JP2010169253A - Countersunk head screw - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a countersunk head screw which does not spoil the appearance of the fastened member after being fastened even if the screwing initial position and the screwing direction deviate relative to a member to be fastened and is capable of enhancing the safety, environmental resistance and productivity. <P>SOLUTION: The countersunk head screw 1 is configured by integrally forming a head 2 formed with a cross groove M as a groove for a tool into which a tightening tool is fitted and an approximately cylindrical shaft 3 formed with a spiral screw-thread 9. The head 2 includes a conical head seat 21 extending from a screw neck N and having a diameter linearly gradually reduced toward the screw neck N, and a conical head crown 22 extending from the head seat 21 and having a diameter linearly gradually reduced toward the end surface 4 of the head 2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a countersunk screw.

  A screw widely used as a fastening component for fastening a plurality of fastening members such as a surface layer material (surface material) and a base material generally has a tool groove into which a fastening tool such as a tribar is fitted or fitted. And a cylindrical shaft portion (body shaft) formed integrally with the head portion and formed with a screw thread or a thread groove.

  The surface layer material or the base material to be fastened has a threaded hole formed in advance, or sometimes a spiral groove is formed on the inner wall of the threaded hole so that the thread of the shaft portion or the thread groove is screwed together. Sometimes. Alternatively, in the case of a low hardness material (relatively soft material) such as wood or plastic, or an extremely thin material that is high in hardness (or relatively hard), a screw hole having a spiral groove is formed. In many cases, screw holes for positioning and guidance are drilled at the work site prior to fastening work with screws, and holes and dents for alignment (such as stamping and micro May be formed only on the surface layer material.

  For such material applications, the tip of the screw shaft is shaped like a cusp, such as a wood screw, drilling screw, or tapping screw with a sharp tip, and the ability to create screw holes in the surface layer or base material If a screw with a screw is useful, or if a screw hole for guiding is provided to some extent, a tapping screw with a sharp tip (having a flat portion) or the like is also used, and tightening with a tightening tool By the operation (screwing operation by a driver or the like), the screw can be screwed into the member to be fastened.

  There are various types of screws, but the appearance of the surface of the fastened member after being fastened by the screw is damaged, or the head of the screw protrudes from the surface of the fastened member. For example, a countersunk screw having a flat surface of the head of the screw in which the tool groove is formed is widely used.

  As the countersunk screw, for example, as described in Patent Document 1, the tip of the shaft portion is sharp, the head surface is flat, and the shape of the head is inverted conical toward the screwing direction of the countersunk screw. Are widely available in the market and are generally widely used for architectural and carpentry applications. In addition, the side portion of the end face of the head is chamfered to a degree that is slightly rounded and has a curvature (see, for example, Patent Document 2), or the end face portion is cut substantially perpendicular to the surface direction. What is (notched) (for example, refer nonpatent literature 1 etc.) is also known. Note that Non-Patent Document 1 also describes one having a sharp tip.

Japanese Utility Model Publication No. 4-77018 JP-T-2002-541413

JIS B0101-1994

  By the way, for example, when fixing a hard surface layer material such as metal on a base material with low hardness such as wood, the surface layer material corresponds to the shaft diameter of the countersunk screw to be used. In some cases, screw holes such as seating surface holes corresponding to the height of the head and the load (clamping load) during tightening may be formed. When screwing a flat head screw into the base material through the screw hole of the surface layer material, after aligning the surface layer material with respect to the base material accurately, the hole center on the surface of the base material exposed to the screw hole of the surface layer material It is necessary that the tip of the countersunk screw is attached to the head and the shaft of the countersunk screw is accurately screwed perpendicularly to the surface of the surface material. However, in the case of using a countersunk head screw with a sharp tip, even if a skilled skill is used, there are many cases where a slight deviation occurs in the initial position of screwing and the screwing direction.

