A manipulator includes a carriage, a base and a longitudinal guide for positioning the carriage. The longitudinal guide contains two guide parts attached to the base to provide a sliding mount for the carriage along an axis. A spindle is coupled to the carriage for moving it longitudinally and is provided with a rotating mount on the base. The manipulator also includes two wedge arrangements between the side parts of the base and the guide parts of the guide to center the carriage and prestress the guide parts in the direction of the axis. Each wedge arrangement comprises two cooperating slant faces one of which is an inner face of each side part of the base and the other of which belongs to a wedge which is moved with respect to the respective guide part for centering the same relative to the spindle. After completion of the centering operation the guide parts will be secured to the base, e.g. by screws.

FIELD OF THE ART 
The present invention concerns a manipulator, i.e., a device with which an 
object such as a tool, a probe, a pipette, etc., can be moved in a 
controlled manner and positioned accurately. 
BACKGROUND OF THE INVENTION 
One essential requirement for manipulators is that they work precisely and 
reproducibly. This makes high demands of the precision of the longitudinal 
guidance which leads to high costs accordingly. However, the precision 
must be guaranteed not only for a manipulator fresh from the factory but 
must be maintained even with the often rough operation in the laboratory. 
The present invention is based on the problem of developing a manipulator 
with a longitudinal guide that will guarantee accurate and reproducible 
operation over long periods of time while being easy to assemble and 
adjust. 
SUMMARY OF THE INVENTION 
This invention concerns a manipulator containing a carriage, a base part 
and a longitudinal guide for the carriage. The longitudinal guide contains 
two guide parts attached to the base part to provide a sliding mount for 
the carriage along an axis and it also includes a spindle coupled to the 
carriage for the purpose of moving it and with a rotating mount on the 
base part. According to a first aspect of this invention, the manipulator 
also contains a wedge arrangement between side parts of the base part and 
the guide parts in order to center the carriage and prestress the guide 
parts in the direction of the axis. 
According to a second aspect of this invention, the guide arrangement 
contains a nut mounted on the carriage to engage with the spindle and made 
of a slightly elastic plastic such as a polymer containing both fluorine 
and carbon ("fluorocarbon polymer") such as PTFE or some other elastic 
plastic such as polyamide [nylon] and having an inside thread that is 
underdimensioned and has a difference in pitch with respect to the thread 
of the spindle (e.g., 2 .mu.m per flight) so that it exerts a radial 
pressure on the spindle and equalizes wear on the thread of the nut. 
According to another aspect of this invention, an overload protection nut 
made of a rigid material, especially metal, preferably bronze, with an 
inside thread that is slightly overdimensioned with regard to the thread 
of the spindle is provided in the bore of the carriage in addition to the 
plastic nut. Normally the carriage is actuated by the plastic nut and the 
overload protection nut is inactive because its thread is too wide. Under 
an overload, the plastic nut gives somewhat, so that the metal nut is then 
engaged with the spindle and overloading and damage to the plastic nut are 
thus prevented. 
The present manipulator assures that the drive of the carriage will operate 
without any tolerance even after prolonged use due to the spindle and 
nuts. In addition, the nut which exerts a certain radial pressure on the 
spindle has a damping effect on the drive which is advantageous especially 
when the drive is by a stepping motor or similar device. 
The fact that the longitudinal guide is adjusted by side wedges makes it 
possible to achieve an accurate guidance with a simple assembly. 
Replacement strips provide protection against soiling and also make it 
possible to easily adapt the manipulator to various applications and modes 
of operation. According to another advantageous embodiment, the carriage 
is optionally motor driven or manually adjusted.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The manipulator illustrated in FIGS. 1a, 1b, 2 and 3 permits an accurately 
controlled linear movement along a given axis A. It may be combined with a 
second manipulator whose direction of movement is at right angles to the 
aforementioned axis and may optionally also be combined with a lifting 
device in order to make it possible to move a certain object such as a 
tool, a pipette, a probe, etc., in two or three axes. 
The uniaxial manipulator illustrated in FIGS. 1a and 1b consists of a 
one-part base 10, which has a trapezoidal recess 12 that is symmetrical 
with respect to axis A and is produced by cutting (as seen from above) and 
is bordered by a frame-like part 10a and a bottom 10b. Recess 12 contains 
a longitudinal guide 14 which contains two rail-like outer guide parts 14a 
connected to bottom 10b of the base by bolts, two inner rail-like guide 
parts 14b connected to a carriage 16 that has an approximately T-shaped 
cross section and a number of roller bearing elements 18 such as rollers 
or balls arranged between the neighboring inside and outside guide parts 
14a and 14b and forming a roller bearing between these two parts. The 
roller bearing elements are held in a cage in the usual manner. 
Base 10 has an integral shoulder 10d at the bottom, forming a T-shaped 
positioning groove 10e. 
Carriage 16 has a longitudinal hole in which a nut 19 of PTFE or some other 
suitable wear-resistant, slightly elastic plastic that has good 
dimensional stability, such as some other fluorocarbon polymer, is glued. 
Nut 19, which is described in greater detail with reference to FIG. 3, is 
coupled to spindle 20. The spindle is held in the parallel side parts of 
frame part 10a by means of two ball bearings 22 that are held under 
tension with respect to each other and whose outer race rings are pressed 
into corresponding recesses in base 10. The nut which is shown on an 
enlarged scale in FIG. 3 has a ring-shaped bonding surface 19a on the 
outside with which it is bonded by means of an epoxy resin adhesive or 
some other suitable adhesive in the longitudinal borehole of the carriage. 
