Lost motion clutch assembly

A lost motion clutch assembly is disclosed which has first, second, and third clutch members. The first and third clutch members are mounted coaxially and contain a plurality of recesses in the surfaces facing each other. The second clutch member is disposed between the first and third, and preferably includes a plurality of balls disposed in arcuate recesses in the first and third clutch members. Each recess has two terminating ends forming engagement shoulders to engage a portion of the balls at the termination of each of the two directions of rotation. Upon inital rotation of the first clutch member in a first rotational direction, the third clutch member is not rotated until a ball has come into contact with the opposite end of the recess in the first clutch member 31 and also in engagement with the opposite end of a recess in the third clutch member. By this construction, an additional angle of angular lost motion is achieved for a given number of balls. Only 80 degrees of motion is achieved on the balls relative to one clutch member, but an additional 80 degrees is achieved between the balls and the other clutch member, for a total of about 160 degrees of lost motion, yet three balls are utilized for symmetry and for carrying the load.

BACKGROUND OF THE INVENTION 
This invention is directed to a lost motion clutch assembly which is a type 
of a positive clutch. A typical lost motion clutch has two parts, the 
first part being permitted to have a certain angular motion before it 
engages a portion of the second clutch part to cause it to start rotating. 
A difficulty with this type of lost motion clutch is that it has only a 
very limited angular amount of lost motion, e.g., about 90 degrees is a 
typical lost motion amount. Where a load is to be accelerated from rest, 
and the load has a high starting torque requirement, this is often 
extremely difficult to accomplish with a single-phase electric motor, 
which usually has a lower starting torque than running torque. Many 
electric motors have a third harmonic dip in the speed-torque curve and 
are suitable only for driving loads with low starting torque requirements. 
Even capacitor induction motors, whether of the capacitor-start or 
capacitor-run type, have a starting torque which is lower than the running 
or pull-out torque. 
The problem to be solved, therefore, is how to construct a lost motion 
clutch with a sufficiently large angular amount of lost motion so that the 
motor driving the load through the lost motion clutch can accelerate to a 
point of near maximum torque to be able to start a load requiring high 
starting torque. 
This problem is solved by a lost motion clutch assembly comprising, in 
combination, first, second, and third clutch members, means mounting said 
first and third clutch members coaxially on a shaft axis for limited 
relative rotation therebetween, means mounting said second clutch member 
between said first and third clutch members for movement in a plane normal 
to said axis, each said clutch member having at least a first engagement 
shoulder and said second member also having a second engagement shoulder, 
all said engagement shoulders being disposed at substantially equal radii, 
said first engagement shoulders of said first and second clutch members 
being disposed in a common plane of rotation and said second engagement 
shoulder of said second clutch members being disposed in the plane of 
rotation of said first engagement shoulder of said third clutch member, 
whereby upon initial rotation of said first clutch member in a first 
direction said lost motion clutch assembly has a predetermined angular 
lost motion before the third clutch member is rotated by engagement of 
said first and second engagement shoulders of said second clutch member 
with said first shoulders on said first and third clutch members. 
Accordingly, an object of the invention is to provide a lost motion clutch 
assembly with an arcuate lost motion exceeding 90 degrees. 
Another object of the invention is to provide a lost motion clutch assembly 
which includes three parts, with a lost motion between the first and 
second parts and another lost motion between the second and third parts. 
A further object of the invention is to provide a lost motion cluch 
assembly which also functions as a thrust bearing during the lost motion 
action. 
Still another object of the invention is to provide a lost motion clutch 
assembly which incorporates planetary action of balls during the angular 
lost motion. 
