Frozen bag of liquid thawer utilizing heat at ambient temperature

This invention is generally directed to a bag thawer device for thawing frozen bags of liquid. More specifically, in the medical field this invention is directed to a bag thawer which utilizes ambient room temperature for thawing frozen bags of intravenous administration solutions.

In the medical field medical solutions are commonly administered to patients by intravenous administration (I.V.) techniques. Frequently, the medical solution is contained within an I.V. bag which is stored, for example, at a hospital pharmacy. The pharmacy freezes many I.V. bags containing medical solutions to obtain a longer storage life. Of course, the frozen bag of solution must be thawed prior to administration to a patient. Frozen I.V. bags are typically thawed to a room temperature of approximately 72° F. or approximately 75° F. After the bag is thawed, the pharmacy may add medications to the solution and apply appropriate labeling to the bag prior to delivery to the patient.

Various techniques and devices have been utilized to thaw a frozen bag of I.V. solution. For example, a frozen bag of solution can be thawed by placing the bag on a countertop and allowing ambient air to warm the frozen solution. However, the countertop thawing method requires use of valuable pharmacy counter space for an extended period of time and creates a messy residue of condensation. The condensation on the bag may interfere with application of the label onto the bag. Furthermore, thawing a frozen bag by contact with ambient air requires an extended period of time because air is a relatively poor heat conductor. This long thawing time may be unacceptable when a patient requires an I.V. bag in an emergency situation.

A frozen bag of solution can be thawed by blowing ambient air at room temperature over the frozen bag. However, this method of thawing exhibits the problems of the countertop thawing method. Although blowing air over the frozen bag reduces thawing time, the thawing time may remain unacceptably long in emergency situations.

A frozen bag of solution can be thawed by blowing heated air over the frozen bag. However, a heated air thawing device exhibits the problems of the countertop thawing method and the blowing ambient air thawing method. Although, blowing heated air over the frozen bag reduces thawing time, the thawing time may remain unacceptably long in emergency situations. The thawing time can be reduced by increasing the temperature of the heated air. However, forced thawing of medical solutions at high temperature is undesirable.

A frozen bag of solution can be thawed by exposing the frozen bag to microwaves. However, forced thawing of medical solutions at high temperature is undesirable.

A frozen bag of solution can be thawed by immersion of the bag into a water bath. However, a water bath thawing device can be cumbersome and messy and requires periodic changing of the water bath. Further, water remaining on the outside of the bag after thawing may interfere with application of the label onto the bag.

Therefore, a need exists to improve the methods of and the devices for thawing frozen bags of medical solutions. The present invention satisfies this need. The present invention quickly and efficiently thaws frozen bags of solution without subjecting the solutions to excessive heat. The present invention thaws frozen bags of solution by placing the frozen bags under pressure between contact plates at room temperature. The present invention quickly transfers heat at room temperature from the contact plates to the frozen solution to thaw the solution.

Accordingly, one advantage of the present invention is to improve devices which thaw frozen bags of liquid.

Another advantage of the present invention is to thaw frozen bags of liquid without exposing the liquid to an excessive temperature.

Another advantage of the present invention is to thaw frozen bags of liquid rapidly.

Another advantage of the present invention is to inhibit condensation from forming on the bags of liquid.

Additional advantages of the present invention will be apparent from reviewing this specification, the drawings, and the claims.

The present invention provides a bag thawer for thawing at least one bag of frozen liquid. Generally, the frozen bags of liquid are I.V. bags containing medical solutions. The bag thawer provides an upper contact plate sized to contain a first quantity of heat at room temperature and a lower contact plate sized to contain a second quantity of heat at room temperature. The upper and lower contact plates are sized such that the total heat contained in the upper and lower contact plates is sufficient to thaw the frozen I.V. bags without applying additional heat to the I.V. bags or rewarming the contact plates. The upper and lower contact plates are hinged together and the upper contact plate is biased towards the lower contact plate. The frozen I.V. bags are placed in between the upper and lower contact plates for thawing.

