Expansion anchor

Abstract

To provide an expansion anchor which achieves downsizing of the entire part and can guide a sharp end of a screw screwed into the expansion anchor into an introduction bush without causing inclination to prevent occurrence of damage of the introduction bush.SOLUTION: In an expansion anchor 1, expansion arms 4 are provided at both sides of a tip of a stem 2 through first hinges 3. Tip sides of webs 6 respectively connected to both expansion arms 4 through second hinges 5 are coupled to an introduction bush 8 through which a screwing hole 14 of a screw penetrates. Reinforcement ribs 13 are respectively provided at the inner surface side, which faces the expansion arm 4, of both webs 6. Recessed parts 15 for screw guide are provided at end parts located at the introduction bush 8 side of the reinforcement ribs 13 provided at both webs 6.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] This invention relates to an expansion anchor made of synthetic resin for use in building materials such as wall materials and plates whose backsides are difficult to reach, and in particular to an expansion anchor that can reliably screw into a lead bush without damaging the lead bush with the screw. [Background technology]

[0002] As shown in Patent Document 1, this type of expansion anchor comprises a cylindrical stem with a screw insertion hole passing through it and a flange on its rear end, expansion arms attached to both sides at the tip of the stem via hinges, webs attached to the middle of the faces of both expansion arms on the opposite sides of the stem, each of which is hinged so that they are inclined inward and forward, and a tubular guide bushing attached between the gathered tips of both webs via a hinge and arranged coaxially at the front of the stem, and the expansion arms are molded into a shape such that they open out to both sides at approximately right angles at the tips of the stem, and both webs are open at the front of the expansion arms to form a product.

[0003] When various components are screwed and fixed to building materials such as wall materials, first, the anchor applies inward force to both expansion arms, bringing them closer to each other, thereby bringing the two webs pushed forward and sandwiching them together, and folding both expansion arms, both webs, and the introduction bush into a single rod-like shape. In this state, when both expansion arms are inserted through the introduction bush into pilot holes provided in the building material, the expansion arms and stem return to their open state on the back side of the building material due to the restoring elasticity of the synthetic resin.

[0004] Next, a screw for fixing various components is inserted into the screw insertion hole of the stem, and when the screw is screwed in with its tip inserted into the leading bush, the leading bush is pulled toward the stem, causing the stem to act as a tension rod, pushing both expansion arms apart and bringing both expansion arms into contact with the back surface of the building material, preventing the expansion anchor from coming loose from the construction component and fixing the various components to the building material.

[0005] With this type of synthetic resin expansion anchor, when various components are screwed into a wall material, when the lead-in bush is pulled in by the screw, a force is applied to the stem in the direction that pushes the expansion arms apart. When fixed to the wall material, the expansion arms must be stretched so that they do not close, so the anchor must be strong enough to prevent bending.

[0006] For this reason, the stem, which is formed in a plate shape, is provided with a reinforcing rib on the inner surface side facing the spreading arm, thereby improving bending resistance.

[0007] The reason for providing this reinforcing rib on the inner side of the stem is to avoid the fact that when both spreading arms are in the closed phase and the web is sandwiched inside, if there is a reinforcing rib on the outer side of the web, the spreading arms will interfere with it and the spreading arms will not be able to close with a low volume.

[0008] Furthermore, when both spreading arms are in the closed phase, the sandwiched webs approach each other. At this time, if the reinforcing ribs were provided on the entire widthwise surface of the inner surface of the webs, the reinforcing ribs would interfere with each other and the spreading arms would not be able to close with a low volume. Therefore, the width of the reinforcing ribs is set to less than half the width of the webs and is positioned along opposing side edges of both webs so that when the webs are folded, each reinforcing rib fits into a position where there is no reinforcing rib on the opposing web.

[0009] Incidentally, expansion anchors like those described above are prepared in different sizes to accommodate the conditions of the various components to be screwed into; however, for example, when trying to commercialize a small expansion anchor, it is necessary to make the anchor's components thinner in order to make them smaller. Naturally, thinning the wall thickness of the pair of webs is also unavoidable, but as mentioned above, the role of the web is to push the expansion arms open and maintain this open state, so it is necessary to ensure bending resistance, and reinforcement by reinforcing ribs is important.

