EP1310681A2

EP1310681A2 - Linear actuator with internal mechanical locking

Info

Publication number: EP1310681A2
Application number: EP02023599A
Authority: EP
Inventors: Giovanni Ghirardo; Giorgio Rolfo
Original assignee: Rolfo SpA
Current assignee: Rolfo SpA
Priority date: 2001-11-13
Filing date: 2002-10-23
Publication date: 2003-05-14
Anticipated expiration: 2022-10-23
Also published as: ITTO20011066A1; EP1310681A3; ATE425373T1; EP1310681B1; DE60231465D1

Abstract

A linear actuator (1) is disclosed that comprises: an elongated containing body (2) with a head (3); and a multi-start driving screw (9) that rotates around the longitudinal axis (A) of the actuator (1) and operatively cooperates with a nut screw (11); and means (15) for bidirectionally locking the driving screw (9) when it has reached its own final operating, pulling or pushing position, wherein such means (15) are equipped with holding means (16) for the screw (9) and cooperate with elastic means (18) in order to occupy an engagement position with the screw (9) for locking it, or a locking-release position of the screw (9).

Description

The present invention refers to a linear actuator with internal mechanical locking, and in particular to a linear actuator of the hydraulic or pneumatic type adapted to be used in any type of handling and lifting means.
In the field of motor vehicles, and in particular of trucks for transporting vehicles, there are nowadays on the market linear actuators that allow reaching an operating pushing position when loading the vehicles, and then keeping it fixed through hooking means. However, such known linear actuators allow reaching and fixing safe operating positions only in an unidirectional way, namely along the pushing direction, not providing however the operators with a complete solution which they need when loading and unloading the vehicles.
Object of the present invention is solving the above prior-art problems, by providing a linear actuator equipped with an internal mechanical locking device that allows it, once having reached an operating pulling as well as pushing position, to be safety locked in such position: such actuator thereby operates in a bidirectional way and therefore can find application in a much wider field with respect to known actuators.
Moreover, due to its nature, the linear actuator of the invention allows reaching a plurality of operating pulling and pushing positions with a continuous movement in both directions on its longitudinal axis, guaranteeing a wider flexibility of assembling and securing conditions and positions.
The above and other objects and advantages of the invention, as will appear from the following description, are obtained by a linear actuator as claimed in Claim 1. Preferred embodiments and non-trivial variations of the present invention are claimed in the dependent Claims.
The present invention will be better described by some preferred embodiments thereof, given as a non-limiting example, with reference to the enclosed drawings, in which:

Figure 1 is a side sectional view of a preferred embodiment of the linear actuator of the present invention when unlocking;
Figure 2 is an exploded side sectional view similar to Fig. 1 with the parts composing the actuator; and
Figure 3 is a perspective detailed view of the surfaces of the driving screw and of the locking means of the actuator of the invention.

