GB2185731A

GB2185731A - Small electro-mechanical linear actuator

Info

Publication number: GB2185731A
Application number: GB08601560A
Authority: GB
Inventors: Stephen George Arnell
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-01-23
Filing date: 1986-01-23
Publication date: 1987-07-29
Also published as: GB8601560D0

Abstract

A small electro-mechanical linear actuator has an electric motor (3), gearing (4-6) and a slipping clutch mechanism (7) contained within one housing assembly (1) with a screw thread mechanism (9-15) which converts rotational movement into linear movement contained in another assembly, the barrel (14) of which may be engaged with or disengaged from the motor housing. Different length barrel assemblies may be screwed into the one motor housing thus enabling it to fit different model configurations such as those made from modular construction kits of the interlocking block type. Mounting holes are provided to allow the actuat`or to be fitted to the models. A slipping clutch (7) is provided to allow the motor to continue to rotate when the limits of travel are reached or the actuator is over loaded, so that the motor does not rapidly overheat. The slipping clutch comprises a spring (7) of U-shape which engages over a flat on the end of threaded shaft (9), the spring allowing rotation of gear-wheel (6) relative to flat (9) on shaft if actuator over-loaded. A disc (8) has light and dark markings to allow an optical sensor (16) to monitor revolutions of shaft (9). <IMAGE>

Description

SPECIFICATION Small electro-mechanical linear actuator This invention relates to a small electro-mechanical linear actuator.

Electro-mechanical linear actuators are used as a compact means of obtaining linear movement for use in a mechanism, without the need for pneumatic or hydraulic cylinders. They are powered by electric motors driving a screw type mechanism via gearing to obtain the necessary linear movement of one part relative to the other.

Electro-mechanical linear actuators are however normally relatively large, expensive, and with a fixed maximum length of travel astheyare made as one assembly,which prohibitstheir use in models and toys, especially in construction kits where several lengths may be required for different models. There is also a requirementto allowfora certain amount of misuse ofthe actuator by children who will not necessarily switch off the power when the limit of travel is reached or the load is too great thus causing overheating of the motor unless some protection is afforded to it.

According to the present invention there is a small electro-mechanical actuator comprising a motor housing assembly which contains an electric motor, reduction gearing and a slipping clutch mechanism, a barrel assembly or barrel assemblies containing a screw mechanism to convert rotational movement into linear movement which may be engaged with and disengaged from the motor housing assembly and the slipping clutch mechanism therein, allowing the substitution of different length barrel assemblies with the one motor housing assembly, the slipping clutch mechanism of which limits the power consumed by the electric motor and prevents the electric motor from rapidly overheating when the limits of travel of the actuator are reached or resistance to movement of the actuator is too great.

Specific embodiments of the invention will now be described by way of examples with reference to the accompanying drawing.

Figure 1. Shows in perspective a complete actuator with a barrel assembly screwed into the motor housing with an indication oftravel shown dotted. There is also another longer barrel assembly shown which could replace the one shown engaged in the motor housing.

Figure 2. Shows in perspective an exploded view ofthe various components.

Figure 3. Shows a full scale section through an assembled actuator.

Figure 4. Shows details of the slipping clutch.

Referring to the drawings, the actuator consists of a motor housing assembly and one or more other barrel assemblies of different lengths each of which may be engaged with the motor housing assembly.

The motor housing 1 contains the motor 3 with its pinion gear 4which drives the intermediate gear 5 which revolving on a pin in the housing end plate 2 drives the clutch assembly comprising the final gear 6, containing the clutch spring 7, held in place by the retaining disc 8.

Each barrel assembly comprises a screwthreaded shaft 9 with a groove near one end for a circlip 10, and with flats machined on the same end. The screw shaft runs within a threaded boss 12 which is fastened into a tube 11 which hasa rod end 13fixed at its other end. The tube is free to slide within a barrel 14, being limited in its travel by the barrel end 15.

A barrel assembly may be screwed into the motor housing assembly, the circlip 10 on the screw shaft 9 being locked in position when the barrel is tightened.

