GB2210241A - Knife for a cutting mechanism of an agricultural machine - Google Patents

Description

a 1 KNIFE FOR A CUTTING NECHAN15N OF AN AGRICULTURAL MACHINE 2210241 The

invention relates to cutting mechanisms for agricultural machines preferably used for cutting coarse-stem and shrubbery plants such as tea plants, and in particular, it deals with a knife for a cutting mechanism of such machines.

Wht in desired Is a knife having'blades which would reduce torces of resistance of the wood of branches being cut through during cutting with an increase in the depth and width of cut. It should also be possible to lower power requirements and reduce deformation of wood in cutting.

The present invention provides a sectional knife for a cutting mechanism of an agricultural machine. having upper and lower faces. blades having a curvilinear profile of cutting edges each being defined by intersection of side and lower chamfers. a base or body, and a tip; the blades are of a varying thickness lengthwise. the thickness increasing gradually from the tip towards the base.

According to an embodiment of the invention. the varying thickness of the blade is defined by additional surtaces or planes formed along the outline of the 1 2 blades on the upper face of the knife and inclined with respect to the lower face from the body towards the tip of the section. It is preferred that the additional inclined surfaces or planes define a ridge with the remainder of the upper face.

The provision of the knife blades which are of a varying thickness lengthwise makes it possible.to reduce the height of cut as the blade penetrates the material being cut through (branch) and respectively reduce detormation of wood. As a result. forces of resistance of wood of the branches to deformation by the upper chamfer and forces of friction between wood and upper and lower chamfers. lower and upper faces decrease, thus lowering power requirements for branch cutting.

The formation of a ridge makes it possible to ensure rigidity of the knife in the transverse plane, thereby avoiding collision of edges of the blade of the cutting knit% and anvil sections in the cutting mechanism.

The above features of the sectional knife in comparison with prior art section knives allow the energy consumption of branch cutting to be substantially reduced so that. at the end of the day, the use of the knife in cutting mechanisms makes it possible to employ a drive of minimum power.

The invention will now be described further. by way of example. with reference to the accompanying drawings, in which:

1 A 3 Figure 1 shows a plan view of a knife; Figure 2 is a front elevation view of the knife; Figure 3 is a plan view of another embodiment of the knife; Figure 4 is a front elevation view of the knife of Figure 3; Figure 5 is a side elevation view of the knife of Figure 3. partly in section; and Figure 6 shows a partial view of a.cutting mechanism having knives according to the invention.

A sectional knife for a cutting mechanism of an agricultural machine has a tip 1 (Figure 1), a body 2. a carrier or rear extension 3. upper and lower parallel faces 4 and 5. respectively (Figure 2), and blades 6 and 7 with a curvilinear profile of their cutting edges 8 and 9. respectively.

The cutting edge 8 of the blade 6 is defined by a side chamfer 10 and a lower chamfer 11, and the cutting edge 9 of the blade 7 is defined by a side chamfer (upper chamfer) 12 and a lower chamfer 13.

The blades 6 and 7 are of a varying thickness lengthwise. the thickness gradually increasing from.the tip towards the body 2. i.e. from a thickness h to a thickness h 1 The knife way be made with the blades 6 and 7 of a varying thickness in different manners, including that shown in Figures 3 to 5, i.e. with the upper face 4 of 4 the knit% having additional planes 14 and 15 extending along the outline of the blades 6 and 7, respectively, Inclined with respect to the lower face 5 from the body 2 towards the tip 1. The additional planes 14 and 15 define a ridge 16 with the upper face 4 of the knife.

The knife is used in a cutting mechanism of an agricultural machine. The cutting mechanism consists of an anvil knife 17 (Figure 6) with sections 18 and knives 19 according to the invention which are movably mounted on the anvil knife 17 by pins 20 and which are connected to the anvil knite 17 by means of pins 21. The anvil knife 17 has longitudinally extending slots 22 at points where the pins 20 are located. and a transversely extending slot 23 is provided in the body 2 and rear extension 3 of each knife 19.

The knives 19 and the anvil knife 17 are mounted on a beam 24 having its pins.20 which are received in the longitudinally extending slots 22 of the anvil knife 17 and in the transversely extending slots 23 of the knife 19. The sections 18 (hereinafter referred to as the anvil sections) have upper and lower parallel faces and cutting blades with a curvilinear profile of cutting edges 25 and 26 which are defined in a conventional manner by side chamfers and the lower face.

Reciprocations of the anvil knife.17 (Figure 6) under the action of a drive mechanism (not shown in Figure 6) are transmitted through the pins 21 to the 1 rear extensions 3 of the knives 19 and are transformed by acans of the pins 20 secured to the beam 24 into an oscillatory motion of the knives 19.

The longitudinally extensing slots 22 of the anvil knit% 17, In coabination with the transversely extending slots 23 of the knives 19. ensure reciprocations of the Rections 18 of the anvil knife 17 and the opposite illatory motion of the knives 19. which engage and sci cut off branches that come into the gaps between the respective anvil sections 18 and knives 19.

A branch clamped in the gap between a knife 19 and an anvil section 18 is cut off in the following manner.

The cutting edge 8 of the blade 6 penetrates the wood of the branch to pre-compress layers of the branch wood and to carry out their further cutting at the moment a breaking contact stress is built-up at the cutting edge 8.

