US1987719A - Safety mechanism for elevators - Google Patents

Description

Jan. 15, 1935. J, SPRA'GUE SAFETY MECHANISM FOR ELEVATORS Filed Oct. 10, 1928 ATTRNEY INVENTOR Patented Jan. 15, 1935 UNITED STATES SAFETY MECHANISM FOR ELEVATORS Frank J. Sprague, New York, N. Y., assignor to Westinghouse Electric & Manufacturing Company, a corporation of Pennsylvania Application October 10, 1928, Serial No. 311,510

16 Claims.

My invention relates to safety devices for elevators and more particularly to means for actuating such safety devices.

In order to provide for the safe operation of elevators, each car is usually supplied with a safety or car-stopping device comprising two pairs of gripping jaws that are disposed underneath the car in position to engage the guide rails at the sides of the car when the car falls and bring itto a stop. In some cases, the gripping jaws are applied to the guide rails by means of stored-up power, such as may be obtained from compressed springs in conjunction with operating wedges. In other cases, the gripping jaws are applied to the guide rails by means of wedgeshaped expanding members that are projected by screw action of a safety cable drum. In either case, the release of the stored-up power or the operation of the rotatable cylinder is usually eifected by a safety rope which is firmly secured to a governor rope. The governor rope is releasably attached to the car, from which it runs to an overhead sheave mounted in the upper part of the hatchway, and thence to and around a' counterweighting sheave and back to the car. Normally, the governor rope moves with the car and rotates the overhead sheave. Attached to the overhead sheave is a centrifugal governor which, when rotated above a predetermined speed, releases a locking device that firmly grips the governor rope and arrests its movement, if the car is descending. When the movement of the governor rope is arrested, it is automatically released from the car by the releasable attachment; thereupon, the continued downward movement of the car causes the governor rope to pull on the safety rope and thereby release the stored-up power or operate the rotatable cable drum to apply the gripping jaws to the guide rails with increasing pressure, until the car is brought to a stop.

Inasmuch as the operation of the safety jaws is initiated and controlled by a centrifugal governor set to operate at some maximum speed above the usual speed at which the car runs, it may properly be called a speed-controlled system. Such speed-controlled systems have been in use for many years, but, since their introduction, the normal running speeds of many elevator cars have been materially increased, largely because of the increased height of buildings and also because of the necessity for increasing the work performed by the individual elevators. When the speed .of a car is increased it follows that the maximum speed at which the centrifugal governor will become effective to stop the car must also be increased accordingly.

Modern elevators are being operated at normal high speeds ranging from 600 to 800 feet per minute, and even 1000 feet per minute and over is proposed.

It is inherent in a speed-controlled systemlthat the speed attained by the car before the speedresponsive device will trip must be in excess of the normal speed by a considerable margin, usually about 25%. In other words, the elevator must attain speeds of from 750 to 1250 feet or more per minute before eveninitiating the action, of the safety system. Since, also, in most safety systems, an additional time elapses before the jaws actually grip the rails, it is obvious that the mass of an elevator car moving at such high rates of speed will require an excessive braking force to bring it to rest within a reasonable distance, this force varying as the square of the attained speed for any predetermined distance and load.

With the usual safety grips now used, the brakingforce must be applied to the guide rails, and, in most cases, such application will distort or. cut them to such an extent that, after a single application of the safety grips, repairs are necessary. Moreover, should the car get out of control either by-breakage of the cables or by'failure of some of the electrical control apparatus, when the car is within a few floors of the lower limit. of travel, it may not attain such speed as will cause tripping of the speed governor before the car reaches the bottom of the hatchway. In other words, the car may approach the lower limit of travel at a speed somewhat under or over its normal maximum speed, and, in the case of a car operating normally at 800 or more feet per minute, it will be extremely difiicult to stop it with oil buffers or other safety stopping devices which the-car will strike at the bottom of the hatchway without serious injury to such buffers or to the car and its occupants.

In addition to failure of cables, a more frequent occurrence is to have the car get out .of

control of the attendant by failure of some of the motor, brake or electrical control apparatus, and, in this case, the car may descend through a relatively great distance in spite of the attempts of the attendant to stop it, but the speed of the car, in such case, may never rise to such value as to trip the safety governor. If a runaway car reaches the lower limit of travel before the speed becomes great enough to trip the governor the car will be broughtlto an abrupt and violent stop at the bottom of the hatchway. These facts all have additional importance if two elevators, one over another, are operated in a single hatchway.

