Spacial structure

An apparatus for joining sections to a knuckle in a spatial structure and including a first hollow base piece having a substantially spherical shaped out shell provided with a first plurality of equidistantly positioned holes and an inwardly bent perimeter area, a second hollow base piece having a substantially spherical shaped outer shell provided with a second plurality of equidistantly positioned holes, components for joining the first and second hollow base pieces to each other to form the knuckle with all holes of the first and second plurality of holes equidistantly positioned from each other, an internally threaded single piece element, a section having a face and being rigidly attached to the internally threaded single piece element so that the face rests upon the outer face of the knuckle, and a tightening screw having a head resting on the inner face of the knuckle and a body passing through one of the equidistantly positioned holes of the knuckle so as to engage by threading the single piece element.

BACKGROUND OF THE INVENTION 
Spacial structures that comprise a number of sections whose ends are joined 
to a number of knuckles to make reticular spacial structures are known. 
In particular, the spacial structure whose knuckles are comprised of solid 
balls to which tubular sections are joined is known. 
The spacial structure whose knuckles are comprised of two spherical shells 
joined together by means of external fins is also known. 
The chief drawback with the first of the aforementioned systems lies in the 
difficulty on site with joining the tubular sections to a solid ball, and 
so it can only be worked on from the outside. 
The second of the systems mentioned presents the serious difficulty of the 
fins for joining to the spherical shells imposing enormous restrictions 
upon the reticular assembly of the relevant tubular members. 
SUMMARY OF THE INVENTION 
The present invention overcomes these disadvantages by developing a knuckle 
that is comprised of two internally hollow parts with no outside 
protrusions to restrict reticulation. 
The spacial structure covered by this invention, which is comprised of 
equidistantly positioned knuckles, an assembly of sections and means for 
joining these sections at each end to said knuckles, is novel because it 
is made up from: 
(a) a first hollow base piece whose external shape is approximately that of 
a spherical shell in which there is a number of equidistantly positioned 
holes at an angular distance of .alpha..sub.1 and with a perimeter area 
that is bent towards the inside, 
(b) the second hollow base piece whose external shape is approximately that 
of a spherical shell in which there is a number of equidistantly 
positioned holes at an angular distance of .alpha..sub.1, 
(c) means of linkage between the first base piece and the second base piece 
which, upon being joined together, forms the knuckle of the spatial 
structure, with all the holes being equidistantly positioned with respect 
to one another at an angular distance of .alpha..sub.1. 
It is a feature of the present invention that the second base piece 
possesses a bent perimeter area facing the bent area on the first base 
piece, making a joining area. 
It is another feature of the present invention that the bent area on the 
second base piece faces outwards. 
It is still another feature of the present invention that the bent area on 
the second base piece faces inwards. 
It is yet another feature of the present invention that the means of 
linkage between the first base piece and the second base piece comprise a 
strength member in internal contact with the poles of both spherical 
shells, and means for tightening the strength member up against the poles. 
It is yet still another feature of the present invention that the means for 
tightening comprise a stud which runs through the middle of the strength 
member, goes through both spherical shells, and has a stop on one end, and 
a thread for tightening on the other. 
It is yet a further feature of the present invention that the means of 
linkage between the first base piece and the second base piece is 
comprised of threaded screws at the joining area. 
It is yet another feature of the present invention that one of the base 
pieces possesses protrusions which engage inside grooves provided for the 
purpose in the joining area upon the other base piece. 
It is still another feature of the present invention that the means for 
joining the sections to the knuckles are comprised of: 
(a) a single-piece element with inside thread and rigidly attached to the 
section to be joined, and with its face supported upon the outer wall of a 
base piece. 
(b) a pressure screw whose head rests against the inner wall of a base 
piece and whose body, after going through one of the equidistantly 
positioned holes, is threaded into the single-piece element. 
It is still yet another feature of the present invention that the contact 
areas between the single-piece element and the base piece, and the screw 
head and the base piece are spherical. 