[0010] For this reason, in the case of a miniaturized expansion anchor, in order to ensure strength for the thinner web, it is necessary to provide the reinforcing ribs on the web over the entire length of the web while maintaining as much thickness as possible.

[0011] When an expansion anchor is used, the two expansion arms are pressed together, the web is folded and sandwiched between them, and the rod-shaped expansion arms and lead-in bushings are inserted into pilot holes in the building material. When the expansion arms are unfolded on the back side of the building material, they elastically extend out on both sides at approximately right angles to the stem, returning to their molded shape before use, and both webs protrude forward from each of the expansion arms, with the lead-in bushings located at the tips of both webs being positioned coaxially with the stem.

[0012] Under such conditions of an expansion anchor, if a reinforcing rib is provided over the entire length of the stem, when both expansion arms of the expansion anchor are in the open state as described above, the corner portion of the end of the reinforcing rib located on the introduction bush side, which is located on the inside in the width direction of the web, will be in a positional relationship in which it protrudes with respect to an imaginary circle extended axially forward on the inner diameter of the insertion hole formed in the stem. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] Special Publication No. 60-21249 Summary of the Invention [Problem to be solved by the invention]

[0014] In the above situation, when a screw is inserted into the stem of the expansion anchor inserted into a pilot hole and screwed in to screw various components into building materials, the screw is guided into the insertion hole of the stem and proceeds in a straight line, but the sharp tip formed at the tip of the shank of the screw comes into contact with the inner corner portion at the end of the reinforcing rib, i.e., the portion that protrudes toward the imaginary circle extended axially forward on the inner circumference of the insertion hole.

[0015] In this way, when the sharp end of the screw comes into contact with the reinforcing rib, the screw, which attempts to advance straight, becomes inclined with respect to the axial extension of the insertion hole, causing the sharp end of the screw to attempt to enter with an inclined attitude relative to the introduction bush.

[0016] If the sharp end of the screw enters the lead-in bush at an angle, the sharp end will pierce or strongly scratch or rub the inner surface of the lead-in bush, which is made of synthetic resin. This will cause holes or cuts in the peripheral wall of the lead-in bush, preventing a secure screw-in between the lead-in bush and the screw screwed into it. The lead-in bush will not be able to be pulled in securely, and the web will not be able to brace itself to support the expansion arms, resulting in a situation where the expansion anchor cannot be fixed.

[0017] Therefore, an object of the present invention is to provide an expansion anchor which has an overall small size and which, even if the reinforcing ribs on the web are provided as thick as possible over the entire length of the web, can guide the sharp end of the inserted screw into the lead-in bush without tilting, thereby preventing damage to the lead-in bush and enabling the screw to be reliably screwed into the lead-in bush. [Means for solving the problem]

[0018] In order to solve the above-mentioned problems, the invention of claim 1 is an expansion anchor in which expansion arms are provided via hinges on both sides of the tip of a stem through which a screw insertion hole passes, and the tips of two webs connected to each of the expansion arms via hinges are connected to an introduction bush through which a screw insertion hole passes, and reinforcing ribs having a length that covers the entire length of the webs in the longitudinal direction and a width that is approximately half the width of the webs are provided on the inner sides of both webs facing the expansion arms, the reinforcing ribs being positioned biased toward opposite side edges of both webs, and a recess for guiding a screw is provided at the corner of the end of the reinforcing rib located on the introduction bush side.

[0019] The invention of claim 2 is such that the screw guide recess provided in the reinforcing rib is set at the end of the reinforcing rib located on the introduction bush side, at the corner portion located on the inside in the width direction of the web, and this recess is formed in an arc shape that coincides with an extended imaginary circle axially forward on the inner circumference of the screw insertion hole provided in the stem.

[0020] Here, the stem has a flange on the outer periphery of the rear end and a rib on the outer periphery to prevent co-rotation, and the screw insertion hole that passes through along the axis is a two-stage hole with a larger diameter at the rear end and a smaller diameter at the tip, and the tip of the stem is a small-diameter cylindrical section to prevent the stem from opening too far, and the stem and the pair of expansion arms are connected via a first hinge on both sides of the cylindrical section.

