US2721424A - Crankshaft grinding machine - Google Patents

Description

OC- 25, 1955 M. R. G. TEISEN CRANKSHAFT GRINDING MACHINE 5 Sheets-Sheet l Filed OCT.. 2, 1953 INVENTOR ATTORNEYS Ot- 25, 1955 M. R. G. Tr-:lsEN

CRANKSHAFT GRINDING MACHINE 3 Sheets-Sheet 2 Filed Oct. 2, 1953 QN mm ATTORNEYS Oct. 25, 1955 M R, G, TE|5EN 2,721,424

CRANKSHAFT GRINDING MACHINE Filed oct. 2, 195:5 s sheets-sheet s INVENTOR ATTORNEYS United States Patent O CRANKSHAFT GRINDING MACHINE Mogens Roesdahl Groth Teisen, Copenhagen, Denmark Application October 2, 1953, Serial No. 383,810

Claims priority, application Denmark October 11, 1952 7 Claims. (Cl. 51-105) This invention relates to a crankshaft grinding machine.

In crankshaft grinding machines of conventional design the crankshaft is set up individually for each crank pin to be ground so that, during the grinding of each individual crank pin, the crankshaft as a whole will rotate about the axis of that pin.

This is a rather irksome procedure, and attempts have therefor been made of developing machines in which a single setting up ofthe crankshaft will suice for the grinding of all the crank pins, and also the journal portions of the crankshaft.

To solve this problem, a crankshaft grinding machine has been proposed which comprises setting up means in which a crankshaft can rotate about its normal axis of rotation, or principal axis, in a horizontal position, and a grinding wheel mounted on a pivoted support and having the shaft thereof connected with the portion of the crankshaft being ground by means of a work engaging arrn in such a manner that the grinding wheel is caused' to oscillate about the axis of the pivoted support in accordance with the circling movement of the work, i. e. a crank pin being ground, about the axis of rotation of the crankshaft.

This machine is based on the well established principle that when a workpiece being ground is kept constantly in contact with both sides of an angular notch of an arm which is xed relative to the axis of the grinding wheel, the workpiece, when caused to rotate during the grinding, will automatically be ground to accurate circular crosssectional shape with the minimum possible removal of material provided that the sides of the angular notch are disposed at suitable, not very critical angles with the tangential plane of the grinding wheel in .thel point of contact between the latter and the workpiece.

By virtue of this principle it has been found possible, with the crankshaft grinding machine described, ina single set up of a crankshaft to obtain a grinding of all the crank pins thereof to circular cross sectional shape with very great accuracy.

However, the machine has the drawback that the crank pins will not get a sufficiently smooth surface so that a post treatment such as honing will as a rule be necessary. The reason for this is that the construction involving a grinding wheel rotating at great speed in a pivoted support cannot, in practice, be built suiciently vibration free to avoid jarring between the grinding wheel, and the workpiece.

It is an object of the invention t'o eliminate this drawback while maintaining the above mentioned principle of mutually guiding the grinding wheel and the crank pins so that these can all be ground in one set up.

The invention is based on the consideration that since,A during the grinding operation, the crankshaft rotates at a speed which is very small, and in fact negligible as cornpared with that of the grinding wheel, a greater freedom from vibration can be obtained by sok constructing the machine that the grinding wheel rotates about an aXis "ice which is stationary relative to the machine frame while the axis of the crankshaft performs the movements necessary for keeping the grinding wheel and the crank pins in correct position relative to one another during the grinding operation.

Thus, according to the invention, there is provided a machine comprising a machine frame, a grinding wheel mounted for rotation about an axis which is stationary relative to said machine frame, setting up means for rotatably supporting a crankshaft to be ground for rotation about the principal axis thereof, means for so guiding said setting up means as to permit transverse movement in any direction of said principal axis as defined by said setting up means while keeping said principal axis rigidly parallel to the stationary axis of rotation of said grinding wheel, and work engaging means for keeping a crank pin to be ground in correct working position relative to said grinding wheel while the crankshaft is rotating about its principal axis.

