Patent Description:
Conventional vibratory screeners usually include a screen carrier frame carrying a screen for separation of solid particles. The screen extends horizontally within the screen carrier frame and is vertically supported by the screen carrier frame. A vibratory screener of this type comprising the features of the preamble portion of claim <NUM> is known from <CIT>. This vibratory screener has a vibration means including a conventional electric motor attached to the frame and driving a shaft via a belt. The shaft is positioned in the centre of the frame. At each end of the shaft are mounted eccentric weights which induce an orbital oscillatory vibration to the system when the shaft is rotated at high speed.

Another vibratory screener including a conventional electric motor and belt drive is known from <CIT>.

Further, a vibratory screener including a vibration motor is known from <CIT>.

In another type of vibratory screener, vibration of the screen carrier frame is generated by means of typically two vibration motors which are arranged opposite each other on the outer circumference of the screen carrier frame. One advantage of vibration motors is that these motors can be mounted directly on the screen carrier frame thereby avoiding any additional transmissions, gear trains, couplings and other moving machine parts that require lubrication and therefore may contaminate the environment of the apparatus with lubricants, which can become a critical issue particularly with pharmaceuticals and food processing.

Vibration motors generate vibrations through rotation of eccentric weights mounted on a rotatable shaft. By employing two counter-rotating vibrating motors it is possible to generate directed vibrations. Mounted on the screen carrier frame, the vibration motors generate not only force components in vertical direction, i.e. up and down, but also force components towards and away from each other. In particular the forces towards and away from each other act on the screen carrier frame. That is, with each rotation of the vibration motors, the radial forces tend to widen and compress the screen carrier frame radially. Such breathing may also be observed for a single vibration motor because of the inertial mass of the frame, as well as for higher numbers of vibration motors. The higher screening forces in vertical direction are required, the higher will be the forces acting radially on the screen carrier frame, which results in corresponding breathing and material fatigue of the screen carrier frame. Material fatigue may cause tiny cracks on the frame or on welds.

High stability of the screen carrier frame could be achieved by using thicker materials or hollow profiles for the screen carrier frame.

However, a heavier frame will require more powerful vibration motors for generating vertical screening forces, which in turn results in increased radial forces. In the end, this would imply an extremely heavy construction that will consume much energy under operation.

The use of hollow profiles could reduce weight but is highly problematic for hygienic reasons. During operation of a vibratory screener capillary cracks may occur that do not necessarily impair safe operation. However, germs may flourish in such tiny cracks and invade hollow spaces within the hollow profiles. Since such hollow spaces cannot be reached by disinfectants during cleaning of the apparatus, it is nearly impossible to remove germs once they have invaded such hollow spaces. In the worst case, germs like salmonellae may spread over a full production line while it will even be difficult to identify their source. In pharmaceuticals and food processing, the only option often will be discarding the whole apparatus.

Against this background, the present invention aims at scaling up materials throughput of a vibratory screener whilst providing a lightweight construction and maintaining hight hygienic safety standards.

This technical problem is solved by vibratory screener comprising the features of claim <NUM>.

This results in a lightweight structure so that the apparatus can be driven by relatively small vibration motors. The at least two internal annular disks and inner sleeve reinforce the screen carrier frame in a space between the two vibration motors to thereby reduce breathing of the screen carrier frame and also the risk of capillary crack.

In addition, the construction is free of any encapsulated hollow spaces. The creation of breeding grounds for germs is therefore reliably avoided. All surfaces of the vibratory screener can be conveniently reached for cleaning and disinfection. Openings in the lowermost internal annular disk assure that all sides of the internal annular disks and inner sleeve will be reached be cleaning detergents and disinfectants. The apparatus therefore meets highest hygienic safety standards.

Advantageous embodiments of the invention are indicated in further claims.

In a first embodiment of the invention, the screen carrier frame has a substantially cylindrical shape, thereby avoiding corners and facilitating cleaning and disinfection.

In a further embodiment of the invention, the diameter of the outer circumference of the screen carrier frame is larger than <NUM> so as to allow high throughput of product to be screened.

In yet another embodiment of the invention, the outer rims of the at least two internal annular disks are welded to the inner circumference of the screen carrier frame so as to keep the overall construction very simple.

Further, the inner sleeve may be welded to the inner rims of said two internal annular disks.

In yet another embodiment of the invention, said at least two internal annular disks include a first, second and third internal annular disk, wherein the diameter of the inner rim of the uppermost of said first, second and third internal annular disks is larger than the diameter of the inner rim of the two further internal annular disks.

In yet another embodiment of the invention, a plurality of webs extending inwardly from the inner circumference of the screen carrier frame and perpendicularly to the at least two internal annular disks, said webs being connected to the inner circumference of the screen carrier frame and at least one of said internal annular disks. This may further increase radial stiffness of the screen carrier frame.