Furthermore, while it is the usual practice to inspect the safety appliances on elevator cars frequently, such inspection seldom consists of any actual test of the operative condition of the safety devices, particularly, the actual setting of the safety jaws, since the difficulties encountered in operating the car at such high speed as will cause the governor to trip are considerable as is also the consequent probability of damage to the guide rails when the safety jaws are actually applied, with the car operating at the necessary speed. Hence, the inspection usually consists in determining that the governor cable is in good condition, that the tripping device is free to operate and that the safety jaws appear, upon visual inspection, to be in operative condition. Therefore, in the interest of general security, the safety apparatus should be such that all the parts on which the safety of the car depends may be readily tested by actual application under different conditions of speed and'rates of acceleration.

In seeking to provide mechanism for operating elevator safety devices that does not embody the inherent objectionable characteristics of the speed-control mechanism, I have discovered that such a predetermined rate of acceleration as will follow when a car starts to fall or starts to run away in a downward direction may be employed to initiate the operation of the safety device to stop the car.

This will be understood when it is considered that, while the rate of acceleration, by reason of gravity, in free falling, is approximately 32 feet per second per second, the rate of acceleration of any car during its normal operation is rarely over one-third of the rate caused by gravity.

It is obvious that a change in the rate of acceleration occurs instantly when a car starts to fall or run away, and, therefore, that a rate of acceleration may be selected which will be just as effective in the first one-fiftieth of a second after failure occurs to initiate the stopping of the car as it will be at the end of any period of time thereafter.

One of the objects of my invention is to provide for stopping a car as soon as it starts to fall or starts to run away in the downward direction.

Another object of my invention is to provide for stopping a falling car before it reaches a dangerous speed.

Another object of my invention is to provide for stopping a car before it reaches a high speed after it starts to run away.

A further object of my invention is to provide a safety mechanism for an elevator that shall be so quickly responsive to dangerous conditions that it will act to stop the car before it attains such high speed that the safety apparatus will be damaged in making a stop.

A further object of my invention is to provide a safety mechanism for an elevator which shall be operatively responsive to the rate of acceleration-of the elevator and independent of the speed of the elevator.

A further object of my invention is to provide a safety mechanism for elevators that may be readily inspected and tested under various conditions of actual operation.

A further object of my invention is to provide a safety mechanism for elevators that may be readily adjusted to approximate different conditions so that it may easily be tested under a variety of circumstances.

A further object is to provide a means for initiating the action of the safety device that may be easily and quickly reset by the attendant on the car.

A further object is to provide a plurality of means for initiating the operation of the safety device for the purpose of insuring its operation upon the occurrence of any dangerous condition.

A further object of my invention is to provide a safety mechanism for elevators that shall be responsive to a predetermined rate of downward acceleration of the car, or an increase in the speed of the car to a predetermined maximum above its normal speed.

A further object of my invention is to provide a safety mechanism for an elevator that shall be responsive to a predetermined rate of acceleration while the car is descending, but which will not be affected by any change in the rate of acceleration or deceleration while the car is ascending.

A further object of my invention is to provide a safety mechanism for an elevator which may be responsive either to the speed of the elevator or to the rate of acceleration of the elevator, and which may be manually operated at the will of an attendant on the elevator.

It is also an object of my invention to provide an elevator safety device that shall be simple and efficient in operation, and adapted for ready and economical installation and maintenance.

Other objects of my invention will, in part, be obvious and will, in part, appear hereinafter.

For an illustration of one of the many forms my invention may take, reference may be had to the accompanying drawing in which:

Figure l is a diagrammatic representation of an elevator embodying means for actuating its safety device constructed in accordance with my invention;

Fig. 2 is a view, in side elevation, illustrating a modification of the electroresponsive means for actuating the cable-locking device shown in Fig. 1; and

Fig. 3 is a top plan view illustrating a modification of the acceleration-controlled device for initiating and effecting the operation of the governor-rope-locking device shown in Fig. 1.

