Patent Application
20080005843
The invention relates to apparatus for supporting a person's body or a part of a person's body. The invention may be embodied, for example, in mattresses, seat cushions, or the like.
Support surfaces such as mattresses and seat cushions that include air chambers have application for supporting people who are bed-ridden, confined to a chair or the like. A wide range of air mattresses and air cushions are suggested in the patent literature. Some such air mattresses and air cushions include controllers that control the operation of pumps and/or valves to inflate or deflate the air chambers and thereby automatically provide a required degree of support while reducing pressure points and the like.
In general it is desirable to minimize the interface pressure between the person and support surface. By doing so one can improve the health and comfort of the occupant. However, if the air pressure is too low then the person may “bottom out”. This is undesirable as bottoming out can be uncomfortable for the occupant and can even negate the benefit that the support surface is intended to provide.
Patents in the field of cushions or mattresses that include inflatable chambers include: U.S. Pat. No. 4,799,276; U.S. Pat. No. 6,721,980; U.S. Pat. No. 4,949,412; and U.S. Pat. No. 5,283,735. U.S. Pat. No. 4,554,930; U.S. Pat. No. 6,030,351 and U.S. Pat. No. 5,253,656 show pressure sensors for use on a bed or the like. U.S. Pat. No. 6,058,537 shows an air mattress with sensors for determining the location of a person. U.S. Pat. No. 5,237,501; U.S. Pat. No. 6,034,526; U.S. Pat. No. 5,539,942; U.S. Pat. No. 4,542,547 and U.S. Pat. No. 6,870,341 disclose related technologies. Other patient supports are disclosed in U.S. Pat. No. 5,630,238 U.S. Pat. No. 5,715,548; U.S. Pat. No. 6,076,208; U.S. Pat. No. 6,240,584; U.S. Pat. No. 6,320,510; U.S. Pat. No. 6,378,152; and U.S. Pat. No. 6,499,167.
Some existing systems have controllers that control the air pressure in the air chambers. In some cases, such controllers determine the pressure of air to maintain in the air chambers based upon the weight of the occupant. Existing systems may require an attendant to enter the desired air pressure, or to enter the occupant's weight. Other existing systems automatically determine the air pressure based on feedback from weight sensors which measure the weight of the occupant.
Such existing systems have several shortcomings. One shortcoming is that the air pressure is determined largely on the basis of the occupant's weight. However, different persons of similar weight may have vastly different body shapes. Consider, for example, a 200 lb, 6′-3″ tall man versus a 200 lb, 4′-11″ tall woman. Although in reality the air pressure that minimizes the interface pressure between the support surface and the occupant is different for each occupant, existing systems cannot automatically accommodate such differences because the necessary sensory inputs are not available.
Another shortcoming of the existing systems is that user interaction is required to set up the air pressure. For example, a user (typically a nurse) may enter the occupant's weight. Alternatively, the user may be required to “tare” the system while the support surface is unoccupied, in order for it to subsequently determine the occupant's weight with the required accuracy.
Other existing systems control the air pressure based on the measurement of the interface pressure between the support surface and the occupant (see for examples U.S. Pat. No. 4,799,276; U.S. Pat. No. 6,721,980, and U.S. Pat. No. 5,283,735). In these systems, the air pressure may be regulated so that the interface pressure between the occupant and the support surface does not exceed a predetermined threshold. In general these systems suffer from the shortcoming that the presence of the sensors required to measure the interface pressure itself causes detrimental interface pressures.
There remains a need for support surfaces that alleviate or overcome these shortcomings.
Some aspects of the invention provide body support surfaces. One aspect provides support surfaces having an inflatable air chamber and a plurality of pressure-sensitive taxels underlying the air chamber. Each of the taxels provides an output indicative of a pressure exerted by the air chamber on a substrate underlying the air chamber at a location of the taxel. Another aspect provides body support surfaces having: an inflatable air chamber and a plurality of pressure-sensitive taxels distributed over a two-dimensional area to sense interface pressures exerted by the air chamber. Each of the taxels provides an output indicative of a pressure exerted by the air chamber at the location of the taxel. Another aspect provides a method for controlling fluid pressure within an air chamber of a body support surface. The method comprises monitoring interface pressures of the air chamber at a plurality of spaced-apart locations and monitoring for a trend toward bottoming out by monitoring for non-uniformities of the taxel values.
