JPH07231992A - Full-rotating bobbin case - Google Patents

Abstract

PURPOSE:To obtain a full-rotating bobbin case which prevents a rotating hook from clattering to allow the rotating hook to smoothly rotate at high speeds for a long term. CONSTITUTION:A rotating hook 2 is turned on a rotation axis L1 at high speeds and the whole or part of it, including a rail guide groove 28, is made of synthetic resin having a low frictional property. A bobbin case holder 6 is made of metal and has a rail 8 around the circumference, and the rotating hook 2 rotates with the rail 8 fitted in the guide groove 28. Therefore, although the rail 8 slides at high speeds along the inner face of the rail guide groove 28 made of synthetic resin having a low frictional property, the amount of wearing is considerably reduced because of the low frictional property even when the rotating hook 2 rotates at a high speed for a long period of time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a full rotary hook provided in a lockstitch sewing machine or the like.

[0002]

2. Description of the Related Art A rail is formed on the outer peripheral surface of an inner hook provided in a lockstitch sewing machine or the like. This rail is fitted in a rail groove formed on the inner peripheral surface of the outer hook. The inner hook is fixed to the machine body of the sewing machine and is fixed by a hook stopper member that fits into a hook stopper recess formed in the inner hook, and only the outer hook is rotationally driven at high speed. Particularly, the outer hook of an industrial sewing machine is rotationally driven at a high speed of about 6000 to 10000 rpm. Therefore, the sliding surface may generate heat due to the sliding of the rail and the rail groove, and seizure between the inner hook and the outer hook may occur. If the friction between the rail and the rail groove is large, the hook stopping member that blocks the rotation of the inner hook and the inner surface of the hook stopping recess of the inner hook make contact with each other with a large force, so that the needle thread comes off. Cannot be done smoothly. As a result, the tension of the needle thread is changed undesirably, the quality of the sewing is degraded, and the rail and the groove are worn, resulting in a decrease in durability.

Further, when the amount of wear becomes large due to long-term use, the inner peripheral surface of the rail groove and the outer peripheral surface of the rail do not evenly wear in the circumferential direction, so if the contact pressure between the rail and the rail groove is uniform. However, there is a problem that vibration occurs when the outer hook rotates, and it becomes impossible to rotationally drive the outer hook at high speed.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a full rotary hook which is capable of smoothly rotating an outer hook at a high speed for a long period of time by reducing wear of rails and rail grooves as much as possible. Is to provide.

[0005]

SUMMARY OF THE INVENTION According to the present invention, a rail of an inner hook made of metal is fitted in a groove of an outer hook, and the outer hook is rotated around its rotation axis while the rotation of the inner hook is prevented. In all driven rotary hooks, the entire outer hook or at least a part including the groove is made of synthetic resin having a small friction coefficient.

Further, the present invention is characterized in that the synthetic resin having a small friction coefficient is a liquid crystal polymer.

Further, according to the present invention, the rail of the inner hook made of metal is fitted into the groove of the outer hook, and the outer hook is rotated about its rotation axis while the inner hook is prevented from rotating. In the rotary hook, the outer rotary hook is fixed to an outer rotary hook main body in which a concave groove is formed on an inner peripheral surface, and is fixed in a concave groove of the external rotary hook main body,
Including a sliding member having the rail groove, the sliding member,
There are even full revolutions characterized by being made of synthetic resin with a low coefficient of friction.

Further, the present invention is characterized in that the synthetic resin having a small friction coefficient is a liquid crystal polymer.

Furthermore, the present invention is characterized in that the synthetic resin having a small coefficient of friction includes a powder made of a metal powder, a ceramic powder, or another material having high hardness and wear resistance.

[0010]

According to the present invention, a rail groove is formed in the outer hook,
A rail is formed in the inner hook, and this rail is fitted into the rail groove, and the outer hook is rotationally driven around its rotation axis while the rotation of the inner hook is blocked. At least a part of the outer rotary hook including the rail, that is, the entire outer rotary hook or a portion forming the rail groove is formed of a synthetic resin having a small friction coefficient. Therefore, the friction between the inner hook rail and the outer hook rail made of metal can be reduced to reduce the amount of wear. By reducing the wear in this way, it is possible to eliminate the occurrence of vibration during the outer hook rotation due to uneven wear. Further, since the friction between the rail and the rail groove is low, heat generation due to this friction is small and seizure does not occur.