In a machine constructed as specified a vibration-free mounting of the grinding wheel can easily be obtained because it is not carried by a pivoted support, and it is likewise easy to keep vibration of the crankshaft at a minimum, partly because the crankshaft is intended to rotate very slowly, as already mentioned, and partly because the crankshaft, during the grinding operation, is supported in the angular notch of the guide arm which in this construction is also stationary so that the setting up means only have to ensure that the principal axis of the crankshaft is kept accurately parallel to the axis of the grinding wheel. ln designing the setting up means the efforts should therefore be concentrated on obtaining rigidity against deflection of the principal axis of the crankshaft out of parallelism to the axis of the grinding wheel.

The invention also comprises means for balancing the weight of a crankshaft to be grounded so as to further reduce the amount of vibration.

Further objects and features of the invention will be apparent from the following detailed description of one embodiment, reference being had to the accompanying drawings, in which Fig. l shows the machine in side elevation,

Fig. 2, an end view of same,

Fig. 3, a plan view of same with certain parts removed and others in section,

Fig. 4, diagrammatically various adjustment means forming part of the machine,

Fig. 5, a partial end view similar to Fig. 2 with parts removed and showing in section a crank pin of a crankshaft;

Fig. 6, a partial end view similar to Fig. 5 showing a modified form of the invention;

Fig. 6a, a sectional view on line 6a-6a of Fig. 6;

Fig. 7, a plan view of the upper elements of the machine;

Fig. 8, a sectional view on line 8-8 of Fig. 10 with certain parts removed;

Fig. 9, aclutching arrangement for driving the rotary valve shown in Fig. 4 and Fig. l0, a locking arrangement for the machine.

As shown in the drawing, the machine has a frame 1 constructed with two vertical columns or towers 2 and 3 at the ends thereof, the tower Z at one end being boxshaped while the tower 3 at the other end has a U-shaped section. On the frame 1, there are provided horizontal guides 4 and 5 on which a slide 6 is slidably mounted as usual in machine tools. In the embodiment shown, the slide 6 is provided with extended guide flanges or lugs 7 and 8 resting on the guides 4 and 5 and capable of being moved to positions so as to embrace the towers 2 andV 3.

In this manner, the slide is very rigidly guided without shortening the travel thereof. In the slide 5 there is mounted a shaft 9 which at one end of the slide carries a grinding wheel 10, and at the other end of the slide carries a V-belt pulley coupled to a V-belt pulley 12 on the shaft of a motor 13 which is also carried by the slide.

At one side of the machine, the slide 6 is constructed with a drum-shaped support f4 carrying an arm 15 which is located opposite the grinding wheel l@ and has a thickness a little .smaller than that of the latter. The arm 15 is provided at one end thereof with an angular notch 16 located close by the grinding wheel and serving to engage and support the workpiece during the grinding operation, as will be described in further detail hereinafter. The arm 15 may, if desired, be rigidly connected with the drum as illustrated in Figs. 6 and 6a, in which case one wall of the notch may be formed by a slidably mounted block 15a in known manner. Alternatively, the arm 1S may be rotatably mounted on the drum-shaped support 14 and may be adjustable relative to the latter by means of a worm gear 17 as illustrated in Fig. 5. Advantageously the connection between the arrn i5 and the drum 14 may in this case be so constructed that the arm I5, and a guard (not Shown) that may be mounted thereon, may be turned completely backand downwards so as not to interfere with the setting up and taking down of a crank shaft to be ground.

On the columns 2 and 3, there is pivoted at 51 a rocking frame comprising two rocking arms 18 and 19 which are connected with each other at the rear side of the machine by means of a rigid tubular member 29, while being connected with each other at the front side by means of a tubular member 21 pivoted thereto at 52. Owing to the rigid connection'between the arms l and 19 at the rear side of the machine the rocking frame as a whole will be very rigid against such deflections that might result in lack of parallelism between the axis of rotation of the tubular member 21 and the axis of rotation of the rocking arms. On the tubular member 21 there are mounted two brackets 22 and 23 between which a crankshaft 24 may be set up. In the embodiment shown the bracket 22 is rigidly connected with the tubular member 21 and is constructed with a chuck 25 connected to suitable driving means (not shown), e. g. located in the bracket, while the other bracket 23 is a tail stock slidable along the tubular member 21. Both brackets are non-rotatably supported on the tubular member Z1, though they mayvparticu larly the bracket 23a-be adjustable relative thereto about the axis of the tubular member. Thus the bracket 23 may be constructed with a hub which is slotted at 23a and is adapted to be clamped around the tubular member 21 by means of screws 23h. Accordingly, the setting up axis defined by the brackets is exactly parallel to the axis of the tubular member 21 which is again parallel to the axis of rotation of the rocking frame and to the axis of the grinding wheel it). The parallelism between all of the said axes will always be maintained irrespective of any movement of the rocking frame relative to the machine frame and of the tubular member 21 relative to the rocking frame.

