MXPA97005350A - Respirator that has a compressable element of adjusting filter to pres - Google Patents

Abstract

A respirator (10) is described which includes a compressible filter element (12), a retainer (14) of the filter element, and a facepiece (16). The respirator is unique since the filter element (12) is compressed when it is installed in the retainer (14), allowing a frictional fit between the filter element (12) and the retainer (14) to be maintained. The friction adjustment makes it possible for the filter element (12) to be easily replaced when its service life has expired.

Description

RESPIRATOR WHICH HAS A COMPRESSABLE COMPONENT OF PRESSURE ADJUSTMENT FILTER DESCRIPTION OF THE INVENTION This invention pertains to a respirator having a press fit filter compressible element. In terms of respirators, many techniques have been used to couple the filter elements to the respirators. A common technique uses threads to couple the filter element to a corresponding threaded fitting on the respirator body; see, for example, U.S. Patent Nos. 5,222,488, 5,063,926, 5,036,844, 5-022,901, 4,548,626 and 4,422,861. Fiber elements typically possess helical threads or possessive coils which are joined with a tapered collar or plug which receives the threaded portion of the filter element. Rotation of the filter element in the proper direction allows the filter element to be coupled to or removed from the respirator. In another described technique of the Patent North American No. 5,148,803, a bellows is used to secure a filter element to a respirator. The bellows, together with a rigid band, form a rigid fold that receives the filter element. The fold is continued in an elastic shirt that surrounds the element REF: 25092 of filter in a gas-tight manner. To change the filter element, the jacket is first folded back to the fold level, allowing the filter element to be removed. During assembly, the filter element is inserted into the fold, and the sleeve is then folded back on the filter element. U.S. Patent Nos. 5,078,132 and 5,033,465 describe a respirator that uses edge seals to secure a filter element to an elastomeric respirator facepiece. The filter element includes bonded activated carbon granules, and the edge seals are placed between the filter element and the elastomeric facepiece, and are made of an appropriate adhesive material such as a hot melt adhesive, a foam adhesive hot melt or a latex adhesive. A shell or shell of a foam mask is used in US Patent No. 4,856,508 to secure a filter element to a respirator. The foam mask shell has a collar that defines an opening for receiving the filter element. The filter element has an extension with an outer dimension approximately equal to the internal dimension of the cylindrical passage through the collar. To mount the filter element, its extension is inserted into the opening where it makes a relatively hermetic friction fit. When this step is performed, the opening expands because the foam material is flexible. To replace the filter element, it - held and twisted back and forth to the time it is pulled away from the shell of the mask. Insert molding is used in U.S. Patent No. 4,790,306 to permanently secure a sorbent filter element attached to a respirator facepiece. A plug frame is described in the Pater. US No. 4,771,771 to secure a filter cartridge in a respirator chamber. The filter cartridge is placed in the chamber by sealing it tightly against the cartridge to hold it in place. The filter cartridge can be adjusted to the respirator by sliding it through an opening in the frame or plug structure. In U.S. Patent No. 4,630,604 securing tabs are employed on a filter retainer to maintain a replaceable filter element in a limiting or abutting relationship to the respirator frame. The filter member can be replaced when undoing the retention member of the frame filter. An additional technique is disclosed in U.S. Patent No. 4,562,837, where the respirator is provided with a guide ring for coupling to a filter housing. The guide ring is carried by a sleeve portion defining an opening through which the gases pass. The filter housing is slidable on the guide ring from a retracted standby position, towards a position of extended use. A bellows located between the filter element and the respirator allows the movement of the filter element between its retracted waiting position and its extended position of use. Sundstrom Safety AB of Lidingó, Sweden markets a respirator under the designation SR-62, which uses an elastomeric rubber filter retainer to accommodate a filter element. The filter element comprises a gas and vapor or particulate filter in a rigid injection molded plastic cartridge. To insert the filter element into the retainer, the retainer is stretched over the periphery of the filter element. Although the respirators discussed above use various techniques to ensure a filter element to a respirator, this technique has a number of drawbacks. For example, filter elements that are screwed to the respirator typically include a housing or basket within which the filter material is retained. The cylindrical geometry of the cartridge typically requires the use of the filter element as an appendix or external cartridge on the respirator, which may interfere with a user's vision. In addition, the screw cartridges employ many parts that can be added to the total volume of the filter element and to the full weight of the respirator. In other types of designs, such as those described in U.S. Patent Nos. 5,078,132, 5,033,465 and 4,790,306, the filter elements are not capable of being easily replaced and thus when the service life of the filter has reached its limit, the Full respirator is discarded as waste. In the model SR-62 respirator sold by Sundstrom, the filter element is displaceable. The retainer, however, lacks physical strength in relation to the filter element and thus, as the placement of a rubber tire on a wheel, a number of manual manipulations are necessary to place the filter element in the retainer of the tire. elastomeric rubber. In addition, elastomeric materials They can be relatively expensive and more difficult to process. Many of the other respirators discussed above have the drawback of using obviously complicated systems for mounting the filter element to the respirator. The respirator of this invention overcomes many of the drawbacks of prior art respirators. The respirator does not use many parts to secure the filter element to the facepiece of the respirator. The filter element is replaceable and lightweight, and this can be mounted to the retainer in a simple movement without excessive handling. In addition, the respirator of the invention allows a filter element to achieve a tight air-tight seal to the facepiece, without using a permanent adhesive. In summary, the respirator of the invention comprises: (a) a face piece sized to fit over a person's nose and mouth; (b) a compressible filter element having first and second faces separated by a peripheral surface; and (c) a retainer of the filter element connected to the facepiece, the retainer of the filter element receives the compressible filter element and includes a wall that frictionally engages the peripheral surface of the filter element, so as to provide an airtight seal to this and to allow the filter element to be removed from the retainer by a manual force. The respirator of this invention differs from known respirators by the use of the compressible filter element which frictionally engages a retainer of the filter element. The compressible filter element in combination with its frictional engagement to the retainer, allows the filter element to be easily removed from a respirator and replaced with minimal effort, and requires a minimum number of parts to assemble from first to last. The invention can also avoid the use of elastomeric rubbers which, as indicated above, can be more expensive and more difficult to process. Figure 1 is a partially cut isometric view of a respirator 10 according to the present invention. Figure 2 is an expanded isometric view of a respirator 10 according to the present invention. Figure 3 is a front elevational view of a respirator 10 according to the present invention, showing the retainer 14 of the filter element displaced from its position of use.

