Pallet feeder

A pallet feeder for a manufacturing plant or fabrication system wherein pallets are fed along a substantially circular-shaped track or path of travel. A number of transfer stations or locations are provided at which the pallets are infed and outfed essentially at right angles to the circular-shaped conveying path or track. At the center of the circular-shaped pallet feeder there is located a pallet displacement device which is pivotable about the axis of the circular-shaped track into a position coacting with the different transfer stations or locations, in order to be able to move the pallets towards and away from the conveying or conveyor track.

BACKGROUND OF THE INVENTION 
The present invention relates to a new and improved construction of pallet 
feeder for feeding pallets along a substantially circular-shaped track or 
path of travel and having a random number of pallet receivers equipped 
with pallet guides arranged essentially at right angles to the feed or 
conveying direction and movable into a number of transfer positions, and 
furthermore, the pallets being automatically shifted in the direction of 
the pallet guides onto the pallet receivers. 
Such type pallet feeders having a rotatable platform which can rotate 
through 180.degree. into two angular positions, carrying only two pallet 
receivers, also are known to the art as pallet changers. Each pallet 
receiver has operatively associated therewith a pallet thrust of push 
drive. By means of each pallet thrust drive the pallets are alternately 
moved to and from the work machine. Both identical pallet thrust drives 
have the same displacement path and two holding or stop positions which 
limit the thrust displacement path. In fabrication systems or 
manufacturing plants having conveying paths or conveyor systems of 
different construction and configuration each working or work machine has 
operatively associated therewith a pallet changer serving as the interface 
or connection unit to the conveying path or track. 
It is known to design the conveying track as a circular conveyor having 
four pallet receivers without any pallet thrust drives, as the same has 
been disclosed in the publication "Werkstatt und Betrieb" 106, (1973) 9; 
"Werkstattstechnik WT" 4, 1973, for the fabrication system known under the 
commercial designation "PRISMA M250" having ten pallet positions or places 
and two working machines. Also with this system design each working 
machine has operatively associated therewith a pallet changer for charging 
the machine and a third pallet changer serves for charging the circular 
conveyor from the chucking station. 
Also there have been proposed to the art pallet changers whose rotatable 
platform likewise carries four pallet receivers and is rotatable into four 
90.degree.-positions. To render possible in each position a pallet 
transfer without shift of the pallet changer each pallet receiver has 
operatively associated therewith a pallet thrust drive. These pallet 
thrust drives are identical and have the same thrust displacement path 
including two stop or holding positions which limit the thrust 
displacement path. Such a system is the subject of a co-pending 
application Ser. No. 867,968, filed Jan. 9, 1978, which corresponds to 
German Pat. No. 2,754,095, of which Norbert Ewertowski is the sole 
inventor. 
SUMMARY OF THE INVENTION 
Hence, with the foregoing in mind, it is a primary object of the present 
invention to provide a new and improved construction of pallet feeder 
affording improved prerequisites for the economic fabrication thereof as 
well as enabling economical and adaptable utilization of fabrication 
systems or manufacturing plants. 
Still a further significant object of the present invention aims at 
providing a new and improved construction of pallet feeder for a 
manufacturing plant, which is relatively simple in construction and 
design, extremely reliable in operation, economical to manufacture and 
operate, and not associated with the aforementioned drawbacks and 
limitations of the prior art proposals. 
Still a further significant object of the present invention is directed to 
an improved construction of pallet feeder for a fabrication system or 
manufacturing plant which allows better utilization and adaptability of 
the fabrication system, while insuring for highly reliable, efficient and 
accurate pallet feeding operations, while employing a pallet feeder which 
is relatively simple in design and construction, easy to use, highly 
economical to manufacture, and not readily prone to disturbances and the 
like. 
Now in order to implement these and still further objects of the invention, 
which will become more readily apparent as the description proceeds, the 
pallet feeder of the present development for feeding pallets in a 
fabrication system or manufacturing plant along a substantially 
circular-shaped track or path of travel, comprises pallet receivers having 
pallet guides arranged substantially at right angles to the conveying or 
feed direction and movable into a number of transfer positions. The 
pallets are automatically displaceable upon the pallet receivers in the 
direction of the pallet guides. According to important aspects of the 
invention a plate thrust drive is arranged at the central region or center 
of the pallet feeder so as to be rotatable about an essentially vertical 
axis into a number of angular positions independently of the 
circular-shaped pallet feeding. The thrust or pushing force of the pallet 
thrust drive, in the angular positions, is effective in the direction of 
the related pallet guide or guide means of a pallet receiver which is 
located in a transfer position. 
The pallet feeder of the present invention has the following advantages 
worthy of mention: 
1. A reduced constructional expenditure, because the functions of pallet 
feeding and pallet change are united in one unit having only one pallet 
thrust drive, even in the case of a greater number of pallet receivers. 
