JPH0618487B2 - Plant cutting equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a plant cutting device such as a mower or a lawn mower.

(Prior Art) Various plant cutting devices have already been proposed which facilitate the removal of plants by mowing, mowing, edging and other similar cutting operations. Generally, these devices use metal blades to effect plant removal. This type of equipment uses prime movers such as electric motors, gasoline engines. As a result, rotating metal blades can be heavy and severely injured to the user.

Around 1960, a cutting edge trimmer (trimmer / edger) was developed in Europe that uses a flexible polymer rope extending from a rotating head to cut plants. This device did not work properly due to some drawbacks in its construction and operating parameters. In the United States, some practical plant cutting devices have been developed that use flexible non-metallic rope carried on a rotating head. These devices are described in US Pat. No. 370.
No. 8967, No. 3826068, No. 3859766
No. 4035912, No. 4052789, No. 40
No. 54992 and No. 4067108, respectively. These patented devices have been very successful by these U.S.-developed organizations by providing safe power tools or gasoline-powered tools for cutting, edging and mowing operations on plants.

The devices disclosed in the above-referenced patents use flexible cutting lines such as those made from nylon polymers. The cutting rope is usually carried on a spool housed inside the rotary head. When it is desired to replenish the rope or extend the additional length of the rope, the head rotation is stopped and the rope is manually pulled from the spool. The rope drawing method such as the above in the patented devices is convenient,
Recognized as easy and reliable. In many of the more powerful devices, especially those driven by electric motors, there is a long felt need for a system that extends the line from the head without interrupting the cutting operation.

The most desirable system would be one that automatically feeds the cut line from the head as the need arises, without depending on any involvement of the operator. A structure directed to such a purpose is disclosed in US Pat. No. 3,895,440,
020550 and 4035915. In common with these structures, a basket weaving supply source of a cutting rope is carried on the peripheral edge of the disk to feed the rope from behind a special post member. These post members are provided with cutting wear edges so that the cutting lines fed from the textile supply source are bent along their edges at their free-moving end portions which extend in the cutting plane. The overall function of the edges, ropes, angular velocities, etc. is configured such that a rope post with such edges cuts the free end portion of the rope when the cutting rope is worn to an ineffective length. Has been done. In practice, these structures are known to waste about 25% of the rope because the excess length of rope is cut at the edge of the post, for example 7.60 cm (3 ″).

Moreover, whenever the cutting line is worn or broken to its undesirably short length, without interrupting the plant cutting operation and without the need for operator intervention, the cutting line is A plant cutting device provided with a mechanism for stretching the plant to its suitable working length has also been proposed.

As such a conventional technique, there is an apparatus disclosed in Japanese Patent Application Laid-Open No. 55-21793 and Japanese Patent Publication No. 57-500767.

(Problems to be Solved by the Invention) The above-mentioned JP-A-55-21793 and JP-A-57-57
The plant cutting device disclosed in Japanese Patent Laid-Open No.-5007677 is designed so that the cutting rope is automatically pulled out when the cutting rope becomes short. ) Was not surely maintained. That is, the spool was in a state in which it could freely rotate when the cutting rope was pulled out. If the drag force (that is, back tension) is not maintained in the cutting rope when the cutting rope is pulled out, the cutting rope cannot be pulled out by an accurate length, and the cutting rope with an excessive length is pulled out. Will end up.

In a plant cutting device in which a tensile force is applied to the cutting rope by a centrifugal force acting on the outer end portion of the cutting rope so as to pull out the cutting rope, the drag force is maintained in the cutting rope when the cutting rope is pulled out. , Has been found to be important for the extraction of the exact length of the cutting rope.

The present invention adopts a balance member having an arm portion that pivots while applying a tensile force to the cutting rope while maintaining such drag force, and adopts a balancing member having an outer end portion of the cutting rope of a predetermined length. It is an object of the present invention to provide a plant cutting device that prevents the spool from being pulled out further when the spool is hit.

(Means for Solving the Problems) When the reference numerals used in the embodiments of the present invention described later are additionally shown for reference, the present invention provides a head 29, which is rotatable about one axis. 36, 200, the head of which is a spool 6 which stores a flexible cut rope.
Enclosing 5, 214, the stored flexible cutting rope is an outer end portion of a length of rope that is rotatable by the head in one cutting plane that projects outwardly from the head. 31 and 212, a centrifugal force F ₁ is generated on the outer end portions 31 and 212 by a centrifugal force having a tendency to pull the cutting rope outward from the head, and the spools 65 and 214 are Mounted within the head for rotation therewith and for rotational movement relative to the head to additionally extend a cutting line in the cutting plane; and A drive device 33 for rotationally operating the heads 29, 36, and 200, and an eccentrically mounted device in the head, which is pivotable between a first pivot position and a second pivot position. Balance member 6 which is
The balance member locks the spool when in the second pivoted position and unlocks the spool when in the first pivoted position. In the plant cutting device further comprising arm portions 80 and 130 for additionally extending the cutting rope, the eccentric pivot axis of the balance members 68, 104 and 230 and the weight thereof are provided while the head is rotating. A centrifugal force F ₂ is generated in the balance member in a direction opposite to the force F ₃ generated in the balance member by the tensile force F ₁ due to the centrifugal force applied to the outer end portions 31 and 212, thereby locking the spool. The balance member is moved toward the first pivot position where the stop is released, and when the outer end portions 31 and 212 reach a predetermined length, the balance member is moved to the first pivot position. Centrifugal to move the balancing member toward F ₂ is defeated in the force F ₃ generated in the balanced member by the tensile force F _1, is adapted to move to said second pivot position in which the balancing member to lock said spool When the length of the outer end portions 31 and 212 becomes shorter than the predetermined length due to wear or damage, the force F ₃ generated on the balance member by the tensile force F ₁ is at the first pivot position. The balance member is adapted to move to the first pivot position for unlocking the spool by being defeated by the centrifugal force F ₂ for moving the balance member toward the outer end. In response to the length of the portions 31 and 212 becoming shorter, the balance member is moved to the first pivot position to unlock the spool, and the spool rotates with respect to the head. At all stages of The pool is slowed by the friction of the cam surfaces 84,88; 92,96 to move the balance member toward the first pivoted position while the cut leash is withdrawn from the spool. A force F ₃ generated by the tensile force F ₁ against the centrifugal force F ₂ is exerted on the balance member, and the tension is maintained in the cutting rope at all stages in which the cutting rope is pulled out. Is characterized by.