With reference to the Figures, a preferred, but non-limiting, embodiment of the linear actuator 1 of the invention is disclosed. Such embodiment provides for an actuator of the hydraulic type, in which the operating fluid is oil, and which can be used in vehicle loading and unloading steps on and from trucks provided for wuch purpose, making it easier for the operators to work, since it guarantees safe operating positions both along the pulling direction, and along the pushing direction.
However, the linear actuator 1 of the present invention is not at all limited to the vehicle field, being it able to be efficiently applied to all handling and lifting systems of the art, such as, still as a non-limiting example, in the agricultural field, in the field of cranes or lift trucks, etc.
With reference now to the Figures, the embodiment shown provides for a linear actuator 1 substantially comprising an elongated containing body 2 equipped with a head 3 and comprising a bush 5 placed at the end where the head 3 is located and a bush 7 placed at the opposite end, that is at the end of the elongated body 2, where the chamber 36 is located, the two bushes 5 and 7 allowing to carry out the various operating connections of the actuator 1.
The linear actuator 1 of the invention further comprises, in a known way, at least one multi-start driving screw 9 placed around the body 2 and adapted to rotate around the longitudinal axis A of the actuator 1: such driving screw 9 cooperates with a nut screw 11 in order to change the working positions of the actuator 1.
The main characteristic of the linear actuator 1 of the invention is that it is equipped with an internal mechanical locking; fur such purpose, in fact, it further comprises means 15 for bidirectionally locking the driving screw 9 when it has reached its own final operating, pulling or pushing position; the means 15 are equipped with holding means 16 for the screw 9 and cooperate with elastic means 18 in order to occupy an engagement position with the screw 9 for locking it, or a locking-release position of the screw 9.
In particular, the means 15 are composed of a head 15 placed in the head 3 of the actuator 1 and equipped with a plurality of holding members 16 adapted to engage corresponding holding members 20 connected to the driving screw 9 to prevent the driving screw 9 from rotating.
In the currently provided best embodiment, the holding members are composed of a plurality of teeth, both of a rectangular shape, and, alternatively, of a trapezoidal shape, namely whose engagement walls with corresponding opposite teeth are slanted. This second type of possible arrangement provides a better safety upon installation: in fact, due to the mutual unmovable engagement of the teeth 16 and 20, respectively of head 15 and screw 9, in order to be able to release such engagement, the mutual movement of such teeth 16 and 20 one away from the other is not enough, but it is also necessary to apply thereto an angular rotation movement in order to free the engagement of their slanted walls. This double operation of rotating and moving away thereby prevents an accidental disengagement between head 15 and screw 9, improving the release safety.
Also in particular, the elastic means 18 are composed of at least one Belleville washer (of the so-called Bauer type), that is a better arrangement with respect to common springs with which the actuator could be equipped. The Belleville spring 18 is kept into a suitable recess by a pin 50 that also operates as guide for the spring 18 itself.
Moreover, the means 15 are equipped with at least one (and preferably two) rotation-preventing key 22 adapted to allow the means 15 only to move in a longitudinal direction with respect to the actuator 1, instead preventing a rotation of the means 15 themselves.
The driving screw 9 is then equipped with at least one pair of bearings 24, 26 adapted to prevent the screw 9 from longitudinally translating with respect to the actuator 1, allowing instead the screw 9 to rotate around the longitudinal axis A of the actuator 1.
The above-described linear actuator 1 is realised so that it can be of any type of drive: while in the most common and preferred way, it can be of the hydraulic type (with oil as typical operating fluid), there are no restrictions to its realisation of a pneumatic type, with pressurised air as typical operating fluid. Numerous other variations of such type are obviously possible.
The operation of the linear actuator 1 of the present invention will now be described, with reference to some possible, but not exhaustive, cases of its actuation.
In order to be hydraulically operated through oil, the linear actuator 1 of the invention is equipped with a circuit 28, 30, 32 for the flow of the operating fluid: the fluid (in this case oil), in order to obtain the operating pushing position of the actuator 1, is sent first into the head 3 in order to unlock the screw 9, and then is sent into a working chamber 34 and is extracted from another working chamber 35 of the body 2 in order to actuate screw 9 and nut screw 11 to take the actuator 1 to the operating pushing position, and then, once having reached such operating position, stopping the supply of the fluid in order to lock the screw 9 through the return of the means 15 into the locking position.
According to a possible operating variation, the linear actuator 1 of the invention, always equipped with the above-mentioned circuit 28, 30, 32, operates so that the oil, in order to obtain the operating pushing position of the actuator 1, is simultaneously sent into the head 3 in order to unlock the screw 9 and into the working chamber 34 and is extracted from the other working chamber 35 of the body 2 in order to actuate screw 9 and nut screw 11 to take the actuator 1 to the operating pushing position, and then, once having reached such operating position, stopping again the supply of the fluid in order to lock the screw 9 through the return of the means 15 into the locking position.
Still as further operating variation, this time for the pulling action, the linear actuator 1 of the invention, always equipped with the above-mentioned circuit 28, 30, 32, operates so that the oil, in order to obtain the operating pulling position of the actuator 1, is first sent into the head 3 in order to unlock the screw 9, and then is sent into the working chamber 35 and is extracted from the other working chamber 34 of the body 2 in order to actuate screw 9 and nut screw 11 to take the actuator 1 to the operating pulling position, and then, once having reached such operating position, stopping the supply of the fluid in order to lock the screw 9 through the return of the means 15 into the locking position.
Still to realise the operating pulling position in a variation that is parallel to the previous one, the linear actuator 1 of the invention, equipped with the circuit 28, 30, 32 for the flow of the operating fluid, operates so that the oil, in order to obtain the operating pulling position of the actuator 1, is simultaneously sent into the head 3 in order to unlock the screw 9 and into the working chamber 35 and is extracted from the other working chamber 34 of the body 2 in order to actuate screw 9 and nut screw 11 to take the actuator 1 to the operating pulling position, and then, once having reached such operating position, stopping the supply of the fluid in order to lock the screw 9 through the return of the means 15 into the locking position.
It is obvious that, in order to enact such operating steps, suitable control circuits, of the hydraulic or pneumatic type, will be necessary, such circuits being placed outside the actuator 1 and connected thereto through suitable operating lines realised according to the type of chosen control.

