Dual action shaker table using parallelogram linkages

A dual action shaker table useful in permitting various modes of shaking the objects. The shaker table provides either a substantially reciprocating shaker motion or a true rotary shaker motion using two cooperating parallelogram linkage constructions in cooperation with a drive link and a driving mechanism. Switching between these two modes of operation is carried out by removably affixing a part of one link or a part of another link to the table.

BACKGROUND OF THE INVENTION 
The present invention relates generally to what are termed shaker tables or 
platforms, and in particular, to a new and improved dual action shaker 
platform. 
By the expression "shaker table" as used herein is meant the provision of a 
surface that may undergo a shaking motion that is useful for shaking 
specimens disposed upon the platform, or, in other embodiments, to shake 
laboratory specimens or other containers in a holder of some sort that, 
whether proximate or remote from the shaker table, undergoes the same 
motion. 
Thus, in some instances, it is desired to shake specimens retained in test 
tubes, flasks, or the like by resting them on a table which directly holds 
the specimens. In other instances, the table is positioned in a certain 
location and attachments thereto, such as peripheral stanchions or the 
like, are used to support a specimen holder that may be disposed in a 
temperature controlled liquid bath, for example. In this instance, the 
table may lie beneath the housing for the bath and permit the specimens to 
be immersed in a bath but, by appropriately positioning the supporting 
stanchions so that the specimen holder is suspended from the open top of 
the bath, there is no need to provide fluid seal with respect to the bath 
contents. 
Among the desired features of the satisfactory shaker apparatus are control 
of speed, amplitude, and, in some cases very importantly, the mode of 
shaking. 
While various kinds of shaker tables or platforms are known to the art, 
there is and has been a need for an improved, mechanically simple and 
highly adaptable shaker platform arrangement, particularly one that could 
be manufactured at low cost and which is very readily convertible from one 
shaking mode to the other. 
While various mechanical and direct drive electrical arrangements are 
available to impart an oscillating motion of one sort or another to a 
batch of specimens or the like, there has been a need for an improved 
shaker table which will provide either a substantially straight line or 
back and forth shaker motion or a true rotary shaker motion, and to be 
convertible between these modes of operation by a simple, foolproof 
manipulation. 
There has also been a need for a shaker platform drive arrangement wherein 
the shaker mechanism is readily adjustable both as to stroke length and to 
mode of operation, and is furthermore adaptable to positioning a load 
carrier in a variety of ways without changing the underlying part of the 
apparatus. There is further need in the laboratory or scientific community 
for an apparatus which is constructed and arranged so that the load 
bearing parts will be durable in use and hence provide long-term economy. 
In view of the failure of the prior art to provide a dual mode shaker table 
or platform of optimum design, it is an object of the present invention to 
provide an improved shaker table arrangement. 
Another object of the invention is to provide a shaker platform arrangement 
that may support a load directly or somewhat indirectly, depending on the 
desired application. 
Still another object of the invention is to provide an apparatus wherein 
shifting or converting the apparatus from the reciprocating cycle to a 
rotary cycle is capable of being carried out with a change to only a 
single part or element. 
A further object of the invention is to provide a shaker platform 
arrangement having a drive mechanism which is equally effective regardless 
of stroke length. 
A still further object of the invention is to provide a shaker platform 
that is able to be controlled in respect to three variables and which is 
free from maintenance-intensive elements and which is comparatively simple 
and reliable in use. 
Yet another object of the invention is to provide a shaker table or 
platform in which the vertical load imposed by the components and the live 
load or articles to be shaken is taken by elements that are independent of 
the elements supplying the shaking motion. 
Another object of the invention is to provide a shaker table mechanism 
wherein two sets of parallelogram linkages are present, one linkage 
including a pair of links mounted to a base and also to one portion of an 
intermediate or idler member forming a fourth link, and wherein the second 
linkage comprises links attached to another part of the intermediate or 
idler member and also to the table, with one set of links permitting 
motion in one direction and the second set of links permitting motion in a 
second, perpendicular direction, with the actual motion being determined 
by the form connection between the table and a rotary crank pin, or 
between the table and another link element. 
An additional object of the invention is to provide two sets of 
parallelogram linkages in a shaker table, with a first set of links 
pivoting relative to the unit base and the other set of links pivoting 
with respect to a plate or L-member carried by the first set of links, and 
with a drive link and one of the second links each including an extension 
which may be removably secured to a portion of the table to determine the 
shaking mode desired. 
