GB2354481A

GB2354481A - Chain saw tensioner

Info

Publication number: GB2354481A
Application number: GB0015847A
Authority: GB
Inventors: Egbert Steinbrueck; Juergen Dolata; Heiko Below
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1999-07-07
Filing date: 2000-06-28
Publication date: 2001-03-28
Anticipated expiration: 2020-06-28
Also published as: GB2354481B; DE19931249A1; GB0015847D0

Abstract

In a chain saw the chain carrying blade 13 is clamped in its extended chain tensioning position by a pot shaped abutment 20 located over a "T" shaped bolt head 181 against which helical ramps slide as the abutment is rotated to thus apply clamping pressure to the blade. The pot shaped abutment is part of a wheel 19 which is rotated to clamp the blade. The blade may be tensioned bu means of a screw threaded rod (figures 1,4 and 5 not shown) or by the spring load slide arrangement of figures 6 and 7 (not shown).

Description

2354481 Chain saw

Background art

The invention relates to a chain saw of the type defined in the preamble of claim In such chain saws with a chain tensioning apparatus, in order to tension the chain the tensioning module is first operated to reduce the application force of the blade against the blade support in the housing, and then by means of the setting module the desired chain tension is adjusted by displacing the blade forward in its longitudinal direction to a greater or lesser extent, i.e. in a direction leading out of the housing. Once the chain tension is achieved, the tensioning module is operated again and the blade is clamped against the housing so as to be friction-locked against displacement.

In a known chain saw of said type (WO 98/33631 Al), the blade guiding the saw chain is fastened between two retaining plates and together with the latter is supported so as to be displaceable along the housing in longitudinal direction of the blade. The tensioning module comprises a bolt, which passes through a bore in an eccentric and through an oblong hole in the housing, is screwed in the retaining plate longitudinally displaceable along the housing and with its bolt head fixes the eccentric. The eccentric is part of the 'Setting module and is supported by its periphery against a housing stop. To tension the saw chain, the bolt is loosened slightly with the aid of a tool and the eccentric is rotated so that the bolt with the retaining plates and the interposed blade is displaced in the direction of the free blade end. The rotation of the eccentric is terminated when the saw chain has I 2 reached a tension which feels adequate. The bolt is then tightened again so that the eccentric and the retaining plates plus blade are fixed in the adjusted position against the housing. In a further embodiment of the tensioning module, the eccentric is pressed against the housing by means of a hydraulically operated piston and so the retaining plates plus blade are clamped in a friction-locked manner against the housing by means of the bolt.

Advantages of the invention The chain saw according to the invention having the features of claim I has the advantage of easy, tool-free operation of the tensioning module, which is realized with a low technical outlay.

The chain saw according to the invention having the features of claim 4 or the features of claim 9 has the advantage of easy, tool-free operation of the setting module, which is realized with a low technical outlay.

The chain saw according to the invention having the features of claim 9 moreover has the advantage that, by virtue of providing at least one tension spring acting upon the blade in chain-tensioning displacement direction, each time the chain is tensioned the same chain tension is always adjusted independently of the subjective perception of the operator.

I Advantageous developments and improvements of the chain saw indicated in claim I are possible by virtue of the measures outlined in the further claims.

3 According to an advantageous embodiment of the invention, the tensioning wheel, which is situated at the outside of an outer casing mounted onto the housing and covering driving pinion and setting module, has as large a diameter as possible so that in tune with the ascent of the helical tensioning surfaces at the pot base of the central tensioning pin the necessary tensioning force may be summoned up manually without any effort.

To prevent the tensioning wheel from working loose during operation of the chain saw, according to an advantageous embodiment of the invention there are provided between tensioning wheel and outer casing detent means which prevent reversed rotation of the tensioning wheel counter to the direction of rotation for tensioning.

According to a preferred embodiment of the invention, the setting module comprises a slide, which acts upon the blade and is loaded by at least one tension spring in chain-tensioning displacement direction. Such a tension spring guarantees that each time the chain is tensioned the chain tension is always the same, and the subjective component, such as arises with individual manual tensioning of the chain, is eliminated.

