EP0359750A1

EP0359750A1 - A working cylinder

Info

Publication number: EP0359750A1
Application number: EP88903250A
Authority: EP
Inventors: Göran Sundholm
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-04-07
Filing date: 1988-03-30
Publication date: 1990-03-28
Also published as: CN88101928A; WO1988008097A1; AU1577088A; KR890700772A; ES2010255A6

Abstract

Un vérin, tel qu'un vérin hydraulique, comporte une partie vérin avec deux portions terminales (1, 2), et une canalisation d'interconnexion (3). L'invention a pour objet de créer un nouveau vérin pouvant être assemblé aisément in situ et répondant aux différentes longueurs de course. Dans un mode préféré de réalisation, la canalisation du vérin est pourvue aux deux extrémités d'un évasement conique (8, 9), les deux portions terminales présentent une surface d'appui (10, 11) reposant sur l'intérieur de l'évasement et un épaulement (12, 13) à l'extérieur de l'évasement, la canalisation étant reliée avec les portions terminales au moyen d'une virole de serrage par compression (14, 15).A cylinder, such as a hydraulic cylinder, comprises a cylinder part with two end portions (1, 2), and an interconnection pipe (3). The object of the invention is to create a new jack which can be easily assembled in situ and which responds to different stroke lengths. In a preferred embodiment, the cylinder pipe is provided at both ends with a conical flare (8, 9), the two end portions have a bearing surface (10, 11) resting on the inside of the flare and a shoulder (12, 13) outside the flare, the pipe being connected with the terminal portions by means of a compression clamping ferrule (14, 15).

Description

A. orking cylinder

^,v ^ ₍ The present invention relates to a working

^", • cylinder comprising a cylinder part with two end por- 5 tions^J,and an interconnecting cylinder pipe, a piston movable within the cylinder pipe and a piston rod at¬ tached to the piston and extending through one end portion.

In prior working cylinders, especially hydrau-

10 lie cylinders, the cylinder pipe of the cylinder part is in most cases secured to the backward end by means of a weld joint and to the forward end by means of a thread connection. Welding has the drawback that the cylinder pipe loses its inner circular cross-section

15 in the vicinity of^' the weld joint, which has to be compensated for later on by inner finishing. On the other hand, a thread connection to the forward end re¬ quires threadings to be formed internally in the cyl¬ inder pipe, which is both difficult and expensive. The

20 threadings have to be relatively deep, which weakens the material to such an extent that the cylinder pipe often has to be made thicker than what is actually re¬ quired by the working pressure of the cylinder. These drawbacks are further aggravated by the fact that the J 25 desired length of stroke of the working cylinder and, consequently, the length of the cylinder pipe, varies greatly depending on the intended use; therefore, long series are seldom possible in view of the cylinder length.

30 '^■ An object of the present invention is to pro¬ vide a new hydraulic cylinder which eliminates the above drawbacks.

°- ^" The hydraulic cylinder according to the inven¬ tion,, is mainly characterized in that

35 • ■ ^' _r ^" the cylinder pipe is at both ends thereof de- -•• formed to provide a clamping surface; both' end portions -are provided with a shoulder outside the respective cylinder pipe end; and the cylinder pipe is connected with the respec- tive end portions by means of a compression clamp fer¬ rule in firm engagement both with the clamping surf ce :^* of the cylinder pipe and .with the shoulder of the end portion.

According to a preferred embodiment, when the cylinder pipe wall is relatively thin, the cylinder pipe is at both ends thereof prov¬ ided with a conical flare; both- end portions are provided with a support surface bearing on the inside of the respective flare and a shoulder outside the flare end; and the cylinder pipe is connected with the respec¬ tive end portions by means of a compression clamp fer¬ rule in firm engagement with both the flare of the cylinder pipe and the shoulders of the end portions. According to another preferred embodiment, when -the cylinder, pipe wall ±s relatively thick, the cyl¬ inder pipe is at both ends thereof provided with an annular groove, and the cylinder pipe is connected with the respective end portions by means of a com- pression clamp ferrule in firm engagement both with the annular groove of the cylinder pipe and with the -^J shoulder .of™the end portion.

In comparison with previous welding and thread¬ ing techniques, the flaring of the ends of the cyl- inder pipe and the compressing of the clamp ferrules are considerably easier to carry out. Simple tools . which do not. require any particular professional skill ^* are available on the market at a low price. The open¬ ings, i.e. the weakened points in the engagement parts of the clamp ferrules are shaped so as to enable an easy disassembly of the clamp ferrules by cutting away that part of the clamp ferrule which connects the en-

^■'* gagement parts, e.g. in order to replace a seal fitted between the cylinder pipe and an end portion. As to 5 the costs, it is insignificant that it is thereby ne¬ cessary to replace the clamp ferrule with a new one.

