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.

Ed Holland commented on 2008-12-04

Do we know what the first threaded insulator was? CD 133? 131? Were they both both produced at the same time? Other candidates?

We know that Brookfield and Tillotson 131s were born-again 731s (and we have threadless 731s embossed with the Cauvet patent). Were there any threadless analogs of the 133?

So . . . what WAS the first threaded insulator?

Gary Kline commented on 2008-12-04

For the first threaded pintype I would look to the CDs styles that were made in both threadless and threaded versions which used the same mold. Here are some designs that saw both threadless and threaded versions.

  • CD731 no name / CD131 no name
  • CD731 Brookfield / CD 131 Brookfield
  • CD728.4 Broofield / CD133 Brookfield
  • CD732.2 no embossing / CD131.4 no embossing
  • CD736 E.R.W. / CD135.5 E.R.W. (I had a matched set of these. The insulators were identical on the outside having been produced from the same mold. The only difference was how the pinholes were formed.)

As to which insulator design was the first to see threads, my money would be on the CD731 / CD131 no name.

Cauvets patent shows a drawing of an odd shaped insulator, that if made, would be the first to have threads. But to me his patent drawing is just a representation of a generic glass insulator. Cavet in his patent states in part....

"The insulator J is made of glass molded to any suitable shape as to its exterior, but having always one or more grooves, f, formed on its circumference, to enable a conducting wire to be wound about it."

"The base or broad part g of the insulator is here shown to be a plane surface near its edge, with a recess about its center. I propose also to form the base g, of a convex shape, instead of partly flat or plane and partly sunken. When it is made convex it will shed rain with more facility"

"'My insulator is made of glass, molded according to the art of the glass-molder'

"'The insulator having been molded to the desired form, with an internal screw-thread formed in all axial perforation, as above explained, it is screwed upon one of the ends of the rod B, where it is retained by means of the articulation of the screw-threads'.

John Badowski commented on 2008-12-05

...and the 743 / 143 series....

Gary Kline commented on 2008-12-05

There is one insulator design that looks very similar to Cauvets patent drawing insulator. A CD131.8

I am not that familiar with that CD so will let someone else express whether it's history allows it to be considered for one of the first threaded insulators.

My sense is that from the time of Cauvets patent in 1865 into the early 1870s there were a lot of insulator designs being tried and used. Like today, some people did not adapt readily to every new design that came along preferring to stay with what they were familiar with or with a design they believed in. Not every insulator design would panned out. The change over to where threaded insulator were universally accepted and exclusively used would take some years.

Rick Jones commented on 2008-12-05

Regarding the 133/131 question about first threaded insulators. I have proposed the 131 as the first threaded due to the shape characteristics of some of my 731s and an unembossed 131 in my collection. I have yet to find a 731 that is identical to an embossed 131, but I'm still looking. Jim Peach may be better to chime in here than me since he specializes in concave skirts, and others like Ray.

I have also considered the 131.4 as a possible first threaded piece as well as the 135.5 ERW. We may never know for sure due to lost records and inaccurate record keeping. After all, these odd pieces of glass we collect never had that much value in the very early days (other than insulation), so scant records were kept.

Maybe some of the more knowledgeable collectors/historians out there can help.

Jim Peach commented on 2008-12-05

Well one 731 that is identical to a 131 is the 731 / 131 Brookfiled. They both definitely came from the same mold (#6). I have noticed the same thing on the 728. Brookfileds #5 & the #1 molds as being from the same molds as their 133 Brookfiled counterparts. I think Gary's observations about threaded insulators that have the same mold as their threaded counterparts (ERW , LGT Co, etc) could all have possibly been the first to be inserted with a threaded mandrel.

Its interesting to note that insulators like the 131.4 LGT Co come with, and without patent dates; and the dates that do show up are later, 1870, than the 1865 Cauvets pat for the invention of the threaded insulator.

Fun to theorize about if the datless 131.4 were from the threadless mold and maybe later the same mold was engraved with patent dates well after the implementation of the threaded system. Maybe a little clue to help think about the timeline and would be fun to examine one of each up close.

None-the-less its interesting for me to think about threadless insulators with patent dates for threads and vice versa.

It only makes sense that there was quite a market for threadless insulators well after 1865...imagine the labor necessary to change out an entire pin system on the long stretches of railroad, with late 1800 technology...