[0021] The stem, the spreader arm and the web have approximately the same width, the web is connected to a position close to the hinge of the spreader arm via a second hinge, and an introduction bush is connected between the tip ends of both webs via a third hinge. Effect of the Invention

[0022] According to this invention, reinforcing ribs are provided in a biased arrangement on opposing side edges of both webs, and a recess for guiding a screw is provided at the corner of the end of this reinforcing rib located on the lead-in bush side.By allowing the sharp end of the screw inserted into the stem to enter the recess, the straightness of the screw is maintained and no wobbling is eliminated, and the sharp end of the screw can be guided into the lead-in bush without tilting, preventing damage to the lead-in bush due to the sharp end of the screw, thereby ensuring that the screw is screwed into the lead-in bush. [Brief description of the drawings]

[0023] [Figure 1] FIG. 2 is a front view of the expansion anchor according to the present invention; [Diagram 2] FIG. 3 is a perspective view of the expansion anchor; [Diagram 3] A longitudinal sectional front view of the same expansion anchor [Figure 4] Cross-sectional view taken along the line aa in FIG. [Diagram 5] FIG. 2 is a perspective view showing the structure of the web and the reinforcing ribs provided thereon, as viewed from the side of the arrow bb in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0025] As shown in Figures 1 to 3, the expansion anchor 1 of this invention comprises a square tubular stem 2, a pair of expansion arms 4 attached to both sides at the tip of the stem 2 via a first hinge 3, a pair of webs 6 attached to the front of both expansion arms 4 on the opposite side to the stem 2, each of which is attached via a second hinge 5 and inclined inwardly forward, and a lead bush 8 attached between the close tips of both webs 6 via a third hinge 7 and arranged coaxially at the front of the stem 2. This expansion anchor 1 is made of synthetic resin and is molded in a shape such that both expansion arms 4 open out to both sides at a substantially right angle at the tip of the stem 2, and both webs 6 protrude forward from both expansion arms 4 at an angle so that the tips of the webs 6 approach each other, and the lead bush 8 is located between the tips of both webs 6.

[0026] The stem 2 has a flange 9 at its rear end and multiple ribs 10 on each surface of its outer circumference to prevent co-rotation, and the screw insertion hole 11 that passes through it along its axis is a stepped hole with a large diameter hole 11a at the rear end and a small diameter hole 11b at the tip end, the diameter of the large diameter hole 11a being larger than the nominal diameter of the screw to act as a guide to aid in the insertion of the screw, and the small diameter hole 11b has a diameter that allows the screw to be screwed in.

[0027] In the illustrated example, the flange 9 is formed in a circular shape, but it may also be in a rectangular or hexagonal shape. The ribs 10 are provided on each surface of the stem 2, and as shown in FIG. 4, are long along the axial direction of the stem 2 and have a trapezoidal cross section that protrudes radially outward from the outer surface of the stem 2. The surface that faces the direction of rotation when the screw is screwed into the stem 2 is perpendicular to the stem 2, and the opposite surface is an inclined surface that widens toward the stem 2 side, and the tip side has an inclined edge that slopes downward from the outer edge toward the stem 2 side. As shown in FIG. 2, the rib 10 on the same outer surface as the spreading arm 4 is long enough that the tip side does not reach the first hinge 3 of the spreading arm 4.

[0028] When the expansion anchor 1 is fixed by screwing in a screw, a high rotational torque is instantaneously applied to the rib 10. However, by giving the rib 10 the shape and structure described above, an effective anti-rotation effect that resists the torque is obtained, resistance when inserting it into a pilot hole in a building material can be reduced, and rotation of the expansion arm 4 at the first hinge 3 is not hindered.

[0029] In the illustrated example, the tip side of the stem 2 protrudes forward beyond the portion where the first hinges 3 on both sides of the stem 2 are connected, and when the screw is screwed in excessively, the tip receives the pulled-in guide bush 8, thereby forming a prevention portion 12 that prevents the spreader arm 4 from opening too far. The rib 10, located on an outer surface different from the first hinge 3, is set to a length such that its tip is positioned close to the tip of this excessive opening prevention portion 12.

