GB2057950A - Testing apparatus - Google Patents

Abstract

Testing apparatus for hand-holdable riveting hammers comprises a bed (1) having a dummy work (3) rigidly secured thereto, a mounting for a hand-holdable riveting hammer (4) under test and a mounting for a dolly (5). The mountings are located on opposite sides of the dummy work (3) and are movable along the bed 1. Two simulators 10, 11 of operator's hand input mechanical impedance are provided. One of the simulators (10) is rigidly connected to the mounting for the hand-holdable riveting hammer (4) and interacts with the hammer, whereas the other simulator (11) is rigidly connected to the mounting for the dolly (5) and interacts with the dolly. A vibration pickup for sensing the vibration of the hammer (4) is connected to a vibration metering device (13). <IMAGE>

Description

SPECIFICATION Testing apparatus The invention relates to testing apparatus and has particular reference to vibration safety testing apparatus for hand-holdable riveting hammers.

The invention provides testing apparatus for hand-holdable riveting hammers, comprising a bed, means for rigidly securing a dummy tool to the bed, a mounting for a hand-holdable riveting hammer under test, a mounting for a dolly, said mountings being located on opposite sides of said dummy work and being movable along said bed, two simulators of operator's hand input mechanical impedance, one of the simulators being rigidly connected to the mounting for the hand-holdable riveting hammer under test for interaction with said hammer, the other simulator being rigidly connected to the mounting for the dolly for interaction with said dolly, and a vibration pickup for sensing the vibration of the handholdable hammer being tested and connected to a vibration metering device.

The simulators of operator's hand input mechanical impedance are constructed in the form of a single-mass resilient damping system. When this system is subjected to vibration of a wide frequency range, the magnitude and nature of the system dynamic reaction corresponds to the reaction of the operator's hand during riveting work under the specified conditions.

Thus, the measured range of vibration of the handle of the riveting hammer under test is analogous to the range of the vibration acting on the hands of the riveting operator when the latter operates said hammer.

Such a testing apparatus provides the maximum possible conditions for securing the hammer under test in the manner of the operator's grasp, whereby true checking of hammer vibration safety can be made without subjecting operators to the harmful effects of vibration.

The apparatus can be used for conducting type tests on hand-holdable pneumatic riveting hammers, for making manufacturer's release checks for permissible hammer vibration or user's acceptance, periodic or overhaul checks on hand-holdable riveting hammers, as well as for research work on vibration insulation of novel hand-holdable riveting hammers.

This apparatus can also be used for conduction vibration safety tests on dollies used in conjunction with riveting hammers, said dollies being likely to be part of vibration-hazardous equipment. The apparatus can be used to advantage for testing electric riveting hammers.

The invention will now be more particularly described, by way of example, with reference to the accompanying drawings, wherein: Figure 1 is a front view of one embodiment of vibration safety testing apparatus for handholdable riveting hammers according to the invention; Figure 2 is an enlarged view of the detail A in Fig. 1 showing the construction of the simulator of the operator's hand input mechanical impedance; Figure 3 is a pneumatic diagram of the apparatus of Fig. 1.

Referring to Fig. 1 a vibration safety test bench shown therein comprises a bed 1 with two ways. A pneumatic vice 2 is mounted at the centre of the bed between the ways.

Rigidly secured in the vice 2 is a dummy work 3 which is essentially a duralumin plate the size and thickness of which are chosen to suit the type of the hammer to be tested.

The construction of the test bed is symmetrical in relation to the dummy work 3. A mounting for a hand-holdable riveting hammer 4 under test and a mounting for a dolly 5 are located on opposite sides of the dummy work 3 and adapted to be moved along the ways of the bed 1. The test bench is used for testing hand-holdable pneumatic riveting hammers.

The dolly 5 which is used in conjunction with the riveting hammer 4, is shaped substantially like the hammer and, therefore, the mountings for the hammer 4 and for the dolly 5 are similar in construction. The hammer mounting includes a hammer holder 6 and the dolly mounting includes a dolly holder 7.

