MXPA97006320A - Varia strength mower - Google Patents

Abstract

The present invention relates to a variable force variable force mower comprising: a metal plate having a first pivot point, a forwardly extending blade and a rearward extending tail provided with a second point of pivoting separated from the first pivoting point by a predetermined distance: a first elongate member pivotally connected to the plate at the first pivot point, the first member has a forwardly extending jaw configured to cooperate with the blade to cut a piece of work received in a depression formed by the jaw, a limb extending backward and a first segment of intermediate gear to the jaw and limb, and a second elongate member having a portion extending backward and a second segment of opposite gear, the second member being pivotally connected to the plate at the second pivot point so that the first and second or gear segments are engaged in the first and second regions, respectively, wherein the second gear segment is configured such that a second distance separating the second pivot point of the second region is smaller at a predetermined point of travel of the blade along the depression

Description

VARIABLE FORCE MOWER FIELD OF L INVENTION The present invention generally relates to variable force tools and in torque to variable force tools such as carriers.

BACKGROUND OF THE INVENTION The cutting of heavy growths such as the branches of trees in the order of about 25 to 50 minutes typically requires considerable force. Cutting shears to cut such heavy growths comprise typically a pair of elongated members arranged for cooperating engagement on a pivot point. Such pruning shears generally include a pair of opposed jaws, such as a blade that cooperates with an anvil, or a pair of blades. In these shears, the jaws, which are typically made of stamped or forged metal or other suitable material, have an opposite end or force application glue connected to a long handle. The long handle configuration provides the user with the extra leverage necessary to carry out the cor + e operation, and provides an extended reach for pruning distant tree branches and the like. Clippers with an anvil and a blade are commonly known as "anvil" trimmers, while those provided with a pair of engaging blades are known as "bypass" shears. To carry out the cutting operation, the handles are pivoted on the pivot point thus forcing the union of the jaws or, in the case of a branch mower, one beyond the other. To support the forces involved in cutting heavy growth, the relatively long pruning shears must be sufficiently strong. Although these handles are made of wood normally, to reduce forearm fatigue the most recent prior art trimmers have included hollow handles made of fiberglass or other strong and firm material of light weight. In all cases, however, the length of the handles tends to be limited due to practical and cost considerations. Since the pruning of heavy growths such as tree branches of approximately 50 nm in diameter requires considerable force, to generate the necessary cutting force without unduly lengthening the handles, those skilled in the art have applied to the tools of pruning or shearing the benefits provided through the use of lever mechanisms. An example of such a lever action mechanism is illustrated in the U.S. patent. No. 4,420,883 issued on December 20, 1993 to Uallace, and others. In the '883 patent, which describes a commonly known device with a tree cutter mounted on a pole, the blade cooperates with a hook that is configured to receive a portion of the branch that will be cut. A link mechanism associated with the cutting blade effects the pivotal movement of the blade through the cutting stroke in response to the pulling of a driver rope by the user. As is readily apparent, tree trimmers such as that described in the '883 patent include many components and are relatively complicated to use. The composite action mechanisms of the prior art have also been used in pruning shears such as those described in the US patent. No. 147,868, issued on February 24, 1874 to Seyer et al .; in the patent of E.U.fl. No. 2,384,822, issued September 18, 1945 to Drrnic; the patent of E.U.A. No. 3,372,478, issued March 12, 1968 to Uallace et al .; and in the patent of E.U.A. No. 5,020,222, issued June 4, 1991 to Gosselm et al. The '478 to Uallace patent describes composite action shears in which the pivoting of the jaws is disposed rearwardly of the pivoting of the handles thereby reducing the included angle formed between the jaws. Although this double pivoting configuration improves the grip of the work piece by the jaws, it does not seem, however, to improve the mechanical advantage of such a tool. As illustrated in Figure 1, those skilled in the art of tree trimming have recognized that the cut resistance designated as F presented by a fibrous and generally round growth such as for example the branch of a tree L, is not uniform but it varies as a function of the penetration of the cutting blade B into the growth. The maximum resistance is typically reached at a point P approximately 60% through the cutting stroke. This is because, up to that point, the penetrating action of the blade B in the branch L results in the compression of an increasing number of fibers as the blade B penetrates more in the branch L, thus increasing the density of the branch l_. As shown in Fig. 1, C represents the compression region of the fibers of the L branch, while q? E Fr represents the friction forces that oppose the shear force applied by a user, there From the point P, which is the point of maximum compression of the fibers, the resistance to the cutting action decreases at the beginning of the blade to cut the fibers (illustrated as the S region, where the growth begins to be cut and, as or reected, the resistance to the cutting action decreases until the L branch is completely cut off). Therefore, it becomes advantageous for a cutting tool to be provided with a variable force mechanism that provides maximum leverage at the point in the cutting stroke that corresponds to the maximum cutting resistance. Gosselin describes such a compound action mower in which an additional lever member connected to one of the jaws increases the cutting force transmitted to the jaws, thus facilitating the cutting operation. Such a structure provides the desired additional lever, without unduly increasing the length of the handles. However, these known composite action shears tend to be disadvantageous in a number of aspects. For example, in Gosselm, the composite action requires that a sliding connection be made between the cutting member and the levering lever. Still other tools of the prior art composite action typically include several components which make it difficult to adjust the blade tension and blade removal for sharpening. Handles of these prior art pruning shears tend to be transmitted to the shearing blades causing the blades to twist with respect to each other, thus preventing their cutting function and tending to overload and damage the pivoting of the blade. The inventor is also aware of other prior art structures typically used to transmit high torques to the jaws of a cutting tool, examples of these other tools are described in US Patent No. 1,689,648 issued October 30. from 1928 to Voleske; the patent of E.U.A. No. 1,065,753 issued June 24, 1913 to Uhitney; the patent of E.U.A. No. 766,941 issued August 9, 1904 to Eddleman; the patent of E.U.A. No. 107,577 issued September 20, 1870 to Uill; and in the application serial number 08 / 484,846 filed on June 7, 1995 by the present inventor. In all those cases, the pivoting movement of at least one of the handles is transmitted to the jaws of the tool by means of meshed concentric gear segments or, as illustrated in Eddlernan, by a rack and pinion arrangement . However, these known gear-type cutting implements do not include composite action mechanisms necessary to maximize the cutting force applied to a work piece received in the jaws at a predetermined point. In light of the foregoing, it is apparently desirable to provide a pod shear that can overcome the problems associated with conventional articles of that type, i.e., in which the composite action provides an increased mechanical advantage at a predetermined point. , but which is nevertheless designed to take advantage of the other benefits provided by high torque torque cutting tools.

