US3886897A

US3886897A - Powder applicator

Info

Publication number: US3886897A
Application number: US444872A
Authority: US
Inventors: Derek Keith Unwin
Original assignee: Chandor Ltd
Current assignee: Chandor Ltd
Priority date: 1973-02-23
Filing date: 1974-02-22
Publication date: 1975-06-03
Anticipated expiration: 1992-06-03
Also published as: FR2218950B1; DE2408607A1; JPS5335665B2; JPS49116654A; IT1004331B; FR2218950A1

Abstract

The invention provides powder processing apparatus including an enclosed processing chamber, powder processing means within said chamber, an air filter associated with said processing chamber for extracting powder from air flowing through the filter, and means operative to extract air from said processing chamber through the air filter so as to tend to establish a negative pressure differential between the interior and the exterior of said chamber, the arrangement being such that, in operation, air entering said chamber from the exterior thereof aids the containment within said chamber of the process powder. The apparatus of the invention is particularly useful for the application of dusting powder. A preferred embodiment of dusting apperatus according to the invention is illustrated and described.

Description

United States Patent 1 Unwin June 3,1975

[73] Assignee: Chandor Limited, Storrington,

England [22] Filed: Feb. 22, 1974 [21] Appl. No.: 444,872

[30] Foreign Application Priority Data Feb. 23, 1973 United Kingdom 8864/73 [52] US. Cl. 118/309; 118/326; 118/612 [51] Int. Cl B05b 7/14 [58] Field of Search 118/309, 50, 612, 326, 118/325, 420, DIG. 5

[56] References Cited UNITED STATES PATENTS 1,926,198 9/1933 Guenst 118/309 2,602,417 7/1952 Medcalf 118/309 2,688,593 9/1954 Nelson ..,118/420 2,875,094 2/1959 Bloem et al 118/612 3,139,044 6/1964 Cole 118/309 3,623,453 1l/l97l Seimiya et a1. 118/309 FOREIGN PATENTS OR APPLICATIONS 1,134,069 11/1968 United Kingdom 118/309 Primary Examiner-Mervin Stein Assistant ExaminerDouglas Salser Attorney, Agent, or Firm-Bacon & Thomas [5 7] ABSTRACT The invention provides powder processing apparatus including an enclosed processing chamber, powder processing means within said chamber, an air filter associated with said processing chamber for extracting powder from air flowing through the filter, and means operative to extract air from said processing chamber through the air filter so as to tend to establish anegative pressure differential between the interior and the exterior of said chamber, the arrangement being such that, in operation, air entering said chamber from the exterior thereof aids the containment within said chamber of the process powder. The apparatus of the invention is particularly useful for the application of dusting powder. A preferred embodiment of dusting apperatus according to the invention is illustrated and described.

10 Claims, 6 Drawing Figures MI -5159mm 1915 3.886 897 SHEET FATENTEMM I975 SHEET POWDER APPLICATOR This invention relates to powder processing apparatus and more particularly to apparatus for applying dusting powder (particularly, though not exclusively, talc) to articles which acquire a tacky or sticky surface during their manufacture. Rubber articles emerging from an extruder or calender for example, are tacky and must be dusted before they are cured in order to prevent them from bonding together.

The dusting of such articles with talc or other powdered materials hitherto commonly has been achieved simply by sprinkling the articles with powder either by hand or using suitable spray guns or by passing the articles through troughs of powder or through chambers pervaded with a powder laden gaseous atmosphere as disclosed, for example, in British Patent Specification Nos. 1,027,103 and 1,134,069. Whilst it has been recognised that a powder laden working atmosphere is detrimental to the health of machine operators, little has previously been done in an effort to reduce this problem in the field of this invention. The public health authorities are not insisting upon cleaner working atmospheres in factory premises, particularly having regard to the dangers of operatives contacting the disease pneumoconiosis, and the present invention is directed to a dusting apparatus which seeks to reduce the amount of dusting powder liberated to the operatives working environment. 3

The present invention resides in the realization that by providing powder processing apparatus adapted, in operation, to provide a negative pressure differential between the air pressure within the processing chamber of the apparatus and the external air pressure, i.e. the pressure of the atmosphere in the operatives working environment, the tendency is for powder to be contained within the apparatus by virtue of air flow from the operatives working environment into the processing chamber.