Other objects and a fuller understanding of the invention may be had by 
referring to the following description and claims, taken in conjunction 
with the accompanying drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 2 illustrates an exploded view of the lost motion clutch assembly 11, 
and FIG. 1 illustrates this clutch assembly 11 in an environment with an 
electric motor 12 driving a load 13 through this clutch. The motor 12 has 
a rotor 17 and a stator 14 mounted in a housing 15 which houses the parts 
of this assembly. The motor 14 is shown as a squirrel cage motor 
energizable from a single-phase A.C. source 16. The motor 12 is typically 
a one-fourth to one-half horsepower, and has two equal field windings with 
leads 18 and 19 and a common lead 20 connected to the A.C. source 16 
through a reversing switch 21. A capacitor 22 is connected across the 
leads 18 and 19 so that the motor becomes a capacitor-run induction motor 
with equal torque in the two directions of rotation. 
The motor 12 has the rotor 17 fixed on a shaft 26 and rotatable about an 
axis 27 by being journaled in the housing 15 by bearings 28 and 29. 
The lost motion clutch assembly 11 is located at the left end of the shaft 
26, and includes first, second, and third clutch members 31, 32, and 33, 
respectively. These are better shown in FIG. 2. The first clutch member 31 
is fixed to the motor shaft 26, such as by the key 34. The third clutch 
member 33 is preferably identical to the first clutch member 31, and is 
keyed at 35 to an output shaft 36. The second clutch member 32 is disposed 
between the first and third clutch members, and in this preferred 
embodiment includes a rollable element shown as a ball. In fact, in the 
preferred embodiment, there are three such balls or clutch members 32, 
which may be disposed in a cage 37. This may be a thin, low friction disk, 
for example, made of nylon, with apertures 38 to closely receive the balls 
32 and space them equiangularly 120 degrees and near the periphery of this 
cage 37. 
The first clutch member 31 has first and second engagement shoulders 41A 
and 42A, respectively, and the third clutch member 33 has the same 
engagement shoulders but labeled 41B and 42B for convenience in referring 
to them. These engagement shoulders are at the termination of arcuate 
recesses in this particular embodiment. Since there are a plurality of 
balls 32, there are an equal number of plurality of recesses 43. These are 
arcuate recesses near the periphery of the clutch members 31 and 33, and 
in cross section each recess is designed to be complementary to 
substantially one-half the rollable element or ball 32, and hence these 
recesses are substantially semicircular in cross section. Also, the 
engagement shoulders 41A, for example, are designed to be complementary to 
the balls 32, and hence are semicircular in a plan view of the front face 
44 of the respective clutch member 31 or 33. The recesses 43 are arcuate 
about the shaft axis 27, and disposed at the same radii as the balls 32 in 
the cage 37. 
The balls 32 are adapted to roll in the recesses 43 and to engage the 
engagement shoulders 41 and 42 when the input or first clutch member 31 is 
rotated in opposite rotational directions. When the respective ball 32 is 
rolled along the recess 43 into engagement with an engagement shoulder 41 
or 42, then the ball 32 may be considered as having first, second, third, 
and fourth engagement shoulders 51-54, respectively, since these clutch 
members 32 are rollable elements, namely balls, and these engagement 
shoulders are different portions on the surface of each respective ball. 
The exploded isometric view of FIG. 2 shows the lost motion clutch assembly 
11 in one limit position. If now the first clutch member 31 is initially 
rotated in a clockwise direction, the balls 32 will roll in their 
respective recesses 43 as a type of planetary movement, with the cage 37 
rotating at one-half the speed of the rotation of the first clutch member 
31. During this initial third clutch member 33 because the angular lost 
motion has not been taken up. The angle between the two limit positions of 
a ball in a particular recess 43 may be about 80 degrees in this preferred 
embodiment, and hence the total angular lost motion of the clutch assembly 
11 is approximately 160 degrees. Therefore, when the first clutch member 
31 has rotated through an angle of about 160 degrees, the cage 37 will 
have rotated about 80 degrees, and then the first engagement shoulders 
41A on the first clutch member will engage the first engagement shoulders 
51 on the balls 32, and at substantially the same time, the second 
engagement shoulders 52 on the balls 32 will engage the first engagement 
shoulders 41B on the third clutch member 33. It is only upon the 
completion of this 160-degree lost motion that torque will begin to be 
applied to the third clutch member 33 to rotate the load 13. When the 
motor 12 is de-energized and rotation stopped, the motor 12 may be 
reversed in rotational direction by the switch 21. The initial 
counterclockwise rotation of the first clutch member 31 will not cause any 
rotation of the third clutch member 33; instead, this first clutch member 
31 will rotate about 160 degrees counterclockwise while the cage 37 is 
rotating about 80 degrees counterclockwise. The angular lost motion is 
taken up when the second engagement shoulder 42A on the first clutch 
member 31 engages the third engagement shoulder 53 on the respective ball 
32. At substantially the same time, the fourth engagement shoulder 54 on 
the ball 32 will engage the second engagement shoulder 42B on the third 
clutch member, and hence counterclockwise rotation will be imparted to 
this third clutch member 33. This will be with the parts in the relative 
positions shown in FIG. 2. 
