Clutch housing for a seat belt pretensioner

A pretensioner clutch housing for a vehicle seat belt arrangement has a housing made of a first housing part arranged to mount a clutch, and a second housing part arranged to mount a pre-tensioning device. The first and second housing parts have cooperating members for connecting the parts together. The cooperating members preferably are a flange on one part and a slot on the other. The clutch housing part is thus universal and only the pretensioner housing part needs to be changed to alter the angle of extension of a tube containing a pretensioner's piston to facilitate different models of cars.

FIELD OF THE INVENTION 
This invention relates to seat belt retractors of the type having a 
pretensioner, and in particular to a housing for a pretensioner clutch. 
BACKGROUND OF THE INVENTION 
A pretensioner commonly has a piston mounted in a tube which is 
mechanically or electrically activated to pretension the seat belt by 
winding in the belt spool a predetermined amount upon the detection of a 
predetermined deceleration rate of the vehicle, which indicates a crash 
situation. The piston may be connected to one end of an actuator cable, 
the other end of which is connected to the belt spool via a clutch 
mechanism. Thus when the piston is activated, the cable is retracted, and 
the clutch engaged so as to wind in the belt spool. This may be achieved 
for example by the cable being wound around an annular member mounted on 
the axle of the spool so as to surround the axle, which annular member 
decreases in diameter when the cable is tightened so as to grip the spool 
axle, such that the axle then rotates with the annular member to wind in 
the belt. 
The tube carrying the piston normally has an outer cover and is mounted on 
an upper part of the clutch housing. Some applications require that the 
tube extend from the clutch housing at a different angle, for example in 
order to fit different vehicles. It is therefore necessary to provide 
clutch housings with different configurations. This necessitates the 
provision of a new clutch housing tool for manufacturing the housing. 
Usually, clutch housings are required in left hand and right hand 
versions, for use on opposite sides of a vehicle, adding further to the 
cost and inconvenience of providing different housings. 
SUMMARY OF THE INVENTION 
According to the present invention, there is provided a pretensioner clutch 
housing for a vehicle seat belt arrangement comprising a belt spool, a 
pre-tensioning device, and a clutch arranged for connecting the belt spool 
to the pre-tensioning device, the housing comprising a separate housing 
part arranged to mount the clutch, and a second housing part arranged to 
mount the pre-tensioning device, the first and second housing parts 
comprising cooperating members for connecting the parts together. 
Preferably the cooperating members comprise a slot or groove on one part 
and a flange, slidable into the slot or groove, on the other part, but 
various arrangements are contemplated such as threaded fasteners, bolts or 
clip-on arrangements. 
Since the pretensioner is mounted in this second separate housing part, 
this part can be interchangeable depending upon the required angle of 
extension of the pretensioner tube, while the clutch housing part remains 
the same. The clutch housing is a major part of the arrangement and its 
manufacture requires a more expensive tool, so the invention represents a 
substantial cost saving in production terms.

DETAILED DESCRIPTION OF THE INVENTION 
Referring to FIGS. 1A and 1B, a housing 2 according to the prior art 
comprises a pretensioner clutch housing part 4 integral with a 
pretensioner mounting part 6. In FIG. 1A a housing 8 for a mechanically 
operated pretensioner is shown in phantom lines. In FIG. 1B a housing 10 
for an electrically operated pretensioner is shown in broken lines. The 
pretensioner housing 8 or 10 is attached to the mounting part 6 of the 
housing 2. It is often required that the pretensioner housing 8, 10 extend 
at a different angle, for example to fit a different car model, and for 
this it is necessary to provide a complete housing 2 having a different 
configuration, with the pretensioner mounting part 6 extending at a 
different angle from the clutch housing part 4. This leads to high 
production costs. 
Referring now to FIGS. 2A, 2B, 2C and 2D, according to the present 
invention, the housing 2 is divided into two separate parts; the first 
part 12 for housing the clutch, and attaching to associated belt spool, 
and a second part 14, 16, 18 or 20 for mounting the pretensioner 
mechanism. The figures shows four alternative second housing parts 14, 16, 
18 or 20. Two of these second housing parts 14, 16 are for mounting 
electrically operated pretensioners 15, 17 as shown in broken lines, each 
extending at a different angle. The remaining two alternative second 
housing parts 18 and 20 are for mechanically operated pretensioners 19, 21 
shown in phantom lines, also extending at different angles. 
Each second housing part 14, 16, 18 20 has a mounting member conveniently 
comprising a transversely extending flange 22, which is shaped so as to 
fit with a cooperating part of the first clutch housing part 12, 
conveniently comprising a transverse slot 24. The flanges 22 enable any 
one of the second housing parts to slide into the slot 24 in the first 
housing part 12 and thus the first housing part can be universal item for 
any type of pretensioner in almost any vehicle. While it is prefered that 
the cooperating members comprise a slot or groove on one part and a 
flange, slidable into the slot or groove, on the other part, various 
alternative arrangements are contemplated such as threaded fasteners, bolt 
fitments or clip-on fitments. 
Since the pretensioner is mounted in this second separate housing part, 
this part can be interchangeable depending upon the required angle of 
extension of the pretensioner tube, while the clutch housing part remains 
the same. The clutch housing is a major part of the arrangement and its 
manufacture requires a more expensive tool, so the invention represents a 
substantial cost saving in production terms. Production costs are thus 
reduced. The open face 26 of the housing part 12 is then fitted to the 
spool housing (not shown) to secure the flange 22 in the slot 24. 
While preferred embodiments of the invention have been disclosed, it should 
be appreciated that the invention is susceptible to modification without 
departing from the scope of the following claims.