  FIG. 11 is a cross-sectional view showing an example of a state in which the conventional flat head screw 100 fastens the member B to be fastened when a deviation occurs in the initial position of the screwing or the screwing direction (screw portion). FIG. 12 is a top view of the countersunk screw 100 and a part thereof in this state as viewed from the head side (upper side) of the countersunk screw 100. As shown in the drawing, when even a slight deviation occurs in the initial position or the screwing direction of the countersunk screw 100, when the countersunk screw 100 passes through the surface layer material Bs and is screwed into the base material Bu, the surface of the surface layer material Bs. In addition, a part of the outer periphery of the end face of the head of the countersunk screw 100 protrudes (projecting part G6), and the outer peripheral part of the end face opposite to the protruding part sinks into a screw hole drilled in the surface layer material Bs. (Recess G7).

  In this case, although the countersunk screw 100 is used, not only the appearance of the surface of the fastened member B is remarkably impaired, but the peripheral edge of the head surface of the countersunk screw 100 is sharp as shown in the figure. During use, clothes, skin, or the like may come into contact with the protruding portion G6, which may cause inadvertent injury or damage to the clothes.

  Furthermore, in the case of a member to be fastened B that is used around water, such as a bathroom or a bathroom, water easily enters the gap (gap) of the protrusion G6, and the water is difficult to be discharged (even if wiped or wiped). Therefore, deterioration such as rust may occur in the metal screw and the surface layer material Bs. Further, when a waterproof coating or paint is applied to the surface of the surface layer material Bs for the purpose of preventing such deterioration, it is prominent in the gap between the peripheral lower surface of the head and the surface material Bs in the protruding portion G6 and the periphery thereof. In addition to further damaging the aesthetics, the coating or painting may peel off from the part where the coating or painting unevenness occurs, and the expected function may not be demonstrated. Can be.

  In order to eliminate the inconvenience due to the protrusion of the head of the countersunk screw 100, it is conceivable to use a countersunk screw having a screw head whose volume is smaller than the internal volume of the screw hole of the surface material Bs. Although the portion G6 does not occur, the volume of the recess formed in the surface layer material Bs increases, and as a result, the aesthetic appearance of the surface of the fastened member B is also significantly impaired, and the recess is attempted to be filled with coating or painting. However, there is a limit, and it takes a lot of work to completely bury the dent and make it smooth.

  Although it is conceivable to cut the protruding portion G6 itself of the screw head later, the work man-hour is increased and the surface layer material Bs may be damaged. Furthermore, in order to eliminate such a deviation of the countersunk screw 100, there may be a method of extracting the countersunk screw 100 once tightened with a tightening tool and re-screwing it. The countersunk screw 100 is screwed and fastened again due to the influence of distortion caused by uneven stress applied to the threaded hole of the base material Bu or the screw hole of the surface layer material Bs. It is extremely difficult to do.

  The above applies not only to the case where a countersunk screw having a sharp tip is screwed into the base material, but also to the case where a screw hole or a recess for positioning or guiding is provided in the base material. That is, in order to screw a countersunk screw having a flat shaft portion into the base material Bu instead of the countersunk screw 100, for example, when a hole is drilled with a conical shape on the surface of the base material Bu, the position of the hole If the direction or direction is deviated, the initial position of screwing in the countersunk screw or the direction of screwing may be displaced or tilted. Since the screwing direction of the countersunk screw may be greatly deviated, a part of the head of the countersunk screw protrudes from the surface layer material Bs, which may cause the same inconvenience as described above.

  Therefore, the present invention has been made in view of such circumstances, and even if a deviation occurs in the initial screwing position or screwing direction with respect to the member to be fastened, the aesthetic appearance of the member to be fastened after fastening is achieved. The object of the present invention is to provide a countersunk screw that can improve safety, environmental resistance, and productivity.

  In order to solve the above problems, a countersunk screw according to the present invention has a cylindrical shaft portion in which a screw thread or a screw groove is formed and a head portion in which a flat end face is formed with a tightening groove. The head has a conical shape (shape) extending from one end of the shaft portion and having a reduced diameter (that is, the diameter gradually decreases) toward the other end of the shaft portion. And a head crown that extends from the head seat and has a conical shape that is linearly reduced toward the end face of the head.