(Operation) When the outer end of the cutting rope becomes shorter than the specified length,
The centrifugal force F ₂ acting on the balance member is larger than the force F ₃ applied to the balance member by the tensile force F _{1 of the} cutting rope caused by the centrifugal force acting on the outer end portion of the cut rope, and the balance member is Moves into a pivoted position that unlocks the spool head. Thus, the cutting rope is pulled out.

When the outer end portion of the cutting rope reaches a predetermined length, the centrifugal force F ₂ acting on the balance member becomes smaller than the force F ₃ applied to the balance member, and the balance member locks the spool with respect to the head. Move to the pivot position. Thus, the withdrawal of the cutting rope is stopped.

On the other hand, while the spool is being rotated with respect to the head by the cutoff line, the spool has cam surfaces 84,88;
By 6, the movement is delayed by friction. That is, no free rotation is performed. Therefore, the tension is always maintained in the cut rope. Since such tension is maintained, the force F ₃ generated on the balance member is
It is always maintained, not zero. Maintaining such tension (drag force) in the cutting rope is important for the balance member to operate properly. In order to maintain the maximum tensile force in the cutting rope at all times, as the cutting rope is pulled out, it supplies an increased predicted drag force to the cutting rope, thereby exerting a centrifugal force on the outer end portion of the cutting rope. The stability of the actuation of the balancing member is achieved by ensuring that P is accurately sensed. This is a method in which the pulling speed is limited so that a drag force that is substantially equal to the centrifugal force in the cutting rope is supplied to the cutting rope with the pulling of the cutting rope at all stages between the controlled drawing, that is, the cutting rope, Can be considered. In other schemes, the cutting rope has no significant tensile force, and therefore the centrifugal force in the cutting rope cannot be accurately measured by detecting the tensile force in the cutting rope, and the detected force is used to cut. I can't finish pulling out the rope.

Maintaining the drag force of the cutting rope enables the balancing member to sense the centrifugal force acting on the outer end portion of the cutting rope, and also reduces the pulling speed of the cutting rope, The balance member reacts before the excess cutting line is pulled out, and allows the length of the outer end portion of the cutting line to be stopped at a predetermined length.

(Effect of the Invention) According to the present invention, by adopting the balancing member and the cam surface having a simple structure, the cutting rope is automatically operated when the length of the outer end portion of the cutting rope becomes shorter than a predetermined length. It can be pulled out from the spool, and can be pulled out with an accurate length.

EXAMPLE Referring to FIG. 1, a plant cutting device constructed in accordance with the present invention is illustrated. For purposes of description herein, the device is a mower 21, but it could be a lawn mower, lawn trimmer or other plant cutting device. The mower 21 has a lower housing 2 which is connected to a handle assembly 24 by a pipe 23.
Have two. The handle assembly 24 has a switch 26 for selectively supplying the electric power supplied by the cord 27 to the electric motor provided in the lower housing 22. An auxiliary handle 28 is installed on the tube 2 for operating the mower 21 with both hands. The lower housing 22 carries a molded plastic head 29 which is rotatable about its axis of rotation and a cut line 31 which extends in a cutting plane substantially perpendicular to the axis of rotation of the head 29.

In FIG. 2, a prime mover 33 housed in the lower housing 22 is shown.
Shown is a lower housing 22 having a plurality of air inlets 32 for introducing a cooling air stream thereon. Prime mover 3
3 has a drive shaft 34 extending downward, and the head 29 is screwed and attached to the drive shaft 34. The upper surface of the head 29 may be surrounded by a plurality of vanes 37 that act as a centrifugal blower to move air radially outward from the head 29 during rotation of the head 29. As a result, the incoming airflow cools the prime mover 33 within the lower housing 22.

The head 29 has a hub 36 and a lower cover 35, and
6 has a hole 38 on its side peripheral surface, through which the cutting rope 31 extends radially outward in the cutting plane. The smoothed bearing surface in the hole 38 protects the cutting rope 31 from excessive wear and tear.