According to the invention, a liquid crystal polymer is used as the synthetic resin having a small friction coefficient. Since this liquid crystal polymer has an extremely high heat distortion temperature and a low linear expansion coefficient, it has dimensional stability equivalent to that of a metal, and can be manufactured into an outer hook by, for example, outsert molding. During this manufacturing, the dimensional change is extremely small, and the manufacturing can be performed with high accuracy. As a result, uneven wear of the rail groove and the sliding surface of the rail does not occur, and therefore vibration of wear can be eliminated. Further, by forming the outer hook in whole or in part with a liquid crystal polymer, no metallic noise is generated when the outer hook is rotated, and it is possible to reduce the occurrence of the hook noise during sewing.

Further, according to the present invention, the outer hook is constituted by the outer hook main body and the sliding member. The sliding member is made of synthetic resin having a small coefficient of friction, and can be integrally formed on the outer hook body by insert molding, for example. The rail is fitted into the rail groove of the sliding member, the wear amount of the rail and the rail groove is reduced, and the outer roller can be stably rotated at high speed.

Further according to the present invention, a liquid crystal polymer is used as the synthetic resin having a small friction coefficient which constitutes the sliding member. Such a liquid crystal polymer has an extremely low heat distortion temperature and an extremely small linear expansion coefficient, and has dimensional stability equivalent to that of a metal. This makes it possible to form the sliding member with a high degree of dimensional accuracy and eliminate the occurrence of vibration when the outer hook is rotated.

Further, according to the present invention, as the synthetic resin having a small friction coefficient which constitutes the sliding member, a synthetic resin containing metal powder, ceramic powder or powder made of other material having high hardness and abrasion resistance is used. To be This also reduces the amount of wear of the rail groove and the rail, and makes it possible to rotate the outer hook stably and at high speed.

[0015]

1 is a sectional view showing the entire construction of a full rotary hook 1 according to an embodiment of the present invention, and FIG. 2 is a full rotary hook 1 shown in FIG.
FIG. The outer hook 2 has a horizontal rotation axis L1.
A rotary shaft 4 which is rotationally driven in the direction of an arrow 3 is fixed by a bolt 5 and is rotationally driven about a common rotary axis with the rotary axis L1 of the rotary shaft 4. The inner hook 6 is housed in such an outer hook 2.

The inner hook 6 has a tubular portion 7, a rail 8 formed on the outer periphery of the tubular portion 7, and an inner hook of the tubular portion 7 formed at one end on the open end side (right side in FIG. 1). It has a flange portion 10 having a detent recess 9, and a bottom portion 11 called a bridge formed at the other end of the tubular portion 7 so as to extend in the one-diameter line direction. A stud 12 is provided upright on the bottom portion 11 so as to extend coaxially with the tubular portion 7 toward the inner hook open end side. The stud 12 has a bobbin 13 inserted therethrough, and a bobbin case 14 is engaged with the tip portion thereof. The bobbin case 14 has a bottomed tubular shape,
The operation piece 15 is provided on the bottom portion 14a exposed from the open end of the inner hook.
1 and a latch piece 16 that can be displaced in a direction perpendicular to the paper surface of FIG. 1 by an angular displacement operation of the operation piece 15. The latch piece 16 has a groove 17 formed at the tip of the stud 16. Engage with. The operation piece 15 is shown in FIG.
By angularly displacing the latch piece 16 toward the front side when viewed from the right side, the latch piece 16 is displaced toward the front side perpendicular to the paper surface of FIG.
The engagement state with 7 can be released. In this way, when the bobbin case 14 is released from the state in which the bobbin case 14 is locked, and when the bobbin thread 18 wound on the bobbin 13 is consumed, the bobbin 13 together with the bobbin case 14 is removed. It is possible to remove the bobbin from 6 and replace it with a bobbin in which the lower thread is newly wound.