In one alternative embodiment, the present bag thawer invention provides a pair of contact plates which contact the frozen bags of liquid. A pair of heaters are placed in contact with the contact plates to maintain the contact plates at approximately room temperature. The heaters are placed on sides of the contact plates furthest away from the frozen bags of liquid. A heater control controls the temperature of the heaters. The pair of contact plates are biased towards the frozen bags of liquid.

FIG. 1 is a perspective view of a bag thawer in accordance with the present invention.

FIG. 2 is an end view of the bag thawer of FIG. 1 showing the bag thawer in an unclamped position.

FIG. 3 is a partial, detail view of the bag thawer of FIG. 2 showing a hinge which is separated.

FIG. 4 is an end view of the bag thawer of FIG. 1 showing the bag thawer in a clamped position.

FIG. 5 is an end view of a bag thawer of FIG. 1 showing an I.V. bag positioned in the bag thawer.

FIG. 6 is an end view of a bag thawer of FIG. 1 showing the bag thawer mounted on a wall.

FIG. 7 is a front elevational view of another embodiment of a bag thawer in accordance with the present invention.

FIG. 8 is an end view of the bag thawer of FIG. 7.

FIG. 9 is a partial view of the bag thawer of FIG. 7 along line A-A showing an I.V. bag positioned in the bag thawer.

FIG. 1 shows a perspective view of a bag thawer 10 made in accordance with the principles of the present invention. The bag thawer 10 comprises an upper contact plate 12 and a lower contact plate 14. The upper contact plate 12 is movably connected to lower contact plate 14 by a hinge 16. The bag thawer 10 further comprises a clamp 18 for biasing upper contact plate 12 towards lower contact plate 14.

FIG. 2 shows an end view of bag thawer 10. The upper contact plate 12 provides a handle 20. Preferably, handle 20 is integral with upper contact plate 12. Handle 20 is provided to lift upper contact plate 12 away from lower contact plate 14 and to lower upper contact plate 12 towards lower contact plate 14. The upper contact plate 12 also provides an upper contact surface 22. Preferably, upper contact surface 22 is substantially flat; although, upper contact surface 22 may have a contoured shape. The upper contact plate 12 is constructed from a material selected for the material's heat transfer and heat capacity properties. For example, upper contact plate 12 may be constructed from aluminum.

The lower contact plate 14 is also constructed of a material selected for the material's heat transfer and heat capacity properties. For example, lower contact plate 14 may be constructed from aluminum. The lower contact plate 14 has a lower contact surface 24. Preferably, lower contact surface 24 is substantially flat; although, lower contact surface 24 may have a contoured shape. At least one bumper 23 is removably attached to lower contact surface 24. Bumper 23 is constructed out of a resilient material, such as rubber, and provides a cushion and space between upper contact plate 12 and lower contact plate 14. The bumper 23 may provide sufficient space between contact plates 12, 14 to allow clearance for an I.V. administration port on the I.V. bag. Feet 25 are removably attached to lower contact plate 14. Feet 25 support bag thawer 10 when bag thawer 10 is placed on a table or countertop. Lower contact plate 14 is adapted to be mounted on a wall. As shown in FIG. 6, a bracket 44 can be fastened to lower contact plate 14 for mounting bag thawer 10 to the wall. Alternatively, as shown in FIG. 4, lower contact plate 14 may provide a support recess 46 which cooperates with a support bracket mounted onto a wall.

