Karman Vibrating Screens offer one of the largest ranges of Vibrating Screens,
which is the result of of sound engineering principles applied. 24 years of practical experience in the South African as well as world wide Materials Handling Industry.

Karman Vibrating have developed and designed a wide range of vibrating screens. This provides the user the best screen for the duty.

• Sizing - Washing
• Drain and Rinse
• Feed Prep.
• Dewatering
• Vibrator Motor Drive Units
• Single and Double Deck Units
• Poly - Wovenwire Wedge Wire Decks

• Robust steel construction with minimum of moving parts for ease and low maintenance single vibratory motor drive, no belts or shafts.
• Long periods between servicing.
• Single and multi-deck arrangements.
• Capacity up to 300 tph at low power use
• Vibrator motor can run
  • flow/contra-flow,
  • Tri-directional screen action for positive and effective screening.
• Choice of screen cloths can be employed.
  • woven wire,
  • poly panels
  • or perforated plate.
• Imaginative design makes for easy replacement of screen cloths with minimum down time.
• Screen mounted on steel coil isolation springs design to give very high degree of isolation of vibration to surrounding structures.
• Screen may be installed at angle of decline between 10 and 20 degrees.

Karman Sub-Resonant Vibrating Screens

• Two Mass...
• Sub Resonant...
• Natural Frequency...
• Long Stroke...
• Low Frequency...
• Electro Mechanical...
• Low Power Consumption...

Karman, SR (Sub-Resonant) vibrating "Screeder" is a combination of a vibrating screen and a vibrating feeder. The Karman Screeder can work under a hopper load thus controlling the material onto the screening surface. In some cases except for "Dewatering" the underpan can be part of the Screeder therefor a cost saving in plant design as well as space saving.

• Two mass...
• Sub Resonant...
• Natural frequency...
• Electro Mechanical
  ... Vibratory Feeder,

producing a long stroke at low frequencies, thus feeding higher feed rates than comparable trough widths found in competitive Feeders.

In the design of a natural frequency mechanical Feeder, 2 masses are considered, trough and excitor, connected by means of of a set of steel coil drive springs. A centrifugal force is created by a vibratory motor and this force is magnified by the drive springs causing the trough to vibrate at a long stroke .

The major consideration in a natural frequency Feeder is whether to tune above or below resonance and how close to tune to resonance. Equally important are considerations of Hopper design and material head-load, as well as the control of the feed rate.

Natural Frequency (NF)
Defining natural frequency on the system, which consists of 2 masses and a spring, is that frequency at which the system will tend to vibrate - once initiated - without stimulation from an external force. All systems will eventually stop vibrating, even when stimulated at their calculated natural frequency due to inherent dampening.

It is also interesting to note that dampening factor has an influence on power consumed by or required, to operate a vibratory system. The higher the dampening factor the more energy or kW required to operate the system.

The Karman Feeder will not dampen under head-load because of the engineered sub-sesonant design, consider that W1 is subjected to a head-load, which will cause an apparent mass increase and corresponding reduction in system natural frequency to have some significance, we must simultaneously understand MAGNIFICATION FACTOR.

Magnification Factor (MF)
Is the concept whereby a force can be applied to 1 member of a vibrating mechanism and magnified through a spring system to another member. In a Karman Feeder, the force is created by the vibrator motor with eccentric masses and is applied to the excitor at the some constant frequency - the motor speed. The force is then magnified, through the drive springs, to cause the trough to vibrate. The sizes of the magnification factor is dependent on the closeness of running speed to natural frequency.

Brute Force Mechanical Vibratory Feeders
The electro-motive drive is older than the magnetic drive for vibrating equipment especially for screens but vibrating feeders require variable feed rate and this was not possible in the early years. There are several other alternative is the systems in use, such as -gear units, eccentric shafts, cranks, etc. The other alternative is the use of the vibrating motor as the unbalanced drive - since we are discussing vibrating feeders which Must have a Linear Stroke Vibration and therefore using a single vibrating unit one cannot achieve a True Linear Stroke . An unbalanced motor exerts a circular rotating force upon its support over its bearings by circulating masses.

A simple method to achieve a Linear Stroke is to use two unbalanced motors and run them in Opposite Directions of rotations. The two induction motors synchronise themselves automatically on the bases of mass effect principles. As with magnetic drive, the unbalanced motors are arranged in such a way that is direct upwards at a selected angle of attack