Apparatus for filling automotive muffler with glass fibers

A process and apparatus for filling a generally tubular autmotive silencer casing with glass fibres are characterized by the feature of filling the casing from both ends simultaneously, preferably with the aid of spacer elements temporarily located on the ends of the casing during the filling step, any overflow of fibres into these elements being subsequently pushed into the casing to give a uniform density fill prior to installing end caps. The process/apparatus preferably also features bulking of the fibres by passing them through a specific jet configuration more than one of which may be used at each filling station.

BACKGROUND OF THE INVENTION 
Glass and/or mineral fibers are widely used for thermal and/or acoustic 
insulation. In the case of glass fibers it is common practice to chop 
continuous filament material into short lengths (staple fibers), 
thereafter forming a mat from the staple fibers produced, or simply 
packing the staple fibers into a supporting member. Thus staple fibers are 
packed into automotive muffler or silencer casings, into cavity walls, or 
are incorporated into sandwich panels for use in building construction. 
The mechanical chopping of glass filaments into staple fibers requires high 
speed rotating machinery; it may also expose workers to the physiological 
effects of staple fibers which are usually harsh, spiky and abrasive. In 
the case of automotive muffler or silencer casings the handling of staple 
glass fibers is a particular problem. It is difficult to accurately meter 
loose fibers entrained in an airstream, which is the usual mode of fiber 
transfer, especially where only a limited time is available to fill each 
casing, as on an automated production line for silencers. In this 
specification and the claims that follow, silencers and mufflers are used 
interchangeably. 
It is well known that a continuous glass fiber roving or sliver can be 
bulked by exposure to a highly turbulent airstream prior to deposition in 
a container as a fleece without breaking the filaments. It has been 
proposed in EP-A-0091413 that this process should be used to fill 
automotive silencer casings with bulked, continuous filament glass fibers, 
using suction applied through the casing to effect deposition of the 
appropriate quantity of glass fiber. 
The process just described employs a conventional textile bulking or 
texturing jet as a means of exposing a continuous filament roving to the 
action of a highly turbulent airstream. It also uses a separate cutter 
device operable to sever the roving on completion of each silencer filling 
operation. 
Common to known processes for filling silencer casings with glass fibers is 
the problem of achieving uniform bulk density of the filled material. As 
the casing fills up it is progressively more difficult for air to escape 
through the fibrous mass, even using suction and an/or an auxiliary 
airflow. Also, the material is both very bulky and very resilient, so it 
tends to spring back towards the outlet of the bulking jet. This 
progressively affects the quality of the bulking operation; it eventually 
slows down the rate of delivery from the jet, by virtue of progressively 
occluding the jet outlet. It also results in the last material supplied to 
a casing being of significantly lower bulk density than the first material 
supplied, to the point where it is even impossible to transfer the filled 
casing to further processing stages such as the installation end caps, 
because the filled material tends to overflow out of the end of the 
casing. EP-A-0091413 discloses a process for filling a silencer casing, 
but only from one open end thereof. Such a process is effective for 
roughly half of the commonly used types of absorptive silencer. There are, 
however, other very commonly used types of absorptive silencer where the 
process just referred to is ineffective and/or inefficient. For example, 
there are `straight-through` silencers, the automated production of which 
includes the step of fitting both end caps at once. For these, it is 
normal to use a glass fiber preform made in situ around a length of 
perforated exhaust gas duct to locate the latter duct inside the casing 
prior to affixing the end caps. Preform manufacture is an essential, extra 
step in this particular process. There are also silencers which have two 
separate fiber-filled absorptive regions either side of a reactive element 
comprising baffles in an intermediate fiber free volume. The absorptive 
regions may be of different shapes and/or sizes, but once again it is 
normal to fit both end closures at the same time. 
It is an object of the present invention to provide an improved process and 
apparatus for filling a silencer casing with glass fibers. 
