Powered hand-held metal cutter

A power driven portable sheet metal cutter includes a head with two blades that mounts to a hand-held electric or pneumatic rotating power unit. The fixed blade has a primary shearing surface that has a convex or radiused cutting edge, a convex or radiused bevel, and a convex or radiused body feature. There is also a clearance radius and a nose radius so that the cutter can cut a wide variety of shapes and configurations of corrugated building panels. A head with a right hand set of blades predominately cuts curves to the right, and a head with a left hand set predominately cuts curves to the left.

FIELD OF THE INVENTION

The present invention relates to powered hand held shears for cutting sheet metal and corrugated building panels used in construction.

BACKGROUND OF THE INVENTION

The construction industry uses sheet metal in various ways. For example, sheet metal is used in ductwork, and as the exterior panels and roofing material of commercial buildings. As the speed of building increased, faster tools for quickly cutting the material were needed. There are several ways of cutting metal corrugated panels: with hand snips, power nibblers and power shears. On massive construction sites professionals use stationary industrial machines with blades designed to cut unique profiles.

Using circular saws is undesirable because they leave a cut edge without any treatments such as paint, zinc coating, or galvanizing. Shears, on the other hand, have a natural “edge sealing” effect, smearing the coating or treatment over the freshly cut edge. Shearing may be done with muscle power, as with tin-snips, or by an electrically or pneumatically powered tool that works similarly, but has greater power and speed.

Examples of portable powered shears to cut sheet metal are found in U.S. Pat. No. 2,635,335 to James, U.S. Pat. No. 4,173,069 to Sidenstick et al., U.S. Pat. No. 4,682,416 to Stolfa, and U.S. Pat. No. 7,093,365 to Peterson. U.S. Pat. No. 4,173,069 was assigned to Kett Tool Company, the assignee of the current application.

U.S. Pat. No. 4,173,069 discloses a single moving blade, having two shear surfaces, working in cooperation with a fixed blade on either side, each of which has one shearing surface. U.S. Pat. Nos. 2,635,335, 4,682,416, and 7,093,365, on the other hand, use only one movable blade and one fixed blade.

Each of these devices can cut materials of various thicknesses with some level of success. Cutting flat sheet metal of low thickness (higher gauge numbers) is the easiest. However, the building industry continues to expand their use of metal corrugated panels. Corrugated panels are now more complex than early versions that had only rolling corrugations similar to the pattern found in common corrugated cardboard. Current corrugations are engineered in a variety of depths, shapes, and patterns. The pitch (spacing) between corrugations may be small or large. When viewed in cross-section, the corrugations may be trapezoidal, with sharp angles and deep valleys. Testing of portable shearing devices on the market reveals that they cannot cut all of the corrugated panels available. Therefore, a need exists for an improved tool, having the geometry and materials necessary to smoothly cut a greater variety of corrugated panels. Such a tool should be easy to use to make curved cuts, and ergonomically comfortable. Preferably the tool would bend the cut metal in a way that does not obstruct the tool, the user's hands, or the user's view of the cut.

SUMMARY OF THE INVENTION

To achieve the foregoing objectives, and in accordance with the purposes of the invention as embodied and broadly described, herein, a power driven portable head for a sheet metal cutter has a housing and a movable  blade pivotally coupled to a fixed blade. The fixed blade has a leg portion attached to the housing, and on the other end of the leg portion is a foot extending laterally away from the plane of the leg portion.

A clearance radius on the foot adjacent the leg portion provides clearance for the blade to maneuver through the material. A primary shearing surface is on the foot adjacent to the clearance radius and displaced laterally away from the plane of the leg portion, on the side opposite the movable blade. The foot has a back surface separated from the primary shearing surface by a thickness. On the back surface is a convex body feature that continues to a convex bevel that intersects the primary shearing surface at a convex edge.

The movable blade is mounted to oscillate about a pivot axis during operation of the head. One end of the movable blade is forked, and arranged to be driven by an eccentric on a portable rotational drive applied to the head. The driving of the fork oscillates the movable blade about the pivot axis. The other end of the movable blade is shaped to pass beneath the foot of the leg portion and to terminate in a secondary shearing surface that co-operates with the primary shearing surface. Both the primary and secondary shearing surfaces are in a plane parallel to the plane of the leg portion, but spaced from it.

DETAILED DESCRIPTION

With reference toFIG. 1, a portable shear10comprises a power unit12and a head14. The power unit may be electric, pneumatic, or driven by another energy source. The head14has a movable blade16and a fixed  blade18assembled in a housing20with three fasteners22a, b, c. A pivot axis24passes through the movable blade and the fixed blade so that the movable blade can oscillate around the pivot axis relative to the fixed blade. A fixed spacer26is on the side of the movable blade16opposite from the fixed blade18. The power unit, housing, pivot axis and method of driving the movable blade are described in other documents, for example, U.S. Pat. No. 4,173,069 for a power shear head issued to Sidenstick and assigned to the same assignee as the current application. U.S. Pat. No. 4,173,069 is hereby incorporated by reference.