According to the present invention, therefore, there is provided powder processing apparatus including an enclosed processing chamber, powder processing means within said chamber, an air filter associated with said processing'chamber for extracting powder from air flowing through the filter, and means operative to extract air from said processing chamber through the air filter so as to tend to establish a negative pressure differential between the interior and the exterior of said chamber, the arrangement being such that, in operation, air entering said chamber from the exterior thereof aids the containment within said chamber of the process powder.

Apparatus according to the present invention is particularly useful for the application of dusting powder and thus according to a preferred embodiment of the present invention there is provided a dusting apparatus including an enclosed dusting chamber, means to envelop an article introduced into the dusting chamber with dusting material, an air filter associated with said dusting chamber for extracting dusting material from air-flowing through the filter, and means operative to. extract air from said dusting chamber through the air filter so as to tend to establish a negative pressure differential between the interior and the exterior of said chamber, the arrangement being such that, in operation, air entering said chamber from the exterior thereof aids the containment within said chamber of the dusting material.

The air filter is preferably self-cleansing and preferably also is of the maximum effective area allowable within the restrictions imposed by the dimensions of the apparatus. To assist the return of dusting material from the filter to the stock of dusting material, it is convenient that the filter be contained within the chamber or on a wall thereof and that the stock of dusting material be contained either in the bottom of the dusting chamber, whereto it will fall having been cleansed from the filter, or in a chamber fed with dusting material therefrom. A particularly convenient arrangement employs a cylindrical drum filter, the curved surface area whereof constitutes the filtering area of the filter, arranged for axial rotation past a scraper spaced a predetermined small distance from the curved filtering surface and adapted to maintain upon the filtering surface a layer of dusting material of no more than a predetermined thickness. The filter preferably has a replaceable filter element which may, for example, be formed of an appropriate air-permeable paper.

For extracting air from the interior of the dusting chamber, the filter is connected in an air passageway venting to the chamber exterior and a suitable impeller is provided to cause air flow in said passageway. With the above described cylindrical drum filter, air is extracted from the hollow interior of the filter and, for example, through a hollow shaft upon which the filter is mounted for axial rotation and which passes through a wall of the dusting chamber; it will be appreciated that no special seals need be provided to seal the passage of the shaft through the chamber wall since any air leakage will be from outside of the chamber to within and will tend to prevent the escape of dusting material.

For enveloping an article introduced into the dusting chamber with dusting material, the article could merely be caused to pass through a hopper of dusting material. Alternatively, the gaseous atmosphere within the dusting chamber could be pervaded with dusting material for example by employing an agitator within a dusting material hopper (which may comprise the bottom of the dusting chamber) to provide a laden atmosphere in the hopper, and an air passageway could be provided having an inlet to accept dust laden air from the hopper and an outlet (or a plurality of outlets) arranged to deliver the dust laden air to the article to be powdered, an impeller being provided in the passageway.

It is desirable to provide a facility for adjusting the amount of dusting material delivered to the article to be dusted. To this end, the abovementioned agitator may have an adjustable speed control to enable adjustment of the dust content of the air drawn from the hopper. Alernatively or additionally, an advantageous arrangement is achieved by providing a valve in the air passageway conveying dust laden air from the hopper and to arrange the valve to be adjustable to adjust the relative proportions, in the dust laden air delivered by the'passageway to its outlet, of dust laden air taken from the hopper environment and relatively clean air taken from another location within the dusting chamber (or from the exterior thereof, though this is not preferred since it increases the task of the means to develop a negative pressure differential between the interior and exterior of the dusting chamber). It would also be possible to provide an adjustable speed control operative to adjust the action of the impeller provided in the air passageway from the hopper, though this also is not preferred since it interferes with the delivery of dusting material to the article to be dusted. Yet another way of adjusting the dusting density, in the abovemen tioned advantageous arrangement, would be to arrange for the location within the dusting chamber from which relatively clean air is taken to be adjustable, for example, by utilization of flexible or otherwise adjustable (e.g. telescopic) hosing.

