Injection mold device

Abstract

An injection mold device comprises plastic product mold bodies, electromagnetic valves, a heating box, a bottom plate and a liquid pump, outer mold cavities of the multiple plastic product mold bodies are each of a hollow two-layer structure, and the injection mold device is further provided with a temperature control mechanism and a detection mechanism; an electric heating plate is mounted at the lower end of the heating box; the heating box and the liquid pump are mounted on the bottom plate; the multiple electromagnetic valves are connected with the heating box, the liquid pump and the plastic product mold body, and the temperature control mechanism and the detection mechanism are installed in the element box and electrically connected with the electric heating plate. Through heat released by hot oil in the heating box, flowing heating circulating oil can be input into the inner side of the hollow outer mold cavity during pouring, so that the flowability of plastic fluid after pouring is improved, and the probability of quality problems such as bubbles of prepared plastic finished products is reduced; and heat can be absorbed through tap water after pouring is finished, so that the cooling forming time of a product after pouring is shortened (mold stripping can be performed quickly), and the working efficiency is correspondingly improved.

Description

Technical Field

[0001] The utility model relates to the field of injection mold equipment, in particular to an injection mold device. Background Art

[0002] In the injection molding industry, the heating and melting equipment melts the plastic raw materials put into the bin during production, and then inputs them into multiple plastic product mold raw material inlets (gates) located at a lower position through fluid pipelines. The fluid raw materials entering the mold through the mold raw material inlets are subsequently cooled to form plastic products (the inner and outer mold cavities are then separated to obtain finished plastic products).

[0003] Take the mold equipment of plastic bucket as an example, it includes outer mold cavity and inner mold cavity. Before pouring, the inner mold cavity is located in the outer mold cavity. After subsequent pouring and cooling, the equipment controls the inner mold cavity to move upward and separate from the outer mold cavity, and then the staff takes out the molded plastic product. With the development of industry, the technology of plastic product molds has also been improved. The authorized patent of my country's patent number "201720091215.8" and the patent name "a dust-proof plastic mold" records that "the utility model has a scientific and reasonable structure, safe and convenient to use, and is provided with a mold dustproof shell. When the plastic mold is not in use, the upper mold of the plastic mold and the lower mold of the plastic mold can be stored inside the mold dustproof shell, which has a certain dustproof effect and is cleaner to use. At the same time, it also prolongs the service life of the plastic mold to a certain extent, and the upper mold of the plastic mold and the lower mold of the plastic mold can be fixedly connected together. When the plastic mold needs to be moved, the plastic mold can be moved well by directly holding the mold handle, which is more convenient to use." As can be seen from the above, although the comparative patent has improved the function of the plastic product mold to a certain extent, it is limited by the structure. Like other existing plastic molds in the field, it still has the following technical disadvantages due to structural limitations. Specifically, when the heating and melting equipment pours the plastic raw material fluid into the plastic product mold through the fluid pipeline, when the heating and melting equipment itself does not heat the raw material to a high temperature, or when the corresponding plastic raw material is affected by the surrounding low temperature environment and has poor fluidity after melting, there is a probability that the fluid flowing into the outer side of the inner mold cavity and the inner side of the outer mold cavity of the plastic product mold will be uneven, bubbles will exist, etc., which will have an adverse effect on the quality of subsequent plastic products. In addition, after pouring the fluid raw material between the outer side of the inner mold cavity and the inner side of the outer mold cavity of the plastic product mold, the outer mold cavity is cooled by the natural environment or by fan blowing, etc., so the relative cooling effect is not good, which will cause the finished product demolding time to be extended, and then lead to relatively low production efficiency. In summary, it is very necessary to provide an injection mold device that can improve the quality of plastic products after pouring and relatively improve work efficiency. Utility Model Content

[0004] In order to overcome the drawbacks of existing plastic product molds due to structural limitations as described in the background, the utility model provides an injection mold device based on a plastic product mold body, which can input flowing heating circulating oil into the inner side of a hollow outer mold cavity during pouring, thereby improving the fluidity of the plastic fluid after pouring and reducing the probability of quality problems such as bubbles in the prepared plastic product finished product. Moreover, after pouring, flowing cooling water can be input into the inner side of the hollow outer mold cavity to reduce the cooling and molding time of the product after pouring (it can be demolded faster), thereby correspondingly improving the work efficiency.

