More particularly, this invention relates to a multi-piece, extendable counterweight for selectively repositioning an elevator car.

2. Description of the Related Art One type of elevator system utilizes an elevator car supported by ropes or belts from a drive sheave. A counterweight is also supported by the ropes opposite the car to counteract the weight associated with the car and its load.

The drive sheave is part of a machine that may be arranged immediately above the elevator car when the elevator is in its uppermost position at the top floor of a building. For example, the machine may be mounted under a roof with very little clearance between the elevator car and roof. Also, the controller, drive and governor are often arranged in the hoistway behind or beside the elevator car when the car is at the top landing. As a result, the car must be lowered to provide the mechanic sufficient clearance to service many of the elevator system components.

The car will not move downward under its own weight because the counterweight is heavier than the empty car by approximately one-half of the duty load. There is also some friction preventing motion of the car of approximately 20% of the duty load. Presently, when the car is stuck at the top landing, the mechanic will either spend considerable time and effort to bring weights to the top floor of the building and put them into the elevator, or the mechanic may disturb the customers by asking them to stand inside the elevator in an effort to lower the car to the next floor to provide access to the machine above the car.

There is a need for an improved elevator system and process for providing additional clearance between the car and machine for service. This invention addresses that need while avoiding the shortcomings and drawbacks of prior approaches.

SUMMARY OF THE INVENTION In general terms, this invention is an extendable counterweight.

In one example, the counterweight has a portion extendable a distance from another portion enabling the elevator car to descend under its own weight and provide additional clearance for a mechanic to access a machine above the car.

One example counterweight always maintains the same tension on the ropes or belts even though the counterweight has first and second lengths. The first length is used during normal elevator system operation. The second, greater length allows the car to move under its own weight for service or maintenance, for example.

In one example, the elevator car has an elevator operation position that corresponds to the car being on the top floor. The car also has a service position in which the car is lower than the elevator operation position to provide sufficient access between the car and the machine immediately above. The machine has a drive sheave with a rope supported by the sheave. The rope has a first portion connected to the car.

An example inventive counterweight is connected to a second portion of the rope.

The counterweight includes first and second weight portions that are movable relative to one another between counterweight operation and service positions. The counterweight operation and service positions respectively correspond to the elevator operator and service positions.

One example counterweight arrangement includes a pin having pinned and unpinned positions. The pin removably secures the first and second weight portions to one another in the counterweight operation position with the pin in the pin position.

The counterweight operation position defines a first spacing between the first and second counterweight portions. A retainer constrains the first and second weight portions to one another maintaining the weight portions in the counterweight service position with the pin in the unpinned position. The counterweight service position defines a second spacing between the first and second weight portions greater than the first spacings. The difference between the first and second spacings corresponds to an additional clearance between the car and the machine. Specifically, for the example shown, the additional clearance is the distance between the elevator operation and service positions. This additional clearance provides the space needed for the operator to access the machine from the top of the car.

The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows: BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 schematically depicts the inventive elevator system with first and second weight portions of the counterweight coupled to one another for normal operation.

Figure 2 schematically depicts the inventive elevator system with the first and second weight portions decoupled to permit the car to descend under its own weight to provide an additional overhead clearance at the top of the car.

Figure 3 depicts the inventive service process according to an embodiment of this invention.

Figure 4 depicts another embodiment of an inventive retainer for the counterweight.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An elevator system 10 is shown in Figure 1 in a normal operation position and also in which an elevator car 12 is located at a top floor of a building. The elevator car 12 is arranged in a hoistway 14, as is well known in the art. The Figures 1 and 2 depict a machine-roomless elevator installation in which the machine 18 is arranged under a roof 16 of the building. A cover 20 is installed over the machine to protect the machine 18 from the elements. Machine-roomless installations provide the advantage of not having to accommodate a large machine room inside the building and they avoid the necessity of a separate structure on top of a building roof.

However, when the car 12 is in a highest position as shown, the space between the car 12 and the machine 18 is very limited such that the car 12 must be lowered to allow a mechanic to service the machine 18.

The machine 18 includes a motor 22 that may include an integrated controller 23, or the controller 23 may be mounted in the hoistway 14 or elsewhere. The motor 22 rotatingly drives a drive sheave 24 that raises and lowers the car 12, as is known in

the art. The machine 18 also includes a brake 26 that regulates the rotation of the drive sheave 24 along with the motor 22. In the event that a component of the machine 18 needs to be serviced, such as a failure of the controller 23, the car 12 must be positioned in the hoistway 14 to provide sufficient overhead clearance.

Ropes or belts 28 are wrapped about the drive sheave, and a first portion 30 of the ropes 28 is secured to a conventional hitch associated with the car 12. An opposing, second portion 32 of the ropes 28 is connected to a counterweight 34 using a hitch 36. The counterweight 34 is heavier than the empty car 12 by approximately one-half of the duty load. There is also friction between the ropes 28 and drive sheave 24 and other components preventing motion by approximately 20% of the duty load. The relative weight between the counterweight 34 and the car 12 ensures efficient and safe operation of the elevator system 10, as is well known in the art.

An emergency and inspection (E & I) panel 38 is connected to the motor 22 and brake 26 and other components so that the mechanic may command components of the elevator system 10 to service the system. The E & I panel 38 may include a brake release switch 39 that releases the brake 26 and any other braking devices associated with the elevator system 10 to enable the counterweight 34, which is heavier than an empty car 12, to pull the car 12 to the top floor for service procedures.

When the car 12 is at the top floor, the top of the elevator is located at an elevator operation position E1, which provides insufficient access between the top of the car 12 and the machine 18 for the mechanic. In the elevator operation position E1, the car 12 blocks access to the hoistway 14 from the landing.

