Anti-pinch electric linear actuator

Abstract

An electric motor 10 driven linear actuator has an inner tube 30 extending into an outer tube 20, a lead screw 40 with a nut 50 screwed onto it inside the tubes, the nut 50 having an abutment portion

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001 ] The present invention relates generally to an electric linear actuator, and more particularly to an anti-pinch electric linear actuator adapted for being used in electric beds, chairs, or the like for providing an anti-pinch function. 2. Description of the Related Art

[0002] Electric linear actuators are commonly used as driving components in electric beds. An example includes U.S. Pat. No. 11,399,998, which discloses a foldable bed with linear actuators that move and allow the adjustment of the back support frame and the thigh support frame relative to the base frame of the bed. When the electric linear actuator extends, it drives the back supporting frame or the thigh supporting frame to swing upwards relative to the base frame of the bed. Conversely, when the electric linear actuator retracts, the back supporting frame or the thigh supporting frame swings downwards relative to the base frame. Taking the swing motion of the back supporting frame for example, when the back supporting frame swings downwards and approaches the base frame, if children, pets, or human hands or feet accidentally enter the space between the back supporting frame and the base frame, they may be pinched or crushed by the electric bed. Similarly, if other objects like furniture are mistakenly placed in the aforesaid space, they might get damaged or damage the electric bed. Therefore, preventing the electric bed from pinching people, other living beings, or objects has become an issue in the industry that needs to be addressed. SUMMARY OF THE INVENTION

[0003] The present invention has been accomplished in view of the above-noted circumstances. It is an objective of the present invention to provide an anti-pinch electric linear actuator, which can effectively prevent people, other living beings, or objects from being pinched or crushed by the movement of part of the electric bed or chair during the operation of the electric bed or chair.

[0004] To attain the above and other objectives, the present invention provides an anti-pinch electric linear actuator comprising an outer tube, an inner tube, a lead screw, a nut, and a sensing unit. The inner tube extends into the outer tube in a way that the inner tube has an inner end located inside the outer tube, and an outer end located outside the outer tube. The lead screw extends inside the outer tube and the inner tube. The nut is screwed onto the lead screw and located inside the outer tube. The nut has an abutment portion, against which the inner end of the inner tube is stoppable. The sensing unit is disposed to the outer tube, the inner tube, or the nut for detecting whether the abutment portion of the nut is in contact with the inner end of the inner tube.

[0005] With the above-mentioned technical features, when the nut is driven by the lead screw to move outward, the abutment portion may push the inner tube to extend outward. When the nut is driven by the lead screw to move inward and the inner tube does not receive an axially external force, the inner tube may stay in place and disengage from the abutment portion of the nut. When the nut is driven by the lead screw to move inward and the inner tube receives the axially external force, the inner tube may abut against the abutment portion and move inward along with the nut. As a result, the anti-pinch electric linear actuator may effectively prevent people, other living beings, or objects from being pinched while it is used in an electric bed or chair during the operation of the electric bed or chair.

[0006] The anti-pinch electric linear actuator of the present invention comprises an outer tube; an inner tube extending into the outer tube in a way that the inner tube has an inner end located inside the outer tube, and an outer end located outside the outer tube; a lead screw extending inside the outer tube and the inner tube; a nut screwed onto the lead screw and located inside the outer tube, the nut having an abutment portion, against which the inner end of the inner tube is stoppable; and a sensing unit disposed to the outer tube, the inner tube, or the nut for detecting whether the abutment portion of the nut is in contact with the inner end of the inner tube. The sensing unit comprises two conductive wires disposed on the inner tube; each of the two conductive wires has a contact end located at the inner end of the inner tube; when the two contact ends of the two conductive wires are in contact with the abutment portion of the nut, the two conductive wires are electrically connected with each other. The abutment portion of the nut is a conductive gasket. The nut is driven by the lead screw to move outward, the abutment portion pushes the inner tube to extend outward; when the nut is driven by the lead screw to move inward and the inner tube does not receive an axially external force, the inner tube stays in place and disengages from the abutment portion of the nut; when the nut is driven by the lead screw to move inward and the inner tube receives the axially external force, the inner tube abuts against the abutment portion and moves inward along with the nut. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention.

