

Other objects and advantages of the invention will become readily apparent from the following detailed description taken in connection with the accompanying drawings,

in which:

FIG. 1 is a schematic view of an elevator safety brake system with a flyball tripping device to which the device of the present invention is added as an accessory;

FIG. 1A is a schematic view of the bottom of the elevator car;

FIG. 2 is an elevational view of the flyball type tripping device of FIG. 1 with portions cut away for clarity;

FIG. 3 is a side elevational view of the flyball tripping device, and shows the structure of the present invention which is added thereto;

FIG. 4 is a fragmentary sectional view of the struc ture of this invention;

FIG. 5 is an elevational view with parts broken away, taken generally along the line 55 of FIG. 4;

FIG. 6 is an elevational view of the safety brake means mounted on the bottom supporting cross beam of an elevator car; and

FIG. 7 is a bottom plan view of the safety brake means of FIG. 6.

As illustrated in FIG. 1, an elevator system is shown to comprise an elevator car 10 movable on T-s haped guide rails 11 which are vertically mounted on the side walls of the elevator shaft. The elevator car moves up and down within the elevator shaft in response to a master control, generally comprising an elevator motor and a hoisting cable (none of which is illustrated in the drawings). A standard flyball brake tripping device, generally designated 12, is mounted above the elevator shaft in the machinery penthouse of the elevator system. Such a device is an over speed control which sets brakes on the guide rails 11 in response to excessively rapid downward travel of an elevator car resulting, for example, from failure of the elevator motor or breakage of the hoisting cable. The tripping device 12 has a control sheave l3; and a cable 14 passes around said sheave, around a tail sheave 15 in the pit, and has a connector, generally designated 16, fixed to the elevator cross head 17 so that the control sheave 13 and its shaft (hereinafter described) rotate at a speed which is directly proportional to the speed of descent of the elevator car. The tripping device 12 and c.ble 14 are divorced from main cable and operating controls of the elevator.

Referring now'to FIGS. 2 and 3 which illustrate the flyball tripping device in detail, a frame 18 supports a pillow block 19 for a shaft 20 on which the control sheave '13 is fixed; and surmounting the frame 18 is a bearing bracket 21 in which a vertical sleeve 22 is journalled. A beveled ring gear 23 on the sheave 13 meshes with a beveled pinion gear 24 on the sleeve, so that the latter is driven by the cable 14 through the sheave 13.

A vertical shaft 25 is journalled and slidably mounted in the sleeve 22 and in a bushing 26 on the frame 18, and a fiyball assembly, indicated generally at 27, is linked to the sleeve 22 through a head 28 and to the shaft 25 through a bracket 29. The fiyball assembly includes lower links 30 which are pivoted at 31 to the head 28, massive flyball discs 32 which are pivoted to the links 30 at 33, and upper links 34 which extend from the pivots 33 and are pivoted at 35 to the bracket 29. The upper end of the shaft 25 is threaded to receive nuts 36 which provide adjustable stops for a compression spring 37 that biases the shaft 25 upwardly.

Journalled at the lower end of shaft 25 is a yoke 38, and a push rod 39 is pinned to the yoke at 40 so that vertical movement of the shaft moves the push rod 39 up and down.

The flyballs 32 rotate with the sleeve 22 and shaft 25, and centrifugal force tends to fling them radially outwardly to lower the links 30 and 34 and move the shaft 25 and push rod 39 down against the bias of the spring 37; and said spring is adjusted so that the flyballs may move outwardly only when the sleeve 22 rotates fast enough for centrifugal force to overcome the spring bias.

The brake tripping mechanism also includes operating linkage means, indicated generally at 41, for moving a brake shOe 42 which clamps the cable 14 against a brake anvil 43. The linkage means 41 includes a lever 44 pivoted on the upper end of an arm 45 at point 46. The arm 45 is pivoted at its lower end to the frame 18 at point 47. A compression spring mechanism 48 which is secured to the arm 45 limits the clamping force on the brake shoe 42 by permitting the arm to rock counterclockwise when clamping thrust on the lever 44 exceeds the force required to compress the spring. An adjustable stop 49 limits upward movement of the lever 41. A stud 50 on the lever 44 impales a slot 51 in the push rod 39, so downward movement of the shaft 25, in response to the centrifugal force acting on the flyballs 32, acts through push rod 39 to urge the lever 44 about pivot 46 in the direction of arrow C and force brake shoe 42 in the direction of arrow D and clamp cable 14. As will be more fully described below, the clamping of cable 14 trips a safety brake mounted on the bottom of the elevator car to clamp the guide rails 11 in the elevator shaft to stop the descent of the elevator car.