The lower housing 22 has a rearwardly extending tail 42 which serves as a protective means to prevent accidental contact of the user with the rotating cutting rope 31. The tail 42 also provides a means for automatically limiting the degree of extension of the cutting rope 31 from the head 29. More specifically, the tail portion 42 has a downwardly extending protrusion 43 having a metal cutting edge 44 implanted therein. As a result, the cutting leash 31 may not have a working length that extends beyond the cutting edge 44 as it is rotated in the cutting plane by the head 29. Even if the cutting rope 31 initially has an excessive length, it is automatically cut by the cutting edge 44.

Referring now to FIGS. 3-5, the head 29 is screwed to the drive shaft 34 by a threaded lower stud portion 47 formed at the lower end of the drive shaft 34 of the prime mover 33. The hub 36 has a spring fastening tab 39 and a lower cover 35.
It is adapted to interfit with the lower cover 35 by means of complementary grooves (not shown) in the inside. The shaft 40 is axially threaded to receive the lower stud portion 47 of the drive shaft 34, and the depending tubular cap post 56 in the hub 36 abuts the shoulder formed on the shaft 40. Head 29
It is fixed inside. The lower cover 35 has an annular lip 45 that receives the lower end of the shaft 40 for stability. A spool or rope spool, generally designated by the reference numeral 65, includes a holding and replenishing source for the cutting rope 31 and is rotatably supported about the shaft 40 and reciprocally movable in the axial direction of the shaft 40.

The head 29 is provided with what may be called an inertial angular velocity governor 66 which constitutes an important feature of the present invention. In the embodiment described below, the inertial angular velocity governing device 66 enables the tensile force of the cutting rope 31 to be sensed by the balancing arm 68 when the cutting rope 31 passes over the balancing arm 68 which is a balancing member. Maintain a tensile force of 31. 8 to 1
As shown most clearly in Figure 0, the balance arm 68 may be constructed from a rigid wire bent into a generally U-shape.
The balance arm 68 is shaped to define an upright straight leg 70 and an opposing leg 76 generally parallel thereto.
The legs 70 are pivotally received in a sleeve 72 (FIG. 3), and the sleeve 72 is friction fit into a vertical pocket 74 in the molded plastic hub 36. The opposite leg 76 has an intermediate offset or arcuate portion 78 over which the cutting rope 31 is guided from the rope spool 65 into the hole 38. An arcuate portion (arm portion) 80 connects the leg 70 and leg 76 to each other at their upper ends. The arcuate portion 80 is arranged to be sandwiched between the hub 36 and the rope spool 65, as described below, to prevent reciprocal movement of the rope spool 65 in the axial direction of the shaft 40. Used for. As the head 29 is rotated, the centrifugal force F ₂ is applied to the balance arm 68.
In the counterclockwise direction from the position shown by the broken line in FIG. 3 (hereinafter called the tightening position (see also FIG. 5)) to the position shown by the solid line in FIG. 3 (hereinafter called the release position (see FIG. (See also Fig. 4))). Against this centrifugal force is the force (vector) F ₃ shown in FIG. ₃ , which is a function of the pulling force F _{1 on} the rope 31 and which is transmitted to the arcuate portion 78 and said release position. To the above-mentioned tightening position, the balance rope 68 is exerted on the cutting rope 31 so as to exert a tendency to be pressed.

The rope spool 65 includes a tubular sleeve 73 having a central hole 75, as will be described with particular reference to FIGS.
And is adapted to be supported around the shaft 40 so as to be rotatable and reciprocally movable in the axial direction of the shaft 40. The lower end of the sleeve 73 is enlarged to define a spool withdrawal knob 81 that allows a user to easily remove the rope spool 65 from the head 29 for service. The sleeve 73 has an annular concentric flange 6
A drum 60 having 9, 71 is connected, and a space 77 is provided between the concentric flanges 69, 71, which is provided with a winding supply source of the cutting rope 31 in a coil state. A plurality of evenly spaced chamfered recesses 82 (see FIGS. 4 and 11-14) are formed on the upper surface of the flange 69. Recesses 82 form cam teeth 84 with sloping sidewalls intermediate each of their adjacent pairs. Similarly, a plurality of similar recesses 86 are formed on the underside of the flange 71, and between these recesses 86, cams having inclined sidewalls aligned with the cam teeth 84. Teeth 88 are defined. Sleeve 7
3 is a plurality of arcuate axially extending recesses 79,
It is generally separated from the drum 60 (see FIGS. 3 and 6). The cutting rope 31 on the drum 60 is the balance arm 6
8 through the hub cavity 89 to follow a route along the arcuate portion 78 of the eight and the through hole 38.