In Fig. 1 of the drawing, I have illustrated an elevator car C supported, by a hoisting cable 11, between a pair of guide rails 12 and 13. Secured to the bottom of the car C is the usual safety-grip device 14 comprising two pairs of jaws l5 and 16 disposed to grip the guide rails 12 and 13 and stop the car when the car starts to fall or run away downwardly. A pair of operating screw rods 17 and 18 connect the gripping jaws 15 and 16, in the usual manner, to a safety-cable drum 19 which, when rotated, causes the jaws to grip the guide rails. The means for rotating the safety-cable drum 19 comprises a safety rope 20, one end of which is secured to, and wound around, the drum, and the other end of which passes over a pair of sheaves 21 and 22 and is firmly fastened to a governor rope 23, such as is usually provided on elevator installations.

The governor rope 23 is releasably attached to the car by means of any suitable yielding connection 24, and passes over a sheave 25 on a centrifugal governor 26, mounted at the top of the hatchway, for the purpose of rotating the governor in accordance with the speed of the up and the down movements of the car.

further movement.

The governor 26 may be of any well known type and is illustrated diagrammatically as having its sheave secured to a rotatable shaft 27 on which is mounted a gear wheel 28 that engages a cooperating gear wheel 29 on an operating sleeve 30 keyed to the lift rod 36. Pivotally mounted on the upper end of the operating sleeve 30 is a pair of weighted governor balls 31 and 32 that are provided with lifting arms 33 and 34 which are adapted to engage a collar 35 on the upper end of a rod 36 and raise it when the balls 31 and 32 are thrown outwardly, as the governor exceeds a predetermined maximum speed.

The rod 36 is journalled in the operating sleeve 30 and extends downwardly through a lever 38 that is fulcrumed in a standard 39 on the governor frame 40. Secured to the lower end of the rod 36 is a collar 41 that engages the underside of the lever 38 and raises it when the rod is raised by the action of the governor balls. A weight 42, attached to the rod 36, determines the speed at which the governor balls will lift the rod 36.

The right-hand end of the lever 38 extends under the cooperating end of a pivotally mounted cam lever 43 in such manner that an upward movement of the lever 38 will raise the cam lever and force its gripping jaw 44 to wedge the governor rope against a cooperating jaw 45 and lock the rope against further movement. Thus, it will be seen that, if the car C, while descending, moves the governor rope to operate the centrifugal governor at a speed in excess of a predetermined maximum speed, the governor will actuate the jaw 44 and lock the governor rope against When the governor rope is locked by the jaws 44 and 45, while the car is descending, it will be pulled free from the yielding connection 24 and unwind the safety rope 20 from the safety-cable drum 19, thereby applying the gripping jaws to the guide rails.

While the means thus far described for actuating the safety device on the car is of a well known type which is responsive to the speed of the car, I have also provided an additional means for actuating the safety device that is responsive to a predetermined rate of downward acceleration of the car.

In the form of the invention illustrated in Fig. 1, the additional means comprises an electroresponsive device 47 for actuating the lever 38, a relay 48 for controlling the electroresponsive means, and an acceleration-controlled device 49 mounted on the car for controlling the relay.

The electroresponsive device 47 embodies a :weighted lever-actuating member 50 and an electromagnet 51. The weighted lever-actuating member 50 is pivotally connected to the standard 39 by an arm 54 in such manner that it will be supported by the electromagnet 51 when the latter is energized but will fall upon an extended portion 55 of the lever 38 when the magnet is deenergized and cause the lever to actuate the locking jaw 44 in the same manner as when it is actuated by the centrifugal governor.

The electromagnet 51 is connected to a suitable source of power represented by supply conductors L1 and L2 through the contact members I) of the relay 48 in such manner that, when the relay is deenergized, the electromagnet 51 will be deenergized to drop the lever-actuating member 50.

The relay 48 for controlling the circuit for the electromagnet 51 of the electroresponsive device 47 may be mounted at any suitable point, in the car or in the upper part of the hatchway adjacent to the electromagnet and the centrifugal governor. When the relay isdeenergized, it may be reset by means of a push-button switch 56 that is mounted in the car at a point where it may be easily reached by the attendant.

