Note: Descriptions are shown in the official language in which they were submitted.
CA 02226379 1998-01-06
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MUT,TI-~XT~ ROBOTS
TTi',CT~NICAT, FTF,T,T)
This invention relates to in~lllstn~l robotics, and in particular to providing an
ition~l axis of movement at a movable tool plate. As one example, the invention can be used
to add z or theta movement to x-y movement of a tool plate. Other examples will be described
herein.
RACKGROUND ART
Until lt;c~ ly, although various designs for positioning a~pal~Lus using belts (or
chains or cables or the like) have been known, the available belts have been too susceptible to
being stretched to be used practically, particularly in applications requiring high precision.
However, belt technology has reached the state where essentially non-stretchable belts are now
economical and viable. Repeatable motion is therefore achievable with belts.
Many two-axis belt or cable arrangements are known, but there remains a need
for belt configurations which can be used to provide reliable and economical movement of
tooling relative to a movable tool plate, without adding substantial mass to the tool plate itself
or to other moving components.
DT~CT,OSURF, OTi' TlWli',NTION
In the invention, various related belt configurations are used to provide an
additional axis of motion to a movable tool plate.
In one configuration, for ~unple" a second belt is added to a single-belt, two-axis
configuration. The second belt provides the third axis. The first belt, driven by two motors,
provides x-y motion of the tool plate, while the second belt can be operated to move relative to
the tool plate, such that the relative motion can be used to provide theta, z-axis or other
movement of the tooling relative to the tool plate.
In the invention as broadly conceived, there is at least one tool plate movable in
at least one axis.of motion by virtue of attachment to a belt, the belt being driven by at least one
motor. The invention provides at least one additional belt and at least one additional motor to
drive the additional belt(s), the additional belt(s) being routed to the tool plate(s) and being
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selectively operable by the additional motor(s) to produce motion of the additional belt(s) relative
to the tool plate(s). The belt motion may be connected in any desired fashion to produce motion
of a tool or tools relative to the tool plate(s).
The invention ee~rnti ,lly permits almost any desired col~ alion of movements
5 to be provided from a "toolkit" of standard components, namely the rails, beams, slides, belts,
pulleys and motors, etc.. This flexibility makes it possible to build inexpensive, high
p~lrulll~lce, high speed robots, with a wide variety of configurations to meet a wide variety of
needs.
RR~.~ Dli,~CRrPTION OF DR~AW~GS
In order that the invention may be more clearly understood, the pl~;r~lled
embodiment thereof will now be described in detail by way of example, with reference to the
accoll~allyhlg drawings, in which:
Fig. 1 is a schematic perspective view of a two-belt, three-axis H-shaped robot;Fig. 2 is a cross-section showing just the belt which moves the tool plate, in this
case the lower belt;
Fig. 3 is a cross-section showing just the upper belt, which provides a third axis
of motion;
Fig. 4 is a sr.hPm~tic perspective view similar to Fig. 1, but showing the upper belt
optionally following a "T" shape instead of following the full "H" shape;
Fig. 5 is a schematic cross-section similar to Fig. 3, but showing the upper belt
configured as in Fig. 4;
Fig. 6 is a srh~m~tic cross-section in which the lower belt also follows only a T-
shape (thus giving up one axis of motion, as will be explained);
Fig. 7 is a schematic cross-section corresponding to Fig. 6, but dispensing with2~ the second rail;
Fig. 8 is a srhrm~tic perspective view illustrating how a second belt added to the
configurations of Figs. 6 or 7 can add a second axis of motion;
Fig. 9 is a schematic perspective similar to Fig. 1, but showing two tool platesdriven by the lower belt, one on each side of the bearn, the two platforms thus moving in concert
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with each other (in opposite directions along the beam), and the third axis operations being in
concert with each other;
Fig. 10 is a s~h~m~tic cross-section showing the lower belt of Fig. 9;
Fig. 11 is a schematic perspective similar to Fig. 9, but showing the addition of
5 a third belt to provide independent operation of the third axis at the two tool plates;
Fig. 12 is a cross-section showing just the lower belt of Fig. 11, which provides
concerted movement of the two tool plates;
Fig. 13 is a cross-section showing just the middle belt of Fig. 1 1, which provides
a third axis of motion at one of the tool plates;
Fig. 1 4 is a cross-section showing just the upper belt of Fig. 1 1, which provides
a third axis of motion at one tool plate, independent from the third axis of motion at the other tool
plate;
Fig. 15 is a schematic perspective view, showing a configuration with two
independently movable beams and tool plates; and
Fig. 16 is a schematic perspective view similar to Fig. 15, showing two toolplates
on each beam.
