Swivel joint

A swivel joint is designed to provide limited and controlled movement in two orthogonal planes running through its symmetrical center. The three major parts of the swivel joint are molded from a material composition of polycarbon-glass-teflon. A swivel top mounts to the object to be provided with controlled movement. A swivel bottom mounts to a support. The swivel top and bottom are held together by a large, curved wafer and a nut and bolt arrangement. The swivel top and bottom interact with each other to provide controlled limited movement in the two orthogonal planes, simultaneously.

BACKGROUND OF THE INVENTION 
The present invention relates generally to improvements in swivel joints, 
and more particularly, pertains to new and improved limited movement 
swivel joints wherein controlled movement in two orthogonal planes is 
provided. 
Limited movement swivel joints that have been used heretofore have 
exhibited the problems of being difficult to maneuver, or binding up, and 
failing. Those swivel joints that do not readily exhibit this 
characteristic are complicated devices that, for example provide locking 
positons and, therefore, are necessarily expensive to manufacture. The 
universal movement swivel joint, such as a gimbal, although providing for 
movement in two orthogonal planes simultaneously, does not provide for 
limited movement in those planes. Nor does it limit movement to just two 
orthogonal planes. In order for the gimbal mechanism to have a long 
service life, a high quality material such as stainless steel is normally 
utilized, thereby again resulting in high manufacturing costs. 
OBJECTS AND SUMMARY OF THE INVENTION 
An object of this invention is to provide a swivel joint having only three 
major components that facilitates controlled movement of a relatively 
heavy object in two orthogonal planes, simultaneously. 
This object and the general purpose of the invention is provided by a 
swivel joint having three major parts, each part being molded from a 
material composition of polycarbonate, glass and teflon. A wafer having a 
certain convex surface of curvature rests within a recess in a swivel top. 
The diameter of the wafer determines the degree of movement permitted in a 
first orthogonal plane. The swivel top mounts to an object to be moved. 
The swivel top has a recess therein which has a defined concave surface of 
curvature, this curvature being equal to the convex surface of curvature 
of the wafer. This recess has a slot therein, said slot having a second 
convex surface of curvature and an oblong aperture therein. The aperture 
has its longer axis parallel to the longer side of said slot. A swivel 
bottom cylindrical in shape, having a diameter slightly smaller than the 
width of the swivel top, has a concave surface of curvature equal to the 
second convex surface of curvature of the slot in the swivel top. A pair 
of pie-shaped segments rest on the second concave surface of curvature of 
the bottom swivel. These pie-shaped segments interact with the edges of 
the slot on the swivel top to determine the degree of movement permitted 
in a second orthogonal plane. The swivel bottom fastens to a stationary 
member. The three major parts are held together in a nested manner by a 
nut and bolt arrangement.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS 
All the major components of the swivel joint of the present invention are 
illustrated in FIG. 1. The swivel joint provides limited controlled 
movement of an object mounted thereto in two orthogonal planes. The swivel 
bottom 21 provides circular rotating movement in a plane in which the 
swivel bottom 21 is located. The swivel top 19 provides pivotal movement 
in a plane perpendicular to the plane in which the swivel bottom 21 
provides circular movement. The curved wafer 18 limits the pivotal 
movement of the swivel joint and provides sufficient friction along the 
pivotal path to maintain an object mounted to the swivel joint at any 
point along this pivotal path. The bolt 13 and nut 25 maintain the 3 major 
components 18, 19 and 21 of the swivel joint in a nested relationship. 
The curved wafer 18, swivel top 19 and the swivel bottom 21 are each molded 
from a material that has as its major components polycarbonate, short 
glass fibers, and teflon. A preferred mix of these three materials has 
been found to be slightly over 50% polycarbonate, the other 50% being made 
up of short glass fibers and teflon. The mix of these three materials is 
adjusted to provide components that are durable and can support 
considerable weight thereon while still providing a sliding relationship 
between the curved wafer 18, swivel top 19 and the swivel bottom 21. 
The wafer 18 has a circular perimeter of a defined diameter and an aperture 
16 through its symmetrical center. As can be seen from FIG. 2 which is a 
cross-sectional view along line 22 of the perspective in FIG. 1, the wafer 
has a certain thickness and a first surface of curvature 45 at a defined 
radius of curvature along its convex surface, and another surface of 
curvature 47 having a differently defined radius of curvature along its 
concave surface. The radius of curvature defining the surface of curvature 
47 is slightly smaller than the radius of curvature defining the surface 
of curvature 45, thereby leaving a flat perimeter 17 around the periphery 
of the wafer 18. In order to facilitate the seating of a bolt 13 and 
washer 15, the area 49 around the aperture 16 is flattened. The diameter 
of the wafer 18 is chosen so that it fits within the recess of the swivel 
top 19, slidably engaging the concave surface of curvature 27 of the 
recess. As the swivel top causes pivotal motion in a vertical plane, the 
wafer 18 moves back and forth between the edges 28 of the recess of swivel 
top 19. The diameter of the wafer 18, therefore, defines the degree of 
pivotal motion in the vertical plane. The larger the diameter of the wafer 
18, the less pivotal motion there will be, and vice versa. 