Yet another object of the invention is to provide a shaker table of the 
type described herein wherein the stroke length adjustment is readily made 
by swinging the crank pin carrier through an arc relative to the center 
line of the drive element to obtain an increased or decreased stroke 
length of the crank pin. 
According to the invention, an arrangement of links and plates is provided 
to permit the choice of a primarily reciprocating or a rotating motion of 
the shaker table. The table is supported at plural, spaced apart points by 
universal joints or the like permitting free but limited movement of the 
table under the influence of the drive mechanism. The drive mechanism 
includes a motor and a rotary element having a crank pin affixed thereto 
and optionally arranged so as to permit variation in the stroke of the 
crank pin. 
An important feature of the invention is that the type of motion 
transmitted by the drive link to the table is determined by the manner in 
which a portion of one link or the other is secured to the table. In one 
mode, the drive link is not only rigid in itself, but is attached to the 
table at two points along its length. Accordingly, with the drive 
connection being affixed to the crank pin, the table will replicate the 
rotary motion of the crank pin. In this mode, the links permit such 
two-axis motion without allowing the table to turn about its own axis. 
In the other mode of operation, the drive link is pivotally connected to 
both the crank pin and the table, allowing its free end (the end opposite 
the crank pin end) of the drive link to swing freely. In this mode, the 
second set of links cannot pivot relative to the table, but the first set 
of links allows a reciprocating motion along an axis determined by the 
location of the fixed pivots for the links. 
The invention achieves its objects and advantages and other inherent 
objects and advantages by providing a base unit, a shaker table supported 
on the base unit, a motor drive arrangement including a rotary crank pin 
and a drive link with one end attachable to the crank pin, an opposite end 
fixable to the table and a center portion pivotally attached to the table, 
first and second sets of parallelogram-forming links, the first set 
permitting movement parallel to a first line or locus and the second set 
permitting movement parallel to a second locus perpendicular to the first 
line, and an auxiliary mechanism for selectively connecting the table to 
the drive link at either the opposite end of the drive link or an 
extension of one of the second pair of links. The objects are also 
achieved by providing an apparatus of the type just described that 
includes preferred forms of table support, stroke length adjustment and 
variation of shaker speed to provide improved versatility and reliability 
in use. 
The exact manner in which the foregoing and other objects and advantages of 
the invention are achieved in practice will become more clearly apparent 
when reference is made to the following detailed description of the 
preferred embodiment of the invention set forth by way of example and 
shown in the accompanying drawings in which like reference numbers 
indicate corresponding parts throughout.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION 
While the inventive principles are able to be adapted to a number of 
different structures, a preferred form of the invention will be described 
wherein the shaker table is of generally inverted T-shaped configuration 
and wherein the links are of simple form, with an idler or like unit 
connecting the two pairs of parallelogram-forming legs being of an 
L-shaped configuration. A number of variations to the described form of 
apparatus will occur to those skilled in the art. 
Referring now to the drawings in greater detail, FIGS. 1 and 3 show a 
shaker table apparatus generally designated 10 and shown to comprise a 
housing generally designated 12 that is adapted to contain a base plate 14 
(FIG. 3) for controlling motion of the table. A motor generally designated 
16 is equipped with a drive connection generally designated 18 that is 
operatively associated with a rotary drive plate 20, surmounted by an 
eccentric crank pin carrier 22 from which a crank pin generally designated 
24 extends axially outwardly, i.e., upwardly as shown in FIG. 3. 
Preferably, a rotary drive shaft 26 extends through portions of a bearing 
assembly generally designated 28 for connection to a driven sprocket 29 
operated by a toothed or "Gilmer" belt 31 trained around a rotary, motor 
driven drive sprocket 33. 
Referring again to FIGS. 1-3, an important feature of the invention is the 
shaker table generally designated 30 and shown to be, in this embodiment, 
of a generally inverted T-shape. The table may be of any shape, and may 
hold specimens to be shaken, or may be associated with any one of a number 
of specimen holders as desired by the user. The major portion of the 
weight of the shaker table 30 is normally borne by four mounting legs, 
32a, 32b, etc., each of which includes an enlarged ball end 27 that is 
receivable in a leg mounting socket 34 positioned on the bottom panel of 
the housing 12. The shaker table 30 also includes leg mounting sockets 
positioned by socket holders 36 removably secured to the upper surface of 
the table 30. Tensioning springs 35 extend between the housing 12 and the 
shaker table 30, with spring retainers 37 being provided in the floor of 
the housing 12 and slots 39 being provided in the shaker table 30 for this 
purpose. Support of the table is also provided in part by the drive and 
movement control components to be described. 
