First Threaded Insulator (ICON)

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First Threaded Insulator

Ed Overstreet commented on 2008-06-21

I am surfacing from lurker mode because I have been selected to ask ICON a question. I am asking the same question that I asked several years ago. At that time, I received zero responses. I'm not sure whether that means that nobody knew the answer or whether it means that the answer was obvious and nobody wanted to stoop to answer such a question from a newbie. In any case, this is the question: what was the first threaded insulator?

We know that Louis Cauvet received a patent on July 25, 1865, for a device that formed threads in glass insulators. We also know that Brookfield bought Cauvet's patent. The McDougald's in "A History and Guide to North American Pin-Type Glass Insulators" report that "Cauvet's patent revolutionized the glass insulator." In addition, the McDougald's report that "The threaded Brookfield glass insulator quickly became the standard for telegraph lines..."

So, one could assume that a Brookfield insulator was the first threaded insulator. But, which CD? There are several Brookfield insulators reported to come embossed with the date of Cauvet's patent, including the CD 126, 126.3, 131, and 133. Was one of these was the first?

But, there are other insulators that are reportedly embossed with Cauvet's patent date, including the BFG Co 133.2, the P&W 133.2, the Paisley 132.2, and the WU 127. Could one of these have been the first?

On the other hand, there were several insulators manufacturers who were producing threaded glass insulators before the Cauvet/Brookfield patent expired. Therefore, one would assume that these insulators were produced with a device that produced threads in a manner other than that described by Cauvet's patent. Could one of these companies have made the first threaded glass insulator?

If there is definitive proof, I want to see it. If there is no definitive proof, I want to hear informed opinion. And in the absence of that, I even want to hear SWAG's.

Again, the question is: which CD and which company was the first threaded glass insulator?

Thanks for your responses and good insulator collecting to all.


Christopher Miller commented on 2008-06-23

I replied to you privately, but your question is interesting and probably has gone unanswered publically in the past because nobody knows for sure which CD was the first to be threaded.

It's almost as difficult to speculate which threaded CD was the first to make it into service, but I'm willing to make a guess. It would make sense that it would be a Brookfield manufactured product, since they held the Cauvet patent and would therefore be actively promoting the benefits to various RR Sup't. I also like the fact that Brookfield was located in a large metropolitan city with relatively easy links to many of the RR's currently using threadless glass, especially the longest railroad in the world at that time, the Erie Railway Company as it became known around 1861. It's possible that they would be willing to try something new to save costs down the road and Brookfield would be wise to approach the biggest user for obvious reasons. The first threaded insulator would most certainly be made from a threadless mould and for this reason I'd have to guess that the 135.5 E.R.W. was the first threaded insulator to see service. The hat style was nearing the end of its preference among Sup't at this time, but apparently not with the Erie as these 135.5's have been found on that line and on it's spurs. Also this CD is the threaded version of the 736 E.R.W. which was manufactured for the Erie Railway Company.

So the 135.5 is my guess, but I'd feel better about it if there was proof that Brookfield was the manufacturer of the 736 E.R.W. or the 135.5 E.R.W.

Interesting Topic.


Ed Overstreet commented on 2008-07-11

I would like to thank all six ICONers who responded to my question asking which was the first threaded insulator. As I expected, no one was able to provide definitive proof. However, there were several informed opinions offered, along with a couple of SWAGs.

The informed opinions leaned toward the idea that the first threaded insulator would have been made with reworked threadless molds, with the addition of the device to form the threads. If this speculation is correct, then it was thought that one of the various CD's from the 131 or 133 series, or the 135.5 might be likely candidates for the first, since many of these insulators have threadless look-a-likes.

Another opinion was the 132.2 or 133.2. One of the SWAGs was the 127.

While we may never have a smoking-gun definitive proof, I appreciate everyone who took the time to send in their opinions and educated guesses. It was apparent that some had given the question considerable thought.


Bill Meier commented on 2008-07-11

Probably the simpliest form to turn a threadless insulator into a threaded one is simply to change the manderal...

I noticed the following Brookfield embossed pieces to have virtually the same shape

CD 731 and CD 131 CD 728.4 and CD 133

(the threaded ones seem 1/8" shorter but that might be a result of some rework to adapt the different maderal.)

While I haven't read the other threads about this, it seems logicial that the first threaded insulator can from it's threadless counterpart. Why create a whole new mold and mold style (i.e. CD number) just to produced a threaded insulator?

