JP4998432B2 - Screw holding structure and watt-hour meter - Google Patents

Description

  The present invention relates to a structure for holding a screw in a terminal cover such as a watt-hour meter for measuring the amount of electricity used or a circuit breaker having a connection terminal for connecting an electric wire.

  For example, as shown in Patent Document 1, a conventional watt-hour meter includes a meter body, a power supply side electric wire from which electric power is led from an electric power company, a load side electric wire that leads electric power to a consumer side, and each electric wire is individually attached and detached. And a plurality of terminals that can be connected. Each of the power supply side electric wire and the load side electric wire is screwed with a terminal screw constituting a terminal, and this terminal is covered with a terminal cover for protection. The terminal cover is fixed to the meter body with terminal cover screws.

  In many cases, the terminal cover screw is used as a sealing screw, and the sealing wire is passed over the sealing screw hole and the sealing wire passing portion of the terminal cover to seal the terminal cover. The conventional watt-hour meter says that the sealing screw is dropped and lost when the terminal cover is removed because the sealing screw is not held by the terminal cover when unsealing and reconnecting the wires to each terminal. There was a problem.

  A screw holding structure for preventing a screw from falling off is disclosed in Patent Document 2, for example. The sealing device for the electricity meter storage box shown here has a plurality of protrusions in the sealing screw through-holes provided in the pressing frame that holds the cover, and the sealing screw is screwed into the protrusions. Even when the cover of the storage box is removed, the sealing screw is caught on the protrusion of the sealing screw through hole.

JP 2007-170998 A (0002 stages, FIG. 10) Japanese Utility Model Publication No. 62-104278 (FIG. 2)

  However, since the conventional screw holding structure is inserted while screwing the sealing screw into the protrusion of the sealing screw through hole, it is difficult to insert the sealing screw into the pressing frame having the sealing screw through hole, and it takes a long time to work. there were.

  The present invention has been made to solve the above-described problems. It is easy to insert the terminal cover screw into the screw through hole of the terminal cover, and the terminal cover screw is held on the terminal cover even when the terminal cover is detached. It is an object of the present invention to obtain a screw holding structure that can be made to occur.

  The screw holding structure according to the present invention has a first convex portion and a second convex portion on an inner surface of a screw through hole of a terminal cover through which a terminal cover screw for fixing the terminal cover to the main body passes. The positions of the convex portion and the second convex portion are different from each other with respect to the axial direction and the circumferential direction of the screw through hole, and the terminal cover screw overlaps the first convex portion and the second convex portion in the axial direction of the screw through hole. Has an overlap. This overlapping portion does not overlap the first convex portion and the second convex portion when the terminal cover screw is obliquely inserted into the screw through hole.

  In the screw holding structure according to the present invention, the terminal cover screw can be easily inserted into the screw through hole of the terminal cover, and the terminal cover screw can be held by the terminal cover even when the terminal cover is detached.

Embodiment 1 FIG.
1 is an external perspective view of a watt-hour meter according to Embodiment 1 of the present invention. The watt-hour meter 100 is capable of detaching a plurality of power-side terminals 12 including a plurality of power-side wires including a ground wire (not shown) and a plurality of load-side wires including a ground wire (not shown). The main body 1 includes a plurality of load-side terminals 13 to be connected, a power-side terminal cover 2a that covers the power-side terminals 12a, 12b, and 12c, and a load-side terminal cover 2b that covers the load-side terminals 13a, 13b, and 13c. The The power supply side terminal cover 2a and the load side terminal cover 2b are each fixed to the main body 1 with terminal cover screws 8 which are sealing screws. The power supply side terminal 12 is protected by the power supply side terminal cover 2a, and the load side terminal 13 is protected by the load side terminal cover 2b.

  The power supply side terminal cover 2a and the load side terminal cover 2b have screw through holes 7a and 7b for inserting the terminal cover screws 8, respectively. After the power supply side terminal cover 2a is fixed to the main body 1 with the terminal cover screw 8, a sealing wire (not shown) is passed over the hole of the terminal cover screw 8 and the sealing projection 15a which is a wire passing portion provided in the power supply side terminal cover 2a. Then, the power supply side terminal cover 2a is sealed. Similarly, after the load side terminal cover 2b is fixed to the main body 1 with the terminal cover screw 8, a sealing wire is spanned between the sealing projection 15b provided on the load side terminal cover 2b and the hole of the terminal cover screw 8 to load side. The terminal cover 2b is sealed.