[0005] The technical solution adopted by the utility model to solve its technical problems is:

[0006] An injection mold device comprises a plastic product mold body, a solenoid valve, a heating box, a base plate, and a liquid pump. The outer mold cavities of the multiple plastic product mold bodies are respectively hollow two-layer structures, characterized in that they also have a temperature control mechanism and a detection mechanism; an electric heating plate is installed at the lower end of the heating box, and a liquid adding pipe, a sealing cover and a one-way air valve are installed on the outer side of the upper end of the heating box. The lower end of the heating box is installed on one side of the base plate, and the liquid pump is installed on the other side of the base plate; there are multiple solenoid valves, and the branch pipes on one side of the lower end of the heating box are respectively connected in parallel with one end of the first solenoid valve and the second solenoid valve, and the other ends of the first solenoid valve and the second solenoid valve are respectively connected in parallel with the liquid inlet end of the liquid pump and the tap water pipe; the lower side of the outer mold cavity of each plastic product mold body is connected One end and the upper end are respectively provided with a liquid inlet pipe and a liquid outlet pipe, the liquid outlet end of the liquid pump is connected in parallel with one end of another plurality of solenoid valves, the other ends of another plurality of solenoid valves are respectively connected to the outer mold cavity liquid inlet pipes of a plurality of plastic product mold bodies, the outer mold cavity liquid outlet pipe of each plastic product mold body is connected in parallel with one end of two solenoid valves A, there are a plurality of liquid return pipes on the upper side of the heating box, the outer ends of the plurality of liquid return pipes are connected to the other end of one of the solenoid valves A of the outer mold cavity liquid outlet pipes of the plurality of plastic product mold bodies, the other end of another solenoid valve A of the outer mold cavity liquid outlet pipes of the plurality of plastic product mold bodies is connected in parallel with a sewage pipe; the temperature control mechanism and the detection mechanism are installed in the component box; the power output end of the temperature control mechanism is electrically connected to the power input end of the electric heating plate.

[0007] Furthermore, the solenoid valve and solenoid valve A are normally closed valve core solenoid valves.

[0008] Furthermore, heating oil is added into the heating box through a liquid adding pipe, and the heating oil is silicone heat-conducting oil.

[0009] Furthermore, the temperature control mechanism includes a relay and a temperature switch. The temperature switch is installed at the side end of the heating box. One end of the temperature switch is connected to the positive power input end of the relay.

[0010] Furthermore, the detection mechanism includes a photoelectric switch, a pressure switch, an alarm light and a buzzer. The liquid inlet pipe of the pressure switch is installed on the outside of the liquid outlet end of the liquid pump. The photoelectric switch is vertically installed on the heating box and the detection head of the photoelectric switch is located at the upper end of the heating box.

[0011] Compared with the prior art, the utility model has the following beneficial effects: (1) The utility model is based on the plastic product mold body, and the outer mold cavity of each plastic product mold body has two layers, inner and outer. The heat released by the hot oil in the heating box can be used to input the flowing heating circulating oil into the inner side of the hollow outer mold cavity during pouring, thereby improving the fluidity of the plastic fluid after pouring and reducing the probability of quality problems such as bubbles in the prepared plastic product; (2) After pouring, tap water can be used to absorb heat, reducing the cooling molding time of the product after pouring (it can be demolded faster), and correspondingly improving the work efficiency. In summary, the utility model has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The utility model is further described below in conjunction with the accompanying drawings and embodiments.

[0013] Figure 1 It is a schematic diagram of the structure of the utility model.