According to an advantageous embodiment of the invention, the setting module is disposed in an outer casing, which is fastened to the housing and covers driving pinion and setting module, and the at least one tension spring is tensionable after the slide has been placed against the blade. This has the advantage that, when the outer casing is placed onto the housing, manual bracing against the entire spring force necessary for tensioning the chain is not required.

4 In an advantageous embodiment of the invention, the at least one tension spring takes the form of a compression spring, which is supported by one end against the slide and by the other end against a tensioning plate, which is displaceable in longitudinal direction of the blade by means of an eccentric, wherein the eccentric is operable by means of a swivelling lever which is accessible from the outside of the outer casing.

In an advantageous embodiment of the invention, the slide comprises a flat part, which rests against the blade and engages with a bent lug into an oblong hole formed in the blade for guidance of the latter, which lug rests under the action of the at least one compression spring against the front end of the oblong hole. The flat part is preferably provided with two laterally projecting, bent limbs, which extend towards the tensioning plate. Two compression springs engage with one spring end over slip-on tongues formed on the limbs and are supported by their other spring end against the tensioning plate, where they are received by guide pins projecting from the tensioning plate. The compression springs and the limbs of the slide are accommodated in guides.

Drawings The invention is described in detail below with reference to embodiments which are illustrated in the drawings. The drawings show in each case in a diagrammatic manner:

Fig. I in a cutout manner a side view of a chain saw in the region of its chain tensioning apparatus, with the outer or protective casing removed, Fig. 2 a view identical to Fig. 1, with the outer casing in place, Fig. 3 in a cutout manner a section of outer casing and chain tensioning apparatus along line III-III in Fig. 2, Figs. 4 in each case a view identical to Fig. 1 of a and 5 chain saw according to two further embodiments, Fig. 6 in a cutout manner a side view of a chain saw in the region of its chain tensioning apparatus according to a further embodiment with setting module and cut-open outer casing, Fig. 7 a section along line VII-VII in Fig. 8, Fig. 8 a side view of the chain saw in Fig. 6, with the outer casing closed, Fig. 9 a plan view and two side views of a slide of the setting module in Fig. 6.

Description of the embodiments

The chain saw illustrated in a cutout manner and diagrammatically in Fig. I comprises a housing 10, in which a chain wheel or driving pinion I I for driving a saw chain 12 is rotatably supported. The driving pinion 11 is driven via gearing (not shown here) by a combustion engine or electric motor and its pinion teeth are inserted into the saw chain 12. On a blade 13, which projects in a forward direction from the housing 10, the saw chain 12 is guided so as to run round along 6 the edge of said blade. To produce the saw chain tension, the blade 13 is supported so as to be longitudinally displaceable along the housing 10, with the result that the distance between blade 13 and driving pinion I I may be varied and the saw chain 12 may therefore be tensioned to a greater or lesser extent. To said end, the blade 13 lies with its rear region against a housing shoulder 10 1 and a guide web 102, which protrudes ftom the housing shoulder 101, projects with guiding clearance into an oblong hole 14 extending in longitudinal direction of the blade 13.

To tension the saw chain 12 and fix the blade 13 in a position on the housing 10 which maintains the adjusted chain tension, a chain tensioning apparatus is provided, which comprises a setting module 15 (Fig. 1) acting upon the blade 13 for displacement of the latter and a tensioning module (Figs. 2 and 3), which fixes the blade 13 in a friction-locked manner on the housing 10 and/or against the housing shoulder 10 1. Driving pinion I I and chain tensioning apparatus are covered by a protective or outer casing 17 which is fixed on the housing 10, wherein the operating elements for the manual operation of setting module 15 and tensioning module 16 are freely accessible at the outside of the outer casing 17.

