WO2020159359A1

WO2020159359A1 - Lift unit

Info

Publication number: WO2020159359A1
Application number: PCT/NL2020/050001
Authority: WO
Inventors: Leopold PEERBOOM
Original assignee: Almotion B.V.
Priority date: 2019-01-29
Filing date: 2020-01-02
Publication date: 2020-08-06
Also published as: NL2022470B1

Abstract

Lift unit (101, 201) for lifting an object such as a product holder, said lift unit comprising: • - a carriage (107, 207) and an elongated base (103, 203) for translating said carriage in a longitudinal direction with respect to said elongated base, • - a pulley (119, 219) which is rotatable about a first rotation axis (123, 223), • - a flexible element that is passed over said pulley, wherein said flexible element at a first end thereof is connected to said carriage • - a constant-force spring (111, 211), connected to said flexible element at a second end of said flexible element such that said constant-force spring is connected to said carriage via said flexible element, wherein said constant-force spring is arranged for providing a constant force acting as a counter force to counter the gravity force acting on said carriage.

Description

Title: Lift unit

Description

The present disclosure relates to a lift unit.

Lift units for translating a carriage in a vertical direction are known. Such a unit comprises two pulleys wherein a flexible element is passed over the two pulleys. The carriage is attached to the flexible element such that by rotating the pulleys the carriage may be moved in the vertical direction.

The lift unit may also be referred to as a linear unit or a motion system and is typically used for positioning an object at a desired height. An example of such a use is in machines for moving a product holder from a lower position to a higher position wherein for the product can only be reliably handled when the product is positioned with sufficient accuracy. An important aspect of the lift unit is to provide for relative safe lifting while maintaining the lift unit relative compact. Another relevant aspect of the lift unit is power consumption for lifting the object to a position and/or maintaining the object at a position.

An object of the present disclosure is to provide a lift unit that is relative safe and compact and has a relative low power consumption for lifting the object to a position and/or maintaining the object at a position.

This objective is realised by the lift unit according to the present disclosure. The lift unit according to the present disclosure comprises a carriage for attaching said object, such as a product holder, to said lift unit and an elongated base for translating said carriage in a longitudinal direction with respect to said elongated base. The carriage is attached to a counter force element via a flexible element. The flexible element is at a first end thereof connect to said carriage and at a second end thereof connected to said counter force element. The lift unit comprises a pulley that is rotatable about a first rotation axis, wherein said flexible element is passed over said pulley. The counter force element is arranged for providing a constant force acting as a counter force to counter the gravity force acting on the carriage. The present disclosure at least partly relies on the insight that by providing a counter force element a relative compact and safe lift unit may be realised. By providing a counter force element a relative low force is required for lifting the object, in use, to a vertical position and/or maintaining the object, in use, at a vertical position. The counter force element furthermore contributes to realising a relative safe lift unit in that the force required for lifting the object may be reduced.

Preferably, the counter force element comprises a constant-force spring, wherein said constant-force spring is arranged for providing said force acting as a counter force to counter the gravity force acting on said carriage. A constant-force spring is beneficial for realising a lift unit having a relative low weight while realising a relative large force to counter the gravity force acting on the carriage. Providing the lift unit with a constant-force spring relies at least partly on the insight that, as opposed to a counterweight, an increase of the force to counter the gravity force acting on the carriage does not increase linear with the weight of the constant-force spring. For this reason a lift unit may be realised that may maintain a carriage having or bearing a relative large weight at a position, by said counter force element, while maintaining the weight of the lift unit to such a level that an operator may install and/or remove the lift unit without the need for additional lifting equipment.

Within the context of the present disclosure, a constant-force spring is to be understood as a spring for which the force it exerts over its range of motion is relatively constant. Preferably, said force, provided by said constant-force spring, acting as said counter force is within 10 % of a nominal force. Preferably, said nominal force is in a range of 50 Newton to 100 Newton.

Preferably, said constant-force spring comprises a rolled ribbon of spring steel. A rolled ribbon of spring steel is beneficial for realizing a relative compact counter force element.

Preferably, said constant-force spring, is arranged in a receiving space provided in said elongated base. By providing the constant-force spring inside the elongated base, the constant-force spring may be shielded from the surrounding of the lift unit and thereby avoid, or at least significantly reduce, the risk of an operator or object to collide with the constant-force spring.

It is advantageous if said lift unit comprises a translation element, wherein said carriage is connected to said elongated base via said translation element. Providing a translation element is advantageous for realising a relative accurate movement of the carriage, thereby realising a functional decoupling for realising a required stiffness, by said elongated base, and an accurate positioning of the carriage. Preferably, said translation element comprises a guide rail.

