Abstract:
Disclosed is a linear shaker apparatus capable of effectively mixing a wide variety of large volume liquid samples that provides a near linear mixing motion so as to allow for the easy break up of solids suspended in the fluid sample. The longer shaking distances and slower operating speeds employed by the linear shaker described herein, which resembles the motion a scientist or lab technician might employ when shaking such a vial by hand, does not lend itself to the electromagnetic technique employed in various prior art shakers. The linear shaker described herein employs an electric motor and linkage that allows varying the speed and stroke of the mixing operation to accommodate different laboratory protocols.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to mixing and shaking devices, and more particularly to vial shakers capable of near-linear shaking of large volumes (e.g., up to at least 50 ml) of liquids with intermixed solids to aid in breaking up solids and mixing the vial contents. 
     BACKGROUND 
     Mixing and shaking devices are widely used in a variety of laboratory applications, and may, for instance, be used in the food safety and water safety industries to test various samples. At times, such samples may initially include undissolved solids that will need to be broken up during the mixing operation. For instance, many test requirements for determining the presence of harmful chemicals, pesticides, bacteria, etc., require that larger volumes of liquid be shaken together with amounts of soil and/or vegetable matter. When shaking a mixture containing solids, it may also be desirable to break up the solids by employing a metal or ceramic ball or cylinder inside the sample tube being used to assist in macerating the solids in order to improve any chemical reaction. 
     While compact shakers have been available in the past for processing biological specimens in microplates, there exists a need for a shaker capable of effectively mixing larger volumes, for example up to 50 ml fluid samples, as may be required in food safety and water safety tests and that will sufficiently mix samples even when solids are present in the samples. 
     Linear, or essentially linear, shaking is desirable in the above instance because the relatively heavy ball or cylinder introduced to aid in breaking up the mixture works best when shaken rapidly in this essentially straight line motion. The heavy mixing ball or cylinder (if employed) can be driven from one end of the liquid containing specimen tube to the other completely breaking up the contained solids uniformly. 
     Larger specimens require a shaker that is well-balanced and that particularly properly balances forces on the apparatus during a mixing operation so as to minimize vibration and noise of the overall apparatus. It is desirable, therefore, to achieve a balance that can simultaneously maximize mixing while minimizing vibration and noise of the apparatus as a whole, without increasing the mass of the apparatus beyond a reasonable size suitable for laboratory use. 
     Moreover, various specimens have varied mixing requirements. Little prior success has been achieved in providing easily adjustable mixing apparatus for large volumes of liquid. 
     SUMMARY OF THE INVENTION 
     Disclosed is a linear shaker apparatus capable of effectively mixing a wide variety of large volume liquid samples that provides a near linear mixing motion so as to allow for the easy break up of solids suspended in the fluid sample. The longer shaking distances and slower operating speeds employed by the linear shaker described herein, which resembles the motion a scientist or lab technician might employ when shaking such a vial by hand, does not lend itself to the electromagnetic or other mechanical or electromechanical techniques employed in various prior art shakers. The linear shaker described herein employs an electric or other type of motor and linkage that allows varying the speed and stroke of the mixing operation to accommodate different laboratory protocols. 
     With regard to certain aspects of a particularly preferred embodiment of the invention, a specimen shaker is provided comprising a base having a first pivot connection and a second pivot connection, a first pivot arm pivotably connected to the base at the first pivot connection and having a first end located adjacent the first pivot connection and a second end opposite the first end, a second pivot arm pivotably connected to the base at the second pivot connection and having a first end located adjacent the second pivot connection and a second end opposite the first end, a first specimen holder attached to the first pivot arm at the second end of the first pivot arm and configured to shake a specimen therein in a direction generally perpendicular to the first pivot arm, a second specimen holder attached to the second pivot arm at the second end of the second pivot arm and configured to shake a specimen contained therein in a direction generally perpendicular to the second pivot arm, a drive affixed to the base and having a crank shaft, a first connecting arm extending between the crank shaft and the first pivot arm, and a second connecting arm extending between the crank shaft and the second pivot arm, wherein rotation of the crank shaft causes each of the first pivot arm and second pivot arm to pivot about the first pivot connection and the second pivot connection, respectively. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The numerous advantages of the present invention may be better understood by those skilled in the art by reference to the accompanying figures in which: 
         FIG. 1  is a front perspective view of a linear shaker according to certain aspects of an embodiment of the invention. 
