US3195655A

US3195655A - Method and apparatus for controlling the degree of tightness of bolts or nuts driven by an impact wrench

Info

Publication number: US3195655A
Application number: US73316A
Authority: US
Inventors: Karden Karl Gosta
Original assignee: Atlas Copco AB
Current assignee: Atlas Copco AB
Priority date: 1960-12-02
Filing date: 1960-12-02
Publication date: 1965-07-20
Anticipated expiration: 1982-07-20
Also published as: BE611003A; DK113700B; CH414493A; GB941753A; DE1295499B

Description

July 20, 1965 K. G. KARDEN 3,195,655

METHOD AND APPARATUS FOR CONTROLLING THE DEGREE OF TIGHTNESS OF BOLTSOR NUTS DRIVEN BY AN IMPACT WRENCH Filed Dec. 2. 1960 2 Sheets-Sheet l July 20, 1965 K. G. KARDEN 3,195,655

METHOD AND APPARATUS FOR CONTROLLING THE DEGREE OF TIGHTNESS OF BOLTS 0R NUTS DRIVEN BY AN IMPACT WRENCH Filed Dec. 2, 1960 2 Sheets-Sheet 2 so 51 L 59 58 ATTORNEY United States Patent O snaasss MlETl-LGD AND APPARATUS QGl lTRfiLLlNG THE DEGREE (ll 'lTilGlld'lNllfid @F lliIlLTg @R NUTS DRlV'EN AN IME ACT WRENQH Karl Gilsia Ha den, Nacho, Sweden, assignor to Atlas Copeo ole-g, Nacho, Sweden, a corporation of weden Filed Bee. 2, 1%5, Ser. No. 73,316 17 Claims. (ill. 173 l) This invention relates to a method and an apparatus for controlling the degree or" tightness of a series of bolts or nuts driven by an impact wrench. Such control is important in many technical applications, for example in the assembly of structural building elements, in order to give the joints the intended maximum of strength.

One object of the invention is to provide a simple and eflicient control of the maximum torque transmitted to the work by an impact wrench so that a series of bolts or nuts can be tightened with suflicient accuracy to substantially the same degree or tightness.

Another object of the invention is to provide a torque control of the foregoing character which avoids constructional complication of the impact wrench proper by performing said control externally of the impact wrench.

A further object of the invention is to provide a torque control of the foregoing character which is applicable together with fluid operated impact wrenches irrespective of type.

For the above and other purposes the invention contemplates a method and apparatus by which the total quantity or" pressure fluid delivered to operate the impact wrench is controlled and the fluid supply to the impact wrench is interrupted upon reaching a delivery of a predetermined fluid quantity.

The quantity of pressure fluid used up by an impact wrench during operation depends normally upon the number of revolutions performed by the wrench motor. If the supply pressure and the total fluid quantity delivered to the Wrench are kept constant the wrench motor is bound to operate a fixed number of revolutions. When a series of similar bolts or nuts are to be tightened and applied under similar conditions, as often is the case in practice, the tightening of each nut will require the same number of running down and impacting revolutions, i.e. will require substantially an equal air quantity to be delivered to the wrench. Accordingly, the invention proposes to deliver for each tightening operation of the wrench a predetermined constant quantity of pressure fluid to the impact wrench, said quantity being chosen so that each bolt or nut will be set with the same required degree of tightness. The quantity of pressure fluid required for each type of work will easily be found in the initial production stage by controlling the torque value attained, for example with the help of a conventional torque measuring spanner wrench.

The above and other objects of the invention will become obvious from the following description and from the accompanying drawings in which three embodiments of the invention are illustrated by way of example. It should be understood that these embodiments are only illustrative of the invention and that various modifications may be made within the scope of the claims without departing from the scope of the invention.

In the drawings, wherein like parts are designated by like reference characters throghout the several views,

FIG. 1 shows a diagrammatic view partly in longitudinal section of an apparatus representing one embodiment of the invention;

PEG. 2 shows a diagrammatic view in longitudinal section of a modified form of the pressure fluid controlling device included in the apparatus according to FIG. 1;

ice

FIG. 3 shows an enlarged longitudinal section of the valved portion of the piston shown in FIG. 2; and

FIG. 4 is a diagrammatic view partly in longitudinal section of an apparatus representing a third embodiment of the invention.

