Fluid injection apparatus

Abstract

 Piston (6,11) is slidable within cylindrical casing (1) to force fluid disposed in collapsible container (C) out through nozzle (14). The piston is spring-biassed to cause automatic fluid discharge, but when withdrawn can be retained against the action of spring (5) by engagement of projections (9) on the piston rod (6) with casing end caps (3). For filling cracks or gaps with liquid sealant, a plurality of such injectors may be used, each secured in position by way of attachment units (15) and/or dowels located in bores.

Description

[0001] The present invention relates to injection apparatus for fluids, particularly but not exclusively hardenable liquid sealants, of a type which operates automatically without any outside power source. The injection apparatus of the invention also specifically lacks a solid piston. In other words, the piston does not have a large wall area in direct sliding contact with the cylindrical inside wall surface of a hollow cylindrical housing of the injector.

[0002] Although not limited thereto, the injection apparatus of the invention is extremely useful in mending cracks in concrete buildings or like structures, in filling up any dangerous idle gap or gaps formed between a concrete or the like main structure and decorative and protective surface panels originally adhered thereto, but, since having been separated therefrom, and for filling void spaces formed around concrete-reinforcing steel bars by chemical corrosion and erosion in reinforced concrete structures. Concrete tunnel cracks may also be mended.

[0003] Nowadays "grease guns" are widely used for concrete crack-mending and for similar jobs as having been described above. In this respect, the term "grease" means a rather sticky, almost paste-like resin filler, having a high value of viscosity. The injection pressure adopted in such a case would be very high, amounting, as an example, to say 200 kg/cm². The operating period is also very short. Manual power is required to empty each grease gun, one man for each individual apparatus, so the procedure is labour intensive.

[0004] A prior fluid sealant injector is disclosed in German patent publication No. 27 56 075 in the name of Artur Fisher. This known apparatus comprises a hollow cylinder, the upper and lower ends thereof being substantially closed except for a piston rod-guiding opening and air bleed open­ings bored through a top cover to enable movement of the piston within the interior space of the cylinder, and a liquid-injection opening bored through the opposite cover wall of the cylinder, for dispensing the liquid sealant. The piston rod extends from the inner piston to outside the cylinder and is operable by a human operator to force the sealant out through the injection opening. In this case, sealant injection is not effected automatically and depends upon the operator's manual effort which obviously cannot be sustained for many hours. Furthermore it would be impractical to operate a large number of such sealant dispensers so as to fill a large and complicated network of cracks, over a wide concrete surface area, with liquid sealant in one working shift period, for example.

[0005] It is an object of the present invention to provide automatic injection apparatus which is capable of perform­ing slow-acting, low pressure injection of low viscosity fluids, particularly hardenable liquid sealants.

[0006] A further object is to provide fluid injection aparatus of the above kind, capable of performing a crack-­mending job on a ceiling, wall or floor, separately or jointly, with a number of similar injectors being in use at the same time.

[0007] A further object of the invention is to provide a liquid sealant injection process for mending cracks with minimum labour expenditure.

[0008] Pursuant hereto, the invention provides fluid injection apparatus comprising a cylindrical casing having an outlet nozzle at one end and a piston which is slidable in the casing to force fluid contained within the casing out of the nozzle, characterised in that a detachable axially collapsible container is disposed within the casing to contain the fluid, and biassing means located within the casing acts via the piston to cause collapse of the contain­er and discharge of fluid contained therein through the nozzle, the piston being adapted to be manually withdrawn and retained against the action of the biassing means.