  In other words, the head of the countersunk screw according to the present invention is not a simple inverted cone as in the prior art, but a head seat formed in an inverted cone (cross-section trapezoidal shape) toward the tip of the shaft, and a head And a crown part formed in a conical shape (trapezoidal cross section) toward the flat end face of the part. Alternatively, the head of the countersunk screw has an outermost diameter larger than the maximum diameter of the shaft portion, and has an annular taper in which the outer diameter of the flat end surface is smaller than the outermost diameter of the head. It can also be expressed as a thing.

  The shaft portion may be solid or hollow, and the other end (the tip; the end where the head is not provided) may have a pointed shape. If the tip is sharp, the tip does not need to have a very sharp point shape, as long as it has a shape or structure that allows the shaft portion to be screwed into the fastened member by a tightening tool. Good. Further, “linearly reducing the diameter” means that the diameter is gradually reduced in a straight line, and the side portion of the end face as seen in some types of the conventional flat head screws described above is used. It means that the ridgeline of the side wall is processed into a substantially straight line rather than a shape that is chamfered so as to be slightly rounded.

  The countersunk screw having such a configuration can be easily screwed into a fastening member such as a surface layer material or a base material by a tightening operation by a tightening tool. Deviation may occur in the initial position of screwing or in the screwing direction.

  However, the head of the countersunk screw according to the present invention does not have a simple conical shape like a conventional countersunk screw, but has a conical shape whose diameter decreases linearly toward the end surface of the head (that is, on the end surface). (With a conical annular taper), even if the screwed state of the shaft is deviated, the boundary between the head seat and head crown of the countersunk screw head Are also embedded inside. Therefore, the peripheral edge of the countersunk screw head is prevented from protruding sharply from the surface of the member to be fastened. It is possible to effectively eliminate problems such as contact with the skin, deterioration of the countersunk screw and the member to be fastened, and easy removal of the coating and paint.

  Moreover, the inclination degree (angle) of the side wall (ridge wall, cone wall) of the head seat part and the head crown part in the head of the countersunk screw is not particularly limited. For example, in the axial section, the head seat part The cross-section internal angle of the head seat defined by the boundary between the head and the crown (the boundary plane perpendicular to the axial direction) is the same as the cross-section internal angle of the head crown, or the interior angle of the head seat is the crown The form larger than the cross-section internal angle of the is mentioned.

  In this way, the inclination of the side wall surface (inclined surface) of the crown portion located on the end surface side of the head approaches the end surface direction, so that when the countersunk screw is fastened to the fastening member, the screwing direction of the countersunk screw is shifted. Even so, the height and sharpness of the step that may occur when a part of the head is positioned above the surface of the fastened member can be further reduced.

  Furthermore, you may provide the cyclic | annular strip | belt part (it has a surface parallel to the central-axis direction of an axial part) chamfered in the boundary of the head seat part and head crown part in a countersunk head. By adopting such a configuration, the boundary portion between the head seat portion and the crown portion of the countersunk screw head is chamfered even when the displacement of the screwing of the shaft portion with respect to the fastened member becomes large ( For example, a non-sharp annular band having a surface parallel to the central axis direction of the shaft is formed, so that the portion is embedded inside the surface of the member to be fastened, It is prevented that the annular belt portion that is the boundary portion of the head protrudes sharply from the surface of the fastened member. As a result, the aesthetics of the surface of the material is impaired, clothes and skin come into contact with the protruding parts, countersunk screws and fastened members are deteriorated, and coating and paint are more easily removed. be able to.

  According to the countersunk screw of the present invention, the head portion has a head seat portion and a crown portion that are conical in opposite directions, so that even in the initial position of screwing or the screwing direction with respect to the member to be fastened. Even if a shift occurs, the aesthetic appearance of the surface of the fastened member after fastening can be maintained, and safety, environmental resistance, and productivity are significantly improved compared to the conventional case. It is possible to achieve a fastened finish.

