EP2107147A1 - Device and method for preparing at least one thread in a backstitch sewing machine - Google Patents

Abstract

The device has thread guides (12, 13) i.e. thread eyes, driven with a predetermined frequency in an oscillating manner, and a deflection device (19) fixable relative to the thread guides. The deflection device for needle threads (6) is arranged in a region of the thread guides, and has deflectors (22) arranged in front of and after the guides in a conveying direction of the needle threads to a needle (5), respectively. The guides are movable along a movement path, which crosses an imaginary plane (23) fixed between the deflectors. An independent claim is also included for a method for operating a backstitch sewing machine.

Description

The invention relates to a device for providing at least one needle thread in a lockstitch sewing machine, in particular a lockstitch sewing machine, with a first thread guide and a second thread guide, which are driven to oscillate at a certain frequency, wherein the needle thread from the first thread guide to the second thread guide and of the second thread guide extends to an oscillating in a certain frequency moving needle. The invention further relates to a method for operating a lockstitch sewing machine, in particular a lockstitch sewing machine, namely for feeding at least one needle thread, in which the needle thread is withdrawn from a storage device and fed to a driven with a specific frequency needle, wherein the needle thread from the storage device coming from a first Thread guide and subsequently a second thread guide is supplied, from where the needle thread of the needle is supplied and wherein at least one, in particular both thread guide (s) is driven to oscillate in a certain frequency or be.

Finally, the subject of the invention is a thread take-up for a sewing machine, preferably for a multi-needle lockstitch machine, with at least one oscillating moved needle and two thread guides for one thread, namely upper thread, the thread guides at a distance from each other to two about its longitudinal axis back and forth Shafts are fastened, wherein furthermore the shafts for the purpose of generating the oscillating movements are each driven swinging by a crank and wherein the cranks are designed and matched to each other, that a thread tightening is generated by the oscillating movements.

It is known from the prior art that sewing machines, in particular lockstitch sewing machines, operate according to the two-thread system, in each case two Threads, namely an upper thread and a lower thread, are linked together. If such lockstitch sewing machines are designed as multi-needle machines, a large number of upper threads are present, which are guided individually to the corresponding needles. For reasons of needle movement and, in particular, the knotting process, each upper thread must be given a certain movement, namely, the upper thread must be tightened quickly to obtain a firm knot in rapid succession, while the return of the upper thread in the time interval between the tightening cycles relative should be slow. In this case, an excessive use of the upper threads must be avoided in order not to run the risk of the upper threads breaking. The upper thread can also be called a needle thread.

It is also known that the real need for the upper thread guide does not correspond to a movement according to a sine curve, but rather that the upper thread should be pulled off quickly in order to obtain a firm knot in rapid succession, while, as already stated above, the return of the Upper thread in the time interval between the tightening strokes should proceed relatively slowly. It is known that a crack of the upper thread is not to be expected during a fast thread tightening, but especially if the upper thread is not given enough slowly in the time interval between the tightening cycles, otherwise a strong tension of the thread occurs and thus the risk that the thread breaks.

From the DE 2 247 050 C3 is a thread take-up device for sewing machines, in particular for multi-needle lockstitch sewing machines, wherein the upper thread passes through two thread guides, which are fixed at a distance from each other on two longitudinal axes about herschwenkbaren waves, further wherein the waves for the purpose of generating the oscillating movements of a respective crank mechanism are driven and wherein finally the crank mechanisms are designed and matched to one another that is generated by the oscillating movements of the thread suit. In this previously known thread feeder, it is provided that one of the two thread guides can be driven with a frequency which is different from the frequency of the needle by a whole multiple, the amplitudes of the two thread guides being in a very specific relationship. The adjustability of the amplitudes of the thread guides is achieved by rods are hinged adjustable to drive levers. It is also known that in this thread take-up the amplitude ratio of the two thread guides is 1: 1/3 to 1: 2/3.