[0009] Further features and advantages of the inventive fluid injection apparatus and specific use thereof will become more apparent when reading the following detailed description or specifically selected preferred embodiments of the invention with reference to the accompanying drawings, in which:

Fig. 1 is a longitudinal cross-section of a first embodiment of fluid injection apparatus according to the invention;

Fig. 2 is a partially sectioned, enlarged elevation of a pressure-charging and discharging unit contained in the injection apparatus shown in Fig. 1;

Fig. 3 is a partially sectioned, enlarged elevation of an axially contractable and expandable sealant container of the apparatus shown in Fig. 1;

Fig. 4 is a cross-section on the line IV-IV in Fig. 1;

Fig. 5 is a cross-section of the hollow cylindrical housing and the operating rod, along the line V-V in Fig. 1;

Fig. 6 is a partially sectioned elevational view illustrating a pedestal unit, which constitutes a part of the injection apparatus shown in Fig. 1 and is provisionally fixed in position for use on the surface of a cracked concrete stucture;

Fig. 7 is an underside plan view of the pedestal unit shown in Figs. 1 and 6;

Fig. 8 is a sectional view illustrating preparatory drilling work to be performed in advance of hardenable liquid injection to fill up an idle gap formed between a basic concrete structure and a floatingly separated covering decorative panel;

Figs. 9a and b respectively are a side view and a cross-section of a radially expandable plug piece or dowel to be hammered into the drilled bore shown in Fig. 8;

Fig. 10 is a longitudinal section illustrating the dowel shown in Fig. 9 installed in position in the bore with connector means attached thereto;

Fig. 11 is a longitudinal section illustrating a similar floating gap fill up operation wherein both the dowel and the connector means are modified compared to those shown in Figs. 9 and 10.

Figs. 12a and b are respective perspective views of two different corner pedestals for use with embodiments of the injection apparatus of the invention;

Fig. 13 is a perspective view illustrating the use of several identical injectors in accordance with the invention to fill up with a liquid sealant, a crack network formed in and on a concrete wall area the crack network having been simplified for purposes of illustration;

Fig. 14 is a flow chart indicating the sequence of operation steps for filling up cracks by simultaneous use of a plurality of injectors in accordance with the invention; and

Fig. 15 is a similar flow chart indicating the steps for filling up a floating wall gap.

[0010] Referring firstly to Figs. 1 and 2, a preferred practical embodiment of the automatic pumpless injection apparatus of the invention can be divided into three main parts which will be called A, B, C. Unit A comprises a wholly or at least partially transparent hollow cylindrical casing 1, preferably made of epoxy resin, and having outer male screw thread portions 1a and 1b at the top and bottom ends thereof, for connection of top and bottom end caps 3 and 4, respectively. In Fig. 1, the top and bottom ends of the cylindrical casing 1 are shown to be closed by these screw-on end caps 3 and 4.

[0011] Within the uppermost portion of the interior chamber 1c of the casing 1, biassing means, preferably a coil spring 5, is located. Although not shown, it is preferable to provide a soft and resilient rubber or plastics disc between the upper cap 3 and the coil spring 5 to even out the spring pressure acting against the inside surface of the upper cap 3.

[0012] An elongate piston rod 6, which can be manually manipulated, passes slidably through a central opening 7 bored through the upper cap 3. At an intermediate height along the rod 6, the latter is integrally formed with a pair of radially extending projections 9 which are adapted for establishing a kind of bayonet joint in co­operation with a pair of radially extending slots 8 formed through the upper cap 3, when the rod 6 has been drawn upwardly so as to compress the coil spring 5, as will be later more fully described.

[0013] At the lower end portion of the rod 6, a plurality of radial vanes 10 are fixedly provided thereon for better guidance of the lower portion of the coil spring 5. A circular disc 11 is attached to the lower end of the rod 6. The lower end of the coil spring 5 is supported upon the disc 11 and transmits spring force thereto evenly and downwardly, substantially in the axial direction of the rod 6. Conversely, when the rod 6 and the disc 11 are drawn manually upwards, as seen in Figs. 1 and 2, the spring 5 is compressed and energy is thus accumulated therein. This upward pulling direction is shown by a small arrow "P" in Figs. 1 and 2. For convenient manipulation of the rod 6, a generally triangular handle 12 is provided at the upper end of rod 6. The handle 12 consists of a hollow metal tube 12b extending laterally through the rod, and a substantially triangular wire grip 12a.

