US20050130570A1

US20050130570A1 - Continuous through-feed grinding machine for machining a workpiece surface and method

Info

Publication number: US20050130570A1
Application number: US11/007,908
Authority: US
Inventors: Friedrich von Schumann
Original assignee: Individual
Current assignee: JAKOB LOWER INH VON SCHUMANN & Co KG GmbH; JAKOB LOWER INH VON SCHUMANN U Co KG MASCHINENFABRIK und EISENGIEBEREI GmbH
Priority date: 2003-12-13
Filing date: 2004-12-09
Publication date: 2005-06-16
Also published as: EP1541285A1; DE20319366U1

Abstract

The subject matter of the invention is a continuous through-feed grinding machine for machining a workpiece surface, said grinding machine having a grinding station with at least two rotating grinding tools, more specifically disc or roll grinders, with the grinding tools being continuously advanced along an endless path. The objective of providing a continuous through-feed grinding machine allowing for even machining of the workpiece surface with even wear of the grinding tools is accomplished by providing the endless path (128) with two work segments (140, 142) alternating with two transfer segments (144, 146) or by continuously advancing grinding tools that are moved along an endless path configured as an oval or elliptical shape.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application claims Priority from German Application No. DE 203 19 366.0 filed on 13, Dec. 2003.

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a continuous through-feed grinding machine and method for machining a workpiece surface, said grinding machine having a grinding station with at least two rotating grinding tools, more specifically disc grinders or rolls.
The manufacturing of pieces of furniture, room doors or the like requires surface grinding of the various components after machining in order to remove possible burs and/or to smooth the surface and to eliminate therefrom fine wood fibers. Only if the surface is thus made smooth can it be varnished properly. This applies in equivalent fashion to pre-varnished workpieces. Further, continuous through-feed grinding machines are utilized for deburring metal workpieces.
Especially if actually plane surfaces comprise raised portions, depressions or recesses, discrete workpieces are transported on a conveyor system along one or several grinding stations in such type continuous through-feed grinding machines, said grinding stations being provided with abrasive discs and/or rolls to which abrasive paper is mounted in a lamellar fashion. The abrasive discs or rolls thereby machine the workpiece, more specifically the profile thereof, from different angles in order to break possible edges and/or to remove burs.
2. Description of the Prior Art
From DE 100 35 977A1 for example it is known to integrate into a continuous through-feed grinding machine both an abrasive flap roll leading over the entire width of the workpiece and a number of abrasive flap discs (also known as “disc grinders”). Thereby, the abrasive flap roll is intended to grind the surface of the workpiece in the direction of transport, while the disc grinders rotate about their vertical axis, thus machining the surface of the workpiece from different directions. The disc grinders are not only rotated, they are also moved in an oscillating manner across the infeed direction so as to machine every point of the workpiece surface from different angles.
A grinding station for a continuous through-feed grinding machine is known from DE 196 11 932 A1 in which four secondary rotation axes are provided on one primary rotation axis, four roll grinders being mounted to each secondary rotation axis. The roll grinders thereby rotate about their horizontal axis and both the primary and the secondary rotation axes cause the roll grinder to rotate once more. As a result, the respective one of the roll grinders is caused to move diffusely across the surface of the workpiece, the objective being to grind each point of the workpiece surface as far as practicable from different angles in order to make it possible to sufficiently grind even complex edges, profiles or other patterns.
A grinding station is known from WO 99/22905 in which a number of roll grinders is mounted to a vertical axis, the roll grinders rotating about their horizontal axis on the one side and about the vertical axis on the other side.
In all the continuous through-feed grinding machines mentioned herein above, the surface of the workpiece is ground by the various grinding tools from different directions and angles. Actually, the surface of the workpiece is not machined uniformly thereby. Accordingly, there are regions of the workpiece surface that are mainly contacted at a certain angle or that are machined at a high or a low relative velocity, which leads to different grinding results and to different wear of the grinding tool. The oscillating movement across the direction of transport, combined with the rotation of the grinding tool and the movement of the workpiece, causes the grinding tool to move relative to the surface of the workpiece in a manner that is locally very irregular. Additionally, this causes the various grinding tools to wear unevenly if the workpiece to be machined does not extend over the entire machining width but only covers a portion of said width. Such unevenly worn grinding tools however compromise the grinding results of subsequent workpiece surfaces since different grinding results within the workpiece are obtained due to differing wear.