Separated chamfered recesses 8 in the rope spool 65
2, 86 and cam teeth 84, 88 each having an inclined side wall interposed between them are recesses 90 (see FIGS. 11 to 14) between the cam teeth 92 formed on the inner lower surface of the hub 36 and the lower portion. It is positioned to cooperate with the recesses 94 between the cam teeth 96 formed on the inner surface of the cover 35. The cam teeth 84, 88 of the rope spool 65 are arranged to be aligned as already mentioned, but the cam teeth 9 of the lower cover 35 are
6 and the cam teeth 92 of the hub 36 are arranged so that they are not relatively aligned to cause axial reciprocation of the rope spool 65, as will be explained. Alignment and misalignment arrangements such as cam teeth can alternatively be reversed, or used in combination. In order to understand the operation of the inertial angular velocity governor 66, in FIG. 7, the contours of the cam teeth are inclined so that the locking between the cam teeth does not occur during the engagement and disengagement process. It must be noted that it is formed symmetrically with "A". This angle "A" is, for example, about 30 degrees, and such an angle is such that the cam teeth that are in contact with each other cause the cam teeth that are in mutual contact to slide the rope spool 65 axially alternately in the upward and downward directions. Sliding between the teeth can be guaranteed. The actuation of disengagement of the opposing cam teeth can be clearly understood by sequentially examining the repetitive actuations schematically depicted in FIGS. 11-14, as will be explained later. For illustration purposes, the lower cover 35 and the hub 36 rotate in the direction of arrow 98, and the rope spool 65 moves in the direction of arrow 1.
In the direction of 00 (between the rope drawers), the tensile force F of the cutting rope 31
Suppose it is rotated by ₁ . The rope spool 65 causes an arrow 1 by the tensile force F ₁ of the cutting rope 31 generated from the centrifugal force.
The upper and lower cam teeth 84, 88 of the rope spool 65 alternate between opposite camshaft teeth 92, 96 of the hub 36 and lower cover 35 as they are forced to rotate in the direction 00. It operates to reciprocate the rope spool 65 in the axial direction.

The balance arm 68 (FIG. 3) is rotated in a counterclockwise direction from the tightening position shown by the broken line contour to the release position shown by the solid line contour in FIG. Subject F ₂ to the centrifugal force. The force F ₃ exerted on the balance arm 68 by the tensile force F ₁ of the cutting rope 31 is
It acts on the balance arm 68 in a direction to pivot the balance arm 68 clockwise from the released position to the tightened position. When the balance arm 68 is in the clamped position, the arcuate portion 80 of the balance arm 68 is located between the upper flange 69 of the rope spool 65 and the hub 36, as shown in FIG. The rope spool 65 cannot move upward and is locked by the interlocking lower cam teeth 88 of the rope spool 65 and the cam teeth 96 of the lower cover 35. When the cutting rope 31 is to be pulled out, the centrifugal force F ₂ received by the pivotally mounted balancing arm 68 overcomes the force F ₃ of the cutting rope 31 acting on the balancing arm 68, so that the balancing arm 68 is of the upper flange 69. Pivoted outward from the circumference to allow vertical movement of the rope spool 65, allowing rotation of the rope spool 65, thus the rope spool 65 precisely controlling and delaying the withdrawal of the cutting rope 31. To enable that.

Starting from the position of the rope spool 65 of FIG. 11 where the balance arm 68 is assumed to be in its released position, the rope spool 6
8 cam teeth 88 are lowered into the lower cover recess 94 for incremental rotation in the direction of arrow 100 until engaging the next successive cam teeth 96 of the lower cover 35. As shown in FIG. 12, cam tooth 88 then slides up along the ramped surface of cam tooth 96 until it moves away from cam tooth 96. As the rope spool 65 moves upwardly toward the position shown in FIG. 13, the cam teeth 84 of the rope spool 68 will cause the hub 36 to move until the cam teeth 88 move away from the cam teeth 96.
Into the recess 90. By that time, the cam teeth 84
Is incrementally advanced by rotation to the next successive cam tooth 92 on the hub 36 (FIG. 14). This operation is repeated as the cam teeth of the rope spool 65 continuously advance, engage and slide vertically. Therefore, as each cam tooth of the rope spool 65 is displaced into the recesses 90, 94 of the opposing hub 36 or lower cover 35, the post-cocoon sliding displacement between the mutually engaging cam teeth is 65
Is pressed to the opposite side in the axial direction. The friction to some extent between the sliding cam teeth and the energy required to accelerate the rope spool 65 in the reciprocating direction along the axis are the force (drag force) that opposes the tensile force F ₁ of the cutting rope 31. Said) is always a cutting rope 3
1 and thus the greater the tension F ₁ of the cutting rope 31 is, the more force is required to accelerate the rope spool 65 axially and the more drag force is required. growing. This means that the tension of the cutting rope 31 between the drawers is equal to the tensile force F ₁ resulting from the centrifugal force of the cutting rope 31 (the intermittent tension at least at high frequencies is equal to the tensile force F ₁ ). As a result, the centrifugal force that causes the tensile force F ₁ on the cutting rope 31 and the centrifugal force F that acts on the mass of the pivoted balance arm 68.
₂ can be balanced.