[0014] The component indicated by reference numerals 3 to 12 aforesaid may be considered as a self-contained pressure charger and discharger assembly which is designated as unit B.

[0015] Unit C consists of a replaceable, liquid sealant container (13) which is closed at its top end and is axially compressible upon reception of pressure force applied from the side of the foregoing unit B.

[0016] The said container C is made of slightly pliable plastics resin and is top-closed at 13a, as specifically shown in Fig. 3.

[0017] The container C includes a main body portion 13b, which preferably has a bellows-mode structure, integral with a mouth portion 13d and an outlet portion 13e, the latter being formed with external screw threads for a mechanical connection to be described. These portions 13d and 13e may, if desired, be made in two pieces mechanically connected with each other, preferably by a screw connection, although such a construction is not shown. Furthermore, if desired, in place of the bellows-­mode structure, a structure comparable to fine pitched screw threads may be employed, although again this is not illustrated.

[0018] The lower end portion of 13d, 13e has a reduced discharge passage 13g in communication with the interior space 13f of the container.

[0019] Reference letter D (Fig. 6) indicates an attachment assembly, which comprises a nozzle 14 formed with a socket having internal screw threads 14a adapted for establishing a screw connection with the external screw threads 13e on the container C. The bottom end cap 4 of the casing 1 is concentrically and detachably connected to the nozzle 14 which has a downward externally screw threaded exten­sion 14b. The latter is fitted into a socket-and-flange piece or pedestal 15 comprising a socket portion 15a and an integral flange portion 15b, as shown in Fig. 6. An injection passage d is formed through the flange 15b and the screw threaded extension 14b, extending upwards so as to communicate with the relatively enlarged inside space 14c of the socket region of the nozzle 14. In Fig. 7, the attachment assembly D is shown in an inverted plan view.

[0020] A two-component type of liquid sealant is recom­mended for use in the aforesaid apparatus to avoid premature hardening of the sealant. In addition, mixing of the two components can be carried out at the site in a simple manner.

[0021] Several preferred combinations of sealant components and the overall characteristic data of the mixture are set forth hereinbelow:

a) First example: sealant I, usable in spring and autumn seasons:

[0022] As the first component, named "A", modified epoxy resin, 370 cps/20°C, specific gravity: 1.15, may be used.

[0023] As the second component, named "B", modififed polyamine, 100 cps/20°C, specific gravity: 1.03, may be used.

[0024] Mixing ratio of these components may be 2:1 by weight.

[0025] Usable period of the mixture is 130 min. at 20°C and 60 min. at 30°C, respectively.

[0026] Hardening period is 15 hours at 30°C and 6 hours at 30°C, respectively.

[0027] Physical properties of the mixed sealant are as follows, as measured after a week upon grouting at 20°C.

compressive strength      780 kg/cm²;
tensile strength      370 kg/cm²;
elongation percentage      410%;
bending strength      660 kg/cm²;
hardness, Shore D      75;

b) Second example: sealant II, usable in summer season:

[0028] As the first component, named "A", modififed epoxy resin, 300 cps/30°C, specific gravity: 1.15, may be used.

[0029] As the second component, named "B", modififed polyamine, 40 cps/30°C, specific gravity: 1.03, may be used.

[0030] Mixing ratio of these components may be 2:1 by weight, as before.

[0031] Usable period of the mixture is 250 min. at 20°C and 100 min. at 30°C, respectively.

[0032] Hardening period is 35 hours at 20°C and 15 hours at 30°C, respectively.

[0033] Physical properties of the mixed sealant are as follows, as measured after a week upon grouting at 20°C.

compressive strength      765 kg/cm²;
tensile strength      370 kg/cm²;
elongation percentage      410%;
bending strength      520 kg/cm²;
hardness, Shore D      70;

[0034] Generally speaking, the usable liquid sealant may have a viscosity range of 50 to 1,000 cps. For winter use, high viscosity is recommendable.

[0035] Concrete cracking may frequently take the form of a three-dimensional tree-like configuration covering a surface area of wall, in other words a main crack or cracks, branch cracks and hair cracks communicating one with another in sequence.