Another example, although not Brookfield embossed, is CD 732.2 and CD 131.4.


Rick Jones commented on 2008-07-12

I just saw your post on this topic and I want to add my opinion on the first threaded insulator. I agree that it was probably a 131, but not the style typically found on the embossed styles.

I've tried to attach a photo of one I have in my collection of 731s that is an unembossed 131. The shape is identical to several of my unembossed 731s. If you compare this one to the embossed 131s, you can see some distinct differences. The embossed 131s have a very flat dome and a bit more of an outward curvature to their skirt.

I think my 131 is truly an unembossed 731 where the same 731 mold was used, only with a threaded plunger. Now, this certainly doesn't mean that the embossed 131s weren't re-worked 731s that were not only engraved for embossing, but possibly the mold cavity was re-shaped somewhat as well--due to wear or whatever (just a guess).

To me the 131 I've pictured (or I hope I did) looks to be one of the very earliest threaded pieces.

Another piece I would suggest that was a quite early threaded piece is the ERW. Maybe somebody mentioned that in an earlier post. This 736 looks identical to its 135.5 threaded counterpart, but the size difference is more significant. One final thought would be the 131.4 and the 732.2. Very close but with an eighth inch difference in size.

My thoughts.


Rick Jones commented on 2008-07-13

I posted a photo of the unembossed 131 that I think is the transition piece between the 731 and the first threaded insulator. It truly looks like some of the unembossed 731s in my collection and is a different shape than my embossed 131s.


Christopher Miller commented on 2008-07-13

As soon as it gets light out, I'll post a picture of my un-embossed 131. I just went over and looked at it and to me it has a flat dome, but I haven't compared it to your photos and in all honesty I'm not up on the variations of the 131's=A0and 731's. What I will say is=A0that the threading looks to be very well done (maybe this employee got lucky) versus some of the pin holes on the 133 ER's with the Cauvet patent I have which have severe twists of the glass near the=A0base of the pin hole and the threading is very poor as if this was an early attempt at the threading process. There is no doubt that these ER's came later and would not be the first threaded, even though the some of the moulds look the same as the as the 728.4. My point is if the un-embossed 131 were to be considered the first (and I agree with your logic 100%) threaded, then why is the threading and overall appearance of the pin hole so much better than the Cauvet embossed 133 ER's which presumable came later?

I also have a couple Cauvet embossed 131's and the threading also is very good, but still not quite as good as the unembossed. Yes, additional examples of both would be better to make a more compelling statement. Here's another point of confusion; with Brookfield holding the rights to the Cauvet patent, we're comfortable in saying that the first threaded should be a Brookfield product. The unembossed 131, at least the one I have, is pretty clean and looks to be of exceptional quality for this time frame. It just doesn't have the have the Brookfield "ring" to it. Take a look at your unembossed and see what you think.

I personally like the 135.5 E.R.W. as being the first. The twisting of the glass near the base of the pin hole is consistent with some of the early Cauvet embossed CD's. I agree that the dimentions of the 135.5 being larger than it's 736 counterpart lead one to believe that a different mould was cast and thus it came about later in production,=A0but wouldn't the insertion of the threading mandrel into the glass change the shape of the threadless mould and make the new end result larger? Going back to the "Brookfield made the first threaded" premise, I don't believe it has been proven that they made the E.R.W.'s eventhough the timeline fits, there are characteristic similarities, etc. etc. I have the feeling we'll figure out the "chicken or the egg" before we catagorically determine the first threaded.


Rick Jones commented on 2008-07-13

Forgot to say that I posted the photo of the 131 in the Collector's Album in the Picture Poster gallery.


Rick Jones commented on 2008-07-14

Chris---thanks for your response. You make some good points. Maybe some of the collectors out there who are more versed in the molding process can answer your questions. I'm not very knowledgeable in that area. I do know that the 731s were made by a variety of glass houses, we just don't know which ones for sure. I suppose it's the same for the unembossed 131s---unsure of manufacturer. Mine does look pretty well made, although the threading is off center. I'll check the actual threads when I get home tonight. Maybe someday I'll come across a 731 that I can match perfectly with my 131 and determine that both came from the same mold. Wouldn't tell us who made it, but it would confirm that it was a re-used 731 mold.


Glenn Drummond commented on 2008-12-09

Brent asked essemtially "What do we know for certain?"