  2 is a top view of the screw through hole 7 of the power supply side terminal cover 2a and the load side terminal cover 2b. FIG. 3A is a cross-sectional view of the screw through hole 7 taken along the line AA in the left direction of FIG. FIG. 3B is an AA cross-sectional view of the through hole 7 as viewed from the right in FIG. The screw through hole 7 has three convex portions 4, 5, 6 on its inner surface. The convex part 4 is provided in the upper part of the screw through hole 7, and the convex part 5 and the convex part 6 are provided in the lower part of the through hole 7. In the top view of the screw through hole 7, D4 is the length between the convex walls, which is the length from the convex portion 4 to the inner surface of the screw through hole 7. Similarly, D5 and D6 are the convex through portions 5 and 6 to the screw through hole. 7 is the length between the convex portion walls, which is the length to the inner surface of 7.

  4 is a top view of the screw through-hole 7 showing the cutting position including the convex portion 4 and the convex portion 5, and FIG. 5 is a diagram showing a CC cross section of the through-hole 7 and the terminal cover screw 8 in FIG. The terminal cover screw 8 includes a screw head 9, an effective screw portion 10, and an ineffective screw portion 11. The effective screw portion 10 is screwed with the female screw portion of the main body 1. The outer diameter D10 of the effective screw portion 10 is smaller than the lengths D4, D5, and D6 between the convex portion walls. As a result, the terminal cover screw 8 can be inclined inside the screw through hole 7 even in the effective screw portion 10. The outer diameter D11 of the ineffective screw portion 11 is smaller than the outer diameter D10 of the effective screw portion 10, and the screw head 9 is larger than the inner diameter D7 of the screw through hole 7. When the screw through-hole 7 is projected from this axial direction, the diameter D19 of the smallest inscribed circle 19 that contacts each of the convex portions 4, 5, and 6 is smaller than the outer diameter D10 of the effective screw portion 10. 5 is cut so as to be the shortest from the center O1 of the screw through-hole 7 to the convex portions 4 and 6, d1 is the length in the radial direction of the convex portion 4, and d2 is the diameter of the convex portion 6. The length of the direction.

  Next, a method for inserting the terminal cover screw 8 into the screw through hole 7 will be described. FIG. 6 is a view showing a process of inserting the terminal cover screw 8 into the screw through hole 7. The cross section of the screw through hole 7 is a cross section seen from the direction of the arrow in FIG. FIG. 5 shows a state before the terminal cover screw 8 is inserted into the screw through hole 7.

  As shown in FIG. 6A, the terminal cover screw 8 is inclined with respect to the screw through-hole 7 so as to avoid the convex portions 4, 5, 6 of the terminal cover 2, and the effective screw portion 10 of the terminal cover screw 8. Is inserted into the screw through-hole 7. As shown in FIG. 6B, the effective screw portion 10 of the terminal cover screw 8 passes through the screw through hole 7. Thereafter, as shown in FIG. 6 (c), the terminal cover screw 8 returns substantially perpendicular to the screw through hole 7, that is, the axis of the terminal cover screw 8 is returned almost parallel to the axis of the screw through hole 7. The screw head 9 is brought into contact with the terminal cover 2 by making the screw through hole 7 of the terminal cover 2 substantially vertical, and the axis of the terminal cover screw 8 is substantially parallel to the axis of the screw through hole 7.

  After the terminal cover screw 8 is inserted into the screw through hole 7 of the terminal cover 2, the terminal terminal cover 2 is attached to the main body 1.