[0036] A relatively low viscosity sealant should generally be used if fine hair cracks must be substantially fully filled up with the sealant. If it is desired to fill up substantially main cracks only, the sealant may have a high viscosity value. For wider width cracks the sealant may naturally have a higher viscosity value.

[0037] In place of the resinous sealants mentioned as examples, polymer-cement slurries may be used.

[0038] The use of a single injector (frequently called a dispenser) of the above-described type will be described in detail hereinunder as an example.

[0039] In Fig. 6, a concrete wall structure is schematically represented and designated by the letters CS.

[0040] Upon selection of a suitable mounting position for the dispenser, a hardenable resin paste ring 16 is formed around the selected position, extending twice across the tap G in the wall surface which naturally extends perpendicular to the plane of the drawing. Then, the entire assembled apparatus is placed upright upon the hardenable paste ring 16 under light pressure and left to stand for a certain period, such as 30 minutes, until the paste solidifies.

[0041] Next, an operator grips the handle 12 and pulls it upwards in the direction P shown in Figs. 1 and 2, until the bayonet projections 9 on the rod 6 have completely passed through the corresponding openings 8, the spring 5 meanwhile being compressed to its shortest possible length. The handle 12 together with the rod 6 is then turned through a small angle, say 20 to 30 degrees in either direction so as to establish under pressure a bayonet locking relationship between the projections 9 and the upper surface of the upper cap 3.

[0042] Then, the upper cap 3 is unscrewed and the unit B (Fig. 2) is taken out from the cylindrical casing 1. As a next step, the container C is unscrewed from the nozzle 14 and taken out from the casing 1.

[0043] The thus removed container C is inverted and charged with a hardenable liquid sealant, a mixture of epoxy resin and hardening agent. Then, the casing 1, the nozzle 14 and the lower cap 4 are dismantled, leaving the pedestal 15 in the standard position shown in Fig. 6.

[0044] Lastly, all the components including the sealant-­charged container C are reassembled and connected to the pedestal 15. Thus, the preparatory job been completed and the apparatus is now ready to be used for discharge of sealant under pressure.

[0045] The interior space 1c of the hollow cylindrical casing 1 (without the sealant container C, the compression spring 5 and the piston rod 6) may be used as a water bath chamber, for conditoning the viscosity of the liquid sealant. In winter, the bath water may be hot to warm the liquid sealant contained in the container C and thus reduce its viscosity. Conversely, in summer, the bath water may preferably be chilled so as to increase the viscosity of the charged sealant.

[0046] To initiate sealant injection, the handle 12, together with the integral piston rod 6, is turned in the reverse direction by small angle, such as 30 to 40 degrees, from the bayonet-locking position, so as to bring the locking projections 9 into registration with the pair of openings 8 formed through the upper screw cap 3 and release the bayonet locking. At this stage, when the operator releases the handle 12, spring pressure stored in the coil spring 5 is released and drives the piston rod 6 and the end disc 11 gradually downwards in Fig. 1. The charged container C is consequently compress­ed without substantial increase of its diametral dimension and the stored liquid sealant is discharged through the injection passage d in the gap G to effect gap-mending.

[0047] The sealant discharge pressure is generally less than 1 kg/cm², preferably 0.8 to 0.2, and most generally about 0.6 kg/cm². The injection period generally extends for 3 to 5 hours or in extreme cases overnight. In this manner, low pressure slow injection, of a low viscosity sealant, can be attained, although the invention is not limited thereto.

[0048] The use of a sealant container C, having a sharply corrugated cylindrical wall is aimed at prevention of formation of a bubbled sealant which may, in other cases, occur when a small amount of air enters the interior of the container C from the crack gap G and which may result in a foamed and rather weak crack filling. With the present design, air bubbles will be collected at the corrugated peripheral zone of container C, thus preventing redischarge thereof.

