Steel rack

Abstract

To provide a steel rack that is easy to structure and can reliably prevent static electricity. [Solution] In the electrostatic dissipative steel rack, shelf support members 4 are hung in pitch grooves, and a strip of conductive rubber 13 is installed on the load-receiving portion 9 of the shelf support member 4. The shelf board 6 and shelf support member 4 have a primer layer that serves as an insulating layer applied to the base iron plate, and a conductive paint applied to the outermost surface. The conductive rubber 13 ensures that the shelf support member 4 and the shelf board 6 are in even contact, providing stable electrostatic dissipation without variation.

Description

[Technical Field]

[0001] This invention relates to a steel rack equipped with anti-static measures. [Background technology]

[0002] Steel racks are widely used in various factories and office workshops because they can store and organize heavy objects. Although steel racks are made from steel plates, which are much cheaper than those made from stainless steel or other metals, they are painted because iron is a metal that corrodes easily.

[0003] Storage units used for electronic components require electrostatic treatment to protect against electrostatic discharge (ESD) damage. In typical steel racks, shelf supports are inserted into pitch grooves on the side posts, allowing for adjustable shelf spacing, and the shelves are then placed on top of these supports. Even if conductive paint is applied to the entire steel rack of this type, the shelf supports and shelves do not make even contact, making it impossible to avoid variations in conductivity.

[0004] For example, in the storage cabinet for electronic components disclosed in Patent Document 1, conductive long bolts that penetrate the bottom plate and top plate are connected to shelves coated with conductive paint, thereby allowing discharge through the long bolts. A similar technique is known from Patent Document 2.

[0005] According to the technology described in Patent Documents 1 and 2, the spacing between shelves is adjusted using long bolts and fixing nuts that clamp the shelves from above and below, thereby ensuring stable conductivity. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2010-40492 [Patent Document 2] Official Gazette No. 3145626 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Conductive paints contain conductive fillers such as carbon, and their adhesion is not always as good as that of ordinary paints. A common method to improve adhesion to metal shelves is to use a primer as a base for the conductive paint. However, primers are insulators, and they electrically insulate the conductive paint from the metal shelves. Therefore, when adjusting the spacing of the shelves, the structure of fixing the shelves to long bolts by sandwiching the front and back of the shelves with fixing nuts is rational because, even if a primer is used as a base for the conductive paint, the fixing nuts are in close contact with the conductive paint, ensuring stable conductivity without relying solely on the metal base material of the shelf as a conductive path.

[0008] On the other hand, conventional storage units, which use fixing nuts to secure the shelves to long bolts in order to ensure stable conductivity, have a more complex structure and require more effort to adjust the height compared to steel racks that simply place the shelves on general shelf support members.

[0009] Therefore, the objective of this invention is to provide a steel rack that is easy to structure and can reliably prevent static electricity buildup. [Means for solving the problem]

[0010] To achieve the above objective, the steel rack of this invention has a rectangular shape in plan view, with numerous pitch grooves provided at equal intervals in the vertical direction, one groove at each of the four corners, and shelf support members are placed in a bridging manner over any pitch groove of the two pitch grooves provided at the front and rear that have matching heights, and the height of the pitch groove on which the shelf support members are placed can be arbitrarily changed, and shelves are mounted on the shelf support members that are placed on the left and right so that their heights match, The shelf board and the shelf support member are made by applying a primer layer, which serves as an insulating layer, to an iron plate that serves as the base material, and then applying a conductive paint to the outermost surface. A strip-shaped conductive rubber is installed on each load-bearing part of the shelf support members that are horizontally spanned so that their heights match. The main surface on the lower side of the conductive rubber is electrically connected to the conductive paint on the surface of the load-bearing part. The left and right lower edges of the shelf board are placed on the main surface on the upper side of the conductive rubber, so that the conductive paint on the surface of the lower edge and the main surface on the upper side of the conductive rubber are electrically connected.

Advantages of the Invention

[0011] According to the present invention, a steel rack with stable electrostatic diffusibility without variation can be provided, in which the shelf support member and the shelf board are evenly contacted by the conductive rubber.

Brief Description of the Drawings

[0012] [Figure 1] It is a perspective view of the steel rack according to the present invention. [Figure 2] It is an exploded and enlarged explanatory view of a part of the components of the steel rack. [Figure 3] FIG. 3A is an exploded and enlarged explanatory view of a part of the components of the steel rack, and FIG. 3B is a view showing the back side of the shelf board. [Figure 4] It is a cross-sectional explanatory view showing the engagement state of the shelf support member and the shelf board. FIG. 4A is a view of the engagement part of the top member and the shelf board, and FIG. 4B is a view of the engagement part of the shelf support member and the shelf board.