As shown in FIG. 6A, the terminal cover screw 8 is inclined with respect to the screw through hole 7 so that the opening of the screw through hole 7 when the terminal cover screw 8 is inserted is formed by the protrusions 4, 5, 6. Since it becomes larger than the diameter D19 of the inscribed circle 19 in contact with each of them, the effective screw portion 10 whose outer diameter is D10 larger than D19 can be inserted into the screw through hole 7. After the effective screw portion 10 of the terminal cover screw 8 is inserted into the screw through hole 7, the condition that the terminal cover screw 8 can be perpendicular to the screw through hole 7 is D19> D11, and the terminal cover screw 8 is in the screw through hole. The condition for preventing the vertical movement from 7, that is, in the axial direction is D10> D19. Therefore, the condition that the effective screw portion 10 of the terminal cover screw 8 is inserted obliquely into the screw through-hole 7 and then the terminal cover screw 8 does not come out vertically from the screw through-hole 7 is expressed by Equation 1.
D10>D19> D11 Formula 1

  In other words, if the condition D10> D19 is satisfied, the terminal cover screw 8 has the upper convex portion 4 and the lower convex portion 5 or the upper convex portion 4 and the lower convex portion 6 in the axial direction of the screw through-hole 7. It has an overlapping part that overlaps. Here, the effective screw portion 10 serves as an overlapping portion. Since the effective screw portion 10 of the terminal cover screw 8 is screwed with the main body 1 and is also an overlapping portion, there is an advantage that the structure of the terminal cover screw 8 is not complicated. Note that at least two convex portions are sufficient, and there may be three or more convex portions.

  As described above, the screw holding structure and the watt hour meter according to the first embodiment of the present invention have different positions on the inner surface of the screw through hole 7 of the terminal cover 2 with respect to the axial direction and the circumferential direction of the screw through hole 7. Since it has the 1st convex part 4 and the 2nd convex part 6, the terminal cover screw 8 can be inserted in the screw through-hole 7 diagonally. Further, since the terminal cover screw 8 has an overlapping portion 10 that overlaps the first convex portion 4 and the second convex portion 6 in the axial direction of the screw through hole 7, the terminal cover screw 8 is pulled out in the axial direction of the screw through hole 7. Even so, the overlapping portion 10 of the first convex portion 4 and the second convex portion 6 and the terminal cover screw 8 interferes to prevent the terminal cover screw 8 from falling off and to hold the terminal cover screw 8. it can.

  Further, unlike the conventional method of inserting the screw into the protrusion of the screw through hole, the terminal cover screw 8 can be inserted obliquely into the screw through hole 7 without being screwed. The terminal cover screw 8 can be easily inserted into the through hole 7, and the time required for the insertion work into the screw through hole 7 can be shortened. Since the strength of the convex portion does not need to consider that the terminal cover screw 8 is screwed into the convex portion, the convex portion need not be thickened for strengthening. When the terminal cover screw 8 is inserted into the screw through hole 7, the convex portions 4, 6 of the screw through hole 7 do not need to be deformed by hitting the terminal cover screw 8, so that the convex portions 4, 5, 6 are connected to the terminal cover 2. The same material can be used, and a screw holding structure can be created by integral formation.

  In the watt-hour meter according to the first embodiment of the present invention, the terminal cover 2 or the main body 1 is provided with the wire passing portion 15 through which the sealing wire for sealing the terminal cover 2 is inserted together with the through hole of the sealing screw. Can be sealed.

Embodiment 2. FIG.
The outer diameter D10 of the effective screw portion 10 and the outer diameter D11 of the ineffective screw portion 11 of the terminal cover screw 8 are preferably selected from the screw holding structure of the first embodiment, and the lower convex portions 5 and 6 and the terminal cover screw 8 By increasing the interference with the effective screw portion 10, it is possible to make it difficult to come out after being inserted into the screw through hole 7. This will be described below.

  FIG. 7 is a top view of the screw through hole 7 in the screw holding structure according to Embodiment 2 of the present invention. The length d2 of the convex part 5 and the convex part 6 in the radial direction is larger than the radial length d1 of the convex part 4. The convex portion 6 is located at a position shifted clockwise by an angle α from the convex portion 4 with the center O1 of the screw through hole 7 as the center, and the convex portion 5 is a convex portion center line 21 passing through the center O1 and the center of the convex portion 4. Is in a position symmetrical to the convex portion 4. The convex part center line 22 passing through the center of the convex part 6 and the center O1 intersects with the convex part center line 21 passing through the convex part 4 at an angle β, and similarly the convex part passing through the center of the convex part 5 and the center O1. The center line 23 intersects the convex part center line 21 passing through the convex part 4 at an angle β. Here, the angle β is π−α. When the screw through-hole 7 is projected from the axial direction, the center O2 of the inscribed circle 19 indicated by a broken line inscribed in the convex portions 4, 5, 6 is on the convex portion center line 21, and the center O1 of the screw through-hole 7 is obtained. It is in the convex part 4 side rather than.

