Jack with fixed piston for handling, moving and manipulating a workpiece

A jack consists of a body of the jack (2) sliding on a fixed piston (9) mounted on a support (6) by means of a piston rod (4), and at least one element for guiding the body on the support. The body of the jack is an extruded section (2) containing at least one longitudinal bore (3) used as the piston chamber for the jack, and equipped with at least two guide rods (5) mounted on the section (2) in the longitudinal direction. Bearings (15) adapted to the shape of the guide rods (5) are mourned on the fixed support (6). At least one of the bearings is adjustable. Advantageously, the extruded section (2) is equipped with two hydraulic shock absorbers intended to contact limit stops (21). Limit stops (21) have adjustable positions, and can be retracted and fixed on an L-shaped groove (20) of the fixed support (6).

FIELD OF THE INVENTION 
The present invention relates generally to guided jacks having a fixed 
piston. 
BACKGROUND OF THE INVENTION 
Jacks with a fixed piston are known for handling, moving and manipulating 
workpieces. In this type of jack, the body of the jack moves in relation 
to the piston, and a guiding element is provided to ensure the 
longitudinal motion of the body and to prevent rotation between the piston 
and the body. Such a jack is also advantageously used in handlers and 
robots. 
Patents FR 2 566 847 and FR 2 588 328 held by the applicant, describe a 
jack with a fixed piston, in which the body of the jack consists of a tube 
sliding on the fixed piston. A guiding element is also provided. The 
guiding element is installed parallel to the body of the jack and is held 
in place by blocks. The guiding element is connected to the body of the 
jack through a connecting piece of an appropriate shape. To reduce the 
overall dimensions, the guiding element remains inside the casing when the 
body of the jack moves outward. 
The inconvenience of this type of jack is that the body of the jack is a 
tubular part, ill-adapted to form the arm of a robot and to be equipped 
with a tool because of its shape, and also because of its mechanical 
resistance. In addition, there are difficulties in manufacturing the body 
of the jack. 
Further, the guiding of the body of the jack is bulky and its fabrication 
cost is high. While other known guiding systems might allow a shorter 
length, the width and height can still be substantial, i.e., in the 
traverse directions of the jack movement. 
It can also be desirable to be able to stop the jack movement, before it 
reaches its end of travel. This stop should take place both on the 
occasion of an outward movement and during the return of the body of the 
jack. 
Patent FR 2 588 328, mentioned above, describes a jack which makes it 
possible to obtain intermediate stops. For this purpose, the jack contains 
a reversible screw which is also used as the guiding element. The length 
of the screw is approximately equal to the total travel of the jack and is 
equipped with a blocking component to stop the rotation of the screw for a 
given travel of the body of the jack. The blocking component is activated 
by sensors or by a rotating coder. This device is electrical and its 
realization cost is high. 
As shown in Patent EP-B-0 472 778, it is also known to stop the arm of a 
jack-activated handler during its movement by placing an adjustable limit 
stop in a "T" shaped groove of the handler arm. In this jack, the handler 
is provided with a double-effect jack controlling the movement of a shock 
absorber. The double-effect jack retracts to intercept the limit stop to 
stop movement of the handler arm. However, this device only allows a small 
adjustment range at the end of travel of the jack, and the stop can only 
occur when the rod moves outward. In addition, three shock absorbers are 
necessary: (i) one for the limit stop at the end of travel of the handler 
arm, (ii) one at the end of travel of the withdrawal, and (iii) one for 
the intermediate stop. 
As such, it is believed there is a demand in the industry for an improved 
guided jack with fixed piston for handling, moving and manipulating 
workpieces. 
SUMMARY OF THE INVENTION 
The jack of the present invention consists of a body sliding on a fixed 
piston. The piston is installed on a support by means of a piston rod. The 
body of the jack is an extruded section with at least one longitudinal 
bore to receive the piston, and equipped with at least two guide rods 
mounted longitudinally on the extruded section to guide the body on the 
support. Bearings adapted to the shape of the guide rods are mounted on 
the fixed support. The bearings cooperate with the guide rods to support 
the extruded section of the jack for sliding in the longitudinal direction 
and prevent rotation thereof. At least one of the bearings is adjustable 
such as by a cam. 
