JP2007187178A - Nut for screw fastening - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nut for screw fastening, which can prevent the non-rotation loosening in which the bolt axis force decreases owing to a seating surface depression, a permanent set in fatigue, settling of a member to be fastened, etc., caused after the screw fastening of a member to be fastened, which can prevent the non-rotation loosening caused owing to the back rotation of the nut, and also which can increase the workability when fastening the screw of the member to be fastened. <P>SOLUTION: The nut for screw fastening is provided with a boss having an opening through which a male screw of a bolt passes without screw-engaging to bring predetermined spring characteristics to the nut for fastening in the seating surface side toward the member to be fastened when the member to be fastened is thread-fastened, and a slit tilting in the direction opposite to the tilting direction of the spiral of a female screw with respect to the centerline axis of the nut for thread fastening. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is a screw fastening structure having a bolt and a nut, and is used for a screw fastening structure that fixes a member to be fastened by providing a pretension by rotating and fastening the bolt or nut to the member to be fastened. The present invention relates to a screw fastening nut.

  A screw fastening body having a bolt and a nut and rotating and tightening the bolt or the nut with respect to the member to be fastened is a tensile force (hereinafter referred to as a tensile force generated in a shaft portion of the bolt by the rotational fastening of the bolt or the nut). It is known that they are integrated by a bolt axial force) and a compressive force (hereinafter also referred to as a tightening force) generated in a fastened member. These forces are balanced with each other when no external force is applied to the screw fastening body, and there is a difference between tensile force and compressive force, but the magnitude of the force is the same. Collectively.

  On the other hand, it is also known that the magnitude of the pretension provided to the screw fastening body during the tightening of the bolt or nut may decrease for some reason during long-term use after the initial screw fastening. Such a decrease in pretension is referred to as “screw loosening”. In general, it is known that there are two types of screw loosening. One is the so-called “rotation looseness” that occurs when the bolt or nut is affected by vibrations and the nut returns and rotates. The other is that there is no return rotation of the nut, but there is a so-called “non-rotation looseness”, for example, a looseness caused by a seat surface depression, a sag of a member to be fastened, or a familiarity.

  When tightening screws with bolts and nuts, the tightening torque generated on the shaft of the bolt when the bolt or nut is tightened by rotation, that is, the bolt axial force, must be controlled using a torque wrench or the like. It is generally managed indirectly. However, even when the initial tightening torque management is performed using a torque wrench or the like, during the period of use after the initial tightening, the return rotation of the nut, the seat surface depression, the sag of the fastened member, Rotation looseness or non-rotational looseness that lowers the bolt axial force and lowers the tightening force due to familiarity, etc. may occur, and the original function of the screw fastening structure that fixes the member to be fastened by screw fastening may be impaired This can result in failure of the device assembled using such a screw fastening structure. Therefore, it is possible to suppress as much as possible the decrease in bolt axial force caused by the return rotation of the nut after the initial tightening, the seat surface depression, the sag of the fastened member, the fitting, etc., and prevent the rotation looseness and non-rotational looseness. It is necessary to take measures from what is possible.

  In the prior art, several measures have been proposed to prevent such loose rotation caused by the return rotation of the nut, non-rotational looseness caused by the seat surface depression, the to-be-fastened member sag, or the familiarity. Has been.

  For example, Japanese Patent Laid-Open No. 10-169628 discloses one measure for preventing rotational looseness. Specifically, when the nut is screwed into the bolt, the thin wall portion that is integrally formed around the screw hole on the top surface of the nut and extends substantially in the axial direction is bent, and is engaged with the notch formed in the bolt top portion. Thus, a nut detent device is disclosed that prevents the nut from easily rotating with respect to the bolt due to the thin wall portion.

  Japanese Patent Laid-Open No. 2001-187911 discloses one measure for preventing non-rotational loosening. Specifically, by using a disc spring washer having a predetermined spring property, a screw fastening structure that suppresses a decrease in bolt axial force to the minimum even if a seat surface is depressed, a to-be-fastened member sags or fits in. It is disclosed.

