Shear blade with positive camber and method to impart a positive camber to a shear blade

Abstract

Hydraulically actuated shears (18) comprising: a first jaw (26); a second jaw (28) configured to slide past the first jaw (26) in a shearing motion; and a first cutting plate (40) attached to one side of at least one of the first (26) and second jaws (28), wherein the first cutting plate (40) defines a shearing edge (76) and a shearing surface (78), the shearing surface (78) having a positive camber with respect to a plane perpendicular to the jaws (23), wherein at least one of the first (26) and second (28) jaws is actuated by a hydraulic cylinder (30); and wherein the first cutting plate (40) is inserted into a cutting plate recess (74) defined within at least one of the jaws (23);wherein the scissors (18) further comprise a spacer plate (61) which is arranged between the first cutting plate (40) and the cutting plate recess (74), wherein the spacer plate (61) is dimensioned such that it provides at least part of the positive camber.;

Description

Technical FieldThis disclosure relates generally to scissors, and more particularly to scissors with cutting tips having a positive camber.BackgroundScissors are often used to cut articles. Whether scissors for cutting paper or large hydraulic scissors for cutting metal or other materials, all operate according to similar principles. Two relatively flat surfaces move past each other and are close enough to slide against each other. The material to be cut is located between the two surfaces and gives way to shear, thereby cutting the material.While this system is well suited for cutting a variety of objects, problems may still arise. For example, simple paper scissors cannot always cut if the paper can move substantially parallel to the scissors and the two shearing surfaces move past the paper. The problem that the material rather than being cut slides along the shearing surface is not, however, limited to paper scissors, but occurs with all types of scissors. This may cause problems not only in paper scissors but also in large hydraulic scissors.For example, if large hydraulic scissors are used to cut articles such as metal, the scissors cannot cut when worn or improperly adjusted, or for a number of other reasons. In such cases, the metal may rather slide along the sides of the shear surfaces. This may cause a situation in which the metal that should be cut clamps the jaws of the scissors. Under certain circumstances, it may even become cold welded to the shearing surfaces on the shearing jaws. This can result in substantial delays while the operators of the hydraulic scissors must use heavy tools to remove the pad from the scissors jaws.Heavy-duty scissors, such as hydraulically actuated scissors, often use shear plates that are inserted into shear plate recesses. The shear plates are often removable from the shear jaws so that the shear plates (associated with the high wear parts) can be inverted, removed for maintenance or replaced when worn. Spacer plates can provide a desired positioning of the shear plate within the shear plate recess. Traditionally, the shear plates are deployed in a neutral position or, in other words, at an angle of 0 with respect to the opposite jaw. This can be referred to as a neutral camber. If the shear plates have a negative angle, sometimes referred to as a negative camber, they may even draw the workpiece to be sheared toward the jaws or cause other problems.An exemplary scissors is described in U.S. Pat. No. 6,926,217 B1. This patent describes a scissors jaw in which a transverse cutting blade located at one end or tip of the jaw is disposed at an acute angle between 1 and 30 degrees. While the transverse cutting blade may aid in the sharpening of material at the end or tip of the jaw, it does not eliminate the problems associated with the cutting surfaces on the sides of the jaw. The sides of the jaw are the locations where most of the cutting or shearing problems most often occur. As a result, the embodiment illustrated in this patent does not specifically address the problems described herein.In addition to these problems, considerable force may be required to cause the shearing of some materials. As a result, scissors are constructed very robust and operated by robust hydraulic systems. Moreover, scissors are often used for many cutting operations. As a result, the shear surfaces or the edges that help define the shear surfaces may become rounded or otherwise blunt.Accordingly, it would be desirable to provide a set of scissors having one, more, or all of the following characteristics: the material is cut more reliably rather than slipping along the shearing surfaces; the amount of force required to cut the material is reduced; and many cutting operations are permitted before any adjustments become necessary.DE 10 2009 059 940 A1 discloses a shear blade for cutting devices.DE 856 985 B teaches scissors for cutting panels and bars of metal, cardboard, plastic and other materials.The present invention is directed to overcoming one or more of the problems or disadvantages associated with the prior art.SummaryThe object of the present invention