The following is a timeline of actions that I can put definate dates to. Do y'all know of anything that I have overlooked? Let me know and I'll stick it into the timeline.

More to follow, perhaps tomorrow, depends on life here in the third world. Information will be sound but without dates.

  • 7 Aug 1855 Amasa Stone, Phildadelphia, Awarded patent 13,402 for "Forming Screw Threads, etc., in the Necks of Glass Bottles and Similar Articles." Includes screw threads in an insulator pin cavity.
  • 25 Jul 1865 Cauvet, Louis A. New York Awarded patent 48,906 for "Improvement In Insulators For Telegraph-Wires."
  • Winter 1867-1868 Homer Brooke, New York Homer Brooke testified that he conceived the design of a glass press to manufacture threaded insulators and discused it with others.
  • Aug 1868 Robert Hemingray Covington, KY Testifies that he made threaded glass insulators in either July or August 1868.
  • 11 Dec 1869 Homer Brooke, New York Application for patent "Improvement in the Manufacture of Insulators for Telegrapy-Poles."
  • 11 Dec 1869 Homer Brooke, New York Application for patent "Improvement in the Manufacture of Insulators for Telegrapy-Poles."
  • 25 Jan 1870 Homer Brooke, New York Awarded patent no. 99,145 for "Improvement In The Manufacture Of Insulators For Telegraph-Poles."
  • 22 Feb 1870 Cauvet, Louis A. New York Reissue of patent no. 48,906
  • 31 May 1870 James M. Brookfield New York Awarded paten no. 103,555 for "Improved Mode of Forming Glass Insulators."
  • 19 Dec 1871 Robert Hemingray Covington, KY Awarded patent no. 122,015 for "Improvement in Molding Telegraph-Insulators."

Bill Meier commented on 2008-12-09

Something that fits in well with this, and is a source of some of Glenn's information, is this document:

[Interference Document]

BROOKFIELD AND HEMINGRAY vs. BROOKE Interference.

[Appeal from the decision of the Board of Examiners-in-Chief in the matter of interference between the applications of James M. Brookfield and Robert Hemingray and the patent of Homer Brook, for IMPROVEMENT IN THE MANUFACTURE OF INSULATORS. Decided July 3, 1873]

Of significant interest, as Glenn referred to, is some specific dates of the manufacture of early unembossed Hemingray. Well, ones without DEC 19, 1871 at least.

"Hemingray does not fix the date of his invention definitely in his testimony, but says he made it before the 4th of February, 1869, in warm weather, and he thinks in July or August, 1868. At that time a number of insulators were made by the process in question. This is amply proven. and is conceded by Brooke. At least one of the insulators then made was put into use. In May, 1869, he manufactured and sold a large number."

So, proof of Hemingray insulators being made with the 1871 patent press in 1868... One has to wonder what a "large number" was at that time!!


Rick Jones commented on 2008-12-09

Glenn---this looks complete to me from a recorded historical perspective taken from patent information. Has anyone ever researched old court records of the proceedings where testimony in the cases cited in your timeline (and Bill's post) may be public record? Those proceedings in their entirety could shed even more light on what was going on in these patent battles at the time. Maybe it could help us more accurately determine what actually happened when. For example, could we find out from those records when the first threaded insulator was produced, by whom, and where? It would seem to me that court records would be the most dependable for accuracy.


Bob Stahr commented on 2008-12-10

Glenn has been the one who has found the most court records in his lifetime regarding the Hemingray operation. Most of what Glenn has found, dealt with the Hemingray family, and less about the company. In daddition, many of the old court records of long ago are also no longer in existance.

I can say from the patent office perspective, it's quite difficult to search for other documents. For instance, I want to know what the July 1, 1882 patent applied for date on the CD 116 is all about. Since it was not a granted patent, it is not published anywhere by the government. There may however be an applications index or something, Same goes for transfers of patents, these are not published, but are recorded by the patent office. I have records of some Hemingray transfers only by reference to a volume of the transfers book. I sure wouldl like to kwow whose patent they gained the rigths to.

I have been able to find some tidbits from some on-line legal indexes, which in turn allows me to find the law journal for the whole citation. This is just a synopsis of the case, without much testimony info though, and these journals only cite legally important (setting a new precendent or such) cases.

If anyone has access to New York Court records, please contact me. I am trying to track down a lawsuit between Hemingray and Brookfield from 1880 that did not appear in the law journals.


