Patent Grant
6858811
The present invention relates generally to binary switches for use in the medical monitoring and other fields and to methods for manufacturing same. More particularly, the instant invention involves the construction, manufacture, and operation of pressure actuated switches of the sort commonly used to detect when a patient has, for example, left a chair or a bed and, more generally, in other settings where membrane-type switches would be useful including use as part of the user interface in a piece of electronic equipment.
It is well documented that the elderly and post-surgical patients are at a heightened risk of falling. These individuals are often afflicted by gait and balance disorders, weakness, dizziness, confusion, visual impairment, and postural hypotension (i.e., a sudden drop in blood pressure that causes dizziness and fainting), all of which are recognized as potential contributors to a fall. Additionally, cognitive and functional impairment, and sedating and psychoactive medications are also well recognized risk factors.
A fall places the patient at risk of various injuries including sprains, fractures, and broken bones—injuries which in some cases can be severe enough to eventually lead to a fatality. Of course, those most susceptible to falls are often those in the poorest general health and least likely to recover quickly from their injuries. In addition to the obvious physiological consequences of fall-related injuries, there are also a variety of adverse economic and legal consequences that include the actual cost of treating the victim and, in some cases, caretaker liability issues.
In the past, it has been commonplace to treat patients that are prone to falling by limiting their mobility through the use of restraints, the underlying theory being that if the patient is not free to move about, he or she will not be as likely to fall. However, research has shown that restraint-based patient treatment strategies are often more harmful than beneficial and should generally be avoided—the emphasis today being on the promotion of mobility rather than immobility. Among the more successful mobility-based strategies for fall prevention include interventions to improve patient strength and functional status, reduction of environmental hazards, and staff identification and monitoring of high-risk hospital patients and nursing home residents.
Of course, direct monitoring of high-risk patients, as effective as that care strategy might appear to be in theory, suffers from the obvious practical disadvantage of requiring additional staff if the monitoring is to be in the form of direct observation. Thus, the trend in patient monitoring has been toward the use of electrical devices to signal changes in a patient's circumstance to a caregiver who might be located either nearby or remotely at a central monitoring facility, such as a nurse's station. The obvious advantage of an electronic monitoring arrangement is that it frees the caregiver to pursue other tasks away from the patient. Additionally, when the monitoring is done at a central facility a single person can monitor multiple patients which can result in decreased staffing requirements.
Generally speaking, electronic monitors work by first sensing an initial status of a patient, and then generating a signal when that status changes, e.g., he or she has sat up in bed, left the bed, risen from a chair, etc., any of which situations could pose a potential cause for concern in the case of an at-risk patient. Electronic bed and chair monitors typically use a pressure sensitive switch in combination with a separate electronic monitor which conventionally contains a microprocessor of some sort. In a common arrangement, a patient's weight resting on a pressure sensitive mat (i.e., a “sensing” mat) completes an electrical circuit, thereby signaling the presence of the patient to the microprocessor. When the weight is removed from the pressure sensitive switch, the electrical circuit is interrupted, which fact is similarly sensed by the microprocessor. The software logic that drives the monitor is typically programmed to respond to the now-opened circuit by triggering some sort of alarm—either electronically (e.g., to the nursing station via a conventional nurse call system) or audibly (via a built-in siren) or both. Additionally, many variations of this arrangement are possible and electronic monitoring devices that track changes in other patient variables (e.g., wetness/enuresis, patient activity, etc.) are available for some applications.
General information relating to mats for use in patient monitoring may be found in U.S. Pat. Nos. 4,179,692, 4,295,133, 4,700,180, 5,600,108, 5,633,627, 5,640,145, and 5,654,694 (concerning electronic monitors generally). Additional information may be found in U.S. Pat. Nos. 4,484,043, 4,565,910, 5,554,835, and 5,623,760 (switch patents), the disclosures of all of which are all incorporated herein by reference.
By way of general background, in a typical arrangement, a pressure-sensing mat of the sort discussed herein is a sealed “sandwich” composed of three layers: two outer layers and an inner (central) layer positioned between the two outer layers. The outer layers are usually made of some sort of plastic and are impermeable to fluids and electrically non-conductive on their outer faces, where “outer” is determined with respect to the middle layer. The inner surface of each of the outer layers—which inner surfaces are oriented to face each other from opposite sides of the central layer—is made to be electrically conductive, usually by printing a conductive (e.g., carbon-based) ink on that surface. The compressible middle “central spacer” is made of a non-conductive material and serves to help keep the two conductive faces apart when a patient is not present on the sensor. The central spacer is discontinuous, which makes it possible for the two conductive inner surfaces to be forced into contact through the one or more discontinuities when weight is applied to the switch. By attaching a separate electrical lead to each of the conductive inner faces, it can readily be determined via a simple continuity (or low voltage) check whether a weight is present on the sensor (e.g., a patient is seated thereon). Removal of the weight causes the central spacer to expand and press apart the two conducting faces, thereby breaking the electrical connection between them. Thus, a device that monitors the resistance across the two electrical leads may determine when a patient has moved from a seated or prone position.
