1. Field of the Invention
The invention is related to the field of syringes.
2. Description of the Prior Art
A syringe is a device that includes a plunger configured to move in a bore. The plunger is used to draw in a volume of fluid when the plunger is moved to a retracted position. The volume drawn in is dependent on the cross-sectional area of the bore and also on the stroke length. Conversely, the plunger expels fluid when it is moved to an extended position. Precise movement of the plunger enables the syringe to draw in and expel precise volumes of fluid.
A syringe includes only a single port, wherein fluid is drawn in or expelled out through the single port. Consequently, only one side of the syringe plunger does work. Only one side is substantially closed off and moves and/or pressurizes a fluid being acted on.
A syringe may be used to move and/or meter out fluids. In an automated instrument, for example, a syringe may be used to provide dosing volumes, repeatedly drawing in and expelling fluids. A predetermined fluid volume tolerance may be achieved in the syringe through careful design and construction.
Tolerances are important for the precise metering of fluids. Tolerances are even more important when the fluid volumes being drawn in and expelled are small. Wear and damage may be especially problematic in a small, repetitive-use syringe. Even a small amount of wear may impact the close tolerances required to make such a syringe accurate and reliable in operation. Consequently, leakage and loss may have a disproportionately large impact on the reliability of a small, repetitive-use syringe that is metering out tiny fluid volumes.
Repetitive use may lead to wear. In a syringe having small tolerances between a plunger shaft and bore, any non-linear (i.e., side-to-side) movement of the plunger shaft may lead to contact with the side of the bore and may result in wear or other damage, such as premature wear of the plunger head. The wear to the plunger head may result in contamination of the fluid, for example Small syringe components cannot withstand much wear.
In some aspects of the invention, a centering syringe plunger guide comprises:
Preferably, the centering syringe plunger guide is formed of a material having predetermined wear characteristics.
Preferably, the centering syringe plunger guide is formed of a plastic material.
Preferably, the centering syringe plunger guide is formed of a bearing-grade plastic material.
Preferably, the guide body further includes a guide textured region on an external circumferential surface.
Preferably, the precision guide bore holds the centering syringe plunger guide in a predetermined substantially coaxial alignment with a plunger bore of the syringe barrel.
Preferably, the precision guide bore holds the centering syringe plunger guide in a predetermined substantially coaxial alignment with a plunger bore of the syringe barrel and wherein the guide plunger bore is smaller than the plunger bore.
Preferably, the centering syringe plunger guide includes a corresponding guide coupling feature in the coupling bore.
Preferably, the precision guide bore of the centering syringe plunger guide is adapted to fit over the barrel precision diameter of the syringe barrel with a predetermined clearance.
Preferably, the coupling bore, the precision guide bore, and the guide plunger bore are substantially coaxial.
Preferably, the coupling bore, the precision guide bore, and the guide plunger bore are substantially coaxial and further are substantially coaxial with a guide body axis BB.
In some aspects of the invention, a self-centering syringe assembly including a centering syringe plunger guide comprises:
Preferably, the centering syringe plunger guide is formed of a material having predetermined wear characteristics.
Preferably, the centering syringe plunger guide is formed of a plastic material.
Preferably, the centering syringe plunger guide is formed of a bearing-grade plastic material.
Preferably, the guide body further includes a guide textured region on an external circumferential surface.
Preferably, the precision guide bore holds the centering syringe plunger guide in a predetermined substantially coaxial alignment with a plunger bore of the syringe barrel.
Preferably, the precision guide bore holds the centering syringe plunger guide in a predetermined substantially coaxial alignment with a plunger bore of the syringe barrel and wherein the guide plunger bore is smaller than the plunger bore.
Preferably, the coupling sleeve includes a sleeve coupling feature and with the centering syringe plunger guide including a corresponding guide coupling feature in the coupling bore.
Preferably, the precision guide bore of the centering syringe plunger guide is configured to fit over the barrel precision diameter of the syringe barrel with a predetermined clearance.
