[0001] The present invention relates to a device by means of which to transmit power to
through feed wheels as used in automatic machinery, and more especially in through
feed moulders.
[0002] The art field of automatic woodworking machinery embraces a number of devices for
transmitting drive to the friction wheels of through feed machines. Automatic machines
of the type in question are equipped conventionally with a system by which the work
is transferred from one machining station to the next, propelled along a horizontal
bed by feed wheels that are disposed transversely to the bed and variable for angle
and height in relation to the horizontal surface to accommodate different thicknesses
of work.
[0003] Each wheel is keyed onto a supporting shaft coupled to a drive system, and thus rotates
together with the shaft. The coupling between the single shaft and the drive system
is effected in most instances adopting one of two devices accommodated by a back rail
disposed parallel with and to the rear of the horizontal bed. A first such device
consists in a yoke associated coaxially with the support shaft and coupled at the
end farthest from the wheel to a universal constant velocity joint that allows the
variations in height of the feed wheel above the horizontal bed and connects the supporting
shaft to the low speed shaft of a speed reducer. The speed reducer will consist in
a conventional train of cylindrical or worm gears, and is connected on the input side
to a drive motor.
[0004] The speed reducer serves to adapt the high angular velocity at the output of the
drive motor to the low speed requirement of the feed wheels. The yoke is also hinged
to a vertically disposed pneumatic cylinder, through which pressure is applied to
the supporting shaft in order to keep the feed wheel permanently and firmly in contact
with the work. The second device is similar in structure to the first, but dissimilar
as regards the type of power transmission adopted. In this instance, drive is transmitted
to the feed wheels by a single chain positioned to the rear of the wheels, which extends
parallel to the horizontal bed and is connected to the speed reducer of each feed
wheel. The coupling in this system consists in two universal joints, synchronized
one with the other and interconnected by a flexible element that permits the transmission
of drive from the chain to the supporting shaft while allowing variations in angle
to accommodate the passage of the work.
[0005] Whilst reflecting the feed drive arrangements most widely adopted for through feed
moulders, devices of the type thus outlined betray certain drawbacks, from engineering
and cost standpoints alike. The first device is encountered normally in automatic
machines constructed to high output and efficiency specifications, as drive can be
transmitted from the speed reducer to the supporting shaft without subjecting the
feed wheel to sudden acceleration (for example, due to the gear geometry of the speed
reducer), any jerkiness being absorbed through the splined coupling of the constant
velocity joint. Thus, one has a high efficiency power transmission, but also a high
capital outlay and in consequence a restricted market.
[0006] The second device is certainly the more economic option, and may be found incorporated
into machines of more modest specifications, given its relatively lower efficiency
and shorter working life. A chain drive is the poorer option in engineering terms
however, as a higher drive ratio is required to give the correct angular velocity
at the support shaft, hence a greater number of speed reductions; moreover, chain
drive is not always acceptable to the users of such machinery.
[0007] Accordingly, the object of the present invention is to overcome the drawbacks mentioned
above through the adoption of a device that affords economy, and at the same time
ensures high operating efficiency by virtue of the engineering expedient adopted in
embodiment of the element that ultimately supports the feed wheel, which ensures that
no unnecessary torque is transmitted to the wheel.
[0008] The stated object is fully realized in a device as characterized in the appended
claims
Such a device essentially comprises a first drive transmission shaft disposed parallel
to the axis of a feed wheel and rotatably supporting a yoke; this shaft is keyed coaxially
to a worm wheel rotating internally of a support housing and in mesh with a second
transmission shaft that incorporates a worm profile and is coupled mechanically to
driving means in such a way as to permit of transmitting rotation from the driving
means to the first shaft; the feed wheel is keyed to a third shaft disposed parallel
with the first, which thus supports and transmits drive ultimately to the wheel. The
device further comprises an idle gear supported centrally in the yoke, positioned
between and meshing with corresponding gears afforded by the first and the third shafts
in such a way as to transmit rotation from the first to the third shaft while creating
a mechanical linkage such as will eliminate vector forces acting on the two shafts.
[0009] One of the advantages afforded by the invention consists essentially in the fact
that the structure and arrangement of the components by which power is transmitted
from the drive motor to the feed wheel are such as to provide the user of the machine
with a high transmission ratio, thus giving high torque values at high speeds; this
is attributable mainly to the worm gear pair (worm drives are capable of notably high
transmission ratios), but also to the idle gear, which eliminates any rotational forces
deriving from sudden acceleration that often affect drive shafts, the result being
to produce a machine of high operating efficiency.