Embodiment for Carrying Out the Invention

[0013] The steel rack according to the present embodiment is a steel rack with electrostatic countermeasures. The following were set as the goals as the criteria for evaluating the electrostatic countermeasures. In the steel rack, a plurality of measurement points were set to measure and evaluate the resistance value. Referring to RCJS-5-1 (International Electrotechnical Commission (IEC)) and IEC61340-5-1, 5-2 (Electrostatic Countermeasures Council), the allowable range as a storage shelf was set as the following values. The resistance r between two points: 1×10 10 Ω ≧ r ≧ 1×104 Ω Ground resistance R: 1×10 9 Ω ≥ R ≥ 7.5×10 5 Ω Furthermore, the resistance r between two points is the resistance value of the member alone, and the ground resistance R is the comprehensive resistance value between the shelf board surface and the lower end of the support column as a finished product.

[0014] If the resistance value is lower than 1×10 5 Ω, a strong current is likely to flow at once, increasing the possibility of causing "spark discharge". Therefore, a low resistance value is not preferred in an environment where the human body comes into contact. Also, if it is higher than 1×10 11 Ω, almost no charge escapes, and it becomes substantially the same as an "insulator that is easily charged", and the parts and trays will remain charged for a long time. In the storage shelf, the resistance value classified as electrostatic dissipation property is 1×10 9 Ω ≥ R ≥ 1×10 5 Ω (based on EC61340-5-1, 5-2 standards).

[0015] Hereinafter, the steel rack 1 of the present embodiment will be described based on the drawings. FIG. 1 is a perspective view of the steel rack 1. The steel rack 1 has a large number of pitch grooves 7 provided at equal intervals in the vertical direction, one by one, at the four corners of a rectangular shape in plan view. Among the two pitch grooves 7 provided front and back, the shelf receiving member 4 is hung in a bridging manner on any pitch groove 7 having the same height. The height of the pitch groove 7 on which the shelf receiving member 4 is hung can be arbitrarily changed. The shelf board 6 is mounted on the shelf receiving members 4 bridged left and right so as to have the same height. In this way, the height position of the shelf board 6 can be adjusted.

[0016] The steel rack 1 comprises four support columns 2, one at each of the four corners of its rectangular shape in plan view; a top member 3 connecting the front and rear support columns 2; shelf support members 4; a wide beam 5; and shelves 6 provided between the left and right support columns 2. The top member 3, located at the very top, connects the upper ends of a pair of opposing support columns 2 and supports the left and right edges of the shelf 6 located at the very top. The wide beam 5 connects the upper and lower ends of a pair of opposing support columns 2. The shelf support members 4 support the left and right edges of the other shelves 6. The arrangement of the shelf support members 4, including the bottommost shelf, is arbitrary according to the pitch grooves 7.

[0017] As shown in Figure 2, each support column 2 is formed by bending a steel plate into a U-shape in its cross-section. Numerous pitch grooves 7 are provided at equal intervals in the vertical direction on the side portion of each support column 2. A positioning hole 17 is drilled next to the uppermost pitch groove 7. Multiple receiving grooves 14 are drilled on the front portion to connect the ends of the upper and lower wide beams 5.

[0018] The wide beam 5 has locking portions 8 formed at both ends, which connect to the receiving grooves 14 of the support column 2. The locking portion 8 is cut out from a sheet of steel and hammered out on the support column side in the drawing, with a widened portion 8a in the center and bridge portions 8b and 8c above and below it. It has a tapered shape, with the width decreasing from bridge portion 8b to bridge portion 8c. The receiving groove 14 has a circular hole 14a on the upper side through which the widened portion 8a can pass, and a tapered rectangular hole 14b on the lower side that narrows in width towards the bottom.

[0019] The top member 3 is formed by bending a steel plate into an L-shape to create a horizontally extending upper surface. Locking portions 10 are formed at both ends to connect to the pitch grooves 7 of the support columns 2, and load-bearing portions 9 are formed to receive the load of the shelf board 6. A projection 16 is also provided next to the locking portion 10. The shelf support member 4 also has locking portions 10 formed at both ends to connect to the pitch grooves 7 of the support columns 2, and a load-bearing portion 11 is formed by bending a steel plate horizontally to receive the load of the shelf board 6. The locking portion 10 is cut into a tapered shape that narrows in width downwards and then bent into a hook shape. The pitch groove 7 is a tapered rectangular hole that narrows in width downwards. The top member 3 and the shelf support member 4 are connected by inserting the locking portion 10 into the pitch groove 7. In addition, the projection 16 of the top member 3 is inserted into the positioning hole 17, so that the top member 3 is fixed to the uppermost part.

