These systems are very similar to passenger elevators except for the car interior and the door opening mechanism. The car does not have to be furnished like a passenger elevator.
The car doors also can be manually operated, which lowers the cost of the unit, although many high-rise hotels are installing automatic motorized door-opening systems similar to passenger elevators.
Maintenance, safety systems, and controls are the same as for passenger elevators. Service elevators often require more maintenance than passenger elevators because of frequency of use. Many hotel managers stress passenger elevator maintenance over service elevator maintenance, but both require an equal level of maintenance.
The carrying capacity per hour of freight elevators is determined by its capacity and the time required for a round trip. Round trip time is made up of four components –
(i) Running time which is equal to the distance travelled divided by car speed.
(ii) Starting and stopping time which consists of the time required to accelerate and retard the car for each stop. This can be averaged at 2 seconds.
(iii) Door-operation time is the time required to open and close car gate and hoist way doors. For power operated doors, this is about 8 seconds; for manual operation, about 24 seconds.
(iv) Loading time requires the most careful study. It is influenced by the nature of the material transported, the method of loading, the distance which the material has to be moved, and so forth.
For a well engineered installation the choice of freight elevators require a close consideration of such facts as size, weight of the materials to be transported, the method of handling etc. to provide freight elevator installations suited to any operating conditions.
The same types of push button or supervisory control used for passenger elevators can be used. For small capacity, moderate-use elevators, the constant pressure button is satisfactory, the car moves only while the control button is held in.
Automatic traffic pattern control is, of course unnecessary. Cab gates are of expanded steel mesh or hardwood slats which are counter balanced and rise vertically. Hoist way doors are generally counter balanced, centre-parting, vertical- sliding and fireproof.
On all but moderate-use elevators, these gates should be power operated in order to reduce door operation time. Gates and doors are electrically interlocked to prevent movement of the car until both are closed.
Where required cars open on two opposite ends. Usual height of door opening is 225 cm and minimum floor-to-floor height is 1.5 times door opening plus 15 cm.
Design Data for Freight Elevator:
Capacity requirements of freight elevators must take in to account not only the load to be transported but the weight of power truck which may, be needed for loading. The truck introduces an eccentric load as it rolls onto the car platform. This causes additional trees on the car structure, guide rails, and leveling control.
Platform sizes have been standardized by the elevator industry. The probability of overloading is reduced if one chooses the smallest platform that is adequate to carry the load. The dimensions of the freight units handled, and the size of pallets, skids, or trucks used will influence the dimensions of the car for a given capacity.
Directly and indirectly, modern freight elevators made for efficient operations throughout a building. The results of properly planned freight elevator installation show up in increased material handled volume and greater earning power.