Rick Jones commented on 2008-12-05

Thanks for adding your comments, Jim. The one piece I need for my collection right now is that 731 Brookfield #6 mold that you mention. Now, it appears I'll need the 131 with the #6 mold as well. I have not had the opportunity to compare these two pieces.

Gary Kline commented on 2008-12-05

Just wanted to add something to the 732.2 / CD131.4 train of thought.

I included the CD 732.2 / CD131.4 in the group of earliest threaded because of the shared design shape only. I feel they came a bit later than the CD731 / CD131. I have not tried to match up a set to see if an exact same mold was used to make both threadless and threaded insulators. I consider the CD 732.2 a very late arrival in the threadless scene. I suppose it could be possible that the 131.4 style was actually designed first to primarily be a threaded insulator that saw limited threadless applications during the late 1860s early 1870s.

The example of CD732.2 I have has a conventional smooth threadless pinhole and was formed in a three piece mold. Other CD732.2s seen have a Floyd pinhole design which used a split pin and are three piece molds. The patent for that design was issued May 14 1867. I believe the Patent Dec 19 1871 examples use this Floyd design and were found in use on a lightning rod protection system. Bill Meier can elaborate on those. My example has the look and feel of a Hemingray product . The Floyd pinhole and Patent Dec 19 1871 examples do too.

I have not personally seen the CD 732.2 Tillotson example listed in the price guide. I assume it is possible to have been made with the same mold as the threaded version. Threaded CD131.4 examples are readily available where the threadless version is, well, relatively nonexistent. The threaded example is a two piece mold that has the feel of a Brookfield product to me. There is a threadless example in McDougald Pintype Guide and it appears to be a two piece mold also although it is hard to tell from the photograph.

The CD135.5 E.R.W is another style that is readily more available than it's threadless counterpart , the CD736 E.R.W. The New York & Erie Railroad changed it's name to Erie Railway in 1861 . It would make sense, at least as far as threaded insulators used on the Erie, that the CD135.5 would be one of the first.

Rick Jones commented on 2008-12-05

Great input, Gary. Thanks. I suppose it becomes a toss up among the 131, 131.4, and 135.5 as to first threaded pintype, with a good possibility the 131.4 was the latest of the three. That pretty much leaves us with the 131 and 135.5 as the most likely first threaded pieces. Now, which came first---the egg or the chicken?

Maybe Bill or Glenn can add something about the 732.2 and their ideas of when the 131.4 threaded first occurred. My guess is it didn't come along until around 1870 possibly just prior to the addition of the 1871 date. The 131.4 LGT & CO. has the early 1870 patent dates. Does that necessarily mean it was produced 11 months before any 131.4s with the 1871 date were produced? And what would the date for the Floyd slotted pinhole be?

Now, you add the uncertainty of when changeovers occurred from threadless to threaded mandrels and Jim's comment about how the cost of that changeover could have caused threadless pieces to be made well into the 1870s, the plot thickens.

Brent Burger commented on 2008-12-05

As the story goes, Louis Cauvet walked into the Brookfield offices one day while the bosses were away at luncheon, trying to sell his patent (or rights thereto). Employees present scoffed at Cauvet's pitch, going so far as to NOT get contact information for Mr. Cauvet. Upon their return, said bosses were informed of the visitor (now long gone) and said employees were then sent out into the city to find Mr. Cauvet. Upon location of Mr. Cauvet, the Brookfields then bought his patent (or rights thereto) and added insulator production to their list of other products already made by their firm.

It is known that Cauvet's patent dates to 25 July 1865. But is it known when he sold said rights to Brookfield ????

There is no saying Brookfield went into immediate production or that Louis Cauvet was on their doorstep the moment he got his patent granted. It could have literally been years. I highly doubt it, as the idea was clearly in the heads of Homer Brooke and the Hemingray gang as early as 1868. Even so, there is a three year window here.

I suspect whatever Brookfield ordered from Brooke was something more in order of a general press and NOT the first threaded insulator equipment they ever had.

Is a Brookfield threadless insulator known to have been made WITHOUT the Cauvet patent date ? I am unaware of such a critter, although threadless are not my forte.

I would submit that the story clearly states that Brookfield never made insulators until being prompted by the crossing of paths with Louis Cauvet sometime between 25 July 1865 and the summer of 1868. I had always assumed / understood this to be some time close to the 1865 date, but realize this has never been substantiated ( to me, anyway).

