You likely use things made with the help of my maternal grandfather’s patent every day. From cars to jet airliners, from garden hoses to welding torches, reinforced hose is used. You need an inner layer that stands up to whatever flows through the hose, you need a reinforcing layer to keep the hose from bulging and bursting under pressure, and you need an outer coating to protect the hose from the external environment. So, how do you make that? Therein lies a tale.
F. Merrill Galloway was my maternal grandfather. Born in 1908, he went home at 95. He worked his entire adult life until the Transient Ischemic Attacks (TIA) or mini-strokes ended his ability to work in his late 80s. He worked with both his hands and his mind, from his garden, to clocks, to rebuilding a violin from broken pieces in a cigar box. Then there was the work that paid the bills and in which he took enormous pride.
He worked in the rubber industry his entire adult life. He was hired after college by Quaker Rubber, which was eventually bought by H.K Porter, which is now part of HBD Industries. He was moved to Ohio to establish a continuous hose production plant. The manufacturing plants in which he worked made hoses and belts, of the sort found in a car’s engine compartment, for instance. These are now organized under one of the venerable brand names: Thermoid. Into the plant came raw materials, and out the other end went finished products on pallets.
Rubber, whether natural or synthetic, is only useful when combined with certain additives and heated. The heating process is called vulcanization, or “curing.” Curing chemically fixes the additives in among the rubber molecules so that the product does not sag into a puddle in the summer or crumble into pieces in the winter. American Innovations offers a creative telling of Charles Goodyear’s lengthy trial and error discovery of vulcanization. A Royal Society of Chemistry podcast on rubber chemistry offers a more technical, but accessible, explanation.
Vulcanisation crosslinks rubber by creating sulfur bridges between chains, which generally vary in length between one and eight sulfur atoms. Short crosslinks produce a more heat resistant rubber, whereas longer crosslinks produce a more elastic material. The amount of crosslinking also affects the mechanical properties – the higher the degree of crosslinking, the stiffer the rubber. For example, rubber bands have a much lower crosslink density than car tyres. On its own, sulfur is a slow, inefficient crosslinker, so accelerating agents are added to catalyse the process, and other additives are added to stop the reaction and stabilise the final product.
The flexibility and ability to hold air, water, and other liquids or gasses make hoses superior to metal tubes or pipes, in many applications. Yet, you do not want a hose to bulge, like a party balloon. So, you can add lateral or sidewall strength by wrapping the hose in thread, applied in a crosswise manner by several bobbins rotating in opposite directions as the hose passes between them.
Before the reinforcement step, the raw materials, following a recipe for the particular desired product, are combined and heated into a near liquid mass. That mass is then extruded with the desired cross-section interior and exterior diameters. Another rubber company gives this explanation of the rubber extrusion process:
The rubber extrusion process begins with the soft, unvulcanized rubber compound being fed into the extruder.
Next, the flutes of the revolving screw will begin to carry the rubber forward into the die, with an increase in pressure and temperature occurring as the material gets closer to the die itself.
Once it reaches the die, the built-up pressure forces the material through the openings, where it will consequently swell in various degrees based on the material compound and hardness. Because of this tendency toward swelling, many extruded parts require plus or minus tolerances on their cross sections. During the vulcanization, the extruded rubber will well or shrink in both its cross section and its length, depending on the type of rubber compound used.
With the extruded, but not vulcanized, hose wrapped with reinforcing material, repeat the extrusion process with the same or different materials to create the outer layer. Now we need to get the whole thing to set with the characteristics we desire for use. Time to bring the heat.
One way to vulcanize hose is to make a desired length and heat it all at once. Obviously, this limits the speed of production, and the length, depending on the heating system. What we really want is a continuous system, a sort of assembly line. Yet, the length of time you need to apply heat suggests the assembly line could get quite long, just to keep the moving hose in the heating system long enough for vulcanization.
Ah, but what if we had a system of pulley wheels at two ends and at point through a shorter heating system? Now the hose could be passed back and forth several times through the heating system. Here is where my grandfather enters the picture.
He was involved in the patented invention and improvement of the most efficient system for curing “elasticized polymer” or “rubber” in a continuous moving production line. A bed of glass beads, as small as fine sand, but smooth, is both heated and suspended in air by forces hot air from below. It looks like a bubbling liquid, and the hose dips down in and passes through the liquid-like glass bead bath. The roller or pulley system is adjustable, to maintain the right tension or slack on the moving hose, preventing distortion.
The U.S. Patent Office has the drawing in PDF format, part of the pre-digital application archive. Google offers both the drawing and the text for the patent. Justia Patents offers the last improvement credited to my grandfather in 1979:
This invention constitutes an improvement upon the existing practice of manufacturing reinforced automotive heater hose and the like in a continuous operation which comprises continuously extruding an elastomeric tube, continuously applying to the outer surface of the tube an appropriate reinforcing layer of textile yarns or the like, continuously extruding over the reinforcing layer an elastomeric covering layer, and continuously curing the elastomeric components in an elongated chamber containing heat exchange elements the improvement residing in the provision of a method and means for elongating within certain limits the uncured or partially cured hose during the curing process whereby reduction of pressure and temperature within the extruding units and other advantages in production of reinforced automotive heater hose and the like may be realized.
As I and my oldest sister, who worked several summers at the plant, recall, there were three of these lines, so three different types of hose could be produced at once. There were workers posted near the initial mixing station, to ensure the extruder was properly fed, and near the reinforcing material bobbin systems to ensure they were feeding correctly and reloaded as needed. Towards the end, hose was cut at specified lengths, and could be finished with various fittings. Each lot had a small sample cut for quality control testing by the in house lab.
How do you ensure the product is being produced within specifications? Well, that takes some measurement devices, and a quick search shows my grandfather, around 80 years old, inventing and patenting two such tools. This exemplifies the man, who was still going to work in the R&D department of the plant. It was a family joke that “work will be the death of Daddy.” My uncles joked “oh, the shame, I’ll retire before him!” He taught his children and grandchildren that if you put in the time to weed your garden, consistently, it would eventually be easy. As soon at the Farmers’ Almanac said it was safe, he was putting into his garden the young plants he had started in the basement under fluorescent grow lamps. His hands and mind were always turning to sustaining or improving something.
Grandpa Galloway spent most of his working life in the same Ohio town, yet his expertise made him part of the company team flying to Europe and Asia when foreign companies inquired about licensing the continuous manufacture of reinforced hose process. I’m not sure of the outcome of those trips, although I recall Grandpa’s comment that the Chinese would likely just steal the process. That was surely a safe assessment, one which no Congress or president has effectively addressed until, perhaps, President Trump.