One disadvantage of the current generation of pressure sensitive mats is that they cannot be completely (e.g., hermetically) sealed around their perimeters against the external environment. The reason for this should be clear: if the interior of the mat were completely sealed, air pressure inside of the mat would tend to oppose the urging of the mat faces into contact, thereby making it difficult or impossible to complete the circuit (e.g., think of compressing an “air pillow”). Of course, the fact that the interior of the mat must be kept open to the atmosphere results in a mat that is highly susceptible to invasion by bodily fluids or cleaning solutions, as the in-rushing air that enters when the switch expands tends to carry fluids along with it into the interior of the mat. Further, it is well known that some common disinfecting cleaners can loosen the adhesives that hold the layers of a conventional mat together, thereby ruining the sensor. Thus, cleaning soiled mats becomes problematic. In summary, what is needed is a pressure sensitive mat that is more resistant to invasion by fluids than has heretofore been available.
Methods of manufacturing conventional pressure sensitive mats for use in medical applications of this sort of sensing device typically begin at a single station punch, wherein the upper and lower plastic/nonconductive members are cut from a larger sheet of material. This step would typically be followed by the application of a conductive material to one face of each member. For example, the conductive material could be printed onto the surface using a carbon-based ink, although other variations have been employed. A popular alternative method involves the use sheets or rolls of material on which the conductor has been pre-applied.
The inner non-conductive member may be a discrete layer of material that has dimensions somewhat smaller than those of the exterior member, or it could take the form of a pattern of non-conductive raised ridges or dots which is deposited on top of the ink (the raised ridges separating the two conductive faces wherever they are present). Either way, the non-conductive material must be discontinuous to the extent that it allows the conductive materials to come into contact when the assembled mat is compressed. Thereafter, separate isolated electrical leads are attached to the inner faces of the mats so that they make contact with the conductive surface. The two conductive inner surfaces are oriented so that they face each other across the insulating layer and, if a separate central spacer is used, it is positioned between them. Finally, the apparatus is sealed at its edges to protect against invasion of moisture, typically through the use of an adhesive that is applied to the edges of the facing members.
However, mats assembled in this manner are subject to a variety of well-known problems. For example, if the non-conductive member is bent, it is possible to introduce breaks in the conductive ink pattern that has been printed thereon. If the break extends the width of the conductive surface, dead (i.e., nonresponsive) regions may be created in the mat or the mat may cease to function altogether.
Additionally, the seal between the two outer members is dependent on the quality of the adhesive bond between them. Depending on the choice of adhesive and the environmental conditions at the time the seal was formed—e.g., the relative humidity, temperature, etc.—the adhesion between the two outer members may be imperfect, which can allow moisture into the interior of the assembled device, thereby shortening its active and or shelf life.
Further, prior art mats are susceptible to cord pull out and may fail to open after being compressed, which failure is often because the air inside has been expelled and air pressure continues to hold the halves of the mat together after weight is removed.
Because of variability that is inherent in the current technology of printing conductive inks—which is typically done via some sort of screening process—the mats produced thereby can be unreliable and it can be difficult to create printed mats that exhibit specific electrical properties when the circuit is closed. Further, the screen process does not lend itself to repeatability, so it can be difficult, say, to produce a mat that has a particular resistance when closed.
Finally, and more generally, those of ordinary skill in the art will recognize that electronic equipment is subject to infiltration and attack by foreign gases, solids and liquids. Of course, the presence of such foreign compounds can damage or destroy sensitive electronic components. Externally operated switches are especially prone to contamination because they are usually located on the exterior of the device where they can be accessed by the user. As a consequence, membrane switches have become a staple in many settings because of their impermeability to most gases and chemicals and the ease with which they can be manufactured and marked.
However, conventional methods of manufacture of membrane switches require the creation of a mold or a hardened polished die which adds substantially to the cost of manufacture. Further, currently known methods of manufacture utilize a hydraulic or similar high pressure press to form the switches from the raw materials. Thus, what is needed is a method of manufacturing membrane switches which can be implemented using equipment made of softer metals (e.g., aluminum) which are cheaper to form. Of course, softer metals are only feasible if the pressure required to form the switches can be reduced, e.g. to presses utilizing pneumatic (rather than hydraulic) energy.
Heretofore, as is well known in the patient monitoring and switch arts, there has been a need for an invention to address and solve the above-described problems. Accordingly, it should now be recognized, as was recognized by the present inventor, that there exists, and has existed for some time, a very real need for a electronic patient monitor that would address and solve the above-described problems.
Before proceeding to a description of the present invention, however, it should be noted and remembered that the description of the invention which follows, together with the accompanying drawings, should not be construed as limiting the invention to the examples (or preferred embodiments) shown and described. This is so because those skilled in the art to which the invention pertains will be able to devise other forms of this invention within the ambit of the appended claims.
In accordance with a preferred embodiment of the instant invention, an apparatus for patient monitoring is taught herein that is constructed via heat sealing according to the methods described hereinafter. The instant method and apparatus are designed to produce a patient monitoring switch that is more reliable and can be manufactured with less cost than has heretofore been available in the prior art.