With such a thread take-up movements of the two associated thread guides are possible, which allows the operation of such a lockstitch sewing machine with relatively high speeds, the risk of thread breakage is relatively low. Due to the used in the previously known thread encoder crank mechanisms eyelets lead sinusoidal movements, with the two eyelets of the thread guides perform movements of different sine lines. The frequency of one eyelet corresponds to the needle frequency, while the frequency of the other eyelet is in an even integer ratio to the frequency of the first eyelet. In addition, a certain stroke ratio of the two eyelets is provided. The addition of the respective stroke values of the two sine curves then results in a resulting curve which corresponds to the thread profile. Preferably, the resulting curve steeply falls within a relatively small angular range from a maximum to a minimum, which in practice corresponds to a fast Fadenanzug while each between these steep curve pieces is given a flat curve, which corresponds to a relatively slow yarn return.

The technology described above has basically proven itself in practice, but reaches its limits with increasing sewing speeds. It can be observed in particular that vibrations are generated at higher drive speeds of the needles and thus also the thread guides, which are transmitted to the entire drive system, so that an accurate guidance of the thread guides is no longer possible with the required accuracy.

Based on this prior art, the invention is therefore an object of the invention to provide a device for providing at least one thread in a lockstitch sewing machine or a method for operating a lockstitch sewing machine, with or with the high-speed multi-needle stitch sewing machines, in particular multi-needle lockstitch Sewing machines can be operated, the forces occurring and the associated vibrations of the components can be reduced to a minimum.

To solve this problem , it is provided in a device according to the invention that at least in the region of a thread guide a fixable relative to the thread guide deflection device is arranged for the needle thread, which has at least two deflections, of which a deflection in the yarn conveying direction to the needle in front of the yarn guide and a deflection is arranged in the thread conveying direction to the needle after the thread guide and the thread guide is moved along a movement path which intersects an imaginary plane spanned between the deflections.

To solve the above-described problem is provided in a method according to the invention that the needle thread is passed over at least one deflection with two deflections and that the thread guide with the thread along an imaginary plane spanned between the deflections imaginary plane moving path is oscillating, wherein the movement path has two turning points, which lie on both sides of the imaginary plane.

Finally, the abovementioned task is inventively achieved in a thread take-up for a sewing machine in that both thread guides are driven at the frequency of the needle and that at least in the region of a thread guide a relatively fixed to the thread guide deflection device for the needle thread is arranged, the at least two Deflections has, of which a deflection in the conveying direction of the needle thread to the needle before the thread guide and a deflection in the conveying direction of the needle thread to the needle after the thread guide is arranged and the thread guide is moved along a movement path which intersects an imaginary plane spanned between the deflections.

This is a key feature of the invention, since the drive speed of the thread guide can be maintained by the additional deflection and at the same time the frequency of the resulting from thread guide and thread deflection yarn curve is doubled. An addition of the substantially sinusoidal movements of the two yarn guides thus results in a resulting yarn curve, which in a thread-gentle operation, the previously known advantages, for example, a take-up according to the DE 2 247 050 C3 provides, however, a significantly increased operating speed of the lockstitch sewing machine without accompanying complementary natural vibration of the construction elements is possible.

Thus, a significant improvement is achieved with the device according to the invention, the method according to the invention or a thread take-up according to the invention in that a higher needle frequency and thus a higher sewing speed are possible.

In a device according to the invention, it has proven to be advantageous according to a further development to arrange the first thread guide below the second thread guide and to guide the needle thread along a substantially S-shaped path. With this embodiment, not only a space limited system is provided, but also achieved the advantage that the two essential requirements for a smooth sewing process are met, namely the provision of a sufficiently long needle thread, which is grasped with a rotary gripper and linked to the lower thread and then a sufficient stroke of the thread guide to pull the needle thread with sufficient force from the fabric.

According to a further feature of the invention, it is provided that the frequency of the needle movement corresponds to the frequency of the oscillating movement of at least one thread guide. In this embodiment, it is particularly advantageous that the matching frequencies do not lead to excessive resonance vibrations, so that the need for vibration-compensating measures in a lockstitch sewing machine can be kept low.

The deflections may be formed as eyelets or rods, wherein the rods preferably have a round cross-section. In the case of multi-needle sewing machines, the bar embodiment has proven to be effective since these rods can extend over a plurality of needles, with a configuration in which the rods extend over the entire length of the sewing area of such a lockstitch sewing machine.

The deflection device is preferably fastened to a machine frame of the lockstitch machine. Preferably, the deflection device is adjustable relative to the machine frame and fixable in different positions. By this configuration, the movement path of the thread guide can be adjusted relative to the deflection, so that different courses of substantially sinusoidal movements depending on the further construction of the lockstitch sewing machine, namely, for example, the gripper, the sewing process and the stitch formation can be set. In this way, the course of the substantially sinusoidal movements of the thread guides with respect to a fast thread tightening and a relatively slow yarn return can be accurately adjusted.