The acceleration-controlled device 49 comprises a weighted member 60 mounted on the'free end of an arm 61 which is pivotally attached to the car or a casing in the car by a pin 62, and a pair of contact members 63 and 64 associated with the weighted member and actuated thereby for controlling the circuit of the coil of the relay 48.

The contact member 63 is mounted on, and movable with, the weighted member 60, while the contact member 64 is stationarily secured to the car in such position as to engage the contact member 63 and support the weighted member in a horizontal position while the car is operating normally.

It will be seen, therefore, that, inasmuch as the weighted member 60 merely rests upon the contact member 64 and is free to move upwardly therefrom, if the rate of down acceleration or up deceleration of the car is increased to a rate above approximately 32 feet per second per second, it will cause the weighted member, by reason of its inertia, to separate the contact member 63 from the contact member 64 and thereby open the circuit for the relay 48.

In order that the weighted member 60 may be made effective to open the contact members 63 and64 at any selected rate of acceleration between zero and 32 feet per second, it is partially supported by a tension spring 65, the upper end of which is secured to a screw threaded member 66 that is mounted in a bracket 67. A thumb nut 68 on the screw threaded member 66 permits adjustment of the tension of the spring 65, and a pointer 69, attached to the upper part of the screw threaded member, cooperates with a scale 70 to indicate the adjustment in terms of acceleration rate. After the scale and pointer are properly calibrated, the device may be quickly set or reset to operate in response to any predetermined rate of acceleration of the car.

The spring 65 may be adjusted to a point where it is entirely slack and at which the weighted member 60 will be entirely supported by the contact member 64. With this adjustment, the spring has no material value and it would require a downward acceleration or and upward deceleration exceeding 32 feet per second per second to cause any relative movement between the weighted member 60 and the car to open the contact members 63 and 64.

If the tension of the spring 65 is increased until it takes one-half of the weight of the member 60, then acceleration at a rate exceeding 16 feet per second per second will cause relative movement between the weighted member 60 and the car, thereby separating the contact members 63 and 64. Also, if thespring is adjusted so that it takes, say, three-fourths of the weight of the member 60, the contact members 63 and 64 will be separated when the rate of acceleration exceeds eight feet per second per second. In all cases, where the rate of acceleration exceeds the point for which the spring 65 is set, the contact members 63 and 64 will be separated.

It should be noted that, by reason of the convenient manner in which the spring may be adjusted, the acceleration-controlled device 49 may be set to operate at very low rates of acceleration, and thereby permit testing of the safety apparatus by actual application thereof at such low speeds as will not damage the guide rails and the gripping jaws or place excessive strains on the car and the apparatus connected therewith. Furthermore, it facilitates the testing of the car at a variety of speeds and rates of acceleration and deceleration. By reason of having a scale and a pointer on the adjusting members, they may be reset readily to their original positions after testing.

For the purpose of preventing the minor movements of the jolting of the car, or vibration, from causing the weighted member 60 to separate the contact members 63 and 64, the contact member 63 may be constructed of spring material, to give a slight margin of movement before opening the circuit, and its free end is disposed between a pair of lugs or stop members 71 and 72 on the weighted member. With this construction, if the member 60 moves only slightly with reference to the contact member 64, the contact member 63 will, by reason of its resilient characteristics, stay in contact with the contact member 64. However, if the movement away from the contact member 64- is continued, the lug '72 will engage the free end of the contact member 63 and carry it away from the contact member 64.

In order to prevent the weighted member 60 from separating the contact members 63 and 64' any farther than is necessary to insure the opening of the relay circuit, a stop member 73 is provided at such point above the weighted memher as will limit its upward movement to the desired extent. The limiting of the upward movement of the weighted member 60 also makes it possible for that member to effect engagement of the contact members 63 and 64 very quickly, and this, in conjunction with a time relay on the relay 48, prevents the setting of the safety device on a quick up-stop, as will be more fully explained later.

A normally closed push-button switch 74 is mounted in the car and connected in the circuit of the relay 48, in order to enable the attendant to effect the operation of the safety device at any time he desires by opening the switch and thereby deenergizing the relay.

As a further safeguard, the circuit for the relay 48 is also connected through the normally closed contact members of a switch 75, which is connected to the centrifugal governor 26 in such manner that it will be opened when the governor exceeds a predetermined maximum speed and thereby deenergize the relay.