Preferably, the coupling bore, the precision guide bore, and the guide plunger bore are substantially coaxial.
Preferably, the coupling bore, the precision guide bore, and the guide plunger bore are substantially coaxial and further are substantially coaxial with a guide body axis BB.
The same reference number represents the same element on all drawings. It should be understood that the drawings are not necessarily to scale.
The syringe barrel 104 includes a plunger bore 105, a barrel precision diameter 108 on one end, and a second barrel precision diameter 109 on the other end. The plunger bore 105 comprises a bore through the syringe barrel 104 that is configured to receive the syringe plunger 110. The plunger bore 105 is preferably substantially cylindrical in shape, but can comprise other cross-sectional shapes. The plunger bore 105 may be substantially coaxial with a central axis of the syringe barrel 104.
The plunger bore 105 is shown as being much smaller in diameter than the outer diameter of the syringe barrel 104, as may be the case where the self-centering syringe assembly 100 is used in some manner of laboratory or industrial instrument that operates on relatively small volumes of fluids. For example, the syringe barrel 104 may be formed of glass and may be employed to meter out small but precise volumes of fluid. In some embodiments, the diameter of the plunger bore 105 may be less than one-eighth inch, for example. In other embodiments, the diameter may be one-quarter inch or less. However, it should be understood that these are just examples, and the plunger bore 105 is not limited to any particular size or size range.
The syringe plunger 110 includes a plunger shaft 114 that is connected to a plunger head 112. The plunger head 112 is configured to sealingly fit into the plunger bore 105 in the syringe barrel 104. The syringe plunger 110 is configured to be reciprocatingly moved in the plunger bore 105.
The plunger shaft 114 in some embodiments is directly and rigidly connected to the plunger head 112. In some embodiments, the plunger shaft 114 and a portion of the plunger head 112 are formed as a single unit. Consequently, any slop in the plunger shaft 114 will result in the plunger head 112 being canted in the plunger bore 105. When the plunger head 112 is misaligned, a sealing contact may be reduced or minimized. Further, misalignment may cause wear of the plunger head 112, the plunger bore 105, and/or the plunger shaft 114. For example, if the syringe barrel 104 is made from glass and the plunger shaft 114 is made from metal or stainless steel, misalignment could cause the plunger shaft 114 to contact the glass, which would cause burnishing or wear of the plunger shaft 114. Such wear to the outer surface of the plunger shaft 114 could subsequently lead to corrosion or oxidation and further degradation and/or contamination. Moreover, wear may result in contamination of the fluid with worn-away particles of the syringe assembly 100.
The coupling sleeve 120 includes a coupling sleeve bore 123 configured to fit over the barrel precision diameter 108. The coupling sleeve 123 may be substantially annular in shape, and may comprise a band that fits over the barrel precision diameter 108. The coupling sleeve 120 further includes a sleeve coupling feature 126 on the exterior.
The centering syringe plunger guide 140 fits over the barrel precision diameter 108 and over the coupling sleeve 120 when the coupling sleeve 120 is in place on the barrel precision diameter 108 (see
The centering syringe plunger guide 140 includes a guide plunger bore 145 (see
The centering syringe plunger guide 140 operates to keep the plunger shaft 114 substantially centered in the plunger bore 105. Further, the centering syringe plunger guide 140 retains the syringe plunger 110 in the self-centering syringe assembly 100.
The centering syringe plunger guide 140 may include a guide textured region 154. The guide textured region 154 may provide additional friction and aid a user in grasping and manipulating the centering syringe plunger guide 140. The guide textured region 154 can comprise any manner of surface texturing or roughening, including ridging, grooving, knurling, or irregular surface texturing, for example.
The centering syringe plunger guide 140 is preferably removably affixed to the coupling sleeve 120 by the sleeve coupling feature 126. Alternatively, in some embodiments the centering syringe plunger guide 140 can be permanently affixed to the coupling sleeve 120 by the sleeve coupling feature 126.
