Patent Application
20120167890
Persons who work in polluted environments commonly wear respirators to protect themselves from inhaling airborne contaminants. Respirators typically have a fibrous or sorbent filter that is capable of removing particulate and/or gaseous contaminants from the air. When wearing a respirator in a contaminated environment, wearers are comforted with the knowledge that their health is being protected, but they are, however, contemporaneously discomforted by the warm, moist, exhaled air that accumulates around their face. The greater this facial discomfort is, the greater chances are that the wearer will remove the mask from their face to alleviate the unpleasant condition.
To reduce the likelihood that a wearer will remove the mask from their face in a contaminated environment, respirator manufacturers often install an exhalation valve on the mask body to allow the warm, moist, air to be rapidly purged from the mask interior. The rapid removal of the exhaled air makes the mask interior cooler, and, in turn, benefits worker safety because mask wearers are less likely to remove the respirator from their face to eliminate the hot moist environment that is located around their nose and mouth.
For many years, commercial respiratory masks have used “button-style” exhalation valves to purge exhaled air from mask interiors. The button-style valves typically have employed a thin circular flexible flap as the dynamic mechanical element that lets exhaled air escape from the interior gas space. The flap is centrally mounted to a valve seat through a central post. Examples of button-style valves are shown in U.S. Pat. Nos. 2,072,516, 2,230,770, 2,895,472, and 4,630,604. When a person exhales, a circumferential portion of the flap is lifted from the valve seat so that the air can rapidly pass into the exterior gas space.
Button-style valves have represented an advance in the attempt to improve wearer comfort, but investigators have made other improvements, an example of which is the “butterfly-style” valve shown in U.S. Pat. No. 4,934,362 to Braun. The valve described in this patent uses a parabolic valve seat and an elongated flexible flap mounted in butterfly fashion.
After the Braun development, another innovation was made in the exhalation valve art by Japuntich et al.—see U.S. Pat. Nos. 5,325,892 and 5,509,436. The Japuntich et al. valve uses a single flexible flap that is mounted off-center in cantilevered fashion to minimize the exhalation pressure that is required to open the valve. When the valve-opening pressure is minimized, less power is required to operate the valve, which means that the wearer does not need to work as hard to expel exhaled air from the mask interior when breathing.
Other valves that have been introduced after the Japuntich et al. valve also have used cantilevered mounted flaps—see U.S. Pat. Nos. 5,687,767 and 6,047,698. In yet another development, the seal surface of the valve seat has been made of a resilient material to allow a more rigid, yet stiffer flap to be used, which improved the valve efficiency—see U.S. Pat. No. 7,188,622 to Martin et al.
Although the evolution of exhalation valve design has been centered mainly around structural changes relative to the valve seat and the mounting of the flap to it, investigators also have made structural changes to the flap itself to improve valve performance. In U.S. Pat. No. 7,028,689 to Martin et al., multiple layers were introduced into the flap to enable a thinner, more dynamic flap to be used, which allowed the valve to open easier under less pressure drop. And in U.S. Patent Application 2009/0133700 to Martin et al., slots were provided in the valve flap at the hinge to improve valve performance.
The present invention provides a new respirator that comprises a mask body, a harness, and an exhalation valve. Both the harness and the exhalation valve are secured to the mask body. The exhalation valve comprises a valve base and a flap that has a surface that has been ablated.
The present invention also provides new a method of making a respirator, which method comprises the steps of: providing a valve base and a mask body; securing an ablated flap to the valve base; and securing the valve base to the mask body.
The provision of an ablated flap is beneficial in that the flap can be tailored to have characteristics in stiffness and thickness at specifically desired areas on the flap, which specifically tailored areas can enable the flap to open with minimal force or can alter a particular valve attribute in a desired manner. A valve that can open continuously under minimal force, with little pressure drop across the valve, requires less energy to operate. Since the wearer is the power source for operating the valve, the wearer does not need to work as hard when wearing a respirator where the valve exhibits optimal performance. Improved valve performance, in turn, can make respirators more comfortable to wear over extended time periods, which is particularly beneficial from a safety standpoint, since wearers are less likely to remove the mask from their face in contaminated environments.
The present invention also may be beneficial from a manufacturing standpoint since individual flaps can be tailored during product manufacture to satisfy specific quality control/performance requirements. By ablating certain flap portions during valve assembly, less products may be rejected for failing to meet desired performance requirements during the quality control assessment.