SUMMARY OF THE INVENTION 
According to the present invention a process for filling a silencer casing 
with glass fibers is characterised by the steps of presenting oppositely 
directed open ends of the casing substantially simultaneously to glass 
fiber filling stations and filling the casing from both ends thereof. 
Subsequently closures are affixed to these ends, preferably 
simultaneously. 
According to a further aspect of the invention, apparatus for filling a 
silencer casing includes two glass fiber feeding stations and means for 
presenting oppositely directed open ends of the casing to said stations 
substantially simultaneously. Preferably each feeding station comprises at 
least one bulking jet operable to bulk a continuous filament glass fiber 
roving prior to deposition in the casing by the jet as bulked continuous 
filaments. 
The invention further includes a silencer production line equipped with the 
apparatus of this invention, or modified to carry out the process of this 
invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Preferably the process includes the steps of feeding a continuous filament 
glass fiber roving to each filling station and converting the roving to 
relatively bulky form prior to filling the casing with it. The roving may 
also be cut into staple fibers prior to bulking, but preferably it remains 
in continuous filament form throughout the process. 
The roving is preferably converted to relatively bulky form by the step of 
subjecting it to an air treatment in the filling station a known bulking 
jet. More preferably, however, the air treatment is carried out by causing 
the roving to pass through a bulking jet having novel constructional 
features, which will be discussed in detail later in this specification. 
The process of the invention is preferably further characterised by the 
step of temporarily locating one end of a tubular spacer element on each 
open end of the casing prior to the filling step. Advantageously the 
filling step is in this particular instance carried out until an overflow 
or excess of fibers has been deposited in the spacer element and this is 
then followed by the further step of pushing the overflow from the spacer 
elements into the casing prior to removing the spacer element and 
subsequently affixing the closures to the ends of the casing. 
The use of a spacer element effectively increases the volume to be filled, 
so that not only is any overflow completely contained within the spacer 
element, but by pushing the overflow out of the spacer element into the 
casing, the latter can be filled to a substantially uniform density. 
Metering the feed of glass fiber by length is relatively easy and 
accurate, so that the actual quantity (mass) of bulked fibers (stable or 
continuous filament) can be fully controlled. It remains only to monitor 
the quality of bulking and the pressure applied to push the overflow into 
the casing. 
Where filling is to be accomplished around an otherwise unsupported 
perforated tube, as in the case of a straight-through silencer, the 
process of the invention should be further modified by addition of the 
steps of locating and/or temporarily retaining the tube axially and 
radially with respect to the casing at least until there is sufficient 
in-filled material to do so. 
Each filling station may have more than one bulking jet together with 
individual roving supply means for each such number and disposition of 
jet, the jets being arranged to reflect the cross-sectional shape and 
volume of the casing to be filled. 
According to a particularly preferred feature of the present invention, a 
bulking jet comprises a roving entry passageway, an airstream entry 
passageway and means for distributing the airstream evenly around the 
roving as an essentially annular sheath in the region of contact 
there-between, together with a common outlet passageway for the airstream 
and roving, characterized in that the flow restriction due to that area of 
the annulus defining said sheath immediately prior to said region of 
contact is significantly less than that due to the common outlet 
passageway. It will be understood that the latter restriction is referred 
to the outlet passageway in use, that is in the present of both air and 
glass fiber roving. 
The effect is that the throughput of air is no longer restricted by the 
means for forming the airstream into an annular sheath around the roving. 
Instead, the common outlet passageway now becomes a very critical element. 
It has been found that in the special context of bulking continuous 
filament glass fiber rovings is an automated process for filling 
automotive silencer casings, the length to diameter ratio of the 
preferably cylindrical, parallel sided common outlet passageway should be 
in the range 5 to 10, with a ratio of 8 being especially preferred. With 
typical roving throughout speeds of at least 500 meters/minute being 
required to achieve high speed filling of silencer casings on a production 
line basis, the construction of the bulking jet has been found to have very 
significant effect on the efficiency of the process, to the extent that 
conventional textile bulking/texturing jets are unsatisfactory by 
comparison with a jet according to this invention. 