In the drawings l designates a fluid operated impact wrench of conventional design, having a suitable impact clutch mechanism, driven for example by a compressed air motor of the rotary sliding vane type. The impact wrench may be carried out according to Swedish Patent Number 126,061 or in other way. The illustrated impact wrench 1 has a handle 3 to which is coupled an air conduit 2 supplying compressed air to operate the wrench motor. The air supply is controlled by a trigger operated throttle valve 4 arranged in the tool handle 3. The impact wrench ll has the usual tool socket 5 for cooperation with the work, such as a bolt or nut s to be tightened. The conduit 2 receives air from a compressed air source 7 with great enough a capacity to deliver compressed air of substantially constant pressure to the impact Wrench 3 when the latter is operating.

According to the invention and referring to FIG. 1 there is arranged a device generally designated 8 between the compressed air source 7 and the impact wrench l for controlling the pressure fluid quantity delivered for the operation of the impact wrench l. The device 8 consists of a cylinder 9, one end of which is connected by a conduit ltil to the compressed air source 7. The other end of the cylinder 9 is connected to the conduit 2 leading to the impact wrench ll. Within the cylinder 9 is reciprocably arranged a differential piston 11 dividing the cylinder into a pressure chamber 13 and a delivery chamber 19. The piston 13 has a threaded stem 12., which projects int-o and to which is threaded a hollow member 13 projecting through one end wall 9a of the cylinder 9. Inside of the cylinder 9 the hollow member 13 forms a stop flange 14 cooperating with the end wall 9a through which said member 13 projects. A lever 15 is fixedly secured to the free end of the hollow member 13. Turning of the threaded hollow member 13 by the lever 15 brings about a displacement of the stop flange i l with respect to the piston ll so that the upper end position of the piston 11 in the cylinder 9 is changed. A sealing ring 15, carried by the piston 11 and another sealing ring 17 in the end wall 9a of the cylinder 9 around the hollow member 13 seal the pressure chamber 18 and the delivery chamber 19.

The

chambers

18 and 19 of the cylinder are in com munication with each other through a restricted bleed passage 29 which extends axially through the piston 11 inside of an annular sealing pad 21. The sealing pad 21 is coaxial with the piston ll and in the dotted line or lower position of the piston in FIG. 1 contacts an annular rib 22 or valve seat inside of the cylinder on the end wall 9b thereof whereby the portion of the delivery chamber 19 which is radially outside of the rib 22 may be separated from the conduit 2. to th impact wrench ll. Near said end wall 912 of the cylinder there is a communication through a conduit 23 and an adjustable needle valve 24 between the delivery chamber 19 and the pressure chamber 18. By adjusting the bleed opening of the needle valve 24 an adjustable additional quantity of live air may pass from the pressure chamber 8 to the delivery chamber 19 during the downward stroke of the piston until the annular sealing pad 21 contacts the rib 2.2 and cuts oil the communication between the

conduits

23 and 2.

