The present invention relates to a holder for an interchangeable knife blade, commonly referred to as a hobby knife, or utility knife. More specifically, the holder is of the type which has a blade-holding chuck with a longitudinal slot in one end for receiving a flat blade and with a threaded portion at the other end for threading into a handle. The slotted end of the chuck has a cam surface which flares outwardly toward the slotted end. A tubular ferrule is slidably mounted on the chuck between the handle and the cam surface. As the chuck is threaded into the handle, the ferrule is forced onto the cam surface, thereby closing the slot and clamping the blade which is located in the slot. Currently, blade holders of this type are made out of metal, particularly aluminum.
The present day hobby knives or utility knives as described above are extremely popular due to the fact that they are easy to use and are extremely versatile, so that they can be used for a wide range of applications. However, there are many problems associated with these knives. During use of the knife, any torque which is applied to the blade tends to unscrew the chuck, so that the blade becomes loose in the chuck. In order to prevent loosening of the blade, the chuck is screwed tighter into the handle and the ferrule tends to dig into the chuck. Eventually, the ferrule forges down the cam portion of the chuck, so that the ferrule can no longer be tightened. However, very often the ferrule splits before the chuck is completely forged down. These and other difficulties experienced with the prior art devices have been obviated by the present invention.
It is, therefore, an outstanding object of the invention to provide a blade holder which clamps a flat blade securely, so that it does not become loose during use.
Another object of the invention is the provision of a blade holder having a ferrule which will not split even after extensive use.
A further object of the present invention is the provision of a blade holder having a ferrule which will not dig into the chuck after an extended period of use.
It is another object of the instant invention to provide a blade holder in which the ferrule is made of a material which is elastic and yet is stiff enough to exert a high clamping pressure on the chuck.
A still further object of the invention is the provision of blade holder having means to prevent the ferrule from going beyond the major diameter of the cam portion of the chuck.
With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.