Because the air throughout is only limited by the outlet passageway, very 
considerable forces are applied to the roving in the latter. This results 
not only in excellent bulking, but can also be used to eliminate the need 
for any external mechanical cutting device for the roving. It has been 
found that the forces exerted on the roving in the outlet passageway are 
in fact sufficient to break the roving if the supply is halted. 
To eliminate any risk of roving being blown backwards out of the roving 
entry passageway it may be desirable to include some form of roving clamp 
operable to hold the roving, for example against a thread guide at the 
point of roving entry after breaking in the jet. 
Conventional bulking jets normally have an outlet passageway which includes 
a venturi throat, immediately followed by an outwardly flared region in 
which the bulk is developed progressively. By contrast, the jet of this 
invention preferably not only has a parallel sided outlet passage but also 
the latter terminates abruptly to give sharp, almost explosive expansion of 
the air/roving mixture emerging from it. Because of the unusually high 
forces developed on the roving in the outlet passageway itself, it is 
necessary to minimize air leakage back along the roving entry passageway. 
However, it is also highly desirable that the latter should accept not 
just the roving but also a splice therein, since it is advantageous to be 
able to join roving packages end-to-end to give essentially continuous 
running. The diameter of such a splice will usually be at least twice the 
diameter of the roving itself, so the roving entry passageway must be 
considerably larger than the roving alone. 
It has been found that these conflicting requirements of low leakage and 
free passage of a splice can be met by using an entry passageway having a 
length to diameter ratio in the range 10 to 20, with a ratio of 16 being 
particularly preferred when operating with rovings of linear density 2000 
to 5000 tex. Single or multiple rovings may be used to obtain a desired 
roving density at the jet. 
Common to silencer filling processes using the jets of this invention is 
the need to minimize the risk of loops or snarls developing in the (or 
each) roving being fed to the jet. This problem is made very much worse by 
the fact that silencer filling is a batchwise process resulting in rapid 
stop-start operation. In practical terms, the roving feed has to be 
stopped from and then re-started a high linear speed, typically over 500 
meters/minute. It has been found that this can be accomplished by 
eliminating conventional tension control devices, yarn accumulators and 
the like. Instead, a capstan or godet wheel driven through a clutch/brake 
unit is used, the clutch/brake serving to give a fully controlled rate of 
deceleration from and acceleration to the desired speed. This enables a 
continuously running drive means to be employed; it minimizes the mass of 
hardware to be stopped and started. It is particularly preferred to use an 
electrically or electronically controlled clutch/brake unit, so that the 
start-stop characteristics can be adjusted to minimize roving tension 
changes to the point where they are not a significant factor. 
While the jet of this invention has especial utility in the manufacture of 
glass fiber filled silencer casings per se, it will be appreciated that it 
is equally applicable to a process for making shaped glass fiber preforms 
for subsequent insertion into silencer casings. Such preforms, rendered 
coherent by treatment with a very minor amount of binder, are necessary 
for silencer casings which do not readily lend themselves to automatic 
filling processes by reason of their shape and/or internal complexity. 
Further aspects of the preferred jet construction will be described later, 
with reference to the drawings. 
The apparatus preferably includes a tubular spacer element associated with 
each feeding station, together with means for presenting the spacer 
element to one open end of the casing so as to constitute an extension of 
the casing intermediate the casing and the feeding station itself. The 
apparatus then preferably includes presser means operable to push any 
overflow of glass fibers from the spacer element into the casing prior to 
transfer of the latter to apparatus operable to affix closures to the ends 
thereof. 
The volume of the spacer element is not critical, but it is preferred that 
it should be of the order of up to 50% of that of the silencer casing 
itself. Advantageously the spacer element is of similar cross-sectional 
shape to the silencer casing to be filled. It is also advantageous that it 
should have a resilent facing on that region which is in use to be abutted 
against the silencer casing. This is useful to minimize both leakage and 
mechanical alignment problems. It will be appreciated that the actual 
cross-sectional shape of the spacer element and/or silencer casing is not 
critical; the invention can cope equally well with the oval, elliptical or 
circular sections encountered in the automotive industry. 
