Screw fall prevention structure and electricity meter

Abstract

To provide a screw falling-off preventing structure and a watt-hour meter capable of preventing a tightening screw from falling off accompanying the operation of loosening the tightening screw including a terminal screw.SOLUTION: A screw falling-off preventing structure includes: a terminal screw 12 which can be screwed into a screw hole 18; a base member 10 whose screw hole 18 is formed and in which a guide hole 19 for guiding the insertion of the terminal screw 12 is formed on the insertion port side of the screw hole 18; and a cover member 13 which covers the base member 10 including the terminal screw 12 and has a stopper 16 for restricting a head part 12a of the terminal screw 12 from moving in the loosening direction of the terminal screw 12 and a screw guiding space ER for guiding the terminal screw 12 from the stopper 16 toward the guide hole 19 formed therein in a state where a tip part of the terminal screw 12 is engaged with the guide hole 19.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a screw falling-off prevention structure capable of preventing a tightening screw including a terminal screw from falling off when the tightening screw is loosened, and to a watt-hour meter. Background Art

[0002] Various mechanical parts and the like are often fixed and assembled using fastening screws. For example, in wiring work for instruments such as watt-hour meters and wiring breakers, a current lead-in wire is inserted into a terminal portion, and the current lead-in wire is electrically connected using a terminal screw.

[0003] Patent Document 1 discloses a terminal screw that electrically connects an electric wire inserted into a terminal hole to a terminal fitting. Prior Art Documents Patent Documents

[0004] Patent Document 1 Japanese Unexamined Patent Publication No. 2001-215244 Summary of the Invention Problem to be Solved by the Invention

[0005] By the way, in wiring work for instruments such as watt-hour meters and wiring breakers, before inserting a current lead-in wire into a terminal hole of a terminal portion, work is performed to loosen the screwed terminal screw. If the terminal screw is loosened excessively, the terminal screw will fall off, which delays the wiring work and consumes extra time and labor.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a screw falling-off prevention structure capable of preventing a tightening screw including a terminal screw from falling off when the tightening screw is loosened, and a watt-hour meter. Means for Solving the Problem

[0007] To solve the above-mentioned problems and achieve the objective, the screw fallout prevention structure according to the present invention is characterized by comprising: a tightening screw that can be screwed into a screw hole; a base member having the screw hole formed therein and a guide hole formed on the insertion side of the screw hole to guide the insertion of the tightening screw; and a screw cover member that covers the base member including the tightening screw and has a stopper that restricts the head of the tightening screw from moving in the loosening direction of the tightening screw when the tip of the tightening screw is engaged with the guide hole, and a screw guide space that guides the tightening screw from the stopper toward the guide hole.

[0008] Furthermore, the screw fallout prevention structure according to the present invention is characterized in that, in the above invention, the screw cover member has an operating hole formed therein through an operating groove formed in the head of the fastening screw, through which an operating tool for tightening and loosening operations can be inserted and removed.

[0009] Furthermore, the screw fallout prevention structure according to the present invention is characterized in that, in the above invention, the tightening screw has a flange formed on its head that engages with the stopper.

[0010] Furthermore, the screw fall prevention structure according to the present invention is characterized in that, in the above invention, a notch is formed in a part of the circumferential direction of the flange, the screw cover member has a projection corresponding to the notch as a stopper, and the fastening screw can be inserted and removed by passing the notch and the projection through it.

[0011] Furthermore, the screw fall prevention structure according to the present invention is characterized in that, in the above invention, the tightening screw is a terminal screw that fixes the current lead wire inserted into the terminal hole of the terminal fitting attached to the base member via the screw hole of the terminal fitting.

[0012] Furthermore, the screw fall prevention structure according to the present invention is characterized in that, in the above invention, the fastening screw is a mounting screw that attaches the conductive connection part and the current bar to the base member by screwing it into a screw hole provided in the base member via a first connection hole in a conductive connection part which is one end of a terminal fitting for connecting an electric current supply line and a second connection hole provided at one end of a current bar in the base member, and the first connection hole and the second connection hole function as guide holes.

[0013] Furthermore, the electricity meter according to the present invention is characterized by having a screw fallout prevention structure as described in any one of the above inventions. [Effects of the Invention]

[0014] According to the present invention, it is possible to prevent fastening screws, including terminal screws, from falling out during the process of loosening them. [Brief explanation of the drawing]

