GB2464398A - Portable saw with blade chuck inside protective tube - Google Patents

Abstract

A manual-lift sawing machine, such as a keyhole saw (10, fig 1), comprises a lifting rod 30, and a chuck 38 for releasably holding a saw-blade 36. The lifting rod is configured as a tube 31, which at a free end receives the chuck. The chuck extends inwards into the tube and projects beyond the lower end of the lifting rod. The lifting rod is capable of being operated for the purpose of changing the saw-blade by virtue of the fact that the chuck bears at least two clamping bodies, such as rollers 46. In the course of the clamping of the saw-blade the rollers are supported on the two opposing flat sides of the saw blade at the same height in the chuck, and move along oblique surfaces 53 of the chuck into a clamping position towards the saw-blade.

Description

Description Title

Manual-lift sawing machine State of the Art The present invention takes as its starting-point a manual-lift sawing machine according to the precharacterising portion of Claim 1.

From unpublished German patent application DE 102008003739.7 a chuck is known which is integrated into a round lifting rod of a keyhole saw and which projects with its outermost region only minimally beyond the lower end of the lifting rod and which serves as an operating button for releasing the clamped saw-blade from the chuck.

The holding function of this chuck is good but capable of being improved.

From EP 1 328 368 Bl a manual-lift sawing machine is known with a flat lifting rod and with a box-like chuck with an externally seated sliding sleeve arranged on said lifting rod. This combines good ease of operation with high clamping force. But, as distinct from tubular lifting rods with a chuck arranged in the interior, flat lifting rods have relatively large chucks protruding laterally at the bottom. Since only the part of the lifting rod reaching from the top down to the chuck, but not the chuck itself, can be guided in lifting-rod bearings, the guided part of the flat lifting rods is shorter than that of round lifting rods with a chuck seated in the interior. Accordingly, the spacing between upper lifting-rod bearing and lower lifting-rod bearing of flat lifting rods is small. The externally seated chuck thereof must, for the purpose of implementing the sawing stroke, project beyond the lower lifting-rod bearing with a part of the free end of the lifting rod having the length of the sawing stroke. As a result, a higher flexural moment acts on the protruding region of the flat lifting rod than on a tube-like lifting rod with chuck seated in the interior and with larger spacing of the lifting-rod bearings. Under certain circumstances, the flat lifting rod is deformed by the operating forces in the course of sawing, so that the saw-blade can work its way out of the channel that is provided and can make accurate sawing difficult. The holding function of this chuck is good but is to be improved further in conjunction with a lifting rod made of tubular material.

Disclosure of the Invention

By virtue of the combination of the features according to Claim 1, a manual-lift sawing machine is created that by reason of the integrated, easily manageable, safe chuck of the saw-blade enables a tube-like lifting-rod structure that is particularly secure against deformation in the course of sawing, with a large spacing of the lifting-rod bearings, whereby as a consequence of the arrangement of the clamping body in the clamping position of the saw-blade the clamping force increases with each action of longitudinal force on the saw-blade in the direction out of the chuck, but in the direction into the chuck the clamping force is diminished.

By virtue of the fact that the clamping bodies consist of two pairs of rollers, which are arranged with an axial spacing along the lifting-rod axis and relative to the clamping end in the chuck, the saw-blade is securely clamped on the flat sides at two axially spaced points by linear contact on both sides.

By virtue of the fact that the rollers are mounted in the clamping slide, the transverse spacing of each roller-pair being variable in limited manner, the releasing and clamping operations can be actuated in low-friction manner and without delay or directly.

By virtue of the fact that the clamping slide consists of several parts, in particular two slide-halves forming a cylinder-like body, said slide-halves can be configured in weight-saving manner.

By virtue of the fact that the slide-halves are supported on one another in positive manner, the clamping slide as a whole functions reliably and directly.

By virtue of the fact that each roller is rotatably mounted in each instance on two slide-halves, in particular on the opposing insides thereof, preferentially in a recess between the slide-halves, assembly of the operational clamping slide is particularly simple.

By virtue of the fact that each roller is rotatably mounted with its ends in elongated holes introduced on the opposing insides of the slide-halves and oriented at right angles to the lifting-rod axis, the rollers function as clamping bodies, because they can both rotate and move along the elongated hole.

By virtue of the fact that in the case of an axial displacement of the clamping slide the rollers are capable of rolling along in free-running guided manner in relation to a raceway extending in angled manner relative to the lifting-rod axis, in particular in relation to a stationary raceway carrier, the clamping and releasing positions of the rollers are reproducibly defined.

By virtue of the fact that the clamping slide serves for releasing the rollers from the clamping end of the saw-blade, the chuck can be operated easily.