is achieved by a scissors according to claims 1 and 11. The dependent claims relate to preferred embodiments of the invention.In one aspect, the disclosure describes a hydraulically actuated scissors. The scissors comprises: a first jaw; a second jaw configured to slide past the first jaw in a shearing motion; and a first cutter plate attached to a side of at least one of the first and second jaws, the first cutter plate defining a shearing edge and a shearing surface, the shearing surface having a positive camber with respect to a plane perpendicular to the jaws, wherein at least one of the first and second jaws is actuated by a hydraulic cylinder.In another aspect, the disclosure describes a hydraulically actuated scissors. The scissors comprise: a first shearing means; a second shearing means configured to slide past the first shearing means in a shearing motion; and means for providing a cutting edge secured to a side of at least one of the first and second shearing means, the first shearing means defining a shearing edge and a shearing surface, the shearing surface having a positive camber with respect to a plane perpendicular to the jaws, at least one of the first and second jaws being actuated by a hydraulic cylinder.In yet another aspect, the disclosure describes scissors. The scissors comprise a first jaw having a shearing surface on the first side; a second jaw having a second shearing surface, the first and second jaws being configured to slide past each other, and the first and second shearing surfaces being almost but not completely parallel, the first shearing surface having a positive camber and the camber facing the second shearing surface.Brief Description of the DrawingsFIG. 1 is a perspective view of a machine equipped with a hydraulic shear in accordance with the disclosure. FIG. 2 is a perspective view of scissors in accordance with the disclosure. FIG. 3 is an exploded view of certain components of a scissors in accordance with the disclosure. FIG. 4 is a perspective view of scissors in accordance with the disclosure. FIG. 5 is a perspective view of a cutting tip and a spacer plate disposed in a cutting tip recess of a scissors jaw in accordance with the disclosure. FIG. 6 is a partial cross-sectional view of a cutting tip mounted within a beveled cutting tip recess in accordance with the disclosure. FIG. 7 is a partial cross-sectional view of a cutting tip mounted within a beveled cutting tip recess in accordance with the disclosure. FIG. 8 is a partial cross-sectional view of a beveled tip mounted within a tip recess in accordance with the disclosure. FIG. 9 is a partial cross-sectional view of a beveled tip mounted within a tip recess in accordance with the disclosure.Detailed DescriptionReferring to the drawings, like reference numerals designate like elements. FIG. 1 illustrates a machine 10 having an arm 12. the arm 12 includes a boom 14 pivotally attached to a stick 16. The jib 16 includes scissors 18. the jib 14 is raised and lowered by hydraulic pistons and cylinders 20. In the machine 10 illustrated in FIG. 1, the arm 12 is also rotated along with the cab 19 on a track undercarriage 21. The machine 10 illustrated in FIG. 1 is an example of a machine 10 that may use scissors 18 in accordance with the disclosure. However, other types of machines may be used in other embodiments. Moreover, in some embodiments, scissors 18 may not even be hydraulically actuated. However, in the illustrated example, as well as the drawings and discussion herein, the scissors 18 are hydraulically actuated.As shown in FIG. 1, the stick 16 is pivoted by a hydraulic piston and cylinder 22. The stick 16 is connected to the boom 14 via a pivot connection 24. Scissors 18 includes a set of jaws 23. jaws 23 include a fixed jaw 26 and a movable jaw 28. movable jaw 28 is actuated by a hydraulic piston and cylinder 30 connecting movable jaw 28 to pivot connection 32. The jaws 23 pivot relative to each other about the pivot connection 34. However, in other embodiments in accordance with the disclosure, both jaws 23 may be movable. Furthermore, the jaws 23 are not limited only to pivot connections. In some embodiments, the jaws 23 may move laterally relative to each other or in some other way.FIG. 2 illustrates a perspective view of scissors 18 in accordance with an embodiment. Scissors 18 include jaws 23, jaws 23 include a fixed jaw 26 and a movable jaw 28, fixed jaw 26 and movable jaw 28 each having a hole 36 through which a pivot shaft 34 (shown in FIG. 1 ) is disposed. The jaws 23 pivot relative to each other about the pivot shaft 34. while the jaw 26 is referred to as a fixed jaw and jaw 28 is referred to as movable, it will be apparent to those skilled in the art that the two jaws 26 and 28 pivot relative to each other. In other embodiments, the jaws 26 and 28 may be movable. The movable jaw 28 also includes a hole 38 to provide a pivotal connection 32 (as shown in FIG. 1 ) to the hydraulic piston and cylinder 30. It is a hydraulic piston and cylinder 30 that actuates or moves the movable jaw 28. In other embodiments, the jaws 23 may be actuated by other means.Both the fixed jaw 26 and the movable jaw 28 include cutter inserts 