CLEANING THE SANDING BELT BY BLOWING IT OFF WITH AN AIR KNIFE

Abstract

A process for cleaning an abrasive belt using an air blade extending continuously over the entire working width, or several segmented air blades, as well as a device which encloses this air blade or these air blades having an extraction hood serving to guide away the dust-laden air. If this device is used for a belt grinding machine equipped with a workpiece vacuum device, the air supply requirements are optimised by use of a diverter to reduce the number of fans.

Description

TECHNOLOGY FIELD

The invention relates to the field of belt abrasion technology.

PRIOR ART AND OBJECT OF THE INVENTION

The prior art relates to devices on belt grinding machines for blowing off grinding dust on workpieces and on abrasion belts. The dust on the latter is blown off during the abrasion procedure in continuous, temporary or pulsating manner either by a bar-shaped pipe provided with holes or slots, also a nozzle operating over the entire width of the grinding belt, or by rotatable, star-shaped discharge nozzles driven in rotation by the stream of air. The compressed air requirement is especially considerable in the first solution and the costs are correspondingly high. In the case of the second device the technical outlay also comes with considerable additional costs. The added disadvantage of both the devices popular to date is that in spite of their mostly oscillating movements they function selectively only, and on sensitive component surfaces, when it is cleaned unevenly, the abrasive belt as a result leaves behind a correspondingly conspicuous unevenness in the surface finish.

The present invention on the other hand solves the task of generating a stream of air acting on the abrasive belt by way of a technically straightforward and energy-saving, and therefore also cost-effective, process and describes the device required for this. In the process, for the first time it is making use of a device known in other areas of application, the so-called air blade (also known as air knife). This is usually used for separating air masses (e.g. air curtains for entrance gates), for drying surfaces or for cleaning workpieces or other items.

The air blade is distinguished in that a volume of air supplied by a fan and a supply pipe to a receptacle is reduced by lessening of its cross-section to a narrow gap of a few millimetres in slot width, from which a continuous stream of air escapes, in the present case relating to an abrasive belt.

The invention comprises such an air blade also in a serial, upstream and downstream expansion of the process, which describes both solutions for supplying air and also for discharging it.

In addition to qualitative improvement in the removal of dust from the abrasive belt, which is more uniform, the invention offers economic advantages over the most popular device today, which has an air tube provided with holes. Whereas the latter operates on compressed air, therefore based on the potentially rising energy requirement for generating high pressure and achieving an efficiency factor of approximately only fifty percent, with its additionally greater airflow based on a linear energy requirement the air blade accounts for an efficiency factor of close to one hundred percent.

The following documents also describe the relevant prior art:

• • DE 10 2017 117715 A1 (HOMAG GMBH) 7 Feb. 2019, which in comparison to the present invention does not describe the grinding dust being blown off by way of an air blade, but rather suctioning of the grinding dust, therefore a vectorially opposite process having no effect on the abrasive belt itself, but on the layer of air to the side of the abrasive belt.
  • JP H07 40242 A (AMITEC KK) 10 Feb. 1995, which, in contrast to the present invention, does not comprise an air blade blowing from top to bottom and installed for the purpose of cleaning an abrasive belt, but an air curtain blowing from bottom to top, which is intended to prevent the ejection of dust and chips from the grinding machine.
  • US 2020/346395 A1 (PANKOKE RENÉ) 5 Nov. 2020, which describes a method and a device acting on a fluid layer of a workpiece surface.
  • US 2012/145347 A1 (PONKA PHILIP V C), 14 Jun. 2012, which relates to a transport system with modules for supplying and discharging air in selected areas.
  • DE 35 17 677 A1 (RAUMA REPOLA OY) 2 Jan. 1986, which presents a dedusting device for grinding machines having a single blowing nozzle.
  • CH 674 331 A5 (STEINEMANN ULRICH AG), 31 May 1990, which generates an air curtain produced by a blowing nozzle, which deflects the sanding dust into a suction nozzle and accordingly prevents it from remaining in the machine.