[0008] FIG. 1 is a perspective view of an anti-pinch electric linear actuator according to a first preferred embodiment of the present invention.

[0009] FIG. 2 is a cut-away cross-sectional view of the anti-pinch electric linear actuator, showing the main components of the first preferred embodiment of the present invention.

[0010] FIG. 3 is a cross-sectional schematic view showing the anti-pinch electric linear actuator of the first preferred embodiment of the present invention - showing in use without something blocking the moving frame. [0011 ] FIG 4 is a cross-sectional schematic view showing the anti-pinch electric linear actuator of the first preferred embodiment of the present invention - with something blocking the movable frame, and the sensor disengaged.

[0012] FIG. 5 is a sectional view of a part of an anti-pinch electric linear actuator according to a second preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] The structure and technical features of the present invention will be described in detail hereunder by two embodiments and accompany drawings. As shown in FIGS. 1-2, an anti-pinch electric linear actuator 1 provided by a first preferred embodiment of the present invention comprises a motor 10, an outer tube 20, an inner tube 30, a lead screw 40, a nut 50, and a sensing unit 60. For convenience of illustration, the left side of FIG. 1 is referred to as the base side, and the right side is referred to as the moving side. There is a base attachment 71 that attaches the linear actuator 1 to the base frame of the bed or other article of furniture, and an adjustable frame attachment 73 that attaches the moving end of the linear actuator to the adjustable frame of the bed, or other moving portion of an article of furniture.

[0014] The motor 10 serves as the power source for the anti-pinch electric linear actuator 1. The motor is mounted at the base side of the outer tube, and rotates the lead screw 40. The nut 50 is disposed on the lead screw 40 and moves towards or away from the motor 10 depending upon which way the lead screw 40 is rotated. The outer tube 20 extends in a direction perpendicular to the output shaft of the motor 10. However, in other embodiments, there is no limitation on the relative angle between the outer tube 20 and the output shaft of the motor 10. The inner tube 30 extends into the outer tube 20 and can extend outwards and extract inwards relative to the outer tube 20. That is, the outer tube 20 and the inner tube 30 collectively serve as a telescope tube. The inner tube 30 has an inner end 31 located inside the outer tube 20, and an outer end 32 located outside the outer tube 20. The lead screw 40 is rotatably attached adjacent to the motor, extends inside the outer tube 20 and the inner tube 30, and is drivable by the motor 10 to rotate.

[0015] The nut 50 is screwed onto the lead screw 40 and located inside the outer tube 20 and the inner tube 30. When the motor 10 rotates it turns the lead screw 40, and the nut 50 moves up away from the motor 10 or down towards the motor along the lead screw 40. The nut 50 has a large diameter portion 51, a small diameter portion 52 located at the front end of the large diameter portion 51 and extending into the inner tube 30, and an abutment portion 53 located at the junction of the large diameter portion 51 and the small diameter portion 52 for being stopped by the inner end 31 of the inner tube 30. Generally the inner end 31 abuts the abutment portion 53, and as the lead screw 40 turns the nut 50 pushes the inner tube 30 away from the motor 10. The outer diameter of the small diameter portion 52 is smaller than that of the large diameter portion 51, and the abutment portion 53 may comprise or be realized as an electrically conductive gasket.

[0016] The sensing unit 60 includes two conductive wires 61 disposed on the inner tube 30. The two conductive wires 61 extend from the inner end 31 along the wall of the inner tube 30 towards the outer end 32, and further extend outwardly to electrically connect to a controller (not shown). The two conductive wires 61 each have a contact end 62 located at the inner end 31 of the inner tube 30. When the two contact ends 62 contact the abutment portion 53 of the nut 50, the two conductive wires 61 are electrically connected with each other, and this electrical connection can be sensed by the controller. In this way, the sensing unit 60 can detect whether the abutment portion 53 of the nut 50 is in contact with the inner end 31 of the inner tube 30. To simplify components, the nut 50 may be made of conductive material, meaning that the abutment portion 53 is not an independent component but a part of the nut 50.

