DE2363941A1 - PISTONS FOR HYDRAULIC REVERSE UNITS - Google Patents

Description

i. G.abur ", It. December 1-173

Priority: Dec 21 1972, V ".St.Λ. Pat .Ami. 317 415

Applicant:

Caterioillar Tractor Co.

Peoria, 111., V. St.A.

Pistons for hydraulic converter units

The present invention relates to a Baufora piston for use in hydraulic converter units.

These fluid converter units provided with a reciprocating piston are used in pumps and motors used. In particular concerns the. present invention a piston with a core. of low Weight sun use in the aforementioned facilities and an improved device for securing the core

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axially occurring displacements during operation of the piston and ultimately improved Shaping of the core to increase the strength of the piston against the high stresses developed in the converter unit to enlarge.

Conventionally, the weight of the pistons contained in such converter units is reduced because the I ^1. = Part of the piston is provided with a recess. However, this increases the dead volume of the fluid that is inside the converter unit are moved nv-2, and this has the effect of reducing the efficiency of these devices. It is therefore common to fill the recess with a material with a lower weight than the basket material of the piston, this material having a sufficiently high modulus of elasticity In order to withstand the compression under the compressive forces during operation. Such filler material must be anchored in the piston so that: 3 It is not displaced during operation of the adjuster unit, potentially causing great damage to such devices could.

Previous attempts have been made to make pistons small Weight, for use in these hydraulic converter units ζΐΐ create. Often, however, the gowns, to secure the filling material in the piston, complex and expensive or inadequate and lead to loosening txfer detachment of the

Core during operation of the piston, and often both disadvantages are present. Albeit previously known configurations of pistons also usually result in pistons of lighter weight have the consequent reduced strength The piston occasionally causes the piston not to undergo the high stresses developed during operation resistance.

Accordingly, it is an object of the present invention to provide an effective and inexpensive device for anchoring to create a core made of filler material within a recess in the shell part of a piston, which in with piston to provided hydraulic converter units can be used.

Another object of the present invention is to provide a to create an improved design of a core made of filler material, resulting in a piston of low weight, which has an improved ability to withstand stress because it has greater strength in the area where the stress forces are concentrated.

A piston according to the invention has one through one substantially conical or step-shaped in diameter widening inner wall of the piston formed recess, which are filled with a core made of a light material is. Furthermore, according to the invention, at least one annular groove is formed in the inner wall of the piston and it holding means are provided for anchoring the core made of filler material within the recess, which at least one,

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include resilient ring which is positively inserted into the annular groove and held there and for formation firm engagement with the filler material in the recess protrudes.

The novel and advantageously improved device according to the invention for holding the core ensures a relatively ■ simple and economical process for Securing a core made of filler material of low weight within a recess in the shell part of a piston, wherein the strength of the piston is advantageously increased by the design of the piston according to the invention.

"Further features and advantages of the present invention emerge from the claims, as well as from the following the description and the drawings, in which preferred embodiments of the invention are explained, for example, and are shown. Show it:

Fig. 1. a sectional view in the longitudinal direction

a piston for a hydraulic pump or a hydraulic motor, of a device according to the invention for anchoring a core made of filling material and illustrates one possibility of maximum weight reduction to create the piston through a conical bore,

ig. 2 '. a sectional view of the piston according to

Fig. I in the longitudinal direction, the generally conical core of filler material in

the piston is inserted, 409826/0408 - 5 -

ORIGINAL INSPECTE

Fig. 3 is a view of the unfilled

Eolbens in the direction of arrows IHr-IIi of Fig. 1,

Fig. 4 is a view of the piston with a

Filling is provided, in the direction of arrows IV-IV of Fig. 2, and

Fig. 5 is a sectional view of another Aus

guide form according to the present invention; the piston is with a straight, provided with a stepped hole.

Figures 1, 2, 3, 4 and 5 illustrate pistons that are shown in FIG hydraulic converter units can be used. In particular according to FIGS. 1 and 3, the piston IO is made of a hollow one Ilantelteil 11 and and a spherical lower part 12 composed, the latter with a conventional one Piston Club. or a barrel cooperates. The lower part

12 is provided with a drilled through channel 14 ·, which with a substantially conical bore or recess

13 is in connection and thereby a channel for supplying a lubricant between the lower part 12 and the with this cooperating liner creates. The wall 17 of the iLantelteiles, which delimits the recess 13, is conically tapered, so that the thickness of the wall on the lower part 12 is higher, and thus a 'higher strength is created in the zone where the stress forces are concentrated. At the opposite end of the piston 10

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ο -.

the wall is 17 stupid

This shape of the piston creates greater strength than ' for pistons with walls of constant wall thickness, where nevertheless the weight of the piston according to the invention is low remain.

