EP0825914B1

EP0825914B1 - Sawing machine

Info

Publication number: EP0825914B1
Application number: EP96913566A
Authority: EP
Inventors: Eero Kivimaa; Antti Kivimaa
Original assignee: Wintersteiger AG
Current assignee: Wintersteiger AG
Priority date: 1995-05-12
Filing date: 1996-05-13
Publication date: 2002-07-17
Anticipated expiration: 2016-05-13
Also published as: WO1996035559A1; AU5651496A; DE69622399D1; CA2220731A1; ATE220602T1; EP0825914A1; DE69622399T2

Abstract

The invention relates to a sawing machine having a blade set reciprocating in the direction of the blades (2) and means (20) for effecting a transverse yielding movement of the blades. The speed of the blades (2) can be increased if the yielding movement is effected by an eccentric element (20c) connected to the end of the blade set via a connecting rod (20a).

Description

The invention relates to a sawing machine having a blade set comprising at least one elongated blade and blade fixing means to which the ends of the blade are fixed, means attached to one end of the blade set for reciprocating the blade set essentially lengthwise of the blade, and means attached to at least one end of the blade set to produce a yielding movement of the blade essentially perpendicularly to the longitudinal direction of the blade, said means being formed from a connecting rod, one end of which is attached to the blade set, and from an eccentric element.

The background of the invention is traceable to the applicant's investigations conducted on gang saws in the 1950's. The investigations showed that the blades were subjected to great power peaks caused by the fact that the teeth on the blades had to 'cut' with their backs at the start of a return stroke. This in high-power gang saws (stroke length 700 mm) required a stretching force of about 80000 N per blade, a mass of about 600 kg for the reciprocating parts, and a small stroke number, about 350 1/min.

First was developed a 'lever saw', in which a sufficient blade stretching force was about 1/20 of the above. Tests performed with three laboratory test saws and one industrial prototype (stroke length 500 mm and stroke number 470 1/min) showed promising results. The drawback of the lever saw was its complicated structure, which prevented serial production of the machine.

Background art is also represented by a gang saw disclosed in EP 0,412,958, the saw comprising means, a connecting rod and an eccentric element for producing a linear reciprocating sawing movement. The end of the connecting rod spaced apart from the blades is mounted via two rods on the frame of the machine and on the eccentric, respectively.

The document SU 946 925 discloses a frame saw in which the saw blades follow a substantially elliptic path. Such a path is obtained by providing the top frame rail 7 at both ends with rockers 8, 9, the ends of which are connected to two pairs of top levers 2, 3. The other end of these top levers is connected to each other with rotatable shafts which are mounted in the body of the device. The top levers are also provided with counterweights 5. The movement of the frame in the vertical direction causes the top frame rail 7 to move slightly in a horizontal direction as a result of the inclined position of the top levers 2, 3.

The object of the present invention is to provide a sawing machine having a simple structure and blades that perform highly advantageous sawing movement. The sawing machine of the invention is characterized in that the other end of the connecting rod is connected to the eccentric element, the rate of rotation of the element being synchronized with the lengthwise movement of the blade so as to make the blade move along an essentially elliptic path in the sawing region.

When the end of the connecting rod is connected directly to the eccentric element, the path of the blade becomes essentially elliptic, which is highly advantageous to the sawing result.

During the research, the structure of a sawing machine according to the invention has been successfully developed by scale model technology, which has helped to simplify the structure of the machine and eliminate a large number of 'unnecessary' moving parts.

Research and development have resulted in a sawing method having the following main characteristics:

the teeth on the blade have an advantageous elliptic cutting path, which is essentially straight (or slightly curved toward the feed direction) during the working stroke of the blades, rounded at the dead points of the reciprocating movement of the blade, and curved backward during the return stroke;
a reciprocating sawing movement is effected with a drive connecting rod connected to one (lower) end of the blades or blade set;
in the cutting plane of the blades, the cutting path of the teeth is effected with a control connecting rod, the eccentric movement of which is synchronized with the drive crank wheel of the machine;
in the cutting plane, the blade set is supported with wide control rods and with blade guides located above and below the timber to be cut;
the blade set is assembled with assembly bolts passing through blades, spacers and end pieces;
stretching of blades and a blade frame can usually be eliminated.

A preferred embodiment of the invention is characterized in that the control connecting rods are connected to both ends of the blade means.

A sawing machine according to the invention is illustrated by the following schematic drawings. The simple means for feeding and controlling the timber to be sawn are not shown in the drawings, nor is the adjustment of the overhang of the blades, since they are not the object of the present invention.

Fig. 1 shows a first embodiment of a sawing machine of the invention, seen from the left-hand side in the direction of feed of the timber;

fig. 2 shows a reduced view of the sawing machine from the opposite side;

fig. 3 is a cross-section taken along line A-A of fig. 1;

fig. 4 shows an enlarged front view of a blade set;

fig. 5 shows a side view of the blade set; and

fig. 6 shows an enlarged view of the cutting path 4d of the teeth in the middle section of the blade.

The cutting path of the teeth on the blades is drawn with a model machine constructed in the scale 1:2 of the planned prototype saw with a stroke length of 300 mm and stroke number of 1200-1500 1/min.

In the figures, a frame of the machine is indicated by reference number 1. Number 2 indicates a blade or a blade set comprising blades, and 2a indicates a blade beam on which a blade set assembled from blades 2, spacers 2b separating them and end pieces 2c is arranged with assembly bolts 2d and an assembly shaft 2e. The fit between the blades 2 and the shaft 2e is rendered so wide in the longitudinal direction of the blades that minor unequal heat expansion of a blade can take place without obstruction. The blades are guided in the lateral direction by a guide unit 2f from beneath the timber to be sawn and by a movable guide unit 2g from above.