[0030] The first hinges 3 provided on both sides of the stem 2 are bent in an arc in opposite directions at an angle of approximately 90°, and the expansion arms 4 connected to the tips of the first hinges 3 and extending out on both sides are slightly wider than the first hinge 3 and approximately the same width as the stem 2, and are thicker than the first hinge 3.

[0031] The web 6 is a relatively thin rectangular plate having the same width as the spreading arm 4, and its rear end is connected to the spreading arm 4 via a second hinge 5 located on the front side of the spreading arm 4 in a position close to the first hinge 3, and its tip side is inclined toward the spreading arm 4 toward the extension line of the axis of the stem 2, and an introduction bush 8 is provided between the tips of both webs 6 via a short third hinge 7.

[0032] On the inner surface of each of the webs 6 facing the stem 2, a reinforcing rib 13 is provided for improving the bending resistance of the web 6.

[0033] The reinforcing rib 13 has a rectangular shape with a length spanning the entire length of the web 6 and a width half that of the web 6, and is provided at different positions in the width direction along opposite side edges of both webs 6. When both spreading arms 4 are closed to sandwich the web 6 between their opposing surfaces, both webs 6 can be folded without interference from the reinforcing rib 13.

[0034] As shown in FIG. 3, the lead-in bush 8 is rectangular with a long side equal to the width of the web 6 and a short side shorter than that, with a screw hole 14 passing through along its axis, and is provided between the tips of both webs 6 at the front position of the stem 2 with the screw insertion hole 11 and the screw hole 14 arranged coaxially, and the tip ends of both webs 6 face the open ends of the screw hole 14 at the rear end side of the lead-in bush 8 via a short third hinge 7.

[0035] For this reason, if a thick reinforcing rib 13 is provided over the entire length of the web 6, the end of this reinforcing rib 13 located on the side of the lead-in bush 8 will have an inner corner portion that intrudes into the axially extended imaginary circle of the inner circumference of the small diameter hole 11b in the insertion hole 11 formed in the stem 2. If such an intruding portion is present, when a screw is screwed from the stem 2 into the lead-in bush 8, the sharp end of the screw will come into contact with the intruding portion, preventing the screw from advancing straight and causing wobbling, and the sharp end will intrude into the lead-in bush 8 at an angle, causing damage to the inner circumference of the lead-in bush 8.

[0036] To prevent this, in this invention, as shown in Figures 3 and 5, a recess 15 for guiding a screw is provided at the inner corner portion in the width direction at the end portion of the reinforcing rib 13 located on the lead-in bush 8 side, so as not to impede the straight advancement of the screw into the screw-in hole 14 of the lead-in bush 8.

[0037] This screw guiding recess 15 is formed in an arc shape that coincides with an axially extended imaginary circle of the inner circumference of the small diameter hole 11b of the insertion hole 11 by removing a portion of the thickness of the reinforcing rib 13. As a result, the inner surface of the recess 15 is arranged in phase with a portion of the inner circumference of the screw-in hole 14 at a position just before the introduction bush 8, and the screw can be guided accurately and reliably.

[0038] In the case of FIG. 5, the reinforcing rib 13 has a chamfer 16 at the end located on the spreading arm 4 side at the inner corner in the width direction, so that even when the web 6 is not fully opened, the screw first penetrates between the chamfers 16 and pushes the web 6 open to both sides, so that the sharp end of the screw can be guided into the lead-in bush 8.

[0039] The expansion anchor 1 of the present invention is configured as described above. When the expansion anchor 1 is used, as shown in FIG. 1 , the two expansion arms 4 that spread out on both sides are pushed forward toward each other from the first hinge 3 so as to close, and when these expansion arms 4 are closed, the pair of stems 2 are pushed forward via the second hinge 5, and the ends on the second hinge 5 side approach each other and close in a parallel manner until they are sandwiched between the two expansion arms 4, with the introduction bushing 8 being located at the tips of the rod-shaped expansion arms 4.

