Automatic Dust-Removing Eraser of a Rolling-Friction Type for Blackboard

This invention relates to an automatic dust-removing eraser for blackboards, and in particular to an eraser arrangement for easily and automatically removing the chalk dust on the surface of a blackboard without sprinkling the dust and beating the eraser.

Conventionally, all known felt-pad blackboard erasers have to be beaten periodically to remove the chalk dust from the eraser following prolonged use. This dust-removing method through constant beating of the eraser is inconvenient and troublesome. To overcome the above-noted defect, an electrical eraser is known for removing chalk dust by means of electrical vibrations. However, electrical erasers are generally bulky and do not completely remove blackboard chalk dust.

It is accordingly an object of this invention to provide an automatic dust removing eraser with master and slave rolling means arranged in a rolling-friction type arrangement with spare spaces for dust storing and discharging action so that the eraser can be continuously used in erasing without beating the dust from the eraser.

It is another object of this invention to provide an automatic dust-removing eraser of reduced weight, that is easy to use and of long life.

According to the present invention, these and other objects can be achieved by providing an automatic dust-eraser of a rolling-friction type for the blackboard, which comprises a casing having an open central section, a plurality of different guiding slots and cotter holes formed at both ends of side walls defining the open section thereof, and a spare space separately provided at each end portion of the casing with an escape clack valve and a discharge door respectively disposed on opposing end walls defining the spare spaces. A pair of supporting members each having a horizontal parallel plate and vertical parallel plate integrally formed therewith are laterally secured in the guiding slots at both ends of the open section in the casing. A plurality of cylindrical master rolling members, together with a plurality of columnar slave rolling members, are disposed justaposed to the parallel plates over the open section of the casing in a parallel interrelated coupling to effect automatic dust-removing action through the interrelated rotation of both rolling members during the erasing operation.

These objects and advantages of the present invention will become apparent from the following description referring to a preferred embodiment when read in conjunction with the accompanying drawings.

FIG. 1 is a perspective view of the preferred embodiment of an automatic dust-removing eraser of a rolling-friction type for a blackboard according to this invention;

FIG. 2 is a partial cross sectional view of the embodiment in FIG. 1; and

FIG. 3 (a, b) is an illustrative schematic plan view of the preferred embodiment of FIG. 1, indicating the moving condition of the rolling members during erasing.

Referring to FIGS. 1 and 2, the preferred embodiment of an automatic dust-removing eraser of a rolling-friction type for a blackboard according to this invention comprises a planar elliptical casing body 1 having an oblong open section 12 in the central portion, a plurality of guiding slots 121 and 122 of different lengths and cotter holes 123 formed at both ends at the side walls defining the oblong open section 12. A closed spare space 11 is provided at each end portion with a discharge door 111 and an escape clack valve 112 respectively provided in the opposing side walls defining the spare space 11 thereof. A pair of supporting members 2 are respectively fixed at both ends of the open section 12 through the guiding slots 121 and 122; and a plurality of cylindrical master rolling members 3 and columnar slave rolling members 4 are mounted on the supporting members over the open section 12 in a parallel interrelated coupling so as to form a closed rolling-friction structure for automatic dust-removing operation.

As shown in FIGS. 1 and 2, each of the supporting members 2 includes a horizontal plate 22 having a plurality of evenly spaced orifices 221 integrally formed therein, a vertical plate 23 integrally linked with a horizontal plate 22 and provided with toothed portions at the lower end, and a connecting lug 222 with a cotter hole 223 in the center provided at both ends of the plate 22 for overlapping with the cotter holes 123 in the casing 1 and secured by screw bolts 100 thereat. In addition, each of the master rolling members 3 has a journal 31 integrally formed at both ends, and each of the slave rolling members 4 also has a journal 41 at each end with a reversing member 42 fixed thereat. The plate 23 is slightly longer than the horizontal plate 22, and is secured in the guiding slot 122 in the casing 1. As shown in FIG. 2, the vertical plate 23 has toothed portions at the lower end with a plurality of spaced orifices 233 formed therein. A plurality of protruding support projections 231 each have a movable check piece 232 movably provided at one side with a spring (not shown) for allowing the check pieces to move in a reversible semicircular direction. The pieces 232 are installed on the projections 231 along the spaces between orifices 233. When the journals 41 of the slave rolling members 4 are respectively disposed in the orifices 233, the reversing members 42 are rotatably engaged with the movable check pieces 232. As the movable check pieces 232 located at the same side of the support projections 231 are arranged in such a way that they can only be reversibly moved at one side against the support projections 231, the slave rolling members 4 controlled by the reversing members 42 thereof can only make a reversible semicircular movement thereat in connection with the check pieces 232. The outer surface of the cylindrical master rolling members 3 is a woolen material suitable for erasing while the outer surface of the columnar slave rolling members 4 is of a sponge material for brushing purposes.

