US2722740A

US2722740A - Pruning tool

Info

Publication number: US2722740A
Application number: US495119A
Authority: US
Inventors: Robert L Hubbard
Original assignee: Individual
Current assignee: Individual
Priority date: 1955-03-18
Filing date: 1955-03-18
Publication date: 1955-11-08
Anticipated expiration: 1972-11-08

Description

Nov. 8, 1955 R. L. HUBBARD PRUNING TOOL 2 Sheets-Sheet 1 Filed March 18, 1955 l l l I I WM. 51!

INVEN TOR. F055 1. M49 5422 Nov. 8, 1955 R. L. HUBBARD 2,722,746

PRUNING TOOL Filed March 18, 1955 2 Sheets-Sheet 2 1 W W P J w my Qm Q Q L M v r v; H mm N 7 R w m\ hm wm w United States Patent PRUNING TOOL Robert L. Hubbard, Florham Park, N. J.

Application March 18, 1955, Serial No. 495,119

Claims. (Cl. 30-180) This invention relates to devices for one-stroke cutting of small limbs and the like and for pruning trees and shrubbery, and in particular it relates to such devices that are hand operated.

An object of this invention is to provide an improved pruning tool which is lightweight and simple in construction and operation.

Another object is to provide such a tool which can With ease cut through relatively large and tough tree limbs.

In cutting tree limbs or shrubs which are high or difficult to reach it is desirable to have a quick acting, onestroke cutting tool which is so compact and light-weight that it can be mounted on a long extension pole without becoming unwieldy. It thus may be brought within cutting distance of remote or lofty limbs by an operator standing on the ground. However, in the past, such cutting tools were of such low power that they were not much help or else they were complicated, bulky, and/or expensive. The present invention therefore seeks to provide a high power, lightweight and inexpensive pruning tool.

In accordance with the present invention, in one specific embodiment thereof, an improved hydraulic cylinder of long, thin configuration is built into the frame of a cutting tool and controlled by a relatively light hand pull to exert a tremendous pressure on a knife blade to move it against an anvil in the process of cutting a limb or the like. Because of the advantageous arrangement of the parts of this tool, a minimum number of parts is needed and these are simple and easily assembled. Accordingly the tool is lightweight and inexpensive.

A more complete appreciation of the many advantages of this invention together with a better understanding of its general nature will best be gained from a study of the following description given in connection with the accompanying drawings in which:

Figure 1 is a longitudinal sectional view of the top part of a cutting tool embodying features of the present invention, showing the knife blade and anvil together with the upper portion of the hydraulic cylinder;

Figure 2 is a longitudinal sectional view of the middle part of the tool, showing the lower part of the hydraulic cylinder and the hand operated mechanism for controlling the cylinder;

Figure 3 is a side elevational view of the bottom part of the tool; and

Figure 4 is a longitudinal sectional view of the top part of the tool taken on the lines 44 in Figure 1.

Figure 1 shows the head 11 of a cutting tool 10 having a long tubular frame 12 which extends the length of the tool. Head 11 consists of an anvil 14 screwed to the top end of the frame and a knife blade 16 adapted to move along the axis of the frame toward and away from the limb supporting surface 17 of the anvil. (Blade 16 is shown advanced into contact with surface 17.) This blade is fixed by means of screw 18 and plug 19 (see Figure 4) to a hollow cylinder 20 which fits slidably within the end part of frame 12 and forms the piston for the hydraulic chamber 22. Fluid within this chamber is prevented from leaking through or past cylinder 20 by a plug 24 which carries a sealing ring 25. Plug 24 is force fitted into the lower end of the cylinder 20 and supports at its inner end a compression spring 26. The other end of this spring pushes against pin 28 which passes through two slots 30 in cylinder 20 and through frame 12 and the lower part of anvil 14, the pin being securely fixed to these last two members. Thus when the pressure in chamber 22 is released, spring 26 pushes cylinder 20 downward and retracts blade 16 from anvil 14. Cylinder 20 and blade 16 are kept in alignment with anvil 14 by this pin 28 riding in slots 30.

Fluid pressure within chamber 22 is raised by the advance upward of plunger 32. This plunger is a solid rod having a diameter substantially less than the diameter of chamber 22 and a length great enough so that when moved into chamber 22, blade 16 can advance from its back limit into contact with surface 17.

As seen in Figure 2, the lower part of plunger 32 passes through the center of the neck portion 34 of a housing 36 which is tightly and firmly fitted within the end of frame 12. Sealing rings 37 and 38 prevent leakage of fluid from chamber 22 through or around shoulder 34. Housing 36 receives and tightly grips the end of tube 13 which serves as a continuation of frame 12. A filler plug 39 screwed through the wall of frame 12 provides a simple means of filling chamber 22 with a suitable hydraulic fluid.

The bottom end of rod 32 is bifurcated and carries a pulley 41) around which rope 42 passes. One end of the portion of this rope passing around pulley 40 is attached by means of a bushing assembly 44, having mating inner and outer sleeves and extending through housing 36 and tube 13, to the frame of the tool. The other end of the rope passes around a second pulley 46 which is mounted on housing 36. As seen in Figure 3, this end of the rope continues outside the tube 13 to an anchor point 47 near the bottom end of the tube to which, for convenience, it is afiixed. A handle 48 which provides a grip for the operators hand is attached to the rope at a suitable place above point 47. The bottom end of tube 13 is fiared to permit the insertion of a like diameter extension arm if desired.