Referring toFIGS. 1-4, the housing has a longitudinal slot28. On one side is a first seat30ending in a first shoulder32, and on the opposite side is a second seat34ending in a second shoulder36. The housing can accept both right hand and left hand versions of the movable and fixed blades, but the right hand and left hand versions must be installed as a set. The fixed spacer26can be used with either the right hand set38or the left hand set (not shown, as it would simply be a mirror image of38).

A housing having a right hand set38makes a right hand embodiment, as described and illustrated inFIGS. 1-13. The term right-hand refers to a person standing behind and over the portable shear looking down at the view ofFIG. 3and seeing that the fixed blade and the moving blade are on the right-side of the power shear. For the right-hand embodiment the fixed blade18mates against the first shoulder32and the first seat30and a fixed spacer26locates on the second seat34against the second shoulder36with the moving blade16between the two. As illustrated inFIGS. 9-13, a right-handed embodiment is convenient for a right-handed person to use while  standing to the left of the work material that they need to cut. A right-hand embodiment will easily cut curves to the right as shown inFIG. 13. If the left handed blades were installed (not shown), the fixed blade would be installed where the spacer is shown inFIG. 3, and the spacer would be installed where the fixed blade is currently shown. The blades would be to the left as viewed from the top and the tool would cut curves to the left.

First the details of the components used for assembly will be further described. After that, details of the individual blades that are relevant for cutting performance will be described.

The exploded viewFIG. 4shows details of the assembly. The fixed blade18has an outer face40(FIG. 5), an inner face42, a first hole44, and a second hole46. The first hole is larger than the second hole. The fixed spacer26also has an outer face48, an inner face50(FIG. 3), a first hole52, and a second hole53. The first hole is again larger than the second hole. The movable blade16has a blade face56(FIG. 8C), a spacer face58, and a pivot hole60that is larger in diameter than the first holes44,52. A bearing sleeve54has a major diameter55, a minor diameter57a,57b, an inner diameter59, and a length62from an end66to an end68. The diameters55,57a,57bhave a sliding fit with the first holes and the pivot hole so that the moving blade may operate precisely with the fixed blade but be free to oscillate around the pivot axis24. The bolt22apasses through the housing20, fixed spacer26, bearing sleeve54, movable blade16, and fixed blade18and screws into a threaded insert (not shown) in the opposite side of the housing. The bolt22bpasses through the housing20, fixed spacer26, a spacer bushing70, and the fixed blade18, and screws into a threaded insert (not shown) in the opposite side of  the housing20. The spacer bushing70has an outside diameter72greater than the inside diameter of the second holes46,53, so the spacer bushing70does not enter the second holes46,53. The bolt22c(FIG. 1) passes the through the housing20and screws into a threaded insert (not shown) in the opposite side of the housing20. The bolt22cdoes not pass through the blades16,18or fixed spacer26. The length62of the bearing sleeve54is less than the combined thicknesses of the blades16,18, and the fixed spacer26. The length of the major diameter55is greater than the thickness of the movable blade16therefore the bearing sleeve54is squeezed by the inner face42and the inner face50. This squeezing prevents the bearing sleeve54from rotating when the movable blade16oscillates.

The features of the blades16and18that make the cutting process convenient and durable will now be described and are best viewed inFIGS. 3-8Cwith occasional reference to other figures. Note that one of ordinary skill in the art may often use the term “radiused” as synonymous with “convex”, as in a “radiused cutting edge” or “convexed cutting edge”. However, that is not quite correct. Convex edges or surfaces may be more complex than a single radius, or be of a shape other than a radius. In this description and the claims that follow, the term “convex” is used for the broad scope of the invention. When being more specific for certain embodiments, the term “radius” will be used.

The fixed blade18has a leg74and a foot76at an angle α to the leg74. The movable blade16has a leg78and a foot80at an angle β to the leg78. The angles α and β are the same, and it has been found by experimentation that 45 (range 40-50) degrees is a preferred value. It is this angle α, β that places the feet of the blades16and18to the right of the legs74,78, when viewed from the top as inFIG. 3. The fixed blade18and movable blade16contact along a straight (when viewed from the top) contact plane82that is parallel to a center plane84of the portable shear10, but offset from it. The contact plane82is offset from inner face42and blade face56by an offset86. The offset86allows the movable leg78to move up and down relative to the fixed blade18, without having to bend the cut metal88(FIG. 9) as much as it would if the contact plane82was not offset.