When a crankshaft is to be ground, it is set up between the brackets 22 and 23 and, to grind a crank pin, the latter is then introduced into the notch 16 and kept in rm contact with both walls thereof, e. g. by means of torsional spring members, such as torsion rod 53 between the rocking frame and the machine frame, and torsion rod 54 between the bracket supporting tubular member 21 and the rocking frame. rhe crank shaft is now rotated at a relatively low speed about its principal axis while the grinding wheel I0 is at the same time caused to rotate at high speed about its axis. The arm i5 is gradually fed forward in the direction of the grinding wheel until the grinding wheel engages the crank pin at a uniform pressure around the whole surface thereof. The crank pin has then been ground to accurately cylindrical shape with the minimum possible removal of material, and the ground surface will result so smooth that no post treatment is necessary.

During the grinding of a crank pin, the rocking frame oscillates about its axis relative to the machine frame, and the bracket supporting member 21 rotates about its axis relative to the rocking frame in such a manner that the principal axis of the crank shaft is permitted to perform the circling movement which is necessary in order that the crank pin being ground may rest iirmly supported against both walls of the notch 16.

Since the crank pin remains in a fixed position in space, it is easy to inspect the crank pin during the grinding operation, and if desired to apply measuring or gauging devices which constantly record the diameter of the crank pin. It is also an advantage that the arm 15 remains fixed in space so that the feeding motion may be performed on a fixed part rather than on an oscillating part as is the case in the known machines above referred to.

Since the rocking frame and the bracket supporting member with the brackets and the crankshaft set up between the latter perform oscillating movements during the grinding operation, it will be preferable, in order to increase the stability of the machine, to perform a static i balancing of these movable parts. Since the crankshaft can be assumed to be balanced about its principal axis, the crankshaft may be regarded as a mass concentrated in the principal axis, and it will therefore sufice to establish a balance partly about the axis of the bracket supporting member and partly about the axis of the rocking frame.

A balancing about the rst named axis can be obtained by mounting a suitable counter weight on the bracket supporting member. For practical reasons, it will be preferable, however, to establish this balancing by means of a spring force, and for this purpose, in the embodiment shown, a counter balancing arm 26 rigidly carried by the tubular member 21 is connected through a hinged rod 27 with one end of a balance arm 2S mounted in the machine frame, the other end of the balance arm being connected through a hinged rod 29 comprising a built-in spring 30 with a point of the rocking frame at the opposite side of the axis of rotation of the latter. In this manner, the hinged rod 27 is subjected to a downward pull which by adjustment of the spring 30 can be so adjusted as to balance the moment about the axis of the bracket supporting member resulting from the weight of the crankshaft, the brackets etc. Strictly speaking, to obtain complete balance, the rod 27 should always be exactly vertically disposed, and the force of the spring 30 shoud be constant. This condition cannot be exactly fulfilled with the construction shown, but when the balance arm 2S is disposed at a great distance vertically below the rocking frame, and the spring 30 is made comparatively long relative to the variations of length to which it is subjected during the oscillations of the bracket supporting member, a satisfactory approximation to balance is obtained. In this connection it should again be remembered that the oscillations of the bracket supporting member about its axis will be relatively slow so that the mass forces will be small.

The rods 27 and 29 should preferably be located at equal distances from the axis of the rocking frame, so that the pulling forces acting along these rods will not create any moment of rotation about the said axis. To establish balance about this axis, it is therefore suicient to counter balance the weight of the bracket supporting member, the brackets, and the crankshaft, calculated as a concentrated weight in the axis of rotation of the bracket supporting member. This counter balancing may be obtained by supplying a greater or smaller quantity of liquid e. g. water to the interior of the drum 20, which thus, besides constituting a rigid connection between the rocking arms 18 and 19, will form a drum for balancing pur- POSeS.

