US2917896A - Fluid actuated clamping device - Google Patents

Description

Dec. 22, 1959 F. DE BUIGPIE FLUID ACTUATED CLAMPING DEVICE 2 Sheets-Sheet 1 Filed Dec. 31, 1956 L71 M a T V4 05 m my V m HR a 5m x 4 m n F T n. 0 3 M 8 w Dec. 22,

F. DE BUIGNE FLUID ACTUATED CLAMPING DEVICE Filed Dec. 31, 1956 V RliL.

2 Sheets-Sheet 2 n I INVENTOR 35 FRANK De Bum/v5 K0775 SHiR/D/JN United States Patent 2,917,896 FLUID ACTUATED CLAMPING' DEVICE Frank De Buigne, Birmingham, Mich assignor to La Salle Tool,: Inc., Detroit, Mich a corporation of Michigan Application December- 31, 1956; Serial N0 631,668

5 Claims. (Cl. 6 01-52) The present invention relates to'a fluid operated clamping device known as a power wrench.

A. power wrench has recently become a widely'used and accepted tool in modern industry and has proven extremely valuable in automation techniques requiring high production and rapid clamping and unclamping of aworkpiece during a work cycle at a specific-time and station in the cycle of operation. The use of power wrenches in connection with automatic machines has increased substantially, as'have the specific demands which are placed on the power wrench construction in general. When the power wrench is used with automatic machines, it must be more reliable than heretofore; it must be sufiiciently powerful to securely lock and unlock the clamping devices, while holding'the workpiece se' curely during the work cycle; and must-require the least possible amount of power consumption and maintenance.

The clamping or locking of'the workpiecewhich i s-provided' by the action of apowerwrench is accomplished by means of the wrench turning a nut or bolt typedevice until such time as the nut or bolt typedevice has reached a. predetermined torque tightness; The unclamping of the workpiece after the work cycleis thereverse action of the clamping operation, exceptthat the wrenchvmust deliver a higher. torque than previously: requiredin the clamping operation, to break the frictional engagement of the nut or bolt type devicefrom its locked position.

Thus, an acceptable power. Wrench must. be able to deliver a suflicient locking torque to hold the workpiece securely; it must bevalved to shut off at a predetermined torquebefore any part failure occurs; and then it must furnish asomewhat greater torque to' accomplish the un clamping of the workpiece.

One form of power wrench which has beenused is electricalin nature and comprises a'heavy-rotating mass or flywheel which is brought into sudden locking engagement with the bolt or shaft-which is'to be turned. Building up sufficient inertia in the flywheel on these wrenches consumes large amountsofpower. Also, the sudden locking engagementof the rotating mass or flywheel With the nut or shaft, which is at rest, causes ext cessive shock damage not only to the part to be turned,- but also to the power wrench itself.

Frequent breakdowns of the electrical'power'Wrenches are caused by this condition, which in turn causes'production slowdowns and damaged-parts which.are'very undesirable in todays age of modern mass production.

Therefore, it is a principal object of the presentinvention to provide a power wrench-which will be safe to operate, which will give uninterrupted production of finished parts of the highest possible quality and numher; and also to provide a machine which because of its design and construction will operate efliciently for many years.

It isa further-object of'the present'invention, to-provide a fluid aetuatedpower wrench which will beex tremely economical to operate, and which is so construct'ed and arranged as to'renderthe torque-developed 2,917,896 Patented Dec. 22, 1959 I 2. thereby controllable in both the clamping andunclamp= ing directions.

Another object of the present invention is to provide a: reliable, sturdy power wrench construction which will not require frequent servicing; while still meeting the increased demands of production automation equipment;

Other objects of this invention will appear in the fol lowing description and appended claims, reference being had'to the accompanying drawings forming a part of this specification wherein like" reference characters designate corresponding parts-in the several views. l

I have found the foregoing and related objects can be accomplished in a power wrench construction which encompasses a plurality of pressure sources. 'More specifically, in the preferred embodiment of the invention a fluid'motor is used in combination with a high pressure, lowvolume pump and a low pressure, high volume pump. In this system, high volumes of low pressure fluid are provided for rapid forward movement of the clamping means, and high pressure and low volumes of fluid are provided for maximum rotational torque requirements in clamping and unclamping of the workpiece in a fixture mounted on a machine. v

In order to simplify the application, details of the fluid motor, the hydraulic control cylinder and the electric hook-up have been omitted. These details will be apparent to one skilled in the art upon reading this specification.

In the drawings: a a

Fig. l is a schematic diagram of a power wrench system embodying the present invention, the control valves being shown in unclamped neutral position.

Fig. 2 is a schematic diagram of the power wrench of the present invention showing only the clamping ofthe workpiece and the position of the valves therein.

Fig. 3 is a schematic diagram similar to Fig. 2, showing only the unclamping of the workpiece and the position of the valves therein.