  The outer circumference circle 24 is the outer circumference of the effective screw portion 10 of the terminal cover screw 8, and the arrangement of the outer circumference circle 24 in FIG. 7 is the case where the axis of the terminal cover screw 8 passes through the center O 2 of the inscribed circle 19. . Point A is the intersection of the inscribed circle 19 and the convex center line 21, and is on the side opposite to the convex part 4. Point B is the intersection of the boundary circle of the screw through-hole 7 and the convex part center line 21, and is on the opposite side of the convex part 4. When the length from the point A to the point B is expressed by a component in the direction of the convex part center line 21 of the convex part 5 and the convex part 6, it is d2 cos β. Point C is an intersection of the outer circumference circle 24 and the convex center line 21, and is on the side opposite to the convex part 4. r7 is the radius of the screw through hole 7, and r19 is the radius of the inscribed circle 19.

  Even when the terminal cover screw 8 moves in the radial direction or circumferential direction of the screw through-hole 7, a condition in which the lower convex portion 5 or the convex portion 6 interferes with the effective screw portion 10 of the terminal cover screw 8, that is, the effective screw Consider a condition in which the portion 10 and the convex portions 5 and 6 overlap. A direction along the convex part center line 21 is defined as an X direction, a direction perpendicular to the convex part center line 21 is defined as a Y direction, and an arrow direction in FIG.

  First, consider a case where the terminal cover screw 8 is moved in the Y direction. When the terminal cover screw 8 is moved in the positive direction in the Y direction, the overlap between the outer circumference circle 24 and the convex portion 6 is increased, so that interference between the convex portion 6 and the effective screw portion 10 of the terminal cover screw 8 is increased. Further, when the terminal cover screw 8 is moved in the negative direction in the Y direction, since the overlap between the outer circumference circle 24 and the convex portion 5 becomes large, interference between the convex portion 5 and the effective screw portion 10 of the terminal cover screw 8 becomes large.

  Next, consider a case where the terminal cover screw 8 is moved in the X direction. When the terminal cover screw 8 is moved in the positive direction in the X direction, since the overlap between the outer circumferential circle 24 and the convex portion 5 and the convex portion 6 becomes large, the convex portion 5 and the convex portion 6 and the effective screw portion 10 of the terminal cover screw 8. Interference with is increased. On the other hand, when the terminal cover screw 8 is moved in the negative direction in the X direction, the overlap between the outer circumferential circle 24 and the convex portions 5 and 6 is reduced. However, even when the terminal cover screw 8 is moved in the negative direction in the X direction, if the overlap between the outer circumferential circle 24 of the effective screw portion 10 and the convex portion 5 and the convex portion 6 remains, the terminal cover screw 8 has the convex portion 5. And interference with the convex part 6 can be maintained.

The overlap length between the effective screw portion 10 of the terminal cover screw 8 and the inscribed circle 19 in the state of FIG. 7, that is, the overlap length dx that is the length between the points A and C is expressed by Equation 2.
dx = r10−r19 Equation 2
Here, r10 is the radius of the effective screw portion 10.

A gap length dd that is the length of the gap between the ineffective screw portion 11 of the terminal cover screw 8 and the upper convex portion 4 in the state of FIG.
dd = r19−r11 Equation 3
Note that r11 is the radius of the ineffective screw portion 11.

When the terminal cover screw 8 is moved in the negative direction in the X direction, the terminal cover screw 8 can be moved until the ineffective screw portion 11 contacts the convex portion 4. Therefore, the maximum movement length in the negative direction in the X direction is dd. Even when the terminal cover screw 8 is moved in the negative direction in the X direction, the condition that the overlap between the outer circumference circle 24 and the projections 5 and 6 remains is that the length obtained by subtracting the gap length dd from the overlap length dx is positive. If it is. Therefore, it can be expressed by Equation 4.
dx−dd> 0 Formula 4

Substituting Equations 2 and 3 into Equation 4 gives the following.
r10 + r11-2r19> 0 Formula 5
When formula 5 is transformed, the following formula is obtained.
r10 + r11> 2r19 Formula 6