The apparatus according to FIG. 1 operates in the following manner: In the illustrated full line position of the piston lit and assuming the needle valve 24 to be closed, the operator grasps the impact wrench by the handle 3 and places the socket 5' of the wrench over the nut or bolt 6, whereupon he presses the trigger to open the throttle valve 4. Such actuation brings the delivery chamber 19 and the conduit 2 into communication with the motor of the wrench 1 and starts the motor which by consuming air creates a pressure drop in said conduit 2 and the chamber 19 with respect to the pressure chamber 18 of the cylinder 9 The value of this pressure drop is defined by the difference-in effective pressure areas on the opposite sides of the differential piston 11. As soon as the pressure in the delivery chamber 19 falls just below the value necessary for balancing the piston 11, the piston begins to move downward and feeds the fluid volume trapped in front of it to operate the wrench ll. Upon reaching the end of its stroke the piston 11 is arrested in its bottom position in cylinder 9 interrupting further delivery of sufficient live air to operate the wrench 1 so that the tightening of the nut 6 ceases. The pressure drop causes an uninterrupted leakage of a small amount of live air through the restricted bleed passage 2% of the piston 11 into the chamber 1)- This leakage is too small to build up pressure in the delivery chamber 19 as long as the throttle valve 4 is open as it is vented to the atmosphere through the wrench motor. Upon release of the throttle valve 4 the pressure in the conduit 2 and the delivery chamber 19 increases until the pressures-on both sides of the piston 11 are again equal. During this increase the piston 11 is urged back to its upper position in the cylinder 9, which position is defined by the stop flange 1d of the hollow member 13 contacting the end wall 9a of the cylinder 9. With the piston 11 in its upper position the apparatus is ready for the next tightening cycle. During each cycle equal quantities of live air will be dispensed in the delivery chamber 1% of the device 8 and fed to operate the wrench 1 as long as the pressure in the supply 7 remains substantially constant.

By'rotating the lever 15 to displace the adjustable holloW member 13 along the threaded piston stem 12 away from the piston 11 the piston stroke and consequently the pressure fluid quantity dispensed by the delivery chamber 19 may be decreased so as to set the device for a smaller number of revolutions of the wrench in case fewer revolutions prove suificient to give the desired degree of tightness of the bolt or nut. If on the other hand an increase of the dispensed pressure fluid quantity is demanded in order to increase the number of revolutions performed by the wrench, such increase may be accomplished by opening and pre-setting the needle valve 24 to a suitable bleed value. In operation, as soon as the pressure drop between the

chambers

18 and 19 is established, an additional live .air quantity is bled from the chamber 18 through the needle valve 24 and the conduit 23 to the delivery chamber 19 and further to the conduit 2 and the wrench 1. At'the end of the downward stroke the annular sealing pad 21 of the piston 11 contacts the annular rib 22 of the cylinder 9 and cuts off the additional'bleed supply to the conduit 2. The piston 11 remains as before in this lower position as long as the throttle valve is kept open. Upon closing of the throttle valve the leakage through thepiston passage 29 is able to build up the necessary pressure in the conduit 2 and inside of the annular rib 22 to initiate the piston return. Once initiated the return stroke is effectively accelerated by the live air bleeding through the needle valve 24, which results in a short resetting time for the next tightening cycle.

With the needle valve 24 opened the piston 11 additionally to its air delivering action has the function of a timer for controlling the duration of the air flow to the conduit 2 through the conduit 23.

As an alternative the restricted bleed passage 20 may with equal performance of the device be arranged in the walls or outside of the cylinder 9, directly connecting the conduits it and 2 and by-passing the

cylinder chambers

18, 19 as indicated in chain-dotted lines at 29 in FIG. 1. Additionally there may in order to accelerate the piston return he provided a further needle valve 24 even in such external bleed bypass, which makes possible a pre setting of the bleed to suit the changing volumes of the 4t conduit 2 if the device it is to duits 2 of different lengths.

in the modified embodiment of FIGS. 2 and 3 the needle valve arrangement 24 has been omitted While a valve mechanism generally designated 25 and shown in detail in FIG. 3 has been incorporated in the piston 11 primarily in order tossecure a rapid return of the piston H to its upper position.

The valve mechanism 25 incorporates a cylindrical cup shaped valve body 25 having bottom perforations 27 and a central projection 28 extending outwardly from its bottom. The valve cup 26 is reciprocably arranged centrally within a counter bore 29 extending axially through the piston 11 from the bottom of a counter bore 2% in the piston. The counter bore 2% is covered by a disk having perforations S t-ta therethrough and being fixedly secured to the piston for example by screws, not shown. The disk 3% carries centrally a sealing pad 31, which cooperates with the rim of the valve cup at. A central restricted bleed passage 32 extends axially through the disk 3% and the pad 31. A helical spring 34 is compressed between the sealing pad 31 and the bottom of the valve cup 26 and urges the valve cup 26 into open position away from the sealing pad 31. Normally the spring holds the valve cup 25 pressed against a shoulder 33 in the counter bore 29 in which position the valve mechanism 25 is open, there being a communication between the