[0010] The invention will now be described in detail, by way of example, with the aid of
the accompanying drawings, in which:
- fig 1 illustrates a feed station in a through feed moulder incorporating the device
according to the invention, viewed in perspective from above with certain parts omitted
better to reveal others;
- fig 2 is the section through II-II, fig 1;
- fig 3 is the section through III-III, fig 1;
- fig 4 is a frontal elevation showing a feed wheel associated with the device of fig
1, with certain parts omitted better to reveal others and with the addition of a further
constructional feature;
- fig 5 illustrates an alternative embodiment of the device according to the invention,
shown in frontal elevation and with certain parts omitted better to reveal others;
- fig 6 shows the device of fig 5 in side elevation with certain parts omitted better
to reveal others. Referring to the drawings, the power transmission device disclosed
is designed for use in automatic machines such as are employed for woodworking, and
in particular a through feed moulder (visible in part in fig 1), of the type comprising
at least one station denoted 1 in its entirety, through which workpieces 2 are fed
along a horizontal bed 3, thus passing from one machining station to another.
[0011] The feed station 1 is flanked by a rail 4 extending parallel with and to the rear
of the horizontal bed the purpose of which is to carry a set of wheels 5 serving to
feed the work 2 horizontally along the bed 3; this same back rail 4 also carries the
tools (conventional, and therefore not illustrated) by which the work 2 is machined
at further stations of the moulder.
[0012] The feed wheels 5 are disposed transversely with respect to the horizontal bed 3
and associated each with means, denoted 6 in their entirety, by which rotation originating
at driving means 7 installed behind the rail 4 is transmitted to the wheels 5; such
means 6 are accommodated for the most part within or beneath the back rail 4.
[0013] Transmission means 6 comprise a first cylindrical shaft 8 (fig 2), disposed parallel
to the axis of the feed wheel 5 and rotatably supporting a yoke 9 at two journal points,
of which the end positioned farthest from the horizontal bed 3 carries a keyed worm
wheel 10 accommodated internally of a support housing 11; to advantage, the housing
will be of substantially arched embodiment (see figs 1 and 2) to the end of supporting
the first shaft 8 with maximum rigidity.
[0014] 12 denotes a second transmission shaft accommodated partly by the support housing
11 (figs 2 and 3), which incorporates a worm profile in mesh with the worm wheel 10
of the first transmission shaft 8; in the example of figs 2 and 3, the worm shaft
12 is disposed vertically with one end (the topmost end) projecting from the support
housing 11 and carrying two coaxial keyed pulleys 13a and 13b.
[0015] 14a and 14b denote two belt loops passed around the respective pulleys 13a and 13b,
of which the first also passes around an expanding pulley 20 keyed to the driving
means 7 behind the back rail 4 and the second around the corresponding pulley of a
further second shaft constituting part of the transmission means 6 for a successive
feed wheel; in this way, drive is relayed to all the wheels 5 constituting the feed
station 1 (as discernible from fig 1).
[0016] The feed wheel 5 is keyed to and rotatable about the axis of a third shaft 15, carried
by the yoke 9 in a position parallel to the first shaft 8 (see fig 2), which is coupled
to and driven from the first shaft 8 by way of an idle gear 16 supported rotatably
by the yoke 9 in a substantially central position, between the two shafts 8 and 15;
meshing contact occurs by way of gears 8a and 15a keyed to the respective shafts in
alignment with the idle gear 16. With this arrangement, the first and third shafts
8 and 15 are caused to rotate in the same direction, and the resulting mechanical
linkage is capable of eliminating unwanted rotational forces transmitted through the
assembly 6.
[0017] As shown in fig 4, the device further comprises means denoted 17 in their entirety,
by which to select a degree of rocking movement allowed to the yoke 9 about the axis
of the first shaft 8 (see arrow F) during passage of the work 2 beneath the feed wheel
5. More exactly, such means 17 comprise a bifurcated pin projecting toward the back
rail 4 and associated with the part of the yoke 9 occupied by the first shaft 8, which
serves to establish the lower limit of the arc of rotation allowed to the yoke 9,
and a second pin 21, located alongside the bifurcated pin 17 and nearer to the outermost
end of the first shaft 8, extending likewise toward the rail 4, which is set at angle
and height different to those of the bifurcated pin 17 (in relation to the horizontal
bed 3), and positioned to enter into contact with the bottom face of the back rail
4, thereby establishing the upper limit of the arc of rotation allowed to the yoke
9.
