The invention pertains to laboratory products and in particular to clamps for laboratory shakers.
Shakers are widely used in laboratories to stir liquids held in beakers, flasks or test tubes. The shaker has a platform that oscillates horizontally when the shaker is operating. A shaker platform will normally include an array of threaded holes to enable attachment of clamps to the platform with screws. Metal flask clamps for Erlenmeyer flasks typically include a pair of intersecting bands that extend horizontally to form a base and bend upward to extend above the hip of the flask and along the tapered wall of the flask. Normally, a spring coil is attached around the ends of the bent bands. The flask is inserted into the clamp by expanding the spring coil and the bands outwardly by pressing the base of the flask into the opening created by the spring coil. One of the issues with metal clamps of that flasks tend to spin within the clamps when the shaker operates. The spinning can cause marring if the flask is made of glass, and in fact can cause substantial damage if the flask is made of plastic. Another issue is that metal springs require extreme forces to insert or remove the flask, and there is the danger of flask breakage. In addition, the metal springs tend to deform and loosen after repeated use and the flasks tend to rattle loosely inside the metal flask clamp creating significant noise pollution in the workspace. If the flask contains a large volume of fluid significant torque is generated which can cause the flask to spin excessively within the clamp especially if the metal springs are loose. Plastic clamps have been offered in the industry, but have not been widely accepted primarily because they do not conform well to the flask.
In addition, it is inconvenient for laboratory workers to detach and replace the clamps because the clamps are screwed to the shaker platform. For example, the laboratory worker must first retrieve a screw driver with a correct head and then physically screw and unscrew the clamps onto the platform. It is relatively common for laboratory workers to lose the screws, or to strip the threads on the screw or on the platform or strip the screw heads. As such, reconfiguring the clamp arrangement on the platform can be quite time consuming. Since most shaker platforms are removable, most laboratory workers simply remove the shaker platforms with the flask clamps attached for cleaning, autoclaving, or even sometimes to change the size of clamps attached to the platform. It is typical for a laboratory to have several shaker platforms with different flask clamps screwed to the platform. Storage can be an issue because space in the laboratory is often limited.
Clamps for other laboratory containers are also known in the prior art. For example, clamps for test tubes or test tube racks can be mounted onto a laboratory shaker platform as well.
In one aspect, the invention pertains to a flask clamp that uses permanent magnets to attach the flask clamp to the shaker platform thus allowing the flask clamp to be easily removed from the platform without the use of tools. The clamp simplifies installation, as well as cleaning, autoclaving and configuration changes. Moreover, the invention allows the user to use one platform in the laboratory, and thus avoids the hassle of removing and storing several platforms with flask clamps screwed thereto.
In its preferred form, the clamp has a generally circular base constructed of two generally circular plates. One or more permanent magnets are attached and exposed below the base, preferably three nickel-coated, rare earth magnets equally spaced around the periphery of the base. The top circular base plate is desirably magnetic, e.g. non-magnetized stainless steel. The bottom circular plate includes holes through which the rare earth magnets extend. The bottom base plate with the magnet holes is desirably made of a non-magnetic material, such as non-magnetic stainless steel. The nickel-coated, rare earth magnets are preferably flat magnets, and the flat bottom surface of the magnets (as well as a magnetic base plate) are magnetically attracted to the shaker platform, which is preferably made of magnetic, non-magnetized stainless steel. The nickel coating helps to protect the rare earth magnets from corrosion and chipping and also provides an improved surface for adhesion of the magnets to the clamp base. In addition, the use of a nickel coating does not compromise the viability of biological cells in the laboratory, as would for example a zinc coating.