Further aspects of the invention and features of specific embodiments of the invention are described below.
In drawings which illustrate non-limiting embodiments of the invention,
Throughout the following description, specific details are set forth in order to provide a more thorough understanding of the invention. However, the invention may be practiced without these particulars. In other instances, well known elements have not been shown or described in detail to avoid unnecessarily obscuring the invention. Accordingly, the specification and drawings are to be regarded in an illustrative, rather than a restrictive, sense.
The invention provides air support apparatus and methods.
Air chamber 14 may comprise a suitable bladder, for example and preferably has walls that do not stretch significantly at the normal operating pressures experienced by air chamber 14.
System 10 includes a pressure sensor 30 that provides signals 32 that carry information regarding a distribution of pressure on pressure sensor 30 caused by an occupant P. Controller 20 receives signals 32 from pressure sensor 30. In the illustrated embodiment, pressure sensor 30 is disposed underneath air chamber 14.
Pressure sensor 30 may be disposed on a substrate 34 supported by a bed frame 35 for example. It is preferable but not mandatory that pressure sensor 30 be disposed on a hard or firm surface such as a layer of high density foam, a board, or the like. If body support 10 is not required to articulate, then the substrate is preferably a hard material (such as wood or a rigid plastic). If support 10 is required to articulate, then the substrate may be a firm but flexible material, such as a high-density foam or semi-rigid plastic.
Pressure sensor 30 preferably measures a distribution of pressure over a surface beneath person P. For example, pressure sensor 30 may comprise a plurality of spatially-distributed pressure sensing elements 30A. Pressure sensing elements 30A may be called “taxels” (shorthand for “tactile elements”). The taxels are preferably spaced evenly in the area that underlies the portion of person P being supported (e.g. the person's mid-section in
The taxels of pressure sensor 30 are capable of detecting variations of pressure in an expected range. The forces acting on pressure sensor 30 will be directly related to the weight of the person P and the support area over which the person's weight is distributed. When the support area is large (as occurs, for example, when a person is lying on a bed) the expected pressures are in the range of approximately 0.05 to 0.2 pounds per square inch (roughly 300 to 1,500 Newtons/M2). If the support surface is relatively small (for example, the seat of a chair) the expected pressures could be, for example, in the range of about 0.5 to 2.0 pounds per square inch (roughly 3000 to 15,000 Newtons/M2).
Pressure sensor 30 may, for example, comprise a pressure sensor of the type described in Lokhorst et al. (PCT international patent application publication WO 2004/006768). Such sensors are available under the brand name KINOTEX™ from Tactex Controls Inc. of Victoria, Canada.
Pressure sensor 30 may be provided in the form of a separate assembly lying between air chamber 14 and substrate 34 (or optionally lying between substrate 34 and another substrate (not shown) or bed frame 35).
In the alternative, pressure sensor 30 may be integrated with the lower face of air chamber 14 or integrated with substrate 34. What is required is that pressure sensor 30 be disposed to detect a pattern of pressure applied by air chamber 14 to the underlying substrate that supports air chamber 14. As described below, it is also possible to provide an interface pressure sensor above air chamber 14.
Taxels 30A preferably each measure the interface pressure at a particular location and respond (i.e. provide output) generally in proportion to that interface pressure. Taxels 30A are preferably spaced evenly within the area under air chamber 14. In preferred embodiments, pressure sensor 30 has taxels that are distributed over a two-dimensional area. For example, the pressure sensing mat 31 of
The number and spacing of taxels 30A can be varied depending upon the specific shape, size, and bottom configuration of air chamber 14. For air chambers that have generally flat bottoms, the inventors have found that a regular arrangement of taxels 30A, spaced in the range of about 1″ (2½ cm) and 4″ (10 cm) apart, is preferable. For air chambers that assume more 3-dimensionally shaped bottoms when inflated (for example, air chambers that are cylindrical in cross-section or ribbed on their surface that contacts pressure sensor 30) it is preferable to arrange taxels 30A such that the bottom of the air chamber is in contact with taxels 30A at all air pressures. For example, if a lower surface of the air chamber is ribbed, taxels may be arranged along ribs of the air chamber.