Before explaining the present invention in detail, it is to be understood that the invention is notlimited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various Ways. Also, it is to be understood that the invention is not limitedin ment of parts illustrated in the accompanying drawings,

since the invention is capable of other embodiments and of being practiced or carried out in various Ways. Also, it is to be understood that the phraseology or terminology employedherein is for the purpose of description and'not of limitation. I

One'form of the present invention is shown in Fig. 1 ofthe drawings and includes a hydraulic sump or reservoir 2; a high pressure, low volume pump 4, and a low I pressure, high volume pump fi actuated by a constantly running motor 7 and connected in parallel through fluid line 9 which has a check valve 8 in said fluid line 9; a high pressure relief valve 10 in series with the high pressure pump 4 in fluid line 13; a low-pressure relief valve 12 in series with the low pressure pump 6 in fluid line 11; and a return line 14- to'the hydraulic sump or reservoir 2. A fluid line 9 connects fluid lines 11, 13 and 16 leading from the pumps 4 and 6. Fluid' line 16 hasmounted thereina pressure guage lsfor immediate ob servation of the fluid pressure in said fluid line 16. Fluid line 16 branches into fluid lines 16:: and 16b and has connected in fluid line 16a, a four-way, three position, solenoid operated, non-rotary motion control valve 22'to c011- trol the forward and return motion of thewrench 32. Located between the non-rotary motion control valve -zz and the branchin fluid line 16 is a pressure reducing;

valve 20 which maintains a regulated fluid pressure to the non-rotary motion control valve 22. Fluid line 16b is connected to a four-way, three position, solenoid operatedcontrol valve 36, which controls the rotational movement of the wrench 32 and the clamping means 56.

The three positions'of the non-rotary motion control valve will be referred to as positions A, B and C. The positions of the rotational control valve 36 will be known as positions D, E and F. Pilot solenoids 23 and 23a controlling non-rotary motion control valve 22 will have similar positions a, b and c while the pilot solenoids 35 and 35a will have positions d, e and f. Fluid lines 24 and 26 which are in communication with the non-rotary valve 22 are also connected to a hydraulic cylinder 28 having a piston 39 mounted therein. Fluid pressure is maintained against the right end of piston 30 by check valve 27 in line 26 when the lateral motion control valve 22 is so positioned. Movement of the hydraulic piston 30 within the cylinder 28 controls the forward and reverse motion of the wrench 32 by action of the nonrotary motion control valve 22 and also actuates a limit control switch 34 to control the action of the rotational control valve 36. I

Fluid line 16b is in communication with rotational control valve 36 which controls the rotational direction of the fluid motor 42 through fluid lines 38 and 40. Fluid flowing through fluid line 46 causes the fluid motor 42 to rotate in a clock-wise direction causing a clamping action at the jaw or clamping means 56. A pressure relief valve 44 in communication with the fluid line 40 eliminates any excessive fluid pressure in fluid line 40. After fluid is by-passed through the pressure relief valve 44 a pressure switch 48 located in fluid line 46 and a needle valve 50 located in the fluid line 46 further control the fluid pressure of the escaping fluid through the pressure relief valve 44 into the fluid line 46. Should a reverse rotation of-the clamping means be required for any reason, it is only necessary to reverse fluid lines 38 and 40 which will completely reverse the direction of rotation of the clamping jaws and will permit the work cycle to be carried out in the same manner.

Clamping cycle Although Fig. 1 of the drawings shows a complete circuit layout of the present invention, Fig. 2 of the drawings illustrates only the position of the valves which relate to the clamping cycle. Referring to Fig. 2 of the drawings, the electric motor 7 runs continuously and drives both the high pressure, low volume pump 4 as well as the high volume, low pressure pump 6. Constant operation of the motor and pumps eliminates the necessity of frequent stopping and starting of the system and the sudden shock loads which occur and tax the system causing excessive power consumption and ineflicient operation. Pilot solenoid 23 in non-rotary motion control valve 22 is actuated by any suitable means, such as a control panel (not shown), and moves the solenoid operated pilot valve 23 to a position a, thus moving the fluid non-rotary motion control valve 22 to position A shown in Fig. 2 of the drawings. Fluid now flows through line 16a into fluid line 24, moving the piston 30 in the hydraulic cylinder 28 to the right. Movement of the piston 30 causes the fluid which is trapped in the right end of the hydraulic cylinder 28 to be moved through line 26 causing the wrench 32 to move forward and engage the slidable screw type clamp device 54. Phantom line 52 is a mechanical linkage connecting piston 30 and shaft 32A together. Movement of the piston 30, finger 31 trips the control limit switch 34 which energizes the pilot solenoid 35 in the rotational control valve 36, causing the solenoid 35 of pilot valve 36 to move said valve to the position d. The solenoid operated pilot valve of valve 36 being in position d fluid is directed to move the main valve portion of the rotational control valve 36 to position D which action ports fluid through fluid line 16b and fluid line 40, rotating the fluid motor 42 in a clockwise direction to clamp the workpiece (not shown) in proper position and fluid line 38 exhausts to the sump. Initially, the fluid flow is rapid because there is little resistance to the rotation of the wrench 32. As the clamping device 56 begins to tighten, against the workpiece, the resistance increases and the motion decreases, and consequently the fluid pressure in line 40 builds up to overcome this resistance through the action of the high pres,- sure, low volume pump 4 and the low pressure, high volume pump 6, which are driven continuously by the motor 7.