In particular, at least two of said webs are arranged in parallel to each other at the inner circumference opposite to one vibration motor on the outer circumference to further increase the radial stiffness of the screen carrier frame especially in the direction of the radial forces generated by the vibration motors.

In yet another embodiment of the invention, each vibration motor has an axis of rotation running in a tangent plane of the outer circumference of the screen carrier frame, the tangent planes of the vibration motors being parallel to each other. By inclining the axis of rotation, it will be possible to adjust the screening forces as required.

Preferably, the axes of rotation in the tangent planes are symmetrically inclined with respect to a vertical axis of the vibratory screener.

In yet another embodiment of the invention, the vibration motors are attached to the outer circumference of the screen carrier frame by brackets, which are secured to the outer circumference of the screen carrier frame. This simplifies adjustment of the orientation of the axes of rotation of the vibration motors.

In yet another embodiment of the invention, the vibratory screener comprises a spring assembly vertically supporting the screen carrier frame against a machine base or base plate.

The vibratory screener may further comprise a hood sealingly covering the screen carrier frame. In this case, the screen is clamped between an upper rim of the screen carrier frame and a lower rim of the hood by clamping means.

Additionally, an output hopper may be clamped between the screen and the upper rim of the screen carrier frame.

In the following, the invention will be described in greater detail with reference to the accompanying drawing, in which:.

<FIG> show an embodiment of a vibratory screen apparatus <NUM> according to the present invention.

This vibratory screen apparatus <NUM> comprises a screen carrier frame <NUM>, a screen <NUM> for separation of solid particles, one or more vibration motors <NUM>, a hood <NUM>, an output hopper <NUM>, clamping means <NUM>, and a spring arrangement <NUM>.

The screen carrier frame <NUM> may have a substantially cylindrical shape with an inner <NUM> circumference and an outer circumference <NUM>. It may be made from sheet metal, preferably stainless steel, by forming a rounded sleeve and welding the ends together. However, a non-circular shape, e.g. rectangular shape of the screen carrier frame <NUM> may be contemplated as well.

The screen <NUM> for separation of solid particles is vertically supported by the screen carrier frame <NUM> and extends horizontally (x, y) within the screen carrier frame <NUM>. In the embodiment shown, the screen <NUM> may include a wire mesh <NUM> mounted on an apertured support plate <NUM>, which in turn is supported by an upper rim <NUM> of the screen carrier frame <NUM>. The screen <NUM> is removable from the screen carrier frame <NUM> and secured by clamping means <NUM> arranged at the outer circumference <NUM> of the screen carrier frame <NUM>.

In the embodiment shown, vibration forces are generated by two vibration motors <NUM> which are arranged opposite each other on the outer circumference <NUM> of the screen carrier frame <NUM>. However, the number of vibration motors <NUM> may be less, implying a single vibration motor, or higher than two. The vibration motors <NUM> are arranged and configured to generate a component of vibration in a direction z perpendicular to the screen <NUM>. Each of the vibration motors <NUM> preferably includes eccentric weights mounted on a rotatable shaft. The vibration motors <NUM> are operated in a counter-rotating manner to generate directed vibrations, which, apart from the vertical component in direction z, i.e. up and down, also includes a radial component in the xy-plane of the screen <NUM>.

As shown in <FIG>, the axis of rotation A of each vibration motor <NUM> extends in a tangent plane of the outer circumference <NUM> of the screen carrier frame <NUM>, while the tangent planes of the two vibration motors <NUM> are parallel to each other. By inclining the axes of rotation A of the vibration motors <NUM> with respect to the vertical axis V of the vibratory screener <NUM>, it is possible to adjust the radial and vertical components of the vibration forces.

In the embodiment shown, the axes A in the tangent planes are symmetrically inclined with respect to a vertical axis V of the vibratory screener <NUM>, so that per revolution of the vibration motors <NUM> the vertical components add to each other while the radial components cancel out each other.

As already mentioned, the vibration motors <NUM> are arranged at the outer circumference <NUM> of the screen carrier frame <NUM>. They may be fitted directly to the outer circumference <NUM> or, as shown, by brackets <NUM>, which are secured to the outer circumference <NUM> of the screen carrier frame <NUM>, e.g. by welding. The vibration motors <NUM> may be screwed to the brackets <NUM>, which each have a mounting plate <NUM> for the vibration motors <NUM>. The mounting plate <NUM> is spaced apart from the outer circumference <NUM> of the screen carrier frame <NUM>. Optionally, an adjustment mechanism may be provided between the vibration motors <NUM> and brackets <NUM> for facilitating adjustment of the rotation axes A.

