US3867871A

US3867871A - Piston-to-rod detachable connection

Info

Publication number: US3867871A
Application number: US354724A
Authority: US
Inventors: Daniel B Shore
Original assignee: International Harverster Corp
Current assignee: Komatsu America International Co
Priority date: 1973-04-26
Filing date: 1973-04-26
Publication date: 1975-02-25
Anticipated expiration: 1992-02-25

Abstract

Detachable connection of a piston onto a reduced diameter section of a rod, at a location thereon between spaced apart shoulders provided by the reduced diameter section. The piston is wedged into final tightness by clamped double angle wedging segments, the clamping being accomplished by a plurality of diametric pairs of threaded, piston hold-down devices.

Description

0 United States Patent 1 [111 3,867,871 Shore 1 1 Feb. 25, 1975 PISTON-TO-ROD DETACHABLE 2,211,717 8/1940 Fitzgerald et a1. 92/258 x CONNECTION 2,979,903 4/1961 Beck 92/255 X 3,397,893 8/1968 Kampert.... 92/258 X [7 In ntor: D niel B or N l Ill- 3,426,656 2/1969 Bimba 92/255 [73] Assignee: International Harvester Company, v

Chicago, 111. Primary Examiner-Jrwin C. Cohen Filed: p 1973 grafting, Agent, or F1rmJ0hn W. Games; Floyd B.

[211 App]. No.: 354,724

[57] ABSTRACT [52] US. Cl 92/258, 92/257, 403/261 Detachable Connection of a piston Onto a reduced i [5 6 ameter ection of a rod at a location thereQn between [58] Field of Search 92/257, 258, 255, 251; Spaced apart Shoulders provided by the reduced i 403/261 eter section. The piston is wedged into final tightness by clamped double angle wedging segments, the [56] References C'ted clamping being accomplished by a plurality of diamet- UNITED STATES PATENTS ric pairs of threaded, piston hold-down devices.

936,717 10/1909 Hampson 92/257 X 1,294,792 2/1919 Gray 403/261 10 Clams 6 Draw F'gures Ill im-1E:

PISTON-TO-ROD DETACHABLE CONNECTION This application relates to a detachable connection of a piston onto a reduced diameter section of a. rod, at a location thereon between spaced apart shoulders provided by the reduced diameter section. The piston and rod assembly reciprocate under power in a work performing device, including but not. limited to hydraulic power cylinders, for example. I

My invention has the objects of the drop hammer cylinder US. Pat. No. 2,211,717 and the Pat. No. 3,1 15,071 for hydraulic cylinders for large earth moving machines, the disclosures of which patents are incorporated in entirety herein by reference. One of several such objectives is to avoid certain limitations encountered with threaded connections, involving the necessary cutting of threads at one or more points on the rod end. It is well known to have a piston retainer internally threaded, or the piston internally threaded, or both, for securement onto companion threads of the rod.

My invention has the additional objective of avoiding certain things encountered in the patented structures, namely, the limitations encountered from taking resort to a split piston construction, a split retainer construction, and a split clamp, if any, as disclosed in the patents. That is to say, the patented structures while entirely feasible and doubtless commercially attractive, employ several pairs of complementary halves or parts which collectively contribute to a multiplicity of separate parts in the assembly and which in the patented designs produce manifestly limited final tightness and solidarity available in the connection.

Various features, objects, and advantages will either be specifically pointed out or become apparent when, for a better understanding of the invention, reference is made to the following written description, taken in conjunction with the accompanying drawings which show a preferred embodiment thereof, and in which:

FIG. 1 is a longitudinal view of a hydraulic power cylinder embodying the present invention;

FIG. 2 is a cross sectional longitudinal view of the connection between piston and rod within the cylinder of FIG. 1;

FIG. 3 is a top plan view of a ring formed of plural pairs of wedging segments in the connection of FIG. 2; and

FIGS. 4, 5, and 6 show individual details respectively isometrically, in top plan, and longitudinally.

More particularly in FIG. 1 of the drawings, a double acting hydraulic cylinder assembly 10 comprises a cylinder 12 having a relatively smooth bore. The head end of the cylinder 12 carries an end closure member 13 provided with a hole therethrough, and a bushing 14 within the hole for pivotally connecting the head end of the cylinder assembly in a tool working arrangement.

for a piston rod 21 of the piston assembly 11. An end- 1 less circular seal 22 about the hole seals the piston rod 21 as the latter axially reciprocates.

The rod 21 at its internal end carries a piston head generally indicated at 25 and the rod carries at its external end an eye 26 with a bushing 27 therein for pivotally connecting the cylinder assembly in a tool working arrangement. Sealing between the mutually confronting piston girth and smooth cylinder bore is provided by the usual piston rings or piston packing, not shown.

