GB2180893A - Segmented annular wiper lip for reciprocating rods - Google Patents

Abstract

A wiper more specially for the removal of dirt or dust from moving machine parts, such as shafts and piston rods or the like has an annular wiper lip (1) engaging the moving cylindrical machine element (3) and encompasses it circumferentially. At least the part of the wiper lip (1) engaging the machine part (3) is subdivided into a circumferentially extending array of segments (4). These segments (4) are able to move radially and circumferentially independently of each other. The wiper lip (1) is made of a semi-rigid resin material or a material with similar properties. <IMAGE>

Description

SPECIFICATION A rod wiper The present invention relates to wipers, more especi allyforthe removal ofdirtordustfrom moving parts of machines in the form of rods such as shafts or piston rods and the like, comprising an annularwiper lip which contacts the rod or moving cylindrical machine part and surrounds itcoaxially.

So far rod wipers have been designed with a single-piece, continuous stripper or wiper lip consist ingofan elastomericmaterial.Thewiperlipsur- roundsthe moving machine part, as for example the said piston rod, and has a wiper edge ofthe wiper lip resting the machine part. Any motion ofthe machine part, as for example a reciprocating stroke, in relation tothewiperwill cause any dirt or dustto be wiped off the machine part by the wiper edge of the wiper lip.

Such wipers are used more especially for pneumatic cylinder actuators ofthetype in which the piston rod runs through the cylinder housing, in which case it is mandatorythat no dirt be allowedto make its way through the piston rod opening into the inside ofthe piston. In order to ensure that this is so, it is however necessary for the wiper edge to be pressed very firmly against the piston rod. However, this leads to the significant shortcoming that the wiper edge or indeed the entire wiper lip is subjected to heavy wear, more especially in a dusty environment as for example in foundaries, grinding shops orthe like, since in such cases the part ofthe piston rod extending out ofthe cylinder housing gathers heavy deposits of dirt very quickly.

Another known design of a rod wiper is one in which the wiper lip is made of a hard material in orderto obtain a more radical wiping action and at the same time reduce the wear rate ofthe wiper lip.

However, such metal wipers have the critical disadvantage of being excessively stiff and not allowing for radial inaccuracy of the piston rod diameter. This leads two skew running ofthe metal wiper lip andthe piston rod orto heavy damageto the piston rod with the result that the complete cylinder actuatorfails and becomes dueforreplacement.

Consequently one object ofthe present invention is to remedy these shortcomings.

Afurther objective ofthe invention is to devise a rod wiper which leads to a maximum and efficient wiping action even when used in a dusty environment.

A still further aim of the invention is to create a wiperthat has a very lowwear rate and/orissimple to manufacture.

In accordance with the invention a rod wiper isto be provided that has a long service life and which allows for radial in-accuracy of the rod and any other machine element with which it is required to cooperate without detriment to the wiping action and without damageto the said machine element.

In order to achieve these or other objects, the wiper lip is made of a semi-hard resin material or of a mat trial with similar properties and at leastthe partof the wiper lip in contact with the machine element is subdivided circumferentially into separate lip seg ments that are able to move independently from each other radially and circumferentially. The effect of this is that on the one hand the wiper lip makes veryfirm contact with the moving machine element and on the other hand is able to yield or give way in a radial direction owing to its being divided into separate lip segments.

One advantage ofthe invention isthatitguaran- tees a very efficient wiping action while atthesame time ensuring minimum wear. On the one hand the material of the wiper lip is so hard that it only has a lowwear rate, while on the other hand however it is soft in comparison with the moving machine el ementwith which the wiper lip is in contact. Owing to the segmented form of the wiper lip the radial rigidity is somewhat reduced so that the individual segments are able to shift in relation to each other in the radial direction,while on the other handthere are,taken separately, still stiff enough to produce a firm contact pressure where they engage the machine element.

The consequence of all these effects is that the rod wiper in accordance with the invention has an extended working life, it being particularly significant in this respect when used in a dusty environment in which there is prone to be rapid and heavy contamin ation of the machine elementto be wiped. Afurther advantage is that the novel rod wiper is very simple to produce, seeing that the segmented form may be produced simply by cutting slits in the wiper lip.

In accordance with a further development ofthe invention the segmentation is such that the lip segments are directly adjacent to each other so thatthe wiper simultaneously serves a seal. There isthen no need to have a sealing ring in addition to the rod wiper.