It is yet another feature of the present invention that the single-piece 
element in revolution has at least one side surface which is shaped like a 
conical frustrum.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the drawings in detail, and firstly to FIG. 1 thereof, the 
knuckle according to the invention includes a lower base piece 2 and an 
upper base piece 1. 
Generally, base piece (1) is larger than base piece (2), giving an 
asymmetrical joint, but it is perfectly feasible for both pieces to be 
practically alike. 
As shown in FIG. 1 the outside shape of the two base pieces 1 and 2 is 
spherical in order that its external form in the assembly would be 
approximately a complete sphere. 
Holes (3) provided upon each of the spherical shells or base pieces are 
equidistantly positioned with respect to one another. As shown in FIG. 3 
an angle .alpha..sub.1 is defined between central axes of adjoining holes 
different spherical shells when they lie together. (See FIG. 3). 
These holes (3) form part of the joint between the spacial knuckle and 
sections (6). 
Said angles .alpha..sub.1 can be altered for each knuckle and each 
different structure. 
The first base piece (1) possesses a perimeter area (12) which is bent upon 
itself and is provided with open holes (13) which are preferably threaded. 
Said holes (13) form part of the joint between the two base pieces (1) and 
(2). 
The other base piece (2) possesses in turn a lip (21) into which engages 
the lip (12) provided on base piece (1). 
In these drawings, the lip (21) is shown as engaging externally with lip 
(12), but the invention also includes the idea wherewith lip (21) is given 
a similar shape to lip (12), so that the two can engage together by means 
of protrusions like those depicted in FIG. 4. 
As shown in FIG. 1 the lip 21 of the base piece (2) is provided with slots 
(25) which facilitate the engagement and joining with tubular sections 
(6). 
As shown in FIG. 2, the base piece (2) is furthermore provided opposite the 
holes (13) in base piece (1), with open holes (26), and joining screw (5) 
is housed in said holes (13) and (26). 
As mentioned above in the embodiment of FIG. 4, base piece (2) is provided 
with protrusions (30) which are engaged in slots (31) formed in base piece 
(1), although it is more logical to think of the reverse construction. 
As shown in FIG. 3, the knuckle of this spacial structure is completed with 
a strength member (7), which may be a tubular element the ends of which 
abut abuts against the inner walls of the base pieces. 
A stud (71) is provided inside tubular element (7), whose head (23) abuts 
against pole (22), and by means of nut (4), it abuts under pressure 
against washer (11), thus securing base pieces (1) and (2) to one another. 
FIG. 5 shows a single-piece element (16) in revolution which is attached to 
tubular section by weld (15). 
Said single-piece element (16) has a conical frustrum side surface 14 in 
order for it to suit different diameters of tube (6). 
A tightening screw (20) has a head (8) which, either directly or by means 
of widened area (9) or an additional member such as a washer having the 
same shape, is attached to the inside surface of base piece (1), (2). The 
contact face of the widened area (9) is spherical so as to facilitate 
contact. 
The single-piece element (16) further has a face (10) which is attached to 
the outside face of the same base piece (1), (2), and said contact face is 
spherical as well for the reasons given above. 
Screw (20) and single-piece element (16) are threaded together in 
engagement, thus accomplishing the joint between tubular section (6) and 
base piece (1), (2). 
The design can also be such that a side surface (14') adjacent to the 
joining face (10) is shaped as a conical frustrum, thus preventing said 
contact face (10) from being excessively large. 
It is to be noted that the joining means comprised (a) of the strength 
member (7) with its stud (71) and fittings, and (b) of screw (5) in the 
engagement area, can be used either individually or together, and the 
presence of protusions (30) is always optional. 
It will be understood that each of the elements described above, or two or 
more together, may also find a useful application in other types of 
constructions differing from the types described above. 
While the invention has been illustrated and described as embodied in a 
joining arrangement it is not intended to be limited to the details shown, 
since various modifications and structural changes may be made without 
departing in any way from the spirit of the present invention. 
Without further analysis, the foregoing will so fully reveal the gist of 
the present invention that others can, by applying current knowledge, 
readily adapt it for various applications without omitting features that, 
from the standpoint of prior art, fairly constitute essential 
characteristics of the generic or specific aspects of this invention.