The guide is intended for use within a driving mechanism (chain hoist) such as used with an overhead shaft of a door operation assembly such as for garage doors and sectional doors used in industry.

Background and need

Door assemblies with chain hoists are well-known state-of-the-art, and that of a sectional door with an overhead shaft is also described in the patent. Such doors will include a counterbalance mechanism, generally using torsional springs, to make operation easier, but the rapid downfall of an inappropriately counterbalanced door can sometimes result in excessive rotation of the main shaft. A manual operational chain will be suspended around a pocket wheel on the shaft. If the door descends quickly the chain will lose its tension and may be drawn outside of the pockets of the pulley wheel due to centrifugal force.

In extreme, though unlikely cases, the chain can come off to hit the inside of the hoist, causing it to jam there. This creates pressure on the internal components of the hoist, which may have to bear the weight of the door suddenly. When certain chains are used, say the inventors, undesirable knots could also jam in the chain hoist.

A third possible problem tackled by the patented development is excessive noise due to hoist internal components and the corresponding chain co-operating adversely with each other. Faster turning chain carries a greater risk of vibrations affecting internal components. A metallic casing will often amplify any chain noise.

Thus, the developments in the patent are aimed at solving some of the above problems, by, for example, maintaining the chain within the pockets of the chain pulley if the latter is turned excessively rapidly. The flexible band of the invention is able to deform itself and/or allow the passage of knots or twists in the chain. It is designed to resist certain impacts through deformation.

How it works

In addition to the chain guide outlined above, an aspect of the invention includes a drive mechanism comprising a casing, a first wheel pivotally mounted within the casing and centrally bored to receive a drive shaft, a second wheel also mounted in the casing and thread-engaged to the first wheel to drive it, and a drive chain around the second wheel. The chain guide is positioned within the casing and around the second wheel in an elongated, arched form within the chain hoist. Chain receiving portions on the inside of the guide comprise a pair of protruding shoulders to define an open channel sized to receive a portion of chain as it slides in. The first and second chain receiving portions are connected.

Various aspects of the invention provide additional features. These include a door assembly with the above chain hoist, a method of operating the chain hoist, a kit for assembling the chain guide and hoist, and a method of assembling the components of the kit.

The expression ‘garage door’ below is taken to mean all types of cable-operated or sectional doors, including access opening, using one or more torsion springs to counterbalance the weight of the door. The invention can also be used with similar mechanisms.

In the diagrams the drive mechanism (3) and chain guide (1) are the key elements. According to the inventors, although there are several devices available that enable correction and alignment as much as possible of the drive chain (5), there seems to be no device that enables the chain to be guided all around the given chain pulley (7 in the invention). The chain hoist is provided for manual operation for when a mechanical operator is not appropriate. Manual chain hoists are used typically when a door is heavy, where it is difficult to overcome the inertia of the counterbalancing springs when trying to open it, and when it is impossible for somebody to completely raise a very high door. Such chain hoists differ according to the components used, the desired ration and the utility sought out. As a conventional commercial garage door with sectional panel joints does not generally require the use of a very high force ratio to raise it, a chain hoist according to the invention can be used.

Fig 1 shows a simple chain hoist with a main gear (first wheel – 9), and chain and a chain pulley (second wheel – 7). Their connection by bearings, washers, gears etc, and method of operation, are well known. The chain guide of the invention is fixed to the casing (11) and surrounds the chain pulley to guide the chain as in Fig 2. The chain guide has an elongated body (13), first and second chain-receiving portions (15 – two), and a connecting portion (17). Part 19 and 21 (Fig 3) show the inner and outer side of the body respectively. As shown in Fig 3 the body, made of flexible material, curves into an arch.


Each chain-receiving portion comprises first and second shoulders (27 & 29) protruding from the inner side to form a channel (31) shaped and sized to receive the chain. The flexibility of the connecting portion allows it to deform and twist as below. The connecting portion should be integral with the main body and has a middle section (33) of a width smaller than that of the neighbouring sections (35). According to the inventors this is advantageous in that it enables guide deformation by twisting or other suitable motion to allow the passage of knots.

