Backpack Power Sprayer Product

Overview

A backpack power sprayer applies liquid agrochemicals — herbicides, insecticides, fungicides, foliar fertilisers — from a tank carried on the operator's back. Where a manual knapsack sprayer requires constant lever pumping with one arm, this machine replaces the lever with a battery-driven Diaphragm Pump, so the operator's only job is aiming the Wand & Hose. The practical gain is consistency: pressure no longer sags between pump strokes, so droplet size and application rate stay inside the band the chemical label assumes.

The machine divides into a carried liquid system (the 16 L Chemical Tank, pump and hose), an electric drive (the Motor Drive and Battery Pack), and the Carrying Harness that makes 22 kg of filled weight tolerable for hours.

How it works

The pump is a positive-displacement diaphragm type. An Eccentric Cam on the motor shaft flexes the Pump Diaphragm back and forth about 3 mm; each stroke alternately enlarges and shrinks the chamber in the Pump Head. Two Check Valves rectify this oscillation: liquid is drawn from the Tank Outlet on the suction stroke and pushed into the Delivery Hose on the discharge stroke. Diaphragm pumps dominate this application because the chemical never touches the drive side — only EPDM rubber, polypropylene and Viton seals from the O-Ring Set see the liquid, all tolerant of the solvents and surfactants in pesticide formulations.

Pressure regulation is two-layered. Mechanically, the Pressure Regulator bypasses excess flow back to the tank when the trigger closes, so the pump can run continuously without dead-heading. Electronically, the controller in Control Electronics reads a Pressure Sensor in the discharge line and adjusts motor speed through three Power MOSFET phase drivers to hold the set-point chosen on the Speed Dial. Closed-loop control also saves energy: at low pressure settings the motor idles along at a fraction of full power, which is where the 8-hour runtime figure comes from.

Spray delivery

Application quality is set at the nozzle, and the Nozzle Set covers the standard cases. A flat-fan tip at 0.2–0.3 MPa lays an even band for herbicides on weeds; a hollow-cone tip at 0.4–0.6 MPa makes the fine 100–200 µm droplets that coat foliage undersides for insecticides; the adjustable cone trades reach against droplet size for spot work. Droplet size matters beyond coverage — droplets under ~100 µm drift on light wind, which is the main off-target risk of knapsack spraying, so labels specify coarser sprays near sensitive crops.

The Trigger Valve gives instant on/off at the lance with a lock-on clip for long runs, and a Swivel Fitting stops the hose winding up as the operator sweeps the Wand Tube side to side.

Tank and filling

The Tank Shell is blow-moulded UV-stabilised HDPE, translucent so the level is visible against moulded litre graduations — operators dose chemical by tank volume, so the scale is a metering instrument, not a convenience. The wide Fill Lid accepts a bucket pour through the Fill Strainer, which catches the debris and undissolved wettable-powder lumps that would otherwise block nozzles. The lid vent admits air as liquid leaves; without it the tank would pull vacuum and starve the pump.

Battery and electrics

The Battery Pack is a 3S2P pack of six Li-ion Cell, 18650 cells with a BMS Board handling cell balancing, over-discharge cut-off and charge control through the Charge Port. The pack slides into a sealed dock in the Battery Case below the tank, deliberately away from fill splashes, and the IP65 Power Switch is the only exposed control. Everything electrical sits behind seals because the failure environment is explicit: dripping chemical, hose-down cleaning at end of day, and rain.

Ergonomics and safe use

A filled unit weighs about 22 kg, at the upper edge of what is acceptable for sustained carrying. The Carrying Harness addresses this with wide padded Shoulder Straps, a ventilated Back Pad, and a Waist Belt that shifts load to the hips, all anchored to a Frame Plate bolted to the tank.

Operationally, the sprayer is a pesticide application device and falls under the same hygiene rules as any other: triple-rinse the tank after use (running rinse water out through the wand, not the Tank Outlet drain alone), never leave mixed chemical standing overnight, and store the unit with the Pump Diaphragm depressurised. Diaphragm and check valves are the routine service items, typically replaced yearly under professional use.