Where there is an otherwise unsupported perforated tube to be located 
within and relative to the casing, the apparatus preferably includes means 
for so doing at least until the tube is sufficiently supported by the 
in-filled glass fibers. Magnets associated with each filling station are 
the preferred means of temporarily locating the tube to be supported by or 
to the filling station so that the air can escape down the tube and through 
the filling station without interfering with the filling process. 
The filling stations may be carried by headstocks mounted on a common 
support rail arrangement so that they can be advanced, for example by 
pneumatic cylinders, towards one another, to meet the oppositely directed 
open ends of a silencer casing which is presented between them by a 
conveyor system. The headstocks themselves may be caused to traverse with 
the latter conveyor system during the filling operation and prior to 
return to their starting point where they move inwards to engage the next 
casing to be filled. Obviously the precise arrangement adopted will 
reflect the nature of the associated silencer production line itself, but 
the bulking jets and the spacer element/presser means are preferably those 
disclosed above. 
In FIG. 1 a cylindrical casing 1 has a centrally-disposed perforated tube 2 
extending between and through end closures 3 and 4. The volume surrounding 
the tube is filled with glass fiber 5. The tube is otherwise unsupported 
until the closures are seamed to it and to the casing, except by the glass 
fiber filling 5. 
In FIG. 2 the preferred same casing 1 and closures 3 and 4 are used, but 
the tube 2 is in two portions 6, 7 respectively, the ends of which overlap 
inside the casing to abut against internal partitions 9, 8 respectively. 
The partitions and casing together define a blind volume 10 between two 
separate volumes filled with fibers 11, 12. 
Referring now to FIGS. 3 and 4, one open end 16 of a silencer casing of 
FIG. 1 (the straight-through kind) is shown with a length of perforated 
tube 17 lying inside it. Advancing axially towards it is a filling 
station, parts only of which are shown, in the interests of simplicity. 
The casing is supported by a conveyor (not shown) having an associated 
magnet operable to hold the tube 17 relative to the casing until engaged 
by the filling station. The magnet is shown in FIGS. 12(a) through 12(f) 
and will be further described in relation to those figures. The filling 
station comprises a tubular spacer element 13 having resilient marginal 
portion 14 configured to locate and seal against the open end of the 
casing 16. A central support 15 advances with the spacer element until its 
shaped end 18 engages the tube 17 and lifts it away from the casing to a 
desired position relative to the center line of the casing, as shown in 
FIG. 4. The center 19 of the support 15 is hollow, to enable air to escape 
from the casing through the perforations in the tube 17. It will be 
appreciated that exactly the same arrangement applies at the opposite end 
of the casing as shown in FIGS. 11 and 12, so that filling can take place 
from both ends at once. 
The length of the tube 17 will normally be greater than that of the casing 
and if so the length of the support 15 can be suitably changed to 
accommodate the projection of tube 17 beyond the end of the casing. Also 
not shown in this particular diagram are the presser means which are used 
to pack any overflow of glass fibers into the casing from inside the 
spacer element 13. After such a packing operation, the tube 17 will not 
normally require further support; the silencer casing, the tube and 
in-filled material can be forwarded for installation of the end closures 
in the usual way. 
FIGS. 5 and 6 show a modified apparatus in which a backing plate 31 carries 
two bulking jets 32, each of which is supplied with continuous filament 
glass fiber roving 34 and high pressure air (typically at 450 KN/M.sup.2) 
through pipe 33. The jets are preferably of the kind discussed below. The 
plate 31 has a resilient face 35 which abuts against the open end of a 
silencer casing 36. The casing contains a perforated exhaust gas duct 37, 
the free end of which is located by and against a locating stud 38 on the 
plate 31. This also serves to prevent glass fibers from being blown down 
into the duct, the opposite end 39 of which is open to allow the free 
escape of air from the casing during filling. The rovings 34 are metered 
from roving packages (not shown) by means of capstan or godet wheels 110 
(shown only in FIGS. 12(a) through 12(f) and operated in the manner 
discussed earlier. 