Preferably, said lift unit comprises an end part that is connected to said elongated base, wherein said pulley is provided in said end part. Providing a separate end part is beneficial for allowing said elongated base to have a relative low complexity. Preferably said end part is connected to an end face of said elongated base.

In a practical embodiment of the lift unit according to the present disclosure, said end part provides an end stop for limiting said translation in said longitudinal direction. This is beneficial for realising a relative safe lift unit, wherein translation of said carriage is limited to a predetermined height.

Preferably, said lift unit comprises a further end part that is connected to said elongated base, wherein said counter force element, preferably said constant- force spring, is at least provided in said further end part. Providing a further end part is beneficial for allowing said elongated base to have a relative low complexity. Preferably said further end part is connected to a further end face of said elongated base.

It is beneficial if said lift unit comprises a drive arrangement connected to said pulley for rotating said pulley about said first rotation axis and thereby translating said carriage in said longitudinal direction.

Preferably a perimeter of said elongated base, in a direction perpendicular to said longitudinal direction, is closed. This is beneficial for shielding the counter force element the surrounding of the lift unit and thereby avoid, or at least significantly reducing, the risk of an operator or object to collide with the counter force element.

It is advantageous if said flexible element comprises a toothed belt and wherein said pulley comprises teeth arranged for cooperating with teeth of said toothed belt. A combination of a toothed belt and a toothed pulley is beneficial for avoiding, or at least significantly reduce, the risk of the flexible element moving relative to the pulley and thereby reduce a positioning accuracy of the carriage.

Preferably, said counter force, provided by said constant-force spring, to counter said gravity force acting on said carriage is larger than said gravity force acting on said carriage. This is beneficial for realising a lift unit wherein, in the absence of a driving force for driving the pulley, a drop of the carriage to a lower position is avoided, or at least, the a speed of lowering the carriage is reduced.

It is beneficial if said elongated base comprises an extruded profile.

In an embodiment said elongated base is arranged for attachment of the lift unit to a structure for holding the lift unit. This is beneficial for realising a lift unit having a relative low complexity while being relative compact

In an embodiment of the lift unit according to the present disclosure, said elongated base, at a side of said elongated base opposite a side of said elongated base attached to said translation element, is arranged for attachment of the lift unit to a structure for holding the lift unit. This is beneficial for avoiding deformation of the elongated base due to weight of the object that is to be positioned and translated in the vertical direction.

In an embodiment of the lift unit according to the present disclosure, said end part comprises a pulley receiving space that is bound by an internal wall of said end part, wherein said pulley receiving space is dimensioned such that, in use, said internal wall limits a movement of said flexible element for maintaining said cooperation between said teeth of said pulley and said toothed belt. This is beneficial for avoiding the flexible toothed element to move relative to the toothed pulley.

In an embodiment of the lift unit according to the present disclosure, said lift unit, preferably said counter force element, comprises a further counter-force element for providing a further constant force acting as a further counter force to counter the gravity force acting on said carriage. This is beneficial for realising a relative large force acting as a counter force to counter the gravity force acting on said carriage while realising a relative compact lift unit.

Preferably said constant force spring and said further constant-force spring are arranged in parallel such that said gravity force acting on said carriage is countered by a force that is equal to a summation of said counter force provided by said constant-force spring and said further counter force provided by said further constant-force spring. This is beneficial for realising a relative large force acting as a counter force to counter the gravity force acting on said carriage while realising a relative compact lift unit.

In an embodiment of the lift unit according to the present disclosure the counter force element comprises a counterweight, wherein said counterweight is arranged for providing said constant force acting as said counter force to counter the gravity force acting on said carriage. Preferably, said counterweight element is connected to said flexible element at said second end of said flexible element such that said counterweight element is only connected to said carriage via said flexible element. Preferably, said counterweight element is arranged in said receiving space provided in said elongated base such that said counterweight element is displaced in said receiving space when translating said carriage in said longitudinal direction. Preferably, a dimension of said counterweight element in a direction perpendicular to said longitudinal direction is in the range of 1 mm to 3 mm smaller than a corresponding inner dimension of said receiving space.

The present disclosure will now be explained by means of a description of a preferred embodiment a lift unit according to the present disclosure, in which reference is made to the following schematic figures, in which: Fig. 1 : an exploded view of parts of a lift unit according to the present disclosure are shown;

Fig. 2: a side view of a lift unit according to the present disclosure is shown;

Fig. 3: a cross-section of the lift unit from Fig. 2 is shown;

Fig. 4: another side view of the lift unit from Fig. 2 is shown;

Fig. 5: elements of the lift unit from Fig. 2 are shown;

Fig. 6: a side view of the lift unit from Fig. 2 is shown;

Fig. 7: an exploded view of parts of a lift unit according to the present disclosure are shown;

Fig. 8: a side view of a lift unit according to the present disclosure is shown;

Fig. 9: a cross-section of the lift unit from Fig. 8 is shown;

Fig. 10: another side view of the lift unit from Fig. 8 is shown;

Fig. 1 1 : elements of the lift unit from Fig. 8 are shown;

Fig. 12: a side view of the lift unit from Fig. 8 is shown.

