Fluid handling – Line condition change responsive valves – Direct response valves
Reexamination Certificate
2002-12-24
2004-11-23
Krishnamurthy, Ramesh (Department: 3753)
Fluid handling
Line condition change responsive valves
Direct response valves
C137S512400, C137S853000, C137S605000, C604S247000
Reexamination Certificate
active
06820652
ABSTRACT:
TECHNICAL FIELD
The present invention relates to the field of fluid handling and control; particularly, to a passive multi-channel valve capable of completely purging a terminal channel.
BACKGROUND OF THE INVENTION
Those in the fluid handling industry have long-recognized the need for systems capable of delivering two or more fluids from respective reservoirs while preventing contaminants from entering the reservoirs, and systems that facilitate purging of critical fluid delivery channels. However, these desired characteristics have not previously been incorporated into a single valve.
The fluid handling industry has long-recognized the value in the simplicity of passive valves. Examples of such valves include U.S. Pat. No. 4,846,810 to Gerber, U.S. Pat. No. 5,080,138 to Haviv, and U.S. Pat. No. 5,836,484 to Gerber. In their most general sense, the valves of the '810, '138, and '484 patents incorporate an elastomeric sheath that tightly fits onto a valve body and controls the delivery of the fluid. Fluid is delivered through a channel in the valve body to a point in which the channel terminates against the inside surface of the annular sheath. Upon, a rise in fluid pressure above a predetermined level, known as the cracking pressure, the fluid forces the elastomeric sheath away from the valve body, thereby allowing the fluid to create a chamber between the sheath and the body into which it can flow. In the '810 and '138 devices, as the chamber expands due to the ingress of the pressurized fluid, the sheath is forced away from the body in the vicinity of a discharge channel, or channels, thereby permitting the fluid to exit the chamber through the discharge channel. As the fluid pressure falls below the cracking pressure, the sheath returns to a normal position tightly against the body, thereby sealing off the delivery channel and forcing the fluid remaining in the chamber into the discharge channel. The mechanism is similar in the '484 device, except that the elastic rebound of the sheath, instead of forcing fluid into a discharge channel, forces the fluid from the chamber to atmosphere.
The elastomeric sheaths of the '810, '138, and '484 valves function quite well in preventing contamination via backflow and migration of contaminants with a single fluid source. However, these do not satisfy the demand for a passive valve that can be effectively purged and can handle multiple fluids, and the unique challenges associated with multiple fluid control. In fact, the handling of multiple fluids and the associated challenges is often as important, if not more important, than the prevention of backflow.
Addressing the purge function, the prior art devices all lack a true purging capacity. In the '810, '138, and '410 devices, the elastic rebound of the sheath tends to force the fluid out of the chamber created by the distention of the elastomeric sheath, and into either a discharge channel or to atmosphere, as described above. At no point is the discharge channel or atmospheric chamber completely purged of fluid. In this sense, the prior devices might be most accurately seen to have a “volume reducing” capacity, in that the closing action of these valves does not truly purge but does tend to reduce the amount of fluid remaining in the valve when the fluid pressure drops below the predetermined cracking pressure.
To consider the practical aspects of this problem from a more concrete perspective, by way of illustration and not limitation, consider an application requiring the management of two fluids, one a fluid that for some reason is best handled by completely expelling it from the valve after closing, another a fluid that may remain in the valve after closing. By adjusting aspects of the design as will be discussed in detail below, possibly including the relative volumes of the respective fluid chambers, the valve of the instant design can be made to purge the first fluid from the valve. In such an exemplary construction, the second fluid may flow sequentially or for a longer time than the first fluid through the discharge channel as the valve is closing, thus purging the discharge channel of the first fluid with the second. A possible application, by way of example and not limitation, might be the provision of a heparin flush following the infusion of another pharmaceutical ingredient, to discourage in vivo clotting at the delivery point of the infusion.
An additional problem not addressed in the prior art relates to the problem of diffusion of small molecules through the elastomeric sheath. Numerous prior art valves are exposed in large part to the atmosphere, unless they were to be enclosed in a separate and specially designed chamber. Exposure to atmosphere would allow the continuous escape of small molecules through the elastomeric sheath in response to the concentration gradient present between the fluid in the valve and the atmosphere. Such diffusion would tend to increase the concentration of those elements of the fluid which are unable to move across the elastomeric sheath. To utilize a concrete example, by way of example and not limitation, if an active ingredient with a relatively large chemical structure were dissolved in ethanol, which has a very small chemical structure, ethanol molecules would tend to migrate across the elastomeric sheath to the atmosphere, thereby increasing the relative concentration in the fluid of the large molecules that were unable to diffuse across the barrier. If these large molecules were a drug with critical concentration dispensing requirements, it could pose adverse medical effects. Therefore, minimum exposure to the atmosphere is highly desirable.
Since the instant invention has a relatively small area of exposure to atmosphere, in certain embodiments, it may obviate a great deal of this problem. Any diffusion that should occur across a first elastomeric sheath diffusion area occurs into a closed space, and must then diffuse through a second portion of elastomeric sheath, generally having a smaller area for diffusion than the first diffusion area, in order to escape to atmosphere. This double barrier diffusion path may act to slow diffusion.
Perhaps most importantly, unlike the prior art designs, the present invention adds the capacity to effectively mix two or more fluids. Most obviously, a multiple chamber valve has the capacity to dispense multiple components at the same time in a mixed dispensing action, but the instant invention also adds considerably more than mixing to the fluid management capacity of the art.
For example, the traditional means of regulating the cracking pressure of the valve's elastomeric sheath, as seen in the prior art devices noted above, is by varying the thickness of the sheath and the bulk modulus of the elastomeric material. The instant invention, as will be described in detail below, adds new methods for regulating the cracking pressure of the valve, as well as tuning the cracking pressure at various locations on the sheath. By way of example, and not limitation, the cracking pressure can be regulated by varying the location of divisions of the chambers in a generally circumferential manner, or by varying the size of the divisions giving one chamber a larger arc of the elastomeric sheath than that of the other, or others. Such an increase would effectively create one chamber exposed to a longer spring with the same spring constant as the other, thus creating a lower cracking pressure.
As an additional fluid management tool, the instant invention, as will be described in detail below, offers the capacity for enhanced features to prevent fluid backflow. By way of example, and not limitation, the valve can be constructed with fluid entrance and exit ports of differing sizes and geometries. For example, a first port that supplies fluid to a chamber requires a first cracking pressure to force the seal from the opening. Fluid may then exit the chamber from a second port. If reverse flow tried to enter the chamber via the second port and the second
Adams Theodore Robert
Gaydos Peter A.
Dawsey David J.
Gallagher Michael J.
Gallagher & Dawsey Co. LPA
Krishnamurthy Ramesh
Ventaira Pharmaceuticals, Inc.
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