Device for stopping a needle at a predetermined position

This invention concerns a machine for making a textile product comprising a needle carrier shaft, reciprocation means for reciprocating said shaft, yarn feeding means for feeding yarn to a needle carried by said shaft, and control means for ensuring that the needle carrier shaft can be stopped only at an end of its reciprocation.

This invention concerns a method and machine for making a textile product 
and, although the invention is not so restricted, it is more particularly 
concerned with a method and a machine for making a tufted fabric such, for 
example, as a tufted carpet or rug. 
Machines previously known for producing tufted fabrics have been provided 
with a machine head having a multiplicity of tufting needles. The tufting 
needles have been reciprocated into an out of a base material to apply 
yarn thereto, relative movement being effected between the machine head 
and the base material in the plane of the latter. 
The means which have been employed for effecting such reciprocation of the 
needles, however, have been such that it has not been possible to ensure 
that the needles were fully retracted from the base material at the 
beginning and at the end of the said relative movement. As a result, the 
first and last stitches effected during the said relative movement did not 
necessarily pass properly through the base material and therefore were 
liable to be of poor quality. 
According to the present invention, there is provided a machine for making 
a textile product comprising a needle carrier shaft, reciprocation means 
for reciprocating said shaft, yarn feeding means for feeding a yarn or 
yarns to a needle carried by or integral with said shaft, and control 
means for ensuring that the needle carrier shaft can be stopped only at an 
end of its reciprocation. 
Preferably, the reciprocation means comprises a magnetically permeable core 
member which is mounted for reciprocating movement and which is drivingly 
connected to said shaft to effect reciprocation of the latter, and two 
electromagnetic devices which are respectively disposed on opposite sides 
of the core member, the said control means effecting alternate 
energisation of the electromagnetic devices. 
The control means preferably comprises an electrical device which, on 
receiving a stop signal, permits reciprocation of the needle carrier shaft 
to continue until the latter is at the said end of its reciprocation when 
a holding current is passed to the respective electromagnetic device to 
hold the needle carrier shaft at the said end of its reciprocation. 
The control means may be adjustable to alter the frequency of the 
reciprocation of the needle carrier shaft. 
The control means may ensure that the rate of change of frequency of 
reciprocation of the said shaft is controlled to a predetermined value. 
The needle carrier shaft is preferably arranged to be set in a plurality of 
predetermined angular positions, there being provided a control device 
which is arranged to be programmed to rotate the said needle carrier shaft 
to the said predetermined angular positions. 
The invention also comprises a method of making a textile product 
comprising feeding a yarn or yarns to a needle carried by or integral with 
a needle carrier shaft, disposing a base material adjacent to said needle, 
causing the needle to be reciprocated into and out of the base material so 
as to apply the yarn or yarns thereto, effecting relative movement between 
the needle and the base material in the plane of the latter, stopping the 
reciprocation of the needle at predetermined times, and ensuring that the 
needle is so stopped only at an end of its reciprocation when it is fully 
retracted from the base material. 
The direction of the said relative movement may be changed at predetermined 
times, and, at each such change of direction, the needle carrier shaft may 
be rotated so that a predetermined portion of the needle always faces 
forwardly, the needle being fully retracted from the base material at the 
beginning and at the end of the said relative movement. 
The needle is preferably reciprocated into and out of the base material, at 
the beginning and at the end of the said relative movement, at a speed 
which is lower than a speed of reciprocation which the needle is given 
between the said beginning and end.

Terms such as "left" and "right", as used in the description below, are to 
be understood to refer to directions as seen in the accompanying drawings. 
Referring first to FIG. 1, a frame or housing 10 of magnetically permeable 
material houses a rear solenoid coil 11 and a forward solenoid coil 12. 
The coils 11, 12 are respectively disposed on opposite sides of a 
magnetically permeable annular wall member 13 which is mounted 
concentrically in the frame 10. Although the wall member 13 is shown in 
FIG. 1 in a central position in the frame 10 this is not necessary since 
coils 11, 12 of different dimensions may be used if desired. Each of the 
coils 11, 12 is wound about a non-magnetic bobbin 14. 