BRIEF DESCRIPTION OF THE INVENTION The present invention provides a particularly advantageous variable force gear lever mechanism which is constructed to generate a maximum mechanical advantage (ie maximum leverage) at the most desirable point through the cutting stroke, without, however, unduly increasing the total weight of the shear. More specifically, according to one aspect of the invention, a variable force cutting tool includes a metal plate provided with a first pivot point separated from a second pivot point by a predetermined distance, the plate having a blade that it extends forward and a tail that extends backwards. The tool also includes a first elongated member that is pivotally connected to the plate at the first pivot point. The front portion of the first member is configured as a jaw cooperating with the blade to cut a workpiece received in a depression formed by the jaw. The first member comprises a limb which extends rearward, to which a handle is preferably fixed, and a first segment of intermediate gear to the jaw and the limb. A second gear segment, formed in the forward portion of a second elongated member, cooperates with the first gear segment when the second member is pivoted towards the plate on the second pivot point. The second member also preferably includes a handle mounted on a rearwardly extending portion. The first and second gear segments are engaged in the first and second regions, respectively, so that the distance separating the second pivot point of the second region varies as the blade travels through the depression. According to another aspect of the invention, the gear segments are configured so that the distance q? E separates the second pivot point of the second region from reaching a minimum at a predetermined point of travel of the blade through the depression. . According to yet another aspect of the present invention, the variable force geared tool is configured as a pruning shear which can be anvil type or bypass. Other aspects of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific modalities are given by way of illustration only, since from this detailed description several changes and modifications within the espiri +? and scope of the invention will become apparent to those skilled in the art.

