GB2320665A

GB2320665A - Cutting tool with a divisible guide tube

Info

Publication number: GB2320665A
Application number: GB9726721A
Authority: GB
Inventors: Thomas Stark; Thomas Schweigert; Martin Lambe; Klaus-Martin Uhl
Original assignee: Andreas Stihl AG and Co KG
Current assignee: Andreas Stihl AG and Co KG
Priority date: 1996-12-24
Filing date: 1997-12-18
Publication date: 1998-07-01
Also published as: FR2757344A1; GB9726721D0; JPH10191748A; DE19654348C1

Abstract

The invention relates to a free-cutting tool with a guide tube, located at one end of which is a drive motor 3 and whereof the other end supports a cutting head 5. A drive shaft for connecting the drive motor 3 to the cutting head 5 is mounted in the guide tube, in which case the guide tube can be separated into an upper tube section 14 connected to the drive motor 3 and a lower tube section 16 connected to the cutting head 5. The facing ends of the tube sections are detachably connected to each other by way of a coupling member 1. To achieve reliable mounting and dismantling of the guide tube, the tube section 16 of the guide tube axially releasable from the coupling member can be locked by way of a locking device (50) and can be fixed with frictional contact in the coupling member by way of a clamping device (23).

Description

The invention relates to a free-cutting tool according to the preamble of Claim 1.

A free-cutting tool of this type is known from US-A 4.122.601.

For easier carrying of the free-cutting tool, the guide tube can be separated, the end of one tube section supporting a coupling sleeve, into which a coupling section fixed on the end of the other tube section engages. The coupling sleeve and the coupling section each support an outer annular flange, which bear against each other when the guide tube is assembled and are secured by a fixing clip, which engages jointly over the annular flanges.

For fitting the fixing clip, the tube sections must be kept inserted one in the other, in order that the annular flanges lie closely one against the other and the fixing clip can be fitted appropriately by a second person. The assembly of the guide tube is therefore awkward and time-consuming. Also, dismantling must be undertaken with care, since after releasing the fixing clip, the coupling section may slide in an uncontrolled manner out of the coupling sleeve.

It is the object of the invention to develop a free-cutting tool with a guide tube which can be separated, so that simple assembly and dismantling is possible, which can readily be carried out safely even by only one person.

The object is achieved according to the invention by the characterising features of Claim 1.

Since the tube section which can be released axially from the coupling member, can be locked undetachably to the coupling member by way of a locking device, after inserting and locking the tube section, an axially secure connection is created, which reliably prevents uncontrolled sliding of the releasable tube section from the coupling member. The coupling member may also be fixed with frictional contact by way of the clamping device so that a connection free from play is provided, which is secure for operation, which also withstands powerful vibrations. Also, the dismantling of the guide tube can be carried out simply and safely by one person. First of all the clamping device has to be released, without there being any risk that the releasable tube section slides in an uncontrolled manner out of the coupling sleeve. Then the user will grip the releasable tube section with one hand and the tube section with the coupling member with the other hand. With the other hand holding the tube section, the locking device can be simultaneously unlocked, for which purpose an actuating section of the locking device preferably faces the tube section held securely in the coupling sleeve. Only after unlocking the locking device can the releasable tube section be removed axially from the coupling member, in which case both tube sections of the guide tube can be held securely by respectively one of the user's hands.

The coupling member is preferably a coupling sleeve engaging over the ends of both tube sections, with a quick-action clamping device, the end of the other tube section appropriately being clamped in a stable manner in the coupling sleeve.

In order to ensure mounting in the correct position, it is provided that the tube section can be inserted in the coupling sleeve in advantageously only one preferred rotary position. For this purpose, in the development of the invention, provided in an inner stop ring of the coupling sleeve defining the insertion depth is at least one axial insertion opening, which is constructed to receive an axial insertion projection of the tube section to be inserted.

