BACKGROUND

[oooi] Elevator systems typically include a car that moves along guiderails within a hoistway between different levels in a building. A variety of machine configurations are used to move the car as desired. Various braking arrangements are used to maintain the elevator car at a desired landing.

[0002] Another feature typical of elevator systems is a safety braking arrangement. A governor device typically detects an overspeed condition and activates a safety braking device that is mounted on an elevator car or counterweight, for example. A safety braking device typically applies a braking force to the guiderail to decelerate the car or counterweight and bring it to a stop. One example arrangement is shown in U.S. Patent No. 4,538,706. As shown in that document, a brake pad is forced against a surface of the guiderail during a brake application.

[0003] One attempt at avoiding applying a braking force to the guiderail surface is shown in the published application WO 2004/033354. In that document, brake pads apply a braking force to the sides of rollers that are disposed on opposite sides of the guiderail. SUMMARY

[000 ] An exemplary elevator braking device comprises a brake housing. At least one roller is supported by the brake housing. The roller is arranged to be selectively moveable between a first position in which the roller does not engage a guide rail and a second position in which the roller can engage and roll along the guide rail. At least one biasing member is supported by the brake housing. The biasing member biases the roller toward the guide rail. At least one braking surface is supported by the brake housing. The braking surface engages a periphery of the roller that faces the side of the guiderail. Friction between the periphery of the associated roller and the braking surface provides a stopping force.

[0005] An exemplary method of decelerating a vertically moving mass in an elevator system includes providing at least one braking device on the vertically moving mass. The braking device has at least one roller that engages a surface of the guiderail. The roller is biased toward the guiderail. The roller is permitted to roll along the guiderail without sliding along it. A braking force is applied to a periphery of the roller that faces the guiderail using at least one braking surface that engages the periphery of the roller.

[0006] The various features and advantages of the disclosed examples will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 schematically shows selected portions of an elevator system.

[0008] Figure 2 schematically shows an example elevator braking device designed according to an embodiment of this invention.

[0009] Figure 3 illustrates an example roller and braking member configuration.

[oooio] Figure 4 illustrates another example roller and braking member configuration.

[oooii] Figure 5 illustrates an example biasing member configuration.

[00012] Figure 6 illustrates another example braking device embodiment. DETAILED DESCRIPTION

[00013] Figure 1 schematically shows selected portions of an elevator system 20. An elevator car 22 is supported for vertical movement within a hoistway along guiderails 24. Braking devices 26 are supported on the car to selectively prevent vertical movement of the car along the guiderails 24. One feature of the braking devices 26 is that they do not have any components (such as a brake pad) that slide along the guide rails 24. The energy of the descending elevator car 22 is dissipated through friction that is internal to the braking device 26. Using internal friction for stopping the car provides a more robust braking device because any variation in the coefficient of friction along the rail, which could result from lubricants, moisture, rust, or debris, for example, does not have an effect on the coefficient of friction used to stop the elevator car 22 from moving.

[0001 ] Figure 2 illustrates one example braking device 26. This example includes a housing having a base 30 that is configured to be mounted to an appropriate portion of the elevator car 22. A plurality of rollers 32 are supported by the base 30. The rollers 32 are received on opposite sides 34 of the guiderail 24. The rollers 32 in this example are selectively moveable between a first position (shown in phantom at 32') in which the rollers do not engage the guiderail 24 and a second position (shown in Figure 2) in which the rollers 32 engage the sides 34 of the guiderail 24. As can be appreciated from the illustration, when the rollers 32 are in the first position 32' they are spaced apart a first distance. A second, smaller distance is between the rollers 32 when they are in the second position.

[00015] The example of Figure 2 includes biasing members 36 that bias the rollers 32 toward each other at least in the second position. The biasing force of the biasing members 36 urges the rollers 32 into engagement with the surfaces 34 on the guiderail 24. The biasing force also serves to achieve appropriate frictional forces within the device 26 for applying a braking force to stop movement of the elevator car 22.

[00016] The example of Figure 2 includes braking members 38 having braking surfaces that engage a periphery of the rollers 32 that faces the guiderail surface 34. Applying a frictional force to the periphery of the rollers 32 achieves a braking force sufficient to stop the elevator car from continuing to move vertically at an undesired speed. In one example, the braking members 38 remain fixed relative to the base 30.

[00017] Figure 3 shows one example arrangement in which the rollers 32 each include a first portion 40 and a second portion 42. In this example, the first portion 40 has a larger outside diameter compared to that of the second portion 42. The first portion 40 contacts the surface 34 on the guiderail 24. The braking member 38 in this example includes corresponding portions 44 and 46. The portions 46 only engage the surfaces of the periphery of the roller 32 at the second portion 42. The portion 44 of the braking member 38 does not contact the first portion 40 of the roller 32. The braking force applied due to the frictional engagement between the second portion 42 and the portion 46 of the roller 38 provides the braking force for stopping vertical movement of the elevator car 22. The first portion 40 rolls along but does not slide on the surface 34 of the guiderail 24.

[00018] In one example, the biasing members 36 each have a contour corresponding to shape of the periphery of the rollers 32 so that the biasing members 36 do not engage the portion 40 but does engage the portion 42. This allows for applying braking force by the biasing members 36, for example. [00019] As can be appreciated from Figure 3, the peripheral surface of the roller 32 that engages the braking surfaces is parallel to an axis of rotation 48 about which the roller 32 rotates.

[00020] Figure 4 illustrates another example in which the first portion 40 of the roller 32 is positioned near one end of the roller with the second portion 42 positioned near another end of the roller 32. In the example of Figure 3, the first portion is located between the second portions 42 of the roller 32. In the example of Figure 4 the braking member 38 is simplified compared to the configuration shown in the example of Figure 3 because there is no requirement for a reduced diameter portion 44, which accommodates the first portion 40, between larger sized portions 46.

[00021] Figure 5 illustrates an example configuration in which the biasing member 36 comprises a leaf spring. In this example, a leaf spring base material 50 constitutes a portion of the biasing member 36. A frictional surface material 52 is provided on one side of the leaf spring that faces and engages the periphery of the roller 32. This example allows for providing a braking force using the engagement between the roller 32 and the biasing member 36. As shown in the example of Figure 2, braking surfaces can be used on the biasing members 36 and the braking member 38 to achieve a desired braking force.

[00022] Figure 6 illustrates another example braking device 26. In this example, one roller 32 engages at least one braking surface internal to the braking device for stopping the elevator car 22. Another roller 132 is provided that is essentially free-wheeling for rolling, without sliding, along the guide rail 24. The braking forces are applied in this example without relying upon any frictional engagement between the roller 132 and a braking surface internal to the braking device.

[00023] Another example includes having the roller 132 has a corresponding braking surface internal to the braking device. The roller 132 is this example remains in a single vertical position relative to the base and engages the guiderail when the braking device 26 (and the elevator car) shifts laterally responsive to the roller 32 engaging the guide rail.

[0002 ] One feature of the illustrated examples is that they provide a progressive safety device. The resilience of the biasing members 36 (e.g., leaf springs or another resilient member) and the presence of the rollers 32 on opposite sides of the guiderail 24 allows for progressively applying a braking force as the rollers 32 are urged further toward the second position.

[00025] The illustrated examples avoid the drawbacks associated with attempting to apply a braking force to a guiderail surface. A variety of actuating arrangements including known governor configurations are useful for moving the rollers 32 between the first and second positions for a brake application using the example elevator braking device arrangements.

[00026] The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the scope of legal protection given to this invention, which can only be determined by studying the following claims.