The self-centering syringe assembly 100 can comprise a component or sub-assembly of an instrument, such as a laboratory or industrial instrument where fluids are drawn in and expelled by the self-centering syringe assembly 100. The fluids can include any liquids, gasses, or mixtures. To this end, the syringe barrel 104 can include a second barrel precision diameter 109 that can be used to mount or affix the self-centering syringe assembly 100 to another component or assembly, wherein the fluid to be handled is communicated to the syringe barrel 109 at the second barrel precision diameter end.
In an instrument, the self-centering syringe assembly 100 must deliver accurate and reliable operation, even under repeated and long-term use. Wear to the plunger bore 105 may result in leakage at the extreme of plunger retraction travel. Wear to the plunger bore 105 may lead to breakage or damage to the syringe barrel 104. Wear to the plunger head 112 may result in leakage and/or contamination of the fluid. Wear to the plunger shaft 114 may lead to damage to or breakage of the shaft. Wear could further include abrasion to metal components and therefore could permit corrosion or oxidation, which in turn could result in accelerated wear to the plunger head 112 and may further result in leakage and/or contamination of the fluid with corrosion/oxidation by-products.
The self-centering syringe assembly 100 may comprise a physically small component, wherein the plunger bore 105 is of a diameter that requires a thin, rigid plunger shaft 114. For example, the plunger bore 105 in some embodiments may be one-eighth inch or less in diameter. As a result, the plunger shaft 114 may be formed of a metal or other substantially rigid material. Consequently, a plunger shaft 114 made of plastic or other soft materials would not provide a needed rigidity and would likely flex during use, allowing the plunger shaft 114 to contact the sides of the plunger bore 105. Contact with the plunger bore surface may abrade and wear the plunger shaft 114. Contact with the plunger bore surface may abrade and wear the plunger bore 105. Flexing or movement of the plunger shaft 114 may cant the plunger head 112 and cause wear on the plunger head 112 and on corresponding regions of the plunger bore 105. Therefore, it is important that the plunger shaft 114 be kept centered in the plunger bore 105.
During assembly of the self-centering syringe assembly 100, the syringe plunger 110 is inserted into the plunger bore 105 and the coupling sleeve 120 is placed on the barrel precision diameter 108 (see
In some embodiments, the guide coupling feature 146 and the sleeve coupling feature 126 comprise threaded surfaces, wherein the centering syringe plunger guide 140 can be rotated and threaded onto and off of the coupling sleeve 120. Alternatively, the guide coupling feature 146 and the sleeve coupling feature 126 can comprise other coupling features, including frictional fit components, resilient or snap fit components, or any other suitable coupling features.
The guide body 141 includes three bore sections in the embodiment shown. The bore sections are coaxial along a guide body axis BB. In some embodiments, the guide body axis BB is a substantially central axis of the centering syringe plunger guide 140.
A coupling bore 143 extends partially into the guide body 141 from the proximal end 142. A precision guide bore 144 extends partially through the guide body 141 from the coupling bore 143. A guide plunger bore 145 extends from the precision guide bore 144 to the distal end 149 of the guide body 141. The bores 143, 144, and 145 together create a stepped bore that passes completely through the guide body 141.
In some embodiments, the coupling bore 143, the precision guide bore 144, and the guide plunger bore 145 are substantially coaxial. In some embodiments, the coupling bore 143, the precision guide bore 144, and the guide plunger bore 145 are substantially coaxial and further are substantially coaxial with a guide body axis BB.
The bores 143, 144, and 145 each have a different function. The coupling bore 143 is configured to fit over and interact with the coupling sleeve 120. To this end, the coupling bore 143 includes the guide coupling feature 146.
