US2915018A - Track tamping machine - Google Patents

Description

1959 F. PLASSER EI'AL 2,915,018

TRACK TAMPING MACHINE Filed March 7, 1957 2 Sheets-Sheet 1 I N V EN TOR) Fra nz Pmssaz 3 JIM 7/7502 :2

BYgfJ /w F. PLASSER ETAL 2,915,018

Dec. 1, 1959 TRACK TAMPING MACHINE Filed March 7; 1957 2 Sheets-Sheet 2 1N VENTORS BY 6M2 %;4

arrow United States Patent TRACK TAMPING MACHINE Franz Plas'ser and Josef Theurer, Vienna, Austria Application March 7, 1957, Serial No. 644,638 Claims priority, application Austria March 10,, 1956 2 Claims. ((31. 104-12) The present invention relates to track tamping machines which are movable along railroad tracks to pack ballast under the railroad ties. More particularly, this invention relates to ballast tamping machines of the type wherein vibratory tamping tools are arranged in pairs, each tool being linked to a nut mounted on a rotatable threaded spindle whereby the distance between the tamping tools of each pair may be varied by rotating the spindle and thereby moving the nut therealong.

Purely mechanical tamping tool distance varying devices were, found unsatisfactory because it was not possible to avoid breakage of machine parts, andmore particularly of the distance varying devices, under the increased pressures encountered in the tamped ballast despite many safety means developed for the purpose of limiting the maximal density of the tamped ballast and, accordingly, the pressures to which the devices were subjected.

Therefore, track tamping machines have more recently been developed, in which the tamping tool distance varying devices are hydraulically operated. Machines of the latter type have been particularly successful where the hydraulic cylinder chambers of a complete tamping tool aggregate were connected to a single hydraulic :system so that the tamping tools could be adjusted individually, independently from each other and asynchronously ac cording to the resistance encountered by each tool in the ballast. 7

While the hydraulically-operated devices had many advantages, it was found diflicult to make the center of vibration of the tamping tools, :i;e. the theoretical point of rest during their vibrations, coincide with the *connecting pivots linking the tools to the hydraulicallymoved actuating elements. For, instance, in our application Serial No. 462,086, filed October 13, 1954, now Patent No. 2,876,709, the tamping tools are linked to cylinders which are slidably mounted :onpistons dividing the cylinders into two chambers. While it was possible to hold these cylinders more or less .in .place by maintaining both -cylinder chambers under constant pressure and to effect sliding movement of the'cylinders by increasing the pressure in one of the chambers, the necessary damping of residual vibrations nevertheless required additional devices to meet practical operating conditions.

,It is the principal object of the present invention to provide a track tamping machine wherein the advantages of the mechnical and hydraulic operation of the tamping tool distance varying devicesare' combined While the respective disadvantages of each of these prior systems are fully tavoided.

This object is obtained in accordance with this invention by moving the tampingtools with rotatable threaded spindles whichare driven by hydraulically-operated transmission means. Preferably, each tamping tool has its own, separately rotatable spindle and, accordingly, its own hydraulically operated driving means so :that the tools may be adjusted asynchronously and individually 2,915,018 Patented Dec. 1, 1959 ice in response to the pressure encountered by each tool in the ballast. The separate driving means for each tool of a tamping tool aggregate are preferably connected to a single hydraulic fluid pump and are interconnected by a single conduit system.

The prior hydraulically-operated tamping tool distance varying devices had additional. disadvantages. While the tamping tools remained immobile, the hydraulic fluid coming from the continuously operating pump had to be returned to the fluid storage tank by means of safety valves mounted in the fluid conduit to delimit the maximum pressure therein. During extended operations, the passage of the fluid through the safety valve caused it to be undesirably heated. Furthermore, while the tamping tool's stood idle, the entire driving energy applied to the pump was uselessly, wasted.

A similar waste of energy was encountered in the mechanically operated devices hereinabove described. While the tamping tools were at rest, i.e. when theywere prevented from further movement by lateral stops provided for this purpose, the mechanical driving elements were subjected to increased wear.

In accordance with a preferred feature of the invention, therefore, an infinitely variable pump is provided to supply hydraulic fiuid to the spindle driving means. The capacity or delivery rate of this pump is automatically varied between zero and a predetermined maximum by the pressure the moving tamping tools encounter in the ballast or at a stop.