[0014] Figure 2 This is a circuit diagram of the utility model. DETAILED DESCRIPTION

[0015] Figure 1 , 2As shown in, an injection mold device includes a plastic product mold body 12, a power supply mechanism W1, a solenoid valve DCN, a heating box 1, power switches SN and SN1, a bottom plate 2, and a liquid pump M (220V, power 2KW). The outer mold cavities 3 of the plurality of plastic product mold bodies 12 are respectively hollow two-layer structures (a connecting plate 31 is provided at a certain interval between the inner and outer layers, and the connecting plate 31 serves to connect and reinforce the inner and outer layers of the outer mold cavity 3, and the connecting plate 31 does not isolate the channel between the inner and outer layers), and also has a temperature control mechanism and a detection mechanism; an electric heating plate RT is installed on the lower end of the heating box 1, a liquid adding pipe 101 is installed in the middle of the outer side of the upper end of the heating box 1, a sealing cover 102 is installed on the upper end of the heating box 1, and a liquid adding pipe 101 is installed in the middle of the outer side of the upper end of the heating box 1. A one-way air valve 103 is installed on the right side of the bottom plate 2 (to discharge the over-pressure gas in the heating box), the lower end of the heating box 1 is installed on the right side of the bottom plate 2, and the liquid pump M is installed on the left end of the bottom plate 1; there are eight solenoid valves, the other end of the branch pipe welded in the middle of the left side of the lower end of the heating box 1 is connected to the first end of a three-way pipe through a threaded connection, the three-way pipe and one end of the first solenoid valve DCN and the second solenoid valve DCN are respectively connected through a pipe joint, and the other ends of the first solenoid valve DCN and the second solenoid valve DCN are respectively connected to the liquid inlet end of the liquid pump M and the tap water pipe through a pipe; a liquid inlet pipe 32 and a liquid outlet pipe 33 that are interconnected with the inner and outer layers are respectively welded at the middle of the lower right side end and the upper part of the left side end of the outer mold cavity 3 of each plastic product mold body 12, and the liquid outlet end of the liquid pump M is respectively connected to the inner and outer layers. A connecting pipe 4 is installed with threads, and the left side of the connecting pipe 4 is a closed structure; eight circulation pipes 5 interconnected with the interior thereof are welded from left to right on the upper end of the connecting pipe 4, and the upper ends of the eight circulation pipes 5 are connected to one end of another eight electromagnetic valves DCN through threads, and the other ends of the other eight electromagnetic DCN are connected to the outer sides of the liquid inlet pipes of the outer mold cavity 3 of eight plastic product mold bodies 12 through metal hoses 6 with a length margin, respectively, and the outer mold cavity liquid outlet pipe 33 of each plastic product mold body 12 is connected to the first end of a three-way pipe A through threads, and the other two ends of the three-way pipe A are respectively connected to one end of two electromagnetic valves ADCN1 through pipe joints, and eight return pipes 7 interconnected with the inside of the heating box are welded from front to back on the left side of the upper end of the heating box 1, and the eight return pipes 7 are respectively connected to the outer sides of the outer mold cavity 3 of the eight plastic product mold bodies 12 through metal hoses 6 with a length margin. The outer end of the liquid pipe 7 and the other end of one of the solenoid valves ADCN1 of the liquid outlet pipes of the outer mold cavity of the eight plastic product mold bodies 12 are respectively connected through a metal hose A with a length margin, and the other end of another solenoid valve ADCN1 of the liquid outlet pipe of the outer mold cavity 3 of the eight plastic product mold bodies 12 and eight joints at one end of a connecting pipe A8 (the two side ends are closed structures) are respectively connected through a metal hose B9 with a length margin, and the sewage pipe welded at the other end of the connecting pipe A89 and interconnected with its interior is connected to a sewage hose 10, and the other end of the sewage hose 10 is located on the wastewater tank; the power supply mechanism W1, the power switch, the temperature control mechanism, and the detection mechanism are installed in the component box 11, and the component box 11 is installed in the electric control box at the right front side end of the base plate 1.All power switch handles are located outside the front opening of the component box.