More particularly and according to a first preferred aspect of the instant invention, there is provided a hermetically sealed binary switch that is constructed of a “sandwich” of alternating polyester and polyethylene layers. In the preferred embodiment, the mat consists of an upper member, a central spacer, and a lower member. The upper and lower members are both non-conductive on their outer surfaces and conductive on their inner surfaces, which inner surfaces face each other across the central spacer. The upper and lower members are both preferably composed of two elements: an outer nonconductive layer (preferably of a material such as polyester) and an inner nonconductive layer upon which has been deposited a conductor such as aluminum. The central spacer is also nonconductive and is preferably formed of a central core of polyester that has been placed between two layers of polyethylene. Additionally, the central spacer has at least one aperture passing therethrough, the purpose of the aperture being to allow the two conductive elements of the upper and lower members to come into contact when a weight is placed on the mat.
A critical aspect of this embodiment of the instant mat is that its perimeter is hermetically sealed against the atmosphere, thereby making it resistant to fluid invasion during use. Preferably, its interior will have been caused to contain rarified air during manufacture, which makes it possible to compress its two halves together in spite of the sealed perimeter. Alternatively, and in another preferred embodiment, the instant mat will be completely sealed along its perimeter, but a breathing tube will penetrate into the interior of the mat, thereby assisting the movement of air into and out of the mat during use.
According to another preferred mat embodiment, the upper and lower units are each composed of three elements: an outer nonconductive layer (preferably polyester), bonded to an inner adhesive layer (preferably polyethylene), and an inner conductive layer (preferably a layer of polyester upon which has been deposited a conductor such as aluminum). Preferably, the central spacer will be generally as described previously, with one or more apertures therethrough so that the conductive layers on the upper and lower members can come into contact when the mat is compressed.
Finally, there is provided hereinafter a method of manufacturing hermetically sealed binary switches which utilize heating to the glass transition temperature accompanied by a concomitant vacuum effect to create raised areas in the upper and, optionally also the lower surface, of a mat-like assembly. In more particular, according to the preferred embodiment a mat-like assembly that consists of alternating polyester and polyethylene members is placed in a heated press, wherein heat is preferably applied bi-directionally (e.g., from above and below). While the press is closed and the mat is being compressed and heated, a vacuum force is applied which tends to pull apart the heat-softened outer members of the mat, and draws those members into an incised, or otherwise formed, pattern of one or more depressions that have been formed in a special platen mold. These depressions or recessed region(s) are designed to become embossments or protrusions in the finished product, each of such embossments or protrusions yielding a membrane switch. The preferred final step is to rapidly cool the recently-formed mat to room temperature, thereby permanently setting the imprint of the platen into the surface of the mat.
Of critical importance for purposes of one preferred manufacturing embodiment is that the mat and/or membrane switches be formed by placing the various layers together into a packet and heat-sealing the unit along its periphery, preferably using heat that is simultaneously applied from both sides (i.e., from the directions of both the upper and lower member). It is a further preferred aspect that vacuum be used to pull apart the upper and lower laminar members of the mat during heat sealing, thereby creating pockets(s) or protuberance(s) in the outer surfaces of the mat and rarifying the air remaining therein.
The foregoing has outlined in broad terms the more important features of the invention disclosed herein so that the detailed description that follows may be more clearly understood, and so that the contribution of the instant inventors to the art may be better appreciated. The instant invention is not to be limited in its application to the details of the construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. Rather, the invention is capable of other embodiments and of being practiced and carried out in various other ways not specifically enumerated herein. Further, the disclosure that follows is intended to be pertinent to all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims. Finally, it should be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting, unless the specification specifically so limits the invention.
While the instant invention will be described in connection with a preferred embodiment, it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.
Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings in which:
Turning first to
It should be noted at the outset, however, that although the language that follows is largely confined to illustrations involving bed-type sensors, the range of application of the instant invention is much broader and could include chair sensors, potty sensors, and any other type of pressure-sensitive switch that is used in a patient monitoring environment where invasion by fluids is a concern. Thus, when “bed mat” or “mat” are used herein, those terms should be construed as broadly as possible to include any or all of the foregoing applications. As a specific example,
Generally speaking, the mat 100/monitor 50 combination works as follows. When a patient is placed atop the mat 100, the patient's weight compresses the mat 100 and closes an electrical circuit, which closure is sensed by the attached electronic patient monitor 50 through interconnecting line 55, which line 55 would typically be a conventional multi-element electrical line.
When the patient attempts to leave the bed, weight is removed from the sensing mat 100, thereby breaking the electrical circuit. The patient monitor 50 senses the change in electrical condition and signals the caregiver per its pre-programmed instructions, preferably through nurse-call connection 60. Note that additional electronic connections not pictured in this figure might include a monitor 50 to computer connection, and an A/C power cord for the monitor 50—although the monitor 50 can certainly be configured to be battery powered as is generally illustrated, for example, in FIG. 2.
