A universal power transmission joint having a pair of drive pins fixed in parallel by a tie member

A power transmission joint comprises a pair of rotational members each having a rotation axis and arranged so as to be axially spaced from each other. A guide pin is disposed between the pair of rotational members and has an end portion thereof rotatably and swingably engaged with opposite end portions of the rotational members at rotation axes, respectively. A pair of drive pins are arranged symmetrically with respect to and in parallel to an axis of the guide pin and each is engaged with the opposite ends of the rotational members so as to transmit torque while allowing the drive pins to slide in a radial direction on the rotational members, swing and axially slide. A member is disposed between the pair of rotational members and rigidly ties the guide pin and the drive pins to keep a prescribed fixed relation therebetween.

BACKGROUND OF THE INVENTION 
The present invention relates to a power transmission joint and, more 
particularly, to a universal rotational power transmission joint for 
transmitting torque from a first rotational member to a second rotational 
member, with a rotational axis of the first rotational member being 
inclined with respect to the rotational axis of the first rotational 
member or in parallel to and radially spaced from the first rotational 
member. 
A uniform rotational joint which connects a drive shaft and a driven shaft 
the axes of which are parallel and eccentric is disclosed in Japanese 
Patent Laid-Open No. 56-116923/1981. 
The joint comprises drive and driven discs each having a through hole at 
the center, a pipe on a backside thereof and a flat surface on a front 
side, with an intermediate disc disposed between the drive disc and driven 
disc so as to be guided by the flat surfaces of the drive and driven 
discs. The intermediate disc has a hole at the center and a pair of 
radially slits formed symmetrically with respect to the central hole with 
a lever passing through the central hole of the intermediate disc. A 
central portion of the lever is pivotally mounted on the intermediate 
disc, with the lever having, at both ends thereof, balls which pass 
through the through holes of the drive and driven discs and are disposed 
in the pipes whereby an axis of the intermediate disc is disposed on a 
line passing the axes of the drive and driven discs. A pin has one end 
secured to the drive disc and the other end inserted in the slit of the 
intermediate disc and another pin is disposed symmetrically to the 
previously mentioned pin with respect to the central hole of the 
intermediate disc, one end of which pin is secured to the driven disc and 
the other end inserted in the slit of the intermediate disc. When the 
drive disc is rotated, the rotation is transmitted to the intermediate 
disc through the pin secured to the drive disc, and the rotation of the 
intermediate disc is transmitted to the driven disc through the pin 
secured to the driven disc, whereby the rotation is transmitted from the 
drive disc to the driven shaft, with uniform rotation. 
The conventional joint is not constructed so that the drive shaft smoothly 
transmits the rotation thereof to the driven shaft with uniform rotation 
when the rotational axis of the drive disc is inclined against the 
rotational axis of the driven disc. In such a case, the intermediate disc 
can not be sufficiently guided by the driven and drive discs so that 
swinging motion takes place. The pins each comes to contact with an edge 
of the slit of the intermediate disc, whereby rotation transmission 
becomes unstable. Noises also take place because of plays due to 
mechanical wear. 
Further, pulsation takes place at a high speed rotation because the 
rotation transmission between the drive disc and the intermediate disc, 
and between the intermediate disc and the driven disc is effected by a 
single pin, whereby rotation balance is destroyed when the discs rotates 
at a high speed. 
Therefore, conditions under which the conventional joint can be utilized 
are limited and there are problems with respect to power transmission of 
large torque and high speed rotation, or life of the joint. 
Another joint which can be used for a pair of shafts to be connected which 
are inclined or eccentric with respect to each other is disclosed in 
Japanese Patent Laid-Open No. 56-46120/1981. The joint comprises a pair of 
sleeves each fixedly receiving the shaft, annular members each fixed to 
the sleeve and having sockets formed therein and annularly and 
equiangularly spaced from each other, balls each movably inserted in the 
socket and having a through hole, and pins each slidably inserted in the 
through holes of the balls thereby providing a joint. 
An opening, of each of the ball sockets of one of the annular members, 
positioned at an opposite side to the other annular member is tapered so 
that inclination of each pin is allowed. The joint can transmit torque or 
rotation in case the shafts to be connected are inclined to or eccentric 
to each other, however, the joint can not transmit at a constant velocity 
rotation. Further, when the rotation is transmitted from one shaft to 
another, the pins each incline in the rotational direction as well as 
inclination against rotating axes thereof, and torque or rotation is 
transmitted through a contact of ball and pin and a contact of pin and the 
opening portion of the annular member. Thus, the joint is unlikely to 
smoothly rotate at high speed. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a power transmission joint 
which is simple in construction and can effect uniform rotation both in 
case a drive shaft inclines against a driven shaft, and in case the drive 
shaft is in parallel and eccentric to the driven shaft. 
