Improvements in Screw Unions or Couplings.
Year: 1898

page_text: Date of Application, 11th Jan., 1898-Accepted, 2nd Apr., 1898
COMPLETE SPECIFICATION.
Improvements in Screw Unions or Couplings.
I, CLINTON ALLEN HIGBEE, of 1615, North Twenty-third Street, in the City and
County of Philadelphia, in the State of Pennsylvania, United States of America,
Manufacturer, do hereby declare the nature of this invention, and in what manner the
same is to be performed, to be particularly described and ascertained, in and by the
following statement :-
My invention relates to the construction of screw unions or couplings by which I
mean any screw union formed between threaded inetallic parts; the object of
my invention to increase the tightness of the joint formed between
the male and female members of the coupling so as to adapt such unions
for use in pipes or chambers of any description where gas or liquid is contained under
pressure, and for which uses screw joints have heretofore been found unsatisfactory,
or defective. While my invention is, as stated, of general application, it is
especially adapted for use in pipe joints, and I have accordingly illustrated it as
applied to a pipe joint.
Heretofore in adapting screw joints for use in connection with pipes or chambers
containing fluid under pressure the leakage of the fluid through the joint has been
attempted to be prevented by the nice and accurate fit of the threads upon each
other, and by the use of various lutings, but, as I have already stated, the best screw
joints are found to be defective under great pressure, and it is desirable in many, if
not most cases, to avoid the use of any luting for reasons which are familiar.
I have discovered that by so forming the threads of the members of a screw
coupling, upon one of which the threads lie as upon the surface of a cone, that in thé
act of screwing the members together pressure is exerted upon the sides of the
threads in such a way as to tend to cause the metal of the thread to flow outward.
towards the top of the thread and by forming the bottom of the threads in such a
way as to permit of an appreciable flow of the metal toward the top of the thread
that not only will the form of the thread be changed by the application of power, but
the flowing metal will not only fill the spaces or cavities left to permit its flow, but
fill them with a completeness and closeness unattainable in any other way, and which
will effectually prevent the passage of high pressure fluid through the completed
joint; and my invention consists in so forming the threads (one or both members of
the coupling being cone shaped as stated) as to.leave between the top and bottom, or
inner and outer apices of the threads an open space into which the metal can flow on
the application of power to drive the members together.
Reference being had to the drawings in which my invention is illustrated,
Figure 1 represents the male and female members of a screw pipe union embodying
my invention.
Figure 2 represents the same two members screwed together.
Figure 3 is an enlarged view of some of the upset threads of the union shown in
Fig. 2, the original form of the threads being indicated in dotted lines.
Figure 4 is a sectional view indicating the effect of applying my invention to
a screw coupling in which one member is of cast iron and the other of soft iron, and
Figure 5 is a view indicating a slight modification.