Consequently, there is rendered superfluous the need for additional 
separate pallet changers having a number of pallet thrust drives, rotary 
drives and control devices. 
2. A more adaptable and simpler construction, because the pallet thrust 
drive can be effective for a number of thrust lengths in random thrust 
directions and in each thrust direction. As a result, there can be 
designed more price favorable fabrication systems, which are suitable for 
use both with independent, manually controlled machine charging and 
requisite good accessibility to the machine table as well as also being 
capable of accomplishing a centrally controlled, dependent charging for 
automatic single stage and multi-stage operation. 
3. There is afforded a space saving construction for exclusively centrally 
controlled fabrication systems which can operate, without the need for 
manual manipulations, at the palletized workpieces at the machine. 
4. In the case of larger fabrication systems having pallet cars or the like 
it is possible to interlink a number of the inventive pallet feeders at a 
spacing from one another which is coordinated to the distance between the 
working machines and without the need for any additional pallet thrust 
devices, and such are effective as a buffer having a high capacity. The 
work or working machines are directly charged by the pallet feeders, and 
between such, in the case of multi-stage operation, there is a direct 
pallet flow which relieves the pallet cars. Even in critical phases of a 
3/1-shift operation of the plant and with flexible operating procedures 
with a number of different types of workpieces having different 
fabrication priorities there can be avoided downtime of the machines. 
5. Particularly in the case of multi-stage operation and intensive material 
machining work it is oftentimes desired to perform an intermediate 
cleaning prior to carrying out further processing of the workpieces at the 
next working machine. The inventive pallet feeder fulfills this 
requirement without the need for special transport means and with small 
equipment expenditure and spatial demands.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Describing now the drawings, the exemplary embodiment of pallet feeder or 
pallet conveying device as illustrated in FIGS. 1, 2 and 3 will be seen to 
comprise a pedestal or base 10 which essentially is composed of two 
multi-cornered rings 11 and 12 interconnected with one another by vertical 
supports or posts 13 or equivalent structure. At the underside of the 
upper ring or ring member 11 there are threadably connected or otherwise 
fastened two transverse supports or carriers 7 between which there is 
fixed, typically for instance as by welding, the base hub 9. The top 
surface or face of the upper ring 11 is structured as a substantially 
ring-shaped support track or path composed of hardened plates or plate 
members 14 upon which there is mounted a rotatable platform 15. This 
rotatable platform 15 is centered by means of a bearing journal or pin 16 
flanged perpendicular to the base hub 9 and the roller bearing or roller 
bearing means 17. An hydraulic-control unit or assembly 8 is arranged 
within the hollow base or pedestal 10. 
The rotatable platform 15 consists of an eight-cornered intermediate or 
central part 18 at whose eight substantially upright or vertical outer 
walls 8a there are fixed, as by threading or screwing thereat, eight 
pallet receivers or receiver means 19. Each pallet receiver 19 embodies at 
its upper surface a pallet guide or guide means, generally designated by 
reference character 19a, constituted by the rolls or rollers 20 and upon 
which there are radially displaceable the pallets 21 shown in broken lines 
in FIG. 1. At the underside of each pallet receiver 19 there are provided 
two recesses 19b in which there are mounted at total of sixteen 
substantially cone-shaped support rolls or rollers 22 which roll upon the 
plates 14 and support the rotatable platform 15. In order to drive the 
rotatable platform 15 through 45.degree.-angular positions there is 
provided a hydromotor 23 arranged within the base 10 and having a pinion 
24 which meshes with a toothed rim or ring gear 25 threadably or otherwise 
connected with the intermediate or central part 18. 
For radial displacement of the pallets 21 there is arranged centrally of 
the pallet feeder a pallet thrust or push drive 26, which, in the 
embodiment under discussion, comprises a finite chain 30 functioning as 
the thrust element. As best seen by referring to FIG. 3, the chain links 
30a of the chain 30 are provided in conventional manner at their lower or 
left side of such showing with a respective impact or stop plate 29 in 
order to prevent any upwardly directed kinking of the chain under load and 
also to render possible a free-supporting pushing-out action. The chain 30 
is moved in both directions by means of a hydromotor 27 or equivalent 
structure through the agency of a drive gear or wheel 28 and at its outer 
end there is attached a coupling element or piece 34 which coacts with 
pallet latches or pawls 35 or equivalent structure. During chain movement 
the inner end of the chain 30 winds-up and winds-off within a guide frame 
36 located at the support or bearing housing 31 for the hydromotor 27 and 
the drive wheel or gear 28. The support or bearing housing 31 is 
threadably arranged coaxially with regard to the bearing journal 16 at the 
upper face of an arm 44, which, in turn, is flanged at the upper end face 
of an adjustment sleeve 32 rotatably mounted in the bore 16a of the 
bearing journal or pin 16. By means of an angle orientation or angle 
positioning device 33 it is possible to turn the adjustment sleeve 32 
together with the arm 44 and the bearing or support housing 31 independent 
of the rotatable platform 15. 