40. The cutter inserts are collectively designated by the reference numeral 40. Specific cutting inserts have specific reference numerals which will be described below. The cutting inserts 40 are removable from the jaws 23 for servicing, replacement and / or changeover. It is the movement of the cutter tips 40 on various jaws 23 which move past each other, which develops the shearing or cutting action. The cutting inserts 40 are highly subject to wear and are therefore, in some optional embodiments, removable to be replaced, repositioned or maintained.The side inserts 42 are located on the movable jaw 28. an end insert 44 is located on an end or tip of the fixed jaw 26. the movable jaw 28 also includes a left tip insert 46 and a right tip insert 48. The fixed jaw 26 may also be equipped with a small right side cutter 50 and other left side cutters 52. Also, fastening plates 53 are disposed on the fixed jaw 26. The fixing plates 53 will be described in more detail below.FIG. 3 is an exploded view of some of the components associated with scissors 18. The fixed jaw 26 and the movable jaw 28 are not shown to obscure the figure. Screws 54 having threaded portions 56 are used with washers 58 to secure the tips 42 to the jaws 23. The inserts 40 have holes 60 therein to facilitate attachment of the inserts 40 by the screws 54. In some embodiments, spacer plates 61 are used to provide a desired orientation of the cutting inserts 40 when mounted to the jaws 23. For example, the small right side cutting insert 50 has a corresponding spacer plate 61. The spacer plate 61 is provided with slots 63 which allows the spacer plate 61 to be positioned without displacing the position of the screws 54 within the holes 60. In some embodiments, the holes 60 in the inserts 40 are threaded and thereby engage the threaded portions 56 on the screws 54 to hold the screws 54, the spacers 61 and the inserts 40 in place on the jaws 23. In some embodiments, and as shown in FIG. 3, different spacer plates 61 may be used for different cutting plates 40. For example, the spacer plates 62 correspond to the inserts 42 on the movable jaw 28. a spacer plate 64 corresponds to the end insert 44. the spacer plates 66 are used with the side inserts 52 disposed on the fixed jaw 26.In addition to the inserts 40, mounting plates 53 may also be used to facilitate mounting of the inserts 42 to the jaws 23. The attachment plates 53 provide a surface for the screws 54 to clamp and thus retain the fixed jaw 26 between the cutting inserts 52 and the attachment plates 53, thereby securing the cutting inserts 53 to the fixed jaw 26. In some embodiments, as shown in FIG. 3, spacer plates 68 may be used with the mounting plates 53. Spacer plates 68 may also include slots 63 similar to those described with respect to the other spacer plates 61.FIG. 3 also shows other features, such as a bushing retainer 70 used to position and secure the end cutting tip 44 to the fixed jaw 26.FIG. FIG. 4 is a perspective view of scissors 18. a portion of left side cutter 52 on fixed jaw 26 and a portion of fixed jaw 26 are shown in phantom lines. This portion is enlarged in FIG. 5. FIG. 5 illustrates a portion of scissors 18 in accordance with the disclosure. Scissors 18 include a cut-out portion referred to as a cutter slot 74. A fixed left side cutter 52 is disposed in the cutter recess 74. A left side cutter spacer 66 is disposed between the left side cutter 52 and a side wall 72 of the cutter recess 74. In some embodiments, the base 80 of the side cutting insert 52 may rest against a horizontal wall 73 of the cutting insert recess 74. In other embodiments, the spacer 66 and / or the side cutting tip 52 may be spaced from the horizontal wall 73. The side cutter 52 is secured to the scissors 18 by the threaded portion 56 of the screw 54 disposed in the hole 60.In the illustrated embodiment of FIG. 5, the spacer plate 66 is tapered so that the thickness of the spacer plate at the base as illustrated by arrow A is thinner than the thickness at the top of the spacer plate 66 as illustrated by arrow B. In other words, the taper may be defined by an angle φ. In some embodiments, the angle φ is between 0.2 and 2 degrees. In other embodiments, the angle φ is between 0.45 and 1 degree. In the figures, the angles and distances represented by arrows marked with letters are illustrated in exaggerated form and are not drawn to scale in order to better illustrate the fact that the chamfer is present and the general shape of the chamfer.The angle or taper is continued on the tip 52 such that the cutting surface 78 of the side tip 52 is at approximately the same angle. If the cutting surface 78 is angled, this is referred to as a camber. A positive camber occurs when, as illustrated in the figures, the cutting edge 76 is closer to the opposing jaw 23 than the remainder of the cutting surface 78. if the cutting surface 78 were straight up and down relative to the opposing jaw 23, the position would be referred to as a neutral camber. If the distance illustrated by arrow A were greater than the distance illustrated by arrow B, the cutting edge 76 would be farther from the opposing jaw 23 than the remainder of