A shaft 15 has portion constituted by a magnetically permeable core member 
16 secured to and disposed between shaft members 17, 18. The shaft members 
17, 18 are made of non-magnetic material and are respectively mounted 
radially inwardly of the coils 11, 12. The shaft 15 passes through the 
frame 10 and is rotatably mounted in non-magnetic bearings 19 mounted 
within the frame 10. 
When the core member 16 is in a central position, as shown in FIG. 1, the 
core member 16 is separated from the adjacent magnetically permeable 
annular parts 20, 21 of the frame 10 by air gaps 22, 23 respectively. The 
shaft members 17, 18 respectively extend through the parts 20, 21, the 
parts 20, 21 constituting stator members which are surrounded by and 
arranged to be magnetised by the coils 11, 12 respectively. 
An electrical control device 24 is provided for effecting alternate 
energisation of the coils 11, 12, the device 24 including means for 
adjusting the frequency of the said alternate energisation. Alternatively, 
the coils 11, 12 may be alternately energised by respective electrical 
devices (not shown). 
The shaft members 17, 18 are respectively provided with buffer end stops 
28, 29. The buffer end stops 28, 29 are respectively provided with impact 
absorbing members 28a, 29a each of which is engageable with a fixed buffer 
(not shown). 
When a voltage is applied to the rear solenoid coil 11, the forward 
solenoid coil 12 being de-energised at this time, a magnetic field is 
generated in the surrounding frame 10 which causes the core member 16, and 
hence the shaft 15, to move in the direction of arrow C so as to reduce 
the size of the air gap 22. When the voltage to the rear solenoid coil 11 
is cut off and a voltage is applied to the forward solenoid coil 12, the 
core member 16, and hence the shaft 15, will move in the direction of 
arrow D so as to reduce the size of the air gap 23. Thus the shaft 15 can 
be reciprocated by alternately energising the coils 11, 12, while the 
limits of the reciprocation are exactly defined by the abutment between 
the impact absorbing members 28a, 29a and the said fixed buffers at 
opposite ends of the stroke of the core member 16. 
The shaft 15, which is thus reciprocated by a solenoid drive, is connected 
by a rod 25 to a pusher member 31 (see FIG. 2). The pusher member 31 
carries a thrust bearing 32 in which is rotatably mounted a hollow shaft 
33, the hollow shaft 33 being coaxial with and secured to a hollow needle 
carrier shaft 34. The left hand end of a hollow needle 26 is mounted in 
the hollow shaft 34, the needle 26 having a flange 35 which is urged by a 
spring 36 into the driving contact with the right hand end of the hollow 
shaft 34. Thus reciprocation of the shaft 15 produces reciprocation of the 
needle 26 so that tufting yarn 40, which has been fed, by means described 
below, to a pointed leading end 27 of the needle 26, may be passed through 
base material (not shown) to produce tufts therein. 
Yarn feed air, from a compressed air source (not shown) is supplied to a 
conduit 41 and passes thence via a conduit 42 to a chamber 43 through 
which the hollow shaft 33 passes. The wall of the hollow shaft 33 is 
provided with an aperture 44 therethrough which, when the parts are 
disposed as shown in FIG. 2, establishes communication between the chamber 
43 and the interior of the hollow shaft 33. Thus, in operation, air will 
pass from the chamber 43 to the interior of the hollow shaft 33 except 
when, during each reciprocation of the hollow shaft 33, it moves to the 
left of the position shown, when the aperture 44 will be sealed by a bush 
45 mounted in a machine frame 46 within which the hollow shaft 33 is 
mounted. Thus the air to the interior of the hollow shaft 33 is shut off 
throughout at least a portion of the time during which the needle 26 does 
not extend through the base material. 
The machine frame 46 is mounted in a machine head (not shown) which is 
movable in two orthogonal linear directions over the said base material by 
a traversing mechanism, e.g. as shown in the co-pending U.S. Pat. 
application Ser. No. 772,839 of William J. Barnes et al, filed Feb. 28th, 
1977, U.S. Pat. No. 4,109,593. 