[0017] With the above-disclosed structural features, when the nut 50 is driven by the lead screw 40 to move outward and away from the motor 10, the abutment portion 53 pushes the inner tube 30 to force the inner tube 30 to extend outward from the outer tube 20, as shown in FIG. 3. In operation on a bed, this forces the adjustable frame attachment 73 away from the base attachment, and moves the movable portion of the bed, either the adjustable back support frame or the adjustable thigh support frame, rotating them upwardly. When the nut 50 is driven by the lead screw 40 to move inward towards the motor, thus rotating the back support or thigh support frames downwardly, there are two scenarios: one is when the inner tube 30 receives an axially external force, the inner tube 30 still abuts against the abutment portion 53 and moves inward along with the nut 50 to retract into the outer tube 20, as shown in FIG. 2; the other is when the inner tube 30 does not receive an axially external force, the inner tube 30 stays in place and disengages from the abutment portion 53 of the nut 50, as shown in FIG. 4. This is explained in more detail below.

[0018] This can be explained best when the anti-pinch electric linear actuator 1 is installed on an electric bed (not shown). When the motor 10 turns the lead screw 40 the nut 50 moves outward and causes the inner tube 30 to extend outward, the back supporting frame (or thigh supporting frame) will swing upward relative to the base frame. Conversely, when the nut 50 moves inward, because the gravitational force of the back supporting frame (or thigh supporting frame) exerts on the inner tube 30, the inner tube 30 will abut against the abutment portion 53 and then move inward along with the nut 50 to retract into the outer tube 20, such that the back supporting frame swings downward relative to the base frame. When any object, including people, pets or other living beings, or objects are jammed between the back supporting frame and the base frame, the back supporting frame is unable to continue swing downward due to the obstruction of the foreign objects, resulting in that the axially external force applied by the back supporting frame to the inner tube 30 is counteracted by the foreign objects. At this time, the inner tube 30 no longer receives the axially external force, such that the inner tube 30 will stay in place and the inner end 31 will disengage from the abutment portion 53 of the nut 50 and break the electronic connection between the components. As soon as the sensing unit 60 senses that the abutment portion 53 of the nut 50 has disengaged from the inner end 31 of the inner tube 30, the sensing unit 60 immediately sends a signal to the controller. After receiving this signal, the controller may control the anti-pinch electric linear actuator 1 to reverse its direction of rotation, causing the nut 50 to stop moving or even move outward, thereby extending the inner tube 30 again and driving the back supporting frame to swing upward, releasing the pressure of the back supporting frame against the foreign objects. Thus, the anti-pinch electric linear actuator 1 effectively prevents injuries to people, other living beings, or objects during the operation of the electric bed or chair, thereby achieving the objective of the present invention.

[0019] Based on the above-mentioned structural features, various modifications to the anti-pinch electric linear actuator 1 may be made. For example, FIG. 5 shows a part of an anti-pinch electric linear actuator 1 provided by a second preferred embodiment of the present invention. The antipinch electric linear actuator 1 provided in this embodiment is basically similar to that of the first embodiment, except that that the sensing unit 60 further comprises a micro limit switch 63 disposed at the inner end 31 of the inner tube 30 and electrically connected with the two conductive wires 61. When the inner end 31 of the inner tube 30 abuts against the abutment portion 53 of the nut 50, the limit switch 63 is pressed by the abutment portion 53. When the inner end 31 of the inner tube 30 disengages from the abutment portion 53 of the nut 50 due to the presence of an object blocking the movement of the adjustable frame, the limit switch 63 is no longer pressed by the abutment portion 53. The signal of the limit switch 63 can be transmitted to the controller through the two conductive wires 61, thus achieving the effect of anti-pinch. In other embodiments, the sensing unit may be disposed at the nut 50, and the limit switch 63 may be disposed at the abutment portion 53.

