GB1569570A - Hydraulic pressure generation apparatus - Google Patents

Description

(54) HYDRAULIC PRESSURE GENERATION APPARATUS (71) We, AVDEL LIMITED, a British Company of Mundells, Welwyn Garden City, Hertfordshire, England, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is ;to be performed, to be particularly described in and by the following statement: The invention relates to hydraulic pressure generation apparatus for use with hydraulically operated riveting apparatus, that is, riveting apparatus in which operation of the riveting head is effected by the application of pressure to the riveting head. The invention also relates to hydraulically operated riveting apparatus including hydraulic pressure generation apparatus. Such apparatus is described in British Patent No.

578,105.

The invention provides hydraulic pressure generation apparatus for use with hydraulically operated riveting apparatus in which operation of the riveting head is effected by the application of hydraulic pressure to the riveting head, which hydraulic pressure generation apparatus comprises: a hydraulic pressure generator for generating hydraulic pressure; pneumatically-operated control means for controlling the operation of the generator, the control means responding to a reduction in pneumatic pressure applied thereto; and a venturi device having its negative pressure branch connected to the control means to provide the aforesaid reduction in pneumatic pressure.

The invention includes hydraulically operated riveting apparatus in which operation of the riveting head is effected by the application of hydraulic pressure to the riveting head, including hydraulic pressure generation apparatus as aforesaid.

A specific embodiment of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Figure 1 is a schematic hydraulic circuit diagram of a hydraulically operated riveting apparatus in the normal or rest position, and its associated pressure generator and control means, and Figure 2 is a similar diagram showing the apparatus at the end of its working stroke.

In this example, the riveting apparatus comprises a riveting head 11, and a separate hydraulic pressure generator 12. These are interconnected by two flexible hoses, a hydraulic pressure hose 13, and an air hose 14. The general design, construction and operation of such head and generator are well known and will be described here only briefly.

The riveting head 11 is designed to place blind rivets of the type in which an inner stem or mandrel has to be pulled through an outer body or shell to produce deformation of the latter. It may alternatively be designed to place the non-blind type of fas- tener known as a lockbolt, in which an outer sleeve or collar is swaged onto an inner stem or pin. In both cases the head is required to retract an inner member forcibly with respect to an outer member. To this end, the head includes an annular anvil 15 for abutting the outer member and a pair of jaws 16 for gripping the inner member. The anvil is connected to a head cylinder 17 and the jaws are connected via drawrod 18 to a single-acting head piston 19. The application of hydraulic pressure via hose 13 to cylinder 17 causes retraction of the drawrod and jaws against the urging of a return spring 21.The riveting head also contains a push-button valve 22 which is connected to hose 14. When the valve 22 is operated it opens against a return spring and vents hose 14 to atmosphere, as illustrated in Figure 2, thus actuating the generator as will be described below.

The generator 12 comprises a pneumatic/ hydraulic intensifier 23 and its associated pneumatic control gear. Compressed air from an air line is connected via input coupling 24 to a number of branches; firstly via conduit 31 to the input of a 5-port single pilot spring return valve 25; secondly via conduit 32 and conduit 26 to the input of a venturi T-piece 28 and thus via the out put of the venturi to hose 14 and valve 22; and thirdly via conduit 32 and conduit 34 to the input of a 5-port single pilot spring return valve 29. The negative pressure branch of venturi 28 is connected via conduit 33 to the control input of valve 28.

One output of valve 29 is connected via conduit 35 to the pilot input of valve 25 and also via branch conduit 27 to one side of the pneumatic section 57 of priming valve 47. -The- other~output of valve 29 is con- nected via conduit 3-Ht-o the other side of the pneumatic section 57 of valve 47. The two outputs of valve 25 are connected via conduits 37 and 38 to the two sides of the double-acting pneumatic piston 41 of the intensifier 23. The single output of the hydraulic cylinder 42 of the intensifier is connected to hose 13 and thus to riveting head cylinder 17.

When compressed air is supplied through the coupling 24 and spring biassed push button valve 22 is in the normally closed position, the condition of the apparatus is as shown in Figure 1. Conduit 32 is pressurised but since valve 22 is closed air cannot flow along pipes 14. Instead of a negative pressure in conduit 33, this conduit is pressurised with air and therefore valve 29 is held open against the urging of its spring.

Conduit 35 is thus connected via conduit 36 and valve 29 to conduit 34 and is pressurised. Conduit 36 is vented so that, as viewed in Figure 1, valve 25 is held to the right and compressed air is fed to the left of the intensifier piston whilst the rear is vented, thus holding the intensifier piston 41 to the right and the piston rod 44 retracted.

When the push button valve 22 is opened, hose 14 and conduit 32 are vented. There is thus produced a relatively high velocity flow of air, from the input 24, through conduits 32 and 26, through the venturi 28, and then through hose 14 and valve 22, to atmosphere. The high velocity air flow through the venturi 28 produces a negative air pressure in the conduit 33, which cooperates with the urging of the spring of valve 29 to cause valve 28 to change over very rapidly. This connects conduit 35 to pressure air, so that valve 25 also changes over against its spring, as shown in Figure 2.