chambers

13 and 19 of the cylinder 9 through the perforations Eda of the disk 30, the bore 29a, the annular opening between the rim of the valve cup 26 and the pad 31 and the perforabe used together with contions 27. In this open valve position the projection 28 of the valve cup 26 extends into the delivery chamber w of the cylinder 9 In the lower position of the piston Ill illustrated in chain dotted lines in FIG. 2, however, the projection 28 has been arrested by the cylinder 9, see FIG. 3, to effect closing of the valve mechanism 25 with the valve cup rim pressed against the pad 31. in this position the piston chambers 18- and 19 communicate solely through the restricted passage 32 in the disk 30.

In operation, the piston 11, in analogy with the em bodiment of FIG. 1, feeds the pressure fluid quantity trapped in the delivery chamber 19 through the conduit 2 to operate the wrench motor. As the valve mechanism 25 is open during practically the whole downward stroke, an additional pressure fluid quantity will pass from the pressure chamber 18 through the openings defined by the valve mechanism 25 to the chamber 19 and further to the conduit 2. Upon reaching the lower or dotted line position of FIG. 2 the valve mechanism 25 is closed by the valve projection 23 contacting the end wall of the cylinder. This stops further tightening of the bolt or nut since the pressure fluid now delivered is solely the small quantity bleeding through the passage 32. Upon closing of the throttle valve, however, this small quantity is able to build up pressure in the conduit 2 as well as in the chamber 19 to initiate the piston return, which is elficiently accelerated as soon as the valve mechanism 25 is reopened by the spring 34.

Adjustment of the pressure fluid quantity dispensed is performed by setting the hollow member 13 axially on the piston stern by turning the lever 15 as previously described with reference to FIG. 1. In order to change the additional flow of pressure fluid passing through the valve mechanisrnZS, said valve mechanism may be substituted by another valve mechanism having wider or more restricted pressure fluid passages therethrough.

While in the embodiments of FIGS. 13 as a main feature there is dispensed a predetermined volume of pressure fluid to operate the impact wrench, the modified embodiment of FIG. 4 controls the quantity of pressure fluid delivered to the wrench by measuring the time elapsed from the actuation of the throttle valve of the wrench and by shutting off the fluid supply to the impact wrench after apredetermined time corresponding to a predetermined total fluid delivery.

Referring now to FIG. 4 there is inserted between the conduits it) and 2 a solenoid operated shut-oat valve 35 of suitable construction, for example having a spring pressed plunger 36 keeping a membrane 37 tightly pressed. against the seat of the valve 35. Upon energization of a solenoid 38 the plunger is retracted whereupon the fluid pressure in the conduit is able to force the membrane 3'7 from the seat of the valve 35 to open the connection between the conduits it? and 2.

A cylinder 41 forming a servo motor has a piston l2 reciprocably arranged therein, the rod of the piston 32 projecting through one end wall of said cylinder A conduit 39 connects the conduit it to the piston rod end compartment 41a of the cylinder ill, while the opposite end compartment 41b of the cylinder 41 is connected by a conduit it? to the conduit 2. In the conduit ll there is arranged a check valve 44- opening for flow in the direction towards the conduit 2. Between the end compartments 41a and @312 of the cylinder 41 there is a bleed connection, for example attained by an insuificient tightness between the piston 42 and the cylinder 41 or by a separate connecting conduit 45 having therein an adjustable needle valve 46. The end compartment ll]? of he cylinder 41 is furthermore connected by a conduit 47 to a solenoid operated exhaust valve dd, in which for example a spring pressed plunger 49 seats a valve pad against the seat or" the valve 48. Upon energization of a solenoid 5d the plunger 4% together with the valve pad is retracted from the seat of the exhaust valve 28 thereby connecting the end compartment 41b of the cylinder 41 to the atmosphere.

