DESC:FIELD OF INVENTION
The present invention introduces a modified electric rod style linear actuator. More preferably, the present invention is a new technology for powering a linear actuator for heavy weight lifting. Wherein, the invention uses a stepper motor to operate the modified linear actuator. This invention provides a compact and portable linear actuator for lifting or pushing a very high load, more specifically it can be used to lift a 600 kg or more weight. It is useful to area wherein space constrains and it does not use any oil cylinder or compressor so one can easily use for heavy duty application in small working area.

BACKGROUND OF THE INVENTION
An actuator is a component of a machine that is responsible for moving by converting the source energy into mechanical motion. Generally, Hydraulic and pneumatic cylinders inherently produces a linear motion. But in electric actuators, the mechanisms are used to generate linear motion from a rotating motor.
Hence, electrical actuators can be used primarily in automation applications when a machine component, tool, etc. requires a controlled movement to a particular position. Typical applications include opening and closing dampers, locking doors, braking machine motions, etc. Wherein, an electric linear actuator is a device that converts the rotational motion of AC or DC motor into linear motion – that is, it will provide both push and pull movements. By pushing and pulling it is possible to lift, drop, slide, adjust, tilt, push or pull objects, simply by pushing a button.
There are numerous compact types of actuators are known for application in incorporation in furniture, hospital and nursing beds. And working of those are possibly hydraulic or pneumatic. Since these actuators are fully or partly with an additional requirement of oil tank or compressor, that the actuators are not compact and not portable.
Second type of actuators are called a linear actuator (Ball screw/nut screw based) that is driven by a DC power source is known as a DC linear actuator that easily meet various industrial requirements due to their advantages like maintenance free, controllability, reduce downtime. But it fails to provide a heavy-duty load application.
In the heavy-duty applications such as bending very thick plates or lifting a heavy load, such DC motor actuator cannot be use due to its inability to withstand a force and often fails at industrial performance.
Therefore, the inventors of the present invention developed the modified rod style linear actuator to make it feasible for heavy duty such as lifting of load upto 600 Kg, more preferably 1000 Kg, and more preferably 1500 kg. The developed linear actuator is driven by 1.8º hybrid stepper motor and hence compact as well as applicable for heavy-duty industrial applications. Stepper motor gives very high torque at low rpm, almost twice that of the DC motors.
A modified design of heavy-duty actuator without a compressor housing or oil tank housing for industrial purposes is based on a nut-screw actuator with an integrated load bearing mounting from which the forces are transmitted. Hence, the said modified actuator is suitable for lifting or exerting a high load. Stepper motor driven linear actuators are also more accurate, the accuracy is in microns compared to that of DC linear actuators. Stepper motor driven linear actuators does not use any micro switch inside the cylinder for to and fro motion, instead it has a in-built driver cum controller which is programmed for the to and fro motion.
OBJECTIVES OF THE INVENTION
• The primary objective of the present invention aims to provide a compact and powerful linear actuator.
• The second objective of the present invention aims to provide a two stage powerful linear actuator.
SUMMARY OF THE INVENTION
This summary is provided to introduce a selection of concepts in a simplified format that is further described in the detailed description of the invention. This summary is neither intended to identify key or essential inventive concepts of the invention and nor is it intended for determining the scope of the invention.
The present invention relates to a heavy-duty, single-staged or two staged rod style linear actuator (100) comprising of:
-a cylindrical housing (5),
-a bottom flange (2) and top flange (1) configured to close the cylindrical housing (5),
-a piston rod (7) configured to provide push or pull movement in linear direction by protruding out of the cylindrical housing (5),
-a screw (10) rotating in axial direction having helical groove on external surface and mounted inside the thrust/piston rod (7),
-a nut (8) mounted on grooves of said screw (10),
-a key (11) to prevent rotation of nut (8) and to provide linear motion to said nut,
-a top bearing (3) configured to moving piston rod (7),
-bottom bearing (4) configured to both end of the said screw (10),
-a top fix bush (6),
-a bottom movable bush (9).

In said actuator further the key (11) is fixed on internal wall and along the length of cylinder housing (5) using screw (12), the nut (8) comprising of cut on outer surface for linking it with cylindrical housing key (11).