A protrusion 20 of an inner hook retaining member 19 fixed to the machine body of a sewing machine (not shown) is fitted in the inner hook stopping recess 9 of the flange portion 10 to allow the inner hook to rotate when the outer hook rotates. The rotation of 6 is blocked. A needle drop hole 21 is formed in the cylindrical portion 7, and an axis L2 perpendicular to the rotation axis L1 is formed.
A needle 22 that reciprocates in synchronization with the rotating operation of the rotating shaft 4 and the outer hook 2 is inserted through the upper portion. The needle thread 23 inserted into the needle 22 by the needle 22 is caught by a sword tip 24 provided on the outer hook 2 and passes over the inner hook 6 to form one stitch. The inner hook 6, bobbin 13 and bobbin case 14 are made of stainless steel or steel.

The outer hook 2 has a tubular portion 25 to which a sword tip 24 is fixed by a screw or the like (not shown), and a base portion 26 integrally formed with the tubular portion 25 and into which the rotary shaft 4 is inserted.
And an inner hook holding piece 27 fixed to the open end of the tubular portion 25 by a screw or the like (not shown). Tube 2
A rail groove 28 into which the rail 8 is fitted is formed on the inner circumference of the rail 5. The outer hook 2 is entirely made of a liquid crystal polymer which is a synthetic resin having a small friction coefficient.

The liquid crystal polymer has a rod-shaped rigid component in the main chain of the polymer and a large intermolecular force between the rigid linear components,
In addition, since it is well oriented and crystallized at the time of molding, its heat resistance is extremely excellent.
Even if the temperature rises due to the friction with the inner hook due to the rotation of, the heat deformation temperature is extremely high, so that it does not deform. Further, the liquid crystal polymer has a high strength and a high elastic modulus because it is made of a rigid molecular chain and is highly oriented in the flow direction during molding, and the molecular chains are arranged in a fully extended state in the orientation direction. Therefore, even if a tensile force is applied, it does not extend any further and exhibits excellent creep characteristics. The coefficient of linear expansion is extremely small, and particularly the coefficient of linear expansion in the flow direction is about 1 × 10 ⁻⁵ cm / cm / ° C. Such a linear expansion coefficient is one digit lower than that of other synthetic resins, and it is possible to obtain dimensional stability equivalent to that of metal. From this, the dimensional change due to the difference in environmental temperature and humidity such as summer and winter is almost zero. Further, since this liquid crystal polymer has high weather resistance, it can be used for a long time. Further, the liquid crystal polymer has a similar structure in a molten state and a solidified state, and therefore has a small phase change and a small volume change when solidified.

As a characteristic of the liquid crystal polymer, there is a characteristic of damping vibration. Generally, a soft material such as rubber is excellent in the property of damping vibration, but the liquid crystal polymer has a large vibration damping property while having a high elastic modulus. In order to improve the abrasion resistance, 30% of carbon fiber may be mixed with the liquid crystal polymer in order to reduce the specific abrasion amount and the dynamic friction coefficient. The liquid crystal polymer is a copolymer of para-hydroxybenzoic acid and 2-hydroxy-6-naphthoic acid. As another material, two or more kinds of naphthalene groups may be used as a constituent component of the main chain bond and a copolymer with another constituent component may be used. The naphthalene group is
1.2th, 1.4th, 1.5th, 1.8th, 2.3th,
It is a compound having a functional group at two or more substitution positions selected from the 2.6-position and the 2.7-position, and the functional group may be a functional group capable of forming a polyester and / or a polyesteramide. That is, the functional group is a hydroxy group,
It is selected from a carboxyl group, an amino group, an ester group and the like.

The naphthalene group may be hydroxynaphthoic acid, dihydroxynaphthalene and / or naphthalenecarboxylic acid.

The constituents other than the naphthalene group are the p-position phenyl group, the 4,4'-biphenyl group and / or the general formula of Chemical formula 1, that is,

[0023]

[Chemical 1]

(However, X is alkylene (having 1 to 1 carbon atoms)
4) alkylidene (having 1 to 4 carbon atoms), -O-, -S-,
A group selected from —SO—, —SO ₂ —, and —CO—, R,
R'is a reactive group such as a hydroxy group or a carboxyl group or an ester thereof. ) And a substituted derivative thereof.

