With these components the hoist motor is mounted without installation of electrical wiring. The motor is driven by a power source (battery) from a portable control unit. The development is aimed at eliminating the permanent electrical connection to the hoist normally required for electrical hoists. The inventors say that such a permanent connection makes hoist installation expensive and cumbersome, especially when multiple hoists need to be installed.
The patent incorporates US Provisional Application 60/592,738 filed in July 2004, and was itself filed in July 2005.
Description and operation
In the assembly described in the invention the hoist motor (Fig 1 – 10) is located within the hoist housing and rives a spool (2) upon which webbing (7) or wire rope is wound for load handling. An optional multidirectional automatic cut-off system is used to ensure that the load is not raised above a safe level. A power cable extends down from the hoist motor with a power connector at its lower end. A strain relief device can be included to decrease wear on the connection between the power cable and the hoist casing. Alternatively the power connector can attached directly to the motor or hoist housing.
One type of cut-off system includes a lever with a centre pivot point allowing it to hinge in both directions, plus two switches. A stopper on the lower end of the webbing is shaped to push the lever when the object has reached optimal height. Thus the cut-off will operate no matter which direction the webbing is spooled.
The hoist housing is designed so that the power cable with the power connector can be wrapped around the housing. Hooks on the housing can be used to adjust the height at which the power connector hangs. This allows the hoist unit to be hung and operated from various heights. Alternatively the hoist power connector cable can be attached to the mounting beam for the hoist at a variable distance away from the hoist unit, so using up some of the cable as required to adjust the position of the power connector.
Several hoist units can be ‘daisy-chained’ together to enable the use of a common power source at the end of the chain. An electronic controller can be used to choose which hoist unit is to be raised or lowered, preferably with AC-motor-driven hoists.
In Fig 1 the gearbox (8) is also shown and, in this example, the drive is from a DC motor (10). Although various types of gear system, such as worm gears, may be used, this example uses a two-stage planetary gear system for its efficiency.
Once the load has been lifted to the desired height the spool must be locked to prevent the load from lowering due to its own weight. One way of doing this is to connect the motor leads by the hoist power switch (Fig 3 – 36). The internal wiring of the switch, located in the remote power pole (Fig 2 – 150 for example), can be configured such that, when the switch is in the neutral position, both motor leads are connected to the negative lead of the battery. Alternatively the leads can be connected in the hoist power connector. A switch in the hoist power connector shorts the motor leads once the user removes the remote power unit, and disconnects the short once the emote power unit is put back in place. If both of these devices are in place the load will be held securely in place until the user activates the hoist motor to move the object up or down.
Additional braking can be added by using a solenoid (Fig 3 – 11) and spring combination to apply pressure to resist rotation of the motor shaft when no power is applied to the motor. Once power is on the motor, the solenoid and spring combination releases pressure. The resistance to motion on the motor side of the gearbox requires less force to prevent spool rotation. If resistance is applied on the spool side, more resistance is required to prevent spool rotation.
A further safety mechanism, such as a post or other mechanical interlock may extend through the openings in the spool edge when no power is applied to the motor, and retracted when not required.
The spool can be made of any sturdy and fairly durable material including metal, wood and plastics, the latter being to reduce abrasion and noise. As previously mentioned, the load-suspension components can be webbing, wire rope or other material that can support the load and wind onto the spool. Webbing may be used to prevent failure due to tangling or kinking, and also tends to prevent the load from rotating during lowering or raising. In addition, as webbing wraps over itself it consistently increases the functional diameter of the spool as it winds. Consequently the lifting speeds up as the object is raised and slows down as the object is lowered. The slower speed close to the ground allows safer and more precise lowering.
The load can also be lifted by reeving a rope or rod through a hole, ring, pulley or block. The motor can also be used to drive a sprocket gear to engage a chain for load handling. The loose end of the chain can be left dangling or drop into a collection chamber to prevent it from tangling with the load and other objects.
The hoist unit can be mounted on virtually any type of structure capable of supporting the load, such as by using mounting holes in the hoist housing and perhaps custom mounting hardware to fix the hoist to L-beams, box beams, laminated beams and other common large building ceiling structures. Alternatively the hoist can have a simple hook system that allows it to be installed without tools. An optional worm gear can be used to reduce the spool speed and prevent back drive.