In order that this invention might be clearly understood, several exemplary embodiments thereof will now be described with reference to the accompanying drawings wherein:

FIG. 1 shows a schematic side view of a first embodiment of a dusting apparatus according to this invention;

FIG. 2 shows another schematic side view of the apparatus of FIG. 1, from an orthogonal direction;

FIG. 3 shows a view similar to that of FIG. 1 of another, but similar, embodiment of this invention;

FIG. 4 shows a view of the embodiment of FIG. 3 similar to that in FIG. 2 of the embodiment of FIG. 1;

FIG. 5 shows a schematic side view of another embodiment of this invention adapted for dusting electrical cables subsequent to the provision on the individual conductors thereof of an electrically insulating covering but prior to the encapsulation with plastics material of the several conductors constituting the cable; and

FIG. 6 shows a schematic side view of the embodiment of FIG. 5 from an orthogonal direction.

Referring first to FIGS. 1 and 2, there is therein shows a dusting apparatus comprising a resin bonded glass fibre container 1 shaped as shown to define therewithin a dusting chamber 2 and an integral hopper 3. The apparatus shown is adapted for the dusting of continuous extrusions which, in use of the apparatus, will pass through the upper part of the dusting chamber 2. Rotatably mounted within the container 1, near the dusting chamber 2, is an air filter 4 comprising an axially journalled hollow cylindrical drumhaving a perforated curved surface supporting a replaceable paper element. Mounted adjacent the curved surface of filter drum 4 is a scraper blade 5 adapted to provide a cleansing function for the filter by ensuring that the build-up of dusting material on the filter surface does not exceed a predetermined thickness. Rotatably mounted in the hopper part 3 of the container 1 is an agitator in the form of a rotary paddle 6. The filter drum 4 and the rotary paddle 6 are both driven by an electric motor 7 through appropriate chain-and-sprocket drives.

Adjacent to the hopper part 3 of the container 1 is the inlet end of an air passageway 8 leading to a centrifugla impeller 9 and thence to dusting nozzles (not shown) arranged in dusting chamber 2. A second air passageway 10 is also provided having an inlet at an adjustable height snorkel 1 1. A simple flap valve 12 operated by remote control lever 14 determined the relative resistances to air flow therethrough and into air passageway 8 and impeller 9 of the air flow path proviided through snorkel 11 and passageway 10 and the alternative flow path provided directly from the hopper region through the valve 12. In operation of the apparatus, rotation of the paddle 6 will produce a highly dust laden atmosphere in the region of the direct inlet through valve 12 to passageway 8 and impeller 9, as opposed to there being a relatively clean atmosphere in the region of snorkel 11, so it will be seen that valve 12 provides a simple and convenient means of adjusting the dusting density by adjustment of the relative proportions of dust laden air intake and relatively clean air intake.

A second electric motor 14 is provided for driving impeller 9 and serves also to drive an impeller 15 connected by means ofa duct 16 (only partly shown) to extract air from the interior of hollow filter drum 4 for venting at 17. The extraction of this air tends to reduce the pressure within the container 1 (a closure member being provided though not shown in the Figures) so as to establish a negative pressure differential between the interior and the exterior of the container 1; dust entrained in the atmosphere of the container thus is restrained against escape into the surrounding atmosphere.

In use of the apparatus thus described, dusting powder (e.g. tale) is introduced into the hopper part 3 to a level not significantly above the rotational axis of the paddle 6, and, upon rotation of the paddle at a speed determined by the speed setting of electric motor 7 (which speed setting preferably is adjustable), dusting powder pervades the atmosphere in the region of the inlet through valve 12 to air passageway 8 and impeller 9 and thence to the dusting nozzles. An inlet 18 is provided for topping up the level of dusting powder in the hopper 3; as can be seen, the inlet 18 is screened by means of a screen 19 from the filter 4. The drive motor 7 also rotates the air filter 4 which ensures that dusting powder accumulating on the filter is removed by scraper 5. At the same time as powder laden air is introduced to passageway 8 via valve 12 directly from the region of hopper 3, relatively clean air is introduced via snorkel 11, passageway 10, and valve 12; the setting of valve 12, as hereinbefore explained, determines the dusting density and this can be adjusted by adjusting the setting of control lever 13.