         FIG. 2  is a front view of the linear shaker of  FIG. 1  and including an encoding device. 
         FIG. 3  is a side, partial cross-sectional view of the linear shaker of  FIG. 1 . 
         FIG. 4  is a top view of the linear shaker of  FIG. 1 . 
         FIG. 5  is a side view of the linear shaker of  FIG. 1 . 
         FIG. 6  is a front view of the linear shaker of  FIG. 1 . 
         FIG. 7  is a top, partial cross-sectional view of the linear shaker of  FIG. 2 . 
         FIG. 8  is a front perspective view of a linear shaker according to further aspects of an embodiment of the invention. 
         FIG. 9  is a side perspective view of the linear shaker of  FIG. 9 . 
         FIG. 10  is a top view of the linear shaker of  FIG. 9 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description is of a particular embodiment of the invention, set out to enable one to practice an implementation of the invention, and is not intended to limit the preferred embodiment, but to serve as a particular example thereof. Those skilled in the art should appreciate that they may readily use the conception and specific embodiments disclosed as a basis for modifying or designing other methods and systems for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent assemblies do not depart from the spirit and scope of the invention in its broadest form. 
     First, by way of summary of certain aspects of the invention, and with particular reference to  FIGS. 1 ,  8 , and  9 , a shaker  100  is provided having a base  110  and a variable speed electric motor  120  preferably rigidly attached to base  110 . Electric motor  120  is provided a drive shaft extending from one end of electric motor  120  and connected to an eccentric crank shaft assembly  125  that rotates about the drive shaft when electric motor  120  is operated. Crank shaft  125  extends into a first end of each of two connecting arms  130  and  132 . Connecting arms  130  and  132  are mounted to crank shaft  125  such that they generally point away from one another in opposite directions. The opposite end of each of connecting arms  130  and  132  are adjustably attached to pivot arms  140  and  142 . Pivot arms  140  and  142  are pivotably mounted to base  110  at pivot connections  150  and  152 , respectively, and at their opposite ends to specimen trays  160  and  162 , respectively. Thus, when electric motor  120  is operated, the rotation of eccentric crank shaft  125  causes connecting arms  130  and  132  to cyclically push and pull pivot arms  140  and  142 , causing each of them to pivot about their respective pivot connections  150  and  152 , and in turn cause each of specimen trays  160  and  162  to travel through a slightly arcuate but near-linear path A, thus shaking specimens positioned within specimen trays  160  and  162  through a back and forth, nearly linear shaking motion. 
     More particularly, and with reference to  FIGS. 1 and 2 , shaker  100  may be configured so as to cause near-linear path A (through which specimen trays  160  and  162  travel) to be nearly horizontal. In this configuration, base  110  is provided a plurality of flexible feet  111 , such as (by way of non-limiting example) rubber or generally elastomeric suction cups configured to hold shaker  100  in its intended position on a smooth, flat surface. Base  110  is also provided pivot mounting brackets  112 , each of which is configured to receive pivot connections  150  and  152 . More particularly, a pivot pin extends through each of pivot mounting brackets  112  and a lower end of each pivot arm  140  and  142 , thus allowing each pivot arm  140  and  142  to pivot about its pivot connection without separating from base  110 . Preferably, base  110  has a generally planar top wall  113  and two generally vertical walls  114 , and each pivot mounting bracket  112  is positioned on an outside face of one of the vertical walls  114 . Base  110  also includes motor support walls  115  extending upward from the top wall  113  of base  110  and configured to mount electric motor  120  between them. This, in turn, positions the motor assembly and specimen trays  160  and  162  vertically above base  110  allowing easy access by a system operator. 
     Variable speed electric motor  120  is positioned between and affixed to motor support walls  115 . As shown in  FIG. 3 , a drive shaft  121  extends from electric motor  120  through wall  115  and into eccentric crank shaft assembly  125 , and is affixed to crank shaft assembly  125  such that rotation of drive shaft  121  likewise causes rotation of crank shaft assembly  125  about drive shaft  121 . A retaining ring  122  is preferably situated between crank shaft assembly  125  and each connecting arm  130  and  132  allowing relative pivoting of each connecting arm about crank shaft assembly  125 . While not shown, a SCR (Silicon-Controlled-Rectifier) unit of standard configuration may be provided and electrically connected to motor  120  so as to allow electric motor  120  to operate at variable speeds as an operator may see fit for particular mixing operations. Alternatively, other drive and/or control mechanisms may be provided without departing from the spirit and scope of the invention, such as (by way of non-limiting example) a mechanical variable speed pulley assembly. 
