Patent Application
20110225831
Not applicable.
The subject matter of the present application is in the field of handheld utility knives of the type used for cutting drywall.
Utility knives with short, thin blades that are disposable or replaceable are well known, and can be found in just about any handyman's toolbox or workbench. The blades are usually pointed and triangular, with a single straight edge, and often can be advanced from or retracted into the handle to adjust the amount of blade available and the depth of cut. The blades are of a thin and uniform thickness, unlike standard knife blades, so that they can be manufactured and replaced inexpensively. Utility knife blades are known for their thin profile and their corresponding sharpness, and are often used for cutting drywall. They require a pulling motion to cut (a “draw cut”).
It is also known to use rotary cutting disks for devices such as pizza and dough cutters. These are relatively thick and dull, are not precision cutting devices, and would not be suitable for use as utility knives. The cutting disks are fully exposed at the end of the handle, and have a fixed pivot connection to the handle so that the amount of blade available and the depth of cut cannot be varied.
I have invented a utility knife with a rotary blade, especially useful for cutting drywall and other materials requiring a thin, sharp blade. The blade is circular and connected to a handle with a fixed pivot connection to roll freely relative to the handle. The upper part of the blade is shrouded by a portion of the handle to protect the user's hand. Depth of cut is adjusted with a spacer associated with the blade that can be moved toward and away from a work-piece between the edge of the blade and its center of rotation, generally parallel to the blade, and then selectively secured in place at the desired distance. The spacer has a roller tip or surface that engages and rolls or slides smoothly over the face of the work-piece as the rotary blade makes a cut in the work-piece. “Roller” is used herein to include both rolling and sliding structures. The spacer may be external to or integrated with the handle.
The rotary blade can be permanent, or it can be replaceable, for example mounted to the handle with a removable screw or bolt that also adjustably secures the spacer arm.
In a further form, the rotary blade has a relatively thick body with a discontinuous interior body profile and a continuous circumferential edge. The thicker interior body has a circumference defining a series of scallops or edge bodies interrupted by points that help the blade “walk” or gain traction as it is pushed or pulled through a thick workpiece.
The handle optionally includes a circular storage compartment for storing spare blades. In the preferred form the storage compartment is located at the end of the handle opposite the rotary cutting end to define an enlarged “knob” or pommel that helps maintain a secure grip when making draw cuts. In yet a further preferred form, the forward portion of the handle that shrouds the upper part of the rotary blade defines an enlarged knob or guard for leverage and protection when making push cuts. The rotary blade of the knife allows both push and draw cuts to be made.
In yet a further form, the knife includes a device for measuring distance along the surface of the workpiece. In one form the measuring device is a tape measure device integrated with and retractable into the handle.
In yet a further form, the knife includes a device for aligning or guiding the knife along a cutting line. In one form, a laser type light is projected from the knife onto the work surface in front of the knife, in line with the rotary blade.
These and other features and advantages will become apparent from the detailed description below, in light of the accompanying drawings.
Referring first to
Blade 12 is rotatably mounted on a “forward” end 14a of a handle 14. The main gripping portion of the handle between forward end 14a and rear end 14b preferably has a shape that makes it comfortable and secure in a user's hand. Rear end 14b is preferably enlarged, for example with a rounded wheel or pommel as illustrated, to improve grip when making a draw cut. Illustrated blade 12 is made from an appropriate metal such as steel, and illustrated handle 14 is made from an appropriate polymer or “plastic” material. Both blade 12 and handle 14 can vary in terms of the materials used, and are not limited to metal and plastic materials.
Blade 12 is mounted to rotate on an axis 16 generally perpendicular to the handle 14 at the forward end 14a of the handle. Pivot axis 16 can take various forms, in the illustrated embodiment including a removable shaft in the form of a thumbscrew 18 with a threaded shaft 18a securing the shaft in threaded holes or sockets 20 aligned with each other in the forward end of the handle, with a space between them for the blade to rotate. The illustrated shaft has a smooth portion 18b aligned with and engaged by the blade's hub 12a when the threaded portion(s) 18a is/are secured in the sockets 20 in forward end 14a of the knife 10 (shown in
An upper part of blade 12 is shrouded in a hollow portion of forward end 14a of the handle, for example a generally hemispherical slot 14c molded or machined into forward end 14a with sufficient clearance to cover an upper portion (preferably the upper half) of blade 12 above axis 16 and to allow blade 12 to rotate. A person using knife 10 can accordingly place a hand above blade 12 when making a cut, for example if more control is desired; or, if a person's hand slips forwardly from a different part of the handle 14, the hand is protected from being cut on the upper portion of the blade 12. In the preferred form, as illustrated, the blade-shrouding forward end 14a swells upwardly from the main handle for added control and safety when making push cuts.
The relatively thin continuous edge 32 will make an initial precise cut into the workpiece 100, while the thicker “points” 36 of central body 30 will help force the cut workpiece material apart. Additionally, the points 36 will provide an interrupted frictional purchase on the workpiece material against the sides of the cut to help rotate blade 12 as the blade is pushed or pulled through the workpiece material, creating a more efficient cutting action.
Illustrated knife 10 includes a vertically adjustable spacer 40 associated with blade 12, adjustable toward and away from the exposed workpiece-contacting edge of the blade (and thus toward and away from the surface of workpiece 100) to limit the depth of the cut made with blade 12. In the illustrated example of
It will be understood that while a linearly adjustable spacer 40 is illustrated, other spacer mechanisms are possible without being limited to a linearly adjustable elongated slotted member. By way of non-limiting example, a cam-type rotating adjustment for a non-linear spacer is believed to be possible. It will also be understood that various mechanisms may be used to adjust the spacer up and down and to selectively secure it in place, including but not limited to sliding friction mechanisms and click adjustment mechanisms. Spacer 40 may be located on the outside of handle 14, as illustrated, or partially retractable into a receptacle or chamber in handle 14.
In operation, spacer 40 is set at the desired position with thumbscrew 18 (
It will finally be understood that the disclosed embodiments are representative of presently preferred forms of the invention, but are intended to be explanatory rather than limiting of the invention. Reasonable variations and modifications of the invention as disclosed in the foregoing written specification and drawings are possible without departing from the scope of the invention as defined in the claims. It should further be understood that the use of the term “invention” in this written specification is not to be construed as a limiting term as to number or scope, but as a descriptive term which has been used conveniently to describe advances in technology for many years. The scope of the invention is accordingly defined by the following claims.
