Abstract:
A jack (1) has a jack body (2) with a peripheral wall (3) which forms a jack chamber (4). Two pistons (5a, 5b) attached to piston rods (6) are movably mounted in the jack chamber. The jack (1) has an automatic locking section (MV) to lock the two pistons (5a, 5b) and their respective rods (6) in at least one of two extreme positions. The locking is done automatically during the movement of the pistons (5a, 5b) by locking balls (11a, 11b) which move in locking grooves (10a, 10b) in the piston (6). There is also a manual unlocking device (MDV) connected to the pistons (5a, 5b) through unlocking rods (21). The manual unlocking device (MDV) is attached to two unlocking collars (7a, 7b) which rotate to unlock the piston (5a, 5b) and piston rod (6). The rotation, in turn, moves adjustment screws (23) to displace the unlocking rods (21) along their axes.

Description:
BACKGROUND OF THE INVENTION 
     The present invention is directed to a mechanically operated jacks and, more particularly, an improvement for a jack in which the extreme positions of its piston are automatically locked and can be unlocked manually or automatically. 
     Traditionally, there are many different types of jacks, for example, hydraulic jacks, pneumatic jacks, and others, which are used for various applications. These jacks frequently encounter problems associated with their particular utilization, such as, when the operating energy of the jack fails, for example, a pressure drop in a pneumatic jack, so that the piston/piston rod unit becomes motionless. Likewise, in certain jacks, a drop in gas pressure automatically locks the piston in position and the piston cannot be unlocked or moved until the necessary operating energy is reestablished. 
     Further, the different devices in existence which allow locking of the piston and its rod usually require additional pieces or meticulous machining of some of its component parts, making their manufacture delicate, long, and onerous. 
     Thus, it is the object of the present invention to resolve the aforementioned problems with the aid of simple means, which are reliable and less onerous. The present invention contemplates a new and improved jack which can be unlocked in its extreme position and which can be unlocked easily either manually or automatically in case of a breakdown. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, there is provided a jack body having a peripheral wall which forms a jack chamber in which at least one piston is integral with a piston rod is displaced. The jack includes locking means for locking the piston and its rod in at least one of its extreme positions. The locking takes place automatically based on the movement of the piston. 
     In accordance with a more limited aspect of the invention, the locking means includes locking devices which slide along at least one locking groove of the piston rod. The locking devices are preferably balls arranged annularly around the piston rod in ball housings of a ferrule, which is integral with the body of the jack. The balls move radially along the locking groove of the rod when the piston(s)/piston rod(s) set(s) reaches an extreme position. 
     In accordance with a more limited aspect of the invention, the locking means allows the piston/piston rod set to lock in the two extreme positions and the jack includes two pistons which move relative to each other when they are urged by a resilient contact means, such as a spring. The pistons are located apart from each other and are urged against two stops. The piston rod includes two locking grooves which accept associated locking balls. 
     In accordance with another more limited aspect, manual locking means are provided. 
     In accordance with a more limited aspect of the invention, the piston or pistons move longitudinally along the piston rod. The manual unlocking means includes at least one drive member which is connected to the piston or pistons and moves the piston or pistons longitudinally. 
     In accordance with a more limited aspect of the invention, the drive member or members include two unlocking collars which are arranged on the outside and at each extremity of the body of the jack. Each collar can be activated by rotation through manual action on the part of a user. The unlocking of the collars against one another initiates the displacement of the corresponding piston. Movement of the connection means, i.e., unlocking rods or shafts, forces the piston to unlock itself against the action of the spring. The unlocking rods or shafts are displaced along their axes by an adjusting screw activated by rotation of the corresponding unlocking collar. 
     In accordance with a more limited aspect of the invention, the dimensions of the elements of the locking means and the unlocking means are selected such that the unlocking of the set of piston/piston rod requires a rotational angle from 0 to 180°. 
     According to another aspect, the unlocking collars contain a torsion spring which permits the resetting of the collar to its initial position after it has been actuated. 
     According to another aspect, the jack is a pneumatic jack and compressed air flows in one or more hollow tubes in the jack. The tubes are longitudinally located through the chamber of the jack. 
     A principle advantage of the invention is a jack which has simple, reliable, and less onerous parts that can be locked in its extreme positions automatically and can be unlocked easily either manually or automatically. 
     Still further advantages of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description of the preferred embodiments. 
    
    
     BRIEF DESCRIPTION OF THE FIGURE 
     The invention may take form in various components and arrangements of components, and in various steps and arrangements of steps. The drawings are only for purposes of illustrating a preferred embodiment and is not to be construed as limiting the invention. 