Referring now to the table, as particularly shown in FIGS. 1-3, this 
element is of generally inverted T-shaped configuration and includes a 
full length edge 38, a pair of opposed side edges 40, an offset or stem 
portion of the "T" 42, an offset end edge 44 which may be stiffened with a 
reinforcing plate 45. An adjustment access port 46 is provided in the 
cross bar portion of the "T" or main section of the table 30. As is 
further shown in the above figures, there are plural openings 47 arrayed 
in a generally straight line perpendicular to the edges 40 to permit 
insertion of shoulder screws 48 therethrough. These openings 47 are 
preferably in a straight line arrangement parallel to the edges 38, 44 and 
perpendicular to the table side edge 40. The openings 49a, 49b for another 
or mode control shoulder fastener 49x extend through the reinforcing plate 
45 and are also aligned parallel to the edges 38, 44. 
Referring now to another principal component of the invention, a multi-link 
assembly generally designated 50, when properly connected to the motor and 
drive mechanism and also to the shaker table, accounts for the desired 
motion of the shaker table 30. This multi-link assembly 50 includes a 
first parallelogram linkage formed by first and second links 52, 54, 
pivotally held in position relative to openings 15 in the base plate 14 by 
shoulder screws 56 that extend through bushing style fittings 58 at the 
inner ends 60 of the links 52, 54. The screws 56 and openings 15 for 
receiving them are aligned along a reference locus 62 (FIG. 3). 
Preferably, this locus is parallel to the sides 13 of the housing 12, and 
the end edges 40 of the table 30. 
Because the subject mechanism involves parallel linkages, this locus 62 is 
sometimes referred to herein and in the claims as a "first axis" or a 
"first locus". While the end and side edges of the table, the housing, and 
other elements need not come before functional purposes, be parallel or 
perpendicular to this locus, such components normally are for simplicity 
and neatness. The motions in question take place with respect to this 
first locus and a second locus lying perpendicular to it and to be 
referred to elsewhere herein. 
The outer ends 64, 65 of the first and second links 52, 54 are pivotally 
mounted to an idler plate 66 which is preferably L-shaped and preferably 
has a first, shorter leg 68 parallel to the locus 62 and a second, longer 
leg 70 perpendicular to the locus 62. A pair of fasteners 72, 73 form 
pivotable connections permitting the edge of the shorter leg 68 to move 
toward and away from the front wall 17 of the housing 12, parallel to 
locus 62. In this arrangement, depending on the position of the two links 
52, 54, a rectangle or a parallelogram is formed by opposed parallels, 
i.e., the locus 62 and the link 68, and the links 52, 54. 
As shown in FIG. 3, the longer link 70 serves as a base for a second 
parallelogram linkage. This leg 70 locates the near ends 74, 76 
respectively of table positioner links 78, 80. Spaced apart portions 82, 
84 of the legs 78, 80 contain bushed openings for receiving the shoulder 
screw fasteners 48 extending downwardly through the plate 30. A locus 
connecting these openings 47 lies perpendicular to locus 62 and parallel 
to link 70. 
Accordingly, when the apparatus 10 is assembled, the table 30 is pivotally 
fixed to parallel, spaced apart portions of the links 78, 80 which are in 
turn carried at the leg 70 of the plate or L-member 66. With this 
arrangement, the table forms the fourth link of a second rectangle or 
parallelogram. 
Because the leg 70 is fixed perpendicular to the leg 68 of the plate or 
L-member 66, the loci of the two parallelogram linkages are perpendicular 
to each other. 
Further, according to the invention, the link 80 is provided with an 
extension 86, the end portion 88 of which includes a tapped opening 90 
which, in use, is registrable with the opening 49b in the plate 45. The 
fastener 49x can thus secure the table 30 to an end 88 of the link 80. 
The multi-link assembly 50 is completed by the addition of a drive link 
generally designated 92. This link includes a connecting rod portion 94 
having a bushed, crank pin receiving end 96 and which also includes a rod 
or link extension 98 terminating in a tapped end opening 100. This opening 
100 is registrable with the opening 49a in the plate 45, and the fastener 
49x can be used to secure these parts together. 
