GB2040210A - A portable power cutting device - Google Patents

Abstract

A portable power cutting device comprises a movable cylinder (2) disposed within a cylindrical body (1) so as to be reciprocally driven by a crank mechanism operatively connected to a gasoline engine (5a) or an electric motor mounted to the cutting device, a free piston (6) reciprocable within the movable cylinder, the free piston having a projection (9) which is operatively projectable out of an end opening of the movable cylinder, a slide rod (15) disposed within a holder (10) mounted to the front portion of the cylindrical body (1) so that the slide rod is percussively struck at its rear end by the forward end of the projection (9), a knife-edge cutting tool (18) secured to the slide rod, an upwardly extending suspender (20) pivotally mounted to a rear portion of the cutting device and an upwardly extending grip handle (22) mounted to a front portion of the cutting device. <IMAGE>

Description

SPECIFICATION A portable power cutting device This invention relates to a portable power cutting device, particularly for use with plants, and more particularly to a one-hand manipulatable cutting device for cutting branches of trees, leafstalks and/or fruiting stems of tropical plants such as palms, and the like.

The conventional power cutting device is normally provided with either a rotary blade or a chain saw.

The rotary saw blade type device now available must be carried and manipulated by both hands of an operator, and therefore it is very difficult or dangerous for an operator to climb up a ladder or the like with the device in order to cut off the branches or the like. On the other hand, although some of the chain saw type devices now available are so designed as can be carried and manipulated by a single hand of the operator, it has such a disadvantage that, when the saw blade must be applied to a branch from its under side, the saw blade is pressed down with such a great force of gravity developed at a severed section of a half-cut branch having a number of twigs, leaves, or fruits, that the chain is often prevented from its running motion, resulting in interruption of the cutting operation.

It is an object of the present invention to provide a power cutting device which overcomes the above problems.

With this in view, according to the present invention, there is provided a portable power cutting device comprising a cylindrical body having a reciprocally driven movable cylinder disposed therein, a free piston disposed within said movable cylinder and formed with a projection operatively projectable out of an end opening of said movable cylinder, a tool holder mounted to the forward end of said cylindrical body, a slide rod reciprocable within said holder, the rear end of said slide rod being arranged so as to be percussively struck by the forward end of said projection, a knife-edged cutting tool secured to said slide rod, a suspender pivotally mounted on a rear portion of the cutting device and adapted to be supported on an operator's forearm, and a grip handle mounted on a front portion of the cutting device.

Afeature of the invention is to provide an improved handy type of power cutting device in which a cutting tool is not prevented from its operating motion by a force of gravity of a half-cut branch of a tree.

Embodiments of this invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a side elevation, partially in section, of a portable power cutting device; Figure2 is a similarviewto Figure 1, but showing another embodiment of the invention; Figure 3 is an enlarged, fragmentary cross sectional end view taken along the line Ill-Ill of Figure 2; Figure 4 is a side elevation showing a further modified embodiment of the invention; Figure 5 is a similar view to Figure 4, but showing a further modification of the invention, and, Figure 6is a schematic illustration showing operation of the device according to the invention.

As shown in Figure 1,the power cutting device of the invention has a cylindrical body 1 within which a movable cylinder 2 is disposed so as to slidably reciprocate. The body 1 is connected at its rear end to a casing 3 within which a known crank mechanism (not shown) is disposed. Said movable cylinder 2 is operatively connected at one end to said crank mechanism by means of a known connecting rod 4.

A power source, preferably in the form of a known light weight gasoline engine 5a, is mounted for example to the under side casing 3, so that the driving power from the engine can be transmitted through the crank mechanism to the movable cylinder 2. The gasoline engine 5a may be replaced, if desired, by a known electric motor 5b as shown in Figure 5.

Within the movable cylinder 2, a free piston 6 is disposed so as to slidably reciprocate at a considerable high speed under the known function of compressed air confined in a pair of air chambers 7, 8. The free piston has a cylindrical projection 9 which is operatively projectable out of an end opening formed in the free end 2a of the movable cylinder 2.

The construction and arrangement of such air chambers and the free piston per se are known and not an important feature of the invention, the detailed description thus being omitted herein.

Atool holder 10 having a cylindrical outer surface 11 is connected to the forward end of the body 1. The tool holder 10 is formed with an axial bore 12 having polygonal shape, for example, a hexagon, in cross section and extending through the entire length of the holder 10. The holder 10 may preferably be connected, for example, by means of a flanged boss 13 engageable with an annular shoulder 14 of the holder, to the body 1 so as to slidably rotate about the longitudinal axis of the body. It is obvious, however, that the holder may be fixedly secured to the body 1 so as not to rotate.

Within the holder 10 there is disposed a slide rod 15 having a polygonal cross section corresponding to the polygonal section of said bore 12, so that the rod 15 is axially slidable but not rotatable within the holder. Preferably, the rod 15 may be so arranged that the reciprocal sliding movement thereof may be restricted by cooperation of a cross pin 16 fixed internallyofthe holderwith an axial recess 17 formed in the rod 15. The rear end of the rod 15 is so arranged that it can be percussively struck by the forward end of the projection 9 of the free piston 6 as it reciprocates.

To the forward end of the slide rod 15 is secured a cutting tool 18 having a knife edge 19 which extends transversely of the longitudinal axis of the rod 15.

Otherwise, the knife edge 19 may extend obliquely with respect to said longitudinal axis. It is obvious that the construction of the cutting tool 18 may be varied in many ways and, therefore, should not be limited to the specific construction and arrangement as illustrated in the accompanying drawings.

A suspender 20, by means of which the cutting device can be supported by an operator's forearm, is pivotally connected at its ends to the casing 3 by means of pins 21. The suspender may be formed in various ways, but it should be designed so that one forearm of the operator can pass through the inside thereof and be comfortably engageable with the operator's forearm art a position adjacent to the bend of his arm, as particularly shown in Figure 6. For example, the suspender 20 may be in the form of an inverted U-shaped member 20a as shown in Figure 1 and 2, or otherwise it may be in the form of a hook 20b pivotally connected at one end to the casing 3 by means of a pin 21 as shown in Figure 4.The suspender 20 may also be in the form of a tubular member 20c pivotally mounted to the casing 3 so as to turn about a pin 21 as shown in Figures.

An upright grip handle 22, preferably slightly inclined forwardly, is rigidly secured to the holder 10, so that the operator can manipulate the handle to make the holder relatively rotate about its axis with respect to the body 1 in order to change the angle of the cutting tool 18, as shown in Figure 1. The distance between the handle 22 and the suspender 20 should be so determined as to be substantially equal to the length of an operator's forearm. It is also possible to fix the holder 10 to the body 1 so that the former does not relatively rotate with respect to the latter. The grip portion of the handle 22 may preferably be provided at its top with a flange 23 for preventing the operator's hand from slipping off the grip portion.

As shown in Figures 2 and 3, the grip handle 22 may be mounted on an extension 1a of the cylindrical body 1. In this case, the handle has a threaded shaft 24 which is engaged with a threaded hole 25 formed in a wall of said extension 1 a, so that, when the shaft 24 advances by threads, its forward end comes into tight contact with the external wall of the holder 10 for restricting the relative rotation of the holder. If desired, the forward end of the threaded shaft 24 may have a contact pice 26 secured thereto as best shown in Figure 3. Thus, when the contact piece 26 is not in contact with the holder 10, the same is permitted to rotate about its axis to a selected angular position of the cutting tool 18.

While the contact piece 26 is in tight contact with the holder, the handle is locked at a selected angular position.