     FIG. 1 is a side view of the jack in its assembled condition; 
     FIG. 2 illustrates a side view of the jack with half of the jack longitudinally in cross section; 
     FIG. 3a represents the piston body of one of the pistons in longitudinal cross section; 
     FIG. 3b illustrates the piston/piston rod set in longitudinal section; 
     FIG. 4 illustrates the unlocking mechanism of the piston and piston rod in section; 
     FIG. 5 illustrates the body of jack in transverse section; 
     FIGS. 6a-6d illustrate schematically the unlocking of the piston/piston rod set, with the body of the jack omitted for simplicity of illustration; 
     FIG. 6a represents schematically the locked piston, the piston and its rod; 
     FIG. 6b represents the displacement of the piston under action of the unlocking collar; 
     FIG. 6c illustrates the exit of the locking member from the piston rod; and, 
     FIG. 6d represents the displacement of the piston rod leaving its extreme position. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to FIGS. 1 and 2, a jack 1 includes a jack body 2 defined by a peripheral wall 3 forming a jack chamber 4 in its interior. At least one piston 5, which is integral with a piston rod 6, momves in the jack chamber. 
     The jack 1 includes a locking means MV which locks the piston 5 and its interconnected rod 6 in its two extreme positions automatically. 
     It is to be appreciated that even though the preferred embodiment of the jack 1 according to the invention describes locking in two extreme positions of the piston/piston rod combination, other locking and unlocking means can be provided, such as those described hereinafter for only one of the extreme positions. 
     With continuing reference to FIGS. 1 and 2, preferably the jack 1 is a pneumatic jack in which the piston is moved by compressed air flowing in a section of the jack chamber 4. It is to be appreciated that the present locking and unlocking device can also be used with a hydraulic type jack or any other type jack. 
     Turning to FIG. 2, the locking means MV includes locking members 11a, 11b which move into a locking groove 10a, 10b of the piston rod 6 when the piston rod 6 is positioned in an extreme position thus locking the piston rod 6. The piston rod 6 includes two locking grooves 10a, 10b which allow the piston rod 6 to lock in either of two extreme positions. The locking members preferably include two locking ball units 11a, 11b which position themselves, respectively, in locking grooves 10a, 10b when the piston/piston rod combination is positioned in one of the two extreme positions. 
     In the preferred embodiment, the first set of the locking balls units 11a includes four balls, arranged on a front ferrule 15a; the balls 11b of the second unit are, respectively, arranged on the rear ferrule 15b. The rear ferrule 15b includes an internal opening 13 into which the piston rod 6 slides along its longitudinal axis ZZ&#39;. The balls of the annular peripheral wall displace radially to become lodged in the groove 10b in order to lock the rod 6. Likewise, the front ferrule 15a includes, at its rear extremity, a hollow cylindrical casing 16 into which the end of the piston rod 6 is inserted. The balls 11a of the first unit are arranged annularly in the peripheral wall to allow movement in radial direction insuring the locked position of the piston rod 6, while the balls 11a slide in the locking groove 10a. It is to be appreciated that the locking ball units 11a, 11b may include a different number of balls, for example two balls diametrically opposed. 
     Turning to FIGS. 3a and 3b, the radial movement of the locking organs 11a, 11b in their respective grooves 10a, 10b is obtained via action of the piston 5, 5a, 5b. In order to be able to lock in the two extreme positions, the jack 1 includes two pistons 5a, 5b supported by the piston rod 6. Each presents a support surface which includes the internal peripheral wall 17 of an opening 30 located, respectively, at the front or rear end where the surface interacts with the balls 11a, 11b in order to provoke their radial movement toward the groove 10a, 10b of the piston rod 6. 
     Looking now to FIG. 6a, the balls 11a are maintained by the support surface 17 of the first piston 5a in the groove 10a of the piston rod 6 when the piston/piston rod set is one of its extreme positions. The rod 6 and its pistons 5a are then locked. In the other extreme position, the locking is insured in a similar manner by the second piston 5b, the second groove 10b, and the second set of balls 11b. 
     In order to permit unlocking, the two pistons 5a, 5b glide toward each other along the longitudinal axis ZZ&#39; of the piston rod 6 while they press against resilient compression means, preferably a spring 8, which is located between them. The two pistons 5a, 5b are urged apart until they engage, respectively, two stops 9a, 9b one on a front wall of the furnished piston 5a and one on a rear wall of the rear piston 5b where they are supported when the piston/piston rod combination is unlocked. As seen in FIG. 3b, in a position which is called the initial position, the front and rear walls are the end wall 36 of a well or recess 30. Based on this, when the jack is in a locked position, as is illustrated in FIG. 6a, the introduced pneumatic pressure initiates the longitudinal movement of the piston 5a against the action of the spring 8 until such point when the support surface 17 of the piston 5a no longer cooperates with the locking members 11a, which are released, unlocking the jack 1 and the two pistons 5a, 5b, return their initial position. 