As the resistance to the rotation of the clamping device 56 increases, there is little need of any appreciable volume of fluid to'flow through fluid lines 16, 16b and 40. Thus when a predetermined pressure is exceeded in the pressure relief valve 12, the high volume, low pressure pump 6 recirculates fluid into the sump or reservoir 2, and the check valve 8 in fluid line 9 prevents the high pressure, low volume pump 4 from feeding any fluid into this idling circuit which is now ported to the sump or reservoir 2, allowing the high pressure, low volume pump 4 to alone complete the clamping action.

Thus, at the start of a clamping cycle when the wrench 32 can rotate freely the fluid motor 42 is fed a large volume of fluid by the high volume, low pressure pump 4 and the high pressure, low volume pump 6 to rapidly engage the workpiece. When the rotational movement of the clamp actuating device 54 is reduced as it engages the workpiece, the high volume, low pressure pump 6 is cut out of the circuit. This variable volume and pressure system operates to reduce heat loss and the resultant power loss in the high volume, low pressure pump 6 which would occur if this pump were not cut out of the circuit as previously described. If the high volume, low pressure pump 6 remained in the system as the wrench 32 tightened, the output of the high volume pump would be restricted, and unnecessary heat would be generated. The system of the present invention reduces the usual amount of generated heat and yet provides the large volume of fluid required by the fluid motor 42 initially when the motion of the wrench 32 is not impaired or restricted.

As the wrench 32 tightens fixture 54 and the clamping device 56, the increased fluid pressure in fluid line 40 causes the fluid motor 42 to exert a torque which is limited by the predetermined setting of the spring-loaded relief valve 44. When the pressure in the relief valve 44 exceeds a predetermined limit, the pressure relief valve 44 permits fluid to escape through line 46 to actuate a pressure switch 48, which causes some phase of a machine tool to operate, such as a drill press, etc. A machine tool has not been shown in relation to pressure switch 48, since anyone ordinarily skilled in the art will know how to connect a switch 48 into the operating circuit of a machine tool. Several power wrenches may be used on a single machine which drills, countersinks, taps, hollow mills and surfaces an automobile brake cylinder. The flow reduction needle valve 50 is placed in line 46 beyond the pressure switch 48 to assure positive action ofpressure switch 48. The needle valve 50 will control and provide sufficient pressure in line 46 to operate pressure control switch 48.

Unclamping cycle After the work cycle has been completed, the system is then ready for the unclamping cycle. Pilot solenoid 35a is actuated by the drill head or tool or any suitable means such as a control panel, etc. The pilot control solenoid 35a moves the pilot control valve to position 1 as shown in Fig. 3 of the drawings. This movement causes rotational control valve 36 to move to position F also shown in Fig. 3 of the drawings. In this position the flow of fluid from line 16b is through fluid line 38 to the fluid motor 42 causing acounterclockwise unclamp ing rotation of the wrench 32 and fixture 54, moving the clamp mechanism 56 to the left. Initially in the clamped position the clamping device 56 is in extremely tight engagement with the workpiece, with little rotational motion available. Therefore, only the high pressure, low volume pump 4 has suflicient power for this purpose to disengage the clamping means and is supplied high pressure, low volume fluid through lines 16, 16b and 38. Since a greater torque is necessary for unclamping than is required in the case of clamping, fluid line 38 does not have a relief valve in the line such as the relief valve 44 in the clamping pressure line 40. The fluid line 38 is limited only by the predetermined setting of the pressure relief valve 10, which is preset at a higher pressure than the pressure relief valve 44 in the clamping circuit. As soon as the frictional engagement of the clamp 56, is broken and rotation occurs, a drop in fluid pressure causes the high volume low pressure pump to augment the fluid supply and move the clamping means 56 rapidly to a retract position. After the rotational unclamping has reached the desired retracted position, the pilot solenoid 35 is actuated by a means such as a limit switch (not shown) and the rotational control valve 36 is moved to the neutral position shown in Fig. 1 of the drawings. This cuts ofi the fluid flow through fluid line 38 to the fluid motor 42 and the rotational unclamping of the wrench '32 is halted. At this point the pilot solenoid 23 is actuated to move the motion control valve 22 to the position shown in Fig. 3 of the drawings which allows fluid to flow from line 16a through line 26. This causes piston 30 in hydraulic cylinder 28 to move to the left, disengaging the wrench 32 from the clamping fixture 54. As the finger 31 disengages itself from the limit switch 34, the switch 34 is then reset in position A for the next clamping cycle.

