EP0236865A2

EP0236865A2 - Structure of a honing head for double-rotation cylindrical grinding wheels, particularly for the working of stones marble, granite and the like

Info

Publication number: EP0236865A2
Application number: EP87102749A
Authority: EP
Inventors: Sergio Gassani
Original assignee: MARMOTECNICA MILANO Srl
Current assignee: MARMOTECNICA MILANO Srl
Priority date: 1986-02-28
Filing date: 1987-02-26
Publication date: 1987-09-16
Also published as: IT8621083V0; IT209647Z2; EP0236865A3

Abstract

The honing head (1) comprises: a main framework (2) which rotatbly supports a main shaft (3) which can be operated to rotate around its own axis and a secondary framework (30) rigidly coupled in rotation with the main shaft (3). The secondary framework (30) supports at least one pair of secondary shafts (5) arranged radially and counterposed with respect to the axis of the main shaft (3). The secondary shafts (5) are operatable to rotate around their own axis and are provided with one end thereof projecting from the secondary framework (30) and engageable with a cylindrical grinding wheel (21). Said secondary framework (30) is provided with a supporting bush (20) which extends around the respective secondary shaft (5) and partially extends inside the cylindrical grinding wheel (21) supporting the secondary shaft (5) for most of the length thereof.

Description

The present invention relates to a structure of a honing head for double-rotation cylindrical grinding wheels, particularly for the working of stones, marble, granite and the like.
Honing heads for cylindrical grinding wheels are known which are generally composed of a main framework which rotatably supports a main shaft, usually arranged with a vertical axis, and of at least one secondary framework rigidly coupled in rotation with the main shaft; the secondary framework rotatably supports at least one pair of secondary shafts which are arranged radially with counterposed axes with respect to the main shaft; usually, four secondary shafts are provided, mutually angularly spaced by 90°.
The secondary shafts, which can be operated to rotate around their own axis, are provided with an end projecting from the secondary framework and engageable with a cylindrical grinding wheel.
Usually, the main shaft and the secondary shafts are kinematically connected to each other, in order to obtain the simultaneous rotation of the grinding wheels around their own axis and around the axis of the main shaft, and so that the peripheral speed of the grinding wheels, in the region of contact with the material to be honed, due to the rotation of the grinding wheels around their own axis, is opposite in direction with respect to the peripheral speed iue to the rotation of the grinding wheeis around the axis of the main shaft.
Said honing heads, by virtue of the double rotation, though having proved to be particularly effective in the roughing, semifinishing and finishing work of materials such as marble and granite, have a number of disadvantages.
The main one of said disadvantages is the onset of deformations in the secondary shafts due to the high stresses and vibrations to which they are subject during operation; which deformations have the effect of increasing in turn the vibrations and of reducing the life of the honing head.
Another disadvantage is the quick erosion of the secondary shafts in the region of coupling with the grinding wheels, due to the high stresses to which they are subject and to the presence of abrasive material which drops off the grinding wheels and off the material being worked.
The poor seal which can be achieved, due to the vibrations, between the secondary shafts and the secondary frame is furthermore the cause of damage to the elements provided inside the honing head, with consequent frequent maintenance interventions for repairs or replacements.
The aim of the present inventiop is to eliminate the above described disadvantages by providing a honing head which is provided with such a structure as to offer adequate assurances in terms of resistance to the high stresses to which it is subject, so as to achieve a longer life.
Within the scope of this aim, an object of the invention is to provide a honing head which features reduced vibrations and deformations in use.
A further object of the invention is to provide a honing head which is provided with an effective protection against the infiltrations of abrasive or in any way harmful material into its interior so as to reduce the interventions for maintenance.
This aim, as well as this and other objects which will become apparent hereinafter, are achieved by a structure of a honing head for double-rotation cylindrical grinding wheels, particularly for the working of stones, marble, granite and the like, comprising a main framework which rotatably supports a main shaft which can be operated to rotate around its own axis and a secondary framework rigidly couple in rotation to said main shaft, and supporting at least one pair of secondary shafts with the axes arranged radially and counterposed with respect to the axis of said main shaft, said secondary shafts being operatable to rotate around their own, axis and being provided with an end projecting from said secondary framework and coaxially engageable with a cylindrical grinding wheel, characterized in that said secondary framework is provided, at each of said secondary shafts, with a supporting bush extending around the respective secondary shaft for a portion of the length thereof in the direction of the end thereof which is associable with said cylindrical grinding wheel, said supporting bush defining a rotatable supporting region for the respective secondary shaft and extending partially inside the cylindrical grinding wheel associated with the end of the secondary shaft.
Further characteristics and advantages will become apparent from the detailed description of a structure of a honing head according to the invention, illustrated only by way of non-limitative example in the accompanying drawings, where:

Fig. 1 is a front elevation view of the honing head according to the invention; and
Fig. 2 is an enlarged cross section view along the axis of the main shaft, illustrating a detall of the honing head according to the invention.

With reference to the above described figures, the honing head according to the invention, generally indicated with the reference numeral 1, comprise a main framework 2 which rotatably supports a main shaft 3. which is operatable to rotate around its own axis and which is usually arranged vertically.
Downwardly, the main shaft 3 rigidly supports a secondary framework 30 which comprises a block 4, which in turn supports rotatably at least one pair of secondary shafts 5 arranged radially and counterposed with respect to the main shaft; in the case illustrated, four secondary shafts are provided with their axes arranged horizontally and mutually angularly spaced apart by 90°.
More in detail, the block 4 supports the ends of the secondary shafts facing the main shaft by means of bearings 6 and is in turn rotatably supported by the main framework 2 by means of the main bearing 7, with which it is associated by means of a transmission 8.
Proximate to its upper end, the main shaft 3 is associated with a main wheel 9 which engages with a transmission gearwheel 10 which is rotatably supported, by means of a pair of bearings 11a and 11b, by a small shaft 12 fixed to the main framework 2.
The transmission gearwheel 10, besides with the main gearwheel, is furthermore engaged with a secondary gearwheel 13 which is rigidly coupled to one end of a transmission shaft 14 which extends outside and coaxially around the main shaft and which is provided, at the other end, with conical teeth 15.
The secondary gearwheel is provided with a number of teeth which is different from the number of teeth of the main gearwheel, so that the transmission shaft 14 is provided with a rotary motion with respect to the main axis, with which it is rotatably associated by means of the bearings 16 and 17.
The conical teeth 15 engage with conical gearwheels 18 which are keyed, by means of tabs 19, onto the end of the secondary shafts facing the main shaft.
According to the invention, the secondary framework 30 comprises, for each. secondary shaft, a supporting bush 20 which extends around the respective secondary shaft for a portion of its length in the direction of the end thereof which is opposite with respect to the main shaft and which extends at least partially inside a cylindrical grinding wheel 21 associated with said end of the secondary shaft.
More in detail, the supporting bush is fixed to the block 4 and defines, for the secondary shaft, a rotatable supporting region which is arranged inside the axial volume of the cylindrical, grinding wheel 21 fitted coaxially on the secondary shaft; said rotatable supporting region is composed of a pair of bearings 22a and 22b.
Moreover, the end of the secondary shaft which bears the grinding wheel is provided with a threaded portion 23 and, successively thereto in the direction of the main shaft, with a portion 24 in the shape of a truncated cone, both of which serve to fix a covering element 25 fitted onto the end of the secondary shaft.
Said covering element; proximate to its end opposite with respect to the main shaft, is provided with a threading ₂6 which extends circumferentially on its outer surface and is engageable with the cylindrical grinding wheel 21,
The covering element, around which the grinding wheel 21 is fitted, is provided with a portion of its length extending around the supporting bush with some backlash, so as to reduce as much as possible the distance of the grinding wheel from the main shaft.
Furthermore, in order to avoid infiltrations of harmful material into the secondary framework and into the main framework, a sealing element, e.g. a ring-shaped gasket 27, is provided on the outward facing end of the supporting bush, and is interposed between the secondary shaft and the supporting bush. For the same reason, a sealing gasket 28 is provided between the main framework and the secondary framework.
For the sake of descriptive completeness, it should be added that the fastening between the secondary shaft and the covering element can be increased by means of a dowel screw 29.
From what has been described, the operation of the honing head according to the invention is evident.
By operating the main shaft 3 to rotate around its own axis, the rotation of the secondary framework, which is rigidly coupled thereto, is achieved. As an effect of the rotation of the main shaft, it is achieved the actuation of the main gearwheel 9, of the transmission gearwheel 10, of the secondary gearwheel 13, of the transmission shaft 14 and of the secondary shafts 5, which thus rotate around their own axes.
The cylindrical grinding wheels 21 thus, rotate around their own axis and around the axis of the main shaft.
In practice it has been observed that the honing head, provided with the structure according to the invention, fully achieves the intended aim, since the configuration of the supporting bush allows a supporting action of the secondary shafts inside the axial volume of the respective cylindrical grinding wheel, and thus allows to have only a portion of the secondary shaft, with a very small length, arranged protrudingly; this fact reduces the deformations of the secondary shafts and the vibrations thereof during the operation of the honing head.
Another advantage is due to the covering element, which, as mentioned, extends for a portion around the supporting bush; in this manner the material which drops from the grinding wheels and from the stones must follow a relatively long path, passing between the covering element and the supporting bush before it reaches the gasket ₂7 which, by virtue of this fact, together with the reduction of the vibrations, can effectively contrast the entry of harmful materials inside the honing head.
A further advantage is that a great speed in the maintenance operations is achieved, since the elements which are most subject to wear, i.e. the grinding wheels and the covering elements, can be easily disassembled and assembled without requiring the opening of the honing head.
The honing head according to the invention, provided in particular for roughing, semifinishing and finishing work for stones, marble and granite, can also be used for the machining of metallic materials.
In practice, the materials employed, as well as the dimensions, may be any according to the requirements and the state of the art.

