GB2196898A

GB2196898A - Hand-guided machine tool

Info

Publication number: GB2196898A
Application number: GB08724001A
Authority: GB
Inventors: Gunter Schaal; Heribert Schramm; Gunther Berger; Gerhard Kramer
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1986-10-16
Filing date: 1987-10-13
Publication date: 1988-05-11
Anticipated expiration: 2007-10-13
Also published as: GB8724001D0; IT8722269A0; IT1222905B; CH673975A5; JP2905975B2; DE3635159C2; GB2196898B; DE3635159A1; JPS63127881A

Abstract

A hand-guided machine tool equipped with a support plate (2) has guide bars (15 and 16) of a parallel stop (40) guided in guide ways (3 and 4) in the support plate (2). The guide bars (15 and 16) are bent away from the main body of the parallel stop (40) and are provided with stiffening corrugations (41, Fig. 1). The guideways (3 and 4) are formed by upper and lower bridges (e.g. 5). The guideways (3 and 4) are transversely interconnected by a guide passage (9) which is formed by upper bridges (10) and lower bridges (11). The guide passage accommodates a pressure piece (12) and, in a widened portion (13), a cam plate (14). The guide bars (15 and 16) are simultaneously clamped, or this clamping action is released, by turning the cam plate (14). The tool (22) may be a circular saw, a milling disc, or a grinding disc. A handle (20) is provided. The depth of cut is adjusted by turning a screw (38). A helical spring (35) urges the tool (22) towards a retracted position away from the workpiece. The tool (22) can he adjusted in axial position by turning a knob (29). <IMAGE>

Description

SPECIFICATION Hand-guided machine tool The invention relates to a hand-guided machine tool having a support plate by which the tool can rest against a workpiece.

A hand-guided machine tool, in which two guide bars having a round cross section are guided in corresponding bores within the support plate is already known. One of these guide bars is fixable in its bore by means of a clamping screw. The cost of material and the expediture of labour required for this kind of guidance and clamping is relatively high. Nevertheless, safety when working with the parailel stop clamped one-sidedly is unsatisiactory; the stop under load can frequently assume a sloping or inclined position, so that it can no longer be used to an optimum extent as a guide means.

In accordance with the present invention there is provided a hand-guided machine tool equipped with a support plate which comprises a slot, a tool which extends at right angles to the said support plate and is movable through the slot, and a parallel stop which is guided on the support plate and which has two guide bars which are spaced apart from one another and which are insertable into two guideways in the support plate, the guideways being interconnected by a guide passage into which at least one pressure piece is inserted, one end of which pressure piece can abut against one of the guide bars and its other end can abut against a cam plate for the purpose of clamping the two guide bars by means of the cam plate which presses directly or via another pressure piece against the other guide bar.

The present invention thus has the advantage that the parallel stop is accuratley guided and securely clamped by the simplest means.

The two guide bars are clamped, and tolerances are effectively compensated, by virtue of the clamping means which acts upon the two guide bars and which comprises a pressure piece and a loosely inserted cam plate.

In one embodiment, the hand-guided machine tool's parallel stop is manufactured from sheet metal with angled arms serving as guide bars, and the manufacture of the support plate with guideways for the guide bars and a guide passage which is provided for the pressure piece or pieces and which interconnects the guide ways, are particularly advantageous with respect to an inexpensive construction, these guideways and the guide passage being formed by bridges which alternately define the cross section of the guideways towards the base surface of the support plate and towards outer surface of the support plate.

By way of example only, a specific embodiment of the present invention will now be described with reference to the accompanying drawings in which: Fig. 1 is a side elevation of the hand-guided machine tool equipped with a support plate and guide bars in accordance with the present invention; Fig. 2 is a cross section taken on the line II11 of Fig. 1, without the hand-guided machine tool; Fig. 3 is a fragmentary cross section taken on the line Ill-Ill of Fig. 2; and Fig. 4 is a cross section taken on the line IV-IV of Fig. 2.

A hand-guided machine tool 1 is equipped with a support plate 2 which can rest against a workpiece (not shown) to be sawn or machined and in which there are two guideways 3 and 4 whose cross sections are determined by upper bridges 5 and 6 and lower bridges 7 and 8. The two guideways 3 and 4 are interconnected by a guide passage 9 which, in the same manner as the guideways 3 and 4, is formed by upper bridges 10 and lower bridges 11. The guide passage 9 accommodates a pressure piece 12 and, in a corresponding widened portion 13, a cam plate 14.