The sizes of upper and lower contact plates 12, 14 are selected such that upper and lower contact plates 12, 14 contain sufficient heat at room temperature to thaw a desired number of frozen I.V. bags. More specifically, upper contact plate 12 is sized such that upper contact plate 12 contains a first quantity of heat at room temperature. Upper contact plate 12 contains the first quantity of heat due to upper contact plate's 12 size of mass. Upper contact plate 12 has a temperature of approximately room temperature because upper contact plate 12 is allowed to contact ambient room temperature air. If upper contact plate 12 is cooler than room temperature, alter sufficient time the ambient room air will warm upper contact plate 12 to room temperature. One size of a preferred solid aluminum upper contact plate 12 has been found to be approximately 161/2 inches wide× 81/4 inches deep ×1 inch thick. Likewise, lower contact plate 14 is sized such that lower contact plate 14 contains a second quantity of heat at room temperature. Lower contact plate 14 contains the second quantity of heat due to lower contact plate's 14 size of mass. Lower contact plate 14 has a temperature of approximately room temperature because lower contact plate 14 is allowed to contact ambient room temperature air. If lower contact plate 14 is cooler than room temperature, after sufficient time the ambient room air will warm lower contact plate 14 to room temperature. One size of a preferred solid aluminum lower contact plate 14 has been found to be approximately 161/2 inches wide×75/8 inches deep×11/2 inches thick. For reference, the 161/2 inch width is along the front of bag thawer 10 as can be seen in FIG. 1. The first quantity of heat contained in the mass of upper contact plate 12 combined with the second quantity of heat contained in the mass of lower contact plate 14 is the total amount of heat contained in bag thawer 10. The total amount of heat at room temperature contained in bag thawer 10 is sufficient to thaw a desired number of frozen I.V. bags without applying any additional heat to the I.V. bags or rewarming contact plates 12, 14. For example, a bag thawer 10 sized as set forth above has been found to thaw four 100 ml frozen I.V. bags in less than 10 minutes.

As shown in FIG. 2, hinge 16 movably connects upper contact plate 12 to lower contact plate 14 at a hinge location 26. Hinge 16 allows upper contact plate 12 to pivot in relation to lower contact plate 14. Upper contact plate 12 pivots around an axis of rotation at hinge location 26. Preferably, hinge 16 also allows upper contact plate 12 to move away from lower contact plate 14 at hinge location 26. Specifically, with contact plates 12, 14 positioned horizontally as shown in FIG. 2, upper contact plate 12 can move in a linear, vertical direction. The vertical direction is perpendicular to the axis of pivotal rotation of hinge 16. As such, hinge 16 provides upper contact plate 12 with both pivotal and linear movement at hinge location 26. In a preferred embodiment, hinge 16 comprises a projection 28 and a projection seat 30. The projection 28 is integral with and extends from upper contact plate 12. The projection 28 comprises an enlarged end 28a and a shaft 28b which connects enlarged end 28a to upper contact plate 12. As shown in FIG. 3, the enlarged end 28a has a width 29b and a height 29b. The width 29b is greater than the height 29b. Preferably, width 29b and height 29b form an oblong shaped enlarged end 28a. The enlarged end 28a cooperates with projection seat 30 as described below.

Projection seat 30 is defined by an opening 31 and a recess 33 in lower contact plate 14. Opening 31 is smaller than width 29b and larger than height 29b. As such, enlarged end 28a can pass through opening 31 when enlarged end 28a is pivoted so that height 29b faces opening 31. Similarly, enlarged end 28a cannot pass through opening 31 when enlarged end 28a is pivoted so that width 29b faces opening 31. The recess 33 is sufficiently large to allow enlarged end 28a to pivot and to move vertically regardless of the pivotal orientation of enlarged end 28a. This configuration of hinge 16 allows complete separation of contact plates 12, 14 at hinge location 26 only when contact plate 12 is pivoted to a position where the height 29b of enlarged end 28a can pass through opening 31 of projection seat 30. Thus, projection 28 and projection seat 30 are shaped and sized such that projection 28 is both pivotal in projection seat 30 and linearly moveable in a vertical direction perpendicular to the axis of pivotal rotation. The projection 28 and projection seat 30 preferably extend along substantially the entire width of bag thawer 10.

The end view of bag thawer 10 in FIG. 2 also shows an end view of clamp 18. Clamp 18 comprises a clamp handle 32, a pair of rocker arms 34, and a pair of springs 36. One spring 36 and one rocker arm 34 are positioned at one side of bag thawer 10 and the other spring 36 and rocker arm 34 are positioned at the opposite side of bag thawer 10. Spring 36 has a first spring end 38 and a second spring end 40. The first spring end 38 is attached to lower contact plate 30. The second spring end 40 is attached to rocker arm 34. Preferably, first and second spring ends 38, 40 are removably attached to lower contact plate 14 and rocker arm 34, respectively. Rocker arm 34 is pivotally connected to upper contact plate 12. Clamp handle 32 is connected to both rocker arms 34.

When clamp 18 is in the unclamped position, as shown in FIG. 2, spring 36 is in a relaxed, unstretched condition. Alternatively, spring 36 may be in a slightly stretched condition when bag thawer 10 is unclamped. Thus, in the unclamped position spring 36 exerts a minimal force or zero force biasing upper contact plate 12 towards lower contact plate 14.

FIG. 4 shows the end view of FIG. 2 with bag thawer 10 in the clamped position. The rocker arm 34 is pivoted from the unclamped position to the clamped position. As rocker arm 34 is pivoted from the unclamped position to the clamped position spring 36 is stretched. Thus, in the clamped position, spring 36 exerts an increased force biasing upper contact plate 12 towards lower contact plate 14. The biasing force can be varied by selecting appropriate springs 36 and varying the amount of spring stretch. A desirable combined biasing force from the pair of springs 36 has been found to be approximately 15 lbs. to 30 lbs. In addition to the biasing force from the pair of springs 36, a gravitational force may bias upper contact plate 12 towards lower contact plate 14. The gravitational force on an upper contact plate 12 having a size of the dimensions discussed above has been found to be approximately 15 lbs. As such, the pair of springs 36 together with gravity may exert a biasing force of approximately 30 lbs. to 45 lbs.

In operation of bag thawer 10 from the unclamped position, upper contact plate 12 is lifted away from lower contact plate 14 by handle 20. A frozen I.V. bag 42 is placed on the lower contact surface 24. Preferably, I.V. bag 42 is positioned so that the I.V. bag administration ports will not be pinched between the upper and lower contact plates 12, 14. The upper contact plate 12 is lowered to allow upper contact surface 22 to contact I.V. bag 42 as shown in FIG. 5. The clamp handle 32 is pulled to pivot rocker arms 34 to the clamped position as shown in FIG. 4. As such, springs 36 are stretched and upper contact plate 12 is biased towards lower contact plate 14. Because I.V. bag 42 may be highly deformed due to the freezing process, upper and lower contact plates 12, 14 may rest unparallel to each other. The dual movement of hinge 16 allows upper and lower contact surfaces 22, 24 to adjust position to maximize contact with I.V. bag 42.

With upper and lower contact surfaces 22, 24 in contact with I.V. bag 42 heat will start to transfer from upper and lower contact plates 12, 14 to I.V. bag 42. The rate of heat transfer is dependent on a heat transfer coefficient, the contact area, and a temperature differential between I.V. bag 42 and contact surfaces 22, 24. The area of contact between upper and lower contact surfaces 22, 24 with I.V. bag 42 may initially be limited because I.V. bag 42 may be deformed. However, the contact area is the first area to thaw. Alter only a small portion of I.V. bag 42 has thawed, there is sufficient fluid, with the clamping force, to cause upper and lower contact plates 12, 14 to realign and to increase the contact area. The heat transfer rate increases with the increase in contact area. Additionally, the formation of condensation on I.V. bag 42 is minimal or eliminated. Condensation does not form because thawing occurs in contact with contact plates 12, 14 and not in contact with ambient air which contains moisture.

The clamp 18 is returned to the unclamped position after I.V. bag 42 is thawed. The upper contact plate 12 is lifted by handle 20 and thawed I.V. bag 42 is removed. Bag thawer 10 is allowed to return to room temperature by transferring heat from ambient air to bag thawer 10.

Bag thawer 10 may be sized to thaw multiple frozen I.V. bags 42 during a single thawing operation. Further, bag thawer 10 may be sized to contain sufficient heat to thaw multiple frozen I.V. bags 42 during more than one thawing operation without reheating bag thawer 10 between thawing operations. For example, a bag thawer 10 may be sized to thaw tour 100 ml frozen I.V. bags 42 in less than 10 minutes.