To understand the associated forces thereby causing the rope spool 65 to be actuated and stopped in the manner described above, consider again FIG.
₁ results from centrifugal forces on the cutting rope 31 that are maintained by the rope spool 65 being fixed or retarded from rotation during rope payout by the action of inertia and friction caused by the interengaging cam teeth. It will be understood that it is power. The pulling force F ₁ acts to additionally pull the cutting rope 31 outwards from the head 29 and can therefore be called “centrifugal pulling force”. The force F ₄ is the net difference between the force F ₃ exerted by the tensile force F ₁ of the cutting rope 31 and the centrifugal force F ₂ acting on the mass of the balancing arm 68. In the relationship shown in FIG. 3, the cutting rope 31 outside the hole 38 is
For the purpose of explanation, the force F ₃ exerted by the tensile force F ₁ of the cutting rope 31 exerted on the balancing arm 68 is the net force F _4.
Is assumed to be a length L ₁ which is maintained to exceed the centrifugal force F ₂ on the balance arm 68 so as to turn to the left when viewed in FIG. Therefore, the balance arm 68 is the rope spool 6
5 is in the tightening position, which prevents the reciprocating movement (and thus the rotation) of the cord 5, so that the rope spool 65 is clamped and prevents the cutting rope 31 from being unwound.

As the length of the part of the cutting rope 31 extended outward starts to wear or the breaking of the cutting rope 31 occurs,
The tensile force F _{1 and} thus the force F ₃ on the cutting rope 31 is
The upper centrifugal force F ₂ becomes unbalanced with respect to the force F ₃ , the net force F ₄ is directed to the right in FIG. 3, and the balance arm 68 pivots outwards and the rope spool 65. You will be reduced until you release him. Then, the rope spool 65 is accelerated in the axial direction first upward and then downward while maintaining the drag force described above on the cutting rope 31. Particularly high drag forces are generated at the beginning of axial acceleration after a small rotation when the cam teeth are continuously engaged. This means that if the length of the cutting rope 31 extended outward is
The balancing arm 68 is effectively pivoted inward and, once again, the rope spool 65 is tightened again, as long as the force F ₃ against the centrifugal force F ₂ on the balancing arm 68 is unbalanced.
Guaranteed to prevent feeding after cocoon 1. If the drag force is not maintained, the rope spool 65 continues to reciprocate, rotate and cut rope until the force F _{3 of the} rope 31 moves the balance arm 68 to its inner clamping position. Will pull out 31.

The pulling of the cutting rope 31 is based on the speed increase.
Note that any increase in the pulling force F ₁ above is counterbalanced by a corresponding increase in the centrifugal force F ₂ acting on the mass of the balancing arm 68, so it is essentially dependent on the rotational speed of the head 29. . Thus, the device of the present invention is a device driven by a gasoline engine in which the critical rpm range is not constant due to rich fuel, polluting spark plugs, etc., and the rpm is not changeable based on cut rope wear. Works well in. Moreover, the device of the present invention also functions in an electric power drive device in which the number of revolutions per minute increases substantially as the cutting rope 31 becomes shorter. It should also be noted that the cutting rope 31 cannot be unwound while the head 29 is stationary, as the balance arm 68 can be released from the rope spool 65 when the head 29 rotates. Further, should the cutting rope 31 be caught on a chain link, a fence or the like, excessive force acting on the cutting rope 31 always overcomes the centrifugal force in the balance arm 68 and is tightened so that the rope spool 65 does not rotate. Guarantee.

Another embodiment of the present invention is illustrated in FIGS. 15 and 16. This embodiment is substantially the same as the previously described first embodiment, but with a balance beam 1 which is a balance member.
04 engages with the tightening teeth on the periphery of the rope spool 65 to tighten and release the rotation of the rope spool 65. For ease of explanation, the rope spool 65 of FIG.
Are split along the axis and, on the left side of the axis of rotation, the cam teeth 84 are disengaged from the cam teeth 92 of the hub 36, while the lower cam teeth 88 and the cam teeth 96 of the lower cover 35. Engaged and shown in the lower reciprocating position of the rope spool 65. In contrast, this device is shown with the cam teeth 84 meshing with the cam teeth 29 of the hub 36 on the right side of the axis of rotation, while the lower cam teeth 88 are disengaged from the cam teeth 96 of the lower cover 35. Has been done.

For this embodiment, the head 92 is coupled to the drive shaft 34 of the prime mover 38 as in the first embodiment. The rope spool 65 also has the drum 60, and the cutting rope 31 is wound around the circumference of the drum 60 between the flanges 69 and 71. Inertia drag brake 66, flange 6
9 and is formed by cam teeth 84 provided with an arcuate space 82 upright and spaced evenly around its circumference. In this embodiment, rather than the recesses, the cam teeth 84,88 are chamfered, while the intervening recesses formed between adjacent cam teeth are in contrast to the first embodiment. Not chamfered. Similarly, the flange 71 has a spacer 86 and a cam tooth 88, and the cam tooth 88 is provided on the lower cover 3.
5 are aligned with cam teeth 84 for engaging spacer 94 with cam teeth 96. The sleeve 73 is coupled to the drum 60 via the plurality of spokes 102.

