Conveying apparatus for tree trunks

A conveying apparatus for conveying tree trunks through a measuring device is disclosed in which the conveying apparatus comprises at least one transport chain and a plurality of drivers for receiving the tree trunks which are driven by the chain and slide on a guide track. A reliable supporting of the tree trunks on the drivers during transport through the measuring device is achieved which also prevents tilting of the tree trunks by providing drivers which are spaced apart in the conveying direction of the chain. Additionally, the engaging faces of the drivers are designed for receiving the tree trunks and extend perpendicularly to the conveying direction of the chain and are inclined where at least two drivers have oppositely extending inclines in the conveying region.

BACKGROUND OF THE INVENTION 
The invention relates to a conveying apparatus for tree trunks, and, in 
particular, to an apparatus for transporting tree trunks through a trunk 
measuring means. The apparatus comprises at least one transport chain 
which is movable in the transport direction and drivers which are secured 
at intervals to the transport chain and are driven by the latter. The 
drivers have engagement faces which are inclined in a direction transverse 
to the transport direction and are capable of sliding or rolling on a 
guide track. 
Chain conveyors with pusher or driver chains are widely used in sawmill 
technology. The drivers, dogs or pushers consist generally of blocks which 
are connected to the chains or vertically disposed plate elements having a 
slightly V-shaped angled support or engaging face. The lowermost point of 
the driver is disposed in the center of the driver and the legs rise 
laterally in a direction .transverse to the conveying direction. The 
inclination angles of the driver legs are frequently between 10.degree. 
and 20.degree. to the horizontal. The engaging faces at the upper side of 
the drivers may be toothed to prevent trunks slipping on the drivers when 
starting up and accelerating the conveyor or under the action of any other 
forces acting on the conveyed trunks. The purpose of the V-shaped angled 
construction is to make the trunks assume as central a position as 
possible on the drivers under the action of gravity. 
It is also known to optically measure tree trunks for an optimum cutting 
division. This measuring can take place in the region of a chain bed 
conveyor, with both an intermittent or a continuous advance of the trunks 
on the conveyor. 
Generally, the opitcal measurement of trunks has been restricted to 
measuring the diameter of the trunk at predetermined intervals in order to 
determine the cutting possibilities and thus the utilizability of the 
trunk cross-section over the length of the trunk. If with a raster camera 
or a photo-cell means both outer trunk side borders are simultaneously 
detected at a point to determine the trunk diameter from their position 
difference, it is of no consequence whether the trunk on its advance up to 
the next measuring position changes its position on the chain conveyor 
because of certain support instabilities. The measurement result is not 
influenced by the three-dimensional position the measuring point has on 
the trunk. 
Since tree trunks are only very rarely ideally straight, however, further 
steps in optical measuring have recently been taken where, apart from the 
trunk diameter, attempts are made at various points to detect the position 
of the trunk axis in order to determine the curvature variation thereof in 
the manner of a locus curve. From the data acquired and evaluated with the 
aid of a computer on the basis of the trunk curvature, the optimum 
severing cut positions are determined to obtain individual portions which 
are as straight as possible for an optimum cross-section utilization. 
In measuring methods in which the path of the trunk axis is measured, it is 
important that the trunk in the necessary intermittent or continuous 
advance movement through the measuring station retains the 
three-dimensional position it has assumed. This requires stable support of 
the trunk on the chain conveyor. In particular, relatively large trunks 
having branch stubs can assume a position on the previously described 
integrally angle-shaped drivers in which although they rest relatively 
centrally on the drivers they are located on branch stubs. When this 
occurs the trunks are in an unstable support position in which they can 
easily rock to and fro between two locations due to the movement forces of 
the conveyor. 
SUMMARY OF THE INVENTION 
It is therefore an object of the present invention to provide a conveying 
apparatus of the aforementioned type for tree trunks which ensures that 
even curved tree trunks having branch stubs rest on the drivers during 
transport through a measuring apparatus in a more stable position than 
known drivers. 