The movement path of the thread guide runs essentially in the middle between the deflections of the deflection device. However, it is also possible here to make this orientation of the thread guide adjustable relative to the deflections in order to be able to make influences on the movement sequences of the threads with regard to a fast thread tightening and a relatively slow thread return.

Further adjustment possibilities result in an advantageous manner in that the thread guides are moved in an oscillating manner with different frequencies. On the one hand, there is the possibility of being able to set the different frequencies and, on the other hand, it is possible, via these different frequencies, to set the thread suit and the thread return as a function of the machine parameters.

In accordance with the above statements on the design of the deflections is also possible to form the thread guide as an eyelet or rod, which preferably has a round cross-section. A training this Embodiment provides that at least the, a movement path between the deflections continuous thread guide is formed of two parallel and spaced-apart rods. The thread is guided in this embodiment between the two rods, these rods should have a surface with low frictional resistance, so that the thread runs with the least possible frictional resistance on the rods. It has been shown that in such an embodiment, the rods in cross-section need not be circular. It is already sufficient if the rods are rounded in the area of their mutually facing surfaces, so that the rods can furthermore have a cross section deviating from a circular cross section. Of course, it is also possible here to select a different cross-section, which is for example elliptical, partially elliptical or parabolic.

The above features of the embodiments and advantageous developments of the device according to the invention are particularly suitable for carrying out the method according to the invention. In the method according to the invention is provided for further development that the needle is driven at a frequency corresponding to the oscillating movement of the thread guide. It can be provided that the needle is driven at a frequency corresponding to the frequency of both thread guides or only a thread guide.

The thread guides can also be moved in an oscillating manner with different frequencies in order to allow an advantageous thread suit and a favorable thread return.

The deflection device is preferably fixed relative to the thread guide as a function of a desired, substantially sinusoidal course of movement of the first and / or second thread guide, wherein the adjustment of the deflection device can take place in a region which corresponds to the length of the movement path of the thread guide.

Finally, it has proved to be advantageous that the thread guide is guided substantially centrally through the imaginary plane between the deflections of the deflection.

Further advantages and features of the invention will become apparent from the following description of the accompanying drawings in which preferred embodiments of a device according to the invention are shown.

Figur 1

ein Nähaggregat einer Vielnadelsteppstichnähmaschine mit einer Vorrichtung zur Bereitstellung eines Fadens in Seitenansicht und

Figur 2

ein Nähaggregat einer Steppstichnähmaschine mit einer Vorrichtung zur Bereitstellung eines Fadens in einer zweiten Ausführungsform in Seitenansicht.

Figur 3

eine vergrößerte Darstellung des Nähaggregats gemäß Figur 1;

Figur 4

eine vergrößerte Darstellung des Nähaggregats in einer dritten Ausführungsform;

Figur 5

eine vergrößerte Darstellung des Nähaggregats gemäß Figur 2;

Figur 6

die beiden Fadenführungen des Nähaggregats gemäß Figur 1 in einer ersten Stellung;

Figur 7

die beiden Fadenführungen gemäße Figur 6 in einer zweiten Stellung und

Figur 8

die beiden Fadenführungen gemäß den Figuren 6 und 7 in einer dritten Stellung.

In the drawing show:

FIG. 1

a sewing unit of a multi-needle stitch sewing machine with a device for providing a thread in side view and

FIG. 2

a sewing unit of a lockstitch sewing machine with a device for providing a thread in a second embodiment in side view.

FIG. 3

an enlarged view of the sewing unit according to FIG. 1 ;

FIG. 4

an enlarged view of the sewing unit in a third embodiment;

FIG. 5

an enlarged view of the sewing unit according to FIG. 2 ;

FIG. 6

the two thread guides of the sewing unit according to FIG. 1 in a first position;

FIG. 7

the two thread guides gemäße FIG. 6 in a second position and

FIG. 8

the two thread guides according to the FIGS. 6 and 7 in a third position.

