LOCKING DEVICE

Abstract: The invention relates to a device for locking against rotation a piston (1) on a piston rod (5), for example in a hydraulic or pneumatic cylinder. The piston (1) is provided with at least one radial through-hole (15), which is intended to be positioned over a notch (20) in the piston rod (5). A locking clip (10, 10'), which comprises a first straight end part (7) and a curved part (45), is intended to have its first end part (7) extending through the radial hole (15) in the piston (1) and into the notch (20) in the piston rod (5), in addition to the piston (1) being equipped with a peripheral groove (50), in which a part of the curved part (45) of the locking clip (10, 10') is intended to rest in a piston-locking position. The invention also concerns a locking clip for locking at least two bodies in relation to each other and a piston intended to be fixed onto a piston rod by means of a locking clip according to the invention.

Description: Locking device The mvention concerns a device for locking a piston onto a piston rod, for example for a hydraulic or pneumatic cylmder The invention also concerns a locking clip and a piston intended to be locked onto a piston rod by the locking clip There are a number of known solutions to how a piston can be locked onto a piston rod for a hydraulic or pneumatic cylinder A known example is when the piston is threaded onto the end of the piston rod after which a hole is bored radially through the piston and the piston rod Subsequently, a locking means in the shape of a cylindrical pin is pressed into the hole, whereby relative rotation between the piston and the piston rod is prevented In another known example a two-piece piston is used where both parts of the piston are threaded onto a piston rod The outer part is piovided with a number of axiall directed screws which are screwed against the other part so that an axially directed force occurs m the threaded joint between the piston rod and the piston parts In this way a firm locking of the piston parts onto the piston rod is achieved When changing the packmg in a cylinder end through which the piston rod passes, the piston, because of the design of the piston rod, must be dismantled from the pis¬ ton rod In big cylmders this dismantling must sometimes be performed m un¬ comfortable circumstances, e.g m the field, wherefore a complicated locking device which consists of a number of small parts is unsatisfactory Large forces and load changes act between the piston and the piston rod Because of the elasticity of the matenal of the piston and the piston rod, the large forces can produce a relative movement between the piston and the piston rod in the axial di- rection If the locking means of the locking device then takes up the whole of the force which acts between the piston and the piston rod, the locking device will be destroyed because of fatigue. An object of the present invention is to produce a cheaper, better and more secure device for locking against rotation a piston onto a piston rod, which device consists of only a small number of components. A further object is to achieve a device for locking a piston onto a piston rod, which device permits assembly and disassembly with simple tools and manipulations. Yet another object is to achieve a device for locking a piston onto a piston rod which device is designed to cope with large forces and load changes. These objects are achieved through the piston being equipped with at least one radial through-hole which is intended to be positioned over a groove in the piston rod and by a locking clip, which comprises a first straight end part and a curved part, being intended to have its first end part extend through the radial hole in the piston and into the groove in the piston rod, in addition to which the piston is provided with a peripheral groove in which a part of the curved part of the locking clip is intended to rest in a piston-locking position. Owing to the curved part of the locking clip describes an arc which is less than 180° a simple mounting of the locking clip on the piston and the piston rod is made pos¬ sible. The piston comprises a circular body with an axial through-hole for the introduction of a piston rod and a circumferential groove which is in the same radial plane on the piston as the radial hole. The invention will be described below in more detail by means of an embodiment with reference to the appended drawings, in which: Fig. 1 shows an end view of a piston which is mounted on a piston rod and fastened by means of a first embodiment of a locking clip according to the invention; Fig. 2 shows a lateral view of the device in Fig. 1 ; and Fig. 3 shows a lateral view of a second embodiment of the locking clip according to the invention. Figs. 1 and 2 show a piston 1 which is equipped with a threaded, axial through-hole 3 and which is screwed onto a threaded part of a piston rod 5. In order to prevent the piston 1 from loosening, i.e. unscrewing, from the piston rod 5, a first end part 7 of a locking clip 10 is introduced into a radial through-hole 15 in the piston 1. The first end part 7 of the locking clip 10 is straight and extends through the radial hole 15 in the piston 1 and into one of three notches 20 which are formed in the piston rod 5. The notches 20 are preferably shaped like elongated grooves which extend in the axial direction in an end part 25 of the piston rod 5. The notches 20 are