Figure 4 is a rear view of a retainer 14 of the filter element, in accordance with the present invention. Figures 5A and 5B are partially cut away side views of the filter elements 12 '12"in a retainer of the filter element 14 according to the present invention Figure 6 is a cross-sectional view of a filter element 12 according to the present invention With reference to figure 1, there is shown a respirator 10 which includes a compressible filter element 12, a retainer 14 of the filter element, and a facepiece 16. The compressible filter element 12 includes a fluid-permeable structure 18 capable of removing gaseous and / or particulate contaminants from a gaseous fluid, such as air A peripheral member 20 surrounds the peripheral surface 22 of the fluid-permeable structure 18, preferably includes the projecting flange 23a The projecting flange 23a is designed to prevent the penetration of contaminants at the interface of the peripheral member 20 and the peripheral surface 22. The peripheral surface 22 extends between the first (input) and the second (output) faces 24 and 25, respectively. The filter element 12 It is held in the retainer 14 of the filter element by having the peripheral member 20 frictionally coupled to the wall 26 of the retainer 14. The friction coupling provides a hermetic seal at the interface of the peripheral member 20 and the wall 26. The filter element 12 can be manually placed in the retainer 14 simply by inserting the element 12 into the opening defined within the wall 26, and pressing the filter element towards the rear of the retainer 14. The frictional engagement also allows the element of filter 12 is easily removed from the retainer 14 by manual force as described below. The frictional coupling is provided in part by the compressible filter element 12. The filter element 12, and particularly the retainer 14, of the filter element, are constructed of materials that make it possible to filter the filter element 12 when it is inserted inside. of the retainer 14. Before being inserted into the retainer 14, the filter element 12, as defined by the peripheral member 20, circumscribes a cross-sectional area slightly larger than the transverse area defined by the interior of a wall 26. In other words. , the outer diameter of the filter element 12 is larger than the internal diameter of the wall 26. Thus, with reference to the filter element of this invention, the term "compressible" means that the cross-sectional area of the filter element (normal to the direction of fluid flow) is reduced more than the area The cross-section of the retainer (defined by the inner side of the retainer wall of the filter element) is expanded when the filter element is inserted therein In other words, the wall 26 is stiffer than the filter element; When the filter element 12 is placed in the retainer 14, the filter element 12 is compressed more than the retainer 14 expands, and the wall of the retainer exerts a compressive tension on the filter element. non-compressed filter element (before being inserted into the retainer) it has a normal cross-sectional area to the fluid flow, which is within the range of 10 to 200 square centimeters (era '), more preferably 30 to 80 cm2. The area circumscribed by the wall of the retainer is preferably smaller than the area circumscribed by the wall of the retainer, but is not more than about 10 percent smaller than the cross-sectional area of the uncompressed filter element, more preferably, it is no more than 5 cm. percent lower, and still more preferably no more than 2 percent less, than the cross sectional area of the non-compressed filter element. In a preferred embodiment, the filter element is compressed to absorb at least 75 percent of the interference between the filter element and the retainer, and in a more preferred embodiment is compressed to comprise at least 90 percent of the interference between the filter element and the retainer. The "interference" is defined as the cross-sectional area of the non-compressed filter element, normal to the direction of the fluid flow, which exceeds the cross sectional area encompassed by the interior of the retainer wall of the filter element. A filter element 12, preferred, has a peripheral shape that lacks any internal curves; that is, there are no inflection points along the peripheral surface. A more preferred filter element has a circular peripheral surface as shown in the drawings, so that the radially compressive forces are uniformly distributed along the peripheral surface of the filter element. The filter element is generally cylindrical in shape, but may also have a tapered peripheral surface which engages a flat or correspondingly tapered wall of a mirror. With reference to figures 2-4, it is shown in detail how the respirator 10 can be constructed. As shown, the retainer 14 of the filter element can be detachably secured to the facepiece 16. The facepiece 16 can comprise a soft, elastic facial coupling portion 28 and a rigid structural portion 30. Such a facepiece can be elaborated, for example, as described in U.S. Patent No. 5,062,421 to Bu-sis and Reischel. The soft, elastic facial adjustment portion 28 has a shape that is adapted to fit comfortably on the nose and mouth of a user and can be made of a polymer such as styrene-ethylene / butylene-styrene block copolymer as KRATON G 2705, Shell Oil Company. The rigid structural portion 30 may be made of a rigid plastic such as a polypropylene resin, for example, Pro-Fax ™ 6523, Himont United States of America, Wilmington, Delaware. The stiff structural portion 30 includes an opening 32 for receiving the retainer 14 of the filter element. The retainer 14 of the filter element can be provided by a plurality of securing tabs 34 (Figure 4) which engage the opening 32 in the piece 16. For attaching the retainer 14 to the facepiece 16 of the respirator, the securing tabs 34 are inserted into their corresponding spaces 35 in the opening 32. The retainer 14 is then rotated from the position shown in Figure 3 to the position shown in Figure 1. A package 38 such as a 0-1038 silicone sponge can be provided.

