U.S. patent number 3,864,048 [Application Number 05/307,342] was granted by the patent office on 1975-02-04 for quick-acting releasable tube connectors.
Invention is credited to Alene McCall Parker.
United States Patent |
3,864,048 |
Parker |
February 4, 1975 |
Quick-Acting Releasable Tube Connectors
Abstract
A positive, reliable, quickly connectable and disconnectable
means of connecting lengths of telescoping tubing in a selected one
of a large number of relatively axial adjustment positions. While
capable of a very wide range of uses, the invention is of
particular value for take-down walking aids such an canes, crutches
and walkers constructed of aluminum or magnesium tubing.
Inventors: |
Parker; Alene McCall (Windsor,
NC) |
Family
ID: |
23189313 |
Appl.
No.: |
05/307,342 |
Filed: |
November 17, 1972 |
Current U.S.
Class: |
403/27;
248/188.5; 403/108; 248/423; 403/13; 403/328 |
Current CPC
Class: |
F16B
7/105 (20130101); Y10T 403/604 (20150115); Y10T
403/32459 (20150115); Y10T 403/20 (20150115); Y10T
403/1616 (20150115) |
Current International
Class: |
F16B
7/10 (20060101); F16B 7/00 (20060101); F16b
007/10 () |
Field of
Search: |
;403/324,325,326,327,328,107,108,4,13,14 ;248/188.5,354P,408,423
;108/146 ;135/46T,50 ;285/4 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Schroeder; Werner H.
Assistant Examiner: Berman; Conrad L.
Attorney, Agent or Firm: Dew, J. D.; Elizabeth Newton Dew,
J. D.; Arthur Wells
Claims
I claim:
1. Apparatus comprising inner and outer telescopically interfitting
tubular sections having a common longitudinal axis, said outer
section having a plurality of regularly- and axially-spaced radial
holes in and through its walls, said inner section also having a
plurality of axially-spaced radial holes in and through its walls
and spaced differently from the spacing of the holes in said outer
section, all said holes being the same diametral size, a plug
entirely fitting within and axially adjustable in and along said
inner section, bayonet slot means formed on one end of said plug,
said plug having a bore extending diametrically thereacross,
generally cylindrical latch means movably fitting within said bore
and having an outer end of reduced diametral size to smoothly fit
within and extend through any selected registering pair of radial
holes in and through said sections, said reduced outer end forming
an annular shoulder with the body of said latch means, actuating
means within said bore operaable to move said latch means radially
outwardly along said bore, from a first position entirely within
said plug, outwardly to a second and latching position with its
reduced end extending through any selected registering pair of
holes in said sections and in registration with said bore, to thus
releasably lock said sections in selected telescopic relation, and
abutment means cooperating with said shoulder on said latch means,
positively limiting radially outward movement thereof in said
second position.
2. The apparatus of claim 1, said bore being reduced in diametral
dimension at its end adjacent said first-named shoulder to thereby
define a second annular shoulder abutment means, to contact said
first-named shoulder when said latch means is in second
position.
3. The apparatus of claim 1 said bore being threaded, said latch
means being a holding screw engaging the threads of said bore and
of larger diameter than the holes in said tubular sections, turning
of said screw outwardly to second position causing said annular
shoulder to abut the perimeter of the selected hole in said inner
tubular section.
4. The apparatus of claim 1, said generally cylindrical latch means
having an integral axial extension of reduced diameter within said
bore, and extending oppositely from said reduced outer end thereof,
and a coil spring within said bore encompassing said axial
extension and urging said latch means radially outwardly to second
and latching position.
5. In combination, a first tubular section, a second tubular
section telescopically and axially slidably fitting about said
first section, a plug discrete from and slidably fitting within
said first section for axial adjustment to any selected position
therealong, bayonet slot means formed on one end of said plug,
latch means movable in and along a diametral bore formed in said
plug, and operating means in said bore, operable to move said latch
means in and along said bore, outwardly into any selected
registering pair of a plurality of regularly and axially spaced
apertures formed in and through the walls of said sections, to
thereby releasably lock said sections together in a selected one of
a plurality of axially-related positions, the axial spacing of the
apertures in one section differing from the spacing of the
apertures in the other said section.
