Free ring synchronizer having oppositely acting spring means

A free ring synchronizer is provided with improved resilient means for circumferentially biasing a pair of axially spaced friction rings in opposite directions. The resilient means is a coil spring mounted within a shiftable coupling collar interposed between the friction rings. The coil spring includes radially extending legs for engaging oppositely extending pins which are fixed to the friction rings and pass through openings in the shiftable coupling collar. Coacting blocking surfaces are provided on the pins and in the coupling collar openings and are releasably held in contact by the reaction of the legs against the pins.

BACKGROUND OF THE INVENTION 
The present invention relates to synchronizing devices in general and more 
particularly to a synchronizing device of the free ring type. 
Prior art synchronizing devices of the free ring type consist of a pair of 
friction rings which are spaced apart and have a shiftable coupling collar 
disposed therebetween. The friction rings include pins rigidly connected 
to each ring and adapted to pass through suitable openings in the coupling 
collar. The pins and openings have coacting blocking surfaces maintained 
in contact by resilient means to insure that the blocking action occurs 
prior to the shifting of the coupling collar in either direction. 
In known prior art devices, the resilient means have taken different forms 
and also have been located in a number of different positions with respect 
to the elements that make up the synchronizing device. For example, some 
devices have resilient means located in adjacent gear elements of the 
transmission and adapted to react against at least one of the friction 
rings to provide the desired result. Others have been directly associated 
with one or more of the elements of the synchronizing device. These 
devices require special mounting arrangements in which the pins are 
modified, or in which one or both of the friction rings are modified to 
achieve the desired operation. In addition, constructions of this type are 
difficult to assemble. Extra care must be taken to assure that the 
resilient means do not pop-out as the unit is preassembled. The cost of 
replacement due to wear is another undesirable factor to a vehicle owner 
and operator. 
The present invention is intended to solve the above problems by providing 
a synchronizing device of the free ring type wherein a single resilient 
means is supported in the coupling collar for biasing the spaced friction 
rings in opposite circumferential direction. 
Another object of the invention is to provide an improved resilient means 
for a free ring synchronizer which is simple in design and easily 
replaceable in the event of failure. 
SUMMARY OF THE INVENTION 
The above objects are achieved by providing an improved torsion spring 
having a coiled center section and radially outwardly directed legs. In 
the preferred embodiment, the torsion spring is disposed in openings in 
the shiftable coupling collar so as to have the outwardly directed legs 
resiliently engage one of the pins associated with each of the friction 
rings thereby circumferentially biasing the same in opposite directions 
with respect to the coupling collar. 
Other objects and advantages of the invention will become apparent from a 
reading of the following description when taken in conjunction with the 
accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1, a pin type range synchronizing device is shown 
generally at 10 for cooperating with a pair of axially spaced gears 12 and 
14 of a constant mesh change speed gear unit. Gears 12 and 14 are 
rotatably mounted on an output shaft 16 so as to be located on opposite 
sides of an enlarged diameter hub 18 which has longitudinal extending 
external splines 20. Preferably, the hub 18 is constructed as an integral 
part of the shaft 16 so as to be rotatable therewith. 
Gears 12 and 14 are mounted on the shaft 16 in a well-known manner so as to 
be rotatable relative thereto while being axially fixed thereon. Each gear 
is provided with friction and positive clutch portions adapted to 
cooperate with mating friction and positive clutch portions of the 
synchronizing device 10. The friction portions serve to establish a 
preliminary frictional connection between the respective gear and shaft so 
that the relative speeds of the positive clutch portions will be prevented 
from engaging until synchronization is effected. 
More particularly the friction clutch portions of each gear 12 and 14 
consist of tapered friction elements 22 and 24 and the positive clutch 
portions include external clutch teeth 26 and 28 respectively. Clutch 
teeth 26 and 28 are constructed on the axially inner ends of gears 12 and 
14 so as to be adjacent to and correspond in shape to external splines 20 
of hub 18 of the shaft 16. 
The friction clutch portion of the synchronizing device 10 comprises a pair 
of cone type friction rings 30 and 32 while the positive clutch portion is 
an axially shiftable coupling collar 34 having axially extending internal 
splines 36. The splines 36 mate with external splines 20 of the shaft hub 
18 and are axially movable relative thereto into selective engagement with 
either clutch teeth 26 on gear 12 or clutch teeth 28 on gear 14. The axial 
movement of the coupling collar 34 is accomplished by a conventional 
operator controlled shift fork 40, partially shown. 
Shift 40 is operable to move the coupling collar 34 from a neutral 
position, as shown in FIG. 1, in opposite directions into either of two 
operative positions. In one direction, the splines 36 engage clutch teeth 
26 to drivingly connect the gear 12 to shaft 16 and, in the opposite 
direction, splines 36 engage clutch teeth 28 to connect the gear 14 to 
shaft 16. 