In order to reduce or prevent breathing, i.e. elastic deformation, of the screen carrier fame <NUM> under radial force components of the vibration motors <NUM>, the screen carrier frame <NUM> is provided with a particular internal reinforcement structure.

This reinforcement structure includes at least two internal annular disks. In the exemplary embodiment shown in the drawings, the reinforcement structure includes first, second and third internal annular disks <NUM>, <NUM>, and <NUM>, each having an inner rim <NUM>, <NUM>, and <NUM> and an outer rim <NUM>, <NUM>, and <NUM>, wherein each of said first, second and third internal annular disks <NUM>, <NUM>, and <NUM> is attached to the inner circumference <NUM> of the screen carrier frame <NUM> by its outer rim <NUM>, <NUM>, and <NUM>, preferably through welds. These welds extend along the whole outer rim <NUM>, <NUM>, and <NUM> to thereby avoid any gaps between the internal annular disks <NUM>, <NUM>, and <NUM> and the inner circumference <NUM>.

The first, second and third internal annular disks <NUM>, <NUM>, and <NUM> are spaced apart from each other in parallel planes, which are preferably horizontal planes. In the embodiment shown, the first internal annular disk <NUM> is arranged above and in parallel to the second internal annular disk <NUM> and the latter is arranged above and in parallel to the third internal annular disk <NUM>.

The reinforcement structure further includes an inner sleeve <NUM> arranged within the screen carrier frame <NUM> and attached the inner rims <NUM>. and <NUM> of two of said first, second and third internal annular disks, here the second and third internal annular disks <NUM> and <NUM>.

The inner sleeve <NUM> is of substantially cylindrical shape and preferably connected to the inner rims <NUM> and <NUM> through annular welds.

As shown in <FIG>, <FIG>, the upper internal annular disk <NUM> of said two internal annular disks that are connected to the inner sleeve <NUM> and the inner sleeve <NUM> provide an unbroken surface, i.e., free of any openings, whereas the lower internal annular disk <NUM> is provided with openings <NUM> towards the outside environment, preferably facing downwardly. The two internal annular disks <NUM> and <NUM>, the screen carrier frame <NUM> and the inner sleeve <NUM> form an annular channel 18a having a box-shaped cross-section, which, together with the single first internal annular disk <NUM> substantially increases the radial stiffness of the screen carrier frame <NUM>.

In some cases, however, the first internal annular disk <NUM> may be omitted. In some other cases, the first internal annular disk <NUM> may be replaced by a second circular channel 18a having a box-shaped cross section, resulting in total in four internal annular disks.

The openings <NUM> are sufficiently large for the purpose of cleaning and disinfection so that breeding of germs in the circular channel 18a can be prevented by flushing the circular channel 18a with cleaning detergents and/or disinfectants.

Optionally, a plurality of webs 19a, 19b may be provided between the screen carrier frame <NUM> and the internal annular disks <NUM>, <NUM>, and <NUM>. The webs 19a, 19b may extend inwardly from the inner circumference <NUM> of the screen carrier frame <NUM> and perpendicularly to the internal annular disks <NUM>, <NUM>, and <NUM>. In particular, the webs 19a, 19b may be connected, e.g. welded, to the inner circumference <NUM> of the screen carrier frame <NUM> and at least one of said internal annular disks <NUM>, <NUM>, and <NUM>.

In the embodiment shown in the drawings, upper webs 19a are provided at an upper side of the uppermost, i.e. first internal annular disk <NUM> and lower webs 19b are provided at a bottom side of the lowermost third internal annular disk <NUM>.

At least two of said webs 19a, 19b may be arranged in parallel to each other at the inner circumference <NUM> opposite to one vibration motor <NUM> on the outer circumference <NUM> to thereby further increase the radial stiffness of the screen carrier frame <NUM> in the direction of the radial forces generated by the two vibration motors <NUM>.

The output hopper <NUM> is inserted vertically from the top into screen carrier frame <NUM> and clamped between the screen <NUM> and the upper rim <NUM> of the screen carrier frame <NUM>. The output hopper <NUM> collects any material that passes through the screen <NUM> and may have an output opening <NUM> for attaching e.g. a bag, container or the like. The output opening <NUM> may also lead towards an output conveyor.

It is noted that the diameter of the inner rim <NUM> of the uppermost of said first, second and third internal annular disks is larger than the diameter of the inner rim <NUM>, <NUM> of the two further internal annular disks <NUM>, <NUM>. The inner rims <NUM>, <NUM> and <NUM> of the internal annular disks <NUM>, <NUM>, and <NUM> are clear off the outer walls of the output hopper <NUM>.

The hood <NUM> sealingly covers the screen carrier frame <NUM> and screen <NUM>. It is provided with an inlet opening <NUM> for product to be screened and has at least one radial outlet <NUM> for solid materials that are too large to pass through the screen.