6. The combination of claim 5 said latch means comprising a smooth
cylinder having an outer end of reduced diametral size and forming
with said cylinder a first annular shoulder, the contiguous end of
said bore being of reduced diameter to form a second shoulder, said
shoulders abutting when said reduced outer end of said cylinder
projects into a selected registering pair of apertures in said
tubular sections to thereby positively prevent further outward
movement of said cylinder, said operating means comprising a coil
spring engaging and urging said cylinder into outward limiting
position wherein said shoulders abut.
7. The combination of claim 5, wherein said bayonet joint slot
means formed on one end of said plug is adapted to engage with a
rod to be inserted axially into said inner section from one end
thereof and constructed and arranged for detachable connection with
said bayonet joint slot means of said plug so as to adjust the same
axially in and along said first section.
8. The combination of claim 5, said first section being formed with
an indicating line extending longitudinally thereof and in
registration with each aperture therein, and circumferential
indicating lines in intersecting relation with each said aperture,
respectively.
9. The combination of claim 5, said latch means comprising a first
screw having an outer end of reduced diameter sized for a smooth
fit in and through any selected pair of said registering apertures
in said first and second sections, said operating means comprising
threads on the wall of said bore, and in engagement with the
threads of said screw, there being slot means formed in the
reduced-diameter outer end of said screw, for engagement with a
screwdriver adapted to be inserted through the selected registering
pair of apertures in said tubular sections.
10. The combination of claim 9, the reduced outer end of said first
screw forming therewith an annular shoulder, said shoulder engaging
the perimeter of any selected aperture in said first section, to
thereby positively limit outward movement of said first screw
relatively to said sections.
Description
BACKGROUND OF THE INVENTION
At the present time there is a great need for a connector for
telescoping tubes which can be rapidly and reliably interconnected
and disconnected, for use in building up items such as those
commonly transported by automobile. Among these may be mentioned
bicycles, tricycles, invalid chairs, walking aids, ski poles and
other athletic devices, tripods, and like items. While attempts
have been made to provide reliable connector means of the type
stated, by which such articles may be quickly taken down into a
number of easily-loaded transportable parts, and rapidly
re-assembled for use, without special tools, such means have
heretofore been either excessively complicated and costly to
manufacture, or unreliable in operation by reason of parts becoming
loose or disconnected during use, and permitting undesired and
perhaps dangerous collapse.
SUMMARY OF THE INVENTION
It is the basic purpose of this invention to provide connecting
means for telescoping tubes, in particular tubes of aluminum or
magnesium, and which are quickly and easily operated to
interconnect relatively short lengths of tubing in axial alignment,
to form or build up articles of common use.
While as will subsequently appear, the invention is readily adapted
to the formation or building up of take-down articles over a wide
range of use, it is of particular utility in connection with canes,
crutches and similar items.
Thus a principal object of the invention is to provide coupling or
connector means by which relatively short tubular and telescoping
parts may be readily, positively and reliably interconnected and
formed into attractive and useful articles.
Another object is to provide tube connecting means as aforesaid,
which can be assembled and taken down, as desired, without tools or
with only a simple tool such as a screwdriver and which, once
assembled into a unitary instrument, can be relied upon to hold
but, at the same time can when desired be as easily taken down into
a compact and readily-transportable group of parts or elements.
A further object is to provide a tube or rod connection in which
the assembled elements form a utility such as a crutch, a table,
chair or the like, having a strength and rigidity comparable to a
prior art utility made by welding, screw threading, soldering,
sweating and like well known means of permanent connections.
Another object is to provide means for axially and positively
interconnecting two tubular telescoping sections or objects, in any
selected one of a large number of relative positions.
Still another object is to provide tube or rod connecting means as
aforesaid, which can be made up from simple and readily-obtainable
tubing, rods, screws and springs, and which can be produced with a
minimum of machining, tapping, threading, or like mechanical
procedures.
A further object is to provide a connection for tubular or rod-like
elements which can be interchanged and assembled for different uses
or purposes such as table and chair legs, bar stools, curtain rods,
clothes rods, flag poles, handles, and wherever an elongaated item
is required of variable and extensible lengths, and positively held
in the selected length adjustment and arrangement of parts until
manually released.