BRIEF SUMMARY OF THE INVENTION

In view thereof, it is the object of the present invention to provide a continuous through-feed grinding machine of the type mentioned herein above that permits to achieve even machining of the workpiece surface and even wear of the grinding tools.
As a technical approach to achieve this object, the invention proposes a continuous through-feed grinding machine according to the features of claim 1 or the features of claim 5. Advantageous developed implementations of this continuous through-feed grinding machine will become apparent from the subordinate claims.
A continuous through-feed grinding machine formed in accordance with this technical teaching has the advantage that the endless path permits to achieve a defined movement of the grinding tools over the workpiece surface, said grinding tools being at all times evenly guided over the surface of the workpiece so that even machining of the workpiece surface and even wear of the grinding tools are achieved.
Another advantage is that this defined movement may be used by the machine upsetter to place the various workpieces on the conveyor in accordance with their profile in such a manner that they are optimally contacted with the grinding tools, thus ensuring thorough grinding.
In a preferred embodiment, the endless path is dimensioned such that only a portion of the endless path is located in the region of the expected workpiece surface whilst another portion of the endless path is disposed outside of the workpiece surface. The endless path is advantageously configured in such a manner that those segments of the endless path in which the grinding tools are moved linearly or almost linearly are disposed above the expected workpiece surface, more specifically above the conveyor, whilst those portions of the endless path that are sharply curved or in which the workpieces are merely transferred are disposed outside of the expected workpiece surface. As a result thereof, the grinding tools are moved exclusively or almost linearly over the workpiece surface. It may thereby be left open whether the grinding tools are moved along the direction of transport of the workpieces or across thereto or at an angle of between +45° and −45° to the direction of transport. In any case, uniform movement of the grinding tools is achieved through the linear movement in the region of the grinding process.
This offers the advantage that the relative velocity of the tools relative to the workpiece surface is always the same so that even grinding is achieved. Another advantage is that this even grinding also results in even wear of the grinding tools, which on the one side enhances the quality of the grinding result and on the other side leads to a more profitable utilization with the capacity of the grinding tools being better utilized.
In a preferred embodiment the grinding station includes a guide rail configured to conform to the endless path and on which a number of carriages are guided, each carriage in turn holding one grinding tool. This has the advantage that the grinding tools can be reliably guided at lower cost. The utilization of a guide rail-carriage combination also allows for a low-friction, failure free movement of the grinding tools.
It has been found advantageous to connect via a tie rod said carriages to a positively driven chain so that a chain that is driven by an electric motor pulls the carriage.
In a particularly preferred developed implementation, a gear rim is held on the guide rail, said gear rim cooperating with a gearwheel mounted to the grinding tool so that the grinding tool rotates about its vertical axis as long as the carriage is moved forward. The rpm of the grinding tools is thereby coupled to the revolving velocity of the grinding tools along the endless path. This permits to achieve at low cost rotation of the grinding tool about its vertical axis so that the grinding tool does not grind the workpiece surface in a direction across the direction of transport only but also performs grinding at any other angle as a result of its motion of rotation. By thus indirectly driving the grinding tools, the entire grinding station can be driven with but one drive motor, which again reduces the cost of manufacturing.
In an alternative embodiment, each grinding tool is driven by its own electric motor. This has the advantage that the rpm of the grinding tools may be adjusted independently of the speed of the carriages revolving on the endless path. The grinding tools may likewise be operated at much higher speed. As a result, it is possible to machine both wood or wood substitutes (low rpm) and metal (high rpm) using but one continuous through-feed grinding machine. This widens the range of applications and, as a result thereof, increases the profitability of the continuous through-feed grinding machine of the invention.
Another advantage is that, as a result of the higher rpm of the grinding tools, the entire grinding process is completed sooner, which increases the throughput.
In a preferred embodiment, the grinding tools are individually controllable. This has the advantage that, depending on the required grinding conditions, the grinding tools may be connected on or off or their speed may be adjusted or they may be operated in the desired direction of rotation, which makes it possible to optimally adjust the grinding process to the requirements of the workpiece.
In another preferred embodiment, the grinding station is equipped with disc grinders only since these offer advantages in the multi-sided machining of workpieces.
In another preferred embodiment, the grinding station is equipped with roll grinders only since these allow for more aggressive machining. Such type machining is particularly advantageous for deburring metal pieces.
In still another preferred embodiment, the grinding station is provided with both disc grinders and roll grinders. The roll grinders may thereby be disposed with their rotation axis in the infeed direction, across the infeed direction or at any angle, more specifically at an angle of 45°, to the infeed direction. This has the advantage that the grinding station may be adapted to the workpieces to be ground in order to achieve the best possible grinding result with, as far as possible, even wear of the grinding tools.
Another advantage is that a desired grinding pattern can be achieved by individually arranging the grinding tools. This grinding pattern may thereby be oriented in the direction of the set angle of the angle grinder but may also be diffuse if different grinding tools are being utilized or if the grinding tools are differently aligned.
In a most preferred embodiment, the grinding station is equipped with three identical groups of grinding tools, each group of grinding tools including one disc grinder, one roll grinder mounted in the infeed direction, one mounted across the infeed direction and one inclined at an angle of 45° to the infeed direction. As a result, the depressions and raised portions as well as the borders and edges of the workpiece are ground from many different sides so that the workpiece is thoroughly machined.
Another advantage is that while the workpiece is so thoroughly and completely machined the transport speed of the workpiece may be increased without compromising the machining quality. This increased speed results in greater throughput and in greater profitability of the continuous through-feed grinding machine of the invention.
Further advantages of the continuous through-feed grinding machine of the invention will become apparent in the appended drawings and in the following description of embodiments thereof. Likewise, the above mentioned features and those described herein after may be used alone or in any combination with each other within the scope of the present invention. The embodiments discussed herein are merely exemplary in nature and are not intended to limit the scope of the invention in any manner.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWING

In the drawings:
FIG. 1 is a top view of a first embodiment of a grinding station of a continuous through-feed grinding machine of the invention;
FIG. 2 is a front view of the grinding station of FIG. 1;
FIG. 3 is a front view of an enlarged detail of a part of the grinding station of FIG. 2 taken along line III of FIG. 2;
FIG. 4 is an enlarged detail of a part of a second embodiment of a grinding station of a continuous through-feed grinding machine of the invention;
FIG. 5 is a top view of a third embodiment of a grinding station of a continuous through-feed grinding machine of the invention;
FIG. 6 is a front view of an enlarged detail of a part of the grinding station of FIG. 5;
FIG. 7 is a top view of the continuous through-feed grinding machine of FIG. 5, but with obliquely mounted roll grinders;
FIG. 8 is a top view of the continuous through-feed grinding machine of FIG. 5, but with crosswise mounted roll grinders;
FIG. 9 is a top view of the continuous through-feed grinding machine of FIG. 5, but with both obliquely and crosswise mounted roll grinders;
FIG. 10 is a top view of a fourth embodiment of a grinding station of a continuous through-feed grinding machine of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The FIGS. 1 through 3 illustrate a first continuous through-feed grinding machine in which workpieces 112 having a plane workpiece surface are conducted on a conveyor 110 past a grinding station 114. Generally, the workpieces 112 are doors, boards or other furniture components or the like made of wood or wood substitute, with the substantially plane or profiled surfaces being uniformly ground, polished or roughened. After the surface of these workpieces 112 has been mechanically machined, it must be ground in order to remove burs and protruding wood fibers and to smooth the surface. Depressions and raised portions such as for example milling cuts, mounted ledges or the like which are oriented across or along the infeed direction or at any angle thereto should thereby also be ground uniformly as far as practicable. The workpieces may be metal parts comprising milling cuts, holes, openings or recesses.
The grinding station 114 includes an electric drive 116 and a return pulley 118, an endless moving chain 120 being guided about the electric drive 116 and the return pulley 118. Said chain 120 pulls a number of grinding tools which, in the embodiment illustrated herein, are configured to be disc grinders 122. On its side turned towards the workpiece, each disc grinder 122 is equipped with a number of grinding lamellae and on the side turned toward the grinding station, the grinding tool 122 comprises a vertical axis. 124. The disc grinder 122 is retained at its vertical axis 124 on a travellable carriage 126 and can be caused to move along an endless path 128 by the carriage 126. The endless path 128 is implemented as a guide rail 130 that retains the respective one of the carriages 126 and slidably guides them along the endless path 128. The carriage 126 is connected to the chain 120 through a tie rod 132, said tie rod 132 being pivotally carried both on the chain 120 and on the carriage 126.
A gearwheel 134 that meshes with a gear rim 136 mounted to the inner side of the guide rail 130 is mounted to the vertical axis 124. This gear rim 136-gearwheel 134-combination causes the grinding tool 122 to rotate about its vertical axis 124 as soon as the disc grinder 122 is advanced. This construction makes it possible to readily move the grinding tools 122 along the endless path 128 using but one single electric drive 116.
The endless path 128 is composed of four segments, namely a first work segment 140, a second work segment 142, a first transfer segment 144 and a second transfer segment 146. Like the two transfer segments 144, 146, the two work segments 140, 142 are oppositely disposed from each other. The actual grinding process only occurs in the work segments 140 and 142 which are located above the expected workpiece surface. The work segments 140 and 142 thereby extend over the entire width of the conveyor 110. The transfer segments 140 and 146 are disposed outside of the conveyor 10 and merely serve to transfer the respective disc grinder 122 from the first work segment 140 to the second work segment 142 and reverse.