In this embodiment, the actuating means for actuating and stopping the inertia drag brake 66 based on the drag force is a stamped metal balance beam 104, which is at its center at an obtuse angle 106. Bifurcation 108 for bending and mounting on pivot shaft 100
Are divided in. The pivot shafts 110 are aligned with the hub 36 and the lower cover 35, and the pockets 1 are provided in the recesses.
Supported in 12,114. Balance beam 104 has a relatively lighter first portion 116 and a relatively heavier weighted second portion 118 so that when the head 29 is rotated, FIG. , Will tend to pivot the balance beam 104 in a counterclockwise direction. The second portion 118 engages the inwardly projecting clamping teeth (defined by the radially outer end portions of the cam teeth of the rope spool) projecting from the periphery of the rope spool 65 and the rope spool 36. Has an end 130 which serves to clamp it against rotation. Cutting rope 31 is rope spool 6
5 through the hole 125 and then the balanced beam 104
It goes out of the hole 38 in the same way as in the first embodiment, beyond the smooth curved surface that guides the cutting rope 31 on the end of the cord, and as a result, the pulling of the cutting rope 31 due to the centrifugal force due to the rotation occurs. The force F ₁ creates a force component that counteracts the centrifugal force of the balance beam 104 and serves to pivot the balance beam 104 clockwise about the axis of the pivot axis 110.

Elongated leaf springs 140 are contained at their ends 142, 144 projecting in opposite directions. The leaf spring 140 serves to provide the balance of the head 29 to the head 2.
9 on the opposite side from the balanced beam 104. The leaf spring 140 is secured via its end 144 in the pocket 146 of the hub 36, from which the post 152 in the cavity 148.
After extending past, the end 142 bends inward past the edge of the cam tooth 88. In this connection, the leaf spring 140
Until the centrifugal force overcomes the spring force and releases the rope spool 65 at a relatively low rpm.
It works by tightening and fixing 5. At the time of partial entanglement of the cutting rope 31 during operation or at start-up, a low rpm can occur until a minimum rpm is exceeded. The leaf spring 140 may provide a two-stage starting action, thereby preventing the possibility of any chaotic rope-feeding movement during tug entanglement or starting.

During operation, the operation of balance beam 104 closely resembles that of balance arm 68 previously described. Balance beam 104 is part 11
Being relatively heavier in section 118 compared to 6, the balancing beam 104 is pivoted between the inner clamping position and the outer releasing force in response to the net force F ₄ . As described above, the force component that constitutes the net force F ₄ includes the force of the balance beam 104 generated by the tensile force F ₁ forcing the clockwise rotation and the balance beam 104 counterclockwise about the pivot axis 110. It is represented by the difference from the centrifugal force that pivots. For a period of time such that the cut leash 31 is of a defined length, the balance beam 104 is in the clamped position so that the distal inflection end 130 engages the cam teeth 84 of the leash spool 65. The rope spool 65 is in a position that prevents the rope spool 65 from rotating. When the cutting rope 31 is to be unwound, the force F ₄ rotates the balancing beam 104 counterclockwise and releases the rope spool 65. Inertial drag brake 66 then operates in the manner described with reference to FIGS. 11-14 to cause a controlled payout of cutline 31. As soon as the rope length recovery is achieved, the force F ₄ exerted on the balancing beam 104 causes the balancing beam 104 to pivot clockwise to the inward clamping position, where the end 130 is on top or It engages the lower cam teeth 84 or 88 to prevent subsequent rotation of the rope spool 65.

In response to the centrifugal force F ₅ exerted on the end 142, the pillar 1
Leaf spring 1 exposed to bending moment about 52
04 is used to prevent rotation of the rope spool 65 unless the head 29 rotates above a minimum number of revolutions per minute. The characteristics of the leaf spring 140 are selected to allow release of the rope spool 65 when the rotational speed of the head 29 exceeds a specified magnitude, so that rope pulling out under reduced speed conditions is obviated. It Leaf spring 140
Is optional and any impact force is exerted on the exposed rope 31 which causes the rope payout to begin before the restraint of the rope spool 65 is properly caused by the balancing beam 104. It is primarily intended to provide precautionary measures in some cases. Therefore, in this mechanism, the end portion 142 of the leaf spring 140 reacts to the centrifugal force F _5.
15 is in the position shown by the solid line in FIG. 15, and the rope spool 65 intervenes in the space 82 between the cam teeth 84 at the prescribed minimum reduction speed and inhibits the rope spool 65 from operating. When the set minimum speed is exceeded, the leaf spring 140 is bent outward to reach the position indicated by the chain line, from which point the balancing beam 104 controls the rotation and stall of the rope spool 65.

17-21, a head in yet another embodiment of the present invention is indicated generally by the reference numeral 200. The head 200 is driven by a shaft 202,
The shaft 202 itself is driven by a suitable prime mover, such as an electric motor or gasoline engine, none of which is shown. Head 200 has an upper housing portion 204, which is generally inverted cup-shaped, and has a shaft 205 threaded onto shaft 202. The upper housing portion 204 has an outer cylindrical body 206 and an inner cylindrical body 208. The lower housing part 210 is
The outer cylindrical barrel 2 is provided in any suitable manner so that it can be easily removed to allow access to the interior of the head 200.
And a cap coupled to 06. The upper housing portion 204 defines a make-up cavity 211 for receiving a coiled make-up source of cutting rope 212 of monofilament material that can be conveniently retained within a bobbin type spool 214. The bobbin spool 214 is sized smaller than the inner cylindrical barrel 208 of the housing portion 204 so that it can rotate freely within the inner cylindrical barrel 208. The supply part of the cutting rope 212 is
It will be withdrawn from the middle of the coiled replenishment source through the central opening 218 in the bobbin spool 214, as will be described in greater detail.