It is a side view which shows roughly the structure of 1st Embodiment of the countersunk screw by this invention. It is a front view of the countersunk screw shown in FIG. It is a rear view of the countersunk screw shown in FIG. It is sectional drawing which shows an example of the to-be-fastened member fastened with the countersunk screw shown in FIG. FIG. 5 is a top view of the countersunk screw shown in FIG. 4 and a part of the periphery thereof. It is sectional drawing which shows the other example of the state by which the to-be-fastened member is fastened with the countersunk screw shown in FIG. FIG. 7 is a top view of the countersunk screw shown in FIG. 6 and a part of the periphery thereof. It is a side view which shows roughly the structure of 2nd Embodiment of the countersunk screw by this invention. It is an expanded sectional view which shows an example of the to-be-fastened member fastened with the countersunk screw shown in FIG. It is sectional drawing which shows the other example of the state by which the to-be-fastened member is fastened with the countersunk screw shown in FIG. It is sectional drawing which shows an example of the state which the conventional flat head screw has fastened the to-be-fastened member. FIG. 12 is a top view of the conventional countersunk screw in the fastening state shown in FIG. 11 and a part of the periphery thereof.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. Further, the positional relationship such as up, down, left and right is based on the positional relationship shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios in the drawings are not limited to the illustrated ratios. Further, the following embodiments are exemplifications for explaining the present invention, and are not intended to limit the present invention only to the embodiments. Furthermore, the present invention can be variously modified without departing from the gist thereof.

  FIG. 1 is a side view schematically showing a configuration of a preferred embodiment of a countersunk screw according to the present invention. FIG. 2 is a side view of the countersunk screw as viewed from the left side (the head side described later) in FIG. FIG. 3 is a rear view of the countersunk screw as viewed from the right side (front end side described later) in FIG.

  The flat head screw 1 corresponds to a flat head of a flat head screw, and has a head 2 formed with a cross groove M as a tool groove into which a tightening tool is fitted, and a shaft portion 3 having a substantially cylindrical shape. It is formed.

  The head portion 2 extends from a screw neck N (one end of the shaft portion 3) that forms a boundary between the head portion 2 and the shaft portion 3, and linearly toward the screw neck N. A conical head seat portion 21 that is gradually reduced in diameter, and a conical shape that extends from the head seat portion 21 and is gradually reduced in diameter linearly toward the end face 4 of the head portion 2. The head crown part 22 is comprised. As described above, the head 2 has a structure in which portions having conical shapes (cross-sectional trapezoidal shapes) opposite to each other are in contact with each other.

  More specifically, the annular inclined surface 21a that forms the side wall (ridge wall, cone wall) of the head seat portion 21 is centered on the central axis C (virtual axis) of the countersunk screw 1, and the head seat portion 21 and the crown. It extends linearly between the circumference 11 that defines the periphery of the boundary with the portion 22 and the screw neck N of the countersunk screw 1. Further, the annular inclined surface 22 a that forms the side wall (ridge wall, cone wall) of the head crown portion 22 does not reach each end portion Mt of the cross groove M and the end surface 4 centering on the central axis C of the countersunk screw 1. Is extended linearly between a circumference 12 that defines the periphery of the head and a circumference 11 that defines the periphery of the boundary between the head seat portion 21 and the crown portion 22.

  Here, the method of forming (processing) the annular inclined surface 22a of the head crown portion 22 is not particularly limited. For example, the peripheral edge of the surface portion of the head (dish) of a general flat head screw is a polishing tool such as a grinder. You may form by cutting off with a cutting tool, or you may use the method of cutting out using another appropriate cutting tool.

  Moreover, although the cyclic | annular inclined surfaces 21a and 22a inclination degree (angle) of each of the head seat part 21 of the head 2 and the head crown part 22 are not specifically limited, The following examples are mentioned. That is, for example, in the cross section in the direction of the central axis C, the boundary between the head seat part 21 and the crown part 22 (boundary surface orthogonal to the central axis C; a surface defined by the circumference 11) and the annular shape of the head seat part 21 The cross section internal angle θ1 formed by the inclined surface 21a is preferably substantially the same (θ1≈θ2) as the cross section internal angle θ2 formed by the same boundary and the annular inclined surface 22a of the head crown portion, and the cross section internal angle θ1 of the head seat portion 21 is preferably the head crown portion 22. It is preferable that the annular inclined surface 22a of the head crown portion 22 is gentler than the annular inclined surface 21a of the head seat portion 21 (θ1> θ2).