The acceleration-controlled device 49 is not limited in action to down acceleration but may respond to nip-deceleration on sudden stopping, but the difference between down-acceleration and Lip-deceleration is important in that the former is of a continuing character and tends to hold the contact members 63 and 64 separated, while deceleration on a sudden up-stop is momentary and immediately drops to zero. With continued down-acceleration, the weighted member 60 will separate the contact members 63 and 64 and keep them separated, whereas, on excessive up-deceleration in stopping, the contact members 63 and 64 will be separated and re-engaged very quickly, that is, in a small fraction of a second, by reason of the fact that the upward travel of the weighted member is limited by the stop member 73.

Therefore, in order to have the mechanism differentiate between down-acceleration and updeceleration, a discharge resistance '79 is shunted across the terminals of the relay 48 to slightly delay its action. This delay, although operating equally for either direction, will not interfere in any practical manner with the operation of the safety device on the down-movement of the car but will prevent the operation of the safety device on a too sudden up-stop because the latter influence is of very short duration.

Assuming, for example, that the shunt resistance 79 on the relay 48 delays its action for one twenty-fifth of a second and that the travel of the weighted member 60 is so limited by the stop member '73 that, on an excessive up-stop deceleration, the contact members 63 and 64 will be separated and re-engaged within that time. Obviously, under these conditions the relay 48 will not open. On the other hand, a down-acceleration rate above the predetermined rate for a period exceeding one twenty-fifth of a second will cause the contact members 63 and 64 to be separated and to remain separated for a sufficient length of time to deenergize the relay 48. Inasmuch as the free fall of a body under the influence of gravity for the first one twentyfifth of a second amounts to only a fraction of an inch, and the speed of the body is still low, a little over one foot per second, a delay of one twenty-fifth of a second in initiating the operation of the safety device when the car starts to fall is of no moment.

The invention may be best understood by an assumed operation of the apparatus shown in Fig. 1.

Assuming that the car C is at rest at the top of the hatchway and that the push button of switch 56 has been pressed to energize the relay 48 and the electromagnet 51 for operation, the closing of the push-button switch 56 completes a circuit for energizing the relay 48 that extends from supply conductor L1, through conductor 81, the coil of relay 48, conductor 82, the contact members of push-button switch 56 and conductor 83, to supply conductor L2. When the relay 48 is energized, it closes its contact members a and completes a holding circuit for itself independent of the button 56 that extends from supply conductor Ll, through conductor 81, the coil of relay 48 conductors 82 and 85, the contact members a of relay 48, conductor 86, the contact members of switch 75, conductor 88, the normally engaged contact members 63 and 64 of the acceleration-controlled device 49, conductor 89, the normally closed contact members of push-button switch 74 and conductor 91, to supply conductor L2.

The closing of the contact members I) on the relay 48 completes a circuit for energizing the electromagnet 51 that extends from supply conductor L1, through conductor 92, the contact members I) of relay 48, conductor 93, the coil of electromagnet 51 and conductor 94, to supply conductor L2. The electromagnet 51 being energized, the lever-actuating member is lifted and suspended above the left-hand end of the lever.

Assuming now that the spring 65 has been adjusted, by the operation of the thumb nut 68, to such point that the acceleration-controlled device 49 will become effective to deenergize the relay 48 when the rate of down-acceleration of the car exceeds sixteen feet per second per second, and that the car has started down the shaft and, for any reason whatever, gotten beyond control of the operator and has started to fall; then, as soon as the rate of acceleration exceeds the pre- "member 102.

determined "rate of sixteenfeet per second per second at which the acceleration-control device has been set to operate, the weighted member 60 will separate contact members 63 and 64 to open the circuit which energizes the coil of the relay 48, thereby deenergizing the relay and causing it to separate its contact members I). The separation of the contact members I) of the relay 48 opens' the circuit for the electromagnet 51 and deenergizes it, thereby causing the weighted lever-actuating member 50 to drop on the extended portion 55 of the lever 38 and actuate the lever. The actuation of the lever 38 operates the locking jaws 44 and 45 and locks the governor rope 23 against further movement, thereby causing the car, as it falls, to pull the safety rope 21 from the cylinder 19 and thus apply the gripping jaws 15 and 16 to the guide rails 12 and 13 to stop the car.