The above and other objects, features and advantages of the present invention will be more fully explained 'in the following detailed description of a now preferred embodiment thereof, taken in conjunction with the accompanying drawing which illustrates certain structural details without limiting the invention thereto. In the drawing,

Fig. l'is aside view, partly in section, of the front part of 'a track tamping machine;

Fig. 2 schematically illustrates the hydraulic fluid conduit and control means actuating the driving mechanism for the spindle of each tamping tool;

Fig. 3 is a sectional view of the hydraulic fluid pump; and.

Fig. 4 shows a detail of the pump control means.

Referring now to Fig. 1, there is shown a track tamping machine moving on track 42 mounted on ties 43 which are supported in ballast 41.. In a manner well knownper se, the tamping tool carrier 3 is vertically slidably supported on posts 2 mounted in the carriage frame. Eccentric'shaft 5 is journaled in the carrier 3 and vibrates the tamping tools 4 by reciprocating or oscillating tool mounting arms '6 when the shaft is rotated. The tamping tools are pivoted to arms 6 at their upper ends. .All .this structure is conventional and is described, for instance, in our above-mentioned patent application.

The mechanism for varying the relative distance of the tamping tools 4 will now be described.

Each tool is pivoted intermediate its ends at 10 to a longitudinally s'hiftable nut 7 mounted on a rotatable threaded spindle 8. The spindles are rotatably journaled in bearings '8 and 8", 8 being centrally mounted to receive the inner ends of two adjacent spindles controlling themovement of one pair of tamping tools and a bearing 8" being mounted for receiving the outer end of each tool. For added stability, an integral portion 7 of each nut is slidably supported and guided on longitudinal guide rod 9 rigidly mounted in tamping tool carrier 3.

The outward and inward movement of tamping tools 4, which are pivotably linked to nuts 7 at 10, is limited by suitable stops mounted for cooperation and engagement with nuts 7 when the same have reached the position of the stops. The outer :stops are shown 'at 1 Such a. device is shown,

and 11', stops 11 being removable from guide rod 9 to permit a wider outward stroke of the tamping tools to fixed stops 11'. This is desirable in case of tamping wider ties. A'preferred arrangement for moving stops 11 is described and claimed in our copending application Serial No. 629,183, filed December 18, 1956, now Patent No. 2,872,878.

A gear wheel 15 is keyed to each rotatable spindle 8 outside bearing 8", each gear 15 meshing with a gear wheel 14 which, in turn, is engaged by pinion 13. This gear transmission serves to transmit rotary motion from the hydraulically operated drive 12 to the associated spindle 8. Hydraulically operated driving systems which convert the hydraulic pressure of a fluid supplied to it under pressure by a pump, for instance, into a rotary motion like a turbine are well known per se. Many types of such hydraulically operated rotary driving systems are known and, since their specific structure is of no importance in respect of the present invention, they are not further described so as to limit the description to the specific improvement provided by this invention 1.

The supply conduit system of hydraulic fluid, such as oil from storage tank 18 to the driving systems 12 is schematically illustrated in Fig. 2. Pump 19 is mounted on the tamping tool carrier 3 in supply pipe 16 which leads from the oil storage tank to the pump. The hydraulic fluid is delivered through pump output pipe 21 to the cylinder 22 which houses a slidable rod with a plurality of pistons 23 to regulate the fluid supply to the driving systems 12. Return pipe 26 is connected to cylinder 22, leading back to the oil storage tank.

As shown in Fig. 2, there are four driving systems with their pinions 13 to drive the associated spindles 8 moving the four tamping tools of a tool aggregate adapted to tamp ballast at both sides of track 42. Supply conduit systems 24 and 25 lead from cylinder 22 to each of the driving systems 12. The slidable rod with its pistons 23 is reciprocable in cylinder 22 by actuating the lever 27. A branch pipe 28 leads from pump output pipe 21 to a control element which consists of cylinder 29 housing piston rod 31 with piston 30. The piston is biased by spring 34. The piston rod is linked to rod 32 which engages pin 33 mounted on the pivotable element 20 of pump 19, the pin cooperating with longitudinal slot 32' of rod 32 (see Fig. 4).

