Document OzpKqLBdjxRN4zKaBO5vXQGBL

United States Patent. 4,240,530 Page 3 of 6 One method of suppressing the brake noises is based on the principle that two bodies of different mass possess different characteristic frequencies, such that if the two bodies are bonded together and their 'masses are suitably matched, their vibration frequencies interfere with and impede one another m such a way as to dampen vibration In accordance with this principle, a brake pad has been manufactured where a metallic earner plate has a composition friction matenal on one side and a plastic or aluminum back plate which is bonded using a resin adhesive on the other side. Although good heat insulation can be achieved with the plastic back plate, the vibration damping is not effective It is also known to manufacture brake pads based on the pnnciple of damping or absorbing vibration by interposing an elastic damping element between one surface which is vibrating and a second surface which is to be isolated from the vibration. According to this pnnciple, a brake pad has been manufactured where the earner plate is subdivided into two metal plates with a layer of an elastic, heat insulating matenal, such as rubber, interposed between the two plates A problem with this type of pad is that it is extremely expensive to manufacture, and there is a significant reduction in the mechanical strength of the pad A typical brake pad has a earner plate which is approximately five millimeters thick. Consequently, even after the friction matenal has worn off the earner plate, a portion of the earner plate is retained m the brake housing during braking In other words, a portion of the brake housing supports the earner plate. However, in the case of a brake pad having a multi-layered plate of the type desenbed above, also called a sandwiched lining, it is not desirable to increase the thickness of the earner plate This is because, if the earner plate thickness is increased, the friction lining thickness must be decreased which results m shortening the working life of the pad Consequently, the multi-part earner plate must have a total thickness of approximately five mihmeters Each part of the earner plate must be made two to three millimeters thick However, after the friction lining has worn off, one part of the earner plate is completely outside of the brake housmg dunng braking Only the second part is retained m the brake ^fciousmg. As a result, the elastic bonding layer between the two parts is subjected to the high shear stress ^^dunng braking The layer cannot withstand the stress and one part of the earner plate is displaced relative to the other, i e , the part of the earner plate which engages the disc and is out of the brake housmg will be displaced relative to the other part Under this condition, the part outside of the housmg cannot retract into the housing after braking and the brake can no longer be released. In an extreme case, the protruding part of the earner plate can lock the brake In another brake pad having a multi-part earner plate, a relatively thm self-adhesive, plastic film has been used in place of rubber for the damping-elastic interlayer of the sandwich plate This film is incapable of satisfactonly absorbing the above-desenbed shear stresses and possesses the additional following disadvantages. If the parts of the carrier plate with the plastic film are placed m a mold in the manner initially desenbed in order to simultaneously press the friction lining and bond the lining to the sandwich plate, the film softens and flows from between the parts of the earner plate. This is because the plastic film is unable to withstand the temperature and pressure required to shape and cure the friction lining. It is possible to have friction lining first pressed onto one part of the carrier plate and the parts of the earner plate subsequently bonded in a second die However, this requires an additional working step which adds to the cost of the pad Further, this requires an expensive die which accurately surrounds the parts of the earner plate so that the metal plates are not mutually displaced when the film softens. Customanly, the finished pressed brake pads are ground to exact dimensions on their side faces and are then lacquered at an elevated temperature, in this procedure there is a nsk of the film softening and the metal plates bemg mutually displaced In order to manufacture a brake pad which has a multi-part earner plate in a single working step and ^fcvhich is capable of absorbing the shear forces generated dunng braking, a multi-part earner plate has ^^been made with a plurality of matching through bores and a layer of rubber interposed between the parts of the earner plate When the friction lining is pressed, the earner plate bores are filled with lining composition which bonds the sandwiched layers of the earner plate to one another in a method similar to httn //oatft usnto eov/netacgi/noh-Parser^Sectl=PT02&Sect2=HITOFF&u:=/netahtml/sea . 10/18/2003