MULTI-TURN LIMITING DEVICE AND METHOD OF LIMITING THE MOVEMENT OF A MOTOR DRIVEN ELEMENT

Abstract

A multi-turn limiting device for limiting movement of an element driven by a motor includes a sensor configured to provide a sensor signal corresponding to a position of the element, a movable member mechanically couplable to the element via a transmission having a non-unitary first transmission ratio and a further sensor configured to provide a further sensor signal corresponding to the position of the movable member. A controller switches the motor via a switching signal determined on the basis of the two sensors. A method of limiting movement of an element driven by a motor includes sensing the position of the element using two sensors and a movable member which is coupled to the element via a non-unitary transmission ratio.

Claims

1. A multi-turn limiting device for limiting movement of an element driven by a motor, the limiting device comprising: a memory configured to store a value corresponding to a limit position of the element; a sensor configured to provide a sensor signal corresponding to a position of the element; an output for providing a switching signal to the motor, and a controller connected to the sensor for receiving the sensor signal and to the memory for retrieving the value and to the output for providing the switching signal, wherein the controller is configured to provide the switching signal depending on the sensor signal and the value; and wherein the multi-turn limiting device further comprises: a movable member, the movable member being mechanically couplable to the element via a transmission having a non-unitary first transmission ratio; and a further sensor configured to provide a further sensor signal corresponding to the position of the movable member, and wherein the controller is further connected to the further sensor for receiving the further sensor signal, and wherein the controller is configured to provide the at least one switching signal further depending on the further sensor signal.

2. The limiting device according to claim 1, wherein the sensor and optionally the further sensor is an angular position sensor.

3. The limiting device according to claim 2, wherein the sensor and optionally the further sensor is a hall-effect sensor.

4. The limiting device according to claim 1, comprising a second movable member, the second movable member being mechanically couplable to the element via a second transmission having a second transmission ratio, the second transmission ratio being different from the first transmission ratio, wherein the sensor is configured to provide the sensor signal depending on the position of the second movable member.

5. The limiting device according to claim 4, wherein the first transmission ratio expressed in integers is $\frac{p_1}{q_1}$ and the second transmission ratio expressed in integers is $\frac{p_2}{q_2},$ wherein $\left(n\frac{p_1}{q_1}\right)\mathrm{mod}1=\left(n\frac{p_2}{q_2}\right)\mathrm{mod}1$ has no non-zero integer solutions for n below 25.

6. The limiting device according to claim 1, wherein the controller is configured to compare the sensor signal and the further signal, and to provide an error signal based on said comparison.

7. The limiting device according to claim 1, comprising a movable engaging member for engaging the element, the engaging member being mechanically coupled to at least the movable member and optionally to the further movable member.

8. The limiting device according to claim 1, wherein at least one of the following comprises cogs: the movable member, the second movable member, and the engaging member.

9. The limiting device according to claim 8, wherein the engaging member is provided with two sets of cogs of which the amount of cogs differs mutually.

10. The limiting device according to claim 8, wherein the movable member and the second movable member are both provided with a set of cogs of which the amount of cogs differs mutually.

11. The limiting device according to claim 1, further comprising a housing, wherein at least the controller, the sensor, the movable member, and the further sensor are housed in the housing, the output being provided to the exterior of the housing.

12. The limiting device according to claim 11, the housing defining an infeed for an axle, the axle being the element driven by the motor.

13. An assembly of a multi-turn limiting device according to claim 13 and an element that is drivable by a motor, the limiting device engaging the element with the engaging member for mechanically coupling at least the movable member and optionally the further movable member to the element, wherein optionally the assembly further comprises a motor connected to the element for driving it.

14. A method of limiting the movement of an element driven by a motor, the method comprising: sensing a position of the element; sensing a position of a movable member which is mechanically coupled to the element via a transmission having a non-unitary first transmission ratio; comparing the sensed positions with a predefined limit position; and switching the motor based on said comparison.

15. The method according to claim 14, wherein sensing the position of the element comprises sensing a position of a second movable member which is mechanically coupled to the element via a second transmission ratio different from the first transmission ratio.