Another branch pipe 35 leads from supply conduit 25 to a second control element consisting of cylinder 36 housing piston rod 37 with piston 37. Piston 37 is biased by spring 38. Piston rod 37' is connected to rod 39 which also engages pin 33 with its longitudinal slot 39' (see Fig. 4). i The pivotable element 20 of the pump is biased by spring 40 connected to its outer end and to the tamping tool carrier to hold the element 20 normally at an angle in position I (see Fig. 3).

Infinitely variable pumps are well known and have been used for many purposes where it is desired to adjust the pump delivery rate or capacity smoothly and gradually. A preferred pump of this type is shown in Fig. 3.

Pump drive shaft 17 is journaled in the fixed pump portion 19, inlet pipe 16 and output pipe 21 being connected to portion 19 at opposite sides thereof. Cylinder 19" is mounted on pump portion 19 and glidably houses two pistons 19' whose piston rods are connected to pivotable pump portion 20 by means of universal X joints 20". The pivotable pump portion is mounted on cylinder 19" by means ofa shaft with the universal joint 20'.

Position I indicates the maximal angle of pivotable pump element 20, at which point the capacity of the pump is also at a maximum because the length of the stroke of pistons 19' is at a maximum. vIn position H, the pump portions are coaxial and the pump will deliver for instance in Letters Patent No. 956,570, dated May 3, 1910.

v 4 a no fluid during rotation because the length of the piston strokes is zero in this position.

The tamping tool distance varying mechanism of the invention operates as follows:

When the track tamping machine is moved into tamping position so that the pairs of tamping tools forming the tamping tool aggregate are placed over a tie and the tamping tool carrier is lowered to position the lower ends of the tamping tools into the ballast, as shown in Fig. 1, control lever 27 is thrown into position A (full lines). In this position, the rotating pump will deliver hydraulic fluid, i.e. oil, through output pipe 21 to cylinder 22 whence the fluid will flow under pressure through conduit system 24 into the four driving systems 12. The hydraulic pressure in the driving systems will rotate pinions 13 and accordingly meshing gears 14 and 15. The direction of rotation of pinions 13 is so selected in this case that the corresponding rotation of spindles 8 will force nuts 7 and tamping tools 4 inwardly so that the ballast between each pair of tools is tamped under the tie. After the hydraulic fluid has exhausted its pressure in the driving systems, it will leave them through conduit systems 25 and will return without pressure to storage tank 18 by way of return pipe 26.

As soon as the approaching movement of the tamping tools has sufficiently densified and compressed the ballast therebetween, i.e. when all tamping tools 4 encounter the same resistance in the ballast, regardless of the individual position of each tool, the pressure in conduits 21 and 24 will correspondingly increase. This, on the other hand, will also cause a pressure increase in branch pipe 28 so that piston 30 of the first control element will slowly be pressed downwardly against the load of spring 34 as the pressure in pipe 28 mounts. The movement of the piston will actuate a corresponding movement of rods 31 and 32 which will force down the pin 33, thus displacing the pivotable pump portion 20 against the bias of spring 40. As pump portion 20 is slowly moved toward axial alignment with pump portion 19, a correspondingly slow reduction of the pump delivery rate will gradually take place.

The characteristics of spring 34 are preferably so chosen that that pressure in conduit system 24 and, therefore, the compression force of tamping tools 4 increases slowly.

Finally, when the maximal pressure has been reached, the pivotable portion 20 is moved into axial alignment with the pump portion 19 so that the pump is in position II. In this position, no further fluid is delivered by the pump. Thus, the pump will use no energy when the tamping tools stand still or only so much energy as is required to maintain the pressure in the conduits.

It will be seen that this hydraulic conduit system requires no safety valves since the fluid flow automatically stops when the tamping tools are at rest.

