Washer assembled screw

Abstract

To provide a washer assembled screw capable of preventing an elastic ring from coming off.SOLUTION: A washer assembled screw 10 is composed of a head 21, a shank 23 with a screw thread formed on an outer periphery, an elastic ring 30 disposed on a seating face of the head, and a washer 26 assembled on a neck lower part of the shank 23 to support the elastic ring from below. In the washer assembled screw, when the head is seated, the washer moves in an axial direction of the shank to be housed inside the elastic ring, and working 22a for preventing the moved washer from being fixed to the seating face is applied to the seating face of the head.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a screw with a assembled washer having a sealing function. [Background technology]

[0002] Conventionally, as shown in Patent Document 1, there is known a washer assembled screw which has a head with a circular ring-shaped step formed on the seating surface, a shank which is continuous with the head and has a thread formed on its outer periphery, and an elastic ring which is attached so as to fit along the outer periphery of the step of the head, and which is configured so that when the head seats on a fastened member, the elastic ring is pressed against the fastened member and deforms, thereby providing a sealing function. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Jpn. Jpn. Published No. 46-21289 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in conventional washer assembled screws, the elastic ring could fall off the step on the head due to the effects of vibration during transportation.

[0005] Therefore, an object of the present invention is to provide a washer assembled screw in which the elastic ring is less likely to fall off. [Means for solving the problem]

[0006] The present invention was created in consideration of the above-mentioned problems, and provides a washer assembled screw which comprises a head, a shank which is molded integrally with the head and has a thread formed on its outer periphery, an elastic ring which is placed on the seating surface of the head, and a washer which is attached to the neck portion of the shank and supports the elastic ring from below, in which when the head is seated, the washer moves in the axial direction of the shank and is accommodated inside the elastic ring, and the seating surface of the head is processed to prevent the moved washer from adhering to the seating surface. It is also preferable that the seat surface of the head is provided with a plurality of protrusions. Effect of the Invention

[0007] According to the washer assembled screw of the present invention, the washer supports the elastic ring from below, which has the advantage of preventing the elastic ring from falling off. In addition, because the washer is configured to be housed inside the elastic ring, when the head is seated, the elastic ring is sandwiched from above and below by the head seating surface and the fastened member, and is in close contact with both, providing an airtight seal. On the other hand, when the washer is housed inside the elastic ring, there is a risk that it will be pressed against and fixed to the head seating surface, but the head seating surface has been processed to prevent this, so such a problem does not occur. [Brief description of the drawings]

[0008] [Figure 1] FIG. 2 is a partial cross-sectional side view showing the structure of a washer assembled screw according to the present invention. [Diagram 2] FIG. 2 is a partial cross-sectional side view showing a state before the washer assembled screw according to the present invention is screwed into a fastening member. [Diagram 3] FIG. 2 is a partial cross-sectional side view showing a state after the washer assembled screw according to the present invention has been screwed into a fastening member. [Figure 4] FIG. 2 is a partial cross-sectional side view showing a second embodiment of a washer assembled screw according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The following describes an embodiment of the present invention with reference to the drawings. In Fig. 1, 10 is a screw with assembled washer 10 that is fastened to a fastened member 50. This screw with assembled washer 10 is composed of a threaded fastener 20 and an elastic ring 30 attached to this threaded fastener 20.

[0010] The screw fastener 20 is a headed rod-shaped member in which a head 21 and a shank 23 are integrally formed as shown in Fig. 1. The head 21 of the screw fastener 20 is configured in a disk shape with a substantially hexagonal fitting hole 211 formed on its upper surface into which a fastening tool can be fitted, and a substantially disk-shaped step 22 smaller in diameter than the head 21 is provided on the lower part along the same axis. The step 22 is continuous with the shank 23 on the same axis, and a circular relief groove 221 recessed upward along the boundary with the shank 23 is formed on the seating surface of the step 22. The seating surface of the step 22 formed on the seating surface of the head 21 is provided with a plurality of protrusions 22a as processing to prevent the flat washer 26 from adhering to the seating surface of the step 22, as will be described in detail later.

[0011] The shaft portion 23 is composed of a neck portion 24 continuing from the step portion 22, and a threaded portion 25 continuing from the neck portion 24. The neck portion 24 is formed in a generally cylindrical shape continuing from the inner diameter of the escape groove 221, and a retaining projection 241 that projects radially outward is formed at the boundary with the threaded portion 25 continuing from its lower end. The threaded portion 25 has a male thread 251 formed on its outer periphery, and the male thread 251 is configured so that its outer diameter is larger than the outer diameter of the retaining projection 241.