the cutting surface 78.The positive camber may be achieved in some cases by the cutting tip 52 having a substantially rectangular cross-section. By creating an angle or taper of the cutting surface 78, a cutting edge 76 is defined. The cutting edge 76 extends further out of the tip recess 74 than the cutting surface 78 on the base 80 of the tip. This provides some features. For example, when scissors 18 pinch a workpiece within jaws 23, cutting edge 76 assists in cutting or shearing the workpiece. By maintaining the cutting surface 78 in a beveled condition such that the cutting edge 76 extends toward the jaw 23 opposite the base 80 of the cutting surface 78, the force required to move the jaws 23 past each other decreases as the cutting edge 76 passes a corresponding cutting edge on the corresponding jaw. As a result, less energy is required to move or displace the jaws 23 past each other.FIG. 6 illustrates a partial side view of scissors 18 according to another embodiment. Unlike the embodiment shown in Figure 5, the embodiment shown in Figure 6 does not use a spacer plate 61 to provide a chamfer to the cutting surface 78. Instead, the vertical wall 72 of the cutter blade recess 74 is not truly vertical, but is chamfered. The distance from the vertical is illustrated by the arrow C. It may also be expressed by an angle starting at the intersection of the vertical wall 72 with the horizontal wall 73 of the cutter blade recess 74. The angle φ may be the same as described above. In some embodiments, the angle φ is between 0.2 and 2 degrees. In other embodiments, it is between 0.45 and 1 degree. The cutting edge 76 extends further out of the opposing jaw 23 (not shown in FIG. 6 ) than any other portion of the cutting surface 78 To accommodate the chamfer in the wall 72, the horizontal wall 73 may also be chamfered to allow the generally rectangular tip 40 to remain within the tip recess 74 with a desired camber.In the embodiment shown in FIG. 6, no spacer plates 61 are used. However, in other embodiments, spacer plates 61 may be used. The chamfer on the cutting surface 78 is provided by the chamfer on the vertical wall 72. In other embodiments, the chamfering of the cutting surface 78 may be a result of a chamfered spacer plate 61 and a chamfered vertical wall 72. In the embodiment shown in FIG. 6, the cutting plate 40 is substantially rectangular in cross section. As a result, each chamfer on the vertical wall 72 translates to the cutting surface 78, and the side cutter plate 40 is secured to the scissors 18 by the threaded portion 56 of the screw 54. The screw 54 may also enter the tip at an angle to make it easier to install different tips 40 into the tip recess 74. The base 80 of the tip 40 may be in contact with the horizontal wall 73 of the tip recess 74, or the base 80 may be spaced from the horizontal wall 73 of the tip recess 74, depending on the individual requirements of a given situation.FIG. 7 illustrates a jaw 23 opposite the jaw 23 illustrated in FIG. 6, which jaw 23 may be a movable jaw 28. Similar to the embodiment shown in Figure 6, wall 72 of the tip recess 74 provides a taper and wall 73 is also tapered to accommodate the generally rectangular cross-section of the tip 40. As a result, the distance from the position of the horizontal wall 73 illustrated by the arrow D becomes longer from an actual horizontal line represented by a broken line, the farther away from the horizontal wall 73. Another possibility of expressing the bevel is an angle φ. In some embodiments, the angle φ is between 0.2 and 2 degrees. In other embodiments, the angle φ is between 0.45 and 1 degree. The side cutter plate 40 is secured to the jaw 23 by the threaded portion 56 of the screw 54. The base portion 80 of the tip 40 may or may not be in contact with the horizontal wall 73 of the tip recess 74. As described with respect to the previous figures, the cutting edge 76 extends furthest to an opposing jaw 23 further than all other parts of the cutting surface 78.In the embodiments shown and described in Figures 5, 6 to 7, the tips 40 have a substantially rectangular cross-section and therefore impart any taper as a result of the spacer 61 or the tip recess 74 to the cutting surface 78. The fact that the tips 40 are substantially rectangular in cross-section allows the tips to be rotated in position or between various positions as the cutting edge 76 or the cutting surface 78 begin to show indicia of an undesirable amount of wear.In the embodiment shown in Figs. 8 and 9, the cutting inserts 40 are generally not rectangular in cross section but are chamfered. FIGS. 8 and 9 will be described next because they illustrate opposing jaws 23 according to another embodiment. The tips 40 are secured to the jaws 23 by the threaded portions 56 on the screws 54. In the embodiment shown in FIGS. 8 and 9, the cutting inserts 74 are generally rectangular in cross-section. In other words, the vertical wall 72 and the horizontal wall 73 extend substantially at a right angle. However, the tips 40 themselves are chamfered as illustrated by arrows E and F. Arrows E and F illustrate a position of the cutting surface 78 with respect to the actual horizontal line