(Lauren Co., New Philadelphia, Ohio) to ensure that there is an air tight fit between the retainer 14 of the filter element and the facepiece 16. The air inhaled by the user passes through the opening 32 and the valve inhalation 33 after being filtered through the filter element 12. The exhaled air passes through the exhalation valve 40. A harness 42 can be attached to the facepiece to secure the mask to a user's head. The harness 42 may be a descending harness such as described in US Patent Application Serial No. 08 / 121,697, entitled Respirator having a Descending Harness presented by David C. F -ram on September 15, 1993. The element 12 can be manually removed from the retainer 14 by various methods. What is meant by "manually" or "manual force" is that the filter element can be easily removed of the filter element retainer by using the hands of a person without the help of any mechanical source separate from the respirator. There is no need for any external tool or instrument, or any need to destroy or dismember the respirator to remove the filter element from the retainer. The force is typically applied exclusively to the filter element and is generally within the range of about 5 to 100 Newtons (N), and preferably within the range of about 15 to 50 N. In one embodiment shown in Figure 1 , the filter element 12 can be projected into the retainer 14 so that the first can be grasped around the peripheral surface 22 and pulled out of the retainer 14. In yet another embodiment shown in Figure 5A, a tab 43 can be provided on the filter element 12 'to make the latter easier to hold. The tab 43 can be particularly beneficial when the filter element 12 'does not project into the retainer 14. By holding the tab 43 and the pull on it with sufficient force to overcome the frictional force between the peripheral element 20 and the 26, the filter element 12 can be removed from the retainer 14. Instead of a tab 43, a protrusion can be provided. flange 44 shown in Figure 5B on the filter element 12 to facilitate manual removal of the filter element 12 from the retainer 14. The flange 44 can be formed when the filter element 12 is molded. In a further embodiment shown in the figure 2-4, a button 46 (Figure 4) can be used to force the filter element 12 from the retainer 14. The button 46 can include a tang 48 (Figure 2) which is slidably placed in a sleeve 50 (Figure 2) ). By manually pressing the button 46 a force can be exerted on the back surface 25 of the filter element 12, causing the filter element 12 to be released from the retainer 14. With reference to Figure 6, a cross-section of an element of the compressible filter 12 is shown, which includes a sorbent filter 52 for removing gaseous contaminants, and a fibrous filter 54 for removing particulate contaminants. The sorbent filter 52 includes sorbent granules 56 joined together in the form of a compressible porous body as shown, for example, in U.S. Patent Nos. 5,033,465 and 5,078,132 to Braun and Rekow, the descriptions of which are incorporated by reference in the I presented. Such attached sorbent structure includes sorbent granules attached together by polymeric binder particles to form the unified body. The sorbent granules are uniformly distributed throughout the unified body, and they are spaced to allow a fluid to flow through them. The sorbent granules may be, for example, activated carbon granules, alumina, silica gel, bentonite, earth, diatomaceous earth, ion exchange resins, powdered zeolites (either natural or synthetic), molecular sieves and catalytic particles, and The polymeric binder particles can be, for example, polyurethane, ethylene vinyl acetate and polyethylene. Other bound sorbent structures, which may be useful in the present invention, are described in the following North American Patents: 3,091,550; 3,217,715, 3,353,544, 3,354,886, 3,375,933, 3,474,600, 3,538,020, 3,544,507, 3,645,072, 3,721,072, 3,919,369 and 4,061,807. The descriptions of these patents are incorporated by reference herein. A canvas 57 can be placed over the inlet faces 24 and outlet 25 of the sorbent filter 52, to help retain any loose, disjointed granules. The fibrous filter 54 can be, example, a non-woven network of electrically charged microfibers, preferably hot-blown microfibers, or a nonwoven web of electrically charged fibrillated fibers. Fibrous filters comprising electrically charged microfibers blown in molten form are well known as evidenced by U.S. Patent 4,215,682 to Kubik et al. And U.S. Patent 4,592,815 to Nakao, the descriptions of which are incorporated by reference in the I presented. Fibrous filters comprising electrically charged fibrillated fibers are well known in the art as evidenced in US Patent RE 32,171 to Van Turnout, the disclosure of which is incorporated by reference herein. The fibrous filter may also contain sorbent or chemically active particles such as are described in US Pat. No. 3,971,373 to Braun. The sorbent and fibrous filters 52 and 54 are placed on a peripheral member 20 that extends around the peripheral surface 22 of the filter element 12. The peripheral member includes the projecting flange portions 23a and 23b to inhibit the penetration of contaminants into the membrane. peripheral surface 22 of the attached sorbent structure 52. The protruding flange portions 23a and 23b preferably extend radially inward from the peripheral surface 22, approximately 1 to 20 millimeters (mm), more preferably 2 to 8 mm. The peripheral member 20 can be made essentially of any material that allows the filter element to be compressed when frictionally applied with the filter element retainer. The peripheral member 20 can be made from a polymeric material which is impervious to the fluid, and which can maintain a firm, intimate contact with the peripheral surface 22 of the attached sorbent structure 52. The polymeric material can be a polymeric film such like a heat shrink film. Heat shrink films can be advantageous because they do not need an adhesive or other means to intimately secure the film to the peripheral surface of the attached sorbent structure 18.