By virtue of the fact that a push-button emerging axially from the lifting rod at the bottom serves as part of the clamping slide for the purpose of actuating the chuck and is held above the lifting rod at maximal overhang at the bottom, in particular by means of a compression spring, the chuck is operationally safe.

By virtue of the fact that in each case a leaf spring is arranged in a longitudinal recess of a slide-half, there is a friction-reducing and wear-reducing supporting surface for the clamping slide in relation to the narrow sides of the saw-blade.

By virtue of the fact that the support tube displaceably receives the clamping slide in the interior of the chuck, the flexural stiffness of the lifting rod is considerably improved.

By virtue of the fact that the casing tube, the raceway carrier and the fastening spring with the support tube serve as a rigid carrier region of the lifting rod, together with the rollers and the leaf springs the clamping slide forms a chuck that is particularly robust against unintentional deflecting in the course of sawing.

Drawing The invention is elucidated in more detail below on the basis of an exemplary embodiment with associated drawing.

Shown are: Figure 1: a partial longitudinal section through a keyhole saw with the new chuck, Figure 2: the side view of the lifting rod with saw-blade and chuck in the form of a detail, Figure 3: an enlarged side view of the chuck with parts of the lifting rod according to Figure 2, Figure 4: the view according to Figure 3 without lifting rod and support tube, Figure 5: a guide element of the chuck in the form of a detail, Figure 6: the view of the clamping slide according to Figure 4 with leaf spring, Figure 7: the clamping slide according to Figure 6 without leaf spring, Figure 8: the leaf spring in the form of a detail, Figure 9: the casing tube according to Figure 2 in the form of a detail and Figure 10: a fastening element for retaining the chuck on the casing tube.

Description of the Exemplary Embodiment

The keyhole saw 10 represented in Figure 1 consists of a housing 12 in which a symbolically represented motor 14 is arranged. The motor 14 serves for driving a lifting rod 30 and imparts to the latter via a transmission 20, 22, 26, 28 an oscillating motion which is transmitted to a saw-blade 36. For this purpose the saw-blade 36 has to be releasably clamped in a chuck 38 at the end of the lifting rod 30.

The housing 12 is pivotably connected on its underside to a foot plate 54, through which the saw-blade 36 passes downwards in order to be able to saw below the foot plate 54.

The lifting rod 30 -which in the lower region is configured as a smooth, round tube 31 -is mounted in the housing 12 in rectilinearly displaceable manner by means of an upper and a lower lifting-rod bearing 32, 34 and bears at its lower end the chuck 38, integrated in the interior of the tube 31, for receiving the saw-blade 36. The tube 31 is mounted between its outermost ends in the lifting-rod bearings 32, 34 which are widely spaced from one another.

In this connection, the large spacing between the upper and the lower lifting-rod bearings 32, 34 brings about a stable, straight guidance of the lifting rod 30. Since the chuck 38 is arranged at the lower free end in the interior of the tube 31, without going radially beyond this there, the tube 31 can be encompassed as far as precisely this outermost end by the lower lifting-rod bearing 34 and can move therein in oscillating manner. As a result, at the end of the upward stroke or at the start of the upward stroke of the lifting rod 30 the saw-blade 36 clamped in the chuck 38 passes with its shank 37 through the region of the lower lifting-rod bearing 34.

By virtue of the fact that the elongated saw-blade 36 is seated in clamped manner relatively close to the lower lifting-rod bearing 34, the lever lengths for the forces acting on saw-blade 36 and lifting rod 30 in the course of sawing are smaller than in the course of stroke sawing with more closely spaced lifting-rod bearings 32, 34.

Consequently the saw-blade 36 and also the lifting rod 30 absorb the flexural moments arising in the course of sawing as a consequence of their high stiffness. Hence sawing can be effected more accurately and more quickly.

The motor 14 has a motor shaft 18 rotating in a motor bearing 15 in a rear housing wall 13 of an inner housing 16, which projects forwards right up close to the lifting rod 30. On the end of the motor shaft 18 there is seated a motor pinion 20 which meshes with an eccentric gear 22.

The latter is rotatably mounted on a gear axle 24 which is seated in a bearing bush 25 of the rear housing wall 13. 2 roller bearing 23 is arranged between eccentric gear 22 and gear axle 24, and an axial locking device 21 for the eccentric gear 22 is arranged at the end of the gear axle 24.

The eccentric gear 22 bears an eccentric pin 26 projecting axially towards the lifting rod 30, which engages in a link 28 firmly connected to the tube 31 at the top and converts the rotary motion of the eccentric gear 22 into an oscillating motion of the lifting rod 30 or of the saw-blade 36. In addition, a housing-side guide roller 56 for supporting the back of the saw-blade 36 is provided, which when required imparts to the saw-blade 36 an oscillation moving in the direction of feed.

