Coiling machine

A machine is provided for coiling wire about a core filament, particularly for producing heat exchanger coils. The machine comprises a main frame, two coiling elements spaced from each other and mounted in the frame for rotation about substantially the same axis, a hollow mandrel on which the wire is to be coiled, the longitudinal axis of the mandrel substantially coinciding with said axis, and a wire guide on each of the coiling elements spaced from the said axis whereby a loop of wire may be formed with its ends substantially on the said axis and the remainder thereof spaced from the said axis. The machine further comprises means for rotating the two coiling elements in a substantially synchronous fashion so that wire guided about the elements is coiled on to the mandrel, means for preventing the mandrel from rotating relative to the frame, and means for feeding a core filament through the hollow mandrel. The mandrel carries a plurality of pins around which coils of wire are formed, the mandrel having a tapering portion up which a coil in the process of being formed sides and thereby pushes off from the pins a previously formed coil.

FIELD OF THE INVENTION 
This invention relates to a coiling machine and, in particular, to a 
machine for making helical coils of wire. The machine of the invention is 
adapted so that the helical coil can enclose one or more filaments and 
more particularly the machine can be used for the manufacture of a heat 
exchange tube in which the helical coils are themselves wound round a tube 
and the enclosed filament or filaments are of materials for bonding and/or 
binding the coils to the tube. 
SUMMARY OF THE INVENTION 
According to the invention, there is provided a machine for coiling wire 
about a core filament comprising a main frame, two coiling elements spaced 
from each other and mounted in the frame for rotation about substantially 
the same axis, a hollow mandrel on which the wire is to be coiled, the 
longitudinal axis of the mandrel substantially coinciding with said axis, 
a wire guide on each of the coiling elements spaced from the said axis 
whereby a loop of wire may be formed with its ends substantially on the 
said axis and the remainder thereof spaced from the said axis, means for 
rotating the two coiling elements in a substantially synchronous fashion 
so that wire guided about the elements is coiled on to the mandrel, means 
for preventing the mandrel from rotation relative to the frame, and means 
for feeding a core filament through the hollow mandrel, wherein the 
mandrel carries a plurality of pins around which coils of wire are formed, 
the mandrel having a tapering portion up which a coil in the process of 
being formed rides and thereby pushes off from the pins a previously 
formed coil. 
By the term "in a substantially synchronous fashion", it is meant that the 
two coiling elements have the same mean rotational speed, when averaged 
over a number of revolutions of the elements. In other words, as the 
coiling elements are rotated, opposed points on the elements must not 
become out of phase by more than a few degrees. The precise amount of 
out-of-phase relationship which is allowable depends on the particular 
construction of the machine. 
In a preferred embodiment, the mandrel forms part of a mandrel assembly 
which extends along the said axis and which is freely and rotatably 
mounted between the two coiling elements. A spool or spools for supplying 
a central filament or filaments may be mounted on the mandrel assembly 
between the two coiling elements. In this case, the loop of wire, at it 
rotates, passes round the filament spool or spools and depending on the 
spacing of the wire guides from the axis, and the axial spacing of the two 
coiling elements, relatively large filament spool or spools can be 
accommodated. 
Means may also be provided for shaping the helical coils and, preferably, 
means are provided for keeping the tensions of the filament or filaments 
within predetermined limits. 
The two coiling elements may be arranged for synchronous rotation in any of 
several ways. For example, they may be driven by two synchronous electric 
motors; or they may be driven from a single motor with the coiling 
elements either linked by means of a connecting member, in which case only 
one of the elements need be directly driven, or they may both be driven by 
means of a common lay shaft. 
Where the mandrel assembly is freely mounted between the two coiling 
elements, it is clear that for coiling to take place, the mandrel assembly 
must be held stationary while the two coiling elements rotate around it. 
The means holding the mandrel stationary in this way must nevertheless 
allow passage of the loop of wire continuously around the assembly. 
Various types of holding means are envisaged for this purpose. Thus, the 
holding means may be of a positive nature, for example a swashing gear (a 
gear which is toothed over only part of its circumference) acting between 
part of the mandrel assembly and the main frame; a gear and pulley system; 
or a mechanical latch acting between the mandrel assembly and the main 
frame. Alternatively, the mandrel assembly may be held substantially 
stationary by a non-positive holding means, for example by magnetic means, 
means for causing a fluid dynamic force to act between the main frame and 
the mandrel assembly, or simply by weighing the mandrel assembly in the 
fashion of a pendulum, so that the rotational force imparted to the 
mandrel assembly by the coiling elements rotating around it is sufficient 
only to displace the pendulum by a limited amount. 
