Abrading device

A device for abrading objects comprising a supporting surface for the object, abrading means operative near the supporting surface and a driven, endless conveyor belt arranged at a distance above the supporting surface, whereas the lower run of the belt is pressed upon the object, wherein the device is provided with a suction cabinet supported by the frame of the conveyor belt and having suction apertures turned towards the top side of the lower run for drawing the lower run against the suction cabinet; the cabinet is connected through a conduit with an outlet channel for conducting away chips.

The invention relates to a device for abrading the objects comprising a 
supporting surface for the object, abrading means operative near said 
supporting surface and a driven, endless conveyor belt arranged at a 
distance above said supporting surface, the lower run of said belt 
pressing against the object. 
Abrading machines comprising a conveyor belt located above the object 
involve the problem that the lower run tends to sag. One of the solutions 
for this problem consists in stretching the belt, but nevertheless after 
some time said lower run again tends to sag. 
The invention has for its object to obviate the aforesaid disadvantage and 
proposes to this end to equip the device with a suction cabinet supported 
by the frame of the conveyor belt and having suction apertures turned 
towards the top side of the lower run for drawing the lower run against 
the suction cabinet. 
With the exception of the parts located opposite the abrading means the 
suction surface of the cabinet preferably has chambers in which the 
suction apertures open out. 
In this way a uniform suction force is exerted on the lower run of the 
belt. 
If the abrading device is equipped with a nozzle arranged near the abrading 
means and communicating through an outlet channel with a source of 
subatmospheric pressure for conducting away chips, the invention proposes 
to connect the suction cabinet through a conduit with the outlet channel 
at a point thereof lying at a distance from the nozzle. Owing to this 
disposition the subatmospheric pressure of the suction cabinet can be 
derived in a very simple manner from the subatmospheric pressure 
prevailing in the outlet channel for conducting away the chips. This 
provides a high economy of energy for such an abrading device. 
In order to be able to rapidly draw the lower run of the conveyor belt 
against the suction cabinet, when the device is put into operation, 
without appreciable loss of suction air, the invention proposes to hold 
the edges of the lower run in guiding profiles connected with the suction 
cabinet. 
The invention will be described more fully with reference to an embodiment.

The device mainly comprises a box-shaped substructure 1 and two abrading 
belt aggregates 2 arranged therein. The abrading belt aggregates comprise 
endless abrading belts 3 passed in known manner around drive and guide 
rollers 4. The disposition of the abrading belt aggregates with respect to 
the substructure 1 is such that at the top side the belts just emerge 
above the supporting surface 5 of the substructure 1, so that an abrading 
surface becomes available. At a distance above the abrading belt 
aggregates 2 is arranged a pressure table 6 comprising a supporting frame 
7, in which rollers 8 are arranged for guiding an endless belt 9. The 
rollers 8 are directly driven by a motor (not shown) in the framework 7 so 
that on the lower side the belt is driven in the direction of the arrow 
P1. 
At the front and at the rear the framework 7 is provided with two stub 
shafts 10 about which angular levers 11 are pivotable. One end of the 
angular lever 11 is pivotally connected with the lower end of screw 
spindle 12, whereas the other limbs of the angular levers 11 are 
interconnected by a coupling rod 13 on the same side of the framework 7. 
The screw spindles 12 co-operate with a screw-like body 14 having inner 
screwthread and being rotatably supported in an eyelet 15 of a 
cabinet-like superstructure 16. The rotatable body 14 is provided with a 
sprocket wheel 17, around which a chain 18 is passed, which is furthermore 
passed to the sprocket wheel 17 of the second screw spindle 12 arranged at 
a distance in the superstructure. 
The chain 18 can be reciprocated by a chain drive 19 comprising a motor 
supported in the superstructure 16, said motor driving a sprocket wheel 20 
through an orthogonal transmission. 
On both sides the framework 7 is provided with rotatably fastened discs 21, 
around which a passed a flexible element, for example, a rope or chain 22, 
at one end 23 this flexible element is fastened to the superstructure 16 
and is furthermore guided along a disc 24 also fastened to the 
superstructure 16 to a compensation weight 25 in the lower side of the 
substructure 1. 
It should finally be noted that the other limb of one of the angular levers 
11 is provided with a fastening eyelet with which is coupled a tensile 
spring 26 which bears on a plate 27 connected with the superstructure 16. 
Through the plate 27 is passed a screw spindle 28 to which the tensile 
spring 26 is fastened. This screw spindle 28 is provided with a 
control-knob 29 screwed thereon, the left-hand surface of which bears on 
the plate 27. 
According to one feature of the invention a suction cabinet 30 is arranged 
above the lower run of the conveyor belt 9 and between the framework 7, 
FIG. 2 showing the lower side of said cabinet. The lower side has suction 
apertures 31, which in the embodiment shown open out in chambers 32 
recessed in said lower side (see also FIG. 3). These chambers extend 
substantially over the whole width of the suction cabinet 30 in a 
direction transverse of the direction of movement of the belt 9. The 
chambers ensure a uniform subatmospheric pressure above the lower run of 
the belt 9 so that the lower run is effectively held against the lower 
side of the suction cabinet 30 when the subatmospheric pressure is 
prevailing. 
FIG. 2 clearly shows that no suction apertures 31 or chambers 32 are 
provided in those parts of the lower surface of the suction cabinet 30 
which are located opposite the abrading belt aggregates 2 in order to 
ensure a uniform pressure of the work piece on the abrading belts. 
FIG. 4 shows an embodiment in which the edges of the framework 7 are 
provided on the lower side with horizontal flanges 33 extending beyond the 
side edges of the belt 9. When the device is out of operation and no 
subatmospheric pressure prevails in the suction cabinet 30, the lower run 
of the belt tends to sag. In order to limit this phenomenon the flanges 33 
are provided so that when the device is again put into operation and 
subatmospheric pressure is again prevailing in the suction cabinet 30, the 
space between the lower run of the belt and the suction cabinet 30 will 
not be excessively large, as a result of which an effective contact with 
the lower run is ensured. 
In the embodiment shown the subatmospheric pressure in the suction cabinet 
30 is obtained by connecting this suction cabinet 30 through a conduit 34, 
for example, a flexible conduit with a chip outlet channel 35. At the 
right-hand abrading belt aggregate 2 the outlet channel 35 is provided 
with a nozzle 36 for directly conducting away chips from the belt, whilst 
the outlet channel 35 furthermore communicates with a subatmospheric 
pressure source. According to a further feature of the invention the 
flexible conduit 34 is connected at a point of the outlet channel 35 
located at a distance from the nozzle 36 so that an effective 
subatmospheric pressure in the suction box 30 is guaranteed.