GB2346109A

GB2346109A - A hand-held machine saw

Info

Publication number: GB2346109A
Application number: GB9928723A
Authority: GB
Inventors: Nicolantonio Aldo Di
Original assignee: Scintilla AG
Current assignee: Scintilla AG
Priority date: 1998-12-28
Filing date: 1999-12-03
Publication date: 2000-08-02
Anticipated expiration: 2019-12-03
Also published as: CH693871A5; DE19860462A1; GB2346109B; DE19860462B4; GB9928723D0

Abstract

A hand-held machine saw having a sawing tool driven by an electric motor 11 is characterized in that the sawing tool is an endless saw belt 17 tensioned between a rotating driving pulley 13 and a return pulley 14. The endless saw belt is tensioned in the region between the two pulleys with a small parallel interval between the belt sections which lie opposite one another. Preferably rollers 211, 221, 212, 222 are provided as guiding and tensioning elements, which press elastically or rigidly against one of the two belt sections from the outside. A guide rail 23 may also be provided to guide the inwardly facing belt sections and the belt back 24. Removable end caps 25, 26 may be provided for the purpose of changing the endless saw belt.

Description

2346109 Hand-held machine saw The starting point of the invention is a

hand-held machine saw of the kind defined in the pre-characterising clause of claim 1.

A known hand-held machine saw of this type (CH 434 694), which is designed as a compass saw, has a lifting rod which is guided in a vertically displaceable manner in the machine housing and projects out of the said machine housing with one of its ends and which carries, at this point, a clamping chuck for clamping-in a compass saw blade. The lifting rod is driven by an electric motor, via a toothedwheel gear unit and an eccentric unit in a vertical up and down movexnent and the compass saw blade is supported, with its saw-blade back, against a supporting roller mounted on the machine housing.

Advantages of the invention The hand-held machine saw according to the invention having the features 'in claim I has the advantage of permitting the same work as with a compass saw, but of being superior to a compass saw in respect of constructional requirements and manufacturing costs and also in the results of sawing operations and in sawing or cutting performance. The two belt sections of the endless saw belt which are guided at a close parallel interval form two cutting tools which cut in both directions, upwards and downwards. As a result of this simultaneous engagement in the workpiece by two cutting tools operating in opposite directions, and as a result of the continuous cutting by the saw without the acceleration and slowingdown of the saw blade which is customary in other compass saws, on the one hand, the results of sawing operations are improved and, on the other hand, the I a substantially higher cutting speed and a longer life-span of the sawing tool are achieved. In addition, as a result of the simultaneous engagement of the cutting tools, which move in opposite directions, no reaction forces occur, that is to say the reaction forces brought about by the two cutting tools cancel each other out. As a result of the elimination of the oscillating movement of the sawing tool, which is replaced by a simple rotating movement, there is no expensive gear unit for converting the rotation of the electric motor into a lifting movement of the sawing tool, and the bearings for the moving parts are simplified, so that the handheld machine saw becomes substantially simpler in its constructional make-up and can therefore be produced in a more cost- effective manner.

As a result of the measures set out in the other claims, advantageous ftirther developments of, and improvements to the hand-held machine saw indicated in claim I are possible.

Drgyjngs The invention is explained in greater detail 'in the following description with the aid of an exemplified embodiment represented in the drawings. In a diagrammatic representation in each case, figure I shows a longitudinal section through a hand-held machine saw which is to be used as a compass saw, figure 2 shows a view of the hand- held machine saw, in the direction of the arrow Il in figure 1, with the housing caps removed, and figure 3 shows an enlarged representation of the section HI-111 in figure 2.

3 Description of the exemplified embodiment

The hand-held machine saw represented, diagrammatically in each case, 'in longitudinal section 'in figure I and "in end view in figure 2, serves as a replacement for an electric motor-driven hand-held compass saw of conventional type. It has a machine housing 10 which receives an electric motor I I driving, via a toothed-wheel gear unit not represented here, a driving pulley 13 which is rotatably mounted in the machine housing 10 and is disposed, in a torsion-proof manner, on a shaft mounted 'in the said machine housing 10. A fan which is seated on the shaft, together with the driving pulley 13, is indicated by 12. A return pulley 14 is rotatably mounted in a return housing 15, vertically underneath the driving pulley 13 and at a great distance from the latter. Altematively, the return pulley may be disposed in a stationary manner, so that it acts as a sliding element for the saw belt. The return housing 15 is rigidly fastened to the machine housing 10 by means of a long, bar-shaped holding element 16 which tends vertically downwards, away from the machine housing 10. An endless saw belt 17, one end face of which is set with saw teeth 18 (only two saw teeth 18 are indicated in figure 1), rests with one broad side on the driving pulley 13 and on the return pulley 14 and is tensioned between the said pulleys in such a way that those belt sections which are situated between the two pulleys 13, 14 lie opposite one another at a slight parallel interval. For the purpose of producing this belt tension, there is disposed in the machine housing 10 and in the return housing 15, 'in each case, directly at the housing slots, 19 and 20 respectively, constructed therem' for the passage of the two belt sections of the endless saw belt 17, a pair, 21 and 22 respectively, of guiding and tensioning elements in each case, which are constructed, 'in the exemplified embodiment, as rotatingly mounted rollers, 211, 212 and 221, 221 respectively, and which press elastically or rigidly in each case against one of the two belt sections firom outside. The rollers 211, 212 and 22 1, 4 222 are constructed so as to be mutually adjustable vertically and/or horizontally, so that the desired belt tension can be set as a result of their horizontal and/or vertical displacement.

