SUMMARY OF THE INVENTION

This problem is solved by a sieve cleaner  frame comprising a sieve covering, a bottom, and at least one sieve cleaner having a foot and a plurality of cleaning heads having, for example, a brush-like or nubby configuration. The heads are configured to move erratically on the bottom in response to a shaking or vibrating movement of the sieve frame. One of the foot and at least part of the foot closest to the cleaning heads resiliently supports the sieve cleaner, for example by a spring, such that the cleaning heads are under a elastic initial tension against the sieve covering. The problem further is solved by a sieve cleaner for use with the sieve frame, the foot of the sieve cleaner being arranged so as to be offset with respect to the cleaning heads. The part of the foot closest to the cleaning heads is located between the cleaning heads and the center of gravity of the sieve cleaner.

Various advantageous embodiments of the invention can be taken from the appended claims.

With the sieve frame in accordance with the invention the cleaning devices are resiliently prestressed against the sieve covering by a foot supported by a spring so that potential dimensional tolerances in the distance between the sieve bottom and the sieve covering, e.g. owing to a slight arching of the sieve bottom, do not cause the sieve cleaner to get jammed.

The cleaning effect is not provided by hitting against the sieve covering, but instead by the fact that the cleaning devices are running over the sieve covering. The fact that all cleaning devices are continually and efficiently cleaning the sieve more than compensates for forgoing the hits against the sieve covering. Another advantage results from more evenly distributed contact of the cleaning devices with the bottom, thus resulting in less wear and tear in one particular area.

According to another aspect of the invention, in an embodiment of the sieve cleaner, the bulk of the cleaning devices is essentially arranged in a line, and a spacer that is not, or at least less densely, fitted with cleaning devices protrudes from the line of cleaning devices toward one side.

When the sieve cleaner bumps against the edge of the sieve frame, it can be aligned in such a manner that the line of cleaning devices is almost in parallel with the edge of the sieve frame. This assists in a relatively large surface of the sieve covering being treated by the cleaning devices in the area close to the edges, while the spacer—protruding to the inside at this moment—is less or not at all involved in the cleaning. In this way, on the statistical average, a more even cleaning of the sieve covering is achieved and an excessive wear of the sieve covering in the central area of the sieve is avoided.

Preferably, the spacer is not fitted with cleaning devices and is arranged in a T-shape in reference to the line of cleaning devices. Also preferably, the foot on which the sieve cleaner rests on the level sieve bottom, which can simultaneously serve as a bottom-clearing-device, is provided under the spacer so that it is in contact with the sieve bottom in at least two places. This serves the purpose of limiting the possible movement of the sieve cleaner so that the entire line of the cleaning devices is permanently kept in contact with the sieve covering.

The sieve frames of a plansifter usually are of a square layout. It is possible to obtain a specifically even cleaning effect when the length of the sieve cleaner measured from the line of the cleaning devices to the free end of the spacer has almost half the edge length of the sieve frame.

The preferred embodiments will be explained in detail by means of the following drawings.