It should be noted that the downward movement of shaft 25 also acts through a switch link 52 leading to a known switching mechanism, generally designated 52a, to shut down the elevator motor. The entire structure as described to this point is old mechanism.

As best illustrated in FIG. 3, the accelerometer device of the present invention, indicated generally at 53, may be used as an accessory to be mounted on the shaft 20 of the control sheave 13 of a standard flyball governor. Of course, the device is equally adaptable as an improved safety brake system for newly installed elevators. Referring to FIG. 4, the device operates on the basis of an accelerometer means which is comprised of a plurality of relatively movable members which move relative to one another only when the maximum permissible rate of acceleration of the elevator car is exceeded. It includes a firsts rotating plate member 54 fixed to the shaft 20 and an inertia member 55 journalled on the shaft 20 as by ball bearings 56. The inertia member 55 is of a relatively large 4 mass so that upon acceleration of the shaft 20 the inertia member tends to lag behind the first plate 54 to afiord relative movement between the first plate and the inertia member.

Referring to FIG. 5, a tension spring 57 is connected at one end to a bracket 58 which extends outwardly from the first plate 54 and is connected at its other end to a lug 59 which extends inwardly from the inertia member 55 through a slot 60 in the first plate 54. The spring 57 predetermines the maximum rate of acceleration permissible for the elevator car. At all rates of acceleration below said maximum rate, the spring 57 connected to the first plate 54 drags the inertia member 55 along for simultaneous rotation with the plate 54. The slot 60 in the first plate 54 is elongated so the lug 59 may move in the direction of arrow E (FIG. 5) when the maximum permissible rate of acceleration is exceeded and the inertia member 55 lags behind the first plate 54. It should be noted that the spring 57 is threadedly connected to the bracket 58 and lug 59 to permit its tension to be changed and thus adjust the rate of acceleration at which the inertia members lag behind the first plate 54.

The device includes a second plate member 61 mounted on the shaft 20 for rotational movement therewith and for rectilinear sliding movement relative to the first plate 54. A spring 62 urges the second plate 61 away from the first plate 54. A latch means is fixedly mounted on the lug 59 of the inertia member 55 and includes a finger 63 extending through an aligned release recess 64 (FIG. 5) in the second plate 61 to restrain the latter against movement under the urging of spring 62. A latch lug 65 on finger 64 bears against the inner face 66 of the second plate 61. When the maximum rate of acceleration is achieved, rotation of the first plate 54 relative to the inertia member 55 causes the latch lug 65 to move into the release recess 64 in the second plate member 61. The second plate 61 then snaps to the left (in FIG. 4) under the force of spring 62. A bell crank 67 is pivoted on frame 18 and has a first leg 68 with a follower roller 69 which bears against the inner face 66 of the second plate 61. A second leg 70 of the bell crank 67 makes a pin and slot connection 71 with the upper end of a brake shoe trip rod 72, which is guided in an eye 73 on the frame 18. As the plate 61 slides to the left in FIG. 4, the bell crank is moved about pivot 74, as illustrated in an exaggerated phantom position in FIG. 4, causing the second leg 70 of the bell crank to move the trip rod 72 downwardly. Thus, the plate 61 serves as actuating means for the brake tripping means. Referring to FIGS. 2 and 5, as the trip rod 72 moves downwardly it moves lever 44 to force brake shoe 42 into clamping relationship with cable 14 as above described.

In operation, the inertia member 55, the first plate 54, and the rectilinearly movable second plate 61 rotate together with shaft 20 at all rates of acceleration below the rate at which spring 57 stretches. At these normal rates of acceleration, the inertia member 55 is dragged along with first plate 54. If a sudden rate of acceleration beyond the permissible limit of the tension in spring 57 is caused by malfunctioning of the elevators main controls, for instance, the first plate 54 will run away from the inertia member 55 because of the relatively large mass of the latter. The latch lug 65 will then move into the release recess 64 in the second plate 61 thereby permitting spring 62 to rectilinearly move the second plate 61 against the cam follower 69 of bell crank 67, thus pivoting the bell crank about point 74 to cause the brake shoe trip rod 72 to move downwardly against lever 44 connected to the brake shoe 42, as above described.

FIGS. 1, 6 and 7 disclose the safety brake which is set in response to the clamping of cable 14, The connector 16 (FIG. 1) connecting cable 14 to the cross head 17 of the elevator car includes a well known releasable jaw to releasably secure cable 14 to the elevator cross head. A brake actuating cable 75 is secured to connector 16 at one end and extends the height of the car and is wrapped around a first vertically oriented pulley P1 on the bottom of the elevator car (FIG. 1A). The cable 75 then wraps a second horizontally oriented pulley P2 and leads to a cable drum 76 (FIGS. 5 and 6) on the bottom of the elevator car. Thus, when cable 14 is clamped by the accelerometer controlled brake tripping device, the descent of the elevator car releases the jaw means of the cable connector 16 and the upper end of brake actuating cable 75 which is secured to cable 16. As the car continues its descent, the cable 75 unwinds from the brake drum 76, causing the drum to rotate and set the safety brake on the elevator car.