Lift unit 101 comprises an elongated base 103 and a carriage 107. The elongated base 103 extends in a longitudinal direction A and comprises a single part of an extruded profile. Extruded profiles are well known and commonly used for motion systems. Lengths of these profiles in a lift unit can vary depending on the desired length of the unit. Extruded profiles provide required stiffness to the lift unit 101 for allowing a relative accurate movement of the carriage 107. In particular any bending of the lift unit 101 due to for instance a load of an object that needs to be lifted is prevented, or at least significantly reduced, by said extruded profile 103. This allows for a decoupling of a required stiffness of the lift unit 101 and an accurate positioning of the carriage 107 in the longitudinal direction A. The extruded profile 103 is a so- called closed profile having a perimeter, in a direction perpendicular to said longitudinal direction A, that is closed. In other words, the outer perimeter of the extruded profile 103 is continuous, apart from through holes and openings that may be provided in the extruded profile 103 after extrusion of the extrusion profile 103. Alternatively, it is conceivable that the elongated base 103 is formed from a profile made from bending sheet material, such as a steel plate. At a first side of the extruded profile 103 a translation element in the form of a rail guide 109 is attached to the extruded profile 103. The carriage 107 is designed such that the carriage 107 may be guided along the rail guide 109 in said longitudinal direction A. At a side of the carriage 107 opposite said rail guide 109, the carriage 107 is provided with an interface element 105 for attaching an end effector (not shown) or object (not shown) to the lift unit 101. At a second side of the extruded profile 103, opposite said first side of the extruded profile 103, the elongated base 103 is arranged for attachment of the lift unit 101 to a structure (not shown) for holding the lift unit 101 at a predetermined position.

The lift unit 101 is further provided with an end part 121 that is attached to the extruded profile 103 at an outer end thereof, that in use, wherein the extruded profile 103 is positioned substantially vertically, preferably vertical, borders to an upper outer end of the extruded profile 103. The end part 121 is dimensioned such that the translation of the carriage 107 at an upper translation range is limited by the end part 121. In other words, the end part 121 provides an end stop for limiting a translation of the carriage 107 in the vertical direction to a predetermined height. The end part 121 houses a toothed pulley 1 19 that may be driven by a drive arrangement formed by an electromotor (not shown) for rotation of the pulley 1 19 about a rotation axis 123.

A counter force element comprising two constant-force springs 1 11 is provided inside the extruded profile 103. Each of the constant-force springs 1 11 is tightly wound around a drum 133. The drum 133 is rotatably attached to said extruded profile 103 via fastening means 125 for rotation about a respective rotation axis B and C. The fastening means may be formed by an axis extending through the extruded profile and the drum. Alternatively, as shown in Fig. 1 the fastening means 125 may be formed by screws that are screwed in the centre of the drum 125. In a further alternative embodiment of the lift unit according to the present disclosure, the constant-force springs 11 1 are arranged to move relative to the drum for realising said counter force.

The constant-force springs 1 1 1 are connected to said carriage 107 via a toothed belt 1 13. The constant-force springs 1 11 are attached to the toothed belt 1 13 through a first connection arrangement 1 15 and the carriage 107 is attached to the toothed belt trough a second connection arrangement 1 17. The toothed belt 1 13 is passed over said pulley 1 19 such that said constant-force springs 1 1 1 provide a counter force to counter the gravity force active on said carriage 107. The teeth (not shown) of the toothed belt 113 are arranged to cooperate with teeth of said pulley 1 19 to avoid, or at least significantly reduce, the risk of the flexible element 113 moving relative to the pulley 1 19. The counter force, provided by said constant-force spring 1 1 1 , to counter the gravity force acting on the carriage 107 is larger than the gravity force acting on the carriage 107 such that in a situation wherein said pulley 1 19 is not powered by said drive arrangement the interface element 105 collides with said end part 121.

Lift unit 201 , shown in Fig. 7, differs from lift unit 101 mainly in that a counter force element comprising two constant-force springs 21 1 is provided at least partly outside the extruded profile 203. Elements of lift unit 201 that are similar to elements of lift unit 101 are provided with a reference number equal to the reference number of the element for lift unit 101 raised by 100. Lift unit 201 comprises a counter force element housing 227 comprising a first housing part 229 and a second housing part 231. The counter force element housing 227 is attached to the extruded profile 203 at an outer end thereof, that in use, wherein the extruded profile 203 is positioned substantially vertically, preferably vertical, borders to a lower outer end of the extruded profile 203.