In FIG. 1 a sewing unit 1 a lockstitch sewing machine is shown in side view. The sewing unit 1 has a needle carrier 2, which has in the region of its longitudinal edges needle holder 4 with interchangeable arranged needles 5. The needle carrier 2 is shown in side view and extends into the image plane, so that along its longitudinal edges a plurality of needle holders 4 are arranged with needles 5. FIG. 1 shows by way of example a needle 5 to which a thread 6 is fed, which thread 6 is withdrawn from a storage device (not shown), for example in the form of a thread spool.

The needle carrier 2 is connected to a rotationally oscillating moving drive 7, which moves the needle carrier 2 parallel to the longitudinal axis of the needles 5 and up. The drive 7 consists of a rotationally oscillating moving shaft 8 and a connecting cam 9 which is rotatably mounted on the shaft 8 and connected to one end of the needle carrier 2 via a screw connection.

To guide the needle carrier 2, a handlebar 10 is further provided, on the one hand articulated on the needle carrier 12 and on the other hand articulated on the machine frame eleventh is attached.

The sewing unit 1 also has a device for providing the thread 6, which has a first thread guide 12 and a second thread guide 13. The first thread guide 12 consists of two spaced apart and parallel aligned rods 14, between which the thread 6 runs. The rods 14 extend parallel over the entire length of the sewing unit 1. The rods 14 are arranged at a free end of an L-shaped lever 15 which is rotatably connected to a rotationally driven shaft 16 driven.

The second thread guide 13 also consists of a rod 14 which is arranged at a free end of a lever 15 arranged above the lever 17 and also extends over the entire length of the sewing unit 1, wherein the lever 17 is rotatably connected to a shaft 18, which is rotationally driven.

In the FIG. 1 shown device for providing the thread 6 also has a deflecting device 19, which consists of a substantially U-shaped support 20, which in each case has a deflection formed as a rod 22 at its legs in the region of the free ends of these legs. The carrier 20 is connected via a cantilever 21 to the machine frame 11.

Between the deflections 22 of the deflection 19 an imaginary plane 23 is spanned.

In FIG. 3 is the sewing unit 1 according to FIG. 1 shown in detail, wherein in addition the rotational vibration movement directions of the shafts 8, 16 and 18 are represented by corresponding circular arc segment-shaped double arrows. In addition, the thread 6 has an arrowhead which indicates the usual conveying direction of the thread 6. Finally, a double arrow is also provided in the region of the right needle 5, which indicates the directions of movement of the needle carrier 2.

• Während des Nähvorgangs wird der Nadelträger 2 von der Welle 8 über den Verbindungsnocken 9 oszillierend auf- und abbewegt. Der Faden 6 wird während des Nähvorgangs der nicht näher dargestellten Bevorratungseinrichtung entnommen und einer ersten Umlenkung 22 der Umlenkeinrichtung 19 und anschießend der ersten Fadenführung 12 zugeführt, wobei der Faden 6 zwischen den beiden Stangen 14 der ersten Fadenführung 12 geführt ist. Von der ersten Fadenführung 12 wird der Faden 6 sodann der zweiten Umlenkung 22 der Umlenkeinrichtung 19 und anschließend der zweiten Fadenführung 13 zugeführt, von wo aus der Faden 6 über zwei Führungselemente 24 der Nadel 5 zugeführt wird.

The operation of the apparatus described above is as follows:

• During the sewing process, the needle carrier 2 is oscillated up and down by the shaft 8 via the connecting cam 9. The thread 6 is removed during the sewing process of the storage device, not shown, and a first deflection 22 of the deflecting device 19 and subsequently fed to the first thread guide 12, wherein the thread 6 is guided between the two rods 14 of the first thread guide 12. From the first thread guide 12, the thread 6 is then the second Deflection 22 of the deflecting device 19 and then fed to the second yarn guide 13, from where the yarn 6 is supplied via two guide elements 24 of the needle 5.

The first thread guide 12 and the second thread guide 13 are driven in an oscillating manner via the shafts 16 and 18 such that they likewise perform an up and down movement. Here, the first thread guide 12 is moved in such oscillating that the two rods 14 between a first position below the deflecting device 19 and an upper position, represented by the reference numeral 12 ', above the deflecting device 19 is moved, so that the first yarn guide 12 along a Moving path is performed, which intersects the spanned between the deflections 22 imaginary plane 23. (please refer FIGS. 3 to 8 )

In this embodiment, the thread is moved at twice the frequency of the actual thread guide.

