GB2191138A - Pruning shears - Google Patents

Abstract

Pruning shears comprise first and second handles 12, 14 pivotally connected at 32, and having respectively gripping ends 16, 18 and mounting ends 20, (22 Figure 1). A cutting blade 26 is carried by the first handle 12 on the mounting end (22) and an anvil member 24 is pivotally connected 34 to the mounting end (22) of the second handle 14. The anvil member 24 includes an arcuate cam slot 36, with the two ends 38, 38' of the slot 36 extending radially outwardly relative to the surface 30 of the anvil 24 positioned opposite the cutting surface 28 of the cutting blade 26. A cam follower 40 is carried by the first handle 12 and extends within the cam slot 36 whereby pivotal movement of the handles 12, 14 relative to each other produces relative movement between the cam follower 40 and cam slot 36. This results in the anvil moving along the cutting blade 26 as the handles are moved towards each other, so that the surface 30 is substantially parallel to the cutting surface 28 during a substantial portion of the cutting stroke. The anvil has a serrated angled end portion to retain e.g. a branch being cut. <IMAGE>

Description

SPECIFICATION Pruning shears This invention relates to cutting devices such as pruning shears our similar lopping shears and in particular, to shears having an amplified cutting force.

Pruning or lopping shears are employedforcut- ting twigs, small branches and other difficult-to-cut objects. Such cutting devices generally comprise two cutting elements, one a blade member and the other an anvil member. The two members move toward and away from one another to sever an object placed between them. If the blade and anvil members are to cooperate successfully, their relative alignment must be closely controlled during the cutting operations.

When the blade and anvil members are substantially parallel with one another, the cutting force developed bysuch members is at its maximumeffectiveness. Heretofore, complex linkages have been used to obtain parallel relationship between the anvil and cutting members. Further, to increase the cutting force, force multiplying arrangements have been used. Typically, such force multiplying arrangements utilizerelatively complex linkage connectionsto obtain the force multiplying effect. Either the cutting blade oranvil,typicallythe anvil, is urged longitudiallyforward while moving toward the other of the cutting members to increase the cutting force.

Although pruning shears utilizing complex linkages to increase the cutting force and achieve a parallel relationship between the cutting and anvil members have improved cutting performance, the relatively intricate linkage mechanisms not only increase the cost of the pruning shears but also make them more susceptible to breakage.

It is accordingly an object ofthe invention to amplify the cutting force and achieve a parallel relationship between the cutting blade and anvil during the cutting stroke without using relatively complex linkage arrangements.

The foregoing object and other objects of the invention are obtained in a pruning shears comprising first and second pivotally connected handles, each of the handles having a gripping end and a mounting end; a cutting blade having a cutting surface carried by the first handle on the mounting end thereof; an anvil member pivotally connected to the mounting end of the second end ofthe second handle and including a cooperating surface facing toward the cutting surface of the cutting blade; means defining an arcuate cam slot formed in a selected one of the anvil and thefirst handle, with the two ends oftheslotex- tending radially outwardly relative to the cooperating surface; and means defining a cam follower carried by the other of said first handle and said anvil and extending within said cam slot, with pivotal movement ofthe handles relative to each other producing relative movement between the cam follower and cam slot, the end of the anvil facing toward the gripping end ofthe second handle moving axially towards said second handle mounting end as the cutting and cooperating surfaces are moved toward each other.

Figure lisa plan view of a pruning shears in accordance with the present invention, with the pruning shears being in a closed position; Figure2isaviewsimilarto Figure 1,withthe shears being in a partially open position; Figure 3 is a viewsimilarto Figures 1 and 2 with the shears in a fully open position; and Figure 4is an isometric view ofthe cutting portion of the shears.

Referring to the figures of the drawing, there is disclosed a preferred embodiment ofthe present invention. In referring to the various figures of the drawing, like numerals shall referto like parts.

Pruning shears l0generallycomprisesafirst handle 12 and a second handle 14, each of the handles have gripping ends, respectively 16 and 18, for manual manipulation byan operator. Each ofthe handles also have mounting ends respectfully 20 and 22.

The handles are pivotally connected via pivot pin 32. Cutting blade 26 is carried on mounting end 20 of first handle 12. In the preferred embodiment, the handle and cutting blade form a unitary structure.

Anvil member 24 is carried on mounting end 22 of second handle 14. Anvil member 24 is pivotally attached via pivot pin 34to handle 14for reasons two be more fully explained hereinafter.

Cutting blade 26 has a cutting surface 28 facing towards cooperating surface 30 of anvil member 24.

The opposed cutting and cooperating surfaces are moved towards each other during the cutting stroke of shear 10.

Anvil member24 includes an arcuate cam slot 36.

Thetwo ends 38 and 38' of slot 36 extend radially outwardly relative to cooperating surface 30 of anvil 24. It should be notedthatthe diameter of end 38 is slightly smallerthan the diameter of end 38'.

Acamfollower40 is carried by first handle 12 between the gripping and mounting ends thereof. Cam follower40 extends within cam slot 36. The diameter of cam follower 40 is slightly less than the diameter of slot36whichenablestheanvil membertomove slightly in a lateral direction. When the handles are in the position illustrated in Figure 3, cam follower40 is located atthe upper end 38' ofslot 36. The follower is located atthe bottom end 38 of slot 36 when the handles are in the position illustrated in Figure 1 .As the handles are brought toward each other during the cutting stroke, the cam follower moves down wardlywithin slot 36 as illustrated by Figure 2. Anvil member 24 terminates in a nose portion 42 having a serrated article engaging surface 44 facing cutting surface 28 of blade 26.