evenly distributed around the periphery of the end part 25 in or¬ der to cooperate and coincide with the radially directed hole 15 in the piston in a desired position between the piston and the piston rod. Owing to the notches 20 be¬ ing shaped as axially directed longitudinal grooves, the first end part 7 of the locking clip 10 will not take up any forces in the axial direction, but only in the rotational direction. The piston rod 5 has a threaded portion 30 which is adjacent to the end part 25 which has the notches 20. The threaded portion 30 is intended to cooperate with the thread in the axial hole 3 in the piston 1. Being adjacent to the threaded portion 30 is a region which comprises a shoulder surface 35 which is intended to cooperate with a corresponding shoulder surface 40 on the piston 1. This co-operation occurs during the mounting of the piston 1 on the piston rod 5, when the piston 1 is screwed onto the piston rod 5 so far that the shoulder surfaces 35, 40 about each other. Subse¬ quently, the piston 1 is unscrewed backwards so that the radial hole 15 in the piston 1 coincides with the first reached groove in the piston rod 5 that it meets. As well as the first straight end part 7, the locking clip 10 also comprises a curved part 45 which is intended to cooperate with a circumferential groove 50 in the pe¬ riphery of the piston. The locking clip 10 preferably has a circular cross-section with a radius which can correspond with the cross-sectional radius of the circumferential groove 50. The curved part 45 of the locking clip 10 can comprise one or more bent parts. In the embodiment according to claim 1, the lockmg clip 10 has a first, a sec¬ ond and a third bend 55, 60 resp. 65. In the locked position of the locking clip, parts of the first and second bends 55 resp. 60 are outside the circumferential groove 50 This permits dismantling of the locking clip 10 by a dismantling tool, e.g. a screw¬ driver, bemg introduced into a free space 66 between the locking clip 10 and the piston 1. The tool is introduced until it comes into contact with a first cnciirnferen- tial shoulder 70 (Fig. 2), whereafter the locking clip 10 is prized out of the circum¬ ferential groove 50 by leverage. When the lockmg clip 10 has partially been prized out of the cncumferential groove 50, it may become necessary to change the pur¬ chase of the tool, whereby it is placed against a second circumferential shoulder sur¬ face 75 on the piston 1, after which the disassembly can be completed The first, second and third bent parts 55, 60 resp 65 have respectively a first, a sec- ond and a third bending radius The second bending radius is greater than the third bending radius, and the third bending radius is greater than the first bending radius According to the embodiment in Fig. 1, it is only the third bent part 65 which is in contact with the circumferential groove 50 It is, howevei , conceivable that also the second bent part 60 can be m contact at least partially with the circumferential groove 50 The locking clip 10 has essentially a C-shape with an angle α of less than 180° Fig. 3 shows an alternative embodiment of a locking clip 10' according to the ven- tion. The locking clip 10' compnses, as well as a first straight end part 7, a curved part 45 and a second straight end part 80 The curved part 45 comprises a first, a second and a third bent part 55, 60 resp 65 with respectively a first, a second and a third bendmg radius, wherem the first bent part 55 is adjacent to the first end part 7, the third bent part 65 is adjacent to the second end part 80 and the second bent part 60 is arranged between the first and third bent parts 55 and 65 The second bending radius is greater than the third bending radius, and the third bending radius is greater than the first bending radius. The first end part 7 has a first end surface 85 and the second end part 80 has a second end surface 90, wherein the normal of the respective end surfaces 85, 90 cut each other at a point. The locking clip 10' has essentially a C-shape which describes an angle β of less than 180°. During assembly of the locking clip 10, 10', the first straight end part 7 is introduced into the radially directed hole 15 in the piston 1 and into one of the notches 20 in the piston rod 5, with the clip lying essentially coincident with an axial plane through the centre line of the radial hole 15, whereafter the locking clip 10, 10' is swung around the centre axis of the radial hole 15. This is only possible in the case that the curved shape of the locking clip 10, 10' is less than 180°. By applying a mounting tool, e.g. a screwdriver, between the locking clip 10, 10' and the circumferential groove 50 in the piston 1, the locking clip 10, 10' can be prized into the circumferen¬ tial groove 50. The locking clip 10, 10' is preferably manufactured from spring steel but also other materials are conceivable, such as stainless steel, aluminium or polymer materials. The cross section of the lockmg clip 10, 10' is preferably round. Another cross- sec¬ tion is also conceivable. The above embodiments concern a locking clip for locking a piston onto a piston rod. It is also conceivable to lock two or more randomly shaped bodies in relation to each other by means of a locking clip according to the invention. Such bodies could for example be formed of an internally threaded ring element on an externally threaded pin or spindle, such as a screw and nut.