     As seen in FIG. 3b, the release of the locking members 11a, 11b is assisted by the locking grooves 10a, 10b of the piston rod 6 including an inclined annular slope or chamfer 20. 
     Turning to FIG. 4, the jack 1 includes manual unlocking means MDV shown as control members 7a, 7b which initiate the longitudinal displacement of the piston or pistons 5, 5a, 5b as described previously, with the aid of connection means, such as unlocking rods or shafts 21. In the manual unlocking means MDV, the control members 7a, 7b include two rotating unlocking collars 7a, 7b arranged on the outside and at each extremity of the body of the jack 2. Each collar 7a, 7b can be rotated via manual action on the part of the user. The rotation of one or other of the unlocking collars initiates the displacement of the corresponding piston 5a, 5b through the movement of the unlocking rod or shafts 21 which force the piston 5a, 5b to unlock against the pressure of the spring 8. Sleeves or rods 21 are displaced along their longitudinal axis because threaded member 23 is advanced by rotation of the corresponding unlocking collar 7a, 7b. 
     Turning to FIGS. 6a-6d, the rotation of the collar 7a moves in a known manner, for example, by cooperation of an internal thread 35a of the collar and external thread 35b of the adjustment screw (FIG. 4). The displacement of the adjustment screw 23 is along the longitudinal axis ZZ&#39; of the unlocking sleeves or rods 21 in the direction indicated as arrow F1 in FIG. 6b. The piston 5a is unlocked by releasing the locking element 11a, as shown in FIG. 6c. Following that, the unlocked piston rod 6 moves in a direction of F2 which permits the piston/piston rod combination to return to its initial position by moving it in the longitudinal direction, as shown in FIG. 6d. It should be noted that the jack 1 includes two end stops 50a, 50b, respectively, integral with the rear and front ferrules 15a, 15b in such a manner so as to block the unlocking collars in either longitudinal direction. 
     The jack 1 has two rod sets or sleeves 21, one at each of its extremities, which are positioned in a diametrically opposed location relative to the axis ZZ&#39; and parallel thereto. The rods or sleeves 21 are in abutment against the front and rear extremities 19a, 19b of the respective pistons 5a, 5b. It is important to note that the piston rod 6 includes a central stop 12 situated between the stops 9a, 9b and which is arranged between the two pistons 5a, 5b in order to limit the travel approaching each other. 
     According to the preferred embodiment of the jack, he dimensions of the various elements which make up the locking means MV and the manual unlocking means MDV such as the unlocking collars 7a, 7b, the pistons 5a, 5b, the spring 8, the adjustment screw 23, or the unlocking buttons 21, for example, are selected in such a manner that the rotation of the collar which is necessary for unlocking the piston is at an angle ranging between 0° and 180°, and advantageously is equal to 120°. The rotation amplitude of the collar can be different without going outside of the protected field of the invention; likewise, the control elements or the connection elements of the manual unlocking means MDV can be replaced by equivalent means. It should be noted that the unlocking collars 7a, 7b are advantageously equipped with a torsion spring 22 intended to invoke an inverse rotation of the unlocking collar in order to bring it back into its initial position. The same is true of the adjustment screws 23 and the unlocking push buttons 21 which are connected with it. 
     It should be noted that according to the preferred embodiment, the unlocking collars 7a, 7b are arranged at each extremity of the jack in such a manner so as to be able to rotate around the longitudinal axis ZZ&#39; of said jack. 
     In addition, as depicted in FIGS. 1 and 5, the passage of the compressed air into or out of the pneumatic jack 1 takes place longitudinally through jack in one or several hollow cylindrical tubes 14 of the body of the jack 2 arranged on the outside of the chamber 4. 
     According to the preferred embodiment, the number of tubes 14 amount to four and beneficially permit passage of compressed air through the front and rear ferrules 15a, 15b through connection screw 26a, 26b. One screw 26b is in part perforated in order to permit the flow of compressed air. It should be noted that a passage or duct 25 connects the tube 14 to the front extremity of the chamber of the jack 4 to introduce the compressed air which acts on the piston 5a. 
     It is to be appreciated that the jack could include locking means for only one of its extreme positions and thus, only one movable piston and its associated unlocking means. 
     The invention has been described with reference to the preferred embodiment. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.