As is further indicated in
Affixed to the inner surface of each of the outer members 330 and 340 is a conductive layer (435 and 445, respectively) which, for safety purposes, preferably does not extend to the edges of the mat 300. As should be clear, pressure on the mat 100 tends to urge the conductive faces 435 and 445 into contact through aperture 320, thereby completing an electrical circuit. When the compressive pressure is released, the central spacer 310—which is constructed of a compressible and resilient material such as closed cell foam rubber—expands and pushes the conductive layers apart. The central spacer 310 is assisted in that effort by the elastic nature of the outer layers 330 and 340.
As is suggested in
As is generally illustrated in
Turning now to
As can be seen most clearly in
The central spacer 510 has at least one aperture 520 cut therethrough, which aperture is designed to allow the conductive inner faces 610 and 620 of the upper 530 and lower 540 members, respectively, to come into contact when the mat 500 is compressed by the weight of a patient. Additionally, the instant embodiment will preferably have protuberances 535 created in the outer faces therefore that are symmetrically positioned on either side of an aperture 520 of about the same size, orientation, and location (e.g., FIG. 6). That being said, it should be noted that it is not an absolute requirement that the protuberances 535 and the apertures 520 be of about the same size, orientation, and location. In fact, it is only necessary that the size and locations of the apertures 520 be such that they allow the two conductive inner faces 610 and 620 to meet when the mat is compressed: there is no requirement that the respective sizes must be the same or even similar. That being said, for purposes of specificity in the instant disclosure, it will be assumed that the protuberances 535 and apertures 520 are comparable in size and orientation. Those of ordinary skill in the art will readily appreciate how the respective sizes and orientations can be varied without changing the functionality of the invention taught herein.
It can be seen that a central purpose of the protuberances 535 is to provide additional separation between the respective conductive surfaces 610 and 620 when there is no weight on the mat 500, as the conductive surfaces 610 and 620 are formed into and become a part of the concave side of the protuberances 535. This obviously then moves further apart the conductive surfaces 610 and 620 when the mat is uncompressed. However, upon the application of a patient's weight, one or more of the protuberances 535 will collapse and bring together the conductive surfaces 610 and 620 through at least one aperture in the spacer 510, thereby completing an electrical circuit which can be sensed through electrical connector 550 by electronic monitor 50.
Turning now to
As is generally indicated in the cross section of
Additionally, as was mentioned previously, for purposes of patient safety it is preferable that the conductive layer 610 does not extend to the edge of the mat where it could come into contact with a patient. In a typical situation, though, the conductive surface will have been pre-applied by a materials provider and it would extend to the edges of polyethylene layer 920, contrary to the configuration of the preferred embodiment. In such a case, it is well within the skill of one of ordinary skill in the art to remove the conductive material near the periphery of the polyethylene layer 920 by, for example, abrasion or other means.
Finally, although aluminum is the preferred conductive material, those skilled in the art will recognize that any number of conductive materials might be utilized instead depending on the particular needs of the situation and the goals of the user. For example, conductive materials such as silver, copper, gold, platinum, stainless steel, and any sort of carbon-based, polymer-based, or metal-based ink, would be suitable for use with the instant invention. In the preferred embodiment, the conductive layer 610 will have a thickness of about 1-15 mils.
Lower member 540 is preferably constructed of the same materials as upper member 530, i.e., a combination of a polyester layer 910 and a polyethylene 920, with the polyethylene being treated so as to be conductive at least on its inner face. The aluminum/conductive layer 610 is preferably formed as described previously.
Central non-conductive spacer 510 is preferably made of polyester 910 which has been positioned between two layers of polyethylene 920. This combination is non-conductive as required and particularly suitable for manufacture as is described previously
In operation, the instant hermetically sealed mat 500 functions as follows. The mat 500 is placed on a bed, seat, etc., where a patient is to be rested. When the patient places his or her weight on the mat, the two conductive surfaces 435 and 445 are urged into contact with each other through the apertures 320 in central spacer 310 when the protuberances 535 collapse. This process is made more reliable by way of the inclusion of air channel 560 (see, e.g., FIG. 6), which permits free movement of air from regions in the mat 500 which are compressed to other portions of it which do not bear as much of the patient's weight. This helps prevent an “air pillow” effect which might make it more difficult to force the two conductive surfaces into contact. That is, if air were separately trapped within each pocket or “bubble” in the mat 500, the trapped/compressed air would provide support for the patient's weight, possibly to the point of preventing contact between the opposing conductive sides. However, by providing fluid/pneumatic communication between the protuberances 535 and, preferably, by additionally rarifying the air trapped in the protuberances 535 and air channel 560 as described hereinafter, the instant invention can be reliably compressed and contact established between the conductive surfaces. Additionally, this same communication pathway helps reduce the opposite problem, i.e., a failure to reinflate after compression.