The operation of the station just described results in rapid filling of the 
casing with bulked glas fibers 40, at least until the bulk density 
approaches about 50 kg/m.sup.3, or roughly half of a typical target bulk 
density in the range 80 to 100 kg/m.sup.3. The quality of the bulking 
process then falls off, to the point where free passage of material into 
the casing becomes severely impaired and eventually stops. This gives 
unstable running conditions for the apparatus/process and results in 
variable bulk density, together with some overflow of material from the 
casing on transfer to the next production step, which is the installation 
of an end cap for the casing. 
FIGS. 7 and 8 show the apparatus of FIGS. 5 and 6 further modified in 
accordance with a preferred feature of the invention. Thus a spacer 
element 50 having a resilient, silencer casing--contacting margin 51 is 
interposed between the casing 36 and the backplate 31. A corresponding 
extension 58 of the original stud 38 is provided to locate and close the 
perforated duct 37. A press plate 52 is included together with rods 53 
operable to displace the plate as indicated by dashed lines towards and 
into the mouth of the casing (54). The press plate is configured to slide 
around the stud 58 and incorporates cut-outs to clear the jet nozzles. 
Operation is exactly as before, except that for a given mass of glass fiber 
there is now the added volume of the spacer element available to be filled. 
By making this volume approximately 50% of the volume of the silencer 
casing, the problems of the previous apparatus/process discussed are 
eliminated. There will however be some bulked material overflow into the 
spacer element itself. Operation of the press plate to transfer/compact 
this overflow material well into the silencer casing completes the filling 
process and the casing can be forwarded for installation of its end cap. 
To further illustrate particularly preferred features of the invention, 
FIG. 9 shows a diagrammatic cross-sectional side view (on an enlarged 
scale) of a bulking jet 32' of the type generally as shown at 32 in FIGS. 
5 through 8 in accordance with the invention. 
The jet comprises a body 62 provided with airstream entry passage 65, a 
needle 61 in which there is a thread guide 64 opening into a roving entry 
passage 67, together with an outlet section 63 provided with an outlet 
passageway 69 terminating abruptly in a flat surface. The needle 61 
terminates in an annular space 66 defined inside the body 62. The open end 
of the needle in that space and the opposed entrance to the outlet 
passageway 69 together define an annular gap 68 between the space 66 and 
the inside of the passageway 69. Unlike a conventional bulking jet it is 
not necessary that the needle should be slidably mounted so that the 
effective area of the space 68 can be changed by relative axial movement 
of the needle, while retaining a constant, acute angle of contact between 
air and roving. As previously explained, the outlet passageway 69 is the 
critical factor. 
In use, compressed air is applied to the passage 65. Continuous filament 
glass fiber roving was fed through the needle at about 600 m/minute using 
a range of outlet passageway diameters. The quality of the bulking 
achieved and the time it took to break the roving (on halting the supply) 
were observed and the results were as follows. 
TABLE 1 
______________________________________ 
Outlet Pressure Cutting 
diameter at jet Air flow 
Bulking Time 
(mm) Tex (KN/M.sup.3) 
M.sup.3 /minute 
quality (seconds) 
______________________________________ 
4.5 2400 550 1.08 excellent 
1.0 
4.5 2400 515 0.99 very good 
1.1 
4.5 2400 470 0.89 good 1.4 
4.5 2400 425 0.80 fairly good 
1.7 
4.5 2400 390 0.74 fair 2.3 
4.5 4800 All All nil no cut 
4.5 4800 550 1.44 good 1.5 
6.0 4800 515 1.33 fair 1.8 
6.0 4800 480 1.25 poor 2.3 
6.0 2400 345 1.1 excellent 
1.0 
8.0 4800 415 1.84 excellent 
1.0 
______________________________________ 
It was observed that cutting took place just prior to leaving the outlet, 
approximately 6 mm inside the passageway, thereby clearly confirming the 
severity of the forces developed. Tests on the roving entry passageway 67 
were also carried out using both ordinary and spliced roving. 