BRIEF DESCRIPTION OF THE DRAWINGS

The following illustrate the present patent application:

• • the drawing of FIG. 1, showing the invention, an air blade with the air supply pipe (1) acting on the abrasive belt (7), the air discharge gap (2), from which the stream of air (3) escapes, optional connecting air pipes (4) and the air blade housing (5) with inside deflectors (6),
  • the drawing of FIG. 2, in turn with the air blade and its air discharge gap (2), the air supply pipe (1) and the air discharge flows (3) and the air chamber (5), supplemented by the extraction hood (8), its opening (17) and the discharge pipe (9)
  • the drawing of FIG. 3, showing the device, the blowing-off stream of air 3 and the air extraction flow 16 of the drawing of FIG. 2 in cross-section,
  • the drawing of FIG. 4, showing the air movements, if the belt grinding machine along with the air blade has a workpiece vacuum clamping device (10) with transport carpet table and work table perforations for fastening a workpiece (15), in this case generating the air supply (11), so that in this installation a single fan (12) and a switch (13) with an actuator (14) for regulating the additional ambient air supply (18) are sufficient to optimize air supply in the connecting pipe (1).

DESCRIPTION OF THE EMBODIMENTS

The object of the invention is an air blade cleaning an abrasive belt (7) during the abrasion procedure, as described at the outset under “Prior Art and Object of the Invention”. With reference to the requirement (which cannot be fulfilled with the previous sanding belt blow-off devices) of not allowing the air contaminated with grinding dust to escape into the machine (and consequently foul it), this arrangement is also characterised by one or more further chambers and openings enclosing the air blade, through which the contaminated air is drawn off to a dust-filtering extraction unit, for example in the form of a dust extraction hood (8). To achieve a stream of air (3) preferably of approximately 25-40 m/s speed, the slot width of the air discharge gap (2) will in general be approximately 1-5 mm, the openings for circulating the contaminated air a multiple of this. The air chamber (5) for producing an even and continuous stream of air (3) can also be fitted with correspondingly effective deflectors (6).

The required air supply is extracted from the ambient air by means of fans. If the belt grinding machine has a vacuum clamping device (10) for fastening the workpieces (15), the air supply can come from there, whereby an additional fan can be omitted.

In the process, the ambient enters the air blade via the perforations of the feed table and the conveyor belt. However this is possible only insofar as the perforations remain clear (that is, do not fulfil their actual purpose for workpiece fastening). If holes are covered over by workpieces, the reduced air supply must be compensated in some other way. The air supply reduction is determined by formation of negative pressure, unless it is already detected and equalized by the control system during workpiece feeding. Compensation in both cases is provided by a valve or switch (13), for example fitted with an actuator (14) in the ambient air suction pipe.

The device, which can be used fundamentally not only for air but also for all types of gases, can be modified or expanded if needed. For example, by combining it with an ionisation plant, which eliminates the electrical charging of the abrasion dust.

The device is optimized by segmented division into several air blades over the entire width of the abrasive belt, which however are used only in the region where grinding dust accumulates. The air can then be supplied either with a single connection or with several connections (4) both laterally and from above.

Claims

1-9. (canceled)

10. A process for blowing off an abrasive belt for the purpose of cleaning it during the abrasion process, wherein a stream of air acting on the abrasive belt is generated by an air blade.

11. The process as claimed in claim 10, wherein several air blades arranged over the width of the abrasive belt, and operationally controlled if required, are used.

12. An air blade for blowing off an abrasive belt, wherein it has an extraction hood having one or more openings and a discharge pipe for recirculation of grinding dust-laden air from the grinding machine interior enclosing the air blade.

13. An air blade for blowing off an abrasive belt, wherein air supply of the air blade occurs multilaterally.

14. An air blade for blowing off an abrasive belt, wherein it is part of a grinding unit having a workpiece vacuum clamping device, and it draws air entering the grinding unit across the perforations of the feed table and of the conveyor belt of this vacuum clamping device.

15. An air blade as claimed in claim 12, wherein deflectors in the air chamber of the air blade optimize uniform escape of air from the air chamber.

16. A process, wherein an air blade as claimed in claim 14 regulates an air supply by way of a valve or switch.

17. A process for blowing off an abrasive belt by means of an air blade which is part of a grinding unit having a vacuum device as claimed in claim 14, wherein the air blade fitted with an extraction hood having one or more openings and one or more exhaust pipes for circulating the dust-laden air draws the incoming air from this vacuum device via a vacuum fan and an air supply pipe.

18. An air blade as claimed in claim 14, wherein deflectors in an air chamber of the air blade optimize uniform escape of air from an air chamber of this air blade.