The polymer binding unit is preferably an ester and / or an ester amide, and the functional group forming them is selected from a hydroxy group, a carboxyl group, an amino group, an ester group and the like, and preferably terephthalic acid, hydroquinone, p-diacetoxyphenylene, p
-Hydroxybenzoic acid and their esters, 4,
4'-dihydroxybiphenyl, 4,4'-carboxy biphenyl, 4-hydroxy-4'-carboxy biphenyl and esters thereof, of 1 of the general formula X is methylene, propenyl or -SO ₂ - in which each dihydroxy Form, dicarboxyl form, hydroxycarboxy form and esters thereof, and more preferably terephthalic acid, hydroxybenzoic acid, 4,4′-dihydroxybiphenyl, 4,4′-dihydroxybiphenyl and their esters are selected. To be elected.

By using such a liquid crystal polymer, even if the sewing operation is performed at a high speed for a long period of time, the wear of the surfaces of the rails 8 and the rail grooves 28 is extremely small, and the durability can be remarkably improved. Moreover, it is light in weight, and the rotational torque of the rotary shaft 4 is small, which makes it possible to downsize the motor for rotationally driving the rotary shaft 4.

As another embodiment of the present invention, as shown in FIG. 3, a coating film 29 having a thickness of about 0.1 to 0.3 mm is formed as a part of the outer hook 2 including at least the rail groove 28. You may do it. Such a film can be formed by outsert molding a liquid crystal polymer, for example.

In another embodiment of the present invention, polytetrafluoroethylene (abbreviated as PTFE) is preferably used as the synthetic resin having a small friction coefficient. This PTF
E is a tetrafluoroethylene copolymer, which has excellent heat resistance, chemical resistance, and impact resistance, is easy to process, and since such polytetrafluoroethylene is inexpensive, it is possible to use existing polytetrafluoroethylene. The present invention can be implemented at low cost for the outer hook.

FIG. 4 is an enlarged cross-sectional view of a portion near the rail 8 and the rail groove 28 according to still another embodiment of the present invention. In this embodiment, a concave groove 30 is formed on the inner peripheral surface of the outer hook 2 and a sliding member 31 having a U-shaped cross section is fixed in the concave groove 30. The groove 30 has an outer hook 2 at the open end of the tubular portion 7.
A first end face 32 extending in a plane perpendicular to the axis of rotation of
A first inner peripheral surface 33 that extends in a right cylindrical surface that is continuous to the end surface 32 at right angles and that is coaxial with the rotation axis of the outer hook 2, and the inner hook holding piece 2
7, the second inner peripheral surface 35 that extends continuously from the first inner peripheral surface 33 to the inward protruding portion 34, and the first end surface 32 that connects the inner hook inward protruding portion 34 perpendicularly to the second inner peripheral surface 35. And a second end surface 36 that is parallel to and opposite to.

The sliding member 31 is adhered only to the second inner peripheral surface 35 and the second end surface 36 with an adhesive, and not to the first end surface 32 and the first inner peripheral surface 33 of the tubular portion 7. . As a result, when it becomes necessary to remove the sliding member 31 from the groove, the inner hook holding piece 27 is removed from the tubular portion 25, so that the sliding member 31 can be removed from the tubular portion 25. The thickness of the sliding member 31 is, for example, 0.
It is selected to be 3 to 1.2 mm. The thickness of the sliding member 31 is 1.
If it exceeds 2 mm, the outer peripheral portion 3 forming the first inner peripheral surface 33
7 is too thin and its strength is too low to easily deform. Further, if the thickness of the sliding member 31 is less than 0.3 mm, the service life due to wear is shortened and the vibration absorbing effect is reduced. Therefore, the sliding member 31
Has a thickness of 0.3 to 1.2 mm.

The sliding member 31 is made of a liquid crystal polymer, and the liquid crystal polymer is the same as that of the first embodiment.

By using such a liquid crystal polymer, even if the sewing operation is performed at a high speed for a long period of time, the wear of the surfaces of the rails 8 and the groove 28 is extremely small, and the durability can be remarkably improved. Moreover, it is light in weight, and the rotational torque of the rotary shaft 4 is small, which makes it possible to downsize the motor for rotationally driving the rotary shaft 4.

In still another embodiment of the present invention, the sliding member 31 is made of a synthetic resin having a small friction coefficient such as metal powder,
It may be formed from a synthetic resin containing ceramic powder or a powder of other high hardness and wear resistant material.