[0049] As shown in Fig. 7, the flange 15b is formed with a plurality of concentrically arranged elongate, curved perforations 15c which are filled with the paste 16 and thus providing a firmer fixing for the pedestal 15.

[0050] To replenish the sealant, the units A and B are removed from the apparatus while it stands in position, and the empty container C can then be removed and a new one filled with the sealant fitted into place in the cylindrical casing 1. For this container exchanging operation, only two or three minutes are generally requir­ed so the entire sealant-filling operation can be carried out in a practically continuous manner, with only very short intermittent idle times, until the concrete gap G and related branches, firstly coarser and lastly very fine hair cracks (not shown) have been completely filled up. The fully filled condition, i.e. the termination the crack-mending operation, can be easily adjudged by seeing if sealant delivery has halted or not, through the wall of the casing 1, which is at least partially transparent.

[0051] It will be appreciated from the foregoing that once the operation of the inventive liquid sealant injector has been initiated manually it will continue to operate without reliance on any outside power source. This feature is of considerable significance. The present inventive sealant injector is of an automatic type, with exception of manual sealant container exchange and the preparatory energy storing operation.

[0052] It should be further noted that the inventive sealant injector does not incorporate a solid piston kept in slid­able contact with the inside wall surface of the hollow cylindrical casing 1. Instead, it is provided with an axially expandable and contractable sealant container C, preferably formed with a sharply indulating wall, positioned within the internal space of said cylindrical casing 1. Thanks to adoption of this specifically select­ed sealant container configuration, any air which enters in reverse direction through the nozzle is prevented from disadvantageous intimate admixing with the contained liquid sealant. In this respect, the container's corru­ gated wall structure serves for collection of air bubbles to avoid injection thereof.

[0053] In Figs. 12, (a) and (b), two modifications of the foregoing pedestal 15 are shown at 15ʹ and 15ʺ, respect­ively. They have generally angular-shaped flanges 15bʹ and 15bʺ, respectively, in place of the foregoing disc flange 15b. Sleeve portions 15aʹ and 15aʺ are substan­tially the same as the sleeve 15a in the foregoing embodi­ment. Each of the elongate perforations 15c in the previous embodiment has been modified into a straight linear slot 15cʹ or 15cʺ, respectively. Sealant passage outlet openings dʹ and dʺ corresponding to passage d in Fig. 7.

[0054] These modified pedestals 15ʹ and 15ʺ are used for filling sealant into idle spaces or cracks which occasion­ally occur around corners of reinforcing steel bars in a concrete building. It will be understood that the pedestal 15ʹ is used from outside the building, while that shown at 15ʺ is set into position from inside.

[0055] Next, referring to Figs. 8 to 11, the applicability of apparatus of the invention to charge sealant into float­ing gaps formed spontaneously between a main concrete structure and a decorative and protecting tiling cover or a mortar surface layer will be explained.

[0056] In Fig. 8, part of a concrete structure is again designa­ted CS and a decorative and protecting surface layer is designated TL. These are separated by a gap Gʹ and an artificially drilled anchor hole 100 extends across the gap Gʹ, the latter having an areal extension substantially in parallel with the surface layer TL, while the previous crack G (in Fig. 6) had a three-dimensional, mainly depthwise extent. Both kinds of gaps can be filled with the liquid sealant, according to the general principles of the invention. The anchor hole 100 is bored with a drill and suitably has a diameter of 10 to 11mm and an overall length of 40 to 50mm. After being bored, the hole 100 is cleaned off with a compressed air gun which removes drill chips and powder.

[0057] An expansion dowel 101 of hollow cylindrical config­uration is shown in Fig. 9. This has an internal threaded portion 102 at its end opposite to the insertion direction and a plurality of longitudinal slits 103 extending from its insertion end into a central region as well as an internal frustconical surface 104ʹ provided at its inser­tion end.

[0058] After insertion of the plug 101 into the anchor bore 100 by application of pressure, usually by hammering, a cone member 104 is coaxially introduced, and under pressure from hammer blows, through the intermediary of an intermediate rod (not shown), it causes expansion of the slitted insertion end zone. In this way, the dowel 101 is firmly positioned in the anchor bore 100.

