Ergonomic cutting shears

Abstract

A pair of scissors has a first cutting blade with a thumb handle and a thumb ring and a second cutting blade with a finger ring. The second cutting blade is pivotally attached to the first cutting blade, and the first and second cutting blades pivot relative to one another within a first plane. The thumb ring is slidably attached to the first cutting blade by a shaft that moves freely but with a certain amount of friction along a longitudinal slot in the thumb handle of the first cutting blade when the scissors are in use. The longitudinal slot in the thumb handle is situated within a second plane that is perpendicular to the first plane.

Claims

1. A pair of scissors comprising: (a) a first cutting blade comprising a thumb handle having a substantially flat upper surface and a substantially flat lower surface and a thumb ring; (b) a second cutting blade comprising a second handle having a finger ring, wherein the second cutting blade is pivotally attached to the first cutting blade, and wherein the first and second cutting blades pivot relative to one another within a first plane that is defined by a first axis and a second axis, the thumb handle substantially flat when compared to the second handle; wherein the thumb ring is slidably and rotatably attached to the first cutting blade by a shaft having at least a threaded portion, the shaft moves freely but with a certain amount of friction along a longitudinal slot in the thumb handle of the first cutting blade when the scissors are used to cut, a micro thrust bearing disposed on the shaft adjacent the substantially flat lower surface of the thumb handle, and an upper slide washer disposed on the shaft adjacent the substantially flat upper surface of the thumb handle and the thumb ring rotates on one end of the shaft; and wherein the longitudinal slot in the thumb handle is situated within a second plane that is defined by the first axis and a third axis and by the substantially flat upper surface of the thumb handle and the substantially flat lower surface of the thumb handle, the second plane perpendicular to the first plane, the shaft perpendicular to the second plane, the thumb ring rotating on the one end of the shaft.

2. The pair of scissors of claim 1, wherein a bumper is disposed at one end of said longitudinal slot.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) FIG. 1 is a perspective view of the first embodiment of the present invention, showing a user's fingers inserted into the thumb and finger rings of the scissors.

(2) FIG. 2 is a side view of the first embodiment of the present invention, in which the scissors bumper is installed rearward of the thumb ring.

(3) FIG. 3 is a side view of an alternative embodiment of the present invention, in which the scissors bumper is installed forward of the thumb ring.

(4) FIG. 4 is a side view of the first embodiment of the present invention including the thumb ring assembly and a portion of the thumb handle.

(5) FIG. 5 is an exploded perspective view of the first embodiment of the present invention including the thumb ring assembly and a portion of the thumb handle.

(6) FIG. 6 is a side view of the second embodiment of the present invention including the thumb ring assemble and a portion of the thumb handle.

(7) FIG. 7 is an exploded perspective view of the second embodiment of the present invention including the thumb ring assembly and a portion of the thumb handle.

(8) FIG. 8 is a side view of the third embodiment of the present invention including the thumb ring assemble and a portion of the thumb handle.

(9) FIG. 9 is an exploded perspective view of the third embodiment of the present invention including the thumb ring assembly and a portion of the thumb handle.

(10) FIG. 10 is a side view of an alternate embodiment of the present invention comprising a shaft with a square portion that allows the rotational orientation of the thumb ring 4 to be preset and locked prior to use.

(11) FIG. 11 is an exploded perspective view of the embodiment shown in FIG. 10.

(12) FIG. 12 is a side view of the first embodiment of the present invention that shows the thumb ring rotated approximately forty-five (45) degrees as compared to the view shown in FIG. 4.

(13) FIG. 13 is a side view of the first embodiment of the present invention that comprises a thumb ring capable of rotating along two perpendicular axes.

(14) FIG. 14 is a perspective view of the first embodiment of the present invention, illustrating the planar relationship between the cutting blades and thumb handle.

