Resin coating screw

Abstract

To provide a resin coating screw that easily removes a resin cap from a metal screw member.SOLUTION: A resin coating screw of the present invention comprises a metal screw member 4 with a shaft part 3 and a head part 2, and a resin cap 5 that coats the head part 2 of the screw member 4. The head part 2 of the screw member 4 is provided with a chamfered part 8 at a boundary portion between a seating surface 2b and a side surface, and the cap 5 is attached to the head part 2 so as to coat top and side surfaces of the head part 2 as well as partway through the chamfered part 8. The resin coating screw has a coating mechanism in which a plurality of knurled grooves 7 communicating with the chamfered part 8 are formed on the side surface of the head part 2, and an end surface 5a of the cap 5 intersects with the boundary between the groove 7 and the chamfered part 8.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a resin-coated screw in which the head of a metal screw is covered with a resin cap. [Background technology]

[0002] Conventionally, a resin-coated screw shown in Patent Document 1 is known as a resin-coated screw. This resin-coated screw has a metal screw member consisting of a shaft portion on which a thread is formed and a head portion integrally molded at one end of the shaft portion, and the head portion of the metal screw member is covered with a resin cap. The head portion is cylindrical and extends in the circumferential direction from the shaft portion, and its peripheral side surface is knurled. This knurling process forms a plurality of grooves extending parallel to the axis of the shaft portion over the entire circumference of the peripheral side surface of the head. In addition, the peripheral side surface of the head and the seat surface are configured to be continuous with a curved portion, and the boundary portion between the peripheral side surface and the seat surface is configured to be a curved surface over the entire circumference due to this curved portion.

[0003] The cap is molded to cover the head of the metal screw with a predetermined thickness, and the cap seat is configured to be substantially flush with the head seat. The cap is attached to the head by injection molding, and during this injection molding, resin material is filled into the curved portion and the knurled grooves, preventing the cap from coming off or rotating relative to the screw. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2022-171373 A Summary of the Invention [Problem to be solved by the invention]

[0005] Conventional resin-coated screws have a cap that covers the entire curved surface of the boundary between the head and the seat of the metal screw, so the cap can be firmly prevented from coming off. However, when the resin-coated screw is discarded, it is difficult to remove the cap from the screw for separate disposal. In addition, because the head seat of the screw and the cap seat are located almost on the same plane, if the processing and molding accuracy of the screw or cap is poor, or if the resin-coated screw itself is left under high temperature for a long time, the cap seat may protrude slightly from the head seat. If this is tightened as it is, only the cap will seat on the workpiece and the head seat of the screw will not seat, resulting in a tightening failure similar to so-called screw floating, so attention was required to the processing accuracy of the resin-coated screw and temperature management during storage. [Means for solving the problem]

[0006] The present invention was created in consideration of the above problems, and has a first object to provide a resin-coated screw in which the resin cap is easily removed from the metal screw member, and a second object to provide a resin-coated screw in which the head seating surface of the metal screw member can be securely seated on the workpiece when fastened.

[0007] In order to achieve the above object, the present invention provides a resin-coated screw having a metal screw member having a shaft and a head, and a resin cap that covers the head of the screw member, characterized in that the head of the screw member has a chamfered portion at the boundary between its seat and side, and the cap is attached to the head so as to cover the top and side of the head and the chamfered portion up to the middle. Since the cap covers the chamfered portion up to the middle of the head in this resin-coated screw, a step is formed between the seat of the head and the cap, making it easy to apply force when removing the cap from the head. In addition, the amount of engagement between the cap and the head can be reduced compared to the conventional method. Therefore, a resin-coated screw that is easy to remove the cap from the head can be provided. Moreover, since a step is formed between the head seat and the cap, the cap does not protrude beyond the seat due to thermal expansion or the like. Therefore, a resin-coated screw that can reliably seat the head seat of the metal screw member on the workpiece when fastened can be provided.

[0008] It is preferable that the side of the head has a plurality of grooves that communicate with the chamfered portion, and that the end face of the cap intersects with the boundary between the groove and the chamfered portion, thereby reducing the amount of catching between the cap and the head, and improving the ease of disassembly of the screw member and the cap.