The base of the flask clamp also includes downwardly extending positioning bosses, for example three positioning bosses made of engineered thermal plastic such as polyoxymethylene. The downwardly extending bosses are sized and configured to fit into clamp positioning holes or indentations on the shaker platform when the flask clamp is positioned on the shaker platform with the magnets exerting magnetic pressure to hold the flask clamp on the shaker platform. The positioning bosses prevent the flask clamp from sliding on the surface of the shaker platform while the shaker is in use. The clamp positioning holes or indentations on the shaker platform are preferably non-threaded such that the positioning bosses can be easily set in the holes or indentations without a tool.
The flask clamp also includes a flask holding mechanism attached to the clamp base. The flask holding mechanism provides one or more inwardly biased holding surfaces located above the hip line on the Erlenmeyer flask thus exerting pressure along the tapered portion of the sidewall of an Erlenmeyer flask. Preferably, the holding mechanism consists of three bent wire or sheet metal spring fingers that are connected to the base and extend upward to hold a contoured roller or roller set. The three contoured rollers or roller sets provide equally spaced holding surfaces and are shaped to fit the flask profile so as to reduce point contact and surface stress. The rollers are made of plastic and/or have a soft elastomeric (e.g. silicone) sleeve stretched over the rollers to eliminate metal contact with the flask. The use of three spring fingers and rollers or roller sets significantly reduces the force required to insert and remove flask. The resilience of the spring fingers provides inward biasing of the rollers against the tapered portion of the sidewall of an Erlenmeyer flask placed in the clamp. The normal forces exerted by the rollers on the Erlenmeyer flask include not only an inward radial holding force component but also a downward force component. The soft elastomeric sleeves on the rollers helps prevent spinning of the flask and is especially helpful for large flasks that tend to generate significant spinning torque when liquid inside the flask is stirred.
The clamp base also preferably includes a removable, elastomeric cover that provides a frictional surface for the base of the flask. The frictional forces on bottom surface of the flask prevent the flask from spinning when the shaker is in use. The downward component of the normal force exerted on an Erlenmeyer flask by the clamp rollers facilitates the effect of the frictional surface. The elastomeric cover also preferably includes an overlapping lip that extends over the peripheral edge of the base, and in some places underneath the base. The lip provides a seal against the shaker platform in case of a spill inasmuch as magnetic pressure pulls the base of the flask clamp and the elastomeric lips against the shaker platform. It has been found that the above described configuration including the elastomeric, replaceable cover and the contoured plastic rollers (or roller sets) provide a desired amount of cushioning and significantly quieter operation of the shaker. The three finger configuration also significantly reduces the required insertion and removal forces without compromising security of the flask in the clamp while the shaker is operating. Ease of flask removal is especially helpful when the contents of the flask generate heat and the flask is hot to the touch. It also reduces the likelihood of a spill from a sudden release and enables insertion and removal with one hand.
For stability purposes, it has been found desirable to equally space the magnets from one another and also locate the magnets near the periphery of the clamp base. Placing the magnets near the periphery of the clamp base maximizes flux density of the magnetic field near the periphery of the base, as opposed to using a single magnet centered under the flask. While the flask holding mechanism with spring fingers and rollers (or roller sets) significantly reduces the amount of force necessary to remove a flask, it is still desirable to locate the magnets near the periphery of the base in order to avoid tipping when the flask is removed or during vigorous shaking motion.
The use of multiple rare earth magnets allows for the polar alignment of the magnets to be optimized in order to increase the magnetic flux density between the flask clamp base and the platform. For example, staggered polar alignment may increase magnetic flux density and overall attraction of the clamp to the shaker platform. The rare earth magnets are preferably adhered to the top base plate which is made of magnetic stainless steel. The use of the magnetic stainless steel top base plate reduces the magnetic field in the flask and additionally helps to focus magnetic flux density (magnetic attraction) between the base plate and the shaker platform. In an alternative embodiment, the rare earth magnets can be manufactured with a step peripheral shoulder, and instead of using adhesive to attach the magnets to the top base plate, the magnets are attached to the base by mechanically capturing the shoulders on the magnets between the plates in the base assembly.