BRIEF DESCRIPTION OF THE DRAWINGS The preferred exemplary embodiment of the invention will now be described in conjunction with the accompanying drawings, in which like numbers denote similar elements: Figure 1 shows, schematically, the penetration of a cutting blade into a growth, illustrating the point at which the maximum resistance to the cutting action is typically reached; Figure 2 is a top plan view of a variable force tool in accordance with the present invention, showing a preferred embodiment thereof in a fully open position and receiving a workpiece within its depression; Figure 3 is a bottom plan view of the pruning ra of Figure 2; Figure 4 is a bottom plan view of the carrier of Figure 2, represented approximately sixty percent by the cutting stroke; Figure 5 is a view on the lower floor of the mower of Figure 2, shown at the end of the cutting stroke; Figure 6 is a top plan view of the mower of Figure 2, shown at the end of the cutting stroke; Figure 7 is seen in front elevation of the mower of Figure 2, represented at the end of the cutting stroke; Figure 8 is a top plan view of the first elongated member of the mower shown in Figure 2; Figure 9 is a top plan view of the mower blade shown in Figure 2; Figure 10 is a top plan view of the second elongated member of the mower shown in the figure 2; Figure 11 is seen in partial section, taken substantially along the line 11-11 shown in Figure 6; Figure 12 depicts an elongated detailed illustration of the tooth configuration of the first gear segment of the first elongated member shown in Figure 8; Figure 13 depicts an elongated detailed illustration of the tooth configuration of the second gear segment of the second elongate member shown in FIG. 10; and Figure 14 is a schematic diagram of the pruning shear of the present invention, exemplifying the relationship between the first and second gear segments.

DETAILED DESCRIPTION OF A PREFERRED EXEMPLARY MODALITY Referring to the figures, a mower 10 according to the invention includes first and second elongate members 12 and 14, respectively, and a metal plate 16. The first elongate member 12 includes a first jaw 18 extending forward and An extremity 20 that extends backwards. A first gear segment 22 is formed in a region 24 intermediate the jaw 18 and the end 20. To add convenience to the user, the mower 10 is provided with a pair of handles. A first handle 26 is suitably configured to receive a portion of the limb 20. Preferably, the handle 26 has a hollow front region in which a portion 28 extending rearwardly of the extremity 20 is adjusted to an air pressure. form generally known to those skilled in the art. The first member 12 also includes a first opening 30 formed in the region 24 of the first gear segment 22. In the preferred embodiment, the first jaw 18 extending forward forms a depression 32 configured to receive a workpiece 34 that will be cut. The mower 10 also includes a metal plate 16 having a cooperating jaw 36 extending forward and a tail 38 extending backward. The cooperating jaw 36 preferably has the shape of a blade made by a grinding operation that produces a chamfer 40 of decreased thickness that terminates at a sharp edge 42. A second opening 44 is + formed intermediate the engaging jaw 36 and the tail 38. The tail 38 is also provided with a third opening 46 separated from a second opening 44 by a predetermined distance, the metal plate 16 is pivotally joined to the first member 12 at a first pivot point 50. The pivot point 50 includes advantageously a bolt 52 engaging the first and second openings, 30, 44 respectively. The second elongated member 14 includes a second gear segment 54 and an opposite portion 56 on which a second handle 58 is mounted in the same manner provided for the handle 26. The member 14 also includes a fourth opening 60 formed intermediate to the second segment. of gear 54 and portion 56. Second member 14 is pivotally attached to plate 16 at a second pivot point 62. Second pivot point 62 advantageously includes a 64-pin bolt engages third and fourth openings 46. 60, respect ivarnent e. Referring now more particularly to the figures 12 and 13, the first gear segment 22 comprises a plurality of gear teeth 66 configured to mesh with the gear teeth 68 formed in the second gear segment 54. The particular tooth arrangement of the gear segments 22 and 54 of FIG. the preferred modality is shown in the two tables shown below. In these tables, certain points designated as Pn of the gear segments 22, 54 are identified by a set of X, Y coordinates centered on the first pivot point 50 and the second pivot point 62, respectively. For example and with reference to Figure 12 and Table 1 (the frame of the first gear segment), the P20 of the first gear segment 22 has coordinates -29.516mm / -30.793mm relative to the first pivot point 50. In addition, in these two tables, "R" designates the radius of a curve that extends between two neighboring points. For example and still referring to Figure 12 and Table 1, between the neighboring points P28 and P30 the radius R is 5.9 mrn.

