Retrofittable Motorized Actuator for Wand-Operated Blinds

Wand-Operated Horizontal Blinds are Ideal Targets for Retrofit Automation Products

Automation devices for horizontal blinds are poised to become the hottest products in the automated shading market. This especially true of retrofit automation products for wand-operated horizontal blinds, which have an installed base of more than 380 million units in the U.S. alone. In addition to this huge installed base, wand-operated blinds are ideal targets for retrofit automation for at least three reasons:

• The horizontal blind’s slat-tilt function offers a degree of daylight control unmatched by other shading devices: it can fully block direct sunlight while still admitting substantial diffuse daylight. No other type of shading device can do that—not even the most advanced Smart Windows.
• Only a small motor is needed to automate the slat-tilt function of even a large horizontal blind.  This minimizes cost and facilitates battery or solar-powered operation.
• While all types of venetian blinds can be motorized with a motor mounted inside the blind’s headrail, wand-operated blinds can also be motorized externally by replacing the wand with a motorized module.  External motorization is less expensive and far easier to install than internal motorization, which makes it ideal for retrofit applications (especially for the direct-to-consumer residential market).

As a result, external motorization products for wand-operated blinds are potentially capable of achieving deeper market penetration (especially in the U.S.) than retrofit automation products for any other type of window covering.

Challenges in Exploiting the Full Market Potential of Retrofit Blind Automation

A key challenge in exploiting the full market potential of external motorization products for wand-operated blinds is the huge variety in blind design, including:

• the size of the headrail;
• the point on the headrail at which the tilt-control shaft protrudes;
• the length and inclination of the tilt-control shaft; and
• the configuration of the eye at the end of the tilt-control shaft where the control wand is attached.

For example, the following figure is a cross-sectional view of the headrails of 12 blinds, showing the variation in the position and orientation of the tilt-control shafts and the sizes of the shaft “eyes” (some of which are in the form of removable hooks, and some of which are integral with the shafts).

However, variation in blind design isn’t the only issue.  To penetrate the mainstream market, such a product must also be inexpensive to manufacture, easy to install, visually unobtrusive (or at least reasonably attractive), and amenable to easy integration of batteries, sensors, switches, and other  components.

Conventional Approaches

Due to the variety in blind design, there are only a finite number of practical mechanical configurations for an external motorization product that can achieve broad compatibility with wand-operated blinds.  In fact, currently available products use just three configurations:

• Wall-mounted motor box with flexible drive shaft coupled to the blind’s tilt-control shaft. This offers a simple mechanical design that’s easy to manufacture, but the need for wall-mounting and relatively poor aesthetics are deal-breakers for some potential purchasers.
• Motorized wand to replace the blind’s original manually-operated control wand. This is the easiest of the conventional configurations to install and it has the simplest and least expensive mechanical design, but also suffers from five disadvantages:
  • There is significant backlash in the hook-style coupling between the motor shaft and the blind’s tilt-control shaft, causing imprecision when tilting the slats to specific settings.
  • The rotating parts are exposed, compromising aesthetics.
  • The hook-style coupling can induce forces that cause the assembly to visibly sway while the motor is rotating.
  • The lifetime of the blind’s tilt-control mechanism is potentially reduced because the product’s entire weight is supported by the tilt-control shaft.
  • The tubular wand form-factor can hamper integration of certain electronic components.
• Headrail-mounted motor box with a rotating collar to engage the blind’s original control wand. Unlike the other configurations, this allows the slats to be tilted manually if the motor is inoperative. However, it has the same backlash issues as the motorized wand configuration and the most complex mechanical design.

Our Approach

Our approach to external motorization of wand-operated blinds uses a motor assembly which is magnetically held to a ferrous plate mounted perpendicularly to the front face of the headrail. The magnetic attachment allows the motor assembly to be slid in two dimensions along the plate and rotated on an axis perpendicular to the plate, providing the three degrees of freedom necessary to mate with the tilt shaft of virtually any wand-operated blind. The approach is shown below in use on our IntelliBlind™ Smart Miniblind Actuator:

Also covered in the patent is the use of a cup magnet to concentrate the magnetic flux toward the plate, reducing the required magnet size and allowing the use of a Hall-effect position-feedback sensor on the gear-motor.

Advantages

Our external motorization technology can be used with any wand-operated blind, regardless of size or design (although any decorative headrail valance, if present, must be removed first). It also provides several other key advantages beyond broad compatibility:

• The floating magnetic motor mount enables a simple mechanical configuration, minimizing costs and facilitating manufacturing, assembly, and installation.
• Unlike the motorized-wand or rotating-collar configurations, our approach allows all of the moving parts to be concealed behind a housing, enhancing product aesthetics.
• Because the magnetic motor mount supports the full weight of the motor assembly, it doesn’t put any weight on the blind’s tilt-control shaft (as does the motorized-wand configuration), prolonging the life of the blind’s tilter mechanism.
• Unlike the motorized-wand or rotating-collar configurations, there is no backlash in the coupling between the gear-motor shaft and the blind’s tilt-control shaft, increasing the accuracy with which the slats can be tilted to predetermined settings.
• Unlike the motorized-wand configuration, the magnetic motor mount allows the chassis to be mounted rigidly to the headrail (e.g. with a magnet), eliminating any perceptible oscillation of the product during motor operation. Rigid mounting also enables the use of a control wand as a convenient auxiliary user interface when a smartphone isn’t handy.
• The magnetic motor mount enables a form-factor which is very amenable to integration of components such as sensors, RF transceivers, batteries, and our patent-pending rear-facing photovoltaic panel.

Applications

Our motorization technology is potentially applicable to any retrofit motorization device for wand-operated blinds.  Our IntelliBlind™ reference design is an example of a product concept which fully leverages the technology’s advantages: