Abstract:
There is disclosed a constant force compression tool for measuring a compressible material. In an embodiment, the tool includes a handle having a passageway receiving a plunger. The tool includes a biasing member in communication with the plunger and the handle. The tool includes a retaining element in communication with the plunger and the handle. There is disclosed a system for measuring a compressible material with a measurement tube and a constant force compression tool. There is disclosed a method of measuring a compressible material. In an embodiment, the method includes selecting a measurement tube. The method includes placing a compressible material into the measurement tube. The method includes pressing a plunger against the compressible material. The method includes monitoring an indicator to determine a full volume of compressible material between the end of the plunger and the conical tube. Other embodiments are also disclosed.

Description:
REFERENCE TO PENDING PRIOR PATENT APPLICATION 
     This patent application claims the benefit under 35 U.S.C. 119(e) of U.S. Provisional Patent Application No. 61/589,220, filed Jan. 20, 2012, by Raymond J. Klein for “CONSTANT FORCE COMPRESSION TOOL,” which patent application is hereby incorporated herein by reference. 
    
    
     BACKGROUND 
     Generally, ground cancellous bone material is measured by scooping the material into a measurement tube followed by tamping the material with a solid rod. The amount of compression may vary due to different force amounts exerted by the users. The material expands after transfer from the measurement tube to the jar for distribution. This results in the packaging and distribution of an inconsistent amount of material that may or may not meet advertised amounts. 
     SUMMARY 
     This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key aspects or essential aspects of the claimed subject matter. Moreover, this Summary is not intended for use as an aid in determining the scope of the claimed subject matter. 
     In an embodiment, there is provided a constant force compression tool for measuring a compressible material, the tool comprising: a plunger having a first end and a second end in opposition to one another, the first end having a surface configured to compress the compressible material; a handle having a passageway receiving the plunger between the first end and the second end; a biasing member in communication with the plunger and the handle so as to provide a biasing force between the plunger and the handle; and a retaining element in communication with the plunger and the handle so as to prevent the plunger from disengagement with the handle. 
     In another embodiment, there is provided a system for measuring a compressible material, the system comprising: a measurement tube having a sidewall extending between a closed end and an open end; and a constant force compression including: a plunger having a first end and a second end in opposition to one another, the first end having a surface configured to compress the compressible material, and the second end having a ring configured to identify an appropriate measured volume of the compressible material, wherein the first end has a diameter and a length configured for disposition into the measurement tube through the open end toward the closed end; a handle having a passageway receiving the plunger between the first end and the second end, and a portion to index the ring of the plunger, wherein the handle has a stop sized to rest against the open end of the measurement tube; a biasing member in communication with the plunger and the handle so as to provide a biasing force between the plunger and the handle, wherein the spring has a fully compressed configuration extending the first end of the plunger an appropriate distance toward the closed end of the measurement tube so as to provide a predetermined amount of space within the measurement tube between the first end of the plunger and the closed end of the measurement tube; and a retaining element in communication with the plunger and the handle so as to prevent the plunger from disengagement with the handle. 
     In yet another embodiment, there is provided a method of measuring a compressible material, the method comprising selecting a measurement tube; placing a compressible material into the measurement tube; pressing a plunger of a constant force compression tool to dispose an end against the compressible material; and monitoring an indicator to determine if the plunger is disposed at a predefined distance within the conical tube together with a full volume of compressible material between the end of the plunger and the conical tube. 
     Other objects, features, and advantages of the invention will become apparent from the following detailed description of the invention with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Non-limiting and non-exhaustive embodiments of the present invention, including the preferred embodiment, are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified. Illustrative embodiments of the invention are illustrated in the drawings, in which: 
         FIG. 1  illustrates an existing measurement tube; 
         FIGS. 2-4  illustrate an exemplary embodiment of a constant force compression tool used in tandem with an existing measurement tube; 
         FIG. 5  illustrates a schematic embodiment of a constant force compression tool; 
         FIG. 6  illustrates two examples of measurement tubes; 
         FIG. 7  illustrates compressible material disposed in a measurement tube; 
         FIGS. 8-11  illustrate various features of a constant force compression tool with respect to an exemplary method of measuring a compressible material; and 
         FIGS. 12-14 ,  15 A- 15 C,  16 A- 16 C,  17 A,  17 B,  18 A- 18 C, and  19 A- 19 C illustrate various embodiments and components of a constant force compression tool. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments are described more fully below in sufficient detail to enable those skilled in the art to practice the system and method. However, embodiments may be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. The following detailed description is, therefore, not to be taken in a limiting sense. 
     In an embodiment, there is provided a multiple piece tamp rod  25  to insure a standard force or pressure is applied at a prescribed cancellous measurement. This multiple piece tamp rod  25  is referred to herein as a constant force compression tool  25  and includes a measurement tube  10  as well as the tamp rod  30  or plunger  30 . The constant force compression tool  25  allows a user, such as a technician, to apply a consistent pressure, or load, to a material  20 . The multiple piece tamp rod  25  further allows the user to deliver consistently measured and uniformly compressed materials  20 . Measuring a compressible material  20  with a consistent pressure, or load, ensures that the distributed material  20  is provided in a consistent volume in each container. 
     The constant force compression tool  25  measures a consistent volume of compressible material  20 . In one embodiment, the constant force compression tool measures  25  ground cancellous bone used in tissue banking manufacturing. Cancellous bone is compressible and occupies a different volume space depending upon the applied amount of force/pressure. It is important that the volume of the product measured is accurate so that the end user (e.g., a surgeon) will have the appropriate amount of material  20  available for use (e.g., planned spinal fusion surgery). The constant force compression tool  25  may be utilized in other industries/materials to consistently measure compressible materials  20 . 
     The constant force compression tool  25  may be used in tandem with existing measurement tubes  10  (see  FIG. 1 .) The size of the plunger  30 , the handle  35 , and the spring  40  the tool  25  may be configured to coordinate with the size of the measurement tube  10  so that for a particular volume the plunger  30  on the tool  25  aligns with the prescribed volume  15  and provides the desired compressive force/pressure to the material  20  being measured.  FIGS. 2-4  illustrate an exemplary embodiment of the constant force compression tool  25  used in tandem with an existing measurement tube  10 . 
     With reference to  FIG. 5 , the constant force compression tool  25  may include a plunger  30 , handle  35 , spring  40 , retaining pin  45 , and one or more shims  50 . However, one or more of these features may be omitted or modified. 
     The plunger  30  may perform several functions. The plunger  30  may provide surface to compress the material  20  being measured. The plunger  30  may react with the force supplied by the spring  40  to transmit this force/pressure to the material  20  being compressed. The plunger  30  may provide a contrasting ring  55  to identify when the material  20  being measured is the appropriate height or if material needs to be added or subtracted. The plunger  30  may allow limited movement with the slot  70  provided that interacts with the retaining pin  45 . 
     The handle  35  may perform several functions. The handle  35  may react with the force supplied by the spring  40  to transmit this force to the plunger  30 . The handle  35  may provide a contrasting surface  55 A,  55 B,  55 C with the plunger ring  55  to identify when the material  20  being measured is the appropriate height or if material needs to be added or subtracted. The handle  35  may hold the retaining pin  45 . The handle  35  may provide a knurled surface for the user to hold onto the device  25 . 
     The spring  40  may compress to provide the force exerted by the plunger  30 . 
     The retaining pin  45  may limit the motion of the plunger  30  relative to the handle  35  and keeps the tool assembly  25  together. 
     One or more shims  50  may be added to adjust the spring force for each particular tool assembly  25 . The height of the shims  50  may be modified to account for variation in plunger  30 , handle  35  and spring  40  tolerances. 
     For a manual operation, an embodiment of the constant force compression tool  25  may be used in tandem with existing measurement tubes  10 . As described above, the tool  25  is sized so that for a particular volume the plunger  30  on the tool  25  aligns with the prescribed volume and provides the desired compressive force/pressure to the material  20  being measured. 
     In another embodiment, the constant force compression tool  20  may include a custom manufactured measuring receptacle to optimize to the geometry of the measuring receptacle if needed. The geometry of this receptacle may be configured in a manner to ensure consistent compression of the material being used for the volume required. For example a “short” column of material may tend to be compressed more than a “tall” column of material depending upon the material properties. 
     Another embodiment of the constant force compression tool  25  may provide a sensor with feedback (e.g., visual, auditory, or a combination of both) to identify whether there is a correct amount of material  20 , too little material  20 , or too much material  20 . 
     Another embodiment may utilize feature of the constant force compression tool  25  in an automated or semi-automated piece of equipment to perform some of the manual functions, such as adding or removing material  20 . 
     A primary use of the constant force compression tool  25  includes providing a consistent volume measurement of compressible materials  20 . Another primary use of the constant force compression tool  25  includes reduction of the variance between human users for volume measurements. 
     The constant force compression tool  25  provides a method of volume measurement that eliminates the variation of force applied between different users. The constant force compression tool  25  may be used in conjunction with a measurement device  10  using visual volume graduation on the device. In an embodiment, an indicator  65  may be used on the tool  25  itself to eliminate the need for visual graduations on the measurement device  10 . 
     The constant force compression tool  25  may be constructed of lightweight materials to allow for easy handling. This may include different plastics, aluminum or titanium. 
     For aseptic applications where the constant force compression tool needs to be steam sterilized, materials that are capable of handling higher temperatures are used. Materials with similar coefficients of thermal expansion are used to prevent potential damage during thermal cycling. These may include plastics such as polysulfone, polyetherimide, polyether ether ketone or polyphenylsulfone. 
     The constant force compression tool  25  may be assembled with the spring  40  installed into the handle  35 . The plunger  30  may be installed with the smaller diameter into the spring  40 /handle  35 . The intermediate assembly may be compressed until the indicator line on the plunger aligns with the top of the handle  35 . If the indicator line  55  is not being used, then the distance the plunger protrudes from the handle is obtained. The intermediate assembly of tool  25  (which does not include tube  10 ) is placed into a load measurement device to determine if the desired force is obtained. If the force is not adequate, then one or more shims  50  may be installed and the process is repeated until the desired force is obtained. Next, the retaining pin  45  may be installed into the handle  35 . 
     Use of the constant force compression tool  25  as a manual tool may be limited to applications where the force applied is within human capabilities to apply that force. A machine with higher capabilities may be required for application of higher amounts of force. 
     The constant force compression tool  25  may be used for measurement of other materials where constraints as listed above are described. Some potential users include tissue banks that process musculoskeletal tissues. Other users may include industries where consistent measurement of compressible materials is required (e.g., tea measurement.) Monitoring of production results provides more accuracy than other measurement tools for compressible materials. 
     With reference to  FIGS. 6-10 , an exemplary embodiment of measurement is described. Select the appropriate measurement tube  10  (e.g., 15 ml tube  10 A for smaller volumes, 50 ml tube  10 B for larger volumes, etc.). (See  FIG. 6 .) 
     Using the measurement tube  10 , scoop ground cancellous bone material  20  (referred to herein as “cancellous”) into tube  10 B so the loose amount is more than the targeted tamp amount. (See  FIG. 7 .) 
     Using the appropriate size spring-loaded tamp tool  25  (with a size indicator  65 ) press the plunger against the cancellous until the handle  10  of the tamp tool contacts the end of the tube  10 A at contact  60 . (See  FIG. 8 .) 
     Under adequate lighting, with the end of the tamp tool  25  rotated slightly to view the measurement ring  55 , determine the location of the ring  55  and proceed as follows: 
     1) If the measurement ring  55  protrudes and aligns (at position  55 A) with the end of the handle  35  proceed to package the appropriately measured amount of cancellous  20 . (See  FIG. 9 .) 
     2) If the measurement ring  55  is below (at position  55 B) the end of the handle  35 , add more cancellous  20  and re-tamp. (See  FIG. 10 .) 
     3) If the measurement ring  55  protrudes (at position  55 C) from the handle  35  and white material is showing below the ring  55 , remove some cancellous  20  and/or re-tamp. (See  FIG. 11 .) 
     In one embodiment, the technician should not tamp the same cancellous  20  more than three (3) times. If three tamps are performed and the black ring  55  is not aligned, the technician may remove the cancellous  20  from the tube  10  and start over. 
     In one embodiment, the black ring  55  on the tool  25  is used for volume measurement rather than graduations on the tube. 
       FIG. 12  illustrates two exemplary embodiments of small tube  10 A configured to measure compressible material together with small tool  25 A and large tube  10 A configured to measure compressible material together with large tool  25 A.  FIG. 13  illustrates small tube  10 A and small tool  25 B separated from one another. 
       FIG. 14  is a schematic illustration of an exemplary embodiment plunger  30 , handle  35 , spring  40 , retaining pin  45 , and shim  50 .  FIGS. 15A-15C  illustrate various views of an exemplary embodiment of handle  35 .  FIGS. 16A-16C  illustrate various views of an exemplary embodiment of plunger  30 . 
       FIGS. 17A ,  17 B illustrate various views of one exemplary embodiment of plunger  30 , handle  35 , spring  40 , retaining pin  45 , shim  50 , and slot  70 .  FIGS. 18A-18C  illustrate various views of an exemplary embodiment of an exemplary embodiment of plunger  30 .  FIGS. 19A-19C  illustrate various views of an exemplary embodiment of handle  35 . 
     Although the above embodiments have been described in language that is specific to certain structures, elements, compositions, and methodological steps, it is to be understood that the technology defined in the appended claims is not necessarily limited to the specific structures, elements, compositions and/or steps described. Rather, the specific aspects and steps are described as forms of implementing the claimed technology. Since many embodiments of the technology can be practiced without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.