DE9417830U1 - Tubular component - Google Patents

Description

The invention/innovation relates to a tubular structural element with a metallic tubular body, in particular a structural element for producing frame, scaffolding or rack constructions.

Such structures, such as tanks or warehouses consisting of gravity fed racks or scaffolds or roller conveyors, are made from thin walled steel tubes of 28 to 32 mm diameter, which are coated overall with an approximately 1 mm thick layer of synthetic resin mixed with carbon black as a conductive additive to release the electrostatic charge that may arise due to the operation or handling of the tank or warehouse. Typically, such conventional tubular structures may be made from SPCC-I steel with a wall thickness of 0.7 mm.

However, it has been found that there are various problems and difficulties with such state-of-the-art steel pipes coated with conductive synthetic resin. Firstly, the carbon black, which is normally used as the conductive material for the layer, is expensive and its black colour causes limitations when designers try to give the pipe structure an attractive appearance. In addition, the layer containing the carbon black, especially the film or foil-shaped layer, cannot withstand any impact or shock and is therefore easily torn off the

30 coated surface.

For example, if the thickness of the carbon black-containing layer is less than 5 mm, the tubular component lacks sufficient conductivity to prevent electrification or electrical charging. If the thickness is above 15 mm, the cost of the tubular component becomes too high and

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Due to its black tint, it has an unattractive appearance.

In view of the disadvantages described above of the conventional tubular components coated or encased with conductive synthetic resin, the present invention/innovation is now based on the object of creating an improved tubular component or tube in which such disadvantages are overcome.

According to the present invention/innovation, a tubular component with a metallic tubular body is created, which is characterized in that the metallic tubular body is coated with a layer of synthetic resin and that a strip of a conductive synthetic resin is provided along the entire length of the tubular body

is trained.

Further advantageous embodiments of the tubular component according to the invention/innovation emerge from the subclaims.

Thus, according to the present invention/innovation, there is provided in particular an improved tubular component which is coated with a conductive synthetic resin which is inexpensive and furthermore gives the tubular component a colored appearance. The tubular component is coated as a whole with a layer of synthetic resin which may be colored green or ivory. A narrow strip of synthetic resin, which is mixed with, for example, carbon black as the conductive additive, is formed in the longitudinal direction along the length of the tube, above the formation of the layer, to make the tubular component conductive so that an electrical

trisation or electrical charging is prevented.

The present invention/innovation will now be described in more detail below in the context of exemplary embodiments, with reference to the attached drawings. In these:

Fig. 1 is a perspective view of a conductive

A resin coated steel pipe constructed in accordance with a first preferred embodiment of the present invention/innovation;
5

Fig. 2 is a perspective view of a storage or warehouse

unit having a frame with a feed by gradient or with a gravity feed, said storage or storage unit being in the form of a construction made of coated steel tubes as shown in Fig. 1, and said

Storage or warehousing unit intended for storing circuit boards or printed circuit boards or circuit boards in a shelf-like manner;

Fig. 3 a perspective view of a coated steel pipe

according to a second preferred embodiment of the

present invention/innovation;

Fig. 4 is a perspective view of a portion of a

Roller conveyor using steel tubes as shown in Fig. 3, with its core components shown

are;

Fig. 5 is a cross-sectional view of a part of the construction

according to Fig. 4; 25

Fig. 6 is a perspective view of a conductive

Resin coated steel pipe with rectangular cross section in accordance with a third preferred embodiment of the present invention/innovation;

Fig. 7 is a perspective view of a coated steel pipe

of rectangular cross-section in an embodiment modified from that of Fig. 6;

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Fig. 8 is a perspective view of a coated steel pipe

with a rectangular cross-section according to a fourth preferred embodiment of the invention/innovation; and
5

Fig. 9 a perspective view of a coated steel pipe

with a rectangular cross-section in a modified embodiment compared to that according to Fig. 8.

Fig. 1 shows a steel pipe 1 provided with a coating made of a conductive synthetic resin, this steel pipe being manufactured in accordance with a first preferred embodiment of the present invention/innovation.