Rick Jones commented on 2008-12-10

Bob---do you know if anyone has searched the archives of the Patent Gazette and focused their search on insulator designs? I would assume somebody like you, Glenn, Bill, Ray, etc. have done this. Is this something that would be public information and accessible online somehow? Since court records of proceedings would be scant from the 1865-1875 period, maybe the Patent Gazette would be a better source of information.


Glenn Drummond commented on 2008-12-10

Actually the record of the "Interference Claim" by Homer Brooke was not held in a court of law rather it was heard by the Commissioner of Patents and his staff. The record, should it still exist, of this action would be found in the Patent Office archives.

FYI. I found the record of the Interference Claim in the Patent Gazette at the Cincinnati and Hamilton County Public Library sometime during the '70s. Perhaps a year later, I was detailed to DC for 10 days. I took advantage of the situation to visit the Patent Office (then in Alexandria, Virginia), in hopes finding additional information. My visit to the Patent Office turned out to be one of the worst experiences of my life with out-of-control employee apathy. The Customer Service desk was staffed by two women who were extremely annoyed by my presence (How dare he come here seeking assistance !!!). Anyway, I asked the question if there were any records pertaining to the Brooke claim of interference against Brookfield and Hemingray in 1873. This was met with an immediate "No." I also had a small list of patent numbers that I wanted to obtain copies of. One woman took the list and disappeared through a door. After about a half hour, I asked the other woman what was happening. She informed me that the first woman had gone to lunch and may return in about an hour. I then asked her if she could make the copies for me. She informed me that she could only make one copy at a time. So she took a number and about 15 minutes later she returned with it and wanted payment before she would take another number. I then left and did not return.

Some years later (1987) I accepted an offer to fill a job vacancy in DC.

After settling in, I made another trip to the Patent Office.  It was then located in Crystal City and I could get there by Metro.  The 

situation was a bit better in terms of Customer Care and I was informed that if any record did exist it would be held at the Patent Office Records Holding Area somewhere in Maryland (I now forget the exact location). An opportunity to visit that site never did present itself so I cannot tell whether or not anything can be found in the Patent Office files.


Glenn Drummond commented on 2008-12-10

I, too, have found searching legal documents to be very frustrating. For instance, I am essentially forbidden to search the Kenton County, Kentucky, Court records for anything pertaining to either the Hemingray family or the Glass Company. A couple of local (Covington) attorneys have told me that that is in violation of Kentucky law. The last time I confronted the Court Clerk I was told that I could see the record if I provide the case number. This is a catch 22 because you cannot find the case number until you search the court docket.

Equally frustrating is the search for Covington City Council Minutes. I go to City Hall and they tell me that the records are at the Kentucky Archives in Frankfort. I go there and they tell me they have never received any records from Covington. I suspect that in this instance the records are lost and no one in Covington wants to admit to it.


Bill Meier commented on 2008-12-10

Ironically, now all that information has been scanned in and archived on-line by the US patent office! Of course, it is just scanned images of pages, not text, and no indexes. But it's no different than dealing with the material on rolls of microfilm at a major library. Except this is accessible by everyone, and will never get lost or destroyed (we can hope!)

However, the master index patent books to my knowledge, are not available on-line. They list all the patents issued on each Tuesday.

I have gone to the Boston Public Library several times over the years doing patent research. Years ago, a number of the large libraries around the country got a one-time distribution of the images of all the patents on microfilm. Boston was one of them.

I looked up my patent by number on draws of microfilm, took out the appropriate roll, loaded it up, and found the patent.

Several years later, I went back. The patent I wanted to look up was in one of the drawers near the bottom of the large filing cabinet. All the bottom draws were empty.... I asked the research assistant where was that material??

It was damaged when the roof leaked. This microfilm was lost. Irreplaceable... One of only a few sets around the country.

Visit [Patent Reference]

for the most complete list of insulator and insulator related patents known to the hobby. There are 2918 patents and counting...


Rick Jones commented on 2008-12-10

Glenn---maybe with the new emphasis on customer service, especially in government offices, someone could have better luck today in DC.

As for the Kentucky efforts, any collectors from the Bluegrass State whose had contact with U.S. Sen. Mitch McConnell or better, Rep. Geoff Davis of the fourth Congressional district (Covington)? State legislators can be very helpful in getting doors opened. It would be helpful to the hobby to find out definitely whether such records have been lost or just institutionally buried.


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