[0016] Figure 1 , 2 As shown, the solenoid valve DCN and the solenoid valve ADCN1 are normally closed valve core solenoid valves with a power of 2W. Five-sixths of heating oil (the heating oil is silicone thermal oil) is added to the heating box 1 through the liquid adding pipe 101. The temperature control mechanism includes a relay J2 and a temperature switch D2. The temperature switch D2 is sealed and installed outside the middle of the lower end of the right side of the heating box 1, and its temperature sensing surface is close to the outer end of the heating box 1. One end of the temperature switch D2 is connected to the positive power input end of the relay J2. The detection mechanism includes a photoelectric switch W2, a pressure switch D1, an alarm light H and a buzzer B1. There is a screw hole on the side end of the liquid outlet of the liquid pump M. The liquid inlet pipe of the pressure switch D1 is screwed into the screw hole and sealed and installed on the outside of the liquid outlet. There is an opening on the left side of the middle of the upper end of the heating box 1. The photoelectric switch W2 is vertically sealed and installed on the outer end of the opening and the detection head of the photoelectric switch W2 is located at the upper end of the heating box 1. The power output end of the pressure switch D1 is connected to the positive power input end of the buzzer B1, and the power output end 3 and 2 of the photoelectric switch W2 are connected to the power input end of the alarm light H. The power input terminals 1 and 2 of the power supply mechanism W1, the control power input terminal of the relay J2 of the temperature control mechanism and the two poles of the AC 220V power supply are connected via wires respectively, the power output terminals 3 and 4 of the power supply mechanism W1 and the other end of the temperature switch D2 at the power input terminal of the temperature control mechanism and the negative power input terminal of the relay J2, the power input terminal 1 and 2 of the photoelectric switch W2 of the detection mechanism, the ten power switches SN, and the power input terminals of the sixteen power switches SN1 are connected via wires, the power input terminal of the liquid pump M is connected in series with the two poles of the AC 220V power supply via wires respectively, the two normally open contact terminals of the power output terminal relay J2 of the temperature control mechanism and the power input terminal of the electric heating plate RT are connected via wires, the power output terminals of the ten power switches SN and the ten solenoid valves DCN are connected via wires respectively, and the power output terminals of the sixteen power switches SN1 and the power input terminals of the sixteen solenoid valves ADCN1 are connected via wires respectively.