Alternatively, at the head, instead of being driven over the base material 
by a traversing mechanism, could be moved by hand thereover. In this case, 
the head is provided with control means (not shown) which are arranged to 
be programmed to rotate the needle to predetermined angular positions, the 
control means being responsive to the direction in which the head is being 
moved over the base material. 
The yarn 40 passes through a narrow opening 47 in a thread inlet member 50 
mounted in the frame 46, the width of the narrow opening 47 being designed 
to admit the yarn 40 but to minimize air loss therethrough. The yarn 40 
passes through the nip between a serrated yarn feed roller 51 and another 
roller (not shown), both rollers being mounted in a chamber 37. The yarn 
passes thence successively through the hollow shafts 33, 34 and through 
the hollow needle 26 and thus out through the pointed leading end 27 of 
the latter, the yarn being in operation propelled therethrough by the flow 
of compressed air. 
The length or height, of the yarn per tuft is controlled by a servo-motor 
52 and tachometer 53, the servo-motor 52 driving the yarn feed roller 51 
and thus pulling the yarn through the opening 47. The servo-motor 52 
receives signals, by means not shown, both from an information store (not 
shown) and from a tape control (not shown) so that the yarn feed roller 51 
is driven at a speed such as to produce a controlled continuously variable 
pile height, a constant pile height, or a pile height changing in steps, 
whichever is required. The tachometer 53 senses the value of the actual 
speed of the servo-motor 52 and this value is compared (by means not 
shown) with a pre-set value in order to produce the signals transmitted to 
the servo-motor 52. 
A gear 55 is fixed to a cylindrical member 56 which is rotatably mounted in 
the frame 46 by means of bearings 60, 61. The hollow shaft 34 has a 
portion of its outer periphery which is square in cross-section and which 
extends slidably through a square cross-section sleeve 57, the sleeve 57 
being mounted within a square cross-section hole in the cylindrical member 
56 and engaging the latter. 
The arrangement is thus such that if the gear 55 is rotated clockwise (by 
means not shown), the hollow shaft 34, and hence the needle 26, will also 
be rotated clockwise, whereas if the gear 55 is rotated counter-clockwise, 
the needle 26 will be rotated counter-clockwise. The gear 55 may be 
respectively rotated clockwise and counter-clockwise from a motor shaft 
(not shown) by means of first and second clutches (not shown), e.g. as 
shown in the said co-pending Application. The gear 55, which may be 
programmed to be set in a plurality of predetermined angular positions, 
thus controls the angular position of the needle carrier shaft 34 and 
hence of the needle 26, the arrangement being such that throughout the 
movement of the said head over the said base material, the tip of the 
needle 26 (for the reasons explained in detail in the said co-pending 
application) always faces forwardly with respect to the direction of 
relative movement of the needle with respect to the base material. 
In operation, therefore, the hollow shaft 34, which carries the needle 26, 
is slidingly reciprocated within the sleeve 57 by virtue of the drive from 
the shaft 15. When, however, appropriate signals are sent to the said 
first and second clutches, the cylindrical member 56 is rotated through 
the shortest angular distance to a different angular position, and this 
rotation of the cylindrical member 56 is transmitted to the needle 26 by 
way of the sleeve 57. 