[0059] A sealant charged and spring-energy loaded injector, from which the pedestal 15 has however been removed, is then screw-connected with the plug 101 through its internal screw threads 102. Upon discharge of the stored spring energy, the sealant will be gradually dispensed from the charged container C through the passage d, the interior space 105 of the dowl 101 (Fig. 9 (b) ), and part of the slots 103 registering with the separating air gap Gʹ and finally into the latter.

[0060] Direct connection of the sealant injector and the anchoring dowel, as mentioned above is not especially favourable as the connection may be stressed by lateral physical forces acting upon the injector. Thus, in practice, the injector is usually attached detachably to the anchor dowel 101 through an intermediate positioning plate 106 in the form of either a plano-convex or meni­scus disc shape, the former being illustrated in Fig. 10. Screw coupled to the disc plate 106 is a mechanical adapter 107 consisting of a hexagonal head portion 107a and an externally threaded, hollow stem portion 107b. The head portion 107a is formed centrally with internal threads 107c for receiving threadingly the externally threaded extension 14b of the nozzle 14, shown in Fig. 6. A central bore passage 107e is in communication with the internally threaded space 107c which, in turn, is fluidically connected to the sealant-charged space 13f of the container C shown in Figs. 1 and 3 by way of the sealant discharge passage d.

[0061] In the ready-for-injection condition, when the stored spring energy is released, as before, by loosening the bayonet joint 8,9, the sealant will be discharged from the container C, through d, 107c, 107e and 103, into the floating space Gʹ for mending of the latter.

[0062] To replenish the finally emptied container C, the dismantling and reassembly operations are naturally exe­cuted in a manner similar to that described above with reference to Figs. 1 to 7.

[0063] In Fig. 11, a modification of the foregoing Fig. 10 embodiment is illustrated. In this case the dowel 101 has been replaced by an elongated frustconical hollow plug piece 108 which is preferably made of plastic resin and the tip end of which may be either opened or closed. In a tip end-closed construction, several rows of sealant discharge openings 108a are formed, although in the drawing only one row is shown. A large number of pointed radial projections are also provided to enable a firm grip against the inside wall surface 100ʹ of the bore to be obtained when the piece 108 is hammered into position as shown.

[0064] A hollow intermediate member 109, similar to the foregoing member 107, is provided, the pieces 108 and 109 being threadedly connected. A support member 110 for threadingly receiving the injector itself is also provided. The support member 110 consists of a hollow tubular portion 110a and a laterally extending and curved seating portion 110b for buffering occasionally applied lateral forces. Additionally, a ring 111 of hardenable resin paste may be provided to seal off the bore and prevent escape of sealant. If necessary, the members 109 and 110 may be fabricated in one piece.

[0065] The mode of use of this modification will be well understood from the foregoing description without need for repetition.

[0066] In practice, a large number of the foregoing sealant injectors, for example 30 to 200 or more, may be used at the same time to repair cracks or floating surface gaps over a wide area of a concrete or similar structure, such as a ceiling, side wall or floor, as shown only partly in Fig. 13. This multiple use of sealant injectors will now be described further.

[0067] As stated in the introduction, a further aspect of the present invention is a process of crack-mending of concrete or similar wall, ceiling or floor surfaces. Such surfaces, even where they are of considerable thick­ness, can be mended substantially in a three dimensional way. The sorts of structures to which the mending process can be applied include bridge piers and abutments, concrete tubes, precast concretes, and brick chimneys. However, as a representative example, a method of concrete wall crack-mending will be described with reference to Fig. 14. In this respect, the method will be described by reference to a complexly cracked concrete surface S, wherein there are two main cracks G1 and G2.

[0068] In the first step I, preparatory surface treatment, namely removal of loose material and detritus, is carried out using a wire brush or similar tool. Oil and grease, if any, should also be removed with an appropriate thinner or solvent.