The frequency of the first thread guide 12 corresponds to the frequency of the oscillating up and down movement of the needle holder 4 and thus the needles. 5

In addition, the second thread guide 13 can be driven to oscillate at a frequency which coincides both with the frequency of the first thread guide 12 and the frequency of the needle holder 4. However, it is also possible here to set the frequency of the second thread guide 13 differently from the frequency of the first thread guide 12 in order to be able to adapt the course of the added sinusoidal movement paths of the two thread guides 12 and 13 to one another.

It is further provided that the cantilever 21 with the carrier 20 in different positions relative to the machine frame 11 can be attached thereto. Preferably, a stepless adjustment is provided for this purpose, so that in this way the course of the imaginary plane 23 relative to inflection points of the first thread guide 12 is adjustable.

The above-described apparatus, and in particular also the method described above, makes it possible to set a resulting curve from the movements of the two thread guides 12 and 13, which falls steeply within a relatively small angular range from a maximum to a minimum, which in practice is a fast thread take-up corresponds, while in each case between these steep curve pieces a flat curve is given, which corresponds to a relatively slow yarn return in practice.

In FIG. 2 a second embodiment of the sewing unit 1 is shown. In this second embodiment according to FIG. 2 are with the embodiment according to FIG. 1 matching design elements with identical reference numerals.

The embodiment according to FIG. 2 corresponds structurally and in terms of their operation essentially the embodiment according to FIG. 1 However, in addition to the second thread guide 13 has a second deflection 19 'with deflections 22', between which a further imaginary plane 23 'is formed.

According to this embodiment FIG. 2 Accordingly, the second thread guide 13 corresponding to the first thread guide 12 according to FIG. 1 but also according to FIG. 2 guided on a path of movement, which intersects between the deflections 22 'imaginary plane 23' intersects. As a result, the movement of the second thread guide 13 with a certain frequency in a substantially sinusoidal curve with twice the frequency is shown.

FIG. 4 shows a further embodiment of a sewing unit 1, which substantially with the embodiment according to the FIG. 3 matches, but the lever 15 and the deflector 19 is disposed above the lever 17 with the thread guide 13.

In FIG. 5 Then, another embodiment of the sewing unit 1 is shown, with the embodiment of the sewing unit according to FIG. 2 However, in addition, with respect to the FIG. 3 described directions of movement of the individual construction elements are supplemented by arrows.

Finally, the show FIGS. 6 to 8 the levers 17 and 15 in different positions relative to the cantilever 21, so that the movement starting in FIG. 6 about the FIG. 7 in the position of FIG. 8 can be seen.

LIST OF REFERENCE NUMBERS

1

sewing unit

2

needle carrier

4

needle holder

5

needle

6

thread

7

drive

8th

wave

9

link cams

10

handlebars

11

machine frame

12, 12 '

thread guide

13

thread guide

14

pole

15

lever

16

wave

17

lever

18

wave

19, 19 '

deflecting

20

carrier

21

cantilever

22, 22 '

deflections

23.23 '

level

24

guide element

Claims (21)