Further features of the invention will become apparent from the other Claims, description and drawings, illustrating embodiments of the invention described in detail hereafter. In the drawings: Figure 1 shows diagrammatically a free-cutting tool carried and guided by a user, Figure 2 is a diagrammatic plan view of a coupling member of the guide tube of the free-cutting tool according to Figure 1, Figure 3 is a section on line Ill-Ill of Figure 2, Figure 4 is a perspective view of the coupling member of the guide tube which can be separated, Figure 5 is a perspective view of the ends of the separated guide tube, Figure 6 is an exploded view of the coupling sleeve according to Figure 2 and the facing ends of the separated guide tube, Figure 7 is a longitudinal section through the coupling member according to Figure 6, Figure 8 is a section through the coupling member on line VIII VIII of Figure 7.

The free-cutting tool illustrated in Figure 1 comprises a guide tube 2, which at its first end 4 supports a drive motor 3.

Located at the second, lower end 6 is a cutting head 5, which supports a cutting thread or - as in the embodiment - a cutting blade 7. The blade 7 is rotated by the drive motor 3 by way of a drive shaft 8 mounted in the guide tube 2. A protective shield 9 is provided on the guide tube 2 above the cutting head 5, for protecting a user 10 carrying and guiding the free-cutting tool.

The free-cutting tool is carried by the user 10 - for example by way of a belt system 11 - ,the user moving the free-cutting device to and fro in the direction of arrow 13 by way of a steering bar 12. The steering bar 12 is attached to the guide tube 2 close to the upper end 4 and comprises two handles 15, which the user 10 grasps. Provided in one handle 15 are members (not shown in detail) for operating the drive motor 3, which in the embodiment is constructed as an internal combustion engine, in particular a two-stroke engine.

For carrying, the guide tube 2 and the drive shaft 8 mounted therein are constructed so that they can be separated. The tube sections 14 and 16 of the guide tube 2 are releasably connected to each other during operation by way of a coupling member constructed as a coupling sleeve 1. When the guide tube 2 is dismantled, the upper tube section 14 remains connected to the drive motor 3, whereas the lower tube section 16 remains connected to the cutting head 5. The shaft sections 44 and 46 of the likewise separated drive shaft 8 are located in the tube sections 14 and 16; they are non-rotatably connected to each other by an axial coupling in the region of the coupling member 1.

Inserted in facing ends 24 and 26 of the tube sections 14 and 16 is respectively an end sleeve 30, which in the embodiment is composed of two half-shells 31 appropriately connected to each other by way of a film hinge and has open ends. The half-shells 31 are constructed in an identical manner and are inserted axially - fitted together - in the open end 24 or 26 of the tube section 14 or 16. In this case, the end sleeve 30 formed by the half-shells 31 is non-rotatably and undetachably held in the tube section 14 or 16; preferably the end sleeve 30 is pressed into the end 24 or 26 of the tube section 14 or 16. Appropriately, for axial securing and non-rotary locking, each half-shell 31 comprises in its outer surface a locking recess 32, in which an inner locking lug 33 of the tube section 14 or 16 engages. The tube section 14, 16 appropriately consists of metal, whereas the end sleeve 30 or its half-shells 31 are advantageously made from synthetic material.

At one end, the end sleeve 30 or its half-shells 31 comprise an outer, radial collar 34, whereof the outer diameter K is smaller than, preferably equal to the outer diameter D of the tube section 14 or 16. The collar 34 forms a step 35 (Figures 3, 5, 6), against which the end face 36 of the end 24, 26 of the tube section 14, 16 comes to bear. The insertion depth of the end sleeve 30 in the tube section 14, 16 is restricted in this way.

