No 897 194 (J. VERHAEGHEN 3) . Therein the rotatable axle is constituted by the first end of a rotatable first arm whose second end is coupled with the movable element and an inter¬ mediate point of which is hingedly connected to a second end of a second arm. The first and second transmission means are able to displace the first ends of both the arms in the prede¬ termined direction, so that a simultaneous and like displace¬ ment ₀ f these first ends gives rise to a displacement of the movable element in the predetermined direction, whereas a relative displacement of these first ends provokes a rotation of the first arm and therefore also of the axle .

A drawback of this known device is that the second transmission means are coupled to the axle via the linked arms and that the linking points can adversely affect the accuracy with which the element can be brought in a predeter¬ mined position of a plane .

An object of the present invention is to provide

an element moving device of the above type, but which does not present such a drawback and realizes a displacement and/or rotation of the axle in a simple way.

According to the invention this object is achieved due to the fact that also said second transmission means operate directly on said axle which is able to be rotated in either one of two selectable directions of rotation by each of said first and second transmission means.

Hence, no linking arms are required between the second transmission means and the axle so that a greater accurary can be realized. Also the transmission means can impart a displacement and/or a rotation to the axle in a simple way. Indeed, a pure displacement, of the axle is obtained when both transmission means exert opposite equal torques thereon; a pure rotation of the axle is realized when both transmission means exert thereon equal torques in the same direction; and a combined displacement and rotation of the axle is obtained ^' when different torques are exerted on this axle . Another drawback of the known device is due to the fact that the movable element is coupled to the rotatable axle via the first arm so that a rotation of this arm gives rise to an angular displacement of its secondend with which the movable element is coupled. To bring this element in a predetermined point of a plane a relatively complicated control of the transmission and of the force exerting means is there¬ fore required.

Another object of the present invention is to provide an element moving device of the above type but which also does not present this drawback.

According to the invention this object is achieved due to the fact that said rotatable axle is coupled to a carriage via third transmission means which are able to displace said ^' carriage in a second direction, said carriage forming part of said element and the first mentioned direction

as well as said second direction being both rectilinear.

In this way a rotary movement of the axle is trans¬ formed into a rectilinear displacement of the element in the second direction so that the control of the first and second transmission means and oftiiβ force exerting means to bring the movable element in a predetermined part of a plane can be relatively simple.

The above mentioned and other objects and features of the invention will become more apparent and the invention itself will be best understood by referring to the following description of an embodiment taken in conjunction with the accompanying drawings in which :

Fig. 1 is a schematic perspective view of an element moving device according to the invention; and Fig. 2 is a schematic perspective view of part II of Fig. 1.

The element moving device shown in Fig. 1 includes a frame generally indicated by reference numeral 1 and the central part of which is cut away. This frame 1 includes a housing 2, a supporting plate 3 and brackets such as 4, 5, 6 and 7. Inside the housing 2 the shafts 8 and 9 of main step¬ per motors 10 and 11 are rotatably mounted in a not .shown but obvious way respectively.

As shown in more detail in Fig. 2 , the larger part of a T-shaped plate 12 which extends below the housing 2 is fixed on the upper side of the body of motor 10, whilst the smaller part of this plate 12 carries an axle 13 in which a nut 14 is mounted in a freely rotatably way. The screw treaded shaft 15 of an auxiliary stepper motor 16 engages with the nut 14. The motor 16 is mounted on a piece 17 which is pivoted about an axle 18 fixed in a support 19 secured to the lower side of supporting plate 3.

The main stepper motor 11 and an auxiliary stepper motor 20 are mounted and connected in a similar way as the stepper motors 10 and 16 respectively.

At the upper side of housing 2 toothed wheels 21 and 22 are fixedly mounted on the upper ends of the above mentioned motor shafts 8 and 9 respectively. This housing 2 also carries two freely rotatable rollers 23 and 24, and the above mentioned brackets 4 and 5 carry freely rotatable toothed wheel 25 and wheel 26 respectively. The wheels 21 and 25 are mounted in a same plane and the same is true for the wheels 22 and 26 and the rollers 23 and 24.