Referring particularly to FIGS. 6 and 7, shafts 77 and 78 extend laterally on the underside of the elevator car from either side of the cable drum 76 and are arranged to rotate in opposite directions as the cable drum rotates. The shafts are threaded into jaw means, generally designated 79, so that rotation of the shafts 77 and 78 causes the opposing jaws 80a and 80b (FIG. 7) to move in the direction of arrows F about pivot 81 and thus clamp the leg portions 11a of the T-shaped guide rails 11 to Stop the elevator car.

Thus it can be seen that I have provided a new and improved safety brake device which operates on the principle of an accelerometer to stop the fall of a malfunctioning elevator car before the car could reach the tripping speed of an ordinary fiyball device. The unit is easily adjustable to various predetermined rates of maximum acceleration. It is simple and easily constructed, and may be employed either as an accessory for presently operated fiyball type brake trips and the like or as a new safety brake tripping device without flyballs.

I claim:

1. In a safety brake system for elevator cars, brake tripping means comprising, in combination: a frame; a shaft journalled on said frame; means for rotating said shaft at a speed which is directly proportional to the speed of descent of the elevator car; accelerometer means on said shaft for detecting a rate of acceleration of said shaft in excess of a predetermined maximum rate, said accelerometer means having a plurality of relatively movable members which move relative to one another only When said maximum rate of acceleration is exceeded; and means carried on the shaft and movable relative to the shaft, said last named means being activated by relative movement of said members for tripping a safety brake on said elevator car.

2. The brake tripping means of claim 1 in which the 6 accelerometer means includes means for adjusting the rate of acceleration at which relative movement of the relatively movable members occurs.

3. The brake tripping means of claim 1 in which the accelerometer means includes a first member which is fixed on the shaft, an inertia member journalled on said shaft, said inertia member being of relatively large mass so that upon acceleration of the shaft the inertia member may lag behind the first member to afford relative movement between the first member and the inertia member, and resilient means connecting the first member and the inertia member for simultaneous rotation and acceleration at all rates of acceleration below said maximum rate.

4. The brake tripping means of claim 3 which includes means for adjusting the tension on the resilient connecting means so as to adjust the rate of acceleration at which the inertia member may lag behind the first member.

5. The brake tripping means of claim 3 which includes a second member mounted on the shaft for rectilinear sliding movement relative to the first member, spri means urging the second member away from the first member, latch means engaging the second member to restrain the latter against movement under the urging of said spring means, said latch means being disengaged from the second member upon relative rotation between the first member and the inertia member, and means operated by sliding movement of said second member for tripping the safety brake on the elevator car.

6. The brake tripping means of claim 5 in which the latch means is fixedly mounted on the inertia member and has a finger extending through aligned openings in the first and second members, a latch lug on said finger bears on the face of the second member remote from the first member, and in which rotation of the inertia member relative to the first member causes said latch lug to move into a release recess in the second member.

References Cited UNITED STATES PATENTS 2,244,893 6/1941 Panter 188--188 2,511,697 6/1950 Clift 187-90 FOREIGN PATENTS 335,056 4/ 1921 Germany.

EVON C. BLUNK, Primary Examiner.

H. C. HORNSBY, Assistant Examiner.

Claims (1)

1. IN A SAFETY BRAKE SYSTEM FOR ELEVATOR, CARS BRAKE TRIPPING MEANS COMPRISING, IN COMBINATION: A FRAME; A SHAFT JOURNALLED ON SAID FRAME; MEANS FOR ROTATING SAID SHAFT AT A SPEED WHICH IS DIRECTLY PROPORTIONAL TO THE SPEED OF DESCENT OF THE ELEVATOR CAR; A ACCELEROMETER MEANS ON SAID SHAFT FOR DETECTING A RATE OF ACCELERATION OF SAID SHAFT IN EXCESS OF A PREDETERMINED MAXIMUM RATE, SAID ASCCELEROMETER MEANS HAVING A PLURALITY OF RELATIVELY MOVABLE MEMBERS WHICH MOVE RELATIVE TO ONE ANOTHER ONLY WHEN SAID MAXIMUM RATE OF ACCELERATION IS EXCEEDED; AND MEANS CARRIED ON THE SHAFT AND MOVABLE RELATIVE TO THE SHAFT, SAID

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