JP7270810B2 - band heater - Google Patents

Description

The present invention relates to a band heater wound around a cylindrical body. In this document, aluminum is an abbreviation for aluminum (including aluminum alloys).

A band heater wound around a cylindrical body is widely put into practical use (see, for example, Patent Document 1 (Figs. 4 and 5)).

Patent Document 1 will be described with reference to FIGS. 12 and 13. FIG.
FIG. 12 is a cross-sectional view of a conventional band heater. A band heater 100 has a C-shape like an annular ring divided at one point, and the inner diameter can be reduced by tightening a bolt 101 between the ends. can be done.

FIG. 13 is a side view of a conventional injection apparatus. A conventional injection apparatus 110 includes a heating cylinder 111 containing a screw, and a pellet-shaped resin material attached to the base of the heating cylinder 111, which is dropped into the heating cylinder 111. , band heaters 100A to 100D divided and arranged from the base to the tip of the heating cylinder 111, and temperature measuring sections 113A to 113D.

The band heaters 100A to 100D are the same as the band heater 100, with A to D added to distinguish the locations.
The temperature of the band heater 100A is controlled so that the temperature measuring portion 113A reaches a desired temperature. Other band heaters 100B to 100D are similarly temperature-controlled so that the temperature measuring portions 113B to 113D reach desired temperatures.

By the way, in the injection device 110, the resin material supplied by the hopper 112 is solid, and in order to melt it, the band heater 100A near the hopper 112 is required to mainly heat. On the other hand, at the tip of the heating cylinder 111, the resin material has already been heated and is kneaded and plasticized, so heating is not required so much and rapid (with good response) temperature control is required.

However, in the prior art, band heaters 100A-100D are all the same band heater 100. FIG. However, when the present inventors made a detailed study, it was found that the band heaters 100A to 100D have room for improvement.
In other words, the band heaters 100A to 100D are required to be improved in preparation for the case where the required performance differs depending on the mounting position.

JP-A-62-128723

SUMMARY OF THE INVENTION An object of the present invention is to provide an improved technique for a band heater, which is mainly used for heating and secondary for temperature control.

The invention according to claim 1 is a band heater wound around a cylindrical body,
The band heater comprises an inner case covering the cylindrical body, an inner electric insulating material covering the inner case, a heating element covering the inner electric insulating material, an outer electric insulating material covering the heating element, and an outer electric insulating material covering the inner electric insulating material. It consists of an outer case that covers the insulating material and a band that covers the outer case,
The heating element comprises an insulating plate provided with through holes in a zigzag pattern, and a heating wire wound around the insulating plate while passing through the through holes,
The insulating plate has an upper surface, a lower surface, a left side, and a right side in a cross-sectional view, and has the left through-hole and the right through-hole penetrating from the upper surface to the lower surface,
The heating wire is
From the top surface to the bottom surface through the left through hole, to the right side along the bottom surface, to the top surface along the right side, and to the right through hole along the top surface ,
Through the right through hole, the upper surface reaches the lower surface, along the lower surface reaches the left side surface, along the left side surface reaches the upper surface, and along the upper surface reaches the left through hole. It is characterized in that it is wound as

The invention according to claim 2 is the band heater according to claim 1,
In the heating wire, L1 is about 70% and L2 is about 30%, where L1 is the length of the heating wire along the lower surface and L2 is the remaining length.

In the invention according to claim 1, the heating element comprises an insulating plate provided with through holes in a zigzag pattern, and a heating wire wound around the insulating plate while passing through the through holes. The heating wire passes through the left through-hole from the top surface to the bottom surface of the insulating plate, along the bottom surface to the right side surface, along the right side surface to the top surface, along the top surface to the right through-hole, and then to the right through hole. Through the through-hole of , from the upper surface to the lower surface, along the lower surface to the left side, along the left side to the upper surface, and along the upper surface to the left through-hole.
If the lower surface of the insulating plate is the surface facing the heating cylinder, most of the heat generated by the heating element goes to the heating cylinder.
According to the present invention, there is provided a band heater which is mainly used for heating and whose secondary function is temperature control.

