Improved circular saw

Abstract: The invention relates to an electric hand tool comprising a housing (2) manufactured from a first material, for instance plastic, a first shaft (5) which is mounted in at least a first bearing (6) and a second shaft (7) which extends parallel to the first shaft (5) and is coupled to the first shaft (5) by means of a transmission and which is mounted in at least a second bearing (8), wherein both bearings are intersected by a plane extending perpendicularly of the shafts, wherein a plate (12) manufactured from a second material that is stronger than the first material is arranged extending perpendicularly of the shafts, which plate fixes the first and second bearing in at least partially confining manner at least in radial direction. The invention also relates to a sawing machine wherein the footplate is connected to the housing by at least two hinges and each hinge comprises a first plate extending perpendicularly of the pivot shaft and connected to the footplate and a second plate extending parallel to the first plate and connected to the housing, wherein a substantially round hole is arranged in the first or second plate and a recess fitting into the hole is arranged in the other plate, wherein the recess extends into the hole and is enclosed by the edges of the hole.

Description: The invention relates to an electric hand tool comprising a housing manufactured from a first material, for instance plastic, a first shaft which is mounted in at least a first bearing and a second shaft which extends parallel to the first shaft and is coupled to the first shaft by means of a transmission and which is mounted in at least a second bearing, wherein both bearings are intersected by a plane extending perpendicularly of the shafts. Such an electric hand tool is generally known. In the known electric hand-tool use is usually made of plastic housings. When the bearings are embedded or enclosed therein without further provision there is the danger of the bearings coming loose due to the comparatively large forces exerted thereon, whereby the shafts are no longer wholly parallel to each other and the transmission no longer operates properly. It is noted herein that heat develops at the bearings due to friction. A higher temperature will therefore usually prevail at the bearing which heats the plastic housing. As a result the housing could become soft when thermoplastic plastics are used, which aggravates the problems. This can result in an increased noise production and reduced power on the output shaft, or jamming of the machine. Constructions are now also known in the art in which the bearings are accommodated in a housing manufactured from a sturdy material, for instance a metal housing. However, this results in a costly construction. DE-A-35 36 464 discloses an electric hand tool, comprising a housing manufactured from a first material, for instance plastic, a first shaft which is mounted in at least a first bearing and a second shaft which extends parallel to the first shaft and is coupled to the first shaft by means of a transmission and which is mounted in at least a second bearing, wherein both bearings are intersected by a plane extending perpendicularly of the shafts, wherein a member manufactured from a second material that is stronger than the first material has been provided, which member is arranged extending perpendicularly of the shafts and fixes the first and second bearing in at least partially confining manner in at least radial direction. This prior art tool has a member of the above mentioned type with a complicated form and being costly to manufacture. The aim of the present invention is to provide such a member which can be produced cheaply. This aim is reached in that the member is a plate, the first and the second bearings protrude from the plate and that fixation of the plate takes only place through contact with the housing. The feature that the member is a plate offers the possibility of cheap manufacture. To obtain a contact between the housing and the bearings, the bearings protrude from the housing. Fixation of the plate only by contact with the housing avoids complicated steps of assembly. It will be apparent that the invention is mainly suitable for absorbing radial forces absorbed by the bearings. When a bearing fixed in such a manner must also absorb axial forces, other steps must then be taken for this purpose. According to a preferred embodiment the invention relates to an electric sawing machine wherein the saw blade shaft is at least mounted in a bearing which is arranged in an extension of the wall of the housing adjacent to the saw blade, and around the extension a strengthening ring is arranged which is manufactured from a material which is stronger than the material from which the housing is manufactured. As a result of these steps the relevant bearing is as it were locked, whereby it is possible to