The tension of the spring 30 andA the quantity' of'water in the drum 20 may, be manually adjusted upon weighing of a crankshaft to beA ground.. However, according to4 the invention, these adjustments may alsol be made automatically by a special operation after a crank shaft hasl been set upy and before the grinding'thereof i's started, the rocking system formed by thev rocking frame, the rodsk 27 and 29, and the balance arm 28, being utilized for this purpose as a kind of weighing machine determining the weight of the crankshaft and performing the necessaryl adjustments accordingly. One example of a regulating system by means of whichthis. opertaion may be performed is illustrated in; Fig- 4.. 31 is a stationary valve casing in which there is mounted a valve body 32 which may be selectively connected to the arm 28; by meansv of a clutching arrangement generally indicated as '5 in Fig. 9. The valve body 32 has two ports 33 and 34 which can establish connection between any two of three conduits, viz. a conduit 35 leading to the cooling water pump of the machine, a conduit 36 leading to the drum 20, and a discharge conduit 37. The valve body 32 also has an arm 38 resting against a piston rod' 39 of a vpiston 40 slidable in a hydraulic cylinder 41. A feeding conduit 42 from the oil pump of the machine opens in the wall of the cylinder 41 close to the bottom of the cylinder, and a return conduit 49 to the oil pump at a somewhat higher level. Moreover, the cylinder 41 is provided at its upper end with a discharge opening 44, and in an intermediate position there is provided a conduit 45 communicating through a flexible conduit 46 with an expansion chamber 47 for the adjustment of the tension of the spring 30.

The operation is as follows:

When the balance is to be established after a crankshaft has been set up, the valve body 32 is coupled by the clutching arrangement 55 to the balance arm 28. Under the influence of the weight of the crankshaft and other non-balanced parts, the balance arm 28 will be urged down at its left hand end. Hereby, the arm 38 of the valve body 32 will urge the piston 40 towards the bottom of the cylinder 41. Now the oil pump of the machine is started and oil is consequently supplied by the conduit 42 whereby the piston 40 is lifted. In this piston there is provided an angular passage 48 which after a certain amount of lifting of the piston is connected with the conduit 45. When this takes place, oil flows to the expansion chamber 47, whereby the spring 30 is put under tension. The piston remains in the said position until the pressure below the piston has increased to a value such that said pressure is capable of further lifting the piston 40 against the force exerted by the arm 38 which force is representative of the masses to be balanced. When an oil pressure of such value has been obtained below the piston, and a pressure proportional to the nonbalanced masses consequently also is present in the cxpansion chamber 47, the piston 40 is further lifted and thereby interrupts the connection to the expansion chamber 47 so that the pressure in the latter will remain at a value keeping the spring 30 under a tension corresponding to the masses to be balanced about the axis of the bracket supporting member.

Now, the arm 38 is gradually urged upwards so much that a connection is established between the conduits 35 and 36 owing to the rotation of the valve body 32 so that water ows into the drum 20. When so much water has been supplied that balance has been established about the axis of the rocking frame, the frame will start rotating in the clockwise direction, and the same therefore applies to the balance arm 28 and the valve body 32 whereby the latter cuts olf the supply of water to the drum 20. The valve body 32 is now released from the balance arm 28 and locked to the machine frame and the grinding can now be commenced. The arrangement for locking valve body 32 is disclosed schematically in Figure 9 which shows a guide block 70 rigidly secured to the casing for valve body 32. A vertical pin 71 is. slidingly received in guide block 7,0 and the lower end of pin 7'1 has a singley tooth which` is shown in engagement with the splines on the right end of valve body 32. Thus it will be seen. that valve bodyv 32 is locked in position. A link 72 pivotally connects the upper end of pin 71 to an arm 73 on the shaft 74 for clutch 55. so that the clutch andk locking arrangements work simultaneously. It will be understood that when shaft 74 is rotated clockwise from the position shown in Figure 9, clutch will connect arm 28 to valve 32 andv pin 71 will be raised out of engagement with the splines on valve 32. Upon termination of the grinding operation the oil' pump is stopped and the valve body 32 is again released from the machine frame and turned to a. position such that, the piston 40 is pushed down to the bottom of its cylinder, Whereafter the valve body is. locked to the. balance arm 28 in this position. Hereby a connection is established between the conduits 36 and 37 so that the water may be discharged from the drum 20,4 and also., in the hydraulic cylinder 41, there is provided a. connection between the conduit 45 and the discharge conduit 44 sor that the expansion chamber 47 is relieved of pressure.

