% Expired Patents = 27.3

CIPO Patents = 1

Forward Citations = 134

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7 inventors (with patents filed for the assignee):

Rex E Duhn (10 out of 17 patents)

Robert K Meek (8 out of 12 patents)

Jay C Duhn (2 out of 2 patents)

4. Gary A Card (1 out of 1 patent)

5. William D Chapman (1 out of 2 patents)

6. Aaron B Speirs (1 out of 1 patent)

7. Kenneth D Webster (1 out of 1 patent)

11 patents: Sort by Forward Citations

1. 7726393 - Wellhead isolation tool and wellhead assembly incorporating the same (2010-06-01),

2. 7520322 - Wellhead isolation tool and method of fracturing a well (2009-04-21),

3. 7493944 - Wellhead isolation tool and method of fracturing a well (2009-02-24),

4. 7416020 - Wellhead isolation tool, wellhead assembly incorporating the same, and method of fracturing a well (2008-08-26),

5. 7322407 - Wellhead isolation tool and method of fracturing a well (2008-01-29),

6. 6920925 - Wellhead isolation tool (2005-07-26),

7. 6588510 - Coil tubing hanger system (2003-07-08),

8. 6543533 - Well tubing rotator (2003-04-08),

9. 6199914 - Drilling quick connectors (2001-03-13),

10. 5303774 - Ring seal packer (1994-04-19),

11. 4974676 - Ground subsiding wellhead (1990-12-04),

Company Overview

Duhn Oil Tool, Inc. is a specialized manufacturer based in Bakersfield, California, focusing on innovative solutions for the oil and gas industry. The company develops a range of tools and equipment designed to enhance drilling efficiency and safety. With a commitment to quality and performance, Duhn Oil Tool leverages advanced engineering techniques and materials to meet the evolving needs of its clients. The organization plays a significant role in supporting energy exploration and production through its tailored products and services.

Profile summary synthesized from public USPTO records and patent filings.

Company Badge

USPTO Data Jan 1 1976 - Oct 20 2026

11 Patents

#10 in Bakersfield, CA

#6,544 in California

#27,529 in US

#51,801 in the World

Bakersfield, CA, United States of America

Duhn Oil Tool, Inc.

Forward Citations = 134

7 inventors:

Rex E Duhn (10 out of 17 patents)

Robert K Meek (8 out of 12 patents)

Jay C Duhn (2 out of 2 patents)

4. Gary A Card (1 out of 1 patent)

5. William D Chapman (1 out of 2 patents)

IDiyas Innovation Intelligence. (2026). Company Patent Portfolio: Duhn Oil Tool, Inc.. Retrieved from https://idiyas.com/company/duhn-oil-tool

Data source: USPTO (United States Patent and Trademark Office) public patent records. Weekly synchronization. How IDiyas builds this profile

Data Sources: USPTO Patent Grant XML, Patent Center, EPO & CIPO • Normalized by IDiyas Innovation Graph. Methodology & provenance architecturePlease report any incorrect information to [email protected]

1 patent (CIPO):

Data Sources: USPTO Patent Grant XML, Patent Center, EPO & CIPO • Normalized by IDiyas Innovation Graph. Methodology & provenance architecturePlease report any incorrect information to [email protected]