Thus, as will be amplified further herein, this arrangement of two 
parallelogram linkages, one leg of an idler plate serves as a ling lying 
on a first locus, and the other leg of the idler plate forms a second 
locus perpendicular to the first locus. 
Referring now to another feature of the invention, which is an optional but 
desirable feature in a shaker table, the stroke or extent of table 
movement may be readily achieved by the use of an eccentric crank pin 
arrangement. For this purpose, reference is made to FIG. 4, wherein it is 
shown that the rotary drive plate 20 includes an eccentric crank pin 
carrier 22 positioning the crank pin 24. The crank pin carrier 22 is 
pivotally connected to the drive plate 20 as by a fastener 110. The side 
of the carrier 22 opposite the fastener contains an elongated slot 112, 
preferably having a beveled upper surface 114, of arcuate oval 
configuration. 
A tapered head set screw 116 is positionable within the slot and received 
in a tapped opening (not shown) in the plate 20. By loosening the locking 
screw 116 and swinging the carrier 22 through an arc about the point 110, 
the position of the crank pin carrier 24 will be moved relative to the 
center line of the drive shaft 26, which is shown as a base circle in 
phantom lines in FIG. 4. According to the invention, the links and the 
table, including the opening 46 in the table 30, are arranged to lie above 
the adjustment mechanism so that the working stroke of the device may be 
changed at any time without removing the table or the links. 
Referring now to FIGS. 1 and 3, it will be noted that in these respective 
figures, the motor generally designated 16 is positioned atop a drive 
housing 17 which is shown in FIG. 1 as being behind the main housing 12 
and within such housing in FIG. 3. These are detailed variations of the 
invention which are considered optional with the designer. Likewise, the 
arrangement of the Gilmer or toothed-belt drive arrangement is an optional 
but presently preferred manner of providing smooth power delivery and 
accessibility for service of these components. Needless to say, different 
sprocket arrangements or change in gearing or mechanical advantage may be 
attended to in a simple manner using different sprocket pairs with the 
toothed belt or the like. 
In a preferred form of the invention, the motor drive is a variable speed 
drive of a known type and not forming a necessary part of the invention. 
Such motor speed control are known by those skilled in the art to be 
available for instruments and machines such as that described herein, and 
it is assumed that, to the extent that incorporating such variable speed 
controls is desired, this may be accomplished without the exercise of 
inventive skill. 
Referring now to the operation of the apparatus of the present invention, 
and the principles behind such operation, an explanation of the operation 
of the invention is believed helpful. While the invention does not depend 
for its success on any particular theory or mode of operation, it is 
believed most easily understood by reference to an explanation of the 
geometry provided by the mechanism providing two associated parallelogram 
linkages. 
According to geometrical principles, in a parallelogram formed by links 
pivotally joined at their ends, two opposed sides of the parallelogram 
will remain parallel to each other during pivotal movement of the other 
two parallelogram legs, which also stays parallel to each other. 
Accordingly, a side, which may be termed the "first" side of the leg 68 
will remain parallel to the locus 62 extending between openings 15, 15. 
Such a leg 68 may swing back and forth, as legs 52, 54 pivot, but the leg 
68 will always remain parallel to a line, such as the line or locus 62 
connecting the pivot points of the links supporting it. Where one side of 
a rigid member remains parallel to a given reference surface, a portion of 
that same member which lies perpendicular to the reference surface will 
also remain perpendicular to the reference surface. In other words, legs 
68, 70 of L-member 66 are always perpendicular to each other, and parallel 
and perpendicular respectively to locus 62. 
According to the invention, therefore a second pair of links 78, 80 is 
attached to the second leg 70 of the idler plate or L-member. A 
parallelogram is formed by these two links, combined with the leg 70 and a 
portion of the table 30, as occurs when the fasteners 48 are positioned in 
the openings 82. Then, the table is permitted to move parallel to the edge 
40, by one linkage and parallel to the edges 38, 44 by the other linkage. 
According to the invention, the drive link and the leg extension are 
alternately affixed to a portion of the table to secure the desired drive 
mode, and the act of affixing one leg extension while releasing the other 
enables a first mode of operation, while affixing the other leg enables 
the second mode. 
Accordingly, when the fastener 49x is inserted in the end 100 of the drive 
link 92, then the table is fastened to the drive link 92 at two points 
namely the opening 100 and the opening 99. This eliminates the possibility 
of pivotal motion between the link and the table. As the crank pin 
revolves, therefore, the table will simply trace the motion of the rotary 
crank pin. During this mode, the fore-and-aft movement of the table is 
permitted by the first pair of links and the side-to-side movement is 
permitted by the second pair of links, each of which in use passes through 
a parallelogram-to-rectangle-to-parallelogram sequence and the reverse of 
that sequence. 
