WO1995007800A1

WO1995007800A1 - A pressure-medium operated tool

Info

Publication number: WO1995007800A1
Application number: PCT/SE1994/000817
Authority: WO
Inventors: Jerzy Janczak
Original assignee: Husqvarna Ab
Priority date: 1993-09-16
Filing date: 1994-09-05
Publication date: 1995-03-23
Also published as: SE9303016D0; SE501778C2; AU7712394A; ZA947109B; SE9303016L

Abstract

A pressure-medium driven tool for cutting, compressing or holding a workpiece (21) includes a frame bar, an anvil (9, 13) firmly mounted on one end of the bar, and an active tool-part (10) which can be moved along the bar towards the anvil. The frame bar is provided with a longitudinally extending channel and the active tool-part (10) includes a bottom part (25) which fits into the channel and which functions to restrain the active tool-part against sideways movement as it moves along the bar. The part of the active tool-part that moves in the channel is provided with at least one through-penetrating hole and each of the channel walls is provided with a respective longitudinally extending guide means (28) opposite the hole. The hole is fitted with a pin (27) whose ends coact with the guide means in a manner to restrain the active tool-part (10) from movement at right angles to its direction of linear movement and to facilitate linear movement of the active tool-part in the channel.

Description

A PRESSURE-MEDIUM OPERATED TOOL

The present invention relates to a pressure-medium operated tool for cutting, compressing or holding a wor piece, compris- ing a frame bar, an anvil surface mounted on one end of the bar, and an active tool-part which can be moved linearly along the bar towards the anvil surface.

Tools of this kind find many uses because of the large forces that can be achieved with the aid of a hydraulic cylinder, for instance. One example is found in the cutting of wood pieces or the branches of trees transversely to the fibre direction, wherein the tool is fitted to a shaft or to a long handle and used as a motor-driven tree pruning tool. In this regard, the tool may be used to cut branches whose thickness would otherwise require the use of a saw. A tool of this kind may also be used for forest cleaning, forest clearing and tree- pruning work, among other things.

A common requirement of all tools of this kind is that the tool shall be capable of exerting a powerful force between a movable active tool-part and a fixed anvil surface, or counter-pressure surface, and that the active tool-part can be driven and guided in a firm and reliable manner. Further- more, this requirement must be achieved with a tool which is of simple construction and which is light in weight. This is particularly important when the tool is to be fitted onto and manoeuvered by a long shaft or long handle.

In accordance with the present invention, there is provided a tool of the kind defined in the first paragraph which fulfils the aforesaid requirements, among other things. The tool is characterized in that the frame bar includes a longitudinally extending channel; in that the active tool-part has a bottom part which fits in the channel therewith to hold the active tool-part against sideways movement as the active tool-part moves along the bar; in that the part of the active tool-part that runs in the channel includes at least one through-penetrating hole; in that each of the channel walls includes opposite said hole two longitudinally extending and mutually opposing guide means; and in that each hole accommo- dates a pin whose ends coact with said guide means such so as to guide the active tool-part and hold said active tool-part against movement in a direction at right angles to the direction of linear movement of said tool part.

A tool of this kind can be manufactured relatively easily and provides very stable and positive guidance of the movable active tool-part. The weight of the tool can be kept low nevertheless, since the active tool-part guide means does not require the addition of material which would add to the weight of the tool.

It is preferred that the channel extends completely through the frame bar, that the guide means have the form of grooves, and that the ends of the grooves are bevelled or chamfered to enable scrap material to be discharged by means of the movable active tool-part and the pin respectively.

So as to enable the working active tool-part to be fitted easily in the channel, the frame bar is provided opposite the grooves with a hole through which the pin can be inserted into the hole in the active tool-part. The hole in the frame bar is located so that the hole in the active tool-part will not reach this position in normal operation. There is thus no risk of the pin falling out accidently.

In one preferred embodiment, the active tool-part is driven by a single-acting piston-cylinder unit having spring return, the active tool-part being hinged to the unit. In this case, force is transmitted between said unit and the workpiece during a working stroke, essentially through the medium of mutually contacting surfaces on both sides of the hinge axis. Other characteristic features of the present invention will be apparent from the following Claims.

The invention will now be described in more detail with reference to an exemplifying embodiment thereof and also with reference to the accompanying drawings.

Fig. 1 illustrates the use of an inventive tool.

Fig. 2 is a side view of the tool.

Figs. 3 and 4 illustrate the tool shown in Fig. 2 in two working states and partly in section.

Figs. 5 and 6 illustrate respectively the tool shown in Fig. 2 from above and from beneath.

Figs. 7 and 8 illustrate fitting of the active tool-part of the tool shown in Fig. 2.