Air regulator 16 may comprise any practical system that can be operated to maintain an air pressure within air chamber 14 at a desired value under the control of controller 20. Air regulator 16 may have any of a wide range of different structures. For example, air regulator 16 may comprise:
Controller 20 may comprise a suitably programmed data processor such as a programmable controller, a programmed computer, or the like together with interface electronics to permit control of air regulator 16. The data processor may run software instructions provided in firmware to perform methods of the invention. Controller 20 may also, or in the alternative, comprise dedicated electronic control circuits that implement suitable control algorithms or process data 32 for use in a control algorithm.
Controller 20 may include a suitable user interface that permits a user to perform functions such as turning system 10 on or off, viewing information regarding the status of system 10 and/or adjusting the operation of system 10.
Pressure sensor 30 provides pressure distribution data 32 to controller 20. Pressure distribution data 32 is essentially a map of the interface pressure between the bottom of air chamber 14 and substrate 34. Controller 20 controls air regulator 16 to cause the pressure within air chamber 14 to have a value that is determined by controller 20 at least in part on the basis of pressure distribution data 32.
In a mattress such as mattress 10A it is desirable to provide three (or more) air chambers because, in general, a higher air pressure is required in the mid-section (air chamber 14A) to support the occupant's weight. Somewhat lower air pressure (perhaps 80% of that of first air chamber 14A) may be provided in second air chamber 14B to support the occupant's torso, and even lower air pressure (perhaps 30% of that of first air chamber 14A) may be provided in third air chamber 14C to support the occupant's feet.
An interface pressure sensor 30 is located under first air chamber 14A.
Pressure sensors 30 could optionally also be provided under one or both of second and third air chambers 14B and 14C. However, in the illustrated embodiment pressure sensor 30 is only provided under first air chamber 14A which would be expected to be most susceptible to bottoming out because it carries the majority of the occupant's weight. If necessary, spacers 33 that are equivalent in thickness to pressure sensor 30 may be provided under air chambers 14B and 14C. In the alternative, the second and third air chambers may be designed with thickness different to that of the first chamber or a pressure sensor 30 of a thin type may be used.
An automatic control system 20 may be configured to individually control the air pressure of each of the air chambers 14 by use of three air pressure regulators. The air pressure in first air chamber 10A may be controlled as described herein based upon signals 32 received from pressure sensor 30. Air pressures in second and third air chambers 14B and 14C may be kept at pressures that are functions of the pressure in first air chamber 14A (for example, the air pressures in the second and third air chambers may have fixed ratios to the pressure within the first air chamber). In this way, interface pressure sensors are not required under the second and third air chambers.
A substrate 34 is provided underneath the interface pressure sensor to prevent any small protrusions on the bed frame from causing the sensor to register spurious signals. The substrate is a firm material. If the mattress is not required to articulate, then the substrate is preferably a hard material (such as wood or a rigid plastic). If the mattress is required to articulate, then the substrate may be a flexible material, such as a high-density foam or semi-rigid plastic.
Air pressure regulator 24 may comprise suitable control electronics or control mechanisms to maintain the air pressure within air chamber 14 at a set-point specified by controller 20. In the alternative, controller 20 may control components of air pressure regulator 24 directly. Any of a wide range of pressure regulator mechanisms may be provided in air pressure regulator 24.
One aspect of this invention comprises a method to operate apparatus, for example the apparatus of
In response to detecting a trend toward bottoming out, controller 20 may take action to prevent bottoming out and/or to operate apparatus 10 in a mode that is less susceptible to bottoming out.
Curve 50 shows that the sum of pressures sensed by high pressure taxels (scale at left vertical axis) initially decreases and then tends to increase, while curve 52 shows a concomitant decrease in the number of taxels supporting the person (scale at right vertical axis). The vertical line indicates a time at which a method according to an example embodiment of the invention first detects a trend toward bottoming out.
Curves 50 and 52 are examples of “indicators” that may be used to identify the bottoming-out trend. Other indicators could be used in addition to or in the alternative to the indicators illustrated in
The indicators do not need to consider the specific locations of individual taxels. The indicators may be based upon statistical functions such as sums of taxel values, average taxel values, standard deviation of taxel values or the like that do not require information regarding the locations of individual taxels.
To enhance reliability one can use more than one indicator to detect the onset of a trend toward bottoming out. For example, the inventors have found that the method is more reliable if three or more indicators are used than if the system relies on a single indicator. It is possible to combine a number of indicators, such as two or more of the indicators listed above, in various ways. One such way is to compute a weighted sum of the indicators.