Power connector
The hoist power connector has three contacts; one being negative and the other two positive. This allows the hoist power to be connected from either direction whilst maintaining the polarity to keep the switch direction constant. Alternatively there could be one positive contacts and two negative. Another variation could use two leads; one positive and one negative or earth.
Various embodiments of the connector can have the hoist connector and power unit connector both hook-shaped or the hoist power connector can be shaped like and inverted cone with a slot such that the connection point on the remote power pole would slide down a wire until it hits the cone to make contact. In this case the remote power-pole connection point would be Y-shaped to reach around the tope of the inverted cone, allowing the hoist power connector to be approached from any direction.
The power unit (Fig 2 – 140 or 150) takes the form of an elongated pole with a coordinating power connector configured to engage the hoist power connector, a set of controls on the handle, and a battery pack (Fig 3 – 25). The power unit incorporates a double pole triple throw switch to short the power pole contacts to the negative terminal of the battery pack when in the neutral position.
A current-limiting fuse can be installed in the power unit in series with the battery pack. This prevents too much current from going through the system, thereby preventing the hoist being forced to lift the load beyond its load-rating and causing harm to the user, an electrical failure or damage to the batteries. A clutch inside the hoist can be used as a load-limiter.
Fig 2 shows types of power unit that are collapsible. In Fig 2 A power unit (140) is foldable, requiring some internal extra length to allow for it to extend around the opening created by the fold. In Fig 2 (B) the power unit (150) telescopes (Fig 2 C) with two to any number of pieces forming the telescopic lengths (three are shown).
The rechargeable type of battery pack uses either a NiMH pack or a NICd pack. Various cell arrangements can be used depending on power needs. The housing is insulated, such as by plastics. One or a series of electrical contacts are used to connect the battery pack to the rest of the power unit.
Fig 3 shows the charger unit (34) in perspective with two battery packs (25). The charging unit includes a body and circuitry to rapidly peak charge one or two battery packs simultaneously. The connection to the battery pack is formed by a charging contact located on the outside of the battery housing. The main bay (50) accepts the battery pack mounted to the power unit and a second bay that accepts a free battery pack (25). The main bay has an arm and retaining clip that engages the power unit support collar (27) to hold the pole upright. The charger can be mounted on the floor or wall. Other arrangements of battery pack chargers are available.
The hoist could be driven by an AC motor but would therefore require an AC power source. One such configuration would include a power unit plugged to a wall outlet or be installed in the building wiring. The corded control unit would then be used similarly to the DC units discussed elsewhere.
The patent also outlines a possible pneumatic power arrangement, and also details various hook arrangements for load handling.
Fig 4 shows an example of circuitry for the electric hoist system.
Alternative embodiments of the invention could use the telescopic rod to move the load horizontally, whilst other embodiments could use pulleys or similar mechanisms to move loads horizontally, vertically or diagonally with rigid load-moving members or along rails or tracks using flexible load-moving members.
Advantages
The host weight and size are reduced since the power components are not a permanent portion of the hoist. This makes installation easier and also reduces the overall number of components necessary and therefore the costs in situations where multiple hoist units are used with a single or smaller number of power units. If the hoist is used primarily to lift less than 200 lb. (90 kg), the hoist can use a relatively small motor capable of being powered for a significant time from a small, portable battery pack.
About the patent
This article is an edited version of US patent 7,227,322, published 5 June 2007, and resulting from US patent application no. 11/192,992. The inventors are Ehsan Alipour, Mike Starssner, Benjamin Toru Minn, Thomas King and Clinton Stone. all of California, for the assignee Unovo, Inc of San Francisco.
Disclaimer
This article is an edited version of the patent and may omit legally or technically important text. To see the full patent go to www.hoistmagazine.com/patents
Fig 1 – An internal view of the hoist mechanism showing the motor, brake, gearbox and spool Fig 1 Fig 4 – A circuit diagram for the hoist Fig 4 Fig 2 – Embodiments of the power unit that are collapsible Fig 2 Fig 3 – Perspective view of the charger unit with two battery packs and a power unit
Fig 3