The problem will be noted at this point that the piston rod 21 requires removal of the piston head 25 in DETACHABLE Connection FIG. 2

A piston 28 in the schematic shape of an endless collar in the head 25 slides over a reduced end portion 30 of the rod 21 for purposes of assembly, and rests against a piston shoulder 32 provided by the reduced section of the rod. A wide radial groove 34 penetrating into the reduced section of the rod overlaps axially slightly with the upper end of the piston 28 as viewed in FIG. 2.

At the upper end, the piston 28 carries adjustable piston hold-down means 36 comprising an endless clamping ring 38 and piston threaded-hold-down devices 40 interconnecting the piston and clamping ring.

An interposed split locking ring generally indicated at 42 has a double slope angle at the top formed by a first, or inner, wedging surface 44 complementary to an outwardly inclining mating shoulder 46 on the upper end of the groove 34. A second, or outer, wedging surface 48 on the ring 42 is complementary to an out wardly sloped mating surface 50 on the bottom of the endless clamping ring 38.

The ring 42 projects radially inwardly into the groove 34 and has a bottom wedging surface 52 undercut at its inner end by the groove 34 and complementary to the normal upper end surface 54 of the piston 28. The frictional interface between the piston and ring 42 has minimal area. Each threaded device 40 passes noninterferingly through a radial slot 56 in tlhe ring 42 and a registering fastener opening 58 in the endless clamping ring 38.

The reduced end portion 30 of the rod 11 is of uniform diameter except for the portion carrying the depth of the groove 34, and so the cylindrical interface of contact between the piston .28 and the rod 21 is shown with a larger diameter than the bottom of the groove 34.

At outset of the adjustment, the pressure of the piston hold-down means causes endwise movement of the ring 38 toward the piston 28. Immediately, the piston 28, clamping ring 38, and near shoulder 46 on the rod, each in active response to pressure of adjustment of the hold-down means 36, and each in active engagement with a

respective wedging surface

52, 48, and 44 of the ring 42 common thereto, cooperate to wedge the ring between the piston and near shoulder 46 to a radially inward locking position locking the piston in compression on the piston shoulder 32.

SPLIT LOCKING RING 42 FIG. 3

The split locking ring 42 is composed preferably of at least 3 or 4 segments as generally indicated at 60. Desirably, a plurality of pairs of the segments is employed so as to act diametrically, as in the case of those segments specifically designated 60a and 60b. The reason is that only the central portion of each segment. represented by an arrow in FIG. 3, acts directly toward the center of the rod 21 and so there is no wasted component of motion. Yet although each end portion of each segment moves in a parallel path, such path is off center and thus wastes motion laterally as it approaches the center. In theory, such path would never, in fact, reach center, but would simply slide past center by the distance of its lateral offset therefrom.

Contact between the piston and radially outer portion of the bottom wedging surface 52 is prevented by a step 62 in the surface providing relief therebetween. The resulting clearance is predetermined and uninterrupted.

The large plurality of pairs of segments, such as the pair 60a 60b, and so forth, is no drawback in my invention because, despite the number, the endless clamping ring 38 thereupon precisely coordinates their radially inward movement as it commonly cams or wedges them in unison inwardly. A large plurality of the pairs, as compared for instance to a single pair of segments each being a semicircle, increases the mechanical advantage because it raises the number of central portions of segments and proportionally reduces the wasted motion attendant with segment end portions.

A large number of pairs of segments, each of which requires a threaded hold-down fastener device passing through the appropriate slot 56, is no drawback because of the large mechanical advantage available. In prior constructions of threaded-on pistons, or threaded-on retainer nuts for the piston received on threads of a rod, torque is applied by tool in an undivided operation and the tightness and solidarity are thus limited. But a plurality of the threaded devices 40 in use according to my invention affords a progressive tightening down system, and dividing the tightening multiplies the available torque.

Or viewed the other way, a large power wrench might be required for tightening down a comparatively enormous piston on rod threads or a comparatively enormous piston retainer nut on rod threads, whereas the connection tightened according to my invention can be taken down in stages with a simple hand wrench.

HOLD DOWN DEVICES FIG. 2

The piston hold-down devices used can be hold-down stud and nut devices for locking the wedging, split locking ring radially in place. The studs of the devices would be threaded into the upper end of the piston 28, as viewed in FIG. 2.

But as herein illustrated, the devices are shown to be hold-down bolts 40 for locking the piston with the wedges. The bolts are threaded into tapped openings which are longitudinally disposed in the upper end of the piston 28 and, at the head end, each bolt head engages the top of the endless clamping ring 38 as viewed in FIG. 2.

DETAILS FIGS. 4, 5, and 6 By way of details, a segment 60 of the split locking ring 42, the endless clamping ring 38, with the bolt heads omitted, and the rod 11 with the piston and connection omitted are shown in respective FIGS. 4, 5, and 6.