The appropriate threshold values to be used in computing the indicators will vary with the construction of apparatus 10. For example, number of taxels provided by pressure sensor 30, the number and distribution of taxels 30A, the configuration and volume of air chamber 14, the nature of the substrate 34 underlying pressure sensor 30 can all effect the values of the indicators that can be considered to indicate the onset of a trend toward bottoming out. The threshold values can be ascertained empirically for a particular construction of apparatus 10.
In block 77 the indicators are compared to criteria for determining the onset of a trend toward bottoming out. In some embodiments of the invention, the criteria involve changes in the indicators relative to indicators computed for one or more previously-obtained sets of taxel values. For example, the onset of a trend toward bottoming out may be identified by determining that the values of one or more indicators are increasing.
In some embodiments the criteria are dependent upon the pressure within air chamber 14. For example, if the air pressure in chamber 14 is decreasing or is remaining reasonably constant then the indicators may be considered to be reliable indicators of the onset of a trend toward bottoming out. On the other hand, if the air pressure within chamber 14 is increasing then the bottoming out indicators may not be as reliable. In some embodiments, method 70 may determine that a bottoming trend has started only in cases where the air pressure within air chamber 14 is not increasing significantly.
If block 78 does not determine that the indicators indicate that a bottoming out trend has commenced then method 70 ends. Otherwise, if block 78 determines that a bottoming out trend has commenced, method 70 proceeds to block 79 where action can be taken in response to detecting the bottoming-out trend. For example, block 79 may involve controlling a support surface such as apparatus 10 to prevent a bottoming out trend from continuing.
In block 88, method 80 receives data from pressure sensor 30. One or more bottoming-out indicators are computed from the outputs of taxels 30A. Block 88 may involve performing method 70, for example. If block 89 detects a trend toward bottoming out then the pressure in air chamber 14 is held constant at block 90. In some embodiments, block 90 involves slightly raising the pressure within air chamber 14 and then holding the pressure within air chamber 14 constant.
If block 89 does not identify a trend toward bottoming out then method 80 returns to block 86. Method 80 cycles through loop 84 until it detects the first indication of a trend toward bottoming out. Method 80 then maintains the pressure in block 90 so that the trend toward bottoming out does not become established.
A method like method 80 may be used to provide an automatic system that optimises the interface pressure between a person and a support surface. The optimum pressure is considered to be the point at which the largest surface area of the occupant is supported, coinciding with the lowest peak pressure at any point. This method takes advantage of the ability of method 70 to detect the onset of a trend toward bottoming out before that trend becomes established (i.e. the bottoming-out indicators provide advance notice of bottoming-out). Based on the assumption that the optimum air pressure is the lowest pressure at which a trend toward bottoming-out does not become established, the advance notification provided by method 70 can be used as a signal that the optimum pressure within air chamber 14 has been reached
In practise, an automatic control system for controlling the pressure within an air chamber 14 must be able to provide suitable support for a person who is moving, changing position, getting in and out of bed (where the support surface is in a bed), as well as responding to changes in articulation of the bed-frame (where the support surface is in a bed having a frame that can be articulated).
Control system 100 provides a number of states 102A through 102G (collectively states 102). States 102 are indicated by circles and transitions between states are indicated by curved arrows 104. The conditions that precipitate a transition from one state 102 to another are labelled on each arrow. Each state 102 may be associated with an action that is performed by control system 100 upon entering the state 102. Once in a state 102 control system 100 monitors for factors that would trigger a transition to some other state 102 and operates in a manner specified for that state 102.
In some cases, the factors that cause a transition are based on a count of the number of indicators meeting a certain condition (e.g. transition 104J occurs when system 100 is in state 102C and “>2 indicators decreasing”). It is to be understood that such conditions may be replaced by comparing a single indicator (or a combination of indicators, such as a weighted sum of indicators) against a suitable threshold.
Control system 100 computes three or more indicators. The indicators are selected such that an increase in the values of the indicators while the air pressure within air chamber 14 is substantially constant or decreasing signifies the onset of a trend toward bottoming out.
Control system initializes in state 102A in which the bed is empty. In state 102A, the control system sets the air pressure set-point to a value sufficient to fully inflate air chamber 14. For example, the control system may cause the air chamber to be inflated to a pressure on the order of 25 inches of water (about 50 mmHg). When an occupant is detected then control system 100 undergoes transition 104A to “valves closed” state 102B. There are a variety of methods by which it can be determined when a person has entered a bed. For example, transition 104A may be triggered in response to:
In “valves closed” state 102B, control system 100 transmits instructions to air regulator 16 to close off airflow into and out of air chamber 14 (essentially, to stop regulating the air pressure for the time being). After a time period has elapsed, preferably about 5 to 30 seconds, control system 100 undergoes transition 104B into “reduce air” state 102C.