Since the diameter D19 (2r19) of the inscribed circle 19 is added to the radial length d1 of the convex portion 4 and the length between the points A and B, the diameter D7 (2r7) of the screw through hole 7 is obtained. A radius r19 of 19 can be expressed by the following equation.
r19 = r7−d1 / 2− (d2cosβ) / 2 Equation 7

Substituting Equation 7 into Equation 6 yields:
r10 + r11> 2r7-d1-d2cosβ Equation 8

  As described above, if Expression 1 and Expressions 4, 6, and 8 are established, even when the terminal cover screw 8 is moved in the negative direction in the X direction, the outer circumferential circle 24 and the protrusions 5 and 6 remain overlapped. Therefore, the terminal cover screw 8 can maintain interference with the convex portion 5 and the convex portion 6.

  Therefore, the screw holding structure in which the formula 1 and the formulas 4, 6, and 8 are satisfied always has the lower convex portion 5 or the terminal cover screw 8 even if the terminal cover screw 8 moves in the screw through hole 7 in a state substantially perpendicular to the screw through hole 7. Since it interferes with the convex portion 6, the terminal cover screw 8 is less likely to be inclined, and the effect of preventing the terminal cover screw 8 from falling off is enhanced compared to the screw holding structure of the first embodiment, and the holding performance of the terminal cover screw 8 is enhanced. Can do.

  As described above, since the total of the radius r10 of the effective screw portion 10 and the radius r11 of the ineffective screw portion 11 is larger than the diameter D19 of the inscribed circle 19 in the screw holding structure and the watt hour meter of the second embodiment. Even if the terminal cover screw 8 moves in the screw through hole 7 in a state of being substantially perpendicular to the screw through hole 7, the terminal cover screw 8 always interferes with the lower convex portion 5 or the convex portion 6. As a result, the effect of preventing the terminal cover screw 8 from falling off can be enhanced as compared with the screw holding structure of the first embodiment, and the holding performance of the terminal cover screw 8 can be enhanced.

  Note that there may be one lower convex portion. In this case, when the angle β is set to 0, even when the terminal cover screw 8 is moved in the positive direction and the negative direction in the Y direction, it is possible to leave an overlap with the lower convex portion. Further, even when the convex portion on the lower side is small and the convex portion and the effective screw portion 10 do not overlap when moved in the Y direction, the radius r10 of the effective screw portion 10 so that the effective screw portion 10 overlaps the terminal cover. Is selected, the effect of preventing the terminal cover screw 8 from falling off can be enhanced, and the holding performance of the terminal cover screw 8 can be enhanced.

Embodiment 3 FIG.
FIG. 8 is a view showing a screw holding structure according to Embodiment 3 of the present invention. A groove 16 is provided in the terminal cover 2 so as to include the screw through hole 7, and a coil spring 14, which is elastic means, is sandwiched between the groove 16 and the screw head 9 of the terminal cover screw 8. 8 is a cross-sectional view as seen from the direction of the arrow in FIG.

  The coil spring 14 urges the screw head 9 having an outer diameter larger than the inner diameter D7 of the screw through hole 7 to be substantially parallel to the groove 16. The terminal cover screw 8 floats in a direction away from the terminal cover 2 due to the elastic force of the coil spring 14, and the effective screw portion 10 of the terminal cover screw 8 abuts against the lower convex portion 5. Therefore, the terminal cover screw 8 is substantially parallel to the axis of the screw through hole 7 and is restricted from moving in the axial direction, the radial direction, and the circumferential direction. Thereby, the terminal cover screw 8 can be reliably held on the terminal cover 2.

  As described above, the screw holding structure and the watt hour meter of the third embodiment are provided with elastic means between the screw head 9 having an outer diameter larger than the inner diameter D7 of the screw through hole 7 and the terminal cover screw 8. Therefore, the terminal cover screw 8 can be securely held on the terminal cover 2.

  Even if there is no groove 16, the same effect can be obtained. When the groove 16 is present, the biasing force of the coil spring 14 can be adjusted according to the depth of the groove 16.

  In the first to third embodiments, the example in which the overlapping portion of the terminal cover screw 8 that overlaps the plurality of convex portions of the screw through-hole 7 is the effective screw portion 10 of the terminal cover screw 8 is described, but the overlapping portion is the terminal cover screw. 8 may be provided separately. In this case, there is an advantage that the overlapping portion can be changed in accordance with the shape and arrangement of the convex portion of the screw through hole 7.