The swivel top 19 has a generally rectangular perimeter, having apertures 
26 at its four corners to accommodate screws or nut and bolt arrangement 
for fastening the swivel top to an object to be moved. It is found to be 
most advantageous to mount the swivel top 19 at the center of gravity of 
the object to be moved. 
The swivel top 19 has a pair of flat surfaces 22 and 24 at opposite ends of 
its perimeter along its shorter edges. Swivel top 19 has a skirt 
therearound which is made up of a pair of flat sides 34 along its two 
longer sides, and a pair of curved sides 33 along its two shorter sides. 
A recess is formed in the swivel top 19. This recess consists of a concave 
surface of curvature 27 having the same radius of curvature as the radius 
of curvature of the first surface of curvature 45 of the wafer 18. This 
first surface of curvature 27 of the recess in the swivel top 19 has a 
groove 29 therein which is parallel to the longer sides of the swivel top 
19. This groove is terminated by the pair of edges 28. The groove has an 
oblong aperture 31 therein which traverses the symmetrical center of the 
swivel top 19. The longer axes of the oblong aperture 31 is parallel with 
the longer sides of the swivel top. 
FIG. 3 illustrates the cross-section of the swivel top 19 taken along 
cross-section line 33. The groove 29 in the recess of the swivel top 19 
has a convex surface of curvature 51 which is defined by a radius of 
curvature that is different from the radius of curvature that defines the 
first surface of curvature 27 of the swivel top. This convex surface of 
curvature 51 can be thought of as the second operative surface of 
curvature of the swivel top 19. Another convex surface of curvature 52 of 
the recess in the swivel top 19 has a radius of curvature that is 
different from the first and second surface of curvatures on the swivel 
top, and can be though of as a third surface of curvature. A pair of 
ridges, running along adjacent to the flat skirts 34 of the swivel top 19 
have a concave surface 53 that is defined by a certain radius of 
curvature. 
The swivel bottom 21 is preferably circular in shape, and has a skirt 41 
therearound. The diameter of the swivel bottom 21 is chosen to be slightly 
smaller than the distance between the internal surfaces of the two flat 
skirts 34 on the swivel top 19. The swivel bottom 21 has a concave surface 
of curvature 35 that is defined by the same radius of curvature that 
defines the convex surface of curvature 51 of the swivel top. The surface 
of curvature 35 has a pair of pie-shaped wedge segments formed thereon, 
each segment having a surface of curvature 37 and 39 respectively, which 
is defined by a radius of curvature that defines the convex surface of 
curvature 52 of the swivel top 19. 
Both pie-shaped segments have a flat portion 40 and 42 respectively, along 
the perimeter of the circular swivel bottom 21. An aperture 20 located at 
the symmetrical center of the swivel bottom 21 is large enough to 
accommodate the bolt 13. The skirt 41 of the swivel bottom has formed 
therein as a part thereof, a pair of extensions 43, which are designed to 
fit into apertures, such as guide slots, in a stationary object. The 
swivel bottom 21 is fastened to such stationary object by means of 
threaded bolts that engage swivel bottom 21 at three threaded bosses, one 
of which, 44, is shown in FIG. 1, and another of which, 55, is shown in 
FIG. 4. FIG. 4 is a cross-section of the swivel bottom 21, taken along 
line 4--4 in FIG. 1. 
In operation, the wafer 18, swivel top 19, and swivel bottom 21 nest 
together and are held in place by bolt 13 and lock nut 25. A pair of 
washers 15 and 23 are also utilized. In an operative relationship, the 
convex first surface of curvature 45 of the wafer 18 engages the concave 
first surface of curvature 27 of the swivel top. The convex second surface 
of curvature 51 of the swivel top engages the concave second surface of 
curvature 35 of the swivel bottom, and the convex third surface of 
curvature 52 on the swivel top engages the concave third surface of 
curvature 37 and 39 of the pie-shaped segments on the swivel bottom. With 
the swivel bottom 21 held stationary by a stationary object fastened 
thereto as above described, the swivel top 19 will rotate about its axis, 
defined by the aperture 20 and the bolt 13 left and right around the 
perimeter of the swivel bottom 21 to the extent permitted by the 
pie-shaped segments 37 and 39. The edges 36 and 38 of the segments 37 and 
39 abutt the edges 32 and 34 defined by the groove 29 in the swivel top 
19. The swivel top 19 will slide back and forth along the second surface 
of curvature 35 of the swivel bottom in a path defined by the oblong 
aperture 31 of the swivel top to an extent permitted by the diameter of 
the wafer 18 in a manner above described. 
What has been described is a swivel joint that has only three major 
components and facilitates controlled movement of a relatively heavy 
object in two orthogonal planes simultaneously. Obviously, many 
modifications and variations of the present invention are possible in 
light of the above teachings. It is to be understood, therefore, that 
within the scope of the appended claims, the invention may be practiced 
otherwise than as specifically described.