WO1999034955A1

WO1999034955A1 - Hydraulic pendulum grinding machine

Info

Publication number: WO1999034955A1
Application number: PCT/SE1998/002282
Authority: WO
Inventors: Johan Vifors
Original assignee: Johan Vifors
Priority date: 1997-12-23
Filing date: 1998-12-11
Publication date: 1999-07-15
Also published as: SE9704843L; SE9704843D0; SE508895C2

Abstract

A pendulum grinding machine (1) comprises an elongated girder means (2), which has a first end, at which a handle (3) is arranged, a second end, at which a counterweight (4) is arranged, a suspension means (5) which is arranged between said ends and with the aid of which the machine is suspendable in pendulum fashion, and a grinding wheel (6) which is arranged between the first end and the suspension means (5) and which is substantially parallel with a long side of the girder means (2) and is non-rotatably connected to a rotor shaft (27). This rotor shaft is arranged to be rotated by a hydraulic motor (7), whose motor shaft is aligned with the rotor shaft and is non-rotatably connected to the same.

Description

_HYDRAULTΓ PENDULUM GRINDING MACHINE

The present invention relates to a pendulum grinding machine comprising an elongated girder means, which has a first end, at which a handle is arranged, a second end, at which a counterweight is arranged, a suspension means which is arranged between said ends and with the aid of which the machine is suspendable in pendulum fashion, and a grinding wheel which is arranged between the first end and the suspension means and which is substantially parallel with a long side of the girder means and is non- rotatably connected to a rotor shaft.

Pendulum grinding machines of the above-mentioned type are known in particular in the foundry industry, where they are used for machining large castings. In general, the grinding wheels have a diameter of about 500 mm and a thickness of slightly more than 60 mm and are approved for use up to a certain maximum working or peripheral speed of, for instance, 50 mps, which implies a maximum permissible speed of about 1800 rp with a grinding wheel having a diameter of 500 mm. Since a grinding wheel works most efficiently within a relatively narrow range of working speed, because otherwise there is a risk of breakage, powerful electric motors with a capacity in the range of 30 kW are used in prior-art pendulum grinding machines. Such big electric motors are, of course, heavy, and to limit the total weight of the grinding machine suspended in pendulum fashion, the electric motors are mounted as a counterweight at the second end of the above- mentioned girder means. For the power transmission from the motor at this second end to the grinding wheel between the suspension means and the first end, use is normally made of a cardan shaft which extends in parallel with the above-mentioned girder means and is connected to the rotor shaft by means of a bevel gear. A pendulum grinding machine designed in this manner suffers from many serious deficiencies. Primarily, the relatively long transmission distance between the electric motor and the grinding wheel always generates vibrations, which are directly harmful to the user of the grinding machine. Another drawback is that the large movable mass of the electric motor and the transmission in combination with the large movable mass of the grinding wheel render it more difficult to provide a quick stop, for instance, when a so-called dead man's handle is activated. In addition, the large movable mass makes it difficult for the grinding machine to attain its working speed, which often results in the user not switching off the machine, when the workpiece needs to be turned after a completed grind- ing operation before the next grinding operation. It is evident that a grinding wheel, rotating at a high speed, of a freely pendulating grinding machine can cause serious personal injuries.

Another problem of the prior-art pendulum grinding machines which are electrically driven is their considerable weight, which causes great strain in particular on the user's shoulders, in spite of the balanced pendulum suspension.

Besides the above problems, it has appeared that it is difficult both for the transmission including the greased bearings and the gear drives and for the electric motors which need cooling to resist for very long the strains during operation in the form of vibrations, grinding dust and the unavoidable high heat in foundries. These problems in terms of service life frequently result in stoppage, which often implies long periods of standstill due to the relatively complicated construction of the prior-art grinding machines.

In the light of the above problems of the prior-art pendulum grinding machines, an object of the present invention is to provide a both simpler and safer pendulum grinding machine, in which the vibration and weight prob- le s are less significant and the periods of standstill, if any, can be reduced to a minimum.