FIGS. 3 and 4 show another embodiment of the invention which in many respects is similar to the embodiment of FIGS. 1 and 2 and functions in an identical manner. The same reference numerals have been used in FIGS. 3 and 4 as were used in FIGS. 1 and 2 to designate identical, like, or similarly functioning parts and it is considered that, beyond this, no further description of the embodiment of FIGS. 3 and 4 is required in order that it might be clearly understood.

FIGS. 5 and 6 show an embodiment of the invention adapted for the dusting of electrical cables subsequently to the provision on the individual conductors of the cable of electrically insulating rubber or synthetic plastics material and prior to the subsequent encapsulation of the multi-conducted cable in its outer electrically insulating sheath. In many respects the apparatus of FIGS. 5 and 6 is similar to the previously described embodiments and, to emphasise this similarity and assist in understanding this embodiment, the same reference numerals are used in FIGS. 5 and 6 to identify like, similar or similarly functioning parts as were used in the preceding Figures.

The embodiment of FIGS. 5 and 6 therefore includes a container 1 having a dusting region 2 and a hopper region 3. A cylindrical drum filter similar to that of the preceding embodiment is mounted in an upper extension of the container 1 but otherwise is identical to the drum filter of the preceding embodiments and serves the same function. A rotary agitator 6 is provided in the hopper 3, however in this embodiment the agitator 6 serves to agitate the power in the hopper only to such an extent as to ensure that it does not become compacted, and is not intended to provide a dust laden atmosphere, since in this embodiment the article to be powered actually passes through the powder in the hopper. Furthermore. since in this embodiment the article to be powdered actually passes through the powder in the hopper, there is no provision (and no need for the provision) in this embodiment of any arrangement for directing air-borne dust upon the article. An electric motor 7 drives the agitator 6 and the drum filter 4.

The agitator 6 in this embodiment comprises an axially rotatable cylindrical drum having throughout its curved surface a plurality of equally spaced parallel circular grooves 21 each provided to accommodate one conductor of an electrical cable in its passage through the apparatus, the conductors being passed underneath of the drum 20 as shown in FIG. 6. The drum 20 itself will not provide any appreciable agitation of the powder in hopper 3, this function being provided by means of shaped side pieces 22 bolted to the ends of drum 20. These side pieces 22 have been found to provide sufficient agitation of the powder, but for different applications or where a less freely flowing powder is to be used otherwise shaped side pieces 22 could be provided or an additional separate agitator provided.

The electrical conductors to be powdered are guided into and out of the apparatus by means of

guide rollers

23 and 24 mounted as shown and provided with circumferential grooves corresponding to those on the agitator drum 20. The conductors enter and leave the apparatus through ports 25 (only one of which is shown) provided with a pair of opposed brushes 26 which serve as a crude air and powder seal such as to aid the establishment of a negative pressure differential within the interior of container 1. A hinged lid 27 provides access to the container 1.

In operation of the apparatus of FIGS. 5 and 6, conductors to be powdered are entrained over

rollers

23 and 24 and under agitator drum 20 as shown. Powder is introduced into the hopper 3 to a level around the top of the drum 20. The agitator drum 20 and the filter drum 4 are both rotated by means of electric motor 7 the speed of which preferably is adjustable. The motor 7 also serves to drive impeller 15 which exhausts air from the hollow interior of filter drum 4 and vents it to the machine exterior at 17; this provides a negative pressure differential between the interior of the apparatus and the surrounding environment which inhibits the escape of powder from the apparatus.

There has thus been described powdering apparatus incorporating means operative positively to inhibit the escape of dusting powder into the surrounding environment thereby enhancing operatives working conditions and reducing the risk of contraction of pneumoconiosis.

While the present invention has hereto been described with particular reference to apparatus for applying dusting materials to articles which acquire a tacky or sticky surface during their manufacture, it will nonetheless be appreciated that, in its broadest aspects, the present invention has application to other processes involving the use of powders not necessarily for dusting purposes. For example, in the pharmaceutical fields, powders are widely used (e.g. in the production of pills and tablets) and it should be of paramount importance to ensure that such powders do not escape into the operative environment, not only to minimize the risk of contraction of pneumoconiosis, but also to minimize any risk resulting directly from exposure of the operatives to the pharmacological properties of the constituents of the powders. The broadest aspect of the present invention, i.e. the realization that the escape of powdered materials from enclosures can be minimized by maintaining a negative pressure differential between the interior and exterior of the enclosure, is applicable to a solution of this problem.