Further, the instant inventors have discovered that by varying the size, location, etc., of the protuberances 535 mats that respond to different compressive forces can be produced. For example, the instant inventors have determined that when the protuberances 535 that have been formed in the mat are made larger, the weight needed to trigger the switch is reduced. Similarly, when the protuberances 535 are made smaller in width or length the weight needed to force the conductive surfaces into contact is similarly increased. Of course, in either case it is assumed that apertures 320 are appropriately resized and repositioned as necessary to make the resulting mat 500 operational.
Further, changing the thickness of the materials that make up the upper and lower units 530 and 540 will similarly change the responsiveness of the instant switch 500 to pressure, although the amount of change may not be linear. For example, if the materials are made thicker, the resulting mat would be less responsive to weight placed thereon. Obviously, the opposite would be true if the thickness of the materials were reduced. It should be noted, however, that the shape of the protuberances 535 is intended to reduce the effect of increased thickness on the central spacer 510.
Still further, it should be noted that the term “hermetically sealed” should be interpreted in its broadest sense to include any complete sealing of the perimeter of the instant device to the point of excluding fluid. That need not mean that the interior of the mat is completely isolated from the atmosphere. For example, the instant inventors have specifically contemplated that a breathing tube of the sort taught in U.S. Letters Pat. No. 6,417,777, for “Pressure Sensitive Mat with Breathing Tube Apparatus,” the disclosure of which is incorporated herein by reference, might be made a part of the instant invention. That is, it is contemplated that a breathing tube might be inserted between the mat layers and completely sealed therein. The breathing tube would then provide a passage for air between the interior of the mat and the atmosphere, thereby ensuring that the mat can be compressed and expanded without problems caused by pressure differentials between the interior of the mat and the atmosphere. Of course, it would be important that the mat be completely sealed around the breathing tube where it enters the mat.
Finally, as is generally indicated in
Those skilled in the art will recognize that the instant air reservoir 2210 of
According to another variation of the above-described invention, there is provided an embodiment substantially as described above, but wherein the protuberances are customized to take the form of membrane switches which are separately useful in patient monitoring, as well as in other applications and fields.
Turning first to
As is further illustrated in
Note that the foregoing are just a few of the many possible configurations that could be employed in constructing the instant membrane switch and those of ordinary skill in the art will be readily able to devise others.
Turning now to the method of manufacturing the preferred binary switch, the instant inventors have discovered that polyester, and especially oriented polyester, is in some ways nearly an ideal material for use as a mat exterior. It is impervious to fluids, non-conductive, relatively inexpensive, and flexible, all of which are important mat properties. Additionally, it is malleable and can be plastically deformed under heat to yield the protuberances 535 and air channels 580 of the sort described previously. However, for all of its useful properties, using polyester in mat construction is somewhat problematic, as it can be difficult to reliably bind together the two outer layers of the mat.
As is well known to those skilled in the art, polyester-to-polyester bonds are notoriously subject to dissolution in the field. Pressure sensitive adhesives, which represent one conventional approach to binding the mat-components together, certainly work well in a pristine laboratory environment but run into limitations when put to work in the field. By way of example, it might be expected that in a hospital environment after a mat is placed into service it will be exposed to a variety of cleaning/disinfecting solutions. However, some of the cleansers to which the mat will be exposed are well known solvents that can be expected to rapidly dissolve conventional adhesive bonds between the mat members. This, of course, will shorten or terminate the useful life of the mat by allowing its interior to be prematurely invaded by (usually electrolytic) fluid, thereby short circuiting its internal switch and exposing the patient to the electrical current that is used to test the switch's closure. Thus, the instant inventors prefer that the mat layers be hermetically joined together via a heating process as is described below.
Although heat sealing is the preferred method of hermetically sealing the mat layers together, those skilled in the art will recognize that heat sealing is not really an option for creating a polyester-to-polyester bond. Because polyester is typically work hardened at the time of its manufacture, any attempt to melt or partially melt it will destroy that structure and render the resulting mat too distorted to be useful.
However, the preferred polyethylene/polyester sandwich suggested above avoids this problem. Since the melting point of polyethylene is below that of polyester, when alternating layers of the two substances are heated to an appropriate temperature the polyethylene melts and bonds the stack together without harming the polyester layers.
Thus, in the preferred embodiment a combination of polyester and polyethylene will be used to form the instant mat: the arrangement of
Turning now to
As a first preferred step, pieces of polyester and polyethylene are cut to the appropriate size for later assembly. The polyester and polyethylene will typically be obtained in rolls that are several hundred feet in length and have a thickness which would usually be somewhere between about 1 and 15 thousandths of an inch, depending on the mat properties that are desired by the creator. Additionally, it is possible and, indeed, preferred to acquire polyester to which has already been adhered the polyethylene layer upon which has been deposited the electrical conductor. Thus, in the preferred embodiment the upper and lower outer members 530 and 540 will be provided pre-assembled.
Further, in the preferred embodiment, the conductive material will be a conductor such as aluminum that has been deposited on the polyethylene to a thickness sufficient to conduct electrical current, i.e., preferably aluminized polyester will be used. That being said, for purposes of specificity herein the instant invention will be discussed in terms of the use of aluminized polyester as the conductive layer, although those skilled in the art will recognize that many other materials could be utilized in the alternative including, e.g., conductive ink.
