US3041725A

US3041725A - Hydraulic cutting implement

Info

Publication number: US3041725A
Application number: US105334A
Authority: US
Inventors: Francis B Harries
Original assignee: Individual
Current assignee: Individual
Priority date: 1960-05-02
Filing date: 1961-04-25
Publication date: 1962-07-03
Anticipated expiration: 1979-07-03

Description

July 3, 1962 F. B. HARRIES HYDRAULIC CUTTING IMPLEMENT Filed April 25, 1961 Inventor FRANCIS BERNARD HARRIES Allorney v United States Patent Office 3,041,725 Patented July 3, 1962 HYDRAULIC CUTTING HVIPLEMENT Francis B. Harries, Dirlrchinburg, P.O. Melmoth, Zululand, Union of South Africa Filed Apr. 25, 1961, Ser. No. 105,334

Claims priority, application Union of South Africa May 2, 1960 11 Claims. (Cl. 30180) This invention relates to hydraulic cutting implements suitable for use in pruning.

According to the invention a pruning and cutting implement comprises a cutting head having a cutting blade, an anvil for cooperating with the cutting blade and slidably mounted on the head, a slave hydraulic cylinder fast with the cutting head, a slave plunger within the hydraulic cylinder and cooperating therewith and fast with the anvil, bias means to bias the anvil to an initial position away from the cutting blade, a master hydraulic cylinder hydraulically connected to and of lesser crosssectional area than the slave hydraulic cylinder, a master plunger within the master hydraulic cylinder for cooperating therewith and having a volumetric displacement in the master cylinder of the same order as the 'volumetric displacement of the slave plunger within the slave hydraulic cylinder, whereby hydraulic fluid in the master cylinder is displaceable by the master plunger into the slave cylinder to displace the slave plunger and anvil against the action of the bias means towards a final cutting position wherein the cutting edge of the head is close to the anvil and wherein it performs a cutting action in cooperation with the anvil.

The invention may include one or more of the fol lowing features.

The master cylinder may comprise a tube-having a handle at one end and a sealing gland at the other, and the hydraulic connection between slave and master cylinders may comprise a small bore tube passing through the sealing gland coaxial with the master cylinder and connected to the master plunger to provide a hydraulic connection between slave cylinder and that side of the master cylinder remote from the sealing gland. A guide may be provided fast with the cutting head for defining a linear pathway for the tube in a direction parallel to the tube axis. The guide may be a guide tube coaxial with the master cylinder tube;

There may be provided an anvil stop on the cutting head, and a shoulder on the anvil to cooperate therewith to limit the final position of the anvil to prevent the cutting edge cutting into the anvil. The anvil may have fast with it a pair of diverging wing edges spaced laterally one on either side of the anvil and of the cutting edge.

The cutting head may be of hatchet shape and may comprise a stem on which takes place the slidable mounting of the anvil, and a transverse limb having the cutting edge disposed at an acute angle to the stem.

The cross-sectional area of the master plunger may no a fraction of that of the slave plunger, say about one tenth to one twentieth, and the master and slave cylinders may conveniently be coaxial.

The handle may screw into one end of the bore of the tube and coaxially with it, the opening at the end of the tube forming a filler opening and the handle forming also a hydraulic fluid filler plug for the opening. There may be provided an extension guide having engaging means for engaging with the guide to provide an extended linear pathway further from the cutting head and parallel to the first linear pathway, and a rod cooperating slidably with the extension guide and having a hand grip at a remote end projecting beyond the extension guide and having attachment means at its opposite inner end for attachment to the handle of the master cylinder tube. The extension guide may be an extension tube and the engaging means may comprise a bayonet type of fitting between guide and extension tube, and the attachment means may comprise a male screw thread for engaging with a female thread in the handle coaxially with the master cylinder tube, the handle having a crosssectional shape to engage slidably with the extension tube bore.

Further features will become apparent from the following description of a specific embodiment of the invention with reference to the accompanying drawings.

- in the drawings: 7

FIGURE 1 shows a part sectional side elevation of the head end of an implement.

FIGURE 2 shows a part sectional side elevation of the handle'end of an implement;

FIGURE 3 shows a part underside plan view of the.

implement and corresponding to FIGURE 1; and

FIGURE 4 shows a part sectional side elevation of a modification of the implement.

Referring to the drawings reference numeral 10 refers generally to a cutting head of general hatchet shape and having a transverse part 12 having a cutting blade 14 defining an acute angle with a stem 16 on which is slidably mounted an anvil 18 having a face 20 for cooperation with cutting blade 14. On either side of the face 20 there is provided a wing edge 21 forming a pair of diverging wing edges.

Fast with cutting head 19 there is provided a stop 22 which is adapted to cooperate with shoulder 24 on the anvil to limit the final position of the anvil to prevent the cutting edge 14 bedding into the face 2i) of the anvil during cutting. The anvil has side walls 26 defining a passage through which stem 16 is adapted'to pass slidably. The anvil is attached via slave plunger rod 28 to slave plunger 30' axially displaceable within slave cylinder 32 attached Via stirrups 34 to stem 16 of cutting head 10. The slave plunger 3% and hence anvil 18 are biassed towards an initial position wherein anvil face 20 and cutting blade 14 are apart, by means of helical spring 36.

The chamber 38 of slave cylinder 32 is in connection via tube 40 and small bore tube 42 with chamber 44 inside tube 46 comprising the master cylinder. Handle cum filler plug 48 screws into the end 50 of tube 46, remote from the cutting head 10. The near end 52 of tube 46 has running gland 54 adapted to coact slidably and sealingly with small bore tube 4-2, which is coaxial with tube 46. In side tube 46 there is provided master plunger 56 connected to small bore tube 42.