In addition, heat shrink films allow the protruding flange portions 23a, 23b (Figure 6) are tightly formed on circumference of the inlet and outlet surfaces 24 and 25. An intimate and firm fit is preferably provided around the periphery of the inlet and outlet surfaces 24 and 25, and the peripheral surface 22. examples of polymeric heat shrink films that can be used in this invention, include: polyolefin heat shrink tubing FP-301, available from 3M, St. Paul, Minnesota; and Paklonw heat shrinkable tape also available from 3M. Other heat shrink films are described in C. Benning, Plásti c Films for Packaging: Technolgy, Appl ica tions and Process Economics, Technomic Publ. Co. (1983); and K. Osborn and W. Jenkins, Plástic Films: Technology and Packaging Applications, Technomic Publ. Co. (1992). Instead of a heat shrink film, the peripheral member 20 can be injection molded, formed vacuum from a plastic sheet, or it can be an adhesive tape. A peripheral injection-molded member is preferred, because it can be molded more accurately and in more detail than a peripheral member formed in a vacuum, and this can form a better fit to the inlet and outlet surfaces than the adhesive tape. , when an outstanding tab is provided. Vacuum training, however, typically uses less expensive tool and processing equipment than injection molding - so this can be favored for proof of concept and initial feasibility work.

The features and advantages of this invention are further illustrated in the following examples. It is expressly understood, however, that while the purposes serve for this purpose, the particular ingredients and amounts used, as well as other conditions and details are not considered in a manner that could unduly limit the scope of this invention.