The upper housing portion 204, the lower housing portion 210 and the bobbin type spool 214 can be easily formed from molded plastic material.

The metal plate 220 has a boss 222 in the center, which is fitted to the drive shaft 202 and has an arm portion 224 that is most clearly seen in the bottom view of FIG. The arm portion 224 extends through a rope passage space 209 formed in the outer cylindrical body 206 and the inner cylindrical body 208. Eyelet eye 224
a is formed at the end of the arm portion 224, thereby providing a secure guide for the cutting line 212 as will be described. A hole 22 is formed in the metal plate 220 adjacent to the boss 222.
6 is formed, so that the cutting rope 212 is pulled out from the inside of the supply coil in the bobbin type spool 214 and the hole 22 is formed.
6 through the rear side of the boss 222 in frictional sliding engagement therewith (see FIGS. 17 and 18), then through the pivoted arm member 230, and the roller 240. Along (see FIG. 20) and finally through eyelet 224a.

The arm member 230, which is a balance member, is attached to a pivot pin 232 that projects downward from the metal plate 220. Arm member 2
The structure of 30 is shown most clearly in FIGS. 20 and 21, and comprises parallel plates 234 and 236.
34, 236 are separated from each other by a spacer 238 at the pivoted end and a support post 239 for the roller 240 at the free end. Spacer 238
Comprises a cam surface which by wedge-like action provides a substantial mechanical benefit as the arm member 230 is pivoted in the clockwise direction in FIG. 21.
12 is progressively tightened against the boss 222, and finally the cutting line 212 is frictionally secured to prevent its payout. This position is shown generally in FIGS. 18 and 21 and is referred to below as the rope tightening position. When arm member 230 is pivoted counterclockwise to reach the position generally shown in FIG.
Is progressively moved away from the boss 222 to progressively release the tightening on the cutting line 212 and, as will be explained, the cutting line 212 is slidably and controllably extended. To enable that.

Thus, the cutting rope 212 passes from the coiled rope supply source in the supply cavity 211 through the hole 226 and the spacer 238.
That is, it extends between the cam surface and the boss 222, around the roller 240, and then through the eyelet 224a and extends to a specified length therefrom. As the head 29 is rotated at high revolutions per minute, the free end of the cutting leash 212 extending from the eyelet 224a is pivoted in a cutting plane disposed substantially perpendicular to the drive shaft 202. The diameter of the cutting disc is maintained at the desired defined diameter by automatically maintaining the length of the cutting line 212 as will be described.

The pivoted arm member 230 rotates about the pivot pin 232, and when rotated, pivots the arm member 230 outward in a counterclockwise direction when referring to the bottom view of FIG. work. The tensile force of the cutting rope 212 resulting from the centrifugal force produces a force that acts to rotate the arm member 230 in a clockwise direction. Needless to say, cutting rope 21
The tensile force of 2 is a function of the length of the cut rope extending into the cutting plane. When the length of the cutting rope 212 extending from the dovetail metal 224a is a desired length, the force acting on the arm member 230 is larger than the centrifugal force acting on the arm member 230. As a result,
The arm member 230 is pivoted inward in the radial direction so that the spacer 23
8 or the cam surface tightly tightens the cutting rope 212 to prevent it from moving, and prevents subsequent feeding. Any additional force exerted on the cutting line 212, such as that resulting from entanglement with a hedge or other obstruction, only increases the clamping force that prevents subsequent payout. It should also be noted that as the arm member 230 moves inward, the effective center radius of the arm mass is reduced, and thus the centrifugal force acting to open the arm member 230 is also slightly reduced. This exerts a positive overcenter type tightening action on the cutting rope 212. The cutting rope 21 to the extent that centrifugal force is adequate to pivot the arm member 230 radially outward.
When 2 is shortened due to its wear or breakage, the clamping force on the cutting line 212 is reduced. As this begins to occur, the cutting line 212 begins to slip between the spacer 238 or cam surface and the boss 222, thus allowing the cutting line 212 to be dispensed to the desired length and at the same time the arm member 23.
The drag force that causes the force that acts on the roller 240 necessary to pivot 0 back to the tightening position
Can be maintained at 12. Further, from the hole 226 to the spacer 23
8 or the boss 22 up to the tightening point between the cam surface and the boss 222.
The capstan effect of the cutting line 212 sliding along 2 provides a drag force to ensure that the pulling force of the cutting line 212 can be effectively sensed by the arm member 230. This drag force tends to increase significantly as the cutting line 212 attempts to deliver it at a higher speed, thereby causing the spacer 238 or cam surface to cut as the cutting line 212 passes through the tightening point. Rope 212
Is always kept in a state of exerting a drag force on. The stopper 223 limits the movement of the arm member 230 to a maximum open position sufficiently close to the cutting rope 212, thereby maintaining sliding contact with the boss 222 from the hole 226 to the tightening point, and thus Cutting rope 2 to maintain drag force
Guarantees the minimum drag force required for 12. In this regard, it will be noted that the bobbin type spool 214 provides the lowest possible friction within the rope replenishment recess 211. Similarly, the roller 240 minimizes friction between the clamp point and the free end of the line 212. Thus,
Due to the capstan effect of the boss 222 and the drag force provided by the spacer 238 or cam surface, the cutting rope 212 is
The drag force maintained at is highly stable and predictable to achieve optimum operation.