Other objects and advantages of the invention will become apparent
to those skilled in the art, after a study of the following
disclosure in connection with the accompanying drawing. While the
invention will be described as for the interconnecting of tubular
parts, it is also useful for connecting an outer tube with a rod of
wood or metal telescopically fitting therein, or as a coupling
uniting the ends of two tubes.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a view in longitudinal section, of one form of tubular
connecting means embodying the invention;
FIG. 2 is an exploded perspective showing a plug connector of the
type used in FIG. 1, provided with means by which it may be readily
axially adjusted within its tube, to any selected one of a number
of positions axially therealong, then positively but releasably
locked in such position;
FIG. 3 is a view in longitudinal axial section of another form of
tubular connecting means embodying the invention;
FIG. 4 is an exploded perspective view of a connector plug using
the form shown at FIG. 3 and provided with means by which it may be
adjusted within its tube to a selected one of a number of axial
locations;
FIG. 5 is a perspective view of a walking aid such as a cane
equipped with the invention;
FIG. 6 is a side elevation showing two telescoping tubes embodying
the invention, with the inner one provided with guide markings or
lines which facilitate re-location thereof into a different
position of selected adjustment;
FIG. 7 is a transverse sectional view showing how two tubes may be
interconnected by two holding screws to afford greater strength in
tension or compression when that is needed;
FIG. 8 is a perspective view showing a chair seat or table provided
with legs embodying the invention;
FIG. 9 is a perspective view of an inner tube showing in greater
detail the locating lines or markings thereon as in FIG. 6;
FIG. 10 is a perspective view of a connector plug for coupling
together the ends of two tubes by means of externally and
internally threaded ends, respectively; and
FIG. 11 is a view corresponding to FIG. 10 showing a similar plug
utilizing pinned ends.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIG. 1, an outer tube 1 shown as cylindrical but which
may have other regular geometrical cross sectional form such as
square, hexagonal or elliptical, slidable and telescopically fits
about an inner tube 2. The tubes are shown as metallic such as
aluminum or magnesium. Within inner tube 2 slidably fits a plug or
plunger 3 shown as a section of solid rod and having a
diametrically extending threaded hole 4 within which a holding
screw 5 engages. See also FIG. 2. The screw has a smooth coaxial
outer end 6 of reduced diameter provided with a slot which may
receive an ordinary screw driver, a Phillips head driver or an
Allen wrench.
The axial dimension of the reduced end 6 is at least equal to the
combined radial wall thicknesses of tubes 1 and 2. Further, it
forms with the body of the screw, an annular shoulder as indicated
at 7, FIG. 2. It will also be noted from FIG. 1 that the lengths of
holding screw 5 and threaded hole 4 are so related that when the
screw is fully turned into plug 3 from the position shown, head 6
clears or is flush with the right end of hole 4 or, if desired,
inset a short distance inside the hole. Although not indispensable
when as shown, plug 3 is discrete from inner tube 2, a hole 8 is
disposed in the wall of tube 2 diametrically opposite the one
occupied by head 6, and is enlarged to allow screw 6 to freely pass
or slide therethrough. This is a convenience in assembly.
Plug 3 has an axially-extending tapped bore receiving a set screw
9, the end of which may engage and fix holding screw 5 against
turning. A fiber, plastic or neoprene washer 10 is sized for a
frictional fit within outer tube 1 and acts to afford a degree of
resistance to sliding of tube 2 and plug 3 in and along tube 1, as
well as to prevent loose play of tube 2 within tube 1. A lock nut
11 threaded on screw 9 holds the washer or disk in position and
also provides frictional resistance to turning of screw 9.
FIG. 1 shows the two tubes 1 and 2 adjusted to have a minimum
overlap. Outer tube 1 has a number of axially-spaced radial holes
in and through its walls, each sized to receive head 6 with a
smooth accurate fit as shown at 12. A second one of these holes is
identified at 12a. The number and spacing of the holes is a matter
of choice and selection depending upon the intended purpose of the
instrument with which the invention is related. Preferably as
subsequently explained, the spacing of holes 12, 12a, etc., bears a
certain relation to the spacing of the locating holes in tube
2.
Assuming the two tubes 1 and 2 separated initially, the user takes
a plug 3 and after turning its holding screw 5 to make sure that
its reduced end 6 is at least flush with hole 4, inserts the plug
into tube 2 and slides and turns it until end 6 registers with a
hole through the wall thereof. Then he inserts a screw driver
through the hole and turns the screw outwardly until its head fits
but does not protrude from the hole. This locks together and unites
tube 2 and plug 3. Next he inserts the parts into outer tube 1 and
by sliding and rotation thereof, locates head 6 in registration
with one of the holes such as 12, in the wall of tube 1. Then using
the screwdriver he backs screw 5 out further until its head fits
into the selected hole in the outer tube. Thus the parts are locked
together positively and firmly. If desired, set screw 9 can be
turned down to bind holding screw 5 in position.