EXAMPLES Test Procedure Filter elements were tested for service life by snapping the filter element into a molded plastic filter element retainer containing a plenum chamber and a means for directing air flow to an analyzer of gas by infrared beam Miran 103 (Foxboro Company, South Norwalk, Connecticut). The plastic retainer of the filter element used in the following examples was an injection molded part, of polypropylene, with an internal diameter (DI) of 78 mm (3,070 inches), a filter depth of 9.1 mm (0.36 inches) and a camera depth Impeller of 3.3 mm (0.13 inches). There was a central hole with a diameter of 36 mm (1.4 inches) in the plastic retainer of the filter element that was connected in an air-tight manner to a tapered glass fitting. The tapered glass fitting allowed the filter element retainer to be coupled to the test chambers used to test the service life and penetration of the particles. To test the quality of the seal, the pressure-adjusted filters inside the plastic filter holder were tested against an air flow of 30 liters per minute (lpm) that contained 50 percent relative humidity and 300 parts per million (ppm) ) of carbon tetrachloride (CC14). An airflow of such conditions is typical for testing half-mask industrial respirators and in particular is representative of the conditions required by the Ministry of Labor in Japan (Standards for Gas Masks, Notice number 68 of the Ministry of Labor, 1990 )). As the filter was being challenged with 300 ppm of carbon tetrachloride in air, the filter effluent was periodically checked by a Miran 103 gas analyzer for the penetration of tetrachloride. The time between time zero and the time it takes the affluent to reach 5 ppm of tetrachloride, is referred to as the service life of the cartridge. A minimum service life of 50 minutes is required by the Japanese Labor Ministry. Filter elements were treated for the penetration of particles by coupling the filter elements to the filter holder as described above, and challenging the filter element with a flow of 95 bpm of sodium chloride particles.

(NaCl) at a concentration of 12 milligrams per cubic meter. The filter effluent was periodically checked with a TSI model 8110 automatic filter tester available from Thermal Systems, Inc., Saint Paul, Minnesota. Model 8110 generates the NaCl particle challenge and then measures and computes the percentage penetration of the NaCl aerosol.

Example 1 Activated carbon Kuraray GG with a mesh size of the North American Standard of 12 x 20 (1.68 mm x 0.84 mm) was mixed in a thermal process with a polyurethane thermoplastic resin, Morthane PS455-100 (Morton Thiokol Company), the last of the which was reduced to dust powder by polymer emollient and then the collection of the part that could pass through of a 50 mesh screen of the North American standard (297 micrometers (μm)). The size range of the resulting polymer powder was approximately 37-297 μm with an average particle diameter (MPD) of approximately 150 μm. The carbon granules comprised approximately 88 percent or 24.6 grams (g) by weight of the resulting mixture. A 76.5 mm (3.01 inch) diameter spinneret polyester canvas (Reemay number 2250, Reemay Company, Old Hickory, Tennessee) was placed on the bottom of a 77.2 mm aluminum mold (3.04 inches) in diameter and 28 grams of the above mixture were added to the mold in such a way that the mixture was evenly packed. Once the mixture was in the mold and leveled, another polyester sheet was placed on top of the mixture in the mold, and the material was heated to the melting point of the polymeric binder particles. After 10 seconds, the molten bound sorbent was transferred to a mold of similar dimensions, where it was compressed into a disk-shaped sorbent. This produced a joined cylindrical sorbent with a nominal thickness of 12.7 mm (0.5 inches) and a diameter of 77.0 mm (3.03 inches).

A heat-shrink tubing made of polyolefin, FP-301 available from 3M, St. Paul, Minnesota with a nominal diameter of 76.2 mm (3 inches) was cut to a width of 25.4 mm (1 inch) and this cut band was then placed around the peripheral surface of the cylindrically joined sorbent structure, in such a way that the tube would also extend beyond both filter surfaces in the axial dimension by approximately 6.4 mm (one-quarter inch). The sorbent attached to the FP-301 pipe around its peripheral surface was then placed in an oven at 165 ° C for one point five minutes to shrink the pipe to the peripheral surface. The resulting filter element had the heat shrunk film secured in intimate contact to the peripheral surface. A protruding or hanging flange extending radially inward of about 3.2 mm (one-eighth of an inch) was formed on the faces and surfaces of the filter element inlet and outlet. To demonstrate that the filter elements attached to this invention provide a hermetic seal, the filter elements were tested against tetrachloride according to the test procedure described above. Table 1 shows the service life data for three test samples.