[0020] Figure 3A is an enlarged diagram illustrating a disassembled part of the steel rack, and Figure 3B shows the underside of the shelf board 6. The shelf board 6 has a base material made of steel plate and has a deck surface portion 12a on which the contents are placed and reinforcing ribs 12b provided on the underside of the deck surface portion 12a to prevent deflection. In the example shown in the figure, three reinforcing ribs 12b are provided parallel to each other in the length direction of the shelf board 6. The reinforcing ribs 12b are made by bending a steel plate and are formed over almost the entire length of the shelf board 6 (only the right side is shown in Figure 3A). The bottom surface 12c of the reinforcing rib 12b is a surface parallel to the deck surface portion 12a. The left and right lower edges 12d of the bottom surface 12c of the reinforcing rib 12b (the parts lightly shaded in Figure 3B) are the left and right edges of the shelf board 6, and the shelf board 6 is supported by the left and right edges being placed on the load-receiving portion 9 of the top member 3 or the load-receiving portion 11 of the shelf support member 4.

[0021] On one side, a strip-shaped conductive rubber 13 is installed on the load-receiving portions 9 of the pair of left and right top members 3 and the load-receiving portions 11 of the shelf-receiving members 4. In FIGS. 4A and 4B, the lower main surface of the conductive rubber 13 is electrically connected to the conductive paint on the surface of the load-receiving portion 9 or the load-receiving portion 11. When the lower edge 12d of the shelf board 6 is placed on the upper main surface of the conductive rubber 13, it is electrically connected to the conductive paint on the surface of the shelf board 6. By arranging a conductive adhesive or a conductive adhesive on the lower main surface of the conductive rubber 13, it is electrically connected to the surface of the load-receiving portion 9 or the load-receiving portion 11 and is stably fixed. The conductive rubber 13 may be arranged on the front surface of the load-receiving portion 9 or the load-receiving portion 11, or may be arranged only in the range where the lower edge 12d is mounted.

[0022] Hereinafter, the evaluation of the steel rack 1 according to this embodiment will be described. For all the surfaces of each member of the column 2, the top member 3, the shelf-receiving member 4, the wide beam 5, and the shelf board 6 that constitute the steel rack 1, a primer layer that becomes an electrically insulating layer is applied to the base, and a conductive paint is applied to the outermost layer. The electrical resistance of the two-point resistance r is 1×10 6.9 Ω ≧ r ≧ 1×10 5 Ω or so. The resistance value of each member alone was numerically within the allowable range.

[0023] On the other hand, although the base materials of these members are iron plates, the electrical connection between the members is realized by the contact of the conductive paints on the outermost layer. Just the connection between the receiving groove 14 of the column 2 and the locking portion 8 of the wide beam 5, or the connection between the pitch groove 7 of the column 2 and the locking portion 10 of the top member 3 or the locking portion 10 of the shelf-receiving member 4 will not scrape the primer layer on the base, and electrical connection by the iron plate of the base material cannot be expected.

[0024] [Comparative Example 1] The shelf board 6 was directly placed on the load-receiving portion 9 of the top member 3 or the load-receiving portion 11 of the shelf-receiving member 4. In this case, the electrical resistance of the ground resistance R was 1×10 9.9 Ω ≧ R ≧ 1×10 5.2 Ω, exceeding the numerically set allowable range and having a large variation (standard deviation 1.43).

[0025] In this state, when a load was applied to shelf 6, a stable resistance value was achieved above a certain level. It is thought that because no load was applied to shelf 6, the top member 3, shelf support member 4 and shelf 6 were not in even contact, resulting in a low degree of contact. The steel rack in Comparative Example 1 is unsuitable because it must be designed to have a constant load applied to the shelves at all times.

[0026] [Comparative Example 2] The shelf board 6 was placed directly on the load-receiving portion 9 of the top member 3 or the load-receiving portion 11 of the shelf support member 4 and fixed with screws. In this case, the electrical resistance of the ground resistor R is 1 × 10 5.2 Ω ≥ R ≥ 1 × 10 4.9 The result was Ω, which is numerically below the acceptable range. The variability had a standard deviation of 0.09. (1 × 10⁻¹⁰) 5.0 Variations below ohm could result in the production of products that potentially generate unpleasant discharges. A common advantage of typical steel racks is that the shelf spacing can be freely changed without using screws, but this advantage is lost in the steel rack in Comparative Example 2 because it is fixed with screws.