The clamp base as described above can be used to hold other types of laboratory containers or racks besides an Erlenmeyer flask. For example, one embodiment of the invention involves the use of a clamp base having one or more permanent magnets and at least two positioning bosses as a support for a test tube rack holder. Since test tubes racks are typically rectangular in shape, the holder and clamp base are also desirably rectangular in shape. In addition to the other features described above, stabilizing feet are desirably used at the corners of the rectangular base in order to improve stability without requiring the use of additional magnets. Stabilizing feet can of course be used in connection with circular clamp bases if deemed necessary.
In another embodiment of the invention, the flat magnets extend downward from the base farther than in the previous embodiments, and serve the dual purpose of functioning as the positioning bosses as well. In the embodiment, the shaker platform must include position indentations and not positioning holes.
In yet another embodiment of the invention, the permanent magnets are not located on the clamp base, but rather are located underneath the shaker platform. In this embodiment, the platform should be made of non-magnetic material such as magnetic stainless steel. In addition, the base of the clamp should be made from a magnetic, non-magnetized material such as non-magnetized stainless steel. This approach has the advantage of eliminating the permanents magnets from the construction of the clamp base.
Other features and advantages of the invention may be apparent to those of ordinary skill in the art upon reviewing the following drawings and description thereof.
Referring now to
The flask clamp 20 also includes three contoured plastic rollers 38 which are attached to bent wire forms 40 forming resilient spring fingers. The wire forms are preferably made of spring stainless steel having an appropriate strength for the given size of the flask clamp. It has been found that constructing the spring fingers from wire forms is suitable for flasks sized 500 ml or less. The bent wire forms 40 and the contoured plastic rollers 38 are preferably spot welded to the bottom of the top base plate 22. The shape of the contoured plastic rollers 38 is chosen to correspond to the radius of the Erlenmeyer flask for which the clamp 20 is designed to hold.
The flask clamp 20 includes three (3) downwardly extending positioning bosses 32, preferably made of engineered thermal plastic such as polyoxymethylene. The downwardly extending bosses are sized and configured to fit into clamp positioning holes 52 on the shaker platform 12. Those skilled in the art will appreciate that positioning indentations in the shaker platform can be substituted for the positioning holes. Note that the distance between the positioning bosses 32 may vary depending on the size of the clamp 20, but in any event the distance is selected so that the clamp positioning bosses 32 will fit into clamp positioning holes 52 in the platform. The positioning bosses 32 include a shoulder 42, see
The magnets 36 are preferably round, flat rare earth magnets which have been nickel coated. It is desirable that the magnets remain magnetized if the flask clamp 20 is submerged in boiling water, or if the flask clamp 20 is treated in an autoclave. Most autoclaves operate at about 135° C. It has been found desirable to use magnets 36 that do not lose significant strength (maintain at least 50% of their strength) when exposed to temperatures at or below 150° C. The magnets 36 are attracted to the top base plate 22; however, it is desirable to attach the magnets 36 to the bottom of the top base plate 22 with adhesive. The nickel coating improves adhesion of the magnets to the top base plate 22, reduces oxidation of the magnetic material and wear of the magnet.
Locating the magnets 36 near the periphery of the clamp base, as mentioned, focuses the magnetic attraction force near the periphery of the clamp base and thus improves stability of the clamp on the platform 12. The use of multiple magnets also enables the magnets to be adhered to the base plate 22 with alternating polarity direction if desired. In some instances, alternating polarity has been found to improve overall magnetic field strength. Since the top base plate 22 is made of a magnetic stainless steel, the top base plate tends to isolate the magnetic field from the flask on the clamp, and also refocuses the magnetic field towards the platform 12. In fact, it has been found that the magnetic attraction due to the magnetic field in the top base plate 22 improves overall stability of the clamp 20 when it is on the platform 12.