[0020] Furthermore, the sensing unit may be realized by any suitable types of sensors, such as optical sensing devices (for example, infrared sensing devices or laser sensing devices) or magnetic reed switches, and may be installed on the inner tube 30, the outer tube 20, or the nut 50. Any such readily conceivable structural changes should be encompassed within the scope of the claims of the patent application.

Claims

We claim:

1. An anti-pinch electric linear actuator, comprising:an outer tube;an inner tube extending into the outer tube in a way that the inner tube has an inner end located inside the outer tube, and an outer end located outside the outer tube;a lead screw extending inside the outer tube and the inner tube;a nut screwed onto the lead screw and located inside the outer tube, the nut having an abutment portion, against which the inner end of the inner tube is stoppable; anda sensing unit disposed to the outer tube, the inner tube, or the nut for detecting whether the abutment portion of the nut is in contact with the inner end of the inner tube.

2. The anti-pinch electric linear actuator of claim 1:wherein the sensing unit comprises two conductive wires disposed on the inner tube;each of the two conductive wires has a contact end located at the inner end of the inner tube; when the two contact ends of the two conductive wires are in contact with the abutment portion of the nut, the two conductive wires are electrically connected with each other.

3. The anti-pinch electric linear actuator of claim 2, wherein the abutment portion of the nut is a conductive gasket.

4. The anti-pinch electric linear actuator of claim 1, wherein the sensing unit comprises a limit switch disposed at the inner end of the inner tube or at the abutment portion of the nut.

5. The anti-pinch electric linear actuator of claim 1, wherein the sensing unit comprises an optical sensing device or a magnetic reed switch.

6. The anti-pinch electric linear actuator of anyone of claims 1-5:wherein when the nut is driven by the lead screw to move outward, the abutment portion pushes the inner tube to extend outward; when the nut is driven by the lead screw to move inward and the inner tube does not receive an axially external force, the inner tube stays in place and disengages from the abutment portion of the nut; when the nut is driven by the lead screw to move inward and the inner tube receives the axially external force, the inner tube abuts against the abutment portion and moves inward along with the nut.AMENDMENTS TO THE CLAIMS HAVE BEEN FILED AS FOLLOWS:-02 04 25CLAIMSWe claim:I. An electric linear actuator, comprising:an outer tube;an inner tube extending into the outer tube in a way that the inner tube has an inner end located inside the outer tube, and an outer end located outside the outer tube;a lead screw extending inside the outer tube and the inner tube;a nut screwed onto the lead screw and located inside the outer tube, the nut having an abutment portion, against which the inner end of the inner tube is stoppable; anda sensing unit disposed to the outer tube, the inner tube, or the nut for detecting whether the abutment portion of the nut is in contact with the inner end of the inner tube.

2. The electric linear actuator of claim 1:wherein the sensing unit comprises two conductive wires disposed on the inner tube;each of the two conductive wires has a contact end located at the inner end of the inner tube; when the two contact ends of the two conductive wires are in contact with the abutment portion of the nut, the two conductive wires are electrically connected with each other.

3. The electric linear actuator of claim 2, wherein the abutment portion of the nut is a conductive gasket.

4. The electric linear actuator of claim 1, wherein the sensing unit comprises a limit switch disposed at the inner end of the inner tube or at the abutment portion of the nut.02 04 255. The electric linear actuator of claim 1, wherein the sensing unit comprises an optical sensing device or a magnetic reed switch.

6. The electric linear actuator of anyone of claims 1-5:wherein when the nut is driven by the lead screw to move outward, the abutment portion pushes the inner tube to extend outward; when the nut is driven by the lead screw to move inward and the inner tube does not receive an axially external force, the inner tube stays in place and disengages from the abutment portion of the nut; when the nut is driven by the lead screw to move inward and the inner tube receives the axially external force, the inner tube abuts against the abutment portion and moves inward along with the nut.

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