DESC:INTEGRATED SPRING IN DIGITAL LINEAR ACTUATOR

FIELD OF THE INVENTION
The present invention relates in general to a digital linear actuator (DLA) and, more particularly to an integrated spring in a Canstack Stepper DLA.

BACKGROUND
In a Canstack Stepper DLA, the rotary motion of the permanent magnet rotor is converted to linear motion of a lead screw driven by internal threads of the rotor.

In the existing systems there is loss of energy as the torque is applied in the rotary direction and the resultant force is required in linear direction. Also, in the existing systems, DLA being required to have an equal push and pull force even in cases where a unidirectional load is present in application. Thus, there is a need to provide a system to mitigate the problems indicated in the existing art.

In most of the applications the load is applied only in one direction, for such applications then the idea is to use a spring under compression to help the DLA in the load direction, in the other direction as no load is required to be driven the DLA energy is used to compress the spring. This art consists to balance energy needed in both directions, in one direction we load the spring, and in the other direction the spring helps to increase DLA capacity.

OBJECTS OF THE INVENTION
It is an object of the invention to provide a digital linear actuator that requires optimal energy to push or pull a load when load is in one unique direction.

It is another object of the invention to provide a digital linear actuator with higher efficiency.
It is yet another object of the invention to provide a digital linear actuator that reduces back drive.
It is yet another object of the invention to provide a digital linear actuator with improved life.
It is still another object of the invention to provide a digital linear actuator which reduces construction cost (smaller size).
It is still another object of the invention to provide a digital linear actuator which is simple in construction.
It is still another object of the invention to provide a digital linear actuator with simple operation.

SUMMARY OF THE INVENTION
The present invention provides a new and novel DLA. A particular advantage of this new DLA is optimization of energy for pushing or pulling a load in case the load is in one unique direction. The DLA comprises a preloaded integrated spring and a lead screw wherein the integrated spring stores energy when the leadscrew is in retracted position and releases energy when the leadscrew is in extended position thus optimizing the amount of force required to push or pull a load.

BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 illustrates a captive DLA with integrated spring according to an embodiment of the present invention.
Fig. 2 illustrates a non-captive DLA with integrated spring according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION
The detailed description set forth below in connection with the appended drawings is intended as a description of various embodiments of the present invention and is not intended to represent the only embodiments in which the present invention may be practiced. Each embodiment described in this disclosure is provided merely as an example or illustration of the present invention, and should not necessarily be construed as preferred or advantageous over other embodiments. The detailed description includes specific details for the purpose of providing a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without these specific details. The embodiment provided herein is for the purpose of filing the present provisional specification; however, further embodiments within this disclosure are possible and shall/may be covered in the complete specification.

According to an embodiment of the present invention a DLA is provided with an integrated spring. The spring is integrated in the DLA such that it stores energy when the leadscrew is retracting and releases energy when the leadscrew is extending. The use of the integrated spring in the DLA increases load carrying capacity of the DLA with respect to the DLAs without the integrated spring. In the present invention the force boosting spring used in the DLA increases its load rating in one direction.

According to an embodiment of the present invention, the spring is assembled either externally or internally in the DLA. The spring used is guided wherein one end of the spring is in contact with an adaptor (moving axially but not in rotation) and other end is in contact with a front or a rear cap (stationary). The spring is designed in such a way that, when the DLA leadscrew is fully extended, the spring is pre-compressed to a desired preload. The preload varies according to the compression exerted on the spring. According to an embodiment of the present invention, the maximum preload is achieved when the DLA leadscrew is fully retracted and the minimum preload when it is fully extended. The maximum preload is ensured to be less than the DLA load rating without a spring so that the DLA can compress the spring fully when retracting. In an application such as extending of the leadscrew requiring the DLA to carry load in one direction, the spring energy is released and therefore the DLA can carry more load than its rating. The Force of the spring in such a case is half of the force of the load, in order to compress the spring during retraction and boost the force during extension.

According to an embodiment of the present invention, the integrated spring may be used in both captive and non-captive DLA. Figure 1 illustrates a captive DLA with an integrated spring. In the captive DLA, anti-rotation mechanism is in the DLA itself. As shown in the figure, stepper DLA 101 is connected to the force booster spring 100 at one end which is stationary. The other end of the spring 100 is connected to an adaptor 104 that moves axially but not in a rotary motion. The spring 100 is pre-compressed to a desired load when the leadscrew 103 is fully extended. In the present embodiment, preload varies according to the amount of compression of the spring 100. The maximum preload is achieved when the DLA leadscrew 103 is fully retracted and minimum preload is achieved when the DLA leadscrew 103 is fully extended. In cases where unidirectional load carrying is required, energy stored in the spring is released during extension of the leadscrew, thus pushing the load. According to another embodiment of the present invention, the use of the integrated spring 100 also addresses the problem of back drive in the leadscrew 101.

Figure 2 illustrates a non-captive DLA with an integrated spring 200 according to an embodiment of the present invention. In a non-captive DLA, anti-rotation mechanism is in the application in which DLA is being used. Since, figure 2 has same elements as Figure 1, their working is not repeated here for the sake of brevity.

Since other modifications and changes to fit particular requirements and environments will be apparent to those skilled in the art, the invention is not considered limited as described by the present preferred embodiments which have been chosen for purposes of disclosure, and covers all changes and modifications which do not constitute departure from the spirit and scope of this invention.

,CLAIMS:WE CLAIM:
1. A digital linear actuator comprising:
a spring 100 stationary at one end;
an adaptor 104 connected to the said spring at other end having movement in an axial direction;
wherein the spring 100 is pre-compressed to a desired load when a leadscrew 103 is fully extended.
2. The digital linear actuator as claimed in claim 1 wherein, preload on the spring varies according to the compression of the spring 100.
3. The digital linear actuator as claimed in claim 1 wherein, the maximum preload is achieved when the DLA leadscrew 103 is fully retracted.
4. The digital linear actuator as claimed in claim 1 wherein, the minimum preload is achieved when the DLA leadscrew 103 is fully extended.