Another object of the invention is to provide a new method of assembling a working cylinder. One pre¬ ferred embodiment, for cylinders with relatively thin 10 walls, comprises cutting a cylinder pipe to a desired length, flaring both ends of the cut cylinder pipe, joining both flared ends of the cut cylinder pipe to the respective hydraulic cylinder end portions 15 each provided with a support surface for abutment with the internal surface of the respective flare and with a shoulder outside the end of the respective flare, and compressing a metal ferrule into firm engage- 20 ment both with the external surface of the flare and with said shoulder of the respective hydraulic cyl¬ inder end portion.

Another preferred embodiment, for cylinders with relatively thick walls, comprises '25 cutting a cylinder pipe to a desired length, forming an annular groove a't both ends of the cut . cylinder pipe, joining both ends of the cut cylinder pipe to the respective hydraulic cylinder end portions each

30 provided with a shoulder outside the respective cyl¬ inder pipe end, and compressing a metal ferrule into firm engage¬ ment, both with said annular groove and with said shoulder of the respective hydraulic cylinder end por-

35 tion. The^major advantage of the invention is that the costs for manufacturing hydraulic cylinders are dramatically reduced, because there is no need for ex¬ pensive working machines, no need for large stores and long series, and no need for skilled labour. The re¬ quired stroke length of each hydraulic cylinder can without extra costs be individually determined at the very place, anywhere where the hydraulic cylinder shall work, and the cylinder can easily be assembled there by means of simple, portable tools.

The same idea can be applied with advantage to the piston rod structure of working cylinders which "can be made considerably simpler as -compared with prior piston rods. In prior piston constructions for working cyl¬ inders, primarily hydraulic cylinders, the piston is mounted on the piston rod at least partly by means of threading, sometimes in combination with further locking means. Due to the required high accuracy, the threading of the piston rod and the piston, respect¬ ively, is difficult as well as expensive to effect, especially in constructions of large dimensions.

A further object of the invention is to provide a new piston construction which is easier to mount than previous constructions.

The piston construction according to the in-

-vention ^"is mainly characterized in that, for holding the piston in position on the piston rod, the piston rod is provided with an annular groove on both sides of the piston for receiving a press ring.

In principle, the press rings are massive, and

..when they .are pressed into the annular grooves of the piston rod with simultaneous reduction in the diameter of the rings, the ring material "flows" slightly out- wards to the sides into close contact with the re- spective piston ends. Therefore the location of th annular groove of the piston rod need not precisel correspond to the length of the piston positione therebetween. In order to be able to remove the press ring later on if necessary, the inner edges thereof ar preferably provided with two diametrically positione recesses, whereby the recesses should preferably be a least as deep as the respective annular grooves. Tha portion of the press ring which projects from the an nular groove is cut at the recesses, whereafter th press rings can be knocked off. ,

Neither the piston rod nor the piston need b provided with a threading, but the piston is simpl pushed on the piston rod.

In the following the invention will be de¬ scribed more closely by way of example, referring to the attached drawing.

Figure 1 is a partial longitudinal section of an embodiment for relatively thin cylinder pipes.

Figure 2 is likewise a partial longitudinal section of an embodiment for thick cylinder pipes.

Figures 3 and 4 are a front view and a partial sectional side view, respectively, of a clamp ferrule. Figures 5 to 8 show different stages of the mounting of the piston on the piston rod in a partial longitudinal section.

Figures 9 and 10 are end views of Figures 6 and 7, respectively. The reference numeral 1 designates a forward end portion of the cylinder part of the working cyl¬ inder, 2 designates a backward end portion, 3 desig¬ nates a cylinder pipe interconnecting the end portions 1 and 2, 4 designates a cylinder piston movable within the pipe 3, 5 designates a piston rod secured to the piston 4, 6 and 7.designate inlets for a press¬ ure liquid or a desired displacement of the piston 4 by means of the piston rod 5 in the desired direction within the pipe 3. The novelty lies in the way the pipe 3 is con¬ nected to the end portions 1 and 2. As distinct from J prior weld, and thread connections, the pipe 3 is pro¬ vided with flares 8 and 9 at both ends thereof; the end portions 1 and 2 are provided with support sur- faces 10 and 11 bearing internally on the flares 8 and 9; shoulders 12 and 13 are formed in the end por¬ tions outside the ends of the flares 8 and 9; and the pipe 3 is .arranged to be maintained in place by means of compression clamp ferrules 14 and 15 which comprise edge flanges 16 and 17 which get into engagement with the shoulders 12 and 13 and on the respective other side are in close engagement with the flares 8 and 9 of the pipe 3 by means of engagement parts 18 and 19 formed internally. The pipe 3 is simply cut into the required length, aαid* the ends to not require any surface finishing. The flares 8 and 9 are easy to be formed with standard tools; the clamp ferrules with the re¬ quired inner configuration are likewise inexpensive to manufacture. Similarly, a variety of tools for com¬ pressing the ferrules 14 and 15 in place are available -on the market and easy to use. For facilitating the disassembly thereof, the ferrules 14 and 15 are pro¬ vided with local openings 25 extending axially through the parts 16 and 18 and 17 and 19, respective¬ ly. These openings, at least two in number, are not visible in. Figure 1, whereas they appear from Figures 3 and 4.