The angle orientation or angle positioning device 33 comprises a stepping 
motor 38 having a step-down gearing 43 and attached to the transverse 
strut or support 7. The pinion 39 of the stepping motor 38 cooperates with 
a spur gear 40 which is keyed or otherwise fixed below the bearing pin or 
journal 16 at the protruding or overhang part of the adjustment sleeve 32. 
The stepping motor 38 can be controlled in such a fashion that the 
adjustment sleeve 32, the arm 44, the support or bearing housing 31 and, 
thus, the thrust direction of the chain 30 can be oriented in any required 
45.degree.-angular position. In FIG. 2 there is shown in broken or phantom 
lines a thrust direction which is not situated in the plane of the drawing 
of FIGS. 1 and 3. For the precise fixation of each thrust or pushing 
direction there is advantageously employed the arm or arm member 44 
together with the indexing-piston drive 45. This indexing-piston drive 45 
has an indexing roll or roller 46 which is mounted at the end of the 
piston rod 45a and cooperates with an indexing prism or lock member 47 or 
equivalent structure located at each pallet receiver 19. 
As best seen by referring to FIGS. 1, 2, 3 and 4 the impingement of the 
hydromotor 27 for purposes of pallet shifting or displacement is 
accomplished by the infeed bushing or sleeve 41 mounted at the lower end 
32a of the adjustment or setting sleeve 32. For this purpose, there are 
utilized two of the three connections or infeed lines 50 of the infeed 
bushing 41 and the oil or other fluid bores 42 and 43 located in the 
adjustment sleeve 32. The third connection and a third not particularly 
illustrated oil or fluid bore serve for the impingement at one face of the 
indexing-piston drive 45, the resetting of which is accomplished by means 
of, for instance, a spring which has not been particularly shown in order 
to improve the clarity of illustration. 
With this exemplary embodiment of pallet feeder which has a great number of 
applications, the coupling element or piece 34 with or without the pallets 
21 can be moved into an inner thrust position I and three outer thrust 
positions II, III and IV. It is possible to move into the inner thrust 
position I for any angular position of the pallet thrust drive 26, whereas 
it is only possible to move alternately into the other thrust positions 
II, III, and IV as will be explained more fully hereinafter in conjunction 
with the description of the fabrication system. In order to control the 
thrust positions I and IV there are arranged at one side of the chain 30, 
in a switching track, two upwardly effective switching or indexing 
elements 48 and 49. These switching elements 48 and 49 can activate two 
flow regulating valves 51 and 52 located at the arm 44 and connected in 
series, these valves, in turn, in conjunction with standard and therefore 
not particularly shown signal transmitters and together with an 
electromagnetic valve 53 arranged in the hydraulic-control unit 8 initiate 
the movement into the thrust positions. By shifting the position of the 
switching element 48 at the chain 30 it is possible to accommodate the 
maximum thrust displacement path, with unaltered pallet feeder, to the 
requirements of the relevant fabrication system or manufacturing plant. At 
the inner, non-altered switching position I the pallets 21 are fixedly 
arrested at the pallet receivers 19 by means of the arresting or fixing 
cylinder 75 and at the same time the pallet pawls 35 are raised into their 
free position, as will be likewise explained more fully hereinafter. In 
this free position of the pallet pawls 35 it is possible for the angle 
orientation or positioning device 33 to rotate the pallet thrust or 
pushing drive 26 into the angular orientation or position needed for the 
next pallet transfer. 
The movement of the coupling element or piece 34 out of the thrust position 
I into the thrust positions II or III is controlled by the series 
connected flow regulating valves 58 and 59 which are arranged at a spacing 
"r" and "R", respectively, related to the axis of rotation of the 
rotatable platform 15, in the base 10 in a number and angular position as 
required by the transfer positions of the relevant fabrication system. 
Actuation of the flow regulating valves 58 and 59 is accomplished by means 
of the switching elements 54 and 55 which are downwardly effective and 
arranged at both chain sides and in two further switching tracks, by means 
of the plungers 56 and 56a and the plunger rods 57 and 57a, respectively. 
