Patent Description:
Governors in elevators systems are used for two purposes. One use of an elevator governor is for activating or dropping the machine brake and interrupting power to the machine motor in the event of an over speed condition. The other use is for activating elevator safeties that engage the guide rails, for example, in the event of a further over speed condition. Given that the governor reaction to each over speed condition is not independent, it is difficult to achieve specific control over the speed at which the governor performs both functions. Additionally, relying upon a single governor tripping mechanism for both functions introduces additional challenges when satisfying some codes for low speed elevators. <CIT> discloses a device for releasing the parachute of a lift cage comprising a crosspiece articulated about a horizontal pin on a fixed structure of the cage, maintained in a ready position by a bolt co-operating with the fixed structure. The bolt is integral with a carriage mobile on the crosspiece: The carriage bears a pulley, and a second pulley is mounted on the crosspiece. <CIT> describes an apparatus for properly decelerating or securely stopping an elevator even upon the fall thereof or the like by concurrently operating two governors whenever necessary. A connecting bar internally extending over two drums is supported between the drums. The free end of the bar is laid so as to be rotatable along a drum radial direction in such state as adjacent to a rotor. <CIT> discloses an elevator apparatus equipped with a generator for generating a power corresponding to a speed of a car, and an emergency stop device for forcibly braking the car. The emergency stop device is operated owing to the power generated by the generator when the speed of the car is abnormal. The car is mounted with the emergency stop device.

An exemplary elevator system according to the invention includes the features of claim <NUM>.

Particular embodiments may include any of the following optional features, alone or in combination:.

An exemplary method according to the invention includes the features of claim <NUM>.

The separate governor tripping mechanisms each supported on its own governor sheave provides specific control over the tripping mechanism reaction at a desired, corresponding threshold speed. The separate tripping mechanisms on their own governor sheaves also provides more flexibility and a more reliable arrangement compared to using a single tripping mechanism to perform both functions.

The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description.

<FIG> schematically shows selected portions of an elevator system <NUM>. An elevator car <NUM> is supported in a known manner for movement along guide rails <NUM>. An elevator machine <NUM> includes a motor and brake for controlling movement of the elevator car <NUM> in a generally known manner.

A governor assembly <NUM> is provided for protecting against over speed conditions in which the elevator car <NUM> moves at a speed that is higher than a desired speed. The governor assembly <NUM> includes a first governor sheave <NUM> supported on the elevator car <NUM> for movement with the elevator car <NUM> as it moves along the guide rails <NUM>. The first governor sheave <NUM> rotates relative to the elevator car <NUM> as the car <NUM> moves along the guide rails <NUM>. A second governor sheave <NUM> is also supported on the elevator car <NUM> and is rotatable relative to the elevator car <NUM>. A governor rope <NUM> has ends that remain near ends of the hoistway, for example, in which the elevator car <NUM> is situated. In one example, an upper end is fixed and a lower end is attached to a hanging mass to maintain a desired tension on the governor rope <NUM>. The hanging mass is situated to allow for limited, guided vertical movement in some examples. The governor rope <NUM> at least partially wraps around each of the governor sheaves <NUM> and <NUM> so that each sheave rotates as the elevator car <NUM> moves relative to the governor rope <NUM>.

<FIG> diagrammatically illustrates an example arrangement of the governor assembly <NUM>. A first governor tripping mechanism <NUM> is supported on the first governor sheave <NUM>. A plurality of centrifugal elements <NUM> rotate with the first governor sheave <NUM> as the elevator car <NUM> moves. The centrifugal elements <NUM> are maintained in an inactivated position by biasing members <NUM>. When the speed of rotation of the first governor sheave <NUM> exceeds a selected first threshold, the centrifugal force exerted on elements <NUM> overcomes the force of the biasing members <NUM> and the elements <NUM> move at least partially in a radially outward direction relative to an axis of rotation <NUM> of the first governor sheave <NUM>. When the centrifugal elements <NUM> move outwardly, they interact with an actuator mechanism (not illustrated) that works in a known manner to perform a first governor function. In one example, the first governor function is to cause activation (e.g., dropping) of the machine brake <NUM> for slowing down movement of the elevator car <NUM> and interrupting power to the machine motor. In another example the first governor function is to control a speed of movement of the elevator car <NUM> in either an upward or a downward direction.

In this example, the biasing member <NUM> comprises a magnet that cooperates with a magnetic portion <NUM> for maintaining the centrifugal elements <NUM> in a first inactivated position (illustrated in <FIG>, for example) relative to the first governor sheave <NUM> whenever the first governor sheave <NUM> rotates at a speed below the first threshold speed. When the speed of the elevator car <NUM> exceeds the first threshold, the corresponding speed of rotation of the first governor sheave <NUM> and centrifugal force on the elements <NUM> overcomes the magnetic force of attraction between the magnet <NUM> and the magnetic portion <NUM>, such that the centrifugal elements <NUM> move outward to provide an indication to perform the first governor function.

Although the illustrated examples include magnetic biasing members, other embodiments include different biasing members such as springs.