Claims: Claims 1. Arrangement for locking a piston ( 1 ) onto a piston rod (5), for example, for a hy¬ draulic or pneumatic cylinder, characterized in that the piston (1) is provided with at least one radial through-hole (15) which is intended to be positioned over a notch (20) in the piston rod (5), and in that a locking clip (10, 10'), which comprises a first straight end part (7) and a curved part (45), is intended to have its first end part (7) extending through the radial hole (15) in the piston ( 1) and into the notch (20) in the piston rod (5), in addition to which the piston ( 1) is provided with a peripheral groove (50) in which a part of the curved part of the locking clip is intended to rest in a piston-locking position. 2. Arrangement according to Claim 1, characterized in that the locking clip ( 10') comprises a second straight end part (80). 3. Arrangement according to Claim 1 or 2, characterized in that the piston (1) has an axial hole (3), which is internally threaded and in that the piston rod is provided with an externally threaded portion (30), which is intended to cooperate with the thread in the hole (3) in the piston ( 1). 4. Arrangement according to Claim 2 or 3, characterized in that the curved part (45) comprises a first, a second and a third bent part (55, 60 resp. 65) with respectively a first, a second and a third bending radius, whereby the first bent part (55) is adja¬ cent to the first end part (7), the third bent part (65) is adjacent to the second end part (80) and the second bent part (60) is arranged between the first and third bent parts (55 resp. 65). 5. Arrangement according to any of Claims 2 - 4, characterized in that the periph¬ eral groove (50) is a circumferential groove and in that the curved part and/or the second end part (80) of the locking clip ( 10, 10') are/is arranged to be resiliently forced in contact with the circumferential groove (50). 6 Arrangement according to any of Claims 1 - 5, characterized in that the number of notches (20) in the piston rod (5) is preferably three and that they are shaped like elongated grooves which extend axially into the piston rod (5) 7 Arrangement accordmg to any of Claims 4 - 6, characterized in that a part of the curved lockmg clip part which is positioned nearest to the first straight end part is outside the cncumferential groove (50) m the locking position of the clip 8 Lockmg clip for lockmg at least two bodies in i elation to each other, which have notches which can be placed in alignment with each other, and where one of the parts has a peπpheral groove, characterized in that the locking clip ( 10, 10') com¬ pπses a first straight end part (7), which is intended to be introduced mto the notches in the respective bodies, and a curved part (45) intended to rest in the penpheral groove m a position which mutually locks the bodies togethei, and in that the curved part (45) of the lockmg clip ( 10, 10') descnbes an angle α of less than 180° 9 Lockmg clip accordmg to Claim 8, characterized in that the lockmg clip ( 10') compπses a second straight end part (80), which together with the curved part (45) descnbes an angle β of less than 180° 10 Lockmg clip according to Claim 9, characterized in that the first end part (7), the curved part (45) and the second end part (80) e in the one and the same plane 11 Lockmg clip accordmg to Claim 9 or 10, characterized in that each of the first end part (7), the curved part (45) and the second end part (80) preferably have a round cross-section 12 Lockmg clip according to any of Claims 9 - 1 1, characterized in that the curved part (45) compπses a first, a second and a third bent part (55, 60, 65) with a respec- ϋve first, secemti and thrrd bending radius, whereby the first bent part (55) is adja¬ cent to the second end part (7), the third part (65) is adjacent to the second end part (80) and the second bent part (60) is arranged between the first and third bent parts 13. Locking clip according to Claim 12, characterized in that the second bending radius is greater than the third bending radius, and in that the third bending radius is greater than the first bending radius. 14. Locking clip according to any of Claims 8 - 13, characterized in that the locking clip ( 10, 10') is manufactured from aluminium or polymer material. 15. Locking clip according to any of Claims 8 - 14, characterized in that the bodies which are to be locked in relation to each other are a piston ( 1 ) on a piston rod (5), for example for a hydraulic or pneumatic cylinder. 16. Locking clip according to any of Claims 8 - 14, characterized in that the bodies which are to be locked in relation to each other are an internally threaded ring- shaped element on an externally threaded pin or spindle, such as a screw or nut. 17. Piston, intended to be fastened onto a piston rod, for example for a hydraulic or pneumatic cylinder, characterized in that the piston ( 1) compnses a circular body with an axial through-hole (3) for the introduction of a piston rod (5), at least one radial through-hole ( 15) which is intended to be positioned over a notch (20) in the piston rod (5), and a circumferential groove (50) which lies in the same radial plane on the piston ( 1) as the radial hole ( 15). 18. Piston rod according to Claim 15, characterized in that the axial hole (3) has an internal thread. 19. Piston according to Claim 15 or 16, characterized in that at least one circumfer¬ ential shoulder surface (70,75) is formed axially near to the circumferential groove (50).

Inventors: ARMOE SVERKER, ARMOE, SVERKER
Applicants: ARMOE SVERKER, VOLVO WHEEL LOADERS AB, ARMOE, SVERKER
Application year: 1996
Main classification: F16J1
IPC codes: F16B21, F16J1