REFERENCE NUMBERS

(15) 1 Scissors 2 Thumb 3 Hand 4 Thumb ring 5 Thumb ring assembly, first embodiment 6 Third finger 7 Finger ring 8 First finger 9 Second Finger 10 Finger handle 11 Adjustment slot 12 Thumb handle 13 Bumper 14 Lower standard washer 15 Tensioning washer 16 Lower slide washer 17 Upper slide washer 18 Upper standard washer 19 Screw 20 Arrow indicating longitudinal movement 21 Arrow indicating rotational movement 22 Thumb ring assembly, second embodiment 23 Micro thrust bearing 24 Thumb ring assembly, third embodiment 25 Thumb ring with integral threaded shaft 26 Integral threaded shaft 27 Spacer 28 Magnet 29 Nut 30 Thumb ring assembly, first embodiment (modified to incorporate threaded shaft) 31 Magnet with square center hole 32 Threaded shaft with square (non-threaded) center portion 33 Lower slide washer with square center hole 34 Upper slide washer with square center hole 35 Blades of scissors

DETAILED DESCRIPTION OF THE INVENTION

(16) The present invention is cutting shears or scissors that incorporate a multiply adjustable thumb ring. As used herein, the terms “shear,” “cutting shears” and “scissors” are used interchangeably. Modes of adjustment of the thumb ring include adjustment of the longitudinal position of the thumb ring along the length of the handle and adjustment of the angular orientation of the thumb ring around an axis that is perpendicular to the long axis of the handle. Each mode of adjustment can be accomplished with the cutting hand without removing the thumb from the thumb ring or the finger from the finger ring. The ability to adjust the scissors as needed for a particular cutting operation and to adjust the scissors to fit the user's hand size and shape is important for reducing fatigue and for minimizing repetitive-motion injuries.

(17) The ability to quickly and easily slide the thumb ring longitudinally along the sliding surfaces (i.e., the upper and lower surfaces) of the thumb handle is particularly useful for cutting hair. For example, when the thumb ring is slid forward (toward the blades), the cutting strokes are more precise, which is useful for making delicate and high-precision cuts around the eyes and ears. Conversely, when the thumb ring is slid rearward, more force can be applied to the blades, which is useful for making fast cuts on non-critical areas, such as initial cropping of long hair. During haircutting, the hairdresser or barber typically switches from using scissors to using a comb multiple times; therefore, it is highly beneficial for the scissors thumb ring to remain in place when the thumb is temporarily removed from the ring for combing, etc. because the thumb can then be easily reinserted into the ring without minimal loss of time or energy. In a similar manner, it is beneficial for the rotational position of the thumb ring to remain fixed when the thumb is temporarily removed from the ring. The present invention is superior to the prior art because the adjustments of the thumb ring are easily and quickly made with the user's thumb and finger inserted into the rings of the scissors handles, and the adjustments maintain their positions until they are purposely readjusted. None of the inventions of the prior art has this capability.

(18) The materials and design of the present invention are purposely optimized to provide low friction when longitudinal or rotational adjustments are desired, but they also provide adequate friction to hold the desired position of the thumb ring when movement is not desired. There are three major embodiments of the present invention. Different thumb ring assembly components are used in each of the three embodiments to provide controlled friction for the adjustable thumb ring. All of the embodiments comprise identical handles in which the sliding surfaces of the thumb handle are perpendicular to the flat sides of the scissors blades. Each thumb handles incorporates a longitudinal slot through which the thumb ring components are attached. The present invention may be used in combination with most types of conventional scissors by installing a slot in the thumb handle of the scissors. The slot provided a track for the moving components. The sliding surfaces of the thumb handle are highly polished to eliminate undesired friction.

(19) In the first embodiment, the thumb ring is attached to the handle by a screw that passes through the handle slot. (As used in the claims, the term “shaft” is intended to encompass the shaft of a screw.) Several washers are mounted on the screw. These washers include low-friction slide washers installed on each side of the handle and in contact with the polished faces of the handle, one rubber tensioning washer and standard metal washers in contact with the thumb ring and the underside of the screw head. The slide washers are preferably made of polytetrafluoroethylene (PTFE; e.g., trade name TEFLON™), plastic or other slide-enhancing materials. The tensioning washer is preferably made of a compressible synthetic rubber such as neoprene or nitrile having durometer hardness in the range of about 40 A to 80 A. The tensioning washer preferably has an uncompressed thickness of about 0.1 to 0.2 inch. During assembly, the screw is threaded into a threaded hold in the base of the thumb ring until the tensioning washer is compressed sufficiently to provided proper sliding and rotational friction for the thumb ring.

(20) The second embodiment is similar to the first embodiment, except that the lower slide washer and tensioning washer of the first embodiment are replaced with a micro thrust bearing. The thrust bearing provides a very low-friction contact with the outside surface of the handle, while the required friction for the assembly is supplied by the slide washer in contact with the inside surface of the handle. The micro thrust bearing may be any suitable commercial product, such as part number 6655K12 from McMaster-Carr Supply Company of Aurora, Ohio. The latter part has steel ball bearings and an outside diameter of 0.5 inch, although the present invention is not limited to any particular outside diameter of the micro thrust bearing. The micro thrust bearing a preferably comprised of a ring in which ball bearings are embedded. The ring of the micro thrust bearing may be comprised of any suitable material, for example, plastic or nylon, and the ball bearings may be comprised of any suitable material, for example, steel or ceramic.

(21) The third embodiment is similar to the first embodiment except that the tensioning washer is replaced by a cylindrical magnet. In this embodiment, friction between the outside slide washer and the contact surface of the handle is provided by a compression force resulting from the magnetic attraction between the magnet and the handle. For the third embodiment, the handle must be made of a metal material, such as stainless steel or chrome-plated carbon steel, that attracts magnets. Rare earth magnets, which have strong magnetic field compared to iron magnets of the same size, are preferable for this invention because they are lighter and smaller than comparable-strength iron magnets.

(22) It is possible to combine the features of two or more of the three embodiments to form a hybrid configuration. For example, the thumb ring assembly may comprise a micro thrust bearing (from the second embodiment) on one or both contact surfaced of the thumb handle in combination with a magnet (from the third embodiment) on one side of the handle.

(23) The present invention preferably incorporates a polymer bumper mounted on the inner surface of one handle. This bumper contacts the inner surface of the opposing handle when the scissors are fully closed. The purpose of the bumper is to set the position of the blades relative to each other when the scissors are fully closed and to minimize wear that would otherwise occur if the hard inner surfaces of the handles came into direct contact during closing of the scissors. The bumper may optionally be placed either forward of the thumb ring (i.e., closer to the blades) or rearward of the thumb ring. Each of the embodiments of the present invention will operate correctly with either a forward-mounted or rearward-mounted bumper.

(24) Each of the three embodiments comprises a threaded shaft that passes through the slot of the thumb handle and slides back and forth within the slot to provide longitudinal adjustment of the thumb ring. The threaded shaft may optionally be manufactured either as an integral piece of the ring component, or alternately, it may be a separate screw component or non-integral threaded shaft that threads into the ring component. The configuration of the threaded shaft (integral threaded shaft, non-integral threaded shaft or separate screw) does not affect the operation of the invention.

(25) Each of the three embodiments may optionally comprise a threaded shaft with a square (non-threaded) center portion in lieu of a fully threaded shaft. The purpose of the square portion is to prevent rotational movement of the thumb ring. In this configuration, the angle of the thumb ring is preset and locked into position prior to use, while longitudinal movement is still permitted. The fixed rotational option may be preferred by some users. This embodiment is shown in FIGS. 10 and 11. As used herein, the term “square” is intended to also encompass rectangular.

(26) FIG. 1 is a perspective view of scissors that incorporate the first embodiment of the present invention, shown with a user's fingers inserted into the thumb and finger rings of the scissors. Referring to FIG. 1, the scissors 1 are grasped so the thumb 2 of the user's hand 3 is inserted into the thumb ring 4 of the first embodiment of the thumb ring assembly 5, while the third finger 6 is inserted into the finger ring 7, and the first finger 8 and second finger 9 are rested along the outer surface of the finger handle 10. Also shown in FIG. 1 is the longitudinal adjustment slot 11 in thumb handle 12 and scissors bumper 13. As shown in the figure, the thumb ring assembly 5 is positioned at an intermediate position within the slot 11 (i.e., the thumb ring 5 assembly is rearward of the front edge of the slot 11).

(27) FIG. 2 is a side view of the embodiment shown in FIG. 1, in which the scissors bumper 13 is installed rearward of the thumb ring assembly 5. FIG. 3 is a side view of an alternate embodiment of the present invention, in which the scissors bumper 13 is installed forward of the thumb ring assembly 5. Note that in the embodiment shown in FIG. 3, the thumb ring may slide all the way to the rear of the longitudinal slot (not shown) with the scissors in a fully closed position. FIGS. 2 and 3 illustrate that the present invention is equally compatible with scissors having either a rearward- or forward-mounted bumper.

(28) FIG. 4 is a side view of the first embodiment of the present invention that shows the ring assembly 5 installed on the thumb handle 12. FIG. 5 is an exploded perspective view of the thumb ring assembly of the first embodiment. As shown in FIGS. 4 and 5, components of the thumb ring assembly 5 include the thumb ring 4, lower standard washer 14, tensioning washer 15, lower slide washer 16, upper slide washer 17, upper standard washer 18, and screw 19. During assembly of the thumb ring assembly 5 to the thumb handle 12, the screw 19 is passed through the adjustment slot 11 and then screwed into the threaded portion of the thumb ring 4. The screw 19 is tightened until the tensioning washer 15 is partially compressed. The compression of the tensioning washer 15 produces friction between the lower slide washer 16 and the lower contacting surface of the thumb handle 12 and friction between the upper slide washer 17 and the upper contacting surface of the thumb handle 12.

(29) The compression of the tensioning washer 15 is increased by tightening the screw 19 until the resistance of the thumb ring 4 against rotational and longitudinal movement is at the correct level. The arrow 20 shown in FIG. 5 indicates the direction of longitudinal movement of the thumb ring assembly 5, and the arrow 21 indicates the direction of rotational movement of the thumb ring assembly 5 relative to the thumb handle 12. As previously described, the correct level of friction is preferably low enough to allow the user to adjust the longitudinal and rotational position of the thumb ring 4 when the thumb 2 is positioned within the thumb ring 4, while at the same time the friction level is great enough to cause the thumb ring 4 to stay in the set longitudinal and rotational positions when the thumb 2 is removed from the thumb ring 4.

(30) As shown in FIG. 14, the cutting shears pivot about an x and a y axis in a two-dimensional plane, whereas the longitudinal slot lies with in a z axis that is perpendicular to the x and the y axes. This orientation of the longitudinal slot is important to the present invention because it enables the shaft 19, 26, 31 to move more freely within the longitudinal slot then the slot of Yusufov, for example, which is oriented solely within the x-y plane. The shaft of Yusufov is not intended to move freely during use of the scissors.

(31) FIG. 6 is a side view of the second embodiment of the present invention that shows the ring assembly (second embodiment) 22 installed on the thumb handle 12. FIG. 7 is an exploded perspective view of the thumb ring assembly 22 of the second embodiment. As shown in FIGS. 6 and 7, the thumb ring assembly 22 of the second embodiment comprises a thumb ring 4, a lower standard washer 14, a micro thrust bearing 23, and upper slide washer 17, and upper standard washer 18, and a screw 19. In the second embodiment, the components of the thumb ring assembly shown in FIGS. 6 and 7 are connected to the thumb handle 12 by passing the screw 19 through the adjustment slot 11 and then tightening the screw 19 until the proper level of friction is achieved against longitudinal and rotational movement of the thumb ring 4.

(32) FIG. 8 is a side view of the third embodiment of the present invention that shows the ring assembly (third embodiment) 24 installed on the thumb handle 12. FIG. 9 is an exploded perspective view of the thumb ring assembly 24 of the third embodiment. As shown in FIGS. 8 and 9, the thumb ring assembly 24 of the third embodiment comprises a thumb ring 25 with integral threaded shaft 26, a spacer 27, a magnet 28, a lower slide washer 16, and upper slide washer 17, and a nut 29. In the third embodiment, the thumb ring assembly 24 is assembled to the thumb handle 12 by passing the integral threaded shaft 26 through the adjustment slot 11 and threading the nut 29 onto the threaded shaft 26. The tightening tension of the nut 29 is not critical in this embodiment because friction is supplied by the force of the magnet toward the thumb handle 12, which pushes the lower slide washer 16 against the lower contact surface of the thumb handle 12. The proper level of friction against longitudinal and rotational movement in this embodiment is set by adjusting the size of the magnet 28. For example, installing a longer magnet, or a second identical magnet, will increase the friction of the thumb ring 25. Although one or two magnets is/are preferred, the present invention is not limited to any particular number of magnets.