  The shaft portion 3 has a maximum diameter slightly smaller than the diameter of a screw hole H (described later) formed in the surface layer material Bs that is one of the members to be fastened B (fastening target). The shaft body 30 is formed with a spiral thread 9 on the peripheral surface 8 and the pointed head 31 has a sharp tip toward the screw tip 13 (the other end of the shaft 3). With the shape of the pointed head 31, the countersunk screw 1 is screwed into the base material Bu to form a screw hole (so-called pierced), and the fastened member B is fastened.

  FIG. 4 is a cross-sectional view showing an example of a state in which the fastened member B made of the surface layer material Bs and the base material Bu is accurately fastened by the flat head screw 1 according to the present invention (the flat head screw 1 is a non-cross section). FIG. 5 is a top view of the countersunk screw 1 in the fastened state shown in FIG. 4 and a part of the periphery thereof, as viewed from the head 2 side (upper side) of the countersunk screw 1.

  In FIG. 4, the surface material Bs has a higher hardness than the base material Bu and is provided so as to cover the base material Bu. The flat head screw 1 is formed on the surface material Bs in an initial state of the screwing. Aligned with the center of the screw hole H, the approach axis S perpendicular to the upper surface of the base material Bu of the fastened member B and the center axis C of the countersunk screw 1 (see FIGS. 1 and 2) coincide. It is screwed in exactly. In this case, the fastening operation is completed in a state where the annular inclined surface 21a which is the seating surface of the head seat portion 21 of the countersunk screw 1 is in contact (contact) with the inner wall of the funnel-shaped seating surface hole 40 formed in the surface layer material Bs. Then, the surface layer material Bs and the base material Bu are fastened.

  According to the countersunk screw 1 configured in this way, the peripheral part of the head crown part 22 of the countersunk screw 1 is notched in a taper shape to form the annular inclined surface 22a. As shown in the figure, the boundary (circumference 11) between the head seat portion 21 and the head crown portion 22 is a seat surface hole. 40, between the circumference 41 of the open end of the seating surface hole 40 and the circumference 12 of the end surface 4 of the crown portion 22, annular recesses G <b> 1 are formed at equal intervals in the circumferential direction. .

  And since this annular recessed part G1 has a sufficiently small volume as compared with the cross groove M of the countersunk screw 1, the appearance of the surface of the fastened member B to be fastened is not impaired, and on the contrary, it has an excellent functional beauty. In addition to being able to be in a state, even if coating or painting is applied later, it is possible to suppress the influence of extreme depressions or depressions in the coating or painting.

  FIG. 6 shows another example of the state in which the fastened member B is fastened by the countersunk screw 1. The fastened member B made of the surface layer material Bs and the base material Bu FIG. 7 is a cross-sectional view showing a state in which the countersunk screw 1 is fastened in a state deviated from FIG. 7, and FIG. 7 shows the flat head screw 1 in the fastened state shown in FIG. It is the top view seen from.

  In FIG. 6, when the surface layer material Bs is covered with the base material Bu, and the surface layer material Bs is fastened and fixed at an appropriate position, the flat head screw 1 is in the initial state of the screwing with respect to the approach shaft S. It is screwed in a state of being offset. That is, the fastened member B is fastened by the countersunk screw 1 in a state where the central axis C of the countersunk screw 1 does not coincide with the approach axis S. In this case, the annular inclined surface 21a, which is the seating surface of the head seat portion 21 of the countersunk screw 1, comes into contact (contact) with the inner wall of the funnel-shaped seating surface hole 40 formed in the surface layer material Bs. As a result, the fastening operation is completed in a state in which a part of the annular inclined surface 21a of the head seat portion 21 of the countersunk screw 1 is biased so as to be deformed by pressing the inner wall of the seat surface hole 40. Bs and the base material Bu are fastened.