In the final outward position of screw 5, its shoulder 7 abuts the
annular area about the hole in the wall of tube 2. This not only
forms a very convenient way of locating the screw in final desired
locking position, it also creates friction between the screw and
tube and thus frequently makes it unnecessary to resort to turning
down of set screw 9. It also creates a thrust on the aforesaid area
of the inner wall of tube 2 and thus slightly distorts it at that
location and helps to assure a snug tight fit between the tubes, it
being understood that when screw 5 is again turned in to release
position, the natural resilience of the metal of the tube causes it
to resume true circular cross section. In the locking position
shown, the end of head 6 will be essentially flush with the outer
wall of tube 1.
When a different relative axial adjustment of the tubes is desired
as, for instance, to shorten or lengthen the effective length of a
ski pole embodying the invention, each leg of a chair or table, or
a walking aid, it is merely necessary to turn screw 5 until its
reduced end 6 clears the hole such as 12 in tube 1. Then the tubes
may be adjusted axially until head 6 registers with a different and
selected hole in the tube. Then the screw is backed out as
previously described, to positively and firmly lock the tubes in
the new position.
A further advantage of the construction just described, and one
which is also present in the latch form of the invention presently
to be described, is that by forming a number of axially-spaced
holes in and through the wall of inner tube 2, a greatly increased
number of relative positions of axial adjustment between the two
tubes is made possible. For example, if the distance between holes
12, 12a, etc. in outer tube 1 is four inches, and there are a total
of five such holes, then by providing only four holes in inner tube
2, with an axial spacing of one inch, a total of twenty (20)
adjusted positions are made possible in one-inch steps or
intervals. Of course, essentially the same result may be attained
by spacing the holes in inner tube 2 by a distance equal to one or
several times the distance between the holes in tube 1, plus a
fractional distance equal to one such space divided by the
pre-selected number of holes in tube 2. For instance where holes
12, 12a, etc. are spaced 4 inches apart, the holes in tube 2 may be
spaced 5, 9 and 13 inches from the first one, thus affording a
large number of adjustments in one-inch steps.
Thus by making plug 3 adjustable in and along tube 2 to a plurality
of positions a total number of adjustments of the two tubes is made
possible, equal to xy, where x is the number of holes in tube 1 and
y is the number in tube 2.
FIG. 2 is an exploded view showing a modified construction wherein
plug 13 may be readily adjusted to a selected location in and along
a tube such as 2, FIG. 1. Plug 13 is per se generally similar in
function and mode of operation as item 3, FIG. 1, so that it is
only necessary to identify threaded diametral hole 4a and holding
screw 5 with reduced end 6 and shoulder 7.
However, plug 13 has an axial threaded hole 14 in one end thereof
while the other end is provided with a bore defining walls with
bayonet joint slots 15 formed to receive the end of an elongated
adjusting rod 16 on which only one end is shown. The rod has a
transverse pin 17 and has a smooth fit in the bore in plug 13 so
that it may be turned to cause the pin to ride in and along the
slots thus forming a connection by which, when screw 5 is in the
released position, the plug may be axially shifted to any selected
position of adjustment. Rod 16 will be of a length suited to the
length of the inner tube used.
Threaded hole 14 may be used to receive a set screw 18 with an
interposed friction pad of fiber, plastic or neoprene 19 to thereby
bind or fix screw 5 in its desired rotational position. Likewise it
may be used to receive the threaded end of an adjusting rod 16a in
substitution for rod 16.
FIG. 3 shows a second form embodying a quick-attachable connector
which does not require a tool to make, break or adjust the
connection between tubes. An inner tube 20 has one or a plurality
of radial holes 21 spaced axially therealong. A plug 23 which is
similar in purpose to item 3, FIG. 1, slidably fits the tube. The
plug is diametrically bored as at 24. This bore stops short of the
right end as viewed upon FIG. 3 and is followed by a coaxial bore
of smaller diameter thus forming an internal annular shoulder
25.
