Calvin Klein believes in breaking rules.

"They told me that when you find a successful shape for a man's jacket, you should never change it," he says. "You have to become known for it. You should stick to it and keep doing it over and over again."

So Klein has chucked the idea of replacement dressing that is popular in menswear. And as he did with his whoppingly successful collection for women, he has chosen to introduce some new shapes.

In his collection for next fall, which he showed to buyers in his New York showroom yesterday, he introduced the loose, padded-shoulder jacket.One representative specimen is a navy cashmere unlined jacket with broad shoulders, worn with a brown twill shirt, pleated trousers and a skinny tie.

From his designs for women, Klein has borrowed the success formula of constantly injecting fresh colors, fabrics and shapes. Moreover, softness and comfort are a major theme in his women's line -- and he intends to transfer the concept to menswear. Why, he asks, shouldn't jackets be as comfortable as sweaters?

"It may be radical for menswear," he admits, "but I don't think it is unusual at all. It feels loose and comfortable, so why shouldn't men like it?"

Klein has good reason to be both innovative and confident. Last year, his first in the menswear business, his retail volume topped $35 million. The first season he sold 5,000 cashmere T-shirts at $90 retail, 48,000 cotton T-shirts at $26, 30,000 cotton sport shirts and 22,000 pairs of corduroy pants.

The firm is predicting a volume of $100 million for the second year -- a figure which surprises even Klein. "That's an awful lot of clothes," he says, laughing.

"In the beginning, the buyers were afraid their customers wouldn't like the soft, unlined clothes," Klein says about his first menswear collection. But his unconstructed jackets, lacking the stiff shaping which men's jackets traditionally have, sold fairly well in the first collection; and stores liked it much better for spring.

Now it's a major theme in the new collection, along with the broad-shouldered look. By fall he'll be back doing more three-piece suits. "Last fall I emphasized two-piece suits. Now I like the vest again," Klein says. "And I suddenly like to wear a tie again."

The broad-shouldered look carries over into Klein's brightly colored foul-weather gear, which he often shows with narrow-legged, unpleated pants. Even his sweaters have an extended shoulder line.

For women who can't afford Klein's clothes for women, he provides patterns so that they can stitch up the styles themeselves. Vogue Patterns sold over 300,000 Klein items in this last year -- three times more than the patterns of any other American or European designers.

So it's no surprise that the firm is now considering Calvin Klein designer patterns for men.