As the metal powder, an epoxy injection molding resin in which an aluminum powder or an iron powder is filled in an epoxy resin is preferable, whereby the mechanical strength can be improved.

The ceramic powder is generally aluminum oxide (Al ₂ O ₃ ) or a mixture of a small amount of another metal oxide or a binder and press-molded and sintered. It is manufactured by a gas customize method in which it is customized in an atmosphere, and its hardness does not change up to about 1100 ° C. The specific heat is about four times that of cemented carbide, and the thermal conductivity is about half that of cemented carbide, and the thermal expansion is small. Moreover, although cemented carbide is considerably oxidized and denatured at about 1000 ° C or higher, ceramic is stable up to about 2000 ° C, and because it has a low affinity for most metals, it does not easily weld to other objects and wears. It has the property of being strong.

As described above, since a part of the outer hook 2 is formed by injection molding by mixing the ceramic powder and the synthetic resin, the ceramic is a difficult-to-process material, but the injection molding makes it a so-called near net shape. It can be manufactured and the degree of post-processing is greatly reduced. Further, since ceramic has excellent wear resistance and heat resistance, it is possible to provide a sliding member that can be used for a long time.

Other powders made of a material having high hardness and wear resistance may be nickel alloys, superalloys, and alloys obtained by adding carbon powder or carbon fibers. Thus, the sliding member can be formed by injection molding by mixing one or more powders selected from metal powders, ceramic powders, or powders made of a material having high hardness and wear resistance with a synthetic resin. it can. In particular, in the portion where high strength is required in the sliding member, while increasing the mixing ratio of the metal powder, the ceramic powder or the powder made of other material having high hardness and wear resistance to improve the strength, The mixing ratio of each powder may be reduced in a portion that does not require high strength as compared with a portion that requires strength. As a result, the amount of the powder mixed with the synthetic resin can be reduced, the manufacturing cost can be reduced, and the economical efficiency can be improved.

In the above-described embodiment, the vertical full-rotation rotary hook in which the outer rotary hook 2 is rotationally driven around the horizontal rotation axis is described as the full-rotation rotary hook, but as another embodiment of the present invention, it is shown in FIG. Even as a horizontal full rotary hook 41,
The present invention can be preferably implemented. In this full rotary hook 41, an outer hook 43 is fixed to a rotary shaft 42 that is driven to rotate about a vertical rotation axis L3, and an inner hook 44 is housed in the outer hook 43. A rail 45 is formed on the outer circumference of the inner hook 44, and a rail groove 46 into which the rail 45 is fitted is formed on the inner circumference of the inner hook 43. The needle 48 is reciprocated up and down along the axis L4 parallel to the rotation axis L3, and the outer hook 43
The upper thread 23 brought by the needle 48 is caught by the sword tip 49 integrally formed with the needle, and one stitch is formed through the inner hook 44 through the thread.

On the inner surface of the track groove 46, a coating 47 similar to the coating 29 of the embodiment shown in FIG. 3 is formed. The coating 47 is made of a synthetic resin having a small friction coefficient similar to that described above, that is, polytetrafluoroethylene or liquid crystal polymer, and can achieve the same effect as that of the vertical full rotation rotary hook 1.

As still another embodiment of the present invention, the outer hook 43 may be entirely made of a synthetic resin having a small friction coefficient, that is, tetrafluoroethylene or a liquid crystal polymer. Also in this case, the wear of the rail 45 and the rail groove 46 is reduced as much as possible, the bite noise is reduced, and the outer bite 43
It is possible to smoothly rotate the motor at high speed. Moreover, since the rail groove 46 formed by the coating 47 is formed with high accuracy, the rail 45 fitted into the rail groove 46 is formed.
On the other hand, it is possible to obtain a uniform contact pressure in the circumferential direction and prevent uneven wear.

Further, as another embodiment of the present invention, in the horizontal full rotary hook 41, the sliding member 31 similar to the embodiment shown in FIG. 4 may be provided in place of the coating 47. Also in this case, wear of the sliding member and the rail can be reduced and the durability can be improved.