As the barrel assembly is screwed into the motor housing the end of the screw shaft slides through the final gear 6, in which it is free to rotate, and the machined flats pass through the clutch spring 7 located within the gear 6 and also through the retaining disc8. The disc is a snap fit into the gear 6 but is free to rotate independent of it. When barrel and housing are assembled the circlip allowsthe screwshaftto rotate and acts as a thrust bearing in both directions.

To change the length of the actuatorthe first barrel is unscrewed from the housing and another of different length is screwed in its place.

When a voltage is applied to the motor the clutch spring 7 being fixed within the final gear 6 rotates with it and exerts pressure on the flats ofthe screw shaft 9 rotating it and thus causing the tube assembly 11, 12 and 13 to move along the screwshaft. When the travel of the tube assembly is arrested by the barrel end 15 or by an external force then the screwshaftstopsrotating and theclutch spring distorts and slips round the flats of the screwshaft allowing the motor and geartraintocontinueto rotate until power is removed from the motor.

On reversal of the voltage applied to the motorthe pressure of the clutch spring on the flats of the screwshaft rotates it in the opposite direction and the tube assembly moves in the opposite direction until its travel is again arrested or power is removed orthe voltage reversed again.

In order to apply the actuator to a model, toy, or construction kit, pivot pins may be inserted through the housing 1 and the rod end 13which allow itto connect to a mechanism, e.g.the tipping mechanism on a model tipping lorry.

The provision of different length barrel assemblies enables the actuator to be adapted to several models which may be made with a construction kit without requiring more than one motor housing assembly.

There is an additional item, an optical sensor 16 which may befitted to the housing end plate 2 so that it can monitor revolutions ofthe screwshaft by means of light and dark markings on the retaining disc 8 which revolves with the screwshaft. This enables the position of the actuator to be controlled bya computerorsimilardevice. Slipping ofthe clutch during any overload situation does not affect the monitored position of the actuator as revolutions ofthe screwshaft are monitored and not of the motor orgears.