The end sleeve 30 prevents the respective shaft section 44, 46 of the drive shaft 8 from falling out of the tube section 14 or 16. For this purpose, each shaft section 44, 46 comprises a securing member 45 which is substantially fixed in the axial direction, which is preferably constructed by deformation, for example by stamping on the shaft section 44 or 46 and is larger than the diameter of the drive shaft. The securing member 45 cooperates with an inner support wall 37 (Figures 3, 6) of the end sleeve 30 or its half-shells 31. The support wall 37 is provided with a central opening 38, through which the respective end 54, 56 of the shaft section 44, 46 projects. The securing member 45 in this case is located on the side of the support wall 37 facing the interior of the tube 49. The securing member 45 has a larger outer diameter than the inner diameter of the opening 38, so that the shaft section 44, 46 is retained in the tube section 14, 16 by the end sleeve 30.

The end sleeve 30 mounted in the open end 24, 26 is shown in Figure 5 in the example of the end 26 of the lower tube section 16. The plane of separation 39 of the half-shells 31, also dividing the support wall 37, lies at the height of the longitudinal central axis 40 of the drive shaft, which is resiliently mounted in the guide tube 2 by way of a so-called synthetic liner 41. The synthetic liner 41 in this case consists of a central tube 42, which supports radial support ribs 43 arranged in the shape of a star and extending axially, which bear against the inner wall of the guide tube 2. In the embodiment illustrated, provided over the periphery of the tube 42 are three support ribs 43. The end 56 of the shaft section 46 terminates approximately at the open end face 36 (Figure 5) of the tube section 16. Also, the synthetic liner 41 is secured axially in the tube by the end sleeve 30 in the mounted position.

As is apparent from Figure 3, non-rotatably mounted and retained on the end 54 of the upper shaft section 44 is an insertion sleeve 47, whereby in the assembled state of the guide tube 2, the insertion sleeve 47 penetrating the opposite end sleeve 30 of the tube section 16. The end 56 of the lower shaft section 46 preferably constructed as a square, is inserted axially in the insertion sleeve 47 and - on account of the correspondingly selected inner contour of the insertion sleeve 47, brought into driving connection therewith in a non-rotary manner.

The coupling sleeve 1 connecting the two tube sections 14 and 16 one to the other is, as shown in Figures 3 to 6, essentially constructed as a tubular basic member 20, which for limiting the respective insertion depth T of the tube sections 14 and 16, comprises an inner stop ring 17 (Figure 7). The stop ring 17 comprises a plurality of axial insertion openings 18 (Figure 8), which are provided for receiving an axial insertion projection 19 (Figure 5) of the respective end 24 or 26 of the tube sections 14 or 16. In the embodiment, uniformly distributed over the periphery of the stop ring 17 are a plurality of, namely four insertion openings 18. The insertion openings 18 are constructed as continuous gaps open radially towards the inside, in the stop ring 17 and are widened out in the shape of a funnel on one axial side. The funnel-shaped enlargements of the insertion openings 18 lying diametrically opposite each other are preferably located on the same end face; the funnel-shaped enlargements of adjacent insertion openings 18 lie on respectively opposing end faces of the stop ring 17.

According to the arrangement of the insertion openings 18 in the stop ring 17, the end sleeve 30 supports at least one axial insertion projection 19; in the embodiment illustrated, each end sleeve 30 is constructed with two diametrically opposed insertion projections 19. In this case, an insertion projection 19 is preferably integrally formed on respectively one half-shell 31, appropriately on the collar 34. Each insertion projection 19 tapers - preferably corresponding to the funnel-shaped enlargement of the insertion opening 18 - towards its free end.

The coupling sleeve 1 is constructed to be slit at its two ends 27, 29 over an axial partial length, in which case lying at right angles to the slot 21 is respectively one clamping screw 22 or 23, which are held respectively in corresponding flanges 25 of the basic member 20.