Apparatus for providing at least one needle thread in a lockstitch sewing machine, in particular a lockstitch sewing machine, with a first thread guide and a second thread guide, which are driven to oscillate at a certain frequency, wherein the needle thread from the first thread guide to the second thread guide and from the second thread guide to a oscillating in a certain frequency moving needle runs,
characterized,
in that at least in the region of a thread guide (12, 13) a deflecting device (19, 19 ') fixable relative to the thread guide (12, 13) is arranged for the needle thread (6), which has at least two deflections (22, 22') a deflection (22, 22 ') in the conveying direction of the needle thread (6) to the needle (5) in front of the thread guide (12, 13) and a deflection (22, 22') in the conveying direction of the needle thread (6) to the needle (5) is arranged after the thread guide (12, 13) and the thread guide (12, 13) is moved along a movement path which intersects between the deflections (22, 22 ') imaginary plane (23, 23') intersects. Apparatus according to claim 1, characterized in that the first thread guide (12) below the second thread guide (13) and the needle thread (6) is guided along a substantially S-shaped path. Apparatus according to claim 1, characterized in that the frequency of the needle movement of the frequency of the oscillating movement of at least one, preferably both yarn guide (s) (12, 13). Apparatus according to claim 1, characterized in that at least one deflection (22, 22 ') is designed as an eyelet. Apparatus according to claim 1, characterized in that at least one deflection (22, 22 ') is designed as a rod, which preferably has a round cross-section. Apparatus according to claim 1, characterized in that the deflection device (19, 19 ') is fastened to a machine frame (11) of the lockstitch machine. Apparatus according to claim 6, characterized in that the deflection device (19, 19 ') relative to the machine frame (11) is adjustable and fixable in different positions. Apparatus according to claim 1, characterized in that the movement path of the thread guide (12, 13) substantially centrally between the deflections (22, 22 ') of the deflection device (19, 19') extends. Apparatus according to claim 1, characterized in that the thread guides (12, 13) are oscillated with the same frequencies. Apparatus according to claim 1, characterized in that the thread guides (12, 13) are oscillated with different frequencies. Apparatus according to claim 1, characterized in that at least one thread guide (12, 13 ') is designed as an eyelet. Apparatus according to claim 1, characterized in that at least one thread guide (12, 13 ') as a rod (14) is formed, which preferably has a round cross-section. Apparatus according to claim 12, characterized in that at least the, a movement path between the deflections (22, 22 ') passing through thread guide (12, 13) of two parallel and spaced apart extending rods (14) is formed. Device according to one of claims 5, 12 or 13, characterized in that the rod (s) (14) extends or extend at least over a partial area of a needle carrier (2) with a plurality, at least two needles (5). Apparatus according to claim 1, characterized in that the deflections (22, 22 ') of the deflecting device (19, 19') at free ends of legs of a U-shaped support (20) are arranged. Method for operating a lockstitch sewing machine, in particular a lockstitch sewing machine, namely for feeding at least one needle thread, in which the needle thread is withdrawn from a stocking device and one with a needle driven to a specific frequency, the needle thread being fed from the storage device to a first thread guide and subsequently to a second thread guide from where the needle thread is fed to the needle and at least one, in particular both thread guide (s) oscillating in one driven by a specific frequency,
characterized in that the needle thread (6) is guided via at least one deflecting device (19, 19 ') with two deflections (22, 22') and that the thread guide (12, 13) with the needle thread (6) along one between the Deflection (22, 22 ') spanned imaginary plane (23, 23') cutting movement path is oscillated, wherein the movement path has two inflection points, which lie on both sides of the imaginary plane (23, 23 '). A method according to claim 15, characterized in that the needle (5) is driven at a frequency which corresponds to the frequency of the oscillating movement of the thread guide (s) (12, 13). A method according to claim 16, characterized in that the thread guides (12, 13) are moved oscillatingly with different frequencies. A method according to claim 16, characterized in that the deflection device (19, 19 ') is fixed relative to a desired substantially sinusoidal course of the first and / or second thread guide (12, 13) relative to the thread guide (12, 13), wherein the setting the deflection device (19, 19 ') can take place in a region which corresponds to the length of the movement path of the thread guide (12, 13). A method according to claim 16, characterized in that the thread guide (12, 13) is guided substantially centrally through the imaginary plane (23, 23 ') between the deflections (22, 22') of the deflection device (19, 19 '). Yarn feeder for a sewing machine, preferably for a multi-needle double stitch machine, with at least one oscillating moved needle and two thread guides for each needle thread, namely upper thread, wherein the thread guides are fixed at a distance from each other on two about its longitudinal axis back and forth swivel shafts, further the waves for the purpose of generation the oscillating movements are each driven by a crank and wherein the cranks are designed and matched to one another such that a thread suit is produced by the oscillating movements,
characterized,
in that both thread guides (12, 13) are driven at the frequency of the needle (5) and that at least in the region of a thread guide (12, 13) a deflecting device (19, 19 ') for the needle thread which can be fixed relative to the thread guide (12, 13) (6) is arranged, which has at least two deflections (22, 22 '), of which a deflection (22, 22') in the conveying direction of the needle thread (6) to the needle (5) in front of the thread guide (12, 13) and a Deflection (22, 22 ') in the conveying direction of the needle thread (6) to the needle (5) after the thread guide (12, 13) is arranged and the thread guide (12,13) is moved along a path of movement, one between the deflections (22 , 22 ') intersected imaginary plane (23, 23') intersects.

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