This object is achieved by means of a pendulum grinding machine of the type mentioned by way of intro- duction, which is characterised in that the rotor shaft is arranged to be rotated by a hydraulic motor, whose motor shaft is aligned with the rotor shaft and is non-rotatably connected to the same.

By using a simple hydraulic motor instead of the electric motors which have normally been used up to now, the weight of the grinding machine is considerably reduced and it is thus possible to mount the motor adjacent to the actual grinding wheel instead. As a result, it is also possible to dispose of transmission means, such as bevel gears, and it is further possible to carry out both a quick start and a quick stop of the grinding wheel without any problems thanks to the inherent qualities of the hydraulic motor.

Preferably, the motor shaft and the rotor shaft are connected to each other with the aid of a coupling means, which is suitably formed in such manner that the motor shaft or/and the rotor shaft is/are axially insertable in the same. By connecting the motor shaft to the rotor shaft with the aid of a coupling means, in particular a coupling means into which a shaft is axially insertable, it is possible, if necessary, to change a deficient unit in a simple way.

Preferably, the rotor shaft is mounted in bearings in a bearing housing, which is releasably connected to the girder means, the hydraulic motor suitably being accommodated in a motor casing, which is releasably connected to the bearing housing. In particular when combining these two features, a pendulum grinding machine is provided, which is very easy to repair if one of the units included should break.

Alternatively, it is also conceivable to form the motor shaft and the rotor shaft in one piece, at least part of this integral shaft being mounted in bearings in a bearing housing connected with the hydraulic motor. A machine which is designed in this manner constitutes the simplest conceivable solution, but if a defect arises both the hydraulic motor and the connected bearing housing must be changed at the same time.

According to the invention, the rotor shaft is preferably connected to the grinding wheel by means of a cup- shaped hub assembly, which has a circular-cylindrical por- tion, which is pushed over a corresponding circular- cylindrical part of the bearing housing and is sealed against this part by means of a rotary seal. Such a construction permits an efficient encapsulation of the bearing housing and its relatively sensitive bearings and thus increases the length of service thereof.

Preferably, the hub assembly also has an exterior circular-cylindrical portion, which is inserted into a corresponding circular-cylindrical hole in the grinding wheel and which has a circumferential, radially projecting flange at its end facing the hydraulic motor, said flange abutting against one side of the grinding wheel, a cover means being mounted at the end of the hub assembly facing away from the hydraulic motor, said cover means having a radially projecting flange, which abuts against the other side of the grinding wheel. It will be appreciated that a hub assembly designed in this manner together with said cover means makes it very easy to clamp the grinding wheel in a reliable manner and easily change it, when necessary. Suitably, the rotor shaft is, by means of at least one roller bearing, mounted in the bearing housing, which is filled with oil and against which the rotor shaft is sealed by means of a fluidtight rotary seal at the end of the shaft facing away from the hydraulic motor and a fluidtight stationary seal between the hydraulic motor and the bearing housing. Below, a preferred embodiment of the invention will be described in more detail with reference to the accompanying drawings, in which:

Fig. 1 is a side view showing the right side of a pendulum grinding machine,

Fig. 2 is a top plan view of the pendulum grinding machine with portions partially broken away,

Fig. 3 is a sectional view along the line A-A in Fig. 1, Fig. 4 is a sectional view along the line B-B in Fig. 3 and

Fig. 5 is a detailed top plan view showing the hydraulic motor and bearing housing of the pendulum grinding machine with portions partially broken away. Figs 1 and 2 show an inventive grinding machine 1 in its entirety. The machine 1 comprises an elongated girder means 2, here in the form of a square pipe, which has a first end, at which a handle 3 is arranged, and a second end, at which a counterweight 4 is arranged. Between the ends there is a suspension means 5, with the aid of which the machine is suspendable in pendulum fashion, for instance, by means of a so-called balance block (not shown) . Between the first end with the handle 3 and the suspension means 5, a grinding wheel 6 is arranged, which is sub- stantially parallel with the right long side of the girder means 2, i.e. the long side which is visible in Fig. 1 and located in the plane of the drawing. The grinding wheel 6 is non-rotatably connected to a rotor shaft, which will be described in more detail below, and is arranged to be rotated about a rotation axis a by means of a hydraulic motor 7, whose motor shaft, which is described in more detail below, is non-rotatably connected to the rotor shaft and also rotates about the rotation axis a.