Fig. 9 shows the drive motor illustrated in Fig. 1 fitted with a hydraulic pump.

Fig. 10 is a view corresponding to the view of Fig. 9 but with the end-connection of the oil tank removed.

Fig. 11 is a partially sectioned side view of part of the equipment shown in Fig. 9.

Figs. 12 and 13 are vertical sectional views of a valve used in the embodiment shown in Fig. 11, and show the valve in two different states.

Fig. 1 illustrates a workman 1 cutting high branches from a tree with the aid of a pruning tool 3 fitted to a long handle

2. The workman carries an internal combustion engine 4 and a hydraulic pump fitted thereto, for operating the tool. The hydraulic pump is connected to the tool 3 by means of a single hose or delivery line 5, the greater length of which extends inside the handle 2, the tool being driven by a single-acting hydraulic cylinder with spring return. The workman is able to adjust the engine or motor speed by means of a throttle control 6 which is connected to the engine 4 by a throttle cable 7. Connected between the engine output shaft and the hydraulic pump is a speed-dependent coupling which will ensure that the pump is not activated until a predetermined speed is reached. The workman 1 is thus able to control the working strokes of the tool 3 with the aid of the throttle control 6.

The simple connection of the hydraulic pump to the tool shown in Fig. 1 is achieved because the hydraulic hose 5 is used both as a pressure line and as a return line during different working stages. Thus, that part of the line which lies adjacent the body will solely transfer oil under high pressure and for very short working periods, which greatly reduces the risks of accidents. Neither is the system subjected to high pressures in any other respect and the system is essentially pressureless with the exception of when the tool is at work.

As shown in Fig. 2, the tool 3 includes a frame bar 8 which has a counterpressure surface or anvil surface 9 fixedly mounted on one end thereof. The tool also includes a movable active tool-part 10, which in the illustrated case is in the form of a knife. The knife can be moved along the bar 8 towards the anvil 9 by means of a hydraulic cylinder 11. The cylinder is fitted on the end of the long handle 2, or shaft, by means of a pivot coupling 12, see Fig. 1, which in the illustrated case is comprised of a ball coupling with friction locking. Hydraulic oil and return oil pass respectively to and from the cylinder through the common hose 5 contained in the long handle 2.

The reference numeral 13 identifies an anvil pad 13 which is fitted removably to the anvil 9 and which is made of a softer material than the material from which the knife 10 is made. In this way, the knife 10 is able to produce an indication of a groove in the pad 13, therewith ensuring that thin fibres can also be cut effectively.

As will be seen from Figs. 3 and 4, the knife 10 is pivotally attached to the top of the piston 14 in the cylinder 11 by means of a hinge pin 15. The hole in the knife 11 through which the hinge pin passes has a larger diameter than the hinge pin, wherein force transmission from the piston 14 to the knife 10 during a working stroke takes place through the coacting surfaces 16 of the top of the piston 14 and the rear edge of the knife 10 respectively. This ensures that the knife 10 is activated horizontally, without tending to skew and therewith jam. The hydraulic cylinder is single-acting and the piston 14 is returned with the aid of a return spring 17. The spring is mounted between a transverse screw 18 in the rear part of the cylinder housing and a mounting body 20 which is secured to the top of the piston 14 by means of a screw 19.

Fig. 3 shows the cylinder in a rest state, wherein a branch 21 is located between the knife 10 and the anvil pad 13. Fig. 4 shows the tool after completing a working stroke, wherein the hydraulic pressure in the cylinder 11 has forced-out the piston 14 until the knife 10 coacts with the anvil pad 13 and fully severs the branch 21. With the intention of restricting the extent to which the knife 10 will cut into the pad 13 after repeated working operations, the knife is provided with a flat abutment surface 33 which coacts with a corresponding surface 34 on the anvil.

When a very powerful force is required to cut a branch or to perform some other work, it is necessary to guide the active tool-part, in the illustrated case the knife 10, in a reliable fashion. To this end, the frame bar 8 (see also Figs. 5 and 6) is comprised of two mutually connected side-pieces 22 and 23 which define therebetween a through-penetrating channel 24, A lower part 25 of the knife is steered in the channel 24 with a relatively close fit. This provides stable sideways re¬ straint on the knife 10.

For the purpose of restraining the knife against movement in a direction at right angles to its direction of linear movement in the channel, the part 25 is provided with at least one and preferably two holes 26 in which a respective pin 27 is fitted. The length of the pins 27 is greater than the thickness of the part 25 and the defining walls of the channel 24 are provided with two longitudinally extending, correspond¬ ing grooves 28, 29 in which the ends of the pins 27 are guided. The pins 27 thus restrain the knife 10 against vertical movement in the channel while, at the same time, facilitating movement of the knife along the bar 8.