~EST MODE FOR CA~RYING OUT T~F. ~VENTION
Figs. 1-3 illustrate the basic "H" shape of the plhllaly embodiment of the
invention. The robot has parallel first and second stationary rails 11 and 12, which are held
firmly in place on any suitably rigid base (not shown). A movable beam 13is mounted between
slides 14 which are slidably mounted on facing sides ofthe rails.
Fig. 2 shows a first belt 15 (in this case the lower belt) which is routed around
various pulleys so as to achieve the desired x-y movement of a tool plate 16, by operation of
motors 17 and 18, as will be explained. The basic routing of the first belt is as follows: from the
tool plate 16, around a first lower pulley 21 on a slide, thence around a second lo~;ver pulley 22
at one end ofthe first rail, thence around a third lower pulley 23 at the other end of the first rail,
thence around a fourth lower pulley 24 on the slide, thence along the movable beam and around
a fifth lower pulley 25 mounted on the second slide, thence along the second rail and around a
sixth lower pulley 26 at one end of the rail, thence along the second rail and around a seventh
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lower pulley 27 at the other end of the rail, thence around an eighth lower pulley 28 mounted on
the second slide, and thence back to the tool plate 16.
The basic two-axis motion ofthe tool plate is provided by the operation of motors
17 and 18 to drive any two pulleys on opposite rails, such as pulleys 22 and 27 for example.
S .Alt~ tively, it is possible to position the driving means anywhere along the path of the belt so
long as the two drive means are separated by the movable rail; in other words, the drive means
must be on di~LC~ stationary rails.
As can be readily seen from brief consideration of Fig. 2, for example,
coordinated operation of the two motors will produce any desired x-y motion of the tool plate.
10 For example, clockwise rotation of one motor and counterclockwise rotation of the other motor
at the same rpm will produce x-a-Ais motion of the tool plate (i.e. motion parallel to the rails).
Rotation of both motors in the same direction at the same rpm will produce y-aAis motion (i.e.
along the beam). Rotation of just one of the motors will produce 45 degree motion. By varying
the rpms and directions of rotation, any x-y motion can be achieved.
Fig. 3 shows the second (in this case upper) belt 30, which is routed around a tool
drive 31 (shown schematically only), thence around a first upper pulley 32, thence around a
second upper pulley 33 on a slide, thence around a third upper pulley 34 at one end of the first
rail, thence around a fourth upper pulley 35 at the other end of the first rail, thence around a fifth
upper pulley 36 on the slide, thence along the movable beam and around a si-Ath upper pulley 37
mounted on the second slide, thence along the second rail and around a seventh upper pulley 38
at one end of the rail, thence along the second rail and around an eighth upper pulley 39 at the
other end of the rail, thence around a ninth upper pulley 40 mounted on the second slide, and
thence around a tenth upper pulley 41 and back to itself at the tool drive 31. A motor 42 drives
one of the large pulleys, such as the third upper pulley 34, to drive the upper belt.
Ex~min~tion of Figs. 1 and 3 shows that movement of the upper belt 30 in
coordination with the movement of the tool plate can be used to produce a third axis of motion
at the tool plate. The motor 42 can be operated so that there is no movement of the belt relative
to the tool plate as the tool plate moves, or relative motion can be created so as to drive a tool in
a third a-Ais. The a-Ais shown by tool drive 31is theta, i.e. rotation about the central aAis of the
tool drive, but it should be readily ~pa~ that the rotation can be collvel ~ed to z-motion by any
co"~ ional means, for e~A~ullplc by rotating a ballscrew or the like on a threaded rod, to produce
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z-axis movement of the threaded rod, which could in turn be connected to drive a tool mount up
or down.
Similarly, it should be appalen~ that motion of the belt relative to the tool plate
could be used directly if desired for any particular application, for example to slide a tool or tool
mount laterally along the tool plate, that tool or tool mount being connected to the belt.
Fig. 4 is a s~ ;c pel~e~ e view similar to Fig. 1, but showing the upper belt
optionally following a "T" shape instead of following the full "H" shape. Fig. 5 is a
corresponding plan view. Thus instead of the rail 12 being provided with pulleys 38 and 39, arld
the beam 13 being provided with pulleys 37 and 40, the beam is provided only with pulley 45
(or several smaller pulleys could be used). This arrangement is less desirable than the Fig. I
~ g~ nt, due to the potential for skewing of the beam, but is nevertheless certainly possible.