According to the present invention, the extruded section of the jack, which 
forms, for example, a moveable component such as the arm of a robot, is at 
the same time the driving element, since it includes the piston chamber 
for the jack as well as the guiding and anti-rotation element for the body 
of the jack. 
In addition, the overall dimensions of the jack are kept to a minimum. On 
one hand, the driving element is integrated into the moveable component. 
The cylinder wall of the jack body is used both as the leaktight wall for 
the piston chamber of the jack, as well as a support for a tool or 
accessory. On the other hand, since the guide rods are mounted on the 
extruded section, the space necessary to ensure the guiding function can 
be reduced to a minimum as it is enough to have space for the bearings 
only. Further, the use of at least two guide rods makes it possible to 
combine their guiding function with the anti-rotation function. 
In order to reduce the overall dimensions and to effectively ensure the 
anti-rotation function, the guiding elements are rods of circular section, 
partly furred-up (embedded) in the extruded section, on opposite surfaces 
of the extruded section. 
In certain applications, the extruded section can carry a tool at the end. 
This tool can require an electrical, pneumatic or hydraulic supply. To 
facilitate the supply, the extruded section contains two parallel 
longitudinal bores, one of which is used as the piston chamber in the body 
of the jack. Besides being used to supply power to a tool, the other bore 
can be used to house a return spring or a gas-activated shock absorber. 
This way, when the jack is working in a vertical position with the 
extruded section protruding from the jack at the bottom, the spring or 
shock absorber will return the extruded section to a withdrawn 
(non-extended) position for safety reasons in case of power supply failure 
of the jack. 
The second bore in the extruded section can also be used, for example, as a 
second piston chamber for the jack. In this case, the jack has two 
parallel piston chambers. The jack power is therefore doubled. 
The guided jack with fixed piston described above also makes it possible to 
perform intermediate stops along the travel of the section. To this end, 
two hydraulic shock absorbers are attached to the extruded section, one to 
absorb the shocks in the outward direction of the extruded section, and 
the other in its re-entry (withdrawn) direction. 
Advantageously, the extruded section is guided over an "L" shaped support, 
to which is connected the fixed piston. Guiding bearings are mounted on 
the "L" shaped section for support of the piston. For intermediate stops, 
each branch of the "L" has a longitudinal groove which can receive at 
least one limit stop with adjustable position. Each limit stop is situated 
on the path of one of the shock absorbers integral with the section. The 
support can be open to external view and does not have to be a closed box. 
The accessibility to various components of the jack is thereby improved. 
The space gain and the weight reduction of the jack are also substantial. 
Advantageously, each limit stop is mounted on a limit stop jack having an 
orthogonal axis to the translation direction of the extruded section. Each 
limit stop can be moved between a position in which the limit stop is 
situated on the path of a shock absorber, and a position in which the 
limit stop is retracted. This way, the shock absorbers move with the 
extruded section and contact the limit stops to thereby absorb the shock 
when a stop is required. Otherwise, the shock absorbers pass a retracted 
limit stop(s) without contact. 
The jack used for each limit stop can be, for example, a simple-effect jack 
withdrawn by a spring. However, this jack is preferably a double-effect 
jack whose retractable, prism-shaped body which forms the limit stop is 
guided into a block. 
To be able to integrate the jack with fixed piston in an automated system, 
it is necessary to determine the position of the extruded section used as 
the body of the jack and, especially, to determine the position of the 
extruded section at an intermediate stop. For this purpose, a sensor is 
placed near each movable limit stop to detect the presence or absence of a 
shock absorber. For better control, at the level of each jack controlling 
a movable limit stop, a first sensor controls the withdrawn position of 
the limit stop and a second sensor controls the protruding position of the 
limit stop. 
