Toaster Structure: Schematic Diagram and Components
1. Toaster Structure
1.1 Support Components:
- Bottom Plate
- Front and Rear Plates
- Side Support Plates
- Upper Support Board
- Insulation Board
Material: Galvanized sheet (SGCC) or aluminum clad sheet (SA1C), with a thickness of 0.35–0.4mm.
1.2 Heating Plate Assembly:
- Mica Board
- Heating Wire
- Mica Strip
- Lugs
- Socket Nails
- Corns or Staples
For flat wire and heating wire, the thickness should be between 0.07 and 0.3mm. The heating wire is wound densely at the bottom, sparsely in the middle, and more densely at the top. Two winding methods are used: flat winding and waving.
- Flat winding is simple and fast to process.
- Waving helps reduce power density, improves color performance, and extends the heating plate’s lifespan but is more complex to process.
The conductive sheet can be made of aluminum-clad or electrolytic plates. The connection between the heating wire and the conductive sheet is usually done by butt welding, though some use rivet clamping. Mica strips are used to fix the heating wire, which is then secured to the mica board using corns or staples. The correct number and placement of the staples or corns are crucial to preventing short circuits by ensuring the heating wire is effectively secured.
2. Lifting Mechanism
2.1 Metal Lifting Mechanism:
The lifting mechanism serves multiple functions, including lifting the bread, triggering and holding the switch, centering the bread, and providing anti-jam protection. The components include:
- Bread Holder
- Bread Holder Bracket (Metal)
- Lifting Frame (Metal)
- Magnetic Sheet Bracket
- Magnetic Sheet
- Switch Clamp
- Guide Shaft
- Spring and Lifting Arm
2.2 Bread Centering Mechanism:
This mechanism serves two functions: centering the bread slices and preventing accidental contact with the heating wire. The components include:
- Bread Mesh Clip
- Bread Mesh Spring
The bread mesh clip is typically made from stainless steel wire (φ1.2–2.0mm) or cold-drawn steel wire. Stainless steel clips are electropolished after welding, while cold-drawn steel clips are chrome-plated and tested for salt spray resistance. The bread mesh springs are generally made of φ0.7mm stainless steel wire.
3. Shell Components
3.1 Outer Shell:
The toaster shell must maintain a low external temperature for safety, with all surfaces (except the top) not exceeding 83°C. The shell material is typically PP (J800R), sometimes with 15% calcium carbonate added for strength. In some cases, PC plastic is used. The gap between the top cover and the outer shell is designed in a “B” shape to prevent table knife interference. The middle part is supported by insulating particles, and the gap ensures proper heat dissipation, passing the temperature rise test to maintain surface temperature standards.
3.2 Base:
The base of the toaster has several functions:
- Securing the heating components, circuit board, slag tray, and shell components.
- Providing sufficient strength with well-designed ventilation grooves and appropriate feet for stability.
- Material: PP (Plastic).
3.3 Slag Tray:
The toaster’s slag tray is a pull-out design. The connection between the tray and the handle needs to be strong enough to prevent the tray from detaching under its own weight, even when the toaster is moderately shaken.
4. Electrical Control Assembly
- Circuit Board
- Electromagnet
- Switch
The toaster’s circuit diagram includes four heating wires (L1-L4) installed on both sides of the toaster slots. Switch S1 is connected to a pair of relay contacts and can be engaged by an external lever. AC power from L4 is rectified and filtered by D1 and C1 to supply power to the relay. Another power source, passed through R1, C2, and Z1, stabilizes at around 3.9V to supply power to U1. U1 initiates the timing sequence, which engages the relay and locks switch S1. The timing knob W1 is used to set the duration manually. After the time expires, the IC releases the relay, S1 loses power, and the toaster turns off, completing the cycle.
Note: U1 refers to the timing IC PT8A2513 used in this circuit.