The electrical control device 24 of FIG. 1 may be formed as shown in the 
circuit diagram of FIG. 3. In this case, a digital to analogue converter 
63 is arranged to accept from a magnetic tape or tapes a number of digital 
inputs encoded in such a way as to define the required operating speed 
(i.e. the required frequency of reciprocation) of the shaft 15 at any 
given time. The said digital inputs are converted by the converter 63 to 
produce an analogue voltage output which is passed through a filter 64 to 
a voltage controlled oscillator 65. The oscillator 65 is a voltage to 
frequency converter which controls the rate of reciprocation of the shaft 
15. The filter 64 controls the rate of change of the voltage applied to 
the oscillator 65 so as to ensure that the rate of change of frequency of 
reciprocation of the shaft 15 is controlled to a predetermined value. This 
is required because when a change of speed is dictated by the said 
information store or tape control there cannot be an instantaneous change 
in the frequency of reciprocation of the shaft 15 because this would 
require an instantaneous change in the speed by the said traversing 
mechanism. The oscillator 65 is arranged to produce an output signal 
F.sub.o whose frequency is proportional to the required frequency of 
reciprocation of the shaft 15, the output F.sub.o being passed to a 
sequencer 66 which, as described in greater detail below, produces digital 
outputs for the coils 11, 12 respectively, so as to ensure that the latter 
are alternately energised. These digital outputs are respectively applied 
to resistor networks 70, 71 which convert the said digital outputs to 
analogue voltages having the required drive waveform for operating the 
coils 11, 12. These analogue voltages are respectively applied to power 
transconductance amplifiers constituted by voltage to current converters 
72, 73 whose outputs are respectively passed to the coils 11, 12. 
The construction of the sequencer 66 is shown in FIG. 4, while its 
operation is illustrated by the waveform diagram of FIG. 5. As shown in 
FIG. 4, the sequencer 66 comprises logic 79 which receives the output 
signal F.sub.o from the oscillator 65. The logic 79 also receives stop 
signals both from a machine control system and from a magnetic tape 
(programmed operating instructions). 
A stop signal may occur at any time during the reciprocation of the shaft 
15, and the logic 79 is therefore arranged, as described in greater detail 
below, to ensure that, when a stop signal occurs, movement of the shaft 15 
continues until the current of the rear solenoid coil 12 had declined to a 
predetermined value, at which value it constitutes a holding current. At 
this point, therefore, the rear solenoid coil 12 will hold the shaft 15 in 
its rearmost position, i.e. in the position in which the needle 26 is 
fully retracted from the said base material, and the rear solenoid coil 12 
will continue to hold the shaft 15 in the said rearmost position until the 
stop signal is removed. 
The signal F.sub.o is transmitted from the logic 79 to a clock intput of a 
4-binary counter 80. The binary counter 80 has outputs Q.sub.1, Q.sub.2, 
Q.sub.3, Q.sub.4 which are respectively connected to inputs I.sub.1, 
I.sub.2, I.sub.3 and to a select input of a demultiplexer 81. The 
demultiplexer 81 has outputs A.sub.1, A.sub.2, A.sub.3 which are connected 
to the resistor network 71 of the forward solenoid coil 11, and outputs 
B.sub.1, B.sub.2, and B.sub.3 which are connected to the resistor network 
70 of the rear solenoid coil 12. By reason of the connection of the 
highest order output Q.sub.4 of the binary counter 80 to the select input 
of the demultiplexer 81, the inputs I.sub.1, I.sub.2, I.sub.3 are 
alternately connected to the outputs A.sub.1, A.sub.2, A.sub.3 and to the 
outputs B.sub.1, B.sub.2, B.sub.3 so as to ensure alternate energisation 
of the coils 11, 12, whereby to effect reciprocation of the shaft 15. 
The four output lines of the binary counter 80 are also connected to inputs 
A, B, C, D of a decoder 82 which has an output Q which is connected to the 
logic 79. The decoder 82 generates an output signal from Q whenever the 
input to the decoder 82 from the binary counter 80 has the same value as 
that of the holding current when applied to the rear solenoid coil 12. 
As will be seen from FIG. 5, during each normal reciprocation of the shaft 
15 there will be a brief period during which the decoder 82 will transmit 
an output signal to the logic 79, but this will not affect the manner in 
which the shaft 15 is being reciprocated nor will it stop such 
reciprocation. The logic 79 is such, however, that if the stop signal goes 
high, that is to say if the machine control system or the magnetic tape 
produces a stop signal, the signal F.sub.o continues to be applied to the 
clock input of the binary counter 80 until the output from the decoder 82 
goes high. The clock is then gated off, with the result that the rear 
solenoid 12 is maintained energised by its holding current. 