[0015] [Figure 1] Figure 1 is a front view showing the configuration of an energy meter having a screw fallout prevention structure, which is an embodiment of the present invention. [Figure 2] Figure 2 is an exploded perspective view of an electricity meter. [Figure 3] Figure 3 is a cross-sectional view of line AA in Figure 1 with the terminal screw in its maximum tightened state. [Figure 4] Figure 4 is an enlarged perspective view of section B in Figure 1, with the terminal screw in its maximum tightened state. [Figure 5] Figure 5 is a cross-sectional view of line AA in Figure 1 when the terminal screw is in its most loosened state. [Figure 6] Figure 6 is an enlarged perspective view of section B in Figure 1, where the terminal screw is in its most loosened state. [Figure 7] Figure 7 is a front view showing the configuration of an energy meter 2 having a screw fallout prevention structure, which is a modified example 1 of the embodiment of the present invention. [Figure 8] Figure 8 is an exploded perspective view of the electricity meter shown in Figure 7. [Figure 9]FIG. 9 is a cross-sectional view taken along line C-C in FIG. 7 when the mounting screw is in a maximum loosened state. [Figure 10] FIG. 10 is an enlarged perspective view of section D in FIG. 7 when the mounting screw is in a maximum loosened state. [Figure 11] FIG. 11 is a cross-sectional view showing the configuration of a portion corresponding to FIG. 9 in Modification 2. [Figure 12] FIG. 12 is a left side view of FIG. 11. MODE FOR CARRYING OUT THE INVENTION

[0016] Hereinafter, modes for carrying out the present invention will be described with reference to the accompanying drawings.

[0017] Embodiment <Overview of Watt-hour Meter> FIG. 1 is a front view showing the configuration of a watt-hour meter 1 having a screw falling-off prevention structure according to an embodiment of the present invention. FIG. 2 is an exploded perspective view of the watt-hour meter 1. As shown in FIG. 2, in the watt-hour meter 1, a terminal fitting 11 screwed with a terminal screw 12 serving as a tightening screw is fitted into a base member 10; in this state, the terminal screw 12 is screwed into a screw hole 18 of the terminal fitting 11, and a cover member 13 serving as a screw cover member is assembled to the base member 10 so as to cover an opening of the base member 10. Accordingly, the terminal screw 12 is held in a state sandwiched between the terminal fitting 11 and the cover member 13. The watt-hour meter 1 is a single-phase two-wire watt-hour meter, and includes four terminal fittings 11 for fixing two input-side current lead-in wires and two output-side current lead-in wires. For each terminal fitting 11, a current lead-in wire is fixed by two terminal screws 12.

[0018] <Screw Falling-off Prevention Structure> FIG. 3 is a cross-sectional view taken along line A-A in FIG. 1 when the terminal screw 12 is in a maximum tightened state. FIG. 4 is an enlarged perspective view of section B in FIG. 1 when the terminal screw 12 is in a maximum tightened state. FIG. 5 is a cross-sectional view taken along line A-A in FIG. 1 when the terminal screw 12 is in a maximum loosened state. FIG. 6 is an enlarged perspective view of section B in FIG. 1 when the terminal screw 12 is in a maximum loosened state.

[0019] In Figures 3 to 6, the terminal fitting 11 is fitted and mounted onto the base member 10. The terminal fitting 11 has a terminal hole 17 into which a current lead wire drawn in from below in direction AR is inserted. The terminal fitting 11 has two screw holes 18 in the front direction (-Y direction). The screw holes 18 have female threads into which terminal screws 12 can be screwed, and a guide hole 19 is formed on the insertion side (-Y direction side) to guide the insertion of the terminal screw 12. The terminal fitting 11 is incorporated into the base member 10 and functions as a base member in this embodiment.

[0020] The terminal screw 12 has a male thread formed on the threaded portion from the base head 12a to the tip, which screws into the female thread of the screw hole 18. As shown in Figure 3, when the terminal screw 12 is in its maximum tightening state, the tip of the terminal screw 12 reaches the inner wall surface of the terminal hole 17. In Figure 3, the current lead wire inserted into the terminal hole 17 is not shown, and if a current lead wire is present and the terminal screw 12 is pressing against the current lead wire and tightening it, the position of the tip of the terminal screw 12 shifts towards the front side (-Y direction). The head 12a has an operating groove 12b formed therein for rotating the terminal screw 12.

[0021] On the other hand, the cover member 13, which functions as a screw cover member, covers the front opening of the base member 10, which includes the terminal screw 12. As shown in Figure 5, the cover member 13 has a stopper 16 formed thereon that restricts the head 12a from moving in the loosening direction (-Y direction) of the terminal screw when the tip of the terminal screw 12 is engaged with the guide hole 19 in the maximum loosening state. The cover member 13 also forms a screw guide space ER that guides the terminal screw 12 from the stopper 16 toward the guide hole 19. This screw guide space ER is formed by the guide portion 15. The length of the guide space ER in the ±Y direction should be sufficient to allow the terminal screw 12 to screw into the screw hole 18 and not fall out.

[0022] The terminal screw 12 will not fall out as long as it is screwed into the screw hole 18, but it will fall out if it moves in the loosening direction and the screwing into the screw hole 18 is released. For this reason, a stopper 16 is provided to maintain the state in which the terminal screw 12 is engaged with the guide hole 19 after the screwing into the screw hole 18 is released. This prevents the terminal screw 12 from falling out.