The tubular body la is coated on the outside with an approximately 1 mm thick layer Ib of a synthetic resin, such as an acrylate-styrene-acrylonitrile copolymer (ASA). In addition, the tubular body la has a strip Ic of synthetic resin which is above the longitudinal extension of the resin layer Ib along the entire length

20 of the tubular body la.

After coating with the resin layer Ib, the pipe 1 has a diameter that lies between 28 mm and 32 mm.

The resin layer Ib can preferably be colored green or ivory

to provide an attractive, decorative appearance.

The resin strip Ic may preferably comprise a conductive resin, such as acrylonitrile-butadiene-styrene copolymer (ABS) mixed with carbon black as a conductive additive, this resin strip Ic having a width of 15 mm and a thickness of 0.5 mm. The conductive resin strip Ic and the resin layer Ib may preferably be formed as a whole by extrusion molding.

The function of the conductive strip Ic is to release electrostatic charge that may occur in the steel pipes 1, thereby grounding the pipe structure in which the steel pipes 1 are connected with each other with their conductive resin strips Ic aligned end-to-end.

A plurality of vertical and horizontal steel tubes 1 can be connected to one another and assembled into a storage or warehousing unit in the form of a gravity-fed rack for storing circuit boards (printed circuit boards, PCBs)

nen) in a shelf-like manner as shown in Fig. 2.

The storage unit comprises a rack framework 2 having a pair of upright sides each constructed of a number of steel tubes 1 joined end-to-end by mostly L-shaped corner joints 3a, 3b, 3c and 3d in a trapezoidal shape which should be made of a conductive metal or a conductive synthetic resin material.

In this embodiment, as shown in Fig. 2, the front side of the storage unit comprises a plurality of substantially rectangular frames composed of horizontal and vertical steel tubes 1 and connecting pieces 7a, 7b between the trapezoidal sides 5.

The rectangular frames form openings 8 through which the circuit boards (printed circuit boards, circuit boards) are loaded into the storage unit with feeder or unloaded from this storage unit.

Each loading/unloading opening 8 has therein a layer of leveled pairs of feed rails 9 extending between the front and rear sides of the loading unit and inclined downwards towards the front side to receive the circuit boards P in the manner of a drop-feed warehouse. In the drawing, the guide rails 9 are shown only on one side of the pairs for brevity. In this

In this embodiment, separate loading/unloading openings 8 in a storage and feeding system can be labelled or marked to accommodate different types of electronic circuit boards (printed circuit boards, circuit boards) P.
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In addition, each loading/unloading opening 8 is provided with an indicator lamp 10, which can preferably be arranged at a central point of the upper tube of the opening, this indicator lamp 10 being switched on and lighting up in order to facilitate the operator to recognize the location of particular openings 8.

Preferably, a pair of photoelectric scanner and mirror (not shown) are arranged at aligned positions across the loading/unloading openings for each pair of feed rails 9.

The associated scanner and mirror combination detects the loading or unloading of a circuit board P whenever the circuit board interrupts the beam from the scanner to the mirror when an operator is engaging a particular aperture 8. The scanners and indicator lamps 10 are connected by cables (not shown) to a central computer program, also not shown, which maintains the loading or unloading guides for a storage unit with feeder and which energizes a buzzer (not shown) to give a warning signal should an attempt be made to access an incorrect aperture 8.

Furthermore, it is provided that in the lower horizontal section of the tube 1 of one of the lateral trapezoids 5 there is provided a substantially inverted U-shaped grounding terminal 12 which is connected to a supply line 11 in order to discharge static electricity which may arise due to friction of sliding circuit boards (printed boards, circuit boards) P during their loading or unloading against their respective feed rails 9. In the construction of the illustrated storage unit with feed, an electrostatic

Charges that may occur in the steel pipes 1 are discharged via the earthing connection 12 and the supply line 11 and via the conductive connecting pieces 3a, 3b, 3c, 3d, 6, 7a and 7b.

In the particular embodiment of the invention illustrated in Fig. 2, circuit boards (printed circuit boards, circuit boards) P are stored horizontally in the area between feed rails 9, which are arranged on the vertical tubes of the loading/unloading openings 9.