[0012] A flat washer 26 is fitted into the neck portion 24 of the screw fastener 20. This flat washer 26 is a circular plate material having an outer diameter larger than the step portion 22 and a through hole smaller than the outer diameter of the retaining protrusion 241. The plate thickness of the flat washer 26 is thinner than the axial dimension of the neck portion 24, and the flat washer 26 is configured to be movable in the vertical direction between the retaining protrusion 241 and the step portion 22.

[0013] The elastic ring 30 is a ring-shaped member having a substantially circular cross section in the circumferential direction, which is fitted around the outer periphery of the flat washer 26 and the step 22. In this embodiment, the elastic ring 30 is configured such that its outer diameter is larger than the outer diameter of the head 21, and its inner diameter is slightly smaller than the outer diameters of the step 22 and the flat washer 26, so that the elastic ring 30 is constantly expanded. With this structure, the elastic ring 30 is always fitted into the step 22, and its inner lower surface abuts against the upper edge of the flat washer 26 to be supported and prevented from falling off, thereby preventing the elastic ring 30 from falling off the screw fastener 20 during transportation or storage.

[0014] In this embodiment, the wire diameter D1 of the elastic ring 30 is configured to be slightly smaller than the sum of the thickness dimension D2 of the step portion 22 and the thickness dimension D3 of the plain washer 26, and the gap dimension D4 between the plain washer 26 and the step portion 22, so that the plain washer 26 comes into contact with the fastened member 50 before the elastic ring 30 does when fastening. In this embodiment, the thickness dimension D2 of the step portion 22 is designed to be about 50% of the wire diameter D1 of the elastic ring 30, and the sum of the thickness dimension D2 of the step portion 22 and the thickness dimension D3 of the plain washer 26 is designed to be about 80% of the wire diameter D1 of the elastic ring 30 so that the elastic ring 30 is compressed in the axial direction by about 20% when fastening, which will be described later. This prevents the elastic ring 30 from being excessively pressed and crushed when the washer assembly screw 10 is seated on the fastened member 50, and the plain washer 26 is accommodated inside the elastic ring 30 and is not exposed.

[0015] The washer assembled screw 10 as described above is manufactured by subjecting wire of a predetermined thickness to heading or the like to form a preform (not shown) having a head 21 and a shank 23, and then forming the retaining projection 241 and male thread 251 by rolling or the like in a state in which the flat washer 26 is assembled to the shank 23 of the preform. Because it is formed in this manner, the flat washer 26 will not come off the shank 23 of the screw fastener 20. Therefore, the elastic ring 30 arranged along the outer periphery of the step 22 and flat washer 26 of the screw fastener 20 is constantly supported from below by the flat washer 26 to prevent it from coming off.

[0016] The operation of the washer assembled screw 10 will now be described. The fastening member 40 that screws into the washer assembly screw 10 is a part formed with an internal thread that can screw into the male thread 251, and in this embodiment is a nut 40. Furthermore, a fastened member 50 that is fixed by the washer assembly screw 10 and the nut 40 is formed with an insertion hole into which the washer assembly screw 10 can be inserted. This insertion hole has a hole diameter that is larger than the outer diameter of the male thread 251 and smaller than the outer diameter of the flat washer 26, and is configured so that the lower surface of the flat washer 26 can abut against the upper surface of the fastened member 50.

[0017] In the washer assembled screw 10 configured as described above, the threaded portion 25 is inserted into the insertion hole of the fastened member 50, and then the nut 40 is screwed onto the portion of the threaded portion 25 protruding from the insertion hole. During this fastening, the flat washer 26 comes into contact with the upper surface of the fastened member 50 and stops. Meanwhile, the fastened fastener 20 fastened to the nut 40 and the elastic ring 30 pressed from above against the head 21 of the fastened fastener 20 move downward relative to the flat washer 26. As a result, the flat washer 26 is housed inside the elastic ring 30 as shown in FIG. 3. Thereafter, as the fastened fastener 20 moves further downward, the elastic ring 30 also comes into contact with the fastened member 50 and elastically deforms between the head 21 of the descending fastened fastener 20 and the fastened member 50. As a result, the gap between the fastened member 50 and the head 21 is sealed, maintaining airtightness. Thereafter, the step 22 of the screw part 20 of the washer assembled screw 10 is seated on the upper surface of the flat washer 26. At this time, as described above, the relief groove 221 is formed on the seating surface of the step 22, and an R portion (an arc-shaped machining relief formed at the boundary between the step 22 and the neck portion 24 during forging) is not formed at the boundary between the step 22 and the neck portion 24, so that the flat washer 26 does not interfere with the R portion and a gap does not remain between the step 22 and the flat washer 26. As a result, the step 22 and the flat washer 26 are in reliable contact with each other, so that the elastic ring 30 can be compressed by an appropriate amount, and the airtightness between the head 21 and the fastened member 50 can be improved. On the other hand, when the flat washer 26 is housed inside the elastic ring 30, there is a risk that the flat washer 26 will be pressed against and fixed to the seating surface of the step 22, but a protrusion 22a is formed on the seating surface of the step 22 as a processing to prevent this, so that such a problem does not occur.