What I always took this to mean was that Brookfield started out making threaded insulators (as their earliest designs carry the Cauvet patent emb'g), and later made some with threadless mandrels to fill special orders for retro-fit applications to threadless pin systems.

As it relates to the question about which is the earliest threaded design, if Brookfield bought full patent rights to Cauvet's patent, it might be reasonable to project that Brookfield would have been the first to make such an item. If Cauvet sold use rights to others prior to Brookfield buying the patent outright, then maybe others beat them to the punch ?

I know little definitve info on this and what I have read is a little foggy, but applying historical thinking .....

Peter Beshara commented on 2008-12-06

I would put forward that ,the first Canadian threaded insulator was the Montreal 143's in 1876 . Threadless were made at Canada Glass co. in Hudson Quebec, till about 1876-77

The 743-143 type were likely made about 1879 as the St Johns Glass Co closed in July 1877 to be reopened in May 1879 .

Some of what are classed as former threadless molds were not. And were not made till later . The double threaded, former threadless molds were actually made in 1890 at the Burlington plant of the Diamond Glass Co. We in Canada were nowhere near the Cauvet's patent date .

That is why Mc Micking tried to patent a different locking devise for insulators , in 1875. These began to be made at Hamilton Glass Co in 1876 .

Glenn Drummond commented on 2008-12-06

I have heard this story several times over the years. However, there seems to be no documentation of it. Do you know if this is a true story or an "urban myth"  ??

It is known that Cauvet's patent dates to 25 July 1865. But is it known when he sold said rights to Brookfield ????

I don't think that Cauvet did sell rights to Brookfield. Please note that the patent was re-issued to Cauvet on 22 February 1870


That suggests to me that he was drawing royalties from everyone making threaded glass insulators during that time. Or is that what you mean by "selling rights" ?? I'm not real clear on terminology in this regard.

I suspect whatever Brookfield ordered from Brooke was something more in order of a general press and NOT the first threaded insulator equipment they ever had.

Perhaps you are correct, but I don't read the interference document that way. Brooke was pedaling his threading press to any and all takers. Makes you wonder if he stopped by Covington ??

While I suspect that Brookfield was making threadless insulators prior to 1865, I really have no clue. Here we must rely on Brookfield "experts."

As it relates to the question about which is the earliest threaded design, if Brookfield bought full patent rights to Cauvet's patent, it might be reasonable to project that Brookfield would have been the first to make such an item. If Cauvet sold use rights to others prior to Brookfield buying the patent outright, then maybe others beat them to the punch ?

But Cauvet's patent was for the art of making threads in the pin cavity of a glass insulator. He was not in the press business. Or have I missed a critical point somewhere ??

ps Also be aware that Cauvet was not the first of patent the concept of a threaded insulator. See the Amasa Stone patent:


Ten years before Cauvet's time but unfortunately ole Amasa died in the process and did not get to promote his idea. His daughter tried but the times were not favorable to a woman in the gentlemen's = world.

Gary Kline commented on 2008-12-07

I would like to thank Ed Holland for his "what was the first threaded insulator? ' question. It caused me to think a bit deeper about about the mid 1860 to early 1870's time period and insulator production. Also it spurred me to look into and use our online resources like along with ICON and patent listings.

Thanks to Glen and others who added their thoughts and understanding to the thread. It certainly gives one something to chew on.

I guess I never really thought I needed to know exactly when the first threaded insulator was made. Approximate times were good enough for me. My enjoyment and perspective with collecting insulators was elsewhere.

Perhaps though, thru this question, I have adjusted my perspective a bit and have learned that knowing more about this question does add and is in line with my collecting goals.

Having taken in some research along with Glen's comments and other's observations, this is my understanding.

> Cauvet received the patent for screw threads - July 25 1865.

> Brookes appeared to be the first to have the concept of a machine capable of using a threaded mandrel in insulator production. The idea was conceived in the presence of Luther G. Tillotson, B.B. Hagerty, & Horatio Reedlate Late Dec. 1867 with the first insulator press being introduced in Brookfield's shop July 1869 and the first machine delivered Nov. 1869.

> Glen stated that Robert Hemingray in his 1873 Testimony says: “Hemingray does not fix the date of his invention {an insulator press} 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.

> On January 25 1870 Homer Brookes receives patent for press to make screw insulators.

