Conceived, Engineered, and Born, in 1966 by Frank S. Hyer at Thayer Scale, Pembroke, MA, this unconventional belt scale design has steadily matured over more than 4 decades to become one of the most trusted “Belt Scales” in the world. The scale’s appearance is distinguishable from all others as it represents a fundamental departure from conventional design.
The first industrial user of this scale, designated Model RF-1, was the Davison Chemical Division of W.R. Grace, at Bartow, FL. The sales order, SO No. 1413, was entered on September 9, 1966.
The design is so unique that a patent was awarded covering the basic suspension system which incorporates “Rocking Flexure” pivots that provides both frictionless hinging of the suspension elements and also serves as lateral stabilization elements in lieu of the usual “stay rods”. A cable suspended secondary lever provides means for mass counterbalancing of dead loads and isolates the load cell from the effects of foundation distortion, which is a fundamental cause of zero shifting in directly coupled systems.
Mr. Hyer continually improved his basic design over the years by introducing new mechanical features that further distinguished his design from all others.
In 1968 while engineering a heavily loaded system for Bethlehem Steel at Burns Harbor (SO No. 1550), Mr. Hyer introduced what he refers to as the “Movable Poise Method” of applying simulated test loads. Because the test load remains on board during both normal operation and during calibration, the difference in lateral restraining forces on inclined conveyors caused by adding weight only during calibration is eliminated altogether. Also, through proper placement locations of the test weight, it can serve as both mass counterbalancing and the simulated test load.
On September 9-11, 1969 Mr. Hyer, during a lecture at the National Bureau of Standards in Gaitherburg, Maryland, presented his derivation of the “belt stretch” error which was later incorporated in a popular text (Weighing and Proportioning of Bulk Solids) written by one of the attendees to his lecture:
%Error = -100(Tr – Tc)/EA
Additionally, during his series of lectures, he presented a slide show of diagrams illustrating his preferred application guidelines, which can today still be viewed on the NISA (National Industrial Scale Association) web site under the topic heading Belt Scales. On July 2, 1970, THAYER Model RF Belt Conveyor Scales received the first OWM certificate No. 51 from the National Bureau of Standards certifying conformance to the technical requirements of NBS Handbook 44, Specifications, Tolerances, and Other Technical Requirements for Commercial Weighing and Measuring Devices.
It was in 1977, under Sales Order No. 3430A, that Mr. Hyer put many of his ideas to work in providing U.S. Steel in Corbin, KY with a 6 idler version of the RF Belt Scale for meeting an accuracy requirement of ± 0.125%. Performance was repeatedly confirmed by the L & N Railroad over a span of 4 years with no need to change the original K-factor. This particular scale utilized Mr. Hyer’s “Movable Poise” method of providing a simulated test load as well as a totally newly configured Belt Speed Pickup Assembly which used an elastomeric compression hinge to permit the measuring wheel to accurately “steer” itself in the direction of belt movement and an adjustable compression spring mounted between the hinge and the wheel to maintain uniform contact pressure with the belt.
The entire line of Thayer model RF belt scales were fabricated and marketed in South Africa from 1981 to 1990. On June 18, 1981 Mr. Hyer and Mr. D. Gilmore, V.P., Sales & Marketing, Hyer Industries, Inc entered into agreement with J.G. Barnard, Managing Director of Automation Limited, Randburg, South Africa for bringing the entire RF line of belt scales to the south African market. This included a Confidentiality agreement that allowed Process Automation to exclusively manufacturer or have manufactured the complete line of RF Belt Scale weigh bridges from proprietary manufacturing drawings. This was done in recognition of the high freight cost involved in shipping from the USA. However, on October 5, 1990, under competitive pressures, Mr. Barnard made the decision to give up the Thayer agency and join the local group of manufacturers.
By 1990, Thayer Scale had installed a total of 75 six idler scale’s of similar design, with 71 requiring certification for commercial use by the various weighing bureaus (Eastern Weighing & Inspection bureau, Western Weighing & Inspection Bureau, Southern Weighing & Inspection bureau.) All 71 were successful in achieving repeat certifications.
Today, Thayer Scale continues to manufacture its model RF Series of Belt Scales, including 1, 2, 3, 4, and 6 idler versions. The 4 and 6 idler designs are NTEP certified for commercial weighing use.