However, as an alternative to this embodiment, it is possible, as part of a modified embodiment of a storage unit with feed by gravity, for the circuit boards (printed boards, circuit boards) P to be stored or stored in a vertical position, between the upper and lower tubes 1 of the openings 8. In addition, in an alternative embodiment, the earthing connection 12 and the feed line 11 could be replaced by castors or rollers 4 made of an electrically conductive synthetic resin material in order to earth this storage unit with feed.

The latter design avoids the disadvantage that, when the storage unit is rolled around on a floor strewn with objects, the supply line 11 being pulled behind it will be caught by any disturbing obstacles.

A second preferred embodiment of a steel pipe 16 coated with a conductive synthetic resin is explained with reference to Fig. 3. The pipe 16 comprises a pipe body 16a with a thickness of 0.7 mm, with a coating applied to the outer surface of the pipe 16, which consists of a 1 mm thick layer of a synthetic resin 16b, for example acrylate-styrene-acrylonitrile copolymer (ASA).

A pair of parallel ribs 16c are formed in the longitudinal direction along the entire length of the steel pipe 16 and preferably they may be formed integrally with the resin layer 16b. After coating the pipe 16 with the synthetic resin layer 16b

the resulting tube 16 has a diameter in the range of 28 to 32 mm.

In a modified embodiment, the tube 16 could be provided with a single longitudinal rib instead of the pair of ribs 16c.

A strip of conductive synthetic resin 16d is formed above the resin layer 16b along the longitudinal length of the tube body 16a, this strip preferably measuring 15 mm in width and 0.5 mm in thickness. The resin for the strip 16d may preferably be an acrylonitrile-butadiene-styrene copolymer (ABS) mixed with carbon black as the conductive additive.

In addition, the conductive strip 16d and the resin layer 16b may be formed as a unit by an extrusion molding process. Moreover, the strip 16d may be formed parallel to the pair of ribs 16c, being spaced from the ribs by a distance of approximately one-fourth of the circumference of the tube body 16a. The resin layer or film 16b may be colored green or ivory to give the whole an attractive appearance.

In the same way as in the embodiment already described above, the conductive strip 16d serves to transfer the currents in the tube 16 to

to discharge any electrostatic charge that may arise.

In the following, reference is now made to the embodiments shown in Fig. 4 and 5. These are partial sectional views, one in perspective and the other in cross section, of one of the roller frames of a roller conveyor, wherein tubes 16a according to Fig. 3 are used.

The roller conveyor consists of a pair of upright lateral framework or frame parts 17, between which a plurality of

driven by an endless belt, is arranged in a rotatable manner in a horizontal plane to support loads on a moving surface. These side frame or scaffolding parts 17 can comprise a steel tube 16 according to Fig. 3 and a steel tube 18 coated with a conductive resin material.

In detail, the steel pipe 18 has a tubular body 18a, which has a wall thickness of 0.7 mm, with a layer of a synthetic resin 18b, such as ASA, formed on the outer surface, this layer having a thickness of approximately 1 mm. After the pipe 18 is coated with the synthetic resin layer 18b, this pipe has a diameter of 28 to 32 mm.

The resin layer 18 can be colored green or ivory, for example. A single rib 18c is formed along the entire length of the tubular body 18a, which can be formed jointly and integrally with the layer 18b by extrusion. The rib 18c is formed so that it has a dimension that allows the tubular body 18a to be inserted between the pair of ribs 16c of the steel tube

16 to form the double tube frame 17 for the rollers, thus strengthening the construction of the roller conveyor.

When a tube 16 and a complementary tube 18 are connected together by their respective ribs 16c, 18c to form a side frame member 17 for the roller conveyor, the conductive strip 16d should point inwardly into the conveyor to prevent immediate exposure of the conductive surface for safety reasons.

30 to be avoided.

Preferably, the steel tube 16 in the lateral scaffold part

17 of the roller conveyor should be arranged so that it is located above the complementary steel tube 18, whereby under certain circumstances additional support elements can be arranged below the framework part 17, which in

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are not shown in the drawings. Such support elements can, however, also be omitted.

A plurality of roller supports 19 made of a conductive synthetic resin material, which may be, for example, an acrylic butadiene-styrene copolymer (ABS) mixed with carbon black as the conductive additive and polycarbonate, are arranged along the steel pipe 16 of the side frame part 17 of the conveyor at a mutually spaced distance on the two sides of the conveyor.

