US 3427896 A
Description (OCR text may contain errors)
Feb. 18, 1969 L .IHARTMAN, JR 3, ,8 5
VARIABLE COUNTERWE I GHT S YSTEM Filed Aug. ,25, 1967 Thomas L. Hartman. Jr.
United States Patent 4 Claims ABSTRACT OF THE DISCLOSURE A variable counterweight system located on an arm of a centrifuge. A fluid container is supplied with air to expel the fluid from the container through a U-tube, to vary the weight of the combination of the container and the U-tube.
Background of the invention This invention lies in the field of centrifuges. In particular this invention is for a centrifuge with a variable counterweight system. A prior art device for producing a variable weight on a centrifuge arm is a mechanical system wherein weights are slid along the centrifuge arm. This approach is mainly used on large centrifuges. This approach has a slow response time and involves elaborate control apparatus. A large centrifuge will take some unbalance, but the problem is more serious with a small centrifuge. There is no known method of taking care of unbalance on a small centrifuge while operating at high G levels.
Summary of the invention A fluid container is placed on an arm of the centrifuge. This container is filled with a liquid which will initially balance an expendable weight on the other arm of the centrifuge. As the centrifuge rotates, the weight required to balance the centrifuge changes. To vary the balancing weight, a controlled pressure is applied to the container to expel the fluid from the container through a U-tube.
An object of this invention is to provide a variable counterweight system whereby the weight on an arm of a centrifuge may be varied while the arm is in motion.
A further object of this invention is to provide a variable counterweight system whereby the weight on an arm of the centrifuge may be varied at a controlled rate.
Yet another object of this invention is to provide a variable counterweight system that is adaptable to small centrifuges as well as large centrifuges.
Brief description of the drawing FIGURE 1 is a schematic showing of the invention, and
FIGURE 2 is a side view of FIGURE 1 taken in the direction 2-2.
Description of the preferred embodiment Referring to FIGURE 1, a fluid container 2 is fitted with a pressure line having portions 4a and 4b. U-tube 8 is attached to orifice 6 and orifice 6 is attached to pressure line 4a. Pressure line 4b is connected via rotary joint 10 and solenoid valve 12 to pressure source 14. Fluid container 2 and U-tube 8 are located on the radial exice trem-ity of arm 16 of centrifuge 18. Fluid container 2 is proper size so that the weight of liquid therein is equal to the weight of the expendable material in test item 20. As the centrifuge is spun up to obtain the desired acceleration level, the force created by the liquid column of fluid container 2. is balanced by the liquid column 22 in the 'U-tube, because both columns are under the same acceleration force and are the same length. The surface level of the liquid is below the end portion 24 of the U-tube 8. Forces being equal, the liquid will remain in the container until an unbalancin-g force is applied. When solenoid valve 12 is opened, high pressure gas from pressure source 14 will provide the unbalancing force and the liquid will flow through orifice 6 and U-tube 8. The length of time to expel all the liquid is made to correspond with the time required to expend the material in test item 20 and is controlled by selection of orifice diameter and gas pressure.
It is to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described. Many modifications and variations of the present invention are possible in the light of the above teachings. For example, the weight of the system in the preferred embodiment is decreased. The reverse could be accomplished by simply adding fluid to the container instead of expelling liquid from the container. This would result in a positive weight control instead of a negative weight control. Accordingly, the scope of this invention is to be limited only by the appended claims.
1. A centrifuge with a variable counterweight system comprising: a centrifuge having a first and a second arm; a fluid container having a first and a second end, said fluid container located on said first arm; :a fluid disposed in said fluid container and means for varying said fluid in said fluid container.
2. A centrifuge with a variable counterweight system as set forth in claim 1 wherein said first end of said fluid container is disposed adjacent the radial extremity of said first arm; and wherein said system further comprises a U-tube connected to said first end of said fluid container and extending above the other end of said fluid container.
3. A centrifuge with a variable counterweight system as set forth in claim 2- wherein said means for varying said fluid in said fluid container comprises: a rotary joint, a solenoid valve, and a pressure source; said rotary joint, solenoid valve, and pressure source being connected in series; said rotary joint being connected to said second end of said fluid container; and said rotary joint being connected for rotation between said solenoid valve and said centrifuge arms.
4. A centrifuge with a variable counterweight system as set forth in claim 3 further including an orifice located in said U-tube.