TABLE 1 FIRST GEAR SEGMENT X -38.773 -8.6 7.2 -34,327 -9,446 8.36 -30.518 -10.355 1.6 -30,099 -12,431 7.46 -32.508 -15.078 10 7.88 -35.862 -18.288 11 -35.166 -20.306 13 6.98 -30,757 -20,894 15 16.94 -27,179 -21,056 16 1.6 -26,189 -23,275 18 6.7 -28.236 -25.937 20 6.2 -29.516 -30.793 21 -28.252 -31.711 23 6.24 -23.865 -29.855 25 22 -21.552 -27.576 26 1.6 -18.85 -28.418 28 22 -18.322 -31.83 30 5.9 -15.886 -35.897 31 -14.297 -35.671 33 6.58 -12.418 -31.096 35 6.72 -11.274 -27.61 36 1.6 - 9.378 -27.084 38 - 6.729 -29.854 40 8.96 -3.882 -33.453 41 1.768 -32.991 43 7.02 0. 809 -28,437 45 8.1 0.267 -25 .038 46 1.6 2.272 -24 .443 48 5.19 -27. .315 50 8.38 8.213 -30.862 TABLE 2 SECOND GEAR SEGMENT Those skilled in the art will readily appreciate that even if the coordinates of these points are given in millimeters, other units of length or measurement systems are equally applicable. Referring to Figures 4, 12 and 13, the second member 14 is pivotally connected to the plate 16 on a second pivot point 62 so that the first and second gear segments 22, 54 mesh in the first and second regions 70. , 72, respectively. The first and second gear segments 22, 54 are further characterized by first and second separation lines 74, 76 respectively. As seen in FIGS. 12 and 13, the first separation line 74, which represents the imaginary line running without slippage with the second separation line 76 of the second engaging gear segment 54, is not concentric on the First pivot point 50. Instead of this, and also referring to Figure 14, d3, which represents the distance between the first pivot point 50 and the first region 70, varies when pivoted the first and second handles 26, 58 on the first and second pivot points 50, 62, respectively. Similarly, the second separation line 76 of the second engaging gear segment 54 is not concentric on the second pivot point 62. Instead, 2, which is the distance between the second pivot point 62 and the second region 72 also varies with the scissor action of the first and second handles 26, 58. As illustrated in figures 12 and 13, and in tables 1 and 2, d3 reaches maximum at a predetermined point which is found between P20 and P21. Conversely, because the distance between the first and second pivots 50, 62, (is dedr, the distance between the second and third openings 44 and 46) is fixed, d2 necessarily reaches a minimum at that or a point. The effect of this equal but opposite variation of the distances d2 and d3 on the cutting force Fe applied to the workpiece 34 is reflected in the following equation using the moment of the forces: Faith K.FU. efe with K = d3 ^ 2 * where as illustrated in figure 14: Fu is the force applied by a user at point of application along the second member 14; di is the distance between the second pivot point 62 and the point of application; and say, is the distance between the first pivot point 50 and the point at which the Faith is applied to the work piece 34. Fe can also be written as: Fc = K.FU + K.Fu - _ L faith As is easily apparent from the previous equations, K and di are constants, and for the same amount of force Fu applied by the user to the tool 10, Fe will reach a maximum value when 2 is minimum (ie, d3 is maximum), which occurs as explained above at the point between P20 and P21 • Accordingly, the present invention, in which the configuration of coupling of the segments of gear 22, 54 minimizes the d2 at a predetermined point that falls on approximately sixty percent of the cutting stroke, allows the tool 10 to generate maximum leverage at that point, which is the most desired point. of the cutting stroke where the density of the work piece 34 is higher. It is understood that the description above is that of a preferred exemplary embodiment of the invention and that the invention is not limited to the specific forms described. For exampleThe tools according to the invention having first and second gear segments of the type described in the foregoing description, may include a pair of opposing cutting blades, as in shunt trimmers, in place of a blade that cooperates with Anvil as described in the preferred embodiment. In addition, such clippers can be manufactured in various ways. For example, they can be manufactured from patterned plates, or from forged metal; or they may include some components made of a moldable material such as plastic, in each case without affecting their functional characteristics. Moreover, even though the preferred embodiment of the invention shows gear teeth which have a particular configuration, those skilled in the art will appreciate that the gear function can be provided in other ways without departing from the scope of the invention. this invention. However, it is considered that these other strings and configurations are within the scope of this invention. Accordingly, these and other substitutions, modifications, changes and omissions may be made in the design and arrangement of the elements and in the manufacturing steps described herein without departing from the scope of the appended claims.

Claims (20)

NOVELTY OF THE INVENTION CLAIMS

1. - A variable force mower comprising: a metal plate having a first pivot point, a forwardly extending blade and a rearwardly extending tail provided with a second pivot point separated from the first pivot point by a predetermined distance; a first elongate member pivotally connected to the plate at the first pivot point, the first member having a jaw extending forward configured to cooperate with the blade to cut a received workpiece into a depression formed by the jaw , a limb extending backward and a first segment of intermediate gear to the jaw and the limb; and a second elongated member having a rearwardly extending portion and a second opposing gear segment, the second member being pivotally connected to the plate at the second pivot point so that the first and second gear segments engage the first and second regions, respectively; wherein the second gear segment is configured such that a second distance separating the second pivot point of the second region is smaller at a predetermined point of travel of the blade along the depression.