This object is achieved since the engagement faces of the drivers are each 
inclined throughout in only one direction and since the inclination 
direction alternates in subsequent drivers or groups of drivers. 
Generally, the dogs or drivers will be provided alternately with opposite 
inclination but it would also be possible under particular circumstances, 
for example, to make in each case two consecutive drivers with equally 
directed inclination. This might possibly be necessary when the drivers 
are spaced apart with unequal distances so that after a relatively large 
interval two drivers follow each other in close succession. 
The construction of the drivers according to the present invention with 
continuous inclines ensures that the tree trunks have a greater 
possibility of support transversely of the conveying apparatus as well. 
According to its particular curvature, the supported tree trunk may be 
located to a greater or lesser extent in the lower or upper region of the 
incline whereby the inclines extending in alternate directions ensure that 
the tree trunk is held by both sides. Due to the form of the inclines, the 
trunk conducts transverse forces via the drivers into the conveying 
apparatus and these forces must be taken up laterally by the conveying 
apparatus. Accordingly, suitable support means are to be used in the 
conveying apparatus to accommodate these forces. 
The drivers may have various forms. They may be made such that they overlap 
in the center of the apparatus as viewed along the conveying direction or 
they may not overlap or even have a center space. This space, however, 
must be smaller than the smallest thickness of the tree trunks. 
Furthermore, various forms of the support faces of the driver are 
conceivable. For example, the inclined support face of a driver may be 
straight or curved. Also, the curvature need not necessarily be inward 
(concave) but can also be outward (convex). To provide a particularly 
reliable locating of the tree trunks, the respective driver may also have 
a toothed support face, for example, in the form of a sawtooth extending 
in the direction of the downwardly directed incline. With such an 
arrangement of a sawtooth the latter will engage radially into the tree 
trunk and secure the latter so that no return movement of the trunk in the 
rising or upward direction of the incline is possible. 
As was already explained, since the drivers have the inclines, transverse 
forces are introduced into the conveying apparatus and they must be taken 
up by the latter. In one embodiment, the invention accommodates the 
transverse forces by providing drivers which are made laterally movable 
with a certain play under the transverse forces.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The principles of the present invention are incorporated in a conveying 
apparatus generally indicated in FIGS. 1 and 2. FIGS. 1 and 2 illustrate a 
part of a conveying apparatus according to the invention having drivers 
1a, 1b and 1c. The drivers 1a, 1b and 1c are disposed on a guide plate 2 
extending in the conveying direction and having on its upper side a guide 
track 3 on which the drivers 1a, 1b and 1c can slide in the longitudinal 
direction of the plate. 
Each driver 1a, 1b and 1c is comprised of a base 4 extending transversely 
to the conveying direction. The length of the base 4 in the first 
embodiment substantially corresponds to the width of the conveying bed and 
is greater than the width of the plate 2. The base 4 is adjoined by the 
actual support element 5 of each of the drivers 1a, 1b and 1c. The support 
member 5 extends perpendicularly to the base 4 and to the guide track 3. 
The edges 6 and 7 of the drivers 1a, 1b and 1c also extend perpendicularly 
to the guide track 3, the edge 6 being higher than the edge 7 so that the 
engaging face 8 formed between the upper ends of the edges 6 and 7 is 
inclined. The drivers 1a, 1b and 1c are guided in the region of the end 
faces 9 and 10 of the base 4 and possibly in the region of the edges 6 of 
the support element 5 by two guide blocks 11 extending along the sides of 
the plate 2. As is apparent from FIG. 1, laterally of the plate 2 on the 
lower side of the base 4 of each driver 1a, 1b and 1c, coupling members 12 
are provided into which a transport chain (not illustrated) engages and 
acts on the coupling members to displace the drivers 1a, 1b and 1c in the 
longitudinal direction of the plate 5 and the guide blocks 11. 
As FIG. 1 illustrates, the conveying apparatus is loaded with a tree trunk 
13. It can be seen that the tree trunk 13 rests on the point 14 on the 
driver 1b and on the point 15 on the driver 1a. 