[0069] In the next step II, each of the main cracks is measured and for the sake of example they will be consid­ered to have a width of 50mm. The measurement of crack width is preferably accomplished by magnification, using a peak lighted scale loop.

[0070] A number of injectors are then positioned at spac­ ings of about 300mm, i.e. three per meter, along each of the cracks. Of course, these spacings may be modified as occasion requires. For smaller width cracks, the spacing may be correspondingly increased, and vice versa.

[0071] As the third step III, a small ring of hardenable resin paste is applied to each selected position, as shown at 16 in Figs. 6 and 13. Some paste is also used to seal off other portions of each main crack G or Gʹ from above to encourage sealant penetration into deepest zone of each crack during the following treatment. This consititutes step IV.

[0072] Before hardening of the paste rings, the pedestals 15 of the sealant injectors are placed upon the paste rings 16 under light pressure, so as to fill up the perforations 15c of the pedestal flanges 15b, as already shown and described with reference to Fig. 6. Upon hardening of the paste rings 16, all the pedestals 15 are firmly bonded in position.

[0073] Next, the remaining injector components including a sealant-charged container is attached to each of these pedestals, as shown only partly in Fig. 13.

[0074] In the next step V, the sealant discharge operation is initiated in all or some of the positionally set injectors in the manner previously described. In the case of side wall (i.e. vertical wall) treatment, this injecting operation may preferably be carried into effect in divided groupings or in several stage in sequence from upper to lower regions so as to force any water contained inside the cracks to accumulate in the lower regions thereof.

[0075] Occasionally, one or more of sealant injectors may be kept open to allow escape of air from the cracks as sealant injection progresses.

[0076] If necessary, when the sealant in any one of the injectors has been used up, a newly charged container is replaced by the emptied one. It only takes two or three minutes to charge containers so the sealant injection progresses practically in a continuous manner. During the operation, in turn, main cracks, such as G₁ and G₂ in Fig. 13, branch cracks and hair cracks, are fully filled up with the sealant. Hair cracks are filled by capillery tube action, while the coarser cracks are filled under positive delivery pressure.

[0077] In the next step VI, confirmation of sealant filling is obtained by observing when the sealant delivery is practically terminated, possibly after several replace­ ments of depleated sealant containers.

[0078] In the next step VII, the injected liquid sealant, a hardenable resin mixture, preferably of modified epoxy or polyamine with a known hardening agent is subjected to curing. Recommended curing times, in hours, are as follows:

[0079] The exact time varies depending upon the kind of sealant.

[0080] Upon setting and curing of the injected sealant, and as the final step VIII, all the injectors, together with their respective pedestals, are peeled off from the respective provisional resin rings 16 by appli­cation of lateral and manual pressure or light hammer blows. The remaining and partial broken resin seats are then removed from the mended surface S. The emptied containers may be discarded, while other componets of the apparatus are used repeatedly. However, the contain­ers may also be re-used, if desired, being made ready for further use after cleaning with an aqueous alkaline solution. The emptied containers recover their original shape by their own resiliency.

[0081] Referring finally to Fig. 15, a further method of using a number of sealant injectors in accordance with the invention to fill up a floating cavity between a substrate and a covering layer, e.g. of mortar or tiles or decorative panels will be set forth hereinbelow.

[0082] As the first step Iʹ, the floating area must be inspected and its extent determined. Light hammer blows with a small wooden hammer may be utilized for this purpose. A skilled person can quite easily detect localized area of cavities beneath the surface layer.

[0083] At the next stage IIʹ, one or more checking bores are drilled, as shown in Fig. 8, for example. In this case, the gap Gʹ may be deemed as one of the floating cavities. With use of an elongated probe fitted with a magnifying lens and a small electric lamp the state of the cavity under consideration can be observed. The repair method to be adopted is then determined and the distribution and number of sealant injectors to be used, the kind and viscosity of the sealant, and the locations where the sealant injector are to be set, are all decided upon. These are stage IIIʹ and IVʹ.

