US2661721A - Hydraulic power actuator - Google Patents

Description

Dec. 8, 1953 T, SHERWEN 2,661,721

HYDRAULIC POWER ACTUATOR Filed Nov. 8, 1951 INVENTOR.

Theo Jherwen f: y n, ml/fl 0.1255

Patented Dec. 8, 1953 HYDRAULIC POWER `A'J'LUATOR Theo Sherwen, Norton Lindsey, England, assigner to Harry Ferguson, Limited, Coventry, England,

a British company Application November 8, 1951, Serial No. 255,512

1 Claim.

The present invention relates generally to hym draulic ram or actuator devices and, more specifically, to hydraulic actuators which are particularly Well adapted for operating agricultural implements from tractors having hydraulic power systems.

One object of the invention is to provide an actuator of the type set forth and which is of simple, inexpensive construction, most of its parts being susceptible of fabrication from materials requiring little, if any, machining.

Another object is to provide an actuator of the foregoing character and which possesses ample ruggedness and reliability in operation to adapt it for the rigorous usage occurring in agricultural applications.

Other objects and advantages will become ap parent as the following description proceeds, taken in connection with the accompanying drawing, in which:

Figure 1 is a sectional view through an illustrative actuator embodying the present invention,

such View being taken on the longitudinal axis of the actuator.

Fig. 2 is an enlarged transverse sectional View through the actuator of Fig. l and in the plane of the line 2 2.

Fig. 3 is an enlarged, fragmentary detailed sectional view of the gland assembly of the actuator shown in Fig. l.

Fig. 4 is an enlarged fragmentary sectiona view showing a slight modification in the closed end of the actuator cylinder.

While the invention is susceptible of various modifications and alternative constructions, preferred embodiment has been shown in the drawing, and will be described below in consider able detail. It should be uhderstood'however, that there is no intention to limit the invention to the specic form disclosed, but `on the contrary, the intention is to cover all modifications and alternative constructions falling Within the spirit and scope of the invention as expressed in the appended claim.

Upon more specific reference to the drawing, it will be perceived that the invention is there exemplied in illustrative hydraulic actuator it. The same comprises a tube or cylinder l l which telf scopically houses a slidable plunger i2 of subs Li i' stantially smaller diameter thanl that of the cylinder` bore. In the present instance, the plunger l2 happens to be of tubular form for the purpose of conserving weight and material. It may, however, be made in the form of a solid rod, particularly in the case of an actuator of relatively small diameter. One end of the cylinder l l (the left hand end as shown in Fig. l) has a closure member in the form of a anged plug it secured thereto as by means of an annular weld l5.

Fixed to, or integral with the plug it, is an attaching eye It which may be pivotally secured to a reaction point or anchorage. The outer or projecting end of the plunger i2 is provided with a plug 18, secured thereto as by means of an annular Weld l 9, the plug having an eye 2i) adapted for pivotal connection with the mechanism to be actuated. Pressure fluid may readily be admitted to or exhausted from the cylinder l E via an opening2 l in its side wall and an appropriate conduit connection 22 fastened to the cylinder in registry with the opening 2l The end of the cylinder I remote from the plug I4 houses a gland assembly -23 serving as a seal for the slidable plunger i2.

For the vpurpose of guiding the head or left# hand end of the plunger I2 axially of the bore in the cylinder Il, the plunger is provided with a guide collar 2li (Fig. 1). This collar is defined by two arcuate or segmental hearing shoes 25, 26

, which may be of sintered metallic or of diecast construction. The arcuate bearing shoes 25, 25 are mounted Within an annular groove 2l in a spool-shaped member 28 defining the inner end of the plunger I2. The spool-shaped member has an extension zia-which tsinsi'de and closesthe tubularbody of the plunger i 2, being attached to the same by means of an annular weld t. The arcuate shoes 25, 25 have slight clearances C and D relative to the medial portion of the spoolshaped member 28 and the inner periphery of the cylinder El, respectively (see Fig. 2). The shoes 25, 2e also have a more substantial clearance rela# tive'to each other, defining gaps 3l between their adjacent ends. The foregoing arrangement ren; ders the members 25, 2t and hence the guide collar 2t, susceptible of a slight oating move-V ment in aplane transverse to the longitudinal vaxis of the cylinder H and the stroke of the plunger i2. This enables the collar 24 to compensate for slight longitudinal or circumferential irregularities which might exist within the bore of the cylinder II in event the latter is made of seamless drawn tubing without being machined or honed.

In order to receive the gland assembly 23, the right hand end of the cylinder II (as viewed in Fig. l) has a counterbore 32 with a narrow annular groove 34 adjacent its outer end. The

gland assembly 23 is simply telescoped into the counterbore 32 and retained in place by means of a split spring ring 34A which snaps into the groove 34;

The gland assembly 23 comprises inner' and outer cupped rings 35, 35, of sintered bronze or similar bearing material, through which the plunger I2 slidably passes. The cupped ends of the rings 35, 36 face each other and grip between them a reinforced sealing ring, 38 of rubber or similar resilient material, these ports being preferably dimensioned so that the ring 38 will be compressed to a certain extent when initially installed. The sealing ring 38 has bonded there'- in a reinforcing ring 3&3, preferably of steel. The

reinforcing ring 3S has al. stepped-up portion disposed so that it makes metal to metal contact with the adjacent face of the outer cupped ring 36. The inner cupped ring 35, however, con.- tacts only the resilient material ci the sealing ring 38, the adjacent outer contacting edge of the ring 35 being formed with a chamfer 4! to facilitate squeezing of the resilient material oi the ring 38 out against the counterbore 32 and increase the sealing area.