Prior to this positive coupling action, as indicated before, it is 
essential that the relative rotational speeds of the respective gear and 
shaft are approximately synchronized so that a clash-free shift can be 
made. This is accomplished by providing a releasable connection between 
the coupling collar 34 and friction rings 30 and 32. To this end, each 
friction ring 30 and 32 is provided with a plurality of axially extending 
pins 42 and 44 respectively. The pins 42 and 44 are alternatingly and 
equally circumferentially spaced around the rings 30 and 32, as best seen 
in FIG. 2. As illustrated in FIG. 1, each pin 42 and 44 extends through an 
opening 46 and 48, respectively, in the coupling collar 34 toward the 
opposing ring. 
Referring in greater detail to FIG. 1, the individual pins 42 and 44 have 
one end fixed to its associate ring in a well-known manner. Each pin 42 
and 44 is constructed with an enlarged diameter cylindrical portion 42a 
and 44a, and a reduced diameter cylindrical elongated stem portion 42b and 
44b, respectively. Enlarged diameter portions 42a and 44a and cooperating 
openings 46 and 48 are suitably constructed to enable passage of the 
portions 42a and 44a through the openings 46 and 48 when synchronization 
is achieved. 
In order to permit the coupling collar 34 to effect a preliminary 
engagement between the friction rings 30 and 32 and friction elements 22 
and 24 prior to positive clutch engagement, coacting blocking means are 
formed on the pins 42 and 44 and in the mating openings 45 and 48. The 
blocking means are designed to releasably block engagement of the positive 
clutch portions while they are rotating out of synchronism. The blocking 
means are constructed and arranged so as to be operatively associated with 
the side of the coupling collar adjacent the friction ring and adapted to 
provide the preliminary frictional contact. For example, with reference to 
FIG. 1, in connection with friction ring 30 located on the left of the 
coupling collar 34, the blocking means includes a frusto-conical inwardly 
tapered cam shoulder 44c on each pin 44 and a complimentary outwardly 
tapered frusto-conical cam shoulder 48a on the left side of opening 48. 
Similarly, with respect to the right friction ring 32, the blocking means 
is shown including a frusto-conical inwardly tapered cam shoulder 42c on 
each pin 42 and a complimentary outwardly tapered frusto-conical cam 
shoulder 46a on the right side of opening 46. 
It is desirable to provide means to insure correct positioning of the 
blocking shoulders prior to any movement of the coupling collar in either 
direction from its neutral position. This means is normally of a resilient 
nature and serves to maintain the blocking surface in initial contact with 
its mating friction surface. Additionally, during a shift, the resilient 
means effects an increased and relatively heavy pressure engagement of the 
friction elements to force synchronization prior to engagement of the 
positive clutch elements. 
In the presently preferred embodiment of the invention, the resilient means 
is a double acting torsion spring indicated generally at 50. Three equally 
spaced springs are shown in FIG. 2. Referring specifically to FIG. 3, it 
will be seen that each torsion spring 50 comprises a coiled center section 
52 and integral oppositely acting first and second radially outwardly 
extending legs 54 and 56. To properly locate the spring 50 within the 
coupling collar 34, a mounting opening 58 is constructed through the 
coupling collar 34 intermediate a pair of pin openings 46 and 48. Annular 
counterbores 60 and 62 are provided on opposite faces of the coupling 
collar 34 and cooperate with the opening 58. As seen in FIG. 2, the 
counterbores 60 and 62 are constructed in such a manner as to wholly 
encircle the mounting opening 58 and extend partially into the pin 
openings 46 and 48, respectively. These counterbores 60 and 62 serve as 
guides for operating portions of the opposed legs 54 and 56 respectively 
of spring 50. In order to permit springs 50 to be inserted within the 
opening 58, a radially outwardly extending slot 64, as seen in FIG. 2, 
provided for passage of one of the spring legs 54 or 56, depending upon 
the direction the spring is to be assembled. 
In assembled relation, as illustrated in FIG. 3, and with the coupling 
collar 34 in its neutral position, the spring legs 54 and 56 engage 
reduced diameter stem portions 42b and 44b of pins 42 and 44, 
respectively. The spring coil 52 biases the legs 54 and 56 in opposite 
directions. The legs 54 and 56 are forced apart, thereby urging the rings 
30 and 34 in opposite circumferential directions. The pins 42 and 44 are 
therefore displaced to opposite sides of their respective openings and the 
blocking shoulders 42c and 46a, and 44c and 48a, are biased into 
frictional engagement to effect proper alignment of the parts in 
preparation for a shift in either direction. 
From the foregoing it will be seen that a free ring synchronizer has been 
shown and described which accomplishes the objects and advantages 
previously set forth. This has been achieved by provision of a simple 
resilient means that is wholly supported within the shiftable coupling 
member of a free ring type synchronizer. The mounting arrangement within 
the coupling collar is designed to permit easy initial assembly of the 
resilient means and convenient replacement if required. Further, shipping 
as a subassembly is also easier because the resilient means is carried by 
the coupling collar, thereby alleviating the problem of damage or loss to 
the individual resilient means. 
While a single preferred embodiment of the invention has been disclosed, it 
will be understood that variations or modifications may occur to those 
skilled in the art without departing from the spirit and scope of the 
invention as defined in the following claims.