When, however, the stop signal goes low, i.e. when the stop signal from the 
machine control system or the magnetic tape is removed, the signal F.sub.o 
is restored to the binary counter 80 irrespective of the state of the 
decoder 82. Thus the reciprocation of the shaft 15 then continues. 
The reciprocation of the needle 26 by the solenoid drive shown in FIG. 1 
has substantial advantages. In particular it makes it possible to ensure 
that the needle 26 will always be stopped in a position in which it is 
fully retracted from the base material whenever the operation of the said 
head is started or stopped. It can therefore be arranged that the needle 
will always make a complete stroke during both the first and the last of 
the stitches which the needle makes throughout the time that the head is 
moving. This means that both the first and the last stitches will pass 
properly through the base material and will therefore be of good quality. 
Moreover, it is possible to work out exactly how many whole stitches are 
to be effected during a predetermined traverse of the head, and by 
appropriate adjustment of the rate of reciprocation of the needle, it is 
possible to ensure that exactly this number of whole stitches are produced 
in practice. 
The control of the stitches in this way is important for pattern definition 
and the the elimination of faulty stitches at the start and end of a row 
of stitches. It is also important to have such a precise control of the 
number of stitches when the pattern requires the row of stitches to make a 
large angle turn, for example, a right angle. In this case, in order to 
obtain good pattern definition, it is necessary to control the position of 
the individual stitches at the "corner". This can easily be achieved by 
arranging that an appropriate number of whole stitches are made from a 
given starting point. Moreover, pattern features based on changes in pile 
height can be programmed so that the or each such change in pile height 
occurs at a predetermined stitch. 
Additionally, the said solenoid drive allows the needle 26 to be 
reciprocated at a variable rate by means of electrical signals, such 
signals having a short response time and not requiring feed-back. 
The solenoid drive also eliminates the need for mechanical arrangements 
such as cams and crank motions, it enables the stroke to be changed by a 
simple modification of the parts of the solenoid drive, it is easily 
associated with electronic control systems, and it provides improved 
control of the needle reciprocation together with simplicity of 
manufacture. 
The solenoid drive can be operated to provide a constant speed of 
penetration of the needle 26 into the base material, this constant speed 
of penetration being independent of the stitching rate. This improves the 
stitching performance during slow speeds of the said head. Thus the 
machine can be programmed to effect slow speed when starting, stopping, 
and when turning large angle corners, e.g. of 90.degree., the maintenance 
of a constant penetration speed ensuring that the needle penetrates the 
fabric adequately at all times. 
The stop signals which effect stopping of the reciprocation of the needle 
may arise as a result of a fault, e.g. a yarn break, during operation of 
the machine. If such a fault occurs, the needle will not be stopped until 
it is fully retracted from the base material, and consequently the fault 
can be rectified and the machine restarted without the loss of pattern or 
product quality. 
Although in the description above the needle can be stopped only at the end 
of its reciprocation when it is fully retracted from the base material, it 
can if desired additionally be arranged to be capable of being stopped at 
each end of its reciprocation. Moreover, the stopped time at the end of 
each forward and reverse stroke may be variable. 
The provision of the solenoid drive concentrically of the needle carrier 
shaft, or of a shaft which drives the needle carrier shaft, enables the 
latter to be rotated in either angular direction simultaneously with its 
being reciprocated. The construction of the solenoid drive need not, 
however, be symmetrical, that is to say the coils, current and waveform 
used to effect movement of the needle carrier shaft in one linear 
direction need not be the same as those used to effect movement of the 
needle carrier shaft in the opposite linear direction. 
When it is necessary to change the speed of reciprocation of the needle, 
the solenoid drive provides a very accurate control of both the frequency 
of reciprocation and the rate of change of the frequency of reciprocation 
of the needle. This is a very important feature in a fully automated 
machine which is timed in dependence upon the speed of reciprocation of 
the needle. 