Next, preferably upper 530 and lower 540 members are cut from the continuous roll according to methods well known to those skilled in the art. In the preferred embodiment, a custom die will be used to cut these members to length from the roll on which the raw material would be typically provided and to create additional apertures and extensions that are useful during assembly.
As a next preferred step, about one-half inch the conductive material will be removed from each of the edges of the aluminized polyethylene layer. Although it is possible to obtain conductor-coated polyethylene which has not been fully covered out to its edges, in general the instant inventors have determined that it is preferable to order it fully coated and then remove as much conductor as is deemed necessary from its edges. As is well known to those of ordinary skill in the art, if the electrical conductor reaches to the edge of the mat, the patient could be at risk of galvanic burns from the electrical current that is used to monitor the status of the mat. Thus, it is generally advisable to strip the conductor by, for example, utilizing abrasive action on the periphery of the aluminized polyester material to remove the aluminum coating.
Central spacer 510 is preferably cut via a die that also creates apertures 520 therein. In the preferred embodiment, the apertures 520 in the central spacer 510 will be matched to the shape and orientation of the protuberances 535, although, as discussed later, this is not strictly required. Additionally, both this member 510 and the outer members 530 and 540 preferably include mounting holes 650 at each end, the function of which is discussed in detail below.
As is illustrated in
Once the individual components have been assembled, the mat is ready to be sealed.
Turning now to a detailed discussion of the previous method and apparatus, as is generally illustrated in
The upper press 1520 is preferably comprised of two platens 1524 and 1526, between which the assembly tray 1300 is positioned during the heating phase. The two platens are preferably compressed together through the use of multiple pneumatic rams 1550, which are positioned so as to apply pressure uniformly along the length of the platens.
As can best be seen in
Turning now to the method by which the mat is formed using the preferred apparatus discussed previously, the mat in the heating press 1520 is preferably heated to the glass transition temperature of the component parts and kept at that temperature during the time that vacuum is applied. Further, the heating is preferable bi-directional so that the mat is uniformly heated from both sides during sealing. This might be accomplished in many ways, but in the preferred embodiment both platens 1524 and 1526 are electrically heated to the requisite temperature before closing them onto the tray 1300. The temperature should be hot enough to allow the components in the assembly tray 1300 to partially melt and seal, but not so hot as to melt the mat layers. In the preferred case where the mat is some combination of alternating polyester and polyethylene layers, the temperature offered by example previously will melt the polyethylene layers and cause them to bind, without causing any permanent damage to the polyester layers.
Another reason for heating the mat assembly is to soften the upper 530 and lower 540 members so that protuberances 535 can be pulled into them. As is illustrated in
As was indicated previously, vacuum is introduced into the closed platens 1524 and 1526 by way of apertures 1710. The amount of vacuum that is needed to form the protuberances 535 will need to be determined empirically for each mat embodiment, as the particular combination of mat materials thickness, protuberance dimensions, heating temperature, etc., will all influence how much vacuum is necessary to pull apart the layers.
In operation, the heated press 1520 is closed on the tray 1300/mat combination. As the mat is heated, vacuum is applied. Although the preferred level of heat will not melt the polyester outer unit, it is sufficiently hot to soften it. Aided by this softening, the vacuum pulls apart the two outer members 530 and 540 and forces the material into the depressions 1720, thereby forming the depressions in the face of the mat. The platens 1524 and 1526 are then pulled apart and the tray 1300 containing the now-sealed mat is withdrawn.
Now, as a next preferred step, the mat is cooled within the cooling press 1530. Although this step is not strictly required, the instant inventors have determined that the quality of the final product will be improved by this step. As is generally illustrated in
Preferably, the cooling unit 1610 will maintain the upper 1624 and lower 1626 cooling platens at about room temperature until the mat has cooled to the point where the protuberances 535 have stabilized. The cooling platens 1624 and 1626 might, for example, be either air cooled or water cooled, with the precise method of cooling being unimportant to the practice of the instant method. Of course, although it is preferred that the heating (1524 and 1526) and cooling (1624 and 1626) elements be separate platens, those skilled in the art will recognize that it would be possible to combine this functionality into a single element if that were desired.
As a final step, once the cooling unit 1610 has brought the temperature of the mat to approximately that of room temperature, the tray 1300 and the mat 1320 contained therein are removed from the cooling unit 1610. At room temperature, the materials that form the mat will have returned to their pre-heating resiliency, and the protrusions 535 that have been placed therein will be firm enough to be compressed many times before they become too fatigued to rebound. The now-cooled mat is then ready for labeling, packaging, and subsequent shipment to the distributor or buyer.