16. The limiting device according to claim 4, wherein the first transmission ratio expressed in integers is $\frac{p_1}{q_1}$ and the second transmission ratio expressed in integers is $\frac{p_2}{q_2},$ wherein $\left(n\frac{p_1}{q_1}\right)\mathrm{mod}1=\left(n\frac{p_2}{q_2}\right)\mathrm{mod}1$ has no non-zero integer solutions for n below 40.

17. The limiting device according to claim 4, wherein the first transmission ratio expressed in integers is $\frac{p_1}{q_1}$ and the second transmission ratio expressed in integers is $\frac{p_2}{q_2},$ wherein $\left(n\frac{p_1}{q_1}\right)\mathrm{mod}1=\left(n\frac{p_2}{q_2}\right)$ mod 1 has no non-zero integer solutions for n below 50.

18. The limiting device according to claim 4, wherein the first transmission ratio expressed in integers is $\frac{p_1}{q_1}$ and the second transmission ratio expressed in integers is $\frac{p_2}{q_2},$ wherein $\left(n\frac{p_1}{q_1}\right)\mathrm{mod}1=\left(n\frac{p_2}{q_2}\right)\mathrm{mod}1,$ and wherein the lowest non-zero integer solution is n=57.

Description

[0050] The invention will be further elucidated with reference to the attached figures, in which:

[0051] FIG. 1 schematically shows a perspective view of a greenhouse;

[0052] FIG. 2 schematically shows a perspective view of a motor driving an element;

[0053] FIG. 3 schematically shows a perspective view of a multi-turn limiting device;

[0054] FIG. 4 schematically shows an exploded view of the limiting device of FIG. 3; and

[0055] FIG. 5 schematically shows a top view of the inside of the limiting device of FIGS. 3 and 4.

[0056] Throughout the figures, like elements will be referred to using like reference numerals.

[0057] FIG. 1 shows a greenhouse 1 which has transparent walls and a transparent roof 2. The greenhouse 1 shown has an opened window 3 and a closed window 4. Both windows 3, 4 can be hinged open or closed by moving a rod 5 from within the greenhouse 1. In practice, greenhouses have many more windows 3, 4, and series of windows are operated simultaneously by driving their respective rods 5.

[0058] The driving force usually comes from an electric motor 6 (see FIG. 2) mounted on a frame 7 within the greenhouse 1. In this example, the electric motor 6 feeds a gearbox 8 in order to rotate a shaft 9. The shaft 9 transfers force to all windows 3, 4 driven by the motor 6. As an example, the shaft 9 is shown connect to a pinion 10 via a rack (not shown) placed inside a mounting box 11. The pinion 10 may be directly connected to the rod 5 for opening a window 3, 4. As such, it can be seen that rotation of the shaft 9 controls movement of the window 3, 4. In order to prevent damage to the windows 3, 4, the motor 6, the greenhouse 1 or other elements therein/thereof, the movement of the windows 3, 4 must be limited to their allowed range of motion, i.e. to anywhere between their fully closed and fully opened position. As rotation of the shaft 9 defines movement of the windows 3, 4, the movement of the windows 3, 4 can principally be limited by limiting movement of the shaft 9 to within a range that corresponds to an allowed range of motion of the windows 3, 4.

[0059] In order to do so, a limiting device 12 is connected to the shaft 9. The limiting device 12 provides a switching signal to the motor 6. The motor 6 responds to the limiting signal by driving the shaft 9 in accordance with the switching signal. The switching signal may accordingly command the motor 6 to drive the shaft in a particular direction, and/or to stop rotation. In practice, the switching signal is simply the motor current, however another analog or digital switching signal could also be used.

[0060] In order to fully open or close the window 3, 4, the shaft 9 must rotate multiple times. As such, within the range of motion of the window 3, 4, the shaft 9 has the same angular position several times. Thus it is impossible to uniquely determine the position of the window 3, 4 from the angular position of the shaft 9 by itself. Therefore, multi-turn limiting devices exist that track rotation of the shaft 9 and determine the position of the windows 3, 4 accordingly.

[0061] The limiting device 12 as described herein is such a multi-turn limiting device 12, as it allows distinguishing between several positions of the element across multiple turns thereof. The multi-turn limiting device 12 will be described in further detail below with reference to FIGS. 3-5, without further reference to the windows 3, 4, shaft 9 or greenhouse 1, because the invention can also be applied for limiting the movement of greenhouse screens, but also for limiting other components actuated by an element which rotates more than one full turn within the range of motion of the component.