The detachability, solidarity and simplicity will be appreciated which result from my invention. Great mechanical force multiplication is available from the practice thereof. The reason is the presence of a plurality of pairs of segments 60 which display high mechanical efficiency, and a like plurality of pairs of fasteners 40 on which the torque can be concentrated one at a time, yielding an effective torque advantage of that many times.

Applying the piston head 25 is done in a reverse sequence to the steps of detachment. The detachment sequence is to remove the fasteners 40, then the clamping ring 38, next the segments of the split locking ring 42, and finally the piston 28 from the rod.

Two or more fasteners 40 are needed and two or more segments are needed in the split ring 42, and the number of each of the plural fasteners and plural segments can equal or exceed the number of the other. Thus, one embodiment of the invention contemplated has eight of the bolt fasteners 40 and four of the split ring segments 60.

What is claimed is:

1. Detachably connected assembly comprising:

a piston rod provided with a piston shoulder, and a shoulder confronting the piston shoulder with a space therebetween, and so spaced apart therefrom as to be in a position more near to the rod end; and

a piston thereon in the space between the shoulders,

having carrying means and carrying thereby longitudinally adjustable hold-down means including an endless clamping ring, the plane of which ring being at least in near vicinity to the near shoulder;

said piston, clamping ring, and near shoulder having interposed split locking ring means, said means presenting at least first and second wedging surfaces wedged against the clamping ring and against the near shoulder on respective mating surfaces of the latter so that the active engagement, in response to pressure of adjustment of the hold-down means, wedges said interposed split ring means between the piston and near shoulder to a radially inward locking position locking the piston in compression on the piston shoulder.

2. The invention of claim 1, characterized by:

the endless clamping ring, as viewed in cross section with the rod end extending in one vertical direction, presenting a downwardly and outwardly sloped surface forming one of said mating surfaces and actively engaging the first wedging surface in the described way, said first wedging surface being complementary to said sloped surface.

3. The invention of claim 2, further characterized by:

the near shoulder on the piston rod, when the latter is viewed with the rod end extending in one vertical direction, presenting an upwardly and outwardly inclined surface forming another of said mating surfaces and actively engaging the second wedging surface in the described way, said second wedging surface being complementary to said inclined sur face.

4. The invention of claim 1, wherein the split locking ring means is composed of segments exceeding a pair in number.

5. The invention of claim 1, the hold-down means characterized by threaded hold-down devices between the endless ring and the piston to clamp down on the interposed split locking ring means, the devices exceeding a pair in number.

6. The invention of claim 1, characterized by the hold-down means comprising individual threaded devices and the split locking ring means comprising individual ring segments, there being at least two pairs of threaded devices and two pairs of segments.

7. The invention of claim 1, there being angularity to the slopes of the respective first and second wedging surfaces engaged by the clamping ring and near shoulder so as to present oppositely sloping surfaces to the latter.

8. The invention of claim 1, the adjustable hold-down means characterized by threaded fastener means in the carrying means on the piston and received noninterferingly in radial slots in said split locking ring means.

9. The invention of claim 4, the split locking ring means being relieved along the radially outer portion of its interface of engagement with the piston whereby the piston and each segment at said radially outer portion of the interface of engagement have predetermined clearance preventing contact.

10. The invention of claim 9, the near shoulder characterized by a rod groove defining the near shoulder and undercutting said interface of engagement, whereby a radially inner portion of said interface of engagement of each segment overhangs the piston by a clearance gap preventing contact.

Claims

1. Detachably connected assembly comprising: a piston rod provIded with a piston shoulder, and a shoulder confronting the piston shoulder with a space therebetween, and so spaced apart therefrom as to be in a position more near to the rod end; and a piston thereon in the space between the shoulders, having carrying means and carrying thereby longitudinally adjustable hold-down means including an endless clamping ring, the plane of which ring being at least in near vicinity to the near shoulder; said piston, clamping ring, and near shoulder having interposed split locking ring means, said means presenting at least first and second wedging surfaces wedged against the clamping ring and against the near shoulder on respective mating surfaces of the latter so that the active engagement, in response to pressure of adjustment of the hold-down means, wedges said interposed split ring means between the piston and near shoulder to a radially inward locking position locking the piston in compression on the piston shoulder.

2. The invention of claim 1, characterized by: the endless clamping ring, as viewed in cross section with the rod end extending in one vertical direction, presenting a downwardly and outwardly sloped surface forming one of said mating surfaces and actively engaging the first wedging surface in the described way, said first wedging surface being complementary to said sloped surface.

3. The invention of claim 2, further characterized by: the near shoulder on the piston rod, when the latter is viewed with the rod end extending in one vertical direction, presenting an upwardly and outwardly inclined surface forming another of said mating surfaces and actively engaging the second wedging surface in the described way, said second wedging surface being complementary to said inclined surface.