As shown in Figure 4, the handle grip 22 may be carried by a tubular slide member 27 which is axially slidably mounted on a cylindrical body 1. In this embodiment, the grip handle 22 has a threaded shaft 24 whose end is engageable and disengageable with the external wall surface of the body 1 in the substantially same manner as described in the foregoing with reference to Figure 3. Thus, the distance between the grip handle 22 and the suspender 20 can be axially adjusted with the result that the operator can select his most apropriate distance in accordance with the length of his forearm.

As shown in Figure 5, the grip handle 22 with a threaded shaft 24 may be carried by a tubular slide member 27' which is axially slidably mounted on the holder 10 substantially in the same manner as described, so that the distance between the grip handle 22 and the suspender 20 is axially adjustable in accordance with the length of the operator's forearm. In this embodiment, it should be noted that the electric motor 5b is employed in place of the gasoline engine 5a, wherein the known crank mechanism and the motor Sb may be housed within a single casing 3', as shown in Figure 5. Reference numeral 28 in Figure 5 designates a known electric cable connected to an external power source.

In operation, the operator supports the cutting device by suspending it with his forearm A by means of the suspender 20 while grasping the handle grip 22 with his one hand R, as particularly shown in Figure 6. The operator on the ladder F or the like can hold a tree Twith his other hand L in order to secure his safety. When the cutting device is supported in this way, the operator's forearm A is substantially in parallel with the longitudinal axis of the cutting device because of the specific arrangement of the suspender 20 and the grip handle 22 as described.

Further, the forearm A is positioned close to the cutting device. Thus, the operator can easily manipulate the device, resulting in that he can apply the knife edge 19 of the tool 18 quite correctly to the base of a branch B to be cut off.

The power from the engine 5a or the motor 5b is transmitted through the known crank mechanism to the movable cylinder 2 so that the cylinder 2 is reciprocated within the cylindrical body 1. Under the known function of the compressed air within the air chamber 7, 8, the free piston 6 is forcibly reciprocated within the movable cylinder 2, so that the forward end of the projection 9 of the piston 6 imparts percussive impact forces repeatedly to the rear end of the slide rod 15 disposed within the holder 10. Thus, the branches, leafstalks, fruiting stems or trees or the like can be cut off by the knife edge 19 of the cutting tool 18 quite efficiently.

Claims (9)

1. A portable power cutting device comprising a cylindrical body having a reciprocally driven movable cylinder disposed therein, a free piston disposed within said movable cylinder and formed with a projection operatively projectable out of an end opening of said movable cylinder, a tool holder mounted to the forward end of said cylindrical body, a slide rod reciprocable within said holder, the rear end of said slide being arranged so as to be percussively struck by the forward end of said projection, a knife-edged cutting tool secured to said slide rod, a suspender pivotally mounted on a rear portion of the cutting device and adapted to be supported on an operator's forearm, and a grip handle mounted on a front portion of the cutting device.

2. A portable power cutting device as claimed in Claim 1, wherein said slide rod is not rotatable about its axis relatively to the holder.

3. A portable power cutting device as claimed in Claim 1 or Claim 2, wherein said holder is rotatable about its axis relatively to the cylindrical body.

4. A portable power cutting device as claimed in Claim 1 or Claim 2, wherein said holder is nonrotatably secured to said cylindrical body.

5. A portable power cutting device as claimed in Claim 1, Claim 2, Claim 3 or Claim 4, wherein said grip handle is mounted to said cylindrical body.

6. A portable power cutting device as claimed in Claim 5, wherein said grip handle is carried by a slide member axially slidably mounted on said cylindrical body.

7. A portable power cutting device as claimed in Claim 1, Claim 2, Claim 3 or Claim 4, wherein said grip handle is mounted to said holder.

8. A portable power cutting device as claimed in Claim 7, wherein said grip handle is carried by a slide member axially slidably mounted on said holder.

9. A portable power cutting device substantially as hereinbefore described, with reference to and as illustrated in any of Figures 1 to 5 of the accompanying drawings.