The fixed blade18has a primary shearing surface90with a nose radius92at one end, a clearance radius94at the other end, and a convex cutting edge96at the contact plane82. On the other side of the convex cutting edge96is a convex bevel98having a 3 (2.5-3.5 range) inch radius at an angle99to the primary shearing surface90. We have found that an angle99of 82 (80-85 range) degrees works well. The convex cutting edge96continues into an un-ground (as-cast or fabricated) convex body feature100on a back surface102of the foot. The convex cutting edge96and the convex body feature100are particularly visible inFIGS. 5 and 6respectively. It is the convex body feature100, provided in the casting104of the fixed blade18that makes the current invention so durable and able to cut thicker metals. Without this bulge of material, the convex bevel98would not have a uniform width and surface area to distribute the cutting forces from the convex cutting edge96into the foot76of the fixed blade18. In one embodiment (FIG. 7D) the convex body feature100is in the form of a cast material radius100′ at an angle152(FIG. 7B) located at a point150at a distance154and156from a reference point158(FIGS. 7B & 7D). Experimentation has shown that100′ of approximate 3 inches radius at an angle152of approximately 42 degrees, at distance154approximately equal to 2.76 inches and distance156approximately equal to 1.75 inches strengthens the convex cutting edge96, thus allowing metals of greater thickness (lower gauge number) to be cut.

Besides having the strength to cut thicker metals than portable shearing equipment currently sold, the current invention also has the necessary clearance radius94to allow the remnant material to be pushed down by the moving blade16, while the portable shear10is maneuvered as needed to follow corrugations or to make curved cuts. Experimentation has found that a clearance radius94of 0.250 inches (0.188-0.250 range) ground at an angle95equal to 56.5 (45-60 range) degrees, works, and does not create an excessively weakened condition, when used in combination with radius edges105,106(FIG. 7A). The radius edges105,106maintain enough thickness to distribute the stresses transmitted from the foot76to the leg74. It has been found that a 0.025 (0.016-0.032 range) inch radius holds up well without significantly impacting the clearance provided by the clearance radius94.

The nose radius92contributes to cutting a greater range of corrugations, and to cutting curves more easily through those corrugations. A 9/64th(⅛- 3/16 range) inch nose radius92allows the blades16,18to travel inside the radii and pitches of corrugate material with precision, without becoming trapped at the changes of the slope of material. For the fixed blade18, this takes place underneath the material (hidden lines,FIG. 9) and not in view of the operator.

The movable blade16has a secondary shearing surface108with a nose radius110at one end and an extended heel112at the other. The secondary shearing surface ends at a convex cutting edge114having a3inch  radius at the contact plane82. On the other side of the convex cutting edge114is a ground convex bevel116at an angle117to the secondary shearing surface108. In one embodiment (FIG. 8D) the ground convex bevel116is a radius116′ located at a point160that is a distance164and166from a reference point168(FIGS. 8A & 8D). Experimentation has shown that using radius116′ approximately equal to 3 inches at an angle117approximately equal to 82 (80-85 range) degrees works well at distance154approximately equaling 2.48 inches and156approximately equaling 0.54 inches. The approximate values given for the size of100′ and116′ and the distances154,156,164,166and the angles117and152work in cooperation in one embodiment of right hand set38.

The nose radius110is 9/64th(⅛- 3/16 range) inch and works in the same way as the nose radius92does, but it is visible to the operator. The extended heel112provides an extension of the secondary shearing surface108for easy assembly and for blade-to-blade contact during operation to prevent the movable blade16from trying to run on the wrong side of contact plane82. One of ordinary skill in the art may consider it normal practice for a cutting tool to maintain contact of the primary shearing surface90with the secondary shearing surface108, however the improved clearance radius94on the fixed blade18causes engagement to be lost at the end of the movable blade stroke. The solution to this problem is the extended heel112that maintains contact but does not interfere with the clearance radius94.

In keeping with the emphasis of this invention, which is to successfully cut a range of tough corrugated metal panels, the length has been made sufficient to cut up to 4 inch deep corrugated materials. This length is  understood as a distance118(FIG. 1) from the pivot axis24to the intersection of the convex cutting edge96with the convex cutting edge114. Related to this, specifically on the movable blade16, is the length from the pivot axis24to the 45 degree angle that demarcates the feet76,80. Also related, on the fixed blade, is the length from the pivot axis24to the center of the clearance radius94. It was important to make distance118long enough to keep the cut-zone visibly in front of the housing20so the cut zone can be seen by the operator, and also long enough so that when the blade18is being buried in the valleys of the corrugations, there is still enough reach to keep the shearing surfaces90,108in un-cut metal.

While the foregoing description has set forth preferred embodiments of the present invention in particular detail, it must be understood that numerous modifications, substitutions and changes can be undertaken without departing from the true spirit and scope of the present invention as defined by the ensuing claims. The invention is therefore not limited to specific embodiments as described but is only limited as defined by the following claims.