[0017] Figure 1 , 2As shown, the new type is based on the plastic product mold body 12. During casting, the heating and melting equipment melts the plastic raw materials put into the bin during production, and then respectively inputs them into the multiple plastic product mold body 12 raw material inlets (gates) located at the lower position through the fluid pipeline. The fluid raw materials entering the plastic product mold body 12 through the raw material inlets of the plastic product mold body 12 are subsequently cooled to form plastic products (subsequently separate the inner and outer mold cavities of the mold to obtain the finished plastic products); it should be noted that the plastic product mold body 12 is an existing mature technology, and this application does not provide any protection for the structure and function of the plastic product mold. This application protects the improvement of the quality of the plastic product cast by the plastic product mold body 12 and the demolding in the shortest possible time. After the 220V AC power supply enters the power input end of the power supply mechanism W1, the 3rd and 4th pins of the power supply mechanism W1 output a stable DC 12V power supply that enters the power input end of the ten power switches SN, the sixteen power switches SN1 and the temperature control mechanism and the detection mechanism, and the above-mentioned power switches and mechanisms are powered on. After the temperature control mechanism is energized, when the temperature of the heating oil in the heating box is lower than a certain level (for example, lower than 150°C), the internal contacts of the temperature switch D2 are closed, so that the relay J2 is energized to close its control power input terminal and the normally open contact terminal, and the electric heating plate RT heats the heating oil in the heating box; when the temperature of the heating oil in the heating box is higher than a certain level (for example, higher than 150°C), the internal contacts of the temperature switch D2 are open, so that the relay J2 is no longer energized to close its control power input terminal and the normally open contact terminal, and the electric heating plate RT no longer heats the heating oil in the heating box; through the above, the present invention can always keep the oil level in the heating box at a constant 150°C. After the staff turns on the power switch SN2 of the liquid pump M, the corresponding power switch SN of the first solenoid valve DCN, and the power switches SN and SN1 of the corresponding one or more solenoid valves DCN and solenoid valve ADCN1 connected to the corresponding one or more external mold cavity liquid inlet pipes 32 and liquid outlet pipes 33, the first solenoid valve DCN, and the corresponding one or more solenoid valves DCN connected to the corresponding one or more external mold cavity liquid inlet pipes 32 and liquid outlet pipes 33, and the corresponding one of the solenoid valves ADCN1 are opened. In this way, the liquid pump M will extract the hot oil from the heating box and pressurize it, and then pump it into the inner and outer layers of the outer mold cavity through the corresponding one or more external mold cavity liquid inlet pipes, and evenly heat the outside of the inner mold cavity, which is beneficial for the fluid raw materials between the inner and outer mold cavities to fully absorb heat and improve fluidity, thereby reducing the probability of holes in subsequent finished products. After releasing heat, the hot oil flows back into the heating box through the liquid outlet pipes of one or more external mold cavities and is heated by the electric heating plate RT again, so that the hot oil can be recycled.After the subsequent pouring is completed, turn off the power switch SN2 of the liquid pump M, the corresponding power switch SN of the first solenoid valve DCN, and the power switches SN and SN1 of the corresponding one or more solenoid valves DCN and solenoid valve ADCN1 connected to the corresponding one or more external mold cavity liquid inlet pipes 32 and liquid outlet pipes 33. Then, the first solenoid valve DCN, and the corresponding one or more solenoid valves DCN and solenoid valve ADCN1 connected to the corresponding one or more external mold cavity liquid inlet pipes 32 and liquid outlet pipes 33 lose power and the valve core is closed. After the pouring is completed, the staff turns on the power switch SN2 of the liquid pump M, the corresponding power switch SN of the second solenoid valve DCN, and the power switches SN and SN1 of the corresponding one or more solenoid valves DCN and solenoid valve ADCN1 connected to the corresponding one or more outer mold cavity liquid inlet pipes 32 and liquid outlet pipes 33. Then, the second solenoid valve DCN, and the corresponding one or more solenoid valves DCN connected to the corresponding one or more outer mold cavity liquid inlet pipes 32 and liquid outlet pipes 33, and the corresponding other solenoid valve ADCN1 are powered on and the valve core is opened. In this way, the liquid pump M will draw in tap water (using the liquid pump to increase pressure is mainly to prevent insufficient tap water pressure), and then pump it into the inner and outer layers of the outer film cavity through the corresponding one or more outer mold cavity liquid inlet pipes, and absorb heat from the outside of the inner mold cavity, which is beneficial to the rapid cooling of the finished product between the inner and outer mold cavities, and correspondingly improves the work efficiency. After absorbing heat, the hot water is discharged into the wastewater tank through the sewage hose 10. After cooling is completed, turn off the power switch SN1 of the liquid pump M, the corresponding power switch SN of the second solenoid valve DCN, and the corresponding one or more solenoid valves DCN and solenoid valve ADCN1 connected to the corresponding one or more external mold cavity liquid inlet pipes 32 and liquid outlet pipes 33. The second solenoid valve DCN, and the corresponding one or more solenoid valves DC connected to the corresponding one or more external mold cavity liquid inlet pipes 32 and liquid outlet pipes 33, and the corresponding other solenoid valve ADCN1 lose power and the valve core is closed, and tap water no longer enters the liquid inlet end of the liquid pump.

[0018] Figure 1 , 2As shown, in actual situations, when the liquid pump M works normally and pumps out water or hot oil under normal pressure, the internal contacts of the pressure switch D1 are open, and the buzzer B1 will not be powered on to make a sound, indicating that the work is normal. When the liquid pump M works abnormally (for example, the liquid pump M cannot rotate, the tap water is cut off, or the amount of heating oil is too little, etc.), and cannot pump out water or hot oil, the internal contacts of the pressure switch D1 are closed, and the buzzer B1 will be powered on to make a sound, indicating that the work is abnormal; the staff can carry out maintenance in time after hearing the sound. When the amount of oil in the heating box is more than half, the light beam emitted by the detection head of the photoelectric switch W2 is blocked, the 3rd pin of the photoelectric switch W2 has no output, and the alarm light H will not be powered on to work, indicating that there is still a lot of heating oil and no need to add; when the amount of oil in the heating box is less than half, the light beam emitted by the detection head of the photoelectric switch W2 is no longer blocked, and the 3rd pin of the photoelectric switch W2 outputs a high level, and then the alarm light H will be powered on to work and light up, indicating that there is less heating oil and needs to be added. Through all the above technical solutions, the new type improves the fluidity of the plastic fluid after pouring, reduces the probability of quality problems such as bubbles in the prepared plastic product, reduces the cooling and molding time of the product after pouring (can be demolded faster), and can prompt the working condition of the liquid pump M and the amount of oil in the heating box, thereby correspondingly improving work efficiency. Figure 2 In the figure, the power module W1 is a finished product of an AC 220V to DC 12V power module; the pressure switch D1 is a finished product of a normally closed contact electric contact pressure switch; the buzzer B1 is a finished product of an active continuous sound buzzer alarm of model FM12V; the alarm light H is a finished product of a flash alarm with a working voltage of DC 12V and a power of 2W; the photoelectric switch W2 is a finished product of a photoelectric switch of model E18-D80NK, which has two power input terminals and a signal output terminal. When there is an obstacle at the front end of the detection head, the signal output terminal outputs power, otherwise it does not output. The upper end of the housing has an adjustment knob to adjust the detection distance to the left to become closer, otherwise it becomes farther (adjusted to 50 cm in this embodiment); the relay J1 model is DC12V; the power of the electric heating plate RT (or electric heating tube) is 5KW; the temperature switch D2 is a snap-type 150°C normally closed contact temperature control switch of model KSD301.