As shown in Fig. 5, the recess of the piston can be produced in a modified form, the V / ands rather forming stepped cylindrical cavities and not conical walls similar to FIGS. 1 and 2. In this one In a modified embodiment, the wall 17 forming the recess 13 is stepped so that the thickness of the Elantelwandung 17 in the cows of the lower part 12 'is thicker and thereby creates greater strength in the zone where the stress forces are concentrated. The graduated -ibsatzwand 22 can be perpendicular to the wall of the piston skirt run, but from the point of view of the stress the heel walls 22 are preferably beveled or, as shown, form an angle with the wall 17.

In the case of the improved anchoring device according to the invention of the introduced into the recess 13 in the piston IO Filler material against axial displacements within the Piston 10 is the wall 17 of the piston shaft with axial iörten Id and formed at certain intervals over the inner circumference. 19 provided. These hats can "either lie in one plane, the senlcreclit to the outer Wall of the piston runs, or, if desired, with

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- 7 of this wall forms a small angle.

2ν; ei iierliöranliciie Sproiigriiagc, 20 and 21, are resilient iiiid form-fitting in the udder ,. 10 and 19 are inserted and, as can best be seen in FIG. 3, extend over these grooves into the recess 13 in order to create external surfaces into which the filling material can reach. Suitable snap rings for the purposes of the present 3rf ir.dunr, such as those shown in Fig. 3 darre dt ell th, are commercially available. Sd can alternatively Spreiafriii- cre with other iOmirebuiiin; springy and form-fitting into the soot-free grooves on the inner Y / andoberflache of the iiolbeiimantels, as long as they are. Rin {? E into the recess 13 of the piston 10 and form a transversely directed surface, which into the filler into _f > ce if t.

The snap rings 20, 21 preferably have individual projections 27, which extend beyond the inner circumference of the sing as indicated in Fig. 3, extend to the surface of the ring to enlarge the formation of the engagement with The filler material "is available. It is envisaged that two snap rings will in most cases suffice to secure the filler material against axial displacement in the piston during operation to secure, however, for example, in some cases where the filler material is not excessively large forces is subject, a snap ring will suffice. In other cases more than two snap rings are desirable. the

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ORIGlNAL BATHROOM

ijpren.irrinrc have sufficient elasticity, in .accurate in the I'Tuton Io and 13 and reduce possible twisting of the filler material cone within the piston of the ileibunic connection between the snap rings and the. Grooves.

The i'ig. 2, 4- and 5 illustrate an inventive object 10 with a bore 13 which is filled with a light-weight filler material that is firmly engaged with the snap rings 20, 21. Each one has its own filler material low weight can be used to fill the recess or bore 13, for example a was:! hardening Plieriol / ir.r:;, as it is under the trade name ¹¹ LUSSZ ITo. 10975 "or" Ho. 23639 "from the company ¹¹ DUREZ Plastics Division, Hooker Chemical Corporation ", 500 WaleIi Road,!" OrtZi • j? Onawa - "- ('- ir., ITew Yorlc (V.St.A.). This material has sufficient strength, and much more The assembly unit must be able to withstand the high compressive forces i: o.nerlialb the converter unit, although any other material wringing weight, such as metal, epoxy resin, etc. can be used, which has a sufficiently high modulus of elasticity to allow the assembly. to withstand compression at high pressure.

Before the recess 13 is filled, the snap rings 20, 21 are inserted into the grooves 18 and 19. The phenolic resin filler material is then usually compression molded in the recess 13 of the piston to remove any voids and to ensure proper mechanical engagement with the protruding part _.

BAD ORfGiNAL

Tending surfaces of the snap rings to ensure if that Filler material hardens. Alternatively, Sioritzpre ^ f orrrung, Binging or injection molding can be used, Lira the filling material to be introduced into the recess 13, the same as regards the cavities and the mechanical engagement Precautions are to be observed as with the aforementioned compression molding.