The rod 43 of the piston 42 has lived thereto a lever 5ll which upon the partial retraction of tL-e rod 43 into the cylinder il depresses the actuating member 52 of a combined timer and switch T. This combined timer and switch T may be of conventional design and is therefore not described in detail. It may, for example, be carried out according to German Patent Number 937,715 wherein the combined timer and switch incorporates a clockwork mechanism controlled switch, the clockwork being pre-settable to variable time values. The functional characteristics of the timer construction selected is preferably such that upon depression of the actuating member 52 there is performed a simultaneous closure of the timer switch S3 and starting of the clocitworl; mechanism, whereupon, after elapse of the pre-se time value, the timer opens the switch 53.

Of the two leads 53, 59 from a suitable source 61 of electrical energy one is branched and connected to two double throw switches 54-, 5'6, respectively, of a switch assembly while the other lead 5'9 is connected to a third double throw switch 55 of said assembly The circuit between the two leads 5%, 59 incorporates in the right hand position in FIG. 4 of the switch asse i ly the timer switch 53 and the solenoids 38, 5d, the latter coupled in parallel. In the left hand position of the switch assembly the circuit between the leads solely incorporates the solenoid of the shut-otl valve 35. Suitably connected lamps or other signals 5'7 may be coupled to indicate when the respective circuits are completed.

The apparatus according to FIGURE 4- operates briefly in the following manner: If the operator with the respective parts in the illustrated position and with the switch assembly 54456 thrown to the right and the socket 5 over a nut or bolt 6 depresses the trigger of the throttle valve 4 then an initial pressure drop will arise in the conduit 2,. Said pressure drop causes the end compartment lib of the cylinder 5-1 or servo motor to exhaust through the conduit it? and the check valve 44 into the conduit 2, some pressure fiuid simultaneously passing from the conduit it through the conduit 39 into the piston compartment lla of the cylinder moving the piston 42 to the right hand end of the cylinder 41. During this movement the lever 51 depresses the actuating member 52 of the timer T which closes the switch 53 and starts the clockwork mechanism of the timer. liy closing of the switch 53 the circuit 6 between the switches 54-, 525 and 55 of the switch assembly is completed and the

solenoids

38 and 59 are energized. This opens the shut-off valve 35 to deliver pressure fluid to the impact Wrench 1 and opens the exhaust valve 4-3 to connect t e cnd compartment 41b of the cylinder 41 to the atmosphere. A constant bleeding of pressure fluid from the conduit ll) takes place through the conduit 39, the end compartment Alla of cylinder 41, connecting conduit 45, the needle valve 46, the end compartment dlb of cylinder 41, the conduit 47, and the valve 48 to the atmosphere. This bleeding is set by needle valve as to such small value that no pressure can be built up in the end compartment an; of the cylinder 41 which consequently remains in the right hand position. The check valve 44 prevents pressure fluid from the conduit 2 passing through the conduit dill to the cylinder il. After elapse of the predetermined time value at which the timer has been set and which corresponds to a sufiicient quantity of pressure fluid delivered through the shut-off valve 35 to operate the impact wrench the number of revolutions necessary for proper tightening, the timer breaks the circuit by opening the timer switch 53. Both

solenoids

50, 3% are then deenergized and the

respective valves

48, 35 closed which stops the operation of the impact wrench. The bleeding of pressure fiuid through the needle valve 46 continues as long as the throttle valve 4 is kept open, passing now from the needle valve as through the conduit 4%, the check valve 44 and the conduit 2 to the impact wrench. As soon as the operator releases the throttle valve, the bleeding will rapidly increase the pressure in the end compartment ll!) of the cylinder 43 until the piston 42 is returned to its initial left hand position. With the throttle valve 4 closed and the piston 42 returned, the bleeding comes to an end until the next operating cycle is started.

Obviously, by changing the setting of the timer T, the pressure fluid quantity passing the shut-off valve 35 may be pre-set for different work conditions to bring about the number of revolutions necessary to give a desired degree of tightness in the work.

If the impact wrench is to be used without regard to the resulting tightness, the switch assembly is thrown to the left. This energizes solenoid 33 to keep the valve 35 permanently open for conventional use or the wrench l.

The embodiments of the invention above described and illustrated in the drawings should only be considered as examples and the invention may be modified in several different ways within the scope of the following claims.