     As mentioned above, a first end of each of connecting arms  130  and  132  is configured to receive a retaining ring  122  which pivotably mounts each of connecting arms  130  and  132  to eccentric crank shaft assembly  125 . An opposite end of connecting arm  130  terminates in a head  131  that is pivotably attached to preferably a front side of pivot arm  140  with a pivot pin  133 . Head  131  is attached to a rod  134 , the position of which may be adjusted so as to vary the distance of head  131  from the main body portion of connecting arm  130 . Pivot arm  140  is likewise provided a plurality of openings  141  configured to receive pivot pin  133 , such that the position of head  131  with respect to pivot arm  140  may be adjusted, in turn adjusting the stroke of connecting arm  130 , and in turn the total stroke of near linear path A achieved by specimen tray  160 . 
     Similarly, an opposite end of connecting arm  132  terminates in a head  135  that is pivotably attached to preferably a back side of pivot arm  142  with a pivot pin  136 . Head  135  is attached to a rod  137 , the position of which may be adjusted so as to vary the distance of head  135  from the main body portion of connecting arm  132 . Pivot arm  142  is likewise provided a plurality of openings  141  configured to receive pivot pin  136 , such that the position of head  135  with respect to pivot arm  142  may be adjusted, in turn adjusting the stroke of connecting arm  132 , and in turn the total stroke of near linear path A achieved by specimen tray  162 . 
     As mentioned briefly above, pivot arm  140  is pivotably attached at one end to base  110 , and particularly to one of pivot mounting brackets  112 , with a pivot connection  150  comprising a pivot pin extending through mounting bracket  112  and pivot arm  140 . The opposite end of pivot arm  140  is affixed to specimen tray  160 , such that movement of pivot arm  140  about pivot connection  150  causes specimen tray  160  to travel through near-linear path A. Similarly, pivot arm  142  is pivotably attached at one end to base  110 , and particularly to the other one of pivot mounting brackets  112 , with a pivot connection  152  comprising a pivot pin extending through mounting bracket  112  and pivot arm  142 . The opposite end of pivot arm  142  is affixed to specimen tray  162 , such that movement of pivot arm  142  about pivot connection  152  causes specimen tray  162  to travel through near-linear path A. 
     Specimen tray  160  is preferably rigidly attached to the free end of pivot arm  140 . Specimen tray  160  is configured as an open, generally rectangular tray having an outer wall  1601 , an inner wall  1602 , two side walls  1603  connecting outer wall  1601  and  1602 , and a bottom wall  1604 . A slider plate  1605  is positioned within specimen tray  160 , and is attached to a threaded adjustment knob assembly  1606  that allows the position of slider plate  1605  within specimen tray  160  to be modified and locked in place. Thus, a specimen container  200 , such as (by way of non-limiting example) a 50 ml test tube, may be positioned within specimen tray  160  and slider plate may be compressed against a top end of the specimen container  200  to hold the specimen container  200  in place during a mixing operation. Optionally, openings  1607  may be provided in inner wall  1602  to receive and properly position a bottom end of specimen container  200 . 
     Similarly, specimen tray  162  is preferably rigidly attached to the free end of pivot arm  142 . Specimen tray  162  is configured as an open, generally rectangular tray having an outer wall  1621 , an inner wall  1622 , two side walls  1623  connecting outer wall  1601  and  1602 , and a bottom wall  1624 . A slider plate  1625  is positioned within specimen tray  162 , and is attached to a threaded adjustment knob assembly  1626  that allows the position of slider plate  1625  within specimen tray  162  to be modified and locked in place. Thus, a specimen container  200  may again be positioned within specimen tray  162  and slider plate  1625  may be compressed against a top end of the specimen container  200  to hold the specimen container  200  in place during a mixing operation. Optionally, openings  1627  may be provided in inner wall  1622  to receive and properly position a bottom end of specimen container  200 . 
     Those of ordinary skill in the art will recognize that other positioning devices for receiving a properly positioning a variety of specimen containers of varied configuration may likewise be provided to suit particular mixing operations without departing from the spirit and scope of the invention. 