Fast with the slave cylinder 32 and coaxial with tube 46 there is provided guide tube 58 having a ring guide 60 to receive tube 46 axially slidable within it.

By way of development there may be provided an extension guide tube 62 adapted to cooperate bayonet fashion with lugs 64 provided fast with guide tube 58. There is further provided extension rod 66 adapted to screw into the screw threaded socket 68 of handle 48, and slidable in ring guide 70 in the end of guide tube 62. To the end of rod 66 there is screwed hand grip 72. The bore of extension tube 62 and the cross-sectional shape of handle 48 are such that handle 48 is easily slidable within the bore of extension tube 62.

The working stroke of the slave plunger 30 is conveniently of the order of about 2 to 5 cm. and the working stroke of the master plunger is conveniently about 70 em, but may vary from about 20 cm. to about cm. depending upon the ratio required, and the volumetric displacement of the master plunger in a single working stroke is suflicient to displace the anvil a full working stroke. Accordingly the cross-sectional area of the master plunger is a fraction of the cross-sectional area of the slave plunger.

In operation, the cutting head is positioned such that the branch, twig, or other member to be cut lies between cutting blade 14 and anvil 18. Thercupon, handle 43 connected to tube 46 is pushed home, running gland 54 thereby sliding along small bore tube 42 and plunger 56 being displaced within tube 46, to displace hydraulic fluid in chamber 44 in tube 46 via small bore tube 42 into chamber 33 of slave cylinder 32. Shoulder 24 abuts against stop 22 just before cutting edge 14 beds into face and leaves slight clearance between face 2i and cutting blade 14. A single working stroke of the master plunger is suflicient to cause a full cutting stroke of the slave plunger.

The wing edges 21 locate the anvil in relation to the twig being cut and reduces the tendency for the anvil to be deflected by the grain of the wood being cut.

When a long reach is necessary, the extension guide tube 62 is attached and the rod 66 screwed in. The operation is as before, except that handle 48 is now displaced via hand grip 72.

The implement is stored cutting head downward thus ensuring that any air bubbles in the master cylinder will be at the handle 48 end. The fluid may be easily replenished merely by unscrewing handle 48.

I claim:

1. A pruning and cutting implement comprising a cutting head having a cutting blade, an anvil for cooperating with the "Cutting blade and slidably mounted on the head, a slave hydraulic cylinder fast with the cutting head, a slave plunger within the hydraulic cylinder and cooperating therewith and fast with the anvil, bias means tobias the anvil to an initial position away from the cutting blade, a master hydraulic cylinder hydraulically connected to and of lesser cross sectional area than the slave hydraulic cylinder, a master plunger within the master hydraulic cylinder for cooperating therewith and having a volumetric displacement in the master cylinder of the same order as the volumetric displacement of the slave plunger within the slave hydraulic cylinder, whereby hydraulic fluid in the master cylinder is displaceable by the master plunger into the slave cylinder to displace the slave plunger and anvil against the action of the bias means towards a final cutting position wherein the cutting blade is close to the anvil and wherein it performs a cutting action in cooperation with the anvil.

2. An implement according to claim 1 in Which there is provided an anvil stop on the cutting head, and a shoulder on the anvil to cooperate therewith to limit the final position of the anvil to prevent the cutting edge cutting into the anvil.

3. An implement according to claim 1 in which the anvii has fast with it a pair of diverging wing edges spaced laterally one on either side of the anvil and of the cutting edge.

4. An implement according to claim 1 in which the cutting head is of hatchet shape and comprises a stem on which takes place the slidable mounting of the anvil, and a transverse limb having the cutting edge disposed at an acute angle to the stem.

5. An implement according to claim 1 in which the cross-sectional area of the master plunger is about one tenth of one twentieth of the cross-sectional area of the slave plunger.

6. An implement according to claim 1 in which master and slave cylinders are coaxial.

7. An implement according to claim 1 in which the master cylinder comprises a tube having a handle at one end and a sealing gland at the other, and in which the hydraulic connection between slave and master cylinders comprises a small bore tube passing through the sealing gland and being coaxial with the master cylinder and being connected to the master plunger to provide a hydraulic connection between slave cylinder and that side of the master cylinder remote from the sealing gland, and in which a guide is provided fast with the cutting head for defining a linear pathway for the tube in a direction parallel to the tube axis.

8. An implement according to claim 7 in which the guide is a guide tube coaxial with the master cylinder tube.

9.-An implement according to claim 7 in which the handle screws into one end of the bore of the tube and coaxially with it, the opening at the end of the tube forming a filler opening and'the handle forming also a hydraulic fluid filler plug for the opening.

10. An implement according to claim 7, in which there is provided an extension guide having engaging means for engaging with the guide to provide an extended linear pathway further from the cutting head and parallel to the first linear pathway, and a rod cooperating slidably with the extension guide and having a hand grip at a remote end projecting beyond the extension guide and having attachment means at its opposite inner end for attachment to the handle of the master cylinder tube.

11. An implement according to claim 10 in which the extension guide is an extension tube and in which the engaging means comprises a bayonet type of fitting between guide and extension tube, and in which the attachment means comprises a male screw thread for engaging with a female thread in the handle coaxially with the master cylinder tube, the handle having a cross-sectional shape to engage slidably with the extension tube bore.

No references cited.

UNITED STATES PATENT OFFICE CERTIFICATE, OF CORRECTION Patent N0. 3,041,725 July 3 1962 Francis B Harries It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 4, line 11 for "of",

first occurrence, read tO Signed and sealed this 30th day of October 1962 (SEAL) Attest:

ERNEST W. SWIDER Commissioner of Patents