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There are several kinds of patents issued by the USPTO; we will be concerned only with Design and Utility Patents.
Some patents for clamps are design, and they are numbered D 1, and up.
Most patents for clamps are utility, and they are numbered from 1 on up. Almost all utility patents for clamps are in Class 269 "Work Holder", which has several hundred subclasses. I have a page which defines all the subclasses. The original is on a page at the USPTO; it allows you to search for patents in particular subclasses. Unfortunately, the search is only for recent patents.
There are several kinds of patents issued by the UK Patent Office.
Almost all interesting patents are in Class B23b5/10f "hand tools for holding things, with screws", and Class B25b5/16f "hand tools for holding things, with parallel jaws". The classification scheme can be found here.
There is a page that allows you to search for patents using simple criteria. The conditions of use are not onerous.
This material will be organized in chronological order, Design patents first, then Utility patents.
Note that the information here will (eventually) appear in DATAMP, which covers a much wider range of tools.
Pat'd 1883/ 03/ 06
A J Benjamin, of Valley Falls RI, obtained this patent for a unique look, the convex back, used by Hood.
Covers the design of a tool handle.
Pat'd 1882/ 10/ 31
This shows Reno's early interest in improving clamps for use in rapid production. Strictly speaking, it may be considered outside the scope of the site, as it uses ratchets for rapid adjustment, and screws for fine adjustment.
Pat'd 1884/ 04/ 08
This may be the first attempt at a composite clamp. Certainly, Reno acknowledges no prior art, and his specifications indicate that he thought through the consequences of using metal screws.
Pat'd 1885/ 08/ 25
Pat'd 1887/ 02/ 08
Pat'd 1888/ 07 /17
Pat'd 1889/ 08/ 10
This applies the principles of Tarbell's early clamp to a bar clamp.
Pat'd 1901/ 12/ 03
Pat'd 1905/ 02/ 07
Pat'd 1906/ 01/ 23
Pat'd. 1913/ 04/ 08
Pat'd 1915/ 04/ 27
A Work Holding Jaw.
A Work Holding Clamp.
A Ratchet Hand Tool.
A Portable Saw Vise (questionable relevance).
A Clamp Jaw.
A Clamp and method of manufacturing.
A Clamp Tightening Machine.
A Screw (for clamp).
A Welder's Clamp.
A Clamping Device.
A Hand Clamp.
I am grateful to the staff of the Patent Depository at the Boston Public Library. They guided a neophyte through the techniques of finding patents, and explained the resources available for older patents.
Patent Depositories have the following:
Once you have the patent number, you can examine patents online at the USPTO site. All patents are classified according to current classes and subclasses, as explained in the Manual of Classification. Class 269 is Work Holders, and contains wooden clamps (among other things).
Note that the search engine works best for recent patents. All patents can be searched by class and subclass, but only recent patents can be searched on the basis of textual content of specification. Older patents are preserved only as images, scanned from the best preserved originals.
Note also, you will need specialized software, a plug-in for your browser to process the tif format image files containing the illustration and specification of old patents. The USPTO site contains a link to the source of the free plug-in.
I download from the USPTO site the original as pnnn.tif, a monochrome file, and store it in the REF (reference) folder. Its size is 2320 x 3408 pixels.
I crop the blank borders of the original pnnn.tif file to a size of 1700 x 3000 (margins: top = 256, bot = 152, left = 274, right = 346), which works pretty well on current examples. I save the result as pnnn.gif, black and white, in REF folder.
I rescale pnnn.gif to 850 x 1500; the result will (by default) be 256 gray shades. I restrict this to 16 gray shades, using optimized cut with dither, and save the result as hnnn.gif, in WRK (work) folder, to be used as "printable file", linked from page
I rescale pnnn.gif to 248 x 500; the result will (by default) be 256 gray shades. I restrict this to 16 gray shades, using optimized cut with dither, and save result as snnn.gif, in WRK folder, to be used as "viewable file" on the page
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