       FIGS. 4 and 5  show top and side views of the linear shaker  100  described above. Likewise,  FIG. 6  provides a front view of linear shaker  100  with each of specimen trays  160  and  162  at the maximum distant point of near-linear arcuate path A during a mixing operation. 
     Optionally, and as shown in  FIGS. 2 and 7 , an encoder  170 , and more preferably an optical encoder, may be provided to determine the maximum stroke achieved by each of specimen trays  160  and  162 . The measurement of such maximum stroke may be compared to the speed of variable speed electric motor  120  if an operator desires to limit the maximum shaking velocity if the adjustable stroke is too great. This feature may be used to limit excessive vibratory forces from being encountered during a mixing operation. With particular reference to  FIGS. 2 and 7 , encoder  170  is affixed to a bracket  172  positioned at the top of the front motor support wall  15 . Each detection head of encoder  170  has an opening through which each of pivot arms  140  and  142  travel, a first arm  174  including a plurality of light emitters  175 , such as light emitting diodes, and a second arm  176  including a plurality of light receptors  177 , such as photo diode receptors. As best seen in  FIG. 2 , when an encoder is utilized, each of pivot arms  140  and  142  are preferably provided a slit  142  allowing light emitted from emitters  175  to be received by an associated receptor  177 , such that the instantaneous position of pivot arms  140  and  142  may be determined and a calculation made of the maximum stroke that is being achieved at that time. 
     As shown in  FIGS. 8 ,  9 , and  10 , linear shaker  100  may be configured so as to cause near-linear path A (through which specimen trays  160  and  162  travel) to be nearly vertical. In this configuration, base  110  is again provided a plurality of flexible feet  111 , such as (by way of non-limiting example) rubber or generally elastomeric suction cups configured to hold shaker  100  in its intended position on a smooth, flat surface. Base  110  is also provided a pivot mounting bracket  112  configured to receive pivot connections  150  and  152 . More particularly, two pivot pins extend through pivot mounting bracket  112  at positions that are horizontally aligned and vertically separated from one another. Each such pivot pin likewise extends through a pivoting end of each of pivot arm  140  and  142 , thus allowing each pivot arm  140  and  142  to pivot about its pivot connection without separating from base  110 . Base  110  also preferably includes a motor support truss  116  supporting a first motor support wall  115   a  and configured to mount one end of electric motor  120 . A second motor support wall  115   b  is preferably affixed to pivot mounting bracket  112 , such that variable speed electric motor  120  is mounted between first motor support wall  115   a  and second motor support wall  115   b . This assembly, again, positions the motor assembly and specimen trays  160  and  162  vertically above base  110  allowing easy access by a system operator. 
     With continued reference to  FIGS. 8 through 10 , variable speed electric motor  120  is positioned between and affixed to motor support walls  115   a  and  115   b . As described in greater detail above, a drive shaft  121  extends from electric motor  120  through wall  115   b  and into eccentric crank shaft assembly  125 , and is affixed to crank shaft assembly  125  such that rotation of drive shaft  121  likewise causes rotation of crank shaft assembly  125  about drive shaft  121 . A retaining ring  122  is again preferably situated between crank shaft assembly  125  and each connecting arm  130  and  132  allowing relative pivoting of each connecting arm about crank shaft assembly  125 . Once again, an SCR (Silicon-Controlled-Rectifier) unit of standard configuration may be provided and electrically connected to motor  120  so as to allow electric motor  120  to operate at variable speeds as an operator may see fit for particular mixing operations. Alternatively, other drive and/or control mechanisms may be provided without departing from the spirit and scope of the invention, such as (by way of non-limiting example) a mechanical variable speed pulley assembly. 
     Also, as best seen in  FIG. 9 , a first end of each of connecting arms  130  and  132  is configured to receive bearing disc  122  which pivotably mounts each of connecting arms  130  and  132  to eccentric crank shaft assembly  125 . An opposite end of connecting arm  130  terminates in a head  131  that is pivotably attached to preferably a front side of pivot arm  140  with a pivot pin  133 . Head  131  is attached to a rod  134 , the position of which may be adjusted so as to vary the distance of head  131  from the main body portion of connecting arm  130 . Pivot arm  140  is likewise provided a plurality of openings  141  configured to receive pivot pin  133 , such that the position of head  131  with respect to pivot arm  140  may be adjusted, in turn adjusting the stroke of connecting arm  130 , and in turn the total stroke of near linear path A achieved by specimen tray  160 . 