Turning now to a discussion of a preferred method of manufacturing the membrane switch 2410 described previously, sheets of polyester and polyethylene will preferably be arranged into a three-component “sandwich” (FIGS. 25 and 26), with the polyethylene layer 2510 being positioned between the two polyester layers 2505 and 2515, in preparation for heating and the application of vacuum. Additionally, it is preferable that the center/polyethylene layer 2510 be provided with one or more apertures 2525 therethrough. Additionally, it is preferred that the conductive regions 2530 and/or electrical leads 2540 be pre-applied to the upper 2505 and lower 2515 members before the package is placed within the press 1500, and further that the conductive regions be positioned in such a way as to be able to make contract through corresponding aperture 2525. Of course, it is understood that whatever material the conductive regions 2530 are imprinted or placed thereon (i.e., the inner surfaces of members 2505 and 2515), that material should itself be non-conductive to electricity.
The conducting regions 2530 will preferably be created by imprinting the opposing surfaces of the outer members 2505 and 2515 with a pattern of conductive (e.g., carbon-based) ink on that surface. That being said, those of ordinary skill in the art will recognize that many other alternatives are possible (e.g., aluminum/aluminized polyester, etc.). Of course, the only absolute requirement is that the conductive regions 2530 be capable of conducting an electrical current.
Those of ordinary skill in the art will recognize that information related to the function of a membrane switch is typically imprinted thereon, thereby assisting the user operate the attached piece of equipment. Similarly, it is preferable with respect to the instant invention that the outer surface of member 2405 contains some form of descriptive printing to label the membrane switches 2410.
As has been described previously, a contact member will be utilized in the formation of membrane switches 2410 which is similar to element 1700, except that the pattern of indentations created therein will be chosen so as to create protrusions of a size suitable for use as a membrane switch 2410. Additionally, in some cases, rather than manufacturing individual membrane switches 2410, it should be clear that interconnected arrays of such switches can similarly be produced by changing the template pattern incised into element 1700.
Finally, in operation the manufacturer of membrane switches 2410 will take place generally as described above, with the heated press 1520 preferably being closed on the layered combination 2400 while a vacuum is applied. The preferred level of heat will not melt the polyester outer unit but rather to will soften it so that protrusions may be formed therein by the application of vacuum.
Now, as a next preferred step, the switches 2400 will be cooled within the cooling press 1530. This configuration helps maintain the outward extent of the protuberances/switches 2410 during cooling. Preferably, the cooling unit 1610 will maintain the upper 1624 and lower 1626 cooling platens at about room temperature until the mat has cooled to the point where the protuberances 535 have stabilized.
As a final step, once the cooling unit 1610 has brought the temperature of the switches 2400 to approximately that of room temperature, the tray 1300 and the mat 1320 contained therein are removed from the cooling unit 1610. At room temperature, the materials that form the mat will have returned to their pre-heating resiliency, and the protrusions 2400 that have been placed therein will be firm enough to be compressed many times before they become too fatigued to rebound. The now-cooled switches are then ready for labeling (e.g., using pressure sensitive adhesive affixed to labels), packaging, and subsequent shipment to the distributor or buyer.
As is generally illustrated in
Finally, although the preferred membrane switch 2410 will generally have a rounded summit with a circular base, those of ordinary skill in the art will recognize that many other shapes are possible, depending on the desires of the designer and the limits of the deformability of the materials from which it is made. For example, in some circumstances it might be desirable to have membrane switches that are roughly rectangular in dimension, in which case the indentations within the element 1700 would be shaped accordingly. In other instances, it might be desirable to have ridges or other textures placed atop the switch 2410 to help a user find the correct place to apply pressure. These and many other variations are well within the ability of one of ordinary skill in the art to devise.
It should be noted that after the instant switches 2410 are formed and sealed it may be desirable to be die cut them to separate them, after which pressure sensitive adhesive, double sided tape or similar attachment means will preferably be affixed to the mounting surface in preparation for their use in the field. Those of ordinary skill in the art will understand how such adhesives might be chosen and applied to suit the particular application and desires of the designer.
Turning now to another preferred embodiment and as is set out in
Finally, those of ordinary skill in the art will recognize that membrane switches often contain within them an electrically conductive insert which provides tactile feedback to the user and also provides a restoring force that acts to return the switch to an open position after it has been pressed. Such inserts often take the form of thin low-profile metal dome-like structures (sometimes called snap domes) which are designed to precipitously collapse under pressure, thereby creating a snap or click which can be sensed by the user. Of course, the collapse of the dome is designed to coincide with the closure of the associated electrical circuit which allows a user to have some confidence that the selected switch has been engaged. With respect to the instant invention, preferably such inserts would be positioned in line with an aperture 2525 such that when a user presses on the switch 2410 the dome would collapse and bring the conductive regions 2530 into electrical communication with each other. Those of ordinary skill in the art will understand that such inserts can readily be positioned within the layered combination 2400 (within, for example, the openings 2525 in
It should be noted that the various temperatures, thicknesses, and other measurements noted previously are given only for purposes of illustration and should not be used to limit the practice of the subject matter claimed hereinafter. Additionally, although a series of alternating polyethylene/polyester layers is the preferred mat arrangement, those skilled in the art will recognize that many other variations are possible. It is critical, though, that whatever the chosen materials, that they be capable of being joined together along their peripheries to form a hermetic seal and that they be plastic enough to be deformed to form protuberances as has been described previously.