The seal of the piston 4 against the cylinder pipe 3 is designated with the reference numeral 24. In ^• view_j, of the seal 24, the end flare 8 of the pipe also" has the advantage that the piston 4 can be in se ted in the pipe 3 without any risk of the seal 2

•' ^" "^' being damaged. With the prior inner threadings used i 5 the_e.attachment of the pipe 3 to the end portion 1, th edges of the threading often tear the surface of th seal 24.

The required finishing step of a conventiona piston rod is expensive in general and especially be

-10 cause the length of the piston rod varies greatly t the same degree as the length of stroke of the workin cylinder.

The embodiment of Figure 2 differs from the on of Figure 1, as just described, in that the cylinde

15 pipe 3a has a wall of such thickness that a flarin operation is inconvenient, or even impossible.

Instead, annular grooves are formed in the ex ternal surface of the cylinder pipe 3a close to it respective ends, and, consequently, the clamp ferrule

20 14a and 15a have edge flanges 16 b and 17b for fir engagement with said annular grooves. At least on pair of interengaging surfaces between the ferrule 14a^r, 15a and respective parts of the cylinder pipe 3 and/Or cylinder end portions are inclined to ensur

25 tight fitting. A similar clamp ferrule 20 is employe for joining a connection member 21 to the piston rod, as in Figure 1.

Figures 3 and 4 show a separate clamp ferrul 14 with the weakened points mentioned in connectio

30 with Figure 1. The weakened points are formed by re¬ cesses 25, for instance. The respective recess 25, which also can be a boring with narrow inner necks provided at the opening of the recess 25 for enabling .t e breaking, extends axially through the engaging

35 edge parts of the press rings 14 and 15, the parts -being designated with 16_., .18 and 17, 19 in Figure 1. The recesses 25 are e.g two in number and arranged diametrically so that the press ring can be brought into two detachable halves when the outer necks 80 connecting e.g. the edge parts 16 and 18 are cut away. In Figures 5 to & , the reference numeral 40 de¬ signates a"piston rod; 41 designates a piston. The piston rod 40 is provided with an annular groove on both sides of the piston 41, designated with 42 and 43, respectively, and two press rings are designated with 44 and 45^", respectively. 46 designates a periph- ■_^ eral annular recess on the piston 41, intended for re¬ ceiving a sealing means for sealing the piston with respect to a surrounding cylinder wall. 47 designates a support ring of metal, for instance; and 48 desig¬ nates a sealing ring such as a conventional 0-ring. The rings 47 and 48 are received by an annular recess 49 provided on the inside of the piston 41. 50 desig¬ nates two diametrically positioned recesses in the in- ner edge of the press ring 44; and the necks between -.'the outer periphery of tire ring 44 and the bottom of the respective recess 50 are designated with 51.

After the annular grooves 42 and 43 have been formed on the piston rod 40, the piston 41 is mounted in place in the following way:

The press ring 44, the support ring 47, the 0- „ ring 4&, the piston 41 (_^Figure 5), and finally the press ring 45 (Figure 6) are pushed over the end of the piston rod, in Figures 5 to 8 from the right. Thereafter the press ring 44 is pressed into the annu¬ lar groove 42 (Figure 7) and then the press ring 45 is pressed into the annular groove 43 (Figure 8) . In principle, it is, of course, possible to press to¬ gether both press rings 44 and 45 simultaneously; al- . ternatively, the press ring 44 could be pressed into the annular groove 42 before the rings 47 and 48 an the piston 41 are fitted in place.

The rings 44 and 45 are easy to press into the grooves 42 and 43 by means of tools available on the market at a low price. When the rings 44 and 45 are pressed into the grooves, their diameter is reduced, whereas the ring thickness is increased to the same degree, so that a close contact is achieved with both ends of the piston 41 even in cases where the distance between the grooves 42 and 43 does not exactly correspond to the length of the piston 41.