Two longitudinal guide rods 27 and 28 are fixed in the above mentioned brackets such as 6 and 7. A supporting structure or sled 29 which is integral with a cantilever bridge piece 30 which constitutes another supporting structure is slidably mounted on the guide rods 27 and 28 as it is provided at its lower and upper sides with guide pieces such as 31, 32 and 33 which engage with these rods. The cantilever bridge piece 30 entends in a Y-direction perpendicular to the X-direction of. the guide rods 27 and 28. The sled 29 carries fixedly mounted axles 34 and 35 on which respective pairs of rollers 36, 37 and 38, 39 are mounted in a freely rotatable way, as well as a fixed axle 40 about which an assembly of like toothed wheels 41, 42 and 43 is freely rotatable. Wheel 41 is located in the same plane as- the wheels 21 and 25 and the rollers 36 and 38, and an endless toothed conveyor belt 44 engages with these wheels and rollers. Wheel42 is located in the same plane as the wheels 22 and 26 and the rollers 23, 24, 37 and 39 and an endless toothed conveyor belt 45 engages with these wheels and rollere . The cantilever bridge piece 30 carries a bracket 46 bearing a freely rotatable toothed wheel 47 which is located in the same plane as wheel 43, an endless toothed conveyor belt 48 engaging with these wheels. Lateral walls of the bridge piece 30 are provided with T-shaped elements 49 and 50 respectively, the latter element 50 being visible through a cut-out portion of the bridge piece 30. These T-shaped elements constitute guide pieces for rollers such as 51, 52, 53 of a displaceable

10, 16 and conveyor belt 44 by making reference to Fig. 2. By each step of the main motor 10 its shaft 8 is rotated over a predetermined unit angle and the conveyor belt 44 is displaced over a predetermined unit distance. This means that in this way the conveyor belt 44 can only be displaced over multiples of this unit distance . However, by the use of the auxiliary motor 16 this displacement can be. regulated to a fraction of this unit distance . Indeed, supposing, for simplicity reasons, that a step of this auxi- liary motor 16 produces a same unit angular displacement of its shaft 15, as does the main motor 10 with its shaft 8, only a fraction of this unit angular displacement is communi¬ cated to the plate 12 due to the fact that the shaft 15 is screw threaded. By this angular displacement the stator or body 10 of the main motor 10 is pivoted around the axis of its shaft 8 over the same angle . Since the motor 10 is a stepper motor it has a so-called holding torque, i.e. the torque which keeps its rotor in well defined positions with respect to its stator. Hence, the last mentioned' angular displacement of the main motor body by the auxiliary motor is accurately transmitted to the shaft 8 and therefore also to the associated conveyor belt 44.

In a preferred embodiment use is made of stepper motors having an angular speed of 1000 rpm and wherein one step corresponds to 1/800 of a rotation. The coupling between each main stepper motor 10,11 and its associated conveyor belt 44, 45 is such that each step of the motor 10, 11 corresponds to a linear displacement of 0.2 millimeter of the belt 44, 45. The transmission ratio between the main stepper motor 10, 11 and its associated auxiliary stepper motor 1.6, 20 is equal to 1/40, so that the belt 44, 45 may be displaced in steps of -7—— mm. 40

Instead of stepper motors also other motors could be used as auxiliary motor. In another embodiment (not shown) of the above

described element moving device the bridge piece 30 and all the items 46 to 55 are replaced by an arm radially mounted on wheel 43. A rotative motion of this arm 40 is thus substituted for the rectilinear motion of the displaceable carriage 54 in the Y-direction.

By the use of suitable driving devices elements coupled to the carriage 54 or to the end of the last mantionadarm may also be displaced in vertical direction and/or rotated.

The device described above is particularly suitable for use in robots.

While the principles of the invention have been described above in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of the invention.