The end 24 of the upper tube section 14 is inserted in one end 27 of the coupling sleeve 1, until the collar 34 abuts against the stop ring 17. The rotary position of the coupling sleeve 1 relative to the upper tube section 14 is determined in this case by the insertion projections 19 of the half-shells 31, which come to lie in the corresponding insertion openings 18 in the stop ring 17 and fix the basic member 20 of the coupling sleeve 1 in a non-rotary manner on the tube section 14. Then the clamping screw 22 is tightened, which bridges the slot 21 and engages in a nut 22', which is held in the opposite flange 25. With the firm tightening of the screw 22, the end 24 of the tube section 14 is clamped in a stable manner in the coupling sleeve 1. In this case, the clamping screw 22 forms a mounting screw able to be tightened with a tool, which mounting screw basically does not have to be released at the time of regular use of the freecutting tool according to the invention. By clamping the tube section 14 in the end 27 of the basic member 20, the end 24 of the tube section 14 is also connected to the basic member 20 with frictional contact and thus secured in an axially undetachable manner. The insertion projections 19 of the end sleeve 30 of the end 24 of the tube section 14, located in the insertion openings 18, form a non-rotary, form-locking connection in the manner of a claw coupling.

The end 26 of the lower tube section 16 can be fixed with frictional contact in the other end 29 of the basic member 20 of the coupling sleeve 1 by way of the clamping screw 23. The clamping screw 23 bridging the slot 21 is in this case constructed as a tommy screw able to be rotated by hand, due to which a rapid-action clamping device able to be released easily by the user without a tool is created. The tommy screw 23 engages in a nut 23' located on the other side of the slot 21, which nut can be held in the flange 25.

In addition to the quick-action clamping device formed by the clamping screw 23, associated with the end 29 of the basic member 20 is a locking device 50, by which the end 26 of the tube section 16 can be locked in the basic member 20 of the coupling sleeve 1. In the embodiment illustrated, the locking device 50 consists of the locking member 51, which drops under the action of a locking spring 52 into a locking opening 28 in the releasable tube section 16. In the embodiment illustrated, the locking opening 28 is provided as a bore constructed in the tube surface, which is appropriately closed in a sealing manner by the end sleeve 30 with respect to the interior 49 of the tube. For reliable dropping-in of the locking member 51 and for making an adequate engagement depth available, a slot-like locking space 28' is provided in the end sleeve 30 or its half-shells 31, into which the opening 28 or the bore opens. The axial length L of the end sleeve 30 appropriately corresponds approximately to the insertion depth T of the tube section 14, 16 in the coupling sleeve 1. The locking member 51 is appropriately constructed on a locking rocker 53, which is held in an outer rocker dome 55 of the basic member 2. In this case, the locking rocker 53 is appropriately held so that it is able to tilt about a pin 57 lying at right angles to the drive shaft 8. In this case, the locking rocker 53 lies aligned in the longitudinal direction of the guide tube 2 and is provided essentially as a two-armed lever, to one arm of which the locking member 51 is attached and the other arm 59 of which is acted upon by the locking spring 52.

The two arms of the locking rocker 53 in this case lie at an angle 58 of less than 180C with respect to each other. Due to this, in the locked position, the other lever arm 59 of the locking rocker 53 projects from the rocker dome 55 and thus forms an optical indication of a correctly locked locking device 50.

The base 55' of the rocker dome 55 is formed by the basic member 20 of the sleeve 1 and comprises a penetration opening 51' for the locking member 51 (Figure 7).

For the mounting of the guide tube 2, the end 26 of the lower tube section 16 is inserted in the end 29 of the basic member 20, with the quick-action clamping device 23 released, in which case the insertion projections 19 of the end sleeve 30 held undetachably and in a non-rotary manner in the end 26, are to be threaded into the still open insertion openings 18 of the stop ring 17. The tube section 16 can thus be inserted in a preferred rotary position into the coupling sleeve 1, this rotary position being determined on one side by the insertion projections 19 and on the other side by the locking opening 28. For axial insertion, the locking member 51 comprises an inclined face 48 facing the insertion direction, so that at the time of insertion of the tube section 16, the collar 34 of the end sleeve 30 pushes the locking member 51 outwards, until - under the action of the locking spring 52 - it can drop into the locking opening 28.