The adhesive surface 19a is formed by a relatively thick-walled unthreaded 
section of the nut whose inside diameter is larger than the outside 
diameter of spindle 20. The accurate radial positioning (side stability) 
of the spindle nut 19 is assured by means of three ring-shaped contact 
surfaces 19c that have a somewhat larger diameter than the thread section 
and the adhesive surface 19a and are in contact with the inside wall of 
the carriage bore. A relatively thin-walled threaded section with an 
inside thread 19b is next to the adhesive surface. The inside thread 19b 
has a somewhat greater depth of thread than the outside thread of spindle 
20, so that the flights of the slightly elastic nut are compressed when 
the spindle is screwed in and thus nut 19 exerts a certain prestressing 
effect on the spindle. As a result of this prestressing, there is an 
automatic readjustment of the tolerance which equalizes the unavoidable 
wear on the spindle nut and in addition the prestress also has a damping 
effect on the spindle drive. 
In a preferred embodiment, spindle 20 has a pitch of 0.5 mm. The inside 
thread of nut 19 has a 2 .mu.m greater pitch per flight which with a 
thread length of 12 mm and 24 flights corresponds to a total of 
24.times.0.002=+0.05 mm. 
Between the section forming adhesive surface 19a and the section containing 
inside thread 19b, the spindle nut 19 is provided with a ring groove 19d 
cut out on the inside. This slightly weakens the wall of the spindle nut 
at this point, so that when there is a strong axial load in the direction 
of axis A, the part of the thread of the spindle nut consisting of the 
slightly elastic material can shift somewhat with respect to the section 
that is fixed with respect to carriage 16 and has adhesive surface 19a. 
In addition, an overload protection nut 60 is glued in the bore of carriage 
16 with a slight axial distance from the end of spindle nut 19 facing the 
thread. The overload protection nut 60 has an inside thread 60a that is 
slightly overdimensioned with regard to the thread of the spindle so that 
in a normal case (without an overload) the drive of carriage 16 takes 
place exclusively by means of the engagement of the spindle in thread 19b 
of the spindle nut. When there is a severe overload, the spindle nut is 
deformed slightly in its threaded part and/or the part having the inside 
ring groove 19d without undergoing any damage, so that then the spindle 
nut 19 comes into engagement with the thread of the overload protection 
nut 60. The overload protection nut 60 in the embodiment illustrated here 
is made of bronze (red bronze or gun metal), so it can withstand high 
forces and protects spindle nut 19 from damage due to overloading. 
Wedge 24 is inserted between the inclined contrarotating inside walls of 
the sides of the frame-like part 10a and the outer guide parts 14a of 
longitudinal guide 14. The wedge arrangement containing wedges 24 serves 
to center the longitudinal guide and apply an initial stress across the 
axial direction so that carriage 16 sits in the middle despite the greater 
tolerances of the guides and runs in an accurate and reproducible manner. 
For the purpose of adjustment, carriage 16 is arranged with spindle 20 
that can be screwed into spindle nut 19 and overload protection nut 60 
centered accurately in base 10 and then the longitudinal guide is 
subjected to prestress from both sides by means of wedges 24 and finally 
the outer guide parts 14a are secured on bottom 10b of base 10 by screws 
80. 
The upper end of spindle 20 in FIG. 1a extends outward above frame part 10a 
where it is joined, e.g., by bonding, to a coupling part of a metal folded 
bellows coupling 30 (shown in FIG. 4) that has a bore with a locking 
screw. Optionally a drive shaft of an electric motor 32 (FIG. 1a) or a 
hand wheel 34 (FIG. 1b) can be connected to this coupling 30 so that 
carriage 16 can be advanced either by motor drive or by hand. Motor 32 is 
mounted on a motor flange 36 (FIG. 1a) which is in turn bolted to base 
part 10 by means of two spacer bolts 38 which also provide thermal 
insulation. The operation of motor 32, which is especially a stepping 
motor, is damped in an advantageous manner by the inside thread 19b of nut 
19 which has the dimensions described elsewhere. 
Normally, a second manipulator unit is mounted on carriage 16 to permit 
movement along an axis at right angles to the axis of spindle 20. This 
second manipulator unit then covers a large portion of the opening of 
recess 12. However, in the end positions a small slit into which foreign 
bodies and dirt can penetrate may remain on the sides of frame-like part 
10a. In order to prevent this, strip parts can be screwed to the 
longitudinal sides of the frame-like part 10a (preferably made of plastic 
for reasons of weight). In the simplest case, the strip parts are solid as 
illustrated by 38a in FIG. 2. However, the strip parts may also assume 
other functions in addition to the primary protective function in an 
advantageous manner. For example, one embodiment of the strip part 38b as 
shown at the right side of FIG. 1a may be provided, having a somewhat 
U-shaped cross section and a passage 40 on the inside at the bottom in 
FIG. 1a and also having a terminal switch 42 arranged so that it can be 
adjusted longitudinally in the hollow of strip part 38b by means of a 
crank 44. After adjustment of the terminal switch, the crank may be 
secured by means of a bolt 46 passing through an elongated hole 48. 
Terminal switch 42 is coupled to motor 32 by means of line 43 and turns off 
the motor when the carriage 16 has reached the end position. A 
corresponding passage and a corresponding terminal switch are also 
provided on the other end of strip part 38b but only the projecting 
lamellar actuating element of the terminal switch is visible in FIG. 1a. 
Another embodiment of the strip part 38c which is shown schematically in 
FIG. 1b has a U-shaped or L-shaped cross section and is used to mount an 
additional device 49 such as a scale 50 which is made of glass in the 
present case. 
Carriage 16 may have an integral shoulder 16a (FIG.2) at the top forming a 
T-shaped groove 16b which corresponds to T groove 10e.