More than one wire can be coiled round the mandrel, means being provided so 
that the wires to be coiled can, if desired, be twisted about one another. 
Where the machine is used for the production of heat exchangers or 
elements used in heat exchangers, a tube or rod of suitable material and 
which may be of circular or non-circular cross-section is provided, 
together with means for bonding a binding filament and/or the said helical 
coils to the said tube or rod. The tube may be rotated about its axis and 
fed axially so that the core filament and the said wire are wound in a 
helix on the tube or rod at any desired speed. Provision may also be made 
to allow for the variations in winding-on speed associated with 
non-circular tubes or rods, and to drive the filament coiling means and 
the tube or rod at such relative speeds that any desired orientation of 
the said helical coils on the tube or rod may be obtained. 
There are advantages in providing a device in which the mountings and/or 
spindle axes etc. of the said spools etc. can be kept stationary or 
substantially stationary, for the spools generally can be larger and 
heavier, rather than mass being the limiting factor on certain spools. The 
larger spools will require recharging or changing less often, thus saving 
time and money. Furthermore the machine speeds can be increased over those 
machines in which the masses of spools and of filaments wound on them, 
rotating at speed and eccentrically, cause vibration problems. Again this 
reduction in the rotational intertia of the machine enables starting and 
stopping to be carried out more rapidly with improved speed, safety and 
programming possibilities. 
In some such machines there still exist disadvantages of complexity of 
construction, considerable rotating mass associated with certain filament 
guides or lack of provision for filaments to be enclosed by the helical 
coils. With the present invention, these disadvantages may be 
substantially reduced. 
The core filament, may be carried on the machine on a spool and the wire 
for coiling is carried in a loop round the said spool; a bonding filament, 
where it is present and is required to be enclosed by the coils is also 
carried on a spool in a fashion similar to that for the core filament. In 
such a design, the sizes of the spools for the bonding and/or core 
filaments are limited by the maximum size of envelope traced out by the 
rotating loop of the coiling wire. However, this is less of a restriction 
on machine capacity than if such limits were applied to the coiling wire 
spool for, in a typical case, the coiling wire although of similar 
cross-section to the core filament, may be about thirty-five times its 
length. In practice, the limitations on the size of the coiling wire spool 
will probably result from considerations of handling and supply.

DESCRIPTION OF A PREFERRED EMBODIMENT 
In FIG. 1, a mandrel 1 and a core filament spool 2 are both carried on a 
central member 3 which is held substantially stationary with respect to 
the coiling parts of the machine by holding means including latches 4. A 
forepart 5 of the member 3 passes through a bearing 6 mounted coaxially in 
a circular foreplate 7. The forepart 5 carries a duct 8 for a flat 
cross-section core filament 15 and also provides a mounting for the 
mandrel 1. The mandrel 1 may also carry a continuation of the duct 8 or a 
groove or other means whereby a coiling wire or filament 16 in being 
coiled around mandrel 1 encloses the core filament 15. 
The foreplate 7 is carried by three bearing assemblies 9 which are in turn 
carried on spindles 10 fixed in a housing 11. A rear part of the member 3 
is located in a bearing 12 mounted coaxially in a rearplate 13 which is 
carried by bearing assemblies 1A in a manner similar to that by which the 
foreplate 7 is carried. The foreplate 7 and the rearplate 13 are arranged 
to rotate about substantially the same axis and are driven at the same 
angular velocity by a layshaft 17 mounted in bearings 34 located in the 
housing 11. The drive from the layshaft 17 to the rearplate 13 is taken 
via a toothed pulley 1B fixed to the layshaft, a toothed belt 20 meshing 
with the pulley 1B and another toothed pulley 22 fixed to the rearplate 13 
via a spacer 24. The drive from the layshaft 17 to the foreplate 7 is 
taken via a toothed pulley 19 fixed to the layshaft, a toothed belt 21 
meshing with the pulley 19 and a toothed pulley 23 fixed to the foreplate 
7 via a spacer 25. A toothed belt 26 is driven by suitable means, not 
shown, and in turn drives a toothed pulley 27 fixed to the layshaft 17. 
