Sign up for the Design News Daily newsletter.
Pull cord makes winches simpler, safer
March 1, 1999
6 Min Read
Houston, TX--Imagine starting your lawn mower with a handcrank instead of a pull cord. Unless you have arms like Arnold Schwarzenegger's, you probably wouldn't have much luck cranking the cold cylinders to life.
That's why so many lawn mowers are equipped with pull cords. Pull cords are simple. They allow users to set their feet and put all their weight behind each pull, then they snap back in place.
Ian Royle noticed the same thing about pull cords. They're simple. Effective. Then he looked at a conventional winch and wondered: "Why not use a pull cord instead of a crank?"
The result of Royle's musings is a patented, multi-speed pull-cord winch, known as the World Winch Works system. The novel system addresses the conventional winch's age-old problem: The use of a crank. The basic problem with cranks, Royle says, is that they don't allow the user to employ his or her power to its best advantage.
The pull cord winch enables users to apply all their body weight in one direction. Conventional crank winches require a series of motions, in which users cannot apply their full power throughout the full 360 degrees .
At best, the crank enables users to reach 100% of their power only when they pull the crank toward themselves. When they push the crank away, or turn it across their bodies--as they must--their mechanical advantage drops to less than 25%. In some cases, it can go as low as 7%, he says. The result: Users strain and struggle through the 360 degrees path. "It's an extremely complex motion," Royle says. "You have to use almost every muscle in your body, and you're straining those muscles as you go from a push to a pull to a sideways motion."
Worse, users sometimes injure themselves in the process. They lose their grip on the crank handle, crashing their hands into nearby objects. Or they lose their grip and fall onto open gears. The unnatural motion can cause muscles strains, particularly back injuries. Some users have also broken wrists while trying to stop the spinning crank handle after release of the load. Worst of all, because the crank positions users directly in front of the winch, they can be struck by the winch hook.
Royle believes that the pull- cord-winch will solve all those problems. Designed in various forms--including multi-speed and infinitely variable hydraulic and mechanical versions--it addresses the problems of cranks by employing a straight line pull of 100%, rather than a 360-degree complex path.
The key to its design is simplicity--not only in its use of a straight line motion, but also in its mechanical operation. In its simplest form, it includes a pull cord, rope drum, gear set, and sprag clutch.
The multi-speed version of the unit pre-selects the load for each pull. When a load is applied to the winch drum, the spring compresses, thus changing the gear ratios via a lever.
It operates by pre-selecting the correct gearing to match the load on the winch's drum. During operation, a user pulls on the cord, imparting a load to the drum. At the end of each pull, a sprag clutch connected between the winch drum and base housing prevents rotation of the drum as the user goes back for the next "bite." Before that next pull begins, however, the load from the prior pull is balanced by a coil spring inside the mechanism--the larger the load, the greater the compression of the spring.
By using the spring to measure the load on the drum, the system can then pre-select the proper gearing for the next pull. To accomplish that, Royle connected the spring to a detent plate and lever. In this way, compression of the spring is directly related, not only to the load, but to the selection of gearing, as well. As the spring is compressed, it changes the angle of the lever, which adjusts the gearing. The sprag clutch then transmits load torque to a gear plate as the gear ratios are changed.
By the time the user is ready for the next pull on the cord, the gearing has already set the mechanical advantage. If, for example, the load on the drum is small, the gearing might be set for a 1:1 ratio--that is, 1 inch of pull on the cord creates 1 inch of pull on the drum. If, however, the load is great, it might set itself for a 25:1 ratio--meaning that 25 inches on the cord yields 1 inch on the drum. In that way, the system can provide a large mechanical advantage for big loads, or it can automatically offer higher speed operation for smaller loads.
Royle has added other features, including an automatic brake that replaces ratchets, providing smooth controlled release and braking, and a safety strain unit. He has created several series, including basic, marine, industrial, and utility. The basic series is designed for vehicles, such as trailers, RVs, and four-wheel drives, for primary winching or as a backup. The marine series includes windlass, sail control deck units, and halyard winches. The industrial series is for hoisting, and the utility version is for home use, including tennis and volleyball nets and car jacks.
All the systems, however, share the same basic advantages. Because users stand clear of the load path while using the winch, it is unlikely that they'll be struck by a winch hook. They're also able to put their full power into each tug, and therefore less likely to strain muscles. "When you put all your weight in one direction, it's much safer and less complex," Royle says. "This winch provides simpler operation for a complex task."
Additional details...Ian Royle, Technology Transfer Int'l, 10323 Huntington Place Dr., Houston, TX 77099; (281) 879-5532 or www.worldwinchworks.com
Four-wheel drive vehicles
You May Also Like
Autonomous Mobile Robots Rule Supplier NewsFeb 23, 2024|6 Slides
The Mercedes Update from Google Maps Adds a Huge Amount of DataFeb 22, 2024|2 Min Read
Industry Voices: The Coming Restrictions on Forever ChemicalsFeb 22, 2024|3 Min Read
Tech Layoffs Persist Despite Positive BLS Jobs ReportFeb 22, 2024|3 Min Read