As described above, the invention will be well understood with the help of 
the following description, in reference to the schematic drawings attached 
hereto which show, as a non-restrictive example, one form of execution of 
a jack with fixed piston according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIGS. 1-4 illustrate a jack 1 constructed according to the principles of 
the present invention. Jack 1 consists of a body having an extruded 
section 2, which is slidable on a fixed piston 9. Extruded section 2 on 
piston 9 is guided by guide rods 5. The assembly of the extruded section 2 
and piston 9 is mounted on a support 6. 
Section 2 is made of extruded aluminum. The cross-section of the extruded 
section is approximately rectangular and has two parallel bores 3, 7 
extending longitudinally from one end to the other of the section. The 
first bore 3 is used as a piston chamber, and receives the fixed piston 9. 
The second bore 7 makes it possible to have a lighter section 2. In 
addition, in the example shown in FIG. 2, the extruded section 2 is 
intended to be equipped with a tool and to this end, a tool holder plate 8 
is mounted at its extremity. Bore 7 can then serve as a conduit for 
supplying electricity and/or pressure fluid to the tool. 
The fixed piston 9, on which slides the extruded section 2, includes a 
piston rod 4 and is equipped with gaskets 10. 
Piston 9 defines two chambers in bore 3 which pneumatic pressures will be 
sequentially admitted. One chamber 13 is defined in the rear of the bore 
(to the right in FIG. 2) and one chamber 14 is defined in the front of the 
chamber (to the left in FIG. 2). Pressure is supplied to the chambers by 
components not shown on the figures. The rear end 11 of chamber 13 is made 
leaktight by gaskets 12. 
On the upper and lower surfaces of section 2 are two cylindrical guide rods 
5a, 5b made of steel which are at least partially furred-up (i.e, 
embedded) in the section. Through these rods, the extruded section 2 is 
guided with regard to the support 6 on upper and lower guide rollers 15a, 
15b (See FIG. 3). The lower rollers 15b working together with the lower 
guide rod 5b are mounted on axle 16. The head of axle 16 is imbedded in a 
countersunk hole in the support 6, while its other extremity is screwed 
onto support 6. 
The upper rollers 15a working together with the upper guide rod 5a are 
rotatably mounted on an eccentric cam 17 to support block 18. Support 
block 18 is mounted on the support 6. The head of cam 17 is imbedded in 
block 18. The other end of the cam 17 is threaded and screwed in the block 
18. Cam 17 is provided with an internal hex socket which allows the 
adjustment of the rollers by turning the cam, such that rollers 15a, exert 
a preload on the guide rod 5a. Once the adjustment is obtained, a lock nut 
19 makes it possible to lock cam 17 in the selected position. 
The guide rods 5a, 5b work together with the upper and lower guide rollers 
15a, 15b to guide the section 2, in transition, with regard to the support 
section 6. Rods 5a, 5b also fulfill the anti-rotation function. Taking 
into consideration their position on two opposite surfaces of section 2, 
the rotation of the latter around the longitudinal translation axis is 
prevented. 
The support 6 is a support section having an "L" shaped cross-sectional 
configuration. Each branch of the "L" has a groove 20. Blocks 18 used as 
support for upper rollers 15a are mounted on the upper one of these 
grooves (as viewed in FIG. 3). 
Limit stops 21 are also mounted in grooves 20 on the support 6. Stops 21 
are mounted on a double-effect jack 22 and guided in a block 23 with the 
help of a sliding connection. 
On extruded section 2 is attached a support 24 for two self-adjusting 
hydraulic shock absorbers 25. The shock absorbers are mounted parallel to 
the axis of section 2. One of them is oriented to absorb the shocks when 
it meets an obstacle in the outward direction of the section 2, and the 
other one absorb the shocks in the withdrawal direction of section 2. 