To press the hammer 4 and the dolly 5 against the dummy work 3, the hammer mounting has a hammer pressing device 8 and the dolly mounting has a dolly pressing device 9.

Simulators 10 and 11 of operator's hand input mechanical impedance are located at the handles of the hammer 4 and dolly 5, said simulators being adapted for attachment to the hammer and the dolly. The simulator 10 is rigidly secured to the hammer pressing device 8 and interacts with the hammer 4.

The simulator 11 is rigidly secured to the dolly pressing device 9 and interacts with the dolly 5.

The simulators 10 and 11 are constructed so that their input mechanical impedance corresponds to the input mechanical rmpedance of operator's hands.

A control station 1 2 is mounted on the test bench bed 1.

The vibration of the riveting hammer 4 and the dolly 5 is measured and analyzed by means of a vibration metering device 1 3 which is essentially a conventional doubleacting octave analyzer of vibration with a frequency range from 11 to 2800 Hz. It is equipped with indicating lamps for each of the eight octave bands. Each lamp is illuminated when the vibration level in the corresponding octave is exceeded.

The vibration metering device 1 3 is electrically connected to vibration pickups (not shown) which sense the vibration of the riveting hammer 4 and the dolly 5 and which are located inside the operator's hand input mechanical impedance simulators 1 0 and 11.

The operator's hand input mechanical impedance simulator 10 comprises a simulation mass in the form of a metal sleeve 14 (Fig. 2) mounted in a simulator casing 1 5 on balls 1 6. One end of the sleeve 14 has a seat fitted with a resilient damping element 1 7 and adapted to receive the handle of the riveting hammer 4 being tested. The simulator 11, which interacts with the dolly 5, is constructed in the same manner. The resilient damping element 1 7 consists of foam polyurethane ring which is fitted inside the sleeve 1 4 so that one side of the ring bears against a partition 1 8 and the other side contacts a washer 1 9 which is in direct contact with the handle of the hammer 4 (or the dolly 5).

Located in the simulator 10 at the other end of the sleeve 14 is an electromagnetic damper comprising a coil 22 and a yoke 20 whose gap accommodates a copper ring 21. The yoke 20 and the coil 22 are rigidly secured to the barrel of a pneumatic cylinder 23. The ring 21 is rigidly secured to the sleeve 14.

Inside the pneumatic cylinder is fitted an adjusting spring 24 which provides for pressing the hammer 4 (or the dolly 5) against the dummy work 3 with a force of 30 to 200 N.

This force depends on the blow energy of the hammer 4 and is determined by the requirements of the riveting process involved.

The sleeve j 4 with the abovementioned elements mounted thereon simulates the corrected mass of a man hand and has a mass of the order of 1. N.s2/m.

The resilient damping element 17, which has a nonlinear dynamic rate and losses about 80 N s/m, simulates the input stiffness and losses of the hand.

The adjusting spring 24, which has a rate of the order of 3000 N/m, simulates the stiffness of the elbow and shoulder joints.

The electromagnetic damper, which has a damping factor of the order of 80 N.s/m, simulates part of the hand viscous friction.

A vibration pickup 25 is installed inside the sleeve 14 of the operator's hand input mechanical impedance simulator 10.

The housing of the vibration pickup 25 is rigidly secured to the casing 1 5 of the simulator 10, for example, by means of screwed fastenings. For the purpose provision is made of four studs 26 which pass through oval holes in the sleeve 14 and hold the case of the vibration pickup 25 to the case 1 5 of the simulator 10.

The vibration pickups 25 of the hammer 4 and the dolly 5 are conventional feeler-type induction converters. They convert the vibration of the handles of the riveting hammer 4 and the dolley 5 into an electrical signal which is fed through a cable into the vibration metering device 1 3.