Inspection of the foregoing results confirms that optimum (minimum) cutting 
time and best bulking quality go together, both being primarily a function 
of air flow. 
TABLE 2 
______________________________________ 
Tex Passage diameter (mm) 
______________________________________ 
2400 2.5-3.0 
4800 3.0-4.0 
______________________________________ 
At the preferred length to diameter ratio of 16, diameters in the above 
ranges gave acceptable results. 
It is to be noted that the 4800 tex roving referred to above was made up of 
two separate rovings of 2400 tex each, thereby indicating that jets 
according to this invention will successfully handle more than one roving 
and therefore have significantly greater throughputs than conventional 
jets. 
It will be evident that the use of jets of the kind just described is 
extremely advantageous for the purpose of this invention, namely the 
filling of automotive silencer casings with glass fibers. 
The operation of the apparatus thus far described relies on conventional 
walking beam conveyors to move and accurately position individual silencer 
casings through the stages of the process. FIGS. 10(a) through 10(e) show 
schematically how such a conveyor operates, using a diagrammatic side view 
elevation of the conveyor with a single silencer casing on it for purposes 
of illustration. 
In these Figures only one pair of beams are shown although it will be 
appreciated that two simultaneously operable pairs are needed, one pair 
for each end of the casing and located at opposite sides of the machine. 
FIGS. 11 and 12 show this aspect rather more clearly than the side view of 
FIG. 10, where one pair of beams is inevitably concealed by the second pair 
directly in front of them. In FIGS. 10(a) through 10(e) a fixed beam 70 has 
three V-shaped notches 71, 72, 73 equally spaced apart along its length. 
(As shown, that is widthwise in the drawings). Close behind the fixed beam 
70 there is a moving beam 74 with corresponding notches 75, 76, 77. To more 
easily distinguish the beams, the moving beam is indicated by dotted lines 
in all 5 figures. In the first FIG. 10(a) a silencer casing 1 is shown in 
the loading position. It is fed to this location (the notch 73) by rolling 
it in from a magazine of empty casings (not shown, but to the right of the 
drawing). A length of perforated tube 17 (see FIGS. 3, 4) lies loose in 
the casing. The moving beam 74 is raised to lift the casing from the notch 
73, by engaging it in notch 77 until it clears notch 73. At this point the 
moving beam traverses left taking the casing with it until it is above 
notch 72 of the fixed beam 70. The moving beam is lowered to deposit the 
casing in notch 72. This corresponds to the casing centering position 
which will shortly be described with reference to FIGS. 11(a) through 
11(c). 
It will be understood that any casings already positioned in any notch to 
the left of notch 73 will also be picked up and displaced one notch to the 
left and that in the case of the end notch 71, the casing in it will be 
moved clear of the fixed beam 70. In fact the next downward movement of 
the moving beam is used to transfer such a casing to the next stage of the 
manufacturing process, details of which are not directly relevant to the 
instant invention. 
During the centering process and whilst the casing is in fixed notch 72, 
the moving beam is returned to its starting position ready to pick up a 
new casing previously loaded into notch 73. After centering is completed, 
the moving beam is again raised relative to the fixed beam, picking up the 
casing, this time in its notch 76. When clear of notch 72, the moving beam 
traverses left one notch before being lowered to drop the casing into 
notch 71 of the fixed beam. This notch is aligned with the filling station 
shortly to be described with reference to FIGS. 12(a) through 12(f). During 
filling the moving beam 74 is again traversed to the right, back to its 
starting point. 
It will be understood that by simple repetition of this raising, lowering 
and traversing action a succession of silencer casings can be precisely 
moved along through a series of process stages, and then forwarded to 
further treatment. 