[0009] In order to achieve the above object, the present invention provides a resin-coated screw having a metal screw member with a shaft and a head, and a resin cap that covers the head of the screw member, characterized in that the head of the screw member is provided with a chamfered portion at the boundary between its seat and side, and a plurality of grooves that communicate with the chamfered portion are formed on the side of the head, and the end face of the cap intersects with the boundary between the groove and the chamfered portion. This reduces the amount of catching between the cap and the head compared to the conventional method, and provides a resin-coated screw that is easy to remove the cap from the head. It is also possible to create a step between the head seat and the cap, which makes it possible to prevent the cap from protruding from the seat due to thermal expansion or the like. This provides a resin-coated screw that can reliably seat the head seat of the metal screw member on the workpiece when fastened. Effect of the Invention

[0010] According to the present invention, a chamfer is provided at the boundary between the peripheral side surface of the head of a metal screw member and the seat surface, and a groove is formed on the peripheral side surface of the head that communicates with the chamfer, and the seat surface of the cap crosses the boundary between the groove and the chamfer, so that the chamfered portion of the cap is less likely to get caught, making it easier to remove the cap from the screw member. This improves the ease of disassembly of the resin-coated screw and makes it easier to separate and dispose of it, thereby improving environmental performance. In addition, since the covering position of the cap is halfway up the chamfer, the head seat surface of the screw member protrudes from the cap. Therefore, even if there is some variation in processing accuracy or temperature change, the cap will not protrude from the head seat surface, and there are also advantages such as the head seat surface being reliably seated on the workpiece during fastening to obtain an appropriate fastening force. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a perspective view of a resin-coated screw according to the present invention. [Diagram 2] FIG. 2 is a plan view of a resin-coated screw according to the present invention. [Diagram 3]FIG. 2 is a bottom view of the resin-coated screw according to the present invention. [Figure 4] FIG. 2 is an enlarged, partially cutaway bottom view of a main portion of the resin-coated screw according to the present invention. [Diagram 5] 3 is a cross-sectional view taken along line AA in FIG. 2. [Figure 6] FIG. 2 is an enlarged, partially cutaway cross-sectional view of a main portion of a resin-coated screw according to the present invention. [Figure 7] FIG. 6 is a cross-sectional view taken along line BB in FIG. 5. [Figure 8] FIG. 4 is an enlarged, partially cutaway cross-sectional view of a main portion of another embodiment of a resin-coated screw according to the present invention. [Figure 9] FIG. 11 is a partially cutaway cross-sectional view of another embodiment of a resin-coated screw according to the present invention. [Figure 10] FIG. 11 is an enlarged, partially cutaway bottom view of a main portion of another embodiment of a resin-coated screw according to the present invention. [Figure 11] FIG. 4 is an enlarged, partially cutaway cross-sectional view of a main portion of another embodiment of a resin-coated screw according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the resin-coated screw according to the present invention will be described. In Fig. 1 to Fig. 7, 1 is a resin-coated screw, and this resin-coated screw 1 is composed of a metal screw member 4 formed by integrally molding a head 2 and a shaft portion 3, and a resin cap 5 that covers the head 2 of this screw member 4. The screw member 4 is processed, for example, by cold heading and rolling, and a screw thread 6 is integrally formed on the outer circumferential surface of the cylindrical shaft portion 3. The head 2 of this screw member 4 is configured as a thin cylindrical shape with a larger diameter than the shaft portion 3, and its peripheral side surface 2a is knurled. By this knurling, a plurality of knurl grooves 7 (an example of a recess in the claims) extending parallel to the axis of the screw member 4 are formed on the peripheral side surface 2a of the head 2 over its entire circumference and entire length. As a result, the head 2 is configured to have an uneven outer periphery in a plan view. Furthermore, a chamfered portion 8 is provided at the boundary portion between the bearing surface 2b and the peripheral side surface 2a of the head 2 of the screw member 4, i.e., at the peripheral edge of the bearing surface 2b. This chamfered portion 8 is a portion where the boundary portion between the peripheral side surface 2a and the bearing surface 2b is cut off at an angle of 45° to form a flat surface, that is, where a so-called C-chamfer is applied, and the knurled grooves 7 communicate with this chamfered portion 8. Note that this chamfered portion 8 may be configured as an R-chamfer instead of a C-chamfer.