page_text: A is the male and B the female member of the screw union. As shown in
Figs. 1 and 2, the threads in both members are formed upon conical surfaces, that of
the male member, indicated at A¹, having greater angular divergence from the
central line of the coupling than has that of the female member, indicated at B1, in
consequence of which construction the tight joint at which I aim is formed between
the outer threads of the female member and the inner threads of the male member,
as is clearly indicated in Fig. 2. It will be understood, however, that it would make
no difference, so far as my invention is concerned, if the angle of the cone upon which
the threads are formed in the male member was less instead of greater than that
of the female member except that the tight joint would then be formed between
the inner threads of the female member and the outer threads of the male
member. It will also be evident that one of the coupling members may have its
threads formed, as upon the face of a cylinder, instead of as upon a cone, in which
case, if the cylindrical surface was upon the male member the tight portion of the
joint would be formed by the inner threads of the female member, while, if the
cylindrical member was the female member, the tight portion of the joint would
necessarily be formed by its outer threads. I have indicated above the possible
variations with regard to the conical formation of the members from which it will be
seen that whereas I prefer that both members should have their threads formed upon
conical surfaces it is sufficient that either member should be coned.
a a indicate the threads, their tops or upper apices being indicated at a¹, and their
bottoms or lower apices at a³, the threads indicated at b of the female coupling
member have their tops indicated at and their bottoms indicated at 63. The sides
of the threads should be made as is usual, fitting nicely against each other, but, in
accordance with my invention, I either cut away or truncate the tops of the threads,
as is indicated in Figs. 1 and 2, or groove the bottoms of the threads, as is indicated in
Fig. 5, so that, when the coupling members are screwed together, an open space is
left between the tops and bottoms of the threads. This space may be provided for
by the simple expedient of truncating or cutting away the tops of the ordinary
V shaped thread as is, for instance, indicated at a² and b². In the drawings I have
indicated a truncation by two planes which meet and leave a plane point to the
truncated thread, but the truncation may be by a single plane, or the ends of the
threads may be left of curved form, as may be preferred.
The result of coupling the two members constructed in accordance with my
invention is shown in Figs. 2 and 3, and as clearly appears in Fig. 2, the upsetting
of the threads occurs between the outer threads of the female and inner threads of
the male coupling, the rest of the threads serving simply to lend strength to the
joint, the tightness being effected by the threads which are completely upset to fill
the cavities left for the flowing metal. The action upon the metal is indicated and
somewhat exaggerated in Fig. 3, where the distortion of the threads and the new
outline imparted to them is made clearly apparent by comparison with the dotted
lines indicating the original form and relative position of the threads before the
upsetting action begins.
In Fig. 4 I have indicated a coupling in which the portion B is cast iron, while the
portion A is of soft malleable metal. The formation of the threads of the two
members is, before they are screwed together, substantially like that indicated in
Fig. 1, but as the cast metal will not upset or flow the entire distortion necessary to
make the tight joint is effected by the flow of metal in the soft metal member, and
I have found by experiment that a satisfactory joint may be made between two
members of the different materials mentioned.
The modification indicated in Fig. 5 is an obvious one, the recess for the flow of
the metal being formed by a channel at the base of the thread instead of by truncating
the top of the thread. This also I have found to give satisfactory results though,
for obvious reasons, I prefer the construction in which the tops of the threads are
truncated.
While I prefer in all cases that the angular inclination of the thread surfaces to
each other should be different, a construction which results, as I have explained, in'

page_text: the formation of the tight joint at one end of the coupled threads and the utilisation
of the remaining threads as packing for the joint, it is quite possible to apply my
invention to coupling members in which the threads are formed on cones of the same
angular inclination in which case of course all of the engaged threads are subjected
to the upsetting action simultaneously instead of progressively, as is the case when
the cones are of different angular inclination.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what I
claim is :-
1. A screw coupling consisting of male and female members, one or both members
having their threads formed on conical surfaces and said coupling members having
also their threads formed to fit against each other on the sides while leaving open
spaces between them at the outer and inner apices, all substantially as specified, and
so that the screwing together of the members under power will upset the metal of the
threads and change the thread form, causing the metal to flow into and close the
open spaces aforesaid.
2. A screw coupling consisting of male and female members, one or both members
having their threads formed on conical surfaces and said coupling members having
also their threads formed to fit against each other on the sides while leaving their
outer apices truncated so as to leave an open space between them and the inner apices
of the coupled thread, all substantially as specified, and so that the screwing together
of the members under power will upset the metal of the threads and change the
thread form causing the metal to flow into and close the open spaces aforesaid.
3. A screw coupling consisting of male and female members, one or both members
having their threads formed as on conical surfaces and said surfaces being of different
angular relation to the axes of the coupling, the threads of the coupling members
being further characterized by a formation of their apices to leave a space between
the tops and bottoms of the threads when screwed together and before the form of the
threads are changed and to permit of the change in the form of the threads as
the male and female members are screwed together with sufficient force.
4. A screw coupling consisting of male and female members, one or both members
having their threads formed as on conical surfaces and said surfaces being of different
angular relation to the axes of the coupling, the threads of the coupling members
being further characterized by the truncation of their outer apices so as to leave a
space between the tops and bottoms of the threads when screwed together and before
the form of the threads are changed and to permit of the change in the form of the
threads as the male and female members are screwed together with sufficient force.
Dated this 11th day of January 1898.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.