The flask clamp 20 also preferably includes a removable and replaceable soft cover 46. The soft cover 46 is preferably made of an elastomeric material such as injection molded EPDM or silicone. The soft cover 46 provides a frictional surface on the base of the clamp 20 for the bottom surface of the flask. In reference to
The cover 46 is preferably wide enough to wrap entirely around the base of the clamp 20. As shown in the drawings, the soft cover 46 includes a circumferential lip 48. The lip 48 includes slots 50 to accommodate the wire forms 40. As shown best in
One skilled in the art will recognize that locating the positioning bosses 32 in the positioning holes 52 or indentations in the shaker platform, while the magnets 36 provide downward magnetic pressure between the clamp 20 and the platform 12, prevents the flask clamp 20 from sliding horizontally along the shaker platform 12 when the shaker is in use. However, when the shaker is stopped, a user can easily remove the clamp 20 from the shaker platform 12 to either reposition the clamp 20 or to replace it with a clamp of a different size. It is not necessary for the user to remove the entire platform 12 from the shaker 10 in order to clean or autoclave the flask clamps 20, or to change clamp sizes. With respect particularly to
The flask clamp 120 in
Referring again to
As in the earlier embodiment, the base plate includes a soft elastomeric cover 146. The cover 146 includes a slot 150 to accommodate the spring fingers 140 extending upward from the lower base plate 124. The combination of the roller sets 138 with the soft elastomeric sleeves 168 and the soft elastomeric cover 146 on the base has been found to be particularly effective in eliminating spinning of even large volume flasks during shaker operation. At the same time, the forces required to insert and remove flasks from the clamp 120 are significantly less than with metal clamps typically used in the art, and the clamp 120 is significantly quieter than the metal clamps typically used in the art.
While the drawings illustrate exemplary embodiments of the invention, the various aspects of the invention can be implemented independently of the other features of the invention. While the invention has been shown in connection with clamps for Erlenmeyer flasks and test tube holders, various aspects of the invention can be used in connection with other types of laboratory containers such as round bottom flasks, etc. In addition, some of the features of the invention can be implemented differently than demonstrated by the exemplary embodiment. For example, in one embodiment of the invention (not shown in the drawings), the permanent magnets are placed below the shaker platform 12, thereby eliminating the need for the permanent magnets 36 to be located on the base of the flask holder 20. In another embodiment, the positioning holes 52 on the platform 12 and the positioning bosses 32 on the clamp 20 can be replaced with indentations in the platform corresponding to the dimensions of the flask clamp base. In a somewhat similar vein, it is also possible to construct the shaker platform with upwardly extending positioning bosses and construct the clamp base with receptacles for the upwardly extending bosses in order to prevent the clamp from sliding. These and other changes and modifications may be made without departing from the spirit of the invention or from the scope of the appended claims.
Number | Name | Date | Kind |
---|---|---|---|
5593228 | Tannenbaum | Jan 1997 | A |
7059762 | Yi | Jun 2006 | B2 |
20070257021 | Lockwood et al. | Nov 2007 | A1 |
20110309217 | Demsia | Dec 2011 | A1 |
Entry |
---|
2L Flask Clamp, 207704, Lab Safety Supply, http://www.labsafety.com/21-flask-clamp—s—207704, website visited Mar. 8, 2012. |
125/150ml Flask Clamp, 20770, Lab Safety Supply, http://www.labsafety.com, website visited Mar. 8, 2012. |
Dedicated 500ml Flask Platform for Incu-Shaker Mini, Spectrum Scientifics, http://www.spectrum-scientifics.comn/cgi-bin/commercie.cgi?, website visited Mar. 8, 2012. |
Incu-Shaker Mini, The Lab Depot, Inc., http://www.labdepotinc.com/Product—Details, website visited Mar. 8, 2012. |
Number | Date | Country | |
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20120237416 A1 | Sep 2012 | US |
Number | Date | Country | |
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61452250 | Mar 2011 | US |