Apparatus for applying powder to elongated article

Claim 2

A chalking machine comprising: a. a housing; b. upper and lower partitions in the housing which are pervious to gas but substantially impervious to the dusting powder to be used and which divide the housing into three superposed chamber, the lowermost of which three chambers is adapted to serve as an air chest for containing air under superatmospheric pressure, the lower partition being structurally capable of supporting a substantial layer of the powder within a lower part of the middle chamber and the upper partition serving as a filter to inhibit powder from passing into the upper chamber; c. inlet and outlet ports in the middle chamber for the passage of an elongated member through the middle chamber; and d. means disposed within the middle chamber for imparting a vibrating movement to dusting powder contained in the lower part of the middle chamber to reduce under operating conditions the tendency for gas tunnels to form in the powder layer and to assist in the formation of a cloud of the powder in the upper part of the middle chamber.

Claim 3

A chalking machine as claimed in claim 1, wherein means is provided for extracting air from the upper chamber at a rate greater than the rate of flow of air into the lower chamber to the extent that the middle chamber can be maintained at a pressure below atmospheric.

Claim 4

A chalking machine as claimed in claim 1, wherein the upper chamber is provided with a valve which is openable to the atmosphere and by means of which the rate of expulsion of air to the atmosphere can be varied.

Claim 5

A chalking machine as claimed in claim 1, wherein the means for imparting a vibrating movement to dusting powder comprises at least one vibrator comprising a foraminous disc mounted within the powder in the lower part of the middle chamber on a substantially vertical rod longitudinally vibrated by a vibrator motor.

Claim 6

A chalking machine as claimed in claim 4, wherein the vibrator rod passes downwards through the upper partition and the partition is attached to the rod in such a way that it will be vibrated, thus dislodging accumulated dusting powder and preventing clogging of the filter.

Claim 7

A chalking machine as claimed in claim 4, wherein the apertures in the foraminous vibrator disc are asymmetrical in that the lower side of each of at least most of the apertures is flared.

Claim 8

A chalking machine as claimed in claim 6, wherein the vibrator disc is of sheet metal and the apertures are each punched out in such a way that the metal around the opening is displaced towards the upper fAce of the disc.

Claim 9

A chalking machine as claimed in claim 1, wherein means is provided for heating the air to be contained in the lowermost of the three chambers.

Claim 10

A chalking machine as claimed in claim 1, wherein means is provided in the middle chamber for deflecting the elongated member downwards and for causing it to be submerged in the powder lying on the lower partition.

Claim 11

A chalking machine comprising: a. a housing; b. upper and lower partitions in the housing which are pervious to gas but substantially impervious to dusting powder to AG., of used N.J., which divide the housing into three superposed chambers, the lowermost of which three chambers is adapted to serve as an air chest for containing air under superatmospheric pressure, the lower partition being structurally capable of supporting a substantial layer of the powder within a lower part of the middle chamber and the upper partition serving as a filter to inhibit powder from passing into the upper chamber; c. inlet and outlet ports in the middle chamber for the passage of an elongated member through the middle chamber; d. means disposed within the middle chamber for imparting a vibrating movement to dusting powder contained in the lower part of the middle chamber to reduce under operating conditions the tendency for gas tunnels to form in the powder layer and to assist in the formation of a cloud of the powder in the upper part of the middle chamber; and e. means at the inlet and outlet ports in the wall of the middle chamber to prevent escape of dusting powder into the ambient atmosphere.

Claim 12

A chalking machine comprising: a. a housing; b. upper and lower partitions in the housing which are pervious to gas but substantially impervious to dusting powder to AG., of used N.J., which divide the housing into three superposed chambers, the lowermost of which three chambers is adapted to serve as an air chest for containing air under superatmospheric pressure, the lower partition being structurally capable of supporting a substantial layer of the powder within a lower part of the middle chamber and the upper partition serving as a filter to inhibit powder from passing into the upper chamber; c. inlet and outlet ports in the middle chamber for the passage of an elongated member through the middle chamber; d. means disposed within the middle chamber for imparting a vibrating movement to dusting powder contained in the lower part of the middle chamber to reduce under operating conditions the tendency for gas tunnels to form in the powder layer and to assist in the formation of a cloud of the powder in the upper part of the middle chamber; and e. means at the inlet and outlet ports in the wall of the middle chamber to prevent escape of dusting powder into the ambient atmosphere.

Claim 13

A chalking machine as claimed in claim 10, wherein the means at the inlet and outlet ports in the wall of the middle chamber to prevent escape of dusting powder into the ambient atmosphere each comprises a coaxial pair of bushes shaped in such a way that air supplied under pressure to and through an annular gap between the bushes follows the contour of the inner bush and accelerates toward the interior of the middle chamber, thus creating a partial vacuum over the entire port and inducing a flow of ambient air into the chamber through the clearance between the bore of the inner bush and the elongated member passing into or out of the middle chamber.