The Fig. 1 arrangement provides better symmetry of forces.
Fig. 6 is a ~çh~m~tic cross-section in which the lower belt also follows only a T-
shape. This produces only one axis of motion, as can be seen from consideration of Fig. 6. If
the beam is prevented from moving, then movement of the belt 15 will produce y-a~is movement
of the tool plate 16, i.e. along the beam. If the y-axis movement is prevented, i.e. if the tool plate
is secured to the beam, then movement of the belt will produce x-axis movement of the tool
plate, i.e. the beam will move. If neither movement is prevented, then the tool plate movement
will not be properly controlled or constrained, in the absence of additional means.
Fig. 7 is a schematic cross-section corresponding to Fig. 6, but dispensing withthe second rail 12. In Fig. 6, the second rail serves no operational fimction; it merely provides
support for the beam. In Fig. 7, the beam is cantilevered.
Fig. 8 is a schematic perspective view illustrating how a second belt 4$
(essentially corresponding to belt 30 in the earlier drawings), driven by the motor 42, can be
added to the configurations of Figs. 6 or 7 to add a second axis of motion. The belt is attached
to the slide 14, and is routed around pulleys 34 and 35. This routing produces movement of the
slide along the rail when the motor 42 is operated. As in the earlier examples, coordinated
operation ofthe motors 42 and 17 will produce controlled x-y motion ofthe tool plate 16.
Fig. 9 is a s~ perspective similar to Fig. 1, but showing two tool plates 16
and 16' connected to and driven by the lower belt, one on each side ofthe beam 13, the two
pl~l r.., ....~ thus moving in concert with each other along the beam (albeit in opposite directions),
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and the third axis operations also being in concert with each other, for example op~l~Lillg tool
drives 31 and 31'. Fig. 10 is a schematic cross-section showing the upper belt 30 of Fig. 9.
Fig. 11 is a s--hem~tic perspective similar to Fig. 9, but showing the 7~d~itic,n of
a third belt 50, driven by motor 51, to provide independent operation of the third axes at the two
tool plates. Figs. 12-14 are cross-sections showing the lower, middle and upper belts 15, 30, and
50 respectively. As can be readily seen, belts 30 and 50 provide independent control of the tool
drives 31 and 31' respectively, while the lower belt controls movement ofthe platforms 16 and
16'.
In this configuration, as in Fig. 9, the tool plates move in concert. However, Fig.
11 illustrates an important principle of the invention, which is that additional belts can be added
whenever it is desired to obtain additional axes of motion or independence of motion. Thus,
through ~pplupliate routing and driving of additional belts, in a similar manner to than shown
in Fig. 11, it would be readily possible, for c~l~lc, to achieve independent rather than concerted
movement of the tool plates; independent operation of tools on the tool plates; multiple
independently-driven tools on the same tool plate or diLrel~ tool plates; and so on. Obviously,
at a certain point there becomes an undesirable number of belts and an impractical degree of
resulting complexity, but in principle there is nothing preventing the invention from being
implemented with ten or more belts, if desired, however unlikely that may be in practice.
Fig. 15 shows that not only are such variations possible with a single beam, butalso with two (or more) independently operable beams 13 and 13'. The lower belt 15 would
move tool plate 16 via two motors as in the earlier-described embodiment~7 and the upper belt
60 would similarly move the tool plate 61 via two other motors (not shown). Fig. 16 additionally
shows that each beam could be provided with two tool plates, similar to Fig. 9. Independent
operation ofthe tool plates 16, 16', 61 and 61', and/or ofthe individual tools, and so on, could
be achieved as explained in conjunction with the above description of Fig. 11, simply by adding
more belts and motors in similar fashion.
f
INI)USTRIAL APPLICAE~ILITY
The invention provides tremendous flexibility in adding additional functionality30 to a robotic system, without adding any ~i~nific~nt moving mass. The motors remain stationary,
and thus the tools can be moved around without also having to move the mass of the motors. The
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systems can be assembled from essentially a standard kit of parts, inclllt1in~ various rails, slides,
pulleys, belts, motors, etc.. Systems can thus be designed and assembled very quickly and
efficiently, to meet a wide variety of needs.