  Further, the screw holding structure of the third embodiment can be combined with any of the first and second embodiments. The terminal cover screw 8 is not limited to the sealing screw, and other screws may be used.

It is an external appearance perspective view of the watt-hour meter in Embodiment 1 of this invention. FIG. 3 is a top view of a screw through hole of the terminal cover in the first embodiment. It is AA sectional drawing of the screw through-hole in FIG. 4 is a top view of a screw through hole showing a cutting position including a convex portion 4 and a convex portion 5 in Embodiment 1. FIG. It is a figure which shows CC cross section and the terminal cover screw of the screw through-hole of FIG. It is a figure which shows the insertion process to the screw through-hole of the terminal cover screw of Embodiment 1. FIG. It is a top view of the screw through-hole in Embodiment 2 of this invention. It is a figure which shows the screw holding structure in Embodiment 3 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Main body, 2 Terminal cover, 4 Convex part, 5 Convex part, 6 Convex part, 7 Screw through-hole, 8 Terminal cover screw, 9 Screw head, 10 Effective thread part, 11 Invalid thread part, 12 Power supply side terminal, 13 Load side terminal, 14 coil spring, 15 sealing projection, 19 inscribed circle.

Claims (8)

Screw holding for holding a terminal cover screw for screwing a main body provided with a plurality of terminals for detachably connecting a plurality of power supply side wires and load side wires and a terminal cover covering the terminals to the terminal cover Structure,
The terminal cover has a screw through hole into which the terminal cover screw is inserted,
The screw through hole has a first protrusion and a second protrusion on the inner surface thereof,
The first protrusion and the second protrusion are different from each other in the axial direction and the circumferential direction of the screw through hole,
The terminal cover screw has an overlapping portion that overlaps the first convex portion and the second convex portion in the axial direction of the screw through-hole,
The screw holding structure, wherein the overlapping portion does not overlap the first convex portion and the second convex portion when the terminal cover screw is obliquely inserted into the screw through hole. The screw through hole further has a third protrusion on the inner surface thereof,
The position of the third protrusion is different with respect to the circumferential direction of the first and second protrusions and the screw through hole,
When the screw through-hole is projected from the axial direction of the through-hole, the diameter of the inscribed circle in contact with the first convex portion, the second convex portion, and the third convex portion is The screw holding structure according to claim 1, wherein the screw holding structure is smaller than an outer diameter. The terminal cover screw has an ineffective screw portion having an outer diameter smaller than the outer diameter of the overlapping portion;
The sum of the radius of the overlapping portion and the radius of the ineffective screw portion is the inscribed in contact with the first convex portion and the second convex portion when the screw through hole is projected from the axial direction of the through hole. 2. The screw holding structure according to claim 1, wherein the screw holding structure is larger than a diameter of the circle. The terminal cover screw has an ineffective screw portion having an outer diameter smaller than the outer diameter of the overlapping portion, and the sum of the radius of the overlapping portion and the radius of the ineffective screw portion is the first convex portion, the second The screw holding structure according to claim 2, wherein the diameter is larger than the diameter of the inscribed circle in contact with the convex portion and the third convex portion. 5. The screw holding structure according to claim 1, wherein the terminal cover screw has an effective screw portion screwed into the main body, and the overlapping portion is the effective screw portion. 6. The terminal cover screw according to claim 1, wherein the terminal cover screw has a screw head larger than an inner diameter of the screw through-hole, and elastic means is provided between the screw head and the terminal cover. The screw holding structure according to item 1. A main body having a plurality of terminals for detachably connecting a plurality of power supply side electric wires and load side electric wires, and a terminal cover that covers the terminals and is screwed to the main body with a terminal cover screw,
The watt-hour meter according to claim 1, wherein the screw holding structure for holding the terminal cover screw on the terminal cover is the screw holding structure according to claim 1. 8. The terminal cover or the main body, wherein the terminal cover screw is a sealing screw, and a wire passing portion through which a sealing wire for sealing the terminal cover is inserted together with a through hole of the sealing screw is provided in the terminal cover or the main body. Watt hour meter.

Images