     Similarly, and as best seen in  FIG. 10 , an opposite end of connecting arm  132  terminates in a head  135  that is pivotably attached to preferably a back side of pivot arm  142  with a pivot pin  136 . Once again and as described above, head  135  is attached to a rod, the position of which may be adjusted so as to vary the distance of head  135  from the main body portion of connecting arm  132 . Pivot arm  142  is likewise provided a plurality of openings  141  configured to receive pivot pin  136 , such that the position of head  135  with respect to pivot arm  142  may be adjusted, in turn adjusting the stroke of connecting arm  132 , and in turn the total stroke of near linear path A achieved by specimen tray  162 . 
     As described above and with continued reference to  FIGS. 8-10 , pivot arm  140  is pivotably attached at one end to base  110 , and particularly to pivot mounting bracket  112 , with a pivot connection  150  comprising a pivot pin extending through pivot mounting bracket  112  and pivot arm  140 . The opposite end of pivot arm  140  is affixed to specimen tray  160 , such that movement of pivot arm  140  about pivot connection  150  causes specimen tray  160  to travel through near-linear path A. Similarly, pivot arm  142  is pivotably attached at one end to base  110 , and particularly to pivot mounting bracket  112  at a point above the point of attachment of pivot arm  140 , with a pivot connection  152  comprising a pivot pin extending through pivot mounting bracket  112  and pivot arm  142 . The opposite end of pivot arm  142  is affixed to specimen tray  162 , such that movement of pivot arm  142  about pivot connection  152  causes specimen tray  162  to travel through near-linear path A. 
     As shown in  FIGS. 8-10 , specimen tray  160  is again preferably rigidly attached to the free end of pivot arm  140 , and is configured as an open, generally rectangular tray having an outer wall  1601 , an inner wall  1602 , two side walls  1603  connecting outer wall  1601  and  1602 , and a bottom wall  1604 . While a slider plate as described above may be used, alternatively threaded adjustment knob assemblies  1606  may be provided for each specimen container  200  that may clamp each specimen container  200  within tray  160  and, once clamped, remain locked in place. Thus, specimen containers  200 , such as (by way of non-limiting example) a plurality of 50 ml test tubes, may be positioned within specimen tray  160  and adjustment knob assemblies  1606  may be compressed against the top ends of the specimen containers  200  to hold the specimen containers  200  in place during a mixing operation. Optionally, openings may be provided in outer wall  1601  to receive and properly position a bottom end of specimen container  200 . 
     Similarly, specimen tray  162  is again preferably rigidly attached to the free end of pivot arm  142 , and is configured as an open, generally rectangular tray having an outer wall  1621 , an inner wall  1622 , two side walls  1623  connecting outer wall  1621  and  1622 , and a bottom wall  1624 . As with specimen tray  160 , threaded adjustment knob assemblies  1626  may again be provided for each specimen container  200  that may clamp each specimen container  200  within tray  162  and, once clamped, remain locked in place. Thus, specimen containers  200 , such as (by way of non-limiting example) a plurality of 50 ml test tubes, may be positioned within specimen tray  162  and adjustment knob assemblies  1626  may be compressed against the top ends of the specimen containers  200  to hold the specimen containers  200  in place during a mixing operation. Optionally, openings may be provided in inner wall  1622  to receive and properly position a bottom end of specimen container  200 . 
     Once again, those of ordinary skill in the art will recognize that other positioning devices for receiving and properly positioning a variety of specimen containers of varied configuration may likewise be provided to suit particular mixing operations without departing from the spirit and scope of the invention. 
     Optionally, and similar to the configuration described above with regard to  FIGS. 2 and 7 , rotary encoders  180  (configured to measure the angular displacement of each of pivot arms  140  and  142 ) may again be provided to determine the maximum stroke achieved by each of specimen trays  160  and  162 . The measurement of such maximum stroke may again be compared to the speed of variable speed electric motor  120  if an operator desires to limit the maximum speed if the adjustable stroke is too great. This feature may be used to limit excessive vibratory forces from being encountered during a mixing operation, as well as optimizing the mixing and/or macerating procedure. 
     Having now fully set forth the preferred embodiments and certain modifications of the concept underlying the present invention, various other embodiments as well as certain variations and modifications of the embodiments herein shown and described will obviously occur to those skilled in the art upon becoming familiar with said underlying concept. It should be understood, therefore, that the invention may be practiced otherwise than as specifically set forth herein.