The piston rod (7) is comprising of internal hollow circular body to occupy screw (10) and outer dense reinforcing body (13). Wherein, the reinforcing body (13) is extended to surround the nut (8). Further, the reinforcing body (13) is provided with cut for linking it with cylindrical housing key (11).

In the said actuator, the bearings (3 and 4) are selected from plain bearing, fluid bearing and ball bearing and the bush is made up of flexible material selected from rubber, nylon and plastic or phosphorus brass material.
Further, the present invention also provide two-staged linear actuator (100), comprising the outer cylindric housing (5) enclosing inner secondary cylindric housing (16), primary screw (10) at the centre which is configured with secondary screw (14), the secondary screw (14) is configured with reinforcing nut (13) having thrust rod (7) at the top. In according to said embodiment, the two-staged linear actuator operates when piston (16) protrudes from the primary housing (5) and piston (7) protrudes from the secondary housing/piston (16). Further, the actuator is provided with primary bush (6), secondary bush (15), locking keys (17 and 18) to provide two-staged lifting.
The arrangement of motor can be parallel or in-line with respect to a of rod style linear actuator (100). In parallel type the a screw (10) of rod style linear actuator (100) is configured with electric motor (200) using plurality of pulley (203, 204), plurality of belts (205) for receiving rotation motion. And in inline type the a screw (10) of rod style linear actuator (100) is configured with electric motor (200) using coupling (206) for receiving rotation motion.
To further clarify the advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which is illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING
For a more complete understanding of the present invention, reference is made to the following description taken in conjunction with the accompanying drawing. It is to be understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention.
Figure 1: schematically shows a motor with a rod style linear actuator configured according to the invention a) Parallel type, b) Inline Type.
Figure 2: Illustrates perspective view of motor with a rod style linear actuator configured according to the invention a) Parallel type, b) Inline Type.
Figure 3: shows a cross section view of rod style linear actuator (100) with embodiments according to the invention when it is in resting position.
Figure 4: shows a cross section view of rod style linear actuator (100) with embodiments according to the invention when it is in lifting position.
Figure 5: shows a cross section view of Parallel type rod style linear actuator according to the invention in resting position.
Figure 6: shows a cross section view of Inline type rod style linear actuator according to the invention in resting position.
Figure 7: shows a cross section view of Inline type two-staged rod style linear actuator in resting position according to the one more embodiment of the invention.
Figure 8: shows a cross section view of Inline type two-staged rod style linear actuator in lifting position according to the one more embodiment of the invention.

DESCRIPTION OF THE INVENTION
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skilled in the art to which this invention belongs. The system, methods, and examples provided herein
are illustrative only and not intended to be limiting.
For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.
It will be understood by those skilled in the art that the foregoing general description and the following detailed description are explanatory of the invention and are not intended to be restrictive thereof.
Reference throughout this specification to “an aspect”, “another aspect” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrase “in an embodiment”, “in another embodiment” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.
The terms "comprise", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process or method that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such process or method. Similarly, one or more devices or sub-systems or elements or structures or components proceeded by "comprises... a" does not, without more constraints, preclude the existence of other devices or other sub-systems or other elements or other structures or other components or additional devices or additional sub-systems or additional elements or additional structures or additional components.
Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
The present invention introduces a modified electric rod style linear actuator (100). More preferably, the present invention is a new technology for powering a linear actuator for heavy weight lifting. Wherein, the invention uses a stepper motor to operate the modified linear actuator. This invention provides a compact and portable linear actuator for lifting or pushing a very high load, more specifically it can be used to lift a 600 kg or more weight, more preferably 1500 Kg. It is useful to area wherein space constrains and it does not use any oil cylinder or compressor so one can easily use for heavy duty application in small working area.
Referring to accompanied figure 1, the present invention provides a heavy-load rod style linear actuator (100) configured with a stepper motor (200) having power supply (202) and controller assembly, the coupling of actuator with motor is by connecting via gears and belts mounted inside base housing (201).