The bar 8 is provided with a hole 30 opposite the grooves 28, 29, for insertion of the pins 27 into the holes 26 in the knife when fitting the knife to the bar 8. The knife is fitted in the manner illustrated in Figs. 7 and 8.

When fitting the knife to the bar 8, the anvil pad 13 is first removed, so as to enable the knife in the position shown in Fig. 7 to be moved along the bar and towards the anvil 9 until the one hole 26 in the knife is in register with the hole 30 in the bar 8, whereupon a first pin 27 is inserted. The knife 10 is then swung anti-clockwise to the position shown in Fig. 8, whereafter the second pin 27 is inserted. The knife is then moved towards the hydraulic cylinder and the pin 15 is inserted through the hole 31 in the top of the piston 14 and into the slightly oversized mounting hole 32 in the knife. The anvil pad 13 is then replaced on the anvil 9, which prevents the knife 10 from being moved towards the anvil 9 to an extent which would allow the front pin 27 to fall out.

The knife-restraining or knife-guide means provided by the channel 24 and the vertical guide means obtained with the aid of the pins 27 and the grooves 28 and 29 function to accurate¬ ly guide linear movement of the knife while restraining the knife against sideways movement and therewith preventing any tendency of the knife to jam or wedge in the channel. The grooves 28, 29 are kept clean by the pins, which press out any scrap that may be deposited in the grooves. In this regard, the ends of the grooves are bevelled slightly so that the pins will force scrap from the grooves more easily, as illustrated in the enlarged part of Fig. 4. Scrap can also be pressed out through the hole 30 in the bar 8 at the other ends of the grooves.

Figs. 9 and 10 illustrate the internal combustion engine 35 used with the equipment illustrated in Fig. 2. The engine 35 has connected thereto a housing 36 on which there is fitted an end-connection 37, which has not been shown in the Fig. 10 illustration. The housing 36 serves as a tank for hydraulic oil and encloses a hydraulic pump 38 which is immersed in the oil and which is provided with a pressure-controlled valve 39.

As shown in the section view in Fig. 11, a centrifugal coupling 40 is mounted between the engine 35 and the drive shaft 41 of the pump 38, this coupling, or clutch, being shown schematically in the Figure. The drive shaft 41 is terminated in the form of a non-round pin which fits, with a given clearance, into a corresponding opening in a coupling sleeve 42 which is driven by the centrifugal coupling 40 and which is journalled on ball bearings 43. This arrangement reduces the requirement of accurate alignment between the respective drive shafts of the engine and the pump.

The pump 38 is fully immersed in oil 44 in the tank 36 and draws in oil through an inlet 45, see Figs. 12 and 13, and discharges hydraulic oil to the valve 39 mounted on the pump. This valve is provided with a working port 46 having a connection nipple 47 which is connected to the line 5 (see Fig. 9) through which hydraulic oil is delivered to and oil is returned from a tool connected to the pump. Oil returning to the valve 39 is passed back to the tank 38, through a return port 53. The tank is fully closed and consequently a given subpressure will be generated therein when oil is taken therefrom during a working stroke. This facilitates return of the return oil and also the return movement of the piston in the hydraulic cylinder.

Since the hydraulic pump 38 and the valve 39 are both arranged in the oil tank 38, the unit shown in Fig. 11 is very compact.

The construction is further simplified by virtue of the valve

39 (see Figs. 12 and 13) being mounted directly on the pump 38 by means of a hollow screw 48 which is screwed directly into the pump outlet. The screw 48 thus serves as a means for fitting the valve 39 and also as an inlet port 49 to the valve chamber 50, in which a slide 51 is movable against the action of a biassing spring 52. The valve chamber 50 is also provided with the return port 53 and the working port 46 with which the connecting nipple 47 of the line is connected.

The system works as follows: When the engine 35 runs at a speed which is below the speed at which the centrifugal clutch

40 is activated, the pump 38 is at rest. The valve slide 51 will then be located in its rest position, as shown in Fig. 12, in the absence of high pressure on the port 49. The working port 46 is thus connected directly to the return port 53 through the valve chamber 50, meaning that the system is essentially without pressure, the tool 3 being held in its starting position by the associated return spring 17 in the cylinder 11.