A latch pin 26 is sized for a smooth fit within the smaller bore in
plug 23 and is formed with a central flange 27 having an accurate
fit in bore 24. The pin also has a smooth fit within the hole in
inner tube 20 and one or more axially-spaced radial holes through
the wall of an outer tube 28 which as shown, telescopically fits
over and about tube 20. Within bore 24 there is a compression coil
spring 29 loosely fitting over the contiguous end of pin 26 and at
that end abutting flange 27. The left end of bore 24 is milled with
a shallow inside channel or grooove to receive the ends of an
abutment metal strip 30 which may have a bulge in its central
portion for a loose fit within the contiguous end of the spring.
Thus the spring acts continuously to urge pin 26 to the right, into
the position shown wherein flange 27 engages shoulder 25 and the
free outer end of the pin fits registering holes in tubes 20, 28
and thus maintains them locked in a selected position of relative
axial adjustment.
In assembly of the plug mechanism, the pin is inserted from the
left, into bore 24 to the position shown. Then the spring is
emplaced within the bore and the resilient abutment, slightly and
temporarily bent, is pushed in until its ends snap into the groove
in the walls of bore 24, while the spring is compressed.
The operation will be clear from the foregoing description and is
functionally like the form depicted upon FIG. 1. With pin 26
pressed in, plug 23 is inserted into tube 20 and moved axially
therein until the pin snaps out through a selected hole 21. Then
outer tube 28 is moved over tube 20 and while pin 26 is pressed
inwardly, moved axially until the pin snaps into a hole such as 31
therein. This locks the tubes in the selected position of axial
adjustment. As in the case of FIG. 1, both tubes may be provided
with radial holes through its walls, and their spacing may be
coordinated as previously described to provide, for instance, a
considerable number of adjustments in steps of one inch, one-half
inch or other selected distance.
FIG. 3 also shows how plug 23 may be used to attach thereto an item
of utility or decoration such as a handle, a wall bracket, a
flange, a ball-and-socket joint, or a universal joint coupling, the
foot of a chair or table leg, or other article of furniture, the
foot and handgrip of a walking aid, and numerous other items. The
plug is formed with an integrally connected axial extension 32 of
regular geometrical form in cross section and is pierced with a
diametral hole 33 which may be sized to receive a latch pin like
26, or tapped to take a holding screw like 5, FIG. 1. Thus an
article such as a handgrip or foot, FIGS. 5 and 8, and having a
bore to fit smoothly over the extension may be connected thereto by
either the connection of FIG. 1 or that of FIG. 3. This
construction also forms a convenient means by which two tubes such
as 20 may be connected in axial relation, it being understood that
in such case outer tube 28 may be omitted or a short section only
employed for reinforcement.
FIG. 4 is an exploded view showing how the embodiment of FIG. 3 is
assembled. Since parts thereof may be identical with like parts of
FIG. 3, they have been identified by the same reference numerals.
In this form the plug 37 is bored from one end to form walls
provided with bayonet joint slots 35 similar in purpose to those
such as the one identified at 15, FIG. 2. A tapped axial hole 36
may be formed in the other end for connection to an article of
utility or ornamentation, as aforesaid. Such tapped hole may also
form a convenient way of adjusting the plug to a new position of
adjustment in and along a tube. This is done simply by temporarily
threading in one end of an elongated rod 16a.
FIG. 5 shows how the invention may be used in the formation of
alternate types of a cane, crutch or like walking aid. One plug
such as 23, FIG. 3, is located in the upper end of an outer tube
such as 28. A second plug fits and is slidably adjustable along
inner tube 20. Its latch pin 26 releasably fits in registering
radial holes in the two tubes 20 and 28 to afford aan effective and
adjustable over-all length precisely suited to the user and his
needs. A third plug may be used to detachably and replaceably
connect a foot 38 in the lower end of tube 20. While it is
contemplated that two diametral sizes of plugs may be provided, one
to fit each outer tube and a second to fit each inner tube, this is
not necessary because each plug sized to fit the inner tubes may be
readily adapted for the inside of an outer tube, merely by a short
section of an inner tube having a radial hole in its wall to
receive a latchpin such as 26, FIG. 3, or a holding screw such as
5, FIG. 2. Thus only one size of plug is actually required to use
in the separable connection of tubular sections of a very wide
range of articles of utility. It will be noted from FIG. 3 that the
outer end of pin 26 is slightly rounded. This end acts like a cam
so that when slightly pressed in with the finger to essentially
clear the hole in outer tube 28, the two tubes may be readily
adjusted axially either to separate them or to move them to a new
position of adjustment wherein the pin snaps into the selected hole
in tube 28. After the tubes are separated, the pin may be further
manually pressed in to clear the hole in tube 20 thus enabling the
plug to be removed or shifted to a new selected position within the
tube.
