Slipstick horizontal-motion conveyors can be configured in lengths up to 200 ft.
The earliest known roots of today’s horizontal-motion conveyor can be traced back to equipment used in the mining industry almost 100 years ago. Also known as differential-motion conveyors, machines of this type were manufactured by Overstrom & Sons Co., which was later acquired by Sutton, Steele & Steele and which later became Triple/S Dynamics in the 1930s.
Early differential drives were complicated mechanisms involving cams, gears, and rotating elements. All components were assembled in a drive that generated slow-advance/quick-return motion, which is the basis of true horizontal-motion conveying.
The early differential-drive units all but vanished in the mid-20th century, partially because of their inherent mechanical complexity. In addition, the significant unbalanced forces generated by these drives contributed to durability problems.
In 1974, Triple/S Dynamics developed a drive that employed rotating unbalances to deliver the same differential motion as the early units. Now, however, the drive design also provided both mechanical simplicity and inertial balance. When attached to a horizontal trough, this new drive could be used to convey material from several feet to more than 200 ft. With the availability of a dependable drive design, many new applications for horizontal-motion conveyors have been developed over the past 30 years.
Advantages of Horizontal-Motion Conveying
The key to horizontal-motion conveying is the action of the conveyor on the inertia of the conveyed material. During the slow advance of the cycle, material is at relative rest on the conveying surface. The quick return segment of the cycle slides the conveying surface under the material bed. Repeating this cycle 200 to 300 times per minute conveys the material up to 40 ft/min along the length of the conveying surface.
The horizontal-motion conveyor offers a number of advantages over the conventional vibrating conveyors, screw conveyors, and drag conveyors that are often used in bulk-handling applications. Compared with conventional vibrating conveyors, which are usually powered by springs and convey material through impact, the horizontal-motion conveyor provides gentle and sanitary transportation of fragile materials such as food products, agglomerated powders, and extruded, flaked, or pelletized products.
Lacking chains, screws, sprockets, rollers, or other moving parts, the Slipstick horizontal-motion conveyor has a clean design that increases personnel safety.
At the same time, the horizontal-motion conveyor offers a higher level of mechanical simplicity than either screw or drag conveyors. The result is a durable conveying system that requires less maintenance. In addition, the horizontal-motion conveyor has no chains, screws, sprockets, rollers, idlers, or other moving parts outside of the sealed and guarded drive unit, making it intrinsically safer for operating and maintenance personnel.
The gentle conveying of the horizontal-motion conveyor is also suitable for materials that require handling without compaction or segregation. An unintended consequence of conventional material-conveying systems is product variability, which results from the migration of fine particles in the product stream. The “en masse” conveying provided by horizontal motion ensures that material will be delivered as originally mixed and that fine particles will remain evenly distributed throughout the product bed.
Design and operational flexibility are additional benefits of horizontal-motion conveyors. Lacking springs or counterweights, these conveyors do not require tuning, unlike conventional vibrating conveyors.
Finally, without any moving parts outside of a self-contained drive unit, the horizontal-motion conveyor is virtually maintenance-free. Given its relatively slow rotational speed, the typical drive unit usually provides 10 years or more of service between maintenance intervals. It merely requires periodic lubrication.
Versatility: A Key Characteristic
The horizontal-motion conveyor may be completely sealed and equipped with self-sealing intermediate discharge gates, which provides for safe, dust-free operation even in applications calling for multiple intermediate discharge locations. Since the horizontal-motion conveyor has no moving parts that make contact with the conveyed material, it is often preferred for handling caustic or abrasive materials. The conveyor is self-cleaning—a significant benefit in applications in which more than one material is handled.
Horizontal-motion conveyors may be either base mounted or suspended from above. Conveying surfaces can be made of carbon steel, stainless steel, abrasion-resistant steel, polyethylene plastic, or titanium. Single-drive units large enough to power an 8 × 6 × 150-ft long conveyor trough are available. These drives can be positioned at either end of the conveyor, or they can be mounted above or below it. In addition, the conveyors can be operated at variable speeds, and their conveying direction is reversible.
A Broad Range of Conveying Applications
Based on its many advantages, the horizontal-motion conveyor is finding increasing application in powder and bulk materials handling systems. Applications drawing on the special attributes of the horizontal-motion conveyor include:
• Carbon black—The system’s gentle conveying motion reduces fines attrition of the product, while the self-scrubbing action retards the accumulation of sticky materials to the contact surfaces of the conveyor.
• Crushed ores—Abrasion resistance, large-volume capabilities, plus dust containment, make horizontal-motion conveyors a practical choice for this demanding application.
• High-temperature materials—With no springs, the horizontal-motion conveyor can operate in a wide range of extreme temperatures. In certain applications, air or water cooling can be used to handle materials up to 17,000°F.
• Pharmaceuticals—The inherently sanitary design of horizontal-motion conveyors makes them suitable for the most demanding sanitary and cleanability requirements.
• Hazardous or toxic materials—The superior seal-tightness of a completely enclosed horizontal-motion tube conveyor provides total isolation of the conveyed material from the environment.
Durable, effective, easy to maintain, safe, clean, and applicable to a wide range of bulk-handling uses, the horizontal-motion conveyor has long been a valuable tool in transporting even the most difficult bulk materials. As knowledge of its benefits and proven track record spreads within the industry, many more uses will be found for this conveyor design.
Jay Sullivan is the president of Triple/S Dynamics (Dallas, TX), a manufacturer of specialized conveying and material separation equipment for the food, chemical, agricultural, mining, recycling, and related materials-processing industries. He can be reached at 800-527-2116 or [email protected].