Each roller holder 19 has a base element 20 which consists of a C-shaped claw 20a which snaps onto the steel tube 16 and a substantially U-shaped pocket 20b which serves to accommodate the end of a conveyor roller 22 via an end part 21 in

15 in a detachable manner.

The end part 21 comprises a substantially inverted L-shaped engaging element 21a and a hub element 21b arranged to extend perpendicular to the longitudinal axis of the roller conveyor body. The receptacle or pocket 20b engages the end part 21 with the vertically directed portion of the L-shaped element 21a inserted into the vertical slot of the pocket.

The roller holder 19 holds the conveyor roller 22 in a rotatable manner in the receptacle or pocket 20b of the base element 20. The conveyor

Roller 22 consists of a tubular element 23 comprising a steel tube 23a with a wall thickness of 0.7 mm, which is coated on its outer surface with an approximately 1 mm thick layer 23b of a conductive synthetic resin 23b. 30

The conductive resin for the layer 23b may be PE mixed with carbon black as the conductive additive. After the resin layer 23b is applied to the pipe surface by extrusion, the conveyor roller 22 has a diameter in the range between 28 and 32 mm. In addition, the conveyor roller 22 has an end cap 24 which is dimensioned to fit into the pipe body 23 at the end of the roller.

The end cap 24 is made of the same conductive resin that forms the layer 23b for the roller 22. Furthermore, the end cap 24 has an axial bore 24b into which the hub 21b is inserted to enable the roller holder 19 to hold the roller 22 through the end part 21 in a rotatable manner.

A substantially inverted U-shaped ground connection 26 is arranged around the steel pipe 16 in order to ground the roller conveyor via a line 25.

The end cap 24 is preferably provided with a pulley 24b which is arranged concentrically around the periphery of the end cap. The pulley 24b is driven by a drive pulley (not shown) via an endless belt (not shown) with a round or V-shaped cross-section which runs around the pulley 24 to rotate the conveyor roller 24 about its axis.

Static electricity occurring in the conveyor rollers 22 as they rotate is discharged through the ground terminal 26 and the wire 25 via the conductive roller supports 19 and the conductive resin layer 16d of the steel pipes 16 forming the side framework parts 17 of the roller conveyor.

With roller conveyors designed in accordance with the present invention/innovation, there is very little risk of injury to personnel operating the roller conveyors and there is very little risk of damage to products conveyed over the rollers due to static electricity.

Table 1

Run
No.

Room temperature

Room humidity Electrostatic potential (V)

This invention/innovation Conventional conveyor

1
2
3
4
5
6
7
8th
9

25 26 26 32 32 27 27 30 32

76 71 76 63 63 75 60 50 57

- 200 200 - 200 - 200 200 - 300 700 200

6000 I 5000 - 6000 ^ 4500 &igr; ....
9 · 7600 10500 * * * · 4 6000 8000 8000 5000

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Table 1 shows the results of a series of tests carried out over a number of days under different atmospheric conditions (temperature, humidity) to compare the measured values of the electrostatic potential occurring in a roller conveyor manufactured using covered pipes according to the present invention/innovation with those measured in a conventional roller conveyor. To measure the electrostatic potential, a digital voltmeter of type KSD-0102 manufactured by Kasuga DenM KK was used.

Table 1 shows that, compared with the conventional conveyor, the electrostatic potential is very low in the roller conveyor made of coated steel pipes according to the present invention/innovation. In this particular embodiment of a roller conveyor, a double pipe arrangement is used for the side frameworks 17, which comprises steel pipes 16 coated with a conductive resin and steel pipes 18 coated with a resin film, which are connected to each other in the longitudinal direction by their ribs 16c, 18c. However, this construction may optionally be modified such that the side frameworks 17 are formed by a construction of steel pipes 16 coated with a conductive synthetic resin as shown in Fig. 3.