The handle 3, which is arranged at the first end of the girder means 2, is connected to the same by means of a vibration-damping bush 8 and is suitably provided with a microswitch, in a manner that is obvious to the one skil- led in the art and therefore not shown, to operate the hydraulic motor 7 and a dead man's handle for a quick stop of the same.

Suitably, the counterweight 4 at the opposite second end of the girder means 2 has such a weight and design that the pendulum grinding machine 1, when suspended with the aid of its suspension means 5, places itself in a po^¬ sition which is completely balanced and located in the horizontal plane. A slight adjustment of this position can be achieved by moving along the girder means 2 on the one hand the counterweight 4 and, on the other, the suspension means 5, which comprises a long hole 9, which extends in the longitudinal direction of the girder means 2 and which has a plurality of notches 10 along its upper long side, which permit a controlled displacement of the suspension point, which is symbolised with an arrow 11 in Fig. 1.

The grinding wheel 6 placed between the handle 3 and the suspension means 5 is surrounded by a wheel guard 12 along slightly more than half its circumference, which is open downwards and attached to the girder means 2 with the aid of a pivot pin 13 and at least one bolt 14. After removal of the bolt 14, the wheel guard 12 is pivotable upwards about the pivot pin 13, the pivoting being stopped by means of an abutment 15 in a position which is suitable for servicing.

Lines 16, 17 to the hydraulic motor 7 run in a protective cable duct 18 to the suspension means 5 and thus cannot be damaged by the grinding wheel 6. Finally, for the protection against swarf during grinding, there are both a hanging screen 19 adjacent to the handle 3 and an elongated, substantially horizontal screen element 20, which is attached to the girder means 2 under the suspension means 5.

The hydraulic motor 7 is connected to a bearing housing 21, in which the rotor shaft, with which the grinding wheel 6 rotates, is mounted in bearings. In Figs 3 and 4, the attachment of this bearing housing 21 to the girder means 2 is shown in more detail. A lower holder 22 is fixedly connected to the girder means 2 and has two upwardly directed screw taps 23, on which an upper holder 24 is attachable by means of nuts 25. The holders 22, 24 are arranged to clamp between themselves a waist portion of the bearing housing 21, said waist portion being described in more detail below.

Fig. 5 shows the bearing housing 21 and part of the grinding wheel 6 in cross-section and the hydraulic motor 7 connected to the bearing housing 21 on a larger scale. It is evident that the hydraulic motor has a motor shaft 26, which is arranged opposite to a rotor shaft 27 in the bearing housing 21. The two shafts 26, 27 are connected to each other by means of a simple sleeve-shaped coupling means 28, in which the ends of the shafts 26, 27 are insertable in a non-rotatable manner.

The rotor shaft 27 is mounted in roller bearings 29, 30, 31 in the bearing housing 21, which suitably are of such a type as to resist strong forces, axial as well as radial. At the outer end of the rotor shaft 27, i.e. the lower end in Fig. 5, there is a rotary seal 32, which is supported by the bearing housing 21 and has a lip which is arranged to abut against the rotor shaft 27 in a tight but sliding manner. The bearing housing 21 is completely fil- led with oil between the hydraulic motor 7, which is sealed against the bearing housing 21 by means of an 0- ring 33 engaging the casing 34 of the hydraulic motor 7, and the rotary seal 32, which considerably contributes to the prolongation of the service length of the bearings 29, 30, 31.