(33) Although this first and second embodiments are shown with a screw 19, and the third embodiment is shown with an integral threaded shaft 26, any of the three embodiments could be made with a non-integral threaded shaft (similar to be partially threaded shaft 31 and nut 29 shown in FIG. 11).

(34) FIGS. 10 and 11 illustrate an optional feature that may be incorporated into any of the three embodiments previously described and is particularly shown here used with a modified form of the third embodiment. FIG. 10 is a side view of the modified third embodiment of the present invention 30 that allows the rotational orientation of the thumb ring 4 to be preset and locked prior to use. FIG. 11 is an exploded perspective view of the embodiment shown in FIG. 10.

(35) As shown in FIG. 11, the modified thumb ring assembly of the third embodiment 30 is comprised of a thumb ring 4, a spacer 27, a magnet with a square central hole 31, a threaded shaft with a central (non-threaded) square portion 32, a lower slide washer with a square central hole 33, and upper slide washer with a square central hole 34, and a nut 29. (Note that the magnet 31 could also be made with a round central hole if the central (non-threaded) square portion 32 of the threaded shaft were shorter.) The shaft 32 has threads on the lower end that thread into the thumb ring 4 and threads on the upper end that thread into the nut 29. The square portion of the shaft 32 is sized so as to fit snugly but movably in the side and against the sides of the slot 11, thereby allowing the shaft 32 to slide longitudinally along the length of slot 11 but preventing it from rotating with in the slot 11. By this means, when the modified thumb ring assembly 30 is installed on the thumb handle 12, the thumb ring assembly 30 is free to slide back and forth in the longitudinal direction as shown by the arrow 20 but is restrained from rotational movement. The shaft shown in FIGS. 10 and 11 can be used with the tensioning washer of the first embodiment or the micro thrust bearing of the second embodiment, as long as these components have a square central hole.

(36) FIG. 12 is a side view of the first embodiments of the present invention that shows the thumb ring rotated approximately forty-five (45) degrees as compared to the view shown in FIG. 4. The direction of rotational movement is indicated by the dashed arrow. The thumb ring is free to rotate during each opening and closing of the scissor blades during use, thereby allowing the thumb orientation to constantly adjust to an optimal position for comfort and efficiency during each stroke of the scissors.

(37) FIG. 13 is a side view of the first embodiment of the present invention that comprises a thumb ring capable of rotating along two perpendicular axes. The two axes of rotational movement are shown by the dashed arrows. Each direction of rotation is free to move during opening and closing of the blades during use. The dual-rotation thumb ring in FIG. 13 is preferred over the single-rotation thumb ring shown in FIG. 12 by some users and can be combined with any of the embodiments described herein.

(38) FIG. 14 is a perspective view of the first embodiment of the present invention, illustrating relative orientation of the cutting blades and longitudinal slot on the thumb handle. Three dimensional axes are also shown in the figure and are labeled x, y and z. Referring to FIG. 14, the flat sides of the blade 35 lie in a vertical plane (the x-y plane), and the flat side of the thumb handle 12 lies in the x-z plane. The x-z plane is perpendicular to the plane of the flat side of the blades 35. These sliding surfaces are also perpendicular to the flat sides of the blades, as shown in the figure. By contrast, the sliding surfaces of Yusufov (U.S. Pat. No. 6,915,578) are in the same plane as the flat sides of the blades. By orienting the sliding surfaces so they are perpendicular to the flat sides of the blades rather than in the same plane as the flat sides of the blade blades, the thumb ring 4 of the present invention can be more properly positioned to reduce strain on the user's thumb, thereby reducing fatigue and the risk of repetitive-motion injury.

(39) Although the preferred embodiment of the present invention has been shown and described, it will be apparent to those skilled in the art that many changes and modifications may be made without departing from the invention in its broader aspects. The appended claims are therefore intended to cover all such changes and modifications as fall within the true spirit and scope of the invention.