Overview of Vibratory Feeders

A vibratory feeder is a conveying system designed to deliver components or materials into an assembly process through controlled vibratory forces, gravity, and guiding mechanisms that ensure proper positioning and orientation. The system features accumulation tracks of various widths, lengths, and depths, which are specifically selected to match the requirements of the application, material, component, or part.

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The goal of vibratory feeders is to move, feed, and convey bulk materials using various forms of vibrations to ensure proper orientation for integration into a production line. With my extensive experience in the industry, I have found that vibratory feeders greatly enhance efficiency during assembly operations while gently separating bulk materials. The guided movement produced by a vibratory feeder relies on horizontal and vertical accelerations, which generate the precise amount of force needed to position materials accurately.

The accumulation track of a vibratory feeder, whether linear or gravity-based, helps slow the vibrations and aids in directing the movement of materials. Drive units, which can be piezoelectric, electromagnetic, or pneumatic motors, provide the vibrations, rotation, and necessary force to ensure the feeder operates efficiently.

The design of a vibratory feeder starts with a transporting trough or platform, where materials are moved by controlled linear vibrations. These vibrations create jumping, hopping, and tossing motions of the materials. The speed at which materials travel can range from a few feet per minute to over 100 feet (30 meters) per minute, depending on design features such as frequency, amplitude, and the slope angle of the trough or platform.

Vibratory feeders control material flow similarly to how orifices or valves control fluid flow, allowing adjustments to feed bulk materials at a consistent rate. The structure of a vibratory feeder typically includes soft springs that manage vibrations and capacities, supporting the handling of bulk materials from mere pounds to several tons per hour.

One distinct benefit of vibratory feeders is their proficiency in preventing bridging, a common issue that can slow down processes and inhibit efficient material flow. The free-flow design in the throat of a vibratory feeder minimizes bridging caused by friction. The forces that ensure smooth and even material flow fall under two categories: direct force, which applies energy directly to the feeder's deck, and indirect force, which utilizes resonant or natural frequencies to achieve desired material movement.

Recent designs of vibratory feeders frequently feature enclosed, box-shaped constructions with flanged inlets and outlets, enhancing their ability to contain dust and prevent water ingress. This design modification not only helps eliminate spillage but also streamlines installation processes. Additionally, some enclosed models incorporate a vibrating bin bottom activator with the vibratory feeder to further control material flow and improve efficiency.

Chapter 2: Overview of Bulk Material Handling

Bulk materials are dry solids available in powder, granular, or particle forms and commonly grouped randomly to form a bulk. Their behavior greatly varies depending on factors such as temperature, humidity, and time, influencing their flow properties. Unlike liquids and gases, bulk materials have a challenging flow. Handling these materials can lead to erosion and impingement, potentially degrading conveying and handling equipment.

When handling bulk materials, understanding their properties becomes crucial, as outlined below. These properties are critical for the proper design of bulk handling equipment.

• Adhesion: The tendency of a material to stick or cling to another. During gravimetric discharge, materials may bridge or cake, disrupting flow.
• Cohesion: This refers to the material's ability to adhere to similar chemical composition materials, making flow challenging for cohesive materials.
• Angle of Repose: The angle made by the lateral side of a cone-shaped pile with the horizontal, indicating material's flow freeness.
• Angle of Fall: This is the angle made with the horizontal after applying external force to collapse the cone formed by poured bulk material.
• Angle of Difference: Represents the difference between the angle of repose and the angle of fall, with a larger angle aiding free flow.
• Angle of Slide: The angle formed by the surface with the horizontal, indicating flow characteristics of materials.
• Angle of Spatula: Measured by inserting a spatula into material and lifting it for maximum coverage. This is the average angle formed with the horizontal.
• Compressibility: Defined as the percentage difference between packed and aerated density, describing material size, uniformity, deformability, and moisture content.
• Bulk Density: Mass of the material per unit volume, critical for assessing equipment capacity and the compressive strength of bulk materials.
• Particle Size: The average dimension across a single particle, affecting flow characteristics.
• Moisture Content: The amount of water distributed throughout the bulk material, impacting adhesion and cohesion.
• Hygroscopicity: The tendency of materials to absorb moisture, necessitating equipment design to prevent moisture ingress.
• Static Charge: Continuous contact between particles and container walls may cause static charge buildup, reducing flow.
• Abrasion: The material’s ability to wear the surface of handling equipment, requiring abrasion-resistant materials.