The tensioning module 16 shown in Figs. 2 and 3 comprises a tension bolt 18 fastened in the housing 10, namely in the guide web 102, as well as a tensioning wheel 19 rotating on the tension bolt 18. The tension bolt 18, which is preferably screwed by a threaded portion into the guide web 102, extends through the oblong hole 14 in the blade 13 and carries on its end a flange- or T-shaped bolt head 18 1. The tensioning wheel 19 at the rear carries a tensioning pin 20, which is coaxial with the tension bolt 18 and which extends through a circular recess 171 in the outer casing 17 and rests against the blade 13. The tension bolt 18 extends through 7 a rectangular opening 21 in the base of the tensioning pin 20 so that the bolt head 181 is accommodated inside the tensioning pin 20 and projects with slight clearance beyond the base of the tensioning pin 20. The opening 21 is in said case fashioned so that the bolt bead 181 is insertable with slight clearance through the opening 21. Formed on the base of the pot-shaped tensioning pin 20 are two tensioning surfaces 22 ascending helically in axial direction and situated one on either side of the opening 21, as may be seen in Fig. 2. As the tensioning wheel 19 rotates, said tensioning surfaces 22 slide progressively under the Tshaped bolt head 181, with the result that the tensioning pin 20 is pressed increasingly axially against the blade 13 and so the blade 13 is clamped firmly against the housing shoulder 10 1. The diameter of the tensioning wheel 19 is as large as possible so that in tune with the ascent of the helical tensioning surfaces 22 the necessary tensioning force may be summoned up manually without difficulty. Working loose of the tensioning wheel 19 during operation of the chain saw may additionally be prevented by a detent device (not shown here) between tensioning wheel 19 and outer casing 17 or by similarly appropriate constructional measures.

The setting module 15, of which only the setting wheel 23 is shown in Fig. 2 and all of its structural details are shown in Fig. 1, comprises a threaded spindle 24 which is aligned so as to be slightly inclined relative to the axis of the blade 13 and projects with a shaped pin 25, which protrudes at right angles from its one spindle end, positively into a bore 26 provided in the blade 13. The bore 26 in the blade 13 may either be introduced separately or alternatively one of the bores 26 which are already provided in the blade 13 for supplying oil to the saw chain 12 may be used, in the manner shown in Fig. 1. The setting wheel 23 for operating the setting module 16 is screwed onto the threaded spindle 24 and fixed in an axially nondisplaceable manner between two abutments 27, 28, which are fastened either to 8 the housing 10 or to the outer casing 17. The setting wheel 23 itself projects with a peripheral portion through an.opening 172 (Fig. 2) in the outer casing 17 so that it may be operated from outside when the outer casing 17 is closed.

When the outer casing 17 is placed onto the housing 10, the shaped pin 2 5 on the threaded spindle 24 is inserted into the bore 26 and the opening 172 'in the outer casing 17 is placed over the setting wheel 23. At the same time, the recess 171 in the outer casing 17 engages over the tension bolt 18. The tensioning wheel 19 is then slipped, by means of the opening 21 in the tensioning pin 20, over the bolt head 181 of the tension bolt 18 onto the latter and rotated slightly so as to prevent it from falling off the bolt head 18 1. Then, by rotating the setting wheel 23 of the setting module 15, the blade 13 is displaced by the threaded spindle 24 in Fig. I to the right until the desired tension of the saw chain 12 fitted on the driving pinion I I is achieved. In said tensioned situation, the threaded spindle 24 plus shaped pin 25 occupies the position shown by dashes in Fig. 1. The tensioning wheel 19 is then rotated in a clockwise direction in Fig. 2 and its helically ascending tensioning surfaces 22 slide progressively under the T-shaped bolt head 181, with the result that the pot-shaped tensioning pin 20 of the tensioning wheel 19 is pressed increasingly against the blade 13 and the blade 13 is in turn clamped in a ftiction-locked manner against the housing shoulder 10 1. Thus, the blade 13 is fixed in an axially non-displaceable manner with the chain tension adjusted by the setting module 15.