place the bearing directly into the housing of a sawing machine without connection to further structural components. The ring arranged round the extension containing the bearing ring ensures sufficient sturdiness. This moreover results in a more attractive assembly because fewer components have to be joined together. It is pointed out here that the housing must of course be divisible at the position of the bearing in order to enable assembly and disassembly of the bearing. According to yet another preferred embodiment, wherein the tool is a circular sawing machine, the circular sawing machine is provided with at least one fixed guard cover, which fixed guard cover comprises an inner wall extending parallel to the saw blade, a jacket wall and an outer wall extending parallel to the saw blade, wherein at least the inner wall is formed integrally with the housing. This results in an attractive and cost-saving manufacture because the number of components during assembly is reduced, while moreover a guard cover which is in itself difficult to manufacture is formed at least partially by a component which is formed integrally with the housing and which is preferably manufactured from plastic. The use of plastic moreover offers the option of providing the relevant component with a colour through and through, possibly even with different colours. Other attractive embodiments are stated in the dependent claims. The invention will be elucidated hereinbelow with reference to the annexed drawings, in which: figure 1 shows a partly broken away perspective view of a detail of an electric hand tool in which are accommodated a motor and a shaft driving a tool accessory; figure 2A is a perspective view of a variant of the plate shown in figure 1; figure 2B is a perspective view of a component for use in the construction shown in figure 1; figure 3 shows a partly broken away perspective view of a circular sawing machine according to the invention; figure 4 shows a partly broken away perspective view of another circular sawing machine according to the invention; figure 5 is a partly broken away perspective detail view of a first hinge for use in the circular sawing machine shown in figure 4; figure 6 is a partly broken away perspective detail view of the connected hinge shown in figure 5; figure 7 is a perspective detail view of a part of the circular sawing machine shown in figure 4; figure 8 is a perspective detail view of an alternative embodiment of the construction shown in figure 7; and figure 9 is a partly broken away perspective detail view of the mounting of the shaft driving the saw blade. Shown in figure 1 is a part of a sawing machine 1 which comprises a housing 2 and a guard cover 3 of the saw blade (not shown in the drawing). Arranged in housing 2 is an electric motor 4 which is provided with an output shaft 5 which is mounted in housing 2 in a bearing 6 suitable for absorbing radial forces. A second shaft 7 is further mounted in housing 2 by means of a bearing 8 and a bearing 9. The output motor shaft 5 is provided on its end with a toothing 10, while a tooth wheel 11 is arranged on the second shaft 7. Both tooth wheels 10,11 are in mutual engagement, thus forming a transmission. In order to absorb the radial forces between the two shafts a confining plate 12 is arranged in the motor housing. This confining plate 12 is shown in figure 2A. The confining plate 12 serves to absorb radial forces between the two shafts 5,7 and thus between the two bearings 6,8. For this purpose holes 13 respectively 14 are arranged in the confining plate 12. It is pointed out here that the confining plate 12 has no further connection to any structural components inside the sawing machine construction; for its function the confining plate 12 is sufficiently enclosed on all sides by the material of the motor housing. As shown in figure 2A, it is possible to provide the confining plate 12 with a polygonal periphery and polygonal holes. The confing plate 12 shown in figure 2B has a round periphery and is provided with round holes. Polygonal holes are of course only applicable if the periphery of the bearings arranged therein is form-fitting. Both forms can be combined at random. The locking plate 12 must of course be manufactured from sturdy material, for instance a metal. This provides the possibility of manufacturing the housing of a relatively softer material, for instance a plastic. It is even possible to combine the function of the locking plate with that of a cooling element. For this purpose the locking plate will have to be connected to the environment via a small heat resistance, for instance by providing the locking plate with ribs or protrusions extending up to the outer wall of the machine. It is also possible to arrange air channels to the locking plate. Figure 1 further shows how the bearing 9 of the second shaft is received in an extension 15 formed against the guard cover 