GB2293122A

GB2293122A - Hand-held grinding machine comprises grinding belt between grinding roll and deflection roll and guide

Info

Publication number: GB2293122A
Application number: GB9517871A
Authority: GB
Inventors: Rainer Dieringer; Andreas Randecker
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1994-09-16
Filing date: 1995-09-01
Publication date: 1996-03-20
Anticipated expiration: 2015-09-01
Also published as: ITMI951891A0; GB9517871D0; DE4432974A1; JPH0890404A; ITMI951891A1; GB2293122B; DE4432974B4; IT1277565B1; CH691441A5

Description

EleCtric hand-held qrindina machine 2293122

Prior Art

The invention derives from an electric hand-held grinding machine of the generic type def ined in the preamble of Claim 1, also colloquially referred to as a roll grinder.

in a known electric hand-held grinding machine of this type (US-Patent Specification 3 793 782), the grinding roll is composed of two coaxial, cylindrical roll bodies, which are set in rotation, via a centrally disposed cylindrical gearing, by a drive shaf t of an is electric motor, which drive shaft intrudes in a radially central position between the roll bodies. The electric motor is accommodated in the motor housing and the drive shaft is guided in an elongated, tubular housing journal coaxial with the machine housing. Slipped respectively onto the two roll bodies there is a grinding sleeve, for example of sand paper, f orming the grinding tool. At that end of the housing journal facing the grinding roll, there is configured integrally with the housing journal a fastening block to which a guide member is fastened, which guide member is displaceable in an arc shape relative to the fastening block by means of a pin-slot connection and a locking screw. The guide member bears, at the lower end, a guide f ace f or placement onto the surf ace of the workpiece to be treated and serves the guidance and application of a uniform contact pressure of the grinding sleeves onto the workpiece surface. Despite this guide member, lengthy practice is required in order to obtain, with the path-following roll grinder, a sufficiently smooth surface of the treated workpiece. in addition, the grinding sleeves are rapidly worn down and have to be frequently exchanged.

Advantages of the invention The electric hand-held grinding machine having the characterizing features of Claim 1 has the advantage over the above that, on the one hand, by using a grinding belt in place of a grinding sleeve, the durability of the grinding tool is considerably increased and excessive interruption of the work process by frequent changing of the grinding tool is not necessary. On the other hand, a fine surface treatment is obtained in combination with a relatively high material removal rate, whilst, at the same time, a high level of smoothness of the treated workpiece surface is ensured.

The hand-held grinding machine according to the invention combines the advantages of an electric plane and of a belt grinder, exhibiting, on the one hand, the high material removal rate of a plane and, on the other hand, the high surface quality of a surface grinder. These work results are obtained in just one work cycle, thereby implying a considerable time saving. In a certain field of application, the DIY enthusiast thus does not require two separate electric hand tools, but is able to carry out the desired jobs using just one electric tool, the roll grinder according to the invention, whilst achieving good quality, which considerably enhances the attractiveness of the roll grinder in the market place.

The measures quoted in the further claims enable advantageous refinements and improvements to be made to the electric hand-held grinding machine specified in

Claims

Claim 1.

According to a preferred embodiment of the invention, the deflection roller for the continuous grinding belt, which deflection roller is integrated within the machine housing, is disposed such that the angle of inclination of a straight line passing through the roll axes lies, relative to the guide face, within the upper acute angle sector (between 45 and 900). The angle preferably measures 700.

According to an advantageous embodiment of the invention, the guide face is provided on the bottom side of the machine housing and comprises a rear face section situated behind the grinding roll in the direction of advancement of the hand-held grinding machine and a front face section situated in front of the grinding roll in the direction of advancement. Between the two face sections there is left a gap which extends across the whole of the guide face transversely to the direction of displacement and through which a part-sector of the roll periphery of the grinding roll juts with adjustable projection over the front face section. As a result of this configuration of the guide face, the machine-cutting action of the grinding tool upon the workpiece takes place in the grinding gap left in the guide face, whilst an absolutely uniform guidance of the hand guiding is machine is given, thereby achieving a high level of smoothness of the treated workpiece surface. The adjustable projection of the roll periphery over the guide face allows adjustment to be made to the size of the chip removal.