When the workman increases the engine speed by adjusting the throttle setting, the pump 38 is engaged by the centrifugal clutch 40 and oil is delivered under high pressure to the valve chamber 50, through the port 49. This pressure causes the valve slide 51 to move to the position shown in Fig. 13, against the action of the spring 52. The port 49 is therewith connected to the working port 46, causing pressurized oil to be delivered to the tool 3 and the knife to carry out a working stroke. When the workman slackens on the throttle, the pump 38 is deactivated and the spring 52 will return the valve slide 51 to its starting position as soon as the pressure has fallen to beneath a predetermined value, suitably 1-3 bars. This results in reopening of the return connection between the working port 46 and the return port 53.

The aforedescribed valve 39 mounted on the pump 38 provides a very compact construction. However, this valve may be replaced with a separate valve whose pressure port and return port can be connected to the hydraulic pump and to the tank respectively through the medium of conventional lines, if so desired. The working port is connected to the working device in question by means of the line 5, in the same way as that described above. The pump may also be driven by an electric motor.

The aforedescribed tool can be modified in several ways to adapt the tool for use with other types of work. For instance, the knife 10 can be replaced with a different type of active tool-part and the anvil pad 13 may also be given a different form, for instance a form in which it can perform different compressing or shaping operations. Because of this simple exchange facility, one and the same tool can be adapted for use for different purposes, simply by replacing the active tool-part and possibly also the anvil pad 13. The anvil may also be provided with a cutting edge so as to make cutting of materials more effective, or to obtain a scissor-like func¬ tion. The knife guide channel need not be through-penetrating, but may have the form of a deep groove in the frame bar 8. Further, the grooves 28, 29 in the walls of the guide channel may have the form of through slots or other guide means on the inner surfaces of the walls. It will also be understood that the hydraulic cylinder which drives the active tool-part may be replaced with a pneumatic device. The number of guide pins used may also vary according to requirements.

Claims

1. A pressure-medium operated tool for cutting, compressing or holding a workpiece (21) , comprising a frame bar (8) , an anvil (9,13) firmly mounted on one end of the frame bar, and an active tool-part (10) which can be moved along the bar and towards the anvil, characterized in that the frame bar (8) is provided with a longitudinally extending channel (24) ; in that the active tool-part (10) has a bottom part (25) which fits into the channel therewith to hold the active tool-part against sideways movement as the active tool-part moves along the bar; in that said bottom part of the active tool-part received in the channel is provided with at least one through- penetrating hole (26) ; in that each of the walls of the chan¬ nel (24) is provided with a respective longitudinally extend- ing guide means (28,29) opposite said hole; and in that said hole has fitted therein a pin (27) whose ends coact with said guide means so as to restrain the active-tool part (10) against movement in a direction at right angles to its direction of linear forward movement.

2. A tool according to claim 1, characterized in that the channel (24) in the bar (8) is through-penetrating.

3. A tool according to claim 1 or claim 2, characterized in that the guide means have the form of grooves (28,29); and in that the ends of the grooves are chamfered or bevelled to facilitate the discharge of scrap by means of said pin (27) .

4. A tool according to claim 3, characterized in that the frame bar (8) has a hole (30) located opposite the grooves

(28,29) to enable the pin (27) to be inserted into the hole (26) in the active tool-part; and in that the hole (30) in the bar is so located as to prevent the hole in the active tool- part from reaching this position during normal operation.

5. A tool according to anyone of claims 1-4, characterized in that the active tool-part (10) is driven by a single-acting piston-cylinder unit (11) with spring return; in that the active tool-part is pivotally connected to said device; and in that force transmission between said device (11) and the active tool-part (10) during a working stroke takes place essentially through the medium of mutably contacting surfaces (16) on both sides of the pivot axle (15) .

6. A tool according to any one of claims 1-5, characterized in that the active tool-part (10) has the form of or includes a cutting edge for cutting a workpiece (21) located between the active tool-part and the anvil (9,13).

7. A tool according to claim 6, characterized in that the anvil surface (13) that lies proximal to the cutting edge (10) is made of a softer material than the cutting edge material; and in that the body carrying the cutting edge includes an abutment surface (33) which limits the extent to which the cutting edge can penetrate the anvil material.

8. A tool according to any one of claims 1-7, characterized in that the tool is driven by a single-acting hydraulic cylinder (11) ; and in that the cylinder is connected to a source of pressure (38) and an associated tank (36) through the medium of a common pressure-and-return line (5) and a pressure-controlled valve (39) which functions to connect the line either to pressure or to the tank, depending on the input pressure.

9. A tool according to claim 8, characterized in that the pressure source is a hydraulic pump (38) which is driven by a motor (35) via a speed-dependent coupling (40) , conveniently a so-called centrifugal clutch.

10. A tool according to claim 9, characterized in that the pressure-control valve (39) is mounted directly on the hydraulic pump (38) ; and in that the pump unit is immersed in the oil (44) contained in the tank (36) .