I claim:

1. Dusting apparatus including an enclosed dusting chamber, a dusting material hopper, means to pervade the gaseous atmosphere within said hopper with dusting material contained therein, means to transfer dust laden air from said hopper to said dusting chamber for delivery to an article to be dusted therein, proportioning means to vary the relative proportions of dust and air in said dust laden air to vary the amount of dusting material delivered to the article, an air filter associated with said dusting chamber for extracting dusting material from air flowing through the filter, and means operative to extract air from said dusting chamber through said filter so as to tend to establish a negative pressure differential between the interior and the exterior of said chamber such that air entering said chamber from the exterior thereof aids the containment within said chamber of the dusting material.

2. Dusting apparatus as claimed in claim 1 wherein said proportioning means comprises an impeller having a first inlet arranged to accept dust laden air, a second inlet arranged to accept relatively clean air, and at least one outlet arranged to deliver a mixture of said dust laden and said respectively clean air from said inputs to the article to be dusted.

3. Dusting apparatus as claimed in claim 2, said proportioning means further including valve means associated with said first and second inlets of said impeller to vary the relative proportions of dust laden air and relatively clean air in the said mixture delivered by said at least one outlet.

4. Dusting apparatus as claimed in claim 2 wherein said second inlet is arranged to accept relatively clean air from within said dusting chamber, and the location of said second inlet within said dusting chamber is variable to enable the dust content of air entering said second inlet to be adjusted.

5. Dusting apparatus as claimed in claim 3 wherein said second inlet is arranged to accept relatively clean air from within said dusting chamber, and the location of said second inlet within said dusting chamber is variable to enable the dust content of air entering said second inlet to be adjusted.

6. Dusting apparatus as claimed in claim 1 wherein said dusting material hopper is formed in the bottom of said dusting chamber, said air filter is contained within said dusting chamber, and means are provided for cleaning said air filter, dusting material cleaned off said air filter returning to said hopper.

7. Dusting apparatus as claimed in claim 6 wherein the air filter comprises a hollow cylindrical drum the curved surface area whereof constitutes the filtering area of the filter, and said drum is arranged for axial rotation past a scraper spaced a predetermined distance from the curved surface thereof.

8. Dusting apparatus including: an enclosed dusting chamber having a dusting material hopper formed in the bottom thereof, an agitator in said hopper to pervade the gaseous atmosphere therein with dusting material; an impeller having a first inlet arranged to receive dust laden air from one location in said hopper, a second inlet arranged to receive relatively clean air from another location in said dusting chamber. and at least one outlet to deliver a mixture of dust laden air and relatively clean air received by said first and second inlets to be article to be dusted in said dusting chamber; valve means associated with said first and second inlets to vary the relative proportions of dust laden air and relatively clean air in said mixture; an air filter within said dusting chamber; and means to extract air from said dusting chamber through said air filter so as to tend to establish a negative pressure differential

Claims

8. Dusting apparatus including: an enclosed dusting chamber having a dusting material hopper formed in the bottom thereof; an agitator in said hopper to pervade the gaseous atmosphere therein with dusting material; an impeller having a first inlet arranged to receive dust laden air from one location in said hopper, a second inlet arranged to receive relatively clean air from another location in said dusting chamber, and at least one outlet to deliver a mixture of dust laden air and relatively clean air received by said first and second inlets to be article to be dusted in said dusting chamber; valve means associated with said first and second inlets to vary the relative proportions of dust laden air and relatively clean air in said mixture; an air filter within said dusting chamber; and means to extract air from said dusting chamber through said air filter so as to tend to establish a negative pressure differential between the interior and exterior of said dusting chamber; the filter cleaning dusting material from air extracted therethrough.

9. Dusting apparatus as claimed in claim 8 wherein said air filter comprises a rotary drum filter having a replaceable filter element, and a scraper mounted adjacent the filtering surface of the filter for cleaning filtered dusting material therefrom as the filter rotates.