The switching element or piece 54 can act in the one switching track, 
against spring force, upon the plunger 56 which is vertically guided at 
the arm 44 at the spacing "r", and the switching element or piece 55 can 
act at the other switching track, against spring force, upon the 
vertically guided plunger 56a in the arm 44 at the spacing "R". In order 
to transmit the switching stroke of the plungers 56 and 56a there is 
provided at the intermediate or central part 18 of the rotatable platform 
15 of each pallet receiver 19 a respective vertically guided plunger or 
piston rod 57 at a smaller pitch circle diameter of 2.times."r" and a 
respective vertically guided plunger or piston rod 57a at a larger pitch 
circle diameter 2.times."R". The plunger rods 57 and 57a are retained, by 
upwardly effective spring forces and stop rings, in the non-biased or 
non-impinged state of the control circuit, at a small spacing with regard 
to the lower ends of the plungers 56 and 56a, so that the rotatable 
platform 15 and the pallet thrust drive 26 together with the arm 44 can 
rotate without contact and independently of one another. 
Mounted at each pallet receiver 19 is an arresting or stop cylinder 75 
whose upward or vertically extending piston rod 76, during the inward 
movement of the pallets 21 up to the inner thrust position I, can be 
downwardly held under the action of spring pressure, as best seen by 
referring to FIG. 5. After completion of the moving-in operation the 
relevant arresting cylinder 75 is pressure loaded or impinged by the 
infeed bushing or sleeve 77 from the hydraulic-control unit 8 via the 
lines or conduits 82. The infeed bushing or sleeve 77 is fixed at the 
bearing flange 6 of the rotatable platform 15 and bears at the bearing pin 
or journal 16. The piston rod 76 penetrates into the pallet bore 78 and 
presses an angle lever 80 which is mounted to be pivotable about the bolt 
or pivot shaft 79 at the pallet 21 together with the pallet pawl 35 which 
is fixed at such angle lever 80 upwards into a position where it is 
released or freed from the coupling element 34 (FIG. 6). 
Continuing, in FIG. 7 there is shown the simplest construction of a pallet 
feeder according to the invention for use with approximately eight pallet 
receivers and which can be employed for direct pallet transfer to the 
working or work machine with short pallet displacements. In this case, 
during the assembly of the pallet feeder, there is threadably connected at 
the support or arm member 44, instead of the chain thrust drive, a work 
cylinder 60 which can be directly impinged or loaded by the infeed bushing 
or sleeve 41. The piston rod 61 of the work cylinder 60 is displaceable 
into two stop or impact positions by means of a coupling piece or element 
62 located at the outer end 61a of such piston rod 61. 
FIG. 8 illustrates a pallet feeder having a one-part rotatable platform 70 
and two pallet receivers. The pallet thrust or push drive 83 which works 
with a chain 30, and which pallet thrust drive 83 is centered and 
threadably or otherwise affixed by means of a plate 84 at the upper end 
face of the adjustment or setting sleeve 85, allows for a central 
application of force during the pallet shifting or displacement, 
notwithstanding the fact that the pallet receivers are arranted in a space 
saving manner closely adjacent one another at the rotatable platform 70. 
This construction is especially rendered possible by virture of the fact 
that the chain 30 winds-up in guide frame 36 arranged coaxially with 
respect to the bearing journal or pin 86. It is here to be remarked that 
the prior art likewise space-saving pallet changers exhibit at each 
longitudinal side of the rotatable platform a respective work cylinder for 
pallet displacement with lateral application of the force, which 
disadvantageously causes corner moments and requires additional guide 
elements. The 180.degree.-rotation of the rotatable platform 70 is 
accomplished by means of the toothed-piston drive 71 which coacts with a 
radial or end tooth arrangement 69 of the bearing hub 72 flanged to the 
rotatable platform 70. The pallet thrust drive 83 has two thrust positions 
I and II. Furthermore, for the angular positioning of such pallet thrust 
drive 83 in its two 180.degree.-positions there is advantageously provided 
a small toothed piston drive 73 which engages with an end or radial tooth 
arrangement 74 formed at a lower end of the adjustment or setting sleeve 
85. The energy infeed to the arresting cylinders 75 and the hydromotor of 
the pallet thrust drive 83 is accomplished by means of not particularly 
shown, but conventional flexible lines which are guided through the large 
bore 87 of the adjustment sleeve 85. 
Finally, in FIG. 9 there is shown a pallet changer similar to the 
arrangement of FIG. 8, which however accomplishes a pallet change or feed 
only in one thrust or displacement direction. The pallet thrust drive 83 
is fixedly mounted upon the bearing pin or journal 86, and there is 
dispensed with any angle orientation or positioning device. Advantages 
worthy of mention of this constructional embodiment, derived from the 
principles of the invention, are the extremely accommodatable thrust 
lengths of only one pallet thrust drive and the central application of 
force during the pallet shifting or displacement with compact structure of 
the equipment. 
While there are shown and described present preferred embodiments of the 
invention, it is to be distinctly understood that the invention is not 
limited thereto, but may be otherwise variously embodied and practiced 
within the scope of the following claims. ACCORDINGLY,