JP-A-10-169628 JP 2001-187911 A

  However, in the nut detent device disclosed in Japanese Patent Application Laid-Open No. 10-169628, it is possible to prevent rotational looseness caused by the return rotation of the nut, but it is possible to prevent the seat surface from being depressed or the member to be fastened. It is not a measure for preventing non-rotational loosening in which the bolt axial force is reduced due to familiarity or the like, and a measure for preventing non-rotational loosening is not mentioned.

  Further, in the screw fastening structure disclosed in Japanese Patent Application Laid-Open No. 2001-187911, it is possible to prevent non-rotational loosening in which the bolt axial force is reduced due to a seating surface depression, a sag of a member to be fastened, conformance, or the like. However, it is not a measure for preventing the loosening of the rotation that occurs when the nut rotates back, and a measure for preventing the loosening of the nut is not mentioned.

  Furthermore, in the screw fastening structure disclosed in Japanese Patent Laid-Open No. 2001-187911, a disc spring washer having a predetermined spring property is required when fastening a member to be fastened as a new component, I think that there is a problem that the work at the time of screw fastening is difficult.

  In view of the above problems, the present invention can prevent non-rotational loosening in which the bolt axial force is reduced due to the seat surface depression occurring after the screw fastening operation of the member to be fastened, the sag of the member to be fastened, or the familiarity. And a screw fastening nut capable of preventing the loosening of rotation caused by the return rotation of the nut, and screw fastening capable of improving workability when fastening a member to be fastened. The purpose is to provide a nut.

  According to the first aspect of the present invention, in the screw fastening nut having the female screw portion for fastening the member to be fastened in cooperation with the male screw portion of the bolt, a predetermined spring property is provided to the screw fastening nut. Therefore, when the member to be fastened is screw-fastened, an opening through which the male screw portion of the bolt passes without being screw-engaged on the seat surface side facing the member to be fastened, and the screw fastening nut There is provided a screw fastening nut comprising a boss portion having a slit inclined in a direction opposite to a spiral inclination direction of the female screw portion with respect to a central axis.

  That is, according to the first aspect of the present invention, in the screw fastening nut having a female screw portion for fastening the fastened member in cooperation with the male screw portion of the bolt, the fastened member is tightened when the fastened member is screwed. A boss portion having a slit formed with an inclination with respect to the central axis of the screw fastening nut is disposed on the seat surface side facing toward the screw fastening nut, thereby providing a predetermined spring property to the screw fastening nut. The screw fastening nut itself can be easily elastically deformed to a predetermined extent, which reduces the bolt axial force caused by the seating surface depression occurring after the screw tightening operation, the sag of the member to be fastened, and the familiarity. Can be suppressed, and non-rotational loosening can be prevented.

  In addition, the slit formed in the boss portion is formed with an inclination in a direction opposite to the spiral inclination direction of the female screw portion with respect to the central axis of the screw fastening nut, so that the screw fastening nut is in the fastening direction. When rotating, the tip of the slit can smoothly rotate the screw fastening nut without hindering the rotation of the screw fastening nut, and the screw fastening nut returns and rotates. When this occurs, the tip of the slit becomes a wedge or a hook, which prevents the screw fastening nut from returning and prevents the loosening caused by the screw fastening nut from returning. It becomes possible to do.

  Furthermore, the opening formed in the boss portion is formed so that the male screw portion of the bolt can pass without screw engagement, that is, it does not have a female screw portion that engages with the male screw portion of the bolt. By forming the opening as an opening through which the male screw portion of the bolt can pass, the elastic deformation of the boss portion of the screw fastening nut when fastening the member to be fastened is It is possible to avoid being blocked by the screw engagement with the female screw portion. This makes it possible to effectively elastically deform the boss portion of the screw fastening nut when fastening the member to be fastened, thereby suppressing a decrease in the bolt axial force, and preventing non-rotating loosening of the screw. It becomes.

  Furthermore, the boss part is configured as a part of the nut for fastening, and is separate from the screw fastening nut such as a disc spring washer in order to provide spring property to the screw fastening body in order to prevent non-rotation looseness of the screw. Compared with the case where this component is required, it becomes possible to improve workability at the time of screw fastening.

  According to a second aspect of the present invention, the slit is a slit formed in a spiral shape around the central axis of the screw fastening nut. A nut is provided.