Briefly stated, the present invention resides in a power transmission joint 
comprising a pair of rotational members such as, for example, rotatable 
shafts or block members connected to rotatable shafts, each having an axis 
of rotation arranged so as to be axially spaced from each other, with a 
guide pin disposed between the pair of rotational members and having an 
end portion thereof rotatably and swingably engaged with opposite end 
portions of the rotational members at rotation axes, respectively. A pair 
of drive pins are arranged symmetrically with respect to and in parallel 
to an axis of the guide pin and engaged with the opposite ends of the 
rotational members so as to transmit torque while allowing the drive pins 
to slide in a radial direction on the rotational members, swing and 
axially slide. A member is disposed between the pair of rotational members 
and rigidly ties the guide pin and the drive pins to maintained a 
prescribed fixed relation therebetween. 
According to an aspect of the present invention, the drive pins are 
slidably inserted in spherical bearings in bearing grooves formed in an 
opposite end of the each rotational member. The bearing grooves each 
having a pair of partially-cylindrical surfaces for holding the spherical 
bearing so as to rotate and radially slide. 
According to another aspect of the present invention, the guide pin has 
ends formed semi-spherically and inserted movably in the bearing receiving 
hole. The ends serves as bearings. 
According to further another aspect of the present invention, the guide pin 
is engaged with the rotational members such as rotational shafts at both 
ends thereof through spherical bearings rotatably and swingably inserted 
in the rotational members, and the drive pins are engaged with the 
opposite end portions of the rotational members through spherical bearings 
slidably inserted in bearing grooves formed in the opposite end portions. 
The bearing grooves each extend axially and have radially extending 
partially cylindrical surfaces so as to allow the spherical bearings to 
move radially and rotate in the grooves so that the drive pins can be 
swing and slide radially and axially relative to the rotational members. 
The member tying the guide pin and the drive pins is preferable fashioned 
as a disc. 
The guide pin and the drive pins are tied by the member so that the drive 
pins are always in parallel to the guide pin and symmetrical with respect 
to the axis of the guide pin. The drive pins are engaged to be swingable 
and radially and axially slidable in the rotational member groove. 
Therefore, when one of the rotational members is inclined or eccentric to 
the other, the drive pins can be moved radially relative to the rotational 
member while allowing relative axial movement of the rotational member. 
Further, spherical bearings supporting end portions of the drive pins move 
symmetrically with respect to a point when the two rotational members are 
eccentric, and symmetrically with respect to a center line between the two 
rotational members, whereby one of the rotational members rotates at the 
same speed as the other.

DESCRIPTION OF THE INVENTION 
Referring now to the drawings wherein like reference numerals are used 
throughout the various views to designate like parts and, more 
particularly, to FIGS. 1 and 2, according to these figures, a power 
transmission joint constructed in accordance with the present invention 
includes an input shaft 1, rotatably driven by a drive mechanism (not 
shown), and an output shaft 2, driven by the input shaft 1, each shaft 1, 
2 being formed by cold press working or machining in a conventional 
manner. An end portion of each of the input and output shafts 1, 2 is 
provided with a spherical surface hole 11, 21 at a rotation axis thereof, 
and a pair of bearing grooves 12, 22 each formed on a radially extending 
line passing the rotation axis so as to space equidistance from the 
spherical surface hole 11, 21, that is, symmetrically with respect to the 
spherical surface hole 11, 21 as shown in FIG. 2 and so as to axially 
extend from the end surface of each of the input and output shafts. As 
shown in FIG. 3, partially-cylindrical surfaces 12A, 22A extending 
radially and having openings at a peripheral portion of each of the input 
and output shafts are formed in the bearing grooves 12, 22 at inlet side 
of the bearing grooves 12, 22. A pair of the partially cylindrical 
surfaces 12A, 22A rotatably and radially slidably hold a spherical bearing 
therebetween. 
A tie member 3 which is shaped in a disc is disposed between the input 
shaft 1 and the output shaft 2. The tie member, that is, the disc 3 is 
made of light metal such as aluminum, however, any other material, for 
example, steel, can be used for the disc 3. The disc 3 has three holes one 
of which is formed so as to pass through at a central axis thereof, and 
the other holes spaced equidistance from the central hole, that is, 
symmetric with respect to the central hole. 
A guide pin 4, made of steel, is press-fitted into the central hole of the 
disc 3 so that both sides thereof will project preferably equidistantly 
from the disc. 
Drive pins 5, 51, slightly longer than the guide pin 4, each are 
press-fitted into the hole of the disc 3 so that the drive pins 5, 51 will 
project preferably equidistantly from the both sides of the disc 3 and be 
in parallel to and equidistant from the guide pin 4. 
Each of the guide pin 4 and drive pins 5, 51 has conventional spherical 
bearings 6 slidably inserted at ends thereof. The bearings 6 are made of 
steel or alloy bearing material. The guide pin 4 and the drive pins 5, 51 
are preferably tempered taking into consideration wear. 
A plurality of spring washers 7 are provided to stably hold the spherical 
bearings 6 for the guide pin 4 in the spherical surface holes 11, 21 of 
the input and output shafts, 1, 2 while axial position of the disc 3 is 
fixed by the spring washer 7. The number of the spring washers on one side 
of the disc 3 is preferably the same on the other side. Further, 
preferably, a dust cover 8 made of rubber is provided to sealingly cover 
the joint portion of the input and output shafts 1, 2 so as to prevent the 
joint portion from entering of dusts. 
