Hoist system for retrofitting small scissor lift to access enclosed areas in building structure

A portable hoist assembly is mounted on a scissor lift. The hoist includes an elongate cable wound on a shaft. The cable has proximate and distal ends. A pulley is mounted on the cable intermediate the proximate and distal ends. In use, the pulley is secured to the ceiling of a building structure.

This application pertains to a method and apparatus for lifting construction or other materials.

Those of skill in the art have, for many years, endeavored to provide improved apparatus and methodology to safely lift and maneuver construction materials.

Therefore, it would be highly desirable to provide an improved apparatus and method in this respect.

Therefore, it is a principal object of the instant invention to provide an improved apparatus and method to lift and position duct work and other construction materials.

Briefly, in accordance with the invention, provided is an improved portable hoist assembly to retrofit a scissor lift to elevate and position construction materials. The scissor lift includes at least one battery used in the operation of the scissor lift. The hoist assembly includes a hoist mounted on a support structure. The hoist includes a rotatable shaft, and an elongate cable wound on the shaft. The cable has a proximate end mounted on the shaft and a deployable distal end. The cable also includes a structure on the distal end to engage at least one item to be lifted by the hoist. The hoist also includes a motor connected to the shaft to rotate the shaft in at least two directions, a first forward direction to deploy the cable, and a second reverse direction to retract the cable. The hoist also includes an electrical cable having a proximate end connected to the motor and a distal end shaped and dimensioned to connect to the battery of the scissor lift to provide power needed to operate the motor. The hoist also includes a manually operated control unit connected to the motor to operate the hoist to deploy and retract the cable. The portable hoist assembly also includes at least one pulley mounted on the cable intermediate the proximate and distal ends of the cable; apparatus to secure the pulley to an overhead structure in a building; and, apparatus to detachably securely mount the support structure on the scissors lift.

Turning now to the drawings, which depict the presently preferred embodiments of the invention by way of illustration, and not limitation, of the invention, and in which like reference characters refer to corresponding elements throughout the several views, a new hoist system for a scissor lift is described with reference to the attachedFIGS. 1 to 4, along with a method for utilizing the system. The new system is, when used in conjunction with a scissor lift, especially suited to lifting transformers, ducting, etc. in confined spaces in a building. Currently, lifting such pieces of construction equipment43and44in confined spaces is labor intensive, and can be relatively dangerous. The apparatus and method of the invention are believed to greatly facilitate and simplify such operations.