3. This bearing is also not further connected to structural components of the circular saw construction. In order to lock bearing 9 in the cavities formed for this purpose in the extension 15 use is made of a closing plate 16 which is fixed onto bulge 15 by means of bolts 17. This moreover offers the possibility of allowing the closing plate 16 to protrude outside the extension 15, which makes it possible to mount on the extension 15 and axially lock a movable guard cover 18. Figure 3 shows another embodiment of a circular saw machine according to the invention; the housing 2 of the sawing machine forms one whole, possibly containing various components, with the inner wall 3 of the fixed guard cover 19. The latter is otherwise formed by a component 20, which forms the outer side wall, and the jacket wall of the guard cover. Figure 4 shows yet another embodiment; this embodiment of the circular sawing machine is provided with a footplate 21 which is connected rotatably by means of hinges 22,23 to the housing 2 of the circular sawing machine. The shaft connecting hinges 22 and 23 extends parallel to the saw blade, which enables tilting of sawing machine 2 such that mitre-sawing is thereby possible. Hinges 22,23 are shown in more detail in figures 5 and 6. The hinge 23 shown in figure 5 is thus formed by a bent part 24 of footplate 21 in which a substantially round hole 25 is made. The housing 2 of the circular sawing machine is further connected to a plate 26 extending parallel to the bent part 24 of plate 21, wherein a bulge 27 is arranged in plate 26, for instance by a press. Bulge 27 fits into hole 25, this such that bulge 27 can rotate inside hole 25 and the plate 26 can thus rotate relative to plate part 24. Thus achieved is the result that the footplate 21 can rotate relative to housing 2. In order to fix plate part 24 on plate 26 a bayonet fitting is arranged in the form of punched-out ears 28 which fit into broadened portions 29 of hole 25 arranged for this purpose. It is otherwise also possible to make use of only a single ear. The operation of a bayonet fitting is obtained with the thus shown construction. It can be ensured herein that during normal operative positions the bayonet fitting cannot be taken apart. It is also possible however, as in the present embodiment, to embody the other hinge in mirror-image manner, wherein the position of plates 24 and 26 is interchanged. This makes it possible, provided the mutually facing plates 26 are both firmly connected to housing 2, to displace housing 2 axially relative to footplate 21 so that a sufficiently sturdy fixation is obtained. In order to enable assembly hereof the plates 26 must first be placed in their correct position in relation to plates 24, whereafter housing 2 or optional other components for arranging therebetween must be placed in their position and connected fixedly to plates 26. Figure 6 shows the hinge 23 in its assembled situation. This also illustrates the bayonet action of the diverse components. The hinge construction is developed further in the construction shown in figure 7. The footplate 21 is herein provided with a bent calibration plate 30, while plate 26 is provided with an elongation in the form of an indicator 31. The latter is herein bent round on the outside of calibration plate 30 so that a bent portion 32 is formed. A slot 33 is further arranged in calibration plate 30, while both in indicator 31 and in the bent portion 32 thereof is arranged a hole, not shown in the drawing, through which extends a bolt 34. Bolt 34 is provided with a wing nut 35. The calibration plate 30 is further provided with a calibration 36, while indicator 31 is provided with an arrow tip 37. Due to the fact that indicator 31 is folded round to a bent portion 32, the friction surface between indicator 31 and calibration plate 30 is doubled. This makes it possible to obtain a better fixation or to make use of materials with less strength. Figure 8 shows another embodiment, wherein the indicator 31 is not bent round but wherein calibration plate 30 is provided with a bent piece 38. It will be apparent that both calibration plate 30 and the bent portion 38 thereof are provided with a slot 33 and that bolt 34 extends through both these latter components. The operation of this embodiment is otherwise the same as that of the foregoing embodiment. Finally, figure 9 shows by analogy with the embodiment shown in figure 1 a slightly different embodiment of the mounting of bearing 9 in the bulge 15. The closing plate 16 here also extends slightly radially relative to bearing 9 so that bearing 9 is also confined in radial direction. The closing plate 16, which in this case takes rather the form of a ring, is here also used to confine the movable guard cover 18. It will be apparent that changes can be made to the shown embodiments without departing from the scope of the invention as defined in the appended claims.