[0027] [Comparative Example 3] With the shelf board 6 placed directly on the load-receiving portion 9 of the top member 3 or the load-receiving portion 11 of the shelf support member 4, one flange of the L-shaped angle was placed over the top surface of the shelf board 6, and the other flange was positioned so as to be sandwiched between the shelf board 6 and the top member 3 or shelf support member 4. In this case, the electrical resistance of the ground resistor R is 1 × 10⁻¹⁰ 5.3 Ω ≥ R ≥ 1 × 10 5.0 The value was Ω, which was below the numerically acceptable range. Furthermore, the variation had a standard deviation of 0.08. In the steel rack of Comparative Example 2, repeated changes to the shelf spacing posed a risk of paint peeling due to the L-shaped angles.

[0028] [This embodiment] Conductive rubber 13 was placed on the load-bearing parts 9 and 11, and the shelf board 6 was placed directly on the conductive rubber 13. In this case, the electrical resistance of the ground resistance R is 1 × 10⁻¹⁰ 7.6 Ω ≥ R ≥ 1 × 10 7.7 The result was Ω, which is numerically larger than the other comparative examples, but it fell within the acceptable range. Furthermore, the variation among samples was a standard deviation of 0.03, which is extremely low compared to the other comparative examples. Therefore, the resistance value does not fluctuate so much that it approaches or exceeds the lower limit, and the product is stable.

[0029] In the comparative examples and the tests of this embodiment described above, the connection resistance values ​​in the connection between the receiving groove 14 of the support column 2 and the locking portion 8 of the wide beam 5, or the connection between the pitch groove 7 of the support column 2, the locking portion 10 of the top member 3, and the locking portion 10 of the shelf support member 4, were not dominant over the ground resistance.

[0030] In this embodiment, the steel rack 1 has the advantage of being able to prevent static electricity with little variation and stability, without compromising the ability to freely change the spacing between shelves, and also has the effect of reducing the risk of paint peeling.

[0031] In the above embodiment, the steel rack 1 had four support columns 2 erected at each of the four corners of its rectangular shape in plan view. However, the two front and rear support columns may be replaced with a single side panel, and two rows of pitch grooves 7 may be arranged on both sides of the side panel. [Explanation of symbols]

[0032] 1 Steel rack 2 pillars 3 Top part 4. Shelf support members 5 Wide Beam 6 shelves 7 connecting holes 8, 10 Locking parts 9, 11 Load-bearing section 13 Conductive rubber 14 Receiving groove

Claims

1. A steel rack having a rectangular shape in plan view, with numerous pitch grooves provided at equal intervals in the vertical direction, one groove at each of the four corners, and a shelf support member being placed in a bridging manner over any two pitch grooves at the front and rear that have matching heights, the height of the pitch groove on which the shelf support member is placed can be arbitrarily changed, and shelves are mounted on the shelf support members that are placed on the left and right so that their heights match, The shelf board and the shelf support member are made by applying a primer layer, which serves as an insulating layer, to an iron plate that serves as the base material, and then applying a conductive paint to the outermost surface. A strip of conductive rubber is installed on each load-bearing portion of the shelf support members, which are placed on the left and right sides so that their heights are the same, and the main surface of the lower side of the conductive rubber is electrically connected to the conductive paint on the surface of the load-bearing portion. A steel rack characterized in that the left and right lower edges of the shelf board are placed on the upper main surface of the conductive rubber, thereby electrically connecting the conductive paint on the surface of the lower edge with the upper main surface of the conductive rubber.

2. In the steel rack according to claim 1, It is equipped with four support columns, one at each corner of the rectangular shape in plan view, and each support column is provided with one of the aforementioned pitch grooves. The aforementioned support column is a steel rack characterized in that a primer layer serving as an insulating layer is applied to a steel plate used as a base material, and a conductive paint is applied to the outermost surface.

3. In the steel rack according to claim 2, A top member that connects the tops of a pair of opposing support columns, It is equipped with wide beams that connect the upper ends and lower ends of the left and right support columns, The aforementioned top member has a primer layer that serves as an insulating layer applied to an iron plate that serves as the base material, and a conductive paint applied to the outermost surface. A steel rack characterized in that the top member is provided with a second load-receiving portion so that the shelf board can be mounted on it, a strip-shaped second conductive rubber is installed on the second load-receiving portion, and the lower main surface of the second conductive rubber is electrically connected to the conductive paint on the surface of the second load-receiving portion.

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