With limited overhead, Gillespie Corporation found a creative solution for a historic hotel in Boston.
by Victoria Pruitt
When field conditions did not allow for sufficient pit depth or overhead to provide the vertical clearances required by the ASME A17.1 Safety Code for Elevators and Escalators, Gillespie found a solution. With the introduction of the Americans With Disabilities Act (ADA), the company began receiving an increasing number of calls to design a safety system that would automatically and mechanically provide refuge space for tight conditions both above and below the elevator. Some situations involve only insufficient pit depth, some involve low overhead conditions, and others are challenged with both a shallow pit depth and low overhead.
Typically, this need is seen in older and historic buildings with existing structure or in new construction with imposed constraints. Often, structural elements, such as footings or structural beams, make it impossible to provide the required pit or overhead. An elevator is often required to be located above or below occupied space, or both. In these situations, pit depth and overhead are quite often limited. Less frequently, local building codes will not allow for the addition of a “doghouse” at the roof level that would allow for minimal overhead.
Gillespie met this need by designing both its patented Shallow Pit Safety and Low Overhead Safety. These systems are composed of automatic power-operated mechanical devices that will stop the motion of the elevator when deployed to provide the refuge space required per code. They are activated from outside the shaft for maintenance and inspection. If someone gains access to the shaft without operating the safety systems, either below or above the elevator, secondary backup detection will automatically deploy the safety devices and take the elevator out of normal operation. In the case of the Shallow Pit Safety System, this operation can take place even during a power outage.
The first elevator with the Low Overhead Safety System was installed in 1998 at Yale University’s Beinecke Rare Book & Manuscript Library. This safety system was developed by Gillespie with help from Edward A. Donoghue Associates, Inc. Concerns were addressed so that a safe and redundant working system could be employed on those difficult elevators where enough overhead could not be provided.
In addition to the safety systems, Gillespie developed telescoping car aprons, which allow for the shallow pit depth, while providing the front vertical surface height required by code. The telescoping car apron is only allowed to collapse while the elevator approaches the lower landing from above. The apron must be fully extended when the elevator is above the lower landing.
The Revere Hotel Boston Common is south of the Boston Common and across from the Massachusetts State House. The hotel boasts one eye-catching elevator that serves the reception area and other levels.
Occupied space that could not be infringed upon lied directly above the glass and steel elevator shaft. The overhead height from the finished floor at the upper landing to the ceiling in the shaft was limited to 9 ft, 2 in., much less than required by code to provide top-car clearance and refuge space above the cab. This required a variance from the state of Massachusetts’ Board of Elevator Regulations.
The rear structural wall extended only to the upper floor and did not continue to the ceiling of the shaft. The other three shaft walls were tube-steel and glass, with the outer building wall of freestanding design extending from the first floor to the ceiling above. These three walls could bear no structural loads imposed by the elevator. The landings were at 90º to one another, requiring adjacent car openings. The requirement was that the landing and car doors be primarily glass, and both the rear and side cab walls be glass from floor to ceiling.
When standing at the middle landing, looking into the shaft, you would be facing the rear partial building wall. The left wall would be the outside building wall. The right wall would be toward the building interior and have both a landing below and above this middle landing.
Additionally, the architects and consultants required that the inside of the cab and landing doors be finished in brushed stainless steel wherever steel presented itself, and the outside stainless-steel entrance frames, door-panel frames and cab framing be painted a custom gray. The cab exterior was to have a finished appearance, including the car canopy, which was also to be painted custom gray. The hall stations were to be custom, limited to a 4.5-in. faceplate width and extend from the landing floor to the ceiling of the floor above. The hall-fixture faceplates were to be painted in the same custom gray as the surrounding wall tubing and the car itself.
The pit depth was not an issue, being a comfortable 4 ft in depth.
The Solution — Design and Production
Following discussions with the architects and consultants, Gillespie proposed a cantilever car arrangement supported off the rear wall. To provide for top-car clearance and refuge space required by code, Gillespie intended to employ its Low Overhead Safety System. This system is composed of rail-mounted steel safety bumpers operated by 12-VDC actuators. These safety bumpers are designed for substantial dynamic loads. Normal use requires the operator to deploy them from the upper landing lobby using the upper landing access key. In addition, a secondary protection involves the automatic detection of persons or objects on top of the canopy, thereby deploying the safety bumpers if someone were to get onto the car top without operating the safety system. Both the normal access and automatic detection operations of the safety system put the car in inspection mode and take the car out of operation. Due to the limited overhead, the cab height was reduced from a normal height of 8 ft to 7 ft, 3 in., which still allowed for a stainless-steel ceiling with LED downlights underneath the canopy. The door height was limited to 6 ft, 8 in.
In laying out the car in the available hoistway space, it was determined that the right-side entrances would need to be two-speed side-opening doors, while the front opening could be a single-speed door. Gillespie normaly prefers to employ a common strike jamb when doing an adjacent-opening cab, but that was not possible due to space constraints. Therefore, this opening arrangement shares a common corner for the door returns.
The elevator provided has a 6-ft, 5-1/4-in. X 6-ft, 3/4-in. platform within a 7-ft, 6-in. X 7-ft, 4-in. clear shaft. The travel is 14 ft, 1-3/4 in., serving the three adjacent landings. The capacity is 2,500 lb at a speed of 100 ft/min.
The outside building wall was more than 12 in. from the car canopy, which violates code. No car-top handrails in the industry can fold down enough to allow for the limited overhead of 9 ft, 2 in. Instead, Gillespie proposed a metal extension, built into the canopy, to fill the gap on the building wall side. The state code authorities granted approval for this, stipulating that the extension be designed to support the same loads the code requires for the canopy.
To allow for a cantilever car-frame design, the guide rails were supported by substantial structural square tubing, attached at the pit floor, building wall and shaft ceiling above. A telescopic cylinder and matching power unit from ITI Hydraulik was used to lift the car. Due to the glass cab, the platform was isolated from the car frame using Lord’s isolators.
The custom nature of the cab and entrances required us to employ the services of a company that could not only build a stainless-steel-and-glass cab, but one that also had an unusual adjacent opening arrangement. The door operator chosen was a flat-belt operator available through Unitec, the Otis AT 400 linear operator. This was required to reduce the operator height so that upper-car clearances could be met at car overtravel. In addition, the cab and entrances needed to be finished on both sides. Gillespie went to Elevator Manufacturing of Benton, Washington, knowing the combination of door operator, arrangement and style required an imaginative combination of door hardware.
For the car and hall fixtures, Gillespie employed Innovation Industries, Inc., which was able to produce the tall and narrow custom hall stations. Motion Control Engineering, Inc., provided the custom controller, which had to be designed for both normal elevator operation and the operation of the Low Overhead Safety System. As it turned out, satisfying the design requirements for the cab, entrances and fixtures was the most difficult aspect of designing and building this unusual elevator.
To gain access to the car top, it is necessary to put the car into access-enable mode at the car station, open the car and hall doors and lower the car using the access key until the access limit switch stops the elevator at a good working height. This action will cause the safety bumpers to automatically deploy, allowing access to the car top. If the access key is not used and the doors are opened with the elevator parked at a lower landing, the act of stepping out onto the car top will cause the safety system to deploy through physical detection. It is physically impossible for the elevator to rise to the upper landing when the safety system is deployed.
To place the elevator back into service, one must exit the car top and, with the door held open, raise the car using the access key until the doors are engaged and the car is level with the uppermost landing. The safety bumpers will automatically retract out of the way of the elevator as it is raised. At the car-operating panel, one must use the access key to place the car back to normal service.