By pulling down on rope 42, rod 32 is pushed upward into chamber 22 and as it advances, because of the pressure exerted on plug 24, cylinder 20 is forced upward. In this movement, for each 1" upward advance of rod 32, rope 42, because of the arrangement of

pulleys

40 and 46, must move downward 2", i. e. twice the distance rod 32 moves. The volume of chamber 22 remains substantially constant, however, and therefore a given pull on rope 42 is translated into a force twice (this factor of two resulting from the ratio of movement of rope 42 to rod 32) the ratio of the cross-sectional area of plug 24 to the crosssectional area of rod 32. Thus, for the parts of tool 10 proportioned as shown, a 50 pound pull on rope 42 becomes approximately a half ton force pushing knife 16 against anvil 14. When the pull on rope 42 is released, spring 26 acts to return knife 16 to its back position in which the tool is ready to make another cut.

In the above described embodiment frame 12 can, if desired, be made of one continuous length of tubing instead of being formed from two lengths as shown. In addition to this change other changes or modifications may occur to those skilled in the art and these changes and/ or modifications can be made without departing from the spirit or scope of the invention as set forth.

I claim:

1. A pruning tool comprising an elongated tube a portion of whose inside volume forms the chamber of a hydraulic cylinder, a piston slidable within said hydraulic cylinder and projecting through the upper end thereof, a knife blade carried by said piston, an anvil support opposing said knife blade and fixed to the upper end of said tube, and a rod slidable into the chamber of the cylinder from the outside thereof through the lower end thereof to create in said cylinder a pressure sufficient to move said piston and said knife blade toward said anvil support.

2. The combination of elements as in claim 1 in which said rod moves into the chamber in a direction substantially parallel to the axis of said tube and carries on its outer end a rope and pulley lift by which it can be advanced into the chamber.

3. A light, hand-operated pruning tool comprising a tube a portion of whose inside volume is adapted to be the liquid filled chamber of a hydraulic cylinder, a piston slidable inside the upper end of said tube and forming a movable part of the hydraulic cylinder, a knife blade adapted to be moved by said piston, a member opposite said knife blade for holding in conjunction with said blade an object for cutting, means including a spring for retracting said knife from said member, means including a constriction in said tube spaced a distance from the upper end thereof to make the cylinder liquid-tight, and means including a thin rod-like member slidable into the chamber of the cylinder from the outside thereof through said constriction to move said piston, the amount of liquid in said chamber remaining constant throughout this movement.

4. The combination of elements as in claim 3 in which said member opposite said knife blade is fixed to said tube, said means including a spring for retracting also includes a pin fixed to said tube, and one end of said spring pushes against this pin and the other pushes against said piston.

5. In a light hand-operated pruning tool having a long thin frame, a cutting head comprising: a hollow core piston slidable axially in the end of the frame and forming a movable part and the upper end seal of a hydraulic cylinder within the frame, a knife blade carried by said piston, an anvil fixed to the frame and having a supporting surface across the line of advance of said blade, a pin fixed to the frame and passing through an elongated slot in said piston, and a compression spring within the hollow core of said piston pushing against said pin and against said piston to move said blade away from said anvil supporting surface.

6. In a light hand-operated pruning tool having a cutting head, a tubular frame, a piston slidable in the upper end of said frame and forming a movable part and the upper end seal of a hydraulic cylinder extending along an inside portion of the length of said frame, a constriction spaced within said frame a distance below the upper end thereof and forming a portion of the bottom end seal of the hydraulic cylinder, a thin rod-like member movable within said frame along the axis thereof through said constriction into and out of the hydraulic cylinder, handactuated means including a low friction member carried on the end of said rod-like member a low friction member carried by said frame and a flexible cord engaging said low friction members for moving said rod-like member into the hydraulic cylinder thereby to actuate the cutting head of said tool, the volume of the hydraulic cylinder remaining substantially constant.

7. The combination of elements as in claim 6 in which said low friction members are pulleys, and said flexible cord is fixed to said frame at one end, passes around said pulley carried by said rod-like member, then around said pulley carried by said frame, thence along the outside of said frame where it is adapted to be pulled by an operator of said tool.

8. The combination of elements as in claim 6 in which said constriction is an annular plug with a small central opening and is tightly fitted within said frame, and said rod-like member is slidable through the small central opening farther into or farther out of the hydraulic cylinder.

9. The combination of elements as in claim 8 in which said annular plug is an integral part of a housing fixed to said frame, and said frame is in two pieces joined together by said housing.

10. A pruning tool comprising a tubular frame, a hollow core piston slidable in the upper end of said frame and forming a movable part and the upper end seal of a hydraulic cylinder extending along an inside portion of the length of said frame, a housing having an integral neck portion fitted within the inside of the lower end of said frame said neck portion having a small opening parallel to the axis of said frame, a knife blade carried by said piston, an anvil fixed to the upper end of said frame and having a surface across the line of advance of said blade, a pin fixed to said frame and passing through a pair of elongated slots in said piston, a compression spring within the hollow core of said piston pushing against said pin and against said piston to move said blade away from said anvil surface, an extension mem-,

ber fitted within said housing along the axis of said frame and forming a continuation thereof, a thin rod slidable within said extension member through the opening in said neck portion farther into and farther out of the hydraulic cylinder, at first pulley carried on the end of said rod, a second pulley carried by said housing, and a rope attached to a fixed point at a place above said first pulley and passing down around said first pulley, up and around said second pulley and down the outside of said extension member.

No references cited.