What I claim is:

l. A method for controlling the degree of tightness of a series of bolts or nuts driven by the aid of a pressure fluid operated impact wrench having a throttle valve connected to a fluid supply, comprising applying the impact wrench in turn over each bolt or nut to be driven, supplying pressure fluid to operate the impact wrench when in engagement with each bolt or nut in response to actuation of the throttle valve, storing a predetermined quantity oi pressure fluid from said fluid supply, dispensing said predetermined quantity of pressure fluid to the impact wrench upon actuation of said throttle valve, and automatically interrupting the wrench operating fluid supply to the impact wrench upon having delivered said predetermined quantity for the driving of each bolt or nut.

2. A method for controlling the degree of tightness of a series of bolts or nuts driven by the aid of a pressure fluid operated impact wrench having a throttle valve connected to a fluid supply, comprising applying the impact wrench in turn over each bolt or nut to be driven, supplying pressure fluid to operate the impact wrench when in engagerent with each bolt or nut in response to actuation of the throttle valve, storing a predetermined quantity of pressure fluid from said fluid supply, dispensing said predetermined quantity of pressure fluid to the impact wrench upon actuation of said throttle valve and adding thereto a controlled additional pressure fluid quantity, and automatically interrupting the wrench operating fluid supply 3,1 to the impact wrench upon having delivered said predetermined quantity and additional quantity for the driving of each bolt or nut.

3. Apparatus for controlling the degree of tightness of a series of bolts or nuts driven by an impact wrench comprising a fluid motor for driving said wrench, a pressure fluid supply, a supply connection between the motor and the fluid supply, a throttle valve in the supply connection admitting upon actuation pressure fluid to the motor, pre sure fluid dispensing means in the supply connection for delivering a controlled volume of pressure fluid to operate the motor in response to actuation of the throttle valve, and bleed means in parallel with the dispensing means for adding a controlled additional quantity of pressure fluid to said controlled volume, the dispensing means interrupting the wrench operating fluid supply to the motor upon the motor having received said controlled volume and additional quantity. t. Apparatus for controlling the degree of tightness of a series ofbolts or nuts driven by an impact wrench comprising a fluid motor for driving said wrench, a pressure fluid supply, a supply connection between the motor and the fluid supply, a throttle valve in the supply connection admitting upon actuation pressure fluid to the motor, a dispensing cylinder in the supply connection, differential piston means dividing the cylinder into a piston stem end compartment and a dispensirn compartment and deliver ing the fluid volume contained in the dispensing compartment to operate the motor in response to actuation of the throttle valve, an inlet on the cylinder for connecting the piston stem end compartment to the fluid supply, an outlet on the cylinder for connecting the dispensing compartment to the motor, a permanent bleed connection between said inlet and said outlet, an additional bleed connection between said compartments, and means for closing said additional bleed connection upon the piston having delivered the volume contained in the dispensing compartment to the motor. I

5. Apparatus according to claim 4, in which the additional bleed connection is arranged in the cylinder and said means for closing the additional bleed connection consists of a valve seat surrounding the outlet and sealing means on the piston cooperating with the seat.

' 6. Apparatus according to claim 4, in which the additional bleed connection is arranged in the piston and consists of a bleed valve, the means for closing said valve consisting of a projection on the valve contacting the cylinder when closing the valve.

7. In apparatus for controlling the maximum torque applied to each nut or bolt in driving a series of nuts or bolts and including an impact wrench with a fluid motor and a source of pressure fluid therefor, the combination which comprises a supply connection between said motor and said source of pressure fluid, a throttle valve in said supply connection, storage and delivery means in said supply connection for storing a predetermined quantity of pressure fluid from said source and delivering said predetermined quantity of pressure fluid to said motor upon actuation of said throttle valve, said storage and delivery means automatically interrupting said supply of pressure fluid to said motor upon delivery or" said predetermined quantity of pressure fluid, and bleed-means in said storage and delivery means for resetting said storage and delivery means for the next application of said impact wrench upon closing of said throttle valve.