[0040] In this state, if the expansion anchor 1 is inserted from the lead-in bush 8 with both expansion arms 4 into the pilot hole of the building material, the rib 10 of the stem 2 biting into the building material from the inner circumference of the pilot hole, until the flange 9 abuts the building material, the expansion arms 4, which have been unfolded by being positioned on the back side of the building material, will extend at an oblique angle to both sides from the stem 2 due to the restoring elasticity of the first hinge 3, facing the back side of the building material, and both webs 6 will be pulled back via the second hinge 5 and open on both sides, and the expansion anchor 1 will return to a state close to the molded shape shown in Figure 1 before use, with the lead-in bush 8 positioned axially forward of the stem 2.

[0041] Next, when a screw is inserted into the insertion hole 11 of the stem 2 and screwed into the small diameter hole 11b, the screw advances along the axis of the insertion hole 11, penetrating the stem 2, and the sharp end of the screw protruding from the tip of the stem 2 advances forward through the webs 6 opened on both sides toward the introduction bush 8 in front. At this time, the reinforcing ribs provided on the inner surface of the webs 6 on both sides have a recess 15 for guiding the screw at the inner corner portion in the width direction at the end located on the introduction bush 8 side, and this recess 15 is formed in an arc shape that coincides with the axial extension virtual circle of the inner circumference of the small diameter hole 11b in the insertion hole 11, so that no obstacles protrude forward in the direction in which the screw advances.

[0042] Therefore, even if the axial center of the screw deviates during its forward movement after penetrating the stem 2 due to bending of the resin that forms the expansion anchor 1 or differences in the degree of opening of the reinforcing ribs 13, the sharp end of the screw will enter between the recesses 15 on both sides and be guided forward. This guidance causes the screw's axial center to coincide with the axial center of the lead-in bush 8 located in front. As a result, the sharp end of the advancing screw will enter along the axial center of the lead-in bush 8 without being tilted, and will not scratch or damage the inner circumference of the lead-in bush 8.

[0043] When a screw is screwed into the lead bush 8 and the head of the screw is tightened with the screw in contact with the fixed object, the screw rotates in a fixed position, breaking the inner circumference of the small diameter hole 11b. This rotation of the screw in a fixed position causes the lead bush 8 into which the screw is threaded to be pulled toward the stem 2, which pushes both expansion arms 4 through the webs 6 and presses them against the back side of the building material. If the building material is thin, the lead bush 8 will abut against the prevention part 12 at the tip of the stem 2, preventing excessive expansion of the expansion arms 4. The expansion anchor 1 is fixed by clamping the building material between the expansion arms 4 and the flanges 9, completing the attachment of the fixed object to the building material. [Explanation of symbols]

[0044] 1 Expansion anchor 2. Stem 3 First Hinge 4 Spread Arms 5 Second Hinge 6. Web 7 Third Hinge 8 Introduction bushing 9 Flange 10. Ribs 11 Insertion hole 11a Large diameter hole 11b Small diameter hole 12. Over-opening prevention section 13 Reinforcing rib 14 Screw hole 15 Notch 16 Chamfering

Claims

1. An expansion anchor having expansion arms via hinges on both sides of the tip of a stem through which a screw insertion hole passes, and having webs connected to the expansion arms via hinges at their tip sides connected to an introduction bush through which a screw insertion hole passes, wherein reinforcing ribs having a length spanning the entire length of the webs in the longitudinal direction and a width approximately half that of the webs are provided on the inner surfaces of the webs facing the expansion arms, the reinforcing ribs being positioned offset toward opposite side edges of the webs, and a screw guide recess is provided at the corner of the end of the reinforcing rib located on the introduction bush side.

2. 2. The expansion anchor according to claim 1, wherein the screw guide recess provided in the reinforcing rib is set at a corner position located on the inside in the width direction of the web at an end portion located on the lead-in bush side of the reinforcing rib, and the recess is formed in an arc shape that coincides with an imaginary circle extended axially forward on the inner circumference of the screw insertion hole provided in the stem.

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