[0084] At the next stage Vʹ, each of the selected locations is drilled, as was shown in Fig. 8 and described there­with. Standard drill sizes are in the range 260 to 580mm, and there would generally be 4 to 12 drilling locations per m².

[0085] Upon drilling, drill shavings and dust are removed by water jets. For this purpose, the drill may be fitted with a water jet pump.

[0086] At the next stage VIIIʹ, the aforesaid injecting probe fitted with magnifier and illuminating lamp is again used for checking the inside of each of the drilled holes.

[0087] Then, an expandable dowel or plug, as shown in Figs. 9, 10 or 11 and described hereinbefore, is hammered into each of these drilled holes. If there is any water in the cavity Gʹ it may drain out through openings, e.g. 108a, in the body of the dowel or plug.

[0088] At the next stage VIIIʹ, sealant injectors are set in position, as was referred to with reference to Figs. 10 and 11.

[0089] The sealant injection job at the stage IXʹ is carried out in the same manner as described before.

[0090] Curing of the injected sealant at the stage Xʹ is executed as before.

[0091] At the final stage XIʹ, checking of the executed repair may be performed with light hammer blows as well as visual inspection with a magnifying glass.

Claims

1. Fluid injection apparatus comprising a cylindrical casing (1) having an outlet nozzle (14) at one end and a piston (6,11) which is slidable in the casing (1) to force fluid contained within the casing (1) out of the nozzle (14), characterised in that a detachable axially collapsible container (13) is diposed within the casing (1) to contain the fluid, and biassing means (5) located within the casing (1) acts via the piston (6,11) to cause collapse of the container (13) and discharge of fluid contained therein through the nozzle (14), the piston (6,11) being adapted to be manually withdrawn and retained against the action of the biassing means (5).

2. Fluid injection apparatus according to claim 1 wherein the casing (1) is at least partially transparent and is detachable from the nozzle (14).

3. Fluid injection apparatus according to claim 1 or 2 wherein the casing (1) has respective screw caps (3,4) detaching closing its upper and lower ends.

4. Fluid injection apparatus according to claim 1, 2 or 3 wherein the container (13) is generally cylindrical in form and has a wall which is corrugated in the manner of bellows or a screwthread.

5. Fluid injection apparatus according to any preceding claim wherein the biassing means (5) consists of a coil spring.

6. Fluid injection apparatus according to any preceding claim wherein the piston (6,11) is retainable against the action of the biassing means (5) by rotation of the piston (6,11) after withdrawal from the casing (1) so that projections (9) on its shaft (6) engage behind the edge of an aperture in the casing end wall (3) in the manner of a bayonet connection.

7. Fluid injection apparatus according to any preceding claim further including an attachment unit (15,107,110) fitted to the nozzle (14) to enable attachment of the apparatus to a substrate into which fluid is to be injec­ted.

8. Fluid injection apparatus according to any preceding claim wherein the biasing means (5) acts automatically to cause discharge of fluid from the container (13) over a period of several hours.

9. A method of mending cracks comprising the steps of provisionally securing respective attachment units (15) to the surface of a cracked substrate (CS) at selected spacings along the main cracks (G), connecting sealant charged and pressure-loaded injection apparatus as claimed in any of claims 1 to 6 to each of the attachment units (15), releasing the piston (6,11) of each apparatus to allow injection of sealant into the cracks, replacing depleted containers (13) as necessary, and removing the injectors and the attachment units (15) when the mending operation is complete.

10. A method of securing a floating surface layer (TL) to a substrate (CS) by filling a gap (Gʹ) therebetween comprising the steps of forming bores (100) through the surface layer (TL) and into the substrate (CS) across the gap (Gʹ) inserting expandable dowels or plugs (101, 108) into each of said bores (100) connecting sealant-­charged and pressure-loaded injection apparatus as claimed in any of claims 1 to 6 to each of said dowels or plugs (101,108) and releasing the piston (6,11) of each appar­atus to allow injection of sealant into the gap through apertures (103,108a) in the dowel or plug (101, 108).

Drawing