As shown in FIG. 3, first the spherical bearings 6 are inserted in the 
spherical surface holes 11, 21 and the bearing grooves 12, 22 of the input 
shaft 1 and the output shaft 2. Next, the spring washers 7 are mounted on 
the guide pin 4. Finally, the guide pin 4 having the spring washers 7 
mounted thereon and the drive pins 5, 51 are inserted in the holes of the 
spherical bearings 6 at the same time, whereby engagement between the 
input shaft 1 and the output shaft 2 is made. In the joint constructed in 
the above-mentioned manner, an assembly of the disc 3, the guide pin 4 and 
the drive pins 5, 51 can be made by fixedly mounting guide pins and drive 
pins on both side portions of the disc 3 so as to extend symmetrically 
from the side portions, without passing the guide pin 4 and the drive pins 
5, 51 through the disc 3. 
The spherical bearings 6 are slidable in the bearing grooves 12, 22 of the 
input and output shafts 1, 2 in the radial direction, whereby radial 
movement of the spherical bearings 6 for the drive pins 5, 51 is allowed 
when the input shaft 1 and the output shaft 2 are inclined against each 
other as shown in FIG. 1 or eccentric to each other as shown in FIG. 4. 
The input shaft 1 and the output shaft 2 are symmetrical with respect to a 
line spaced equidistantly from the opposite ends of the input and output 
shafts 1, 2 in case of FIG. 1 or with respect to the central point of 
guide pin 4 in case of FIG. 4, so that the input and output shafts 1, 2 
are the same in rotational speed as each other. Therefore, if the input 
shaft 1 rotates uniformly, the output shaft 2 also rotates uniformly. 
Namely, the input shaft 1 rotates uniform, the disc 3 nonuniformly and the 
output shaft 2 uniformly. The joint is theoretically stable and high in 
mechanical efficiency. 
In FIG. 1, there is illustrated an example of use of the input shaft 1 and 
the output shaft 2, wherein their rotation axes are inclined against each 
other, and FIG. 4 is another example of use, wherein the input shaft 1 and 
the output shaft 2 are eccentric to each other. In any example of use, the 
input shaft 1 can rotate uniformly (at a constant rotational speed) the 
output shaft 2. 
According to the above-mentioned embodiment of the present invention, a 
pair of the spherical bearings 6 for the guide pin 4 set rotation centers 
of the input shaft 1 and the output shaft 2, whereby the shafts 1, 2 
rotates around the rotation center. On the other hand, two pair of the 
spherical bearings for the drive pins 5, 51 are allowed to radially slide 
on the input and output shafts 1, 2 according to an amount of eccentricity 
or inclination angle of the two shafts 1, 2. 
Therefore, when the input shaft 1 is eccentric to the output shaft 2, the 
spherical bearings 6 for the drive pins 5, 51 move symmetrically with 
respect to a point and symmetrically with respect to a line between the 
input shaft 1 and the output shaft 2 when the shafts 1, 2 are inclined 
against each other. By this movement, when the input shaft 1 moves 
uniformly, the movement of the output shafts 2 becomes completely uniform. 
Although the disc 3 is moved nonuniform the inertia of the disc 3 is 
small, so that the nonuniform movement of the disc 3 does not make 
vibration. Therefore, the joint can be used for transmission of a high 
speed rotation and a large torque and the joint is high in transmission 
efficiency. Further, since the joint is simple in construction, it is low 
in cost, and the life is long. 
The tie member 3 for tying the guide pin 4 and the drive pins 5, 51 can be 
formed of an elongate plate member 3A as shown in FIG. 5 instead of the 
disc 3. The elongate plate member 3A has a hole 301 for the guide pin 4 at 
a central portion, and a pair of holes 301 for the guide pins 5, 51. The 
plate member 3A is effective to decrease a rotational inertia. 
FIG. 6 is the same as in FIG. 1 except that a pair of spacers tubes 7A are 
used instead of the spring washers 7. 
In FIG. 6, the spacer tubes 7A each are mounted on the guide pin 4 to 
restrict axial movement of the tie member 3 (3A) and to cause the 
spherical bearings 6 to rest on the spherical surface holes 11, 21. 
It also is possible to employ the spacer tube 7a on the guide pin 4 on one 
side of the tie member 3 (3A) and the spring washers 7 on the other side, 
whereby the tie member 3 (3A) can be axially fixed. 
FIG. 7 is the same as FIG. 1 except that a guide pin 4A having ends each 
shaped semi-spherically is used instead of the guide pin 4 and the 
spherical bearings 6 inserted in the ends of the guide pin 4. The guide 
pin 4A has spherical bearing portions at its ends. Therefore, the guide 
pin 4A can position the tie member 3 (3A) at a prescribed axial position 
without using any members such as the spring washers, the spacers, etc. 
The guide pin 4A, therefore, simplify extremely the construction of the 
joint. The guide pin 4A also can bear axial force applied to the shafts 1, 
2.