Figs. 4 and 5 each show a side view of a chain saw, from which the outer casing 17 has been removed and in which the setting module 15 has been modified compared to the previously described chain saw. In both cases, the threaded spindle 24 is aligned at right angles to the blade longitudinal axis and disposed in 9 front of the chain wheel I I towards the blade 13. The threaded spindle 24 is fastened non-rotatably to the housing 10 and carries at one end a rotary button 3 0, which projects from the housing 10. Alternatively, the threaded spindle 24 may be accommodated rotatably in the outer casing 17. The connection between threaded spindle 24 and blade 13 is effected by means of a coupling linkage 3 1, which in Fig. 4 comprises two coupling bars 32 and in Fig. 5 comprises one coupling bar 32. Each coupling bar 32 is coupled at one end to a threaded coupling 33 screwable on the threaded spindle 24 and engages once again with a shaped pin 25, which protrudes at right angles from the other end, positively into the bore 26 provided in the blade 13. In the coupling linkage 31 with two coupling bars 32 shown in Fig. 4, the two threaded couplings 33 are seated on two threaded portions 34, 3 5 with oppositely directed thread leads, while in the coupling linkage 31 in Fig. 5 the threaded spindle 24 has only a single threaded portion 34. In the coupling linkage 31 in Fig. 4, a single shaped pin 25 is associated with both coupling bars 32 and hinge-connects both coupling bars 32 to one another at their free end and projects positively into the bore 26 of the blade 13.

In the chain saw illustrated in various views and sectional views in Figs. 6 - 8, the chain tensioning apparatus comprises an identical tensioning module 16 but a, once more, modified setting module 15. Here, the setting module 15 has a slide 3 6, which acts upon the blade 13 and is loaded by at least one tension spring 3 7, here two tension springs 37, in chaintensioning displacement direction, i.e. in Fig. 6 to the right. The approximately U-shaped slide 36 shown in plan view and in two side views in Fig. 9 comprises a flat part 360 forming the transverse web of the U, which at the front end carries a downwardly bent lug 361 and leading laterally away from which are two offset and bent limbs 362, which each have a slip-on tongue 363 formed on the free end. Provided in the centre of the flat part 360 is a recess 364, by means of which the slide 36 may be slipped over the bolt head 181 of the tension bolt 18 of the tensioning module 16 onto the tension bolt 18. The lug 361 is designed so as to be able to engage into the oblong hole 14 formed in the blade 13 and used to guide the blade 13.

The two tension springs 37 take the form of compression springs, which are supported by one end against the ftee ends of the limbs 362 of the slide 36 and by the other end against a tensioning plate 38 lying opposite the limb ends and which shift the slide 36 far enough forward for its lug 361 to be applied under spring action against the, in Fig. 6, front end of the oblong hole 14 in the blade 13. The tension springs 37 are accommodated on the one hand on slip-on tongues 363 at the end of the limbs 3 62 and on the other hand on guide pins 3 8 1, which project from the tensioning plate 38. The limbs 362 and the tension springs 37 are guided in guides 39 comprising ribs, which are injection-moulded on the outer casing 17 and against which the tensioning plate 38 is supported in the tensioned state. The tensioning plate 38 is displaceable in longitudinal direction of the blade 13 and its rear side remote from the tension springs 37 rests under the preloading force of the tension springs 37 against an eccentric 40, which may be rotated by means of a swivelling lever 41 (Fig. 8). The entire setting module 15 is disposed in the outer casing 17 and the swivelling lever 41 - like the tensioning wheel 19 of the tensioning module 16 - is situated at the outside of the outer casing 17.