The precision guide bore 144 is configured to fit over the barrel precision diameter 108 of the syringe barrel 104 and hold the centering syringe plunger guide 140 in a predetermined substantially coaxial alignment with the syringe barrel 104. The precision guide bore 144 holds the centering syringe plunger guide 140 in a predetermined substantially coaxial alignment with the plunger bore 105 of the syringe barrel 104. The precision guide bore 144 of the centering syringe plunger guide 140 is adapted to fit over the barrel precision diameter 108 with a predetermined clearance.
The guide plunger bore 145 is configured to receive the syringe plunger 110. The guide plunger bore 145 in some embodiments may be smaller in diameter than the plunger bore 105, but are still kept in coaxial alignment. The guide plunger bore 145 is configured to substantially center the syringe plunger 110 in the plunger bore 105 of the syringe barrel 104. The guide plunger bore 145 therefore keeps the plunger head 112 properly aligned in the plunger bore 105 and prevents the plunger head 112 from being canted. The guide plunger bore 145 therefore holds the plunger shaft 114 substantially in the center of the plunger bore 105 of the syringe barrel 104. Consequently, the centering syringe plunger guide 140 will center the plunger shaft 114 in the plunger bore 105 even where the plunger shaft 114 may tend to slop up and down during reciprocating motion. The centering syringe plunger guide 140 will center the plunger shaft 114 when the reciprocating motion is provided from a non-linear source, such as from an eccentric wheel, cam or other such device.
Depending on the material and construction of the centering syringe plunger guide 140, the guide plunger bore 145 may comprise a bearing surface that allows the plunger shaft 114 to move easily into and out of the self-centering syringe assembly 100 in a reciprocating motion. The centering syringe plunger guide 140 may be formed of a material having predetermined wear characteristics. For example, the material may better resist or withstand wear than the syringe barrel material. In one example embodiment, the syringe barrel 104 is formed of the hardest material, the plunger shaft 114 is formed of a second hardest material, and the plunger guide 140 and the plunger head 112 are formed of the relatively softest material. The goal is to have the plunger shaft 112 rub against the plunger guide 140 in the event of misalignment, rather than rubbing against the plunger bore 105. Wearing of the plunger guide 140 is preferable to wearing of any of the other components. As a result, the centering syringe plunger guide 140 will reduce unwanted wear to more critical (and harder to replace) components. This is desirable, as wear on the syringe barrel 104, on the plunger head 112, and/or on the plunger shaft 114 may result in greater damage over time than wear on the centering syringe plunger guide 140. Further, the centering syringe plunger guide 140 may be replaceable, and more easily replaceable than the syringe barrel 104 or the plunger shaft 114.
The centering syringe plunger guide 140 may be formed of a plastic material in some embodiments. The centering syringe plunger guide 140 may be formed of a bearing-grade plastic material in some embodiments. However, other materials are contemplated and are within the scope of the description and claims.
In some embodiments, the tolerance between the plunger shaft 114 and the guide plunger bore 145 may be relatively small. As a result, the centering syringe plunger guide 140 may further act like a seal. Alternatively, sufficient clearance may remain to allow air (or other fluids) to be drawn into and expelled from the plunger bore 105. In some embodiments, the centering syringe plunger guide 140 may include a vent hole.
The detailed descriptions of the above embodiments are not exhaustive descriptions of all embodiments contemplated by the inventors to be within the scope of the invention. Indeed, persons skilled in the art will recognize that certain elements of the above-described embodiments may variously be combined or eliminated to create further embodiments, and such further embodiments fall within the scope and teachings of the invention. It will also be apparent to those of ordinary skill in the art that the above-described embodiments may be combined in whole or in part to create additional embodiments within the scope and teachings of the invention. Thus, although specific embodiments of, and examples for, the invention are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize. Accordingly, the scope of the invention should be determined from the following claims.
This application claims benefit of, and priority from, U.S. provisional patent application No. 61/325,069, filed on Apr. 16, 2010 and entitled “Self-Centering Syringe Assembly and Centering Syringe Plunger Guide”
Number | Date | Country | |
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61325069 | Apr 2010 | US |