To check for contact between the feeler 27 of the vibration pickup 25 and the handle of the hammer 4 (or the dolley 5) an indicator 28 is mounted on the casing 1 5. The indicator is made in the form of a scribed mark on the washer 1 9 and a metal pinter mounted on the casing 1 5 of the stimulator 10. When the pointer registers with the scribed mark, the feeler 27 is in contact with the handle of the hammer 4 (or the dolley 5).

For a better understanding of operation of the test bench reference is made to the pneumatic diagram in Fig. 3. The pneumatic vice 2 for holding the dummy work 3 comprises a fixed jaw 29 and a movable jaw 30 operated through a lever 31 by a pneumatic cylinder 32 which is controlied by a solenoid-operated pneumatic valve 33.

The hammer holder 6 comprises a carrier 34 with rollers 35 mounted on ball bearings and adapted to grip the body of the hammer 4. For setting up the rollers 35 in a vertical direction, the carrier 34 is mounted on a carriage 36 by means of a screw 37, and a nut 38. The carriage 36 is mounted on rollers 39 for movement along the bed 1.

The gripping force exerted on the body of the hammer 4 is regulated by the use of a spring 40 and an air pressure regulator 41 which controls the pressure of the air supplied through a solenoid-operated pneumatic valve 42, a pressure gauge 43 being provided for an indication purpose. Said gripping force depends on the hammer size and blow energy.

The hammer pressing device 8 comprises a carriage 44 mounted on the ways of the bed 1 and adapted to be moved longitudinal by means of a handwheel-operated screw 45 and a nut 46. The carriage 44 accommodates the pneumatic power cylinder 23 which mounts the operator's hand input mechanical impedance simulator 10 and is designed for pressing the riveting hammer 4 against the dummy work 3.

The pneumatic power cylinder 23 is arranged-to be vertically moved in the carriage 44 by means of a handwheel-operated screw 47 and a nut 48.

The pressure exerted by the spring 24 is adjusted by the use of a handwheel-operated nut 49 and a screw 50.

Longitudinal movement of the pneumatic power cylinder 23 is effected by feeding air into said cylinder through a solenoid-operated pneumatic valve 51.

The working pressure exerted on the riveting hammer 4 being tested is controlled by a pressure regulator 52 and indicated by a pressure gauge 53. The air is fed to the hammer 4 through a solenoid-operated pneumatic valve 54.

The mounting of the dolly 5 is analogous in construction to the mounting of the riveting hammer 4. The dolly holder 7 comprises a carrier 55 with four freely rotating rollers 56 for gripping the body of the dolly 5. To enable the dolly holder 7 to be moved vertically, the carrier 55 is mounted on a carriage 57 through the use of a screw 58 and a nut 59. The carriage 57 is mounted on rollers 60 for movement along the bed 1.

The gripping force exerted on the body of the dolly 5 is regulated by the use of a spring 61 and an air pressure regulator 62 which controls the pressure of the air supplied through a solenoid-operated valve 63, a pressure gauge 64 being provided for an indication purpose. The gripping force exerted on the body of the dolly 5 depends on the blow energy of the riveting hammer 4 being tested.

The dolly pressing device 9 comprises a carriage 65 mounted on the ways of the bed 1 and arranged for longitudinal movement by provision of a handwheel-operated screw 66 and a nut 67. The carriage 65 accommodates a pneumatic power cylinder 68 which mounts the operator s hand input mechanical impedance simulator 11 designed to hold the dolly 5 and press it against the dummy work 3. To enable the pneumatic cylinder 68 to be moved vertically, the carriage 65 is provided with a handwheel-operated screw 69 and a nut 70. Longitudinal movement of the pneumatic cylinder 68 is effected by feeding air into said cylinder through a solenoid-operated valve 71. The pressure which forces the dolly 5 against the dummy work 3 is exerted by a spring 72. The spring pressure is adjusted by the use of a handwheel-operated nut 73 and a screw 74.

The air distributing equipment, including an air feed line 85, is installed inside the bed 1.

