Differential case

A differential case has a spider assembly within the case. The spider assembly has a plurality of shafts with each carrying a pinion. The end of each shaft is aligned with a port in the periphery of the case. A rigid retaining band is mounted to the case, and it surrounds the case and covers each of the ports. The band prevents a shaft in the spider assembly from leaving the case whenever the shaft breaks from the assembly.

The invention relates to an improved differential case for a vehicle. The 
purpose of the improved case is to limit any failure of assemblage within 
the case to the internal portion of the case and prevent it from causing 
failure to other parts of the differential which are external to the case. 
PROBLEM PRESENTED TO THE INVENTOR 
Many vehicle differentials have a case formed by two halves known as a left 
half and a right half. The periphery of the case has socket ports at a 
parting plane of the joined halves. A spider assembly with one or more 
shafts is mounted within the case. Each shaft rests within one of the 
socket ports, and the shaft carries a side pinion which meshes with a side 
gear within the differential case. External to the differential case is a 
drive pinion which meshes with a ring gear. The shaft for the drive pinion 
is supported by a pinion bearing which is supported by a pinion bearing 
support. 
Very frequently the spider assembly will fail. The spider assembly shaft 
will fracture because of shock or fatigue due to spinning of the vehicle 
wheels. This is known as initial failure of the differential. When the 
spider shaft breaks or separates from the spider assembly the spider shaft 
will leave the differential case through the socket port due to 
centrifugal forces. The piece of the shaft after it leaves the 
differential case will destroy the pinion bearing support, the drive 
pinion and the ring gear. This has the effect of completely destroying the 
entire differential. The inventor has sought to solve the problem of 
containing the initial failure and preventing the initial failure from 
destroying the entire differential assembly. The cost factors in saving 
the remaining differential assemblage from damage caused by the initial 
failure are great. If it were possible to prevent additional failure after 
the initial failure of the spider assembly the cost of repairing the 
differential would be limited to replacement of the spider assembly and 
the side pinion or pinions affected. 
PRIOR ART 
There is no art presently known to the inventor which is designed to 
contain or limit initial failure of a differential and prevent that 
initial failure from affecting other parts of the differential. 
There is a structure shown in U.S. Pat. No. 3,874,251 issued Apr. 1, 1975 
to Lapitsky et al. for a Bevel Gear Differential which uses a "movable" 
and "flexible" ring member surrounding the differential casing. The ring 
member is movable in a plane normal to the rotational axes of the 
differential casing. Also from what is shown in the drawings there would 
appear to be some movement along the rotational axis of the casing between 
the "stops 16" on the casing designed "to limit the shift of the ring with 
respect to the casing". The purpose of the ring is to insure 
counter-balancing of the thrust acting upon the "satellites" (pinion) and 
provide a more uniform distribution of pressures acting upon the teeth of 
the pinions. The movement of the ring in a plane normal to the rotational 
axis of the casing insures the counter-balancing of the thrust. 
This patent is not directed to the problem which the inventor of the 
improved casing has addressed his design. The ring shown in the above 
patent is constantly flexing and is being deformed (FIG. 13) due to the 
constant forces acting upon it. Under these circumstances the band becomes 
a wearing part and becomes a source of potential initial failure. When the 
ring fails the inserts 17 will eject under centrifugal forces and cause 
the very additional failure that the inventor of the improved casing is 
seeking to avoid. 
THE INVENTOR'S SOLUTION TO THE PROBLEM 
The inventor designed a differential case which will prevent additional 
failure from occurring after there is an initial failure of the spider 
assembly inside the differential case. The design includes a rigid band 
surrounding the case and covering each port in the periphery of the case. 
The band is rigidly mounted to the case so as to maintain the band in a 
fixed relationship with respect to the differential case. The band will 
prevent a spider assembly shaft, which breaks from the spider assembly, 
from being thrown by centrifugal force outside of the case from the port 
in the case periphery. This will prevent additional damage to the pinion 
bearing support, the drive pinion and the ring gear. The band is not 
flexible and is bolted to the casing thereby keeping the band in a fixed 
relation with respect to the casing. The band has no wearing parts and 
always runs concentric with respect to the case. There is no load on the 
band until a shaft in the spider assembly breaks. The reason for this is 
that in the type of differential in which the inventor uses the band, the 
spider assembly's shafts do not float or move radially outward. 
The inventor provides a differential case formed by a left half and a right 
half, and ports in the periphery. A spider assembly is mounted within the 
case, the spider assembly has a plurality of shafts each carrying a 
pinion, each shaft having an outer end aligned with a port, the 
improvement comprising a rigid retaining band surrounding the case and 
covering each of the ports and rigidly mounted to the case so as to 
maintain the band in a fixed relationship with respect to the case. 
The inventor further provides that the band has a plurality of bolt lugs 
along one edge of the band and extending radially inwardly with bolts 
passing through each bolt lug to the case thereby joining the band to the 
case and maintaining the band in a fixed relationship with respect to the 
case.

A DESCRIPTION OF THE STRUCTURE 
The figures show a spider assembly 10 having four spider assembly shafts 
12. Each shaft 12 carries a side pinion 14 which meshes with side gears 
16. The spider assembly 10 with the side pinions 14 and side gears 16 are 
housed within a differential casing generally shown as 18 which is formed 
by a differential case right half 20 and a differential case left half 22 
which are bolted together. The shafts 12 rest within the socket ports 24 
which are formed at the parting plane of the two halves 20,22 and in the 
periphery of the differential casing 18. A ring gear 26 mounted on the 
differential case left half 22 meshes with drive pinion 28 supported by 
pinion bearing 30 which is supported by pinion bearing support 32. The 
drive pinion 28 is also supported by bearings 34 and 36. Shaft 38 is 
coupled to the drive shaft not shown. A differential carrier housing 40 
supports and surrounds the above assembly. Axles 42 and 44 are shown with 
respect to the differential carrier housing 40. 
Due to fatigue or shock one of the spider assembly shafts 12 may break. If 
this occurs the shaft will be thrown from the socket port 24 which 
supports the shaft and will destroy the pinion bearing support 32, the 
bearing 30 and the drive pinion 28 and ring gear 26. To contain the broken 
shaft 12 within the differential casing 18 a rigid retaining band 46 
surrounds the case 18 covering each of the socket ports 24. The band 46 
has a plurality of bolt lugs 48 along one edge of the band 46 and they 
extend radially inwardly to receive bolts 50 which rigidly join the band 
46 to the differential case 18. This maintains the band in a fixed 
relationship with respect to the case 18. Whenever a shaft 12 breaks it is 
prevented from leaving the case 18 by the retaining band 46 and further 
failure of other parts of the differential is prevented. The band 46 does 
not have any wearing areas and therefore is not a source of potential 
failure itself. The only time forces act upon the band 46 is when there is 
an initial failure in the spider assembly. 
It is to be understood that the improvement can be used with a differential 
case which has only one shaft mounted within the case carrying the side 
pinions and one corresponding port in the periphery instead of the spider 
assembly having a plurality of shafts.