  Then, as shown in the figure, a part of the boundary (circumference 11) between the head seat portion 21 and the head crown portion 22 is accommodated in the seat surface hole 40, and the circumference 41 of the open end of the seat surface hole 40 is obtained. And the circumference 12 of the end face 4 of the crown part 22 is formed with a recess G2, and at the opposite side, the end face 4 of the crown part 22 is more than the circumference 41 of the open end of the seat hole 40. Is also located above and a step G3 is formed. Thus, in the state in which the countersunk screw 1 is tilted from the approach shaft S and screwed into the fastened member B, a part of the head 2 of the countersunk screw 1 is positioned above the surface of the surface layer material Bs. As described above, the peripheral portion of the head crown portion 22 of the countersunk screw 1 is cut out in a taper shape to form the annular inclined surface 22a. Even in this state, a part of the periphery of the end surface 4 of the head portion 2 is It is possible to effectively prevent sharp protrusions as in the prior art.

  Therefore, conventional inconveniences that may occur due to the presence of sharp protrusions, i.e., aesthetics are impaired, or clothes or skin etc. come into contact with the protrusions during work or use, and carelessly injuries or clothes , Damage to the countersunk screws when used around water, uneven coating and uneven coating, further aesthetic loss, peeling of coating and coating, or protrusion from the back It is possible to eliminate such inconveniences that the number of working steps is increased by cutting the portion, the surface layer material Bs is damaged, or the countersunk screws that have been fastened once are removed and fastened again. . Further, the concave portion G2 generated in a part of the surface of the fastened member B has a sufficiently small volume as compared with the cross groove M of the countersunk screw 1. Accordingly, the surface of the fastened member B to be fastened is thereby There is no loss of aesthetics.

  Further, as described above, the sectional internal angle θ1 of the head seat portion 21 is substantially the same as the sectional internal angle θ2 of the crown portion 22 (θ1≈θ2), or the sectional internal angle θ1 of the head seat portion 21 is equal to the crown portion. 22 is larger than the internal angle θ2 of the cross section (θ1> θ2), the inclination of the annular inclined surface 22a of the crown portion 22 existing on the end surface 4 side of the head 2 approaches the surface direction of the end surface 4, The height of the step G3 that can be generated when the screw 1 is screwed in a state where the screwing direction is deviated and the sharpness of the portion can be further reduced.

  FIG. 8 is a side view schematically showing a configuration of a countersunk screw 50 according to the second embodiment of the countersunk screw according to the present invention. The countersunk screw 50 has a conical head seat 21 that is gradually reduced in diameter linearly toward the screw neck N in the head 2 and a diameter that gradually decreases linearly toward the end surface 4 of the head 2. It is comprised similarly to the countersunk screw 1 mentioned above except having the annular belt | band | zone part 60 between the cone-shaped head crown parts 22 made. Therefore, in FIG. 8, the same code | symbol is attached | subjected to the site | part which is common with the countersunk screw 1, and in order to avoid the overlapping description, those description is abbreviate | omitted here (it is the same in FIG. 9 and 10). .

  The annular belt portion 60 has a belt surface 64 (surface) defined by concentric circles (circumferences) 62 and 63 centered on the central axis C of the countersunk screw 50 and having the same distance from the center. The plane direction of the surface 64 is parallel to the central axis C.

