Julian Yochum remembers the moment he had the vision. He was walking down a Washington street, dreaming about a fat, juicy hamburger for dinner.

What would happen, he thought, if a giant burger swooped down on Washington and attempted to take over the city?

Yochum imagined ketchup dripping from the White House and a nervous president, on television, "stonewalling" it by denying the burger was roaring down Pennsylvania Avenue.

Yochum rushed home to his wife, Sarah, and their business partner, Ingrid Crepeau. A skit was written, a five-foot diameter hamburger (complete with a shower curtain for lettuce) was made and Patchwork Puppet Productions, Inc., added another puppet to its growing cast of characters.

Not many people would connect a giant hamburger with a puppet show. But, then, not many people understand puppets as the three Patchwork partners do.

"The world 'puppet' is one of those words that means so many different things to so many different people," Crepeau explained.

To some people, it means old socks with button sewn on for eyes; to others, marionettes like Pinocchio, and to a more modern audience, the Sesame Street Muppets. (The Patchwork partners find that people are always calling their puppets "muppets." For the record: Muppets is a trade name, not a type of puppet.)

Most people, however, seem to insist that puppets, whatever their form, are only for children. Nothing, says the Patchwork trio, could be further from the truth. They have produced several adult puppet shows, including political satires. Some other American puppeteers, they add, do only adult shows - and many European countries, puppet shows are a legitimate, and popular, form of adult entertainment.

The Patchwork company prefers, however, to put most of their energy into children's productions. Since forming the company in 1974, the Yochums and Crepeau have produced two successful shows for children, "Sassafras" and Patchwork" (which just finished a ten-show run at Ford's Theater). They also have held puppet workshops at area elementary schools and have done television spots for the Bicentennial Administration, the Department of Agriculture and the Maryland Center for Public Broadcasting, as well as films for Enycylopedia Britannica.

Last year, the company won three regional Emmy Awards for its Saturday afternoon children's television show, "Sneakers." The series follows the adventures of Dynamite Scott (Air Ace) as he pursues his phantom archvillain, Dr. Knuckles.

The Patchwork company works out of the Yochums' small house in Chevy Chase, Md. Inside, the puppets seem to have free run of the place. There are "Sneaker" memorabilia everywhere: Sneaker plant holders, Sneaker posters, Sneaker pillows. Seated in an office behind a giant telephone sits Patchwork's own giant bureaucrat, Peter Principle. Upstairs, in a room that would gladden the heart of any child, many other puppets "rest," waiting only for a tap from the Yochums or Crepeau to bring them to life.

"I feel a little bit like we're running a Ma and Pa grocery store where you live over the store," says Sarah Yochum.

It wasn't always like this for the Yochums. Julian once was a computer programmer for the government; Sarah was a teacher and actress. They met while both were students at Northwestern University in Illinois, long before puppetry crossed their minds.

When they came to Washington, Sarah joined Allen Stevens and Company at the Smithsonian Resident Puppet Theatre, where she met Crepeau, who had been working with puppets for almost 20 years. (Crepeau made up her mind at age 12 to become a puppeteer.)

Julian soon found he was working evenings with Sarah at the theater - enjoying it more than his daytime computer job. When the three of them finally decided to start their own puppet company, it was a big gamble. "There are a lot of people making puppets, but there aren't a lot of people making a living in puppetry," Julian said.

What they really do is work with an art form as old as the theatrer itself. They have built up a supporting cast of 80 puppets - a kind of repertory company they can call on again and again.

Some puppets play a variety of roles. Peter Principle (the bureaucrat), for example, becomes the governor in th Dynamite Scott series and, later former President Gerald R. Ford in a political satire.

This repertory approach gives patchwork its distinctive style, along with the fact that the company relies almost entirely on its own story ideas.

"We have very strong feelings about not doing fairy tales," says Sarah.

"You don't write something for puppets that people can do better," adds Julian.

"That usually means a lot of visual gags . . ."

"Andmusic."

The Yochums write the sketches. Crepeau designs and constructs the puppets and props. All three work as puppeteers for performances.

Most Patchwork puppets are hand puppets - that is, the puppeteer controls them by slipping his or her hads directly in the puppet. (The Muppets also are hand puppets.)

"Puppets," explains Crepeau, "are grouped according to how they are controlled. There are string puppets (controlled from above by strings), rod puppets (controlled from below by rods), shadow puppets (made by throwing shadow images into a wall) and hand puppets."

It usually takes about 40 hours to make a hand puppet, Crepeau said, and she makes them strong enough to last five years, which means triple stitching on all the seams.

Designing a puppet is an exacting art. Many European puppeteers hire full-time engineers to help them. But Crepeau has been tempted to call in an engineer only once - when she was trying to figure out how to balance 40 pounds of dragon costume, including a 17-pound fire extinguisher (for the dragon's fire), on Julian's head. It also had to be something he could slip into in a matter of seconds.

It took a lot of work, but Crepeau finally succeeded with the aid of a hard-hat and the seat belt straps from her truck.

Crepeau has gotten her props from stranger places. She scours local thrift shops regularly and sometimes examines trash cans in her Washington neighborhood.

"A Congressman from Florida didn't get re-elected one year and I got such a haul," she says. "He must have had a grandmother who threw away about ten hats."

Those hats now hang in the Yochums' upstairs storage room. They'll find their way onto a puppet soon.

Maybe even a giant hamburger.