The above description has reference only to the grinding of crank pins. It will be understood, however, that the main journal positions of the crankshaft can be ground in substantially the same manner as the crank pins though in this case, of course, there will be practically no oscillation of the rocking frame and the bracket supporting member. It is, however, not very recommendable to proceed in this manner, because the main journal portions, when supported in the notch 16 during the grinding, may not result mutually co-axial though individually they will in fact be ground to circular cross sectional shape. It is therefore preferable when grinding the main journal portions to hold the principal axis of the crankshaft in a fixed position in space, while the crankshaft rotatesy about the same axis and is at the same time ground. This may be obtained by locking the rocking frame relative to the machine frame and the bracket supporting member relative to the rocking frame, though making allowance for a feeding movement of course. An example of the necessary locking means is schematically illustrated in Fig. lO. In this figure 56 is a lever which is hingedly connected to the column 2 at 57 and is provided with a hook member 58 to engage a projecting pin 59 mounted on the arm 18. Once this engagement has been established the pin 59 will be kept in firm engagement with the hook member 58 under the influence of the torsional spring 53. Moreover, in Fig. 10 the bracket 22 is shown as being provided at its lower end with a forked projection 60 constructed at its rear side with a spherical seat to receive a similarly shaped nut 61 engaged on a screw 62 hingedly connected to the column 2 at 63. It will be understood that the lever 56 and the screw 62 will be used only when grinding the main journal portions of a crank shaft. When the crank pins are to be ground these members will therefore be completely disengaged.

I claim:

l. A crankshaft grinding machine comprising a machine frame, a grinding wheel mounted for rotation about an axis which is stationary relative to said machine frame, setting up means for rotatably supporting a crankshaft to be ground for rotation about the principal axis thereof, means for so guiding said setting up means as to permit transverse movement in any direction of said principal axis as defined by said setting up means while keeping said principal axis rigidly parallel to the stationary axis of rotation of said grinding wheel, a support having two walls forming an open angle between them to receive a crank pin to be ground in a position opposite said grinding wheel, means mounting said support on said machine frame, positive feed means for adjusting said support to rigidly feed a crank pin toward said grinding wheel,

7 and means for constantly urging a crank pin received in said support against both of said Walls.

2. A crankshaft grinding machine as in claim l in which said setting up means are constituted by brackets which are non-rotatably mounted on a bracket supporting member, the latter being rotatably mounted in a rigid rocking frame which is in turn rotatably mounted in the machine frame for rotation about an axis parallel to the axis of rotation of said bracket supporting member.

3. A crankshaft grinding machine as in claim 2 in which said rocking frame is constituted by two rocking arms mounted for rotation about an axis intermediate of their ends, said rocking arms being connected at one end thereof by means of a rigid tubular member and being constructed to rotatably support said bracket supporting member at their other end.

4. A crankshaft grinding machine as in claim l in which said grinding Wheel is mounted on a slide movable longitudinally of the axis of rotation of the grinding w. eel, said slide also carrying said support.

5. A crankshaft grinding machine as in claim 4 in which said support is adjustable relative to said slide about an axis parallel to the axis of rotation of said grinding wheel.

6. A crankshaft grinding machine as in claim 2 in which said bracket supporting member carries a counter balancing arm connected to a point of the rocking frame on the opposite side of the rocking axis thereof throughl a balance systemcomprising adjustable spring means.

7. A crankshaft grinding machine as in claim 6 cornprising means couplable to the rocking system formed by the rocking frame and the balance system for determining the weight of a crankshaft set up in the machine depending on the unbalance of said rocking system caused by said crankshaft, and for automatically adjusting, in accordance with the Weight thus determined, partly the spring means of the balance system to establish balance about the axis of the bracket supporting means, partly a counter Weight variable by liquid supply to establish balance about the axis of the rocking frame.

References Cited in the le of this patent UNlTED STATES PATENTS Long Feb. 24, 1925

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