Claims

1. Lift unit (101 , 201) for lifting an object such as a product holder, said lift unit (101 , 201) comprising:

a carriage (107, 207) and an elongated base (103, 203) for translating said carriage (107, 207) in a longitudinal direction (A) with respect to said elongated base (103, 203),

a pulley (1 19, 219) which is rotatable about a first rotation axis (123,

223),

a flexible element (1 13, 213) that is passed over said pulley (1 19, 219), wherein said flexible element (1 13, 213) at a first end thereof is connected to said carriage (107, 207),

a constant-force spring (1 1 1 , 211), connected to said flexible element (1 13, 213) at a second end of said flexible element (113, 213) such that said constant- force spring (1 1 1 , 21 1) is connected to said carriage (107, 207) via said flexible element (1 13, 213), wherein said constant-force spring (1 1 1 , 21 1) is arranged for providing a constant force acting as a counter force to counter the gravity force acting on said carriage (107, 207).

2. Lift unit (101 , 201 ) according to claim 1 , wherein said lift unit (101 , 201) comprises a translation element (109, 209), wherein said carriage (107, 207) is connected to said elongated base (103, 203) via said translation element (109, 209).

3. Lift unit (101 , 201) according to claim 1 or 2, wherein said lift unit (101 , 201 ) comprises an end part (121 , 221) that is connected to said elongated base (103, 203), wherein said pulley (1 19, 219) is provided in said end part (121 , 221).

4. Lift unit (101 , 201) according to claim 3, wherein said end part (121 , 221) provides an end stop for limiting said translation in said longitudinal direction (A).

5. Lift unit (101 , 201) according to any one of the preceding claims, wherein said lift unit (101 , 201) comprises a drive arrangement connected to said pulley (1 19, 219) for rotating said pulley (1 19, 219) about said first rotation axis (123, 223) and thereby translating said carriage (107, 207) in said longitudinal direction (A).

6. Lift unit (101 , 201) according to any one of the preceding claims, wherein a perimeter of said elongated base (103, 203), in a direction perpendicular to said longitudinal direction (A), is closed.

7. Lift unit (201) according to any one of the preceding claims, wherein said constant-force spring (201 ) is arranged in a receiving space provided in said elongated base (203).

8. Lift unit (101 , 201) according to any one of the preceding claims, wherein said flexible element (1 19, 219) comprises a toothed belt and wherein said pulley (1 19, 219) comprises teeth arranged for cooperating with teeth of said toothed belt.

9. Lift unit (101 , 201 ) according to any one of the preceding claims, wherein said counter force, provided by said constant-force spring, to counter said gravity force acting on said carriage is larger than said gravity force acting on said carriage (107, 207).

10. Lift unit (101 , 201) according to any one of the preceding claims, wherein said elongated base (103, 203) comprises an extruded profile.

1 1. Lift unit (1) according to any one of the preceding claims, wherein said elongated base (103, 203) is arranged for attachment of the lift unit (101 , 201 ) to a structure for holding the lift unit (101 , 201).

12. Lift unit (101 , 201) according to claims 2 and 1 1 , wherein said elongated base (103, 203), at a side of said elongated base (103, 203) opposite a side of said elongated base (103, 203) attached to said translation element (109, 209), is arranged for attachment of the lift unit (101 , 201) to a structure for holding the lift unit (101 , 201).

13. Lift unit (101 , 201 ) according to claims 3 and 8, wherein said end part (121 , 221) comprises a pulley receiving space that is bound by an internal wall of said end part (121 , 221 ), wherein said pulley receiving space is dimensioned such that, in use, said internal wall limits a movement of said flexible element (1 13, 213) for maintaining said cooperation between said teeth of said pulley (1 19, 219) and said toothed belt.

14. Lift unit (101 , 201) according to any one of the preceding claims, wherein said force, provided by said constant-force spring, acting as said counter force is within 10 % of a nominal force.

15. Lift unit (101 , 201) according to claim 14, wherein said nominal force is within a range of 50 to 100 N.

16. Lift unit (201) according to any one of the preceding claims, wherein said lift unit comprises a further end part that is connected to said elongated base, wherein said constant-force spring is at least provided in said further end part.

17. Lift unit (101 , 201) according to any one of the preceding claims, wherein said lift unit comprises a further constant-force spring (1 11 , 21 1) for providing a further constant force acting as a further counter force to counter the gravity force acting on said carriage (107, 207).

18. Lift unit (101 , 201) according to claim 17, wherein said constant force spring (11 1 , 21 1) and said further constant-force spring (11 1 , 21 1) are arranged in parallel such that said gravity force acting on said carriage (107, 207) is countered by a force that is equal to a summation of said counter force provided by said constant- force spring (11 1 , 211) and said further counter force provided by said further constant-force spring (1 1 1 , 21 1).