[0019] The above shows and describes the basic principles and main features of the utility model and the advantages of the utility model. For those skilled in the art, it is obvious that the utility model is limited to the details of the above exemplary embodiments, and the utility model can be implemented in other specific forms without departing from the spirit or basic features of the utility model. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the utility model is defined by the attached claims rather than the above description, and it is intended to include all changes within the meaning and scope of the equivalent elements of the claims. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0020] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in the embodiments may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. An injection mold device, comprising a plastic product mold body, a solenoid valve, a heating box, a bottom plate, and a liquid pump, wherein the outer mold cavities of the plurality of plastic product mold bodies are respectively hollow two-layer structures, characterized in that: It also has a temperature control mechanism and a detection mechanism; an electric heating plate is installed at the lower end of the heating box, a liquid adding pipe, a sealing cover and a one-way air valve are installed on the outer side of the upper end of the heating box, the lower end of the heating box is installed on one side of the bottom plate, and the liquid pump is installed on the other side of the bottom plate; there are multiple solenoid valves, and the branch pipe on one side of the lower end of the heating box is connected in parallel with one end of the first solenoid valve and the second solenoid valve respectively, and the other ends of the first solenoid valve and the second solenoid valve are connected in parallel with the liquid inlet end of the liquid pump and the tap water pipe respectively; each plastic product mold body has a liquid inlet pipe and a liquid outlet pipe at the lower end and the upper end of the outer mold cavity respectively, and the liquid outlet end of the liquid pump and multiple other solenoid valves are connected in parallel. One end of the solenoid valves is connected in parallel, and the other ends of the multiple solenoid valves are respectively connected to the outer mold cavity liquid inlet pipes of the multiple plastic product mold bodies, the outer mold cavity liquid outlet pipe of each plastic product mold body is connected in parallel to one end of the two solenoid valves A, and there are multiple return liquid pipes on the upper side of the heating box. The outer ends of the multiple return liquid pipes are connected to the other end of one of the solenoid valves A of the outer mold cavity liquid outlet pipes of the multiple plastic product mold bodies, and the other end of another solenoid valve A of the outer mold cavity liquid outlet pipes of the multiple plastic product mold bodies is connected in parallel to the drain pipe; the temperature control mechanism and the detection mechanism are installed in the component box; the power output end of the temperature control mechanism is electrically connected to the power input end of the electric heating plate.

2. An injection mold device according to claim 1, characterized in that: Solenoid valve, solenoid valve A is a normally closed valve core solenoid valve.

3. An injection mold device according to claim 1, characterized in that: Heating oil is added into the heating box through the liquid adding pipe, and the heating oil is silicone heat-conducting oil.

4. An injection mold device according to claim 1, characterized in that: The temperature control mechanism comprises a relay and a temperature switch. The temperature switch is installed at the side end of the heating box. One end of the temperature switch is connected to the positive power input end of the relay.

5. The injection mold device according to claim 1, characterized in that: The detection mechanism includes a photoelectric switch, a pressure switch, an alarm light and a buzzer. The liquid inlet pipe of the pressure switch is installed outside the liquid outlet end of the liquid pump. The photoelectric switch is vertically installed on the heating box and the detection head of the photoelectric switch is located at the upper end of the heating box.

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