  That is, in the invention of claim 2, the slit formed in the boss portion of the screw fastening nut is formed around the central axis of the screw fastening nut, like the male screw of the bolt and the female screw portion of the screw fastening nut. By being formed in a spiral, when the screw fastening nut is rotated in the tightening direction, the tip of the slit rotates the screw fastening nut more smoothly without hindering the rotation of the screw fastening nut. Therefore, it is possible to improve the workability of screw tightening.

  According to a third aspect of the present invention, the slits are spaced apart with a uniform angle around the central axis of the screw fastening nut. A screw fastening nut according to claim 2 is provided.

  That is, in the invention of claim 3, the slit formed in the boss portion is disposed with a uniform angle around the central axis of the screw fastening nut so that the boss having the slit is formed. The amount of elastic deformation when the part is elastically deformed can be made uniform between the slits, and the force brought about when fastening the screws can be made uniform between the slits. It makes it possible to prevent looseness.

  According to the invention described in each claim, in a screw fastening nut having a female screw portion for screwing a fastened member in cooperation with a male screw portion of a bolt, the fastened member is fastened when the fastened member is screwed. A slit that inclines in the direction opposite to the inclination of the spiral of the female screw portion with respect to the central axis of the screw fastening nut is appropriately disposed on the seating surface side facing the member, thereby bringing a predetermined spring property to the screw fastening nut. Therefore, it is possible to suppress the lowering of the bolt axial force caused by the seat surface depression, the sag of the member to be fastened, the conformity, and the like that occur after the initial tightening work, and it is possible to prevent the non-rotational loosening. Thus, it is possible to prevent the loosening of rotation caused by the return rotation of the nut, and further, it is possible to improve the workability when fastening the screw.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a schematic view showing one embodiment of a screw fastening body to which a screw fastening nut according to the present invention is applied in order to fix each member to be fastened to each other by screw fastening. In FIG. 1, 1 is a member to be fastened, 2 is a bolt, 3 is a bolt head, 4 is a bolt shaft portion, 5 is a male screw portion, 6 is a plain washer, and 7 is a nut for fastening a main screw.

The screw fastening body shown in FIG. 1 includes a member to be fastened 1, a bolt 2, a flat washer 6, and a screw fastening nut 7 according to the present invention.
The bolt 2 plays a role of screwing the fastened member 1 in cooperation with the screw fastening nut 7, and includes a bolt head portion 3 having a hexagonal shape, a bolt shaft portion 4 having a male screw portion 5, and It is a general hexagon head bolt with a structure. In the present embodiment, the bolt 2 is shown as a hexagon head bolt, but any bolt that can fasten the screw of the fastened member 1 in cooperation with the screw fastening nut 7 may be used. The part 3 may be a square bolt or the like.

  The plain washer 6 serves to prevent the tightening force on the fastened member 1 by the bolt head 3 and the screw fastening nut 7 from being concentrated locally when the fastened member 1 is screwed. is there. Specifically, the plain washer 6 is disposed between the bolt head 3 and the member 1 to be fastened and between the screw fastening nut 7 and the member 1 to be fastened, and the bolt head 3 and the screw fastening. By transmitting the tightening force of the nut 7 to the fastened member 1 evenly distributed to the fastened member 1, the generation of local stress is prevented.

  The screw fastening nut 7 according to the present invention cooperates with the bolt 2 to fasten the member 1 to be fastened, and further, the seat surface depression generated after the screw fastening operation of the member 1 to be fastened, the sag of the member to be fastened, It serves to prevent non-rotational loosening caused by familiarity and the like, and rotational loosening caused by the return rotation of the nut.

  2 is a diagram showing a front view, a top view, and a bottom view of the screw fastening nut 7, and FIG. 3 is a line A- shown in the top view of the screw fastening nut 7 in FIG. It is sectional drawing which shows the cross section along A. 2 and 3, reference numeral 10 denotes a central axis of the screw fastening nut 7, 11 denotes a boss, 12 denotes a slit, 13 denotes an opening, 14 denotes a female screw, and 15 denotes a spiral of the female screw. .

  The screw fastening nut 7 has an opening 13 through which the male threaded portion 5 of the bolt shaft portion 4 of the bolt 2 passes on the seat surface side facing the fastened member 1 when the fastened member 1 is screwed. A boss portion 11 formed with a plurality of slits 12 inclined with respect to the central axis 10 of the screw fastening nut 7 is provided.