To assemble the chain tensioning apparatus, after the blade 13 has been placed against the housing shoulder 10 1 and the saw chain 12 fitted into the driving pinion 11, the slide 36 simultaneously with mounting of the outer casing 17 is laid against the blade 13 in such a way that its lug 361 projects into the oblong hole 14 in the blade 13. The blade 13 is then pushed forward by the slide 36 until the outer 11 casing 17 is able to latch by means of a hook 42 in the housing 10. The opening 21 in the tensioning pin 20 in said case has to be situated in such a way that the tensioning wheel 19 may be fitted over the bolt head 181 of the tension bolt 18. During said assembly of the outer casing 17, the eccentric 40 is disengaged, i.e. its periphery is at the maximum distance from the driving pinion 11. The outer casing 17, after it has been fitted, is supported in a rearward direction against the housing 10, wherein the hook 42 prevents lateral yielding of the outer casing 17. The tensioning wheel 19 is then rotated slightly to prevent the bolt head 181 from passing back out of the opening 21. Then, to tension the saw chain 12, the swivelling lever 41 is moved into the swivelling position shown in Fig. 8, with the result that the eccentric 40 is rotated and the tensioning plate 38 shifts in the direction of the driving pinion 11. The two tension springs 37 in the form of compression springs are in said case preloaded towards the slide 36 in such a way that the force needed to tension the saw chain 12 is transmitted to the lug 361 of the slide 36, the blade 13 is pushed forward and in the process the saw chain 12 is tensioned. The need, during fitting of the outer casing 17, for manual expenditure of the spring force required for the total chain tension is avoided by virtue of the subsequent tensioning of the tension springs 37 by the eccentric 40. After relocation of the lever 41 the saw chain 12 has a predetermined chain tension, which is always the same. The tensioning wheel 19 of the tensioning module 16 is then rotated, in Figs. 7 and 8, in clockwise direction so that - as already described - the tensioning surfaces 22 at the base of the pot-shaped tensioning pin 20 of the tensioning wheel 19 slide under the T-shaped bolt head 181 of the tension bolt 18 and so the tensioning pin 20 of the tensioning wheel 19 non-displaceably fixes the blade 13 in a friction-looked manner against the housing shoulder 10 1 of the housing 10.

12 To readjust the tension of the saw chain 12, the tensioning wheel 19 merely has to be loosened by turning it, in Figs. 7 and 8, in anticlockwise direction. The tensioning module 16 is therefore released and the spring action of the tension spring 37 of the setting module 15 displaces the blade 13 further in the direction of expulsion from the housing 10, with the result that the saw chain 12 is set once more to the same chain tension. The tensioning wheel 19 then bas to be retightened in clockwise direction so that the tensioning module 16 once more fastens the blade 13 to the housing 10.

13

Claims

Claims

1. Chain saw having a housing (10), having a driving pinion (11) supported in the housing (10) for motor-driving a saw chain (12), having a blade (13) which projects in a forward direction from the housing (10) and along its blade edge guides the revolving saw chain (12) fitted in the driving pinion (11) and, for tensioning the saw chain (12), is supported so as to be longitudinally displaceable along the housing (10) in a direction increasing the distance from the driving pinion (11), and having a chain tensioning apparatus, which comprises a setting module (15) acting upon the blade (13) for displacement of the latter as well as a tensioning module (16) fixing the blade (13) to the housing (10) in a friction-locked manner, characterized in that the tensioning module (16) comprises a tension bolt (18), which is fastened in the housing (10) and extends through an oblong hole (14) extending in the blade (13) in longitudinal direction of the latter and carries a T-shaped bolt head ( 18 1), and a tensioning wheel (19), which is rotatable on the tension bolt (18) and lies with a rear, coaxial tensioning pin (20) against the blade (13), tbatthe bolthead (181) lies in the pot-shaped tensioningpin (20) so as to project beyond the latter's pot base and that formed on the pot base are two tensioning surfaces (22), which ascend helically in axial direction and which, when the tensioning wheel (19) is rotated in tensioning direction, slide progressively under the bolt head (18 1).

14 2. Chain saw according to claim 1, characterized in that in the pot base of the tensioning pin (20) a rectangular opening (21) is provided for passage of the bolt head (18 1) and that the two tensioning surfaces (22) are disposed on either side of the opening (2 1).