Because the table is permitted by the universal joint mountings to undergo 
this motion without significant resistance, the shaker mode of the table 
is a rotary motion. During this operation, the end 88 of the leg extension 
86 is free to swing through an arc relative to the table, as dictated by 
the motion of its two pivot points attached respectively to the leg 70 and 
the table by fastener 48. 
When it is desired to provide a reciprocating shaking motion only, the 
shoulder screw 49x is removed from the opening 100 in the end 98 of the 
link 94, and placed through opening 49b into the tapped opening 90 in the 
end 88 of the leg extension 86. The result of this is that the leg 80 is 
affixed to the table 30 at two points, i.e., at the locus of the opening 
47 and the opening 49b. This connection having resulted in freeing the end 
98 of the drive link 92, connecting rod portion 94 of the link 92 is 
permitted to act in part as it would in an automotive connective rod, for 
example, pivoting at both its ends as the crank pin operates through its 
rotary cycle. Its free end swings through an arc. 
In this mode, the rigid connection of the table 30, relative to the link 80 
prevents the table from moving from side to side because a rigid, 
multi-point connection is made at points 90 and 47, and where the link 
ends 74, 76 joins the L-member 66. In other words, the link 78, 80 are not 
permitted to swing relative to the leg 70 and hence remain parallel to leg 
68 of the idler plate. Since fore-and-aft motion is permitted because the 
legs 52, 54 are still free to swing about their pivot points, and because 
the leg extension 98 is free to swing through an arc, the rotary motion of 
the crank is translated exclusively into fore-and-aft shaker motion, as is 
desired according to the invention. 
As was pointed out, this transition between modes is made by simply 
removing a thumb screw or the like from one opening and inserting it 
through another opening into a link end, thus tying the table to one 
mechanism or another and simultaneously releasing it. 
With the combination of adjustable stroke, adjustable shaking speed and 
mode of operation in a simple, multi-link mechanism, highly advantageous 
and economical apparatus is provided. 
In the above description, the expression "fore-and-aft" or "transverse" as 
applied to the motion means substantially although not absolutely 
fore-and-aft. Thus, there may be a slight left-to-right movement in a 
fore-and-aft motion, depending on the length of the movement stroke in 
relation to the angular deflection of the links. However, with the shaking 
distance being perhaps varying from a small fraction of an inch to perhaps 
only about an inch, with the links 52, 54 having a length of one foot or 
more, the side-to-side excursion relative to the fore-and-aft movement is 
very small. 
FIGS. 6-9 schematically show these modes of operation. In FIG. 6, the links 
of 52, 54 are designated as sides I and II, and the other sides formed by 
the locus lines 62 and the leg 68 form parallel sides III and IV. As these 
swing through an arc indicated in part by the dotted lines, the leg 66 of 
the member 66 stays parallel to the locus 62. 
FIG. 7 shows that because the L-member 68 has legs 68, 70 which do not move 
relative to each other, that leg 70 will remain perpendicular to the locus 
62, just as leg 68 remains parallel to such locus. The links 78, 80 may 
swing through an arc without disturbing this relationship. Consequently, 
the table, which is affixed to links 78, 80 may swing from right to left 
as shown in FIG. 7, and counterpart portions of the table will always 
remain parallel to the leg 70. 
FIG. 8 illustrates that where the extension 98 of the drive link 94 is 
fastened to the table as is the center portion of the link 94, there can 
be no pivoting of the table relative to the links 78, 80. The table will 
describe the same circular motion as the crank pin 24, because both sets 
of links can pivot. 
FIG. 9 is similar to that of FIG. 8 except that a rigid connection is made 
between the link 80 and the table. Then, only links 52, 54 may pivot, and 
since the drive link can pivot, the table moves fore-and-aft only. 
It will thus be seen that the present invention provides a new and improved 
shaker apparatus having a number of advantages and characteristics 
including those pointed out herein and others which are inherent in the 
invention. A few preferred forms of the invention, having been described 
by way of example, it is anticipated that a number of modifications and 
variations to the described form of apparatus will occur to those skilled 
in the art and it is anticipated that such variations may be made without 
departing from the scope of the invention, or the spirit of the invention 
or the scope of the appended claims.