The terms set forth below will have the meanings as defined:
“ablation” or “ablated” means having a portion(s) removed from the surface so as to not cut completely though;
“clean air” means a volume of atmospheric ambient air that has been filtered to remove contaminants;
“comprises (or comprising)” means its definition as is standard in patent terminology, being an open-ended term that is generally synonymous with “includes”, “having”, or “containing”. Although “comprises”, “includes”, “having”, and “containing” and variations thereof are commonly-used, open-ended terms, this invention also may be suitably described using narrower terms such as “consists essentially of”, which is semi open-ended term in that it excludes only those things or elements that would have a deleterious effect on the performance of the subject matter to which the term pertains;
“exhalation valve” means a valve that opens to allow exhaled air to exit a filtering face mask's interior gas space;
“exhaled air” is air that is exhaled by a respirator wearer;
“exterior gas space” means the ambient atmospheric gas space into which exhaled gas enters after passing through and beyond the mask body and/or exhalation valve;
“filter” or “filtration layer” means one or more layers of material, which layer(s) is adapted for the primary purpose of removing contaminants (such as particles) from an air stream that passes through it;
“filter media” means an air-permeable structure that is designed to remove contaminants from air that passes through it;
“flap” means a sheet-like article that is designed to open and close during valve operation;
“flexible flap” means a sheet-like article that is capable of bending or flexing in response to a force exerted from an exhale gas stream;
“harness” means a structure or combination of parts that assists in supporting the mask body on a wearer's face;
“interior gas space” means the space between a mask body and a person's face;
“laser” means a device that provides a highly directional monochromatic and coherent beam of light;
“mask body” means an air-permeable structure that can fit at least over the nose and mouth of a person and that helps define an interior gas space separated from an exterior gas space;
“multiple” means more than 5;
“plurality” means two or more;
“respirator” means a device that is worn by a person to filter air before the air enters the interior gas space; and
“valve seat” or “valve base” means the solid part of a valve which has an orifice for a fluid to pass through and which is disposed adjacent to or in contact with the substrate or article to which it is mounted.
In the drawings:
a is a enlarged perspective view of the flap 22 used in with the valve or valve base shown in
b is a perspective view of an alternative embodiment of an ablated flap 44 suitable for use in connection with the present invention;
In the practice of the present invention, a new filtering face mask is provided that may improve wearer comfort and concomitantly make it more likely that users will continuously wear their masks in contaminated environments. The present invention thus may improve worker safety and provide long term health benefits to workers and others who wear personal respiratory protection devices.
Mask body 12 is adapted to fit over the nose and mouth of a person in spaced relation to the wearer's face to create an interior gas space or void between the wearer's face and the interior surface of the mask body. A nose clip 16 that comprises a pliable dead soft band of metal such as aluminum can be placed on mask body 12 to allow it to be shaped to hold the face mask in a desired fitting relationship over the nose of the wearer and where the nose meets the cheek. An example of a suitable nose clip is shown in U.S. Pat. Nos. 5,558,089 and Des. 412,573 to Castiglione. The illustrated mask body 12 is fluid permeable and typically is provided with an opening (not shown) that is located where the exhalation valve 14 is attached to the mask body 12 so that exhaled air can exit the interior gas space through the valve 14 without having to pass through the mask body itself. The preferred location of the opening on the mask body 12 is directly in front of where the wearer's mouth would be when the mask is being worn. The placement of the opening, and hence the exhalation valve 14, at this location allows the valve to open more easily in response to the force or momentum from the exhale flow stream. For a mask body 12 of the type shown in
Mask body 12 can have a curved, hemispherical shape as shown in
The mask body may be spaced from the wearer's face, or it may reside flush or in close proximity to it. In either instance, the mask helps define an interior gas space into which exhaled air passes before leaving the mask interior through the exhalation valve. The mask body also could have a thermochromic fit-indicating seal at its periphery to allow the wearer to easily ascertain if a proper fit has been established—see U.S. Pat. No. 5,617,849 to Springett et al.
The seal surface 24 circumscribes or surrounds the orifice 30 to preclude passage of contaminates through the orifice when the valve is closed. Seal surface 24 and the valve orifice 30 can take on essentially any shape when viewed from the front. For example, the seal surface 24 and the orifice 30 may be square, rectangular, circular, elliptical, etc. The shape of seal surface 24 does not have to correspond to the shape of orifice 30 or vise versa. For example, the orifice 30 may be circular and the seal surface 24 may be rectangular. The seal surface 24 and orifice 30, however, preferably have a circular cross-section when viewed against the direction of fluid flow.