The guiding and tensioning elements, 211, 221 and 212, 222 respectively, are in each case disposed as a pair, 21 and 22 respectively, underneath the driving pulley 13 and above the return pulley 14, in order to fix the small interval between the saw belt sections and also to increase the angle of wrap, particularly at the driving pulley, and reduce drive slip.

In the region between the upper pair of rollers 21 mounted in the machine housing 10 and the lower pair of rollers 22 mounted in the return housing 15, the two belt sections are guided, at side faces which face towards one another, on a guide rail 23 which is constructed on the holdm"g element 16 in one piece. Under these circumstances, the guide rail 23 is constructed in such a way that guidance of the belt sections is effected on the sides which face towards one another and on the belt back 24 of the said sections which is averted from the saw teeth 18. As can be seen in the sectional representation in figure 3, the holding element 16 has, for this purpose, a mushroom-shaped cross-section whose stalk which forms the guide rail 23 points in the direction of advance of the saw, and the breadth of whose head is smaller than the breadth of the saw cut of the endless saw blade 17 which forms, in the region between the pairs of rollers 21, 22, two parallel cutting tools which run in opposite directions, are guided at a small parallel interval in relation to one another and produce a common saw cut in the workpiece. Instead of a mushroom shape, it is also possible to select a T-shaped cross-section for the holding element 16 and guide rail 23, in which case the longitudinal web forms the guide rail 23 and the transverse web engages over the back of the belt sections for the purpose of guiding them.

I For the purpose of changing the endless saw belt 17, the end faces of the machine housing 10 and return housing 15 are masked by removable end caps 25, 26 which are clipped to the particular housing, 10 and 15 respectively. The housing slots 19 and 20 for the passage of the endless saw belt 17 in the machine housing 10 and in the return housing 15 have their openings at the end face of the housings, 10 and 15 respectively, and are covered by the end caps 25 and 26. When the end caps 25, 26 are attached, both housings 10, 15 are completely closed and only those two belt sections of the endless saw belt 17 which extend between the machine housing 10 and the return housing 15 are exposed.

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Claims

1. Hand-held machine saw having a sawing tool driven by an electric motor, characterised in that the sawing tool is an endless saw belt (17) which is tensioned between a rotating driving pulley (13) and a return pulley (14) disposed at a distance from the latter, and is guided, in the region between the two pulleys (13, 14), with a small parallel interval between the belt sections which lie opposite one another.

2. Machine according to claim 1, characterised in that the driving and return pulleys (13, 14) are disposed vertically one above the other in the operational position of the machine. 2a. Machine according to claim 2, characterised in that a pair (21, 22) of guiding elements which fix the parallel interval between the belt sections which lie opposite one another, is disposed, in each case, underneath the driving pulley (13) and above the return pulley (14).

3. Machine according to claim 2, characterised in that the driving pulley (13) is rotatably mounted 'in a machine housing (10) containing the electric motor (11) and the return pulley (14) is disposed in a return housing (15) lying underneath the said machine housing, and that the return housing (15) is rigidly fastened to the machine housing (10) by means of an elongated, bar-shaped holding element (16).

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4. Machine according to claim 3, characterised in that the holding element (16) has a guide rail (23) on which the parallel belt sections of the endless saw belt (17) are guided.

5. Machine according to claim 4, characterised in that the guide rail (23) is constructed in such a way that guidance of the belt sections is effected on the sides of the belt which face towards one another and on the belt back (24) which is averted from the saw teeth (18).

6. Machine according to claim 5, characterised in that the guide rail (23) is constructed on the holding element (16) in one piece, and the said holding element (16) has a T-shaped or mushroom-shaped cross-section, whose longitudinal web or mushroom stalk which forms the guide rail (23) points in the direction of sawing, and whose transverse web or head breadth is smaller than the breadth of the saw cut.

7. Machine according to one of claims 4 to 6, characterised in that there is disposed, at either end of the guide rail (23), a pair (21, 22) of guiding and tensioning elements in each case, whose elements (211, 212, 221, 222), which lie on mutually averted sides of the belt sections and serve to guide and tension the belt, rest against one of the two belt sections in each case "in such a way as to be mutually adjustable vertically and/or horizontally.

8. Machine according to claim 7, characterised in that the upper pair (2 1) of elements is disposed in the machine housing (10) and the lower pair (22) of elements is disposed in the return housing (15).

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9. Machine according to one of claims I to 8, charactenised 'in that the machine housing (10) and the return housing (15) have, 'in each case, a removable end cap (25, 26) which completely masks the driving pulley (13) and the return pulley (16) respectively.

10. Machine according to one of clainis I to 9, characterised in that there is constructed in the machine housing (10) and in the return housing (15), in each case, a housing slot (19, 20) for the passage of the endless saw belt (17), which housing slot emanates from the end face covered by the end cap (25, 26), and that the housing slots ( 19, 20) are covered, at the end faces, by the end caps (25, 26).

11. A hand-held machine saw substantially as herein described with reference to the accompanying drawings.

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