GSA Courthouse Management Group
Mechanical Lift Analysis
(1)
SOUTHWORTH / T.L. SHIELD
(INVISIBLE LIFT)
This model was the most frequent installation at the courthouses
visited during the Analysis. (Eleven of 16 facilities had the Invisible
Lift.)
Southworth manufactures the lift platform and its supporting frame;
and the T.L. Shield Company provides both the operational controls
and coordination of the lift installation. The Invisible Lift design has
evolved from industrial models used to move bulk materials between
various levels within a warehouse environment. The typical courtroom
installation had the platform surface clad with carpet; gate controls
mounted in the millwork; and lift movement controls placed within a
stanchion mounted to the platform. (Many installations also included
wall-mounted controls in lie of the stanchion.)
The problems related to the use of this unit were consistent, though not
apparent at every installation. The primary issue was sinking of the
platform, due to the dependence on hydraulic pressure, if it was
maintained in a raised position for a long period of time.
The manufacturer should investigate the possibility of providing
retractable struts to support the platform at elevated positions over an
extended period of time, without the dependence on hydraulic
pressure. The typical position for ambulatory access to the raised
courtroom functions should be with the platform at its lowest position,
resting on the base frame, flush with the courtroom well floor.
None of the Invisible Lift installations observed during the site visits
had a handrail mounted on the platform. The manufacturer's
representative indicated that a code variance to eliminate this
requirement was not difficult to obtain due to the minimum variations
in height between landings. (Southworth has provided handrails
mounted to the platform when it was absolutely deemed necessary by
the jurisdiction.)
The area under the platform is only accessible for service within the
dimensional limits from the courtroom well floor to the highest
landing, which is typically 24 in. (Some installations accommodate
the witness box level only, with the resultant service clearance of
approximately 7 in.)
Check valve replacement on this hydraulic/scissors lift system has
eliminated the sinking platform issue, according to a manufacturer's
representative, and they have no immediate plans to incorporate
retractable struts into the system to maintain a raised platform over an
extended period of time.
HDR Architecture, Inc.
Section 6-2
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