The lost motion clutch 11 is shown in FIG. 1 as part of a motor assembly. 
The output shaft 36 is journaled in a bearing 58, which is a radial and 
flange bearing and a thrust bearing 59 is disposed between the flange of 
the bearing 58 and a friction clutch plate 60 which carries a clutch 
lining 61 engaging the rear face 62 of the third clutch member 33. The 
output shaft 36 drives the load 13 in some manner, for example, by the 
pinion 57. The friction clutch 60-62 is urged into engagement by a 
compression spring 63 adjustably held by an adjusting screw 64 and acting 
through a thrust bearing 65 on the right end of the motor shaft 26. By 
this means, the friction clutch 60-62 may slip upon a predetermined 
overload. Also, in this environment it will be noted that the lost motion 
clutch assembly 11 acts not only in its lost motion capacity during 
initial rotation of the motor, but also acts as a thrust bearing to 
transmit the force of the compression spring 63 to the friction clutch 
60-62. In an environment where this thrust bearing action was not 
required, the ball 32 would not necessarily have planetary action, and the 
lost motion clutch assembly 11 could function in a manner that the first 
clutch member 31 would rotate clockwise about 80 degrees and then engage 
the balls 32 so that the balls rotated clockwise another 80 degrees before 
the third clutch member 33 was engaged and caused to rotate. 
The lost motion clutch assembly 11 is shown as utilizing three balls with 
recesses which permit about 80 degrees of rotational movement between a 
ball and a particular clutch member 31 or 33. By utilizing two such clutch 
members 31 and 33, the 80-degree movement may be increased to about 
160-degree movement, yet retaining three balls 32 for symmetry of the 
positioning of the balls and distribution of load. With three engagement 
shoulders to take the shock of starting the load 13, the outer diameter of 
the lost motion clutch 11 may be reduced for a given load carrying 
capacity. 
With the construction shown, it will be seen that the first and third 
engagement shoulders 51, 53 of the balls 32 are disposed in the plane of 
rotation of the first and second engagement shoulders 41A and 42A of the 
first clutch member 31. Also, the second and fourth engagement shoulders 
52 and 54 of the balls 32 are on the other side of the cage 37, and hence 
are disposed in the plane of rotation of the first and second engagement 
shoulders 41B and 42B of the third clutch element 33. The first and third 
clutch members 31 and 33 may conveniently be made from carbon steel 
powdered metal, which are oil-impregnated for good lubrication of the 
balls 32. These balls may be the type used as ball bearings, and in the 
present embodiment the first and third clutch members were two inches in 
diameter with 3/8 inch diameter balls for use with a one-fourth to 
one-half horsepower electric motor 12. This 160 degrees of rotation of 
lost motion before torque is applied to the third clutch member 33 is 
sufficient to allow the motor 12 to be accelerated to a condition of 
substantially maximum torque, so that when the lost motion is taken up, 
the full torque is able to be applied to the load 13. 
The present disclosure includes that contained in the appended claims, as 
well as that of the foregoing description. Although this invention has 
been described in its preferred form with a certain degree of 
particularity, it is understood that the present disclosure of the 
preferred form has been made only by way of example and that numerous 
changes in the details of construction and the combination and arrangement 
of parts may be resorted to without departing from the spirit and the 
scope of the invention as hereinafter claimed.