8. In apparatus for controlling the maximum torque applied to each nut or bolt in driving a series of nuts or bolts and including an impact wrench with a fluid motor and a source of pressure fluid therefor, the combi nation which comprises a supply connection between said motor and said source of pressure fluid, a throttle valve in said supply connection, storage means in said supply connection for storing a predetermined quantity of pressure fluid from said source, a moveable feeding member in said storage means for delivering said predetermined quantity of pressure fluid to said motor upon actuation of said throttle valve, said feeding member automatically interrupting said supply of pressure fluid to said motor upon delivery of said predetermined quantity of pressure fluid, and bleed means in said feeding member for resetting said storage means and feeding member for the next application of said impact wrench upon closing of said throttle valve. r

9. Apparatus as recited in claim 8 which also includes means connected to said feeding member for adjusting the predetermined quantity of pressure fluid to be stored in said storage means.

it). In apparatus for controlling the maximum torque applied to each nut or bolt in driving a series of nuts or bolts and including an impact wrench with a fluid motor and a source of pressure fluid therefor, the combination which com rises a supply connection between said motor and said source of pressure fluid, a throttle valve in said supply connection, storage means in said supply'connection for storing a predetermined quanity of pressure fluid from said source of pressure fluid, a feeding memher in said storage means for delivering said predetermined quantity of pressure fluid to said motor upon actuation of said throttle valve, said feeding member automatically interrupting said supply of pressure fluid to said motor upon delivery of said predetermined quantity of pressure fluid, bleed means parallel with said feeding member for resetting said storage means and feeding member for the next application of said impact wrench upon closing of said throttle valve, and second bleed means from said pressure fluid source to said motor and by-passi'ng around said storage means and feeding member for supplying an additional predetermined quantity of pressure fluid from said pressure fluid source to said motor, said feeding member also automatically interrupting said second bleed means supply to said motor upon delivery of said stored predetermined quantity of pressure fluid.

11. In apparatus for controlling the maximum torque applied to each nut or bolt in driving a series of nuts or bolts and including an impact wrench with a fluid motor and a source of pressure fluid therefor, the combination which comprises a supply connection between said motor and said source of pressure fluid, a throttle valve in said supply connection, metering means in said supply connection for metering and delivering a predetermined quantity of pressure fluid to said motor from said pressure fluid source upon actuation of said throttle valve and for interrupting the flow of pressure fluid from said source to said motor upon delivery of said predetermined quantity of pressure fluid, and bleed means from said pressure fluid source to said motor and parallel with said metering means for supplying an additional predetermined quantity of pressure fluid from said pressure fluid source to said motor and connected to said metering means for the resetting thereof for the next application of said impact wrench upon closing of said throttle valve.

12. in apparatus for controlling the maximum torque applied to each nut or bolt in driving a series of nuts or bolts and including an impact wrench with a fluid motor and a source of pressure fluid, the combination which comprises a supply connection between said motor and said source of pressure fluid, a throttle valve in said supply connection, supply valve means in said supply connection, means connected to said supply valve means and responsive to said throttle for opening said supply valve means upon actuation of said throttle for delivering a predetermined quantity of pressure fluid to said motor and for automatically closing said supply valve means upon delivery of said predetermined quantity of pressure fluid, and bleed means from said pressure fluid source to said motor and parallel with said supply valve means for supplying an additional predetermined quantity of pressure fluid from said pressure fluid source to said motor and connected to said supply valve means for the resetting thereof for the next application of said impact Wrench upon closing of said throttle valve.

13. A method or" controlling the degree of tightness of a series of bolts or nuts driven by the aid of a pressure fluid operated impact wrench having a throttle valve connected to a fluid supply, comprising taking from said supply for each bolt or nut to be driven a predetermined volume of pressure fluid, storing each said predetermined volume of pressure fluid, applying said impact wrench in turn over each bolt or nut to be driven, and supplying each said stored predetermined fluid volume to said impact wrench when in engagement with each bolt or nut in response to actuation of said throttle valve.

