Beds – Mattress – Having confined gas
Reexamination Certificate
1998-08-17
2001-01-30
Grosz, Alexander (Department: 3633)
Beds
Mattress
Having confined gas
Reexamination Certificate
active
06178578
ABSTRACT:
The present invention relates to a mattress, a mattress overlay, or a mattress replacement system including an air system having air sacks for supporting a person, and more particularly to a pressure control assembly for controlling the pressure of pressurized fluid contained by a plurality of air sacks of an air mattress. Each air sack is in fluid communication with a manifold having an interior region that is maintained at a constant pressure. The constant pressure of the pressurizing fluid within the manifold may be the same as or may be different from the pressure of pressurized fluid within at least one of the air sacks.
Beds including mattresses, mattress overlays, or mattress replacement systems (hereinafter mattresses) can be provided with bladders or air sacks (hereinafter air sacks) to support a person and to provide adjustable support and firmness characteristics. The support and firmness characteristics of the mattress can be adjusted by inflating the air sacks to increase the firmness and support characteristics of the mattress or deflating the air sacks to provide plusher firmness and support characteristics. Additionally, some mattresses have separate and independent air sacks that can be independently inflated or deflated to adjust the firmness and support characteristics of selected portions of the mattress relative to other portions of the mattress.
Maintaining the pressure of a pressurizing fluid received within each air sack typically requires the use of a control system. For example, U.S. Pat. No. 4,694,520 to Paul et al., which is assigned to the assignee of the present invention, discloses a control system including a detector for determining inadequate inflation of the mattress.
For another example, U.S. Pat. No. 4,949,414 to Thomas et al., which is assigned to the assignee of the present invention, discloses a blower supplying pressurized gas to a plurality of elongated inflatable sacks. The disclosed patient support system includes means for maintaining a predetermined pressure in the sacks preferably including a microprocessor and a plurality of pressure control valves. Each pressure control valve can regulate the air delivered through the valve to the air sack and the pressure of air delivered by each valve is monitored by a pressure sensing device. Control electronics maintain the pressure on the downstream side of the blower at a predetermined pressure, for example, by adjusting the blower speed in response to a signal comparing the actual pressure to a desired pressure. Control electronics also control the mass flow rate through each valve and cause the valves to adjust to maintain the pressure on the downstream side of each pressure control valve at its selected pressure. In addition, U.S. Pat. No. 4,745,647 to Goodwin, which is also assigned to the assignee of the present invention, discloses a control system employing control electronics to control valve settings of variable flow gas valves to maintain the pressure in each sack at a preset pressure.
An inexpensive yet effective control assembly that is reliable, easy to manufacture, and easy to maintain is needed. A control system including a minimum number of parts minimizing the number of detectors and feedback loops needed to operate the control system, and particularly a control system including a minimum number of moving parts, would be appreciated by both manufacturers and users of such systems. In addition, such an inexpensive control system that could be adjusted so that the firmness and support characteristics of various portions of the mattress could be easily changed to suit the needs or desires of the person supported on top of the mattress would be appreciated by users of such control assemblies.
According to the present invention, a control system is provided for controlling the pressure of fluid within a chamber upon which a person rests. The control system includes a manifold having a wall defining an interior region in fluid communication with a source of pressurized fluid. An air sack defines the chamber. The air sack includes a wall defining an interior region of the air sack and the wall is formed to include an air loss opening in fluid communication with the interior region of the air sack. Thus, the interior region of the air sack is in fluid communication with the atmosphere outside of the air sack.
A flow control assembly includes a conduit in fluid communication with the interior region of the air sack and in fluid communication with the interior region of the manifold. The flow control assembly further includes a check valve in the conduit to prevent the flow of pressurized fluid through the conduit from the interior region of the air sack to the interior region of the manifold.
In preferred embodiments, the control system includes a blower supplying pressurized fluid to an interior region of a manifold. The pressurized fluid is preferably air, although any generally inert gas, such as nitrogen, could be used without exceeding the scope of the invention as presently perceived. The mattress, mattress overlay, or mattress replacement system (hereinafter mattress) includes a plurality of air bladders or air sacks (hereinafter air sacks), each of which is in fluid communication with the manifold through a control assembly. Preferably, one control assembly is associated with each air sack and only one air sack is associated with each control assembly, although it is within the scope of the invention as presently perceived to have more than one air sack associated with one control assembly.
When the blower is activated, pressurized fluid is provided to the manifold. Pressurized fluid within the manifold preferably remains at a predetermined constant pressure during the operation of the blower. If desired, control electronics including a pressure sensor sensing the pressure of the fluid in the manifold and a feed back loop controlling the operation of the blower can be provided for maintaining the pressure of the pressurized fluid in the manifold. When the system achieves steady state operation, pressurized fluid is provided from the manifold to each air sack through an orifice at a predetermined delivery flow rate. In addition, pressurized fluid is exhausted from each air sack through an orifice at a predetermined exhaust rate. Each sack is thus maintained at a pressure corresponding to the size of the orifice of the delivery line, the size of the orifice of the exhaust line, and the pressure of the pressurized fluid in the manifold. Once steady state is reached, changing the pressure of pressurized fluid in the manifold, changing the size of the orifice in the delivery line, or changing the size of the orifice in the exhaust line will change the pressure of the pressurized fluid in the air sack.
Each control assembly includes a conduit connecting the interior region of the manifold to the interior region of its associated air sack so that the interior region of the air sack is in fluid communication with the interior region of the manifold. An exhaust line is in fluid communication with the interior region of each conduit to allow the escape of pressurized fluid from the air sack and the control assembly. A plate carrying an exhaust control orifice is mounted in the exhaust line to restrict the flow of pressurized fluid through the exhaust line and a plate carrying an inlet control orifice is mounted in the interior region of the control assembly between the manifold and the exhaust line to restrict the flow of pressurized fluid from the manifold to its associated air sack
The pressure within each air sack is related to the pressure of pressurized fluid in the interior region of the manifold, the flow rate of pressurized fluid through the inlet control orifice, and the flow rate of pressurized fluid through the exhaust control orifice which is equivalent to the flow rate of pressurized fluid through the inlet control orifice when the pressure control assembly is at steady state. The flow rate of pressurized fluid through each of the exhaust control orifice and the inlet c
Perez Timothy W.
Romano James J.
Soltani Sohrab
Bose McKinney & Evans LLP
Grosz Alexander
Hill-Rom Inc.
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