By means of its outer end, the rotor shaft 27 supports a cup-shaped hub assembly 35, which has an interior circular-cylindrical portion 36. The portion 36 is pushed over a corresponding circular-cylindrical part 37 of the bearing housing 21 and is sealed against this part 37 by means of a rotary seal 38. The above-mentioned waist portion, designated 39 in Fig. 5, is arranged in connection with the part 37 of the bearing housing 21. On the outside, the hub assembly 35 has a circular-cylindrical portion 40, which is inserted into a corresponding circular- cylindrical hole 41 in the grinding wheel 6 and which has a circumferential, radially projecting flange 42 at its end facing the hydraulic motor 7. This flange 42 abuts against one side of the grinding wheel 6, a cover means 43 being mounted at the end of the hub assembly 35 facing away from the hydraulic motor 7, and having a radially projecting flange 44, which abuts against the other side of the grinding wheel 6.

The thus-constructed inventive pendulum grinding machine is considerably simpler and lighter than the prior-art pendulum grinding machines and also exception- ally robust. In addition, the machine is very easy to repair if a component should break, among other things, because obviously the components are easy to replace individually. Finally, the machine causes considerably less vibrations thanks to the direct drive and is considerably easier to stop quickly because of the comparatively smaller movable mass of the driving assembly.

Claims

1. A pendulum grinding machine comprising an elon- gated girder means (2), which has a first end, at which a handle (3) is arranged, a second end, at which a counterweight (4) is arranged, a suspension means (5) which is arranged between said ends and with the aid of which the machine is suspendable in pendulum fashion, and a grinding wheel (6) which is arranged between the first end and the suspension means (5) and which is substantially parallel with a long side of the girder means (2) and is non- rotatably connected to a rotor shaft (27), c h a r a c t e r i s e d in that the rotor shaft (27) is arranged to be rotated by a hydraulic motor (7), whose motor shaft (26) is aligned with the rotor shaft (27) and is non- rotatably connected to the same.

2. A machine according to claim 1, wherein the motor shaft (26) and the rotor shaft (27) are connected to each other with the aid of a coupling means (28) .

3. A machine according to claim 2, wherein the coupling means (28) is formed in such manner that the motor shaft (26) or/and the rotor shaft (27) is/are axially insertable in the same.

4. A machine according to any one of claims 1-3, wherein the rotor shaft (27) is mounted in bearings in a bearing housing (21) , which is releasably connected to the girder means (2) .

5. A machine according to claim 4, wherein the hyd- raulic motor (7) is accommodated in a motor casing (34), which is releasably connected to the bearing housing (21) .

6. A machine according to claim 1, wherein the motor shaft (26) and the rotor shaft (27) are formed in one piece, part of this integral shaft being mounted in bear- ings in a bearing housing (21) connected with the hydraulic motor (7).

7. A machine according to any one of claims 1-6, wherein the rotor shaft (27) is connected to the grinding wheel (6) by means of a cup-shaped hub assembly (35), which on its inside has a circular-cylindrical portion (36) , which is pushed over a corresponding circular- cylindrical part (37) of the bearing housing (21) and is sealed against this part by means of a rotary seal (38) .

8. A machine according to claim 7, wherein the hub assembly (35) has an exterior circular-cylindrical portion (40), which is inserted into a corresponding circular- cylindrical hole (41) in the grinding wheel (6) and which has a circumferential, radially projecting flange (42) at its end facing the hydraulic motor (7), said flange abutting against one side of the grinding wheel (6), a cover means (43) being mounted at the end of the hub assembly

(35) facing away from the hydraulic motor (7), said cover means having a radially projecting flange (44), which abuts against the other side of the grinding wheel (6).

9. A machine according to any one of claims 6-8, wherein the rotor shaft (27) is, by means of at least one roller bearing (24-31) , mounted in the bearing housing (21), which is filled with oil and against which the rotor shaft (27) is sealed by means of a fluidtight rotary seal (32) at the end of the shaft facing away from the hydrau- lie motor (7) and a fluidtight stationary seal (33) between the hydraulic motor (7) and the bearing housing (21) .