14. A method of controlling the degree of tightness of a series of bolts or nuts driven by the aid of a pressure fluid operated impact wrench having a throttle valve connected to a fluid supply, comprising taking from said supply for each bolt or nut to be driven a predetermined volume of pressure fluid, storing each said predetermined volume of pressure fluid, applying said impact wrench in turn over each bolt or nut to be driven, supplying each said stored predetermined fluid volume to said impact Wrench when in engagement with each bolt or nut in response to actuation of said throttle valve, and passing a controlled additional flow of pressure fluid from said supply to said throttle valve while supplying said stored fluid volume.

15. Apparatus for controlling the degree of tightness of a series of bolts or nuts driven by an impact Wrench comprising a fluid motor for driving said wrench, a pressure fluid supply, a supply connection between said motor and said fluid supply, a throttle valve in said supply connection for admitting upon actuation pressure fluid to said motor, collapsible chamber means in said supply connection upstream of said throttle valve, means responsive to closing of said throttle valve for expanding and filling said collapsible chamber means by pressure fluid received from said supply thereby to store a predetermined volume of pressure fluid therein, and means responsive to opening of said throttle valve for collapsing said collapsible chamber means and for delivering said predetermined volume of pressure fluid contained therein to operate said motor.

16. Apparatus according to claim 15 in which the volume of said collapsible chamber means in the expanded state thereof is adjustable.

1'7. Apparatus for controlling the degree of tightness of a series of bolts or nuts driven by an impact wrench comprising a fluid motor for driving said Wrench, a pressure fluid supply, a supply connection between said motor and said fluid supply, a throttle valve in said supply connection for admitting upon actuation pressure fluid to said motor, collapsible chamber means in said supply connection upstream of said throttle valve, first bleed means between said supply and said throttle valve responsive to closing of said throttle valve for expanding and filling said collapsible chamber means by pressure fluid received from said supply thereby to store a predetermined volume of pressure fluid therein, means responsive to opening of said throttle valve for collapsing said collapsible chamber means and for delivering the predetermined volume of pressure fluid contained therein to operate said motor, second bleed means between said supply and said collapsible chamber means, and valve means associated with said collapsible chamber means and responsive to collapse thereof for closing said second bleed means.

References Cited by the Examiner UNITED STATES PATENTS 1,589,080 6/26 Kyle. 2,365,537 12/44 Fisher et a1 81-5235 2,664,106 12/53 Livers. 2,820,566 1/58 Van Hecke 121-3 2,825,353 3/58 Voytech 121-35 2,830,560 5/58 Doeden 121-34 2,852,965 9/5 8 Wallace.

3,005,444 10/61 Steibel 121-38 3,033,236 5/62 Rayman et al. 121-33 FOREIGN PATENTS 741,344 11/55 Great Britain.

BROUGHT ON G. DURHAM, Primary Examiner.

KARL I. ALBRECHT, RALPH H. BRAUNER,

Examiners.

Claims

1. A METHOD FOR CONTROLLING THE DEGREE OF TIGHTNESS OF A SERIES OF BOLTS OR NUTS DRIVEN BY THE AID OF A PRESSURE FLUID OPERATED IMPACT WRENCH HAVING A THROTTLE VALVE CONNECTED TO A FLUID SUPPLY, COMPRISING APPLYING THE IMPACT WRENCH IN TURN OVE EACH BOLT OR NUT TO BE DRIVEN, SUPPLYING PRESSURE FLUID TO OPERATE THE IMPACT WRENCH WHEN IN ENGAGEMENT WITH EACH BOLT OR NUT IN RESPONSE TO ACTUATION OF THE THROTTLE VALVE, STORING A PREDETERMINED QUANTITY OF PRESSURE FLUID FROM SAID FLUID SUPPLY, DISPENDING SAID PREDETERMINED QUANTITY OF PRESSURE FLUID TO THE IMPACT WRENCH UPON ACTUATION OF SAID THROTTLE VALVE, AND AUTOMATICALLY INTERRUPTING THE WRENCH OPERATING FLUID SUPPLY TO THE IMPACT WRENCH UPON HAVING DELIVERED SAID PREDETERMINED QUANTITY FOR THE DRIVING OF EACH BOLT OR NUT.