FIG. 7 shows a front elevational view of a bag thawer 110 in accordance with the present invention. Bag thawer 110 provides a pair of contact plates 112, 114. Contact plate 112 is an upper contact plate and contact plate 114 is a lower contact plate. When thawing a frozen I.V. bag 42, I.V. bag 42 is placed between contact plates 112, 114. In this manner, contact plates 112, 114 contact I.V. bag 42 on opposite sides of I.V. bag 42. In this embodiment of the invention, contact plates 112, 114 may not be sized to contain sufficient heat at room temperature to thaw frozen I.V. bag 42.

Rather, a pair of heaters 116, 118 are provided to supply sufficient heat to thaw frozen I.V. bag 42. Each one of heaters 116, 118 is coupled to one contact plate 112, 114 on a side of the contact plate 112, 114 away from I.V. bag 42. Heater 116 is an upper heater and contacts upper contact plate 112 on the side of upper contact plate 112 away from I.V. bag 42. Likewise, heater 118 is a lower heater and contacts lower contact plate 114 on the side of lower contact plate 114 away from I.V. bag 42. With this construction, heat from heaters 116, 118 must pass through contact plates 112, 114 to reach I.V. bag 42.

A pair of back plates 120, 122 are provided to support heaters 116, 118 and contact plates 112, 114. Each back plate 120, 122 is coupled to one heater 116, 118 on a side of the heater 116, 118 away from the contact plate 112, 114. The back plate 120 is an upper back plate and contacts upper heater 116 on a side of upper to heater 116 away from upper contact plate 112. Likewise, back plate 122 is a lower back plate and contacts lower heater 118 on a side of lower heater 118 away from lower contact plate 114.

The lower back plate 122 is supported on a base 124 which supports bag thawer 110 on a table. The base 124 has a bottom side 126 facing the table and a top side 128 facing away from the table. A resilient support 130, such as a set of springs, flexibly supports one of the pair of back plates on the top side 128 of base 124. More specifically, springs 130 contact top side 128 and lower back plate 122, to flexibly support lower back plate 122. The flexible support of lower back plate 122 allows parallel and unparallel alignment of contact plates 112, 114. A flexible alignment of contact plates 112, 114 provides improved contact with frozen I.V. bag 42 when I.V. bag 42 has an irregular shape.

FIG. 8 shows an end elevational view of bag thawer 110 of FIG. 7. A hinge 132 is pivotally attached to base 124 and upper back plate 120. The hinge 132 allows back plates 120, 122 to be separated. Contact plates 112, 114 are also separated because contact plates 112, 114 are coupled to back plates 120, 122 by heaters 116, 118, respectfully. When contact plates 112, 114 are separated, I.V. bag 42 can be placed into contact or out of contact with contact plates 112, 114.

Bag thawer 110 biases contact plates 112, 114 towards I.V. bag 42. This ensures contact between I.V. bag 42 and contact plates 112, 114 during a thawing procedure. A set of clamps 134, for example, may be utilized to bias contact plates 112, 114. The clamps 134 are attached to back plates 120, 122 to bias back plates 120, 122 towards each other. Therefore, clamps 134 are coupled to contact plates 112, 114 via back plates 120, 122 and heaters 116, 118. Clamps 134 may cooperate with springs 130 to ensure a continuous biasing force during thawing.

FIG. 9 shows a cross-sectional view of a portion of bag thawer 110 of FIG. 7 along line A--A. A heater control 136 is electrically connected to heaters 116, 118. The heater control 136 controls the temperature of heaters 116, 118. By controlling the temperatures of heaters 116, 118, heater control 136 limits the temperatures of contact plates 112, 114. More specifically, heater control 136 limits the temperature of contact plates 112, 114 to a maximum temperature of approximately room temperature. Typically, room temperature is approximately 72° F. or 75° F. Thus, I.V. bag 42 is exposed to maximum temperature of room temperature.

A pair of thermocouples 138, 140 may be electrically connected to heater control 136. Each one of the thermocouples 138, 140 contact one contact plate 112, 114. Each one of the thermocouples 138, 140 may also contact one heater 116, 118. The thermocouples 138, 140 measure the temperature at these locations and send a signal to heater control 136. As such, heater control 136 controls the temperatures of heaters 116, 118.

Various changes and modifications to the embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present invention and without diminishing its attendant advantages. Therefore, the inventors intend that such changes and modifications be covered by the appended claims.