In the construction shown in FIG. 2, at each change of direction of the 
relative movement between the needle and the base material, the needle 
carrier shaft 34 is rotated so that the tip of the needle 26 always faces 
forwardly. In certain circumstances, however, such rotation of the needle 
is not necessary. For example, if a fine or thin yarn is used, since the 
diameter of the yarn will be small in comparison with the diameter of the 
needle, the needle can deflect the yarn away from the point at which the 
needle is about to penetrate the fabric, and consequently it may not be 
necessary to arrange that the needle is pointing in any particular 
direction. In this case, the shaft 15, can be made hollow so that a yarn 
or yarns may be passed therethrough, the shaft 15 being integral with a 
needle 62, as illustrated diagrammatically in FIG. 1. The needle 62 will 
in this case be merely reciprocated into and out of the base material (not 
shown) but will not be capable of being rotated. 
Alternatively, the shaft 15 may be made hollow and the yarn passed 
therethrough to the needle 62, the latter being rotated at predetermined 
times by a stepper motor drive as shown in our said co-pending patent 
application. 
In the machine illustrated in the drawings, only one needle is employed and 
the mechanism is, in operation, disposed on one side only of the base 
material to which the yarn or yarns are being applied. However, the 
present invention is applicable to the manufacture of textile products 
which require mechanism on opposite sides of the base material. For 
example, the present invention is applicable not merely to a machine which 
produces a tufted fabric by the method discussed above, but equally to a 
known machine for producing a tufted fabric which incorporates a looper 
(not shown). Such a looper is disposed on the side of the base material 
opposite that to which the needle 26 is retracted, the looper being 
arranged to reciprocate parallel to the base material and into and out of 
engagement with each newly formed loop so as to assist in its formation. 
If the invention is applied to such a machine, it is necessary to rotate 
the looper as required to the same angular position as the needle, while 
it is also necessary to rotate the needle to ensure that the plane of the 
needle always lies in the direction of the traverse of the needle and thus 
faces forwardly. 
The present invention is also applicable to a known machine which produces 
cut pile tufting and which in addition to the said looper, is also 
provided on the side of the base material remote from that to which the 
needle is retracted, with a knife which reciprocates towards and away from 
the base material and thus towards and away from a position in which it 
cuts a loop or loops held by the looper. If the invention is applied to 
such a machine, it is necessary to rotate both the looper and the knife to 
the same angular position as the needle, while it is also necessary to 
rotate the needle to ensure that the plane of the needle always lies in 
the direction of the traverse of the needle and thus faces forwardly. 
The invention is applicable to the production of textile fabrics of all 
kinds, e.g. woven fabrics, knitted fabrics, needled fabrics and spun 
bonded fabrics. 
The needle employed in the present invention, instead of being used to 
effect tufting, may be used to effect sewing, e.g. the stitching of two or 
more fabrics together, or may be used to effect embroidery, e.g. the 
stitching of a decorative yarn onto a base fabric. 
Such sewing or embroidery may involve the use of needles on opposite sides 
of the base material, each such needle being rotated when necessary to 
ensure that its leading end is always correctly disposed. 
Alternatively, the stitches may be "chain" stitches which use only one yarn 
or thread, the mechanism involving the use of a reciprocating "gripper 
hook" or "looper" on the opposite side of the fabric to that to which the 
needle is retracted. 
If, however, a "lock stitch" is required, two yarns are used. In this case 
the needle 26 may be used to take one yarn through the base material to 
form a loop, while a shuttle (not shown) may be employed to take a second 
yarn through this loop. A rotary hook mechanism can be used for this 
purpose, and in this case the loop of yarn from the needle is taken by the 
hook around a bobbin case, to enclose the second yarn as the latter is 
unwound from the bobbon. 
The tufting and sewing methods discussed above require that the mechanisms 
disposed on opposite sides of the base material operate in timed sequence 
in relation to each other. In conventional machines the mechanisms are 
provided with a common mechanical drive but this imposes a severe 
restriction on the design of such machines. If, however, the mechanisms on 
opposite sides of the base material are both driven by a solenoid drive as 
shown in FIG. 1, the timing and associated controls can be remotely 
mounted and require only electrical connections. The electronic control of 
the voltages applied to the solenoid coils 11, 12 can also provide a 
remote timing function for an electrical drive for those parts of the 
stitching mechanism operating on the opposite side of the base material.