The screen <NUM> is clamped between the upper rim <NUM> of the screen carrier frame <NUM> and a lower rim <NUM> of the hood <NUM> by the clamping means <NUM>.

In a preferred embodiment, the output hopper <NUM>, the screen <NUM> and the hood <NUM>, are subsequently stacked on the upper rim <NUM> of the screen carrier frame <NUM> and are all together secured by the clamping means <NUM>, which are configured to pull the hood <NUM> against the screen carrier frame <NUM>.

The vibratory screener <NUM> rests on a spring assembly <NUM> vertically supporting the screen carrier frame <NUM>.

In one particular embodiment, the vibratory screener <NUM> comprises a screen carrier frame <NUM> having an inner circumference <NUM> and an outer circumference <NUM>, a screen <NUM> for separation of solid particles extending horizontally within the screen carrier frame <NUM> and being vertically supported by the screen carrier frame <NUM>, one or more vibration motors <NUM> arranged on the outer circumference <NUM> of the screen carrier frame <NUM> and configured to generate a component of vibration in a direction z perpendicular to the screen <NUM> and a component of vibration in a radial direction xy of the screen <NUM>, at two internal annular disks <NUM>, <NUM> each having an inner rim <NUM>, <NUM> and an outer rim <NUM>, <NUM>, wherein each internal annular disks <NUM>, <NUM> is attached to the inner circumference <NUM> of the screen carrier frame <NUM> by its outer rim <NUM>, <NUM>, and wherein these two internal annular disks <NUM>, <NUM> are spaced apart from each other in parallel planes, and an inner sleeve <NUM> arranged within the sleeve carrier frame <NUM> and attached to the inner rims <NUM>, <NUM> of said internal annular disks <NUM>, <NUM>, wherein the upper one of the internal annular disks <NUM>, <NUM> and the inner sleeve <NUM> provide an unbroken surface, free of any openings, whereas the lower internal annular disk <NUM> is provided with openings <NUM> towards the outside environment, thereby defining, together with the screen carrier frame <NUM>, an annular channel 18a that is open at said openings <NUM>. Optionally, this particular embodiment may be modified further by features already illustrated above, e.g. by adding another internal annular disk <NUM> or varying the number of vibration motors <NUM>.

The vibratory screener <NUM> of the embodiments is able to meet highest hygienic safety standards with regard to pharmaceuticals and food processing. In particular, the apparatus <NUM> and its parts can be cleaned and disinfected without raising biological hazards. All surfaces can be reliably reached by cleaning detergents and disinfectants. Secluded hollow spaces with access only via capillary cracks or the like, in which germs may breed practically undisturbed, are avoided completely.

In addition, by using vibration motors <NUM> on the outer circumference <NUM> of the screen carrier frame <NUM>, the risk of contamination by lubricants is minimized.

Because of the lightweight construction of the reinforced screen carrier frame <NUM>, relatively small vibration motors <NUM> may be used.

Radial forces are readily absorbed by the high radial stiffness of the reinforced screen carrier frame <NUM> so that large diameters of <NUM> and more for high throughputs will be possible.

Claim 1:
Vibratory screener (<NUM>), comprising
a screen carrier frame (<NUM>) having an inner circumference (<NUM>) and an outer circumference (<NUM>),
a screen (<NUM>) for separation of solid particles extending horizontally within the screen carrier frame (<NUM>) and being vertically supported by the screen carrier frame (<NUM>), and
at least two internal annular disks (<NUM>, <NUM>, <NUM>) each having an inner rim (<NUM>, <NUM>, <NUM>) and an outer rim (<NUM>, <NUM>, <NUM>), wherein each of said at least two internal annular disks (<NUM>, <NUM>, <NUM>) is attached to the inner circumference (<NUM>) of the screen carrier frame (<NUM>) by its outer rim (<NUM>, <NUM>, <NUM>), and wherein said at least two internal annular disks (<NUM>, <NUM>, <NUM>) are spaced apart from each other in parallel planes,
characterized by
one or more vibration motors (<NUM>) arranged on the outer circumference (<NUM>) of the screen carrier frame (<NUM>) and configured to generate a component of vibration in a direction (z) perpendicular to the screen (<NUM>), and
an inner sleeve (<NUM>) arranged within the screen carrier frame (<NUM>) and attached to the inner rims (<NUM>, <NUM>) of two (<NUM>, <NUM>) of said at least two internal annular disks, wherein the upper internal annular disk (<NUM>) of said two internal annular disks and the inner sleeve (<NUM>) provide an unbroken surface whereas the lower internal annular disk (<NUM>) of said two internal annular disks is provided with openings (<NUM>) towards the outside environment.