From the above detailed description of several preferred embodiments of the present invention, the preselected length of the cutting line, and thus the cutting diameter, of the cutting line during operation without operator command or attention.
It will be appreciated that a plant cutting device has been described that automatically maintains the.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a plant cutting device constructed according to the present invention driven by an electric motor. FIG. 2 is a partially cutaway enlarged view of the lower portion of the apparatus shown in FIG. FIG. 3 is a cross-sectional view of the head of one embodiment of the device of the present invention taken along line 3-3 of FIG. FIG. 4 is a cross-sectional view of the head taken along line 4-4 of FIG. FIG. 5 is a fragmentary view of the right side portion of FIG. 4, showing the changed relative arrangement direction of the components. FIG. 6 is a cross-sectional view taken along the axis of the rope spool of the head of FIG. 7 is a cross-sectional view of the lower spool cam teeth of the apparatus of FIG. 3 taken along line 7-7 of FIG. FIG. 8 is a bottom view of the balancing arm of FIGS. 3 and 4. FIG. 9 is a right side view of the balancing arm of FIG. FIG. 10 is a perspective view of the balancing arm of FIG. 11 to 14 are schematic views showing the successive operating stages of the cam teeth of the device according to the invention, in which the rope spool is shown axially shortened for illustration purposes. FIG. 15 is a bottom view of another embodiment of the head of the present invention with the lower cover portion of the head removed and the lower circumferential portion of the hub cut away for illustration purposes. 16 is a cross-sectional view taken along line 16-16 of FIG. 15, showing the lower cover in its original position. FIG. 17 is a sectional view of a head according to still another embodiment of the present invention. 18 is a cross-sectional view of the head shown in FIG. 17 taken along line 18-18 of FIG. 19 is a bottom view of the rope pulling mechanism of the head of FIG. 18 which serves to explain the operation of the device. FIG. 20 is a perspective view of the mechanism shown in FIGS. 18 and 19. FIG. 21 is a bottom view of the mechanism of FIG. 19 with the balancing arms in different positions. On the drawing, 21 …… Mower, 22 …… Lower housing, 29
...... Head, 31 ...... Cutting rope, 34 ...... Drive shaft, 35 ...
… Lower cover, 36… Hub, 38… Hole, 40… Shaft,
44: cutting edge, 60: drum, 65: rope spool,
68 ... Balance arm, 69, 71 ... Flange, 70, 76
...... Legs, 77 ...... vacant spaces, 78 ...... bow-shaped parts, 80 ...... arc-shaped parts, 82,86,94,96 ...... recesses, 84,8
8,92,96 ... Cam teeth, 33 ... motor.

Claims (1)

[Claims] 1. A head (29,36,200) rotatable about an axis, the head enclosing a spool (65,214) storing a flexible cutting line. The stored flexible cutting rope is provided with an outer end portion (31, 21) of the rope of a predetermined length rotatable by the head in one cutting plane projecting outward from the head.
2) is included so that a tensile force (F ₁ ) due to a centrifugal force having a tendency to pull the cutting rope outward from the head is generated in the outer end portions (31, 212). 65, 214) is mounted in the head for rotation therewith and is also mounted for rotational movement relative to the head to additionally extend a cutting line in the cutting plane. And a drive device (33) for selectively rotating the head (29, 36, 200) and an eccentrically mounted inside the head, the first pivot position and the second pivot position. A balance member (68, 104, 230) that is pivotable between a moving position and the balance member,
An arm portion (80, 13) that locks the spool when in the second pivoted position and unlocks the spool when in the first pivoted position to additionally extend the rope.
0) having a eccentric pivot of the balancing member (68, 104, 230) and its weight, the outer end portion (31, 212) while the head is rotating. A centrifugal force (F ₂ ) in the opposite direction to the force (F ₃ ) generated in the balance member by the tensile force (F ₁ ) applied to the balance member is applied to the balance member to lock the spool. The balance member is moved toward the first pivot position for releasing the first pivot position when the outer end portions (31, 212) reach a predetermined length. The centrifugal force (F ₂ ) that moves the balance member toward the armature is defeated by the force (F ₃ ) generated in the balance member by the tensile force (F ₁ ), and the balance member locks the spool. To move to the second pivoting position to stop And Tsu, when the length of the outer end portion (31,212) has become shorter than the predetermined length due to wear or damage, the force generated in the balanced member by the tensile force (F ₁₎ (F ₃₎ is ,
Moved to the first pivot position where the balance member is unlocked by being defeated by a centrifugal force (F ₂ ) that moves the balance member toward the first pivot position. The balance member is moved to the first pivotal position in response to the length of the outer end portion (31, 212) being shortened to lock the spool. At all stages when the spool is released and the spool is rotating with respect to the head, the spool moves to the cam surface (84, 88; 92, 9).
6) a centrifugal force (F ₂ ) that slows the movement due to friction and moves the balancing member towards the first pivoted position while the cutting rope is being pulled out of the spool.
To maintain the force (F ₃ ) exerted on the balance member by the tensile force (F ₁ ) against the force, and the tension is maintained in the cutting rope at all stages in which the cutting rope is pulled out. A plant cutting device.