DESC:SYSTEM AND METHOD FOR AXLE STUD PRESSING

Field of the invention:

The present invention generally relates to stud pressing and more particularly it relates to axle stud pressing in automobiles.

Background of the invention:

On automobile vehicle axles, studs are press fitted for tightening the wheels on axle shafts. These studs are made from forged steel and are press fitted on the axle shaft by using special designed and developed hydraulic as well as pneumatic press machines. These special machines are having disadvantage that they can press only one stud at a time in one press machine stroke. That is if any axle has four numbers of studs then the press machine requires four press strokes. These machines are high cost machines and used only for axle stud pressing.

On field, vehicle axle shaft studs are found broken in running condition. After analysis, it is observed that the studs are not press fitted fully in the axle shaft and 0.4 mm gap was observed between the stud rest area and the axle flange area. This is one of the reasons for the stud breakages. Earlier and known method to press the stud into the axle shaft is discussed as below.
1. All required studs were pressed in one single stroke of the press machine by using a round plate (17) as shown in Figure 2 and Figure 2a.
2. Due to allowable forging variation in a stud head (14h) thickness, a gap is generated between the stud (12) rest surface and axle shaft flange (15) surface.

To avoid the quality concern, the automobile industries developed single stud press machines as shown in Figure 1, which are of high cost and low productive. These machines are operated on hydraulic and some machines are on pneumatics. Number of press strokes depends upon the number of studs (12) required to press on the axle shaft (11).

A prior art patent application number US9751199B2 discloses disk brake wheel stud insertion and removal tool. It reveals a drive system which uses pressurized fluid to unthread the stud from the wheel and engage the stud to the wheel flange. Another prior art patent application number US5839180 reveals a replacement of the broken stud without requiring the removal of the inner hub and its bearing and seal. Yet, another prior art patent US7066699 discloses fastener tensioning apparatus and method for tensioning a bolt, stud or similar tension member. But in all the mentioned prior arts involve more number of press strokes and high machine cost.

The existing method for the stud pressing in the axle shaft is shown in the figures 1, 2a and 2b. Figure 2 refers to drawing of the stud (12) having a head (14h) thickness of minimum 3.8mm and maximum 4.2mm. These are forged studs (12). Allowable variation in the head thickness is 0.4mm. Four studs (12) are pressed in to the axle shaft (11) by using an axle holding machine fixture (16). To press these studs (12) in one setting, plain dolly was being used. In this method, all four numbers of stud (12) is press fitted in one press stroke, but all four studs (12) do not rest on the flange because of variation in stud thickness. A gap (14) is observed between stud head (14h) bottom face and axle flange (15) resting face. Due to this gap (14), the studs (12) break in vehicle running condition.

To nullify this quality concern, special machine is designed and developed for single stud pressing as shown in figure 1. Where the axle shaft (11) is placed in machine fixture (16) with the studs (12) placed in axle shaft flange holes; a press ram (13) presses only one stud. Then the table indexes 90 degree and then the second stud gets pressed, in a similar fashion all the remaining studs gets fixed. In this method, the quality concern is resolved but leads to low productivity and high investment costs.
Accordingly, there exists a need to provide system and method for axle stud pressing that will be of low cost, ease for operation and can press all required studs in one press stroke only and overcome the above-mentioned drawbacks of the prior arts.

Objects of the invention:

An object of the present invention is to provide a cost effective hydraulic dolly for axle stud pressing which can press multiple studs in one press stroke only.

Another object of the present invention to enable the hydraulic dolly for using on any hydraulic press machine at very low cost without any major modification.

Summary of the invention:

Accordingly, in one aspect, the present invention provides a system for axle stud pressing. The system comprises an axle shaft, a plurality of studs with each stud having a stud head, a hydraulic press machine having a press ram and a fixture base. The hydraulic dolly comprises a top plate, at least three ‘O’ rings, a bottom plate and a master set ring. The at least three ‘O’ rings includes an outer ‘O’ ring, an inner ‘O’ ring and a floating punch ‘O’ ring. The bottom plate includes at least four liners, at least four floating punches, a plurality of grooves configured therein, at least four bores and at least four tapping holes. The plurality of grooves includes a first groove provided for fitting the inner ‘O’ ring, a second groove provided for fitting the outer ‘O’ ring and a third groove acting as an oil groove. The at least four bores act as hydraulic oil reservoirs and are interconnected through the oil groove. The liner is press fitted in the each of the bore and then the floating punch is slidably fitted to the liner in each of the bore.