Air preparation is carried out by the use of a filter 76 and an oiler 77.

In conducting vibration safety tests on hand-held riveting hammers, the test bench described above operates as follows: The dummy work 3 (Figs. 1 and 3) is chosen to suit the type of the hand-held riveting hammer to be tested. The work 3 is placed in the pneumatic vice 2 and gripped with the movable jaw 30.

The hammer 4 to be tested and the dolly 5 are installed in the hammer holder 6 and the dolly holder 7 respectively and the required gripping force is set by reference to the pressure gauges 43 and 64.

Then the hammer 4 and the dolly 5 are forced against the dummy work 3 by exerting the required pressure with the hammer pressing device 8 and the dolly pressing device 9.

By the use of the indicator 28 a check is made to ascertain that the feeler 27 of the vibration pickup 25 is in contact with the handle of the hammer 4.

The timer (not shown) in the control station 1 2 is set to the required hammer working time. A signal from the timer initiates delivery of compressed air from the feed line 75 through the valve 54 to the hammer 4. The hammer working pressure is indicated by the pressure gauge 53. The hammer 4 comes into operation and the vibration pickup 25 senses the vibration level which is registered by the metering device 13, measured in each octave band and compared with the vibration level permissible for the band involved. Illumination of an indicating lamp signals that the hammer does not meet the test conditions.

If the level of vibration of the dolly 5 has to be determined also, the metering device 1 3 alternately measures the level of vibration of the hammer 4 and the dolly 5.

All the operations are performed automatically by the agency of the control station 1 2.

The vibration pickup 25 need not be attached to the hammer under test and, therefore, the change of hammers of the same type takes only 15-20 seconds. The analysis of vibration in all the octave bands involved takes 2 to 3 seconds, giving go-no-go results.

The working capacity of the test bench is 100 riveting hammers per hour. Thb test bendh is simple and dependable in operation and, apart from hammer testing, can be used for determining rivet upsetting time.

Claims (9)

1. Testing apparatus for hand-holdable riveting hammers, comprising a bed, means for rigidly securing a dummy work to the bed, a mounting for a hand-holdable riveting hammer under test, a mounting for a dolly, said mountings being located on opposite side of said dummy work and being movable along said bed, two simulators of operator's hand input mechanical impedance, one of the simulators being rigidly connected to the mounting for the hand-holdable riveting hammer under test for interaction with said hammer, the other simulator being rigidly connected to the mounting for the dolly for interaction with said dolly, and a vibration pickup for sensing the vibration of the hand-holdable hammer being tested and connected to a vibration metering device.

2. Apparatus as claimed in claim 1, further comprising a hammer pressing j device and a dolly pressing device for pressing the hammer and dolly respectively against opposite sides of the dummy work.

3. Apparatus as claimed in claim 1 or claim 2, wherein the vibration metering device comprises a double-acting octave analyzer equipped with indicating lamps.

4. Apparatus as claimed in any one of the preceding claims, wherein each simulator comprises a casing, a body slidably movable in the casing, a seat at one end of the casing, the seat being adapted to receive a handle of the riveting hammer under test or dolly and being provided with a damping element, and an electromagnetic damper at the other end of the body.

5. Apparatus as claimed in claim 4, wherein at least the body of said one simulator comprises a sleeve in which the vibration pickup is located.

6. Apparatus as claimed in any one of the preceding claims, wherein the mounting for the riveting hammer comprises a carrier having means whereby the hammer can be gripped with a gripping force which is regulated.

7. Apparatus as claimed in claim 6, wherein the carrier is vertically adjustable and longitudinally movable.

8. Apparatus as claimed in any one of the preceding claims, wherein a further vibration pickup for sensing the vibration of the dolly is provided.

9. Testing apparatus for hand-holdable riveting hammers, substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

1 0. A method of vibration safety testing a hand-holdable riveting hammer using testing apparatus as claimed in any one of the preceding claims.