[0018] As described above, the washer assembled screw 10 of the present invention is configured so that the flat washer 26, which is larger than the outer diameter of the step 22, is movable axially and inside the elastic ring 30, so that the elastic ring 30 is supported from below by the flat washer 26, which is arranged with a gap between it and the step 22, and is prevented from falling off during assembly and transportation. On the other hand, when the gap between the flat washer 26 and the step 22 closes when the flat washer 26 is seated, the flat washer 26 is housed inside the elastic ring 30, so that the elastic ring 30 is sandwiched between the head 21 and the fastened member 50 from above and below, making intimate contact with both and providing airtightness.

[0019] Furthermore, in this embodiment, the flat washer 26 is set to come into contact with the fastened member 50 before the elastic ring 30 does, and can be accommodated inside the elastic ring 30 before the elastic ring 30 begins to deform as a result of coming into contact with the fastened member 50. This prevents the elastic ring 30, compressed by the head 21 and the fastened member 50, from penetrating into the gap between the step portion 22 and the flat washer 26, preventing damage to the penetrating portion.

[0020] The specific configuration of each part of the present invention is not limited to the above-mentioned embodiment, and various modifications are possible within the scope of the present invention. For example, the fitting hole 211 is not limited to a hexagonal shape, and may be a cross recess, a hex lobe, or other shapes. In the above embodiment, the thickness of the step 22 is set to 50% of the wire diameter D1 of the elastic ring 30, but it is sufficient to design it within a range in which the elastic ring 30 does not come off, and it is sufficient to have a thickness of 45% or more of the wire diameter D1 of the elastic ring 30. Furthermore, the thickness of the step 22 and the flat washer 26 is set to a thickness that crushes the elastic ring 30 by about 20% in the axial direction, but the design can be changed within a range in which the elastic ring 30 compressed in the axial direction exhibits airtightness and is not crushed by excessive pressure. Moreover, the flat washer 26 is configured to be larger than the step 22 and to be accommodated inside the elastic ring 30 when pressed from below. As described above, it is preferable that the design of the step portion 22 and the flat washer 26 be appropriately changed in accordance with the elastic ring 30 to be used.

[0021] Furthermore, the flat washer 26 is one example of a washer assembled to the neck portion 24, and a tapered disc spring 27 that slopes downward as it moves radially outward may be assembled instead of the flat washer 26 as shown in Fig. 4. In such a washer assembled screw 10' that has a disc spring 27 instead of a flat washer 26, the disc spring 27 is configured to have a tapered shape, which widens the gap between the step portion 22 and the disc spring 27, making it easier to attach the elastic ring 30. [Explanation of symbols]

[0022] 10 … Screw with washer 20 … Threaded fasteners 21 … Head 211… Fitting hole 22 … Stepped section 221…Relief groove 23 … Shaft 24 … Lower neck 241… Anti-slip protrusion 25 … Threaded section 251… Male thread 26 … Flat washer 30 ... Elastic ring 40 ... Fastening members 50 … Part to be fastened

Claims

1. A washer assembled screw including a head, a shaft portion that is integrally molded with the head and has a screw thread formed on its outer periphery, an elastic ring that is placed on the seating surface of the head, and a washer that is assembled to a neck portion of the shaft portion and supports the elastic ring from below, A washer assembled screw, characterized in that when the head is seated, the washer moves in the axial direction of the shaft portion and is accommodated inside the elastic ring, and the seating surface of the head is processed to prevent the moved washer from adhering to the seating surface.

2. 2. The screw according to claim 1, wherein a plurality of protrusions are provided on the bearing surface of the head.

Images