A method utilized in accordance with one embodiment of the invention comprises the following steps:1. A hoist assembly is obtained which includes a hoist14mounted on a plate11(FIG. 1) or some other support structure. The hoist assembly also includes a control unit20to operate an electric hoist motor14B and includes electrical leads17,18. The hoist assembly also includes an extendible cable15with a hook16attached to the distal end of cable15. Cable15is wound on shaft14A. The proximate end of the cable15is, in conventional fashion, mounted on shaft14A. Motor14B turns shaft14A in one direction to deploy cable15and turns shaft14A in another direction to retract cable15. Control unit20is connected to motor14B by electrical lead or cable21. Unit20is preferably manually held and operated to rotate shaft14A to deploy cable15, to rotate shaft14A to retract cable15, or to stop rotation of shaft14A.a. The electrical leads17,18are adapted to be attached to the battery(s)70or electrical system of a scissors lift40(FIG. 2) so that the batteries71of the scissors lift can be utilized to power the motor14B hoist assembly.b. Plate11, or another structure12attached to plate structure11or hoist14, is configured to be mounted on a scissors lift40(FIG. 2) or other piece of equipment or other structure. The plate11(or structure12) preferably is adapted to be removably mounted on the scissors lift40. For example, inFIG. 1plate structure12has slots25,26,27,28formed through the plate so that each one of four attachment straps45can be threaded through a different one of slots25to28to engage a selected portion of a scissors lift40and secure detachably plate12(and therefore the hoist assembly) to scissors lift40. Any desired method can be utilized to removably fasten plate11or another support structure12to a scissor lift40.c. The hoist14is securely mounted to plate11or another structure12with bolts29,30,31,32(FIG. 1), by welding, etc.d. The hoist assembly includes a pulley assembly which includes a pulley41(FIG. 2) that can be secured removably to a joist42or other overhead structure, and includes fastening means to secure the pulley assembly to the joist42. The pulley assembly preferably is mounted on cable15and can move along cable15at locations intermediate the distal and proximate ends of cable15. Consequently, when pulley14is fixedly removably attached to a joist42or other overhead structure, the wheel in pulley14turns freely when cable15moves through pulley14.2. A bridle or net structure38is obtained which includes netting38attached to and spanning between a pair of elongate poles34,35(FIG. 3). The ends of a lift cable36,37are attached to each pole34,35, respectively. The netting is sized to fit around a length of ducting44in the manner illustrated inFIG. 4. Netting38can include strands which are each perpendicular to or parallel to poles34,35in the manner epitomized by strands50and51. Importantly, it is preferred that the strands of netting38be canted with respect to poles34,35, as epitomized by the strands52and53drawn in dashed line form inFIG. 3. If desired, sleeves54,55are provided and each removably fit or snap on an end of a pole34and35and also removably receive the end of an extension pole56,57, respectively.3. The hoist assembly and the bridle38are packed together as a portable hoist kit for a scissors lift.4. The portable hoist kit is transported to a building structure in which air conditioning ducting or other construction equipment is being suspended and installed.5. A scissors lift40is provided at the building structure.6. The four mounting straps are used to mount removably plate12—and therefore the hoist assembly—on the scissors lift40in the manner illustrated inFIG. 2.7. The pulley assembly41, which preferably, but not necessarily, is already pre-installed on cable15so that cable15threads through assembly41, is securely removably mounted on the overhead joist42of the building structure in the manner illustrated inFIG. 2.8. Bridle38is laid on the floor in the manner illustrated inFIG. 3.9. A length of ducting44is placed on the bridle38such that the ends of the ducting extend beyond the netting in the manner illustrated inFIG. 3.10. Poles34and35are lifted off the floor.11. Lift cables36,37are each engaged with hook16in the manner illustrated inFIG. 4.12. Control unit20is used to operate the hoist assembly to lift the bridle and ducting44off the floor to a desired height above the floor. When button22of unit20(FIG. 1) is manually depressed, motor14B rotates shaft14A in a direction which winds or retracts cable15onto shaft14A. When button23of unit20is manually depressed, motor14B rotates shaft14A in a direction which deploys cable15from shaft14A. When button24of unit20is manually depressed, rotation of shaft14A stops.13. A worker enters the basket of the scissors lift.14. The scissors lift is operated to raise the basket so the worker can install the ducting44.15. If necessary, unit20is operated to adjust the height of ducting44above the floor.

Electrical wiring or leads17and18are presently preferably in the form of a fifty foot cable which at its distal ends (not shown) has alligator clips which can be attached to the posts of a battery.

Control unit20, motor14B, or another component in the system of the invention preferably includes a sensor which will prevent operation of motor14B or of another portion of the system from operating if the weight being lifted exceeds a selected value. This value can vary but is presently 2000 pounds.

Cable21and the cable housing leads17and18are each preferably coiled (in the same manner that the cable leading from a telephone set to the telephone receiver is coiled) to reduce their length when not in use and to reduce the likelihood they will be run over or stepped on.

In one embodiment of the invention, hoist14includes a magnetic brake which clamps to and prevent rotation of shaft14A as soon as button24is pressed or released, as the case may be. This is an important feature because it prevents ducting44or another article being lifted by the hoist assembly from moving a short distance (i.e., from “drifting”) after motor14A has been stopped. When motor14A is stopped, it is preferred that the rotation of shaft14A stop substantially immediately and completely.

In an alternate embodiment of the invention, the hoist assembly is not mounted on a scissor lift but is mounted on another piece of equipment or is mounted on the wall or ceiling of a building structure, for example in the bay of an automobile repair facility. Pulley41would normally then be mounted at a desired location on the ceiling of the bay.

In addition to straps45, the hoist assembly also preferably includes one or more safety chains59which at one end are welded60or otherwise attached to a support structure12and are also secured to scissor lift40or to another piece of equipment or structure on which the hoist assembly is mounted.

While the size of hoist motor14B utilized can vary as desired, the motor14B ordinarily can be powered by four 12 volt or four 24 volt batteries wired in series. Each such battery may produce from thirty-six to forty-eight amps of current.