2. - The trimmer of "iad with the claim 1, in which in addition the first gear segment is configured so that, at a point where the blade cuts the workpiece, a first distance separating the first pivot point of the first region is smaller.

3. The mower according to claim 1, wherein further the first and second gear segments are configured such that the predetermined point is about sixty percent of the trip of the blade along the depression to the cut- The blade to the work piece.

4. The mower in accordance with the rei indication 1, in which the jaw is configured as a second blade to cooperate with the blade. 5.- The mower in accordance with the claim 1, wherein the first elongate member is formed of metal. 6. The mower according to claim 1, wherein the first and second elongate members are formed of metal. 7. The mower according to claim 1, wherein the first elongate member is formed of plastic. 8. The mower according to claim 1, wherein the first and second elongated members are formed of a mouldable material. 9. The mower according to claim 1, wherein in the first member at least the first gear segment is formed of a mouldable material. 10. The mower in accordance with claim 1, wherein in the second member at least the second gear segment is formed of a rnoldable material. 11. A variable force mower comprising: a metal plate having a first pivot point, a forwardly extending blade and a rearwardly extending tail provided with a second pivot point separate from the first point of rotation; pivoting; a first elongate member pivotally connected to the plate at the first pivot point, the first member having a forwardly extending jaw configured to cooperate with the blade for cutting a received workpiece into a depression formed by the jaw, a limb that extends backwards and? n first segment of intermediate gear to the jaw and the limb; a second elongated member having a portion extending rearwardly and a second second gear segment, the second member being pivotally connected to the plate at the second pivot point for the first and second gear segments to engage in the first and second regions, respectively; and means for imparting a variable cutting force to the workpiece as the blade travels along the depression. 12. The mower in accordance with claim 11, wherein the dividing means comprises the gear segments configured in such a way that a first distance separating the first pivot point from the main window is maximum at a predetermined point of travel of the blade along the depression. . 13. The mower according to claim 11, wherein the variable force imparted to the work piece is a function of the formula: di + <; Faith Fe = K.Fu. faith with K = d3 + 2 cU where: Fe is the shear force applied to the work piece; Fu is the force applied by a user at an application point along the second member; d2 is the distance between the second pivot point and the second region; d3 is the distance between the first pivot point and the first region; di is the distance between the second pivot point and the point of application; and d * is the distance between the first pivot point and a point at which the Fe is applied to the work piece. 14.- The mower in accordance with the claim 13, in which maximum Fe is at a predetermined point of travel of the blade along the depression. 15.- The mower in accordance with the claim 14, in which the gear segments are configured so that the predetermined point is about sixty percent of the trip of the blade along the depression. 16. A pivoted tool of variable force comprising: a first elongated member that has a first jaw that extends forward joining in a first gear segment, a first handle mounted on a limb that extends rearward from the first gear segment and a first opening formed in a region of the first gear segment; a metal plate having a cooperating jaw extending forward, a tail extending rearwards and a second opening intermediate the cooperating jaw and the tail, the tail being provided with a third opening separated from the second opening by a predetermined distance, the metal plate is pivotally connected to the first member at a first pivot point which comprises the first and second openings; and a second elongated member having a second gear segment and a second handle mounted on a portion extending rearwardly from the second gear segment, the second gear segment having a fourth opening, the second member being connected pivotally to the plate at a second pivot point comprising the third and fourth openings; the first and second gear segments are engaged in the first and second regions, respectively, and being configured so that a first distance separates the first pivot point of the first region a second distance separating the second region from the second point of travel. pivoting, they vary in equal but opposite amounts when the first and second handles are pivoted on the first and second pivot points, respectively. 17. The tool according to claim 16, wherein the first jaw and the cooperating jaw are configured as blades. 18. The tool according to claim 16, wherein the first jaw is configured as an anvil and the cooperating jaw is configured as a blade. 19. The tool according to claim 16 and wherein the gear segments are configured so that the second distance is small at a predetermined travel point of the cooperating jaw relative to the first jaw in response to closing movement. of the handles. 20. - The tool according to claim 19, wherein the predetermined point is approximately midway along the travel of the cooperating jaw.