FR2487239A1 - Wood finishing machine with swinging polishing heads - has two pairs of heads operated in phase opposition to keep workpiece in position - Google Patents

Abstract

The finishing machine for wooden workpieces, has a set of four swinging heads (4) which are oscillated above the workpiece as it is advanced by a conveyor underneath. These heads carry abrasive material which is moved against the surface of the wood along a curved path by the swinging action. The heads are in two pairs, with the heads of each pair moving in opposite directions, and the inner heads of each pair moving towards each other, to prevent displacement of the workpiece. These heads are supported by swinging arms (9) at both ends, connected by levers (10) attached to a disc (1) mounted on a driving motor attached to the supporting frame (3). The centre line of the motor is parallel to the plane of the conveyor belt which advances the workpieces.

Description

 The present invention relates to a sander, or sanding machine, with automatic operation.

 To obtain a perfect finish on many pieces of wood, including moldings, we have to subject them to a sanding finish. For this, we know rectilinear sanding, sanding discs etc .. the best results are obtained with what is called sanding in an arc. "

 This last known method consists in moving abrasive grains on the workpiece, each of which describes a curvilinear roof path with a large radius, oriented substantially in the same direction as the grain of the wood. This allows sanding to a greater depth while providing less effort than in the case of straight sanding.

 It is known that sanding in an arc is obtained by means of a sander whose tette essentially comprises a motor with a vertical axis driving eccentrics and rods, which in turn entered two sanding pads which are suspended there. A pendulum movement corresponding to sanding in an arc of a circle is thus defined for the pads, as described for example in Spanish Utility Model NO 210 418 which this Dew mandator holds. In this known device , there is a relative movement of vertical oscillation between the pads which support the abrasive material, and the foot of the connecting rods which support them. This movement is compensated by elastic bands working on alternating bending, while the links are subjected to alternating bending and axial stresses.

 The present invention aims to avoid the drawbacks of known systems, and in particular to eliminate the forces to which the rods are subjected, while widening the field of application of the machine.

 A control head according to the invention, intended to equip an automatic sander, is characterized in that it com.

carries four pads provided with abrasive material, these four pads being aligned with each other in the direction of a conveyor belt, unlike the sanding heads known to date which each had only two pads
According to another characteristic of the invention, the four pads are each driven by a pendulum movement which defines the arcuate trajectory of the abrasive grains, these four pendulum movements being each synchronized in phase opposition with that of the neighboring pad or pads, if although when pads number one and number three advance in one direction, pads number two and number four advance in the opposite direction, which eliminates any relative movement of the workpiece. In addition, the solution according to the invention eliminates the parasitic forces to which the rods were subjected, which gives better reliability to the entire sander whose operation is particularly smooth due to this synchronism.

According to another characteristic of the invention, the sanding head is provided on one of its sides with a control motor whose axis of rotation is oriented parallel to the plane of the belt which transports the work to be sanded. This lateral mounting of the drive motor contributes to eliminating the efforts on the aforementioned links
The motor shaft has eccentric tracks which constitute cams called B left and right controlling the links which actuate the two central sanding pads (pad number two and pad number three). Each of the four pads is suspended from four links and, as previously indicated, the two central pads (number two and number three) oscillate in synchronism but in phase opposition.

 Each of the central runners is connected to one of the end runners (i.e. number two runner to number four runner, number three runner to number one runner), by means of a coupling rod. Thus, skates number one and number three are animated by the same movement, while skates number two and number four are each animated in a synchronous movement but stalled in phase opposition.

 The appended drawing, given by way of nonlimiting example, will allow a better understanding of the invention and the advantages it provides.

Figure 1 is an elevational view of a sanding plate according to the invention, which has been removed a side cover
Figure 2 is a section on plan n outgoing the entire sander seen from 'above
Figure 3 is a view corresponding to a detail of Figure 1, showing on a large scale the path of the brazed grains during the sanding operation
In the drawings, the reference numbers designating the various elements of the machine correspond to the following nomenclature
1: Drive motor
2: Side covers
3: Head body
4: Scoring tree
5: Connecting rods
6: Eccentrics
7: Bolts
8: Body of sanding pads 8a, 8b, 8c and 8d
9: Rods
10: Coupling rods
11: Fixing nut
12: Grain of gold
t3: Sanding piece.

 The automatic sander illustrated in the drawings has a head particularly intended for sanding moldings.

island has four pads ba, eb, 8c, and 8d, driven by a motor 1 arranged laterally. The body 3 of the sanding plate is closed by two side covers 2
The shaft 4 of the motor 1 comprises two eccentrics 6 set in phase opposition, by means of which it sets two connecting rods in reciprocating motion. Thus, these connecting rods 5 are each driven in an alternating movement: their movements are synchronous, but shifted in phase opposition. In other words, one is driven by a "right" movement and the other by a "left" movement, starting from this same shaft 4. The connecting rods 5 are connected by bolts 7 mounted on bearings allowing their rotation, to the bodies of the sanding pads 8.

The connecting rods 5 set in motion only two of the four shoe bodies 8, namely the shoes 8b (shoe number two) and 8c (shoe number three) arranged in the center of the tette. Two coupling rods 10, fixed by bolts 7 and nuts 11, connect
- the first, skate number one 8a to skate number three 8c ;;
- the second, skate number two 8b to skate number four uCd
Thus, the pads number one Sa and number three Se are animated, with their connecting rod 5, of a given reciprocating movement, while the pads nuro two eb and number four 8d and their connecting rod 5 are animated by a synchronous but offset movement in phase opposition. XI results among other things from the absence of an overall reaction on the sanding piece 13, which therefore does not tend to move. This makes it possible to give N the whole a regular advance movement, which guarantees, at the sanding work, a perfect finish.

Each of the four sanding pads is suspended from four links 9 which are articulated, with roller bearings, on the one hand on the body itself of the pad 8, on the other hand on the body of the pumice head 3 The four links of a skate S therefore form cuadril-tères
cross-linked allowing the pendulum movement necessary for the bridging operation called "in an arc
To fully appreciate the advantage of this device, there is shown on a large scale in FIG. 3, the detail of the arcuate path of a theoretical grit of abrasive 12, while it is sanding a piece 13.

Claims (3)

 RssV3NDICATIONS  1. Control head for an automatic sanding machine, characterized in that it comprises four pads provided with abrasive material, these four pads being aligned with each other in the direction of a conveyor belt which carries the piece to be sanded, these four pads each animated by a pendulum movement which defines the arcuate trajectory of the abrasive grains, these four pendulum movements being each synchronized in phase opposition with that of the neighboring pad or pads, so that when the pads number one and number three advance in one direction, pads number two and number four advance in the opposite direction, which eliminates any relative movement of the workpiece  2. sanding pad according to claim 1, characterized in that it is provided on one of its sides with a control motor whose axis of rotation is oriented parallel to the plane d8 the band which transports the part to sand  3. sanding pad according to claims 1 and 2, characterized in that the drive shaft has eccentric tracks which constitute cams said to the left "and i right" controlling the links which actuate the central sanding pads (pad number two and skate number three)