On the side opposed to the eccentric pin 26 the eccentric gear 22 bears a further eccentric in the form of an eccentric disc 27. The latter is arranged with its eccentricity opposed to, or offset by 1800 relative to, the eccentric pin 26 and drives a counterweight, which is not represented, opposed to the lifting rod 30. Said counterweight balances the inertial forces of the lifting rod in the course of the oscillating motion thereof.

The particulars of the chuck 38 will be elucidated in the following with reference to Figures 2 to 5.

Figure 2 shows, in a side view, the lifting rod 30 in the form of a detail, wherein the lifting-rod axis 29 thereof, a flat piece 33 with link 28, a round tube 31 fastened thereto and adjoining in the downward direction, the saw-blade 36 and also a button 41 of a clamping slide 44 of the chuck 38 can be discerned. With the button 41 a clamping slide 44 for releasing or enabling the saw-blade 36 is axially displaceable.

Figure 3 shows the lifting rod 30 without the outer tube 31, so that a central, inner support tube 42 becomes visible which with its upper region is fixed at the bottom to the flat piece 33 and is encompassed concentrically over its entire length by a biased spiral spring 40 designed as a compression spring. The spiral spring 40 is supported at the top on the flat piece 33 and at the bottom on two slide-halves 43, 45 axially supported on one another in certain regions and configured in mirror-image manner, which jointly form the clamping slide 44 and may consist of plastic. In Figure 3 the upper slide-half 45 is disassembled, so that only the lower slide-half 43 is visible. Both slide-halves 43, 45 encompass with their upper region the lower region of the support tube 42 from outside in the manner of a ring and hence form in relation to the support tube 42 and contrary to the force of the spiral spring 40 a sliding guide which permits an axially straight displacement of the clamping slide 44 with a clamping stroke of about 10 mm in relation to the support tube 42.

Between the two slide-halves 43, 45 a slot is formed in which two radially opposing, elongated raceway carriers 50, 51, preferentially stamped parts, are arranged. The latter are fixed axially in positive manner from outside in relation to the outer tube 31 by means of a ring-like fastening spring 49 passing through said tube and are supported with their radial outsides on the inner wall of the tube 31, opposing one another. In the event of axial displacements of the clamping slide 44 on the tube 31 which are operationally necessary, they are imrnobilised in fixed manner and form for said clamping slide a straight guide with only slight sliding friction. Accordingly, the clamping slide 44 is easily displaceable upwards or downwards in relation to the raceway carriers 50, 51. The raceway carriers 50, 51 exhibit or' their radial inside in each instance two raceways 53 which extend obliquely in relation to the lifting-rod axis 29. On the raceways 53 in the two slide-halves 43, 45 there are mounted rollers 46 which in the course of the sliding of the clamping slide 44 along the raceways 53 are displaceable in free-running -10 -manner at right angles to the lifting-rod axis 29, as if actuated by a wedge.

Each of the two slide-halves 43, 45 bears centrally a longitudinally inserted leaf spring 52 which serves as slide rail for the narrow sides of a saw-blade 36 to be clamped and hence protects the two slide-halves 43, 45 made of plastic against wear as a result of frictional contact with the saw-blade 36. At the same time, the leaf springs 52 seek to push the slide-halves 43, 45 radially outwards from one another in biasing manner, so that the lifting rod moves in low-vibration manner in the course of sawing.

At their lower ends the slide-halves 43, 45 bear, on the radially projecting region configured as a button 41, in each instance a cam 47 arranged at right angles to the lifting-rod axis 29 and a hollow 48, which are arranged in inverse mirror-symmetric manner in relation to one another and after the disassembly of the clamping slide 44 set the slide-halves 43, 45 in positionally secure manner, engaging one another.

Figure 4 shows one of the two identically constructed raceway carriers 50, 51 in the form of a detail, wherein radially on the inside the angular contour of its two raceways 53 and also radially on the outside in the lower region a u-shaped groove 56 for engagement of the fastening spring 49 according to Fig. 3 or Fig. 10 are clearly discernible.

Figure 5 shows a view according to Fig. 3 without the raceway carrier 50, arranged therein on the right in the direction of view, and without upper leaf spring 52. As a -11 -result, the configuration of the slide-halves 43, 45 in their interaction with the remaining adjacent functional parts becomes discernible without the particulars according to Fig. 3 needing to be repeated once again here, whereby, going beyond Figure 3, a longitudinal slot 70 and a full-perimeter stop 68 in the lower region of slide-half 43 can be discerned. The latter is supported with the stop 68 in captive manner and, defining the stroke of the clamping slide 44, against the fastening spring 49. The longitudinal slot 70 serves for reducing the weight of the slide-halves 43, 45.