Upon entering “reduce air” state 102C, control system 100 instructs air regulator 16 to reduce the air pressure in air chamber 14 by some increment. After a period of time, the indicators are computed. If the indicators have reduced, then control system 100 reenters “reduce air” state 102C as indicated by transition 104C and initiates another decrement to the air pressure. If one indicator or two indicators are found to have increased, then it means that a bottoming-out trend has started. Control system switches to “hold” state 102D by transition 104D.
In “hold” state 102D, control system 100 instructs air regulator 16 to maintain air pressure in chamber 14 at the value it was when the state was entered. Periodically, the indicators are computed. If there is no significant change in indicators 104D, then the automatic control system remains in “hold” state 102D.
If one indicator increases while control system 100 is in the “hold” state, it may be indicative of the occupant moving. In that case it is desirable to conduct a test to determine if the air pressure presently being maintained in air chamber 14 is optimal. Control system 100 causes this test to be performed by providing a transition 104F to check optimum state 102E upon determining that one indicator is increasing.
In “check optimum” state 102E, control system 100 instructs air regulator 16 to increment the air pressure in air chamber 14 by some amount. After the desired increase in air pressure has been achieved (or, alternatively, after a reasonable length of time has elapsed), the indicators are computed. A decrease in the indicators indicates that another increment in air pressure is required. Upon detecting a decrease in the indicators, control system 100 undergoes transition 104G to “Increase Air” state 102G. To understand this, recall that the indicators in this example are chosen so that they reach their minimum values at or about the optimum air pressure just prior to bottoming-out. Therefore, when the indicators decrease with increasing air pressure, then it indicates that the air pressure is still too low—further increasing the air pressure is likely to further reduce the indicators.
If, when control system is in state 102E, the indicators generally increase after the increment in air pressure, then control system 100 undergoes transition 104H to “reduce air” state 102C because the increase in the indicators shows that the air pressure in air chamber 14 is higher than optimum.
In “increase air” state 102G, control system 100 instructs air regulator 16 to increase the air pressure in air chamber 14 by some increment. After a period of time, the indicators are computed. If the indicators have reduced then control system 100 undergoes transition 104H and reenters increase air state 102G. If one or two indicators are found to have increased, then it means that the bottoming-out trend has been averted, and the automatic control system undergoes transition 104I to “hold” state 102D.
In normal operation, control system 100 moves between states 102C, 102D, 102E and 102G by way of the transitions described above. To ensure proper function of system 100 it is desirable to provide an additional transition 104J between “hold” state 102D and “check optimum” state 102E. As an example of why this is desirable, consider the case where a bed occupant moves while system 100 is in “reduce air” state 102C. Such a movement may cause one or more indicators to increase (where otherwise they would have continued to decrease), incorrectly causing system 100 to switch into the “hold” state. For this reason, it is preferable to set a limit on the length of time that the system remains in the “hold” state. When the time has elapsed, the system undergoes transition 104J to “check optimum” state 102E.
It is preferable to make the time limit (the hold time-out) variable. The first time that “hold” state 102D is entered since control system 100 is initialized, the time limit may be quite short, perhaps only a few seconds. When system 100 subsequently enters a “hold” state (after cycling through the “check optimum” and “reduce” air states), if the air pressure is similar to the last air pressure while in “hold” state, then the hold time-out may be set to a larger value, perhaps several minutes or even hours in length.
In practice, events may occur that necessitate switching control system 100 into additional “bottom-out recovery” state 102F. For example, it also happens occasionally that the occupant may move in a manner that causes air chamber 14 to bottom-out. For example, a bed occupant who is initially lying down may sit up. Although the air pressure in air chamber 14 may have been sufficient to stably support the occupant while lying, the air pressure may be insufficient to stably support the occupant in a seated position. Thus, when the occupant sits up, air chamber 14 may tend to collapse and bottoming-out may occur.