Table 1 The data in Table 1 demonstrate that the filter elements of this invention provide a service life that extends beyond the 50 minute service life required for the test. The good service life is indicative of an airtight seal to the filter retainer, as a poor service life would have meant that the penetration or channeling of the contaminants through the filter element has occurred.

Example 2 This example is provided to show that filter elements of the invention, which contain a fibrous filter and a sorbent filter, can concomitantly demonstrate low particle penetration and good service life.

The gas filter was a bonded absorbent structure made according to the technique described in Example 1. The filter for particulate material was made by cutting a 76.6 mm (3.01 inch) diameter piece of filter media brand Fíltrete '"" of 3M with a base weight of 200 g / m2. The cut pieces of the filter media were then joined or welded around its perimeter with an ultrasonic welding machine to produce a filter with a densified or welded perimeter ring having an outside diameter of 76.6 mm (3.015 inches) and an internal diameter of 65.5 mm (2.58 inches). The FP-301 pipe was placed around the perimeter of the bonded sorbent structure as described in Example 1, and the Filtrete ™ fibrous filter was placed on top of one of the surfaces of the bonded sorbent. 1 fibrous filter was placed on the attached sorbent such that after the shrinkage of the polyolefin heat shrink tubing FP-301 described above, the protruding flanges could hold the welded edges of the fibrous filter, securing the fibrous filter to the sorbent structure attached to the peripheral surface as shown in Figure 6. Three samples were tested against a particulate challenge with NaCl and a challenge with tetrachloride gas for the penetration of the particulate and the service life, respectively. The data is reported in Tables 2a and 2b.

Table 2a Table 2b The data in Tables 2a and 2b demonstrate that a filter element of the invention can be processed in a relatively simple manner, and that low penetration values of particulate materials and satisfactory service lives can be obtained. The low particle penetration values and good service life data are indicators of an adequate airtight seal between the filter element and the retainer.

Example 3 This example illustrates yet another embodiment of a filter element of the present invention. In place of the heat shrink tubing FP-301 of Example 1, a black Paklon'R heat-shrinkable tape, one inch thick, 0.05 mm (0.002 inch) thick was employed. Heat shrinkable tape Paklon? it includes a polyvinyl chloride (PVC) film that has an adhesive reinforcement. The bound sorbent structures were processed as described in Example 1, except that the outer diameter of the filter was 78.4 mm (3085 inches) instead of 77 mm (3.03 inches). After the bonded sorbent structures were made, a 304 mm (12 inch) strip of the Paklony'p adhesive tape was measured and cut. The tape was applied around the peripheral surface of the bonded sorbent structure such that the tape extended beyond the entrance and exit surface of the bonded structure, approximately 6. 4 mm (one quarter of an inch) and overlapping itself by approximately 76.2 mm (3 inches). The purpose of the overlap can ensure that the film, when shrunk, comes into full contact with the peripheral surface of the attached sorbent structure and does not crumble. The cartridges made with the adhesive shrink tape were tested for the life of the service. The results of the service life tests for three samples are reported in Table 3 below.

Table 3 The data in Table 3 demonstrate the filter elements of the invention provide service lives well in excess of the 50 minutes required by the Japanese Ministry of Labor. In addition, the service life data are indicators of a proper seal between the filter element and the retainer.

Example 4 The purpose of this example is to demonstrate that polymeric materials other than heat shrink tubing can be secured to the peripheral surface of a bonded filter element to provide a secure press fit that does not leak. The filter elements were made according to Example 3, except that the 3M ScotchR 33+ tape was used instead of the Paklon1 ^ shrinkable film. Scotchv, R 33+ is a 19.1 mm (0.75 inch) wide vinyl tape that does not shrink, but can be securely attached to the peripheral surface of a bonded sorbent structure. By securing the tape to the peripheral surface, the tape was slightly stretched and pressed to the peripheral surface to form an adhesive bond thereto. A protruding flange (1.6 mm) was provided by adhering equal portions of the excess tape width to the inlet and outlet faces of the bonded sorbent structure. Two filter elements were developed and then tested for service life, the results of which are described in Table 4 below.

Table 4 The data in Table 4 demonstrate that the filter elements of this invention provide a service life that extends well above the 50 minutes of the service life required for the test. The good service life is indicative of an airtight seal of the filter retainer, as a poor service life would have meant that the penetration of the challenge aerosol has occurred.