According to a preferred embodiment of the invention, the adjustable projection measure of the roll periphery over the guide face is achieved by the rear face section of the guide face being configured in a fixed arrangement directly on the housing and by the front face section of the guide face being connected, at right angles to its plane of extent, adjustably to the machine housing.

According to an advantageous embodiment of the invention, the front face section of the guide face is herein configured on a feed housing connected separably to the machine housing. This removable feed housing means that the field of application of the hand-held grinding machine is able to be considerably extended. Since, when the feed housing is removed, the driven grinding roll is exposed and the grinding roll constitutes, at the level of its centre, the foremost point of the hand-held grinding machine, it is thereby possible to grind with the hand-held grinding machine even in poorly accessible regions, such as in angled corners.

in an advantageous embodiment of the invention, for the detachable connection of machine housing and feed housing, there are pressed into the latter two guide pins, which are insertable into the machine housing. By means of a hand wheel, the feed housing can be fixed to the machine housing. Alternatively, the detachable connection between the housings can also be configured as a dovetail guide.

According to an advantageous embodiment of the invention, the grinding roll has a coaxial cavity, which is open in the direction of a front side and preferably extends over more than half the axial length of the grinding roll. The grinding roll is slipped in a rotationally secure manner onto the free end of a drive is shaft protruding from a bearing socket, such that it at least partially receives in its cavity, with a small radial gap, the bearing socket. The grinding roll is connected detachably to the drive shaft on the front side of the drive shaft. This design produces a high rigidity and a simple and rapid exchangeability of the grinding roll. And this rapid exchangeability means that, in place of the grinding belt, brushes and forming rolls can also additionally be used as grinding tools, which are of considerable interest, in particular, when the feed housing is removed for certain jobs. Drawing The invention is explained in greater detail in the following description with reference to an illustrative embodiment represented in the drawing, in which:

Fig. 1 shows a side view of an electric hand-held grinding machine conceived as a roll grinder, Fig.
2 shows a section along the line II-Il in Fig. 1, Fig. 3 shows, selectively, a side view of the hand-held grinding machine in Fig. 1 having a modified feed housing, partially in sectional representation, Fig. 4 shows a view of the hand-held grinding machine in the direction of arrow IV in Fig. 3.

Description of the illustrative embodiment The electric hand-held grinding machine represented in Fig. 1 in side view and in Fig. 2 in cross-section represents a roll grinder, the grinding roll of which enters in a partsector of the roll periphery into machine-cutting engagement with a workpiece to be treated. The hand-held grinding machine has a machine housing 10 with handle 11 moulded onto it and a feed housing 12 attached detachably to the machine housing 10. On the bottom side of the handle 11 there protrudes an on-off switch 13 for switching on and off an electric motor 14, which is simultaneously coupled with a solidshaft actuator for influencing the speed of the electric motor 14. The electric motor 14 drives, via a toothed belt step 15 and a cylindrical gearing 16, a grinding roll 17 armed with a grinding tool. The grinding tool is is here configured as a continuous grinding belt 18, which is guided via the grinding roll 17 and via a deflection roller 19 mounted rotatably above the grinding roll 17 in the machine housing 10 and is clamped by means of a clamping device 20 between the grinding roll 17 and deflection roller 19. The deflection roller 19 is herein disposed such that a straight line 21 passing through the axes of the grinding roll 17 and deflection roller 19, relative to a guide face 22 provided on the bottom side of the machine housing 10, forms an angle of inclination of around 70.