Afurther outgrowth of the invention based on a design with slits between the adjacent lip segments offers the advantage of being extremely simple to produce. It is then simplestto producethe wiper lip withoutanyslitsandto producethem in asubse quentstage of manufacture.

As part of the invention the slits may be filled with elastomeric material which connects the individual lip segments together without limiting their freedom of movement. The beneficial effect of this is that it is then not possible for dust or other dirt to make its way through the gaps. It is more especially in the case of double-ended cylinder actuator units that it is necessary to seal off the interior ofthe cylinderfrom the outside. This is a function satisfactorily fulfilled bythenovel rodwiperwithawipingandsimultan- eous sealing function. Accordingly it is then possible to dispense with the necessity of having a separate sealing ring and to reduce the costs of producing the actuator cylinder unit.

It is furthermore possible to make the elastomeric filling material andthe lip segments integrallywith each other,this making it possible for the filling material to be made integrally even in the manufacturing stage.

Afurther advantage of the invention is that thefilling material and the lip segments may also be prod uced separately but a re firrnlyjoined together, as for example by bonding so that rod wipers with different numbers of segments may be offered, such wipers being connected with the filling material later as required.

Ifthe lateral segment faces subdividing the wiper lip intoseparate lip segmentswhile atthe sametime dividing the lip segments are laid in the direction of the annular cross section so that lines normal to their surface pointtowards the periphery ofthe rod wiper lip, there is then advantagethatthe manufacture becomes highly simple and may be undertaken with a tool such as a broach for example. The advantageous feature of the invention of fixedly joining the rod wiperlipwith acoaxiallyplaced annularcasing body, which isableto be located in a wiperseatin a hous ing orthelike, makes itpossibletofixthe position of the rod wiper without in anyway limiting thefreedom of motion of the lip segments.

If the wiper lip and the casing body are made integrally one will then have the benefit of simple and cheap manufacture, as for example by injection casting.

In the event of the casing body being made with an L-shaped cross section, whose first side is generally radial and whose second side is aligned so as to be approximately parallel to the machine element, there will then be a saving in material and weight.

The wiper lip may be anchored atthe inner per iphery ofthe washer-like floor so as to be directed like a collarin the same axial direction as the collar of the casing body and this gives the useful effect that the radial mobility ofthe individual lip segments is not impaired.

In accordance with a still further beneficial dev elopment ofthe wiper the wiper lip is constructed in the form of a frustoconical shell so that the outer per- iphery narrowstowardsthe machine element engaged by the wiper. This useful feature of the invention causes the wiper lip to only engage the machine part in the vicinity of its free end. The result is then that there is a very sharp and thorough wiping effect.

If a wiping edge informed on the end, nearestthe machine element, of the wiper lip to rest againstthe machine element, the wiping zone will be clearly defined. The edge will restfirmly on the machine element and so enable there to be a very good wiping action. This is also true for the embodiment ofthe invention in which the wiper lip has a v-like, angled cross section where it contacts the machine element, the tip of the v serving as a circumferentiallyexten- ding wiper edge.

If the wiper lip is directed like a collar towards the side ofthe machine element that is to be cleaned it is possible to prevent dirt on the machine part from lifting up the wiper lip to the detriment ofthe wiping action. In fact, in this form of the invention, when dirt moves against the wiper lip, the latter is more strongly pressed against the machine element and the wiper action enhanced as a result.

By adopting the beneficial feature ofthe invention of having a circumferential groove in the outer limit of the wiper lip where there is engagement with the machineelementand having agarterspring orthe like in such groove the pressing force of the wiper lip on the machine element is increased. Any wear of the wiper lip where it is in engagement has the effect of its being forced into the engagement position by the holding force of the garter spring orthe like.

If the casing body is reinforced by having a stiffening ring let into it there will bea particularlysecure seat, for example in the groove of a housing. There is a further advantage to be gained if the stiffening ring has the same outline of cross section as the casing body and is set completely within it and at the same time is completely surrounded by it. This gives the advantage that the casing body may be produced in as single working step, as for example by molding the casing body around the reinforcing body. This is more particularly simple if the casing body is made of resin material.

Afurther possible design ofthe stiffening ring using metal leads to a very high strength ofthe wiper.