Referring now to FIGS. 11(a) through 11(c) the conveyor of FIGS. 10(a) 
through 10(e) serves to present a casing 1 containing a loose perforated 
tube 17 to a centering station. FIGS. 11(a) through 11(c) show the 
centering station partly in section looking from the right in FIGS. 10(a) 
through 10(e), along the axes of the walking beams 70, 74. In this case 
both pairs of beams are shown at 70, 74 and 70' and 74' respectively. They 
are located at opposite sides of the silencer filling machine. As shown it 
will be appreciated that the notches cannot be seen as such, although by 
referring to the FIGS. 10(a) through 10(e) it is clear that the casing 1 
is always supported and located by one pair of V-shape notches, whether on 
the fixed or the moving beam, according to the stage of progress. 
In FIG. 11(a) a right hand side plate 80 of the machine has a fixed stop 81 
aligned centrally of the casing 1 and engageable with one end 82 of the 
perforated tube 17. It also has a casing location step 83 aligned to 
engage one end 84 of the casing 17. The left hand side of the machine has 
a side plate 85 with a fixed casing location stop 86. The plate 85 also 
has a perforated tube detector 87 comprising a sensor head 89 mounted on a 
rod 90, the rod being operably connected to a piston and cylinder device 
91. This device is supported to the side plate 85. 
As shown in FIG. 11(a) the casing 1 is off-center with respect to the 
walking beams and to the side plates 80 85. The loose perforated tube 17 
is also off-center. 
For purposes of illustration this is exaggerated. In practice, most casings 
and perforated tubes will be loaded onto the walking beam more or less 
correctly aligned centrally of the machine. 
FIG. 11(b) shows the initial phase of centering. Both side plates 80, 85 
form part of respective headstock units extending generally axially 
parallel to the walking beam conveyor. These headstock units are 
displaceable towards and away from the walking beams, by pneumatic piston 
and cylinder means not shown herein for reasons of clarity. In FIG. 11(b) 
the side plates have been displaced inwardly towards the walking beams so 
that the casing location stops 83, 86 engage with respective opposed ends 
of the casing 1, pushing it sideways along the supporting V-shaped notch 
(FIG. 10) until it is centered relative to the side plates and walking 
beams. Whilst held in this centered position in FIG. 11(c) the piston and 
cylinder device 91 is operated to urge the sensor head 89 via rod 90 
against the end 92 of the perforated tube 17, thereby pushing the latter 
through the casing 1 until the opposite end 82 hits the fixed stop 81. The 
perforated tube is thereby centered precisely within the casing, which is 
itself centered between the side plates 80,85. 
If for some reason the perforated tube is missing, for example through some 
malfunction, the sensor head 89 will not engage with it. As a result the 
sensor head will obviously overtravel. This can be used to operate a 
warning system so that the machine can be halted to correct the error. 
It will be appreciated that if the silencer casing includes fixed 
partitions which also serve to locate and retain the perforated tube, it 
is not necessary to have centering means for the latter. In such case only 
the fixed casing stops 83, 86 would be needed. 
With the casing and tube accurately centered, the walking beams can be used 
to lift them to the next fixed beam notch, the filling station. 
The operation of this has already been generally described in relation to 
FIGS. 3 through 8 which show only one side of the machine. FIGS. 12(a) 
through 12(f) show both sides of the machine, so that the sequence of 
operations can be more readily understood. 
Starting with FIG. 12(a), (in conjunction with FIG. 3) the casing 1 arrives 
between side plates 80,85. The latter support tubular spacer elements 13 
each carrying a resilient marginal seal 14 around their open ends. Inside 
the tubular spacers 13 there are central supports 15 with shaped ends 18, 
the supports 15 having hollow centers, 19. Both sides of the machine are 
identical, but of opposite hand, of course, and in particular there are 
glass fiber filling stations with bulking/injection jets and yarn supplies 
at both sides, each exactly as shown in the left-hand side view of FIG. 5. 
Taking FIG. 12(a) first, the casing 1 and perforated tube 17 are delivered 
by the walking beams 70, 74 and 70' 74' to the notch 71 of FIGS. 