[0023] The inner wall surface of the stopper 16 has an operating hole 14 through which an operating tool such as a screwdriver can be inserted and removed for tightening and loosening operations via an operating groove 12b formed in the head 12a of the terminal screw 12. Therefore, the stopper 16 can be formed by making the diameter of the operating hole 14 smaller than the diameter of the head 12a. Note that the stopper 16 does not have to be provided around the entire circumference of the operating hole 14, but may have a discrete projection shape.

[0024] [Example 1] Figure 7 is a front view showing the configuration of an energy meter 2 having a screw fall-off prevention structure, which is a modified example 1 of the embodiment of the present invention. Figure 8 is an exploded perspective view of the energy meter 2 shown in Figure 7. Figure 9 is a cross-sectional view of line CC in Figure 7 with the mounting screw 22 in its most loosened state. Figure 10 is an enlarged perspective view of part D in Figure 7 with the mounting screw 22 in its most loosened state.

[0025] As shown in Figure 8, the energy meter 2 has a terminal portion 23 that functions as a screw cover member. A terminal fitting 21 corresponding to the terminal fitting 11 is assembled to the terminal portion 23. The terminal fitting 21 has a screw hole 18 into which a terminal screw 12 (not shown) is screwed, similar to the terminal fitting 11, but a conductive connection portion 21a is also formed at one upper end of the terminal fitting 21.

[0026] When assembling the terminal fitting 21 to the terminal section 23, the mounting screw 22, which is a tightening screw, is inserted into the first connection hole 21b of the conductive connection section 21a and then assembled to the terminal section 23. Although not shown in the figures, similar to the embodiment, a terminal screw 12 (not shown) is screwed into the screw hole 18 of the terminal fitting 21 and then assembled to the terminal section 23. The terminal section 23, into which the terminal fitting 21 with the mounting screw 22 and terminal screw 12 engaged is assembled, is mounted so as to cover the lower part of the base member 20.

[0027] As shown in Figure 9, the conductive connection part 21a is a component that has the function of electrically connecting the terminal fitting 21 and the end 31a of the current bar inside the base member 20 by tightening the mounting screw 22. By connecting the terminal fitting 21 and the end 31a of the current bar, the current lead wire, which is inserted into and fixed in the terminal hole of the terminal fitting 21, is electrically connected to the current bar inside the base member 20. In addition, the mounting screw 22, along with connecting the terminal fitting 21 and the end 31a of the current bar, is screwed into the screw hole 28 formed in the base member 20, thereby attaching the terminal part 23 to the base member 20. The terminal screw 12 to the terminal fitting 21 is provided with the same screw fall prevention structure as the cover member 13.

[0028] When the terminal portion 23 is attached to the base member 20, the mounting screw 22 is interposed between the conductive connection portion 21a and the operation hole 24 formed in the terminal portion 23. Here, the mounting screw 22 has a flange 22b formed on its head 22a, and in the fully loosened state, the flange 22b abuts against the stopper 26 formed around the operation hole 24, preventing the mounting screw 22 from moving in the loosening direction. In the fully loosened state of the mounting screw 22, the first connection hole 21b of the conductive connection portion 21a and the second connection hole 31b formed in the end portion 31a of the current bar function as guide holes 19 in this embodiment, and the mounting screw 22 is engaged with these guide holes. This prevents the mounting screw 22 from falling out. The operation hole 24 also functions as a guide portion 15 in this embodiment. Furthermore, although the mounting screw 22 had a flange 22b formed on it, the flange 22b may be omitted, and the stopper 26 may contact the head 22a when it is in its most loosened state.

[0029] With the mounting screw 22 prevented from falling out, the mounting screw 22 is driven through the operating hole 24, causing the mounting screw 22 to be inserted through the first connection hole 21b and the second connection hole 31b and screwed into the screw hole 28. By tightening, the conductive connection part 21a and the end part 31a of the current bar are electrically connected, and the terminal part 23 is attached to the base member 20. Even if the mounting screw 22 is loosened, the screw fallout prevention structure prevents the mounting screw 22 from falling out.

[0030] [Differentiation 2] Figure 11 is a cross-sectional view showing the configuration of the part corresponding to Figure 9 in Modification 2. Figure 12 is a left side view of Figure 11. In this Modification 2, there is a screw fallout prevention structure, and the mounting screw 22 is configured to be able to be inserted and removed from the outside through the operation hole 44.