If the wiper is simultaneously to produce a very ef- ficientsealing action, it is best to place two wipers axially in sequence so asto be in engagement with a machine element. A respective lip segment of the one wi per will then be generally aligned axially with a point on the second wiper, atwhich there is a slit between two segments. This arrangement is part icularlyadvantageous, if thewiperlip is divided by slits. The placing ofthe slits in the one wiper ring so asto be axially aligned with segments in the other prevents axial passage of dirt th rough the two wiper rings.

A more detailed account ofthe invention will now follow on the basis of the drawings, which show further advantageous forms of the invention: Figure 1 A rod wiper in accordance with the invention as seen from the front.

Figure 2A section of the rod wiper taken on the line A-A of Figure 1.

Figure3An advantageous embodimentofthe wiper in a partial view.

Figure4Acrosssectionthroughafurtherformof rod wiper. As will be seen from Figures 1 and 2 a rod wiper in keeping with the present invention comprises an annularwiper lip 1, which is securelyjoined to an annular casing body 7 which is coaxial to it. The wiper has its wiper lip 1 in engagement with a moving machine eiement3, as for instance in the form of a piston rod,thewiper lip extending righttheway round the machine element 3.

The casing body 7 ofthe wiper is anchored in a groove-like wiper seat 8 of a housing 9, as for example the cylinder housing.

The casing body7 is bell-like and has afloor 19 like a washer, whose central hole has a diameter greater than the external diameter of the encompassed machine element 3. The washer is placed so asto be coaxial to the machine element 3, the plane ofthe washer surface being radially aligned. On the outer periphery 10 of the floor 19 there is atube-likecoaxial collar 20so that the cross section of the casing body7 has an L-like form and the collar 20 is approximately perpendicularto the floor 19.

The machine element 3 extends through the housing in a hole 22, which surrounds the machine element 3 with play. The hole 22 diverges from the outer side 23 of the housing to a depth corresponding to the length of the collar 20 so that its diameter 24 is generally equal to the external diameter ofthe collar 20. This wider part ofthe hole 22 functions as a seat8forthewiper, in which the casing body7 ofthe wiper is anchored in such a way that the floor 19 engages the axial end 25 ofthe wiper seat 8. It is an advantage if the diameter 24 is made a little lessthan the external diameter of the collar20 and the casing body 7 is press fitted in the wiper seat 8.

Inside the casing body 7 there is a coaxiallyarran- ged stiffening ring 17, which also has a bell-like forn7, but whose size is somewhat less than that ofthe casing body. The stiffening ring 17 is so anchored in the casing body that it is completely surrounded by same. It would however naturally also be possible for the stiffening ring to be mounted on the outer side of the casing body. The stiffening ring offers the special advantage that the strength of the casing body is increased, this guaranteeing a very secure anchoring in the wiper seat 8.

Atthe inner periphery ofthe washer-like floor 19, which is identical to the periphery of the hole 18, the wiper lip 1 is formed integrally. The lip may however also be made separately with the casing body joined to it securely in some suitable way, as for instance by bonding. Starting at the floor 19,thewiper lip 1 extends inthesame axial direction as the collar 20. i.e.

both the wiper lip and also the collar ofthe casing body 7 are directed towards the outer side 23 of the housing. The axial length ofthewiperlip 1 isapproximately equal to the axial longitudinal extent of the collar20. At its free end 14, which is directed away from the floor 1 9, the wiper lip 1 engages the machine element 3. Since the hole 18 is larger in its diameter than the outer diameter of the machine element3, as seen in crosssection,there is an axially and radiallydirected oblique form of the wiper lip 1 from the floor 19, in the direction of the zone of en gagementwiththemachineelement3attheend 14.

As considered three-dimensionallythe wiper lip 1 is formed like a frusto-conical face, which starting from the floor 19 has a tapering shape running towardsthe end 14. The cross section of the wiper lip 1 is gener ally wedge-like and tapers towardsthe end 14.The part, directly engaging the machine element 3, ofthe end 14 is designed intheform ofwiperedge 6 so that the zone of engagement between the wiper lip 1 and the machine element3 is limited to an imaginary conter line along the periphery of the machine element3.

This clearly delimited zone of ensures a highly efficient wiper action.

Along itsperipherythewiperlip 1 isadvantageously regularly slitted so as to generate individual lip segments 4. The lips 2 are in planes, corresponding to the longitudinal direction ofthe machine element 3 and its radial directions. The segment side faces 12 and 12" limiting the slits in the peripheral direction are generally opposite each other.