Having thus described my invention, I claim:

1. In a fluid actuated clamping device for positioning a work piece, a high pressure low volume fluid pump; a low pressure high volume fluid pump; means for driving said fluid pumps; a fluid motor operatively connected to said high pressure low volume fluid pump and said low pressure high volume fluid pump; a slidably mounted clamping means; a lateral motion control valve; a rotational motion control valve; a fluid actuated piston having a mechanical linkage for moving said slidably mounted clamping means to engage a work piece; said fluid actuated piston being operatively connected to said rotational control valve co-operable with said fluid motor so as to cause rotation of said clamping means and lock said work piece into proper position using high pressure low volume fluid; control means for said high pressure low volume fluid to clamp and unclamp said work piece; and control means for said high volume low pressure fluid to effect a rapid traverse non-rotational return of said hydraulic cylinder piston and said slidably mounted clamping means.

2. In a fluid actuated clamping device, the combination of a fluid motor; a fluid source comprising a low pressure fluid pump and a high pressure booster pump; said low pressure fluid pump and said high pressure booster pump being operatively connected to said fluid motor; means for driving said pumps; a clamping means operatively connected with said fluid motor; a hydraulic cylinder having a piston therein for moving said clamping means; a mechanical link interposed between said piston and said fluid motor; and controlmeans for said fluid source which provides a high volume of fluid during the initial clamping action; a decrease in volume and increase in fluid pressure during the final clamping action; a high pressure low volume of fluid during the unclamping action; and means for using high volume low pressure fluid for rapid traverse non-rotational return of said hydraulic cylinder piston and said clamping means.

3. In a fluid actuated clamping device for positioning a work piece, the combination of a plurality of fluid pressure and volume sources; a fluid motor operatively connected with said fluid sources; a slidably mounted clamping means operatively connected wtih said fluid motor; a lateral motion control valve; a lateral motion member; a rotational control valve; a fluid operated piston using high volume low pressure fluid for moving said lateral motion member at a rapid traverse rate forward to initiate the initial non-rotational clamping of said slidably mounted clamping means; said fluid actuated piston being operatively connected to a rotational control valve cooperable with said fluid motor to rotate said clamping means and to lock said work piece into proper position using high pressure low volume fluid; control means for using high pressure low volume fluid for rotational unclamping of said work piece; and means for using high volume low pressure fluid for rapid traverse non-rotational return of said hydraulic cylinder piston, said lateral motion member and said slidably mounted clamping means.

4. In a fluid actuated clamping device for positioning a work piece, a high pressure low volume pump; a low pressure high volume pump; means for driving said pumps; a fluid motor operatively connected to said pumps; a first fluid line from said high pressure low volume pump; a second fluid line from said low pressure high volume pump; each line having a pressure regulator therein; said first fluid line connection being between said highpressure' fluid pump and said pressure regulator; said second fluid line connection being between said low pressure fluid pump and said pressure regulator; a check valve interposed between said first and said second fluid lines; said pressure regulator outlet exhausting into a sump reservoir; a third fluid line conected between said first and said second fluid lines with a check valve therebetween; said third fluid line connected to a fourth fluid line and a lateral motion control valve; a fifth fluid line connected to said fourth fluid line and in communication with a rotary motion control valve; a hydraulic cylinder having a piston therein; means for controlling said lateral motion control valve for lateral movement of said piston; a fluid motor for rotational clamping and unclamping of the work piece; and a pressure regulator between said fifth line and said fluid motor.

5. In a fluid actuated clamping device comprising a fluid operated high pressure low volume pump; a fluid operated high volume low pressure pump; a means for driving said pumps; a fluid motor operatively connected to said pumps; a movable clamping means operatively connected with a fluid operated piston and a mechanical link to said fluid motor; control means for controlling said fluid pumps to provide a high volume of low pressure fluid for the initial non-rotational clamping action and a decrease in volume and an increase in pressure during the final rotational clamping action and a high pressure low volume of fluid during the rotational unclamping action; and control means for said high volume low pressure fluid to effect rapid traverse non-rotational return of said hydraulic cylinder piston and said movable clam ing means.

References Cited in the file of this patent UNITED STATES PATENTS 2,297,381 Wylie Sept. 29, 1942 2,518,782 Hipp Aug. 15, 1950 2,616,323 Leifer Nov. 4, 1952 2,627,770 Hautau Feb. .10, 1953 2,745,253 Towler et a1. May 15, 1956

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