FIG. 6 shows a feature which makes adjustments easy. An inner tube
or section such as 2 is milled or otherwise formed with a shallow
linear channel 39 extending longitudinally and centrally of each
hole therein, and also with a circumferential channel 40, one for
each hole. The channels may be filled with a colored enamel to aid
ready observation. Thus when the two tubes are to be adjusted to a
new axial relative position, the head 6 of holding screw 5 is
turned in to release the connection as previously described, and
the tubes are moved until the longitudinal line 39 or a
circumferential line 40 appears through a hole 12 in tube 1. This
positively locates screw head 6 or pin 26, as the case may be, in
registration with the selected hole in the outer tube.
The inner telescoping tube section or element shown in previous
figures as a metal tube like 2, FIG. 1, may be of wood or plastic.
Such a construction is shown upon FIG. 7. It also illustrates the
use of two aligned and diametrically disposed holding screws in
those cases where extra tensile or compressive strength of the
united telescoping elements is desirable or required. In this
figure, outer tube 1 may be the same as in FIG. 1. However the
inner element 42 is shown as a rod of wood. It may also be of
plastic or like material. At selected intervals along its length
element 42 is drilled with diametrically-extending holes into each
of which is pressed or adhesively secured an internally-threaded
metallic tube section or liner 43 preferably with its ends flush
with the surface of the element. Two holding screws 45 are threaded
from the respective ends of the liner until their reduced smooth
ends 45 are flush with or slightly within the liner. Then the
assembly is inserted into outer tube 1 until the ends of the screws
register with a selected pair of aligned holes therein. Then a
screwdriver is used to back out both screws to the position shown
wherein the shoulder formed by the reduced end of each screw, abuts
the contiguous inner wall of the tube. This not only provides
friction effectively locking each screw in operating position, it
also tends to slightly reduce the size of the outer tube along a
diameter normal to the axis of the screws and thus prevents or
absorbs any play which might otherwise be present between the
elements 1 and 42. It will be understood that a selected number of
liners 43 may be provided at spaced intervals axially along element
42. Also a number of pairs of holes in and axially spaced along
tube 1, such as the one indicated at 12, 12a, FIG. 1, are
contemplated, with spacings related to the spacing of liners 43, in
accordance with the feature described in connection with FIG.
1.
FIG. 8 shows one leg of a table or chair T embodying the invention
and utilizing outer and inner combined tubular parts 46, 47
interconnected by pin 26 for a selected effective length. A foot 48
may also be detachably connected with inner tube 47 by the
releasable connection depicted upon FIGS. 1 or 3. Of course, while
the choice of the connection shown upon those figures will depend
upon the particular use or purpose of the article, both are
eminently satisfactory and reliable. Each may be made as strong and
rigid as the situation requires; and each is operative under
adverse conditions of stress and vibrations.
FIG. 9 shows in greater detail the feature of locating and
positioning lines 39, 40, as applied to an inner tube such as 2.
While upon FIG. 8 the holes 21 and 31 are exposed for clarity of
illustration, they will usually be located at 180.degree. rotation
from the position shown and thus be less conspicuous where improved
appearance is a factor.
In FIG. 10 is shown a modification 3a applicable to the plugs 3, 13
and 23 wherein there is an integral threaded extension 18a at one
end of the plug and an axial threaded bore 36 at the other end,
serving thereby to connect two tubes together when they are
installed in the ends of tubes by one of the latching means
previously described.
FIG. 11 shows a modification similar to FIG. 10 but having a smooth
integral reduced extension 32 at one end with diametral hole 33 for
a locking pin, and a bore 35a at the other end with transverse hole
33a for a second locking pin. Since one form may be placed at one
end of a tube and another plug reversed with the other form exposed
at the opposite end of the tube, they serve to unite two, or a
series of tubes in axially aligned connection. A second tube can be
placed over the joint between the tubes thus connected, for
reinforcement if desired.
The foregoing description is to be taken in an illustrative rather
than a limiting sense, for the invention has a very wide range of
usefulness, limited only by the skill and imagination of the
designer.
* * * * *