1. Asmall electro-mechanical actuator

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Small electro-mechanical linear actuator This invention relates to a small electro-mechanical linear actuator. Electro-mechanical linear actuators are used as a compact means of obtaining linear movement for use in a mechanism, without the need for pneumatic or hydraulic cylinders. They are powered by electric motors driving a screw type mechanism via gearing to obtain the necessary linear movement of one part relative to the other. Electro-mechanical linear actuators are however normally relatively large, expensive, and with a fixed maximum length of travel astheyare made as one assembly,which prohibitstheir use in models and toys, especially in construction kits where several lengths may be required for different models. There is also a requirementto allowfora certain amount of misuse ofthe actuator by children who will not necessarily switch off the power when the limit of travel is reached or the load is too great thus causing overheating of the motor unless some protection is afforded to it. According to the present invention there is a small electro-mechanical actuator comprising a motor housing assembly which contains an electric motor, reduction gearing and a slipping clutch mechanism, a barrel assembly or barrel assemblies containing a screw mechanism to convert rotational movement into linear movement which may be engaged with and disengaged from the motor housing assembly and the slipping clutch mechanism therein, allowing the substitution of different length barrel assemblies with the one motor housing assembly, the slipping clutch mechanism of which limits the power consumed by the electric motor and prevents the electric motor from rapidly overheating when the limits of travel of the actuator are reached or resistance to movement of the actuator is too great. Specific embodiments of the invention will now be described by way of examples with reference to the accompanying drawing. Figure 1. Shows in perspective a complete actuator with a barrel assembly screwed into the motor housing with an indication oftravel shown dotted. There is also another longer barrel assembly shown which could replace the one shown engaged in the motor housing. Figure 2. Shows in perspective an exploded view ofthe various components. Figure 3. Shows a full scale section through an assembled actuator. Figure 4. Shows details of the slipping clutch. Referring to the drawings, the actuator consists of a motor housing assembly and one or more other barrel assemblies of different lengths each of which may be engaged with the motor housing assembly. The motor housing 1 contains the motor 3 with its pinion gear 4which drives the intermediate gear 5 which revolving on a pin in the housing end plate 2 drives the clutch assembly comprising the final gear 6, containing the clutch spring 7, held in place by the retaining disc 8. Each barrel assembly comprises a screwthreaded shaft 9 with a groove near one end for a circlip 10, and with flats machined on the same end. The screw shaft runs within a threaded boss 12 which is fastened into a tube 11 which hasa rod end 13fixed at its other end. The tube is free to slide within a barrel 14, being limited in its travel by the barrel end 15. A barrel assembly may be screwed into the motor housing assembly, the circlip 10 on the screw shaft 9 being locked in position when the barrel is tightened. As the barrel assembly is screwed into the motor housing the end of the screw shaft slides through the final gear 6, in which it is free to rotate, and the machined flats pass through the clutch spring 7 located within the gear 6 and also through the retaining disc8. The disc is a snap fit into the gear 6 but is free to rotate independent of it. When barrel and housing are assembled the circlip allowsthe screwshaftto rotate and acts as a thrust bearing in both directions. To change the length of the actuatorthe first barrel is unscrewed from the housing and another of different length is screwed in its place. When a voltage is applied to the motor the clutch spring 7 being fixed within the final gear 6 rotates with it and exerts pressure on the flats ofthe screw shaft 9 rotating it and thus causing the tube assembly 11, 12 and 13 to move along the screwshaft. When the travel of the tube assembly is arrested by the barrel end 15 or by an external force then the screwshaftstopsrotating and theclutch spring distorts and slips round the flats of the screwshaft allowing the motor and geartraintocontinueto rotate until power is removed from the motor. On reversal of the voltage applied to the motorthe pressure of the clutch spring on the flats of the screwshaft rotates it in the opposite direction and the tube assembly moves in the opposite direction until its travel is again arrested or power is removed orthe voltage reversed again. In order to apply the actuator to a model, toy, or construction kit, pivot pins may be inserted through the housing 1 and the rod end 13which allow itto connect to a mechanism, e.g.the tipping mechanism on a model tipping lorry. The provision of different length barrel assemblies enables the actuator to be adapted to several models which may be made with a construction kit without requiring more than one motor housing assembly. There is an additional item, an optical sensor 16 which may befitted to the housing end plate 2 so that it can monitor revolutions ofthe screwshaft by means of light and dark markings on the retaining disc 8 which revolves with the screwshaft. This enables the position of the actuator to be controlled bya computerorsimilardevice. Slipping ofthe clutch during any overload situation does not affect the monitored position of the actuator as revolutions ofthe screwshaft are monitored and not of the motor orgears. CLAIMS

1. Asmall electro-mechanical actuator comprising a motor housing assemblywhich contains an electric motor, reduction gearing and a slipping clutch mechanism, a barrel assembly or barrel assemblies containing a screw mechanism to convert rotational movement into linear movement which may be engaged with and disengaged from the motor housing assembly and slipping clutch mechanism therein, allowing the substitution of different length barrel assemblies with the one motor housing assembly, the slipping clutch mechanism ofwhich limits the power consumed by the electric motor and prevents the electric motor from rapidly overheating when the limits of travel of the actuator are reached or resistance to movement of the actuator is too great.

2. A small compact electro-mechanical actuator as claimed in Claim 1 wherein means are provided in or about the motor housing assembly to include a disc and sensor to enable the motion of the actuator to be monitored and controlled by external electronic or electrical devices.

3. A small compactelectro-mechanical actuator as claimed in Claim 1 or Claim 2wherein a screw mechanism is provided with a thrust bearing in the form of a circlip running in a groove in a screwed shaft.

4. A small compact electro-mechanical actuator as claimed in Claim 3 in which the barrel assembly or barrel assemblies are located within the motor housing assembly by means of a screw thread.

5. A small compact electro-mechanical actuator substantially as described herein with reference to Figures 1-4 ofthe accompanying drawing.