Bottle Washing Machine

Overview

A bottle washing machine cleans returnable glass bottles so they can be filled again. Returnable bottles come back from the market dirty, with old labels, dried product, dust, cigarette ends and the occasional insect inside. The washer takes that mixed stream and returns bottles that are clean inside and out, free of label, and rinsed of any cleaning chemical, ready for the filler. It does this by carrying bottles neck-down through a sequence of heated caustic baths and spray zones, then through fresh-water rinses, all on a single endless chain so the line never stops between stages.

The machine is built around the Carrier Conveyor System, an endless chain that holds bottles in pockets and pulls them through every tank. Bottles enter at the Infeed Station, pass through the Caustic Soak Tanks and the Jetting System, get flushed in the Fresh-Water Rinse Section, and leave clean at the Discharge Station. Tank temperatures are held by the Heating System, the chain is pulled by the Main Drive System, and the whole cycle is sequenced from the Control Cabinet.

Loading the bottles

Bottles arrive from the depalletizer in a loose mass on the Accumulation Table. They have to be lined up in even rows before they can drop into carriers, so guide rails on the Infeed Guide Rail funnel them into columns and a Row Pusher Bar sweeps a full row sideways into the waiting pockets. The push is timed by the Infeed Timing Cam so that a row of pockets is always in position when the pusher fires. A Pressure Sensor watches for jams; if a bottle tips or a pocket is blocked, the machine stops before glass is crushed. Each bottle ends up neck-down in a Bottle Carrier Pocket, which is the position it keeps until discharge. Neck-down matters because it lets liquid drain freely and lets the internal spray reach the base of the bottle.

Soaking in caustic

The heart of the clean is the Caustic Soak Tanks section, a run of three Tank Shell basins filled with hot caustic soda. The first tank is a pre-soak that warms the bottle and softens the worst soil so the main tank is not fouled too quickly. The main caustic tank, held at 60 to 85 C and 1.5 to 2.5 percent caustic, does the real work: it dissolves dried product, kills microorganisms, and lifts paper labels off the glass. As labels float free they are dragged out by the Label Extractor, a mesh belt that skims the surface, so they do not recirculate and clog the system. A Circulation Pump keeps each bath moving so heat and chemistry stay even, and a Strainer Screen traps label scraps before they reach the pump. A Liquid Level Probe holds the bath level steady and a Tank Drain Valve lets the tank be emptied for a chemistry change. Total immersion runs three to six minutes, which is the dwell needed to sanitize a bottle that has been sitting in a warehouse for weeks.

Jetting inside and out

Soaking softens the soil but moving water is what removes it. The Jetting System drives detergent and water into each bottle through a Spray Nozzle aimed up the neck. Because the carriers are always moving, a fixed nozzle would only hit a bottle for an instant, so each spray rides on a Tracking Jet Tube that tracks the carrier for part of the stroke, driven by the Jet Cam Track. This keeps the stream pointed at the bottle base for a useful length of time. The tubes are fed from a Jet Manifold supplied by a high-pressure Jetting Pump, and a Pressure Sensor confirms the jets are actually flowing. The inside jet scours dried rings and sediment from the base, while outside sprays rinse the body and the area where the label was.

Rinsing clean

A bottle that still carries caustic cannot be filled, so the Fresh-Water Rinse Section flushes it out in stages. Water flows counter to the bottles: clean fresh water enters at the very last Rinse Manifold, and as it gets used it cascades back through the Cascade Recovery Tray stages to do earlier, dirtier rinsing before going to drain. This counterflow keeps fresh-water use low while still finishing each bottle with clean water from the Rinse Nozzle. A Rinse Pump recirculates the recovered water and a Fresh-Water Valve admits make-up. To prove the result, a Conductivity Sensor checks the rinse for residual caustic; if conductivity climbs, the machine flags that bottles may be leaving with chemical still on them.

Heat, drive and discharge

The baths only clean if they stay hot, so the Heating System runs a Steam Heating Coil in each tank, fed through a Steam Control Valve that a Temperature Probe modulates to setpoint, with a Condensate Trap draining spent steam. The whole carrier chain is pulled by the Main Drive Motor through a Gearbox Housing and Helical Gear Pair, with a Torque Limiter that slips rather than snap the chain if a bottle jams. At the end of the loop the Discharge Cam rolls each carrier upright so the clean bottle slides out neck-up onto the Outfeed Table and on to the filler. The full recipe of temperatures, dwell, indexing and dosing is held in the PLC Module and set from the LCD Panel, with motor and pump speeds trimmed by the Variable Frequency Drive to match line rate.