Although I have described the operating force as exerted by a weighted member, it is to be understood that this term is not used in a limited or specific sense, and that any equivalent mechanism representing stored-up energy, held in a state of equilibrium, may be used on, for exa l-- ple, a spring or the combination of a weight and a-spring.

When the car is again ready for operation, after being stopped and the safety device and the governor-rope locking jaws 44 and 45 have been reset in a well-known manner, the relay 48 may be reenergized to cause the'electromagnet 51 to pick up the lever-actuating member 50 and again place the safety mechanism in condition for operation, by the attendant pressing the push-button of switch 56 to close the circuit for the relay; or, if desired, the actuating member may be set in place manually and then held there by the energized magnet.

In the modified form of the electroresponsive device illustrated in Fig. 2, a weighted lever-actuating member 95, similar to Weight 50 (Fig; 1), is pivotally attached, by means of arm 96, to the standard 39 in such position that it will, when dropped, hit the extended portion 55 of the lever 38 and actuate the lever. Mounted on the top of the lever-actuating member is a catch 9'7 adapted to receive a latching member 98 that is controlled by an electromagnet51 which is also mounted on the upper part of the standard 39.

A tension spring 99 is provided for so biasing the latching armature 98 away from the catch 9'7 that, when the electromagnet 51 is deenergized by the opening of the relay 48, the lever-actuating member 95 will be released to fall upon the extended portion 55 of the lever 38.

In resetting this modified device, it is necessary to raise the weighted member 95 after the electromagnet 51 is energized until the catch 97 is engaged by the latching armature 98.

The modified form of the acceleration-controlled device 49, illustrated in Fig. 3, comprises a disk 100 that may be secured to a rotating mem-- ber of the usual speed-controlled means for op-- erating the safety device, such as the governor shaft 27 upon which the sheave 25 is mounted. The disk is secured to the shaft so that it'will rotate therewith. Rotatably mounted upon the hub 101 of the disk 100 is a weighted member 102 corresponding, in function, to the weighted member 60 shown in Fig. 1. Acontact member 103 is mounted upon andinsulated from the disk 100 for the purpose of engaging a contact spring member 104 that is mounted on the weighted These contact members correspond,

in function, to the contact members 63 and 64.

A tension spring 105 is mounted upon the disk 100 and connected to'the end of the'weighted member 102 opposite to that on which contact member 104 is mounted for the purpose of biasing the weighted member to a position where the contact members 103 and 104 will be closed. The spring 105 is secured to the disk 100 by means of a screw-threaded member 106 that may be'adjusted by a thumb nut 107 in a manner similar to the device illustrated in Fig. 1. The contact member 104 on the weighted member 102 may be connected in the circuit of the relay 48 by means of an annular contact ring 108 and a contact brush 109, while the contact member 103 on the disk 100 may be connected in the circuit by'means of a contact ring 110 and a cooperating contact brush 111. A stop member 112 is attached to the disk 100 for the purpose of limitingthe movement of the weighted member 102.

In this form of the device/the spring 105-'cooperates with the disc 100 to cause movement of the weighted member 102. If the disc 100 is accelerated at a certain rate, due to some external force, the spring 105 must exert a sufiicient force on the member 102 to causeit to assume the same rate of acceleration. If, now, the force required to accelerate themember 102 at this "rate is in excess of the strength of the spring, the member 102 will move at a lower rate than the disc, and the contact members 103*and 104 will be separated.

As the contact members 103 and 104are separated, of course, the spring 105is' elongated, and, therefore, exerts a greater force. The contact members 103 and 104 will, therefore, be separated to such an extent that the force exerted by spring 105 is just equal to the force required to accelerate the member 102 at the certain rate. This rate may be varied, as described, by means of the adjusting screw 107.

It will thus be seen that, in this modified form of the acceleration-controlled device, the weighted member 102 will rotate with the disk 100 until such time as the rate of acceleration exceeds the predetermined'maximum for whi'chthe device has been set. 'Whenthis predetermined point is reached and passed, the inertia of 'the weighted member 102 will cause the contactmemhere 103 and 104 to separate and thereby open the circuit for the relay '48 to deenergize the electroresponsive device 47 and effect an application of the safety device 14 onthe car.