As is evident from Fig. 2, the grinding roll 17 has a coaxial cavity 23, which is open in the direction of its one front side and extends over more than half the axial length of the grinding roll 17. Inside a bearing housing 24 fitted to the machine housing 10 there is mounted a drive shaf t 25, which on both sides of the bearing housing 24 protrudes from the latter. The mounting of the drive shaft 25 in the bearing housing 24 is effected by means of a plain journal bearing 26 and a deep-groove ball bearing 27, which are disposed at a respective end of the bearing housing 24. The deep-groove ball bearing 27 is herein assigned to the free, so-called mounting end 241 of the bearing housing 24. On that end of the drive shaft 25 protruding over the plain journal bearing 26 there is seated, in a rotationally secure manner, a spur wheel 161 of the cylindrical gearing 16, the other spur wheel 162 of which is seated on a pinion shaft 28 driven by the toothed belt cone 15. The grinding roll 17 is mounted in a rotationally secure Twenner on that end of the drive shaf t 25 which protrudes on the mounting and 241 of the bearing socket 24, the cavity 23 for the most part receiving the bearing housing 24, leaving a small annular gap 29. The grinding roll 17 is connected, on the front side of the drive shaft 25, detachably to the latter. To this end, the grinding roll 17 has a frontal recess 30 with an adjoining axial through bore, which serves the reception of the grinding roll 17 by the drive shaft 25. The transportation of the is grinding roll 17 is effected via the duogonal piece shaped onto the drive shaft 25 and the driver plate 44, which is pressed against the grinding roll 17 by a clamping screw 31 screwed frontally into the drive shaft 25. The screw head of the clamping screw 31 rests in the recess 30.

The guide face 22 provided on the bottom side of the machine housing 10 is composed of a face section 221 situated behind the grinding roll 17 in the direction of advancement of the roll grinder and a front face section 222 situated in front of the grinding roll 17. The rear face section 221 is herein configured directly and fixedly on the machine housing 10, whilst the front face section 222 is assigned to the feed housing 12 and is disposed at right angles to its plane of extent adjust ably on the feed housing 12. Between the two face sec tions 221 and 222 there is left a wide gap 32, which extends transversely to the guide face 22 and through which juts a part-sector of the roll periphery of the grinding roll 17. The tangent applied to the lowermost point of the grinding roll 17 is in this case aligned with the rear face section 221, whilst the grinding roll 17, according to the setting of the front face section 222, projects to a greater or lesser extent over the latter. The adjustable front face section 222 is herein 2 configured on the bottom side of a feed plate 33, which can be guided in a vertically displaceable manner an the feed housing 12 and can be raised or lowered by means of a knob 34.

The adjustment mechanism for the feed plate 33 is represented in detail in Figs. 3 and 4. The feed plate of U-shaped cross-section (Fig. 4) covers the bottom side of the feed housing 12 and is guided with its U-legs lat erally on the feed housing 12. By means of a screw 35 jutting perpendicularly upwards from the feed plate 33, the feed plate 33 is connected to the knob 34, the screw being screwed with its thread in a nut 36 fixed in the knob 34 and being secured with its screw head, by means of a check nut 37, to a journal 331 moulded- integrally is onto the rear side of the feed plate 33. The knob 34 is connected by press fit on its bottom side to a disc 38, which is mounted rotatably in the feed housing 12. If the knob is turned in the one or other direction of rotation, then the screw 35 screws deeper into the nut 36 or further out of the nut 36. The feed plate 33 consequently, in Fig. 3, moves upwards or downwards and predetermines the working depth at which the roll grinder realizes the machine-cutting material removal on the workpiece. The disc 38 is provided with a catch mechanism (not here visible), which, with the aid of a securing ring, fixes the cutting depth which is set. A pressure spring 39, which is slipped onto the screw 35 and is supported between the disc 38 and the check nut 37, minimizes the play between the screw 35 and nut 36 and prevents rattling noises.

The detachable connection of the feed housing 12 to the machine housing 10 can be variously executed. In Fig. 1, a dovetail guide 40 is provided, which extends parallel to the axes of the grinding roll 17 and deflec tion roller 19, so that the feed housing 12 can be slipped onto and pulled off the machine housing 10 by lateral displacement motion.

in the case of the roll grinder in Fig. 3, for the detachable connection of the feed housing 12 and machine housing 10 there are pressed into the feed housing 12 two guide pins 41, which protrude partially out of the feed housing 12 and can be inserted in a precise fit into the machine housing 10. Two tabs 43 of the feed housing 12, which, in the end position of the feed housing 12, come to rest upon the machine housing 10 (Fig. 4), are clamped by a hand wheel 42 to the machine housing 10, so that the guide housing 12 is secured by means of the guide pins 41 and tabs 43, without play, to 10 the machine housing 10.