The counterweight 34 rides along rails 40, as is well known in the art. A stop or buffer 42 is arranged in a pit 44 of the hoistway 14. The counterweight 34 is located within the pit 44 and is just above the buffer 42 when the car 12 is located at the top floor. In one example, the counterweight 34 includes first 46 and second 48 counterweight portions. Although the portions 46 and 48 can be arranged in other configurations, in the example embodiment, the first counterweight portion 46 rests on the buffer 42, and the bottom of the second counterweight portion 48 corresponds to a counterweight operation position Wl when the car 12 is in the elevator operation position E1.

The counterweight portions 46 and 48 are removably secured to one another by latching members 50. The illustrated example includes pins 50 received in holes 51 in the counterweight portions 46 and 48. The pins 50 secure the counterweight portions 46 and 48 together when the pins 50 are in a latched or pinned position, placing the counterweight 34 in condition for normal elevator operation. The pins 50 may be bolts or any other suitable fastening arrangement.

The counterweight 34 includes retainers 52 that, for the embodiment shown, comprise longitudinal members 54 extending from the first counterweight portion 46.

The longitudinal members 54 are disposed within apertures 56 that permit the second counterweight portion 48 to slidably move relative to the first counterweight portion 46 when the pins 50 are removed from the holes 51. The retainers 52 include enlarged ends 58 that limit the travel of the second counterweight portion 48 relative to the first counterweight portion 46 when in the extended, decoupled position, best shown in Figure 2.

Another example retainer is shown in Figure 4. The retainer 52 may include straps 53 that unroll and extend as the counterweight portions 46 and 48 move away from one another. The strap 53 may be secured to each of the counterweight portions 46 and 48 by securing members 55.

Turning now to Figure 2, a part of the second counterweight portion 48 is <BR> <BR> configured to permit the relative movement (i. e. , the movement from the position in Figure 1 to that shown in Figure 2) and to contact the enlarged end 58 at an extended position. The enlarged end 58 may include a buffer constructed from a spring, polyurethane foam, or any other suitable material to limit the impact forces on the connecting members when the counterweight portions 46 and 48 are decoupled from one another.

When the pins 50 are removed or moved to an unlatched or unpinned position, the second counterweight portion 48 is permitted to move away from the first counterweight portion. The counterweight portions 46 and 48 have a first spacing between one another when in the counterweight operation position Wl. When the counterweight portions 46 and 48 are decoupled from one another, the second counterweight portion 48 is permitted to move away from the first counterweight portion 46 creating a second spacing that is greater than the first spacing. In other

words, the example counterweight has a first length and a second, greater length. One feature of the example embodiment is that the counterweight maintains the same tension on the ropes or belts 28 regardless of whether the counterweight portions 46 and 48 are coupled adjacent each other or spaced from each other.

When the counter portions are decoupled, the bottom of the second counterweight portion 48 moves to a counterweight service position W2. Movement of the second counterweight portion 48 from the counterweight operation position Wl to the counterweight service position W2 corresponds to a movement of the car 12 from the elevator operation position E1 (Figure 1) to the elevator service position E2 (Figure 2). The difference D between the counterweight operation position Wl and the counterweight service position W2 corresponds to a clearance C that is the difference between the elevator operation position E1 and the elevator service position E2.

An example elevator service procedure 60 is summarized in flowchart form as depicted in Figure 3. Using the brake release switch 39 on the E & I panel 38, the brake 26 and any associated braking devices are released to allow the counterweight 34 to move to a desired position, such as the position in which the first counterweight portion 46 rests on the buffer 42, as shown in Figure 1. At this time, the second counterweight portion 48 is in counterweight operation position W1, and the car 12 is in elevator operation position E1. The counterweight 34 may already be in the desired position, in which case step 62 is already performed.

The mechanic may then enter the pit 44 to decouple the counterweight portions 46 and 48, as indicated by step 64. The mechanic may move the pins 50 from the pinned position, shown in Figure 1, to the unpinned position, shown in Figure 2. In the case of the pins 50 being bolts, the bolts may be unthreaded from the holes 51.

The brake release 39 is typically a momentary switch that, once the mechanic removes his hand from the switch, the brakes re-engage. As a result, the car 12 is held in the elevator operation position El when the counterweight portions 46 and 48 are decoupled from one another. Accordingly, to lower the car 12 from the elevator operation position E1 to the elevator service position E2, the mechanic must return to the E & I panel 38 and actuate the brake release switch 39 once again, as indicated at

step 66. The weight of the second counterweight portion 48 is less than the weight of the empty car 12 so that the weight of the empty car 12 will cause the car to descend and will raise the second counterweight portion 48 to the counterweight service position W2 upon the release of the brake 26. The retainer 52 constrains the second counterweight portion 48 to the first counterweight portion 46 to prevent the portions 46 and 48 from detaching from one another. As a result, the counterweight portions 46 and 48 together hold the weight of the car 12 in the elevator service position E2.

The buffer 58 dampens any vibration or noise as the second portion 48 moves into the extended position. The mechanic can then enter the area of the hoistway 14 beneath the machine 18 by stepping on top of the car 12, as indicated at 68.

Subsequent to the elevator system 10 being serviced, the car 12 may be driven upward by the motor 22 to return the second counterweight portion 48 to its original position at the counterweight operation position Wl so that the counterweight portions 46 and 48 may be coupled to one another using the pins 50, as indicated at steps 70 and 72.

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 essence of this invention. The scope of legal protection given to this invention can only be determined by studying the following claims.