As depicted in figure 1 (a) the mounting of rod style linear actuator (100) and stepper motor (200) is selected from parallel type or as depicted in figure 1 (b) the mounting of rod style linear actuator (100) and stepper motor (200) is selected inline type.
Further, figure 2 (a) shows that the connection of a stepper motor (200) with heavy-load rod style linear actuator (100) of present invention in parallel style. The small pulley (204) is attached to the motor shaft with the help of rectangular key and the grub screw (not shown). Similarly, the larger pulley (203) is attached to the actuator with the key and the grub screw (not shown). Both the pulleys are connected with the respective timing belt (205). The central rotating screw of actuator (100) is positioned vertically in the housing (201) fixed with the bearing and the lock nut at the bottom of the actuator. The angular contact bearing/ taper roller bearing depending on the application which provides better load capacity and the rotating screw of actuator rotates freely in the bearing when the power is transmitted from the motor.
Working of present invention of heavy rod style actuator system is that, the main driving force is the stepper motor (200). The stepper motor generates rotational force and torque as per its ratings. The rotational movement of the motor along with its respective speed and torque is transmitted to the actuator (100). The actuator is the main mechanism which converts the rotational movement into axial movement to lift the desired object. The transmission between the motor and the actuator is done with the help of timing pulleys and timing belt configured within the housing (202). Wherein, the ratio between the two pulleys is reduction ratio. The ratio can be changed as per desired output. The reduced gear ratio provides low rpm and generates more torque than the motor at the output (i.e at the actuator (100)).
Further, figure 2 (b) shows as per second embodiment of present invention, the connection of a stepper motor (200) with heavy-load rod style linear actuator (100) in inline style is same as implies in the parallel style system only eliminating the timing pulley system and the housing. As the motor is placed in line with the actuator at the rear end. The motor shaft and rotating screw of actuator (100) are connected with the help of a coupling (206). Hence, the gear ratio is eliminated and we get 1:1 output ratio at the end.
The actuator mechanism comprises of a screw and nut, which may be selected from ball screw/nut or lead screw/nut. The rotational movement of the ball screw/ lead screw is converted into the linear movement of the nut when the nut is locked.
In accordance to further embodiment and as referring to accompanied figure 3, the present invention provides a rod style linear actuator (100) comprising of a cylindrical housing (5) enclosing a screw (10) having threading on peripheral side, ball screw rod/piston rod (7), nut (8) configured on said screw (10), top bush (6), bottom bush (9) and bearings (3 and 4) respectively. The cylindrical housing is closed using top flange (1) and bottom flange (2). Further, one side of the cylindrical housing (5) is provided with a vertical key (11) to engage the screw nut (8) in it. The said key plate (11) is fixed on the cylindrical housing (5) using fixing screw (12).
The ball screw rod/piston rod (7) is hollow at the centre to occupy rotating screw (10). Further, in an important embodiment, the nut (8) is enforced at the bottom with bush (9), which is flexible bush. The nut (8) is also enforced with extended portion (13) [reinforcing body] of ball screw rod (7) as shown in figure 3. The lifting rod support assembly defines a reinforcing means (13) which is extended till the nut (8) entire exposed part, wherein the said reinforcing body (13) is reinforcing firstly to nut (8) and secondly to hollow circular body and hence providing heavy duty lifting capacity.
In the illustrated embodiment and in accordance to embodiment of present invention, the cylindrical housing (5) is enclosed by top flange (1) and bottom flange (2) fixable using threading to the outer body of said cylindrical housing (5).
In a further embodiment, the cylindrical housing (5) defined by centre rotating screw (10) which is connected to a pulley of motor as shown in figure 2. The said rotating screw (10) configured with moving nut (8). In the illustrative embodiment, the nut (8) is movable upwardly and downwardly but non-rotating as it is engaged in key (11) provided on internal wall of said cylindrical housing (5). Wherein, the nut is provided with key to fix in linear direction, so that the screw rotates while the nut do not rotate but it moves forward or backward as per left or right rotation of screw (10).
In an important embodiment of the present invention, there are provided with the one fix bush at the top (6), which is made up of metal like brass and secondly a moving bush at the bottom (9), just below the nut (8), which is made up of flexible material like plastic, nylon or rubber.