The pressure piece 12 and the cam plate 14 bridge the distance between two guide bars 15 and 16 in the guideways 3 and 4. Thus, the two guide bars 15 and 16 are simultaneously clampable in their guides 3 and 4 by turning the cam plate 14. An angled wrench can be inserted into a hexagonal hole 17 in the cam plate 14 for the purpose of turning the latter. When the angled wrench is not being used, it is held in two clips 19 on the surface of the support plate 2. A handle 20 is also secured to the surface of the support plate 2. The tool end of the support plate 2 is provided with a slot 21 for receiving a tool 22. The tool 22 is surrounded by a protective casing formed by an angled portion 23 of the support plate 2 and a cover 24. An extractor connection piece 25 leads into the protective casing.A bearing and adjusting spindle 28 is journalled in two bearing lugs 26 and 27 on the support plate 2. The spindle 28 has an adjusting knob 29 and a spindle thread 30. A support arm 31 serves to receive the handguided machine tool 1 and is clamped on the bearing and adjusting spindle 28 by means of a clamping screw 32. The spindle collar of the hand-guided machine tool 1 is clampable in an opening 34 in the support arm 31 by means of another clamping screw 33. A helical torsion spring 35 is slipped onto the bearing and adjusting spindle 28 and one of its free legs, the leg 36, engages the support arm 31.

Another free leg 37 of the helical spring abuts against the cam plate 14. The helical spring thus constantly seeks to lift the hand-guided machine tool 1 into its inoperative position in which the tool 22 is retracted from the workpiece. A stop screw 38 makes it possible to limit the depth to which the tool 22 penetrates the workpiece. The stop screw 38 co- operates with a stop 39 on the support plate 2.

The guide bars 15 and 16 are parts of a parallel stop 40. They are bent from the main sheet metal body of the parallel stop and are provided with stiffeneing corrugations 41.

They fit into the guides 3 and 4 when the stop body 40 is directed upwardly and when it is directed downwardly. They can also be inserted into the guideways 3 and 4 from either side. Hence, there are four different possible basic positions of the parallel stop 40 relative to the support plate. These positions are indicated in Fig. 4 (dash-dot lines, and one position shown by solid lines).

The spindle thread 30 engages the thread of a nut 42 which is secured in the support arm 33. A locking washer 43 secures the bearing and adjusting spindle 28 in its axial position. Hence, fine adjustment of the position of the tool 22 in the direction of the guide ways 3 and 4 is possible by turning the bearing and adjusting spindle 28 by means of the adjusting knob 29. A scale 44 on the guide bar 15 is located opposite a fixed mark 45 on the support plate 2.

The clamping of the guide bars 15 and 16 must be released by turning the cam plate 14 in order to adjust the parallel stop 40 to the desired distance from the tool 22. The guide bars 15 and 16 of the parallel stop 40 can then be displaced in the guide ways 3 and 4.

The scale 44 gives a reference point for this.

The guide bars 15 and 16 are then clamped by the cam plate 14 and the pressure piece 12. After a test cut, the fine adjustment can then be effected by means of the bearing and adjusting spindle 28 by which the support arm 31 with the hand-guided machine tool 1, and hence with the tool 22, is adjusted relative to the support plate 2.

The tool 22 is illustrated as a circular saw blade but it could be a milling disc or a grinding disc.

Claims

1. A hand-guided machine tool equipped with a support plate which is provided with a slot, a tool which extends at right angles to the said support plate and is movable through the slot, and a parallel stop which is guided on the support plate and which has two guide bars which are spaced apart from one another and which are insertable into two guideways in the support plate, the guideways being interconnected by a guide passage into which at least one pressure piece is inserted, one end of which pressure piece can abut against one of the guide bars and its other end can abut against a cam plate for the purpose of clamping the two guide bars by means of the cam plate which presses directly or via another pressure piece against the other guide bar.

2. A hand-guided machine tool as claimed in claim 1, wherein the cam plate is inserted with clearance into a recess in the run of the guide passage for the pressure piece or pieces and is provided with a collar which is overlapped by the pressure piece or pieces in the guide passage, whereby the cam plate is held in the recess and, by virtue of its movability in the direction of the guide passage, can compensate for tolerances in the clamping device and can automatically find its clamping position.

3. A hand-guided machine tool as claimed in claim 1 or 2, wherein the parallel stop is made from sheet metal, and its guide bars are angled arms provided with a longitudinal corrugation.

4. A hand-guided machine tool as claimed in claim 1,2 or 3, wherein the guideways for the guide bars, and the guide passage which is provided for the pressure piece or pieces and which interconnects the guideways, are formed by bridges which alternately define the guide cross section towards the base surface of the support plate and towards the upper surface of the support plate, so that the guideway remains open at that side of the support plate which is located opposite the respecitve bridges.

5. A hand-guided machine tool as claimed in claim 4, wherein the support plate is made from die cast metal.

6. A hand-guided machine tool as claimed in claim 4, wherein the support plate is made from sheet metal by stamping out the bridges towards opposite sides in each case.

7. A hand-guided machine tool as claimed in any preceding claim, which is connected to the support plate by means of a pivot bearing and is fine adjustable relative to the guide bars and thereby relative to the support plate by means of a bearing and adjusting spindle.

8. A hand-guided machine tool equipped with a support plate constructed substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.