  As understood from FIGS. 2 and 3, the slit 12 has an inclination in a direction opposite to the inclination direction of the spiral 15 of the female thread portion 14 with respect to the central axis 10 of the screw fastening nut 7, and the screw fastening nut 7. Are formed in a spiral shape around the central axis 10. In addition, a plurality of slits 12 are disposed in the boss portion, and the slits 12 are spaced apart with a uniform angle α around the central axis 10 of the screw fastening nut 7.

  As shown in FIG. 3, the opening 13 is an opening that does not have the female screw portion 14 that engages the male screw portion 5 formed in the bolt shaft portion 4 of the bolt 2, and Is formed as an opening for guiding the male screw portion 5 of the bolt 2 to the female screw portion 14 of the screw fastening nut 7.

  A description will be given below of the operational effects brought about by the screw fastening of the fastened member 1 by using the screw fastening nut 7 having such a structure.

  First, the effect of non-rotating loosening of the screw brought about by using the main screw fastening nut 7 in screw fastening of the fastened member 1 will be described. As described above, the non-rotating loosening of the screw is a loosening in which the bolt axial force and the tightening force are reduced due to, for example, the seat surface depression, the sag of the fastened member, or the familiarity.

  Here, let us consider the non-rotational loosening of the screw that occurs due to the sag in the member contact surface where the members to be fastened come into contact with each other during screw fastening. The surface of each member to be fastened with screws is somewhat uneven. Therefore, in the initial tightening state of the screws to be fastened between the members to be fastened, the member joining surfaces where the members to be fastened are in contact with each other are not completely closely joined and formed with a certain gap. Will be. However, after the initial tightening of the screws to be fastened between the members to be fastened, the unevenness of the member joint surface progresses under the influence of some repeated external force, and the gap between the member joint surfaces formed in the initial tightening state May be reduced and the fastened members may approach each other. In general, the phenomenon that the members to be fastened come close to each other after the initial fastening of the screws between the fastened members is referred to as “sagging”, and the final contact is made at each contact portion of the screw fastening body. The amount of approach in the direction of the screw axis that is provided as a result is referred to as “sagging amount”.

If a sag (displacement) of ΔXc occurs on the joint surface where the fastened members are joined, the decrease in tightening force at this time, that is, the compressive force that fastens the fastened body, is expressed by Equation 1.
ΔFc = Kc · ΔXc Equation 1
In Expression 1, ΔFc represents a decrease in compression force, and Kc represents a compression spring constant.
At the same time, the bolt axial force also decreases and the bolt shaft portion shrinks. However, since the bolt axial force and the compressive force are balanced, the relationship shown in Equation 2 is established.
ΔFc = ΔFt = Kb · ΔXb Equation 2
In Equation 2, ΔFt represents a decrease in bolt axial force, Kb represents a tension spring constant, and ΔXb represents a contraction amount of the bolt shaft portion.
From Equations 1 and 2, the total shrinkage amount ΔX in the screw fastening body when ΔXc sag occurs on the member joining surfaces where the fastened members are joined together is the sum of ΔXc and ΔXb. A relationship will be established.
ΔX = ΔXc + ΔXb = ΔFc ÷ Kc + ΔFt ÷ kb Equation 3
If equation 3 is transformed, the relationship of equation 4 is obtained.
ΔFc = ΔFt = {1 / (1 / Kc + 1 / Kb)} · (ΔXc + ΔXb) Equation 4
In Equation 4, if {1 / (1 / Kc + 1 / Kb)} is Z and (ΔXc + ΔXb) is ΔX, the relational expression shown in Equation 5 holds.
ΔFc = ΔFt = Z · ΔX Equation 5
Z shown in Equation 5 is generally called a sag coefficient, and is a parameter for calculating the amount of decrease in pretension with respect to the sag amount.

  According to Equation 5, it can be seen that by reducing the sag coefficient, it is possible to suppress a decrease in compressive force or bolt axial force when sag occurs on the member joining surface where the fastened members are joined together. . Therefore, it can be seen that reducing the sag coefficient is one effective measure for preventing non-rotational loosening of the screw.