Provision is made for effecting a further increase in the sealing action of the ring 3c as the plunger I2 reaches the outer end oi its stroke. -This is accomplished by the simple expedient of applying a thrust from the plunger against the gland assembly 23, thereby forcing the inner cupped ring 35 closer toward the outer ring 3S and effecting a supplemental squeeze on the sealing ring 3S. In other words, the compressive force on the ring 33 due to its initial compression and also due to the action of pressure fluid on the exposed annular area of. the cupped ring 35 has superimposed thereon an additional compressive force due to the action of pressure fluid against the inner end. face of the plunger I2. In

Ythe present instance, a stop sleeve 4I is interposed between the inner cupped ring 35 and the guide collar 24 on the plunger I2. The sleeve 4I, the length of which deines the outer extremity of the plunger stroke, is of somewhat larger diameter than the body of the plunger I2 l and may be fastened to the inner cupped member 35 or, alternatively, may simply be disposed in free oating relation on the body of the plunger I2.

In operation of the actuator IB, it will be appreciated that as the plunger I2 approaches the outermost extremity of its stroke, the arcuate bearing shoes 25, 2B of the guide collar 24 will be accosted by the inner end of the stop sleeve 4i. At this point, the inner cupped ring 35 will be subjected to an outward compression force resulting from the application of pressure fluid over a total area equivalent to the full crosssectional area of the bore of the cylinder II. Under these conditions, the inner portion of the resilient sealing ring 38 is dared or swelled out inside the recess deiined within the cupped rings 35, 36 to provide a relatively large sealing face 42 bearing against the plunger I2. To facilitate effective contact between the face 42 and the plunger I2, the former may initially have a slight concave contour.

With the actuator I3 in the condition shown. in Fig. l and the plunger I2 at the inner eX- tremity of its stroke, the pressure fluid acting on the spool member 28 will normally create a sufficient outward thrust to start the plunger I2 in motion. In actual practice this initial starting thrust would probably be enhanced due to the fact that a certain amount of inherent roughness on the contacting faces of the plug It and the spool member 28 would permit pressure fluid to enter between them and create an additional starting thrust'. In some. instances, however, it might be desirable to make more positive provision for the application oi a consistently high starting. thrust. to the plunger I2. Referring to Fig. 4, there may be interposed between the adjacentV faces'oi the plug Ill and the spool-shaped member 28' a suitable stop abutment or spacer l? capable of maintaining a deiinite and predetermined space 55 between these members s0 that pressure fluid may immediately exert a substantial thrust upon the inner end of the plunger. The abutment eli may be of relatively small size and may be attached either to the plug Ill or to the spool-shaped member of the plunger.

The construction described herein embodies a number of features, all contributing to the production of an inexpensive hydraulic actuator which may be applied, for example, to agricultural implements associated with tractors hav ing hydraulic power systems to perform move ments hitherto requiring manual operation and without making the cost prohibitive. In the event that the cylinder II should be made from cold drawn seamless tubing, its inner bore need not be machined or honed because it is only called upon to form a guide and not a sealing surface for the arcuate shoes of the g ide collar 2G. Since the latter are susceptible cf slight floating movement, they may readily adapt themselves to small irregularities in the inner surface of the cylinder II, either in the axial or circumferential direction. The clearances which make such oating movement possible, as well as the gaps 3I between the ends oi the members 25, 25, also permit oil to flow readily past them during operation of the actuator. In addition, the readily insertable and easily secured gland assembly 23 obviates the use oi a screwed gland and the necessity for forming relatively large diameter screw threads inside the bore of the cylinder II.

I claim as my invention:

In a hydraulic actuator, the combination comprising a tubular cylinder having a counterbore adjacent one end thereof, a flanged plug closure member rigidly fixed to the opposite end of said cylinder, said plug having an anchoring connection thereon, means for admitting pressure fluid into said cylinder or exhausting it from the same, a plunger slidably housed within said cylinder and terminating at its inner end in a spool shaped member, the opposite end of Said plunger terminating in a xed plug having connecting means thereon, a pair of arcuate guide shoes mounted on the medial portion of said spool shaped member with their adjacent ends in spaced apart relation, said arcuate shoes being susceptible of limited iioating movement in a direction transverse to the plunger stroke, a pair of cup-shaped ring members mounted within said counterbore in straddling relation with a resilient sealing ring, means adjacent the outer end of said counterbore for retaining said cup-shaped members and sealing ring in place, and a stop sleeve -disposed in surrounding relation with the body of said plunger, said stop sleeve being constructed and arranged to accost said arcuate shoes on said plunger to define the outer extremity of plunger stroke and to`permit the application to said sealing ring of a total compression thrust equal to that produced over an area equivalent to the total cross-sectional area of the bore in said cylinder.

THEO SHERWEN.

References enea in the fue ofV this patent UNITED STATES PATENTS Number 5 Re. 23,309 344,038 1,174,788 2,194,209 2,308,761

Number Name Date Weaver Dec. 19, 1950 Fitts June 22, 1886 Winn Mar. 7, 1916 Mott Mar. 19, 1940 Komph Jan. 19, 1943 Trevaskis July 22, 1952 FOREIGN PATENTS Country Date France Mar. 17,'1938y France Mar. 31, 1947 Switzerland May 16, 1942

Images