When tamping is completed and it is desired to move the tamping tools apart again, the control lever 27 is thrown into position B (broken line). In this position, pistons 23 will so divide cylinder 22 that pump output pipe 21 communicates with conduit system 25 while conduit system 24 is in communication with fluid return pipe 26.' Since there is very little resistance to the opening movement of the tamping tools, the hydraulic pressure in pipe 28 and cylinder 29 will decrease considerably so that the pivotable pump portion 20 may return to its normal position I under the bias of spring 40. Thus, the pump again delivers oil through output pipe 21 into cylinder 22 and conduit system 25 to each of the driving systems 12, the pinions 13 now being rotated in the opposite direction to reverse the rotation of spindles 8 and move the tamping tools 4 apart. Since there is little resistance in the path of the opening tamping tools, this movement is effected relatively rapidly. The return of the exhausted hydraulic pressure fluid from systems 12 to the oil storage tank is eflected through conduit system 24. As soon as the nuts 7 or their upper parts 7 encounter stops 11 or 11' during the outward movement of the tamping tools, increased pressure is immediately created in conduit system 25. This causes a correspondingly increased pressure in branch pipe 35 and cylinder 36 of the second control element. The increased pressure will move piston 37 and piston rod 37' downwardly and pulls down the pivotable pump portion 20 which is connected to rod 37' by means of rod 39 and pin 33. Thus, portion 20 is slowly depressed against the load of spring 38 in cylinder 36 and spring 40 which is biased to hold portion 20 under angle a.

As above described, the pump delivery rate is thus slowly decreased to zero. When the tamping tools are at rest, the pump will also stop until control lever 27 is thrown into position A again to start a new tamping cycle.

The second control element 36, 37, 38' is so dimensioned and arranged that it responds much more quickly to increased pressure in the pipe 35 than the first control element 29, 30, 34 responds to increased pressure in pipe 28. The reason for this is that the first control element is designed to become effective during the tamping movement of the tamping tools, i.e., at high pressure, while the second control element should act quickly during the pressureless opening movement of the tamping tools.

Fig. 4 illustrates the purpose of elongated slots 32' and 39 used to connect the above control elements to the pivotable pump portion 20. With this arrangement, each control element can act upon pin 33 of portion 20 independently of the other control element, i.e. the rod 32 can depress pin 33 by the length of slot 39' without moving rod 39 while rod 39 can pull the pin down by the length of slot 32 without disturbing rod 32.

As will be clear from the above description, the present invention is based on the concept that unexpected improvements in a tamping tool distance varying mechanism can be achieved when the known tool spindle drives are actuated hydraulically, inasmuch as such an arrangement avoids all the disadvantages of the purely mechanically operated drives while eliminating the faults of the newer purely hydraulic drive means.

While a preferred embodiment of the new andimproved tamping tool spacing adjustment mechanism has been described and illustrated in detail, it will be clearly understood that many modifications and variants of the described principle of combining a mechanical and hydraulic drive may occur to the skilled in the art, particularly after benefiting from our teaching, without departing from the spirit and scope of the invention as defined in the appended claims.

What we claim is:

1. A mechanism for varying the relative distance between two tamping tools of pairs of opposing vibratory tools of a track tamping machine wherein the tamping tools are mounted on a carrier and reciprocate parallel to the track, and means is arranged on the carrier for imparting a reciprocating vibratory motion to the tamping tools, comprising, in combination: a rotatable threaded spindle mounted on the carrier substantially parallel to the track, a nut mounted on the spindle and linked to an associated one of said tools at a point intermediate its ends whereby said nut constitutes a dead center substantially free of vibrations for said tool, a hydraulicallyoperated driving system mounted on the carrier, mechanical power transmission means connecting said driving system with the spindle for rotating the same, the hydraulically dn'ven spindle constituting the sole positive drive for reciprocation of said nut andits associated tool, and a maximum amount of vibratory force being transmitted to said tool while the nut constituting the dead center thereof is reciprocated, and means for supplying hydraulic pressure fluid to the system.

'2. The mechanism of claim 1, wherein the hydraulically-operated driving system includes a separate drive for each spindle and the hydraulic pressure fluid supply means comprises a single fluid pump and fluid conduit system interconnecting the separate spindle drives, and comprising means for reversing the direction of rotation of each spindle drive, said reversing means comprising an adjustable control valve connected in the fluid conduit system between the pump and the separate spindle drives, said conduit system including two separate conduits each connected between the control valve and all spindle drives, and means for adjusting the control valve to connect selectively one and the other of said two separate conduits to the pump.

References Cited in the file of this patent UNITED STATES PATENTS 2,791,971 Schnellmann May 14, 1957 FOREIGN PATENTS 285,504 Switzerland Dec. 16, 1952 1,029,682 France Mar. 11, 1953 1,101,408 France Apr. 20, 1955

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