The work segments 140 and 142 are configured to be linear, meaning rectilinear, and are oriented exactly across the direction of transport of the workpieces 112. This arrangement of the disc grinders 122 ensures that the disc grinders 122 extend uniformly over the entire width of the workpiece, independent of the actual width of the individual workpiece. Moreover, it is thus achieved that the disc grinders 122 are caused to move over the workpieces 112 at a uniform speed so that machining of the workpiece surface is perfectly uniform. In thus designing the grinding station 114, the surface of the workpiece is optimally ground across the direction of transport and by having the disc grinders 122 rotating about their vertical axis 130 the workpiece 112 is also ground at a great variety of different angles. It has thereby been found advantageous to adjust the distance between two neighboring disc grinders 122 as a function of the infeed direction of the workpieces 112 in such a manner that a grinding tool 122 is passed over actually each point of the workpiece surface.
The entire grinding station is height adjustable by means of a hoist, thus being capable of machining workpieces of different sizes.
FIG. 4 illustrates a second embodiment of a continuous through-feed grinding machine of the invention that only differs from the first embodiment by the kind of drive used for the disc grinder 222. In this embodiment, each disc grinder 222 has its own electric motor 248 that drives the vertical axis 224 of the disc grinder 222. In an embodiment that has not been illustrated herein, each disc grinder 222 is individually driven.
To supply the electric motors 248 with energy, an open power supply line 250, which has not been illustrated in detail herein, is mounted in the inner side of the guide rail 230. On the electric motor 248, there is provided a corresponding sliding contact 252 that is carried along by the disc grinder 222 and rests against the power supply line 250. Through this sliding contact 252, the electric motor 248 can be supplied with power at any time.
In a preferred developed implementation that has not been illustrated in detail herein, a control line is additionally mounted in the guide rail and a corresponding control device to the electric motor so that each electric motor of every single grinding disc can be individually controlled. This makes it even easier to individually control the various grinding tools.
The FIGS. 5 and 6 illustrate a third embodiment of a continuous through-feed grinding machine of the invention in which the grinding tools retained on the grinding station 314 are configured to be roll grinders 323. Said roll grinders 323 are driven by an electric motor 348 and rotate about their rotation axis 354. In the illustration according to FIG. 5, the roll grinders 354 are disposed in the infeed direction, meaning the rotation axis 354 is oriented at right angles to the direction of movement of the roll grinder 323 (revolving direction). As a result, the rotation axis 354 is coaxial with the direction of transport of the workpieces 312.
The electric motor 348 is retained in a frame 356 to which the roll grinder 323 is also secured, said roll grinder 323 being driven by the electric motor 348 via a V-belt 358. The frame 356 is retained on the carriage 326 by a screw 360, said carriage being guided on the guide rail 330. A peripheral power supply line 350 through which the necessary power is carried to the electric motor 348 is mounted parallel to the guide rail 330. The power supply line 350 is thereby configured to be a contactless energy transfer rail.
The FIGS. 7 through 9 also illustrate the continuous through-feed grinding machine according to the FIGS. 5 and 6, with the roll grinders 323 being now positioned differently. In FIG. 7, the roll grinders 323 are disposed so that their rotation axis is inclined at an angle of 45° to the infeed direction whilst the roll grinders 323 of FIG. 8 are disposed across the infeed direction. In FIG. 9, the roll grinders are alternately disposed in the infeed direction, at an angle of 45° to the infeed direction and across the infeed direction. Three differently mounted roll grinders 323 thereby form one group of grinding tools, three such groups of grinding tools being mounted to the grinding station 314.
