Lawn Sprinkler (How Products are Made)
The lawn sprinkler is a mechanism through which water is distributed in a spray so that a residential lawn or garden is irrigated. Sprinklers may take extraordinarily large forms, such as the irrigation systems used by professional farmers to water crops in the field. Many serious gardeners employ landscaping firms to develop and install expensive, permanent sprinkler systems in the ground. However, the average American simply purchases an inexpensive plastic and metal sprinkler and attaches it to a garden hose so that the sprinkler disseminates the water evenly. Residential use lawn sprinklers take a wide variety of forms and are available in a wide variety of materials and associated prices. However, the oscillating sprinkler, with a metal arm that sprays out a fan-shaped curtain of water in an area approximately 600 ft2 (55.7 m2), is likely the most popular. Such oscillating sprinklers sell for well under $10, but can be over $40. The permanency of the materials generally determines the price.
The less expensive, plastic and aluminum oscillating sprinkler is very simple in construction and in operation. Most include only a base that enables the piece to seat securely on the lawn, an oscillating arm, a bracket with regulating cam (it controls the width of the fan spray as it moves the spray arm), the mechanical motor, and the connectors to the garden hose. The oscillating sprinkler works on the principle that water provides the power to move the elliptical cam (or heart-shaped cam in some models) which moves the sprinkler arm. Water spins a simple turbine which must be attached to a series of gears stacked up (called a gear train) to slow down the speed of the water.
Without the insertion of the gear train the cam and the oscillating arm would move much too quickly. The gear train reduces the speed of the incoming water so that the cam moves at only about one mile per hour.
The advent of the residential lawn sprinkler is inextricably bound with Americans' desire to cultivate the yard for fun and aesthetic reasons and not for farming purposes. In fact, Americans of the seventeenth and eighteenth centuries did not think much of developing bucolic spaces in and around their homes. The town square in New England, now gorgeous green pastures, was a scruffy piece of land in which cattle could graze. In the nineteenth century attitudes toward the cultivation of the lawn change for two reasons. First, more Americans moved out of the city to the evolving suburbs as rail transportation enabled them to live further from places of business. As they moved out where there was space for gardens there was the urge to work the lawn as a hobby. Beautifying the home and garden were thought to strengthen the family. Secondly, Victorian Americans began to long for the rural New England they thought they were losing while others wanted to emulate the pastoral estates developing in England. Notable landscape architects urged Americans to beautify their property and published treatises and designs to help them achieve this goal.
Lawn sprinklers require a city water delivery system because they are generally used with a hose. Such systems were not in place in large measure until about 1870. The very wealthy used fountains to water the lawn and dazzle neighbors. Patents on lawn sprinklers follow in short order; the first patent on an American lawn sprinkler was issued in 1871. Hose reels, nozzles, and sprinklers were advertised by 1900. Sprinklers took various forms. Large contraptions that rolled on carts with immense yardage of rubber hose were popular with some in the early twentieth century. By about 1930 the mechanisms took other forms such as cast metal with a three or four-arm rotating head that shot water as it spun around. Some were formed in the shape of animals with a rotating arm on the top. Plastic-bodied sprinklers followed in the later 20th century.
The oscillating lawn sprinkler may be made from a variety of materials based on price point of the sprinkler. The best selling models are made from very inexpensive materials. These include aluminum tubing, plastic, and rubber. The aluminum forms the oscillating arm. The base of the sprinkler is generally of injection molded plastic. The motor or the mechanical head that forces the sprinkler to oscillate is generally of plastic gears as well. The 0-rings that fit onto various joints are of rubber. Most oscillating sprinklers also have steel washers to ensure a tight fit at important junctures.
The Manufacturing Process
The oscillating sprinkler is manufactured in batches or smaller steps that are generally referred to as sub-assemblies. The sub-assemblies put together various larger portions at one time and then manufacture entails the assembling of all these sub-assemblies.
- First, the mechanical motor that drives the oscillating sprinkler is assembled. The motors are made in huge quantity and set aside for inclusion in any one of the sprinkler models. The parts of the motors are generally injection molded. This entails melting plastic pellets and then forcing the melted, viscous plastic into a hollow mold at high speed and using great force. Once formed, the plastic parts of the motor are carefully assembled. The motor essentially works like a water-powered turbine. It includes gears built into a stack. The small, plastic water-driven motor is assembled by hand. Parts are loaded on an assembly line and they come to the operator who presses them into place by hand. The motor is set aside until needed.