Claims

Linear actuator (1) comprising:

an elongated containing body (2) equipped with a head (3); and

at least one multi-start driving screw (9) placed around said body (2) and adapted to rotate around the longitudinal axis (A) of said actuator (1), said driving screw (9) being adapted to cooperate with a nut screw (11) in order to change the working positions of said actuator (1);

characterised in that it further comprises:

means (15) for bidirectionally locking said driving screw (9) when it has reached its own final operating, pulling or pushing position, said means (15) being equipped with holding means (16) for the screw (9) and cooperating with elastic means (18) in order to occupy an engagement position with said screw (9) for locking it, or a locking-release position of said screw (9).
Linear actuator (1) according to Claim 1, characterised in that said means (15) are composed of a head (15) placed in the head (3) of said actuator (1) and equipped with a plurality of holding members (16) adapted to engage corresponding holding members (20) connected to said driving screw (9) to prevent said driving screw (9) from rotating.
Linear actuator (1) according to Claim 1 or 2, characterised in that said holding members are composed of a plurality of rectangularly-shaped teeth.
Linear actuator (1) according to Claim 1 or 2, characterised in that said holding members are composed of a plurality of trapezoidally-shaped teeth, namely whose engagement walls with corresponding opposite teeth are slanted.
Linear actuator (1) according to Claim 1, characterised in that said elastic means (18) are composed of at least one Belleville washer.
Linear actuator (1) according to Claim 1, characterised in that said means (15) are equipped with at least one rotation-preventing key (22) adapted to allow said means (15) only to move in a longitudinal direction with respect to said actuator (1), instead preventing a rotation of said means (15).
Linear actuator (1) according to Claim 6, characterised in that said rotation-preventing keys (22) are two.
Linear actuator (1) according to Claim 1, characterised in that said driving screw (9) is equipped with at least one pair of bearings (24, 26) adapted to prevent said screw (9) from longitudinally translating with respect to said actuator (1), allowing instead said screw (9) to rotate around the longitudinal axis (A) of said actuator (1).
Linear actuator (1) according to Claim 1, characterised in that it is equipped with a circuit (28, 30, 32) for the flow of an operating fluid, said fluid, in order to obtain the operating pushing position of said actuator (1), being sent first into said head (3) in order to unlock said screw (9), and then being sent into a working chamber (34) and being extracted from another working chamber (35) of said body (2) in order to actuate screw (9) and nut screw (11) to take the actuator (1) to the operating pushing position, and then, once having reached such operating position, stopping the supply of said fluid in order to lock said screw (9) through the return of said means (15) into the locking position.
Linear actuator (1) according to Claim 1, characterised in that it is equipped with a circuit (28, 30, 32) for the flow of an operating fluid, said fluid, in order to obtain the operating pushing position of said actuator (1), being simultaneously sent into said head (3) in order to unlock said screw (9) and into a working chamber (34) and being extracted from another working chamber (35) of said body (2) in order to actuate screw (9) and nut screw (11) to take the actuator (1) to the operating pushing position, and then, once having reached such operating position, stopping the supply of said fluid in order to lock said screw (9) through the return of said means (15) into the locking position.
Linear actuator (1) according to Claim 1, characterised in that it is equipped with a circuit (28, 30, 32) for the flow of an operating fluid, said fluid, in order to obtain the operating pulling position of said actuator (1), being first sent into said head (3) in order to unlock said screw (9), and then being sent into a working chamber (35) and being extracted from another working chamber (34) of said body (2) in order to actuate screw (9) and nut screw (11) to take the actuator (1) to the operating pulling position, and then, once having reached such operating position, stopping the supply of said fluid in order to lock said screw (9) through the return of said means (15) into the locking position.
Linear actuator (1) according to Claim 1, characterised in that it is equipped with a circuit (28, 30, 32) for the flow of an operating fluid, said fluid, in order to obtain the operating pulling position of said actuator (1), being simultaneously sent into said head (3) in order to unlock said screw (9) and into a working chamber (35) and being extracted from another working chamber (34) of said body (2) in order to actuate screw (9) and nut screw (11) to take the actuator (1) to the operating pulling position, and then, once having reached such operating position, stopping the supply of said fluid in order to lock said screw (9) through the return of said means (15) into the locking position.
Linear actuator (1) according to any one of the previous Claims, characterised in that it is a linear actuator (1) of the hydraulic type.
Linear actuator (1) according to Claim 13, characterised in that the operating fluid of said actuator (1) is oil.
Linear actuator (1) according to any one of Claims 1 to 12, characterised in that it is a linear actuator (1) of the pneumatic type.
Linear actuator (1) according to Claim 15, characterised in that the operating fluid of said actuator (1) is air.