Each shock absorber 25 is mounted so that, when limit stops 21 situated on 
the corresponding groove 20 are in the protruding position, the shock 
absorbers collide with these limit stops during the travel of extruded 
section 2. Conversely, when these limit stops 21 are in the withdrawn 
position, the shock absorbers pass in front of the limit stops 21 without 
collision. 
Shock absorbers 25 are also used to absorb the shock at the end of travel 
of extruded section 2. They collide in one direction with a plate 26, to 
which the piston rod 4 is also attached, and in the other direction with a 
casing 27. Plate 26 and casing 27 are both attached to the support section 
6. 
Limit stops 21 can be placed so that section 2 can stop, both in the 
outward direction of section 2 and in the withdrawn direction of section 
2, in any one (or several) intermediate position. 
The "L" shape of support 6 is very advantageous, since it allows 
accessibility to the limit stops 21. It is enough to remove casing 27 to 
immediately gain direct access to limit stops 21 and to all the other 
components of the jack. 
When the jack 1 is integrated in an automated assembly, it is necessary to 
determine the position of section 2 and that of the limit stops 21. 
Sensors (not shown) are in this case provided. A first sensor--for example 
a PNP or NPN inductive sensor--makes it possible to detect the presence of 
support 24 of the shock absorbers near a limit stop 21. The sensor can be 
placed on the axis 28 (FIG. 4). A second sensor placed on the axis 29 
detects if the limit stop 21 is withdrawn, while a third sensor, placed on 
axis 30, detects if the limit stop 21 is protruding. The information given 
by these sensors is then sent to a central control unit which manages the 
automated assembly to which the jack 1 is integrated. 
Of course, variations on the structure of the jack described above are 
contemplated. For example, the section constituting the body of the jack 
does not necessarily have a parallel-piped shape, but it can have, for 
example, another prismatic shape. In the same way, the second bore 7 
inside the extruded section 2 used to supply power to a tool can have 
other functions than the one described in the example above. 
The second bore 7 can also be used to hold a spring or a gas-activated 
shock absorber, which returns the extruded section to the withdrawn 
(non-extended) position. This way, in case of power supply failure of the 
jack, the section is automatically withdrawn. This is in general the 
position in which there is the least risk of collision. 
In order to double the jack power, the second bore 7 can be used, like the 
first one, as a piston chamber for the jack. In this case, the body of the 
jack slides on a second fixed piston, also connected to the support 6. Of 
course, the section can have a third piston and a third bore for a third 
piston chamber, if necessary, parallel to the other two, to further 
increase the power of the jack. 
In addition, as described earlier, the guide rods 5a, 5b are partly 
furred-up (embedded) in the extruded section 2. Non furred-up rods are 
also acceptable. In this case, the overall dimensions of the jack would be 
larger, but the guiding and anti-rotation function of the rods are 
maintained. 
Further, the several limit stops can be placed in the same groove of the 
support section (i.e., in the upper or lower groove 20). For reasons of 
clarity of the drawing, only one limit stop per groove is illustrated. 
These limit stops are controlled by double-effect jacks. A simple-effect 
jack, withdrawn by spring, is also acceptable. 
Also, three sensors per limit stop are provided to control the position of 
the section and that of the limit stop. Depending on the applications, the 
number of sensors can be reduced (or increased). 
As described above, the present invention thereby provides a jack with a 
fixed piston for handling, moving or manipulating a workpiece, consisting 
of a guiding and anti-rotation system of reduced overall dimensions and 
made with few elements. The jack guarantees high precision, which makes it 
possible to perform intermediate stops through the entire length of the 
travel of the body of the jack, both when moving outward and when 
withdrawing. 
The principles, preferred embodiments and modes of operation of the present 
invention have been described in the foregoing specification. The 
invention which is intended to be protected herein should not, however, be 
construed as limited to the particular form described as it is to be 
regarded as illustrative rather than restrictive. Variations and changes 
may be made by those skilled in the art without departing from the scope 
and spirit of the invention as set forth in the appended claims.