The discrete roll grinders 323 can readily be brought from one position to another by untightening the screw 360 and by rotating the frame 358 accordingly prior to again tightening the screw 360. The roll grinder 323 may thus be mounted in any position.
FIG. 10 illustrates a fourth embodiment that only differs from the embodiment shown in FIG. 9 by the fact that here one group of grinding tools comprises one disc grinder 422 in addition to the three differently mounted roll grinders 423.
As a matter of course, other combinations and arrangements of the grinding tools are possible even if these are not explicitly represented herein.
The grinding stations 114, 214, 314 illustrated herein can be complemented by further grinding stations 114, 214, 314 and at need by roll grinders for example that extend over the entire width of the workpiece. Also, there may be provided spindles with rotating cylinder bodies having abrasive lamellae, said spindles being disposed across the infeed direction or belt grinding units disposed across or along the infeed direction or cylinder bodies across which an abrasive paper is stretched and that are disposed across the infeed direction.
In another embodiment that has not been illustrated herein, the endless path is configured as an oval or elliptical shape with the sharply curved regions being again disposed outside of the conveyor. With such an oval or elliptical endless path, the above mentioned advantages are achieved in much the same way.
In still another embodiment that has not been illustrated herein, the work segments are inclined at an angle of between 45° and 135° to the direction of transport of the workpieces. Depending on the design of the workpiece surface and on their profile, such an angled arrangement may yield a further optimized grinding result.
In still another embodiment that has not been illustrated herein, the grinding tools are driven with compressed air.
During the actual grinding process, it is possible to cause the discrete grinding tools to rotate at different speeds or to operate discrete grinding tools in opposing directions. This depends on the respective one of the workpieces that is to be ground.
It has been found out that wood or wood substitute is preferably to be ground with grinding tools at a speed of 100 to 500 rpm whilst metal is preferably to be ground at a speed of 1000 to 3000 rpm, the speed of the grinding tools revolving along the endless path being preferred to range from 1 m/min to 10 m/min. It has thereby also been found advantageous to equip the grinding station with multiple disc grinders for machining wood and wood substitutes, whereas multiple roll grinders are advantageous for machining metal. A workpiece made of wood or wood substitute is moved on the conveyor at a transport speed ranging between 1 m/min and 20 m/min whereas a workpiece made of metal is moved at a transport speed of from 0.5 m/min to 10 m/min.
It has also been found advantageous to choose the speed at which the workpieces revolve to be about four times the transport speed of the workpieces in order to make certain that the grinding tool sufficiently passes over the respective workpiece.
In order for the roll grinders to be readily rotatable on the grinding station, it has been found advantageous to configure the roll grinders as a square shape so that the diameter (including the abrasive means) corresponds approximately to the width of the roll.
The abrasive means mounted to the grinding tools are lamellae of abrasive paper. Preferably, the back side of the lamellae rests against bristles or bristle bundles supporting the lamella.
Further, pure abrasive bristles may be mounted to the disc or roll grinder for machining metal workpieces, the abrasive bristles being formed from a plastic bristle provided with an abrasive means.