[0018] 18 denotes means fixed to the support housing 11, by which to adjust the travel limit
of the yoke 9; in the example of fig 4, such means 18 appear as a fixed horizontal
screw 22 of which the projecting thread end is freely accommodated by the bifurcated
pin 17. The screw 22 carries a threaded collar 23 that permits of selecting an exact
setting for the lower limit of the rotation allowed to the yoke 9. In practice therefore,
the bifurcated pin 17 serves to determine a maximum descent angle of the yoke 9 in
relation to the horizontal bed 3, by striking against the stop collar 23, while the
second pin 21 establishes a maximum ascent angle by striking against the rail 4.
[0019] Still in fig 4 of the drawings, 19 denotes a small, vertically disposed hydraulic
cylinder rigidly associated with the support housing 11, of which the reciprocating
end impinges on the part of the yoke 9 occupied by the third shaft 15 (a trunnion
type connection might also be used if appropriate). The cylinder 19 is adjustable,
and serves to keep the wheel 5 steadily in contact with the work 2 during its passage,
avoiding any possible slippage (due, for example, to irregularities in the surface
of the workpiece).
[0020] As discernible from the foregoing description, the operation of a device according
to the invention will occur substantially in this manner: power is supplied to the
driving means 7 (depicted in fig 1 as a motor mounted to the back rail 4, and keyed
to its spindle, the expanding pulley 20 which permits of varying the input speed),
whereupon rotation is transmitted by the belt 14a to the pulley 13a of the first worm
shaft 12 (or indeed to any one of the linked worm shafts), and relayed by way of the
individual linked pulleys 13a and belt loops 14b to all remaining worm shafts 12;
drive is transmitted by each worm shaft 12 to the corresponding worm wheel 10 and
the keyed first shaft 8, thence by way of the idle gear 16 to the third shaft 15.
The feed wheel 5 is thus set in rotation, and, engaging each workpiece 2 fed forward
by the wheels of preceding stations, adapts to the thickness of the wood by virtue
of the angle of the yoke 9 while remaining firmly in contact with the work 2 as the
result of pressure applied through the yoke by the hydraulic cylinder 19.
[0021] Sliding movement of the work 2 along the horizontal bed 3 can be optimized further
by elongating the worm shaft 12 down beyond the support housing 11 and below the horizontal
bed 3 to permit of meshing with a second worm wheel 10'. Thus, it becomes possible
to provide a structure below the bed 3 similar to that above (as illustrated schematically
by the phantom lines of fig 4), comprising yoke 9', transmission shafts 8' and 15',
housing 11' and feed wheel 5', all driven synchronously by the one shaft 12. Naturally
enough, the bottom yoke 9' will be subject to respective travel limiting means 17'
and 21' allowing the wheel 5' a degree of rocking movement such as will ensure continuous
contact with the work 2 above. Sandwiched thus between two wheels 5 and 5' in this
manner, the work 2 can be effectively pinch driven along the bed 3, ensuring a steady
and accurate rate of feed that can also be governed to suit subsequent machining operations.
It will be observed from the foregoing description that a device structured according
to the invention affords advantages of economy, together with higher performance;
the adoption of a belt drive signifies the elimination of chains, and of costly and
bulky gear trains, whilst the inclusion of an idle member has the effect of absorbing
any sudden acceleration attributable to the operating characteristic of the high ratio
worm gear pair.
[0022] In an alternative embodiment of the device shown in figs 5 and 6, the second transmission
shaft or worm shaft, denoted 112, is horizontally disposed above the first shaft 8,
parallel with the bed 3 and in mesh with a worm wheel 110 occupying the vertical plane
directly beneath. In this instance, the worm wheel 110 is keyed coaxially to an intermediate
gear 31 of smaller diameter located between and in mesh with a pair of gears denoted
110a, each keyed in turn to a relative first shaft 8; to advantage, the entire train
comprising worm shaft 112, worm wheel 110, intermediate gear 31 and driven gears 110a
will be accommodated internally of a removable support housing 111 carrying two first
shafts 8 and two feed wheels 5.
[0023] The worm shaft 112 is fitted at its opposite ends with respective flexible couplings
32a and 32b emerging from the housing 111, which permit of connecting the shaft permanently
in rotation both to the power shaft 33 of driving means 7 (e.g. a geared motor not
illustrated in the drawings), and to the worm shafts 112 of successive and preceding
housings 111.
[0024] The alternative embodiment thus described affords distinct mechanical advantages,
in that with two ratios established by the first reduction stage (worm gear pair)
and the second (intermediate gear and driven gears), one obtains high torque at the
feed wheels deriving from a nonetheless relatively limited torque value at the worm
gear pair, this by reason of the high input speed. Advantage is gained also from the
constructional standpoint in that each housing 111, easily replaceable if need be,
carries two drive shafts with two corresponding feed wheels as a modular assembly.