As to the mounting, the press rings can be quite massive; however, if the rings are to be dis¬ mounted later on, it is of advantage to provide the inner edge with two diametrically positioned recesses 50 preferably at least equally deep as the grooves 42 and 43. When the rings 44 and 45 are pressed in place, the recesses 50 are, as appears from Figure 10, clamp¬ ed together, possibly up to a mutual surface contact. By first cutting off the neck 51 between the bottom of the recesses 50 and the outer periphery of the press ring, the ring halves can thereafter be removed with suitable tools without any greater difficulty.

When the mounting of the piston construction is completed, it can be fitted in a cylinder in a conven¬ tional manner, as illustrated in Figures 1 and 2. It should not be necessary to more closely describe the mounting of the piston construction in the cylinder nor the cylinder itself. ^■■ The sealing rings 47 and 48 can also be ar¬ ranged adjacent to the press ring 45; other sealing solutions can be used alternatively. The recesses 50 in the inner edge of the press rings can be more than two in number, and the ratio between the dimensions of the piston -rod 40 and the piston 41 as well as the shape of the piston in general can vary considerably.

Claims

Claims:

1. A working cylinder comprising a cylinder part with two end portions and an interconnecting cyl- inder pipe, a piston movable within the cylinder pipe and a piston rod attached to the piston and extending through one end portion, c h a r a c t e r i z e d in that the cylinder pipe (3) is at both ends thereof deformed to provide a clamping surface; both end portions (1, 2) are provided with a shoulder (12, 13) outside the respective cylinder pipe end; and the cylinder pipe (3) is connected with the re- spective end portions by means of a compression clamp ferrule (14, 15) in firm engagement both with the clamping surface of the cylinder pipe and with the shoulder of the end portion.

2. A working cylinder according to claim 1, c h a r a c t e r i z e d in that the cylinder pipe (3) is at both ends thereof- provided with a conical flare (8, 9); both end portions (1, 2) are provided with a support surface (10, 11) bearing on the inside of the respective flare (8, 9) and a shoulder (12, 13) out¬ side the flare end; and the cylinder pipe (3) is connected with the re¬ spective end portions (1, 2) by means of a compression clamp ferrule (14, 15) in close engagement with both the flare (8, 9) of the cylinder pipe and the shoul¬ ders (12, 13) of the end portions.

3. A working cylinder according to claim 1, c h a r a c t e r i z e d in that the cylinder pipe is at both ends thereof provided with an annular groove, and that the cylinder pipe is connected with --•-- the respective end portions by means of a compression clamp ferrule in firm engagement both with the annular groove of the cylinder pipe and with the shoulder of the end portion.

4. A working cylinder according to claim 1, c h a r c t e r i z e d in that the clamp ferrule (14, 15) is provided with at least two openings (25) extending through .engagement parts (16, 18; 17, 19) thereof.

5. A method for assembling a working cylinder, comprising cutting a cylinder pipe to a desired length, flaring both ends -of the cut cylinder pipe, joining both flared ends of the cut cylinder pipe to the respective hydraulic cylinder end portions each provided with a support surface for abutment with the internal surface of the respective flare and with a shoulder outside the end of the respective flare, and compressing a metal ferrule into firm engage- ment both _with the external surface of the flare and with said shoulder of the respective hydraulic cyl¬ inder end portion.

6. A method for assembling a working cylinder, comprising cutting a cylinder pipe to a desired length, '^"forming an annular: groove at both ends of the cut cylinder pipe, joining both ends of the cut cylinder pipe to the respective hydraulic cylinder end portions each provided with a shoulder outside the respective cyl- --.;- inder pipe, end, and compressing a metal ferrule into firm engage¬ ment both with said annular groove and with said ■shoulder of the respective hydraulic cylinder end portion.

^■fe ,,

7. A piston construction for a working cyl- t ' ^•' in&er, comprising a piston rod and a piston mounted 5 thereon, c h a r a c t e r i z e d in that for hold¬ ing the piston (41) in position on the piston rod (40) the piston rod is provided with an annular groove (42, 43) on both sides of the piston for receiving a com¬ pression ring (44, 45). 10 .

8. A piston construction according to claim 7, c h a r a c t e r i z e d in that the inner edge of the compression ring (44, 45) is provided with two diametrically positioned recesses (50) and that the recesses are at least as deep as the respective annu-

15 lar groove (42, 43) in the piston rod (40).

9. A piston construction according to claim 7, c h a r a c t e r i z e d in that the piston (41) comprises, at least at one end thereof, an inner annu¬ lar recess (49) for receiving a sealing ring (48). 0 10. A piston construction according to claim 9, ch a r a c t e r i z e d in that a support ring (47) is-•arranged between the sealing ring (48) and the ad¬ jacent press ring (44).