Claims

1. Structure of a honing head for double-rotation cylindrical grinding wheels, particularly for the working of stones, marble, granite and the like, comprising a main framework which rotatably supports a main shaft which can be operated to rotate around its own axis, a secondary framework rigidly coupled in rotation to said main shaft and supporting at least one pair of secondary shafts with their axes arranged radially and counterposed with respect to the axis of said main shaft, said secondary shafts being operatable to rotate around their own axis and being provided with an end thereof projecting from said secondary framework and coaxially engageable with a cylindrical grinding wheel, characterized in that said secondary framework is provided, at each of said secondary shafts, with a supporting bush extending around the respective secondary shaft for a portion of its length in the direction of the end thereof which is associable with said cylindrical grinding wheel, said supporting bush defining a rotatable supporting region for the respective secondary shaft and extending partially inside the cylindrical grinding wheel associated with the end of the secondary shaft.

2. Structure of a honing head according to claim 1, characterized in that said rotatable supporting region is arranged within the axial dimensions of said cylindrical grinding wheel associated with the respective secondary Shaft.

₃. Structure of a honing head according to claim ₁, characterized in that it comprises, for each of said secondary shafts, a covering element rigidly associated with the respective secondary shaft and insertable in said cylindrical grinding wheel, said covering element having at least a portion of its length extending, with backlash, around said supporting bush.

4. Structure of a honing head according to claims 1 and 3, characterized in that each of said secondary shafts is provided, at its end projecting from said secondary framework, with a threaded portion and, successively to said threaded portion in the direction of said secondary framework, with a portion in the shape of a truncated cone, for the coupling of said covering element.

5. Structure of a honing head according to one or more of the preceding claims, characterized in that said covering element is provided, proximate to its end opposite said secondary framework, with a threading which extends circumferentially on its outer surface and is engageable with said cylindrical grinding wheel.

6. Structure of a honing head according to one or more of the preceding claims, characterized in that said supporting bush is provided, proximate to its outward facing end, with a sealing element interposed between said supporting bush and the respective secondary shaft.

7. Structure of a honing head according to one or more of the preceding claims, characterized in that in said rotatable supporting region at least one bearing is arranged and associated with said supporting bush and with the respective secondary shaft.