The depth ofthe individual slits, starting from the end 14 and extending towards the floor 19 of the floor 19 ofthe casing body 7, extendsforthefull axial and radial length of the wiper lip 1, although it would also be possible to make the depth ofthe slits somewhat less or alternatively long and short, as may be required in a specific case.

An account will now be given ofthe application of the novel rod wiper.

The machine element 3, as for instance a piston rod, moves backwards and forwardsforexample in the hole 22 of the housing 9 in relation to the housing 9. The machine element 3 is guided in a bearing which is notshown so thatthe motion is limited to the direction of the axial extent of the machine element 3. The wiper prevents dirtthat becomes deposited on the section 27 ofthe machine element 3 located in the vicinity of the outer side 23 of the housing,from making its way into the interior ofthe hous- ing 26 opposite to the outside 23 of the housing. The wiper edge 6, that engages the machine element 3, of the wiper lip 1, which is divided up into separate lip segments 4, ensures that the dirt deposits are stripped from the machine element 1.If the machine element3 has variations in its radial dimensions, suchdiscrepancieswill beallowedforbytheindi- vidual segments 4 because they pivot about the zone ofthe inner periphery 11 ofthefloor 1 9 with the result that the wiper edge performs a generally radial movement. If the individual lip segments 4 move in a radial direction, there will be an accompanying change in the respective distance in the peripheral direction between two adjacent lip segments. If the wiper lip 1 were not divided up into segments, there would be have to bean additional application of force in orderto stretch the wiper lip in the peripheral direction if there were to be any radial motion ofthe wiper edge 6. Such stretch would only be possible with elastomeric material however.The construction in accordance with the invention therefore offers the advantage that relatively hard material may be employed forthe wiper lip 1, since even so a radial adaptation to the outer form of the machine element 3 is guaranteed.

As will be seen from Figure 3the separate slits 2 between respective lip segments may be filled with an elastomeric material 5. This filling material 5 serves to prevent dirt making its way through the slits 2 without however hindering the relative motion ofthe individual adjacent segments in the radial and also in the peripheral direction. This design offers the especial advantage that one may be dispense with the use of a separate sealing ring, since the wiper guarantees both a wiping and a sealing action.

Figure 4 shows a furtherform ofthe wiper in keeping with the invention using a specially formed wiper lip 1. As seen in cross section this lip is bent like a lettervwhereitengagesthemachineelement3.The tip 28 ofthe letterv serves, as considered threedimensionally, as a wiper edge 6', which surrounds the machine element 3. The open part of the letterv, which is placed in the outer periphery 13 of the wiper lip 1 like a peripheral groove 15, serves to accommodate an annulartightening element 16, as for example a spiral garter spring, which at all times pressesthewiperlip 1 and therefore the wiper edge 1 6' onto the machine element 3. This ensure that the wiper lip 1 is always in direct engagement with the machine element even after wear has taken place.

If a wiper in keeping with Figures 1 and 2 is also to function as a sealing ring without the slits therein being filled with filling material, two wipers are placed in axial succession on the machine element 3. In such a case it is convenient to use two wipers with different external diameters, that are set in succession in a stepped wiper seat in a housing. The wipers are in this case so placed in relation to each otherthat in each case one lip segmentofthe onewiperisaxi- ally aligned with aslitinthesecond wiper. Thisalign- ment of segments with slits, or circumferential offsetting ofthe segments of the two respective wipers prevents the penetration of dirt past the two wipers.

In such an arrangementthefree ends ofthewiper lips ofthe two wipers are directed towards the section ofthe machine element that is to be cleaned.

The number of segments is selected in accordance with particular requirements so that in applications where radial mobility of the wiper lip is required, the numberofthe segments will be low. The largerthe number of segments, the better their radial mobility.

Ifthe hole 22 in the housing 9 is to be efficiently sealed off, it is convenient to have a sealing ring such as a shaft sealing ring axially behind the wiper, such sealing ring they being placed between the wiper and the interior 26 of the housing. Its sealing lip is directed inthe same direction asthewiperlip 1 ofthe wiper and is continuous and non-segmented. In the case ofthis arrangementthe wiper has the function of cleaning the machine element and the commerciallyavailablesealing ring has the function of sealing offthe interior ofthe housing 26 from the outside.

At last it shall be added, that the tightening element 16 also can be advantageously an elasticlyyielding ring ofthe shape of a letter o or a springy metal ring.