[0031] Specifically, a notch 22c is formed in a part of the circumferential direction of the flange 22b, and a projection 46 corresponding to the notch 22c is formed in the operating hole 44 to function as a stopper for the mounting screw 22. As shown in Figure 12, the diameter of the operating hole 44 is larger than the diameter of the flange 22b, allowing the mounting screw 22 to be inserted into and removed from the outside. However, in the maximum loosening state, the projection 46 abuts against the flange 22b other than the notch 22c, preventing the mounting screw 22 from falling out. Insertion and removal of the mounting screw 22 is performed by rotating the mounting screw 22 to align the position of the notch 22c with the position of the projection 46, and passing the projection 46 through the notch 22c. In this modified example 2, the mounting screw 22 will not fall out except when the notch 22c and the projection 46 are aligned. It is preferable to align the notch 22c and the projection 46 for only one rotation angle of the mounting screw 22.

[0032] Furthermore, the screw fall prevention structure for fastening screws shown in the above embodiments and modifications can be applied to fastening screws inside electricity meters, and can also be applied to the connection and disassembly of various components using fastening screws.

[0033] Furthermore, the configurations illustrated in the above embodiments and modifications are functionally schematic and do not necessarily have to be physically represented as shown. In other words, the forms of distribution and integration of each device and component are not limited to those shown, and all or part of them can be functionally or physically distributed and integrated in any unit according to various usage situations. [Explanation of symbols]

[0034] 1,2 Energy meter 10,20 Base members 11,21 Terminal fittings 12 terminal screws 12a,22a head 12b Operation groove 13 Cover component 14,24,44 Operation hole 15 Information Department 16,26 Stopper 17 terminal holes 18,28 screw holes 19 Guide hole 21a Conductive connection 21b First connection hole 22 Mounting screws 22b flange 22c Notch 23 Terminal section 31a End of current bar 31b Second connection hole 46 Protrusion AR direction ER screw guide space

Claims

1. A fastening screw having a tip portion comprising: a first cylindrical portion continuous with the head and having an outer diameter smaller than the outer diameter of the head; a tapered portion continuous with the extended end of the first cylindrical portion and having an outer diameter that gradually decreases as it moves away from the first cylindrical portion; and a second cylindrical portion continuous with the extended end of the tapered portion and having an outer diameter smaller than the outer diameter of the first cylindrical portion, wherein the first cylindrical portion can be screwed into a screw hole, A base member to which a terminal fitting is attached, having the aforementioned screw hole formed therein and a guide hole formed on the insertion side of the screw hole to guide the insertion of the tightening screw, A screw cover member having a stopper that covers the base member including the fastening screw, and the first cylindrical portion detaches from the screw hole while the second cylindrical portion passes through the guide hole, thereby restricting the head of the fastening screw from moving in the loosening direction when the fastening screw is engaged with the guide hole in its most loose state, and a screw guide space that guides the fastening screw from the stopper toward the guide hole, A screw fallout prevention structure characterized by having the following features.

2. The screw fallout prevention structure according to claim 1, characterized in that the screw cover member has an operating hole through which an operating tool for tightening and loosening operations can be inserted and removed via an operating groove formed in the head of the tightening screw.

3. The screw fallout prevention structure according to claim 1 or 2, characterized in that the tightening screw is a terminal screw that fixes the current lead wire, which is inserted into the terminal hole of the terminal fitting attached to the base member, through the screw hole of the terminal fitting.

4. A fastening screw having a tip portion comprising a cylindrical portion continuous with the head and having an outer diameter smaller than the outer diameter of the head, and a tapered portion continuous with the extended end of the cylindrical portion and having an outer diameter that gradually decreases as it moves away from the cylindrical portion, wherein the cylindrical portion can be screwed into a screw hole, The base member having the aforementioned screw hole, A terminal fitting attached to the base member and connected to the current supply line, Equipped with, The aforementioned fastening screw is a mounting screw that attaches the conductive connection part and the current bar to the base member by screwing it into the screw hole through a first connection hole in the conductive connection part which is one end of the terminal fitting and a second connection hole provided at one end of the current bar in the base member. The first and second connection holes function as guide holes for guiding the insertion of the fastening screw into the screw hole. A screw fallout prevention structure characterized by comprising a screw cover member that covers the base member including the fastening screw, the cylindrical portion of which detaches from the screw hole and the second connecting hole, and the tapered portion which passes through the second connecting hole, thereby restricting the head of the fastening screw from moving in the loosening direction when the fastening screw is engaged with the guide hole in its most loose state, and a screw guide space formed therein that guides the fastening screw from the stopper toward the guide hole.

5. The screw fallout prevention structure according to claim 4, characterized in that the tightening screw has a flange formed on its head that engages with the stopper.

6. The flange has a notch formed in a part of its circumference. The screw fallout prevention structure according to claim 5, characterized in that the screw cover member has a projection corresponding to the notch as a stopper, and the fastening screw can be inserted and removed by passing the notch through the projection.

7. An energy meter characterized by having a screw fall prevention structure as described in any one of claims 1 to 6.

Images