  Here, the method of forming (processing) the annular belt portion 60 is not particularly limited, and for example, the peripheral edge of the surface portion of the head (counter) of a general countersunk screw is scraped with a grinding tool such as a grinder or a cutting tool. As a result, an annular inclined surface 22a of the head crown portion 22 is formed (first scraping), and the boundary circumference 11 (not shown in FIG. 8) described in the first embodiment is generated at that time. A method of scraping again so as to form a band surface 64 parallel to the traveling direction, that is, the direction of the central axis C may be used (second scraping). In other words, the chamfering process may be performed by an appropriate method on the circumference 11 that defines the periphery of the boundary between the head seat portion 21 and the head crown portion 22 in the first embodiment. An appropriate cutting tool may be used in these two scraping steps. At this time, if the degree of the second scraping is increased (scraping deeply in the direction of the central axis C), the concentric circle 62 is closer to the tip 13 of the countersunk screw, and the concentric circle 63 is closer to the end face 4 of the head crown 22. As a result, the band surface 64 of the annular band 60 becomes wider. Conversely, when the degree of the second scraping is reduced, the band surface 64 becomes narrower. The degree of this scraping can be appropriately determined according to the situation of the fastened position of the fastened member.

  FIG. 9 is a sectional view showing an example of a state in which the fastened member B made of the surface layer material Bs and the base material Bu is accurately fastened by the flat head screw 50 according to the present embodiment (the flat head screw 50 is a non-cross section). is there. In FIG. 9, the countersunk screw 50 is aligned with the center of the screw hole H formed in the surface layer material Bs in the initial state of screwing, and is perpendicular to the upper surface of the base material Bu of the fastened member B. And the central axis C of the countersunk screw 50 (see FIGS. 1 and 2) are accurately screwed. In this case, the fastening operation is completed in a state where the annular inclined surface 21a that is the seating surface of the head seat portion 21 of the countersunk screw 50 is in contact (contact) with the inner wall of the funnel-shaped seating surface hole 40 formed in the surface layer material Bs. Then, the surface layer material Bs and the base material Bu are fastened.

  According to the countersunk screw 50 configured in this manner, as shown in the figure, the annular cylindrical surface 60 formed at the boundary between the head seat portion 21 and the head crown portion 22 is housed in the seat surface hole 40 and is seated. Between the circumference 41 of the open end of the surface hole 40 and the annular band 60, annular recesses G4 are formed that are evenly spaced in the circumferential direction. Here, below the annular recess G4 (a position deep when viewed from the surface of the surface layer material Bs), a lower recess G5 is formed that extends to the seat surface hole 40 outward from the central axis C of the annular strip 60.

  And since this annular recessed part G4 has a sufficiently small volume compared with the cross groove M of the countersunk screw 50, the appearance of the surface of the fastened member B to be fastened is not impaired, and on the contrary, it has an excellent functional beauty. In addition to being able to suppress the effects of extreme dents and dents in the coating and painting even when coating or painting is applied later, the paint bites into the lower recess G5. By fixing with, the flat head screw 50 is fixed more firmly to the member to be fastened.

  FIG. 10 shows another example of the state in which the fastened member B is fastened by the countersunk screw 50. The fastened member B made of the surface layer material Bs and the base material Bu It is an expanded sectional view which shows the state fastened in the state which shifted | deviated greatly from.

  As in the first embodiment shown in FIG. 6, the flat head screw shown in FIG. 10 covers the base material Bu with the surface layer material Bs and fastens the surface layer material Bs at an appropriate position for fixing. 50 is screwed in a state of being displaced with respect to the entry shaft S in the initial state of the screwing, but the displacement with respect to the entry shaft at that time is larger than that in the case of the first embodiment. Thus, if a large shift in the countersink entry direction occurs, for example, even when the countersunk screw 1 according to the first embodiment is used, one of the boundary circumferences 11 is sharp on the surface of the surface material Bs. (Virtual boundary circumference 70 indicated by a broken line in FIG. 10). However, in the countersunk screw 50 according to the present embodiment, the vicinity of the boundary circumference 11 corresponding to the protruding portion described above is cut off to form the annular band portion 60, so that the countersunk screw 50 is screwed in as shown in FIG. Even if the direction is largely deviated, it is possible to more effectively prevent the sharp protruding portion 70 from occurring when the fastening operation is completed.