The majority of the valve seat 20 is typically made from a relatively lightweight plastic that is molded into an integral one-piece body using, for example, injection molding techniques and the resilient seal surface would be joined to it. The seal surface 24 that makes contact with the flexible flap 22 is preferably fashioned to be substantially uniformly smooth to ensure that a good seal occurs. The seal surface 24 may reside on the top of a seal ridge 29 (
a shows a valve flap 22 that has first and second opposing ends 46 and 48 and first and second opposing sides 50 and 52. The flap 22 has a rectangular shape to it, while the flap 44 shown in
An automated method employed laser cutting and ablation may be used to assemble and performance certify flap valve assemblies of the present invention.
In
In
Employment of the method described enable continuous assembly, performance assessment, performance mitigation, and certification of valves for a wide range of critical applications. Many variations on the sequence of the operations could be envisioned. Regardless of the assembly stage approach of the method, the basic certification stage may be employed and ablation may be carried out using a variety of techniques other than laser ablation. For example, abrasion, micromachining, water jet, and the like may be used.
The filtration layer optionally could be corrugated as described in U.S. Pat. Nos. 5,804,295 and 5,763,078 to Braun. And the mask body 12 may also include inner and/or outer cover webs (not shown) that can protect the filter layer 18 from abrasive forces and that can retain any fibers that may come loose from the filter layer 18 and/or shaping layer 17. The cover webs also may have filtering abilities, although typically not nearly as good as the filtering layer 18 and/or may serve to make the mask more comfortable to wear. The cover webs may be made from nonwoven fibrous materials such as spun bonded fibers that contain, for example, polyolefins, and polyesters—see, for example, U.S. Pat. Nos. 6,041,782 to Angadjivand et al., 4,807,619 to Dyrud et al., and 4,536,440 to Berg.
When a wearer inhales, air is drawn through the mask body, and airborne particles become trapped in the interstices between the fibers, particularly the fibers in the filter layer 18. In the embodiment shown in
Filtering materials that are commonplace on negative pressure half mask respirators—like the mask 10 shown in FIG. 1—often contain an entangled web of electrically charged microfibers, particularly meltblown microfibers (BMF). Microfibers typically have an average effective fiber diameter of about 20 micrometers (μm) or less, but commonly are about 1 to about 15 μm, and still more commonly be about 3 to 10 μm in diameter. Effective fiber diameter may be calculated as described in Davies, C. N., The Separation of Airborne Dust and Particles, Institution of Mechanical Engineers, London, Proceedings 1B. 1952. BMF webs can be formed as described in Wente, Van A., Superfine Thermoplastic Fibers in Industrial Engineering Chemistry, vol. 48, pages 1342 et seq. (1956) or in Report No. 4364 of the Naval Research Laboratories, published May 25, 1954, entitled Manufacture of Superfine Organic Fibers by Wente, Van A., Boone, C. D., and Fluharty, E. L. Meltblown fibrous webs can be uniformly prepared and may contain multiple layers, like the webs described in U.S. Pat. No. 6,492,286B1 and 6,139,308 to Berrigan et al. When randomly entangled in a web, BMF webs can have sufficient integrity to be handled as a mat. Electric charge can be imparted to fibrous webs using techniques described in, for example, U.S. Pat. Nos. 6,454,986B1 and 6,406,657B1 to Eitzman et al.; U.S. Pat. Nos. 6,375,886B1, 6,119,691 and 5,496,507 to Angadjivand et al., U.S. Pat. No. 4,215,682 to Kubik et al., and U.S. Pat. No. 4,592,815 to Nakao.
Examples of fibrous materials that may be used as filters in a mask body are disclosed in U.S. Pat. No. 5,706,804 to Baumann et al., U.S. Pat. No. 4,419,993 to Peterson, U.S. Reissue Pat. No. Re 28,102 to Mayhew, U.S. Pat. Nos. 5,472,481 and 5,411,576 to Jones et al., and U.S. Pat. No. 5,908,598 to Rousseau et al. The fibers may contain polymers such as polypropylene and/or poly-4-methyl-1-pentene (see U.S. Pat. Nos. 4,874,399 to Jones et al. and 6,057,256 to Dyrud et al.) and may also contain fluorine atoms and/or other additives to enhance filtration performance—see, U.S. Pat. Nos. 6,432,175B1, 6,409,806B1, 6,398,847B1, 6,397,458B1 to Jones et al. and U.S. Pat. Nos. 5,025,052 and 5,099,026 to Crater et al., and may also have low levels of extractable hydrocarbons to improve performance—see U.S. Pat. No. 6,213,122 to Rousseau et al. Fibrous webs also may be fabricated to have increased oily mist resistance as described in U.S. Pat. No. 4,874,399 to Reed et al., and in U.S. Pat. Nos. 6,238,466 and 6,068,799, both to Rousseau et al.
