Thayer Scale’s range of Loss-in-Weight screw feeders are designed for precise and reliable feeding of cohesive, easily aerated and difficult to control powders.
- Handle a wide range of material bulk densities at low to medium feed rates.
- Patented “compound flight” feed screw design works in conjunction with patented “U-trough” feed chamber to eliminate common problems associated with feeding powders such as screw starvation and binding.
- Patented Force Measurement Suspension System (FMSS) mass counterbalanced, electronic weigh scale features high precision measurement, exceptional durability and excellent long-term stability. Scale system weighs only the material, not the feeder, for minute-to-minute accuracy and sensitivity. The systems are designed to assure uniform, non-pulsating accurate feeding of a wide range of materials, from free-flowing to friable to cohesive.
- Exclusive Powder Feeder Technology.
- Patented “U-trough” feed chamber with independently driven agitator assures precise, reliable material delivery to the feed screw. Eliminates material build-up, controls material aeration and delivers a steady constant flow of material.
- Optional (patented) “compound flight” feed screw can be used with most materials to downwardly extend the operating range of the feeder by a factor of 10 (typically).
- Fast and easy to clean.
- Thayer Scale’s screw feeders are designed for fast, easy and thorough cleanout. Feeders completely disassemble in less than one minute. High-quality, rugged, stainless steel construction assures years of reliable, trouble-free operation even in the most severe industrial environments.
Weight Measurement System
The heart of any gravimetric feeder is its scale system. Thayer Scale’s feeders incorporate a unique flexure suspension scale designed exclusively for use on Loss-In-Weight Feeders:
- High efficiency “dead load” counterbalancing
- Non-tilting platform design
- Tolerant of shocks and overloads
- Mechanical force “summing” to a single load sensor
- Full range sensor utilization = maximized resolution
- Low mechanical resonance frequency
Flexure plate system eliminates all wearing parts, such as bearings, pivots and knife edges and is not susceptible to vibration. The flexure suspension system transfers all loading forces to a single load transducer, accurately measuring load regardless of load position. Most platform scales are not designed to be immune to side loading and/or torsional loading caused by the plant environment and the movement of the feed screw, agitator, etc. These factors can cause poor accuracy and poor calibration stability. Thayer Scale’s flexure system cancels all horizontal force vectors and allows heavy tare loads (weight of feeder and hopper) to be completely mass counterbalanced, permitting load cell sizing based on net rather than gross weight.
- Accurately measures load regardless of load position.
- Immune to support structure deflections and process vibrations.
- Inherently self-aligning to gravity.
- Nulls out heavy tare loads.
- 1,000% overload capacity.
- Scale may be suspended from above or supported below.
- Immune to shock or impact loads.
- Easily accessible load cell can be accessed without removing the feeder.
Two Types Load Cells to Choose From
LVDT Load Cell
The Thayer Scale LVDT Load Cell was developed as the ideal adjunct to Thayer Scale’s “reverse-action” Force Measurement Suspension System. It is a precision and extremely durable “tension-style” force transducer manufactured in a fine series of force ranges to produce scale capacities from 10 to 500 lbs. depending on the application. The LVDT is the ideal load cell for “light loading” applications where mechanical tare loads represent as much as 10 to 40 times the net material load and provides unparalleled overload protection at 1000% of rated output.
Strain Gauge Load Cell
The Strain Gauge Load Cell is available in force ranges from 25 to 500 lbs. with an overload protection of 300% of rated output.
Thayer Scale Patented Powder Feeder
Proven ability to feed difficult powders.
Thayer Scale’s Powder Feeders control both flooding and clogging problems associated with difficult-to-handle powders. They are deep tear-drop “U” trough screw feeders, featuring a dual wound horizontal agitator that moves material away from both front and back walls of the conditioning chamber above. The deepness of the trough assures that the screw is completely submerged in “quiet” material, free of the usual surface disturbances arising from the turning agitator above. This, along with an inherently larger trough “wrap-around” angle, provides for complete and efficient filling of each flight. The tear- drop shape of the trough is tapered in the direction of flow so as to relieve dynamic compaction forces as each flight advances toward the feed-tube entrance. This helps to maintain a more uniform material density throughout. Another advantage of the deep-trough design is that it is less susceptible to transient overfeeding that accompanies hopper refilling.
Patented system that assures reliable metering
The patented Thayer Scale “U-Trough” hopper and feed section provide the first practical and economical means for metering difficult powders. The geometry of the trough and agitator effectively de-aerate and contain the powder on initial fill to help prevent flooding. Independently driven agitator maintains optimum material conditioning while screw speed can vary to control flow rate. The material does not build up within the trough or within the continuous screw tube, preventing blinding or erratic feed. The combination of unique features provides the most reliable and accurate feed system for difficult powders.
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