The at least four tapping holes are used to assemble the top plate therethrough by inserting Allen bolts therein. The master set ring is provided to set position of the floating punch for obtaining clearance of 2 mm. The floating punches provided in the hydraulic dolly work as pistons and body of the hydraulic dolly works as a cylinder. The hydraulic oil gives pressure equally in all directions with applied force, so that the plurality of studs with allowable variations in the stud head thickness is successfully pressed in one press stroke.

In another aspect, the present invention provides a method for axle stud pressing carried out by the system. The method includes inserting the axle shaft on the fixture base of the hydraulic press machine. The studs are secured in the holes provided on the axle shaft. Then, the hydraulic dolly is guided into axle shaft and the floating punches are rested on the studs. The method further includes pressing the hydraulic dolly downward through the press ram of the hydraulic press machine, with one of the floating punch resting on the stud head and the movement of the floating punch is stopped with pressure transferred to the hydraulic oil.

Due to the pressure, the hydraulic oil starts moving from one bore to another bore through the oil groove provided. The hydraulic oil moves the remaining floating punches to down-ward direction for resting on the studs heads. Further the method includes transferring applied force to the body of the hydraulic dolly, which in turn is transferred on oil and from oil the force, is transferred to floating punches and hence floating punches press the studs on the axle. The, all desired quantity of the studs with allowable variations in the thickness of the stud head are secured and pressed in the axle shaft in one press stroke by using the hydraulic dolly.

Brief description of the drawings:

The objectives and advantages of the present invention will become apparent from the following description read in accordance with the accompanying drawings wherein,

Figure 1 shows a single stud press machine, in accordance with a prior art;

Figure 2, wherein 2a and 2b shows press machine using round plate to press studs in one single stroke, in accordance with the prior art;

Figure 3 shows different parts of a hydraulic dolly for axle shaft stud pressing, in accordance with the present invention;

Figure 4 shows top view of bottom plate of hydraulic dolly, in accordance with the present invention;

Figure 5 shows inner view of bottom plate of hydraulic dolly, in accordance with the present invention;

Figure 6 shows cross sectional view of bottom plate placed on master set ring to set floating punch position, in accordance with the present invention;

Figure 7 shows cross sectional view of the hydraulic dolly, in accordance with the present invention;

Figure 8 shows assembly of bottom plate and top plate of hydraulic dolly through Allen bolts, in accordance with the present invention;

Figure 9 shows a press machine using the hydraulic dolly for the axle stud pressing, in accordance with the present invention; and

Figure 10 shows a flowchart of a method for using the hydraulic dolly for the axle stud pressing, in accordance with the present invention.

Detailed description of the invention:

The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiments.

The present invention provides a cost effective hydraulic dolly for axle stud pressing. The hydraulic dolly can press multiple studs in one press stroke only. The hydraulic dolly can be used on any hydraulic press machines at very low cost without any major modification.

The present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures. These reference numbers are shown in bracket in the following description and also provided in a table as given below:

Reference No. Part name
10 Single Stud Press machine
13 and 53 Press Ram (as per prior art and present invention respectively)
11 and 51 Axle Shaft (as per prior art and present invention respectively)
12 and 52 Stud (as per prior art and present invention respectively)
14h and 64h Stud head (as per prior art and present invention respectively)
15 Flange
14 Gap observed in the studs, when fixed with plain dolly
16 and 56 Press machine fixture base (as per prior art and present invention respectively)
17 Round Plate
50 Hydraulic Dolly
30 Bottom Plate
31 Liner
32 Floating punch
33 Bore
34 Oil groove
35 First Groove
36 Second Groove
29 Floating punch groove
37 Outer ‘O’ ring
38 Inner ‘O’ ring
39 Floating punch ‘O’ ring
40 Top Plate
41 Allen Bolt
42 Master set Ring
43 Tapping Holes

Referring to figures 3 to 10, a system for axle stud pressing (100) (hereinafter “system (100)”), in accordance with the present invention is shown. The system (100) comprises an axle shaft (51), a plurality of studs (52), a hydraulic press machine having a press ram (53) and a fixture base (56). Each stud (52) is configured with a stud head (64h) thereon.

The system (100) is characterized with the hydraulic dolly (50). The hydraulic dolly (50) comprises a top plate (40), at least three ‘O’ rings, a bottom plate (30) and a master set ring (42). The at least three ‘O’ rings includes an outer ‘O’ ring (37), an inner ‘O’ ring (38) and a floating punch ‘O’ ring (39).