Thus valves 29 and 25 change over, and the air connections to the intensifier are reversed thus forcing the piston and its piston rod 44 forwards (i.e. to the left of Figure 1) and applying hydraulic pressure to actuate the riveting head piston, towards and into the position shown in Figure 2. On release and closing of push button valve 22, the intensifier reverses to its original position and the spring 21 returns the head piston to its original position shown in Figure 1.

The whole space within the hose 13, in tensifier hydraulic cylinder 42 and the working side of head cylinder 17 is of course filled with hydraulic working fluid 40.

In order to provide make-up of hydraulic fluid to compensate for losses due to leakage or cavitation, there is provided a hydraulic fluid- reservoir 45 which is mounted above the intensifier hydraulic cylinder 42 and connected to it by a conduit 46 and a pneumatically actuated priming valve 47.

The valve 47 comprises a valve chamber 48 communicating with the intensifier hydraulic cylinder 42 by means of a bore 49.

The chamber contains an annular valve seat 51 which is closed by a valve member 52 fitted with a face seal ring 53. On the other side of the seat 51, a passage 54 communicates via bore 55 with conduit 46 from the reservoir. The valve member 52 is mounted on a rod 56 which is reciprocated by a double-acting pneumatic piston and cylinder device 57, including a piston 60 secured to rod 56. The stroke of the rod 56 is limited by a stop 61 within the pneumatic cylinder. One side of this device is connected to pneumatic conduit 35, and the other side to pneumatic conduit 36, such that when conduit 35 is pressurised and con duit 36 vented, the valve 47 lis closed. Thus the pilot valve 29 controls both the intensifier pneumatic piston 41 and the priming valve 47.However, the valve 47 has low inertia, whereas the intensifier piston 41 and 44 has higher inertia, coupled to the frictional resistance to flow of the hydraulic fluid, and a slight delay in actuation due to the interposition of valve 25 between it and valve 29. Consequently, whenever valve 29 changes position, priming valve 47 also changes position before there is any effective movement of intensifier piston 44 and corresponding change in hydraulic fluid pressure. Thus the priming valve 47 shuts as soon as the intensifier starts to pressurise the hydraulic fluid, and thereby cloes the connection between the pressurised working hydraulic fluid and the reservoir. As soon as the intensifier piston starts its return stroke the valve 47 opens, thereby reconnecting the working fluid to the reservoir until the start of the next pressure stroke of the intensifier. In this way, if the intensifier piston returns faster (as far as volume displacement is concerned) than the head piston, the negative pressure created will draw such fluid from the reservoir instead of causing cavitation. When the intensifier has completed its return stroke, the head piston will still be returning under the urging of the head spring 21 and will thus return the excess fluid to the reservoir.

leaving sufficient fluid from the reservoir in the working fluid space to make up for any deficiency caused by leakage, thereby ensuring that the working fluid space is completely filled with hydraulic fluid. As soon as the intensifier piston starts its next pressure stroke, the priming valve 47 closes, sealing off the reservoir from the rest of the hydraulic circuit. Moreover, as soon as the pressure of the working hydraulic fluid rises, it forces the valve member 52 firmly into sealing relationship with its seat 51, thereby reducing the possibility of any leakage of pressurised fluid through the valve 47.

Attention is directed to our co-pending application No. 14767/76 (Serial No.

1,509,569).

The invention is not restricted to the details of the foregoing example.

WHAT WE CLAIM IS: 1. Hydraulic pressure generation apparatus for use with hydraulically operated riveting apparatus in which operation of the riveting head is effected by the application of hydraulic pressure to the riveting head, which hydraulic pressure generation appar atus comprises: : - a hydraulic pressure generator for generating hydraulic pressure, pneumatically-operated control means for controlling the operation of the generator, the control means responding to a reduction in pneumatic pressure applied thereto; and a venturi device having its negative pressure branch connected to the control means to provide the aforesaid reduction in pneumatic pressure.

2. Hydraulically operated riveting apparatus in which operation of the riveting head is effected by the application of hydraulic pressure to the riveting head, including hydraulic pressure generation apparatus as claimed in Claim 1.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (2)

**WARNING** start of CLMS field may overlap end of DESC **. as the intensifier piston starts its next pressure stroke, the priming valve 47 closes, sealing off the reservoir from the rest of the hydraulic circuit. Moreover, as soon as the pressure of the working hydraulic fluid rises, it forces the valve member 52 firmly into sealing relationship with its seat 51, thereby reducing the possibility of any leakage of pressurised fluid through the valve 47. Attention is directed to our co-pending application No. 14767/76 (Serial No. 1,509,569). The invention is not restricted to the details of the foregoing example. WHAT WE CLAIM IS:

1. Hydraulic pressure generation apparatus for use with hydraulically operated riveting apparatus in which operation of the riveting head is effected by the application of hydraulic pressure to the riveting head, which hydraulic pressure generation appar atus comprises: : - a hydraulic pressure generator for generating hydraulic pressure, pneumatically-operated control means for controlling the operation of the generator, the control means responding to a reduction in pneumatic pressure applied thereto; and a venturi device having its negative pressure branch connected to the control means to provide the aforesaid reduction in pneumatic pressure.

2. Hydraulically operated riveting apparatus in which operation of the riveting head is effected by the application of hydraulic pressure to the riveting head, including hydraulic pressure generation apparatus as claimed in Claim 1.