The sag coefficient Z is calculated from Equation 6 according to the above-described replacement.
Z = {1 / (1 / Kc + 1 / Kb)} Equation 6
In Expression 6, Kc represents a compression spring constant, and Kb represents a tension spring constant. According to Equation 6, it can be seen that the sag coefficient can be reduced by reducing the compression spring constant or the tension spring constant.

  In the above description, the measures for suppressing the reduction of the compressive force or the bolt axial force when the sag occurs at the member joining surface where the fastened members are joined to each other have been described. Alternatively, the compression spring constant or the tension spring constant is similarly applied to the non-rotational looseness caused by the displacement generated in the bolt axis direction, such as the depression of the seating surface of the member to be fastened in contact with the screw fastening nut. A person skilled in the art understands that by reducing the sag coefficient, the reduction of the compression force or the bolt axial force can be suppressed, and the non-rotational loosening of the screw can be prevented. I think it can be done.

  According to the screw fastening nut 7 according to the present invention, when the member 1 to be fastened is screwed, the seat surface side facing the member 1 to be fastened is inclined with respect to the central axis 10 of the screw fastening nut 7. By providing the boss portion 11 having the slit 12 having the screw fastening nut 7 itself, it is possible to contribute to reducing the compression spring constant Kb by facilitating the compression elastic deformation, and the influence of some external force is exerted. Accordingly, it is possible to suppress a decrease in compressive force or bolt axial force when a slack or displacement occurs in the bolt axial direction in the screw fastening body. In a conventional screw fastening nut structure having no slit 12, it is technically difficult to provide a large spring property that can contribute to reducing the compression spring constant Kb. It is considered that the effect of the spring property of the fastening nut is hardly considered.

  FIG. 4 shows a state before and after elastic deformation of the boss portion 11 having the slit 12 of the screw fastening nut 7 when the bolt 2 or the screw fastening nut 7 is rotationally fastened and the fastened member 1 is screwed. FIG.

  As shown in FIG. 4, when the bolt 2 or the screw fastening nut 7 is rotationally tightened and the fastened member 1 is screwed, the boss portion 11 of the screw fastening nut 7 is pressed and has a slit 12. Compared to a conventional general screw fastening nut that is not present, it is easily compressed and elastically deformed in the direction of the central axis 10 of the screw fastening nut 7.

  The degree of springiness of the screw fastening nut 7, that is, the degree of ease of elastic deformation, is appropriately determined according to the design conditions for screw fastening. Then, by appropriately determining the length of the slit 12 in the direction of the central axis 10, the inclination angle with respect to the central axis 10, the separation distance around the central axis 10 of each slit 12, and forming the slit 12 in a desired shape A predetermined spring property that conforms to the screw fastening design conditions can be provided to the screw fastening nut 7.

  Next, the effect on the loosening of the screw brought about by using the screw fastening nut 7 in the screw fastening of the member 1 to be fastened will be described. As described above, the rotational loosening of the screw is a loosening that occurs when the bolt or nut is affected by vibrations and the nut returns and rotates.

  According to the screw fastening nut 7 according to the present invention, the slit 12 formed in the boss portion 11 of the fastening nut 7 has the inclination direction of the spiral 15 of the female screw portion 14 with respect to the central axis 10 of the screw fastening nut 7. When the screw fastening nut 7 is rotated in the fastening direction, the tip end portion of the slit 12 does not hinder the rotation of the screw fastening nut 7. The screw fastening nut 7 can be smoothly rotated. Further, when the behavior of the screw fastening nut 7 returning and rotating occurs, the tip end portion of the slit 12 becomes a wedge or a hooking portion, and the return rotation of the screw fastening nut 7 can be prevented. It is also possible to prevent rotational looseness caused by the return rotation of the screw fastening nut 7.

  The opening 13 formed in the boss portion 11 of the screw fastening nut 7 is formed so that the male screw portion 5 of the bolt 2 can pass without screw engagement, that is, the male screw portion of the bolt 2. 5 is formed as an opening through which the male screw portion 5 of the bolt 2 can pass, and thus the elasticity of the boss portion 11 at the time of screw fastening. It is possible to avoid that the deformation is prevented by the screw engagement between the male screw portion 5 and the female screw portion 14. Accordingly, when the member to be fastened 1 is screw-fastened, and when the seat surface is depressed or the member to be fastened is sunk or fit after the initial fastening, the boss portion 11 of the screw fastening nut 7 is effectively elasticized. It is possible to deform, and it is possible to suppress a decrease in the bolt axial force.