Concurrently with the breakage of further wood lyers by the cutting edge 8 of the blade 6, the layers that have been cut through before are defomed by the side chaater 10 and lower chaater 11 of the blade 6 of the knife 19 and by the chamfer of the blade 25 or 26 of the anvil section 18. As the blade 6 penetrates the branch being cut through. the chamfer 10 or 11 and, e.g. the cheater of the blade 26 are subjected to the action ot Increasing forces of resistance to compression directed against the direction of their movement and 6 forces of resistance to squeezing directed at right angles to the lower face. The chamfers taking part in cutting are subjected to forces of resistance to deformation of wood which are the sum of components of forces of resistance to compression and forces of resistance to squeezing in the direction of a perpendicular to the chamfers taking part in the cutting process.

Friction forces caused by normal forces of r%uiatoncc to deformation of wood are built up on the Chdaters 10 and 11 and the chamfers of the anvil section 18 the lower face 5 of the knife 19. and the lower face of the anvil section 18 taking part in cutting.

The sum of forces of resistance to deformation of the branch wood at the chamfers 10 and 11 of the blade 6 at this stage is much lower than the force of resistance to deformation of the branch wood at the chamfer of the blade of the anvil section 18. This is caused by the tact that the oscillatory motion of the knife 19. the convex profile of the cutting edge 8, and the configuration of the planes of the chamfers 10 and 11 ensure an increase in the sharpening angle of the blade 6 in the direction towards points of the cutting edge 8. The angle of grinding of the anvil section 18 in the direction of velocity of reciprocations remains unchanged. In addition. the cutting edge 6 simultaneously performs work of destruction of wood 1 7 layers of the branch by the cutting edge 8 and their 4%tormation by the chamfers 10 and 11 along a smaller length than the blade of the anvil section 18. which j due to the convex cutting edge of the knife 19, the concave cutting edge of the anvil section 18. and a convex (circle or elliptical) configuration of the branch in the cross-section. It should be noted that sharpness of the convex cutting edge 8 performing oscillatory motion in the cutting knife 19 decreases during its angular movement. and the sharpness of the concave cutting edge 25 or 26 of the anvil section 18 remains unchanged.

The above-described conditions of operation of the cutting blade 6 of the knife 19 in comparison with conditions ot operation of the cutting blade of the anvil section 18 ensure a reduction of the force of resistance to deformation of the branch wood by the knit% 19. thus determining a greater depth at which the cutting blade 6 penetrates the branch being cut through.

The resultant component of the forces of resistance to squeezing at the chamfers 10 and 11 of the cutting section 19 and the force of resistance to squeezing at the chamfer of the anvil section 18 result in an ite b opposi ending of the parts 19 and 18 in the longitudinally extending vertical planes.

As the blade 6 of the knife 19 penetrates deep into the branch being cut at a depth greater than the width 8 of the chamfer 10. the inclined plane 14 ensures a gradual decrease in the width of the chamfer 10 and thickness of the blade 6 that cuts off the branch. This facility determines a decrease in the height of the cut in the branch as its depth increases.

The decrease In the height of the cut in the branch with an Increase in its depth concurrently with an increase in the length of the cut as determined by the configuration of the blade 6 and cross-section of the branch at the point of cut makes it possible to minimize the volume of deformation of the branch wood during its cutting so as to minimize forces of resistance to compression and squeezing at the chamfer 10 of the blade 6 of the knife 19. Minimizing forces of resistance to compression and squeezing at the chamfer 10 minimizes normal force and results in a decrease in the forces of friction between the wood and chamfers 10 and 11 and faces 4 and 5 as well.

The opposite bending of the knife 19 and sections 18 tt the anvil knits 17 during cutting of the branch, caused by forces of resistance to squeezing. is compensated tor by the distance from the cutting edge 8 to the face 5 of the knife 19 defined by the lower cheater 11 so as to avoid contact between. and crumbling-out of, the cutting edges 8 and 25 or 26.

The width of the inclined plane 14 ensures unsupported cutting of the branch without its being A.

1 Ir f 9 supported during cutting by the ridge 16 which reinforces the knife 19 against bending in the longitudinal vertically extending plane.

Minimizing all reaction forces of resistance at the charAter 10 and 11 of the blade 6 and at the face 5 of the knife 19 makes it possible to cut off the major part of the branch cross-section and lowers energy consumption In cutting branches of shrubbery and coarse-stem plants with a diameter which is greater than the overall width of the wide chamfers of the knife 19 and anvil knife 18.

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Claims (5)

Claims:

1, A knit% tor a cutting mechanism for an agricultural machine. having a body and a tip. upper and lower faces, and blades having cutting edges of curvilinear profile, tach cutting edge being defined by intersection of upper and lower chamfers, the blades being of a varying thickness lengthwise, the thickness gradually increasing from the tip towards the body.

2. A knit% as claimed in claim 1, having additional surfaces extending along the outline of the blades on the upper face of the knife. the additional surfaces being inclined with respect to the lower face from the body towards the tip.

3. A knife as claimed in claim 2. in which the additional surfaces define a ridge with the adjacent part of the upper face.

4. A knife tor a cutting mechanism of an agricultural machine, substantially as described with reference to, and as shown in. Figures 1 and 2 or Figures 3 to 5 of the accompanying drawings.

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5. A cutting mechanism for an agricultural machine.

comprising knives according to any preceding claim mtvohly munted on an anvil knife having sections which cooperate with the knives.

published 198B at The Patent Mce. State HouSe 6671 RiCh Fc;!.-::,r.. London WC1R 4TP Pl=her cepies inay be obtatned Ircn The Patent OffIce.