When the end 26 is only partly inserted, the locking rocker 53 is in an intermediate position, which is an optical indication for the user that the locking device 50 is still open.

When the tube section 16 lies in the predetermined rotary position in the coupling sleeve 1, the locking member 51 engages and the locking rocker 53 arrives in the locking position illustrated in Figure 3. The tube section 16 is held in an axially undetachable manner in the coupling sleeve 1; the tube section 16 can be released by the user, in order - appropriately with the same operating hand - to tighten the tommy screw 23 of the quick-action clamping device, due to which the end 26 of the tube section 16 is then also held in a force-locking manner and without clearance in the coupling sleeve 1.

For dismantling the guide tube 2, first of all the tommy screw 23 can be released, without there being any danger that the tube section 16 drops out of the coupling sleeve 1. After releasing the tommy screw 23, the user is able to grip the tube section 16 with one hand, in order to hold the coupling sleeve 1 with the other hand and at the same time to depress the locking rocker 53 for releasing the locking device 50. The end 26 of the lower tube section 16 can be withdrawn from the coupling sleeve 1, in which case at the same time the end 56 of the lower shaft section 46 is withdrawn axially from the insertion sleeve 47. As shown in Figure 3, neither does the drive shaft project from the end 26 of the released tube section 16 nor does the insertion sleeve 47 project from the coupling sleeve 1.

Appropriately, the ends 24 and 26 of the tube sections 14 and 16 have an identical construction (Figure 6), so that the coupling sleeve 1 may be fixed in a stable manner both on one or other tube section 14, 16 and the respective other tube section 16, 14 is releasable by way of the quick-action clamping device 23 and the locking device 50 from the coupling sleeve 1.

Claims

1. Free-cutting tool with a guide tube (2), with a drive motor (3) located at one end (4) of the guide tube (2) and a cutting head (5) located at the other end (6) of the guide tube (2), with a drive shaft (8) mounted in the guide tube (2) for connecting the drive motor (3) to the cutting head (5), the guide tube (2) and the drive shaft (8) being able to be separated into an upper section (14, 44) connected to the drive motor (3) and a lower section (16, 46) connected to the cutting head (5) and the facing ends (24, 26) of the sections (14, 16) of the guide tube (2) being releasably connected to each other by way of a clamping coupling member (1), and the upper section (44) of the drive shaft (8), connected to the drive motor (3) is nonrotatably, but axially releasably connected by way of an axial coupling (47) to the lower section (46) of the drive shaft (8) connected to the cutting head (5), characterised in that the coupling member (1) is fixed on one tube section (16) of the guide tube (2) and the other section (16) of the guide tube (2), which can be released axially from the coupling member (1), is kept locked in the coupling member (1) by way of a locking device (50) and is fixed with frictional contact in the coupling member (1) by way of a clamping device (23).

2. Free-cutting tool according to Claim 1, characterised in that the locking device (50) consists of a locking member (51) held in the coupling member (1) and accessible from the outside, which member drops under the action of a locking spring (52) into a locking opening (28) of the releasable tube section (16), the locking opening (28) advantageously being constructed as a radial bore in the wall of the tube section (16).

3. Free-cutting tool according to Claim 2, characterised in that the locking member (51) is constructed on a locking rocker (53), which is held in the coupling member (1) preferably so that it is able to tilt about a pin (57) located at right angles to the drive shaft (8).

4. Free-cutting tool according to one of Claims 1 to 4, characterised in that the coupling member (1) is a coupling sleeve engaging over the ends (24, 26) of both tube sections (14, 16), with a quick-action clamping device, the end (24) of the other tube section (14) being clamped in a stable manner in the coupling sleeve (1) and the tube section (14, 16) being able to be inserted in the coupling sleeve (1) in a preferred rotary position.