The coiling filament 16 passes from a spool, not shown, via suitable 
tensioning and other control devices of known design (not shown) and runs 
on to a guide pulley 28 which is mounted on the spacer 24. The said 
control devices are so positioned that the coiling filament 16 approaches 
the guide pulley 28 approximately coaxial to the rearplate 13. The coiling 
filament 16 passes round the guide pulley 28 and outwards between the 
rearplate 13 and the pulley 22 to a second guide pulley 29 mounted on the 
rearplate 13 and thence to a third guide pulley 30 mounted on the 
foreplate 7 and inwards between the foreplate 7 and the pulley 23 to the 
mandrel 1. 
It will be seen that in this embodiment considerable saving in weight and 
increased simplicity in construction is achieved by eliminating the need 
for a guide for the coiling filament 16 as it passes between the second 
and third guide pulleys 29 and 30 across the spool 2. In some cases it 
will be advantageous to have a guard ring (not shown) passing round the 
spool 2 to prevent the filament 16 catching in the spool 2 for any reason; 
such a guard ring may also be rotatably mounted on the member 3 and 
increases in the size of the spool 2 may also be achieved by causing the 
filament 16 to deflect outwards by contact with the guard ring. 
The latches 4 pivot about pins 31 locating in one end of the latches and 
fixed in the housing 11. The other end of each latch carries a pin 32 
fixed in the latch and slidably located in a groove 33 carried in or on 
the rearplate 13, the groove 33 being eccentric with respect to axis of 
rotation of the rearplate 13. The coiling filament 16 is free to pass 
between the member 3 and the housing 11 since the eccentric groove 33 is 
arranged to lift the latch 4 clear of the member 3 via the pin 32 when the 
filament 16 passes. The central member 3 is prevented from rotating by a 
sufficiency of latches 4 engaging the member 3. In a preferred design, the 
latches will only prevent rotation of the member 3 in the direction of the 
torque applied to the member 3 by the filament 16 as it is coiled on to 
the mandrel 1. This design has certain advantages of simplicity and 
robustness. 
FIG. 2 indicates how such a latch mechanism works, not all features being 
shown. One latch is shown in two positions; lowered to prevent rotation of 
the member 3 and raised to allow passage of the filament 16. The arrow 
indicates the direction of motion of the filament 16 in a particular 
embodiment. This has been chosen so that the torque due to coiling tends 
to hold the member 3 against the latches 4. 
In such a design, since the member 3 can become displaced away from the 
latches if the tension in the filament 16 is not sufficient, a biassing 
torque should be provided and this can be done conveniently by weighting 
the member 3 eccentrically so that it tends to turn in the same direction 
as coiling. The latches 4 can have other configurations and be operated by 
any known means. 
Furthermore, the holding means preventing rotation of the member 3 and 
associated parts can have other forms which include magnetic, fluid 
dynamic, e.g. aerodynamic, or other forces acting across an airgap between 
the housing 11 and the member 3 and through which airgap the filament 16 
passes. 
In a magnetic (or electromagnetic) device known means may be used to 
generate the necessary magnetic forces to hold the member 3 in 
non-rotating relationship with the housing 11. 
Referring to FIG. 5, during coiling, the plate 13 rotates while the member 
3 is held stationary by the latches 4, only one of which is shown in FIG. 
5. Each latch 4 is pivotally mounted by a pin 31 secured at one end to the 
stationary housing 11, the other end being connected rotatably to the 
first end of latch 4; the second end of latch 4 carries a second pin 32. 
The second pin 32 is engaged in a groove 33 eccentrically formed (with 
respect to the axis) in the face of plate 13. 
As the plate 13 rotates, the pin 32, being engaged in the notch 33, causes 
pivotal movement of the latch 4. During most of the period of operation, 
each latch 4 is engaged in a notch formed in the circumference of member 
3. Each latch 4 disengages from the notch in member 3, when the plate 13 
rotates to the position in which the respective pin 32 is in its radially 
outermost position; a small gap is left between the latch 4 and the member 
3. The pulley 29 is mounted on the plate 13 so that the filament 16 is 
synchronised to pass through the gap between the latch 4 and member 3, 
when the latch 4 is raised (see FIG. 1). The member 3 continues to be held 
stationary during the coiling by the other latch 4. 