Example 5 This example illustrates the use of a peripheral plastic member formed in a vacuum for a filter element of the present invention. The first step in the preparation of a vacuum formed part is to manufacture the mold on which the molten plastic film will be formed. In this example, the mold was an aluminum cylinder 28.5 mm high and 78 mm in diameter at the top. In the background of the cylinder the diameter was 78.7 mm. This slight enlargement of the cylinder diameter is commonly referred to as a taper and is needed to assist removal of the part of the cylinder after the part has been formed and cooled. Vacuum holes were placed on the edge of the aluminum cylinder to allow the vacuum to pull the film tightly over the cylinder. Four 0.7 mm diameter vacuum holes were evenly spaced around the upper perimeter of the cylinder. These holes were connected, by means of an air passage, to the vacuum supply of the MBD-212IM vacuum forming machine (AAA Plástic Equipment Company Inc., Fort Worth, Texas). After making the mold, a 0.6 mm thick polypropylene film was cut to bet the vacuum forming machine and placed on a conveyor in the machine. The conveyor was moved between the heating elements where the film was heated until it melted, after which time the conveyor and the film were returned to a position just above the cylindrical mold. before the film was allowed to cool appreciably, the aluminum cylinder was pushed into the molten film simultaneously with the vacuum that was coupled. This created an egativa pressure in the vacuum holes in the cylinder. Negative pressure ensured that the film was pulled down evenly and comfortably on the cylinder. The resulting cup-shaped plastic part was cut out, pulled out of the cylinder and a circle 67 mm in diameter was cut from the center of the upper part. This created an annular ring or protruding plastic flange approximately 6 mm wide around the plastic search perimeter. The wall of the plastic jacket was 28.5 mm high and 0.4 mm thick. The thinning of power (0.7 mm to 0.4 mm) was a result of the stretch suffered by the film in the formation process. The next step was to assemble the filter element by inserting a sorbent filter attached and a particle filter. The construction and dimensions of the bonded and particle sorbent filters are as described in Examples 1 and 2; however, there is an axial extension of the peripheral member 6.4 mm above the joined sorbent filter surface. The axial extension was then laminated on the surface of the sorbent filter attached with an anvil heated to 185 ° C.

The filter elements were then press fit into the filter element retainer described in the Test Procedures section and tested for service life. The results of the service life tests are described in Table 5.

Table 5 The data in Table 5 demonstrate the filter elements of this invention, provide a service life that extends well beyond the service life of 50 minutes, required for the test. The service life data are good indicators of a tight seal to the filter retainer, as a poor service life would have meant that the penetration of the challenge gas occurred.

Example 6 This example illustrates how a compressible particulate filter element that lacks a sorbent binding structure in a filter cartridge of the invention can be used. A commercially available Easi-Air 7255 particulate filter manufactured by 3M Company was modified by shrinking a 19 mm wide band of heat-shrinkable tubing FP-301 around the peripheral surface to produce a filter element having a nominal outside diameter of 78.2 mm. The Easi-Air 7255 is a lightweight filter element made of folded glass fiber and a flexible, injection molded plastic structure which will compress when snapped into a filter element retainer. The filter element was press fit into the retainer of the filter element previously described and tested against a challenge with NaCl particles. Penetration results for three test samples are shown below.

Table 6 The data in Table 6 demonstrate that a compressible particulate filter element of this invention provides very low penetration. The low penetration values are indicators of an appropriate airtight seal between the filter element and the retainer.

Example 7 This example shows how a filter element can be easily removed from a respirator of the invention. To demonstrate the importance of having a compressible filter element, an experiment was performed using an Instron Model 4302 material testing machine. With the machine set to compression test mode, it was able to measure the force and energy required to remove the filter elements of different constructions from the rigid retainer. The filter elements provided those described in the previous examples, as well as an Easi-Air 7152, a commercially available gas and vapor cartridge manufactured by 3M Company. The Easi-Air 7152 cartridge is a rigid structure that includes a packed bed of activated carbon in a galvanized steel basket. The Easi-Air cartridge was modified by shrinking FP-301 around its edge, in the same way as described for the joined sorbent filters. All the cartridges were snapped into the retainer of the rigid filter element previously described, and adapted to the machine so that a 25 mm diameter cylinder acting on the center of the cartridge could push it out of the holder. The cross-sectional areas of the filter elements and the retainers were measured before and after the filter elements were placed in the retainers. It was determined that the filter element Easi-Air 7152 was not compressible; that is, the retainer expanded more than the compressed Easi-Air 7152 filter element when the last element was inserted into the first one. The speed of the crosspiece of the Instron instrument was 25 mm per minute. While the crosshead is advancing, it pushes the cartridge from the cartridge retainer and regresses the force detected by the load cell. The withdrawal force was the maximum force detected by the machine, and the withdrawal energy was the area under the voltage curve. The results are reported in Table 7 below.