[0062] The multi-turn limiting device 12 comprises a housing 15, 16 with a feed-through 14 for an axle. The housing 15, 16 consists of a bottom part 15 and a top part 16, which are mounted to each other using snap connectors 17. On the exterior of the housing 15, 16, an output 18 is provided in the form of several electric connectors. By attaching wires to the electric connectors of the output 18, signals provided by the multi-turn limiting device 12 can be used elsewhere.

[0063] In FIGS. 4 and 5, it can be seen that the multi-turn limiting device includes an engagement member 19 which has a through-hole lining up with the feed-through 14. The engagement member 19 has a spline 20, with which it can be connected to an axle. The spline 20 transfers rotational movement of the axle to the engagement member 19. The engagement member 19 has two different set of cogs 21, 22, which rotate together with each other and the spline 20.

[0064] The first set of cogs 21 is connected to a movable element 23 via a set of cogs 24 thereof. Accordingly, rotation of the engaging member 19 is transferred to the movable element 23 via a transmission ratio defined by the two interacting sets of cogs 21, 24. The second set of cogs 22 is connected to a second movable element 25 via a set of cogs 26 thereof. Accordingly, rotation of the engaging member 19 is transferred to the second movable element 25 via a transmission ratio defined by the two interacting sets of cogs 22, 26.

[0065] Two permanent magnets 27, 28 are mounted in a receiving space of the movable elements 23, 25 respectively, so that they rotate with the movable elements 23, 25. The limiting device 12 further includes a printed circuit board 29, to which several components are attached. For the sake of clarity, the components of the printed circuit board 29 are shown separate form the board in FIG. 4. Among the components are two Hall-effect sensors 30, 31, which are configured for measuring the angular position of the movable element 23 and the second movable element 25 by means of the magnetic field caused by the permanent magnets 27, 28. Since the angular position of the movable elements 23, 25 is coupled to movement of the engaging member 19, and therefore can be coupled to the movement of the element driven by the motor, the Hall-effect sensors 30, 31 indirectly measure the angular position of the element. However, as the transmission from the element to the movable element 23, 25 is different for each sensor 30, 31, the sensor measurements are related, but not equal. The sensors 30, 31 are connected to a controller 32, which receives signals from the sensors 30, 31. The controller 32 provides a switching signal at the output 18. The controller has a built-in memory, however an external memory could also be used.

[0066] Every movement of the element causes a corresponding movement of the movable elements 23, 25. As long as a movement of the element does not result in an integer amount of rotations of both movable elements 23, 25, the combination of readings from the sensors 30, 31 is unique. Thus, said combinations are unique within a predetermined range. The range is determined by the number of turns of the element between two equal combinations of positions of both movable elements 23, 25. By selecting suitable transmission ratios, the range may be relatively wide. In the limiting device 12 shown in the figures, the engaging member has two sets of cogs, having 26 and 35 cogs respectively. The movable element 23 has 19 cogs and gears with the 35 cogs of the engaging member 19. The second movable element has 39 cogs and meshes with the 26 cogs of the engaging member 19.

[0067] Accordingly, for n rotations of the engaging member 19, the movable element 23 moves

[00005]$m_1=n.Math.\frac{35}{19}$

rotations, and the second movable element 25 moves

[00006]$m_2=n.Math.\frac{26}{39}$

rotations. When n=57, m.sub.1=105 and m.sub.2=38. No lower n exist for which both m.sub.1 and m.sub.2 are integers. As such, between 0 and 57 rotations of the engaging element, each combination of angular positions of the movable elements 23, 25 is unique. Of course, the engaging member 19 could be coupled to the element via a unitary transmission or some other transmission. Nevertheless, by using the two different transmissions to the sensors, the position of the engaging member 19, and therefore also the element, can be uniquely determined over a relatively large range.

[0068] Although the invention has been described hereabove with reference to a number of specific examples and embodiments, the invention is not limited thereto. Instead, the invention also covers the subject matter defined by the claims, which now follow.