> On February 22 1870 , reissue of Cauvet's Patent

> Hemingray receives patent on his insulator press Dec. 19, 1871.

Although Brookes might have first had the idea (verified by three witnesses) for a machine to implement Cauvet's patent, it would appear Hemingray actually made the first press (per Robert Hemingray's testimony). There appears to be a race to see who can impliment Cauvet's Patent first. I am left with these thoughts to contemplate:

Could insulators be made employing Cauvet's patent without having a specially designed press machine as discussed above?

How is it that Hemingray used Cauvet's Patent to make insulators in July of 1868?

If Hemingray had licence to make screw insulators / use Cauvet's patent , why wouldn't he patent his press as soon as he had the idea for one or even after making his first press in July 1868? Why did it take 3 1/2 years to patent his insulator press?

Why is it that Brookfield, not Hemingray, is the one to put the July 25th Cauvet's Patent, and the reissued Patent Feb 22, 1870 AND the January 25th 1870 Press Patent on their insulators? Would not Hemingray be entitled to put the original or reissue Cauvet Patent on his insulators considering he was supposedly the first to make threaded insulators on his press?

One interesting insulator to note is the CD131 Tillotson (one of Brooke's witnesses) gives reference to the Brookes and Cauvet's reissued patent. With prominence and big lettering on the front skirt " BROOKE'S PAT / JAN 25TH 1870" . And on the reverse of some molds - "PAT.JAN.25TH 1870 / PAT.FEB.22 1870".

If nothing else, this discussion should cause collectors to take a second look at their early Brookfield and Hemingray insulators and contemplate the race to make threaded insulators.

Bob Stahr commented on 2008-12-07

Please note that Cauvet's patent was for a glass insulator with internal threading in combination with a corresponding wood pin. It would seem (and I am not a lawyer) that to produce an insulator with internal threads is not the issue, once you screw it onto a wooden peg, then you need to have the patent license. It seems that the telegraph companies would have needed the patent rights to impelement the invention.

Cauvet patents: [[3]] [[4]]

In addition, Hemingray & Brooke's patents were for a glass press to form threads. Not a threaded insulator.

Hemingray patent [[5]]

Brooke patent [[6]]

Brent Burger commented on 2008-12-08

Getting back to the general discussion, I too am re-analyzing the old think process on this and a few questions come up.

I guess I had always assumed that the threading of insulators started in close timing proximity to the original 1865 Cauvet patent. I remember Tibbits' books saying something about this, but it might also just be MY own reading that into what he wrote (?) ..... it has been a long time !

Later on, I came onto that written account of Cauvet coming in at lunch to the Brookfield office, trying to sell his patent to them. I am thinking this was in McDougald's book (?), but I could be mistaken. I do not recall if this story had any sort of date attached to it or not.

Do we know when exactly Cauvet and Brookfield crossed paths ?

I suppose it could have been even years after the actual patent granting. In fact, it plays better into the historical overlay of early mfr's. going from threadless to threaded if the actual changeover occurred closer to 1870 than 1865. It always seemed odd to me that Brookfield would solely occupy the market with threaded glass for 5+ years without someone stepping in to be competition.

Secondly, .... and maybe I missed it ? ..... but where was it stated that Brooke was providing Brookfield with their very first apparatus for making threaded insulators ? Is that actually stated, or is it assumed ? Brooke was a machinist and mould maker and had been associated with Brookfield for some time through the 1860's-70's. I am not so ready to jump to this being their first attempt at making threaded insulators (unless is is indeed stated so.

Just don't want to jump to conclusions.  ;-D

Mark Storaasli commented on 2008-12-08

In the case of "patent" medicines the license to make and sell included the proprietary use of a "trade-marked" name without which, the product would be deemed worthless...

Licensing an industrial process can be done by selling machines to perform the process, without the need to "sell the name" because the name means nothing compared to the utility of what was patented.

Processes and machines are sold together with implied "proprietary rights" buy the buy the right to make what it was designed to make...

When you improve the machine, the improvement is yours...license it back to the inventor or hold onto it to beat the competition...or something like that?

I don't think we can even begin to cobble the REAL STORY together, on the basis of the scant evidence we inherited?

But there's no harm trying!

Gary Kline commented on 2008-12-08

Hey Brent, I had the same question. Did Homer Brooke provide Brookfield with their FIRST apparatus for making threadless insulators?