represented by the broken line. This is also represented by the angle φ. In some embodiments, the angle φ is between 0.2 and 2 degrees. In other embodiments, it is between 0.45 and 1 degree. The cross section of the tip 40 is such that the tip 40 is narrower at the base 80 than at the other end defining the cutting edge 76. The base 80 may be in contact with or spaced from the horizontal wall 73 of the cutting recess 74. The base 80 may also be in contact with or spaced from the vertical wall 72 of the cutting recess 74. While no spacer plates 61 are illustrated in FIGS. 8 and 9, they may be optionally used.Industrial applicabilityThe present disclosure is applicable to scissors of all sizes and uses. While the present application is directed primarily to heavy duty hydraulic scissors 18, aspects of the disclosure may be applicable to any type of scissors. By providing a cutting edge 76 extending to an opposing jaw 23 of the scissors and a cutting surface 78 chamfered away from the cutting edge 76 from the opposing jaw 23 of the scissors, a scissors 18 can operate more reliably in cutting or shearing materials. Moreover, less force may be required to move or displace the scissors jaws 23 past each other when the two cutting edges 76 on the two scissors jaws 23 have moved past each other because the cutting surfaces 78 are further away from each other when the scissors jaws 23 close.The extent of the chamfering of the shear surfaces (also referred to as camber) may vary with the application. However, those skilled in the art will understand that the creation of an overturn may result in a cutting edge 76 that wears too quickly and that the creation of an overturn may result in a lack of the advantages of the apparatus described herein.

Claims

A hydraulically actuated scissors (18) comprising: a first jaw (26); a second jaw (28) configured to slide past the first jaw (26) in a shearing motion; and a first cutter (40) secured to a side of at least one of the first (26) and second jaws (28), the first cutter (40) defining a shearing edge (76) and a shearing surface (78), the shearing surface (78) having a positive camber with respect to a plane perpendicular to the jaws (23), at least one of the first (26) and second (28) jaws being actuated by a hydraulic cylinder (30); and wherein the first cutter (40) is inserted into a cutter recess (74) defined within at least one of the jaws (23); wherein the scissors (18) further comprises a spacer plate (61) disposed between the first cutter plate (40) and the cutter plate recess (74), the spacer plate (61) being dimensioned to provide at least in part the positive camber.The scissors (18) of claim 1, wherein the positive camber is within a range of from 0.2 to 2 degrees or from 0.45 to 1 degree.The scissors (18) of claim 1, wherein the first cutter plate (40) is generally rectangular in cross section.The scissors (18) of claim 1, wherein the cutter plate recess (74) is dimensioned to provide the positive camber.The scissors (18) of claim 4, wherein the first cutter plate (40) is generally rectangular in cross section.The scissors (18) of claim 1, wherein the first cutter (40) is beveled and thereby thicker at the portion of the first cutter (40) defining the shear edge (76) than at the opposite side of the first cutter (40).The scissors (18) of claim 1, wherein the first cutter plate (40) is removable from the jaw (23) and is slidable, transitionable and reattachable to the jaw (23) to expose a different edge as the cutting edge (76).The scissors (18) of claim 1, wherein the cutting edge (76) of all other portions of the shearing surface (78) is located furthest from the jaw (23) to which the first cutter plate (40) is attached.The scissors (18) of claim 1, further comprising a second cutter (42) disposed on the jaw (23) opposite the first cutter (40), the second cutter (42) also having a positive camber.The scissors (18) of claim 1, wherein the first jaw (26) is fixed and the second jaw (28) pivots about the first jaw (26).A scissors (18) comprising: a first jaw (26) having a shearing surface (78) on the first side; a second jaw (28) having a second shearing surface (78), the first and second jaws (26, 28) being configured to slide past each other, and the first and second shearing surfaces (78) being almost but not completely parallel, the first shearing surface (78) having a positive camber and the camber facing the second shearing surface (78); the first cutting tip (40) being inserted into a cutting tip recess (74) defined within at least one of the jaws (23); wherein the scissors (18) further comprises a spacer plate (61) disposed between the first cutter plate (40) and the cutter plate recess (74), the spacer plate (61) being dimensioned to provide at least in part the positive camber.Scissors (18) according to claim 11, wherein the camber angle is between 0.45 and 1 degree.The scissors (18) of claim 12, wherein the fall is caused by at least one of: a shim (61) disposed between the jaw (23) and the cutter (40); a cutter recess (74) that houses the cutter (40) and has a beveled surface; and the cutter (40) itself is beveled.

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