According to an alternative embodiment, the lateral frame parts 17 of a roller conveyor can be a double tube construction consisting of

steel tubes coated with a conductive resin, similar to the steel tubes 1 according to Fig. 1, and complementary, ribless steel tubes extruded together with the resin, which are arranged parallel to the former.
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It is not necessary for the roller conveyor to have pipes 16 coated with conductive resin, which are arranged on all lateral frame parts of the roller conveyor, furthermore, in individual cases the total length of each lateral frame part depends on the type of loads to be handled, and the overall mechanical con

structure dependent.

Fig. 6 shows, in the context of a third embodiment of the present invention/innovation, an embodiment of a steel pipe 30 which is coated with a conductive resin material. The pipe 30 comprises a pipe body of rectangular cross-section 30a which is extruded with a layer 30b of synthetic resin. A strip 30c of a conductive synthetic resin running in the longitudinal direction is pressed along one side of the rectangular pipe body 30a, this strip 30c forming a

whole forms.

As can be seen from Fig. 7, in a modified embodiment of a resin-coated pipe 30, a strip 32c of a conductive resin is applied to the resin layer 32b of the resin-coated pipe 32 by means of an extruder press, each such strip 32c extending along a corner edge of the pipe body 32a according to Fig. 7, instead of along a side of a pipe as shown in Fig. 6. Otherwise, the designs of the rectangular pipes 30 (Fig. 6) and 32 (Fig. 6) coated with a conductive resin and their overall dimensions are essentially similar to the design and overall dimensions of the pipe with a round cross section shown in Fig. 1, so that the pipe designs according to Figs. 6 and 7 will not be described in more detail.

Referring to Fig. 8, it is explained that a resin-coated tube 34 having a rectangular cross section includes a pair of fins 34d attached to one side of the rectangular tube body 34a. The purpose of this pair of fins 34d is substantially the same as that of the fin-

pair 16c according to Fig. 3 and is therefore not described in more detail for the sake of brevity.

The tube 34 further comprises a resin layer 34b and a conductive strip 34c extending in the longitudinal direction of the tube 34, in a similar manner to the tube with a round cross section shown in Fig. 3.

Fig. 9 shows a modified embodiment of a steel tube 36 which has a rectangular cross-section and is also provided with a resin coating on the outside. In addition, a strip 36c made of a conductive resin is formed along a corner edge of the tube body 36a which has a rectangular cross-section. Furthermore, the tube body 36a comprises a layer 36b made of a synthetic resin, this layer 36b being formed as a whole together with the conductive strip 36c by means of an extrusion process.

As is apparent from the foregoing description, by using steel pipes manufactured according to the invention/innovation, which are coated on their surface with a conductive synthetic resin layer, a structure can be constructed which is grounded for the purpose of discharging static electricity which may occur in that structure. In addition, the manufacturing costs for the tubular components according to the present invention/innovation are low because the expensive carbon black used as the conductive material for grounding the pipe structure is only coated in the region of a narrow longitudinal strip on the pipe circumference, but not on the entire outer surface of the pipe, as in conventional pipe structures. In addition, the design of the tubular component according to the present invention/innovation allows a relatively large scope for a colored design of the outer tube surface because the narrow conductive strip of carbon black leaves relatively much space and in particular more space than in the prior art on the tube surface in order to give the tube an attractive appearance in a variety of optional colors of the synthetic resin material.

Claims (7)

that the tubular body (la; 30a) is coated with a layer (16; 30b) of synthetic resin and that a strip (Ic; 30c) of a conductive 10 synthetic resin is formed along the entire length of the tubular body. 2. Tubular component according to claim 1, characterized in that the layer (16; 30b) of synthetic resin is an extruded layer and 15 the strip (1c; 30c) as a whole with the extruded synthetic resin layer is formed. 3. Tubular structural element according to claim 1 or claim 2, characterized in 20 that the strip (Ic; 30c) made of a conductive synthetic resin has a width which is in the range between 5 and 15 mm. 4. Tubular component according to one of the preceding claims, characterized, that the tubular component (1) has a round cross-section. 5. Tubular component according to one of claims 1 to 3, characterized in 30 that the tubular component (30) has a rectangular cross-section having. 6. Tubular component according to one of the preceding claims, characterized, that it has one or more ribs (16c) which extend along the length of the tubular component. · t 7. A frame construction consisting of tubular structural elements,
characterized, that it comprises one or more tubular components according to one of claims 1 to 6.