The second governor sheave <NUM> supports a second governor tripping mechanism <NUM> that includes centrifugal elements <NUM>. A biasing member <NUM>, which is a magnet in this example, biases the centrifugal elements <NUM> into a retracted position (shown in <FIG>) as the governor sheave <NUM> rotates about an axis of rotation <NUM>. When the speed of the elevator car <NUM> exceeds a selected second threshold, the corresponding speed of rotation of the second governor sheave <NUM> and centrifugal force on the elements <NUM> overcomes the biasing force of the biasing member <NUM>, and the centrifugal elements <NUM> move in a radially outward direction relative to the axis <NUM>. Under such conditions, the second governor tripping mechanism <NUM> provides an indication to perform a second governor function. In one example the second governor function is to activate supplemental brakes such as elevator safeties <NUM> (generally shown in <FIG>) provided on the elevator car <NUM>. The elevator safeties <NUM> in this example engage the guiderail <NUM> to cause the elevator car <NUM> to stop in a known manner. Another example second governor function is to control elevator car movement in a direction opposite to that associated with the first governor function.

In an illustrative example, the biasing member <NUM> comprises a magnet that cooperates with a magnetic portion <NUM> for maintaining the centrifugal elements <NUM> in a first position relative to the second governor sheave <NUM> at speeds below the second threshold speed.

The illustrated governor assembly <NUM> includes separate governor sheaves <NUM> and <NUM> and separate governor tripping mechanisms <NUM> and <NUM> to provide separate, independent control over the two distinct governor functions. This independent control over each function increases the accuracy with which each function is performed. The independent mechanisms also provide greater flexibility for addressing a variety of situations.

For example, it is possible to independently control the first threshold speed at which the machine brake is dropped (and power to the machine motor is interrupted) and the second, higher threshold speed at which supplemental brakes such as the elevator safeties <NUM> are engaged. The first threshold speed and second threshold speed can be selected to meet the needs of a particular situation. The separate governor sheaves <NUM> and <NUM> and the corresponding separate tripping mechanisms provide precise control over the activation provided by each tripping mechanism to separately address the different over speed conditions associated with the two different threshold speeds. Such an arrangement is superior to a governor assembly that relies upon a single tripping mechanism to provide activation of the machine brake and a supplemental brake, for example, at different threshold speeds.

In one example, each tripping mechanism is dedicated to controlling elevator speed in a specific direction. The first governor sheave <NUM> and its first tripping mechanism <NUM> are used for controlling upward movement of the elevator car <NUM>. The second tripping mechanism <NUM> in such an example is used for controlling a speed of downward movement of the elevator car <NUM>. Having two independently activated tripping mechanisms provides the ability to select different threshold speeds for the respective directions.

The example of <FIG> includes the governor rope <NUM> at least partially wrapping around each of the governor sheaves <NUM> and <NUM>. In this example, the angle of wrap around each governor sheave is at least <NUM>° to provide reliable engagement between the governor rope <NUM> and each of the governor sheaves <NUM> and <NUM>, respectively. In this example, the first governor sheave <NUM> rotates in one direction and the second governor sheave <NUM> rotates in an opposite direction.

The tripping mechanisms <NUM> and <NUM> can comprise the same components. The force exerted by the second biasing member <NUM> in some examples is greater than the force exerted by the first biasing member <NUM>, so that the second tripping mechanism <NUM> provides an indication for activating the supplemental brake at a higher speed compared to that at which the first tripping mechanism <NUM> provides an indication to activate the machine brake <NUM> (and interrupt power to the motor). In one example, a stronger magnet is used for the biasing member <NUM> of the second tripping mechanism <NUM> compared to that biasing member <NUM> used for the first tripping mechanism <NUM>. In another example, the centrifugal elements <NUM> of the second tripping mechanism <NUM> are configured differently than the centrifugal elements <NUM> of the first tripping mechanism <NUM>. For example, different weights may be used to alter the speeds at which the tripping mechanisms provide their respective indications. Different weight allows for all centrifugal elements and magnets to be the same and have different tripping speeds. Those skilled in the art who have the benefit of this description will realize how to configure two tripping mechanisms to realize two separate threshold speeds at which each provides an indication for performing a corresponding governor function.

One feature of the illustrated example is that the governor sheaves <NUM> and <NUM> rotate about separate axes <NUM> and <NUM>, respectively. That arrangement combined with the profile of the tripping mechanisms <NUM> and <NUM> allows for realizing a relatively narrow governor assembly <NUM> having a width w shown in <FIG>. Given that the governor assembly <NUM> is mounted onto an elevator car <NUM>, it is desirable to fit that within the small space constraints of a typical hoistway. The illustrated example allows for positioning the governor assembly <NUM> on the elevator car <NUM> so that it readily fits between a side of the elevator car <NUM> and a hoistway wall adjacent that side.

Claim 1:
An elevator system (<NUM>), comprising:
an elevator car (<NUM>);
a first governor sheave (<NUM>) supported on the elevator car (<NUM>) for movement with the elevator car and for rotational movement relative to the elevator car responsive to movement of the elevator car;
a first governor tripping mechanism (<NUM>) supported on the first governor sheave (<NUM>) that provides an indication to perform a first governor function to control movement of the elevator car (<NUM>) responsive to the elevator car moving at a speed above a first threshold speed;
a second governor sheave (<NUM>) supported on the elevator car (<NUM>) for movement with the elevator and for rotational movement relative to the elevator car responsive to movement of the elevator car;
a second governor tripping mechanism (<NUM>) supported on the second governor sheave (<NUM>) that provides an indication to perform a second governor function to control movement of the elevator car (<NUM>) responsive to the elevator car moving at a speed above a second threshold speed;
characterised in that: the second threshold speed is different to the first threshold speed.