In the invention according to claim 2, when the length of the heating wire along the lower surface is L1 and the remaining length is L2, L1 is approximately 70% and L2 is approximately 30%. If the lower surface of the insulating plate is the surface facing the heating cylinder, most of the heat generated by the heating element goes to the heating cylinder.

It is a sectional view of a band heater concerning the present invention. 3 is a perspective view of a heating element; FIG. FIG. 2 is an exploded view of a section taken along line 3-3 of FIG. 1; FIG. 4 is a cross-sectional view of another band heater according to the present invention; FIG. 5 is an exploded view of the section taken along line 5-5 of FIG. 4; 1 is a side view showing a main part of an injection device equipped with a band heater according to the present invention; FIG. FIG. 7 is a cross-sectional view taken along the line 7-7 in FIG. 6 and is a cross-sectional view of the heating unit; FIG. 8 is an exploded view of a cross section taken along line 8-8 of FIG. 7; (a) is an explanatory diagram of the operation of the heat retaining section, (b) is an explanatory diagram of the operation of the heating section, and (c) is an explanatory diagram of the operation of the preheating section. (a) is a cross-sectional view for explaining a modification of the band, and (b) is a view in the direction of arrow b of (a). (a) is a perspective view illustrating a modification of a heating element, (b) is a cross-sectional view taken along line bb of (a), and (c) is a cross-sectional view illustrating a comparative example. FIG. 3 is a cross-sectional view of a conventional band heater; 1 is a side view of a conventional injection device; FIG.

An embodiment of the present invention will be described below with reference to the accompanying drawings.

The structure of the band heater 10A suitable for the preheating section will be described with reference to FIGS. 1 to 3. FIG.
As shown in FIG. 1, the band heater 10A includes an inner case 11 wound around a cylindrical body, an inner electric insulating material 12 covering the inner case 11, a heating element 20 covering the inner electric insulating material 12, and the heating element 20. It consists of an outer electric insulating material 14 to be covered with the outer electric insulating material 14, an outer case 15 to be put on the outer electric insulating material 14, and a band 16 to be put on the outer case 15. - 特許庁

Band 16 is preferably a one-piece band with one split, but may be a two-piece band with two splits. If it is a one-piece band or a two-piece band, the diameter of the band 16 can be reduced by the bolt 17 .

The split position of the inner case 11, the split position of the inner electrical insulating material 12, the split position of the heating element 20, the split position of the outer electrical insulating material 14, the split position of the outer case 15, and the split position of the band 16. match. Then, by tightening the bolt 17, the inner case 11 is brought into close contact with the cylindrical body, the inner electrical insulating material 12 is brought into close contact with the inner case 11, the heating element 20 is brought into close contact with the inner insulating material 12, and the heating element 20 is brought into close contact with the outside. The electrical insulating material 14 can be brought into close contact, the outer case 15 can be brought into close contact with the outer electrical insulating material 14 , and the band 16 can be brought into close contact with the outer case 15 .

As shown in FIG. 2, the heating element 20 is formed by winding a heating wire 22 around an insulating plate 21 in a helical shape. The heating wire 22 is a bare wire. Therefore, the heating element 20 is insulated by the inner electrical insulating material 12 and the outer electrical insulating material 14 .

FIG. 3 is an exploded view of the 3-3 line cross section of FIG. , and the band 16 .
The inner case 11, the outer case 15, and the band 16 are preferably thin plates of rust-resistant stainless steel (for example, SUS304).

The inner electrical insulator 12 is, for example, 0.4 mm thick mica. Two layers of 0.2 mm thick mica may be stacked.
Outer electrical insulator 14 is mica that is 5 to 10 times thicker than inner electrical insulator 12 . It is preferable to stack 5 to 10 sheets of the inner electrical insulating material 12 having a thickness of 0.4 mm. The outer electrical insulating material 14 and the inner electrical insulating material 12 can be conveniently obtained simply by preparing mica with a thickness of 0.2 mm or 0.4 mm and changing the number of sheets.

A cooling jacket 18 indicated by an imaginary line may be added inside the inner case 11 without any problem. A coolant (water, air, or the like) flows appropriately through the cooling jacket 18 .