[0013] Each of the knurled grooves 7 extends to the boundary between the chamfered portion 8 and the head seating surface 2b, communicating and opening into the chamfered portion 8, and the boundary with each chamfered portion 8 (the shape of the opening end of each knurled groove 7) is roughly triangular in shape, being wider on the head peripheral side surface 2a side and gradually narrowing toward the seating surface 2b.

[0014] The cap 5 is formed by injection molding a thermoplastic resin on the head 2 of the screw member 4, covering the top surface 2c and the peripheral side surface 2a of the head 2 with a predetermined thickness, and its lower end extends to the middle of the chamfered portion 8. The thermoplastic resin constituting the cap 5 can be selected from a group of commonly known resin materials such as PE resin, PP resin, ABS resin, and POM resin, and ABS resin is used in this example. The lower end of the cap 5 wraps around the chamfered portion 8, thereby preventing the cap 5 from coming off the head 2. In addition, the resin material constituting the cap 5 during the injection molding process is filled into the knurled groove 7 of the head 2, thereby preventing the cap 5 from rotating freely relative to the head 2. In addition, the lower end surface 5a of the cap 5 is formed in a flat shape parallel to the seat surface 2b of the head 2, and the cap 5 is attached to the head 2 so that the lower end surface 5a intersects with the boundary line between the chamfered portion 8 and the knurled groove 7 (the opening end of the knurled groove 7 on the chamfered portion 8). Due to such a covering structure of the cap 5, the head 2 and the cap 5 are caught only in the portion where the knurled grooves 7 of the chamfered portion 8 are not connected.

[0015] The top surface 5b side of the cap 5 has a sufficient thickness relative to the head 2 of the screw member 4, and is formed with a slot 9 into which a screw tightening tool (not shown) can be engaged. In addition, a groove 5c resembling a knurl is formed on the outer circumferential surface of the cap 5 over its entire circumference during injection molding.

[0016] Next, the operation of the resin-coated screw 1 according to the present invention will be described. The resin-coated screw 1 is used by screwing it into the female thread (not shown) of a workpiece, and can be screwed in by engaging a screw tightening tool such as a flat head screwdriver with the slot 9 on the top surface 5b of the cap 5 to apply rotation. Of course, it can also be screwed in to some extent by hand. In this case, since a groove 5c similar to a flat knurling is formed on the outer periphery of the cap, it is difficult to slip even when screwed in by hand, and it is easy to turn.

[0017] Since the resin-coated screw 1 has a structure in which the lower end surface 5a of the cap 5 covers up to the middle of the chamfered portion 8, even if, for example, the machining precision of the head 2 is poor or the cap 5 is left in a high temperature environment that causes thermal expansion, the lower end surface 5a of the cap 5 will not protrude beyond the seating surface 2b of the head 2. For this reason, the head seating surface 2b can be securely seated on the workpiece to obtain fastening force.

[0018] The resin-coated screw 1 fastened to the workpiece has its head portion exposed and protruding from the workpiece covered with a resin cap 5, so even if it is used in a high-temperature environment, such as near a heat source, the surface of the exposed portion is unlikely to become hot. Therefore, even if a worker accidentally touches the resin-coated screw 1, he or she will not be burned.

[0019] In the present resin-coated screw 1, the cap 5 is molded integrally with the screw member 4 by injection molding, so that the cap 5 is always firmly fixed to the screw member 4 and prevented from coming off and rotating. However, since the cap 5 only covers the chamfered portion 8 to a midpoint, the cap 5 can be removed from the screw member 4 with less force than before, if necessary. In particular, the head 2 and the cap 5 are caught only in the portion where the knurled groove 7 of the chamfered portion 8 does not communicate, which is a factor in improving the ease of disassembly. In this way, the knurled groove 7 not only contributes to preventing the cap 5 from turning, but also contributes to preventing the cap 5 from coming off. In other words, the open end of the knurled groove 7 to the chamfered portion 8 (the boundary between the knurled groove 7 and the chamfered portion 8) is gradually narrowed toward the seat surface 2b of the head 2, so that the amount of catch of the cap 5 with the head 2, that is, the difficulty (ease) of the cap 5 coming off can be adjusted depending on the setting position of the lower end surface 5a of the cap 5. Furthermore, when the cap 5 has a covering structure in which it only covers partway through the chamfered portion 8, a step is created between the lower end surface 5a of the cap 5 and the seat surface 2b of the head 2, making it easier to apply force when removing the cap 5 and easier to remove the cap 5 from the head 2.