Listing of Numerals

- 110 conveyor
- 112, 312 workpiece
- 114, 214, 314 grinding station
- 116 electric drive
- 118 return pulley
- 120 chain
- 122, 222, 422 disc grinder
  - 323, 423 roll grinder
- 124, 224 vertical axis
- 126, 326 carriage
- 128 endless path
- 130, 230, 330 guide rail
- 132 tie rod
- 134 gear wheel
- 136 gear rim
- 140 work segment
- 142 work segment
- 144 transfer segment
- 146 transfer segment
  - 248, 348 electric motor
  - 250, 350 power supply line
  - 252 sliding contact
    - 354 rotation axis
    - 356 frame
    - 358 V-belt
    - 360 screw

Claims

1. A continuous through-feed grinding machine for machining a workpiece surface, said grinding machine having a grinding station with at least two rotating grinding tools, more specifically disc or roll grinders, with the grinding tools being continuously advanced along an endless path,

characterized in that the endless path (28) comprises two work segments (40, 42) alternating with two transfer segments (44, 46).

2. The continuous through-feed grinding machine as set forth in claim 1,

characterized in that the grinding tools (122, 222, 323, 422, 423) are moved linearly in the work segments (140, 142).

3. The continuous through-feed grinding machine as set forth in claim 1,

characterized in that the work segments (140, 142) are disposed in the region of the expected workpiece surface and that the transfer segments (144, 146) are disposed outside of the expected workpiece surface.

4. The continuous through-feed grinding machine as set forth in claim 3,

characterized in that the work segment (140, 142) is inclined at an angle α of between 45° and 135°, preferably of 90° to the direction of transport of the workpieces (112, 312).

5. The continuous through-feed grinding machine as set forth in claim 1,

characterized in that the grinding station (112, 312) includes a guide rail (130, 230, 330) that is configured to conform to the endless path (128) and along which the grinding tools (122, 222, 323, 422, 423) are guided by means of carriages (126, 326).

6. The continuous through-feed grinding machine as set forth in claim 5,

characterized in that the carriage (126, 326) is connected through a tie rod (132) to an endless, positively driven chain (12) and is pulled by said chain.

7. The continuous through-feed grinding machine as set forth in claim 5,

characterized in that a gear rim (136) is mounted to the guide rail (130), preferably on the inner side thereof, said gear rim cooperating with a gear wheel (13) mounted to the grinding tool (122) so that the grinding tool (122) rotates about its vertical axis (125) as long as the carriage (122) is moving forward.

8. The continuous through-feed grinding machine as set forth in claim 1,

characterized in that a roll grinder (323, 423) and/or a disc grinder (422) disposed across the infeed direction and/or disposed in the infeed direction and/or disposed at an angle of 45° to the infeed direction form a group of grinding tools, two to twelve groups of grinding tools being disposed on one grinding station (314).

9. The continuous through-feed grinding machine as set forth in claim 1,

characterized in that each grinding tool (222, 323) is rotated by its own electric motor (248, 348).

10. The continuous through-feed grinding machine as set forth in claim 1,

characterized in that the grinding station (114, 214, 314) is height-adjustable.

11. A continuous through-feed grinding machine for machining a workpiece surface, said grinding machine having a grinding station with at least two rotating grinding tools, more specifically disc or roll grinders, with the grinding tools being continuously advanced along an endless path,

characterized in that the endless path (28) is configured as an oval or elliptical shape.

12. The continuous through-feed grinding machine as set forth in claim 11,

characterized in that segments of the endless path having a large radius or rectilinear segments are disposed in the region of the expected workpiece surface and that segments of the endless path having a small radius are disposed outside of the expected workpiece surface.

13. The continuous through-feed grinding machine as set forth in claim 11,

14. The continuous through-feed grinding machine as set forth in claim 13,

15. The continuous through-feed grinding machine as set forth in claim 11,

16. The continuous through-feed grinding machine as set forth in claim 11,

17. The continuous through-feed grinding machine as set forth in claim 11,

18. The continuous through-feed grinding machine as set forth in claim 11,

19. A method for machining a workpiece surface with a continuous through-feed grinding machine in accordance with any one of the afore mentioned claims,

characterized in that the rotation speed and/or the direction of rotation of one grinding tool or of a group of grinding tools is individually controlled.

20. A method for machining a workpiece surface with a continuous through-feed grinding machine in accordance with any one of the afore mentioned claims, more specifically in accordance with claim 19,

characterized in that the speed of a revolving grinding tool is twice to eight times, preferably 4 times, the infeed speed of the workpiece.

21. The method for machining a workpiece surface with a continuous through-feed grinding machine in accordance with any one of the afore mentioned claims, more specifically in accordance with claim 19,

characterized in that the grinding tools are driven in the work segment only.

22. A method for machining a workpiece surface with a continuous through-feed grinding machine in accordance with any one of the afore mentioned claims, more specifically in accordance with claim 19,

characterized in that the workpiece is moved forward and back by means of a conveyor.