- In addition to the small plastic motor parts, other parts of the sprinkler that are injection molded include a regulating cam that is attached to a bracket on one end of the oscillating arm, plastic fittings that attach to the hose, and the plastic base that enables the sprinkler to sit upon a flat platform. The base may be heat foiled stamped, a process by which a brand name or decal is embedded in the plastic base according to the model number and whether the piece is being sold under a retailer's name. These parts are put away until needed for assembly.
- Next, hollow aluminum tubing that has O been shipped to the factory must be configured to form the oscillating arm of the sprinkler. The hollow aluminum tube, already the appropriate length for the sprinkler, is carefully bent into an arch on a hydraulic press that gently exerts pressure on the thin tubing.
- Immediately following the bending of the tube, a punch comes down and performs two important functions. First, the punch pierces approximately 20 holes into the hollow tube. Then, the punch inserts plastic jets into these holes. These plastic jet heads are simply pressure fit, meaning they are not soldered or glued in place but simply are forced into place. The hollow tube must have these holes and jets so that the water may cleanly spray from the oscillating arm once the hose, with running water, is attached to the sprinkler.
- One end of the hollow tubehe oscillating arms slightly expanded by a machine so that it may receive the bracket, which includes an elliptically-shaped cam, that regulates the width of the water spray. The machine inserts the bracket and cam onto the tube.
- Then, simple 0-rings and washers are manually put on the end of the hollow tube to keep the water from leaking out there before it gets to the spray jets.
- The tubeith bracket and cams now ready to have the small, plastic motor attached to it. A worker attaches the motor to the tube and embeds the entire assembly
All materials that come to the factory are inspected to ensure they are made according to manufacturers' specifications. A few key components of the oscillating sprinkler may come already fabricated at another factory such as the hollow tubing for the oscillating arm or the planetary gears within the mechanical motor. In these cases, incoming inspection of these parts is essential as they are the most important parts of the sprinkler.
During fabrication and assembly the operators are careful to monitor all aspects of production and physical assembly. Visual inspection is expected of all employees and this occurs generally when sub-assemblies are complete. One sprinkler manufacturer uses part-in-place eye machines that have a sensor that will stop the assembly if it notices that a piece is missing. Perhaps most important is that the mechanical motor works as it is advertised. One manufacturer simulates a jet of water coursing through the completed motor mechanism before installation by performing an air test in which air shoots through the mechanism to see if it is working properly.
While it does not exactly duplicate the water stream the manufacturer does discover faulty motors using the air test.
There is little waste in the fabrication of simple oscillating sprinkler. When there are errors in the injection process, or if a sub-assembly made from plastic is found to be faulty, the plastic parts may be put into a bin and recycled into pellets and reformed. Improperly formed oscillating arms, made from hollow extruded aluminum, may also be recycled if not suitable for use. Some lawn products are sprayed in colors and the powder coating requires some regulation upon its use; however, unless the base is very colorful or unusual the sprinkler is generally not powder coated or layered with additional color.
The oscillating sprinkler is quite effective and extraordinarily low priced. Like other inexpensive consumer products, many are made out of the country but there are a surprising number still made in the United States. The use of in-ground systems installed by professionals at great cost has become more popular recently but the market for simple sprinklers such as the oscillating sprinkler is still strong. Some manufacturers make them so inexpensively so that each year a consumer who leaves the sprinkler out over the winter does not think twice about buying another the following spring.
Sprinkler use of any kind has caused some concern in the arid Western states as drought in a concern. Some communities restrict the use of sprinklers according to the day of the week or the address of the gardener.
Where to Learn More
Jenkins, Virginia Scott. The Lawn: A History of An American Obsession. Washington, D.C.: Smithsonian Institution Press, 1998.
Tice, Patricia M. Gardening in America, 1830-1910. Rochester, NY: Margaret Woodbury Strong Museum, 1984.
L. R. Nelson Company Web Page. December 2001. http//:www.lrnelson.com>.
Oral interview with Mike Simpson, Production Unit Manager at L. R. Nelson Company. Peoria, IL. November 2001.
Nancy EV Bryk