[0020] 8 to 11 show other embodiments of the resin-coated screw according to the present invention. Among them, Fig. 8 shows a resin-coated screw 11 in which the cap 5 in the resin-coated screw 1 is configured so that its lower end surface 5a is disposed on approximately the same plane as the seat surface 2b of the head 2. As described above, the knurled groove 7 of this resin-coated screw 11 extends to and opens at the boundary between the chamfered portion 8 and the seat surface 2b of the head 2, so that even if the lower end surface 5a of the cap 5 is disposed on approximately the same plane as the seat surface 2b, the cap 5 and the head 2 only get caught in the portion where the knurled groove 7 of the chamfered portion 8 does not communicate. Therefore, the effect of easy disassembly described above can be obtained.

[0021] 9 shows a resin-coated screw 12 in which a cross-shaped slot 10 is engraved on the top surface 21c of the head 21 of the screw member 41, and the peripheral side surface 21a is not provided with any unevenness such as the knurled groove 7. The cap 51 in this example is prevented from rotating relative to the head 21 by filling the slot 10 with the resin material that constitutes it, and is prevented from coming off from the head 21 by covering the chamfered portion 81 up to a midpoint. Since there is no knurled groove 7 on the circumference of the head 2 as in the resin-coated screw 1, the cap 5 is firmly prevented from coming off from the head 2, while the step between the lower end surface 51a of the cap 51 and the seat surface 21b of the head 21 makes it easier to apply force to remove the cap 5 and prevents the screw from floating when fastened.

[0022] 10 shows an example in which the depth of the knurled groove 7 of the resin-coated screw 1 is made deeper to form knurled groove 71, which opens up to the seating surface 2b of the head 2. In this example, the lower end surface 5a of the cap 5 is arranged to be substantially flush with the seating surface 2b of the head 2. Even with this configuration, the same effects can be obtained as with the resin-coated screw 1 described above.

[0023] 11 shows a resin-coated screw 13 in which the chamfered portion 8 of the resin-coated screw 1 is a curved R-chamfered portion. Even when the chamfered portion 8 is a R-chamfered portion in this way, the same effect can be obtained as with the resin-coated screw 1. Of course, the configurations shown in FIGS. 8 and 10 can also be applied to the resin-coated screw 13 shown in FIG. 11.

[0024] The resin-coated screw according to the present invention is not limited to the above-mentioned configuration, and various modifications are possible without departing from the spirit and scope of the invention. [Explanation of symbols]

[0025] 1 Resin-coated screw 2 heads 3 Shaft section 4 Screw members 5 Cap 6 Threads 7 Knurled groove 8 Chamfer 9 Slit

Claims

1. A resin-coated screw having a metal screw member with a shank and a head, and a resin cap that covers the head of the screw member, A resin-coated screw, characterized in that a chamfered portion is provided at the boundary between the seat surface and the side surface of the head of the screw member, and the cap is attached to the head so as to cover the top surface and side surface of the head as well as up to halfway through the chamfered portion.

2. The resin-coated screw according to claim 1, characterized in that a plurality of recesses communicating with the chamfered portion are formed on the side of the head, and the end face of the cap intersects with the boundary between the recesses and the chamfered portion, forming a coating structure.

3. A resin-coated screw having a metal screw member with a shank and a head, and a resin cap that covers the head of the screw member, A resin-coated screw characterized in that a chamfered portion is provided at the boundary between the seat surface and the side surface of the head of the screw member, and a plurality of recesses communicating with the chamfered portion are formed on the side surface of the head, and a coating structure is formed in which the end face of a cap intersects with the boundary between the recesses and the chamfered portion.

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