Claims: Electric hand tool (1), comprising a housing (2) manufactured from a first material, for instance plastic, a first shaft (5) which is mounted in at least a first bearing (6) and a second shaft (7) which extends parallel to the first shaft (5) and is coupled to the first shaft (5) by means of a transmission (10,11) and which is mounted in at least a second bearing (8), wherein both bearings (6,8) are intersected by a plane extending perpendicularly of the shafts (5,7), wherein a member (12) manufactured from a second material that is stronger than the first material has been provided, which member (12) is arranged extending perpendicularly of the shafts and fixes the first and second bearing (6,8) in at least partially confining manner in at least radial direction, characterized in that the member is a plate (12), the first and the second bearings (6,8) protrude from the plate (12) and that fixation of the plate (12) takes only place through contact with the housing (2). Electric hand tool (1) as claimed in claim 1, characterized in that the first shaft is formed by the motor shaft (5) and that the second shaft is a shaft (7) driving an implement forming part of the tool (1). Electric hand tool as claimed in claim 2, wherein the implement is a circular sawing machine which is provided with at least one fixed guard cover (19), which fixed guard cover comprises an inner wall (3) extending parallel to the saw blade, a jacket wall and an outer wall extending parallel to the saw blade, characterized in that at least the inner wall (3) is formed integrally with the housing (2) Electric circular sawing machine as claimed in claim 3, characterized in that the jacket wall and the inner wall of the guard cover are formed integrally together with the housing. Electric circular sawing machine as claimed in claim 3, characterized in that the remaining walls of the guard are formed by an integral unit. Electric sawing machine as claimed in claim 2, 3, 4 or 5, wherein the sawing machine comprises a footplate (21) hingedly connected to the housing (2), characterized in that the footplate is connected to the housing by at least two hinges (22,23) and that each hinge comprises a first plate (24) extending perpendicularly of the pivot shaft and connected to the footplate and a second plate (26) extending parallel to the first plate (24) and connected to the housing, wherein a substantially round hole (25) is arranged in the first or second plate and a bulge (27) fitting into the hole is arranged in the other plate, wherein the bulge extends into the hole and is enclosed by the edges of the hole. Electric sawing machine as claimed in claim 6, characterized in that at least one of the hinges is provided with a bayonet fitting (28). Electric sawing machine as claimed in claim 6 or 7, characterized in that the two hinges are placed in mirror image. Electric sawing machine as claimed in claim 8, characterized in that the inner plates are connected to a component extending at least partially between the plates. Electric sawing machine as claimed in any of the claims 2-9, characterized in that the footplate (21) comprises a calibration plate (30) extending perpendicularly of the rotation shaft, that the housing is coupled to an indicator (31) extending parallel to and in the vicinity of the calibration plate and that the indicator is provided with a fixation element for fixing the indicator relative to the calibration plate. Electric sawing machine as claimed in claim 10, characterized in that at least the calibration plate (30) or the indicator (31) is provided with a part extending on the other side of the other part in order to increase the friction-generating surface between the calibration plate and the indicator at the position of the fixation element. Electric sawing machine as claimed in claim 11, characterized in that the part extending on the other side of the other part is bent round. Electric sawing machine as claimed in any of the claims 2-12, characterized in that the saw blade shaft (7) is at least mounted in a bearing (9) which is arranged in an extension (15) of the wall of the housing adjacent to the saw blade, and that around the extension a strengthening ring (16) is arranged which is manufactured from a material which is stronger than the material from which the housing is manufactured. Electric sawing machine as claimed in claim 13, characterized in that the sawing machine is provided with a movable guard cover (18) which is mounted on the extension (15). Electric sawing machine as claimed in claim 14, characterized in that the movable guard cover (18) is confined by the strengthening ring (16).

Inventors: HOUBEN JAN PETER, VAN RIJEN JAN, HOUBEN, JAN PETER, VAN RIJEN, JAN
Applicants: SKIL EUROP BV, SKIL EUROPE B.V.
Application year: 1996
Main classification: B25F5
IPC codes: H02K7, H02K9, B27B9, B23D47, B27G19