10(a)-10(e) using the sequential lift and traverse movements described in 
relation to those Figures. Located in line with notch 71 and midway 
between the walking beams, there is an electromagnet 95. As the casing is 
delivered to notch 71 the magnet is energised, to ensure that perforated 
tube 17 is actually lying in the bottom of the casing 1 in the correct 
attitude for the shaped ends 18 to enter into its opposed ends. In FIG. 
12(b) the side plates 80,85 are shown traversing inwards, the shaped ends 
18 having partway entered the ends of perforated tube 17 so as to lift it 
towards the center line of the casing 1. The electromagnet 95 remains 
energised until the plates 80,85 have advanced the tubular spacers 13 to 
the point where the casing is firmly engaged therewith, as shown in FIG. 
12(c). In this position, both the casing and the perforated tube are fully 
located relative to one another and to the filling stations. As previously 
mentioned, there is a filling station at each side, identical to the one 
shown in FIGS. 5, 6, 7 and 8. Because of the difficulty of showing all 
features in one drawing FIGS. 12(b), 12(c) 12(d) and 12(e) show both 
stations, but FIGS. 12(a) and 12(f) omit the left hand station in favour 
of showing the exhaust through the aperture 39, from the inside of the 
perforated tube (through the passageways 19 in the supports 15 or 38 in 
FIG. 7.). Also shown in FIGS. 12(a) and 12(f) are press plates 52 operated 
by pneumatic means (not shown) through rods 53. Each filling station 
comprises a pair of jets 32 disposed either side of the central axis of 
casing 1 (as best seen in FIGS. 6 and 8). 
FIG. 12(d) shows the start of filling from both ends of the casing, exactly 
as described with reference to FIGS. 5 through 8. Glass fiber rovings are 
delivered to the respective bulking jets by capstan (godet) wheels 103, 
104. The latter are only shown in FIGS. 12(a) and 12(b) in the interest of 
clarity. However, a yarn stop 100 is shown in several of the figures. In 
FIG. 12(a) this yarn stop 100 is shown pressed against the yarn 34 at its 
point of entry to the jet 32. Yarn stop 100 is in fact a circular pad 101 
mounted to the end of a rod 102 which can be moved towards and away from 
the thread guide 64 by a pneumatic cylinder (not shown, for reasons of 
clarity). Because yarn stop 100 traps the yarn against the thread guide 64 
(FIG. 9) no yarn can be withdrawn from conventional fiber supply packages 
(not shown) via the capstan (godet) wheels 103 or 104. This is essential 
when there is no casing to be filled and when the side plates 80,85 are 
displaced away from the walking beams to allow the latter to function 
normally. 
In FIG. 12(d) the casing is firmly held by the tubular spacers 13 and so 
the yarn stops can be withdrawn as shown, thereby permitting the jets to 
draw in yarn, to bulk it and then to project the bulked yarn into the 
casing. The filling operation proceeds as shown in FIGS. 5 and 12(d) until 
a predetermined amount of glass fiber has been delivered into the casing 1 
from each end. 
The amount may be controlled by timing the fill, by length measurements 
based on capstan rotation or by a combination of these. Having achieved a 
controlled fill, yarn stops 100 are operated to stop further entry of the 
glass fiber yarns 34. (FIG. 1 12(e). As previously explained, the airflow 
is left on and the yarn is cut by the latter when the stop engages the 
thread guide 64 jet entrance. This obviates the need for mechanical cutter 
and to re-thread the yarn, since there is enough of it left inside the jet 
passageway 69 to ensure a smooth start-up of the feed when next the stops 
100 are removed from the thread guide. 
Turning now to FIG. 12(f) the press plates 52 are operated by pushing them 
towards one another to press the bulky continuous filament glass fibers 
into the casing from the insides of the two tubular spacers 13. The air 
supply can be turned off at this stage ready for outward movements of the 
plates 80,85 followed by operation of the walking beams to move the 
now-filled casing to the next stage of processing and to present a fresh 
casing for filling, after centering it as described earlier.