Depending on the filling material used, it might be necessary are to increase the surface area of the snap rings that extend into the recess 13 of the piston extend to compensate for excessive shrinkage of the filler material as it cures. An increased radial width of the snap ring ensures that the filling material is properly engaged on the snap rings 20 and 21 and prevents subsequent axial displacement of the filling material during the Operation of the piston. Differences in the coefficient of thermal expansion of the filler material and the Eolbenwerkstoffs must should also be taken into account when selecting appropriate snap rings to prevent a gap between the wall 17 of the piston skirt and the core is made of filler material, which would be sufficient to make the snap rings from the filler material or to let the grooves emerge.

In Figs. 2, 4 and 5, a channel 25 is shown which communicates with a channel 14 in order to connect the flow channel for the lubricant through the piston 10, as explained above, to complete. Channel 25 is preferably dad: nasii.

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BATH ORIGINAL

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formed, cla: 3 a long rod that extends through the entire length of the piston 10 is inserted into the opening of the channel 14 before the recess 13 is filled, as in the patent application also submitted by the applicant. Ho. 115 639 (V.St.A.) filed on February 16, 1971. The filler material is then compression molded around the rod in recess 13 and a channel is exposed when the rod is removed after the filler material has cured. According to another exemplary embodiment, the hole can be drilled through the filler material after it has hardened.

- patent claims -

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Claims (1)

PATE N TAUSP RÜCHE KoITden the design for use in hydraulic converter units, characterized in that the piston (10) has a recess (13) which is formed by the inner wall of the piston (10), that at least one annular groove (18, 19) in the inner wall of the piston (10) is designed that means for holding a core made of filler material are provided within the recess (13) which comprise at least one resilient king (20, 21) which is held in a form-fitting manner in an annular groove (18, 19) and protrudes into the recess (13) to form a firm engagement with the filler material. Piston according to Claim 1, characterized in that the holding means for the filler material are several resilient ones Hinge (20,21) which are positively inserted into the corresponding grooves. Piston according to claims 1-2, characterized in that it has a lower part (12) for positive engagement within the converter unit and a rear end (17) that the piston (10) is provided with a recess (13) which extends into axial direction from behind the lower part (12) - 12 409826/0408 Lying plane extends that means for increasing the axial strength of the piston are provided, which include the substantially conical design of the recess (13), the radius of the cone between the left end dos Jolbcnt increases. - ■ 4. Piston according to claims 1-3 »characterized in that dai'2 it has a substantially conical recess' (13), which through the inner wall of the ■ Piston (10) is formed that- at least one annular hat (l6,19) is formed in the inner wall, a core made of filler material essentially the Filling recess (13), da.3 a device for anchoring this core made of filling material within the Atisahme (13) is provided, the resilient Rings (20,21) unifasst in each of the above Hats (18,19) intervene positively and get in expand the core of filler material inward to form a firm engagement with the filler material. 5. Piston according to claim 2, characterized in that that the recess (13) is designed essentially in the form of stepped cylindrical cavities is, said cylindrical cavities ·. '' from the lower part (12) of the piston to the rear üSnde (17) ctee the latter an increasing one R-adius mifT / iron # . ■ - 13 - 409826/0408 BAOORlQiNAL 6. Piston according to claim. 1, thereby pDl-zennseichnet, since "3 he has a lower part (12) for a form-fitting sing handle of the piston (10) within the converter unit and a rear edge It part, since / 3 the edge part contains a recess (13) which is bounded by the inner wall of the piston (1O) that the inner wall a / enlarged cross-section in the vicinity of the lower part (-12), whereby a first cylindrical The hollow space of the said recess (13) is formed becomes that the Kantelwandung a reduced cross-section in the vicinity of the rear end of the Eolben having, whereby a second cylindrical cavity is formed in the recess (13), such that the diameter of the first cylindrical cavity is smaller than the diameter of the second cylindrical Cavity is that at least one annular hat (13, 19) is formed in said inner wall that a core of filling material essentially fills the recess (13) that a device for Anchoring of the filling material in the recess (13) comprises resilient rings (20, 21), which in each of said annular grooves (18, 19) in a form-fitting manner are inserted and extend into the core of filler material to form a tight engagement between the inner wall of the piston (1O) and the filler material. 40 9-8 26/0408 BATH ORIGINAL