Table 7 Comparative Filter Element The data in Table 7 demonstrate that the withdrawal force and withdrawal energy were substantially lower when a compressible filter element was employed as compared to a rigid or non-compressible filter element.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention. Having described the invention as above, property is claimed as contained in the following:

Claims (21)

1. A respirator, characterized in that it comprises: (a) a face piece of appropriate size to fit at least over a person's nose and mouth; (b) a compressible filter element comprising sorbent granules, and having first and second faces or surfaces separated by a peripheral surface; and (c) a retainer of the filter element connected to the facepiece, the retainer of the filter element receives the compressible sorbent filter element and includes a wall that frictionally engages the peripheral surface of the filter element to provide a watertight seal to this and to allow the filter element to be removed from the retainer by a manual force.

2. The respirator according to claim 1, characterized in that the compressible filter element in an uncompressed condition has a cross-sectional area normal to the fluid flow that is within the range of 10 to 200 cm '.

3. The respirator according to claims 1-2, characterized in that the filter element in an uncompressed condition has a cross-sectional area within the range of 30 to 80 cm2, and wherein the wall of the filter element retainer circumscribes a area that is less than an area circumscribed by the wall of the retainer, but is no more than 10 percent smaller than the transverse area of the uncompressed filter element.

4. The respirator according to claims 1-3, characterized in that the area circumscribed by the wall of the retainer is no more than 5 percent smaller than the transverse area of the non-compressed filter element.

5. The respirator according to claims 1-4, characterized in that there is an interference between the compressible filter element and the wall of the retainer, and where the filter element when inserted into the retainer is compressed to at least absorb at least 75 percent of the interference between the filter element and the wall of the retainer.

6. The respirator according to claim 5, characterized in that the filter element when inserted into the retainer is compressed to absorb at least 90 percent of the interference between the filter element and the retainer.

7. The respirator according to claims 1-6, characterized in that the filter element has a peripheral shape that lacks internal curves, and where the force necessary to manually remove the filter element from the retainer is within the range of 5 to 100 Newtons .

8. The respirator according to claims 1-7, characterized in that the force necessary to manually remove the filter element from the retainer is within the range of 15 to 50 Newtons.

9. The respirator according to claims 1-8, characterized in that the retainer of the filter element includes a button to manually force the filter element from the retainer.

10. The respirator according to claims 1-9, characterized in that the compressible filter element includes a sorbent filter comprising sorbent granules joined together in the form of a porous, compressible, unified cupola, and wherein the sorbent granules are uniformly distributed. throughout the compressed porous unified body, and are spaced apart to allow a fluid to flow therethrough, the sorbent granules being joined together with polymeric binder particles.

11. The comfort respirator with claims 1-10, characterized in that the compressible filter element includes a peripheral member extending around the peripheral surface of the filter element.

12. The respirator according to claim 11, characterized in that the peripheral member includes a protruding flange portion extending radially inward from the peripheral surface from 2 to 8 millimeters.

13. The respirator according to claims 11-12, characterized in that the peripheral member comprises a polymeric material which is impermeable to the fluid and which maintains firm intimate contact with the peripheral surface of the compressible filter element.

14. The respirator according to claims 11-13, characterized in that the peripheral member comprises a heat-shrinkable film.

15. The respirator according to claims 11-14, characterized in that the peripheral member comprises an injectable molded plastic.

16. A method for replacing a respirator filter element, which method is characterized in that it comprises: (a) manually removing a first compressible filter element from a breather filter element retainer; and (b) manually inserting a second compressible filter element, into the retainer, the second compressible filter element is compressed after to be inserted inside the retainer and making an air tight adjustment to it.

17. The method according to claim 16, characterized in that the compressible filter element comprises a sorbent filter comprising sorbent granules, said sorbent granules being unified together in the form of a unified, porous, compressible body.

18. The method according to claim 16-17, characterized in that the compressible filter element includes a peripheral member extending around the peripheral surface of the filter element.

19. A cartridge for removing gaseous contaminants from a gaseous fluid, characterized in the cartridge comprising: (a) a fluid-permeable structure containing sorbent granules joined together as a unit mass, the fluid-permeable structure having an inlet surface and a surface of outlet separated by a peripheral surface; Y (b) a peripheral member extending around the peripheral surface of the porous structure, such that the porous structure is held in compression by the peripheral member.

20. The cartridge according to claim 19, characterized in that the peripheral member comprises an injection molded plastic.

21. A respirator, characterized in that it comprises the cartridge according to claims 19-20 and a retainer for receiving the cartridge, the cartridge being placed in the retainer such that the cartridge can be removed therefrom by a manual force exerted on the cartridge.