Measuring and testing – Liquid analysis or analysis of the suspension of solids in a... – Viscosity
Reexamination Certificate
1999-10-26
2001-09-04
Williams, Hezron (Department: 2856)
Measuring and testing
Liquid analysis or analysis of the suspension of solids in a...
Viscosity
C073S054320, C073S054350
Reexamination Certificate
active
06282948
ABSTRACT:
BACKGROUND TO THE INVENTION
I. Field of the Invention
The present invention concerns rotary viscometry with a low heat-transmissible spindle, as well as the spindle and associated viscometer apparatus with the spindle included therewith.
II. Prior Art and Problems
Standard test method ASTM D 2983 for low-temperature viscosity of automotive fluid lubricants measured by Brookfield viscometer determines the low-shear-rate viscosity in the temperature range from −5 to −40 degrees C. The fluid viscosity, of course, is temperature-dependent, and certain ways and means have been introduced and disclosed to assist in controlling the temperature so as to provide more reliable data. See, e.g., ASTM D 2983-87 (Reapproved 1993) and Selby, U.S. Pat. Nos. 5,526,681 and 5,587,522, which are incorporated herein by reference.
A concern for possible heat-transfer losses through the metal spindle led Theodore W. Selby to develop a spindle having a shaft bisected into upper and lower metal components and tied together by a phenolic composite sleeve. That spindle was an attempt to control a problem of transfer of heat, and it has been used since 1958. As noted by Mr. Selby in abandoned U.S. patent application Ser. No. 08/490,111, several drawbacks attend this bisected-shaft approach:
1) The spindle shaft, being separated into three parts, is subject to imbalance and undesirable, accidental disassembly.
2) The phenolic composite insulator portion of the three-part shaft is typically of a larger diameter than the metal rod portion, commonly twice or more that of the metal spindle portion, and extends for a significant distance along the axis of rotation, commonly an inch.
3) The large insulator portion requires an upper closure to the stator having a larger opening to accommodate the insulator passing through. This engenders the introduction of ambient air into the stator and test fluid, causing an unwanted rise in the temperature of the test fluid, which disturbs the accuracy of the measurement.
4) Manufacture of this item is more involved than desired.
With amelioration of the same concern in mind, Mr. Selby invented a heat-dissipating viscometer rotor comprising an elongate member distributed along an axis of rotation having opposing attachment and sample-immersion ends, and a protuberance (which can be a set of fins) therebetween, all the same typically made from stainless steel, which was set forth in the abandoned '111 application.
Unfortunately, data obtained by the aforementioned ASTM protocol even as improved so well by the disclosures of the Selby patents can be less accurate than desired in today's world of high precision lubricant technology. Furthermore, as noted, data obtained with the buffered-shaft spindle was not highly accurate, and the finned rotor did not dissipate enough heat.
It would be desirable to ameliorate the problems remaining.
SUMMARY OF THE INVENTION
Through dedicated and patient research and study done in the development of the present invention, it has been confirmed or discovered that indeed a source of the problem is that heat was transferred indeed through the metal spindle during conditioning and testing under an ASTM D 2983 type protocol. This transfer of heat through the known metal spindle, and even with employment of the bisected-shaft and finned rotors, would raise the temperature of the test sample enough to affect its viscosity and introduce inaccuracies in the data. In addressing the problem, moreover, heat transfer was not the only cause of inaccurate data as it was also confirmed or discovered that, in use of the bisected-shaft spindle intended to address the problem of heat transfer by a metal spindle in the protocol, inaccurate data was generated indeed through wobble of that spindle. This wobble effect could compound any insufficient heat-transfer retardation from the short buffer segment of the heat-insulating material.
Accordingly, the present invention provides, in one aspect, a low heat-transmissible spindle for rotary viscometry comprising an elongate, radially balanced, straight shaft made of a suitably stiff material having a low heat-transmission value, a viscosity sensing section (head) monolithic with the shaft which can contact interface with a test fluid to yield drag from the contact and interface when the spindle is rotated in the fluid, and a spindle coupling nut attached to the shaft opposite the head. In other aspects, it provides a rotary viscometer equipped with such a spindle, and a method of determining fluid viscosity by employing the same in a rotary viscometric protocol.
The invention is useful in lubricant testing.
Significantly, by the invention, viscometric test data can be improved in kind. In particular, accuracy is notably increased. The spindle is structurally sound and economically manufactured.
Numerous further advantages attend the invention.
REFERENCES:
patent: 3115769 (1963-12-01), Bowen, Jr.
patent: 4643021 (1987-02-01), Mattout
patent: 5301541 (1994-04-01), Joseph et al.
patent: 5349847 (1994-09-01), Lee et al.
patent: 5369988 (1994-12-01), Selby
patent: 5481903 (1996-01-01), King et al.
patent: 5513517 (1996-05-01), Van Meter et al.
patent: 5526681 (1996-06-01), Selby
patent: 5531102 (1996-07-01), Brookfield et al.
patent: 5587522 (1996-12-01), Selby
patent: 5798454 (1998-08-01), Nakazeki et al.
patent: 5874665 (1999-02-01), Larsson
patent: 5874666 (1999-02-01), Bishop
patent: 6167752 (2001-01-01), Raffer
ASTM D 2983—87 (Reapproved 1993).
Catalog, Garolite listings. 1998.
Selby, T., U.S. patent application 08/490,111, filed Jun. 6, 1995, (abandoned), specification as filed.
Miiller Gregory C.
O'Dell Patrick T.
Seer Robert H.
Selby Theodore W.
Rudy Christopher John
Tannas Company
Wiggins David J.
Williams Hezron
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