# How the Modern Waterbed Works > A 1971 patent describing a liquid-filled, heated furniture support designed to cradle human bodies without letting them touch the bottom of the container. - **Patent:** US 3585356 - **Original title:** Liquid support for human bodies - **Owner:** Innerspace Environments Inc - **Granted:** 1971 - **Status:** Public domain (expired) - **Times cited:** 70 - **Field:** consumer_electronics, mechanical ## What it does The patent describes a furniture support, specifically a sofa or bed, that uses a flexible, inelastic bladder filled with liquid to support multiple people. The system requires a rigid frame to hold the liquid and prevent the sides of the bladder from bulging outward. A key feature is that the bladder is filled completely, leaving no air inside, which allows the surface to conform to the body's shape while ensuring the person remains suspended by the liquid. It also includes an optional heating element to keep the liquid at a comfortable temperature and solid particles like styrofoam to stop the liquid from sloshing around when someone moves. ## What it does NOT cover - Does not cover air mattresses or inflatable supports that rely on gas rather than liquid. - Does not cover waterbeds that allow the user to touch the bottom surface (the patent requires the body to be supported entirely by the liquid). - Does not cover flexible bladders that are not contained within a rigid lateral framework. - Does not cover liquid supports that contain significant amounts of air within the bladder. ## The clever bit The invention solves the 'bottoming out' problem by using a rigid frame to force the liquid to support the body's weight, and it uses internal particles to dampen the wave motion that would otherwise make a multi-person bed unstable. ## Real-world examples 1. Traditional hardside waterbeds 2. Heated liquid-filled furniture 3. Medical fluid-support mattresses for pressure sore prevention ## Why it matters This patent is a foundational document for the commercial waterbed industry, which saw a massive surge in popularity during the 1970s and 1980s. By defining the specific requirements for a stable, heated, and comfortable liquid-support system, it helped transition the waterbed from a niche DIY experiment into a standardized piece of home furniture. ## Frequently asked questions ### What does How the Modern Waterbed Works cover? A 1971 patent describing a liquid-filled, heated furniture support designed to cradle human bodies without letting them touch the bottom of the container. ### Who owns patent US 3585356? Innerspace Environments Inc owns this patent, granted in 1971. ### When does this patent expire? This patent has expired and is now in the public domain — anyone can use the invention freely. ### What is patent US 3585356 cited by? This patent has been cited by 70 later patents that build on its ideas. ### What problem does this patent solve? This patent is a foundational document for the commercial waterbed industry, which saw a massive surge in popularity during the 1970s and 1980s. By defining the specific requirements for a stable, heated, and comfortable liquid-support system, it helped transition the waterbed from a niche DIY experiment into a standardized piece of home furniture. ### What does this patent NOT cover? Does not cover air mattresses or inflatable supports that rely on gas rather than liquid. **Full plain-English explainer:** https://patentbrief.org/patent/us/3585356/waterbed-liquid-support **Original patent:** https://patents.google.com/patent/US3585356 --- _Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._ ## Related patents Semantically similar inventions in the PatentBrief corpus: - [How the First Modern Water Slide Was Designed](https://patentbrief.org/patent/us/2982547/slip-n-slide-carrier) — A 1960 patent for a water-based amusement structure featuring a sloped surface and a water supply system to create a sliding experience. - [How a Coffee Maker Uses a Floating Valve to Heat Water](https://patentbrief.org/patent/us/3693535/mr-coffee-drip-coffee-maker) — A 1971 invention for a coffee maker that uses a floating valve to control water flow, ensuring water is heated efficiently without needing a massive, power-hungry heating element. - [How Cup Noodles Are Designed to Cook Perfectly](https://patentbrief.org/patent/us/3997676/cup-noodles-instant-ramen-ando) — A 1976 patent describing the specific shape, density, and placement of dehydrated noodles inside a cup to ensure they cook evenly and quickly when hot water is added. - [How Disposable Diapers Keep Skin Dry Using Porous Plastic Sheets](https://patentbrief.org/patent/us/3489148/disposable-diaper-topsheet) — A 1970 patent by Procter and Gamble describing a specialized plastic top layer for diapers that allows liquid to pass through while keeping the baby's skin feeling dry. - [How Soft Contact Lenses Were Invented Using Hydrogels](https://patentbrief.org/patent/us/3220960/soft-contact-lens-hydrogel) — This patent describes the chemical recipe for soft, water-absorbing plastic materials that form the basis of modern soft contact lenses.