Reference number 3 indicates timber to be sawn, the timber being fed at a feed speed u against the blades moving back and forth essentially vertically. The blades are moved by a connecting rod 4, the rod being mounted on a shaft 2h fixed to a blade beam 2a such that it articulates. The drive connecting rod 4 is moved via a crank 6a by a crank wheel and thereby a flywheel 6 fixed to the shaft, the crank wheel being driven by a drive wheel 7 arranged on the same shaft on the other side of the frame 1 and mounted on the frame, the drive wheel in turn being connected with a band 7a to a driving device 8, preferably an electric motor controlled by a frequency converter.

A control rod 10a of a lower control system 10 is also mounted on the shaft 2h, the rod also being the connecting rod of the system and obtaining the minor control movement from an eccentric element 10e fixed to a crank shaft 10b and mounted on the control connecting rod 10a. The control connecting rod 10a is essentially perpendicular to the longitudinal direction of the blades. The control connecting rod of the upper end of the blade set is, in turn, mounted on the assembly shaft 2e of the blade set. Toothed wheels 10c and 20c fixed to shafts 10b and 20b are moved synchronously via a toothed belt 7d by a pulley 7c of an equal size, the pulley being connected to the drive shaft of the machine and the belt being supported by a tension roller 7e.

By the joint effect of the control of the lower and upper ends of the blades, an advantageous cutting path 4d of the teeth (fig. 1) in the middle of the blades is obtained, the advantageous path approximating an ellipsis, fig. 6. As regards the path, during a downward working stroke of the blade, the path is essentially straight; when the blades are at a lower dead point, the path is rounded; during a return stroke of the blades, the path curves backward and the blade is detached from the bottom of the saw kerf; when the blades are at an upper dead point, the path is rounded.

In the figure, D indicates the diameter of the path of the crank 6a in the drive crank wheel 6 and the stroke length of the blades. Reference d, in turn, indicates the diameter of the crank movement of the control system 10, the diameter here being equal to the corresponding diameter in control system 20.

The advantageous cutting path found in the investigations was examined with simple test equipment and a power-driven model saw having a stroke length of 150 mm. The shape of the path has been noted to depend on the ratio of the stroke length D of the blades to the length of the control connecting rods - in the test, the ratio was 1:2.5 and 1:3 - and on the diameter d of the control rod, which in the above model saw is 18 mm. The shape of the cutting path can also be affected by changing the synchronization of the drive and control connecting rods of the machine.

Alternatively, the lower end of the blade set can be controlled by control rods of a straight movement component arranged below the feeding table of the machine and connected to shaft 2h. This kind of straight movement is known from the Applicant's own patent Fl 77,397.

When a new sawing machine according to the invention is compared with a conventional gang saw the study of which launched the development of a new sawing machine over 40 years ago, the following matters are noted:

The new sawing machine is small, simple in structure and clear and rapid in operation, since the mass of the reciprocating parts of the machine is, due to the advantageous path of the teeth on the blade, only 1 to 2% of that of a conventional gang saw having the same sawing capacity. Since the mobile parts are light, the machine is not difficult to balance. Also, the thin blades are small, simple and easy to maintain; they are well laterally supported at their both ends in the blade set that is assembled outside the machine and can be changed rapidly, the support being helped with blade guides. The system makes it possible to saw very thin boards. The number of the blades sawing simultaneously can also be selected very freely. The higher cutting speed and the blade guides make it possible to obtain thin chips (sawdust), a good sawing result and good timber measuring accuracy. Because of the thin blades and the good measuring accuracy, the new sawing machine makes it possible to produce products from the same raw material with a smaller loss of raw material, whereby the sawing is significantly more economic.

It is possible that the new sawing machine will replace the conventional gang saw due to its above advantages and also take up fields of use from band saws and circular saws, especially in sawing of logs. Since the new sawing machine cannot be defined to belong to any previously known type of sawing machine, its working title has been an ellipse saw due to the cutting path of the teeth on the blade that approximates an ellipse.

Claims

A sawing machine having

a blade set comprising at least one elongated blade (2) and blade fixing means to which the ends of the blade are fixed,

means (4, 6, 8) attached to one end of the blade set for reciprocating the blade set essentially lengthwise of the blade, and

means (10, 20) attached to at least one end of the blade set to produce a yielding movement of the blade (2) essentially perpendicularly to the longitudinal direction of the blade, said means being formed from a connecting rod (10a, 20a), one end of which is attached to the blade set, and from an eccentric element (10e, 20e), characterized in that the other end of the connecting rod (10a, 20a) is connected to the eccentric element (10e, 20e), the rate of rotation of the element being synchronized with the lengthwise movement of the blade so as to make the blade (2) move along an essentially elliptic path (4d) in the sawing region.
A sawing machine according to claim 1, characterized in that the means (20) that produce the yielding movement of the blade (2) are attached to that end of the blade set which is spaced apart from the end to which the means (4, 6, 8) for moving the blade set are attached, and that to the last-mentioned end of the blade set are attached means for effecting straight movement of the blade.
A sawing machine according to claim 1 or 2, characterized in that the means (4, 6, 8) moving the blade set and the means (10; 20) effecting the yielding movement or straight movement of the blade are attached to the blade set at the same point (2h, 2e).