During the cutting stroke, the handles are initially in the position as illustrated in Figure3,whereby blade 26 and anvil member 24 are in their extreme open position with respect to each other. In the open position, the shears is capable of accepting an article, such as a branch of a tree, to be cut or pruned.

It is recognized that the most effective cutting force is developed when cutting surface 28 is parallel to cooperating surface 30. Heretofore, rather complex and relatively expensive link mechanisms have been used to achieve the parallel relationship between the opposed cutting surfaces at a relatively early period in the cutting stroke. The present invention achieves such parallel relationships at approximately the midpoint of the cutting stroke and maintains the same until the cutting stroke is completed. The foregoing is illustrated in Figures 2 and 3. The parallel relationship is achieved between cutting surface 28 and cooperating surface 30 through cooperation of cam slot36 and cam follower40. In particular,thegenerally arcuate cam slot moves relative to the camfollower and is guided thereby.As the gripping ends of handles 12 and 14 are broughttoward each other, the relative motion between the cam slot and cam follower provides a force to move anvil member 24 laterally to achieve the parallel relationship between the opposed cutting and cooperating surfaces.

In addition, as the handles are moved toward each other during the cutting stroke, the end of anvil member 24facing toward gripping end 18 of second handle 14 moves axiallytowardsthe second handle mounting end 22 carrying with it pivot pin 34 about which the anvil rotates. In effect, the movement of pivotpin34axiallyawayfromthegripping end in- creases the mechanical advantage of the pruning device to thus multiplythe cutting force.

By including serrated article engaging nose portion 42 facing toward the cutting surface of the cutting blade, additional means has been provided to prevent the article being cut from being displaced during the cutting stroke.

By enabling anvil member 24to move a limited distance laterally with respect to the cutting blade, a self-compensating feature has been added which compensates for wear of the anvil during normal use ofthe shears. The limited lateral movement occurs during the cutting stroke dueto the diametrical dif- ference between the cam slot and cam follower.

The present invention provides relatively inexpensive and non-complex means for increasing the mechanical advantage of a shears during the cutting stroke, and in addition, achieves a generally parallel relationship between the cutting blade and cooperating surface ofthe anvil at a relatively early point in the cutting stroke.

Claims (9)

1. Apruning shears comprising: first and second pivotally connected handles, each ofsaid handles having a gripping end and amount- ing end; a cutting blade having a cutting surface carried by said first handle on the mounting end thereof; an anvil member pivotally connected to the mounting end of said second handle and including a cooperating surface facing towards said cutting surface of said cutting blade; said anvil member including an arcuate cam slot, with the two ends of said slot extending radially outwardly relative to said cooperating surface; and a cam follower carried by said first handle between said gripping and mounting ends and extending within said cam slot, with pivotal movement of said handles relative to each other producing relative movement between said cam follower and said cam slot, the end of said anvil facing towards said gripping end of said second handle moving axially tow- arts said second handle mounting end as the cutting and cooperating surfaces are moved toward each other.

2. A pruning shears in accordance with claim 1 wherein the cam follower is a pin extending form said first handle into said cam slot.

3. A pruning shears in accordance with claims 1 or 2 wherein said anvil includes a serrated article en gaging nose portion joined at the end thereof and facing towards the cutting surface of said cutting blade.

4. A pruning shears in accordance with claim 2 wherein the diameter of the pin is slightly smaller thanthewidth ofthecam slot along substantiallythe entire length of said slot to permit said anvil member to move laterally relative to said cutting blade.

5. Apruning shears comprising: first and second pivotally connected handles, each of said handles having a gripping end and amount- ing end; a cutting blade carried by said first handle on the mounting end thereof and including an inwardlyfacing cutting surface; an anvil member pivotally connected to the mounting end of said second handle and including a cooperating surface facing towards said cutting surface of said cutting blade; means defining an arcuate cam slot formed in a selected one of said anvil and said first handle, with the two ends of said slot extending radially outwardly relative to said cooperating surface; and means defining acamfollowercarried bytheother ofsaid first handle and said anvil and extending within said cam slot, said cam follower and said cam slot being positioned towards the gripping end of said handles relative to the pivotal connection between said second handleandsaidanvil,thegrip- ping ends of said handles being moved toward each other during cutting operation of said shears resulting in the anvil member moving generally axially outwardly so the cooperating surface thereof is substantially parallel to the cutting surface of said blade during a substantial portion of the cutting stroke of said shears.

6. A pruning shears in accordance with claim 5 wherein the cam follower is a pin extending from said first handle into said cam slot.

7. A pruning shears in accordance with claims 5 or 6 wherein said anvil includes a serrated article engaging nose portion joined at the end thereof and facing towards the cutting surface of said cutting blade.

8. A pruning shears in accordance with claim 6 wherein the diameter ofthe pin is slightly smaller than the width of the cam slot along substantially the entire length of said slotto permit said anvil member to move laterally relative to said cutting blade.

9. A pruning shears substantially as hereinabove described with reference to and as shown in the accompanying drawing.