In accordance to embodiment, the Figure 3 illustrate the nut (8) in resting position whereas the figure 4 illustrates that when the nut (8) is pushed upwardly due to rotation of central screw (10), it lifts and protrudes the piston rod (7) out of housing (5). The protruding of piston rod (7) helps to lift, apply force or move the object.
In an embodiment of the present invention, the figure 5 and 6 illustrates the cross-section view of present invention in parallel type and inline type, wherein the outer cylinder pipe/housing (5) is provided with a rectangular key (11) throughout its length. The key is fixed at the desired location vertically inside the cylinder with the help of screw (12). The ball screw/lead screw nut (8) is attached to the piston rod(7). Both Ball screw/ lead screw nut and the piston rod has a key way cut (slit) into it and the nut slides into the key way which helps it to remain locked and the piston rod mounted on the ball screw/ lead screw moves upward and downward as per the forward and reverse rotation of the motor.
The piston rod (7) is provided with more rigid guide support at the top flange (1) with a bearing(3) and a phosphor bronze bush (6). The phosphor bronze bush is also locked to the top flange restricting its rotational movement with the help of grub screw (14). The piston rod slides freely up and down and provides the required output and serves its purpose. The bearing and phosphor bronze bush also gives transverse support for heavy load lifting. The timing pulley system is enclosed in a housing. The controller and motor are also attached on the housing making it a whole compact assembly.
Further, as per present invention, the present actuator is connected to electronic driver and controller to control the movement of said motor more efficiently and more precisely. The controller system has an integrated circuit at the back of the motor which acts as a driver cum controller for this actuator. The power supply for this actuator like 24 volts to 48 volts goes inside this circuit for starting the motor. The software of this circuit is programmed as per the length and pitch of the screw (10).
In accordance to working of present invention and referring to figure 2, 3 and 4, the screw (10) is rotated using a motor, more preferably selected from stepper motor using chain or belt drive connected at the bottom of said screw. The power provided to said stepper motor is preferably direct power supply or thought a battery.
In an additional embodiment of the invention, and as referring to accompanied figure 7 and 8, the present invention provides a two-staged rod style linear actuator (100). The figure 7 illustrates a resting position linear actuator and figure 8 illustrates a two-staged lifting position linear actuator (100) as per present invention. Such two-stage actuator is useful in lifting vehicles such as for lifting jack.
The two-stage linear actuator (100) is having two-staged lifting system in which the expansion of the piston is taking place in two stages. Two pistons (13 and 16) are occupied within the outer cylinder (5). Similarly, it comprises of two concentric lead screws (10 and 14) configured on one above the other i.e one for each stage also occupied within each other. The one end of primary screw (10) i.e. lead screw is fitted in the housing (201) fixed with the bearing (203) using the lock nut at the bottom of the lead screw. The angular contact bearing provides better load capacity and the lead screw rotates freely in the bearing when the power is transmitted from the motor. The primary lead screw (10) having external threads is in screw contact with the internal threaded bottom of the secondary lead screw (14). Similarly, the external threads of the secondary lead screw (14) is in screw contact with internal threaded nut of bottom of the Piston (13). Here, the lead screw nut converts rotational movement into the linear movement of the piston (13) and piston (13) converts rotational movement into linear movement of the piston (16), where, upon raising at desired height, each piston is locked in respective key. The outer cylinder housing (5) is provided with two rectangular keys (17) on opposite sides throughout its length. Similarly the internal wall of Piston (16) is also provided with keys (18) to lock the movement of piston (13). The keys are fixed at the desired location inside the cylinder with the help of allen csk screw same as shown in figure 6. The piston rod (13) and (16) has a key way cut which slides into the key which helps it to remain locked and the piston rod mounted on the lead screw moves upward and downward as per the forward and reverse rotation of the motor.
In a further embodiment of two-stage linear actuator (100) of the present invention, the piston rods are provided with more rigid guide support at the top flange with a phosphor bronze bush (15). The piston rod slides freely up and down and provides the required output and serves its purpose. The phosphor bronze bush also gives transverse support for heavy load lifting.