- 9 Claims 1. Electric hand-held grinding machine having a grinding roll (17) with grinding tool which is exchangeably fastened thereon and which, for the grinding treatment of a workpiece, enters in a part-sector of the roll periphery into machine-cutting engagement with the workpiece, having an electromotive drive mechanism (14, 15, 16) which drives the grinding roll (17), having a machine housing (10) which receives the drive mechanism (14, 15, 16), and having a guide face (22) which is assigned to the grinding roll (17) so as to guide it on is the workpiece, characterized in that the grinding tool is configured as a continuous grinding belt (18) which is clamped in place between the grinding roll (17) and a deflection roller (19), enwrapping these, and in that the deflection roller (19) is disposed in the machine housing (10) such that a straight line (21) passing through the roll axes runs at an acute angle to the guide face (22). 2. Machine according to Claim 1, characterized in that the angle of inclination of the straight line (21) passing through the roll axes of the grinding roll (17) and deflection roller (19) lies, relative to the _guide face (22), within the upper acute angle sector, preferably measuring about 700.
3. Machine according to Claim 1 or 2, characterized in that the guide face (22) is situated on the bottom side of the machine housing (10) and comprises a rear face section (221) situated behind the grinding roll (17) in the direction of advancement and a front face section (222) situated in front of the grinding roll (17) in the direction of advancement, and in that between the two face sections (221, 222) there is left a gap (32) which extends across the whole of the guide face (22) transversely to the direction of advancement and through 5.

which a part-sector of the roll periphery of the grinding roll (17) juts with adjustable projection over the front face section (222).
4. Machine according to Claim 3, characterized in that the rear face section (221) of the guide face (22) is configured in a fixed arrangement directly on the machine housing (10) and the front face section (222) is connected, at right angles to its plane of extent, adjustably to the machine housing (10).
Machine according to Claim 4, characterized in that the front face section (222) of the guide face (22) is configured on a feed housing (12) connected separably to the machine housing (10).
6. Machine according to Claim 5, characterized in is that for the detachable connection of machine housing (10) and feed housing (12), there are provided two guide pins (41), which are pressed into the feed housing (12) and are insertable in a precise fit into the machine housing (10), and a hand wheel (42), which clamp% the feed housing (12) to the machine housing (10).
7. Machine according to Claim 5 or 6, characterized in that the front face section (222) is formed by the bottom side of a feed plate (33), which is guided in a vertically displaceable manner on the feed housing (12) and can be raised or lowered by means of a knob (34).
8. Machine according to Claim 7, characterized in that the knob (34) is held rotatably on the feed housing (12) and is connected by a threaded spindle (35, 36) to the feed plate (33).
9. Machine according to one of Claims 1 - 8, charac terized in that the grinding roll (17) has a coaxial cavity (23), which is open in the direction of the one front side of the said grinding roll and preferably extends over more than half its axial length, in that the grinding roll (17) is slipped in a rotationally secure manner onto the free end of a drive shaft (25) protruding from a bearing housing (24), such that the drive shaft (25) at least partially receives in its cavity (23), with a small radial gap (29), the bearing housing (24), and in that the grinding roll (17) is connected on the front side of the drive shaft (25) detachably to the drive shaft (25).
10. Machine according to Claim 9, characterized in that the drive shaft (25) is mounted in two running bearings (26, 27), which are disposed at a respective end of the bearing housing (24), the bearing assigned to the mounting end (241) of the bearing housing (24) being configured as a deepgroove ball bearing (27).
11. A grinding machine substantially as herein described with reference to Figures 1 and 2, or Figures 3 and 4, of the accompanying drawings.