The combination of the preferred embodiment as shown in FIGS. 1 and 2 is accomplished by first inserting both journals 41 of the slave rolling members 4 into the orifices 233 located at both sides of the support projections 231 of the supporting members 2, making sure that the reversing members 42 are in movable contact with the movable check pieces 232 at one side, and the adjacent slave rolling members 4 are in slight contact with one another; and, then, install the journals 41 of the master rolling members 3 in the orifices 221, and let the adjacent surfaces of the rolling members 3 not only slightly contact each other but also the bottom surfaces thereof contact the top surfaces of the slave rolling members 4 as well. Finally install the combined guiding members 2 separately at both ends of the section 12 of the casing 1 through the different slots 121 and 122, overlapping the cotter holes 223 of the supporting members 2 over the cotter holes 123 of the casing 1, and securing them in position with the screw bolts 100, so that, the master rolling members 3 can smoothly rotate at the outer side while the slave rolling members 4 only can make a reversible semicircular movement therein.

As shown in FIG. 3, when erasing over the surface of the blackboard in the right direction as shown in FIG. 3(a), the master rolling members 3 with the chalk dust erased rotate to the left (counterclockwise) while every other slave rolling member 4 moves to the right as the arrowheads indicate and the rests are stopped thereat. In other words, since only one of reversing member 42 provided at opposite ends of each roller 4 effectively operates to permit rotation of alternate slave rollers, every other roller remains motionless when the eraser is moved in a particular direction (i.e., left or right) due to locking engagement of their reversing member with the associated check piece 232, while the other alternate rollers therebetween are allowed to rotate. These other alternate rollers rotate through approximately 180.degree. (i.e., in a reversible semicircular arc) due to contact of their reversing members 42 against the resilient yieldable bias of the associated check piece 232 (i.e., due to the slight contact between the master and slave rollers; rotation of every other slave roller causes its associated member 42 at one end of the eraser to exert downward pressing force against its check piece; this check piece yields against its spring bias allowing partial rotation of the roller until the spring force overcomes the force exerted by the master roller on the slave roller; the slave roller thus reverses rotation caused by the restoring force of the spring acting upon the check piece and in turn on the reversing member). Simultaneously, the motionless alternate rollers are maintained stationary since the reversing members thereon located at the opposite end of the eraser exert an upwardly directed force against their associated check pieces; i.e., since the check pieces can only deflect downwards against spring bias, they effectively lock the alternate rollers in stationary position, until the rollers rotate in a reverse direction. Thus, as the rotating rolling members 4 are checked at a certain position by the movable check pieces 232 and the other rolling members 4 remain motionless when erasing occurs in one direction, the chalk dust on the surface of the master rolling members 3 is completely removed therefrom through double brushing actions. When the erasing movement is completed in the right direction, the dust-removing action is the same as that described above except that the rotation direction of the master rolling members 3 is changed and the arc movement of the slave rolling members is accomplished by the previously stationary ones as shown by the arrowheads in FIG. 3(b).

When the dust accumulates to a certain amount in the bottom area of the hollow section of the casing 1, the escape clack valve 112 will automatically open through the action of gravity thereof, and the accumulated dust will fall into the spare space 11 provided in both end portions, from which discharge of the dust can be made any time through the discharge door 111 at each end of the casing 1.

In order to prevent the dust thereof from being sprinkled outside of the eraser during the dust-removing operation, and also for effecting a closed structure of the eraser, the opposing inside walls of the open hollow section 12 (as shown in FIG. 1) are furnished with a soft wool for being kept in touch with the outer surface of the master roller members 3 at both sides thereof.

Having thus described the invention, it is to be understood that many embodiments thereof will suggest themselves without departing from the spirit and scope of the invention. Therefore, it is intended that the specification and drawings be interpreted as illustrative rather than in a limiting sense.