3. Chain saw according to claim I or 2, characterized in that the tensioning wheel (19) extends with its tensioning pin (20) through a circular recess (171) in an outer casing (17), which covers the driving pinion (11) and the setting module (15).

4. Chain saw according to the preamble of claim 1, in particular according to one of claims I to 3, characterized in that the setting module (15) comprises a manually drivable threaded spindle (24), which acts directly or via a coupling linkage (3 1) upon the blade (13) for longitudinal displacement of the latter.

5. Chain saw according to claim 4, characterized in that the threaded spindle (24) extends along or is slightly inclined relative to the longitudinal axis of the blade (13) and projects with a shaped pin (25), which protrudes at night angles from its one spindle end, positively into a bore (26) provided in the blade (13), preferably into an oil bore used for the oil supply, and that a setting wheel (23) screwable on the threaded spindle (24) is rotatably supported between two abutments (27, 28).

6. Chain saw according to claim 5, characterized in that the setting wheel (23) is accessible from the outside through an opening (172) worked in an outer casing (17), which is fastened to the housing (10) and covers driving pinion (11) and setting module (15), and that the two abutments (27, 28) are fastened to the outer casing (17) or to the housing (10).

7. Chain saw according to claim 4, characterized in that the threaded spindle (24) is aligned at right angles to the longitudinal axis of the blade (13) and is rotatably supported on the housing (10) or on an outer casing (17), which is fastened to the housing (10) and covers driving pinion (11) and tensioning module (16), and carries a rotary button (30) lying outside of the housing (10) or outer casing (17), that at least one screwable threaded coupling (33) is seated on the threaded spindle (24) and that a coupling bar (32) is coupled by its one end to the threaded coupling (33) and projects with a shaped pin (25), which protrudes at right angles from its other end, positively into a bore (26) provided in the blade (13), preferably into an oil bore used for the oil supply.

8. Chain saw according to claim 7, characterized in that two threaded couplings (33) are screwable on threaded portions (34, 35) with oppositely directed thread leads and the two coupling bars (32) coupled in each case to one threaded coupling (33) engage with a common shaped pin (25) into the bore (26) in the blade (13).

9. Chain saw according to the preamble of claim 1, in particular according to one of claims I to 3, characterized in that the setting module (16) comprises a slide (26), which acts upon the blade (13) 16 and is loaded by at least one tension spring (37) in chain-tensioning displacement direction.

10. Chain saw according to claim 9, characterized in that the at least one tension spring (37) is tensionable after the slide (36) has been placed against the blade (13).

11. Chain saw according to claim 10, characterized in that the at least one tension spring (37) takes the form of a compression spring, which is supported by one end against the slide (36) and by the other end against a tensioning plate (38), which is displaceable in longitudinal direction of the blade (13) by means of an eccentric (40).

12. Chain saw according to one of claims 9 to 11, characterized in that the slide (26) comprises a flat part (360), which rests against the blade (13) and engages with a bent lug (361) into an oblong hole (14) formed in the blade (13) for guidance of the latter along the housing (10), which lug lies under the spring action of the at least one tension spring (37) against the front end of the oblong hole (14).

13. Chain saw according to claim 12, characterized in that projecting laterally and preferably in an offset manner from the flat part (360) are two bent limbs (362) which extend towards the tensioning plate (38), that two compression springs are provided as tension springs (37), which are supported by one spring end against the limb ends and engage over slip-on tongues (363) formed there and are 17 supported by their other spring end against the tensioning plate (3 8) and are received there by guide pins (381) projecting from the tensioning plate (38), and preferably that the limbs (362) and compression springs are situated in guides (39).

14. Chain saw according to one of claims 11 to 13, characterized in that the setting module (15) with slide (36), tension spring (37), tensioning plate (38) and eccentric (40) is fastened in an outer casing (17), which is fastenable to the housing (10) and covers the driving pinion (11) and the setting module (15), and that the eccentric (40) is operable by means of a swivelling lever (41) which is accessible from outside of the outer casing (17). _ 15. A chain saw substantially as herein described with reference to the accompanying drawings.