5. Free-cutting tool according to Claim 4, characterised in that the coupling sleeve (1) comprises an inner stop ring (17) limiting the insertion depth (T) of the tube section (14, 16) and the stop ring (17) comprises at least one axial insertion opening (18), preferably enlarged in the shape of a funnel, for receiving an axial insertion projection (19) of the tube section (14, 16).

6. Free-cutting tool according to Claim 5, characterised in that the stop ring (17) comprises a plurality of, preferably four insertion openings 18 uniformly distributed over the periphery.

7. Free-cutting tool according to one of Claims 1 to 6, characterised in that inserted in the open end (24, 26) of the tube section (14, 16) is an end sleeve (30) axially securing the shaft section (44, 46), which sleeve is held in a non-rotary and undetachable manner in the tube section (14, 16), preferably is pressed-in, the end sleeve (30) comprising an outer locking recess (32), in which a radial locking lug (33) of the tube section (14, 16) engages.

8. Free-cutting tool according to Claim 7, characterised in that the end sleeve (30) closes off the locking opening (28) associated with the locking member (51) with respect to the inside (49) of the tube, preferably in a sealing manner and the axial length (L) of the end sleeve (30) corresponds approximately to the insertion depth (T) of the tube section (14, 16) in the coupling sleeve (1).

9. Free-cutting tool according to Claim 7 or 8, characterised in that at its one end, the end sleeve (30) comprises an outer collar (34), whereof the outer diameter (K) is smaller than, preferably equal to the outer diameter (D) of the tube section (14, 16).

10. Free-cutting tool according to one of Claims 7 to 9, characterised in that in the region of the coupling member (1), the shaft section (44, 46) supports an axially substantially stationary securing member (45), which cooperates with an inner support wall (37) of the end sleeve (30), through which the shaft section (44, 46) penetrates.

11. Free-cutting tool according to one of Claims 7 to 10, characterised in that the end sleeve (30) supports an axial insertion projection (19), preferably two diametrically opposed insertion projections (19) and the insertion projection (19) is constructed on the collar (34).

12. Free-cutting tool according to one of Claims 7 to 11, characterised in that the end sleeve (30) is composed of two preferably identically constructed half-shells (31).

13. Free-cutting tool according to one of Claims 1 to 12, characterised in that the shaft section (46) terminates approximately at the open end face (36) of the tube section (16).

14. Free-cutting tool according to one of Claims 1 to 13, characterised in that the axial coupling consists of an insertion sleeve (47) attached to one shaft section (14), into which the facing end (56) of the other shaft section (46) can be inserted in a non-rotary manner, the insertion sleeve (47) projecting out of one tube section (14) and engaging in the other tube section (16).

1 5. A free cutting tool constructed and adapted to operate substantially as herein described with reference to, and as illustrated in, the accompanying drawings.

Amendments to the daims have been filed as follows 1. Free-cutting tool with a guide tube (2), with a drive motor (3) located at one end (4) of the guide tube (2) and a cutting head (5) located at the other end (6) of the guide tube (2), with a drive shaft (8) mounted in the guide tube (2) for connecting the drive motor (3) to the cutting head (5), the guide tube (2) and the drive shaft (8) being able to be separated into an upper section (14, 44) connected to the drive motor (3) and a lower section (16, 46) connected to the cutting head (5) and the facing ends (24, 26) of the sections (14, 16) of the guide tube (2) being releasably connected to each other by way of a clamping coupling member (1), and the upper section (44) of the drive shaft (8), connected to the drive motor (3) is non-rotatably, but axially releasably connected by way of an axial coupling (47) to the lower section (46) of the drive shaft (8) connected to the cutting head (5), characterised in that the coupling member (1) is fixed on one tube section (16) of the guide tube (2) and the other section (16) of the guide tube (2), which can be released axially from the coupling member (1), is kept locked in the coupling member (1) by way of a locking device (5) and is fixed with frictional contact in the coupling member (1) by way of a clamping device (23), the locking device being accessible from the outside.