Preferably each pair of shoulders has a first shoulder (27) that is wider than the second shoulder (29). Each chain-receiving portion consists of front and rear sides (37 & 39), each consisting of one protruding insert (41) that can interact with a corresponding hole of the chain hoist to secure the chain guide. Each chain receiving portion also has a rear edge (43) extending along the outer of the body and provided with at least one hook (45) to attach it to at least one support member of the chain hoist. Preferably a pair of hooks and a corresponding pair of support members on the hoist are used. Fixing within the hoist is aided by the width of the shoulders that are intended to occupy and fill out the width of the inner casing. This also enables the guide to act as a damping device to noise and vibrations.

The shoulders of each chain receiving portion should extend on either side of the longitudinal axis (47) of the body so that each have an offset with respect to this axis, with the offset of the first shoulder greater than the offset of the second shoulder. The shoulders should also be arched so that the inner side of the body forms a substantially circular profile when curved into the arched configuration as in Fig 3. The shoulders should define complementary recesses (49) on the corresponding section of the outer side of the body.

The chain guide’s body, chain receiving portions and connecting portion should comprise a single component made of a single material, preferably nylon PA66 with cold impact additive. The guide is made by injection moulding.

The above design and construction enables the guide to carry out its functions, say the inventors, for example, guiding the chain with additional advantages in terms of noise and vibration damping without substantial additional weight in the hoist. Other materials and methods of manufacture can be used but the above nylon injection moulding is believed to provide a cost-effective method.

During an excessive rotation of the main shaft of the door, the flexible band of the chain guide may deform itself on one side or the other depending on the direction of the pressure applied by the chain attempting to come out of the pockets of the chain pulley.

Additional features without departing from the invention may include a support portion (Fig 4 – 51) extending between the shoulders of the first and second chain receiving portions. This support could also carry an orifice for hooking on the chain guide to its chain hoist, particularly in the case of an ‘open’ hoist (without casing).

The chain guide of the invention can also be installed on various types of systems using a chain pulley. For example, the steel guiding plates of a conventional chain hoist can be replaced and provided with a chain guide. The chain guide can also be fitted to other chain hoists, whether open or closed.

The chain hoist and corresponding parts are preferably made of substantially rigid material such as metals (steel, etc), hardened polymers and composite materials, whereas the chain guide may be made of other polymeric material including the nylon previously mentioned. This aids the required deformation and twisting to allow the passage of knots. If there are knots of greater dimensions, which cannot physically pass through the chain hoist, the chain guide is designed to resists resultant impacts, with any necessary deformation, until the necessary inspections and repairs are made.

About the patent

This article is an edited version of WIPO international patent WO/2007/065267, published on June 14 2007, and includes provisional US patent application 60/748,173 filed on December 8 2006. The patent is assigned to Canisco Inc of Drummondville, Quebec, Canada and is attributed to five inventors: Michel Beaudoin, Director of the Torque Force Division of Canisco, Pierre-Louis Foucault, Richard Tremblay, Vincent Roy and Hélène Robert. The invention is also the subject of US patent application no. 2007014539, published on June 28 2007.


This article is an edited version of the patent and may omit legally or technically important text. To see the full patent go to


The patent assignee, Canisco Inc., is a Canadian-based international OEM manufacturer of specialised hardware components for industrial door and access system manufacturers. The chain guide facility of the invention will be available as part of its wide product range. In addition to the Torque Force Division responsible for the invention and other garage door hardware, there are also Mechanical Power Transmission and Fluid Power divisions. Other products of the Torque Force Division include cable drums, rollers, bearings, locking components and security devices. In 2005 Canimex acquired Manaras, a leading manufacturer of commercial and industrial door operators, controls and accessories.

Fig 4 – A perspective view of a chain hoist in another embodiment of the invention showing a support portion for the chain guide Fig 4 Fig 1 – An exploded view of the components of the chain hoist and chain guide according to the preferred embodiment of the invention Fig 1 Fig 2 – A perspective view of a chain hoist, chain and chain guide as for Fig 1 Fig 2 Fig 3 – A perspective view of the chain guide alone Fig 3