Next, the structure of a band heater suitable for the heat retaining section will be described with reference to FIGS. 4 and 5. FIG.
FIG. 4 is a cross-sectional view of a band heater suitable for the heat retaining part, and FIG. 5 is an exploded cross-sectional view taken along line 5-5 of FIG.
In FIG. 5, the thickness of the outer electrical insulator 14B differs from the outer electrical insulator 14 of FIG. Also, the material of the outer case 15B is different from that of the outer case 15 of FIG.
The other inner case 11, inner electrical insulating material 12, heating element 20 and band 16 are the same in shape and material as in FIG.

Unlike FIG. 3, the outer electrical insulating material 14B is mica with the same thickness as the inner electrical insulating material 12. FIG.
The outer case 15B is made of carbon steel plate plated with aluminum (aluminum plated steel plate).

The band heaters 10A and 10B described above are used by winding them around a cylindrical portion. A specific usage example will be described with reference to FIG.
As shown in FIG. 6, band heaters 10A and 10B are used in an injection device 30, for example. In the case of the injection device 30, the heating cylinder 32 corresponds to the cylindrical body.

The injection device 30 includes a heating cylinder 32 having a nozzle 31 at its tip, a screw 33 housed in the heating cylinder 32 so as to be rotatable and axially movable, a drop port block 34 connected to the heating cylinder 32, A hopper 36 is attached to the drop port block 34 to drop the pellet-shaped resin material into the heating cylinder 32 through the drop port 35 .

A band heater 10A suitable for a preheating section is arranged near the base of the heating cylinder 32, and a band heater 10B suitable for a heat retaining section is arranged at the tip of the heating cylinder 32.
In this example, a band heater 10C having a configuration different from that of the band heater 10A and the band heater 10B is arranged in the heating portion between the band heater 10A and the band heater 10B.
A configuration of a band heater 10C suitable for this heating section will be described with reference to FIGS. 7 and 8. FIG.

7 is a sectional view taken along line 7-7 of FIG. 6, and FIG. 8 is an exploded view taken along line 8-8 of FIG.
In FIG. 8, a band heater 10C suitable for the heating portion is formed by stacking an inner case 11, an inner electrical insulating material 12, a heating element 20, an outer electrical insulating material 14B, an outer case 15, and a band 16. .
The inner case 11, the outer case 15, and the band 16 are preferably thin plates of rust-resistant stainless steel (for example, SUS304).
The inner electrical insulating material 12 and the outer electrical insulating material 14B are, for example, 0.4 mm thick mica. Two layers of 0.2 mm thick mica may be stacked.

Table 1 shows the materials described above and the thermal conductivity λ (W/m·K) corresponding to these materials added to the heating section, preheating section, and heat retaining section.

The thermal conductivity λ of mica is 0.5 (W/m·K), which is much smaller than that of SUS304, λ 16.3 (W/m·K). That is, mica has heat insulation performance in addition to electrical insulation performance.

The band heater suitable for the preheating section has an outer electrical insulating material 5 to 10 times thicker than the band heater suitable for the heat retaining section. Five times the thickness reduces the heat transfer to one fifth, and ten times the thickness reduces the heat transfer to one tenth. That is, in the preheating section, heat transfer is interrupted by the outer electrical insulating material.

In addition, the band heater, which is suitable for the heat retaining part, uses an aluminum-plated steel sheet for the outer case. The thermal conductivity λ of SUS304 is 16.3 (W/m K), while the thermal conductivity λ of carbon steel is 54 (W/m K), and the thermal conductivity λ of aluminum is Since it is 204 (W/m·K), the thermal conductivity λ of the aluminized steel sheet is sufficiently large. As a result, the amount of heat transferred from the outer case to the band increases, and the amount of heat released from the band to the atmosphere increases.

Preferably, in another band heater suitable for the heat-retaining section, the band that was made of SUS304 is changed to an aluminized steel plate. Increases the amount of heat released from the band to the atmosphere.
Alternatively, both the outer case and the band may be made of an aluminized steel plate. The amount of heat released from the band to the atmosphere is further increased.

The action described in Table 1 will be described again based on the drawings.
9A shows the action of the band heater 10B suitable for the heat retaining section, FIG. 9B shows the action of the band heater 10C suitable for the heating section, and FIG. 9C shows the band heater 10C suitable for the preheating section. The action of the heater 10A will be explained.