It will be seen, therefore, that I have provided a safety mechanism for elevator cars that will operate upon the first occurrence of dangerous conditions, that may be operated 'by the car attendant at any time, that may be tested under many difierent conditions, and that has embodied in it a plurality of means for ensuring the operation of the safety device so that, if one fails to function another will be brought into action to effect the stopping of the car.

I claim as my invention:-

1. A safety mechanism for an elevator car comprising a safety device and means responsive to only continued acceleration of the car at a predetermined rate for causing the operation of the safety device to stop the car.

2. A safety mechanism for an elevator car comprising a safety device and means responsive to only a continued down a'cceleration'of the car at a rate above a predetermined value for causing car.

3. A safety mechanism for an elevator car comprising a safety device, means for effecting the operation of the safety device to stop the car, a member having stored up potential energy for operating the means for effecting operation of the safety device, an electromagnet, means for energizing the electromagnet to maintain the member having stored up potential energy in an ineffective position and means responsive to a predetermined rate of down acceleration of the car for deenergizing the electromagnet.

4. A safety mechanism for an elevator car comprising a safety device, means for effecting the operation of the safety device to stop the car, a weighted member for operating the means for effecting operation of the safety device, an electromagnet, means for energizing the electromagnet to maintain the weighted member in an ineffective position and means responsive to a predetermined rate of down acceleration of the car for deenergizing the electromagnet.

5. A safety mechanism for an elevator car comprising a safety device, means for operating the safety device to stop the car, means responsive to a predetermined rate of acceleration of the car for actuating said safety operating means and means for retarding the action of the safety operating means for a predetermined length of time.

6. In a safety mechanism for an elevator car, the combination with a safety device, a governor rope, means for locking the governor rope to effeet the operation of the safety device, a centrifugal governor operated by the governor rope for actuating the locking means when the speed of the car exceeds a predetermined maximum speed, and an additional means for actuating the locking means comprising a weighted actuating member, an electromagnet for controlling the weighted actuating member, a circuit for the electromagnet, and means operably responsive to a predetermined rate of down acceleration of the car for controlling the circuit of the electromagnet.

7. A safety mechanism for an elevator car comprising a safety device for stopping the car, an electro-responsive device for effecting operation of the safety device, a circuit for controlling the electroresponsive device, and means operably responsive to a predetermined rate of down acceleration of the car for controlling said circuit, said acceleration-controlled means comprising a movable weighted member and a pair of relatively movable contact members disposed to be actuated by movements of said weighted member, and means for preventing effective actuation of said contact members by minor movements of the weighted member.

8. A safety mechanism for an elevator car comprising a safety device for stopping the car, an electroresponsive device for effecting operation of the safety device, a circuit for controlling the electroresponsive device, and means operably responsive to a predetermined rate of down acceleration of the car for controlling said circuit, said acceleration-controlled means comprising a movable weighted member, a pair of relatively movable contact members disposed to be actuated by movements of said weighted member, one of said contact members being constructed of resilient material to thereby prevent effective actuation of said contact members by minor movements of said weighted member.

9. In a safety mechanism for elevators, a safety device and means operably responsive to a predetermined rate of acceleration for actuating said safety device, said acceleration-responsive means comprising a support movable in accordance with movements of said elevator, a member of relatively large mass mounted on said support for movement relative thereto, means for biasing said member to aid movement thereof in a direction corresponding to one direction of elevator movement and to oppose movement in the opposite direction and means for actuating said safety device controlled by relative movement of said member and said support.

10. In a safety mechanism for elevators, a safety device and means operably responsive to a predetermined rate of acceleration for actuating said safety device, said acceleration-responsive means comprising a support movable in accordance with movements of said elevator, a member having relatively large mass mounted on said support for movement relative thereto, means for biasing said member to aid movement thereof in a direction corresponding to one direction of elevator movement and to oppose movement in the opposite direction, means for actuating said safety device controlled by relative movement of said member and said support, and means for varying the force of said biasing means.