Figure 6 shows the lower slide-half 43 with leaf spring 52 inserted in a longitudinal groove 57, wherein the insertion opening 55 in halves for longitudinally displaceable entry of the support tube 42 can be discerned at the top, in which the upper end of the leaf spring 52 is inserted.

Slide-half 43 bears four mutually spaced elongated holes 58, 59, 60, 61 configured as blind holes. These form two axially spaced pairs 58, 59 and 60, 61 aligned at right angles to the longitudinal axis 29 and arranged on both sides of the longitudinal groove 57. In this connection the elongated holes of pair 58, 59 and of pair 60, 61 are arranged close to one another, the two pairs being, however, further axially spaced from one another. These four elongated holes 58, 59, 60, 61 may also be regarded as corners of a rectangle extending lengthwise symmetrically relative to the longitudinal axis 29, the longer side of which is about 15 mm long, and the shorter side of which is about 4 mm long. The longer sides run parallel to the longitudinal axis 29; the shorter ones run transversely.

-12 -In the elongated holes 58, 59, 60, 61 the ends of the rollers 46 -consisting, in particular, of plastic -: are displaceably mounted so as to be rotatable about their axis and at the same time at right angles to the longitudinal axis 29.

The function of the chuck 38 also becomes comprehensible from this. This function is based on the fact that in the course of the insertion of the saw-blade 36 into the clamping slide 44, preferentially in the vertical position of the lifting rod 30, the rollers 46 are supported in the elongated holes 58, 59 and 60, 61 on the two opposing flat sides of the saw-blade 36 and move aside radially outwards along the raceways 53 of the raceway carriers 43, 45, the elongated holes 58, 59 and 60, 61 are cleared to a certain degree in their longitudinal extent by the contour of the raceways 53.

For the purpose of clamping the saw-blade 36, the button 41 has to be pressed and the saw-blade 36 has to be pushed along the lifting-rod axis 29 into the interior of the chuck 38.

/fter insertion of the saw-blade 36, the rollers 46 move from both sides towards the saw-blade 36. Both pairs of elongated holes 58, 59 and 60, 61 and also 62, 63 and 64, hold the saw-blade 36 or the clamping end 37 thereof firmly along two axially spaced lines in the manner of pincers. In this connection the holding force becomes stronger, the greater the force that seeks to pull the saw-blade 36 downwards out of the chuck 38. Consequently the saw-blade 36 is centred in the chuck 38 with the aid of the raceway carriers 50, 51 and the rollers 46. By axial -13 -displacement of the clamping slide 44 by hand, by pressing the button 41 upwards, a clamped saw-blade 36 is released by the rollers 46 being able to move aside axially outwards along the raceways 53, so that the saw-blade 36 can then be readily taken out, whereby the rollers 46 move outwards in their elongated holes 58, 59 and 60, 61 or 62, 63 and 64, or rotate about their own axis so long as the clamping end 37 of the saw-blade 36 slides past said holes while being taken out.

Figure 7 shows the upper slide-half 45 in the form of a detail without leaf spring 52, wherein the longitudinal groove 57 for inserting the leaf spring 52 can be discerned and also the elongated holes 62, 63, 64, 65 for mounting the ends of the rollers 46. As already in Figures 5 and 6, a full-perimeter stop 68 on the lower region of the slide-halves 43, 45 becomes clear, which limits and locks the axial movement and the operating stroke of the clamping slide 44. Furthermore, as also in Figures 5 and 6, a longitudinal slot 70 for lightweight construction of the clamping slide 44 can be discerned.

Figure 8 shows the leaf spring 52 in the form of a detail and permits the function thereof as a slide rail and also as a positioning spring of the slide-halves 43, 45 relative to one another to become comprehensible.

Figure 9 show the outer tube 31 according to Figure 2 in the form of a detail, two diametrically opposed axial grooves 35 for entry of the flat part 33 of the lifting rod being arranged at the top and two identical grooves 35 being arranged at the bottom. At the bottom, merging axially with the lower grooves 35, transverse slots 39 -14 -situated diametrically opposite one another for the purpose of latching in the fastening spring 49 and passing it through right into the grooves 56 of the raceway carriers 50, 51 can be discerned.

Figure 10 shows the fastening spring 49, configured as a leg spring made of round spring wire, for fixing the chuck 38 to the outer tube 31 for the purpose of passing through the transverse slots 39.