Further, it should be noted that the particular apparatus that is used to manufacture the preferred mat embodiment is one of only many that could be so arranged. Those skilled in the art will recognize that there are many other equipment variations and combinations that could be used to manufacture the preferred mat, including processes that would provide for large scale automation of the entire manufacturing process. In such a case, the single-mat press disclosed previously would be unnecessary, although the general steps that take place during the mat's preferred manufacturing process (e.g., heating, compression, vacuum, cooling, etc.) would need to be implemented on a larger scale.
Still further, those skilled in the art will recognize that the central spacer referred to herein need not be a discrete layer, but could instead be, by way of example, a discontinuous series of ridges, edges, or bumps which are positioned so as to separate the conductive surfaces. Further, a polyethylene layer could be made to serve as a central spacer, although that would not be preferred. What is essential, though, is that the central spacer be non-conductive, that it separates the two conductive faces of the outer members when there is no weight on the mat, and that it be sufficiently discontinuous to allow the conductive faces to come into contact when compressive pressure is applied to the mat. Thus, when the term “central spacer” is used herein, that term should be broadly construed to apply to any structure that satisfies the above-identified key requirements.
Additionally, it should be clearly noted that, although polyethylene and polyester are the preferred materials for use in constructing one embodiment of the mat of the instant invention, there are many other material combinations that could be used. It is critical, though, that the exterior materials be non-conductive so as to protect the patient from contact with the sensing current used by the electronic monitor; that the material allow for creation of two opposed conducting surfaces; and, that the materials used be malleable enough to be formed into protrusions as is described herein. Examples of other sorts of materials that might be used include, but not be limited to, polyethylene napthylate, polypropylenes, polycarbonates, high density polyethylene, polyurethane polystyrene, plastic impregnated textiles and webs, polyvinyl fluoride, plastic impregnated paper, ethyl-vinyl acetate, polyethylene, ethylene methyl acetate in mixture with ionimers, combinations of copolymers, ethylene acrylic acid, acetyl copolymers, laminates of any of the foregoing, etc.
Further, although the preferred embodiment of the instant mat contains protuberances symmetrically placed on opposite sides of the mat, it should be clear that is not an absolute requirement. Indeed, the instant inventors have specifically contemplated various asymmetric arrangements wherein, by way of example, protuberances are only formed into one side/member of the mat, wherein protuberances are formed in both halves of the mat but where the protuberances are not opposite each others (e.g., where a protuberance in one mat half faces a flat portion of the other mat member), etc. Thus, when the instant disclosure speaks of protuberances being formed in a mat, those words should be construed in their broadest sense to include symmetrically—as well as asymmetrically—placed extrusions.
Still further, it should be noted that the particular polyester/polyethylene combination utilized by the instant inventors is itself unique. That is, it would be possible to manufacture a mat that utilizes a structure analogous to that of the mat embodiment of
Even further, although the preferred embodiment utilizes a polyethylene layer upon which has been deposited a conductive surface, it should be clear to those of ordinary skill in the art that the inner surface of the polyester layer could be used in the alternative, provided that the adhesive polyethylene layer has apertures therethrough to allow the conductive surfaces on the polyester layers to come into contact. For example the embodiment of
Still further, it should be noted that electrical line 55 should be understood in its broadest sense to include, not just multi-element electrical lines, but other data transmission modalities including optical fiber. Thus, for purposes of specificity herein, the term “electrical line” will be used to include conventional multi-element electrical lines as well as optical or other data transmission lines.
Finally, although the preceding text has occasionally referred to the electronic monitor of the instant invention as a “bed” monitor, that was for purposes of specificity only and not out of any intention to limit the instant invention to that one application. In fact, the potential range of uses of this invention is much broader than bed-monitoring alone and might include, for example, use with a chair monitor, a toilet monitor, or other patient monitor, each of which is configurable as a binary switch, a binary switch being one that is capable of sensing at least two conditions and responding to same via distinct electronic signals. In the preferred embodiment, those two conditions would be the presence of patient and the absence of a patient from a monitored area. It should be noted that the use of the term “binary” is not intended to limit the instant invention to use only with sensors that can send only two signal types. Instead, binary switch will be used herein in its broadest sense to refer to any sort sensor that can be utilized to discern whether a patient is present or not, even if that sensor can generate a multitude of other signals.
Thus, it is apparent that there has been provided, in accordance with the invention, a monitor and method of operation of the monitor that fully satisfies the objects, aims and advantages set forth above. While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art and in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications and variations as fall within the spirit of the appended claims.
This application is a continuation-in-part application of U.S. patent application Ser. No. 09/878,088, filed Jun. 7, 2001 now U.S. Pat. No. 6,696,653, which application is incorporated herein by reference.
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| Number | Date | Country |
|---|---|---|
| 19802099 | Jul 1998 | DE |
| Number | Date | Country | |
|---|---|---|---|
| 20040144635 A1 | Jul 2004 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 09878088 | Jun 2001 | US |
| Child | 10701581 | US |