Claims (30)

1. Arodwipercomprising anannularwiperlip adapted to engage a moving machine element and to coaxially encompass same, said wiper lip being made of a material with the properties of semi-hard synthetic resin material and at least a zone adapted to engage such machine element being subdivided into separate lip segments forming a circumferential array around the said element, such segments being capable of independent motion radially and in the circumferential direction in relation to each other.

2. Awiperaccording to claim 1,wherein said lip segments make direct contact with each other.

3. Awiperaccordingto claim 1,whereslitsextend between the individual adjacent lip segments.

4. Awiper according to claim 3, wherein said slits are filled with elastomericfilling material, such material connecting the separate lip segments without limiting their mobility in relation to each other.

5. Awiper according to claim 4, wherein said elastomericfilling material and the lip segments are constructed integrally with each other.

6. Awiper according to claim 4, wherein said el astomericfilling material and the lip segments are constructed separately and are joined together securely.

7. Awiper according to any of the preceding claims, wherein side faces of said segments dividing the wiper lip into the individual lip segments and at the same time limiting such segments, are axially aligned and lines drawn normallyto them are directed along the circumference of the wiper lip.

8. Awiper according to any ofthe preceding claims, wherein the wiper lip is securelyjoined to a coaxiallyarrangedannularcasing body adapted to be secured in a wiperseat of a housing.

9. Awiper according to claim 8, wherein said wiper lip and the casing body are integrally constructed.

10. Awiperaccordingto claimors,wherein said casing body is reinforced by a stiffening ring set init.

11. Awiperaccordingtoclaim 10, wherein said stiffening ring has a cross section generallycorresponding to the cross section ofthe casing body.

12. A wiper according to claim 10 or 1 1,wherein said stiffening ring is set completely within the casing body and is completely surrounded thereby.

13. Awiperaccording to any of claims lOto 12, wherein said stiffening ring is made of metal.

14. Awiperaccording to anyofclaims 8to 13, wherein said casing body is made of synthetic resin.

15. Awiperaccording to anyofclaims8to 14, wherein the casing body is bell-like in form and is made up of a floor resembling a washer and a cylin drical collarcoaxiallyformed on its outer periphery, such floor and such collar being generally at a right angle to each other with an L-like cross section.

16. Awiperaccordingto claim 15,whereinsaid wiper lip is secured in thevicinity of the inner per- iphery of the washer-like floor, it being directed like a collar in the same direction as the collar ofthe casing body.

17. A wiper according to claim 16, wherein art a free end thereof pointing away from the casing body the wiper lip is in engagement with the machine element.

18. Awiperaccordingto claim 17,whereinthe wiper lip is frusto-conical in form, its outer periphery diminishing towards the machine element.

19. Awiper according to any of the preceding claims, wherein the wiper lip has a cross section that narrows towards a zone of engagement thereof on the machine element like a wedge.

20. Awiperaccording to claim 19, wherein engagementwith the machine element is limited to the end zone ofthe wiper lip.

21. A wiper according to any ofthe preceding claims, wherein an end ofthe wiper lip nearestthe machine element has a wiper edge which is adapted to engage the said machine element.

22. A wiper according to any of claims 1 to 17, wherein in its engagement zone on the said machine element the wiper lip has a bent cross section in the form of a letterv, the tip of such v cross section being adapted to function as a wiper edge.

23. Awiper according to any ofthe preceding claims, wherein the wiper lip takes the form of a collar directed towards the section of the machine element that is to be cleaned.

24. Awiper according to any ofclaim 17to23 having a peripheral groove in the outer periphery of the wiper lip in the zone of engagement with the machine element, said groove being adapted to accommodate a tightening element.

25. Awiper according to claim 24, wherein said tightening element is a garter spring.

26. Awiper according to anyofthe preceding claims, wherein the wiper lip is regularly subdivided in circumferential direction into three or more than three separate lip segments.

27. Awiping arrangementcomprisingtwo wipers according to any ofthe preceding claims, wherein the wipers are placed in axial succession along the machine element with which they are engaged with their segments circumferentially offset so that each segment in one wiper is axially opposite a slit between two segments in the otherwiper.

28. Awiperarrangementcomprising awiperac- cording to any of claims 1 to 26, and a sealing ring with a continuous sealing lip placed axially behind the wiper.

29. A rod wiper substantially as hereinbefore described with reference to the accompanying drawings.

30. Awiping arrangement substantially as herein before described with reference to the accompany- ing drawings.