The bottom plate (30) includes at least four liners (31), at least four floating punches (32), a plurality of grooves configured therein, at least four bores (33) and at least four tapping holes (43). The plurality of grooves includes a first groove (35) provided for fitting the inner ‘O’ ring (38), a second groove (36) provided for fitting the outer ‘O’ ring (37) and a third groove (34) acting as an oil groove. The at least four bores (33) act as hydraulic oil reservoirs and are interconnected through the oil groove (34). The liner (31) is press fitted in the each of the bore (33) and then the floating punch (32) is slidably fitted to the liner (31) in each of the bore (33).

In an embodiment, the floating punches (32) are made from case carburizing steel, which are hardened and tempered up to hardness 55 to 58 HRC (Rockwell C Hardness) with core hardness up to 25 to 30 HRC. The floating punches (32) are ground with g6 tolerance, wherein g6 is the ISO standard tolerance value defined by basic size followed by tolerance value. Each floating punch (32) is provided with a groove (29) for fitment the floating punch ‘O’ ring (39) therein. In the embodiment, the bottom plate (30) is round in construction having diameter in a range of 160mm-180mm and is made from aluminum material for weight reduction.

The at least four tapping holes (43) are used to assemble the top plate (40) therethrough by inserting Allen bolts (41) therein. The master set ring (42) is provided to set the floating punch (32) position so that clearance 2 mm can be obtained as shown in Figure 6. This master set ring (42) is required at the time of filling the hydraulic oil in the hydraulic dolly (50).

To assemble the hydraulic dolly (50), the bottom plate (30) is assembled with the liners (31) that are press fitted into the bores (33). The liners (31) are hardened and ground. The liner (31) is ground to maintain H7 tolerance, so that the floating punch (32) can slide in the liner (31) smoothly. The floating punch (32) along with fitment of the floating punch ‘O’ ring (39) are inserted into the bottom plate (30) through the liner (31). The bottom plate (30) assembly is then placed on the master set ring (42) for setting position of the floating punch (32). The floating punch (32) is pushed such that it rests on the master set ring (42). The hydraulic oil is poured in head of the each floating punch (32) to fill the bores (33) and the oil groove (34). The first groove (35) and the second groove (36) restrict the flow of the hydraulic oil out of the bottom plate (30). The top plate (40) is assembled on the bottom plate (30) through fastened Allen bolts (41) on the tapping holes (43) provided therein. The movements of the floating punches (32) are checked by exerting force on the floating punches (32) manually.

Now referring to Figure 10, a method (200) for axle stud pressing using the hydraulic dolly (50), in accordance with the present invention is described. The method (200) is described in conjunction with the system (100).

At step (210), the method (200) includes inserting the axle shaft (51) on the fixture base (56) of the hydraulic press machine.

At step (220), the method (200) involves securing the axle shaft (51) with the plurality of studs (52) into the holes provided therein.

At step (230), the method (200) comprises guiding of the hydraulic dolly (50) into the axle shaft (52) and resting the floating punches (32) on the studs (52).

At step (240), the method (200) comprises pressing the hydraulic dolly (50) downward through the press ram (56) of the hydraulic press machine, with one of the floating punch (32) resting on the stud head (64h) and the movement of the floating punch (32) is stopped with pressure transferred to the hydraulic oil. Due to the pressure, the hydraulic oil starts moving from one bore (33) to another bore (33) through the oil groove (34) provided. The hydraulic oil moves the remaining floating punches (32) to down-ward direction for resting on the studs heads (64h).

At step (250), the method (200) includes positioning all the floating punch (32) on the studs head (64h) as per positions of the stud (52) to accommodate the stud head (64h) thickness variations and stopping the floating punch (32) and oil movements.

At step (260), the method (200) comprises, transferring applied force to body of hydraulic dolly (50), which in turn is transferred on the oil and from oil the force, is transferred to floating punches (32) and hence floating punches (32) press the studs (52) on the axle.

At step (270), the method (200) comprises securing all desired quantity of studs (52) with allowable variations in stud head (64h) thickness to be pressed in axle shaft (51) in one press stroke by using the hydraulic dolly (50).

The assembled hydraulic dolly (50) for axle shaft stud pressing uses the property of hydraulic oil which cannot be compressed and gives pressure equally in all directions when applied force on it, when oil is in closed loop. The floating punches (32) provided in the hydraulic dolly (50) works as a piston and body of dolly works as a cylinder. The plurality of studs (52) with allowable variations in stud head (64h) thickness is successfully pressed in one press stroke by using the hydraulic dolly (50). The hydraulic floating punches (32) in floating actions can accommodate fine variations of stud head (64h) thickness and can press all studs (52) in a single press stroke.