What I found in this reference on is that Brooke introduced Brookfield to his screw machine on July 1869 and delivered one screw machine on Dec 2 1869. [[7]]

Did Brookfield , Hemingray , or anyone else for that matter, have the capability of making threaded insulators before the Brookes and Hemingray presses were made? Or were these the only ticket to make threaded insulators. That's my curiousity. From what I read, it appears Hemingray's and Brooke's presses where the machines that proved sucessful in forming the threads.

Gary Kline commented on 2008-12-08

Thanks for your imput , Bob. My understanding is different (and I'm not a patent lawyer either ;-). It seems to me producing an insulator with internal threads is the issue here. Cauvet took out, as his patent says, for "IMPROVEMENT IN INSULATORS FOR TELEGRAPH-WIRES". What was that improvement? Threading to the insulator's pinhole. Cauvet was concerned mainly with the design and improvement of the insulator itself. The ways the insulator would be employed (threaded pins) is the result of the insulator's design improvement . Cauvet by being issued a patent would first be concerned about addressing someone producing his design and making threaded insulators (and pins if you like). After all, if you allow anyone to produce your idea, what is the use of patenting it? It would seem to me that benefit of having ownership of a patent lies first in it's ability to control the manufacturing of one's idea by someone else. I suppose looking at it the other way , Cauvet could sell or grant use of a patent to the telegraph companies which in turn would source out the manufacturing of the insulators to glass houses and the pins to lumber companies. I would think that there would be tons of records showing telegraph companies making agreements to buy or lease patent rights to insulators improvements , batteries designs , poles, guy wire designs, pins, telegraph keys, sounders, relays, etc and every other patent design they would want to use and implement on their lines.

Brookes patent header states "IMPROVEMENT IN THE MANUFACTURE OF INSULATORS FOR TELEGRAPH- POLES." In the first paragraph he state, "have invented a new and useful Improvement in the Manufacture of Insulators and other articles of glass, of like form and character." Further down he states, "My improvement more especially relates to the manufacture of glass insulators, formed with a countersink and hole or recess at the base of the countersink, with a screw-thread cut in it. "

Brookes definitely is saying that his patent is for a press to produce threads. Is he saying it is for producing a specific threaded insulator? No. But by his choice of title on the patent and by his putting the manufacturing of insulators as the main focus and stating that it 'ESPECIALLY' relates to manufacture of glass insulators says he is designing this press to primarily address making threads in insulators and possibly other applications. Weren't these presses initially designed with insulator production in mind?

Curious about this....Hemingray marked their early insulators with the 'glass press to form threads' patent of Dec 19 1871. Did Hemingray emboss any of it's other non insulator glass products with the Dec 19 1871 patent? Did Brookfield put the Jan 25th 1870 patent on any non insulator products? Or, do we know if they used these particular designed presses to produce anything other than insulators?

I'm sure there are a lot brighter and more knowledgable folks on this subject out there. I'll sit back and listen for a while.

Bill Meier commented on 2008-12-08

Of course, you can toss the House Insulator into this mix...

From The Telegrapher November 15, 1873 there is a comment:

Two parties have been fighting in the courts over their rights as
patentees of the screw glass insulators, and spending money freely to
win a victory. The learned Court has decided in favor of one and
injuncted the other, when neither patent is worth a copper.
You will recollect, Mr. Editor, when you worked House, twenty years
ago, that the "hat block" House insulator was an iron one, with a
screw glass inside, and that the line builders carried a cutter, with
which they cut a thread on the top of the sharpened pole, and then
screwed the insulator on.
Then, why this costly lawsuit for a shadow? Will some one explain?

Another article (1895)

He designed an insulator having a glass screw-socket to engage with a
thread cut upon the top of the pole. When the glass manufacturers
insisted that it was impossible to make it he at once designed a
machine for performing the operation, which, in its essential
principle, is in use to this day.

Now, wouldn't you have to call this a threaded glass pin-type insulator? (or something pretty close!) ... Granted the thread was cut on the pole during installation, but that's an implementation detail... I don't believe there was any patent issued related to the concept of threads, a machine to make the threads in the glass, something to thread the pole, etc.

However, it is my understanding that even those this was not patented, you can't later patent something that "has been in use for a period of time" or something to that effect... i.e. your patent has to be for something novel... These days lawyers are great at getting around imposing on other patents, but I don't know that it was true 150 years ago... The former article I think sums that up...

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]


[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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