The weight W is attached to the member 3 to bias the member 3 in a 
clockwise direction, thus keeping a notch in the outer portion of the 
member biased in engagement with one of the latches 4 at all times. 
FIG. 3 shows, schematically, a design for a fluid dynamic device, in which 
35 is a head of suitable dimensions, fixed to the housing 11 and carrying 
a duct with fluid at pressure. A groove 36 of suitable shape is provided 
in the member 3, such that, when the gap between the housing 11 and the 
member 3 is sufficiently small, but still allowing passage of filament 16, 
when the member 3 is rotated relative to the head 35, the pressure in the 
groove 36 changes to produce a restoring torque. 
In any of the holding means where there is a limiting torque due to the 
design it will be necessary to fit a device to indicate rotation or 
incipient rotation and/or to stop the machine in the event of the same. 
Positively acting means may be provided acting between the housing 11 and 
the member 3 such that relative rotation between the housing and the 
member 3 is prevented but free movement of the filament 16 between the two 
can take place in a manner similar or identical to that described. Such 
positively acting means may include toothed elements e.g. gears. Such 
geared assemblies may include swashing gears, and gear trains and/or 
shafts in which the axes of rotation of such gears and shafts may be 
parallel or otherwise to the axis or of rotation of the plates 13 and 7 
and some gears may or may not be identical. Other types of toothed 
assembly may include toothed belts and toothed pulleys. 
The coils formed on the mandrel 1 by the coiling filament 16 are caused to 
be fed along the mandrel as they are formed. The mandrel itself is tapered 
so as to reduce the tendency of the coils to bind, a preferred mandrel 
head being shown in FIGS. 4a and 4b. The mandrel is thus provided with two 
ramps 40 at its base, up which the filament rides to push off a previous 
coil formed round two pins 41. The height of the ramps is greater than the 
diameter of the filament. Preferably, the two opposing sides of the ramp 
have a relative taper to facilitate pushing off of the coils. In order 
that the coils should remain in a shape conforming closely to the shape of 
the mandrel cross-section the material of the filament 16 should possess a 
suitable plastic yield point. Where all portions of the mandrel 
cross-section or cross-sections that affect the shape of the coil are 
rectilinear or convex no additional aids are likely to be required to make 
the filament 16 conform to the said cross-section or cross-sections unless 
the filament 16 is very stiff. However, where portions of the 
cross-section or cross-sections are concave or in such cases of high 
stiffness additional elements such as plungers may be required to press 
the filament 16 against the mandrel 1. These elements may act once or more 
during the formation of coil or with a less frequency, e.g. once every 
other coil, as may be required. Other shaping means such as rolls may also 
be used to shape the coils which shaping means may or may not operate in a 
manner independent of the mandrel. These or other shaping means may also 
be used where it is required that coils are not necessarily all the same 
shape. 
Certain advantages may be gained from a mandrel of circular cross-section. 
However, unlike many cases with a non-circular cross-section, difficulty 
may be experienced in coiling the filament 16 on to the mandrel without 
the coils slipping on the one hand or binding on the other. In such a 
case, it may be necessary to have additional means such as plungers or 
pressure rollers which can grip the coils on the mandrel without impeding 
the feed of the coils along the mandrel. An advantage of the circular 
mandrel is that the filament 16 is coiled at a constant speed. For 
non-circular mandrels it will be usual for the filament to be taken on to 
the mandrel at a speed possessing a cyclic variation. The cyclic speed 
variation could cause problems resulting from varying tension of the 
filament 16 or overspeeding of the coiling filament spool, most of which 
problems increase with speed and the inertia of the coiling filament 
spool. With non-circular mandrels it is therefore particularly desirable 
to introduce tension or other controls but for known reasons it is prudent 
to have them for circular mandrels also. These are conveniently applied to 
the coiling filament spool and to the coiling filament between the said 
spool and guide pulley 28. It is also desirable for controls to be applied 
to the core filament 15 and its spool 2. Such controls and other controls 
for stopping the machine in cases of filaments breaking, spools running 
low of filament, overloading etc. may be of purely conventional design and 
so are not detailed here. 