In FIGS. 1 and 2, the mounting of the plate 2 is not shown in detail, but 
is usually effected in a base frame of the conveying apparatus. Usually 
the drive of the drivers 1a, 1b and 1c is by means of one or two 
circulating transport chains. 
In a second embodiment illustrated in FIG. 7, two such transport chains are 
present and their coupling members are denoted by 12. These transport 
chains extend parallel to each other and enclose a divided guide plate 2. 
Between the two parts of the guide plate beneath the base 4 a guide 
element 17 is disposed which is guided by the divided plates 2. This makes 
it possible to dispense with the guide blocks 11 shown in FIG. 1. 
When a single transport chain is provided as illustrated in the third 
embodiment of FIG. 8, the support plate 2 is preferably divided into two 
sections so that the chain can run in a longitudinal gap disposed in the 
center. This simultaneously provides lateral guiding of the drivers 1a, 1b 
and 1c. For this purpose at the lower side of the base 4 between the 
divided guide plates 2, a pair of buffers 18 are located. Between these 
parts of the pair of buffers 18 coupling members 12 of the transport chain 
are secured. By guiding the pair of buffers 18 between the rigid parts of 
the guide plates 2 it is once again not necessary to provide guide blocks 
11. 
FIG. 2 illustrates only a fragment of the conveying apparatus in order to 
clarify the spaced arrangement of the drivers 1a, 1b and 1c. For a stable 
position of a trunk it is not necessary for the drivers to be arranged in 
close succession. A curved trunk will in any case hardly rest on more than 
three drivers so that the minimum spacing of the drivers can be adapted to 
still provide a reliable conveying. 
It is essential for the tree trunk 13 to come to lie on an engaging face 8 
which is inclined. The drivers 1a and 1b or 1b and 1c have, in the 
illustrated conveying region, engaging faces 8 inclined in opposite 
directions. Due to the inclines, the drivers 1a, 1b and 1c transmit onto 
the guide blocks 11 not only the forces acting due to gravity on the plate 
2, but also transverse forces in the direction of guide blocks 11. When a 
tree trunk 13 rests on the drivers 1a, 1b and 1c the drivers 1a, 1b and 1c 
thus additionally engage the corresponding guide block 11. 
The drivers 1a, 1b and 1c according to the invention may be formed in 
various ways to obtain the advantages according to the invention. Thus, it 
is apparent from FIG. 1 that the engaging face 8 of the drivers does not 
extend from one guide block 11 to the other guide block 11, rather the 
lower edge 7 of the support element 5 terminates at a distance from the 
respective guide block 11. It is essential in the embodiment of FIG. 1 
that the drivers 1a and 1b overlap in their projection as viewed in the 
longitudinal direction. FIG. 3 illustrates two drivers 1a and 1b which do 
not overlap but leave between them a central spacing 16. Not shown in FIG. 
3 are the details of FIG. 1. Basically, the steeper the engaging faces 8 
are the more stable the support and less the drivers 1a, 1b and 1c 
overlap. There are, however, limits here in the practical, technical 
execution. 
FIG. 4 illustrates a driver 1 which is formed substantially similar to the 
drivers 1a and 1b illustrated in FIG. 3, but has an engaging face 8 which 
is inwardly or concavely curved. Alternatively, FIG. 5 illustrates a 
driver 1 similar to the illustration of FIG. 4 in which the engaging face 
8 is outwardly or convexly curved. Additionally, FIG. 6 illustrates a 
driver 1 which is made substantially similar to the driver 1 of FIG. 3, 
but in this case the inclined engaging face 8 has sawteeth 19 directed 
toward the center. It is obvious that drivers 1a, 1b and 1c are similar to 
the drivers 1 illustrated in FIGS. 4 to 6 and may exist in accordance with 
the illustration of FIGS. 1 and 3 and may overlap or not overlap, possibly 
even having a central spacing 16 between them. 
While several embodiments of the present invention have been shown and 
described, modifications may be made without departing from the teachings 
of the present invention. Accordingly, the scope of the invention is only 
to be limited as necessitated by the accompanying claims.