  Further, the boss portion 11 of the screw fastening nut 7 is configured as a part of the screw fastening nut 7, and a disc spring washer is provided in order to impart spring property to the screw fastening body in order to prevent non-rotation looseness of the screw. Compared with the case where a separate component from the screw fastening nut is required, it is possible to improve workability at the time of screw fastening. In this embodiment, the present screw fastening nut 7 is shown such that the boss portion 11 is formed by directly machining the slit 12 and the opening 13 in the screw fastening nut 7. The nut main body portion having the female screw portion 14 and the boss portion 11 having the slit 12 and the opening portion 13 may be separately manufactured, and the nut main body portion and the boss portion 11 may be integrally formed later by welding or the like. .

  Further, the slit 12 formed in the boss portion 11 of the screw fastening nut 7 is formed around the central axis of the screw fastening nut, like the male screw 5 of the bolt 2 and the female screw portion 14 of the screw fastening nut 7. When the screw fastening nut 7 is rotated in the tightening direction by being formed in a spiral shape, the tip end portion of the slit 12 does not hinder the rotation of the screw fastening nut 7, and the screw fastening nut is smoother. 7 can be rotated, and the workability of screw tightening can be improved.

  Furthermore, the plurality of slits 12 formed in the boss portion 11 of the screw fastening nut 7 are disposed with a uniform angle around the central axis 10 of the screw fastening nut 7 so as to be separated from each other. The elastic deformation amount when the boss portion 11 having the slit 12 is elastically deformed can be made uniform between the slits, and the force brought about at the time of screw fastening can be made uniform between the slits. It is possible to prevent the rotation and non-rotation of the screw.

  As described above, according to the screw fastening nut 7 of the present invention, the female screw portion with respect to the central axis 10 of the screw fastening nut 7 is provided on the seat surface side facing the member 1 to be fastened when the member 1 to be fastened is screwed. The slit 12 inclined in the direction opposite to the inclination direction of the spiral 15 of the 14 is appropriately disposed, and a predetermined spring property is provided to the screw fastening nut 7 so that the seat surface is depressed and fastened after the initial screw fastening operation. It becomes possible to prevent non-rotational loosening caused by the sag of the member, conformance, etc., and to prevent rotational loosening caused by the return rotation of the screw fastening nut 7, It becomes possible to improve workability when fastening screws.

It is a general-view figure which shows one Embodiment of the screw fastening body to which the nut for screw fastening which concerns on this invention is applied so that each to-be-fastened member may be mutually fixed by screw fastening. FIG. 2 is a diagram illustrating a front view, a top view, and a bottom view of the screw fastening nut 7. It is sectional drawing which shows the cross section along line AA shown by the top view of the nut 7 for screw fastening in FIG. It is a figure which shows the state before and behind elastic deformation of the boss | hub part 11 which has the slit 12 of the screw fastening nut 7 when the volt | bolt 2 or the screw fastening nut 7 is rotationally fastened and the to-be-fastened member 1 is screwed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fastened member 2 Bolt 3 Bolt head 4 Bolt shaft part 5 Male screw part 6 Flat washer 7 Screw fastening nut 10 Center axis line of screw fastening nut 7 11 Boss part 12 Slit 13 Opening part 14 Female thread part 15 Female screw Spiral part

Claims (3)

In a screw fastening nut having a female screw part for fastening a member to be fastened in cooperation with a male screw part of a bolt,
In order to provide a predetermined spring property to the screw fastening nut, the male thread portion of the bolt is not screw-engaged on the seat surface side facing the fastened member when the fastened member is screwed. A boss portion having an opening to pass through and a slit inclined in a direction opposite to the spiral inclination direction of the female screw portion with respect to the central axis of the screw fastening nut;
A screw fastening nut characterized by that.   The screw fastening nut according to claim 1, wherein the slit is a slit formed in a spiral shape around the central axis of the screw fastening nut.   3. The screw fastening nut according to claim 1, wherein the slits are spaced apart from each other with a uniform angle around a central axis of the screw fastening nut.

Images