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Chapter 3: Working Principles of Vibratory Feeders

The general design of a vibratory feeder includes a drive unit that generates the vibratory action and a deep channel, or trough, that holds the bulk material. The drive unit produces vibrations with both horizontal and vertical force components. When the vibration is sinusoidal and the force components are in-phase, the resulting motion is straight-line. In addition to the drive unit and trough, a vibratory feeder comprises the following parts:

• Feed End: This is the part of the trough located at the most upstream end where the material is fed.
• Discharge End: Opposite the feed end is the discharge end, located at the most downstream part of the trough, where material is ejected.
• Eccentric Weight: A weight attached to the shaft or flywheel, slightly offset from the axis of rotation, creating oscillations as the shaft rotates.
• Reactor Springs: These springs in the vibrating system continuously store and release energy during operation.
• Isolation Springs: Supporting the feeder while protecting the structure from vibrations.
• Tuning Springs: Used to tune the frequency of a feeder by modifying the spring rate.
• Dynamic Balancer: A dynamic balancer that reduces transmitted forces to the supporting structure.
• Liner: Added materials to the trough surface resisting wear, managing heat, reducing noise and friction.
• Screen: Used to separate coarse from fine particles.
• Grizzly: A heavy-duty screen consisting of bars for screening coarser materials.

Vibratory feeders and conveyors typically operate at frequencies ranging from 200 to 1000 vibrations per minute with amplitudes between 1 to 40 mm. The vertical acceleration component generally matches gravitational acceleration (9.81 m/s²), providing gentle shuffling motion that reduces impact and noise, enabling smooth material movement across the trough through sliding action. The materials typically remain in contact with the trough surface, minimizing pressure between the surface and the material. Additional measures may be needed in cases where the material must lift from the trough and fall back down, aiming to manage impact forces and minimize noise levels.

Vibratory feeders differ from other bulk material handling equipment as material moves independently of the conveying medium, unlike conveyor belts where material stays fixed. This unique feature allows various processes to occur during transit. Below are some processes executable during transport with vibratory feeders.

• Scalping
• Screening
• Sorting
• Distributing
• Cooling
• Drying
• Dewatering
• Water Quenching

Other reasons for vibratory feeders' preference include:

Low Headroom Requirement: Ideal for installations with limited vertical clearance, vibratory feeders provide effective gravimetric feeding and the horizontal movement of bulk products.

Handling of Hot Materials: Configured to reduce lift during the oscillation cycle, these feeders allow cooling air circulation while minimizing contact and heat buildup.

Handling Abrasive Materials: By reducing contact with materials, vibration decreases while abrasion-resistant linings enhance durability.

Inherent Self-Cleaning Properties: Due to non-static material, accumulation on the trough's surface is discouraged.

Adherence to Sanitation Requirements: Constructed without cavities or holes, the trough is suitable for food applications by promoting easy cleanup.

Water and Dust Tight: Designed with IP or NEMA-rated covers to prevent water and dust ingress.

No Moving Parts for Material Impingement: Continuous channel designs minimize interruptions, enhancing reliability and making vibratory feeders extensively used in various industries including mining, recycling, food processing, and pharmaceuticals.

Chapter 4: Types of Vibratory Feeders

Vibratory feeders can be classified based on their drive unit, vibration application method, and reactions generated by the supporting structures. It's essential to understand these distinctions during selection. For example, specifying only brute force vibratory feeders is insufficient, as various drive units like electromagnetic or electromechanical exist. This chapter details the working principles for each type and their appropriate applications.