  Here, in forming the annular belt portion 60, the radial lengths from the central axis C to the concentric circles 62 and 63 may be slightly different. In this case, although the direction of the band surface 64 is deviated from the screw traveling direction, that is, not parallel to the central axis C, the flat head screw 50 according to the present embodiment has the boundary circumference 11 (the flat head screw) from the surface of the fastening member. It is only necessary that the sharp part as in 1) is chamfered so that the sharp part of the boundary circumference 11 can be prevented from protruding.

  In addition, as above-mentioned, this invention is not limited to said embodiment, A various deformation | transformation is possible in the limit which does not change the summary. For example, the shaft portion 3 may not be pointed, that is, may be flat instead of the pointed head 31. In this case, holes for positioning and guiding may be provided in the base material. Further, the shaft portion 3 may be one in which a spiral thread groove is formed in the cylindrical body 8 instead of the cylindrical body 8 in which the thread 9 is formed. Further, the surface layer material Bs in which the screw holes H and the seating surface holes 40 are not formed may be used. Instead of these, the embossing or the minute size for aligning the screw tip 13 of the countersunk screw 1 may be used. The countersunk screw according to the present invention is useful even when a concave part is formed.

  As described above, according to the countersunk screw according to the present invention, even if there is a deviation in the initial position of screwing or the screwing direction with respect to the member to be fastened, the appearance of the member to be fastened after fastening is obtained. Since it is possible to improve safety, environmental resistance, and productivity without damage, it can be widely used for applications such as building materials, joinery, construction, and construction.

  DESCRIPTION OF SYMBOLS 1,50 ... Countersunk screw, 2 ... Head, 3 ... Shaft part, 4 ... End surface, 8 ... Cylindrical body, 9 ... Screw thread, 11, 12, 41 ... Circumference, 13 ... Screw tip (the other end of a shaft part) ), 21 ... head seat, 21 a, 22 a ... annular slope, 22 ... crown, 30 ... shaft body, 31 ... pointed head, 40 ... seat hole, 60 ... annular belt, 64 ... belt, 70 ... Virtual boundary circumference, B ... Fastened member, Bs ... Surface layer material, Bu ... Base material, C ... Central axis, G1 ... Annular recess, G2 ... Concave, G3 ... Step, G4 ... Annular recess, G5 ... Bottom recess , G6: Projection, G7: Recess, H ... Screw hole, M ... Cross groove (groove), Mt ... End, N ... Screw neck (one end of the shaft), S ... Entrance shaft, θ1 ... Head seat Of the cross section of the head crown.

Claims (5)

A countersunk screw in which a shaft portion having a cylindrical shape in which a screw thread or a screw groove is formed and a head portion in which a groove for tightening is formed on a flat end surface are integrally provided,
The head portion has a conical head seat portion extending from one end of the shaft portion and having a diameter reduced toward the other end of the shaft portion; and the head portion extending from the head seat portion and the head portion. A conical crown that is linearly reduced in diameter toward the end face of
Countersunk screw. A countersunk screw in which a cylindrical shaft portion in which a thread or a screw groove is formed and a head portion in which a tightening groove is formed on a flat end surface are integrally formed,
The head portion includes a head seat portion formed in an inverted conical shape toward the shaft portion, and a crown portion formed in a conical shape toward the end surface of the head portion.
Countersunk screw. A countersunk screw in which a cylindrical shaft portion in which a thread or a screw groove is formed and a head portion in which a tightening groove is formed on a flat end surface are integrally formed,
The head has an outer diameter that is larger than a maximum diameter of the shaft portion, and an annular taper in which an outer diameter of the end surface of the head is smaller than an outermost diameter of the head. Have
Countersunk screw. A countersunk screw in which a cylindrical shaft portion in which a thread or a screw groove is formed and a head portion in which a tightening groove is formed on a flat end surface are integrally formed,
The head includes a head seat portion formed in an inverted conical shape toward the shaft portion, a crown portion formed in a conical shape toward the end surface of the head portion, and the head seat portion and the head portion. Provided at the boundary with the crown and chamfered and having an annular band.
Countersunk screw. The annular belt portion has a surface parallel to the central axis direction of the shaft portion;
The flat head screw according to claim 4.

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