1. A power transmission device for feed wheels as used in automatic machinery, in particular
a woodworking machine of the through feed moulder type comprising at least one feed
station (1) by which work (2) is propelled along a horizontal bed (3), flanked by
a back rail (4) extending parallel to the bed and supporting a plurality of feed wheels
(5) revolving about axes disposed transversely to the bed, each connected by way of
means (6) located substantially within the back rail and enabling the transmission
of rotation to the wheels (5) from driving means (7) positioned to the rear of the
rail,
characterized
in that such transmission means (6) comprise:
- a first cylindrical shaft (8) disposed parallel to the axis of the feed wheel (5),
serving to transmit rotation and rotatably supporting a yoke (9), of which the end
located farthest from the horizontal bed (3) and directed toward the back rail (4)
is associated with a worm wheel (10) accommodated internally of a support housing
(11, 111);
- a second transmission shaft (12, 112) affording a worm profile in mesh with the
worm wheel (10, 110), accommodated substantially within the support housing (11, 111)
and coupled mechanically to the driving means (7) in such a way as to permit of transmitting
rotation from the driving means to the first cylindrical shaft (8) at a high ratio
of speed reduction;
- a third cylindrical shaft (15) keyed to the feed wheel (5), disposed parallel to
the first shaft (8) and supported by the yoke (9); and
- an idle gear (16), supported substantially in a central position by the yoke (9),
located between and in mesh with gears (8a, 15a) keyed respectively to the first and
third shafts (8, 15) in such a way as to permit of transmitting rotation from the
first shaft (8) to the third shaft (15) by way of a train capable of cancelling out
angularly generated vector forces acting on the two shafts.
2. A device as in claim 1, wherein the second shaft or worm shaft (12), in mesh with
the worm wheel (10), is disposed vertically and orthogonal to the first shaft (8)
with the topmost end extending upward to support at least one coaxially keyed pulley
(13a) about which to loop belt means (14a) connected with the driving means (7), in
such a way as to permit of transmitting rotation from the driving means to the first
cylindrical shaft (8) at a high ratio of speed reduction, and a second coaxial keyed
pulley (13b) about which to loop further belt means (14b) connecting with the worm
shaft (12) of a successive or preceding feed wheel (5).
3. A device as in claim 1, wherein the yoke (9) is able to oscillate about the axis of
the first shaft (8) in relation to the horizontal bed (3) within a given arc of rotation
restricted by means (17) comprising a bifurcated pin, associated externally with the
part of the yoke occupied by the first shaft (8) and projecting toward the back rail
(4) in such a manner as to interact with adjustable travel limiting means (18) associated
with the support housing (11), positioned in alignment with and slidably and horizontally
accommodated by the bifurcated pin (17), to the end of establishing the lower limit
of the arc of rotation allowed to the yoke (9).
4. A device as in claim 1, further comprising a vertically disposed hydraulic cylinder
(19) mounted to the back rail (4) and impinging on the end of the yoke (9) farthest
from the first shaft (8), of which the purpose is to maintain the feed wheel (5) in
uninterrupted contact with the work (2).
5. A device as in claim 2, wherein the second shaft or worm shaft (12) extends externally
of and beyond the support housing (11) and below the horizontal bed (3) in such a
way as to mesh with a worm wheel (10') constituting a part of transmission means comprising
a first shaft (8'), a third shaft (15') and a yoke (9'), substantially identical to
the transmission means (6) located above the horizontal bed (3).
6. A device as in claim 3, wherein means by which to restrict the rotation of the yoke
(9) further comprise a second pin (21) associated with the yoke, positioned alongside
the bifurcated pin (17) and extending toward the back rail (4), which is of length
such as to establish the upper limit of the arc of rotation allowed to the yoke by
locating against the bottom face of the rail (4).
7. A device as in claim 1, wherein transmission means (6) comprise a second shaft or
worm shaft (112) disposed orthogonal to and above the first shaft (8) and parallel
to the horizontal bed (3), a worm wheel (110) in mesh with the worm shaft (112) and
occupying a vertical plane, an intermediate gear (31) keyed to and coaxial with the
worm wheel, and two gears (110a) positioned one on either side of the intermediate
gear and keyed to two respective first shafts (8), all of which are accommodated internally
of a single removable housing (111).
8. A device as in claim 7, wherein the two opposite ends of the second shaft or worm
shaft (112) are associated with respective flexible couplings (32a, 32b) projecting
from the support housing (111), by which the shaft (112) is connected to further shafts
(33) constituting driving means (7) and coupled to the worm shafts (112) of successive
and preceding support housings (111).