Advantages of the invention:

1. The present system (100) provides a cost effective machine for stud pressing and avoid the number of press strokes required to press studs.
2. The present system (100) can press multiple studs in one press stroke and which will fulfill the quality requirements.
3. The present system (100) provides a simple method that enables the hydraulic dolly (50) to be fit on any hydraulic press machine at very low cost without any major modification.

The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omission and substitutions of equivalents are contemplated as circumstance may suggest or render expedient, but such are intended to cover the application or implementation without departing from the scope of the present invention.
,CLAIMS:We claim:

1. A system (100) for axle stud pressing comprising an axle shaft (51), a plurality of studs (52) with each stud (52) having a stud head (64h), a hydraulic press machine having a press ram (53) and a fixture base (56),
characterized in that, the hydraulic dolly (50) comprises:
a top plate (40);
at least three ‘O’ rings including,
• an outer ‘O’ ring (37),
• an inner ‘O’ ring (38), and
• a floating punch ‘O’ ring (39);
a bottom plate (30) including,
• at least four liners (31),
• at least four floating punches (32),
• a plurality of grooves configured therein, wherein a first groove (35) provided for fitting the inner ‘O’ ring (38), a second groove (36) provided for fitting the outer ‘O’ ring (37) and a third groove (34) acting as an oil groove,
• at least four bores (33) acting as hydraulic oil reservoirs and interconnected through the oil groove (34), wherein the liner (31) is press fitted in the each of the bore (33) and then the floating punch (32) is slidably fitted to the liner (31) in each of the bore (33),
• at least four tapping holes (43) for assembling the top plate (40) therethrough by inserting the Allen bolts (41) therein, and
a master set ring (42) provided to set position of the floating punch (32) for obtaining clearance of 2 mm;
wherein, the floating punches (32) provided in the hydraulic dolly (50) work as pistons, body of the hydraulic dolly (50) works as a cylinder and the hydraulic oil gives pressure equally in all directions with applied force, so that the plurality of studs (52) with allowable variations in the stud head (64h) thickness is successfully pressed in one press stroke by using the hydraulic dolly (50).

2. The system (100) as claimed in the claim 1, wherein the bottom plate (30) is round in construction having diameter in a range of 160mm-180mm and is made from aluminum material.

3. The system (100) as claimed in the claim 1, wherein each floating punch (32) is provided with a groove (29) for fitment of the floating punch ‘O’ ring (39) therein.

4. The system (100) as claimed in the claim 1, wherein the floating punches (32) are made from case carburizing steel that are hardened and tempered up to hardness 55 to 58 HRC (Rockwell C Hardness) with core hardness up to 25 to 30 HRC.

5. The system (100) as claimed in the claim 1, wherein the floating punches (32) are ground with g6 tolerance.

6. The system (100) as claimed in the claim 1, wherein the master set ring (42) is provided at time of hydraulic oil filling in the hydraulic dolly (50).

7. The system (100) as claimed in the claim 1, wherein the floating punches (32) in floating actions accommodate fine variations of the stud head (64h) thickness.

8. A method (200) for axle stud pressing, carried out by the system (100) as claimed in claim 1, comprising steps of:
inserting the axle shaft (51) on the fixture base (56) of the hydraulic press machine;
securing the axle shaft (51) with the studs (52) using holes provided on the axle shaft (51);
guiding the hydraulic dolly (50) into axle shaft (52) and resting the floating punches (32) on the studs (52);
pressing the hydraulic dolly (50) downward through the press ram (56) of the hydraulic press machine, with one of the floating punch (32) resting on the stud head (64h) and the movement of the floating punch (32) is stopped with pressure transferred to the hydraulic oil. Wherein the oil due to the pressure will start moving from one bore (33) to another bore (33) through the oil groove (34) provided. The oil will move the remaining floating punches (32) to down-ward direction and will rest on stud’s head (64h);
positioning all the floating punch (32) on the studs head (64h) as per the positions of the studs (52) to accommodate the stud head (64h) thickness variations and stopping the floating punch (32) and oil movements; and
transferring applied force to the body of the hydraulic dolly (50), which in turn is transferred on oil and from oil the force, is transferred to floating punches (32) and hence floating punches (32) press the studs (52) on the axle;
wherein, all desired quantity of the studs (52) with allowable variations in the thickness of the stud head (64h) are secured and pressed in the axle shaft (51) in one press stroke by using the hydraulic dolly (50).

Dated this 12th day of February 2019

Madhavi Vajirakar
Agent for the Applicant
(IN/PA-2337)