11. In a safety mechanism for elevators, a safety device and means operably responsive to a predetermined rate of acceleration for actuating said safety device, said acceleration-responsive means comprising a support movable in accordance with movements of said elevator, a member having relatively large mass mounted on said support for movement relative thereto, means for biasing said member to aid movement thereof in a direction corresponding to one direction of elevator movement and to oppose movement in the opposite direction, means for actuating said safety device controlled by relative movement of said member and said support, means for varying the force of said biasing means, and calibrating means for indicating the force of said biasing means.

12. In a safety mechanism for an elevator car, the combination with a safety device comprising means normally movable in accordance with the movement of the car and means operably responsive to relative movement of said movable means and said car for stopping the car, of means for effecting relative movement of said movable means and the car to cause said stopping means to stop the car, including a weighted member adapted, when unsupported, to effect a restraint upon said movable means and thereby cause relative movement thereof with respect to the car, an electro-responsive means adapted, when actuated, to magnetically support said weighted member and to render it ineffective to cause relative movement of the movable means and the car, and means operably responsive to a predetermined rate of acceleration of said car for causing said electro-responsive means to be ineffective to support said weighted member.

13. In a safety mechanism for an elevator car, the combination with a safety device comprising means normally movable in accordance with the movement of the car and means operably responsive to relative movement of said movable means and the car, for stopping the car, of means for effecting relative movement of said movable means and the car to cause said stopping means to stop the car, including a weighted member adapted, when unsupported, to effect a restraint upon said movable means and thereby cause relative movement thereof with respect to said ear, eleetro-responsive means adapted, when actuated, to efiect a support for said weighted member and prevent it from causing relative movement of said movable means and the car, and means for controlling said electro-responsive means including a circuit for connecting said eleetro-responsive means to a source of energy, relay means aetuable to complete said circuit and effect the actuation of said electro-responsive means, and means operably unresponsive to ac eeleration and deceleration of the car below a predetermined rate for maintaining said relay means actuated and operably responsive to aceeleration and deceleration of the car above said predetermined rate for effecting the de-actuation of said relay means.

14. In a safety mechanism for an elevator car, a safety device operable tostop a car, means including electro-responsive means actuable to prevent operation of said safety device, means including means operably responsive to acceleration and deceleration of the car above a predetermined rate, for causing said electro-responsive means to be ineffective to prevent operation of said safety device, and means for retarding the operation of said safety device for a predetermined time.

15. In a safety mechanism for an elevator car, the combination with a safety device comprising means normally movable in accordance with the movement of the car and means operably responsive to relative movement of said movable means and the ear for stopping the ear, of means for effecting relative movement of said movable means and the ear to cause said stopping means to stop the car, including a Weighted member adapted, when unsupported, to effect a restraint upon said movable means and thereby cause relative movement thereof with respect to the car, electro-responsive means adapted, when actuated, to effect a support for said weighted member and thereby prevent it from causing relative movement of said movable means and the car, and means for controlling said eleetro-responsive means to cause it to effect no support for said weighted member, including means operably responsive to acceleration and deceleration of the car above a predetermined rate for deaetuating said electro-responsive means, and means for retarding the de-actuation of said eleetro-responsive means a predetermined time after the operation of said acceleration and deceleration responsive means.

16. In a safety mechanism for an elevator ear, the combination with a safety device comprising means normally movable in accordance with the movement of the car and means operably responsive to relative movement of said movable means and the car, for stopping the car, of means for effecting relative movement of said movable means and the car to cause said stopping means to stop the car, including a weighted member adapted, when unsupported, to effect a restraint upon said movable means and thereby cause relative movement thereof with respect to said car, eleetro-responsive means adapted, when actuated, to effect a support for said weighted member and prevent it from causing relative movement of said movable means and the car, and means for controlling said electro-responsive means including a circuit for connecting said electro-responsive means to a source of energy, relay means aetuable to complete said circuit and effect the actuation of said electro-responsive means, means operably unresponsive to acceleration and deceleration of the car below a predetermined rate for maintaining said relay means actuated and operably responsive to acceleration and deceleration of the ear above said predetermined rate for eifeeting the de-aetuation of said relay means, and means for retarding the de-aetuation of said relay means a predetermined time after the said acceleration and deceleration responsive means operates to effect its de-actuation.

FRANK J. SPRAGUE.

Images