Pressure drop testing was conducted on the valve with the aid of a flow fixture. The flow fixture provided air, at specified flow rates, to the valve through an aluminum mounting plate and an affixed air plenum. The mounting plate received and securely held a valve seat during testing. The aluminum mounting plate had a slight recess on its top surface that received the valve base. Centered in the recess was a 28 millimeter (mm) by 34 mm opening through which air could flow to the valve. Adhesive-faced foam material was available to be attached to the ledge within the recess to provide an airtight seal between the valve base and the plate. Two clamps were used to capture and secure the leading and rear edge of the valve seat to the aluminum mount. Air was provided to the mounting plate through a hemispherical-shaped plenum. The mounting plate was affixed to the plenum at the top or apex of the hemisphere to mimic the cavity shape and volume of a respiratory mask. The hemispherical-shaped plenum was approximately 30 mm deep and had a base diameter of 80 mm. Air from a supply line was attached to the base of the plenum and was regulated to provide the desired flow through the flow fixture to the valve. For an established air flow, air pressure within the plenum was measured to determine the pressure drop over the test valve.
Pressure drop measurements were made on a test valve using the Flow Fixture as described above. Pressure drop across a valve was measured at flow rates of 15, 20, 30, 40, 50, 60, 70, and 85 liters per minute (L/min; also represented herein as dm3/min) To test a valve, a test specimen was mounted in the Flow Fixture so that the valve seat was horizontally oriented at its base, with the valve opening facing up. Care was taken during the valve mounting to assure that there was no air bypass between the fixture and the valve body. To calibrate the pressure gauge for a given flow rate, the flap was first removed from the valve body and the desired airflow was established. The pressure gauge was then set to zero, bringing the system to calibration. After this calibration step, the flap was repositioned on the valve body and air, at the specified flow rate, was delivered to the inlet of the valve, and the pressure at the inlet was recorded. The valve-opening pressure drop (just before a zero-flow, flap opening onset point) was determined by measuring the pressure at the point where the flap just opens and a minimal flow is detected. Pressure drop was the difference between the inlet pressure to the valve and the ambient air.
Example 1 represents an example of a valve having an ablated flap of the present invention. The flap of the example valve was formed from an extruded sheet of 0.46 mm thick polyisoprene rubber, available from Fulflex, Inc., Brattleboro, Vt. The rubber sheet was cut into a flap in the shape shown in
The flap as prepared was affixed to the flow fixture at its narrow end and evaluated for pressure drop at various flow rates. Results are given in Table 1.
Example 2 was formed and tested as Example 1 with the exception that the laser was operated at a 12% power.
Example A represents an un-ablated control of Example 1 and 2.
As is illustrated by the flow testing of the examples, the valves of the invention have less resistance to opening and reduced pressure drop over the full range of flow rates as compared to the un-ablated control. Lower opening pressures and steady-state pressure drops show that it requires less work to actuate valves using properly ablated flaps. Not only does this demonstrate that ablation can be used to modify the performance of a flap valve but also in a beneficial way. The data also illustrates that by simply changing the power of the ablating laser, the actuation characteristics of the flap valve can be adjusted.
This invention may take on various modifications and alterations without departing from its spirit and scope. Accordingly, this invention is not limited to the above-described but is to be controlled by the limitations set forth in the following claims and any equivalents thereof.
This invention also may be suitably practiced in the absence of any element not specifically disclosed herein.
All patents and patent applications cited above, including those in the Background section, are incorporated by reference into this document in total. To the extent there is a conflict or discrepancy between the disclosure in such incorporated document and the above specification, the above specification will control.
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/427,882, filed Dec. 29, 2010. The present invention pertains to a respirator having an exhalation valve that uses a flap that has one or more ablated areas.
| Number | Date | Country | |
|---|---|---|---|
| 61427882 | Dec 2010 | US |