In general, when bottoming-out occurs, the indicators will increase steeply. The inventors have seen that it is easy to discriminate between the slight increase in indicators that indicates the onset of a trend toward bottoming-out and the steep sudden increase in several indicators that indicates an actual bottom-out event. Therefore, if, in any of the “reduce air” 102C, “hold” 102D, “check optimum” 102E, or “increase air” 102G states, more than two of the indicators increase, system 100 assumes that a bottom-out event has occurred, and control system 100 undergoes a transition 104K, 104L, 104M, 104N to “bottom-out recovery” state 102F.
In “bottom-out recovery” state 102F, control system 100 instructs air regulator 16 to increase the air pressure in air chamber 14 by some increment. After a period of time, the indicators are computed. If the indicators are not consistent with each other (i.e. some are increasing, others decreasing) then system 100 undergoes transition 104O and reenters “bottom-out recovery” state 102F. Inconsistent indicators indicate that the system is still bottomed-out. Upon reentering state 102F, system 100 increments the air pressure set-point again.
If system 100 is in state 102F and all the indicators are increasing, then the system has recovered from bottoming-out and the bottoming-out trend has been averted. In this case, control system 100 undergoes transition 104P to “reduce air” state 102C.
If system 100 is in state 102F and all of the indicators are decreasing, it indicates that the system has recovered from bottoming-out, but that the bottoming-out trend has not yet been averted. In this case, system 100 undergoes transition 104Q to “increase air” state.
Control system 100 may be made to operate stably by controlling the conditions under which transitions can occur. For example, in the illustrated embodiment, there are no direct transitions between “Reduce Air” state 102C and “Increase Air” state. This avoids unstable behaviour (as evidenced by the system oscillating between those states). It is desirable to provide a transition (not shown) by way of which system 100 undergoes a transition from “increase air” state 102G to “reduce air” state 102C upon detecting a maximum pressure or overpressure condition in air chamber 14.
Especially in applications where a body support will be used in a vehicle or other that is susceptible to movement or in cases where a person being supported is active, it may be desirable to modify control system 100 to detect and compensate for movements that could otherwise affect the operation of control system 100.
When control system enters state 102G, air regulator 16 is controlled to isolate air chamber 14 (e.g. by closing inlet or inlet and outlet valves). While in state 102G, control system 100A does not regulate pressure in air chamber 14. Control system remains in state 102G until the motion has subsided for a prescribed period of time, preferably a few seconds.
When the prescribed time has elapsed since motion was last detected, the indicators are computed. The indicator values are compared to stored values that the indicators had prior to control system 100A undergoing transition 104R. If the indicators have not changed significantly from the values they had prior to motion being detected, then control system 100A undergoes transition 104S which takes it back into the state 102 that it was in prior to motion being detected. If the indicators have changed significantly (e.g. the indicators have changed by an amount that exceeds a set tolerance that may be, for example, in the range of 5%-20%) then control system 100A undergoes transition 104T which takes in into “check optimum” state 102E.
It can be appreciated that support surfaces and their associated control systems and mechanisms have a wide range of application including:
As an example of the range of applications of the body supports described herein,
It can be appreciated that a support surface and controller for a support surface may be varied in numerous ways while preserving the basic function of providing support. In one such variation, a pressure sensor is disposed between air chamber 14 and a body being supported.
Top layer 218 is optional and is preferably of a low-density foam material. Mattress 210 does not require a substrate except as may be necessary to properly support air chambers 14 on a bed frame. In this configuration, pressure sensor 216 is necessarily flexible.
Certain implementations of the invention comprise computer processors which execute software instructions which cause the processors to perform a method of the invention. For example, one or more processors in a controller for a support surface may implement the methods of
Where a component (e.g. a software module, processor, assembly, device, circuit, etc.) is referred to above, unless otherwise indicated, reference to that component (including a reference to a “means”) should be interpreted as including as equivalents of that component any component which performs the function of the described component (i.e., that is functionally equivalent), including components which are not structurally equivalent to the disclosed structure which performs the function in the illustrated exemplary embodiments of the invention.
As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the spirit or scope thereof. For example:
For purposes of the United States of America, this application claims the benefit under 35 U.S.C. § 119 of U.S. application No. 60/567,215, entitled PRESSURE RELIEF SUPPORT SURFACE, filed Apr. 30,2004.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/CA05/00658 | 5/2/2005 | WO | 10/30/2006 |
| Number | Date | Country | |
|---|---|---|---|
| 60567215 | Apr 2004 | US |