[0042]

As described above, according to the present invention, at least a portion of the outer hook including the rail, that is, the entire outer hook or the portion forming the groove is formed of a synthetic resin having a small friction coefficient. Therefore, the friction between the inner hook rail and the outer hook rail made of metal can be reduced to reduce the amount of wear. By reducing the wear in this way, it is possible to eliminate the occurrence of vibration during the outer hook rotation due to uneven wear. Further, since the friction between the rail and the rail groove is low, heat generation due to this friction is small and seizure does not occur.

According to the invention, a liquid crystal polymer is used as the synthetic resin having a small friction coefficient. Since this liquid crystal polymer has an extremely high heat distortion temperature and a low linear expansion coefficient, it has dimensional stability equivalent to that of a metal, and can be manufactured into an outer hook by, for example, outsert molding. At the time of this manufacturing, there is very little change in vibration, and it is possible to manufacture with a high degree of dimensional accuracy. As a result, uneven wear of the rail groove and the sliding surface of the rail does not occur, and therefore vibration of wear can be eliminated. Further, by forming the outer hook in whole or in part with a liquid crystal polymer, metal noise is not generated during outer rotation, and it is possible to reduce the occurrence of hook noise during sewing.

Further, according to the present invention, the outer hook is constituted by the outer hook main body and the sliding member. The sliding member is made of synthetic resin having a small friction coefficient, and can be integrally formed on the outer hook body by insert molding or outsert molding. The rail is fitted into the rail groove of the sliding member, the wear amount of the rail and the rail groove is reduced, and the outer roller can be stably rotated at high speed.

Furthermore, according to the present invention, a liquid crystal polymer is used as the synthetic resin having a small friction coefficient which constitutes the sliding member. Such a liquid crystal polymer has an extremely low heat distortion temperature and an extremely small linear expansion coefficient, and has dimensional stability equivalent to that of a metal. This makes it possible to form the sliding member with a high degree of dimensional accuracy and eliminate the occurrence of vibration when the outer hook is rotated.

Further, according to the present invention, as the synthetic resin having a small friction coefficient which constitutes the sliding member, a synthetic resin containing metal powder, ceramic powder or powder made of other material having high hardness and abrasion resistance is used. To be This also reduces the amount of wear of the rail groove and the rail, and makes it possible to rotate the outer hook stably and at high speed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an overall configuration of a horizontal full rotary hook 1 according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view of a horizontal full rotary hook 1.

FIG. 3 is an enlarged cross-sectional view of a part of a rail 8 and a rail groove 28 on which a coating film 29 of another embodiment of the present invention is formed.

FIG. 4 is an enlarged cross-sectional view of a portion near a rail 8 and a rail groove 28 having a sliding member 31 according to still another embodiment of the present invention.

FIG. 5: Full horizontal rotary hook 4 according to still another embodiment of the present invention
It is the front view which notched one part which shows 1.

[Explanation of symbols]

 1,41 Full rotary hook 2,43 Outer hook 4,42 Rotating shaft 6,44 Inner hook 13 Bobbin 14 Bobbin case 17 Inner hook holding piece 28,46 Track groove 29,47 Coating 30 Recessed groove 31 Sliding member

Claims (5)

[Claims] 1. A full rotary hook in which a rail of an inner hook made of metal is fitted into a groove of the outer hook and the outer hook is rotationally driven around its rotation axis in a state in which rotation of the inner hook is blocked, The entire outer hook or a part including at least the rail groove,
A full-rotation rotary hook that is made of synthetic resin with a low coefficient of friction. 2. The full rotation rotary hook according to claim 1, wherein the synthetic resin having a small friction coefficient is a liquid crystal polymer. 3. A full-rotation rotary hook in which a rail of an inner rotary hook is fitted into a rail groove of the outer rotary hook, and the outer rotary hook is rotationally driven around its rotation axis in a state where rotation of the inner rotary hook is blocked, The outer hook includes an outer hook body having a groove formed on an inner peripheral surface thereof, and a sliding member fixed in the groove of the outer hook body and having the track groove, wherein the sliding member has a friction coefficient of A full rotary hook which is made of a small synthetic resin. 4. The full rotary hook according to claim 3, wherein the synthetic resin having a small friction coefficient is a liquid crystal polymer. 5. The full rotation according to claim 3, wherein the synthetic resin having a small friction coefficient includes a powder made of a metal powder, a ceramic powder, or another material having high hardness and wear resistance. Kama.