In the band heater 10C of FIG. 9(b), approximately half q1 of the heat generated by the heating element 20 is transmitted to the heating cylinder 32, and approximately half q2 is radiated to the atmosphere.

On the other hand, in the band heater 10A shown in FIG. transmitted to

In addition, in the band heater 10B of FIG. 9A, at least one of the outer case 15B and the band 16 is made of an aluminized steel plate, so that the amount of heat radiation q5 to the atmosphere increases, and the amount of heat to the heating cylinder 32 increases accordingly. The amount of heat transfer q6 becomes smaller.
When the temperature of the band heater 10B exceeds the predetermined temperature, the heat radiation q5 is large, so the temperature can be quickly lowered to the predetermined temperature. Therefore, the temperature control performance of the band heater 10B is much better than those of the band heaters 10A and 10C.

A modification of the band 16 will be described with reference to FIG.
FIG. 10(a) shows a cross-sectional view of the band 16B, and FIG. 10(b) shows the b arrow view of FIG. 10(a).
As shown in FIG. 10(b), a cooling window 19 of an appropriate size is opened in the band 16B.

The heat radiation q5 shown in FIG. 9A is further increased because the heat is directly radiated from the outer cover 15B to the atmosphere without passing through the band 16. FIG.
Therefore, with the structure of FIG. 10, SUS304 can be adopted as the material of the band 16B, and the selection of materials increases.

Next, a modified example of the heating element 20 will be described with reference to FIG.
As shown in FIG. 11( a ), the heating element 20 has through holes 23 provided in an insulating plate 21 in a zigzag pattern, and a heating wire 22 is wound so as to pass through the through holes 23 . The lower surface of the insulating plate 21 is the heating cylinder side surface.
As shown in FIG. 11(b), the portion indicated by length L1 faces the heating cylinder. The remaining length L2 is significantly shorter than the length L1. L1 is about 70% and L2 is about 30%.

FIG. 11(c) shows a comparative example and corresponds to the cross-sectional view of FIG. In this comparative example, the length L3 faces the heating cylinder. This length L3 is approximately equal to the remaining length L4. Both L3 and L4 are 50%.
Considering that L1 and L3 greatly contribute to the heating of the heating cylinder, it can be said that the heating element 20 shown in FIGS. 11A and 11B is more desirable than the heating element 20 shown in FIG.

That is, in Table 2, the heating element has the form shown in FIGS. 11(a) and 11(b). Others are the same as Table 1.

In addition, the cylindrical body may be various types of pipes and containers other than the heating cylinder, and the type is not limited as long as the shape is cylindrical.

The band heater of the present invention is suitable for injection equipment.

10A to 10C band heater 11 inner case 12 inner electrical insulating material 14 outer electrical insulating material 14B outer electrical insulating material thinner than 14 15 outer case 15B different material from 15 Outer case 16 Band 20 Heating element 21 Insulating plate 22 Heating wire 23 Through hole 32 Cylindrical body (heating cylinder) L1 Length of heating wire facing heating cylinder L2 …remaining heating wire length.

Claims (2)

A band heater wound around a cylindrical body,
The band heater comprises an inner case covering the cylindrical body, an inner electric insulating material covering the inner case, a heating element covering the inner electric insulating material, an outer electric insulating material covering the heating element, and an outer electric insulating material covering the inner electric insulating material. It consists of an outer case that covers the insulating material and a band that covers the outer case,
The heating element comprises an insulating plate provided with through holes in a zigzag pattern, and a heating wire wound around the insulating plate while passing through the through holes,
The insulating plate has an upper surface, a lower surface, a left side, and a right side in a cross-sectional view, and has the left through-hole and the right through-hole penetrating from the upper surface to the lower surface,
The heating wire is
From the top surface to the bottom surface through the left through hole, to the right side along the bottom surface, to the top surface along the right side, and to the right through hole along the top surface ,
Through the right through hole, the upper surface reaches the lower surface, along the lower surface reaches the left side surface, along the left side surface reaches the upper surface, and along the upper surface reaches the left through hole. A band heater characterized by being wound as follows. The band heater according to claim 1,
In the heating wire, when the length of the heating wire along the lower surface is L1 and the remaining length is L2, L1 is approximately 70% and L2 is approximately 30%. heater.

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