Listed below are vibratory feeders classified by their drive unit:

Vibratory Feeders by Drive Unit

Electromechanical Vibratory Feeders

These feeders create vibrations through rotating eccentric weights with electric motors, known as eccentric-mass mechanical feeders.

Electromagnetic Vibratory Feeders

Using cyclic energization of electromagnets, electromagnetic feeders possess fewer moving parts, providing cost-effectiveness for low-volume applications.

Hydraulic and Pneumatic Vibratory Feeders

Beneficial in hazardous areas, these utilize hydraulic or pneumatic oscillating pistons, with motors kept remote to reduce costly explosion-proof specifications.

Direct Vibratory Feeders

Employing a crank and connecting rod for low-frequency oscillations, these feeders transmit substantial vibrations to their supporting structures making their infrequent use necessary.

Vibratory feeders are also classified by how they apply vibration to the trough, varying in spring configurations, frequency, and amplitude of drive units.

Brute Force Feeders

Known as single-mass systems, brute force feeders connect the vibratory drive directly to the trough assembly and mainly cater to heavy-duty applications. While they can be electromagnetic, electromechanical drives are more common.

Centrifugal Feeders

Centrifugal feeders utilize a spinning bowl to advance parts towards the outer edge. They are common in industries requiring rapid handling of uniquely shaped components.

Natural Frequency Feeders

Tuned feeders leverage two or more spring-connected masses, utilizing resonance conditions to amplify oscillations for minimal excitation force.

Vibratory feeders are categorized based on supporting structure reactions. Choosing the right type depends on the structure's rigidity and allowable stress.

Vibratory Feeders by Supporting Structures

Unbalanced Vibratory Feeders

Generates oscillations subjecting structures to reversing load conditions. It is crucial that they install on structures with substantial deformation allowances.

Balanced Vibratory Feeders

These feeders feature dynamic balancing systems to minimize forces transmitted to supporting structures, ideal for less rigid installations.

Horizontal Motion Conveyors

Horizontal motion conveyors convey free-flowing bulk materials using a two-cycle motion, providing smooth transport at varied speeds up to 40 feet per minute.

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This type allows the components to smoothly travel within the confines of the conveyor design while retaining stability.

Chapter 5: Feeder Trough Design

The capacity of a vibrating feeder is determined by several factors including the trough width, depth of material flow, bulk density, and the linear feed rate. This can be expressed using the formula:

C = WdR /

In this formula, C represents the capacity in tons per hour, W denotes the trough width in inches, d is the depth of material in inches, and R indicates the linear feed rate in feet per minute. Charts, tables, and graphs that manufacturers offer highlight different specifications and performance characteristics.

Feeder troughs generally consist of construction materials like mild steel, grade 304 stainless steel, or abrasion-resistant alloys. Ordinary steels may also be lined with rubber, plastic, or ceramics. Various trough shapes include:

• Flat Bottom
• Half Round Bottom
• Radius Bottom
• V Shape
• Tubular

• Grizzly Section
• Dust and water-tight sealing and cover
• Belt-centering Discharge
• Diagonal Discharge
• Screen Decks
• Water-jacketed

Chapter 6: Vibratory Bowl Feeders

These feeders employ troughs wound in a helical pattern, utilizing vibrations to shuffle and advance materials along a gently inclined surface, ensuring proper orientation of irregularly shaped parts.

Vibratory bowl feeders present numerous advantages like efficient conveying and accurate positioning of parts, commonly employed in assembly and packaging lines across various industries.

Conclusion

• Vibratory feeders operate as short conveyors, moving bulk materials through controlled vibratory forces and gravity.
• Bulk materials can be dry solids in varied forms, grouped randomly, that don't flow as easily or predictably as liquids and gases.
• The fundamental design includes a drive unit generating the vibratory action and a trough to contain bulk contents.
• Classifications include feeder types based on their drive unit, application vibration method, and supporting structural reactions.
• Vibratory bowl feeders represent specialized types designed for precise item orientation in feeding applications.