Accordingly, the central primary screw (10) is engaged with pulley (203) at base housing (201) which is further connected to stepper motor through belt (not shown). In accordance to one more embodiment, the said stepper motor can be directly attached to said screw at the bottom without using belt. The stepper motor generates rotational force and torque as per its ratings. The rotational movement of the motor along with its respective speed and torque is transmitted to the driven lead screw. The lead screw is the main mechanism which converts the rotational movement into axial movement to lift the desired automobile. The transmission between the motor and the lead screw is done with the help of timing pulleys and timing belt.
Further, as per method of working of present invention, the said system has an integrated circuit at the back of the motor which acts as a driver cum controller for this actuator. The power supply for this actuator like 12 volts to 72 volts goes inside this circuit for starting the motor. The software of this circuit can be programmed as per the length and pitch of the screw. The stroke of the piston is controlled by rotation which in turn is controlled by stepper motor driver and stepper controller. The stroke is programmable as per application requirement.
The foregoing description of the invention has been set merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to person skilled in the art, the invention should be construed to include everything within the scope of the disclosure. Clearly, the invention may be otherwise variously embodied, and practiced within the scope of the following claims.
,CLAIMS:We claim;
1. A rod style linear actuator (100) comprising of:
-a cylindrical housing (5),
-a bottom flange (2) and top flange (1) configured to close the cylindrical housing (5),
-a piston rod (7) configured to provide push or pull movement in linear direction by protruding out of the cylindrical housing (5),
-a screw (10) rotating in axial direction having helical groove on external surface and mounted inside the thrust/piston rod (7),
-a nut (8) mounted on grooves of said screw (10),
-a key (11) to prevent rotation of nut (8) and to provide linear motion to said nut,
-a top bearing (3) configured to moving piston rod (7),
-bottom bearing (4) configured to both end of the said screw (10),
-a top fix bush (6),
-a bottom movable bush (9).

2. The rod style linear actuator (100) as claimed in claim 1, wherein the bearings (3 and 4) are selected from plain bearing, fluid bearing and ball bearing.
3. The rod style linear actuator (100) as claimed in claim 1, wherein the key (11) is fixed on internal wall and along the length of cylinder housing (5) using screw (12).
4. The rod style linear actuator (100) as claimed in claim 1, the nut (8) comprising of cut on outer surface for linking it with cylindrical housing key (11).
5. The rod style linear actuator (100) as claimed in claim 1, wherein the piston rod (7) is comprising of internal hollow circular body to occupy screw (10) and outer dense reinforcing body (13).
6. The rod style linear actuator (100) as claimed in claim 1, wherein the reinforcing body (13) is extended to surround the nut (8).
7. The rod style linear actuator (100) as claimed in claim 1, wherein reinforcing body (13) is provided with cut for linking it with cylindrical housing key (11).
8. The rod style linear actuator (100) as claimed in claim 1, wherein the bottom movable bush (9) is made up of flexible material selected from rubber, nylon and plastic.
9. The rod style linear actuator (100) as claimed in claim 1, wherein the screw (10) is configured with secondary screw (14), secondary piston (16), secondary bush (15), locking keys (17 and 18) to provide two-staged lifting.
10. The rod style linear actuator (100) as claimed in claim 1, wherein the a screw (10) of rod style linear actuator (100) is configured with electric motor (200) having power supply (202).
11. The rod style linear actuator (100) as claimed in claim 10, wherein the arrangement of rod style linear actuator (100) and motor (200) is selected from parallel type and inline type.
12. The rod style linear actuator (100) as claimed in claim 10, wherein the electric motor is selected from Stepper motor.
13. The rod style linear actuator (100) as claimed in claim 11, wherein in parallel type the a screw (10) of rod style linear actuator (100) is configured with electric motor (200) using plurality of pulley (203, 204), plurality of belts (205) for receiving rotation motion.
14. The rod style linear actuator (100) as claimed in claim 11, wherein in inline type the a screw (10) of rod style linear actuator (100) is configured with electric motor (200) using coupling (206) for receiving rotation motion.