The invention is particularly applicable to machines which assemble the 
coils, a core filament and a bonding filament into heat exchangers or 
elements for use in heat exchangers. A preferred method of bonding the 
coils to a tube or rod includes the use of a core filament or filaments 15 
as a carrier or carriers for a bonding material which may be coated 
thickly or otherwise on the filaments 15. This coating provides protection 
for the core filament, and a means of introducing the bonding material and 
bore filament as one into the coils. The presence of some bonding 
materials inside the coils can aid the process of bonding the coils to the 
tube or rod. Where a single core filament is used it may be found 
desirable, depending upon the shape of the coils in contact with the said 
tube or rod, to flatten the filament since a flattened filament can give 
greater stability to the coils being held on the tube or rod by the core 
filament and prior to bonding the said coils to the said tube or rod. 
Alternatively, a plurality of coated core filaments may be used and it may 
be desirable to bond these together into a composite assembly so that the 
whole is drawn on to the tube or rod as one. Where such a composite 
assembly is used it may with advantage take the form of a flat ribbon. The 
bonding of the coils to the tube or rod may be achieved by using a fusible 
bonding material and materials for filaments and tube or rod compatible 
with the bonding material so that when the bonding process has been 
completed a sufficiently strong bond is attained between the coils and the 
tube or rod. For some heat transfer purposes solder is a suitable bonding 
material and brass or copper are suitable materials for the filaments and 
tube or rod. Other materials may also be used. The bonding process, in the 
case of a fusible material such as solder, consists in fusing the material 
in contact with the elements to be bonded, these elements being in contact 
and allowing the material to solidify. Additional bonding material may be 
supplied as necessary. It may be desirable to include in the pretreatment 
of the tube or rod a partial or complete precoating with bonding material 
in addition to the usual cleaning, fluxing etc., the coiling filament may 
be similarly treated in part or in whole, before or after coiling. Other 
types of bonding process using other bonding materials can include 
adhesives with one or more chemical components or accelerators that are 
applied as required to filaments and tube or rod, heat being applied as 
necessary to speed or improve the bonding process and/or bond. 
Means for starting the coils and filaments on the tube or rod are not 
detailed here nor are the basic methods of driving the tube or rod because 
they follow well-known principles. During most of the operating cycle the 
coiling head and tube or rod drive are geared together. However, at 
certain points in the machine operating cycle relating to the manufacture 
of a heat exchange means or element to be used in such, arrangements are 
made, using for example, electromagnetic clutches, whereby the drives can 
be disconnected and operated independently as necessary. At the start or 
finish of winding coils on to a tube or rod it may be necessary to wind on 
and bond a length of core filament only without coiling; similarly when 
gaps or spaces are to be produced between groups of coils. In finishing a 
group of coils the coiled filament has to be cut at some point between the 
start of coiling and the point of bonding the coils to the tube or rod, 
and the coiling head is stopped. The remaining length of coil attached to 
the coil on the tube or rod is wound on and bonded and then a further 
length of core filament alone is wound on and bonded. In the case of a 
space between groups of coils a further length of core filament is wound 
on, preferably not bonded, and at suitable points bonding of the core 
filament starts again and the coiling head is restarted. Bonding may be 
prevented by such means as inserting some non-bondable material, for 
example a non-combustible tape or a coating of emulsion between filament 
and tube or rod and/or stopping fusing of the bonding material. In the 
case of the last group of coils the bonding filament is cut without 
winding on a length of unbonded core filament. At some point any unbonded 
core filament is removed. In this way groups of coils can be started and 
finished and spaces formed between them. Groups and spaces can be of equal 
or variable size. The control over these various drive, bonding and 
cutting operations may be carried out manually or automatically, and 
actuated directly or indirectly by the tube or rod or coils thereon or by 
any part of the drive mechanism including the coiling head by the use of 
counting mechanisms or in any known manner. 
Where tubes or rods are of non-circular cross-section such tube or rod 
driven at constant angular velocity will wind on the coils and core 
filament at a cyclically varying speed. If necessary such speed variations 
may be largely or wholly eliminated by known means inserted in the drive 
between coiling head and tube or rod or such speed variation can be 
allowed, means such as a sufficient reserve of coils before bonding of 
coils providing a reservior. 
For some heat exchange processes better results may be obtained from heat 
exchange means or elements of the type manufactured by the present 
embodiment when one or more coils are displaced in some manner relative to 
one another and substantially axially or otherwise to the tube or rod. 
Means for achieving such relative displacement may be applied to the coils 
at any suitable time including after bonding of the coils to the tube or 
rod.